Dieqing Zhang

An efficient bismuth tungstate visible-light-driven photocatalyst for breaking down nitric oxide

This paper reports a photocatalytic removal of 400 ppb level of NO in air under visible light irradiation by utilizing three-dimensional (3D) hierarchical bismuth tungstate (Bi(2)WO(6)) microspheres. A facile microwave-assisted hydrothermal method involving bismuth nitrate and sodium wolframate was developed to synthesize the photocatalyst. The Bi(2)WO(6) samples were characterized by using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), Raman and ultraviolet-visible reflectance (UV-vis) spectroscopy. The relationship between the physicochemical property and the photocatalytic performance of the as prepared samples is discussed. The present work demonstrates that the 3D hierarchical Bi(2)WO(6) microspheres are effective visible-light-driven photocatalytic functional materials for air purification.

Inorganic materials for photocatalytic water disinfection

Traditional water disinfection methods such as chlorination and ozonation inevitably form harmful disinfection by-products (DBPs). UV irradiation is a safe alternative but it is very energy intensive. It makes perfect sense to enhance the utilization of photons by integrating engineered photocatalytic nanostructures in the treatment system. UV-light active photocatalytic inorganic nanomaterials, such as titania, are capable of inactivating various bacteria and viruses. They work by generating powerful but short-lived oxygen-based radicals upon irradiation. Unlike conventional chemical disinfectants, the antimicrobial nanomaterials are not consumed in the process. Photocatalytic water disinfection is a green technology because the same materials can be used over and over again. This paper reviews the recent progress in the fabrication of inorganic nanomaterials for photocatalytic water disinfection. A variety of UV and even visible-light driven water disinfection systems are introduced. Their advantages and limitations as well as the antimicrobial mechanisms are discussed.

Green synthesis of a self-assembled rutile mesocrystalline photocatalyst

This paper reports a simple and environmentally benign approach for the synthesis of photocatalytically active rutile TiO2 mesocrystals. It is a microwave-assisted hydrothermal method involving titanium(III) chloride as the only reactant. The resulting 1D rutile nanowires can easily assemble into 3D hierarchical architectures without the help of surfactants or additives. The average aspect ratio for the nanowires is 267. The BET specific surface area of the mesocrystals is 16 m2 g−1. The optical band energy of the product exhibits an obvious red-shift of 0.2 eV with aspect to that of pure rutile TiO2. This red-shift effect may be ascribed to the high aspect ratio of rutile nanowires. The products show excellent photocatalytic activity for NO removal in air and the activity is well maintained after three cycles. Gold modification on the rutile TiO2 results in a 50% improvement in the photocatalytic performance.

Zn:In(OH)ySz Solid Solution Nanoplates: Synthesis, Characterization, and Photocatalytic Mechanism

Zn:In(OH)ySz solid solution nanoplates (Zn:In(OH)ySz-SSNs) with uniform nanoparticle size were synthesized through a simple sodium dodecyl sulfate (SDS)-assisted hydrothermal process. To achieve better photoabsorption in the visible light (VL) region and suitable redox potentials of the Zn:In(OH)ySz solid solution (Zn:In(OH)ySz-SS), the substitution of S(2-) for OH was carried out by adjusting the concentration of thiourea and SDS in the synthesis solution, while the doping of Zn2+ was realized by adjusting Zn2+ concentration. In addition, the morphology and crystallinity of Zn:In(OH)ySz-SSs were also controlled by the concentration of SDS. Using Rhodamine B (RhB) as a target pollutant the photocatalytic performance of these Zn:In(OH)ySz-SSs with different components, diameter sizes, and morphologies was investigated. Remarkably, Zn:In(OH)ySz-SSNs prepared with atomic ratio of Zn2+ and In3+ of 0.6, 45 mmol L(-1) thiourea, and 26 mmol L(-1) SDS, have the highest visible-light-driven (VLD) photocatalytic activity, exceeding 95% for the degradation of RhB after 60 min. The investigation of photocatalylic mechanism further indicates that the holes, superoxide radical (*O2(-)) and surficial hydroxyl radical (*OHs) are the major reactive species for the photocatalytic reactions. More importantly, for the first time, a simple and versatile strategy is developed to confirm the fact that direct contact between the Zn:In(OH)ySz-SS and RhB is the prerequisite for the photocatalytic degradation of RhB. Therefore, we report not only the preparation of a novel and effective VL-driven photocatalyst, but also provide mechanistic insight into semiconductor photocatalysis.

Effects of Cu2O nanoparticle and CuCl2 on zebrafish larvae and a liver cell-line.

The extensive uses of nanomaterials have caused many concerns of their potential hazards to the aquatic environments. As partial dissolution of metal nanoparticles may occur, it is important to study the toxic effects of nanoparticles and determine the no observable effect levels (NOELs) and lowest observable effect levels (LOELs) of these materials in water by using biomarker genes expression in zebrafish (Danio rerio). In this study, the toxic effects of Cu(2)O nanoparticle (NP) on zebrafish larvae and zebrafish liver cell-line (ZFL) were evaluated by determining their 96 h LC50 values (zebrafish larvae: 242.4 ppb; ZFL: 110 ppm), which was less toxic than CuCl(2) (zebrafish larvae: 85.73 ppb; ZFL: 23.04 ppm). However, zebrafish larvae are sensitive to both Cu(2)O NP and CuCl(2). We also examined the effects of elevated Cu(2)O NP and CuCl(2) on the expression of several copper related genes in zebrafish larvae by using real-time quantitative polymerase chain reaction. It was found that Cu(2)O NP and CuCl(2) induced the mRNA levels of metallothionein (MT), Cu/Zn superoxide dismutase (Cu/Zn SOD), metal regulatory transcription factor 1 (MTF1) and copper transporters, ATP7A and 7B, but down-regulated the mRNA levels of glutathione sulfur transferase (GST). Interestingly, the inductions of MT, ATP7A and ATP7B in the Cu(2)O NP exposure groups were much higher than that of the CuCl(2) exposure groups, and resulted in higher copper accumulation in the Cu(2)O NP exposure groups. Furthermore, as determined by using MT, ATP7A and ATP7B gene expression, the NOELs of CuCl(2) and Cu(2)O NP were 11 ppb and 30 ppb whereas the LOELs of CuCl(2) and Cu(2)O NP were 43 ppb and 121 ppb, respectively.

Advanced Photocatalytic Nanomaterials for Degrading Pollutants and Generating Fuels by Sunlight

This chapter focuses on the recent development of sunlight-driven heterogeneous photocatalysts with different chemical compositions and nanostructures. Various photocatalytic nanomaterials, including metal oxides, heterojunction nanocomposites, oxynitrides, oxysulfides, and graphitic carbon nitride, are described. Their preparation methods as well as the mechanisms involved are introduced. These materials can be used to degrade pollutants and generate fuels. Photocatalytic evolution of H2 from water and conversion of CO2 to fuels are discussed in detail. The development of advanced photocatalytic technology involving novel nanomaterials may allow the construction of clean and facile systems for solving the global energy and environmental problems.