Welcome to ourNCNST

• Highly Efficient Visible-light-driven Photocatalytic Hydrogen Production of CdS-cluster-decorated Graphene Nanosheets
  J. Am. Chem. Soc. 2011, 133, 10878-10884. 
  (Top 100 Most Cited Chinese Papers Published in International Journals)
  The production of clean and renewable hydrogen through water splitting using photocatalysts has received much attention due to the increasing global energy crises. Our work has now demonstrated that a high efficiency of the photocatalytic H₂ production from water under visible-light irradiation can be achieved over CdS-cluster-decorated graphene nanosheets. The graphene-CdS nanocomposites reach a high H₂-production rate of 1.12 mmol·h^-1 at graphene content of 1.0 wt% and Pt 0.5 wt% under visible-light irradiation and an apparent quantum efficiency (QE) of 22.5% at wavelength of 420 nm. This high photocatalytic H₂-production activity is attributed predominantly to the presence of graphene, which serves as an electron collector and transporter to efficiently lengthen the lifetime of the photogenerated charge carriers from CdS nanoparticles. Furthermore, the unique features of graphene allow photocatalytic reactions to take place not only on the surface of semiconductor catalysts, but also on the graphene sheet, greatly enlarging the reaction space. This work highlights the potential application of graphene-based materials in the field of energy conversion.
  

• Noble Metal-Free Reduced Graphene Oxide-ZnxCd1-xS Nanocomposite with Enhanced Solar Photocatalytic H2-Production Performance
  Nano Lett. 2012, 12, 4584-4589.

Design and preparation of efficient artificial photosynthetic systems for harvesting solar energy by production of hydrogen from water splitting is of great importance from both theoretical and practical viewpoints. ZnS-based solid solutions have been fully proved to be an efficient visible-light driven photocatalysts, however, the H2-production rate observed for these solid solutions is far from exciting and sometimes an expensive Pt cocatalyst is still needed in order to achieve higher quantum efficiency. Here, for the first time we report the high solar photocatalytic H2-production activity over the noble metal-free reduced graphene oxide (RGO)-ZnxCd1−xS nanocomposite prepared by a facile coprecipitation-hydrothermal reduction strategy. The optimized RGO-Zn0.8Cd0.2S photocatalyst has a high H2-production rate of 1824 μmol h−1 g−1 at the RGO content of 0.25 wt % and the apparent quantum efficiency of 23.4% at 420 nm (the energy conversion efficiency is ca. 0.36% at simulated one-sun (AM 1.5G) illumination). The results exhibit significantly improved photocatalytic hydrogen production by 450% compared with that of the pristine Zn0.8Cd0.2S, and are better than that of the optimized Pt-Zn0.8Cd0.2S under the same reaction conditions, showing that the RGO-Zn0.8Cd0.2S nanocomposite represents one of the most highly active metal sulfide photocatalyts in the absence of noble metal cocatalysts. This work creates a green and simple way for using RGO as a support to enhance the photocatalytic H2-production activity of ZnxCd1−xS, and also demonstrates that RGO is a promising substitute for noble metals in photocatalytic H2-production.

 

• Visible-Light Photocatalytic H2-Production Activity of CuS/ZnS Porous Nanosheets Based on Photoinduced Interfacial Charge Transfer
  Nano Lett. 2011, 11, 4774-4779.

Visible light photocatalytic H2 production through water splitting is of great importance for its potential application in converting solar energy into chemical energy. In
this study, a novel visible-light-driven photocatalyst was designed based on photoinduced interfacial charge transfer (IFCT) through surface modification of ZnS porous nanosheets by CuS. CuS/ZnS porous nanosheet photocatalysts were prepared by a simple hydrothermal and cation exchange reaction between preformed ZnS(en)0.5 nanosheets and Cu(NO3)2. Even without a Pt cocatalyst, the as-prepared CuS/ZnS porous nanosheets reach a high H2-production rate of 4147 μmol h-1 g-1 at CuS loading content of 2 mol % and an apparent quantum efficiency of 20% at 420 nm. This high visible light photocatalyticH2-production activity is due to the IFCT from the valence band of ZnS to CuS, which causes the reduction of partial CuS to Cu2S and thus enhancesH2-production activity. This work not only shows a possibility for substituting low-cost CuS for noble metals in the photocatalytic H2 production but also for the first time exhibits a facile method for enhancing H2-production activity by photoinduced IFCT. 

　　 

• Controllable N-Doping of Graphene
  Nano Lett. 2010, 10(12), 4975-4980.
  (Highlighted by Nature Publishing Group Asia Materials)

Opening and tuning an energy gap in graphene are central to many electronic applications of graphene. Here we report N-doped graphene obtained by NH3 annealing after N+-ion irradiation of graphene samples. First, the evolution of the graphene microstructure was investigated following N+-ion irradiation at different fluences using Raman spectroscopy, showing that defects were introduced in plane after irradiation and then restored after annealing in N2 or in NH3. Auger Electron Spectroscopy (AES) of the graphene annealed in NH3 after irradiation showed N signal, however, no N signal was observed after annealing in N2. Last, the field-effect transistor (FET) was fabricated using N-doped graphene and monitored by the source-drain conductance and back-gate voltage (Gsd-Vg) curves in the measurement. The transport property changed compared to that of the FET made by intrinsic graphene, i.e., the Dirac point position moved from positive Vg to negative Vg, indicating the transition of graphene from p-type to n-type after annealing in NH3. Our approach, which provides a physical mechanism for the introduction of defect and subsequent hetero dopant atoms into the graphene material in a controllable fashion, will be promising for producing graphene-based devices for multiple applications.

•  Label-free attomolar detection of proteins using integrated nanoelectronic and electrokinetic devices
  Small 2010, 6(8), 967-973.

High-sensitivity screening of biomarkers is critical to areas ranging from early disease detection and diagnosis to bioterrorism surveillance. Here we report the development of integrated nanoelectronic and electrokinetic devices for label-free attomolar detection of proteins. Electrically-addressable silicon nanowire field-effect transistors and electrodes for electrokinetic transport are integrated onto a common sensor chip platform, and the nanowire devices are subsequently functionalized with receptors for selective biomarker detection. Nanowire devices modified with monoclonal antibody for prostate specific antigen exhibit close to a 10^4 increase in sensitivity due to streaming dielectrophoresis and corresponding electrostatic contribution to the binding affinity after alternating current electric field application. The devices are also modified with receptors for cholera toxin sub-unit B and achieve a similar enhancement. These results show general applicability of this method, and could open up opportunities in early stage disease detection and the analysis of proteins from single cells. 

 

• Strong Two-Photon-Induced Fluorescence from Photostable, Biocompatible Nitrogen-Doped Graphene Quantum Dots for Cellular and Deep-Tissue Imaging　
  Nano Lett. 2013, 13, 2436-2441.

Bright two-photon fluorescent probes are highly desirable to be able to optically probe biological activities deep inside living organisms with larger imaging depth, minor autofluorescence background, and less photodamage. In this study, we report the biocompatible nitrogen-doped graphene quantum dots (N-GQDs) as efficient two-photon fluorescent probes for cellular and deep-tissue imaging. The N-GQD was prepared by a facile solvothermal method using dimethylformamide as solvent and nitrogen source. The two-photon absorption cross-section of N-GQD reaches 48,000 Göppert-Mayer units, which far surpasses that of the organic dyes and is comparable to that of the high performance semiconductor QDs, achieving the highest value ever reported for carbon-based nanomaterials. More importantly, a study of penetration depth in tissue phantom demonstrates that the N-GQD can achieve a large imaging depth of 1,800 μm, significantly extending the fundamental two-photon imaging depth limit. In addition, the N-GQD is non-toxic to living cells and exhibits super photostability under repeated laser irradiation. The high two-photon absorption cross-section, large imaging depth, good biocompatibility, and extraordinary photostability render the N-GQD an attractive alternative probe for efficient two-photon imaging in biological and biomedical applications.