We have developed a controllable solvothermal method to grow intrinsically conductive MoS2 nanosheet arrays in a metastable 1T phase on carbon fiber cloth (CFC) as binder-free, high-activity Li-ion battery (LIB) anodes. By introducing surface hydroxyl groups on the CFC and tuning the DMF content in the mixed solvent, MoS2 nanosheet arrays were perpendicularly grown to the surface of the carbon fibers with a high coverage. Electrochemical measurements reveal that the 1T phase nanosheet arrays have excellent Li-ion storage performances, including high specific capacity, high rate capability and good cycling stability, outperforming 2H phase arrays. Because of the metallic 1T phase and the highly oriented array architecture, after subtracting the total capacity of CFC, the 1T arrays also deliver a high reversible specific capacity of 1789 mA h g−1 at 0.1 A g−1 and a retained capacity of 853 mA h g−1 after 140 cycles at 1 A g−1.

The wide use of functionalized graphene quantum dots (GQDs) in stable dispersions is currently hampered by the lack of industrially scalable, low-cost, and eco-friendly methods. Herein we report the first realization of the industrial-scale (20 L) production of high-quality fluorescent GQDs via a molecular fusion route from a low-cost, active derivative of pyrene. By a wholly “green”, conventional sulfonation reaction at low hydrothermal temperature, the molecular precursor is wholly converted into highly water-soluble, sulfonated GQDs without byproducts such as insoluble carbon. The GQDs show superior optical properties including strong excitonic absorption bands extended to ∼530 nm, bright photoluminescence (PL) at 510 nm with a quantum yield of up to 42%, and a wide PLE spectrum. The edge-site sulfonic functionalization enables the GQDs to stably re-disperse in water and maintains high fluorescence activities even after annealing up to 250 °C, whereas amino GQDs and graphene oxide sheets markedly aggregate after drying at low temperature. The GQDs are applied as biological fluorescent probes for visualizing and targeting Golgi apparatus in Hela and MCF7 live cells. The low-cost mass production, excellent biocompatibility, and superior optical properties make the GQDs an attractive alternative probe for efficient Golgi targeted imaging in biomedical applications.

Although copper sulfide and/or carbon materials have been utilized in counter electrodes (CEs) due to their good catalytic activity and conductivity, the efficiency of the assembled quantum dot-sensitized solar cells (QDSCs) is still unsatisfactory because of the relatively low photovoltage (Voc), which is commonly less than 0.7 V. In this study, graphene hydrogels (GHs) compressed onto titanium mesh served as the CE and the assembled CdSeTe QDSCs exhibited a photovoltaic conversion efficiency (PCE) of 9.85% and a Voc as high as 0.756 V, which increased by 19.0% and 14.9%, respectively, and are higher than those of the conventional CuS on FTO. By incorporating CuS nanoparticles into GH during gelation, the as-prepared GH–CuS CEs show further improved performance and the maximum PCE and Voc obtained were 10.71% and 0.786 V, respectively. The fill factor of the cells was also continuously increased. The excellent performance of the devices could be attributed to the synergistic effects of the water-rich GH (having a 3D porous structure accompanied by good conductivity) and highly catalytic CuS, reflected from the small series resistance, high catalytic activity, small electron transfer resistance, and stability, which have been confirmed by EIS, Tafel polarization, and CV curves.

•A scale-span electrocatalytic system was designed via a bionic strategy.•Highly edge-active, N and O co-doped GQDs are used as the electrocatalyst.•A mesh carbon network is to address the scale-span transport and diffusion issues.•All-carbon system exhibits ultrahigh electrocatalytic activities in DSSC systems.We report the rational design of an all-carbon and all-scale electrocatalytic system with ultrahigh electrocatalytic activity outperforming Pt-based electrodes by quantum mechanics calculations and bionics. According to the calculations, N and O co-doped graphene quantum dots (N-O-GQDs) could offer an ultrahigh atomic ratio of high-activity edge defects (N-C+-O, O-C+, and N-C+) owing to the most marked edge effect and co-doping effect. To fully activate these atomic-scale defects for catalyzing the two-electron triiodide reduction applied in dye-sensitized solar cells, a mesh-capillary carbon matrix composed of carbon fibers and carbon nanotubes was constructed to well disperse the catalyst and provide fast pathways for both electron transport and electrolyte penetration/diffusion by imitating the sophisticated structure of the blood vessel system. The all-carbon ternary system exhibits high reduction potential (i.e. low overpotential) and low charge-transfer resistance, and delivers high open-circuit voltage of 0.81 V, high short circuit current density of 15.77 mA cm−2, and high conversion efficiency of 7.68%. Our study helps understand and address general and challenging scale-span issues in electrode reactions for developing more efficient and practical electrocatalytic systems merely by assembling facilely derived carbon materials as the catalyst, matrix or current collector without using other materials.Download high-res image (155KB)Download full-size image

Carbon quantum dots (CQDs) are considered ideal fluorescent probes owing to their excellent optical properties and low cytotoxicity. We report a low-cost solvothermal method to synthesize orange fluorescent CQDs from coal tar. The as-fabricated CQDs exhibit bright and stable photoluminescence with long wavelength emission at 605 nm. To improve the biocompatibility of the oil-soluble CQDs, we chose liposomes as a carrier. After being encapsulated by liposomes, the CQDs become water-soluble and show a redshift of fluorescence to 640 nm. The in vitro and in vivo imaging application of the liposome-CQDs is demonstrated. Our work has provided a way for the conversion of low-value coal tar into high-value fluorescent carbon materials.

Carbon quantum dots (CQDs) have attracted much attention owing to their unique optical properties and a wide range of applications. The fabrication and control of CQDs with organic solubility and long-wavelength emission are still urgent issues to be addressed for their practical use in LEDs. Here, organic-soluble CQDs were produced at a high yield of ∼90% by a facile solvent engineering treatment of 1,3,6-trinitropyrene, which were simultaneously used as the nitrogen and carbon sources. The optical properties of the organic-soluble CQDs (o-CQDs) were investigated in nonpolar and polar solvents, films, and LED devices. The CQDs have a narrow size distribution around 2.66 nm, and can be dispersed in different organic solvents. Significantly, the as-prepared CQDs present an excitation-independent emission at 607 nm with fluorescence quantum yields (QYs) up to 65.93% in toluene solution. A pronounced solvent effect was observed and their strong absorption bands can be tuned in the whole visible region (400–750 nm) by changing the solvent. The CQDs in various solvents can emit bright, excitation-independent, long-wavelength fluorescence (orange to red). Furthermore, benefiting from the unique oil-solution properties, the as-prepared CQDs can be processed in thin film and device forms to meet the requirements of various applications, such as phosphor-based white-light LEDs. The color coordinate for these CQD modified LEDs is realized at (0.32, 0.31), which is close to pure white light (0.33, 0.33).

•The GQDs were synthesized at room temperature based on electron-beam irradiation.•The GQDs exhibited highly efficient fluorescence with a quantum yield of 32%.•The possible formation mechanism of GQDs was demonstrated.•The GQDs as a safety fluorescent probe were applied for bright cell imaging.We report a room-temperature strategy for the synthesis of single-crystalline fluorescent graphene quantum dots (GQDs) via electron-beam irradiation. The precursor contained high-activity nitro groups is easy to fusion GQDs with the method. Under optimized conditions (0.02 g 1,3,6-trinitropyrene, radiation dose of 400 kGy and 10 ml 0.5 mol/L hydrazine hydrate), the GQDs exhibit highly efficient fluorescence at 475 nm with a quantum yield of 32%. The PL maximum is well corresponded with the excitation wavelength. Moreover, the single-exponential fluorescence lifetime (4.86 ns) exhibited the intrinsic PL characteristic. The pH stability in neutral and alkaline solution, solid solubility and storage time stability of GQDs are satisfactory. Their application as a safety fluorescent probe for cell imaging is demonstrated.Download high-res image (134KB)Download full-size image

•The all-carbon ternary flexible electrodes have been fabricated by the electrode deposition of nitrogen and oxygen co-doped single-crystalline GQDs.•The flexible electrodes deliver ultrahigh specific capacitance (461 mF cm−2) by inducing a high concentration of active nitrogen and oxygen at edge.•Symmetrical N-O-GQD/CNT/CC all-solid-state flexible supercapacitors offer energy density up to 32 μWh cm−2 and demonstrate the good stability, high flexibility, and folding ability under different deformations.•Nitrogen and oxygen co-doped GQDs can function as a highly active, solution-processable pseudocapacitive materials applicable to high-performance supercapacitors.We present a novel approach for hierarchical fabrication of high-performance, all-solid-state, flexible supercapacitors from environmentally friendly all-carbon materials. Three-dimensional carbon nanotube/carbon cloth network (CNT/CC) is used as a conductive, flexible and free-standing scaffold for the electro-deposition of highly N/O co-doped graphene quantum dots to form the high-activity, all-carbon electrodes. The hierarchical structure of the CNT/CC network with high electrical conductivity and high surface area provides improved conductive pathways for the efficient activation of GQDs with high pseudocapacitance and electrical double layer capacitance. The obtained N-O-GQD/CNT/CC electrodes for all-solid-state flexible supercapacitors exhibit an ultrahigh areal capacitance of up to 461 mF cm−2 at a current density of 0.5 mA cm−2, while keeping high rate and cyclic performances. This work highlights the great potential of highly active GQDs in the construction of high-performance flexible energy-storage devices.Download high-res image (191KB)Download full-size image

•Amine-enriched porous carbon electrodes have been fabricated by the electrostatic fusion of amine-functionalized single-crystalline GQDs.•The carbon films deliver ultrahigh specific capacitance (400–595 F g−1) by inducing a high concentration of active amine moieties at edge.•GQD supercapacitors offer energy density up to 21.8 Wh kg−1 and retain 90% of the initial capacitance after 10,000 cyclic voltammetry tests.•Amine-enriched GQDs can function as a highly active, solution-processable pseudocapacitive materials applicable to high-performance supercapacitors.The applications of carbon-based supercapacitors have been limited by their low energy storage density owing to their limited active storage sites. To overcome this limitation, amine-enriched porous carbon electrodes have been fabricated by the electrostatic fusion of amine-functionalized single-crystalline graphene quantum dots (GQDs) within conductive, vertically ordered TiO2 nanotube arrays as the collectors. The carbon films deliver ultrahigh specific capacitance (400–595 F g−1) even beyond the theoretical upper limit of single-layer graphene by inducing a high concentration of active amine moieties at edge. Symmetrical GQD supercapacitors in H2SO4 electrolyte offer energy density up to 21.8 Wh kg−1 and retain 90% of the initial capacitance after 10000 cyclic voltammetry tests. The results show that amine-enriched GQDs can function as a new kind of highly active, solution-processable, and low-cost pseudocapacitive materials applicable to high-performance supercapacitors.

•Highly reduced and ordered TiO2 nanotube arrays have been fabricated using two-step anodization and three-electrode reduction.•The reduced TiO2 nanotube arrays show a high specific capacitance of 24.07 mF cm-2 at a scan rate of 10 mV s-1, which is 1094 times higher than the capacitance of pristine nanotube arrays (0.02 mF cm-2).•They also show an excellent long-term cycling stability with only 1.9% reduction of capacitance after 2000 cycles.•Under optimized reduction conditions, about 22% of Ti4+ ions in tube surface regions are converted into Ti3+ ions.•A proton-electron coupled reduction mechanism has been proposed based on the combined paradigms of a conventional energy-band model and chemical evolution of basic building blocks of TiO2.Highly reduced and ordered TiO2 nanotube arrays have been fabricated using two-step anodization and three-electrode reduction. A proton-electron coupled reduction mechanism has been proposed based on the combined paradigms of a conventional energy-band model and chemical evolution of basic building blocks of TiO2. Under optimized reduction conditions, about 22% of Ti4+ ions in tube surface regions are converted into Ti3+ ions while the morphology of the highly reduced TiO2 nanotube arrays keeps unchanged. The reduced nanotube arrays show superior electrochemical properties such as high areal capacitance, good rate capability, and high cycling stability. The areal capacitance of the reduced electrode is 24.07 mF cm−2 at a scan rate of 10 mV s−1, much higher than that of the pristine TiO2 nanotube arrays (0.02 mF cm−2). This kind of highly reduced one-dimensional oxide nanostructures can find a large array of applications in supercapacitors, photocatalysis, electrochromic display, and Li ion batteries.

Water-soluble, single-crystalline, and amine-functionalized graphene quantum dots (GQDs) with absorption edge at ∼490 nm were synthesized by a molecular fusion method, and stably deposited onto anatase TiO2 nanoparticles under hydrothermal conditions. The effective incorporation of the GQDs extends the light absorption of the TiO2 nanoparticles from UV to a wide visible region. Moreover, amine-functionalized GQD–TiO2 heterojunctions can absorb more O2 than pure TiO2, which can generate more ·O2 species for MO degradation. Accordingly, the heterojunctions exhibit much higher photocatalytic performance for degrading methyl orange (MO) under visible-light irradiation than TiO2 alone. At optimum GQD content (1.0 wt %), an apparent MO decomposition rate constant is 15 times higher than that of TiO2 alone, and photocurrent intensity in response to visible-light excitation increases by 9 times. Compared with conventional sensitization by toxic, photounstable quantum dots such as CdSe QDs, the sensitization by environmentally friendly GQDs shows higher visible-light photocatalytic activity and higher cycling stability. Monodispersed QD-based heterojunctions can effectively inhibit the fast recombination of electron–hole pairs of GQDs with a large exciton binding energy. The photogenerated electron transfer, energy-band-matching mechanism of GQD/TiO2, and possible MO decomposition pathways under visible-light irradiation are proposed.Keywords: Graphene quantum dots; Heterojunctions; Photocatalysis;

We report the fabrication of long titanium dioxide nanotube arrays with highly c-axis preferentially oriented crystallization and a high concentration of oxygen vacancies by second anodization in ethylene glycol and annealing under poor-oxygen conditions. By optimizing the growth and annealing conditions, the [001] oriented crystallization is maximized, and 31.7% of the total Ti ions exists as Ti3+ ions. The carrier density of the [001]-oriented TiO2 nanotube arrays is two orders of magnitude higher than that of the randomly oriented TiO2 nanotube arrays. The unusual c-textured crystallization confined within nanotubes may involve the formation of TiO62− octahedra with a gradient distribution along the tube axis, preferential nucleation at the top, and preferential growth downwards along the c axis. Because of the c-axis preferential orientation and a high-concentration of oxygen vacancies, long TiO2 nanotube arrays can serve as superior electrodes for both lithium ion batteries and supercapacitors without the addition of any conductive agents. Long c-oriented TiO2 nanotube arrays deliver reversible capacities of 293 mA h g−1 at 0.5 C and 174 mA h g−1 at 5 C with Coulombic efficiencies of over 99%, and hold an areal capacitance of 8.21 mF cm−2 with an 85% capacitance retention after 5000 cycles. Double roles played by oxygen vacancies are identified in increasing electrical conductivity and activating the rich-Li phase.

We report a novel procedure involving polyethylenimine-assisted hydrothermal cutting and subsequent ultrafiltration for fabricating nearly monodisperse graphene quantum dots with a uniform lateral size and confined layer number. The isolated monolayer quantum dots exhibit a sharp band-edge absorption feature and strong photoluminescence (quantum yield of 21%) independent of excitation wavelength and pH. Their preliminary application in bioimaging has been demonstrated.

We report the controllable electrophoretic fabrication of highly robust, efficient, and benign photoelectrocatalysts based on graphene-quantum-dot sensitized TiO2 nanotube arrays. Their catalytic activities under visible-light irradiation remain steady for continuous cycles (400 min) with a negligible decrease, whereas CdS and CdSe sensitized TiO2 nanotube arrays show a high cycling instability due to serious photooxidization.

Uniform, debris-free, fewer-crack, and highly ordered TiO2 nanotube arrays are prepared by a two-step anodic oxidation method, and a surfactant-assisted vacuum impregnation approach is developed to control the incorporation of sub-10-nm TiO2 nanocrystals into the nanotube arrays. By using the double polymer surfactants of polyethylene glycol and Polyvinyl Pyrrolidone as a sacrificed template, nanocrystal over-agglomeration is prohibited, and thin nanocrystal mesoporous layers are formed on both inner and outer nanotube walls. The application of the nanocrystal filled nanotube arrays as the photoanode for dye-sensitized solar cells has been evaluated. The incorporation of the nanocrystals into the nanotube arrays is found to enhance dye absorption and light-harvesting capacities markedly. As a result, the solar cells based on the filled nanotube arrays hold a short-circuit current density 2.06 times and a power-conversion efficiency 1.94 times higher than those based on the unfilled nanotube arrays.Highlights► We report a novel surfactant-assisted vacuum impregnation approach. ► Debris-free and highly ordered TiO2 nanotube arrays were prepared. ► A controllable TiO2 nanocrystal/nanotube composite electrode was prepared. ► The composite electrode exhibits enhanced light-harvesting and dye adsorbing capacities. ► The efficiency of DSSCs was significantly improved with the composite electrode.

We have developed a vapor–liquid–phase combined, layer-by-layer epitaxial growth strategy for fabricating ultralong ZnO one-dimensional vertical arrays. A key point is the activation of the second top epitaxial growth by treating shorter arrays in a growth solution. By alternating solution- and VS-growth steps for three times, we can tune the length of the 1D arrays from 41 to 150 μm. The arrays were found to show an excellent photoelectrocatalytic activity under UV irradiation, higher than that of high-performance TiO2 nanotube arrays.Highlights► We have developed a novel strategy via an alternating VS and solution-growth process for fabricating ultralong ZnO wire arrays with length up to 150 μm. ► ZnO wire arrays show excellent photoelectrocatalytic activity, and the decomposition rate increases with increasing layer number or wire length higher than that of high-performance TiO2 nanotube arrays.

We have performed the first single-particle spectroscopic measurements on individual graphene quantum dots (GQDs) and revealed several intriguing fluorescent phenomena that are otherwise hidden in the optical studies of ensemble GQDs. First, despite noticeable differences in the size and the number of layers from particle to particle, all of the GQDs studied possess almost the same spectral lineshapes and peak positions. Second, GQDs with more layers are normally brighter emitters but are associated with shorter fluorescent lifetimes. Third, the fluorescent spectrum of GQDs was red-shifted upon being aged in air, possibly due to the water desorption effect. Finally, the missing emission of single photons and stable fluorescence without any intermittent behavior were observed from individual GQDs.Keywords: graphene oxide; graphene quantum dots; photoluminescence; single-particle; time-resolved

Water-soluble and well-crystallized graphene quantum dots with lateral size about 3.0 nm were fabricated by a hydrothermal cutting method and their photoluminescence (PL) properties as well as the potential for bioimaging were demonstrated.

The introduction of oxygen vacancies (Vo) in various oxide nanostructures has been extensively used to modify their physical and chemical properties. Here, we report on a N2-flow-annealing method for introduction of Vo in titania (TiO2) nanotube arrays prepared by potentiostatic anodization of Ti plates. The investigation of their Vo-related optical and ferromagnetic properties shows that the arrays annealed in a strong N2 flow exhibit stronger visible-NIR absorption and room-temperature ferromagnetism than the ones annealed in sealed N2. The two enhanced properties may stem from the introduction of a high concentration of Vo, whose formation is facilitated by a strong N2 flow field over the nanotube arrays.Highlights► Highly reduced TiO2-δ nanotube arrays are reported for the first time. ► The reduced arrays exhibit greatly enhanced visible-NIR absorption. ► The reduced arrays also exhibit enhanced room-temperature ferromagnetism. ► The two enhanced properties stem from a high concentration of oxygen vacancies. ► The formation of oxygen vacancies is promoted by annealing in a strong N2 flow.

The use of TiO2 nanotube arrays fabricated by anode oxidation of titanium sheets as a photoelectrocatalyst is limited by low surface activity owing to passive crystallization post-treatment. We report here on a vacuum assisted filling route for modifying TiO2 nanotube arrays using high-activity anatase TiO2 nanoparticles as a filling. Photoelectrocatalytic degradation experiments show that a nearly 4-fold activity enhancement in photoelectrocatalysis is achieved and good photoelectrocatalytic stability is kept after the nanotube arrays are filled with the high-activity TiO2 nanoparticles. The remarkable enhancement in photoelectrocatalysis is ascribed to the key modification of the TiO2 nanotube arrays using the high-activity TiO2 nanoparticles. Our findings provide an insight into designing excellent photoelectrocatalysts by filling TNAs with available high-activity TiO2 nanoparticles.Highlights► TiO2 nanotube arrays were filled with TiO2 nanoparticles via vacuum assisted filling. ► The filled TiO2 nanotube arrays show an excellent photoelectrocatalytic activity. ► The filled TiO2 nanotube arrays show highly stable photoelectrocatalytic performance.

Carbon thin films with blue emission were fabricated on various substrates by spin coating dodecylamine (DDA)-capped carbon nanoparticles (CNPs).

Highly blue luminescent carbon nanoparticles with photo-luminescence quantum yields of 31.6%–40.6% were prepared by a one-step pyrolytic route from ethylenediamine-tetraacetic acid salts and a unique emission that is strongly dependent on pH, solvent, spin, and excitation wavelength was observed.

This paper reports the preparation and Li-storage properties of graphene nanosheets(GNS), GNS supported Sn–Sb@carbon (50–150 nm) and Sn–Sb nanoparticles (5–10 nm). The best cycling performance and excellent high rate capabilities were observed for GNS-supported Sn–Sb@carbon core-shell particles, which exhibited initial capacities of 978, 850 and 668 mAh/g respectively at 0.1C, 2C and 5C (1C = 800 mA/g) with good cyclability. Besides the GNS support, the carbon skin around Sn–Sb particles is believed to be a key factor to improve electrochemical properties of Sn–Sb.

Water-soluble anatase, mixed-phase (anatase and rutile) and rutile TiO2 nanoparticles (NPs) or nanorods were synthesized under mild solution conditions using polyethylene glycol 400 (PEG 400) as a stabilizer and HCl as a phase controlling reagent. The photocatalytic properties of these NPs with different crystal phases were evaluated by photocatalytic degradation experiments of methyl orange (MO). As-prepared pure anatase TiO2 NPs show a higher photocatalytic activity than other samples and commercial P25, which may be related to the high crystallinity, the pure anatase phase, small size and the enhanced absorbability associated with the existence of PEG 400 on the NP surface.

C/Fe3O4 hybrid materials have potential applications in sensors and anode materials for lithium-ion batteries. In this text, a one-step pyrolysis method was used to prepare C/Fe3O4 hybrid materials from EDTA ferric sodium salt. The magnetic Fe3O4 nanoparticles can be homogeneously incorporated into carbon materials to form C/Fe3O4 hybrids during the reaction. The morphology and magnetism of the C/Fe3O4 hybrids are strongly affected by pyrolysis temperature. This method supplies an ideal template to facilely synthesize C/metal-oxide hybrid materials from EDTA metallic salts.

Oleic acid-capped TiO2 nanoparticles (NPs) were directly grown on untreated multiwalled carbon nanotubes (MWCNTs) from a stable titanium carboxylate complex through a solvothermal aminolysis process in organic media. The shape of the TiO2 NPs loaded on the MWCNTs can be controlled from nanodots (∼ 3 nm in diameter) to nanorods (∼ 5 nm in diameter, 30–40 nm in length) by changing solvent components and by Co2+ doping. The resulting hybrids can be well dispersed in apolar organic solvents, which may provide possibilities for manipulating them in solutions for widespread applications.

Graphene has aroused intensive interest because of its unique structure, superior properties, and various promising applications. Graphene nanostructures with significant disorder and defects have been considered to be poor materials because disorder and defects lower their electrical conductivity. In this paper, we report that highly disordered graphene nanosheets can find promising applications in high-capacity Li ion batteries because of their exceptionally high reversible capacities (794−1054 mA h/g) and good cyclic stability. To understand the Li storage mechanism of graphene nanosheets, we have prepared graphene nanosheets with structural parameters tunable via different reduction methods including hydrazine reduction, low-temperature pyrolysis, and electron beam irradiation. The effects of these parameters on Li storage properties were investigated systematically. A key structural parameter, Raman intensity ratio of D bands to G bands, has been identified to evaluate the reversible capacity. The greatly enhanced capacity in disordered graphene nanosheets is suggested to be mainly ascribed to additional reversible storage sites such as edges and other defects.

CdSe quantum dot sensitized solar cells (QDSCs) modified with graphene quantum dots (GQDs) have been successfully achieved in this work for the first time. Satisfactorily, the optimized photovoltage (Voc) of the modified QDSCs was approximately 0.04 V higher than that of plain CdSe QDSCs, consequently improving the photovoltaic performance of the resulting QDSCs. Served as a novel coating on the CdSe QD sensitized photoanode, GQDs played a vital role in improving Voc due to the suppressed charge recombination which has been confirmed by electron impedance spectroscopy as well as transient photovoltage decay measurements. Moreover, different adsorption sequences, concentration and deposition time of GQDs have also been systematically investigated to boost the power conversion efficiency (PCE) of CdSe QDSCs. After the coating of CdSe with GQDs, the resulting champion CdSe QDSCs exhibited an improved PCE of 6.59% under AM 1.5G full one sun illumination.Graphene quantum dots (GQDs) were coated on CdSe to fabricate CdSe-GQDs QDSCs and the improved PCE of 6.59% was achieved. GQD coating effectively suppressed charge recombination.Download high-res image (138KB)Download full-size image

•Pt nanodendrites with controlled size were prepared by a rapid radiolysis route.•Pt nanodendrites display enhanced electrochemical catalytic performances.•Pt nanodendrites exhibit a good CO tolerance for methanol oxidation.Unique Pt nanodendrites with controlled size were prepared by a rapid radiolysis route. The Pt nanodendrites display drastically enhanced electrochemical catalytic performances toward methanol oxidation. They exhibit a better CO tolerance for methanol oxidation compared with commercial catalysts and other nanodendritic Pt-based catalysts.

Highly blue luminescent carbon nanoparticles with photo-luminescence quantum yields of 31.6%–40.6% were prepared by a one-step pyrolytic route from ethylenediamine-tetraacetic acid salts and a unique emission that is strongly dependent on pH, solvent, spin, and excitation wavelength was observed.

We have developed a controllable solvothermal method to grow intrinsically conductive MoS2 nanosheet arrays in a metastable 1T phase on carbon fiber cloth (CFC) as binder-free, high-activity Li-ion battery (LIB) anodes. By introducing surface hydroxyl groups on the CFC and tuning the DMF content in the mixed solvent, MoS2 nanosheet arrays were perpendicularly grown to the surface of the carbon fibers with a high coverage. Electrochemical measurements reveal that the 1T phase nanosheet arrays have excellent Li-ion storage performances, including high specific capacity, high rate capability and good cycling stability, outperforming 2H phase arrays. Because of the metallic 1T phase and the highly oriented array architecture, after subtracting the total capacity of CFC, the 1T arrays also deliver a high reversible specific capacity of 1789 mA h g−1 at 0.1 A g−1 and a retained capacity of 853 mA h g−1 after 140 cycles at 1 A g−1.

The wide use of functionalized graphene quantum dots (GQDs) in stable dispersions is currently hampered by the lack of industrially scalable, low-cost, and eco-friendly methods. Herein we report the first realization of the industrial-scale (20 L) production of high-quality fluorescent GQDs via a molecular fusion route from a low-cost, active derivative of pyrene. By a wholly “green”, conventional sulfonation reaction at low hydrothermal temperature, the molecular precursor is wholly converted into highly water-soluble, sulfonated GQDs without byproducts such as insoluble carbon. The GQDs show superior optical properties including strong excitonic absorption bands extended to ∼530 nm, bright photoluminescence (PL) at 510 nm with a quantum yield of up to 42%, and a wide PLE spectrum. The edge-site sulfonic functionalization enables the GQDs to stably re-disperse in water and maintains high fluorescence activities even after annealing up to 250 °C, whereas amino GQDs and graphene oxide sheets markedly aggregate after drying at low temperature. The GQDs are applied as biological fluorescent probes for visualizing and targeting Golgi apparatus in Hela and MCF7 live cells. The low-cost mass production, excellent biocompatibility, and superior optical properties make the GQDs an attractive alternative probe for efficient Golgi targeted imaging in biomedical applications.

We report the fabrication of long titanium dioxide nanotube arrays with highly c-axis preferentially oriented crystallization and a high concentration of oxygen vacancies by second anodization in ethylene glycol and annealing under poor-oxygen conditions. By optimizing the growth and annealing conditions, the [001] oriented crystallization is maximized, and 31.7% of the total Ti ions exists as Ti3+ ions. The carrier density of the [001]-oriented TiO2 nanotube arrays is two orders of magnitude higher than that of the randomly oriented TiO2 nanotube arrays. The unusual c-textured crystallization confined within nanotubes may involve the formation of TiO62− octahedra with a gradient distribution along the tube axis, preferential nucleation at the top, and preferential growth downwards along the c axis. Because of the c-axis preferential orientation and a high-concentration of oxygen vacancies, long TiO2 nanotube arrays can serve as superior electrodes for both lithium ion batteries and supercapacitors without the addition of any conductive agents. Long c-oriented TiO2 nanotube arrays deliver reversible capacities of 293 mA h g−1 at 0.5 C and 174 mA h g−1 at 5 C with Coulombic efficiencies of over 99%, and hold an areal capacitance of 8.21 mF cm−2 with an 85% capacitance retention after 5000 cycles. Double roles played by oxygen vacancies are identified in increasing electrical conductivity and activating the rich-Li phase.

Carbon thin films with blue emission were fabricated on various substrates by spin coating dodecylamine (DDA)-capped carbon nanoparticles (CNPs).

We report the controllable electrophoretic fabrication of highly robust, efficient, and benign photoelectrocatalysts based on graphene-quantum-dot sensitized TiO2 nanotube arrays. Their catalytic activities under visible-light irradiation remain steady for continuous cycles (400 min) with a negligible decrease, whereas CdS and CdSe sensitized TiO2 nanotube arrays show a high cycling instability due to serious photooxidization.

Although copper sulfide and/or carbon materials have been utilized in counter electrodes (CEs) due to their good catalytic activity and conductivity, the efficiency of the assembled quantum dot-sensitized solar cells (QDSCs) is still unsatisfactory because of the relatively low photovoltage (Voc), which is commonly less than 0.7 V. In this study, graphene hydrogels (GHs) compressed onto titanium mesh served as the CE and the assembled CdSeTe QDSCs exhibited a photovoltaic conversion efficiency (PCE) of 9.85% and a Voc as high as 0.756 V, which increased by 19.0% and 14.9%, respectively, and are higher than those of the conventional CuS on FTO. By incorporating CuS nanoparticles into GH during gelation, the as-prepared GH–CuS CEs show further improved performance and the maximum PCE and Voc obtained were 10.71% and 0.786 V, respectively. The fill factor of the cells was also continuously increased. The excellent performance of the devices could be attributed to the synergistic effects of the water-rich GH (having a 3D porous structure accompanied by good conductivity) and highly catalytic CuS, reflected from the small series resistance, high catalytic activity, small electron transfer resistance, and stability, which have been confirmed by EIS, Tafel polarization, and CV curves.

Water-soluble and well-crystallized graphene quantum dots with lateral size about 3.0 nm were fabricated by a hydrothermal cutting method and their photoluminescence (PL) properties as well as the potential for bioimaging were demonstrated.