As-obtained Nanocomposite Research Articles

Dual Regulation of Metal Doping and Adjusting Cut-Off Voltage for MoSe2 to Achieve Reversible Sodium Storage.

MoSe2 , as a typical 2D material, possesses tremendous potential in Na-ion batteries (SIBs) owing to larger interlayer distance, more favorable band gap structure, and higher theoretical specific capacity than other analogs. Nevertheless, the low intrinsic electronic conductivity and irreversible conversion of discharged products of Mo/Na2 Se to MoSe2 seriously hamper its electrochemical performance. Herein, through a facile hydrothermal method combined with calcination process, Sn-doped MoSe2 nanosheets grown on graphene substrate in the vertical direction are fabricated. Benefiting from the improved electronic conductivity contributed by the abundant defects and expanded interlamellar spacing of MoSe2 originated from Sn doping, combined with a smart strategy of raising dischargecut-off voltageto 0.2V during the actual performance testing for SIBs, the as-fabricated anode material delivers superior Na-ions storage performance in terms of electrons/ions transfer, reversible sodium storage as well as cycle stability. An ultra-stable reversible specific capacity of 268.5mAhg-1 at 1Ag-1 can be maintained after 1600 cycles. Moreover, the great sodium storage property in the SIB full-cell system of the as-obtained nanocomposite illustrates practical potential. Density functional theory calculation andin situ/ex situ measurements are employed to further reveal the storage mechanism and process of Na-ions.

A Multicomponent Polymer-Metal-Enzyme System as Electrochemical Biosensor for H2O2 Detection.

Herein, an Au nanoparticles-polydopamine-poly acrylic acid-graphene (Au NPs-PDA-PAA-graphene) multicomponent nanohybrid is fabricated by surface functionalization of graphene alongside extensive in-situ growth of Au nanoparticles. The as-obtained nanocomposite possesses good hydrophilicity, excellent biocompatibility and high biomolecules loading capacity, which acts as an ideal platform for enzyme modification. Considering this fact, Horseradish peroxidase is expressively immobilized upon Au NPs-PDA-PAA-graphene surface, in order to lay the foundations of a biosensor that is majorly based on enzymatic activity. The biosensor exhibits higher sensitivity towards the determination of H2O2 with linearity ranging from 0.1 μm upto 20 mm, and the limit of detection going down to 0.02 μm. Encouraged by its acceptable electrocatalytic performance, this multicomponent system can also be easily employed for carrying out the real-time tracking of H2O2 coming out of Macrophage cells. Therefore, this work designs an extraordinarily updated platform for biosensing related applications, and also presents a reliable platform for the direct detection of H2O2 in vivo and in vitro, which show great potential in bioelectroanalytical chemistry, cellular biology, and pathophysiology.

Mechanistic insight into the adsorption and photocatalytic activity of a magnetically separable γ-Fe2O3/Montmorillonite nanocomposite for rhodamine B removal

The magnetically separable nanocomposite of γ-Fe2O3/montmorillonite (γ-Fe2O3/Mt) has been synthesized by a hydrothermal method. The as-obtained nanocomposite is composed of a single phase of γ-Fe2O3 nanoparticles homogeneously dispersed in a montmorillonite structure with high photocatalytic activity for rhodamine B photodegradation. Physicochemical characterization revealed particle sizes ranging from 10 to 30 nm with a band-gap energy of 2.3 eV. This study reveals a significant contribution of the adsorption mechanism to the degradation mechanism. The nanocomposite could be easily separated and reused by magnetic separation owing to its magnetism of 22 emu/g. The nanocomposite is also reusable without any chemical change until five cycles.

Green preparation of amorphous molybdenum sulfide nanocomposite with biochar microsphere and its voltametric sensing platform for smart analysis of baicalin

The green preparation of the a-MoS x -BM nanocomposite for smart sensing baicalin. • The a-MoS x -BM nanocomposite as sensing platform was prepared by a green hydrothermal method; • LSSVM displayed more superiority in practical application for smart sensing compared with ANN. Green and sustainable development provides a new idea for solving environmental pollution issues of rural biomass wastes. Amorphous molybdenum sulfide (a-MoS x ) nanocomposite based on biochar microsphere (BM) as voltametric sensing platform for smart analysis of baicalin in real sample was facilely prepared. Pomelo peel was employed as the carbon source for improving electronic conductivity and environmental stability and electrocatalytic capacity of a-MoS x . A mixture consisted of the precursor of both a-MoS x and BM were treated by a co-hydrothermal method. The a-MoS x nanocomposite with porous BM was formed by centrifuging, washing, drying, pulverizing, and calcining. The structure and properties of the as-obtained nanocomposite were characterized, and the electrochemical behaviors of baicalin, parametric conditions and performance of the as-prepared sensor were investigated. Peak currents recorded by differential pulse voltammetry is proportional to baicalin concentrations in wide linear ranges from 10 nM to 5 μM with a low limit of detection of 2 nM. Machine learning algorithms like least squares support vector machine and artificial neural network was built to realize smart analysis and digital output for baicalin. Good cyclic stability, excellent voltammetric response, and satisfactory practicability will provide a promising electrochemical sensing platform for facile preparation of two-dimension nanomaterials functionalized with biochar derived from agroforestry biomass.

Magnetic Fe3O4@CoFe-LDH nanocomposite heterogeneously activated peroxymonosulfate for degradation of azo-dye AO7.

In this study, a novel core@shell magnetic nanocomposite Fe3O4/CoFe-layered double hydroxide (Fe3O4@CoFe-LDH) was successfully synthesized by the co-precipitation method, and then employed as an efficient heterogeneous catalyst for activation of peroxymonosulfate (PMS) in removal of azo-dye acid orange 7 (AO7). The as-obtained nanocomposite was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The results from these characterizations showed Fe3O4@CoFe-LDH to possess good ferromagnetism and a perfect crystalline structure with a typical core@shell morphology. The system of Fe3O4@CoFe-LDH11/PMS (cobalt : iron molar ratio of 1 : 1) achieved 95.1% removal rate of AO7 (40 mg L−1) within 15 min under the optimized conditions, which outperformed bare Fe3O4 and raw CoFe-LDH11. Meanwhile, Fe3O4@CoFe-LDH11 displayed good adaptability in a wide pH range from 4 to 9 and relatively low PMS activation energy (39.9 kJ mol−1). The interference tests revealed HCO3− to possess the strongest restriction effect. Only 57.7% AO7 was removed when 10 mM HCO3− was introduced, which was ascribed to HCO3− not only serving as a radical scavenger, but also increasing the pH of the system. The radical quenching tests demonstrated SO4˙− as the dominant reactive species during the catalytic reaction. Based on X-ray photoelectron spectroscopy (XPS) analysis, the core structure of Fe3O4 served as an electron donor for accelerating the cycle of Co(ii)/Co(iii) at the active site of the LDH outer shell. Also, Fe3O4@CoFe-LDH exhibited outstanding stability and recyclability, and maintained high degradation efficiency of AO7 even after five cycles. In sum, the proposed magnetic Fe3O4@CoFe-LDH nanocomposite has great potential for remediation of wastewater contaminated with synthetic dyes.

Novel photocatalyst and antibacterial agent; direct dual Z-scheme ZnO–CeO2-Yb2O3 heterostructured nanocomposite

Novel excellent antibacterial agent and efficient photocatalyst direct dual Z-scheme ZnO–CeO2-Yb2O3 heterostructured nanocomposite and pristine ZnO, CeO2, and Yb2O3 were prepared via a simple co-precipitation technique. The X-ray diffraction spectra confirmed the formation of pristine ZnO, CeO2, and Yb2O3, and the existence of their peaks ZnO (hexagonal), CeO2 (cubic), and Yb2O3 (cubic) in the nanocomposite. The Scherrer, Williamson-Hall, and Size-Strain plot models were used to measure the microstructural parameters. The UV–vis spectroscopy revealed the energy bandgap 3.0 eV, evident that the grown nanocomposite is a good photocatalyst under sunlight. The formation of the ZnO–CeO2-Yb2O3 nanocomposite is further confirmed by Raman and Fourier transform infrared spectroscopy (FTIR). Current-Voltage (IV) measurements shown the ohmic nature of nanocomposite with high electrical behavior. Scanning electron microscopy (SEM) images revealed a cluster type morphology. The antibacterial activity was carried out for Escherichia coli and Staphylococcus aureus bacteria. The zone of inhibition (ZOI) showed higher antibacterial activity for E. coli bacteria. The nanocomposite showed the highest photocatalytic degradation efficiency against methylene blue as compared to rhodamine-B, methyl orange, cresol red, and safranin-O dyes under 40 min of sunlight illumination. The impact of various parameters on the photocatalytic activity of nanocomposite, including catalyst amount, dye concentration, and solution pH, was also investigated. The scavenger's experiments were performed to ascertain the reactive species and confirmed the mechanism based on Z-scheme. The recyclability test exhibits that the as-obtained nanocomposite has high stability and can be reusable for the 6th cycles.

Microwave-assisted preparation and improvement mechanism of carbon nanotube@NiMn2O4 core-shell nanocomposite for high performance asymmetric supercapacitors

A carbon nanotube (CNT)@NiMn2O4 core-shell nanocomposite is successfully prepared by a facile microwave-assisted hydrothermal process. The as-obtained nanocomposite exhibits low charge transfer resistance (2.19 Ω), high specific capacitance (up to 915.6 F g−1 measured by charge-discharge at 1 A g−1) and excellent cycling stability (93.0% capacity retention after 5000 cycles at 5 A g−1). It is found that the weaker crystallinity induced by microwave treatment, synergism between CNTs and NiMn2O4 in the core-shell heterostructure and more defects and vacancies in CNTs caused by acidifying pretreatment can all devote to improving the electrochemical performance of the as-obtained nanocomposite. An asymmetric supercapacitor device using the as-obtained CNT@NiMn2O4 as positive electrode is also successfully fabricated, which exhibits the maximum energy density of 36.5 Wh kg−1 at a power density of 800 W kg−1 and outstanding cycling stability with 82.8% retains capacitance after 10000 cycles at 5 A g−1. The excellent performance indicates that as-fabricated CNT@NiMn2O4 is one of the competitive electrode materials for energy storage devices.

P- type gas-sensing behavior of Ga2O3/Al2O3 nanocomposite with high sensitivity to NOx at room temperature

In this work, Ga2O3/Al2O3 composite materials were synthesized by a two-step method via hydrothermal and calcining processes. The microstructures and morphology of the as-obtained nanocomposite were characterized by various techniques. It is shown that Ga2O3 nanorods with 26–28 nm in length and 2.6–5 nm in width disperse well on the surface of mesoporous 2D Al2O3 nanosheets. The Ga2O3/Al2O3 composite was tested to exhibit p-type conductivity and shows significantly good NOx gas sensing performance. Its response to NOx from 100 ppm to 500 ppb falls between 58.2% and 6.5% at room temperature. The mechanism related to the n-p transition was investigated and proposed. Our results are expected to provide a new cut-in point to Ga2O3-based composite materials for gas sensing application.

Casein phosphopeptide-biofunctionalized graphene oxide nanoplatelets based cellulose green nanocomposites with simultaneous high thermal conductivity and excellent flame retardancy

In this contribution, a green nanocomposite consisting of casein phosphopeptide-biofunctionalized graphene oxide nanoplatelets (CPGO) and cellulose nanofibers (CNFs) was fabricated via vacuum-assisted self-assembly technique. A ‘natural nacre’ and strong hydrogen bonds network structure was constructed by CNFs and CPGO. In this architecture, the scaffold of one-dimensional CNFs is employed as the structural component to construct hydrogen bonds network and reinforce mechanical strength, while the arranged two-dimensional CPGO in the framework provides a convenient pathway for in-plane acoustic phonon transmission. The as-obtained nanocomposite possesses high in-plane thermal conductivity of 12.75 W m−1 K−1 and favourable tensile strength of 33.45 MPa. The theoretical simulation results indicated it has low thermal resistance between CPGO. Furthermore, a phosphorus-nitrogen flame retardant system was built and fire experiments presented that it could effectively prevent flame spreading. Heat release rate curve results showed that the total heat release and peak heat release rate decreased by 58.6 % and 20 % than CNFs, respectively. Cooling down experiments for LED chips showed that nanocomposites have an excellent cooling rate (8.85 °C min−1) which can transfer efficiently heat energy and demonstrated its potential usefulness in electronic device-cooling applications.

Facilely Synthesized NiCo2O4/NiCo2O4 Nanofile Arrays Supported on Nickel Foam by a Hydrothermal Method and Their Excellent Performance for High-Rate Supercapacitance

NiCo2O4 nanoleaf arrays (NCO NLAs) and NiCo2O4/NiCO2O4 nanofile arrays (NCO/NCO NFAs) material was fabricated on flexible nickel foam (NF) using a facile hydrothermal approach. The electrochemical performance, including the specific capacitance, charge/discharge cycles, and lifecycle of the material after the hydrothermal treatment, was assessed. The morphological and structural behaviors of the NF@NCO NLAs and NF@NCO/NCO NFAs electrodes were analyzed using a range of analysis techniques. The as-obtained nanocomposite of the NF@NCO/NCO NFAs material delivered outstanding electrochemical performance, including an ultrahigh specific capacitance (Cs) of 2312 F g−1 at a current density of 2 mA cm−2, along with excellent cycling stability (98.7% capacitance retention after 5000 cycles at 5 mA cm−2). These values were higher than those of NF@NCO NLAs (Cs of 1950 F g−1 and 96.3% retention). The enhanced specific capacitance was attributed to the large electrochemical surface area, which allows for higher electrical conductivity and rapid transport between the electrons and ions as well as a much lower charge-transfer resistance and superior rate capability. These results clearly show that a combination of two types of binary metal oxides could be favorable for improving electrochemical performance and is expected to play a major role in the future development of nanofile-like composites (NF@NCO/NCO NFAs) for supercapacitor applications.

A simple, one-pot, low temperature and pressure route for the synthesis of RGO/ZnO nanocomposite and investigating its photocatalytic activity

A simple, low temperature and pressure, catalyst-free reflux method was reported for the synthesis of reduced graphene oxide (RGO)/ZnO nanocomposite (NC). Formation of ZnO Nanoparticles (NPs) on the surface of Graphene oxide (GO) sheets was led to reduction of GO and fabricating RGO/ZnO NC. The photoluminescence (PL) analysis showed two broad and intense peaks in PL spectra of ZnO and RGO/ZnO samples which are assigned to the electronic transition from zinc interstitial levels (IZn) to Zinc vacancy levels (VZn) and from conduction band to the oxygen vacancy levels (VO), respectively. Broad and intense peaks in PL spectra of ZnO NPs synthesized by our method makes many photogenerated e-h pairs in trap levels due to large number of trap levels. Hybridizing ZnO NPs with GO considerably improve photocatalytic activity of samples due to transferring these electrons to GO sheets and preventing e-h recombination. XRD and FT-IR analyses confirmed that the as-obtained NC is in the form of RGO/ZnO instead of GO/ZnO. Synthesizing NCs by this route largely enhanced photocatalytic activity of NCs, because this synthesis route generates many trap state energy levels such as VO, VZn and IZn subband energy levels in the band gap of ZnO NPs. These numerous trap states -compared to that of RGO/ZnO NCs obtained by other methods- play an important role in the photocatalytic performance of synthesized NCs by enhancing the visible light absorption due to the resulting ZnO band gap narrowing.

Novel Au Nanoparticles-Strewn MnOOH Nanorod Composites: Simple Fabrication and Application in the Catalytic Reduction of Aromatic Nitro Compounds

In this study, a surface functionalization process was designed for the preparation of Au nanoparticles-strewn MnOOH nanorods with enhanced catalytic performance for reduction of aromatic nitro compounds. (3-Aminopropyl) triethoxysilane was used as a modifier to link MnOOH nanorods and Au nanoparticles. The as-obtained nanocomposite was characterized by powder X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy (TEM/HRTEM), selected area electron diffraction, energy dispersive X-ray spectrometry, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. Our results showed that the MnOOH/Au nanocomposite can be used as a highly efficient catalyst for the reduction of aromatic nitro compounds in the presence of NaBH4 solution.

Removal of lead ion and oil droplet from aqueous solution by lignin-grafted carbon nanotubes

Water contamination is one of the most serious problems afflicting people throughout the world, innovation of nanomaterials with eco-friendliness is important for a greener environment. Here, an eco-friendly nanocomposite based on lignin grafted carbon nanotubes (L-CNTs) is reported as a new type of adsorbent for water remediation. By integrating the tridimensional structure, oxygen-containing functional groups and eco-friendliness of lignin with the high surface area and mechanical stability of CNTs, the as-prepared nanocomposite not only possesses a good water-dispersibility and eco-friendliness, but also exhibits an excellent adsorption capability for lead ion and oil droplet. It shows a high distribution coefficient for lead ion (Kd=3.6×105mL/g) that is comparable to some benchmark materials, including mesoporous carbon and metal-organic frameworks. The large surface area and tridimensional structure also endows L-CNTs with a high removal efficiency for oil droplet from water. Moreover, the cost of the nanocomposite has been minimized by incorporation of the low cost lignin. These results demonstrate the as-obtained nanocomposite with a natural polymer layer has advanced adsorption capability, low-in cost and eco-friendliness, and accordingly is an ideal candidate for water cleanup.

Hierarchical assembly of graphene-bridged Ag3PO4/Ag/BiVO4 (040) Z-scheme photocatalyst: An efficient, sustainable and heterogeneous catalyst with enhanced visible-light photoactivity towards tetracycline degradation under visible light irradiation

A novel graphene-bridged Ag3PO4/Ag/BiVO4 (040) Z-scheme heterojunction with excellent visible-light-driven photocatalytic performance was fabricated using a facile in situ deposition method followed by photo-reduction. The as-obtained nanocomposite was employed to degrade tetracycline (TC) in water under visible light irradiation. Compared to pure BiVO4, Ag3PO4 and other nanocomposites, Ag/Ag3PO4/BiVO4/RGO displayed more superior photodegradation efficiency with 94.96% removal of TC (10mg/L) in 60min, where the optimal conditions was catalysis dosage 0.50g/L and initial pH at ca. 6.75. The influences of TC concentrations, light irradiation condition, coexistence ions and water sources were also investigated in details. The enhanced photocatalytic activities could be attributed to the suppression of charge recombination, high specific surface area and desirable absorption capability of Ag/Ag3PO4/BiVO4/RGO, which were in sequence confirmed by PL, PC, EIS, BET and DRS tests. The synergistic effects of RGO and Ag/Ag3PO4 in the hybrid could also contribute to the improved photo-stability and recyclability towards TC decomposition. In addition, radical trapping experiments and ESR measurement revealed that the photo-induced active species superoxide radical (O2−) and holes (h+) were the predominant active species in the photocatalytic system. The Ag/Ag3PO4/BiVO4/RGO nanocomposite also possessed desirable photocatalytic performance on the degradation of TC from real wastewater, further verifying its potential in practical industries. This work provides a promising approach to construct visible-light response and more stabilized nanocomposite photocatalysts applied in efficient treatment of persistent pollutants in wastewater.

A single-step route for large-scale synthesis of core–shell palladium@platinum dendritic nanocrystals/reduced graphene oxide with enhanced electrocatalytic properties

In this report, a facile, seed-less and single-step method is developed for large-scale synthesis of core–shell Pd@Pt dendritic nanocrystals anchored on reduced graphene oxide (Pd@Pt DNC/rGO) under mild conditions. Poly(ethylene oxide) is employed as a structure-directing and stabilizing agent. Compared with commercial Pt/C (20 wt%) and Pd/C (20 wt%) catalysts, the as-obtained nanocomposite has large electrochemically active surface area (114.15 m2gmetal−1), and shows superior catalytic activity and stability with the mass activities of 1210.0 and 1128.5 mAmgmetal−1 for methanol and ethanol oxidation, respectively. The improved catalytic activity is mainly the consequence of the synergistic effects between Pd and Pt of the dendritic structures, as well as rGO as a support.

High-performance asymmetric supercapacitors with lithium intercalation reaction using metal oxide-based composites as electrode materials

FeOOH–graphene nanosheets (GNS)–carbon nanotubes (CNTs) hybrid material was synthesized by the direct hydrolysis of Fe3+ on the surface of GNS-supported and CNTs-bridged frameworks. Interestingly, the as-obtained nanocomposite (FeOOH/GNS/CNTs) shows the lithium intercalation reaction characteristic in 1 M Li2SO4 aqueous solution as an electrode material for supercapacitor, providing high electrochemical performances. More importantly, benefiting from the nanosized FeOOH and highly coupled with conductive CNTs–GNS networks, which is beneficial to electron and electrolyte ion transport in the overall electrode, the as-fabricated asymmetric supercapacitor, using FeOOH/GNS/CNTs and MnO2/GNS as the negative electrode and positive electrode, respectively, exhibits superior energy density (30.4 W h kg−1) and good rate capability as well as excellent cycling stability (89% capacitance retention after 1000 cycles).

Reduced graphene oxide networks as an effective buffer matrix to improve the electrode performance of porous NiCo2O4 nanoplates for lithium-ion batteries

Transition metal oxides are promising high-capacity anode materials for next-generation lithium-ion batteries. However, their cycle life remains a limiting factor with respect to their commercial applications. The development of transition-metal oxide anode materials with long lifespans through a facile route has become an important issue. A straightforward strategy is designed for the fabrication of a NiCo2O4 nanoplates–reduced graphene oxide sheets (NiCo2O4–RGO) composite. It displays a high reversible capacity of 816 mA h g−1 over 70 cycles with 80.1% capacity retention of the 2nd cycle and excellent rate capability. Its rate capability and cycling stability are enhanced in comparison with those of pure NiCo2O4 nanoplates. The as-obtained nanocomposite avoids the problems of dispersion and aggregation induced by cracking or pulverization of the transition-metal oxide upon cycling. The graphene or reduced graphene oxide not only works as a substrate to provide room for loading scattered grains, but also serves as a conductive network to facilitate the collection and transportation of electrons during the cycling, indirectly increasing the conductivity of NiCo2O4.

Wet milled synthesis of an Sb/MWCNT nanocomposite for improved sodium storage

A uniform mixture of nano-sized Sb particles and MWCNTs is achieved by using wet milling to provide fast ionic diffusion and electronic transportation, and the cycling performance and rate capability of the as-obtained nanocomposite are significantly improved when tested as an anode material for sodium-ion batteries.

Facile electrochemical codeposition of “clean” graphene–Pd nanocomposite as an anode catalyst for formic acid electrooxidation

Highly dispersed Pd nanoparticles (NPs) supported on graphene were successfully prepared by a one-step electrochemical codeposition approach. The as-obtained nanocomposite was very “clean” as a result of the reductant-free and surfactant-free synthesis process. The catalyst remarkably improved the electrocatalytic performance for formic acid oxidation (FAO). This facile and controllable method is of significance for the preparation of graphene–metal NPs with desirable catalytic performance.

Rational synthesis of graphene–metal coordination polymer composite nanosheet as enhanced materials for electrochemical biosensing

The designed synthesis of graphene-based nanocomposites for enhancing their different potential application is of great interest recently. In this paper, we demonstrated a new class of high-quality graphene-based nanocomposites: metal coordination polymer–graphene nanosheets (MCPGNs). The as-obtained nanocomposite, combining the unique properties of graphene (excellent conductivity and high specific surface area) and MCPs (tunable pore size, large internal surface areas and versatility of functionality), can act as an efficient matrix to immobilize glucose oxidase (GOD). Furthermore, the as-prepared MCPGNs exhibit better conductivity and electrocatalytic activity for H2O2 reduction than graphene. Based on these excellent properties, a sensitive electrochemical biosensing platform for glucose was fabricated. This novel biosensor displays a linear response range between 50 nM and 1 mM with a detection limit of 5 nM. Our work not only provides a facile, effective and general route for the synthesis of a variety of MCP–graphene nanohybrids, but also sets an example for fabricating an electrochemical biosensor with this new kind of nanohybrid as an enhanced material and can be easily extended to other biosensors. These interesting results suggested the great potential of MCP–graphene nanocomposites in the field of electroanalytical chemistry.