Showing papers by "Hua Zhang published in 2013"
TL;DR: This Review describes how the tunable electronic structure of TMDs makes them attractive for a variety of applications, as well as electrically active materials in opto-electronics.
Abstract: Ultrathin two-dimensional nanosheets of layered transition metal dichalcogenides (TMDs) are fundamentally and technologically intriguing. In contrast to the graphene sheet, they are chemically versatile. Mono- or few-layered TMDs - obtained either through exfoliation of bulk materials or bottom-up syntheses - are direct-gap semiconductors whose bandgap energy, as well as carrier type (n- or p-type), varies between compounds depending on their composition, structure and dimensionality. In this Review, we describe how the tunable electronic structure of TMDs makes them attractive for a variety of applications. They have been investigated as chemically active electrocatalysts for hydrogen evolution and hydrosulfurization, as well as electrically active materials in opto-electronics. Their morphologies and properties are also useful for energy storage applications such as electrodes for Li-ion batteries and supercapacitors.
7,903 citations
TL;DR: This tutorial review will take MoS(2) as a typical example to introduce the latest research development of 2D inorganic nanomaterials with emphasis on their preparation methods, properties and applications.
Abstract: Two-dimensional (2D) nanomaterials have received much attention in recent years, because of their unusual properties associated with their ultra-thin thickness and 2D morphology. Besides graphene which has aroused tremendous research interest, other types of 2D nanomaterials such as metal dichalcogenides have also been studied and applied in various applications including electronics, optoelectronics, energy storage devices, and so on. In this tutorial review, we will take MoS2 as a typical example to introduce the latest research development of 2D inorganic nanomaterials with emphasis on their preparation methods, properties and applications.
1,748 citations
TL;DR: The as-prepared TiO( 2)@MoS(2) heterostructure shows a high photocatalytic hydrogen production even without the Pt co-catalyst and possesses a strong adsorption ability towards organic dyes and shows high performance in photocatallytic degradation of the dye molecules.
Abstract: MoS(2) nanosheet-coated TiO(2) nanobelt heterostructures--referred to as TiO(2)@MoS(2)--with a 3D hierarchical configuration are prepared via a hydrothermal reaction. The TiO(2) nanobelts used as a synthetic template inhibit the growth of MoS(2) crystals along the c-axis, resulting in a few-layer MoS(2) nanosheet coating on the TiO(2) nanobelts. The as-prepared TiO(2)@MoS(2) heterostructure shows a high photocatalytic hydrogen production even without the Pt co-catalyst. Importantly, the TiO(2)@MoS(2) heterostructure with 50 wt% of MoS(2) exhibits the highest hydrogen production rate of 1.6 mmol h(-1) g(-1). Moreover, such a heterostructure possesses a strong adsorption ability towards organic dyes and shows high performance in photocatalytic degradation of the dye molecules.
1,166 citations
TL;DR: A single-layer MoS2 nanosheet exhibits high fluorescence quenching ability and different affinity toward ssDNA versus dsDNA and has been successfully used as a sensing platform for the detection of DNA and small molecules.
Abstract: A single-layer MoS2 nanosheet exhibits high fluorescence quenching ability and different affinity toward ssDNA versus dsDNA. As a proof of concept, the MoS2 nanosheet has been successfully used as a sensing platform for the detection of DNA and small molecules.
961 citations
TL;DR: A Ni3S2 nanorods/Ni foam composite electrode is prepared as a high-performance catalyst for the oxygen evolution reaction (OER), which exhibits excellent OER activity with a small overpotential of ∼157 mV based on the onset of catalytic current as discussed by the authors.
Abstract: A Ni3S2 nanorods/Ni foam composite electrode is prepared as a high-performance catalyst for the oxygen evolution reaction (OER), which exhibits excellent OER activity with a small overpotential of ∼157 mV based on the onset of catalytic current.
904 citations
TL;DR: The solution-processable two-dimensional MoS(2) nanosheet can be used to direct the epitaxial growth of Pd, Pt and Ag nanostructures at ambient conditions and exhibits much higher electrocatalytic activity towards the hydrogen evolution reaction compared with the commercial Pt catalysts with the same Pt loading.
Abstract: Compared with the conventional deposition techniques used for the epitaxial growth of metallic structures on a bulk substrate, wet-chemical synthesis based on the dispersible template offers several advantages, including relatively low cost, high throughput, and the capability to prepare metal nanostructures with controllable size and morphology. Here we demonstrate that the solution-processable two-dimensional MoS(2) nanosheet can be used to direct the epitaxial growth of Pd, Pt and Ag nanostructures at ambient conditions. These nanostructures show the major (111) and (101) orientations on the MoS(2)(001) surface. Importantly, the Pt-MoS(2) hybrid nanomaterials exhibit much higher electrocatalytic activity towards the hydrogen evolution reaction compared with the commercial Pt catalysts with the same Pt loading. We believe that nanosheet-templated epitaxial growth of nanostructures via wet-chemical reaction is a promising strategy towards the facile and high-yield production of novel functional materials.
738 citations
TL;DR: A bottom-up strategy assisted by atomic layer deposition to graft bicontinuous mesoporous nanostructure Fe3O4 onto three-dimensional graphene foams and directly use the composite as the lithium ion battery anode, which exhibits high reversible capacity and fast charging and discharging capability.
Abstract: Fe3O4 has long been regarded as a promising anode material for lithium ion battery due to its high theoretical capacity, earth abundance, low cost, and nontoxic properties. However, up to now no effective and scalable method has been realized to overcome the bottleneck of poor cyclability and low rate capability. In this article, we report a bottom-up strategy assisted by atomic layer deposition to graft bicontinuous mesoporous nanostructure Fe3O4 onto three-dimensional graphene foams and directly use the composite as the lithium ion battery anode. This electrode exhibits high reversible capacity and fast charging and discharging capability. A high capacity of 785 mAh/g is achieved at 1C rate and is maintained without decay up to 500 cycles. Moreover, the rate of up to 60C is also demonstrated, rendering a fast discharge potential. To our knowledge, this is the best reported rate performance for Fe3O4 in lithium ion battery to date.
727 citations
TL;DR: The ultralow frequency interlayer breathing and shear modes in few-layer MoS2 and WSe2, prototypical layered TMDs, are uncovered using both Raman spectroscopy and first principles calculations and can be perfectly described using a simple linear chain model with only nearest-neighbor interactions.
Abstract: Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have recently attracted tremendous interest as potential valleytronic and nanoelectronic materials, in addition to being well-known as excellent lubricants in the bulk. The interlayer van der Waals (vdW) coupling and low-frequency phonon modes and how they evolve with the number of layers are important for both the mechanical and the electrical properties of 2D TMDs. Here we uncover the ultralow frequency interlayer breathing and shear modes in few-layer MoS2 and WSe2, prototypical layered TMDs, using both Raman spectroscopy and first principles calculations. Remarkably, the frequencies of these modes can be perfectly described using a simple linear chain model with only nearest-neighbor interactions. We show that the derived in-plane (shear) and out-of-plane (breathing) force constants from experiment remain the same from two-layer 2D crystals to the bulk materials, suggesting that the nanoscale interlayer frictional characteristics of ...
616 citations
TL;DR: TCF aerogel shows highly efficient sorption of organic liquids and could be regenerated many times without decrease of sorption capacity by distillation, combustion or squeezing, which depends on the type of pollutants.
Abstract: Twisted carbon fiber (TCF) aerogel with good selective sorption is produced in large scale by using raw cotton as the precursor. TCF aerogel shows highly efficient sorption of organic liquids (pump oil: up to 192 times its own weight; chloroform: up to 115 times its own weight). Moreover, it could be regenerated many times without decrease of sorption capacity by distillation, combustion or squeezing, which depends on the type of pollutants.
579 citations
TL;DR: Interestingly, hexagonal- and monoclinic-structured WO₃ thin films are obtained during the local oxidation of thinner (1L-3L) and thicker (4L and 5L) WSe₂ nanosheets, while laser-burned holes are found during theLocal oxidation of the WSe ₂ single crystal.
Abstract: Single- and few-layer transition-metal dichalcogenide nanosheets, such as WSe₂ , TaS₂, and TaSe₂, are prepared by mechanical exfoliation. A Raman microscope is employed to characterize the single-layer (1L) to quinary-layer (5L) WSe₂ nanosheets and WSe₂ single crystals with a laser excitation power ranging from 20 μW to 5.1 mW. Typical first-order together with some second-order and combinational Raman modes are observed. A new peak at around 308 cm⁻¹ is observed in WSe₂ except for the 1L WSe₂, which might arise from interlayer interactions. Red shifting of the A(1g) mode and the Raman peak around 308 cm⁻¹ is observed from 1L to 5L WSe₂. Interestingly, hexagonal- and monoclinic-structured WO₃ thin films are obtained during the local oxidation of thinner (1L-3L) and thicker (4L and 5L) WSe₂ nanosheets, while laser-burned holes are found during the local oxidation of the WSe₂ single crystal. In addition, the characterization of TaS₂ and TaSe₂ thin layers is also conducted.
540 citations
TL;DR: The MoS2 /3DGN composite, used as an anode material for lithium-ion batteries, shows excellent electrochemical performance, which exhibits reversible capacities and high current density, indicating its good cycling performance.
Abstract: A novel composite, MoS2-coated three-dimensional graphene network (3DGN), referred to as MoS2/3DGN, is synthesized by a facile CVD method. The 3DGN, composed of interconnected graphene sheets, not only serves as template for the deposition of MoS2, but also provides good electrical contact between the current collector and deposited MoS2. As a proof of concept, the MoS2/3DGN composite, used as an anode material for lithium-ion batteries, shows excellent electrochemical performance, which exhibits reversible capacities of 877 and 665 mAh g−1 during the 50th cycle at current densities of 100 and 500 mA g−1, respectively, indicating its good cycling performance. Furthermore, the MoS2/3DGN composite also shows excellent high-current-density performance, e.g., depicts a 10th-cycle capacity of 466 mAh g−1 at a high current density of 4 A g−1.
TL;DR: In this paper, the Ni3S2@Ni(OH)2/3DGN was synthesized using a one-step hydrothermal reaction, and the morphological and structural evolution of the 3DGN has been investigated.
Abstract: A three-dimensional graphene network (3DGN) grown on nickel foam is an excellent template for the synthesis of graphene-based composite electrodes for use in supercapacitors. Ni(OH)2nanosheets coated onto single-crystal Ni3S2nanorods grown on the surface of the 3DGN (referred to as the Ni3S2@Ni(OH)2/3DGN) are synthesized using a one-step hydrothermal reaction. SEM, TEM, XRD and Raman spectroscopy are used to investigate the morphological and structural evolution of the Ni3S2@Ni(OH)2/3DGN. Detailed electrochemical characterization shows that the Ni3S2@Ni(OH)2/3DGN exhibits high specific capacitance (1277 F g−1 at 2 mV s−1 and 1037.5 F g−1 at 5.1 A g−1) and areal capacitance (4.7 F cm−2 at 2 mV s−1 and 3.85 F cm−2 at 19.1 mA cm−2) with good cycling performance (99.1% capacitance retention after 2000 cycles).
TL;DR: Different approaches for the fabrication of graphene and the preparation of graphene-modified electrodes for electrochemical sensors are introduced and recent research results on different graphene-based materials as an electrochemical platform for the detection of various biomolecules and chemicals are reviewed and compared.
Abstract: Graphene, one kind of emerging carbon nanomaterial, has attracted increasing attention recently. Due to its fascinating physical and electrochemical properties, graphene as a promising electrode material has been widely used in electrochemical sensing applications. In this review, different approaches for the fabrication of graphene and the preparation of graphene-modified electrodes for electrochemical sensors are introduced. Moreover, recent research results on different graphene-based materials as an electrochemical platform for the detection of various biomolecules and chemicals are reviewed and compared. More electrochemical studies on this novel material should show up in the near future.
TL;DR: Hollow hierarchical spheres self-organized from the ultrathin nanosheets of α-Fe2O3 were prepared by a simple process as discussed by the authors, which showed high Li ion storage and visible-light photocatalytic water oxidation performance.
Abstract: Hollow hierarchical spheres self-organized from the ultrathin nanosheets of α-Fe2O3 were prepared by a simple process These ultrathin nanosheet subunits possess an average thickness of around 35 nm and show preferential exposure of (110) facets Their Li ion storage and visible-light photocatalytic water oxidation performance are tested Such hierarchical nanostructures show high Li storage properties with good cycling stability and excellent rate capabilities The water oxidation catalytic activity is 70 μmol h−1 g−1 for O2 evolution under visible light irradiation and can be maintained for 15 hours The structural features of these α-Fe2O3 nanocrystals are considered to be important to lead to the attractive properties in both Li storage and photocatalytic water oxidation, eg hollow interior, ultrathin thickness and largely exposed active facets
TL;DR: A universal optical method has been developed for simple, rapid, and reliable identification of single- to quindecuple-layer (1L-15L) 2D nanosheets on Si substrates coated with 90 or 300 nm SiO2.
Abstract: The physical and electronic properties of ultrathin two-dimensional (2D) layered nanomaterials are highly related to their thickness. Therefore, the rapid and accurate identification of single- and few- to multi-layer nanosheets is essential to their fundamental study and practical applications. Here, a universal optical method has been developed for simple, rapid and reliable identification of single- to quindecuple-layer (1L-15L) 2D nanosheets, including graphene, MoS2, WSe2 and TaS2, on Si substrates coated with 90 nm or 300 nm SiO2. The optical contrast differences between the substrates and 2D nanosheets with different layer numbers were collected and tabulated, serving as a standard reference, from which the layer number of a given nanosheet can be readily and reliably determined without using complex calculation nor expensive instrument. Our general optical identification method will facilitate the thickness-dependent study of various 2D nanomaterials, and expedite their research toward practical applications.
TL;DR: In this paper, an atomic layer deposition (ALD) and sacrificial template-assisted hydrolysis were used to construct a hierarchical hollow TiO2@Fe2O3 nanostructures for the application of lithium ion battery.
Abstract: Hollow and hierarchical nanostructures have received wide attention in new-generation, high-performance, lithium ion battery (LIB) applications. Both TiO2 and Fe2O3 are under current investigation because of their high structural stability (TiO2) and high capacity (Fe2O3), and their low cost. Here, we demonstrate a simple strategy for the fabrication of hierarchical hollow TiO2@Fe2O3 nanostructures for the application as LIB anodes. Using atomic layer deposition (ALD) and sacrificial template-assisted hydrolysis, the resulting nanostructure combines a large surface area with a hollow interior and robust structure. As a result, such rationally designed LIB anodes exhibit a high reversible capacity (initial value 840 mAh g−1), improved cycle stability (530 mAh g−1 after 200 cycles at the current density of 200 mA g−1), as well as outstanding rate capability. This ALD-assisted fabrication strategy can be extended to other hierarchical hollow metal oxide nanostructures for favorable applications in electrochemical and optoelectronic devices.
TL;DR: In this paper, a new phototransistor based on the mechanically-exfoliated single-layer MoS2 nanosheet is fabricated and its light-induced electric properties are investigated in details.
Abstract: A new phototransistor based on the mechanically-exfoliated single-layer MoS2 nanosheet is fabricated and its light-induced electric properties are investigated in details. Photocurrent generated from the phototransistor is solely determined by the illuminated optical power at a constant drain or gate voltage. The switching behavior of photocurrent generation and annihilation can be completely finished within ca. 50 ms and it shows good stability. Especially, the single-layer MoS2 phototransistor exhibits a better photoresponsivity as compared with the graphene-based device. The unique characteristics of incident-light control, prompt photoswitching and good photoresponsivity from the MoS2 phototransistor pave an avenue to develop the single-layer semiconducting materials for multi-functional optoelectronic device applications in future.
TL;DR: In this paper, a universal optical method has been developed for simple, rapid, and reliable identification of single to quindecuple-layer (1L-15L) 2D nanosheets, including graphene, MoS2, WSe2, and TaS2.
Abstract: The physical and electronic properties of ultrathin two-dimensional (2D) layered nanomaterials are highly related to their thickness. Therefore, the rapid and accurate identification of single- and few- to multilayer nanosheets is essential to their fundamental study and practical applications. Here, a universal optical method has been developed for simple, rapid, and reliable identification of single- to quindecuple-layer (1L-15L) 2D nanosheets, including graphene, MoS2, WSe2, and TaS2, on Si substrates coated with 90 or 300 nm SiO2. The optical contrast differences between the substrates and 2D nanosheets with different layer numbers were collected and tabulated, serving as a standard reference, from which the layer number of a given nanosheet can be readily and reliably determined without using complex calculation or expensive instrument. Our general optical identification method will facilitate the thickness-dependent study of various 2D nanomaterials and expedite their research toward practical applications.
TL;DR: Graphene and its derivatives, such as graphene oxide (GO) and reduced GO (rGO), are ideal platforms for constructing graphene-based nanostructures for various applications as mentioned in this paper.
TL;DR: As a result of thermal annealing in air, the thinning of MoS2 nanosheet is possible due to its oxidation to form MoO3 .
Abstract: A simple thermal annealing method for layer thinning and etching of mechanically exfoliated MoS2 nanosheets in air is reported. Using this method, single-layer (1L) MoS2 nanosheets are achieved after the thinning of MoS2 nanosheets from double-layer (2L) to quadri-layer (4L) at 330 °C. The as-prepared 1L MoS2 nanosheet shows comparable optical and electrical properties with the mechanically exfoliated, pristine one. In addition, for the first time, the MoS2 mesh with high-density of triangular pits is also fabricated at 330 °C, which might arise from the anisotropic etching of the active MoS2 edge sites. As a result of thermal annealing in air, the thinning of MoS2 nanosheet is possible due to its oxidation to form MoO3 . Importantly, the MoO3 fragments on the top of thinned MoS2 layer induces the hole injection, resulting in the p-type channel in fabricated field-effect transistors.
TL;DR: In this article, a plasmonic enhancement of photocurrent in MoS2 field effect transistors with gold nanoparticles was demonstrated, with significantly enhanced photocurrent peaked at the resonant wavelength around 540 nm.
Abstract: The two-dimensional material, molybdenum disulfide (MoS2), has attracted considerable attention for numerous applications in optoelectronics. Here, we demonstrate a plasmonic enhancement of photocurrent in MoS2 field-effect-transistor decorated with gold nanoparticles, with significantly enhanced photocurrent peaked at the plasmon resonant wavelength around 540 nm. Our findings offer a possibility to realize wavelength selectable photodetection in MoS2 based phototransistors.
TL;DR: A flexible, all reduced graphene oxide non-volatile memory device, with lightly reduced GO as an active layer and highly reducing GO as both top and bottom electrodes, is fabricated by a full-solution process and its performance is characterized.
Abstract: A flexible, all reduced graphene oxide non-volatile memory device, with lightly reduced GO as an active layer and highly reduced GO as both top and bottom electrodes, is fabricated by a full-solution process and its performance is characterized. It provides a convenient method to construct other all-carbon devices.
TL;DR: "Solvophobic" and "electrostatic" interactions are proposed to account for the preferential growth of CP along metal oxides to form core/shell heterostructures to pave the way for developing new functional materials with enhanced properties or new applications.
Abstract: High-quality metal oxide/conducting polymer (CP) heterostructured nanoarrays are fabricated by controllable electrochemical polymerization of CP shells on preformed metal oxides nanostructures for both electrochromic and electrochemical energy storage applications. Coaxial and branched CP shells can be obtained on different backbones (nanowire, nanorod, and nanoflake) simply by controlling the electrodeposition time. “Solvophobic” and “electrostatic” interactions are proposed to account for the preferential growth of CP along metal oxides to form core/shell heterostructures. The coaxial TiO2/polyaniline core/shell nanorod arrays exhibit remarkable electrochromic performance with rich color changes, fast optical modulation, and superior cycling stability. In addition, the Co3O4/polyaniline core/shell nanowire arrays are evaluated as an anode material of Li ion battery and exhibit enhanced electrochemical property with higher and more stable capacity than the bare Co3O4 nanowires electrode. These unique org...
TL;DR: A novel label-free turn-on fluorescent strategy to detect alkaline phosphatase (ALP) under physiological conditions has been developed and may hold a potential application in diagnosis of ALP-related diseases or evaluation of ALP functions in biological systems.
Abstract: On the basis of the inhibition of double strand DNA (dsDNA)-templated fluorescent copper nanoparticles (CuNPs) by pyrophosphate (PPi), a novel label-free turn-on fluorescent strategy to detect alkaline phosphatase (ALP) under physiological conditions has been developed. This method relies on the strong interaction between PPi and Cu2+, which would hamper the effective formation of fluorescent CuNPs, leading to low fluorescence intensity. The ALP-catalyzed PPi hydrolysis would disable the complexation between Cu2+ and PPi, facilitating the formation of fluorescent CuNPs through the reduction by ascorbate in the presence of dsDNA templates. Thus, the fluorescence intensity was recovered, and the fluorescence enhancement was related to the concentration of ALP. This method is cost-effective and convenient without any labels or complicated operations. The present strategy exhibits a high sensitivity and the turn-on mode provides a high selectivity for the ALP assay. Additionally, the inhibition effect of phos...
TL;DR: A novel electrocatalyst of layered MoS2 supported on reduced graphene oxide (RGO) decorated with nano-sized tungsten carbide (WC) shows an enhanced catalytic performance in the hydrogen evolution reaction, which could be attributed to the presence of a conductive and electrocatalytically-active nano-WC dispersant.
TL;DR: The electrode fabricated from the SnS(2) nanoplate exhibits excellent lithium-ion battery performance with highly reversible capacity, good cycling stability and excellent capacity retention after 30 cycles.
Abstract: A facile, environmentally friendly, and economical synthetic route for production of large-amounts (gram scale) of two-dimensional (2D) layered SnS2 nanoplates is presented. The electrode fabricated from the SnS2 nanoplate exhibits excellent lithium-ion battery performance with highly reversible capacity, good cycling stability and excellent capacity retention after 30 cycles.
TL;DR: A mixed film consisting of 2D MoS₂ and graphene oxide (GO) nanosheets is used to fabricate memory devices and exhibits rewritable, nonvolatile, electrical bistable switching with low switching voltage and high ON/OFF current ratio.
Abstract: A mixed film consisting of 2D MoS₂ and graphene oxide (GO) nanosheets is used to fabricate memory devices. The conductive MoS₂ component in the MoS₂-GO film increases the film conductivity, thus facilitating oxygen migration in GO. The MoS₂-GO film-based device exhibits rewritable, nonvolatile, electrical bistable switching with low switching voltage (≤ 1.5 V) and high ON/OFF current ratio (≈ 10²).
TL;DR: In this article, a hierarchical graphene-wrapped TiO2@Co3O4 coaxial nanobelt arrays have been fabricated and further investigated as the electrode materials for lithium-ion batteries.
Abstract: As one of the most important research areas in lithium-ion batteries (LIBs), well-designed nanostructures have been regarded as key for solving problems such as lithium ion diffusion, the collection and transport of electrons, and the large volume changes during cycling processes. Here, hierarchical graphene-wrapped TiO2@Co3O4 coaxial nanobelt arrays (G-TiO2@Co3O4 NBs) have been fabricated and further investigated as the electrode materials for LIBs. The results show that the yielded G-TiO2@Co3O4 NBs possess a high reversible capacity, an outstanding cycling performance, and superior rate capability compared to TiO2 and TiO2@Co3O4 nanobelt array (TiO2@Co3O4 NBs) electrodes. The core–shell TiO2@Co3O4 NBs may contain many cavities and provide more extra spaces for lithium ion storage. The introduction of graphene into nanocomposite electrodes is favorable for increasing their electrical conductivity and flexibility. The integration of hierarchical core–shell nanobelt arrays and conducting graphene may induce a positive synergistic effect and contribute to the enhanced electrochemical performances of the electrode. The fabrication strategy presented here is facile, cost-effective, and can offer a new pathway for large-scale energy storage device applications.
TL;DR: In this article, a tutorial review of 2D inorganic nanomaterials with emphasis on their preparation methods, properties, and applications is presented, taking MoS2 as a typical example.
Abstract: Two-dimensional (2D) nanomaterials have received much attention in recent years, because of their unusual properties associated with their ultra-thin thickness and 2D morphology. Besides graphene which has aroused tremendous research interest, other types of 2D nanomaterials such as metal dichalcogenides have also been studied and applied in various applications including electronics, optoelectronics, energy storage devices, and so on. In this tutorial review, we will take MoS2 as a typical example to introduce the latest research development of 2D inorganic nanomaterials with emphasis on their preparation methods, properties and applications.