Showing papers by "Hua Zhang published in 2011"
TL;DR: The synthesis, characterization, properties, and applications of graphene-based materials are discussed and the promising properties together with the ease of processibility and functionalization make graphene- based materials ideal candidates for incorporation into a variety of functional materials.
Abstract: Graphene, a two-dimensional, single-layer sheet of sp(2) hybridized carbon atoms, has attracted tremendous attention and research interest, owing to its exceptional physical properties, such as high electronic conductivity, good thermal stability, and excellent mechanical strength. Other forms of graphene-related materials, including graphene oxide, reduced graphene oxide, and exfoliated graphite, have been reliably produced in large scale. The promising properties together with the ease of processibility and functionalization make graphene-based materials ideal candidates for incorporation into a variety of functional materials. Importantly, graphene and its derivatives have been explored in a wide range of applications, such as electronic and photonic devices, clean energy, and sensors. In this review, after a general introduction to graphene and its derivatives, the synthesis, characterization, properties, and applications of graphene-based materials are discussed.
2,246 citations
TL;DR: The common feature of these materials is that the bulk material forms are layeredstructures with strong covalent bonding in each layer and weak van der Waals forces between the layers.
Abstract: The common featureof these materials is that the bulk material forms are layeredstructures with strong covalent bonding in each layer andweak van der Waals forces between the layers. Therefore,single or few-layer nanosheets of these materials can beobtained by using adhesive tapes for mechanical cleavage.
1,596 citations
TL;DR: Recently, nanocomposites made by graphene and transition metal oxides have attracted wide attention in the field of supercapacitors due to their synergetic effect, arising from the combination of the redox reaction of metal oxide with the high surface area/conductivity of graphene, to improve the electrochemical performance.
Abstract: The supercapacitor is considered as a promising candidate for energy storage due to its high power performance, long life cycle, and low maintenance cost. [ 3 ] Pseudocapacitive materials, such as transition metal oxides, are being explored for use in supercapacitors with a large specifi c capacitance and high energy density. [ 4 ] However, pseudocapacitors often suffer from the low rate capability and poor stability, because the active materials are usually insulating or semiconducting, which hinders the fast electron transport required for high charge/discharge rates. As an ideal matrix, graphene is commonly used for growth of functional nanomaterials. [ 1a , 2c , 5 ] Recently, nanocomposites made by graphene and transition metal oxides have attracted wide attention in the fi eld of supercapacitors due to their synergetic effect, arising from the combination of the redox reaction of metal oxides with the high surface area/conductivity of graphene, to improve the electrochemical performance. [ 6 ]
986 citations
TL;DR: This report reports the first in situ synthesis of dispersible hcp Au square sheets on graphene oxide sheets, which exhibit an edge length of 200-500 nm and a thickness of ~ 2.4 nm (~ 16 Au atomic layers).
Abstract: Solid gold is usually most stable as a face-centred cubic (fcc) structure. To date, no one has synthesized a colloidal form of Au that is exclusively hexagonal close-packed (hcp) and stable under ambient conditions. Here we report the first in situ synthesis of dispersible hcp Au square sheets on graphene oxide sheets, which exhibit an edge length of 200-500 nm and a thickness of ~ 2.4 nm (~ 16 Au atomic layers). Interestingly, the Au square sheet transforms from hcp to a fcc structure on exposure to an electron beam during transmission electron microscopy analysis. In addition, as the square sheet grows thicker (from ~ 2.4 to 6 nm), fcc segments begin to appear. A detailed experimental analysis of these structures shows that for structures with ultrasmall dimensions (for example, <~ 6 nm thickness for the square sheets), the previously unobserved pure hcp structure becomes stable and isolable.
523 citations
TL;DR: In this article, a facile approach to synthesize nanocomposites with Fe3O4 nanopaticles (NPs) attached to reduced graphene oxide (rGO) sheets by a solvothermal process was reported.
Abstract: We report a facile approach to synthesize nanocomposites with Fe3O4 nanopaticles (NPs) attached to reduced graphene oxide (rGO) sheets by a solvothermal process, which combines the growth of Fe3O4 NPs and the reduction of GOs in one single step. These Fe3O4/rGO nanocomposites were further used to fabricate thin film supercapacitor electrodes by using a spray deposition technique without the addition of insulating binders. It was found that the Fe3O4/rGO nanocomposites showed much higher specific capacitances than that of either pure rGO or pure Fe3O4 NPs. We further carried out electrochemical characterization of the Fe3O4/rGO nanocomposites with different Fe3O4 : rGO weight ratios (e.g. IFe3O4 : rGO) and showed that Fe3O4/rGO nanocomposites with IFe3O4 : rGO = 2.8 exhibited the highest specific capacitance of 480 F g−1 at a discharge current density of 5 A g−1 with the corresponding energy density of 67 W h kg−1 at a power density of 5506 W kg−1. These Fe3O4/rGO nanocomposites also showed stable cycling performance without any decrease in the specific capacitance after 1000 charge/discharge cycles.
411 citations
TL;DR: In this paper, a hybrid nanostructure of porous cobalt monoxide nanowire @ ultrathin nickel hydroxidenitrate nanoflake is directly synthesized on a 3D nickel foam by a facile two-step hydrothermal route.
Abstract: A new hybrid nanostructure of porous cobalt monoxide nanowire @ ultrathin nickel hydroxidenitrate nanoflake is directly synthesized on a 3D nickel foam by a facile two-step hydrothermal route, which demonstrates a specific capacitance of ∼798.3 F g−1 at the current density of ∼1.67 A g−1 and good rate performance when used as electrode material for supercapacitors. The capacitance loss is less than 5% after 2000 charge–discharge cycles.
388 citations
TL;DR: An environment-friendly approach to synthesize transition metal oxide nanoparticles (NPs)/reduced graphene oxide (rGO) sheets hybrids by combining the reduction of grapheneoxide (GO) with the growth of metal oxide NPs in one step is reported, which can be a promising route to produce advanced electrode materials for Li-ion batteries.
Abstract: We report an environment-friendly approach to synthesize transition metal oxide nanoparticles (NPs)/reduced graphene oxide (rGO) sheets hybrids by combining the reduction of graphene oxide (GO) with the growth of metal oxide NPs in one step. Either Fe2O3 or CoO NPs were grown onto rGO sheets in ethanol solution through a solvothermal process, during which GOs were reduced to rGO without the addition of any strong reducing agent, e.g.hydrazine, or requiring any post-high-temperature annealing process. The GO or rGO during the precipitation of metal oxide NPs may act as heterogeneous nucleation seeds to facilitate the formation of small crystal grains. This may allow more efficient diffusion of Li ions and lead to high specific capacities. These metal oxide NPs–rGO hybrids were used as anodes for Li-ion batteries, which showed high capacities and excellent charge–discharge cycling stability in the voltage window between 0.01 and 3.0 V. For example, Fe2O3 NPs/rGO hybrids showed specific capacity of 881 mA h g−1 in the 90th cycle at a discharge current density of 302 mA g−1 (0.3 C), while CoO NPs/rGO hybrids showed a lower capacity of 600 mA h g−1 in the 90th cycle at a discharge current density of 215 mA g−1 (0.3 C). These nanohybrids also show excellent capacities at high C rate currents, e.g. 611 mA h g−1 for Fe2O3/rGO sample in the 300th cycle at 2014 mA g−1 (2 C). Such synthesis technique can be a promising route to produce advanced electrode materials for Li-ion batteries.
366 citations
TL;DR: The fabrication of all-reduced graphene oxide (rGO) thin film transistors by a combination of solution-processed rGO electrodes with a micropatterned r GO channel are reported, and their applications in biosensing are studied to show good sensitivity in detecting proteins in the physiological buffer.
Abstract: Owing to their unique thickness-dependent electronic properties, together with perfect flexibility and transparency, graphene and its relatives make fantastic material for use in both active channel and electrodes in various electronic devices On the other hand, the electronic sensors based on graphene show high potential in detection of both chemical and biological species with high sensitivity In this contribution, we report the fabrication of all-reduced graphene oxide (rGO) thin film transistors by a combination of solution-processed rGO electrodes with a micropatterned rGO channel, and then study their applications in biosensing Our all-rGO devices are cost-effective, highly reproducible, and reliable The fabricated electronic sensor is perfectly flexible with high transparency, showing good sensitivity in detecting proteins in the physiological buffer As a proof of concept, fibronectin as low as 05 nM was successfully detected, which is comparable with the previously reported protein sensors b
310 citations
TL;DR: A field-effect transistor sensor using micropatterned, protein-functionalized rGO film as the conducting or sensing channel is presented, able to detect various metal ions in real-time with high sensitivity.
Abstract: The electrical property of graphene is highly sensitive to its local environment, which makes graphene an ideal channel material in electronic sensors. Reduced graphene oxide (rGO) has been used as the desirable alternative to the pristine graphene due to its low-cost, solution-processable, and scalable production. In this paper, we present a field-effect transistor sensor using micropatterned, protein-functionalized rGO film as the conducting or sensing channel. Such a nanoelectronic sensor is able to detect various metal ions in real-time with high sensitivity.
276 citations
TL;DR: In this paper, a method for fabrication of an efficient surface enhanced Raman scattering (SERS) substrate by combination of metallic nanostructures and graphene, which shows dramatic Raman enhancement and efficient adsorption of aromatic molecules.
Abstract: We report a method for fabrication of an efficient surface enhanced Raman scattering (SERS) substrate by combination of metallic nanostructures and graphene, which shows dramatic Raman enhancement and efficient adsorption of aromatic molecules. As an example, the fabricated Ag or Au nanoparticle (NP)-decorated reduced graphene oxide (rGO) on Si substrate is used as an efficient SERS substrate to detect the adsorbed aromatic molecules with a low detection limit at nM level. Systematic studies on the effects of NP size and substrate morphology on Raman enhancement are presented. This method might be useful for the future application in detection of biomolecules, such as DNA and proteins.
249 citations
TL;DR: Graphene-CNT hybrid materials were synthesized by simple one-step chemical vapor deposition (CVD) using ethanol as a precursor as discussed by the authors, where a graphene film grows uniformly on the substrate while CNTs sprout out from Si NPs to form a network on top.
TL;DR: In this paper, a facile chemical approach has been developed to produce nanohybrids with ultrathin Co oxides nanowall arrays on reduced graphene oxide (rGO) sheets.
Abstract: A facile chemical approach has been developed to produce nanohybrids with ultrathin Co oxides nanowall arrays on reduced graphene oxide (rGO) sheets. The Co oxides exhibited porous structure. The porosity of the Co oxide/rGO nanohybrids and the grain size of the Co oxides could be tailored by varying the annealing temperature, which directly affected their performance as Li-ion battery electrodes. When tested as anode materials for Li-ion batteries, these Co oxide/rGO nanohybrids showed structural-process-dependent performances. For example, Co3O4/rGO hybrids obtained by annealing α-Co(OH)2/rGO at 350 °C showed a high specific capacity of 673 mAh g−1 after 100 cycles at a discharge current density of 180 mA g−1 (0.2 C), which was better than Co3O4/rGO samples obtained at other annealing temperatures. Similarly, CoO/rGO hybrids obtained by pyrolysis of α-Co(OH)2/rGO at 350 °C showed optimum performance, as compared to that of CoO/rGO samples obtained at other annealing temperatures, with a capacity of 732 ...
TL;DR: Reduced graphene oxide (rGO)-modified glassy carbon electrode is used to detect the methicillin-resistant Staphylococcus aureus (MRSA) DNA by using electrochemical impedance spectroscopy and provides a new method to detect DNA with high sensitivity (10(-13)M, i.e., 100 fM) and selectivity.
TL;DR: It is shown that the maximum thermopower of few layers graphene (FLG) films could be greatly enhanced up to ∼700 μV/K after oxygen plasma treatment, due to generation of local disordered carbon that opens the band gap.
Abstract: Inthiswork,weshowthatthemaximumthermopoweroffewlayersgraphene(FLG) films could be greatly enhanced up to ∼700 μV/K after oxygen plasma treatment. The electrical conductivities of these plasma treated FLG films remain high, for example, ∼10 4 S/m, which results in power factors as high as ∼4.5 � 10 � 3 WK � 2 m � 1 . In comparison, the pristine FLG films show a maximum thermopower of ∼80 μV/K with an electrical conductivity of ∼5 � 10 4 S/m. The proposed mechanism is due to generation of local disordered carbon that opens the band gap. Measured thermopowers of single-layer graphene (SLG) films and reduced graphene oxide (rGO) films were in the range of � 40 to 50 and � 10 to 20 μV/K, respectively. However, such oxygen plasma treatment is not suitable for SLG and rGO films. The SLG films were easily destroyed during the treatment while the electrical conductivity of rGO films is too low.
TL;DR: A water-soluble neutral fluorescent conjugated oligomer is integrated with graphene oxide to form a hybrid nanoprobe with extremely low fluorescence background due to the robust quenching capability of GO.
Abstract: A water-soluble neutral fluorescent conjugated oligomer (FBT) is integrated with graphene oxide (GO) to form a hybrid nanoprobe with extremely low fluorescence background due to the robust quenching capability of GO. The contact between GO and FBT can be effectively shielded by Concanavalin A because of the strong specific protein-carbohydrate interaction, which ultimately allows light-up visual detection of lectin and Escherichia coli.
TL;DR: Analysis of all four sulphur isotopes for pyrites in sedimentary rocks from the Meishan section in South China indicate that episodic shoaling of anoxic water may have contributed to the profound biodiversity crisis before the final catastrophe.
Abstract: Global fossil data show that profound biodiversity loss preceded the final catastrophe that killed nearly 90% marine species on a global scale at the end of the Permian. Many hypotheses have been proposed to explain this extinction and yet still remain greatly debated. Here, we report analyses of all four sulphur isotopes (32S, 33S, 34S and 36S) for pyrites in sedimentary rocks from the Meishan section in South China. We observe a sulphur isotope signal (negative δ34S with negative Δ33S) that may have resulted from limitation of sulphate supply, which may be linked to a near shutdown of bioturbation during shoaling of anoxic water. These results indicate that episodic shoaling of anoxic water may have contributed to the profound biodiversity crisis before the final catastrophe. Our data suggest a prolonged deterioration of oceanic environments during the Late Permian mass extinction. A final catastrophe killed 90% of marine species at the end of the Permian period, but significant biodiversity loss preceded this event. In this study, sulphur isotope evidence suggests that incursion of anoxic water into shallow regions may have contributed to biodiversity loss.
TL;DR: In this article, a CNT/Ni hybrid nanostructured arrays (NSAs) are synthesized on a stainless steel substrate through a one-step chemical-vapor-deposition (CVD) method using nullaginite NSAs as starting materials.
Abstract: CNT/Ni hybrid nanostructured arrays (NSAs) are synthesized on a stainless steel substrate through a one-step chemical-vapor-deposition (CVD) method using nullaginite NSAs as starting materials. During the CVD process, the nullaginite NSAs are transformed into Ni NSAs, which can further act as the catalysts to initiate the simultaneous in situ growth of CNTs on their surface, leading to an intriguing three-dimensional (3D) hybrid nanostructure. The resulting ordered CNT/Ni NSAs are highly porous and conductive, which are believed to be quite favorable for electrochemical applications. As a proof-of-concept demonstration of the functions of such a well-designed architecture in energy storage, the CNT/Ni NSAs are tested as the working electrodes of electrochemical capacitors (ECs). After being activated, the composite electrode exhibits both well-defined pseudo-capacitive and electrical double-layer behavior with high areal capacitance (up to ∼0.901 F cm−2), excellent cyclability (nearly 100% capacitance retention after 5000 cycles), and outstanding rate capability. The unique interconnected hybrid structure and virtues inherited from the conductive CNT network and porous NSAs are believed to be responsible for the excellent performance.
TL;DR: It is shown that the anti-amyloidogenic compound resveratrol inhibits oligomerization and amyloid formation via binding to histidine 18, supporting the finding that this residue is crucial for on-pathway oligomer formation.
TL;DR: In this paper, a 1D coronene nanowires with the structure of quartz/ITO/p-coronene nanowsires/n-SiC/Ti (10 nm)/Au (120 nm) has been fabricated, and strong electroluminescence (EL) was detected with a forward bias at 20 V.
Abstract: Coronene nanowires were prepared through the reprecipitation method. The as-prepared one-dimensional (1D) nanostructures were characterized by UV-vis, fluorescence spectra, X-ray diffraction (XRD), optical microscopy, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). We found that coronene nanowires in aqueous solution emitted strong green light instead of blue light for coronene molecules in THF solution. Moreover, the thin film of coronene nanowires on rGO/SiO2/Si electrode produced a strong photocurrent response upon irradiation. In addition, a heterojunction light emitting diode (LED) device with the structure of quartz/ITO/p-coronene nanowires/n-SiC/Ti (10 nm)/Au (120 nm) has been fabricated. The strong electroluminescence (EL) emission centered at ∼430 nm was detected with a forward bias at 20 V. Our result showed that the use of organic nanowires as the p-type hole injection layer could produce diodes with performance better than those with only inorganic thin-film structures.
TL;DR: A water-soluble pyrene-based butterfly shaped conjugated oligoelectrolyte is synthesized and integrated with graphene oxide to form a label-free assay for heparin detection, demonstrating a new synthetic strategy to develop GO-based chemical and biological sensing without the employment of dye-labeled biomolecules.
Abstract: A water-soluble pyrene-based butterfly shaped conjugated oligoelectrolyte (TFP) is synthesized and integrated with graphene oxide (GO) to form a label-free assay for heparin detection. Efficient fluorescence quenching occurs between TFP and GO because of strong electrostatic and π–π interactions, leading to nearly dark emission in the absence of analytes. Addition of heparin into TFP solution significantly minimizes the fluorescence quenching of GO toward TFP, which is less effective for the heparin analogues, such as hyaluronic acid and chondroitin 4-sulfate. As a consequence, the solution emits strong yellow fluorescence only in the presence of heparin, which allows for light-up visual discrimination of heparin from its analogues. Moreover, the linear light-up response of the TFP/GO integrated assay enables heparin quantification in the range of 0–1.76 U/mL with a limit of detection of 0.046 U/mL, which is practical for heparin monitoring during postoperative and long-term care. This study thus demonstr...
TL;DR: Wang et al. as mentioned in this paper developed a spatial multicriteria method to evaluate the nitrogen loss potential at the basin level, which is a low-effort approach since the required data is either already available in a global context or easily produced with limited inputs.
TL;DR: The results show that this type of heteroacene could be a good candidate as a charge-transport material in organic semiconductor devices and investigated a simple heterojunction photovoltaic device based on BIQ 3 as an electron donor and [6,6]-phenyl-C(61) butyric methyl ester as a electron acceptor.
Abstract: We report the synthesis and characterization of a novel, stable and blue heteroacene, 2-methyl-1,4,6,7,8,9-hexaphenylbenz(g)isoquinolin-3(2H)-one (BIQ ). BIQ , with its relatively small π framework, has an absorption λmax at 620 nm, which is larger than that of pentacene (λmax=582 nm), but BIQ is more stable. The solutions of BIQ are observed without any noticeable photobleaching on the order of days. In the solid state, it is very stable at ambient conditions and can be stored indefinitely. Owing to its pyridone end unit, BIQ can display different resonance structures in different solvents (aprotic and protic) or Lewis acids to give different colors. The attractive stability exhibited by BIQ is very desirable in organic semiconductor devices. Herein, we investigated a simple heterojunction photovoltaic device based on BIQ as an electron donor and [6,6]-phenyl-C61 butyric methyl ester as an electron acceptor. Our results show that this type of heteroacene could be a good candidate as a charge-transport material in organic semiconductor devices.
TL;DR: SEM study indicates that the well-organized structure (nanowires) is an important factor in enhancing the performance of OLED devices.
TL;DR: In this paper, uncertainties in simulated hydrological responses were derived from the implementations of different integrated downscaling methods, reflecting our imperfect knowledge of the future climate, and were amplified through the incorporation of different weather generators.
TL;DR: The as-synthesized semiconducting Ag-TCNQ nanowires show good performance in nonvolatile memory devices with multiple write-read-erase-read (WRER) cycles in air.
Abstract: The chemical reaction between Ag nanoparticles (Ag NPs) and 7,7′,8,8′- tetracycanoquinodimethane (TCNQ) microparticles (MPs) in aqueous solution for the formation of Ag-NP-decorated Ag–TCNQ nanowires is reported. Based on the results obtained by UV–vis spectroscopy and scanning electron microscopy (SEM), it is proposed that the reaction between Ag NPs and TCNQ MPs includes three stages, namely, aggregation of NPs and MPs, diffusion and reaction between NPs and MPs, and formation of Ag–TCNQ nanowires. The as-synthesized semiconducting Ag–TCNQ nanowires show good performance in nonvolatile memory devices with multiple write-read-erase-read (WRER) cycles in air.
TL;DR: In this article, the authors demonstrate the electrochemical deposition of Cl-doped n-type Cu2O (Cl-Cu2O) on reduced graphene oxide (rGO) electrodes, and show significant implications in tailoring the properties of materials deposited on rGO electrodes by using electrochemical methods.
Abstract: Reduced graphene oxide (rGO) electrodes can be applied for the electrochemical deposition of various semiconductor oxides. In this study, we demonstrate the electrochemical deposition of Cl-doped n-type Cu2O (Cl–Cu2O) on rGO electrodes. The structure and properties of the deposited Cl–Cu2O have been investigated extensively. Moreover, the effect of Cl doping on the carrier concentration and photocurrent of Cl–Cu2O has also been investigated. Our study shows significant implications in tailoring the properties of materials deposited on rGO electrodes by using electrochemical methods.
TL;DR: This review provides an overview of a range of techniques commonly used for surface patterning, with a particular stress on the patterning and applications of biomolecules.
Abstract: Patterning substrates with versatile chemical functionalities from micro- to nanometer scale is a long-standing and interesting topic. This review provides an overview of a range of techniques commonly used for surface patterning. The first section briefly introduces conventional micropatterning tools, such as photolithography and microcontact printing. The second section focuses on the currently used nanolithographic techniques, for example, scanning probe lithography (SPL), and their applications in surface patterning. Their advantages and disadvantages are also demonstrated. In the last section, dip-pen nanolithography (DPN) is emphatically illustrated, with a particular stress on the patterning and applications of biomolecules.
TL;DR: In this article, two novel shapes of 9,10-diphenylanthracene (DPA) micro/nanostructures: octahedron and sphere together with microrod and nanowire have been synthesized via a surfactant-assisted self-assembling process.
Abstract: Two novel shapes of 9,10-diphenylanthracene (DPA) micro/nanostructures: octahedron and sphere together with microrod and nanowire have been synthesized via a surfactant-assisted self-assembling process. These micro/nanostructures have been characterized by UV−vis, fluorescence spectra, X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and transmission electron microscope (TEM). Our results indicated that the absorption and emission spectra of as-prepared particles were slightly blue-shift when the shape of DPA particles changed from octahedron to microrod and finally to nanowire. This result could be explained by the different growth directions of DPA micro/nanostructures. To study the relationship between shape and devices’ performance, the heterojunction light emitting diode (LED) devices of quartz/ITO/organic particles/n-SiC/Ti(10 nm)/Au(120 nm) have been prepared. The testing results showed that the different shapes of DPA micro/nanostructures did affect the performance of ...