The synthesis of metal nanostructures with plasmon wavelengths beyond ∼1000 nm is strongly desired, especially for those with small sizes. Herein we report on a AgPd-tipping process on Au nanobipyramids with the resultant red plasmon shifts reaching up to ∼900 nm. The large red plasmon shifts are ascribed to the deposition of the metal at the tips of Au nanobipyramids, which is verified by electrodynamic simulations. The method has been successfully applied to Au nanobipyramids and nanorods with different longitudinal dipolar plasmon wavelengths, demonstrating that the plasmon wavelengths of these Au nanocrystals can be extended to the entire near-infrared region. Pt can also induce the tipping on Au nanobipyramids and nanorods to realize red plasmon shifts, suggesting the generality of our approach. We have further shown that the metal-tipped Au nanobipyramids possess a high photothermal conversion efficiency and good photothermal therapy performance. This study opens up a route to the construction of Au nanostructures with plasmon resonance in a broad spectral region for plasmon-enabled technological applications.

•Ammonia sensors based on zinc oxide nanowire-reduced graphene oxide nanocomposites have been fabricated.•The sensors exhibit excellent response, fast response time, and full recovery at room temperature.•The sensors show excellent selectivity toward ammonia.ZnO nanowire-reduced graphene oxide nanocomposites have been prepared and used to detect ammonia at room temperature successfully. The nanocomposites are synthesized through hybridization of ZnO nanowires and graphene oxide sheets, which have been produced in large scale through mechanical mixing and low-temperature thermal reduction process. The micro ammonia sensors based on the as-prepared nanocomposites are subsequently constructed by dip-dropping method. The resultant device exhibits excellent response (∼19.2%) to NH3 at room temperature, which is much better than pure reduced graphene oxide based gas sensors. It is revealed that ZnO nanowires can provide pathways for electron transfer on reduced graphene oxide sheets, thus the ZnO nanowire-reduced graphene oxide nanocomposites based sensors show excellent overall sensing performance with high response, short response and recovery time, good stability and excellent selectivity. Moreover, the sensor has a very small size and low power consumption, which are critical for system integration and portable equipment. Our work can hold a great potential for realistic applications in ammonia detection fields.

•Herein, we present a systematic study on molecular assembly process, the ultimate chemical structure, and multi-level photoluminescence mechanism through the analysis of three states of nitrogen doped carbon dots (N-CDs) obtained by microwave irradiation.•The possible inference proposed to explain the formation process of N-CDs could be simply described as intramolecular and/or intermolecular dehydration, polymerization and carbide nucleation.•Our exploration provides the theoretical basis for synthesis of CDs with different properties and purpose.•In the near future, more high-quality CDs will be developed to better benefit all areas of human beings.In recent years, carbon dots (CDs) have attracted much attention in the material field because of their remarkable performance in various aspects. Therefore, the exploration of complex and variable photoluminescence mechanisms shows great significance. Herein, we present a systematic study on the correlation between the formation process and photoluminescence mechanisms through the characterization and analysis of three states of nitrogen doped carbon dots (N-CDs) obtained by microwave irradiation. At low temperature of 160 °C, the small organic molecule polymer nanodots whose photoluminescence center is molecule state are obtained with superior quantum yield of about 51.61%. Increasing the reaction temperature up to 200 °C, the intermediate transition products named carbon nanodots begin to appear. Prolonging the holding time, the typical carbon quantum dots with a special stable optical properties are finally generated, and their most photoluminescence arises from the carbon cores which are gained through the polymerization, dehydration, carbonation of organic fluorescent molecules. Furthermore, N-CDs have been applied in metal ions detection as well as animal and plant cell fluorescence imaging owing to their excellent water solubility and low cytotoxicity. Our exploration provides the theoretical basis for synthesis of CDs with different properties and purposes. In the near future, more high-quality CDs will be developed in order to better benefit the various fields of mankind.

Graphene is an ideal candidate for gas sensing due to its excellent conductivity and large specific surface areas. However, it usually suffers from sheet stacking, which seriously debilitates its sensing performance. Herein, we demonstrate a three-dimensional conductive network based on stacked SiO2@graphene core–shell hybrid frameworks for enhanced gas sensing. SiO2 spheres are uniformly encapsulated by graphene oxide (GO) through an electrostatic self-assembly approach to form SiO2@GO core–shell hybrid frameworks, which are reduced through thermal annealing to establish three-dimensional (3D) conductive sensing networks. The SiO2 supported 3D conductive graphene frameworks reveal superior sensing performance to bare reduced graphene oxide (RGO) films, which can be attributed to their less agglomeration and larger surface area. The response value of the 3D framework based sensor for 50 ppm NH3 and 50 ppm NO2 increased 8 times and 5 times, respectively. Additionally, the sensing performance degradation caused by the stacking of the sensing materials is significantly suppressed because the graphene layers are separated by the SiO2 spheres. The sensing performance decays by 92% for the bare RGO films when the concentration of the sensing material increases 8 times, while there is only a decay of 25% for that of the SiO2@graphene core–shell hybrid frameworks. This work provides an insight into 3D frameworks of hybrid materials for effectively improving gas sensing performance.

High-performance gas sensors based on metal oxides operated at room temperature are of great interest due to their energy saving and cost effective characteristics. How to improve the sensitivity of metal oxide gas sensors and enable their room-temperature operation are challenging for their realistic applications. In this work, we have designed and fabricated Al-doped NiO nanosheets for greatly enhanced NO2 detection at room temperature. Different amounts of Al were doped into two-dimensional (2D) NiO nanosheets via a fast and facile microwave assisted solvent-thermal technique. Sensing tests of the as-fabricated devices indicated that Al doping could significantly affect the gas-sensing properties of the NiO nanosheets due to increased oxygen vacancies as well as the formation of Lewis acid and base sites. When 12 at% of Al was added to the raw materials, the response value of the device to 10 ppm NO2 was enhanced more than 35 times compared with those of pure NiO nanosheets. In addition, when the amount of Al reached 20 at%, it took only 200 s for the gas sensor to achieve full recovery, which was a breakthrough for room temperature gas sensors based on metal oxides. Above all, the excellent performances of the as-fabricated devices make Al-doped NiO nanosheets a potential candidate for NO2 sensing applications. This design strategy can also give guidance for designing high-performance gas sensors based on other similar 2D sensing materials.

Biosynthesis of gold nanostructures has drawn increasing concerns because of its green and sustainable synthetic process. However, biosynthesis of gold nanoplates is still a challenge because of the expensive source and difficulties of controllable formation of morphology and size. Herein, one-pot biosynthesis of gold nanoplates is proposed, in which cheap yeast was extracted as a green precursor. The morphologies and sizes of the gold nanostructures can be controlled via varying the pH value of the biomedium. In acid condition, gold nanoplates with side length from 1300 ± 200 to 300 ± 100 nm and height from 18 to 15 nm were obtained by increasing the pH value. Whereas, in neutral or basic condition, only gold nanoflowers and nanoparticles were obtained. It was determined that organic molecules, such as succinic acid, lactic acid, malic acid, and glutathione, which are generated in metabolism process, played important role in the reduction of gold ions. Besides, it was found that the gold nanoplates exhibited plasmonic property with prominent dipole infrared resonance in near-infrared region, indicating their potential in surface plasmon-enhanced applications, such as bioimaging and photothermal therapy.

•A new in situ synthesis is conducted to incorporate octahedral Cu2O onto RGO.•The octahedral Cu2O-RGO composites degrade MO completely in 50 min under visible light.•The synergistic effect between RGO and octahedral Cu2O in the photocatalysis process is systematacially explored firstly.The octahedral cuprous oxide (Cu2O) supported by reduced graphene oxide composites (Cu2O-RGO) are compounded via a gentle one-pot in situ method. The reduction of GO and the growth of octahedral Cu2O particles simultaneously occur with the Cu2O particles depositing on RGO nanosheets uniformly. The enhanced photocatalytic properties are appraised by decomposition of methyl orange under visible light irradiation. Compared with the pure octahedral Cu2O particles and RGO, the as-prepared composites degrade methyl orange completely within 50 min with apparent rate constant at 82.88 × 10−3 min−1, ten times of the pure octahedral Cu2O particles and twenty-seven times of RGO. Scavengers are also introduced to investigate the photocatalytic mechanism which turns out that h+ and O2¯ radicals are the main active species in the photocatalysis process. The synergistic effect between RGO and octahedral Cu2O particles in the photocatalysis process is systematacially analyzed for the first time. Carrier generation occurs on the Cu2O particle, and electron is collected and transported by graphene here to prolong the charge carriers' lifetime, leading to strong absorbance in visible light region, instant carrier separation, and fast charge transfer. Thus the efficiency of visible-light-driven photocatalysis is greatly enhanced.Download high-res image (349KB)Download full-size image

The synthesis of anisotropic metal nanostructures is strongly desired for exploring plasmon-enabled applications. Herein, the preparation of anisotropic Au/SiO2 and Au/SiO2/Pd nanostructures is realized through selective silica coating on Au nanobipyramids. For silica coating at the ends of Au nanobipyramids, the amount of coated silica and the overall shape of the coated nanostructures exhibit a bell-shaped dependence on the cationic surfactant concentration. For both end and side silica coating on Au nanobipyramids, the size of the silica component can be varied by changing the silica precursor amount. Silica can also be selectively deposited on the corners or facets of Au nanocubes, suggesting the generality of this method. The blockage of the predeposited silica component on Au nanobipyramids enables further selective Pd deposition. Suzuki coupling reactions carried out with the different bimetallic nanostructures functioning as plasmonic photocatalysts indicate that the plasmonic photocatalytic activity is dependent on the site of Pd nanoparticles on Au nanobipyramids. Taken together, these results suggest that plasmonic hot spots play an important role in hot-electron-driven plasmonic photocatalysis. This study opens up a promising route to the construction of anisotropic bimetallic nanostructures as well as to the design of bimetallic plasmonic-catalytic nanostructures as efficient plasmonic photocatalysts.

Three-dimensional free-standing film electrodes have aroused great interest for energy storage devices. However, small volumetric capacity and low operating voltage limit their practical application for large energy storage applications. Herein, a facile and novel nanofoaming process was demonstrated to boost the volumetric electrochemical capacitance of the devices via activation of Ni nanowires to form ultrathin nanosheets and porous nanostructures. The as-designed free-standing Ni@Ni(OH)2 film electrodes display a significantly enhanced volumetric capacity (462 C/cm3 at 0.5 A/cm3) and excellent cycle stability. Moreover, the as-developed hybrid supercapacitor employed Ni@Ni(OH)2 film as positive electrode and graphene-carbon nanotube film as negative electrode exhibits a high volumetric capacitance of 95 F/cm3 (at 0.25 A/cm3) and excellent cycle performance (only 14% capacitance reduction for 4500 cycles). Furthermore, the volumetric energy density can reach 33.9 mWh/cm3, which is much higher than that of most thin film lithium batteries (1–10 mWh/cm3). This work gives an insight for designing high-volume three-dimensional electrodes and paves a new way to construct binder-free film electrode for high-performance hybrid supercapacitor applications.Keywords: energy storage; nanofoaming; nickel nanowire; supercapacitor; volumetric capacity

Metal-semiconductor-based photocatalysts show high efficiencies and catalytic activities in the photocatalysis process. Herein, the magnetic and one-dimensional Ni–Cu2O heteronanowires have been fabricated via in situ reduction of pre-adsorbed Cu2+ on the surface of prickly Ni nanowires in an ethanol solution for photocatalysis application. The resultant Ni–Cu2O heteronanowires show higher photocatalytic ability than pure Cu2O nanoparticles in the degradation of methyl orange. The enhancement of photocatalytic efficiency can be ascribed to the unique one-dimensional nanostructure and the electron sink effect of Ni nanowires in the heterostructure. It is believed that the low-cost metal Ni is an alternative candidate for substituting the costly metals (Au, Ag and Pt) to improve the photocatalytic ability of semiconductor-based photocatalysts.

Cuprous oxide (Cu2O) is an attractive photocatalyst because of its visible-light-driven photocatalytic behavior, abundance, low toxicity, and environmental compatibility. However, its short electron diffusion length and low hole mobility result in low photocatalytic efficiency, which hinders its wider applications. Herein, we report an in situ method to introduce nitrogen-doped carbon dots (N-CDs) into Cu2O frameworks. It is interestingly found that the introduction of N-CDs drives the morphology of N-CDs/Cu2O to evolve from rough cube to sphere, and the most encouraging result is that all of the obtained N-CDs/Cu2O composites exhibit better photocatalytic activities than pure Cu2O cubes. The optimal N-CDs/Cu2O photocatalyst is synthesized with 10 mL of N-CDs solution, which shows the best degradation ability (100%, 70 min), far superior to pure Cu2O cubes (∼5%, 70 min) and P25 (∼10%, 70 min). Beside the photodegradation of methyl orange, N-CDs/Cu2O(10) composites also exhibit excellent photocatalytic activities in the photodegradation of methyl blue and rhodamine B. It is demonstrated that the excellent photocatalytic performance of N-CDs/Cu2O composites can be attributed to the highly roughened structure and the suppression of electron–hole recombination as a result of the introduction of N-CDs. These findings demonstrate that the conjugation of CDs is a promising method to improve the photocatalytic activities for traditional semiconductors.

Graphene-based gas/vapor sensors have attracted much attention in recent years due to their variety of structures, unique sensing performances, room-temperature working conditions, and tremendous application prospects, etc. Herein, we summarize recent advantages in graphene preparation, sensor construction, and sensing properties of various graphene-based gas/vapor sensors, such as NH3, NO2, H2, CO, SO2, H2S, as well as vapor of volatile organic compounds. The detection mechanisms pertaining to various gases are also discussed. In conclusion part, some existing problems which may hinder the sensor applications are presented. Several possible methods to solve these problems are proposed, for example, conceived solutions, hybrid nanostructures, multiple sensor arrays, and new recognition algorithm.

The desired control of particle size, doping element composition, and surface structure of carbon dots (CDs) are vital for understanding the fluorescence mechanism and exploring their potential applications. Herein, nitrogen-doped CDs (N-doped CDs) have been synthesized with tartaric acid and various alkylol amines (monoethanolamine, biethanolamine and triethanolamine) under microwave irradiation. A systematic investigation was performed to characterize the N-doped CDs. It is found that with increasing nitrogen proportion, the fluorescent quantum yield and lifetime of N-doped CDs increases, whereas cell toxicity decreases. In other words, N-doped CDs synthesized by tartaric acid and monoethanolamine have the highest nitrogen content, the highest fluorescent quantum yield, the longest lifetime and the lowest cell toxicity. A corresponding mechanism has been proposed. Moreover, as-synthesized N-doped CDs have been applied for selectively detecting the Fe3+ ion and writing letters as a fluorescent ink.

Oxygen reduction electrocatalysts with low cost and excellent performance are urgently required for large-scale application in fuel cells and metal–air batteries. Though nitrogen-enriched transition metal/graphene hybrids (N–TM/G, TM = Fe, Co, and Ni and related compounds) have been developed as novel substitutes for precious metal catalysts (PMCs) towards oxygen reduction reaction (ORR), a significant challenge still remains for simple and efficient synthesis of N–TM/G catalysts with satisfactory electrocatalytic behavior. Herein, we demonstrate a universal bottom-up strategy for efficient fabrication of strongly-coupled N–TM/G catalysts. This strategy is implemented via direct polymerization of transition metal phthalocyanine (TMPc) in the two-dimensional confined space of in situ generated g-C3N4 and a subsequent pyrolysis. Such a space-confined bottom-up synthesis route successfully constructs a strongly-coupled triple junction of transition metal–graphitic carbon–nitrogen-doped graphene (TM–GC–NG) with extensive controllability over the specific surface area, nitrogen content/types as well as the states of metal. As a result, the optimized N–Fe/G materials have promising potential as high-performance NPMCs towards ORR both in alkaline and acidic solution.

Carbon quantum dots (CQDs) are novel carbon nanomaterials and are attracting increasing interest due to their good characteristics such as hydrophilicity, chemical stability, quantum yield, small particle sizes, and low cytotoxicity. Herein, we used CQDs as stabilizers and exfoliation agents to exfoliate graphite to graphene in an aqueous medium for the first time. The functions of CQDs are to reduce the surface tension of water to match that of graphite and to make weak interactions (π–π conjugation, hydrophobic force, and the Coulomb attraction) with the graphite surface. Different characterization methods were used to evaluate the presence of layers (<5 layers) of graphene sheets with fewer defects and low oxidation. In the future, CQDs can also be good candidates to exfoliate other two-dimensional materials, such as WS2, BN, MoS2, and g-C3N4, to form two-dimensional heterostructures for a range of possible applications.

To facilely prepare high-performance Fe-N/G oxygen reduction catalysts via a simple and controllable route from available and low-cost materials is still a challenge. Herein, we develop an in situ self-sacrificed template strategy to synthesize Fe-N/G catalysts from melamine, glucose, and FeSO4·7H2O. Fe/Fe3C@graphitic carbon nanocapsules are uniformly formed on the NG surface to create a highly opened and stable mesoporous framework structure. Furthermore, effectively doped N sites and high active Fe-Nx sites are synchronously constructed on such structures, leading to an enhanced synergistic effect for ORR and promising the Fe-N/G catalyst a similar catalytic activity and four-electron selectivity, but superior stability to commercial 30 wt % Pt/C catalysts in 0.1 M KOH solution under the same loading.Keywords: Fe-N/G catalyst; fuel cell; in situ self-sacrificed template; oxygen reduction reaction; synergistic effect

We report the synthesis of a two-dimensional enamine-linked covalent organic framework (COF) using a rapid microwave-assisted solvothermal method in significantly less time and high yield under a relatively low temperature. This COF was found to have a high crystallinity, high stability, high BET surface area, and a high CO2 capacity and adsorption selectivity of CO2/N2.

•Ni@Ni(OH)2 core-sheath nanowire structure is constructed for energy storage.•The active material layer is obtained by a facile electrochemical treatment.•A high volumetric capacity of 111.1 C cm−3 is obtained at 0.12 A cm−3.•The electrode exhibits excellent rate capability and cycle stability.We report a facile approach to fabricate a novel membrane electrode based on unique Ni@Ni(OH)2 coaxial core-sheath structures for electrochemical energy storage application in this work. The Ni nanowire membranes, prepared from vacuum filtration of Ni nanowires with unique embossments, can be used as excellent precursors for preparing Ni@Ni(OH)2 membranes by an electrochemical cyclic voltammetry method. After electrochemical treatment, a layer of amorphous Ni(OH)2 was obtained on the surface of Ni nanowires. An important property of the as-synthesized Ni@Ni(OH)2 membranes is that it can be directly utilized for electrochemical energy storage applications without the need for binders or additional conducting additives. The Ni@Ni(OH)2 electrode demonstrates a high volumetric capacity (111.1 C cm−3 at 0.12 A cm−3), excellent rate capability (83.1 C cm−3 at 1.92 A cm−3), and cycling stability at a high current density (78% capacity retention after 1500 cycles at 1.92 A cm−3). This fabrication method is very simple and paves a new route for designing membrane electrodes based on similar structures for high-performance electrochemical energy storage electrodes.

We report on a method for the preparation of uniform and length-variable Ag nanorods through anisotropic Ag overgrowth on high-purity Au nanobipyramids. The rod diameters can be roughly tailored from ∼20 nm to ∼50 nm by judicious selection of differently sized Au nanobipyramids. The rod lengths can be tuned from ∼150 nm to ∼550 nm by varying the Ag precursor amount during the overgrowth process and/or by anisotropic shortening through mild oxidation. The controllable aspect ratios, high purity, and high dimensional uniformity of these Ag nanorods enable the observation of Fabry–Pérot-like multipolar plasmon resonance modes in the colloidal suspensions at the ensemble level, which has so far been demonstrated only on Au nanorods prepared electrochemically with anodic aluminum oxide templates. Depending on the mode order and geometry of the Ag nanorods, the multipolar plasmon wavelengths can be readily tailored over a wide spectral range from the visible to near-infrared region. We have further elucidated the relationships between the multipolar plasmon wavelengths and the geometric dimensions of the Ag nanorods at both the ensemble and single-particle levels. Our results indicate that the Au nanobipyramid-directed, dimensionally controllable Ag nanorods will be an attractive and promising candidate for developing multipolar plasmon-based devices and applications.Keywords: gold nanobipyramids; multipolar plasmon resonance; plasmon resonance; scattering; seed-mediated growth; silver nanorods;

Compared with traditional semiconductor quantum dots (QDs) and organic dyes, photoluminescent carbon dots (CDs) are superior because of their high aqueous solubility, robust chemical inertness, facile functionalization, high resistance to photobleaching, low toxicity and good biocompatibility. Herein, a green, large-scale and high-output heterogeneous synthesis of N-doped CDs was developed by reacting calcium citrate and urea under microwave irradiation without the use of any capping agents. The obtained N-doped CDs with a uniform size distribution exhibit good aqueous solubility and yellowish-green fluorescence in the solid and aqueous states. These unique luminescence properties of N-doped CDs inspire new thoughts for applications as fluorescent powders, fluorescent inks, the growth of fluorescent bean sprouts, and fingerprint detection tools.

The growth of carbon nanotubes (CNTs) on graphene quantum dot surface has been explored using acetylene as the carbon source in a catalyst free chemical vapor deposition process. Dynamic studies were conducted to observe the CNT growth. The obtained nanotubes have a diameter distribution of 10–30 nm and show medium graphitic quality. Transmission electron microscopy observations and dynamic studies indicate that the formation of CNTs follows a different mechanism from traditional growth models, in which a wire-to-tube process and self-assembling of CNTs are involved. On the basis of these observations, a tentative continuous growth model is proposed for the CNT growth.

•Facile and low-cost approach to synthesize ZnO nanowire (NW)/reduced graphene oxide (RGO) nanocomposites was studied.•The obtained nanocomposites displayed high photocatalytic properties.•The significantly enhanced photocatalytic property of obtained nanocomposites is attributed to the electrons interaction between ZnO NWs and RGO.We have demonstrated a facile and low-cost approach to synthesize ZnO nanowire (NW)/reduced graphene oxide (RGO) nanocomposites, in which ZnO NWs and graphene oxide (GO) were produced in large scale separately and then hybridized into ZnO NW/RGO nanocomposites by mechanical mixing and low-temperature thermal reduction. Rhodamine 6G (Rh6G) was used as a model dye to evaluate the photocatalytic properties of ZnO NW/RGO nanocomposites. The obtained nanocomposites show significantly enhanced photocatalytic performance, which took only 10 min to decompose over 98% Rh6G. Finally the mechanism of the great enhancement about photocatalytic activity of ZnO NW/RGO nanocomposites is studied. It is mainly attributed to that RGO nanosheets can transfer the electrons of ZnO NWs excited by ultraviolet (UV) irradiation, increase electron migration efficiency, and then longer the lifetime of the holes in ZnO NWs. The high charge separation efficiency of photo-generated electron–hole pairs directly leads to the lower recombination rate of ZnO NW/RGO nanocomposites, makes more effective electrons and holes to participate the radical reactions with Rh6G, thus significantly improving the photocatalytic properties. The high degradation efficiency makes the ZnO NW/RGO nanocomposites promising candidates in the application of environmental pollutant and wastewater treatment.

Graphene, as an intermediate phase between fullerene and carbon nanotube, has aroused much interests among the scientific community due to its outstanding electronic, mechanical, and thermal properties. With excellent electrical conductivity of 6000 S/cm, which is independent on chirality, graphene is a promising material for high-performance nanoelectronics, transparent conductor, as well as polymer composites. On account of its Young’s Modulus of 1 TPa and ultimate strength of 130 GPa, isolated graphene sheet is considered to be among the strongest materials ever measured. Comparable with the single-walled carbon nanotube bundle, graphene has a thermal conductivity of 5000 W/(m·K), which suggests a potential application of graphene in polymer matrix for improving thermal properties of the graphene/polymer composite. Furthermore, graphene exhibits a very high surface area, up to a value of 2630 m2/g. All of these outstanding properties suggest a wide application for this nanometer-thick, two-dimensional carbon material. This review article presents an overview of the significant advancement in graphene research: preparation, functionalization as well as the properties of graphene will be discussed. In addition, the feasibility and potential applications of graphene in areas, such as sensors, nanoelectronics and nanocomposites materials, will also be reviewed.

Comprehensive characterization of properties and first-principles calculations were first introduced to analyze tunable band gap Cu2ZnSnS4xSe4(1−x) (CZTSSe) nanocrystals. Interesting aspects of composition and morphology were deeply explored. As the ratio of Se/(S + Se) rises, the parabolic nature of their tunable band gaps from 1.28 to 1.50 eV was revealed and verified.

Manganese oxide (MnOx) has been coated on carbon nanotubes (CNTs) and fabricated as the electrodes for electrochemical capacitors (ECs) by cathodic electrodeposition. In the process, randomly oriented CNT arrays are grown directly onto the Ti/Si substrates by chemical vapor deposition method. Potentiostatic method has been utilized for cathodic electrodeposition of MnOx onto the surface of CNTs while immersed in KMnO4 solution. The highly porosity and fibrous microstructure of the as-prepared MnOx/CNT electrode is beneficial for the electrolyte access to the active material, whereas CNTs provide improved electronic conductivity. Electrochemical investigations show that the increase in the loading mass of MnOx results in a significant reduction in the specific capacitances (SCs) of the MnOx/CNT electrodes. The MnOx/CNT electrode with MnOx loading mass of 50 μg shows a high SC of 400 F g−1 with good long cycle stability at a current density of 10 A g−1, suggesting its potential application in ECs.

A facile route for the large scale production of graphene oxide (GO) papers and their mechanical enhancement has been presented in this work. The novel paper-like GO made from individual GO sheets in aqueous suspension can be achieved in large scale by a simple drop casting method on hydrophobic substrates. Significant enhancement in mechanical stiffness (341%) and fracture strength (234%) of GO paper have been achieved upon modification with a small amount (less than 10 wt%) of glutaraldehyde (GA). The cross-linking reaction takes place between hydroxyl groups on the surface of GO and aldehyde groups of GA, through forming hemiacetal structure, which can result in distinct mechanical enhancement of the GO papers.

•Magnetically separable catalyst is synthesized in an energy-efficient strategy.•High stability and efficiency is observed for 4-nitrophenol reduction with NaBH4.•Improvement relies on accelerated electron transfer and strong synergistic effect.Design supported bimetallic nanoparticles is an interesting and important strategy for developing new catalysts with enhanced activity and selectivity. Herein the magnetically separable reduced graphene oxide supported Ni-Au (RGO-Ni-Au) nanocatalysts were prepared by an in situ co-reduction and surfactant-free method, which exhibited excellent performance both in the catalytic reduction of 4-nitrophenol and degradation of environmentally polluting dyes with NaBH4. The best activity parameters of RGO-Ni-Au-6h nanocomposites for 4-nitrophenol reduction is 36.77 s−1 g−1 with an apparent rate constant of 11.03 × 10−3 s−1. Additionally, the prepared catalyst could be recycled over 6 times without obvious performance decay or even a morphology change. The enhancement in catalytic capability can be ascribed to the electron-enhanced effect of graphene support and strong synergistic effect between noble metal and magnetic transition metal. It is believed that such desirable catalyst with magnetic properties, high activity, and long-life stability make it promising in retrievable catalysis.

Metal-semiconductor-based photocatalysts show high efficiencies and catalytic activities in the photocatalysis process. Herein, the magnetic and one-dimensional Ni–Cu2O heteronanowires have been fabricated via in situ reduction of pre-adsorbed Cu2+ on the surface of prickly Ni nanowires in an ethanol solution for photocatalysis application. The resultant Ni–Cu2O heteronanowires show higher photocatalytic ability than pure Cu2O nanoparticles in the degradation of methyl orange. The enhancement of photocatalytic efficiency can be ascribed to the unique one-dimensional nanostructure and the electron sink effect of Ni nanowires in the heterostructure. It is believed that the low-cost metal Ni is an alternative candidate for substituting the costly metals (Au, Ag and Pt) to improve the photocatalytic ability of semiconductor-based photocatalysts.

We report the synthesis of a two-dimensional enamine-linked covalent organic framework (COF) using a rapid microwave-assisted solvothermal method in significantly less time and high yield under a relatively low temperature. This COF was found to have a high crystallinity, high stability, high BET surface area, and a high CO2 capacity and adsorption selectivity of CO2/N2.

High-performance gas sensors based on metal oxides operated at room temperature are of great interest due to their energy saving and cost effective characteristics. How to improve the sensitivity of metal oxide gas sensors and enable their room-temperature operation are challenging for their realistic applications. In this work, we have designed and fabricated Al-doped NiO nanosheets for greatly enhanced NO2 detection at room temperature. Different amounts of Al were doped into two-dimensional (2D) NiO nanosheets via a fast and facile microwave assisted solvent-thermal technique. Sensing tests of the as-fabricated devices indicated that Al doping could significantly affect the gas-sensing properties of the NiO nanosheets due to increased oxygen vacancies as well as the formation of Lewis acid and base sites. When 12 at% of Al was added to the raw materials, the response value of the device to 10 ppm NO2 was enhanced more than 35 times compared with those of pure NiO nanosheets. In addition, when the amount of Al reached 20 at%, it took only 200 s for the gas sensor to achieve full recovery, which was a breakthrough for room temperature gas sensors based on metal oxides. Above all, the excellent performances of the as-fabricated devices make Al-doped NiO nanosheets a potential candidate for NO2 sensing applications. This design strategy can also give guidance for designing high-performance gas sensors based on other similar 2D sensing materials.