Carbon dots (CDs) obtained from rapeseed pollen with a high production yield, good biocompatibility, good water solubility, low cost, and simple synthesis are systematically characterized. They can be directly added to Hoagland nutrient solution for planting hydroponically cultivated Lactuca sativa L. to explore their influence on the plants at different concentrations. By measuring lettuce indices of growth, morphology, nutrition quality, gas exchange, and content of photosynthetic pigment, amazing growth-promotion effects of CDs were discovered, and the mechanism was analyzed. Moreover, the in vivo transport route of CDs in lettuce was evaluated by macroscopic and microscopic observations under UV light excitation. The results demonstrate that pollen-derived CDs can be potentially used as a miraculous fertilizer for agricultural applications and as a great in vivo plant bioimaging probe.Topics: Biological imaging; Biological transport; Carbohydrates; Cell and Molecular biology; Dyes and Chromophores; Electromagnetic wave; Nanofabrication; Proteins; Quantum dots;

Phosphorescence is difficult to be observed from carbon dot powder due to the deliquescence and self-quenching in the aggregation state. In this study, aggregation-induced room temperature phosphorescence (RTP) is first reported in self-quenching-resistant nitrogen-doped carbon dot powder, which is suggested to take advantage of the moisture-resistance, rigidization and oxygen-barrier induced by PVA-chains. Furthermore, the optical mechanism of RTP as well as fluorescence is investigated through the abnormal excitation-responsive phenomena, and the potential application in temperature sensing is also preliminarily evaluated. This study may benefit in developing phosphorescence from undesirable aggregation through structure design and exploiting emerging applications for carbon dots.

•Sulfur-doped nanoporous carbon spheres (S-NCS) were synthesized.•The obtained S-NCS present an ultrahigh specific surface area up to 3357 m2 g−1.•The S-NCS electrode exhibit excellent supercapacitive performance.Development of facile and scalable synthesis process for the fabrication of nanoporous carbon materials with large specific surface areas, well-defined nanostructure, and high electrochemical activity is critical for the high performance energy storage applications. The key issue is the dedicated balance between the ultrahigh surface area and highly porous but interconnected nanostructure. Here, we demonstrate the fabrication of new sulfur doped nanoporous carbon sphere (S-NCS) with the ultrahigh surface area up to 3357 m2 g−1 via a high-temperature hydrothermal carbonization and subsequent KOH activation process. The as-prepared S-NCS which integrates the advantages of ultrahigh porous structure, well-defined nanospherical and modification of heteroatom displays excellent electrochemical performance. The best performance is obtained on S-NCS prepared by the hydrothermal carbonization of sublimed sulfur and glucose, S-NCS-4, reaching a high specific capacitance (405 F g−1 at a current density of 0.5 A g−1) and outstanding cycle stability. Moreover, the symmetric supercapacitor is assembled by S-NCS-4 displays a superior energy density of 53.5 Wh kg−1 at the power density of 74.2 W kg−1 in 1.0 M LiPF6 EC/DEC. The synthesis method is simple and scalable, providing a new route to prepare highly porous and heteroatom-doped nanoporous carbon spheres for high performance energy storage applications.Download high-res image (311KB)Download full-size image

Mesocrystals are advantageous in providing a large specific surface and favorable transport properties, and have been extensively studied for energy-related applications including supercapacitors, solar cells, lithium-ion batteries, and catalysis. However, the practical applications of mesocrystals are hindered by many obstacles, such as high cost, complicated synthesis processes, and utilization of deleterious additives. Herein, we report a facile one-step and additive-free route for the controllable synthesis of NiO mesocrystals (NOMs) with a cuboctahedral morphology and layered hierarchical structures consisting of self-assembled NiO nanosheets. When employed as an electrode material for supercapacitors, the as-prepared NOMs exhibited an exceptional electrochemical performance such as an ultrahigh reversible specific capacity of ca. 1039 F g−1 at a current density of 1.0 A g−1 and excellent cycling stability (ca. 93% capacitance retention after 10 000 charge/discharge cycles). Moreover, an all-solid-state hybrid supercapacitor based on hierarchical NOMs and three-dimensional nitrogen-doped graphene manifested a high energy density of 34.4 W h kg−1 at a power density of 150 W kg−1 in 2.0 M KOH aqueous electrolyte. These results further demonstrate the potential of NiO mesocrystals as a promising electrode material by constructing a hierarchical mesostructure, which can improve the electrochemical performance for energy storage. The outstanding electrochemical performance may be attributed to their hierarchical mesostructure that can effectively enhance the electrical conductivity and avoid the aggregation of NiO nanosheets, and the exposed {100} facets with a high electrochemical activity.

•Highly mesoporous carbon was prepared by developing a post-treatment-free route.•Carbonization and silica template removal were accomplished simultaneously.•Energy density of 28.3 Wh kg−1 at power density of 180 W kg−1 was achieved.•High capacitance retention was achieved in 1.8 V aqueous supercapacitor.Exploring well-defined pore structure with high porosity has been a long-pursued goal for the development of porous carbon as high-performance supercapacitor electrodes. The pursuit of high surface area while maintaining uniform pore size remains a formidable challenge because their current template-directed synthetic processes are quite complex and time consuming. Here, we report herein a facile and post-treatment-free approach for synthesis of carbon materials with simultaneously high surface area and uniform mesopore size. The key to this preparation strategy is utilization of polytetrafluoroethylene that can in-situ generate hydrofluoric acid to etch out the silica templates during carbonization process. This strategy not only reduces synthesis procedure by combining post-silica-removal and carbonization in a single step, but also eliminates the direct usage of hazardous hydrofluoric acid or corrosive sodium hydroxide. The as-synthesized disordered mesoporous carbon presents higher Langmuir surface area (3257 m2 g−1), Brunauer-Emmett-Teller surface area (2302 m2 g−1) and mesopore rate (99.6%) when compared to traditional mesoporous carbon. With combination of high surface area and uniform mesopore size, the mesoporous carbon exhibits attractive capacitive properties in aqueous electrolytes, including large capacitance of 201 F g−1, high energy density of 28.3 Wh kg−1 and excellent cycling stability.Download high-res image (292KB)Download full-size image

Development of efficient, low-cost and high-performance carbon materials as the electrodes is of significance for supercapacitors. Here we report a new class of hierarchical porous carbon with a three-dimensional network morphology of interconnected nanoparticle units prepared by using natural Indicalamus leaves and polytetrafluoroethylene as carbon precursor and silica-in-situ-remover, respectively. This protocol allows for successful post-treatment-free synthesis of biomass-based hierarchical porous carbon with specific surface area as high as 1801 m2/g without any extra activation process. Accordingly, when used as the electrodes of aqueous symmetrical supercapacitor, the as-prepared carbon material demonstrates superior capacitive behaviors, including high capacitances of 326 and 211 F/g in 1.0-V and 1.8-V supercapacitors, respectively, high energy density of 23.7 Wh/kg at power density of 224.5 W/kg, and excellent cycling stability. With these extremely attractive capacitive properties, this class of hierarchical porous carbon outperforms many typical state-of-the-art carbonaceous electrodes.

A new class of carbon dot (CD) grafted cellulose hybrid phosphors has been prepared in a facile and fast process. The reddish-orange emissive CDs can be effectively dispersed in cellulose matrices through hydrogen binding, and thus highly efficient orange-emissive CD-based phosphors were successfully obtained with a quantum yield of 44%. Moreover, the affinity of CDs for binding cellulose provides them the feasibility for fluorescence mapping of cellulosic plant cell walls. Several model plant tissues have been employed to investigate the pathway of CDs. Confocal analysis demonstrated that plant tissues can readily absorb CDs from aqueous solutions and bind them with cellulose-rich structures. These studies may open up new avenues for the exploration of CDs in long-wavelength emissive solid-state lighting and plant tissue imaging.

Herein, unique S and N co-doped carbon dots (S,N-C-dots) were synthesized via a one-pot hydrothermal method. The S,N-C-dots not only possess a relatively high photoluminescence (PL) quantum yield (QY) (43%), but also present unique optical properties with dual-emission (blue and yellow) and excitation-independent characteristics. It is extremely rare for bare carbon dots (C-dots) to have dual-emission under single excitation wavelength. Herein, we achieved a series of solid-state lighting materials, such as silica-encapsulated C-dots (silica/C-dots), light conversion films (LCFs), and white-light-emitting diodes (WLEDs), using S,N-C-dots as a doping fluorophore. Moreover, we conducted some comparative experiments to prove that the unique properties of the S,N-C-dots were ascribed to the co-doping effects of S and N atoms. The yellow emission originates from the intrinsic state emission and the blue emission originates from the surface energy trap emission. This study presents a facile preparation of highly efficient dual-emissive S,N-C-dots and provides a new strategy to develop various solid-state lighting materials.

•Monodispersed hierarchical Yb(OH)xF3−x microcrystals assembled by nanorod arrays were synthesized.•Yb(OH)xF3−x can be transformed to Yb6O5F8 with the retention of morphology.•Crystallographic relationship between Yb(OH)xF3−x and Yb6O5F8 and their transformation mechanism were disclosed.The fabrication of rare earth luminescent materials with monodispersed and hierarchical morphology is of great importance due to their various applications. In this report, monodispersed hierarchical Yb(OH)xF3−x microcrystals assembled by nanorod arrays were synthesized by a mild hydrothermal route. Calcination of Yb(OH)xF3−x resulted in the formation of Yb6O5F8 with the retention of morphology. The crystallographic structure relationship between Yb(OH)xF3−x and Yb6O5F8 and the transformation mechanism from Yb(OH)xF3−x to Yb6O5F8 were disclosed. The upconversion emission properties of the Er3+ doped samples were investigated. It can be found that Yb6O5F8: 5%Er3+ exhibited an intense red light upconversion emission with the strongest peaks around 658 nm while Yb(OH)xF3−x: 5%Er3+ shows no upconversion emission.Download high-res image (200KB)Download full-size image

•Porous carbon nanosheets (PCNSs) are prepared by a facile one-step method.•No post-activation-process is needed for PCNS synthesis.•The PCNSs presents large surface area and abundant nitrogen content.•The PCNSs exhibit excellent electrochemical performance in aqueous electrolytes.A facile one-step pyrolysis route for the synthesis of hierarchically porous carbon nanosheets (PCNSs) derived from Moringa oleifera stems (MOSs) is reported, in which no post-activation-process in needed. The as-prepared PCNSs possesses unique porous nanosheet morphology with high specific surface area of ca. 2250 m2 g−1, large pore volume of ca. 2.3 cm3 g−1, appropriate porosity as well as heteroatom doping (N and O), endowing outstanding electrochemical properties as electrode material for high-performance supercapacitors. The PCNS-based electrodes are investigated in various aqueous electrolytes including 1.0 M Na2SO4, 1.0 M H2SO4, and 6.0 M KOH. The PCNSs exhibit a maximum specific capacitance of ca. 283 F g−1 (0.5 A g−1), excellent rate capability (ca. 72% of capacitance retention even at an ultrahigh current density of 50 A g−1), and a tremendous long-term cycling stability in the three-electrode system. Moreover, the as-assembled PCNS-based symmetric supercapacitor shows a high energy density of ca. 25.8 Wh kg−1 (in 1.0 M Na2SO4 electrolyte) and remarkable long-term cycling stability (almost no capacitance fade in aqueous electrolytes), indicating the promising of the as-prepared PCNSs for electrochemical energy storage and conversion.A facile one-step pyrolysis strategy is designed to synthesize hierarchically porous carbon nanosheets (PCNSs) with unique two-dimensional nanosheet structure, high specific surface area, and outstanding electrochemical properties for high-performance electric double-layer capacitors.Download high-res image (428KB)Download full-size image

Fluorescent carbon dots (CDs) have been widely studied in bioscience and bioimaging, but the effect of CDs on plants has been rarely studied. Herein, mung bean was adopted as a model plant to study the phytotoxicity, uptake, and translocation of red emissive CDs in plants. The incubation with CDs at a concentration range from 0.1 to 1.0 mg/mL induced physiological response of mung bean plant and imposed no phytotoxicity on mung bean growth. The lengths of the root and stem presented an increasing trend up to the treatment of 0.4 mg/mL. Confocal imaging showed that CDs were transferred from the roots to the stems and leaves by the vascular system through the apoplastic pathway. The uptake kinetics study was performed and demonstrated that the CDs were abundantly incubated by mung beans during both germination and growth periods. Furthermore, in vivo visualization of CDs provides potential for their successful application as delivery vehicles in plants based on the unique optical properties.Keywords: bioimaging; carbon dots; fluorescent; mung bean; phytotoxicity

•Bagasse-derived hierarchical structured carbon (BDHSC) was synthesized.•Sewage sludge was employed to regulate the morphology and porosity of BDHSC.•The BDHSC-based electrode exhibits excellent supercapacitive performance.Bagasse-derived hierarchical structured carbon (BDHSC) with tunable porosity and improved electrochemical performance is prepared via simple and efficient hydrothermal carbonization combined with KOH activation. Experimental results show that sewage sludge acts as a cheap and efficient structure-directing agent to regulate the morphology, adjust the porosity, and thus improve the supercapacitive performance of BDHSC. The as-resulted BDHSC exhibits an interconnected framework with high specific surface area (2296 m2 g−1), high pore volume (1.34 cm3 g−1), and hierarchical porosity, which offer a more favorable pathway for electrolyte penetration and transportation. Compared to the product obtained from bagasse without sewage sludge, the unique interconnected BDHSC exhibits enhanced supercapacitive performances such as higher specific capacitance (320 F g−1), and better rate capability (capacitance retention over 70.8% at a high current density of 50 A g−1). Moreover, the BDHSC-based symmetric supercapacitor delivers a maximum energy density of over 20 Wh kg−1 at 182 W kg−1 and presents an excellent long-term cycling stability. The developed approach in the present work can be useful not only in production of a variety of novel hierarchical structured carbon with promising applications in high-performance energy storage devices, but also in high-value utilization of biomass wastes and high-ash-content sewage sludge.

•Three dimensional nitrogen graphene (3DNG) was synthesized by hydrothermal method.•The 3DNG binder-free electrode exhibits excellent electrochemical performance.•Nitrogen-doping can improve the conductivity and wettability of graphene.•N-configurations play an important role in enhancing the electrochemical behavior.Three dimensional nitrogen-doped graphene (3DNG) with high nitrogen content and improved electrochemical performance is successfully prepared by a facile, lost-cost hydrothermal method with ammonia as reducing-doping agent. The as-prepared 3DNG exhibits a hierarchical and interconnected porous network, which offers favorable pathways for electrolyte penetration and transportation. Remarkably, as binder-free electrode in aqueous electrolyte, the resultant 3DNG-2 with both high nitrogen content (7.71 at%) and large active material density (1.31 g cm−3) exhibits an ultrahigh volumetric capacitance of 437.5 F cm−3 (334.0 F g−1) at current density of 0.5 A g−1 and superior cycling stability (93% capacitance retention after 20 000 cycles at high current density of 10 A g−1). Further analyses indicate that the N-configurations are of great significance to the improvement of electrochemical behavior as well as the N-content. This work provides an effective way to synthesize 3DNG with excellent electrochemical properties for high performance supercapacitor and promotes the in-depth understanding of the enhancement mechanism of N-doping to supercapacitor performance.

Few-layered boron nitride nanosheets (BNNSs) have attracted increasing research interest in the past few years due to their unique material properties. However, the lack of a reliable scale-up production method is an inhibiting issue for their practical applications. In this work, we report a facile one-step and high-yield method for the synthesis of few-layered and hierarchically porous BNNSs through simultaneous etching and in situ nitridation of calcium hexaboride (CaB6) by ammonium chloride under moderate conditions. The output of the few-layered BNNSs is as high as 1.4 g with respect to 1.06 g of starting CaB6 crystals. Transmission electron microscopy and atomic force microscopy characterizations confirm the successful synthesis of few-layered BNNSs, most of which are layered with a thickness less than 3 nm (layer number < 10). The as-prepared BNNSs exhibit a high specific surface area (492–795 m2 g−1) and a high pore volume (0.34–0.50 cm3 g−1). In addition, the as-resulted BNNSs exhibit high and tuneable H2 uptakes from 1.48 to 2.18 wt% at 77 K and at a relatively low pressure of 1.0 MPa, thus guiding the further search of materials for H2 storage. Our results suggest that the simultaneous etching and in situ nitridation of metallic borides is a facile and effective method for reliable production of few-layered BNNSs with hierarchical porosity for potential applications such as gas storage and functional composites.

•It is the first report that direct recombination of CDs and Eu3+ solutions.•Tunable photoluminescence can meet the variable light component requirements for different species of plants.•CDs can be mixed with Eu3+ solutions under the reaction of PVA to prepare the light conversion film.In this work, blue-light-emitting carbon dots (CDs) were composited with red-light-emitting europium ions (Eu3+) solutions under the synergistic reaction of polyvinyl alcohol (PVA) to prepare the light conversion film. The formation mechanism of Eu3+/CDs/PVA film was detailedly discussed. It is the first report that this composite was synthesized through direct recombination of CDs and Eu3+ solutions instead of traditional methods based on Eu3+ coordination compound. Furthermore, tunable photoluminescence property can be successfully achieved by controlling the ratio of CDs to doped Eu3+, this property can meet the variable light component requirements for different species of plants.It is the first report that this composite was synthesized through direct recombination of CDs and Eu3+ solutions instead of traditional methods based on Eu3+ coordination compound. Tunable photoluminescence property can be successfully achieved by controlling the ratio of CDs to doped-Eu3+, this property can meet the variable light component requirements for different species of plants.

•Sub-5 nm monodispersed cubic NaYF4: Yb3+/Er3+ nanocrystals were synthesized.•Increasing the reaction temperature lead to the increase of particle size.•The ratio of OA/ODE and amount of NaOH played an important role in the product.The synthesis of ultrasmall upconversion nanophosphors is of great importance due to their potential applications in biomedicines. In this report, sub-5 nm monodispersed cubic NaYF4: Yb3+/Er3+ nanocrystals were synthesized by a facile method. The nanocrystals have been well characterized and the average diameter was determined to be about 3.5 nm ±0.4 nm, which is one of the smallest grain sizes for NaYF4: Yb3+/Er3+ nanocrystals ever reported. The size of the nanocrystals can be modulated by increasing the reaction temperature. Other reaction conditions including contents of OA and ODE as well as amount of NaOH were also investigated and their effects on the phase and morphology of NaYF4: Yb3+/Er3+ nanocrystals have been elucidated.

•The 4-NP imprinted ratiometric fluorescence sensors were constructed by incorporating carbon dots (CDs) and YVO4: Eu3+ nanoparticles (NPs) within silica networks.•The obtained ratiometric fluorescence sensors have a linear range of 0-12.0 μM and the limit of detection as low as 0.15 μM in the determination of 4-NP.A facilely prepared ratiometric fluorescent molecularly imprinted sensor has been constructed for highly sensitive and selective detection of 4-nitrophenol (4-NP) using carbon dots (CDs) as the target sensitive fluorophore and YVO4: Eu3+ nanoparticles (NPs) as the reference fluorophore. Through the hydrolysis and condensation reactions of the silica precursor, CDs and YVO4 Eu3+ NPs can be incorporated into silica networks through silylation reaction by one pot synthesis procedure. The as-prepared fluorescent molecularly imprinted sensor shows characteristic fluorescence emissions of CDs (blue) and YVO4:Eu3+ (red) under a single excitation wavelength. With the addition of 4-NP, the fluorescence of CDs is selectively quenched, resulting in the ratiometric fluorescence response. Under optimum conditions, the proposed sensor exhibits a high sensitivity with a linear range from 0 to 12.0 μM and shows the limit of detection as low as 0.15 μM in the determination of 4-NP, which is probably benefits from the tailor-made imprinted cavities for binding 4-NP. Furthermore, the proposed method was successfully applied for the determination of 4-NP in real water samples and human urine samples with great potentials for monitoring of 4-NP in environmental application.

In this paper, we demonstrate that Moringa oleifera branches, a renewable biomass waste with abundant protein content, can be employed as novel precursor to synthesize three-dimensional heteroatom-doped and hierarchical egg-box-like carbons (HEBLCs) by a facile room-temperature pretreatment and direct pyrolysis process. The as-prepared HEBLCs possess unique egg-box-like frameworks, high surface area, and interconnected porosity as well as the doping of heteroatoms (oxygen and nitrogen), endowing its excellent electrochemical performances (superior capacity, high rate capability, and outstanding cycling stability). Therefore, the resultant HEBLC manifests a maximum specific capacitance of 355 F g–1 at current density of 0.5 A g–1 and remarkable rate performance. Moreover, 95% of capacitance retention of HEBLCs can be also achieved after 20 000 charge–discharge cycles at an extremely high current density (20 A g–1), indicating a prominent cycling stability. Furthermore, the as-assembled HEBLC//HEBLC symmetric supercapacitor displays a superior energy density of 20 Wh kg–1 in aqueous electrolyte and remarkable capacitance retention (95.6%) after 10 000 charge–discharge cycles. This work provides an environmentally friendly and reliable method to produce higher-valued carbon nanomaterials from renewable biomass wastes for energy storage applications.Keywords: cycling stability; electrode materials; heteroatom doping; hierarchical structured carbons; Moringa oleifera; supercapacitors;

A unique dual-emitting core–shell carbon dot–silica–phosphor (CDSP) was constructed from carbon dots (CDs), tetraethoxysilane (TEOS) and Sr2Si5N8:Eu2+ phosphor through a one-pot sol–gel method. Blue emitting CDs uniformly disperse in the silica layer covering the orange emitting phosphor via a polymerization process, which makes CDSP achieve even white light emission. Tunable photoluminescence of CDSP is observed and the preferable white light emission is achieved through changing the excitation wavelength or controlling the mass ratio of the phosphor. When CDSP powders with a phosphor rate of 3.9% and 5.1% are excited at a wavelength of 400 nm, preferable white light emission is observed, with Commission Internationale de l'Eclairage (CIE) coordinates of (0.32, 0.32) and (0.34, 0.32), respectively. Furthermore, CDSP can mix well with epoxy resin to emit strong and even white light, and based on this, a CDSP-based white LED with a high colour rendering index (CRI) of 94 was fabricated.

A simple and outstanding approach is provided to fabricate amorphous structure Ni–Co binary oxide as supercapacitors electrode materials. We can easily obtain porous Ni–Co oxides composite materials via chemical bath deposition and subsequent calcination without any template or complicate operation procedures. The amorphous porous Ni–Co binary oxide exhibits brilliant electrochemical performance: first, the peculiar porous structure can effectively transport electrolytes and shorten the ion diffusion path; second, binary composition and amorphous character introduce more surface defects for redox reactions. It shows a high specific capacitance up to 1607 F g–1 and can be cycled for 2000 cycles with 91% capacitance retention. In addition, the asymmetric supercapacitor delivers superior energy density of 28 W h kg–1, and the maximum power density of 3064 W kg–1 with a high energy density of 10 W h kg–1.Keywords: amorphous defects; chemical bath deposition; Ni−Co binary oxide; porous structure; synergistic effect

A facile and green approach for preparation of photoluminescent nitrogen-doped carbon dots (N-CDs) is reported, using cheap and extensively available cocoon silk as raw material. The use of H2O2 leads to the enhanced formation of N-CDs. The N-CDs have been synthesized in a short time (50 minutes), and have a high fluorescence quantum yield (24.0%). A small amount of H2O2 solution plays a vital role in shortening the reaction time, which is a brand new way to synthesize N-CDs with the help of H2O2, with both reactants and products being environmentally friendly. The prepared N-CDs are collected by removing the insoluble materials through simple filtration rather than dialysis. As far as we know, this is the first report of N-CDs being synthesized simply with the help of H2O2 solution. The prepared N-CDs solution is sensitive to pH changes, which means they have promise for application in the pH detection area.

Graphitic carbon quantum dots (GCQDs) are obtained by hydrothermal treatment of commercially available activated carbon in the presence of KOH. Transmission electron microscope observation indicated narrow particle size distribution between 1 and 6 nm with an average diameter 3.5 nm and high crystallinity of GCQDs. The as-prepared GCQDs exhibited bright yellow luminescence under UV light irradiation and a quantum yield of maximum 11.6 % at the excitation wavelength of 480 nm is achieved. In addition, GCQDs performed very well in the application of bio-imaging. The successful introduction of oxygen-related groups on GCQDs was evident by Fourier transform infrared and X-ray photoelectron spectroscopy measurements. A new mechanism based on hydrothermal induced crystallization and extraction of GCQDs by cation–π interaction is proposed to explain the formation of GCQDs.

•The porous carbon with highest surface area of 3170 m2 g−1 was prepared from melaleuca bark.•The micropore volume and small mesopore volume (V2–3 nm value) were more important than other parameters for H2 uptakes at 77 K.•The resultant carbon with high surface area showed H2 uptake exceeding 4 wt% at 77 K, 10 bar.•The desorption isotherm and cycle life test of H2 uptake indicated that it was a totally reversible physical sorption.Typical porous carbons were obtained from waster biomass, melaleuca bark activated by potassium hydroxide (KOH), and characterized by XRD, SEM, TEM, FTIR, XPS and N2-sorption. The different samples with tunable morphologies and texture were prepared by controlling synthesis reaction parameters. The resulting samples demonstrate both high surface area (up to 3170 m2 g−1) and large hydrogen storage capacity (4.08 wt% at 77 K and 10 bar), implying their great potential as hydrogen storage materials.

High-performance supercapacitor electrode materials are prepared from the commercially available activated carbon (AC) through a facile and low-cost chemical activation method. The obtained results show that AC activated by KOH with an alkali/carbon ratio of 6/1 (ACK6) possesses a specific surface area of 3405 m2/g, a large pore volume of 2.01 cm3/g, and exhibits the highest initial specific capacitance of 335 F/g at the current density of 0.5 A/g in 6 mol/L KOH, and 85% coloumbic efficiency for 5000 cycles at 20 mV/s.The specific capacitance of porous carbons material reached 335 F/g at current density of 0.5 A/g in 6 mol/L KOH, and 85% coloumbic efficiency for 5000 cycles at 20 mV/s.

SrAl2O4:Eu2+,Dy3+ hollow microspheres were successfully prepared through a facile and mild solvothermal co-precipitation combining with a postcalcining process. The structure and particle morphology were investigated by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM) pictures, respectively. The mechanism for the formation of spherical SrAl2O4:Eu2+,Dy3+ phosphor was preliminary presented. After being irradiated with ultraviolet (UV) light, the spherical phosphor emitted long-lasting green phosphorescence. Both the photoluminescence (PL) spectra and luminance decay, compared with that of commercial bulky powders, revealed that the phosphors had efficient luminescent and long lasting properties. It was considered that the SrAl2O4:Eu2+,Dy3+ hollow microspheres had promising long-lasting phosphorescence with potential scale-dependent applications in photonic devices.Schematic illustration of growth process

Phosphorescence is difficult to be observed from carbon dot powder due to the deliquescence and self-quenching in the aggregation state. In this study, aggregation-induced room temperature phosphorescence (RTP) is first reported in self-quenching-resistant nitrogen-doped carbon dot powder, which is suggested to take advantage of the moisture-resistance, rigidization and oxygen-barrier induced by PVA-chains. Furthermore, the optical mechanism of RTP as well as fluorescence is investigated through the abnormal excitation-responsive phenomena, and the potential application in temperature sensing is also preliminarily evaluated. This study may benefit in developing phosphorescence from undesirable aggregation through structure design and exploiting emerging applications for carbon dots.

Mesocrystals are advantageous in providing a large specific surface and favorable transport properties, and have been extensively studied for energy-related applications including supercapacitors, solar cells, lithium-ion batteries, and catalysis. However, the practical applications of mesocrystals are hindered by many obstacles, such as high cost, complicated synthesis processes, and utilization of deleterious additives. Herein, we report a facile one-step and additive-free route for the controllable synthesis of NiO mesocrystals (NOMs) with a cuboctahedral morphology and layered hierarchical structures consisting of self-assembled NiO nanosheets. When employed as an electrode material for supercapacitors, the as-prepared NOMs exhibited an exceptional electrochemical performance such as an ultrahigh reversible specific capacity of ca. 1039 F g−1 at a current density of 1.0 A g−1 and excellent cycling stability (ca. 93% capacitance retention after 10000 charge/discharge cycles). Moreover, an all-solid-state hybrid supercapacitor based on hierarchical NOMs and three-dimensional nitrogen-doped graphene manifested a high energy density of 34.4 W h kg−1 at a power density of 150 W kg−1 in 2.0 M KOH aqueous electrolyte. These results further demonstrate the potential of NiO mesocrystals as a promising electrode material by constructing a hierarchical mesostructure, which can improve the electrochemical performance for energy storage. The outstanding electrochemical performance may be attributed to their hierarchical mesostructure that can effectively enhance the electrical conductivity and avoid the aggregation of NiO nanosheets, and the exposed {100} facets with a high electrochemical activity.