The morphology-controlled synthesis and near-infrared (NIR) absorption properties of W(18)O(49) were systematically investigated for the application of innovative energy-saving windows. Various morphologies of W(18)O(49), such as nanorods, nanofibers, nanograins, nanoassembles, nanoplates, and nanoparticles, with various sizes were successfully synthesized by solvothermal reactions using organic alcohols as reaction media and WCl(6), W(EtO)(6), and WO(3) solids as the tungsten source. W(18)O(49) nanorods of less than 50 nm in length showed the best optical performance as an effective solar filter, which realized high transmittance in the visible region as well as excellent shielding properties of NIR light. Meanwhile, the W(18)O(49) nanorods also exhibited strong absorption of NIR light and instantaneous conversion of the absorbed photoenergy to the local heat.
[Show abstract][Hide abstract] ABSTRACT: Dark blue W18O49 nanorod (NR) with ~50 nm length and ~4 nm width was synthesized by thermally induced crystal growth process. Pale yellow WO3 NR with the same dimension was also prepared by post-annealing the as-prepared W18O49 NR at 400 °C in air. The W18O49/TiO2 and WO3/TiO2 nanocomposites were then formed by coupling the corresponding NRs and TiO2 by sol–gel process. Under visible-light irradiation (λ ≥ 422 nm), the W18O49/TiO2 showed a remarkably high photocatalytic activity in removing gaseous 2-propanol (IP) and in evolving CO2. Its efficiency (6.9 ppm CO2 in 2 h) was more than twice that of the WO3/TiO2, which seems to be caused by a profound visible-light absorbance of W18O49 NR.
[Show abstract][Hide abstract] ABSTRACT: The rubidium tungsten bronze (RbxWO3) nanoparticles were synthesized by a solvothermal process in CH3COOH–C2H5OH mixed solutions for the application to near-infrared absorption materials. The as-obtained powder products were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and UV-Vis-NIR spectra. The morphologies of samples were greatly changed as large irregular aggregates, aggregates of rod-like and irregular shaped nanoparticles and rod-like microparticles with increasing content of acetic acid in the starting solution. The sample synthesized in a 20 vol.% CH3COOH to 80 vol.% C2H5OH mixed solution consisted of the agglomerated particles of 50–100 nm in diameter, showing a highly disordered microstructure. Promoted by this disordered nature, the thin film of RbxWO3 nanoparticles realized excellent absorption of near-infrared light, meanwhile, it selectively transmitted the major part of visible light.
[Show abstract][Hide abstract] ABSTRACT: Enhancing surface area is one of the efficient ways to improve photochromic sensitivity of WO3·0.33H2O. Hierarchical WO3·0.33H2O mesoporous nanorod assemblies were synthesized via proton exchange by adjusting the concentration of Na2WO4·2H2O. When the concentration of Na2WO4·2H2O is 2.0 g L−1, mesoporous nanorods with 10∼20 nm in diameter and an average pores size of about 4 nm were obtained. The novel WO3·0.33H2O porous structure possesses highly photochromic sensitivity and fatigue resistance properties. It exhibits visible-light-driven photochromic response due to large specific surface area originated from the mesoporous structure. The formation of mesopores is due to the volume decreasing in the transformation process from WO3·H2O to WO3·0.33H2O.
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