Tunable assembly of vanadium dioxide nanoparticles to create porous film for energy-saving applications.

Nanoparticle-assembled vanadium dioxide (VO2) films have been easily prepared with the assistance of cetyltrimethylammonium vanadate (CTAV) precursor which exhibits self-assembly properties. The obtained VO2 film has a micro/nano hierarchical porous structure, so its visible-light transmittance is significantly improved (∼25% increased compared to continuous film). The VO2 particle density as well as the film porosity can be facilely controlled by adjusting experimental parameters such as dip-coating speed. Accordingly, film optical properties can also be tuned to a large extent, in particular the visible transmittance (Tvis) and near-infrared switching efficiency (ΔTnir). These VO2 nanoparticle-assembled films prepared by this novel method provide a useful model to research the balance between Tvis and ΔTnir.

One-step high-temperature solvothermal synthesis of TiO2/sulfide nanocomposite spheres and their solar visible-light applications.

A one-step high-temperature hydrated-sulfate assisted solvothermal method has been developed to synthesize TiO(2)/sulfide nanocomposite spheres. Different hybrid spheres of TiO(2)/CdS, TiO(2)/Cu(2)S, TiO(2)/FeS, TiO(2)/Co(9)S(8), and TiO(2)/ZnS were readily prepared by exploiting different hydrated sulfate. The hydrated sulfate has been proved to play multifunctional roles during the synthetic process, such as spherical template, water supplier, and composition controller. Nanocrystal CdS can be reduced from CdSO(4) at a high solvothermal temperature of 350 °C, and the TiO(2)/CdS nanocomposite spheres prepared by this method exhibit superior visible-light-driven photocatalytic efficiency because of its effective heterointerface and high crystallinity.

Ta2O5 nanowires: a novel synthetic method and their solar energy utilization.

Single-crystalline uniform Ta(2)O(5) nanowires are prepared by a novel synthetic route. The formation of the nanowires involves an oriented attachment process caused by the reduction of surface energy. The nanowires are successfully applied to photocatalytic H(2) evolution, contaminant degradation, and dye-sensitized solar cells (DSCs). The Ta(2)O(5)-based DSCs reveal a significant photovoltaic response, which has not been reported. As a photocatalyst, the Ta(2)O(5) nanowires possess high H(2) evolution efficiency under Xe lamp irradiation, nearly 27-fold higher than the commercial powders. A better performance of photocatalytic contaminant degradation is also observed. Such improvements are ascribed to better charge transport ability for the single-crystalline wire and a higher potential energy of the conduction band. This new synthetic approach using a water-soluble precursor provides a versatile way to prepare nanostructured metal oxides.

Biomolecule-assisted route to prepare titania mesoporous hollow structures.

Amino acids, as a particularly important type of biomolecules, have been used as multifunctional templates to intelligently construct mesoporous TiO(2) hollow structures through a simple solvothermal reaction. The structure-directing behaviors of various amino acids were systematically investigated, and it was found that these biomolecules possess the general capability to assist mesoporous TiO(2) hollow-sphere formation. At the same time, the nanostructures of the obtained TiO(2) are highly dependent on the isoelectric points (pI) of amino acids. Their molecular-structure variations can lead to pI differences and significantly influence the final TiO(2) morphologies. Higher-pI amino acids (e.g., L-lysine and L-arginine) have better structure-directing abilities to generate nanosheet-assembled hollow spheres and yolk/shell structures. The specific morphologies and mesopore size of these novel hollow structures can also be tuned by adjusting the titanium precursor concentration. Heat treatment in air and vacuum was further conducted to transform the as-prepared structures to porous nanoparticle-assembled hollow TiO(2) and TiO(2)/carbon nanocomposites, which may be potentially applied in the fields of photocatalysts, dye-sensitized solar cells, and Li batteries. This study provides some enlightenment on the design of novel templates by taking advantage of biomolecules.

Intelligent hydrated-sulfate template assisted preparation of nanoporous TiO(2) spheres and their visible-light application.

Hydrated metal sulfates (MSO(4)·xH(2)O, M = Zn, Fe, Co, Mg, etc.) were proposed to be intelligent templates to solvothermally synthesize nanoporous TiO(2) spheres with tunable chamber structures from hollow to solid and hybrid compositions. During the reaction, hydrated sulfate serves simultaneously as spherical template, water supplier, and composition controller, and it can be easily removed by washing. The as-prepared anatase TiO(2) spheres were evidenced to contain highly crystallized TiO(2) nanocrystals hybridized with a small amount of metal oxide from the hydrated sulfate. The formation mechanism of the hollow spheres involves the self-conglobation of hydrated sulfate, the hydrolysis of tetrabutyl titanate on the spherical templates, and the subsequent process of solvothermal crystallization. The proposed hydrated-sulfate assisted solvothermal (HAS) strategy was demonstrated to be widely applicable to various systems. When applied to visible-light photocatalysis, the hybrid TiO(2) spheres exhibit excellent photocatalytic performance, benefiting from the reduced charge recombination rate contributed by the heterojunctions of TiO(2) and the hybridized metal oxides.