Hao Zhang

P25-Graphene Composite as a High Performance Photocatalyst

Herein we obtained a chemically bonded TiO(2) (P25)-graphene nanocomposite photocatalyst with graphene oxide and P25, using a facile one-step hydrothermal method. During the hydrothermal reaction, both of the reduction of graphene oxide and loading of P25 were achieved. The as-prepared P25-graphene photocatalyst possessed great adsorptivity of dyes, extended light absorption range, and efficient charge separation properties simultaneously, which was rarely reported in other TiO(2)-carbon photocatalysts. Hence, in the photodegradation of methylene blue, a significant enhancement in the reaction rate was observed with P25-graphene, compared to the bare P25 and P25-CNTs with the same carbon content. Overall, this work could provide new insights into the fabrication of a TiO(2)-carbon composite as high performance photocatalysts and facilitate their application in the environmental protection issues.

Graphene and its derivatives for the development of solar cells, photoelectrochemical, and photocatalytic applications

Due to its unique atom-thick 2D structure and remarkable physicochemical properties, graphene has been making a profound impact in many areas of science and technology. In particular, a great deal of recent attention has been attracted to explore graphene and its derivatives for photoelectrochemical applications, with the potential to harness graphenes excellent properties for opening up new opportunities in next generation photoelectrochemical systems. Over the past few years, much work has been done in the design and preparation of novel graphene-based materials for a wide range of applications in photoelectrochemistry, ranging from photoelectrochemical solar cells, photocatalytic decomposition of organic pollutants, photocatalytic splitting of H2O, photocatalytic conversion for fuels, and so on. In this review article, we summarize the state of research on graphene-based materials from the standpoint of photoelectrochemistry. The prospects and further developments in this exciting field of graphene-based materials are also discussed.

Biofunctional Titania Nanotubes for Visible-Light-Activated Photoelectrochemical Biosensing

The photoelectrochemical detection method is a newly developed and promising analytical method for biosensing. In this work, photoactive TiO(2) nanotubes (TNs) immobilized with horseradish peroxidase (HRP) were prepared and used for visible-light-activated photoelectrochemical detection of H(2)O(2). TNs were fabricated by anodic oxidation of titanium substrate and possessed large surface areas, good uniformity and conformability, and high porosity, which were favorable for enzyme immobilization. Electrochemical and UV-vis spectroscopic measurements demonstrated that TNs provided excellent matrixes for the adsorption of HRP and the adsorbed HRP effectively retained its bioactivities. The photocurrent spectra of HRP/TNs showed an obvious photocurrent response under visible-light irradiation (lambda > or = 400 nm), suggesting the possibility of photoelectrochemical detection of H(2)O(2) upon visible-light irradiation. It was found that the generated photocurrent of HRP/TNs at 400 nm was significantly enhanced after the addition of H(2)O(2) in solution and the photocurrent intensity increased with the increase of the H(2)O(2) concentration. The HRP/TNs electrode displayed a linear range of 5.0 x 10(-7)-3.5 x 10(-5) M and a low detection limit of 1.8 x 10(-7) M for H(2)O(2) determination. Thus, the protein-immobilized TNs would be expected to be a novel photoactive material for photoelectrochemical biosensing. This proposed strategy may open a new avenue for the applications of nanotubular TiO(2) in visible-light-activated photoelectrochemical biosensing, which could largely reduce the destructive effect of UV light and the photoholes generated by illuminated TiO(2) to biomolecules.

Hydrogen evolution from water using semiconductor nanoparticle/graphene composite photocatalysts without noble metals

Semiconductor nanoparticle/graphene composite photocatalysts containing semiconductor CdS or TiO2 nanoparticles are fabricated by one-pot solution methods and their structures are characterized. The photocatalytic hydrogen-generating capabilities of the composite photocatalysts are investigated in the presence of sacrificial reagent and compared with those of the same semiconductor materials with platinum as a co-catalyst under the same conditions. The results obtained by the measurements of time-resolved emission spectra, photocurrent generated response and electrochemical impedance spectra revealed that graphene attached to semiconductor surfaces can efficiently accept and transport electrons from the excited semiconductor, suppressing charge recombination and improving interfacial charge transfer processes. The semiconductor nanoparticle/graphene photocatalysts displayed higher activity for photocatalytic hydrogen evolution, which can be compared with the hydrogen-generating efficiency of systems containing the well-known Pt co-catalyst. This work provides an inexpensive means of harnessing solar energy to achieve highly efficient hydrogen evolution without noble metals.

Energy-efficient photodegradation of azo dyes with TiO2 nanoparticles based on photoisomerization and alternate UV-visible light.

Herein, we demonstrated a UV-vis light alternate photocatalysis (UVLAP) strategy in the photodegradation of azo dyes. The UVLAP of azo dyes over TiO(2) catalysts exhibited significantly higher energy efficiency than the conventional UV process by 40%, which was attributed to the photoisomerization of azo dyes and the resulting diversity of dyes cis and trans states in interfacial properties, including conductance and spatial effects. This UVLAP strategy could contribute to the energy-saving photodegradation of azo dyes and other pollutants with photoisomerization properties and facilitate the practical application of TiO(2) in the environmental remediation.

An excellent enzyme biosensor based on Sb-doped SnO2 nanowires

Sb-doped SnO(2) nanowires were synthesized via thermal evaporation. Scanning electron microscopic, transmission electron microscopic, X-ray diffraction, current-voltage, and electrochemical impedance spectroscopy experiments have been used to characterize the structural and electrical behaviors of the nanowires. A mediator-free horseradish peroxidase-based H(2)O(2) biosensor was constructed through the Sb-doped SnO(2) nanowires used as the immobilization matrix for the enzymes. In comparison with the undoped SnO(2) nanowires, Sb-doped SnO(2) nanowires exhibited excellent electron transfer properties for the enzymes and higher electroactivity toward H(2)O(2). The biosensors displayed good performance along with high sensitivity, wide linear range, and long-term stability. Those can be attributed to the enhanced carrier density arising from Sb doping and biocompatible microenvironment provided by the Sb-doped SnO(2) nanowires. This study demonstrated that Sb-doped SnO(2) nanowires were promising platform for the construction of mediator-free biosensors and provided new further fundamental insights into the study of nanoscience and nanodevices.

Ultrahigh-efficiency photocatalysts based on mesoporous Pt–WO3 nanohybrids

A reliable nanocasting method has been developed to synthesize mesoporous hybrids of platinum (Pt) nanoparticles decorating tungsten trioxide (WO3). The process began with modification of the SBA-15 template with carbon polymers and Pt nanoparticles accompanied by adsorption of W(6+), which was then converted into m-Pt-WO3 composites by heat treatment and subsequent template removal. The synthetic strategy can be easily extended to prepare other mesoporous nanohybrids with metal oxide loaded precious metal composites. Comprehensive characterizations suggest that the as-developed m-Pt-WO3 nanohybrid exhibits unique properties with mesoporous structure, excellent crystalline structure, and high surface area. When the photocatalytic properties of m-Pt-WO3 nanohybrids were systematically investigated, it was revealed that the m-Pt-WO3 nanohybrids showed great promise for degrading the organic dye under visible light irradiation, which shows an excellent photocatalytic activity that far exceeded those of pure phase mesoporous WO3 and commercial TiO2 (P25), and was 10-fold more active than that of the bulk Pt-WO3 catalyst. The as-developed synthetic route opens up a new avenue for designing mesoporous hybrid materials for various applications benefiting from the unique porous structure, high surface area, and synergistic effects among constituents.