Hydrogen production by photocatalytic overall water-splitting represents an ideal pathway for clean energy harvesting, for which developing high-efficiency catalysts has been the central scientific topic. Nanosized CoO with high solar-to-hydrogen efficiency (5%) is one of the most promising catalyst candidates. However, poor understanding of this photocatalyst leaves the key issue of rapid deactivation unclear and severely hinders its wide application. Here, we report a sub-micrometer CoO octahedron photocatalyst with high overall-water-splitting activity and outstanding ability of H2O2-resistance poisoning. We show that the deactivation of CoO catalyst originates from the unintended thermoinduced oxidation of CoO during photocatalysis, with coexistence of oxygen and water. We then demonstrate that introduction of graphene, as a heat conductor, largely enhanced the photocatalytic activity and stability of the CoO. Our work not only provides a new insight of CoO for photocatalytic water splitting but also demonstrates a new concept for photocatalyst design.Keywords: CoO octahedrons; H2O2-resistance poisoning; overall water splitting; photocatalyst; photothermal deactivation;

In this study, electrochemiluminescence (ECL) properties of carbon dots (CDs, less than 10 nm) have been investigated. Such CDs were fabricated via electrochemical etching strategy from graphite rods. Subsequently, a series of CDs were prepared through controlled surface engineering technique by a wet chemical method, including the oxidized-CDs (oCDs), partially reduced-CDs (rCDs), and fully reduced-CDs (F-rCDs). In-depth characterizations including UV–vis, FT-IR, Raman, XPS, etc. revealed significant differences in features of these CDs, especially the condition of surface grafted oxygen containing functional groups. ECL results suggested that all of the annihilation ECL of CDs, oCDs, and rCDs demonstrated a stable positively charged luminophore (R+•) and an unstable negatively charged luminophore (R–•) at the surface of GCE and possessed a 365 nm emission peak and consistent emission range from 550 to 850 nm. During further structural mode investigation and ECL properties simulation, the surface construction nature of CDs was speculated and the significant role of oxygen containing groups in ECL behavior of CDs was also verified. According to the ECL behavior from all of these samples, the probable ECL mechanism of CDs was then proposed, which further interpreted the indispensable contributions of oxygen containing functional groups to the ECL property of CDs.

•CDs/g-C3N4/ZnO composites were synthesized by a facile impregnation-thermal method.•CDs/g-C3N4/ZnO samples were characterized by various characterization technologies.•CDs/g-C3N4/ZnO samples showed high visible-light-induced photocatalytic performance.Tetracycline (TC) in the water environment always brings negative impacts on human health and ecosystem equilibrium. Here we report that the carbon dots (CDs)/g-C3N4/ZnO nanocomposite prepared by a facile impregnation-thermal method exhibits outstanding photocatalytic activities for the total photodegradation of TC. Notably, the 30 wt% g-C3N4/ZnO with introducing 4 mL CDs solution (500 mg/L) photocatalyst displays the best photocatalytic activity in the degradation of TC (100 mL, 10 mg/L; 100% degradation within 30 min) under very weak visible irradiation (λ > 420 nm, 18 mW/cm2). In present system, CDs deposited on the surfaces of g-C3N4/ZnO heterojunction not only increases the visible-light response, but also promotes the efficiency of electron-hole pairs separation due to its electrons transfer property. Experiments further confirm that the superoxide radical (O2−) and hydroxyl radical (OH) formed on the surface of the photocatalyst are in charge of the degradation of TC.

•CDs/Ag/AgBr samples were prepared by a facile precipitation-photoreduction method.•CDs/Ag/AgBr samples were characterized by various characterization technologies.•CDs/Ag/AgBr samples showed outstanding NIR-induced photocatalytic performance.Ever-increasing environmental concerns have stimulated great progresses in photocatalytic technology in collection with the environmental remediation and solar energy utilization. In this study, carbon dots (CDs)/Ag/AgBr nanocomposites were prepared via a facile precipitation-photoreduction method. Moreover, CDs/Ag/AgBr nanocomposites show a strong absorbance in the full solar spectrum due to the interaction of Ag nanoparticles (Ag-NPs) and CDs. Meanwhile, compared with pristine AgBr and Ag/AgBr nanoparticles, a dramatic enhancement in the degradation of tetracycline under near-infrared light irradiation is observed over the CDs/Ag/AgBr nanocomposites. Significantly, the extraordinary photocatalytic performance is attributed to the extended absorption in the full spectrum, effective charge separation, and synergistic enhancement induced by surface plasmon resonance of Ag-NPs and the photogenerated change transfer properties of CDs in the complex nanocomposites.

•CDs/Znln2S4 microspheres with high photocatalytic activity were successfully synthesized by one-step hydrothermal method.•CDs/Znln2S4 samples were characterized by various characterization technologies.•CDs/Znln2S4 complex photocatalysts presented outstanding visible-light-induced photocatalytic performance.To design highly-effective photocatalysts including various fascinating properties of eco-friendly, visible-light response and good durability has been strongly desired in photocatalysis field. Here, we synthetised a series of different proportions of carbon dots (CDs) as an ideal cocatalyst to enhance the photocatalytic activity of ZnIn2S4 microspheres in the range of visible light. Simultaneously, CDs(5)/ZnIn2S4 hybrid photocatalyst exhibits the highest photocatalytic activity for degradating methyl orange (MO) (10 mg/L; 100% degradation within 40 min), which is 2.34 times higher than that of ZnIn2S4 alone. Additionally, the crystalline phases, structure, specific surface area and optical properties of as-prepared samples were characterized. The mechanism of enhanced photocatalytic activity of CDs/ZnIn2S4 composite was also discussed.

•g-C3N4/ZnIn2S4 samples were prepared by a one-step hydrothermal method for the sake of degrading TC.•g-C3N4/ZnIn2S4 samples were characterized by various characterization technologies.•g-C3N4/ZnIn2S4 samples showed outstanding photocatalytic activity compared with the pure g-C3N4 and ZnIn2S4.It is a widespread concern to address the antibiotics in water with low-cost and eco-friendly photocatalysts that could efficiently harvest solar light. Herein, we designed an efficient photocatalyst by integrating the lamellar g-C3N4 into Znln2S4 microflowers through a one-step hydrothermal method. The as-synthesized g-C3N4/Znln2S4 heterojunction photocatalysts exhibited evidently enhancement on the photocatalytic activities for the degradation of tetracycline (100 mL, 20 mg/L) compared with pristine g-C3N4 and Znln2S4. Significantly, g-C3N4/Znln2S4 composite with loading 50 wt.% g-C3N4 showed the highest photocatalytic performance (almost 100% degradation within 120 min), which was around 40 and 22.8 times higher than that of g-C3N4 and Znln2S4, respectively. This enhanced photocatalytic activity of g-C3N4/Znln2S4 is mainly attributed to the formation of heterostructure that can efficiently promote the transfer of photoinduced electrons and holes between g-C3N4 and ZnIn2S4, restricting the recombination of electron-hole pairs. In addition, a possible mechanism was also proposed.

•CDs were applied to combine with CdS for visible light overall water splitting the first time.•CDs-CdS can work without any sacrificial agents.•The stoichiometric ratio of produced H2/O2 can adjust from 9:1 to 2:1 by changing CDs content.•CDs can stabilize CdS as oxidation site in low CDs concentration.•CDs can stabilize CdS as both oxidation and reduction sites with the high CDs concentration.Cadmium sulfide (CdS) has long time been one of the most promising inorganic photocatalysts for hydrogen production driven by visible light. However, the photocorrosion of CdS is the most serious problem which constrains its development. Here, we report the design and fabrication of a carbon dots-cadmium sulfide (CDs-CdS) nanocomposite, showing significant photocatalytic water splitting properties with impressive stability without requirement for any sacrificial agents or cocatalysts. The highest hydrogen production rate was obtained for about 2.55 μmol h−1, with an oxygen evolution rate for about 0.52 μmol h−1, when the concentration of CDs in the sample is 0.03 gCDs/gcatalyst. Even the produced H2 and O2 are not equal to the stoichiometric ratio of 2:1 (H2:O2), the CDs-CdS nanocomposite shows greater stability (8-time repetitive catalytic experiments) than the CdS catalysts reported up to now (without sacrificial agents or cocatalysts). It is also inspiring that when we increased the concentration of CDs in the catalysts, the produced H2 and O2 were gradually adjusted to meet the stoichiometric ratio of 2:1 in spite of low hydrogen production rate (0.13 μmol h−1).We report the design and fabrication of carbon dots-cadmium sulfide (CDs-CdS) nanocomposite, showing significant photocatalytic water splitting properties with impressive stability without requirement for any sacrificial agents under visible light. The CDs can stabilize CdS due to its function as oxidation site in low CDs concentration, and it can work as both oxidation and reduction sites when the CDs concentration is high.Download high-res image (167KB)Download full-size image

•BiVO4/CDs/CdS Z-scheme photocatalyst with CDs as solid-state electron mediator was designed.•BCC50 shows the best photocatalytic activity with stoichiometric ratio of H2/O2 evolution.•BiVO4/CDs/CdS photocatalyst could efficiently photocatalytic overall water splitting.Z-scheme photocatalytic system is an efficient way to achieve high efficiency photocatalytic overall water splitting. However, the acquisition of efficient Z-scheme visible-light photocatalysts is still a huge challenge at present due to the inactive visible light-active component and various low-band-gap for semiconductors. Herein, we constructed the BiVO4/CDs/CdS Z-scheme photocatalyst with carbon dots (CDs) as solid-state electron mediator, which exhibits excellent photocatalytic activity and stability for photocatalytic overall water splitting under visible light. The BCC50 (BiVO4/CDs/CdS with the mass ratio of BiVO4/CdS = 50%) as photocatalyst shows the best photocatalytic activity with stoichiometric ratio of H2 evolution rate of 1.24 μmol/h and O2 evolution rate of about 0.61 μmol/h. The enhanced photocatalytic activity of the Z-scheme photocatalyst can be attributed to high efficiencies for separation and transport of photogenerated charge carriers and extended the lifetime of electrons and holes.We constructed the BiVO4/CDs/CdS Z-scheme photocatalyst with carbon dots (CDs) as solid-state electron mediator, exhibiting excellent photocatalytic activity and stability for photocatalytic overall water splitting under visible light. The BCC50 (BiVO4/CDs/CdS with the mass ratio of BiVO4/CdS = 50%) as photocatalyst shows the best photocatalytic activity with stoichiometric ratio of H2 evolution rate of 1.24 μmol/h and O2 evolution rate of about 0.61 μmol/h. The enhanced photocatalytic activity of the Z-scheme photocatalyst can be attributed to high efficiencies for separation and transport of photogenerated charge carriers and extended the lifetime of electrons and holes.Download high-res image (107KB)Download full-size image

•The Ni3(C3N3S3)2 coordination polymer was firstly synthesized by a simple wet-chemical method.•The as-prepared Ni3(C3N3S3)2 exhibited excellent photocatcalytic H2-producing activity from the half-reaction of water splitting.•The photostability of Ni3(C3N3S3)2 was effectively improved by means of triethanolamine.Sparked by the increasing energy crisis, much research has been focused on seeking board spectrum-driven photocatalysts for water splitting. Herein, the Ni3(C3N3S3)2 coordination polymer was firstly synthesized by a simple wet-chemical method, as a novel board spectrum-driven photocatalyst for water splitting. The as-prepared Ni3(C3N3S3)2 exhibited excellent photocatcalytic H2-producing activity from the half-reaction of water splitting without the help of any sacrificial agents or cocatalysts, and the amounts of H2 production are 65.3, 53.9 and 16.3 μmol corresponding to UV (λ < 400 nm), visible (400 ≤ λ ≤ 760 nm) and near-infrared (λ > 760 nm) irradiation after 24 h, respectively. Another valuable finding is that after adding triethanolamine as a sacrificial donor, the average H2 evolution efficiencies on Ni3(C3N3S3)2 were efficaciously increased by around 2-fold with the H2 production value of 112.6, 93.3 and 30.1 μmol for 24 h under the UV light, visible light and near-infrared light exposure, respectively. More importantly, the stability of Ni3(C3N3S3)2 was effectively improved by means of triethanolamine. The results facilitate the increasing attention of narrow band gap non-noble metal coordination polymers treated as board spectrum-driven photocatalysts for expanding the utilization of solar light.Download high-res image (188KB)Download full-size imageWe have successfully synthesized a novel Ni3(C3N3S3)2 coordination polymer by a facile wet-chemical rout for the first time. Specifically, the as-prepared Ni3(C3N3S3)2 possessed UV–vis-NIR broad spectrum absorption and can be acted as a board spectrum-driven photocatalyst for water splitting into hydrogen. As expected, the H2 production performance from pure water over Ni3(C3N3S3)2 was realized through from UV (λ < 400 nm) to Vis (400 ≤ λ ≤ 760 nm) and NIR (λ > 760 nm) without any sacrificial agents or cocatalysts, and the amounts of H2 production are 65.3, 53.9 and 16.3 μmol corresponding to UV, Vis and NIR irradiation after 24 h, respectively. Significantly, the efficiency of H2 production and the stability over the Ni3(C3N3S3)2 could be improved with the assistance of triethanolamine. And the average H2 evolution efficiencies on Ni3(C3N3S3)2 were efficaciously increased by around 2-fold with the H2 production value of 112.6, 93.3 and 30.1 μmol for 24 h under the UV, Vis and NIR light exposure, respectively.

•CDs-CoO composites were firstly synthesized by one-step solvothermal method.•CDs as co-catalyst modified and stabilized the (111) facets of CoO octahedrons.•CDs-CoO composites exhibited outstanding photocatalytic activity and stability.Octahedral CoO with exposed high-reactive (111) facets holds a promising noble-metal-free material in the photocatalysis. However, the (111) facet is usually unstable and easily deactivated during the photocatalytic process as the result of its poloar catastrophe. In this work, carbon dots (CDs) as co-catalyst modified and stabilized the (111) facets of CoO octahedrons (CDs-CoO) were prepared by one-step solvothermal method. The desired CDs-CoO shows the excellent photocatalytic activity and well stability. Meanwhile, the CDs-CoO (5 wt.%) composite exhibits the highest photocatalytic activity for degradation of tetracycline (87%, 60 min), and presents remarkable photostability after five successive cycles (5 h). This enhanced photocatalytic activity and outstanding stability in CDs-CoO composites could be ascribed to several merits of CDs that not only improve charge separation efficiency but also strengthen the interaction between CDs and high-reactive (111) facets of CoO octahedrons.Carbon dots (CDs) as co-catalyst modified and stabilized the (111) facets of CoO octahedrons (CDs-CoO) were prepared by one-step solvothermal method. Meanwhile, the CDs-CoO composite not only exhibits excellent photocatalytic activity, but also presents remarkable photostability. This enhanced photocatalytic activity and outstanding stability in CDs-CoO composites could be ascribed to CDs not only improve charge separation efficiency but also strengthen the interaction between CDs and high-reactive (111) facets of CoO octahedrons.Download high-res image (103KB)Download full-size image

•Surface functionalized carbon dots were synthesized by hydrothermal method.•NS-CDs can be applied in a variety of detection applications.•NS-CDs always have a satisfactory behavior to quantitative detection of molecules.The surface functionalization will introduce additional functional groups on carbon dots (CDs) surface and then enrich the properties of CDs. Here, we show the various surface functionalized CDs (-COOH, -OH, -SH, -NH2, etc, named as NS-CDs) were synthesized with fascinating features, including high quantum efficiency (38.9%), long-term stability and good biocompatibility. Notably, it can serve as multifunction fluorescent probe in sensing system, including label-free detections in hydrogen peroxide (H2O2) with a wide linear range (1.20 × 10−3 – 8.80 × 10–12 M) and a low limit of detection (LOD, 1.00 × 10–12 M); and glutathione, covering a concentration range of 2.00 × 10−3 – 1.00 × 10−7 M and LOD of 1.00 × 10−7 M. In addition, the NS-CDs as fluorescent probe could selectively detect metal ions (such as, Hg2+, 1.00 × 10−8 − 1.50 × 10−3 M, 1.00 × 10−7 M), antibiotics (tetracycline, 1.00 ×10−10 − 2.50 × 10−5 M, 1.00 ×10−10 M) and toxic pollutant (nitrobenzene, 5.00 × 10−7 to 1.00 × 10−3 g L−1, 5.00 × 10−7 g L−1) with wide linear range and satisfactory detection limits.We show various surface functionalized CDs (-COOH, -OH, -SH, -NH, etc) with fascinating features can be label-free detection in hydrogen peroxide, glutathione, heavy metal ions (Hg2+/Ag+), antibiotics and toxic pollutant with satisfactory detection limits and range.Download high-res image (375KB)Download full-size image

Electrochemical reduction of carbon dioxide (CO2) to methanol (CH3OH) catalyzed by transition metals has been proved feasible and effective in aqueous electrolytes. In this work, we introduce a FeS2/NiS nanocomposite electrocatalyst synthesized by traditional hydrothermal method, which selectively reduces CO2 to CH3OH with an unprecedented overpotential of 280 mV and a high faradaic efficiency up to 64% at the potential of −0.6 V vs. reversible hydrogen electrode (RHE). The FeS2/NiS nanocomposite electrocatalyst exhibits a stable current density of 3.1 mA cm−2 over a 4 hour stability test. The high selectivity towards CO2 electroreduction to CH3OH may be attributed to the special ladder structure of the FeS2/NiS nanocomposite. The active sites are located at the interface between FeS2 and NiS which can effectively suppress the side reaction hydrogen evolution reaction and facilitate the CO2 reduction reaction.

Highly efficient electrocatalysts remain huge challenges in direct methanol fuel cells (DMFCs). Here, a Pt–Co3O4–CDs/C composite was fabricated as an anode electrocatalyst with low Pt content (12 wt%) by using carbon dots (CDs) and Co3O4 nanoparticles as building blocks. The Pt–Co3O4–CDs/C composite catalyst shows a significantly enhanced electrocatalytic activity (1393.3 mA mg−1 Pt), durability (over 4000 s) and CO-poisoning tolerance. The superior catalytic activity should be attributed to the synergistic effect of CDs, Pt and Co3O4. Furthermore, the Pt–Co3O4–CDs/C catalyst was integrated into a single cell, which exhibits a maximum power density of 45.6 mW cm−2, 1.7 times the cell based on the commercial 20 wt% Pt/C catalyst.

Stable bioimaging with nanomaterials in living cells has been a great challenge and of great importance for understanding intracellular events and elucidating various biological phenomena. Herein, we demonstrate that N,S co-doped carbon dots (N,S-CDs) produced by one-pot reflux treatment of C3N3S3 with ethane diamine at a relatively low temperature (80 °C) exhibit a high fluorescence quantum yield of about 30.4%, favorable biocompatibility, low-toxicity, strong resistance to photobleaching and good stability. The N,S-CDs as an effective temperature indicator exhibit good temperature-dependent fluorescence with a sensational linear response from 20 to 80 °C. In addition, the obtained N,S-CDs facilitate high selectivity detection of tetracycline (TC) with a detection limit as low as 3 × 10−10 M and a wide linear range from 1.39 × 10−5 to 1.39 × 10−9 M. More importantly, the N,S-CDs display an unambiguous bioimaging ability in the detection of intracellular temperature and TC with satisfactory results.

Monitoring of bacterial viability is crucial for food safety and human health. Fluorescence staining with dyes is one of the simple and fast methods to assess bacterial viability. However, obtaining stable and non-poisonous dyes is still a huge challenge. Herein, we demonstrate that nitrogen, phosphorus and sulfur co-doped carbon dots (NPSCDs) can selectively stain dead bacteria rather than live ones because they possess a highly negative ζ potential (−41.9 mV), indicating that NPSCDs could serve as an efficient dye for bacterial viability evaluation. The NPSCDs were synthesized by one-step hydrothermal carbonization of a yeast extract, and exhibit favorable photoluminescence (PL) with high quantum yield (QY, 32%), excellent photostability (under acid/alkaline and strong ionic strength), good biocompatibility and low toxicity. Moreover, the designed NPSCDs show a precise response to temperature within the range from 30 °C to 90 °C, in which the fluorescence of the NPSCDs decreased linearly with an increase in temperature and recovered with a decrease in temperature. More importantly, when the live bacteria were incubated with NPSCDs, as the temperature increases, the NPSCDs could selectively stain dead bacteria in real time along with a decrease in fluorescence intensity simultaneously, showing a significant reduction in bacterial viability from 80% to 15% upon heating at 60 °C for more time. The development of NPSCDs paves a new way for the synthesis of a sensitive fluorescent probe that can be used in real-time monitoring of bacterial viability.

Photocatalytic overall water splitting using particulate semiconductors is a potential means of storing solar energy in using the intermittency of sunlight as a primary source of power and zero emission of carbon dioxide. Herein, we constructed a composite material with carbon dots (CDs) anchored on the surface of octahedral CoO as a highly efficient and long-term stable photocatalyst for overall water splitting under visible light irradiation (λ > 400 nm). The structure and morphology of the CDs/CoO composite were investigated by a series of characterization methods. The obtained CDs/CoO composites exhibit more-efficient visible light absorption than pure CoO, leading to higher photocatalytic activity for overall water splitting. The optimized photocatalytic H2 and O2 production was achieved for the CDs/CoO composite with a content of 5 wt% CDs (5% CDs/CoO), showing a H2 (O2) evolution rate of 1.67 μmol h−1 (0.91 μmol h−1) with an expected 2 : 1 stoichiometry, which is up to 6 times as high as that of pristine CoO. Additionally, the 5% CDs/CoO composite also shows outstanding photocatalytic stability for over 15 cycling experiments. This enhanced photocatalytic activity and outstanding stability in CDs/CoO composites could be ascribed to several merits of CDs that not only improved charge separation efficiency and visible-light absorption but also effectively conducted heat generated by the photo-thermal effect of CoO.

Hydrogen is an ideal energy carrier for renewable energy, but a high overpotential is required to achieve reasonable H2 evolution, which makes the design of highly active electrocatalysts for hydrogen evolution reaction (HER) urgent. Here, we report a nitrogen, sulfur co-doped carbon dots (NSCDs)/CoS hybrid with a three-dimensional mesoporous sponge-like nanostructure, fabricated via heat-treatment, which as electrocatalyst exhibits the desired electrocatalytic activity for electrochemical HER. A series of NSCDs/CoS hybrids with different contents of NSCDs were prepared by adjusting the concentration of NSCDs, of which the NSCDs/CoS hybrid with 20 mg L−1 NSCDs exhibits the best electrocatalytic activity towards HER with an onset potential of 0.095 V, an overpotential at 10 mA cm−2 of 165 mV, a small Tafel slope of 56 mV per decade, and a good stability in 0.5 M H2SO4. The excellent electrocatalytic activity of NSCDs/CoS for HER is attributed to synergetic effects of NSCDs and CoS, in which the NSCDs could protect the CoS from dissolution/agglomeration under acidic conditions, and the increased surface area of the NSCDs/CoS hybrid and the high charge transfer efficiency between NSCDs and CoS via Co–S–C bonding enhanced the HER performance.

In recent years, carbon dots (C-dots) have become a rising star for a spectrum of environmental and energy applications, ranging from chemical catalysis, to photocatalysis, electrocatalysis and energy storage, such as batteries and capacitors, due to their unique physicochemical, optical and electrical properties. This review discusses the up-to-date progress on carbon dots, with an emphasis on their environmental and energy applications along with some discussion on the challenges and promises in this exciting and promising field.

Using photocatalysts to split water into hydrogen and oxygen is a promising way to produce renewable energy. Efficient and stable photocatalysts are desired for overall water splitting under visible light. We demonstrate that the cobalt(II) oxide (CoO)/graphitic carbon nitride (CoO/g-C3N4) composites synthesized by a one-step thermal decomposition method exhibit enhanced photocatalytic efficiency for overall water splitting without sacrificial reagents. 10%CoO/g-C3N4 exhibits optimal photocatalytic performance, where H2 and O2 evolution rates are, respectively, 0.46 μmol h−1 and 0.21 μmol h−1 under visible light irradiation without any sacrificial reagents. It is worth mentioning that the H2 and O2 production almost approaches the stoichiometric ratio 2 : 1. The enhanced photocatalytic activity of CoO/g-C3N4 may be ascribed to the efficient charge separation and fast decomposition of H2O2 by CoO.

As the misuse and overuse of tetracycline (TC) contribute to water pollution, it is imperative to explore an efficient and cost-effective approach for the removal of TC in aqueous solution. Photocatalysis is a green and sustainable chemical technique because of its utilization of solar energy. From the view of practical application, it is significant to design a highly efficient, stable, eco-friendly and economical photocatalyst. In this work, CuBi2O4/g-C3N4 p–n heterojunctions with different CuBi2O4 content (10–90 wt%) were prepared via a facile calcining method. The CuBi2O4/g-C3N4 heterojunctions exhibit superior photocatalytic activity in the degradation of TC, compared with pristine CuBi2O4 and g-C3N4. The optimum photoactivity of 70 wt% CuBi2O4/g-C3N4 is up to 4 and 6 times higher than that of CuBi2O4 and g-C3N4, respectively. The enhanced photocatalytic activity can be attributed to p–n junction photocatalytic systems, which effectively promote charge carrier separation and transfer. It is anticipated that the design of CuBi2O4/g-C3N4 could offer the insight needed to construct inexpensive and highly efficient g-C3N4-based heterojunction photocatalysts, to relieve urgent environmental deterioration.

Since the misuse and overuse of tetracycline (TC) increase the pollution of aqueous solution, it is highly desirable to develop highly effective, stable, eco-friendly, economical, and facile photocatalysts for the photocatalytic degradation of TC in an aqueous solution. Herein, we designed and synthesized a highly efficient CoO/g-C3N4 p–n heterojunction via a facile solvothermal method. The experimental results demonstrated that after the coupling of CoO with g-C3N4, CoO nanoparticles were uniformly distributed on the surface of wrinkled g-C3N4 layers not only to readily form a p–n heterjunction, but also to avert the aggregation; and the CoO/g-C3N4 p–n heterojunction photocatalysts exhibited superior visible-light photocatalytic activity and stability for the removal of TC. The high photocatalytic activity could be attributed to the generation of an internal electric field induced by the p–n heterojunctions, effectively promoting the separation of photoinduced charge.

Self-healing is the way by which nature repairs damage and prolongs the life of bio entities. A variety of practical applications require self-healing materials in general and self-healing polymers in particular. Different (complex) methods provide the rebonding of broken bonds, suppressing crack, or local damage propagation. Here, a simple, versatile, and cost-effective methodology is reported for initiating healing in bulk polymers and self-healing and anticorrosion properties in polymer coatings: introduction of carbon dots (CDs), 5 nm sized carbon nanocrystallites, into the polymer matrix forming a composite. The CDs are blended into polymethacrylate, polyurethane, and other common polymers. The healing/self-healing process is initiated by interfacial bonding (covalent, hydrogen, and van der Waals bonding) between the CDs and the polymer matrix and can be optimized by modifying the functional groups which terminate the CDs. The healing properties of the bulk polymer–CD composites are evaluated by comparing the tensile strength of pristine (bulk and coatings) composites to those of fractured composites that are healed and by following the self-healing of scratches intentionally introduced to polymer–CD composite coatings. The composite coatings not only possess self-healing properties but also have superior anticorrosion properties compared to those of the pure polymer coatings.

Chiral nanostructures have attracted extensive interest as components for chiral applications. Carbon quantum dots (CQDs) with superior properties, including low toxicity and good biocompatibility, can render the field of QDs with more potential biological applications in bioimaging, biosensors, and drug delivery. Herein, we report the fabrication of nitrogen and sulfur co-doped chiral CQDs (L-/D-CQDs) with strong symmetrical circular dichroism (CD) signals at about 212 and 240 nm. These chiral CQDs exhibit strong photoluminescence (PL) emission (at 460 nm) and outstanding enantioselective electrochemical recognition ability. A series of experiments further confirms that these chiral CQDs possess independent PL and chiral properties. With a temperature increase, PL is quenched with a good linear correlation of 0.992, whereas the CD signals remain almost the same. On the other hand, the PL of L- or D-CQDs shows no difference towards small chiral molecules detection with right or opposite configuration. In addition, the L- or D-CQDs excited with circularly polarized light (CPL) show similar PL properties regardless of their right or left configuration.

We present a simple hydrothermal method to fabricate multifunctional modified carbon dots (with –COOH, –OH, –SH, and –NH2 groups, named NS-Cdots) using citric acid and L-cysteine as raw materials. The functional NS-Cdots exhibit high fluorescent quantum yield (38.9%), low cytotoxicity and good biocompatibility. A reasonable photoluminescence mechanism of the NS-Cdots was proposed in which the pyridine derivatives serve as conjugating units and dominate the main emission behavior. The NS-Cdots can also be used as excellent fluorescent probes for cell imaging in vitro and as effective thermometers with a wide temperature detection range from 20 °C to 95 °C.

A novel C3N4–CDot composite photocatalyst was very recently shown to be highly efficient and very stable in water splitting by solar radiation without using any sacrificial reagent (J. Liu, et al., Science, 2015, 347(6225), 970). This photocatalyst utilizes a two-electron/two-step process in which the production of H2O2 and H2 is photocatalyzed by using C3N4 in the first step and H2O2 is decomposed by using CDots in the second step. The present work is a study on the generality of this approach by application of a C3N4/MnO2 catalyst. This new catalyst indeed splits water by a two step process in a stable way, without any sacrificial agent. It was however found that though the absorbance of the new catalyst in the visible range of 500–600 nm is much larger than that of the C3N4–CDot catalyst, its water splitting efficiency is much lower. These findings add insight into and assist in the further optimization of this new class of photocatalysts to meet the requirements of commercial water splitting systems.

We developed a facile hydrothermal method to fabricate the carbon quantum dots (CQDs)/MoS2 composite as hydrogen evolution reduction (HER) catalyst. After irradiation with visible light for 30 min, the CQDs/MoS2 composite (as CQDs/MoS2-L30) performed improved HER activity, featured by a small overpotential of ∼0.125 V at 10 mA cm−2, a high current density, a small Tafel slope of 45 mV/decade and a long term stability in 0.5 M H2SO4. This kind of activity improvement towards HER may be due to the high charge transfer efficiency, the decrease of S4+ and the increase of S22−S22− and S2− after the light treatment.

Developing highly efficient and low cost hydrogen evolution reaction (HER) electrocatalysts is still a huge challenge. In this study, we demonstrate a facile method to fabricate a nitrogen, phosphorus co-doped carbon dots/CoS2 (NPCDs/CoS2) hybrid as an electrocatalyst for HER with desirable electrocatalytic activities (low overpotential ∼78 mV and small Tafel slope ∼76 mV dec−1) and long-term stability (after 1000 CV cycles with negligible current loss ∼1 mA cm−2) in acidic media.

Ag3PW12O40/C3N4 nanocomposites were successfully synthesized by loading Ag3PW12O40 into C3N4, in which case Ag3PW12O40 is gained through reaction between AgNO3 and H3PW12O40 at room temperature. The obtained nanocomposites show efficient and light-operated catalytic activity for hydrocarbon selective oxidation (selective oxidation of cyclooctene and cyclohexane) without adding any oxidant at 60 °C. For cyclooctene, the conversion based on cyclooctene is 41.26%, and the selectivity of selective oxidation to epoxycyclooctane can be up to 77.2%. The nanocomposite catalyst yielded oxidation of cyclohexane to cyclohexanone with 8.62% efficiency and >99.0% selectivity. In the catalytic system, the oxidant (H2O2) in the catalysis process can be produced by the irradiation of C3N4 and then decomposed into HO· with the help of Ag3PW12O40. The observed improvement in the activities of photo-induced oxidation of cyclooctene and cyclohexane is mainly attributed to the high BET surface area of C3N4. With the synergistic effect of Ag3PW12O40 and C3N4, the nanocomposite displays considerable catalytic activity, which sheds light on the catalyst design applied in the selective oxidation of hydrocarbon.

Chiral carbon quantum dots (L-carbon quantum dots, L-CQDs; and D-carbon quantum dots, D-CQDs) were synthesized through the facile hydrothermal treatment of carbonated citric acid and L-cysteine (or D-cysteine). The chirality in L-CQDs and D-CQDs was demonstrated by circular dichroism. Both L-carbon quantum dots and D-carbon quantum dots could exhibit good enantioselective recognition ability.

It is highly desired for the development of efficient bifunctional electrocatalyst for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in renewable energy technologies. In this work, cobalt, nitrogen-codoped carbon was prepared by a facile one-step method and demonstrated to exhibit good electrocatalytic performance for ORR and OER via a complete four-electron process. Besides, the catalyst prepared at 900 °C also displayed excellent stability for both ORR and OER. Furthermore, the origin of catalytic activity was also explored, which was attributed to the synergistic effects of metallic Co and quaternary N.发展可再生新能源技术迫切需要寻找既可以在氧还原反应(ORR)中起到催化作用,又具有催化氧析出反应(OER)的双功能催化剂。本文利用900°C热分解方法一步合成制备出钴、氮共掺的碳材料。实验结果表明,它具有较好的ORR和OER催化能力;同时,钴、氮共掺的碳材料对ORR和OER催化反应都是四电子反应过程。

The C3N4-tyrosinase (TYR) hybrid is a highly accurate, sensitive and simple fluorescent probe for the detection of dopamine (DOPA). Under optimized conditions, the relative fluorescence intensity of C3N4-TYR is proportional to the DOPA concentration in the range from 1 × 10−3 to 3 × 10−8 mol L−1 with a correlation coefficient of 0.995. In the present system, the detection limit achieved is as low as 3 × 10−8 mol L−1. Notably, these quantitative detection results for clinical samples are comparable to those of high performance liquid chromatography. Moreover, the enzyme-encapsulated C3N4 sensing arrays on both glass slide and test paper were evaluated, which revealed sensitive detection and excellent stability. The results reported here provide a new approach for the design of a multifunctional nanosensor for the detection of bio-molecules.

Mechanical wear accounts for one third of present global energy consumption. However, it still lacks an efficient lubricant to simultaneously achieve a highly efficient lubrication and metal wear repair. Herein, we report that carbon quantum dots (CQDs)/CuSx nanocomposites show enhanced lubrication and metal wear surface repair abilities when used as additives. The highly efficient lubrication and metal wear repair properties should be attributed to the combination of the multi-layer graphite structure of CQDs and the high chemical activity of CuSx nanoparticles.

A combustion flame method is developed for the convenient and scalable fabrication of single- and dual-doped carbon quantum dots (CQDs) (N-CQDs, B-CQDs, P-CQDs, and S-CQDs and dual-doped B,N-CQDs, P,N-CQDs, and S,N-CQDs), and the doping contents can be easily adjusted by simply changing the concentrations of precursors in ethanol. These single/dual-doped CQDs, especially B,N-CQDs, show high catalytic activities for the oxygen reduction reaction.

The exploration of an efficient electrocatalyst for hydrogen evolution reaction (HER) from water is a key to relieve the energy crisis, which is a great challenge. Herein, a nickel nanoparticle/carbon quantum dot (Ni/CQD) hybrid is synthesized and evaluated as an electrocatalyst for HER under a strongly alkaline medium (1 M KOH solution). The obtained Ni/CQD hybrid shows good catalytic ability for HER with an onset potential comparable to that of Pt wire and a low Tafel slope of 98 mV dec−1, which may be attributed to the Ni–O–C interface between Ni NPs and CQDs. The Ni/CQDs also exhibit high stability after 1000 CV cycles with negligible current loss (around 1 mA cm−2). Moreover, the catalytic ability of Ni/CQDs can be further improved under visible light illumination, suggested by a lower Tafel slope of 77 mV dec−1.

In this study, we provide the quantitative data on the membrane permeability of a HeLa cell in the presence of different sizes of SiO2 nanoparticles (NPs, 50, 100 and 200 nm). SiO2 NPs have low cytotoxicity, but 50 and 100 nm SiO2 NPs can increase the cell membrane permeability (a reversible effect) by 12.5% (0.02 mg mL−1, 4 min) and 9% (0.02 mg mL−1, 6 min), respectively. However, the 200 nm SiO2 NPs cannot affect the cell membrane permeability.

The fluorescent N-doped carbon dots (N-CDs) obtained from C3N4 emit strong blue fluorescence, which is stable with different ionic strengths and time. The fluorescence intensity of N-CDs decreases with the temperature increasing, while it can recover to the initial one with the temperature decreasing. It is an accurate linear response of fluorescence intensity to temperature, which may be attributed to the synergistic effect of abundant oxygen-containing functional groups and hydrogen bonds. Further experiments also demonstrate that N-CDs can serve as effective in vitro and in vivo fluorescence-based nanothermometer.Keywords: cellular imaging; in vivo imaging; linear response; N-doped carbon dots; nanothermometer; temperature-dependent fluorescence

The phosphate functionalized carbon dots (PCDs) with high biocompatibility and low toxicity can be used as efficient additives for the construction of laccase/PCDs hybrids catalyst. A series of experiments indicated that the activity of laccase/PCDs was higher than that of free laccase (increased by 47.7%). When laccase/PCDs hybrids catalyst was irradiated with visible light (laccase/PCDs-Light), its activity was higher than that of laccase/PCDs hybrids without light irradiation (increased by 92.1%). In the present system, the T1 Cu in laccase was combined with the phosphate group on PCDs, which can increase binding capacity of laccase/PCDs hybrids and substrate. Further, the visible light irradiation increased the donating and accepting electronic capability of the laccase/PCDs hybrids, improving their catalytic activity.Keywords: activity tuning; carbon dots; laccase; phosphate modification; visible light;

A deep understanding of the interaction between the nanoparticle and enzyme is important for biocatalyst design. Here, we report the in situ synthesis of laccase–Au NP (laccase–Au) hybrids and its catalytic activity modulation by visible light. In the present hybrid system, the activity of laccase was significantly improved (increased by 91.2% vs free laccase) by Au NPs. With a short time visible light illumination (λ > 420 nm, within 3 min), the activity of laccase–Au hybrids decreased by 8.1% (vs laccase–Au hybrid without light), which can be restored to its initial one when the illumination is removed. However, after a long time illumination (λ > 420 nm, over 10 min), the catalytic activity of laccase–Au hybrids consecutively decreases and is not reversible even after removing the illumination. Our experiments also suggested that the local surface plasma resonance effect of Au NPs causes the structure change of laccase and local high temperature near the Au NPs. Those changes eventually affect the transportation of electrons in laccase, which further results in the declined activity of laccase.Keywords: Au nanoparticle; catalytic activity; hybrid catalyst; laccase; visible-light illumination

Nanocomposites based on transition metal oxides (Co3O4, etc.) and carbon nanostructures with low-cost, high activity and good stability are promising catalysts toward electrochemical water oxidation, which is desirable but remains challenging. Here, we report the design and synthesis of nanocomposite based on carbon quantum dots (CQDs), SnO2 and Co3O4 (CQDs/SnO2–Co3O4) as the electrocatalyst for highly efficient oxygen evolution reaction (OER). In alkaline media, the complex exhibited high electrocatalytic activity and long-term stability, which was better than either pristine Co3O4 or SnO2–Co3O4 composite. Moreover, the CQDs/SnO2–Co3O4 with a molar ratio of Sn:Co at 1:3 revealed the highest catalytic activity toward OER among different molar ratios of CQDs/SnO2–Co3O4 composites. Experimental results indicated that the Co atoms were considered as the active centre, the nano-sized SnO2 enhanced electronic conductivity and the insoluble CQDs layer on the surface effectively protected the catalyst, thus the composite structure resulted in the excellent electrocatalytic activity and high stability.

N-doped carbon dots (NCDs) obtained by one-step reflux treatment of C3N4 with ethane diamine possess good water dispersibility, strong visible fluorescence, low toxicity, proton adsorption capacity, and photo-induced electron-accepting/donating abilities. Based on these unique properties, we demonstrate that the obtained NCDs can be used as a good fluorescent probe for cellar imaging without any further functionalization. Further, the NCDs are combined with laccase (LAC) to form NCDs–laccase (NCD–LAC) hybrids, which are sensitive, stable, and of low cost for the precise detection of catechol and catechol derivatives.

In this work, we report the synthesis, structures and luminescence properties of two pairs of isostructural coordination polymers [Cu(mttz)] (1) and [Cu(ettz)] (3); [Cu2(mttz)Cl] (2) and [Cu2(ettz)Cl] (4) (Hmttz = 5-(methylthio)-1H-tetrazole, Hettz = 5-(ethylthio)-1H-tetrazole). Structural analysis reveals that compounds 1 and 3 exhibit two dimensional (2D) layered structures, which are constructed by two types of one dimensional (1D) chains. Compounds 2 and 4 consist of 1D strip-like chains, which are further assembled into three dimensional (3D) frameworks. Detailed luminescence investigation displays that compound 1 consists of a main peak at 454 nm and a shoulder peak at 585 nm, similar to the luminescent emission of Hmttz ligand (461, 554 nm), whereas compound 2 displays one emission band centered at 475 nm. A similar luminescence phenomenon has also been observed between 3, 4 and Hettz ligand. In the present system, the rigidity, arrangement and hydrogen bonding of ligands in the title compounds play an important role leading to luminescence property trimming.

Here, we have reported the design, synthesis and catalytic properties of a gold nanoparticle/carbon dot/SnO2 nanocomposite photo-electronic catalyst for oxygen evolution reaction.

Three new luminescent coordination polymers (CPs), [Ag2(bpp)(Hsba)]·H2O (1), [Cd(bpp)(Hsba)·H2O] (2), and [Pb(bpp)3(H2sba)2] (3) (bpp = 1,3-bis(4-pyridyl)propane, H3sba = 2,4-dichloro-5-sulfamoylbenzoic acid), have been designed and synthesized by hydrothermal methods. Compound 1 exhibits left- and right-handed helical chains. Compound 2 shows a 2-fold parallel interpenetration sql net with 44·62 topology. Compound 3 displays a supramolecular wavelike chain. These three title CPs are used as fluorescence sensors for highly selective and sensitive detection of nitrobenzene in a wide linear detection range.

A C3N4-sensitized TiO2 nanotube array-based photoanode was designed and fabricated via the in situ growth of C3N4 on the surface of TiO2 nanotubes. It shows stable and significantly improved PEC activity for hydrogen generation under visible light irradiation with a hydrogen production rate of about 19.1 μmol h−1 (a Faradaic efficiency of nearly 100%).

Carbon quantum dots (CQDs) obtained from polyethylene glycol were demonstrated to be easy-to-use photoluminescence probes for the detection of glucose. Here, the photoluminescence of CQDs was significantly enhanced by H2O2 produced from glucose oxidase-catalyzed oxidation of glucose. Moreover, CQDs showed an ultrasensitive detection of glucose, with a detection limit of up to 1 nM.

We demonstrate that the semi-carbonized nanostructures of carbohydrate (cellulose and glucose as precursors) show high performance as photocatalysts directly for selective oxidation of cis-cyclooctene with air as an oxidant. Three dimensionally macroporous carbon spheres (3DMPCS) prepared from cellulose carbonized at 500 °C yielded the highest conversion of cis-cyclooctene (32.6%) and a high selectivity of 2-hydroxycyclooctanone (90.4%) after 24 h reaction, while cellulose carbonized at lower heat treatment temperatures (HTTs) (0–400 °C) or higher (600–900 °C) gave lower cis-cyclooctene conversion. The 3DMPCS synthesized from glucose carbonized at 600 °C shows higher performance in selective oxidation of cis-cyclooctene (12.2% conversion of cis-cyclooctene and 75.4% selectivity of 2-hydroxycyclooctanone) than glucose carbonized at other HTTs (200–500 °C and 700–900 °C) as catalysts. The results indicate that the semi-carbonized nanostructures of carbohydrates are highly efficient photocatalysts.

To develop green catalysts for cyclohexane oxidation with high efficiency and high selectivity is a trend in nanotechnology and nanocatalysis. In this work, we demonstrate that copper nanoparticles/carbon quantum dots (Cu/CQDs) hybrid as photocatalyst exhibits excellent catalytic activity in the oxidation of cyclohexane (conversion based on cyclohexane of 50.2% and selectivity to cyclohexanone of about 78.3%) under a low temperature with tert-butyl hydroperoxide as oxidant. It is worth mentioning that the Cu/CQDs hybrid photocatalyst can be implemented in efficient catalytic oxidation of cyclohexane under a mild condition (60 °C), which may provide a cogent pathway for the development of high-performance catalysts for C–H oxidation.

We demonstrate the fabrication of phosphate functionalized activated carbon by a facile heating method, as a metal-free electrocatalyst, which exhibits excellent electrocatalytic activity for the oxygen reduction reaction in an alkaline medium, it also enhances the durability and tolerance for methanol crossover effects. The improvement of the oxygen reduction reaction activity was closely related to the large specific surface area (976.4 m2 g−1) and high phosphorus content (1.88%) of the electrocatalyst. The newly-developed material represents a promising step towards replacing Pt/C catalysts and could potentially lead to commercial-scale fuel cell production.

Due to methanol being a cheap and widely available fuel, much effort has been devoted to the study of platinum-based catalysts for methanol oxidation. In addition to the development of efficient electro-catalysts, another approach to improve fuel cell performance is to develop alternative catalyst supports. Here, we report mesoporous carbon nanoparticles as a catalyst support which could greatly improve the catalytic activity of the catalyst for methanol oxidation, which can not only promote the formation of a larger electrochemically active surface area (801.038 m2 g−1) to afford more active sites for electrochemical reactions, but also facilitate effective electron transfer through the electrode surface. The mesoporous carbon nanoparticles were synthesized through a simple hydrothermal method using glucose as the precursor and modification with ionic liquids. The Pt nanoparticles deposited onto the resulting mesoporous carbon nanoparticles, as the catalyst, exhibited excellent electrochemical activity compared with commercial Pt/C catalyst and Pt nanoparticles.

We describe the preparation of carbon dots (CDs) from glucose that possess high stability, a quantum yield of 0.32, and low toxicity (according to an MTT assay). They were used, in combination with the fluorogenic zinc(II) probe quercetin to establish a fluorescence resonance energy transfer (FRET) system for the determination of Zn(II). The CDs are acting as the donor, and the quercetin-Zn(II) complex as the acceptor. This is possible because of the strong overlap between the fluorescence spectrum of CDs and the absorption spectrum of the complex. The method enables Zn(II) to be determined in the 2 to 100 μM concentration range, with a 2 μM detection limit. The method was applied to image the distribution of Zn(II) ions in HeLa cells.

The slow photon effect of a photonic crystal (PC) is a promising characteristic for tuning light–matter interactions through material structure designing. A TiO2 bi-layer structure photoanode was constructed by fabricating a TiO2 PC layer through a template-assisted sol–gel process on a TiO2 nanorod array (NR) layer. Gold nanoparticles (Au NPs) with an average size of about 10 nm were deposited in situ into the TiO2 bi-layer structure. The extended photoelectrochemical (PEC) water splitting activity in visible light was ascribed to the energetic hot electrons and holes that were generated in the Au NPs through the excitation and decay of surface plasmons. By alternating the characteristic pore size of the TiO2 PC layer, the slow photon region at the red edge of the photonic band gap could be purposely tuned to overlap with the strong localized surface plasmon resonance (SPR) region of Au NPs. The matching slow photon effect of TiO2 PC (with a characteristic pore size of 250 nm) intensified the SPR responses (central at 536 nm) of Au NPs. Consequently, more hot electrons were generated in the Au NPs and injected into the conduction band of TiO2, resulting in improved PEC water splitting efficiency in the visible light region. Under simulated sunlight illumination, the photoconversion efficiency of the well matching Au/TiO2 photoanode approached 0.71%, which is one of the highest values ever reported in Au/TiO2 PEC systems. The work reported here provides support for designing coupling plasmonic nanostructures with PC-based materials to synergistically enhance PEC water splitting efficiency.

Green strategy for high-efficiency and high-selectivity catalytic oxidation of alkanes is always a huge challenge for current catalysis chemistry and chemical production. Despite extensive development efforts on new catalysts for cyclohexane oxidation, current commercial processes still suffer from low conversion, poor selectivity, and excessive production of waste. We demonstrate the design and synthesis of composites made from carbon nitride (C3N4) and Au nanoparticles for a higher conversion efficiency of 10.54% and 100% selectivity to cyclohexanone photocatalyst systems without any oxidation or initiators under visible light for a total green oxidation of cyclohexane. C3N4/Au composites may provide a powerful pathway for the development of high-performance catalysts and production processes for the green chemical industry.

High-efficiency and high-selectivity catalytic oxidation of alkanes under mild conditions is a major objective of current catalysis chemistry and chemical production. Despite extensive development efforts on new catalysts for cyclohexane oxidation, current commercial processes still suffer from low conversion, poor selectivity, and excessive production of waste. We demonstrate the design and synthesis of composites made from metal nanoparticles and carbon quantum dots (CQDs) for high-efficiency and high-selectivity photocatalyst systems for the green oxidation of cyclohexane. Remarkably, the present Au nanoparticles/CQDs composite photocatalyst yields 63.8% conversion efficiency and 99.9% selectivity for the green oxidation of cyclohexane to cyclohexanone, using H2O2 under visible light at room temperature. Given its diversity and versatility of structural and composition design, metal nanoparticles/CQDs composites may provide a powerful pathway for the development of high-performance catalysts and production processes for green chemical industry.Keywords: carbon quantum dots; composites; cyclohexane oxidation; photocatalysis; selective oxidation

Carbon quantum dots (CQDs) were synthesized by an electrochemical etching method. The CQDs are well-dispersed with uniform size about 5 nm. FT-IR spectra suggest the presence of many hydroxyl groups on the surface of CQDs. Here, CQDs with diameter approximately 5 nm, directly used as effective heterogeneous nanocatalysts for H-bond catalysis in aldol condensations, show excellent photoenhanced catalytic ability (89% yields when 4-cyanobenzaldehyde is used). It demonstrated that aldol condensation between acetone and aromatic aldehydes resulted in higher yields with visible light irradiation than in the dark, confirming visible light is necessary for good conversion. The H-bond catalytic activities of CQDs can be significantly enhanced with visible light irradiation. The high catalytic activities of CQDs are due to highly efficient electron-accepting capabilities. Repeated catalytic experiments suggest that the CQD catalyst can be easily recycled as a heterogeneous catalyst with a long catalyst life.Keywords: aldol condensation; carbon quantum dots; electron acceptor/donor; heterogeneous catalysis; hydrogen bond catalysis

The Co3O4@N doped carbon (Co3O4@N–C) nanocomposites obtained from metal–organic frameworks (MOFs) possess excellent electrocatalytic ability for oxygen reduction reaction (ORR).

A nickel-modified polyoxometalate compound was synthesized which exhibited excellent catalytic activity (conversion: 41.63%; selectivity: 97.21%) for selective oxidation of cyclooctene using air as an oxidant without a solvent.

Carbon dots (CDs) were synthesized by refluxing glucose, as efficient fluorescence probes, which show convenient and sensitive detection of norfloxacin (NOR) over a wide concentration range. It is worth noting that because of the hydrogen bond interactions between the CDs and NOR, the fluorescence intensity of CDs was remarkably enhanced in the presence of NOR, which indicates that CDs are capable of rapid, stable and sensitive determination of NOR. Compared with high-performance liquid chromatography, the fluorescence enhancement method is considerably simpler and faster, and will pave a new way for the determination of NOR.

Water-soluble fluorescent N-doped carbon dots (N-C dots) obtained by enzyme catalyzed degradation of C3N4 show high stability, good biocompatibility, and can be promising candidates for bioimaging.

Enzyme engineering for improved catalysis has wide implications. Here, we report the modulation of enzyme (porcine pancreatic lipase, PPL) catalytic activity in the presence of carbon quantum dots (CQDs) by visible light. Upon visible light irradiation, the activity of PPL/CQDs increased to 10% higher than that of free PPL, whereas without a light source, the activity of PPL/CQDs decreased to 30% lower than that of free PPL. Based on Michaelis–Menten kinetics, CQDs were confirmed to play an important role as a non-competitive inhibitor. Our results present a potential new method for developing hyper-catalytic hybrid enzymes for bio-catalytic applications.

Fluorescent carbon dots (FCDs) were synthesized by refluxing polyethylene glycol, which can emit bright and different fluorescent colours under various wavelengths as well as show stable fluorescence properties with different ionic strength, temperature and time. These FCDs exhibit good biocompatibility and very low toxicity for HeLa cells. Notably, these FCDs, as an efficient live cell fluorescence imaging probe, can selectively stain nucleoli, and the effect is similar to some commercially available dyes (such as Hoechst).

Mesoporous carbons (pore size 5 nm) were successfully synthesized without templates from carbon quantum dots. As catalysts, both mesoporous carbons and Cu nanoparticles on mesoporous carbons show superior catalytic activity and stability for the selective oxidation of cyclooctene.

The interaction between carbon quantum dots (CQDs) and a single living cell was explored in real time. Here, we provide the quantitative data on the permeability of the HeLa cell membrane in the presence of CQDs with different surface functional groups (CQDs terminated with –OH/–COOH (CQD–OH), –PEG (CQD–PEG), and –NH2 (CQD–NH2)). Although these CQDs have very low toxicity towards HeLa cells, they still increase the cell membrane permeability by 8%, 13%, and 19% for CQD–PEG, CQD–OH, and CQD–NH2, respectively, and this kind of permeability was irreversible. These observations are valuable for promoting the bio-applications of carbon nanostructures in living systems.

Developing light-driven acid catalyst will be very meaningful for the controlled-acid catalytic processes towards a green chemical industry. Here, based on scanning electrochemical microscopy (SECM) and ΔpH testing, we demonstrate that the 5–10 nm carbon quantum dots (CQDs) synthesized by electrochemical ablation of graphite have strong light-induced proton properties under visible light in solution, which can be used as an acid catalyst. The 5–10 nm CQDs' catalytic activity is strongly dependent on the illumination intensity and the temperature of the reaction system. As an effective visible light driven and controlled acid-catalyst, 5–10 nm CQDs can catalyze a series of organic reactions (esterification, Beckmann rearrangement and aldol condensation) with high conversion (34.7–46.2%, respectively) in water solution under visible light, while the 1–4 nm CQDs and 10–2000 nm graphite do not have such excellent catalytic activity. The use of 5–10 nm CQDs as a light responsive and controllable photocatalyst is truly a novel application of carbon-based nanomaterials, which may significantly push research in the current catalytic industry, environmental pollution and energy issues.

Plasmonic photoelectrochemical (PEC) water splitting is very promising in the conversion of abundant solar energy into chemical energy. However, the solar-to-hydrogen efficiencies reported so far are still too low for practical use, which can be improved by optimizing the design and synthesis of individual blocks (i. e., the compositions, sizes, shapes of the metal and the coupling semiconductors) and the assembly of these blocks into targeted three-dimensional (3D) structures. Here, we constructed a composite plasmonic metal/semiconductor photoanode by decorating gold nanoparticles (Au NPs) on 3D branched ZnO nanowire arrays (B-ZnO NWs) through a series of simple solution chemical routes. The 3D ordered Au/B-ZnO NWs photoanodes exhibited excellent PEC activities in both ultraviolet and visible region. The improved photoactivities in visible region were demonstrated to be caused by the surface-plasmon-resonance effect of Au NPs. The photoconversion efficiency of Au/B-ZnO NWs photoanode reached 0.52% under simulated sunlight illumination. This is a high value of solar-to-hydrogen efficiencies reported till nowadays for plasmonic PEC water splitting, which was mainly benefit from the extensive metal/semiconductor interfaces for efficient extraction of hot electron from Au NPs and excellent charge-carries collection efficiency of the 3D ordered Au/B-ZnO NWs photoelectrode.Keywords: branched ZnO nanowire; gold nanoparticles; photoanode; surface plasmon resonance; water splitting;

Heteroatom (N, P, and B)-codoped nanocarbons (NPBC) with nanoporous morphology are fabricated via a facile one-step pyrolysis method and exhibit good electrocatalytic activity, durability, and selectivity for the oxygen reduction reaction (ORR) in alkaline media. The ORR activity of NPBC is better than single- (nitrogen-doped carbon (NC)) or dual-doped (nitrogen and phosphorus codoped carbon (NPC) or nitrogen and boron codoped carbon (NBC)) catalysts in terms of onset potential and current density. This synthetic approach is efficient and suitable for large-scale fabrication of metal-free carbon-based catalysts.Keywords: boron; nanocarbon; nitrogen; oxygen reduction reaction; phosphorus; ternary-doped

The design of highly efficient, durable, and earth-abundant catalysts for the oxygen evolution reaction is crucial to a variety of important energy conversion and storage processes. Here, we use carbon quantum dots (CQDs, ∼5 nm) to form hybrids with the ultrathin nickel–iron layered double-hydroxide (NiFe-LDH) nanoplates. The resulting CQD/NiFe-LDH complex exhibits high electrocatalytic activity (with an overpotential of ∼235 mV in 1 M KOH at a current density of 10 mA cm–2) and stability for oxygen evolution, which almost exceed the values of all previously reported Ni-Fe compounds and were comparable to those of the most active perovskite-based catalyst.Keywords: carbon quantum dots; chronopotentiometry; enchanced OER; NiFe-LDH complex; stability;

Two tetrazole-functionalized flexible ligands, bis(1-methyl-1H-tetrazol-5-yl)sulfane (bmps) and 5,5′-((2,2-bis(((1-methyl-1H-tetrazol-5-yl)thio)methyl)propane-1,3-diyl)bis(sulfanediyl))bis(1-methyl-1H-tetrazole) (bpbb), have been designed and used for the role-control of Keggin-type POMs in hybrid frameworks during self-assembly processes. With the isolation of two pairs of new compounds [Cu2(bmps)2(H2O)3(PMo12O40)]·(OH)·2.5H2O (1) and [Ag3(bmps)3(PMo12O40)]·H2O (3); [Cu4(bpbb)2Cl(PW12O40)] (2) and [Ag3(bpbb)(H2O)2(PW12O40)]·4H2O (4), we demonstrate here that it is feasible to achieve the role-control of POMs under hydrothermal conditions. In 1 and 3, the use of the simple and short bmps ligands favours the assembly of discrete and/or low-dimensional metal–organic moieties, and the POMs are utilised as building units to complete the construction of the whole structures. For 2 and 4, the large bpbb ligands facilitate the formation of porous metal–organic networks, in which the POMs are utilised as templates.

Tailoring high performance, stable, and earth-abundant electrocatalysts for water oxidation is of fundamental importance for the development of promising energy conversion and storage technologies. In this work, we report a remarkably simple and efficient approach for the preparation of ZnCo-layered double hydroxides and reduced graphene oxide (RGO/ZnCo-LDH) nanocomposites via a facile one-pot coprecipitation method. The resulting RGO/ZnCo-LDH complex investigated for the first time as a catalyst for oxygen evolution reaction (OER) exhibits higher electrocatalytic activity (with onset overpotential ∼330 mV in 0.1 M KOH) and excellent stability than pristine ZnCo-layered double hydroxides and commercial Pt/C, making it a highly efficient nonprecious metal-based novel LDH composite electrocatalyst for OER.

The porous cobalt, nitrogen-codoped carbon materials (Co/N/C) were synthesized by a facile one-step pyrolysis of vitamin B12 (VB12) and carbon quantum dots (CQDs). Varying the initial mass ratio of CQDs and VB12 leads to controllable concentrations of Co (0% to 3.68%) and N (0% to 5.88%) after pyrolysis. The obtained Co/N/C was evaluated by oxygen reduction reaction (ORR) in both alkaline and acid media. Particularly, the Co/N/C with 1.12% Co and 2.92% N prepared at 700 °C (Co1.12/N2.92/C-700) exhibited the best catalytic ability for ORR with a cathodic peak at −0.165 and 0.185 V (vs. SCE) in 0.1 M KOH and 0.1 M HClO4 solution, respectively, which are comparable to that of Pt/C (20%). The Co1.12/N2.92/C-700 also showed long-term stability and high methanol tolerance, which outperformed commercial Pt/C (20%).

Carbon dots (CDs) with abundant functional groups (–OH, –COOH, CO) on their surface were specially designed to enhance the adsorption capacity and the catalytic activity of gold nanoparticles (AuNPs). The CDs stabilized gold nanoparticles (AuNPs-CDs) were greenly synthesized by a one-step reduction of HAuCl4 with CDs which were used as both the reductant and the stabilizer under visible light irradiation. The resulting AuNPs-CDs exhibit a high catalytic activity towards the reduction of 4-nitrophenol, with a good linear correlation of ln(Ci/C0) versus time and a kinetic rate constant about 0.68 min−1. Further detailed adsorption kinetics data indicated that the present adsorption system follows a predominantly second-order rate model, and the CDs capped on the surface of the AuNPs also enhanced the adsorption capacity and the catalytic activity of the AuNPs.

High-efficiency and high-selectivity catalytic oxidation of alkanes under mild conditions with air is a major aim of current catalytic chemistry and chemical production. Despite extensive development efforts on new catalysts for cyclohexane oxidation, current commercial processes still suffer from low conversion, poor selectivity, and excessive production of waste. Here, we present the design and synthesis of gold nanoparticle/carbon nanotube (CNT) composites for high-efficiency and high-selectivity photocatalyst systems for the green oxidation of cyclohexane. Remarkably, Au nanoparticles confined in carbon nanotubes (Au-in-CNTs) are photocatalytically active for the oxidation of cyclohexane with 14.64% conversion of cyclohexane and a high selectivity of 86.88% of cyclohexanol using air and visible light at room temperature. Given its diversity and versatility of structural and composition design, gold nanoparticle/CNT composites may provide a powerful pathway for the development of high-performance catalysts and production processes for green chemical industry.

The phosphorus-doped macroporous carbon spheres (PMCS) with a high specific surface area (574.68 m2 g−1) were synthesized by a template method. A series of catalytic experiments showed that the PMCS possessed excellent catalytic ability for the selective oxidation of cyclooctene (conversion based on cyclooctene was 50.69% and the selectivity to epoxycyclooctane was 88.47%).

Carbon quantum dots with photoluminescence (PL) upconversion properties were used as spectral converters through near-infrared photon harvesting and conversion for CdSe sensitized TiO2 nanorod array photoanodes.

Mesoporous black TiO2 nanocrystals were obtained by a simple Si quantum dot-assisted chemical etching method with high photocatalytic activity.

TiO2 nanotube arrays loaded with carbon quantum dots were used as a photoanode for efficient hydrogen generation under visible light.

Compared to nature’s photoelectric conversion processes, artificial devices are still far inferior in efficiency and stability. Inspired by light absorption and resonance energy transfer processes of chlorophyll, we developed a highly efficient photoelectric conversion system by introducing Carbon quantum dots (CQDs) as an electron transfer intermediary. Compared with conventional dye-sensitized semiconductor systems, the present CQD-doped system showed significantly higher photoelectric conversion efficiency, as much as 7 times that without CQDs. The CQD-doped dye/semiconductor system may provide a powerful approach to the development of highly efficient photoelectric devices.Keywords: carbon quantum dots; dye−semiconductor complex; energy transfer; enhanced UV−vis light absorbance; photoelectric conversion; power conversion efficiency;

A 3D porous framework [Co3(μ2-OH)4(I)2]·2H2O (I = hypoxanthine) with two types of 1D channels possess excellent catalytic ability for the selective oxidation of cis-cyclooctene.

We report a facile hydrolytic process for the preparation of CQDs/SiO2 porous nanocomposites, which show high catalytic activity and stability for the selective oxidation of cis-cyclooctene under visible light irradiation, with TBHP as a radical initiator and oxygen (in the air) as an oxidant at 80 °C.

Carbon quantum dots (CQDs) were demonstrated to have the ability to enhance the photocatalytic performance of monoclinic BiVO4 with different exposed facets under visible light.

The first-row transition metals (TMs) are applied to induce the assembly of small molybdenum clusters (SMCs) in the molybdenum/TM/phosphate system, and eight SMC-based compounds are synthesized: [(V2O2)(H2PMo8V4O40)]·2(en)·12H2O (1), [CrMo6O18(OH)6]·1.5(H2en)·5H2O (2), [MnMo12O24(OH)6(HPO4)2(PO4)6]·7(H2en)·6H2O (3), {[Co(H2O)]2[CoMo12O24(OH)6(H2PO4)2(PO4)6]}·4(H2en)·4H2O (4), [Ni5(H2O)22(Mo2O4)8(HPO4)20(PO4)6]·32H2O (5), Cu2(en)4(Mo8O26) (6), [Cu(en)2Mo5O15(HPO4)2]·(H2en)·2H2O (7) and {Zn2[Na(H2O)2][NaMo12O24(OH)6(H2PO4)6(PO4)2]}·5(en)·11H2O (8) (en = ethylenediamine). Six kinds of SMCs as molecular building blocks have been observed within these eight compounds, namely, Mo2V, Mo4, Mo5, Mo61, Mo62 and Mo8. In present reaction system, these TMs not only induce the assembly of SMCs, but also regulate the dimensionality of these compounds, ranging from discrete 0D to infinite 1D, 2D and 3D frameworks. Moreover, the electrochemical properties of compounds 1–8 are also investigated.

•Colloidal silica crystal beads were used as the template for the preparation.•Macroporous carbon spheres bearing –SO3H (MPCS-SO3H) were prepared.•MPCS-SO3H possess remarkable catalytic performance for the esterification.Highly ordered three dimensional macroporous carbon spheres bearing sulfonic acid groups (MPCS-SO3H) were prepared by incomplete carbonization of glucose in silica crystal bead template, followed by sulfonation and removal of the template. The composition and porous structure of the obtained carbon spheres were investigated by physical adsorption of nitrogen, scanning electron microscopy, energy dispersive X-ray spectroscopy, and transmission electron microscopy techniques. While the Fourier-transform infrared spectroscopy was used to characterize the functional groups on the surface of carbon spheres. The catalytic properties of the MPCS-SO3H were evaluated by esterification of ethanol with acetic acid, indicating that MPCS-SO3H possess remarkable catalytic performance (high stability and acid catalytic ability) for the esterification.

Au/ZnO nanocomposites have been prepared by a simple chemical method. For the first time, the nanocomposites were directly used as photocatalysts for hydroxylation of aromatic hydrocarbons under UV and visible light irradiation. The results show that the as-prepared photocatalysts display high photocatalytic activity for UV and visible catalytic hydroxylation of benzene. Without the assistance of any solvent or additive, high selectivity and high conversion efficiency were still obtained. Different photocatalytic mechanisms were proposed depending on whether excitation happens on ZnO semiconductor or on the surface plasmon band of Au. The former is Au nanoparticles act as electron buffer due to irradiation by UV light and ZnO nanoparticles as reactive sites for hydroxylation of benzene, the latter is that Au nanoparticles act as light harvesters and inject electrons into ZnO conduction band and as photocatalytic sites under visible light irradiation.

Carbon quantum dots (CQDs)/Cu2O composite with protruding nanostructures on the surface is prepared by facile one-step ultrasonic treatment. We demonstrate for the first time that this photocatalytic system could harness the (near) infrared light to enhance the photocatalytic activity based on the collective effect of superior light reflecting ability of the Cu2O protruding nanostructures and the up-converted photoluminescence property of CQDs.

Porous and hollow metal-layer@SiO2 nanocomposites (metal = Au, Ag, Cu) have high catalytic activity and stability for cyclohexene selective oxidation.

Carbon nanodots (C-dots) have generated enormous excitement because of their superiority in water solubility, chemical inertness, low toxicity, ease of functionalization and resistance to photobleaching. In this review, by introducing the synthesis and photo- and electron-properties of C-dots, we hope to provide further insight into their controversial emission origin (particularly the upconverted photoluminescence) and to stimulate further research into their potential applications, especially in photocatalysis, energy conversion, optoelectronics, and sensing.

A one-step method was developed for the controllable construction of metal–graphene core–shell structures, hollow graphene nanospheres, and a high density of metal nanoparticles supported on graphene. The metal–graphene core–shell nanostructures as nanocatalysts show excellent catalytic ability for the selective oxidation of cyclohexene.

Si quantum dots (SiQDs) based nanospheres (SiNSs) were prepared via a novel synthetic strategy. These SiNSs were demonstrated to possess unique dot spacing dependent photoluminescence (PL) up-conversion and surface dependent (N modified surface) down-converted PL. It was demonstrated that a small distance between SiQDs (<5 nm) is the necessary condition for the PL up-conversion of SiNSs, while the surface state of SiQDs will affect the maximum emission wavelength and the PL intensity. The as-prepared SiNSs feature excellent aqueous dispersibility, and their optical properties were found to be stable enough in a specified temperature and pH range.

(Pt-C60)@SiO2 nanocomposites with a core–shell structure have been successfully synthesized by a step-by-step method. These hollow nanocomposites are capable of reversible hydrogen storage at appropriate temperature and atmospheric pressure, with a capacity of around 1.8 wt% (based on C60).

In this study, we report the facile fabrication of Ag3PO4, CQDs/Ag3PO4, Ag/Ag3PO4 and CQDs/Ag/Ag3PO4 photocatalysts (CQDs, carbon quantum dots). For CQDs/Ag3PO4 and CQDs/Ag/Ag3PO4, because of the insoluble, photoinduced electron transfer, upconversion luminescence and electron reservoir properties of CQDs, the complex photocatalysts exhibit enhanced photocatalytic activity and structural stability over the photodecomposition of organic compounds (methyl orange) under the irradiation of visible light. Furthermore, the synergistic effect of CQDs and the intense surface plasmon resonance of Ag lead to the highest photocatalytic activity of CQDs/Ag/Ag3PO4 among Ag3PO4 and the corresponding complex photocatalysts. Our results provide an invaluable methodology for designing high-performance photocatalysts based on CQDs and related functional materials, which is promising for catalytic and new energy applications.

Nanosized polyaniline, as heterogeneous catalyst directly, possesses excellent catalytic ability for selective oxidation of cyclohexene with H2O2 as oxidant at 60 °C. Systematic experiments confirm that the catalytic activity of nanosized PANI is dependent on particle size and redox state, which is responsible for the catalytic decomposition of H2O2.

Synthesis and tuning the structure of metal–organic nanoclusters in coordination polymer by different charged polyanions ([PMo12O40]3− and [SiMo12O40]4−).

Copper nanoparticles modified silicon nanowires show enhanced catalytic activity for the coupling reaction of benzene halides (iodobenzene, bromobenzene, and chlorobenzene) and aniline.

High quality carbon nanodots (C-dots) with high purity were synthesized through a mild, one-step electrochemical approach, without the assistance of any chemicals but only pure water. This high productivity method makes the synthetic process of C-dots synthesis both economical as well as environment-friendly. The as prepared C-dots are predominantly multi-layer graphene oxide, with luminescence and high up-conversion photoluminescence (emission of light at shorter wavelengths than the excitation wavelength). Meanwhile, C-dots showed peroxidise mimetic function and visible-light-sensitive photocatalytic activity for methyl orange degradation. In addition, a novel photocatalyst (TiO2/C-dots) was obtained by combining C-dots with TiO2 through an easy hydrothermal method. Remarkably, TiO2/C-dots exhibited an excellent visible-light photocatalytic activity.

Cu-/Ag-modified polyoxometalates with 5/10/12 connections were obtained via a sulphur-assisted hydrothermal synthetic strategy.

Ag3PO4/SnO2 semiconductor nanocomposites exhibit much higher photocatalytic activity and good stability than pure Ag3PO4 for the photodegradation of organic compounds (methyl orange) in the absence of electron acceptors under visible light.

ZnO/carbon quantum dots (ZnO/CQDs) nanocomposites were prepared by a one-step hydrothermal reaction and used as superior photocatalysts for the degradation of toxic gas (benzene and methanol) under visible light at room temperature. The as-prepared ZnO/CQDs nanocomposites were characterized by X-ray powder diffraction, Raman spectra, Fourier transform infrared spectroscopy, UV-Vis absorption spectroscopy, scanning and transmission electron microscopy. The results show that these nanocomposites exhibit higher photocatalytic activity (degradation efficiency over 80%, 24 h) compared to N doped TiO2 and pure ZnO nanoparticles under visible light irradiation. In the present catalyst system, the crucial roles of CQDs in the enhancement of photocatalytic activity of the ZnO/CQDs nanocomposites are illustrated.

Large-scale and monodisperse colloidal carbon nanospheres (CNSs) were synthesized with the assistance of polyoxometalates (POMs) under hydrothermal conditions. The POMs could act not only as a catalyst to promote the glucose dehydration process, but also as a stabilizer to prevent the aggregation of CNSs. The products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FT-IR). The diameters of CNSs from 100 nm to 900 nm can be controlled by different acidic and oxidizing properties of POMs. This method was demonstrated to be simple, reliable and reproducible. The conversion yield of CNSs prepared with the addition of phosphomolybdic acid was up to 37%. Based on the experiment, the possible mechanism for CNSs formation was proposed. After modification of CNSs with cysteine, the samples were utilized as electrode materials for sensitive heavy metal ions detection. The detection limits for lead(II) and cadmium(II) were 1 × 10−8 M and 2 × 10−7 M, respectively. The results highlight the potential application of CNSs as electrode materials for biosensors and catalysis.

A novel hydrothermal approach for the preparation of europium(III)-doped yttrium oxide (Y2O3:Eu3+) nanocrystals was reported. The as-synthesized Y2O3:Eu3+ nanocrystals with diameter of about 5 nm are highly uniform and dispersed in water. The Y2O3:Eu3+ nanocrystals were characterized by high-resolution transmission electron microscopy and fluorescence spectroscopy. Due to their well dispersity in water, low toxicity, and good photoluminescence, the Y2O3:Eu3+ nanocrystals can potentially be used in high-definition displays and fluorescence probe in bioimaging.Highlights► Y2O3:Eu3+ nanocrystals with narrow size distribution were prepared. ► The sample were highly uniform and dispersed in water solution. ► Y2O3:Eu3+ nanocrystals show stable fluorescence with high quantum yield (about 15%).

N-doping carbon–TiO2 nanohybrids (NCTs, nitrogen not only in situ doped carbon film but also doped TiO2 nanocrystals, and 5–10 nm TiO2 nanocrystals evenly dispersed on N-doping carbon film) have been successfully prepared by a mild, one-step approach. N–O–Ti chemical bonds between N–Carbon film and N–TiO2 nanoparticles were formed, and here, N–Carbon can not only sensitize and modify TiO2 nanocrystals surface, but also N can dope in the TiO2 nanocrystals. The as-prepared NCTs were investigated by X-ray photoelectron spectroscopy, TEM, FT-IR, electrochemistry method. It was demonstrated that the as-obtained NCTs have a large BET specific surface area of 279.43 m2/g. The NCTs show excellent photocatalytic abilities towards organic (Rhodamine B) and inorganic pollutant (K2Cr2O7) degradation under visible light irradiation. This work provided a new approach for the high performance catalyst design towards new energy sources and environmental issues.Graphical abstractC/TiO2 nanohybrids co-doped by N with excellent photocatalytic performance were prepared.Highlights► C/TiO2 nanohybrids (NCTs) co-doped by nitrogen (N) were prepared. ► N was not only in situ doped in carbon film but also doped in TiO2 nanoparticles. ► N–O–Ti chemical bonds were formed between C film and TiO2 nanoparticles. ► NCTs exhibited excellent visible-light photocatalytic performance.

Au nanoparticles supported on highly uniform one-dimensional ZnO nanowires (Au/ZnO hybrids) have been successfully fabricated through a simple wet chemical method, which were first used for photodegradation of gas-phase benzene. Compared with bare ZnO nanowires, the as-prepared Au/ZnO hybrids were found to possess higher photocatalytic activity for degradation of benzene under UV and visible light (degradation efficiencies reach about 56.0% and 33.7% after 24 h under UV and visible light irradiation, respectively). Depending on excitation happening on ZnO semiconductor or on the surface plasmon band of Au, the efficiency and operating mechanism are different. Under UV light irradiation, Au nanoparticles serve as an electron buffer and ZnO nanowires act as the reactive sites for benzene degradation. When visible light is used as the light irradiation source, Au nanoparticles act as the light harvesters and photocatalytic sites alongside of charge-transfer process, simultaneously.Graphical abstractUnder visible light irradiation, Au nanoparticles, which are supported on ZnO nanowires, dominate their catalytic properties in gas-phase degradation benzene reaction.Highlights► The composites that Au nanoparticles supported on ZnO nanowires were synthesized. ► Au/ZnO composites were firstly used as effective photocatalysts for benzene degradation. ► Two operating mechanisms were proposed depending on excitation wavelength.

Solvothermal synthesis is an efficient synthetic method for preparing nano and micromaterials. Preparation of hematite through alcoholysis of ferric ion under solvothermal condition has been carried out at low concentrations. In this paper, Fe2O3 homogeneous core/shell hierarchical nanostructures were synthesized via solvothermal treatment of FeCl3·6H2O and ethanol. The achievements of such structures can be attributed to two important factors: high temperature and high concentration. Besides, the crystal water and reaction time were also important factors to the synthesis of hematite. The prepared samples were characterized using X-ray powder diffraction, Raman spectra, scanning electron microscopy equipped with an energy-dispersive X-ray spectrometer, transmission electron microscopy and Brunauer–Emmett–Teller surface area and pore size distribution. X-ray photoelectron spectroscopy showed a satellite peak at 719.8 eV, which is the characteristic peak of Fe(III). The formation mechanism of the spheres and the effects of the reactant concentrations and reaction temperatures have been discussed. Moreover, the enhanced catalytic activity of the spheres has also been investigated through oxidation of benzyl alcohol to benzaldehyde with high conversion (42%) and selectivity (95%).Graphical abstractFe2O3 homogeneous core/shell hierarchical microspheres were synthesized by solvothermal method. Owing to the special structure, the synthesized Fe2O3 microspheres exhibit a superior catalytic activity in benzyl oxidation.Highlights► Hierarchical Fe2O3 core/shell microspheres were synthesized. ► Microspheres were assembled by β-FeOOH. ► The sample exhibits a superior catalytic activity and selectivity. ► The high activity and selectivity are due to the hierarchical core/shell structure.

Nanoporous TiO2 nanospheres with excellent visible light photocatalytic abilities and narrow pore size (11 ± 1 nm) distribution can be obtained via a rapid vapor assisted hydrolysis technique.

Monodispersed water-soluble fluorescent carbon nanoparticles (CNPs) were synthesized directly from glucose by a one-step alkali or acid assisted ultrasonic treatment. The CNPs were characterized by transmission electron microscopy, optical fluorescent microscopy, fluorescent spectrophotometry, fourier transform infrared spectrophotometry and ultraviolet-visible spectrophotometry. The results showed that the particle surfaces were rich in hydroxyl groups, giving them high hydrophilicity. The CNPs could emit bright and colorful photoluminescence covering the entire visible-to-near infrared (NIR) spectral range. Notably, the NIR emission of the CNPs could be obtained by NIR excitation. Furthermore, these CNPs also had excellent up-conversion fluorescent properties.Graphical abstractFabrication of water-soluble fluorescent carbon nanoparticles from glucose by a one-step alkali or acid assisted ultrasonic treatment.Research highlights► Monodispersed water-soluble fluorescent carbon nanoparticles (CNPs). ► CNPs emit bright and colorful photoluminescence in visible-NIR spectral range. ► The NIR emission of CNPs can be obtainted by NIR excitation. ► CNPS have excellent up-conversion luminescence properties.

In this study, we report the facile fabrication of Fe2O3/CQDs nanocomposites, and investigate their effective photocatalytic activity for the photodegradation of toxic gas (gas-phase benzene and methanol) under visible light. The crucial roles of CQDs in the enhancement of photocatalytic activity of the Fe2O3/CQDs composites are illustrated.

Fe3O4/carbon nanocomposite has been prepared by a facile chemical method, and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, fourier transform infrared spectroscopy and scanning electron microscopy. The fluorescent and magnetic properties of the sample were investigated by fluorescence spectroscopy and vibrating-sample magnetometer, respectively. The results indicate that the Fe3O4/carbon nanocomposite exhibit good photoluminescent (emission ranging from 425 to 550 nm) and strong magnetic (saturation magnetization of 44.2 emu/g) properties.Graphical abstractThe Fe3O4/carbon nanocomposite posses both magnetic (saturation magnetization of 44.2 emu/g) and photoluminescent (emission ranging from 425 to 550 nm) properties.Research highlights► Fe3O4 nanoparticles were successfully embedded in the carbon nanoparticles. ► Fe3O4/carbon nanocomposites possess both photoluminescent and magnetic properties. ► The composites have potential applications in nanocatalysis and bio-imaging.

A fluorescent carbon nanoparticle ionic liquid hybrids (CNPIL) with high conductivity is synthesized by a facile one-step microwave method from ionic liquid 1-butyl-3-methylimidazolium glutamine salt and Glucose. This CNPIL exhibits excellent PL properties: bright and colorful PL covering the entire visible–NIR spectral range, up conversion PL properties, pH dependent and can be controlled by the reaction condition.Graphical abstractCarbon nanoparticle ionic liquid hybrids with strong photoluminescence and high conductivity.Research highlights► Fluorescent CNPIL hybrids were synthesized by a microwave synthetic method. ► The CNPIL hybrids exhibit colorful PL covering the entire visible–NIR range. ► The CNPIL hybrids possess up conversion PL properties and high conductivity. ► The PL of CNPIL hybrids are pH dependent and can be controlled by water content.

YF3 and YF3:Eu3+ mesoporous hexagonal nanocrystals were successfully synthesized via a simple hydrothermal process based on the in situ assembly of the as-synthesized YF3 and YF3:Eu3+ nanoparticles. The well defined mesoporous nanostructures are formed by phenanthroline assisted assembly of ∼20 nm nanoparticles, and 2–4 nm pores are contained as indicated by N2 adsorption–desorption studies. The obtained YF3:Eu3+ mesoporous hexagonal nanoplates show a significant photoluminescence intensity enhancement compared with other shaped YF3:Eu3+ nanocrystals.Graphical abstractNanoparticles assembly construction for YF3 and YF3:Eu3+ mesoporous (pore size, 2–4 nm) hexagonal nanoplates and the significant enhancement in PL intensity.Research highlights► YF3 and YF3:Eu3+ mesoporous nanocrystals were synthesized by an assembly route. ► YF3:Eu3+ mesoporous nanoplates show a significant PL intensity enhancement. ► This assembly strategy is a novel method for mesoporous materials preparation.

Highly ordered three dimensionally macroporous carbon spheres (3DMPCS) were successfully prepared against removable colloidal silica crystal bead templates by carbonization of glucose. The unique structural characteristics of the well-developed three dimensionally interconnected macropores were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and nitrogen adsorption. The 3DMPCS have uniform large pore structures with size about 250 nm. Pt nanoparticles were supported on the macroporous carbon spheres by two aqueous impregnation methods, and it was found that the 3DMPCS supported Pt exhibited high electrocatalytic activity for methanol oxidation.Graphical abstractFabrication of highly ordered macroporous carbon spheres, which can be used as a good catalyst support for methanol oxidation.Highlights► Three-dimensional macroporous carbon spheres (3DMPCS) were successfully prepared. ► The pore sizes of 3DMPCS can be easily controlled. ► 3DMPCS have large specific areas and the ordered interconnected channels. ► 3DMPCS can serve as ideal candidate for catalyst supports.

Highly fluorescent carbon nanoparticles were synthesized directly from ethanol by a one-step sodium hydroxide-assisted electrochemical treatment. These nanoparticles could emit bright and colorful photoluminescence covering the entire visible spectral range and had excellent up-conversion fluorescent, stable ionic, long fluorescence lifetime and pH-sensitive photoluminescence properties.

Water-soluble carbon nanoparticles (CNPs) were fabricated by a facile, one step hydrothermal synthetic route using acid/alkali as additives. These CNPs emit bright photoluminescence (PL) covering the entire visible-near infrared (NIR) spectral range. PL measurements confirmed that the CNPs have up-conversion of PL properties, and that the NIR PL of the CNPs can also be observed by NIR excitation. Control experiments indicated that different additives can strongly affect the PL properties of the CNPs. With a combination of free dispersion in water and attractive PL properties, these CNPs hold promise for applications in nanotechnology.Graphical abstractWater soluble carbon nanoparticles with visible, up-conversion and NIR photoluminescence properties.Highlights► Water soluble carbon nanoparticles (CNPs) were prepared from carbohydrates. ► Water soluble CNPs possess visible, up-conversion and NIR PL properties. ► NIR PL of the CNPs can also be observed by NIR excitation. ► Water soluble CNPs have potential applications in bio-imaging.

Polyaniline (PANI) can show strong photoluminescence (PL) and well dispersed ability in water after simple refluxing with H2SO4 (sulfonated polyaniline, SPANI). This kind of fluorescent SPANI exhibits pH sensitive PL properties, especially, the strongest PL intensity is obtained in physiological pH environment (pH 7–8). The pH sensitive PL properties of SPANI are mainly attributed to the structure transition under different pH conditions.

A new amino acid ionic liquid (AAIL) based on glutamic acid, 1-butyl-3-methylimidazolium glutamine (BMIGlu), was prepared by Fukumoto’s method and characterized by 1H NMR, differential scanning calorimetry (DSC), and Karl Fischer moisture titration techniques. The density and surface tension of BMIGlu were measured in the temperature range of (308.15 to 343.15) K by the standard addition method (SAM), and then the values of pure BMIGlu were obtained through the linear extrapolation. Furthermore, the volume and surface properties were also discussed.

It is highly desired for the development of efficient bifunctional electrocatalyst for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in renewable energy technologies. In this work, cobalt, nitrogen-codoped carbon was prepared by a facile one-step method and demonstrated to exhibit good electrocatalytic performance for ORR and OER via a complete four-electron process. Besides, the catalyst prepared at 900 °C also displayed excellent stability for both ORR and OER. Furthermore, the origin of catalytic activity was also explored, which was attributed to the synergistic effects of metallic Co and quaternary N.

In this paper, we reported an anodization method for the fabrication of novel uniform Cu(OH)2 nanowires, CuO nanoparticles, and CuO shuttle-like nanoparticles with advanced structures. The possible formation mechanism of Cu(OH)2 nanowires, CuO nanoparticles, and CuO shuttle-like nanoparticles was proposed. The good catalytic properties of CuO nanoparticles converted from Cu(OH)2 nanowires and the CuO shuttle-like nanoparticles were confirmed by evaluating their catalytic ability on the C–N cross coupling of amines with iodobenzene.Highlights► Electrochemical fabrication of uniform Cu(OH)2 and CuO nanostructures. ► The formation mechanism of Cu(OH)2 nanowires and CuO nanostructures was proposed. ► CuO nanostructures exhibited good catalytic ability on the C–N cross coupling.

Hydrogen is an ideal energy carrier for renewable energy, but a high overpotential is required to achieve reasonable H2 evolution, which makes the design of highly active electrocatalysts for hydrogen evolution reaction (HER) urgent. Here, we report a nitrogen, sulfur co-doped carbon dots (NSCDs)/CoS hybrid with a three-dimensional mesoporous sponge-like nanostructure, fabricated via heat-treatment, which as electrocatalyst exhibits the desired electrocatalytic activity for electrochemical HER. A series of NSCDs/CoS hybrids with different contents of NSCDs were prepared by adjusting the concentration of NSCDs, of which the NSCDs/CoS hybrid with 20 mg L−1 NSCDs exhibits the best electrocatalytic activity towards HER with an onset potential of 0.095 V, an overpotential at 10 mA cm−2 of 165 mV, a small Tafel slope of 56 mV per decade, and a good stability in 0.5 M H2SO4. The excellent electrocatalytic activity of NSCDs/CoS for HER is attributed to synergetic effects of NSCDs and CoS, in which the NSCDs could protect the CoS from dissolution/agglomeration under acidic conditions, and the increased surface area of the NSCDs/CoS hybrid and the high charge transfer efficiency between NSCDs and CoS via Co–S–C bonding enhanced the HER performance.

Since the misuse and overuse of tetracycline (TC) increase the pollution of aqueous solution, it is highly desirable to develop highly effective, stable, eco-friendly, economical, and facile photocatalysts for the photocatalytic degradation of TC in an aqueous solution. Herein, we designed and synthesized a highly efficient CoO/g-C3N4 p–n heterojunction via a facile solvothermal method. The experimental results demonstrated that after the coupling of CoO with g-C3N4, CoO nanoparticles were uniformly distributed on the surface of wrinkled g-C3N4 layers not only to readily form a p–n heterjunction, but also to avert the aggregation; and the CoO/g-C3N4 p–n heterojunction photocatalysts exhibited superior visible-light photocatalytic activity and stability for the removal of TC. The high photocatalytic activity could be attributed to the generation of an internal electric field induced by the p–n heterojunctions, effectively promoting the separation of photoinduced charge.

Monitoring of bacterial viability is crucial for food safety and human health. Fluorescence staining with dyes is one of the simple and fast methods to assess bacterial viability. However, obtaining stable and non-poisonous dyes is still a huge challenge. Herein, we demonstrate that nitrogen, phosphorus and sulfur co-doped carbon dots (NPSCDs) can selectively stain dead bacteria rather than live ones because they possess a highly negative ζ potential (−41.9 mV), indicating that NPSCDs could serve as an efficient dye for bacterial viability evaluation. The NPSCDs were synthesized by one-step hydrothermal carbonization of a yeast extract, and exhibit favorable photoluminescence (PL) with high quantum yield (QY, 32%), excellent photostability (under acid/alkaline and strong ionic strength), good biocompatibility and low toxicity. Moreover, the designed NPSCDs show a precise response to temperature within the range from 30 °C to 90 °C, in which the fluorescence of the NPSCDs decreased linearly with an increase in temperature and recovered with a decrease in temperature. More importantly, when the live bacteria were incubated with NPSCDs, as the temperature increases, the NPSCDs could selectively stain dead bacteria in real time along with a decrease in fluorescence intensity simultaneously, showing a significant reduction in bacterial viability from 80% to 15% upon heating at 60 °C for more time. The development of NPSCDs paves a new way for the synthesis of a sensitive fluorescent probe that can be used in real-time monitoring of bacterial viability.

Metal (Au, Ag, and Pt)/silicon hybrid dots were facially prepared by a one-step reaction between Si quantum dots (SiQDs) and metal salts at room temperature without any templates and surfactants. The obtained Au/SiQDs were demonstrated to be a superior catalyst for selective oxidation of cyclohexene. By altering the composition of Au/SiQDs catalysts, the selectivity of main products can be tuned step-by-step.

The porous cobalt, nitrogen-codoped carbon materials (Co/N/C) were synthesized by a facile one-step pyrolysis of vitamin B12 (VB12) and carbon quantum dots (CQDs). Varying the initial mass ratio of CQDs and VB12 leads to controllable concentrations of Co (0% to 3.68%) and N (0% to 5.88%) after pyrolysis. The obtained Co/N/C was evaluated by oxygen reduction reaction (ORR) in both alkaline and acid media. Particularly, the Co/N/C with 1.12% Co and 2.92% N prepared at 700 °C (Co1.12/N2.92/C-700) exhibited the best catalytic ability for ORR with a cathodic peak at −0.165 and 0.185 V (vs. SCE) in 0.1 M KOH and 0.1 M HClO4 solution, respectively, which are comparable to that of Pt/C (20%). The Co1.12/N2.92/C-700 also showed long-term stability and high methanol tolerance, which outperformed commercial Pt/C (20%).

A C3N4-sensitized TiO2 nanotube array-based photoanode was designed and fabricated via the in situ growth of C3N4 on the surface of TiO2 nanotubes. It shows stable and significantly improved PEC activity for hydrogen generation under visible light irradiation with a hydrogen production rate of about 19.1 μmol h−1 (a Faradaic efficiency of nearly 100%).

Nanosized polyaniline, as heterogeneous catalyst directly, possesses excellent catalytic ability for selective oxidation of cyclohexene with H2O2 as oxidant at 60 °C. Systematic experiments confirm that the catalytic activity of nanosized PANI is dependent on particle size and redox state, which is responsible for the catalytic decomposition of H2O2.

Carbon dots (CDs) were synthesized by refluxing glucose, as efficient fluorescence probes, which show convenient and sensitive detection of norfloxacin (NOR) over a wide concentration range. It is worth noting that because of the hydrogen bond interactions between the CDs and NOR, the fluorescence intensity of CDs was remarkably enhanced in the presence of NOR, which indicates that CDs are capable of rapid, stable and sensitive determination of NOR. Compared with high-performance liquid chromatography, the fluorescence enhancement method is considerably simpler and faster, and will pave a new way for the determination of NOR.

Enzyme engineering for improved catalysis has wide implications. Here, we report the modulation of enzyme (porcine pancreatic lipase, PPL) catalytic activity in the presence of carbon quantum dots (CQDs) by visible light. Upon visible light irradiation, the activity of PPL/CQDs increased to 10% higher than that of free PPL, whereas without a light source, the activity of PPL/CQDs decreased to 30% lower than that of free PPL. Based on Michaelis–Menten kinetics, CQDs were confirmed to play an important role as a non-competitive inhibitor. Our results present a potential new method for developing hyper-catalytic hybrid enzymes for bio-catalytic applications.

Fluorescent carbon dots (FCDs) were synthesized by refluxing polyethylene glycol, which can emit bright and different fluorescent colours under various wavelengths as well as show stable fluorescence properties with different ionic strength, temperature and time. These FCDs exhibit good biocompatibility and very low toxicity for HeLa cells. Notably, these FCDs, as an efficient live cell fluorescence imaging probe, can selectively stain nucleoli, and the effect is similar to some commercially available dyes (such as Hoechst).

In this study, we provide the quantitative data on the membrane permeability of a HeLa cell in the presence of different sizes of SiO2 nanoparticles (NPs, 50, 100 and 200 nm). SiO2 NPs have low cytotoxicity, but 50 and 100 nm SiO2 NPs can increase the cell membrane permeability (a reversible effect) by 12.5% (0.02 mg mL−1, 4 min) and 9% (0.02 mg mL−1, 6 min), respectively. However, the 200 nm SiO2 NPs cannot affect the cell membrane permeability.

Carbon quantum dots with photoluminescence (PL) upconversion properties were used as spectral converters through near-infrared photon harvesting and conversion for CdSe sensitized TiO2 nanorod array photoanodes.

A nickel-modified polyoxometalate compound was synthesized which exhibited excellent catalytic activity (conversion: 41.63%; selectivity: 97.21%) for selective oxidation of cyclooctene using air as an oxidant without a solvent.

The Co3O4@N doped carbon (Co3O4@N–C) nanocomposites obtained from metal–organic frameworks (MOFs) possess excellent electrocatalytic ability for oxygen reduction reaction (ORR).

The exploration of an efficient electrocatalyst for hydrogen evolution reaction (HER) from water is a key to relieve the energy crisis, which is a great challenge. Herein, a nickel nanoparticle/carbon quantum dot (Ni/CQD) hybrid is synthesized and evaluated as an electrocatalyst for HER under a strongly alkaline medium (1 M KOH solution). The obtained Ni/CQD hybrid shows good catalytic ability for HER with an onset potential comparable to that of Pt wire and a low Tafel slope of 98 mV dec−1, which may be attributed to the Ni–O–C interface between Ni NPs and CQDs. The Ni/CQDs also exhibit high stability after 1000 CV cycles with negligible current loss (around 1 mA cm−2). Moreover, the catalytic ability of Ni/CQDs can be further improved under visible light illumination, suggested by a lower Tafel slope of 77 mV dec−1.

In this study, we report the facile fabrication of Fe2O3/CQDs nanocomposites, and investigate their effective photocatalytic activity for the photodegradation of toxic gas (gas-phase benzene and methanol) under visible light. The crucial roles of CQDs in the enhancement of photocatalytic activity of the Fe2O3/CQDs composites are illustrated.

Synthesis and tuning the structure of metal–organic nanoclusters in coordination polymer by different charged polyanions ([PMo12O40]3− and [SiMo12O40]4−).

Copper nanoparticles modified silicon nanowires show enhanced catalytic activity for the coupling reaction of benzene halides (iodobenzene, bromobenzene, and chlorobenzene) and aniline.

High quality carbon nanodots (C-dots) with high purity were synthesized through a mild, one-step electrochemical approach, without the assistance of any chemicals but only pure water. This high productivity method makes the synthetic process of C-dots synthesis both economical as well as environment-friendly. The as prepared C-dots are predominantly multi-layer graphene oxide, with luminescence and high up-conversion photoluminescence (emission of light at shorter wavelengths than the excitation wavelength). Meanwhile, C-dots showed peroxidise mimetic function and visible-light-sensitive photocatalytic activity for methyl orange degradation. In addition, a novel photocatalyst (TiO2/C-dots) was obtained by combining C-dots with TiO2 through an easy hydrothermal method. Remarkably, TiO2/C-dots exhibited an excellent visible-light photocatalytic activity.

The first-row transition metals (TMs) are applied to induce the assembly of small molybdenum clusters (SMCs) in the molybdenum/TM/phosphate system, and eight SMC-based compounds are synthesized: [(V2O2)(H2PMo8V4O40)]·2(en)·12H2O (1), [CrMo6O18(OH)6]·1.5(H2en)·5H2O (2), [MnMo12O24(OH)6(HPO4)2(PO4)6]·7(H2en)·6H2O (3), {[Co(H2O)]2[CoMo12O24(OH)6(H2PO4)2(PO4)6]}·4(H2en)·4H2O (4), [Ni5(H2O)22(Mo2O4)8(HPO4)20(PO4)6]·32H2O (5), Cu2(en)4(Mo8O26) (6), [Cu(en)2Mo5O15(HPO4)2]·(H2en)·2H2O (7) and {Zn2[Na(H2O)2][NaMo12O24(OH)6(H2PO4)6(PO4)2]}·5(en)·11H2O (8) (en = ethylenediamine). Six kinds of SMCs as molecular building blocks have been observed within these eight compounds, namely, Mo2V, Mo4, Mo5, Mo61, Mo62 and Mo8. In present reaction system, these TMs not only induce the assembly of SMCs, but also regulate the dimensionality of these compounds, ranging from discrete 0D to infinite 1D, 2D and 3D frameworks. Moreover, the electrochemical properties of compounds 1–8 are also investigated.

A 3D porous framework [Co3(μ2-OH)4(I)2]·2H2O (I = hypoxanthine) with two types of 1D channels possess excellent catalytic ability for the selective oxidation of cis-cyclooctene.

High-efficiency and high-selectivity catalytic oxidation of alkanes under mild conditions with air is a major aim of current catalytic chemistry and chemical production. Despite extensive development efforts on new catalysts for cyclohexane oxidation, current commercial processes still suffer from low conversion, poor selectivity, and excessive production of waste. Here, we present the design and synthesis of gold nanoparticle/carbon nanotube (CNT) composites for high-efficiency and high-selectivity photocatalyst systems for the green oxidation of cyclohexane. Remarkably, Au nanoparticles confined in carbon nanotubes (Au-in-CNTs) are photocatalytically active for the oxidation of cyclohexane with 14.64% conversion of cyclohexane and a high selectivity of 86.88% of cyclohexanol using air and visible light at room temperature. Given its diversity and versatility of structural and composition design, gold nanoparticle/CNT composites may provide a powerful pathway for the development of high-performance catalysts and production processes for green chemical industry.

Here, we have reported the design, synthesis and catalytic properties of a gold nanoparticle/carbon dot/SnO2 nanocomposite photo-electronic catalyst for oxygen evolution reaction.

Nanoporous TiO2 nanospheres with excellent visible light photocatalytic abilities and narrow pore size (11 ± 1 nm) distribution can be obtained via a rapid vapor assisted hydrolysis technique.

Stable bioimaging with nanomaterials in living cells has been a great challenge and of great importance for understanding intracellular events and elucidating various biological phenomena. Herein, we demonstrate that N,S co-doped carbon dots (N,S-CDs) produced by one-pot reflux treatment of C3N3S3 with ethane diamine at a relatively low temperature (80 °C) exhibit a high fluorescence quantum yield of about 30.4%, favorable biocompatibility, low-toxicity, strong resistance to photobleaching and good stability. The N,S-CDs as an effective temperature indicator exhibit good temperature-dependent fluorescence with a sensational linear response from 20 to 80 °C. In addition, the obtained N,S-CDs facilitate high selectivity detection of tetracycline (TC) with a detection limit as low as 3 × 10−10 M and a wide linear range from 1.39 × 10−5 to 1.39 × 10−9 M. More importantly, the N,S-CDs display an unambiguous bioimaging ability in the detection of intracellular temperature and TC with satisfactory results.

We present a simple hydrothermal method to fabricate multifunctional modified carbon dots (with –COOH, –OH, –SH, and –NH2 groups, named NS-Cdots) using citric acid and L-cysteine as raw materials. The functional NS-Cdots exhibit high fluorescent quantum yield (38.9%), low cytotoxicity and good biocompatibility. A reasonable photoluminescence mechanism of the NS-Cdots was proposed in which the pyridine derivatives serve as conjugating units and dominate the main emission behavior. The NS-Cdots can also be used as excellent fluorescent probes for cell imaging in vitro and as effective thermometers with a wide temperature detection range from 20 °C to 95 °C.

Chiral nanostructures have attracted extensive interest as components for chiral applications. Carbon quantum dots (CQDs) with superior properties, including low toxicity and good biocompatibility, can render the field of QDs with more potential biological applications in bioimaging, biosensors, and drug delivery. Herein, we report the fabrication of nitrogen and sulfur co-doped chiral CQDs (L-/D-CQDs) with strong symmetrical circular dichroism (CD) signals at about 212 and 240 nm. These chiral CQDs exhibit strong photoluminescence (PL) emission (at 460 nm) and outstanding enantioselective electrochemical recognition ability. A series of experiments further confirms that these chiral CQDs possess independent PL and chiral properties. With a temperature increase, PL is quenched with a good linear correlation of 0.992, whereas the CD signals remain almost the same. On the other hand, the PL of L- or D-CQDs shows no difference towards small chiral molecules detection with right or opposite configuration. In addition, the L- or D-CQDs excited with circularly polarized light (CPL) show similar PL properties regardless of their right or left configuration.

Carbon dots (CDs) with abundant functional groups (–OH, –COOH, CO) on their surface were specially designed to enhance the adsorption capacity and the catalytic activity of gold nanoparticles (AuNPs). The CDs stabilized gold nanoparticles (AuNPs-CDs) were greenly synthesized by a one-step reduction of HAuCl4 with CDs which were used as both the reductant and the stabilizer under visible light irradiation. The resulting AuNPs-CDs exhibit a high catalytic activity towards the reduction of 4-nitrophenol, with a good linear correlation of ln(Ci/C0) versus time and a kinetic rate constant about 0.68 min−1. Further detailed adsorption kinetics data indicated that the present adsorption system follows a predominantly second-order rate model, and the CDs capped on the surface of the AuNPs also enhanced the adsorption capacity and the catalytic activity of the AuNPs.

Tailoring high performance, stable, and earth-abundant electrocatalysts for water oxidation is of fundamental importance for the development of promising energy conversion and storage technologies. In this work, we report a remarkably simple and efficient approach for the preparation of ZnCo-layered double hydroxides and reduced graphene oxide (RGO/ZnCo-LDH) nanocomposites via a facile one-pot coprecipitation method. The resulting RGO/ZnCo-LDH complex investigated for the first time as a catalyst for oxygen evolution reaction (OER) exhibits higher electrocatalytic activity (with onset overpotential ∼330 mV in 0.1 M KOH) and excellent stability than pristine ZnCo-layered double hydroxides and commercial Pt/C, making it a highly efficient nonprecious metal-based novel LDH composite electrocatalyst for OER.

Carbon quantum dots (CQDs) were demonstrated to have the ability to enhance the photocatalytic performance of monoclinic BiVO4 with different exposed facets under visible light.

We report a facile hydrolytic process for the preparation of CQDs/SiO2 porous nanocomposites, which show high catalytic activity and stability for the selective oxidation of cis-cyclooctene under visible light irradiation, with TBHP as a radical initiator and oxygen (in the air) as an oxidant at 80 °C.

Mesoporous black TiO2 nanocrystals were obtained by a simple Si quantum dot-assisted chemical etching method with high photocatalytic activity.

Water-soluble fluorescent N-doped carbon dots (N-C dots) obtained by enzyme catalyzed degradation of C3N4 show high stability, good biocompatibility, and can be promising candidates for bioimaging.

Carbon quantum dots (CQDs)/Cu2O composite with protruding nanostructures on the surface is prepared by facile one-step ultrasonic treatment. We demonstrate for the first time that this photocatalytic system could harness the (near) infrared light to enhance the photocatalytic activity based on the collective effect of superior light reflecting ability of the Cu2O protruding nanostructures and the up-converted photoluminescence property of CQDs.

(Pt-C60)@SiO2 nanocomposites with a core–shell structure have been successfully synthesized by a step-by-step method. These hollow nanocomposites are capable of reversible hydrogen storage at appropriate temperature and atmospheric pressure, with a capacity of around 1.8 wt% (based on C60).

Porous and hollow metal-layer@SiO2 nanocomposites (metal = Au, Ag, Cu) have high catalytic activity and stability for cyclohexene selective oxidation.

Carbon nanodots (C-dots) have generated enormous excitement because of their superiority in water solubility, chemical inertness, low toxicity, ease of functionalization and resistance to photobleaching. In this review, by introducing the synthesis and photo- and electron-properties of C-dots, we hope to provide further insight into their controversial emission origin (particularly the upconverted photoluminescence) and to stimulate further research into their potential applications, especially in photocatalysis, energy conversion, optoelectronics, and sensing.