[Show abstract][Hide abstract] ABSTRACT: Dendritic MoO3/Ag with good crystallinity has been prepared through an operando method. In the hydrogen evolution reaction (HER), this catalyst, which was designed to utilize the best properties of each component material, showed a high catalytic activity. After the precursor was drop-cast onto a glassy carbon electrode, a reductive potential was applied to the coated electrode, and H2 evolution occurred within the range of potentials. The overpotential required to evolve H2 at the benchmark rate decreased progressively with subsequent voltammetric cycles, until a steady state was reached at which only 145 mV of overpotential was required to pass −10 mA cm−2 of current density. During the electrocatalysis, the precursor was converted to catalyst through an operando method. This operando-synthesized MoO3/Ag catalyst has a low Tafel slope (43 mV dec−1), low overpotential (145 mV), and excellent durability for HER. It has the potential to be a promising material for HER.
[Show abstract][Hide abstract] ABSTRACT: The bimetallic alloy CuAu nanoparticles (NPs) can produce more photogenerated electrons when compared with single metal Au NPs. Moreover, graphene (Gr) sheets can help the charge separation and slow down the recombination of the electron hole pairs of ZnO. Hence, a novel graphene-based bimetallic alloy-semiconductor catalyst: CuAu–ZnO–Gr nanocomposite is synthesized. Due to the synergistic effect among CuAu NPs, ZnO nanopyramids, and Gr sheets, CuAu–ZnO–Gr behaves an enhanced photocatalytic activity for the photocatalytic degradation of synthetic colorants methyl orange (MO), methylene blue (MB), indigotin (IN), sunset yellow (SY), and tartrazine (TT) under the simulated sunlight irradiation. Furthermore, the apparent rate constants (kapp) of MO, MB, IN, SY, and TT degradation are estimated respectively. In addition, the as-prepared CuAu–ZnO–Gr nanocomposite is characterized by X-ray diffraction, UV–vis spectrum, transmission electron microscopy, energy dispersive X-ray analysis (EDX), and EDX mapping. As a result of the facile synthesis route and the enhanced photocatalytic activity, this new material CuAu–ZnO–Gr can be a promising photocatalyst for the degradation of dyes.
Journal of Alloys and Compounds 07/2015; 636. DOI:10.1016/j.jallcom.2015.02.159 · 2.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Transition-metal dichalcogenide (TMD) monolayer alloys are a branch of two-dimensional (2D) materials which can have large-range band gap tuning as the composition changes. Synthesis of 2D TMD monolayer alloys with controlled composition as well as controlled domain size and edge structure is of great challenge. In the present work, we report growth of MoS2(1-x)Se2x monolayer alloys (x = 0.41 - 1.00) with controlled morphology and large domain size using physical vapor deposition (PVD). MoS2(1-x)Se2x monolayer alloys with different edge orientations (Mo-zigzag and S/Se-zigzag edge orientations) have been obtained by controlling the deposition temperature. Large domain size of MoS2(1-x)Se2x monolayer alloys (x = 0.41 - 1.00) up to 20 μm have been obtained by tuning the temperature gradient in the deposition zone. Together with previously obtained MoS2(1-x)Se2x monolayer alloys (x = 0 - 0.40), the band gap photoluminescence (PL) is continuously tuned from 1.86 eV (i.e., 665 nm, reached at x = 0.00) to 1.55 eV (i.e., 800 nm, reached at x = 1.00). Additionally, Raman peak splitting was observed in MoS2(1-x)Se2x monolayer alloys. This work provide a way to synthesize MoS2(1-x)Se2x monolayer alloys with different edge orientations, which could be benefit to controlled growth of other 2D materials.
[Show abstract][Hide abstract] ABSTRACT: Efficient evolution of hydrogen through electrocatalysis at low overpotentials holds tremendous promise for clean energy. Herein, a highly active and stable MoS2 electrocatalyst is supported on reduced graphene oxide-modified carbon nanotube/polyimide (PI/CNT-RGO) film for hydrogen evolution reaction (HER). The PI/CNT-RGO film allows the intimate growth of MoS2 nanoparticles on its surface. The nanosize and high dispersion of MoS2 nanoparticles provide a vast amount of available edge sites and the coupling of RGO and MoS2 enhances the electron transfer between the edge sites and the substrate, greatly improving the HER activity of PI/CNT-RGO-MoS2 film. The MoS2 with a smaller loading less than 0.04 mg cm−2 on the PI/CNT-RGO film exhibits excellent HER activities with a low overpotential of 0.09 V and large current densities, as well as good stability. The Tafel slope of 61 mV dec−1 reveals the Volmer–Heyrovsky mechanism for HER. Thus, this work paves a potential pathway for designing efficient MoS2-based electrocatalysts for HER.
[Show abstract][Hide abstract] ABSTRACT: Based on the excellent properties of dopamine (reduction, self-polymerization and adhesion), we designed a one-step and environment-friendly reduction route to synthesize and simultaneously functionalize polydopamine (PDA)-Ag-reduced graphene oxide (RGO) hybrid. The obtained PDA-Ag-RGO hybrid was characterized by transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, FT-IR and UV-vis analysis. Silver nanoparticles were uniformly dispersed on the surface of RGO sheets and coated with a thin PDA film. The hybrid exhibited good dispersivity in polar solvents (water and acetonitrile). Compared with Ag-RGO hybrid prepared via NaBH4 reduction and commercial Pd/C catalyst, PDA-Ag-RGO hybrid had better catalytic activity for the oxidation of hydroquinone to benzoquinone in the presence of H2O2. Moreover, the hybrid still retained superior catalytic activity over multiple cycles.
Applied Catalysis B Environmental 11/2014; s 160–161(1):400–407. DOI:10.1016/j.apcatb.2014.05.042 · 7.44 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We proposed a facile approach for the synthesis of zinc sulfur-coated poly (3,4-ethylenedioxythiophene)-reduced graphene oxide hybrids film (ZnS-PEDOT-rGO) by using thioacetamide (TAA) as the reducing agent. The ZnS-PEDOT-rGO hybrids film modified glassy carbon-rotating disk electrode (GC-RDE) was then developed for the sensitive simultaneous determination of three deoxyribonucleic acid (DNA) bases: guanine (G), adenine (A), and thymine (T). By cyclic voltammetry (CV), this electrochemical sensor showed a good photoelectronic effect, and the peak currents of G, A, and T increased obviously. Some kinetic parameters were estimated by linear sweep voltammetry (LSV). Under the optimal conditions, the magnified anodic peak currents represented the excellent analytical performance of simultaneous detection of G, A, and T in a wide linear range and low detection limit. This proposed method also has been successfully applied to the assessment of G, A, and T contents in real-life samples, such as herring sperm DNA samples, milk powder and urine sample from human beings, with satisfactory results. The obtained results were also compared to HPLC of analysis for those three DNA bases and no significant differences were found. By the treatment of the experimental data, the electrochemical reaction mechanisms of G, A, and T all involved a two-electron-two-proton-transfer process.
Sensors and Actuators B Chemical 11/2014; 203:271–281. DOI:10.1016/j.snb.2014.06.135 · 4.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Au-SnO2/graphenes (GNs)-single-walled carbon nanotubes (SWCNTs) nanocomposite has been prepared through green chemistry methods. This composite material was deliberately designed to combinethe virtues of metal, semiconductor, and carbon materials. Its successful formation has been confirmedby a series of characterizations, such as transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). A new electrode based on this nanocomposite was fabricated and used as a voltammetric sensor for detection of 2-tert- butylhydroquinone (TBHQ) through cyclic voltammetry (CV) and differential pulse voltammetry(DPV) methods. Under optimized conditions, this electrode presents a linear response in a broad concentration range of 5.0 x 10(-8) to 2.3 x 10(-4) M of TBHQ, with its detection limit reaching 5.8 x 10(-8) M. Thissimultaneous broad-range and ultrasensitive detecting capability for TBHQ is, to our best knowledge, better than all the previously reported modified electrodes. The excellent performance is attributed tothe synergistic effects among the constituent nanomaterials (GNs, SWCNTs, SnO2, and Au) and the uniquenanoarchitecture of this nanocomposite. c 2014 Elsevier B. V. All rights reserved.
Sensors and Actuators B Chemical 11/2014; 203:926-934. DOI:10.1016/j.snb.2014.06.094 · 4.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A novel honokiol electrochemical sensor based on MoS2/graphene nanohybrid was introduced in this work. The hybrid was characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The electrochemical behavior of honokiol on the MoS2/graphene modified glassy carbon electrode was investigated in pH 5.5 phosphate buffer solution by cyclic voltammetry and differential pulse voltammetry. Compared with bare glassy carbon electrode, the proposed electrode showed improved analytical performance characteristics in catalytic redox of honokiol. Under the optimal conditions, the modified electrode showed a linear voltammetric response to the honokiol with a concentration range from1.0×10−9 to 2.5×10-6 mol L-1, and the detection limit (S/N=3) was estimulated at 6.2×10-10 mol L-1. Moreover, the sensor also exhibited good reproducibility and stability, and could be used for the detection of honokiol in pharmaceutical samples.
[Show abstract][Hide abstract] ABSTRACT: A simple and effective approach was demonstrated to synthesize flowerlike Pt nanocrystals on polydopamine (PDA) functionalized reduced oxide graphene (RGO). In-spired by mussels, the PDA/RGO composites were obtained via the reduction of GO nanosheets by dopamine, followed by simultaneous capping by PDA. Then, the synthesis of Pt flowerlike nanocrystals assembled with small elongated nanoparticles on PDA/RGO (Pt(F)-PDA/RGO) was carried out by mixing H2PtCl6 with PDA/RGO in the presence of ascorbic acid under boiling. PDA as a surface-adherent and multifunctional biopolymer played a dual role: dispersing stable RGO into aqueous solution and providing functional groups to bind metal ions and metal nanoparticles. The as-prepared Pt(F)-PDA/RGO catalyst showed considerably improved catalytic activity and stability toward methanol electrooxidation, compared with Pt nanoclusters on PDA/RGO (Pt(C)-PDA/RGO) and Pt nanoparticles on pristine graphene sheets (Pt/RGO). The kinetic characterization of Pt(F)-PDA/RGO was further discussed by cyclic voltammetry. This simple and green approach could be applicable to other metallic nanocrystals as a novel platform in catalysis, fuel cells and biosensors. (C) 2014 The Authors. Published by Elsevier Ltd.
[Show abstract][Hide abstract] ABSTRACT: Diluted magnetic semiconductor ZnMnSe2 has been synthesized on reduced graphene oxide/polyimide (rGO/PI) substrate by a simple electrochemical method. The structure, surface morphology, magnetism and photoelectric property of ZnMnSe2 were examined. For comparison, ZnSe and MnSe were also prepared by electrochemical deposition. Porous structure of ZnMnSe2 was obtained, and the porous structure was consisted of nanosheets. The atomic ratio of Zn, Mn and Se was measured to be 1:1:2 by X-ray photoelectron spectra and energy-dispersive X-ray spectroscopy. The high resolution transmission electron microscopy and X-ray Powder Diffraction pattern confirmed the preferred crystal growth orientation was the (111) direction. The absorption spectrum provided a band gap of 2.4 eV. Open-circuit potential measurement indicated that ZnMnSe2 composite film was a good p-type semiconductor material. The photoelectrical phenomena of ZnSe, MnSe and ZnMnSe2 were observed, and the optoelectronic property of ZnMnSe2 was the best, the potential difference was 0.27 V. Besides, the ZnMnSe2 composite film had prominent magnetism, and it was ferromagnetism material. These results indicated that rGO/PI-ZnMnSe2 composite film by electrochemical deposition was a promising ferromagnetism semiconductor.
Journal of Alloys and Compounds 10/2014; 609:233–238. DOI:10.1016/j.jallcom.2014.04.178 · 2.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Porous structured Ag-Ag2S/MoS2 composite was synthesized by a facile chemical etching method and tested with respect to its application in hydrogen evolution reaction (HER). Extensive spectroscopic and electrochemical characterizations were performed to investigate the origin of the catalytic activity of this Ag-Ag2S/MoS2 composite and understand the property of this material for HER. During the synthesis process, cysteine (Cys) was used to improve the number of highly catalytic S edges as revealed by a low ratio of Mo to S. The high density of active sites that result from the rough and porous structure surface morphology also contributes to the highly catalytic activity. The catalytic activity for HER increases with the change of material morphology from a relatively complete lamellar structure to the porous structure. The electrochemical stability tests indicate that the catalyst remains highly active throughout prolonged operation. Our enhanced understanding of this highly active hydrogen evolution catalyst may facilitate the development of economical electrochemical hydrogen production systems. (C) 2014 Published by Elsevier Ltd.
[Show abstract][Hide abstract] ABSTRACT: Promising catalytic activity of MoSe2 in the hydrogen evolution reaction (HER) is synthesized on a new reduced graphene oxide/polyimide (rGO/PI) substrate by a simple electrochemical method. The MoSe2 nanoparticles have excellent photo-responsive properties; the potential difference could reach 0.45 V with the photo-responsive time just 0.6 s. Furthermore, MoSe2 thin film exhibits superior catalytic activity in the hydrogen evolution reaction (HER). It has a greater cathode current at more positive potential compared to other MoSe2 and MoS2, and the efficiency of H2 evolution is strongly influenced by illumination; this suggests that MoSe2 composite film has good photoelectrocatalysis properties for hydrogen evolution. Besides, both dark and illumination MoSe2 films exhibit extremely high stability in acidic solution as the HER catalytic activity shows no degradation after 100 cycles for two hours. All results indicate that MoSe2–rGO/PI composite film has potential to be a better catalyst for HER.
[Show abstract][Hide abstract] ABSTRACT: Platinum nanoparticles were synthesized with molybdenum disulfide (MoS2) as a template through a facile hydrothermal method. The as-prepared nanocomposites (Pt-MoS2) were characterized by TEM, HRTEM, electrochemical impedance spectroscopy, and X-ray photoelectron spectroscopy, and they were then used to fabricate a biosensor for enzyme-like catalysis of hydrogen peroxide (H2O2). The electrochemical activity for the reduction reactions of H2O2 was evaluated in N2-saturated phosphate buffer solution. The cyclic voltammetry and amperometry results demonstrated that the biosensor modified by the nanocomposites exhibited a fast amperometric response and excellent electrocatalytic activity for reduction of H2O2 with a wide linear range from 0.004 to 48.5 mM and a low detection limit of 0.001 mM at 3σ. Thus, the present work indicates that Pt nanoparticles can be synthesized on the surface of few-layer MoS2 owing to interfacial PtS bonds and that the composites show a clear enhancement in the catalytic activity relative to that of the platinum nanoparticles alone. This method provides a new way to prepare metal nanoparticles for extensive applications in the field of catalysis.
[Show abstract][Hide abstract] ABSTRACT: MoS2-carbon composites which with different morphologies were synthesized by hydrothermal method and tested with respect to their application in hydrogen evolution reaction (HER). Their performances were compared to evaluate how the morphology influence HER. The obtained results showed that the composite containing amorphous MoS2 showed higher activity than composite which contains crystalline MoS2. The catalytic activity of composite was highly correlated to its active surface area which was controlled by the morphology. In addition, compared with composite which contains amorphous MoS2, the composite containing crystalline MoS2 showed higher durability in the long-term operation. However, in acidic and alkaline environments, the stability of composite containing amorphous MoS2 is better than which containing crystalline MoS2. The impedance measurements suggested that the high catalytic activity of the composite stems from the synergistic effect of MoS2 and carbon materials. The enhanced understanding of these highly active hydrogen evolution catalysts can facilitate the development of economical electrochemical hydrogen production systems.
International Journal of Hydrogen Energy 06/2014; 39(18):9638–9650. DOI:10.1016/j.ijhydene.2014.04.092 · 2.93 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A 2D atomic-layer-thickness phototransistor based on a graphene-MoS2 bybrid device is constructed with a photoresponse much larger than that of individual graphene or MoS2 based phototransistors. Strong and selective light absorption in the MoS2 layer creates electric charges that are transferred to graphene layers derived by a build-in electrical field, where they recirculate many times due to the high carrier mobility of graphene. Gate tunable Fermi level in graphene layer allows the responsivity of this hybrid phototransistor to be continuously tuned from 0 to about 10(4) mA/W by the gate voltage. Furthermore, large scale, flexible and transparent 2D phototransistors with high responsivity were constructed from the CVD-grown graphene and MoS2 flakes. The high responsivity, gate-tunable sensitivity, wavelength selectivity, and compatibility with current circuit technologies of this type device give it great potential for future application in integrated nano-optoelectronic systems.
Small 06/2014; 10(11). DOI:10.1002/smll.201303670 · 8.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Alloying in monolayers enables bandgap tuning in twodimensions. On page 2648, L. Xie, J. Zhang, and co-workers demonstrate that by direct evaporation of two end materials (MoS2 and MoSe2 ) and deposition at low temperatures, large-area 2D MoS2(1-x) Se2x monolayers are obtained. By changing the S/Se composition, the bandgap of MoS2(1-x) Se2x monolayers can be continuously tuned.
[Show abstract][Hide abstract] ABSTRACT: We report the fabrication of a catechol (CC) sensor based on an In-modified ZnO/carbon nanotube–polyimide (In-ZnO/PI–CNT) film by using a simple electrochemical method. The decoration of In nanoparticles and control of the size and morphology of In nanostructures provide a great opportunity to improve the catalytic activity of ZnO nanosheets. In nanoparticles supported on the ZnO nanosheets exhibit relatively large surface areas and can enhance the electron transfer. An In-ZnO/PI–CNT film is more active for the catalysis of CC than the ZnO/PI–CNT film and the In(3.79%)-ZnO/PI–CNT film shows the best catalytic activity. The In(3.79%)-ZnO/PI–CNT film sensor exhibits a wide linear range, good long-term stability and reproducibility, and performs well for detection of CC in real water samples. The In(3.79%)-ZnO/PI–CNT film holds great potential for the fabrication of efficient sensors.
[Show abstract][Hide abstract] ABSTRACT: A convenient and low-cost synthesis approach is proposed for the development of a simple and novel electrochemical sensor for the determination of tryptophan (Try). In this synthesis process, graphene-like molybdenum sulfide was successfully obtained, and silver nanoflakes (AgNFs) were directly synthesized on the surface of molybdenum sulfide (MoS2) films, in this process chitosan (CS) and ascorbic acid (AA) acted as the stabilizer and reducing agent, respectively. This nanocomposite was characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were employed to evaluate the electrochemical property of Ag-MoS2/CS toward the oxidation of tryptophan. Under the optimized experimental conditions, the oxidation peak currents are proportional to the concentrations of tryptophan over the range of 0.5 μM to 120 μM, and the detection limit is 0.05 μM (S/N = 3). Moreover, the proposed method is free of interference from other amino acid to other coexisting species.
Sensors and Actuators B Chemical 03/2014; 192:42–50. DOI:10.1016/j.snb.2013.10.096 · 4.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Poly (diallyldimethylammonium chloride) functionalized graphene-MoS2 nano-flower materials (PDDA-G-MoS2) were successfully synthesized, in which the addition of MoS2 wrinkling the graphene further increased the specific surface area. Then, the gold nanoparticles (AuNPs) were assembled on the surface of PDDA-G-MoS2 via electrostatic attractive force and function of AuS bond. The obtained Au/PDDA-G-MoS2 nanomaterial was used to modify glassy carbon electrode (Au/PDDA-G-MoS2/GCE) and determine sensitively eugenol. The oxidation peak currents increased distinctly on the proposed electrochemical sensor by cyclic voltammetry (CV) in 0.10 mol L−1 NaAc-HAc buffer solution (pH = 5.50), indicating that the material shows excellent electrochemical properties. The reaction kinetics was studied and the experimental conditions were optimized. The oxidation peak current of eugenol increased linearly with addition of concentration in the range from 0.1 to 440 μmol L−1 with a low detection limit of 0.036 μmol L−1 (S/N = 3). This sensor exhibited high sensitivity, good stability and fast responses, and also has been applied to determination of eugenol in real samples with satisfactory results. The novel PDDA functionalization graphene-MoS2 nanoflower shows excellent electrocatalysis for determination of eugenol and satisfactory dispersity in water than graphene; these would show its potential application in analysis, medical science and nanodevice field via combining graphene with graphene-like materials (MoS2) for its novel properties.
Sensors and Actuators B Chemical 03/2014; 192:1–8. DOI:10.1016/j.snb.2013.10.087 · 4.29 Impact Factor