Lianzhou Wang

Titania-based photocatalysts-crystal growth, doping and heterostructuring

Semiconductor photocatalysts have important applications in renewable energy and environment fields. To overcome the serious drawbacks of low efficiency and narrow light-response range in most stable semiconductor photocatalysts, many strategies have been developed in the past decades. This review attempts to provide a comprehensive update and examination of some fundamental issues in titania (TiO2)-based semiconductor photocatalysts, such as crystal growth, doping and heterostructuring. We focus especially on recent progress in exploring new strategies to design TiO2-based photocatalysts with unique structures and properties, elucidating the chemical states and distribution of dopants in doped TiO2, designing and fabricating integrated heterostructure photocatalysts with different charge-carrier transfer pathways, and finally identifying the key factors in determining the photocatalytic efficiency of titania-based photocatalysts.

Enhanced photocatalytic hydrogen evolution by prolonging the lifetime of carriers in ZnO/CdS heterostructures

Coupled ZnO/CdS heterostructures based on the Z-scheme mechanism are demonstrated to be highly active photocatalysts for H(2) evolution under simulated solar light irradiation due to the greatly prolonged lifetime of photoexcited carriers.

Nitrogen Doped Sr2Ta2O7 Coupled with Graphene Sheets as Photocatalysts for Increased Photocatalytic Hydrogen Production

In this work we present the synthesis of a new type of nitrogen-doped tantalate, Sr(2)Ta(2)O(7-x)N(x), which exhibited significantly increased visible light absorption and improved photocatalytic hydrogen production by 87% under solar irradiation, compared with its undoped counterpart Sr(2)Ta(2)O(7). The photocatalyst also exhibited a strong capability in photoinduced reduction of exfoliated graphene oxide (GO) to graphene sheets. By using graphene as a support for a Pt cocatalyst, a new type of composite containing graphene-Pt and Sr(2)Ta(2)O(7-x)N(x) was designed, which demonstrated an additional ∼80% increase in hydrogen production and an quantum efficiency of 6.45% (∼177% increase from pristine undoped Sr(2)Ta(2)O(7)) due to the efficient charge carrier separation on the photocatalyst. This work suggests that graphene can play an important role as an electron transfer highway, which facilitates the charge carrier collection onto Pt cocatalysts. The method can thus be considered as an excellent strategy to increase photocatalytic hydrogen production in addition to a commonly applied doping method.

In Situ Growth of a ZnO Nanowire Network within a TiO2 Nanoparticle Film for Enhanced Dye‐Sensitized Solar Cell Performance

ZnO nanowire networks featuring excellent charge transport and light scattering properties are grown in situ within TiO(2) films. The resultant TiO(2) /ZnO composites, used as photoanodes, remarkably enhance the overall conversion efficiency of dye-sensitized solar cells (DSSCs) by 26.9%, compared to that of benchmark TiO(2) films.

Synthesis of anatase TiO2 rods with dominant reactive {010} facets for the photoreduction of CO2 to CH4 and use in dye-sensitized solar cells

Single crystalline anatase TiO(2) rods with dominant reactive {010} facets are directly synthesized by hydrothermally treating Cs(0.68)Ti(1.83)O(4)/H(0.68)Ti(1.83)O(4) particles. The nanosized rods show a comparable conversion efficiency in dye-sensitized solar cells (DSSCs), and a superior photocatalytic conversion of CO(2) into methane to the benchmark P25 TiO(2) nanocrystals.

Twins in Cd1−xZnxS solid solution: Highly efficient photocatalyst for hydrogen generation from water

Cd1−xZnxS solid solution with nano-twin structures are synthesized and exhibit superior photocatalytic activities for H2 evolution from water under visible light irradiation (λ ≥ 430 nm) without noble metal co-catalysts. Such Cd0.5Zn0.5S nanocrystals show the highest activity for hydrogen evolution with an extremely high apparent quantum yield (AQY = 43%) at 425 nm, achieving a hydrogen evolution rate of 1.79 mmol h−1 without noble metals. The hydrogen evolution rate of 1.70 mmol h−1 was achieved under simulated sunlight conditions (without infrared light). The “back to back” potential formed by parallel nano-twins in the Cd1−xZnxS crystals can significantly improve the separation of the photo-generated electrons/holes (preventing their recombination) thus enhancing the photocatalytic activity. Photodeposition experiments of noble metals strongly support such a mechanism. It is found that noble metals were selectively photo-deposited at central regions between the twin boundaries. The concentration of free electrons at the central region of twins was markedly higher and the twins can effectively separate the H2 evolution sites (electrons) from oxidation reaction sites (holes).

Hollow mesoporous organosilica nanoparticles: a generic intelligent framework-hybridization approach for biomedicine.

Chemical construction of molecularly organic-inorganic hybrid hollow mesoporous organosilica nanoparticles (HMONs) with silsesquioxane framework is expected to substantially improve their therapeutic performance and enhance the biological effects beneficial for biomedicine. In this work, we report on a simple, controllable, and versatile chemical homology principle to synthesize multiple-hybridized HMONs with varied functional organic groups homogeneously incorporated into the framework (up to quintuple hybridizations). As a paradigm, the hybridization of physiologically active thioether groups with triple distinctive disulfide bonds can endow HMONs with unique intrinsic reducing/acidic- and external high intensity focused ultrasound (HIFU)-responsive drug-releasing performances, improved biological effects (e.g., lowered hemolytic effect and improved histocompatibility), and enhanced ultrasonography behavior. The doxorubicin-loaded HMONs with concurrent thioether and phenylene hybridization exhibit drastically enhanced therapeutic efficiency against cancer growth and metastasis, as demonstrated both in vitro and in vivo.

Break‐up of Two‐Dimensional MnO2 Nanosheets Promotes Ultrasensitive pH‐Triggered Theranostics of Cancer

Chemically exfoliated two-dimensional MnO2 nanosheets are successfully modified with amino-polyethylene glycol as a theranostic platform for ultrasensitive stimuli-responsive theranostics of cancer. The highly dispersed MnO2 nanosheets exhibit a unique break-up in the mildly acidic microenvironment of tumor tissues, which could substantially enhance their in vitro and in vivo performances in T1 -weighted magnetic resonance imaging. Such a pH-triggered breaking-up behavior could further promote the fast release of loaded anticancer drugs for concurrent pH-responsive drug release and circumvent the multidrug resistance of cancer cells.

A general, one-step and template-free synthesis of sphere-like zinc ferrite nanostructures with enhanced photocatalytic activity for dye degradation

Spinel zinc ferrite nanospheres with diameters of about 212 nm were synthesized in high yield via a general, one-step and template-free solvothermal route. The prepared nanospheres had cubic spinel structure and exhibited good size uniformity and regularity. The absorption edge of ZnFe(2)O(4) nanospheres shifted to a higher energy in the UV-Vis absorption spectrum compared with that of ZnFe(2)O(4) nanoparticles. The ZnFe(2)O(4) nanospheres exhibited remarkably high surface photovoltage response in the UV and visible region, suggesting the enhanced separation ability of photogenerated electrons and holes. The dramatically enhanced photocatalytic activity of the ZnFe(2)O(4) nanospheres was evaluated in the decomposition of rhodamine B under Xe lamp irradiation. Hydroxyl radicals on the surface of photoilluminated ZnFe(2)O(4) nanospheres were detected by the photoluminescence technique, which suggested that hydroxyl radicals played an important role in the photocatalytic reaction. This study provided new insight into the design and preparation of functional nanomaterials with sphere structure in high yield, and the as-grown architectures demonstrated an excellent ability to remove organic pollutants in wastewater.

Characterization of MCM-41 mesoporous molecular sieves containing copper and zinc and their catalytic performance in the selective oxidation of alcohols to aldehydes

MCM-41 mesoporous molecular sieves containing copper and zinc with different metal contents were synthesized at room temperature (RT) by the method of direct insertion of metal ions as precursors in the initial stage of synthesis. The physicochemical properties of the materials were thoroughly investigated employing X-ray powder diffraction, high-resolution transmission electron microscopy. UV-Visible diffuse reflectance spectroscopy, electron paramagnetic resonance spectroscopy, temperature programmed reduction and N adsorption-desorption methods, The results indicated that MCM-41 materials with long range hexagonal ordering could be successfully synthesized at RT in the presence of copper and zinc salts with the (Cu + Zn) contents of around 2-3 wt.%. A further increase in the metal content deteriorated the ordering of the materials. Removal of the template upon calcination resulted in the formation of CuO-like species with a distorted octahedral coordination. The Cu2+ ions in the MCM-41 materials were reduced completely to metallic copper in the temperature range 230-260 degreesC. On the other hand, the presence of zinc together with copper impeded the Cu2+ reducibility. The catalytic partial oxidation of methanol and ethanol over CuMCM-41 and CuZnMCM-41 materials yielded corresponding aldehydes as predominant products. The activity for alcohol conversion increased with increasing copper content, and this indicated that the Cu2+ ions in the CuMCM-41 and CuZnMCM-41 materials were located on the readily accessible interior surfaces of the mesopores