Novel synthesis of WO3 nanocrystals through pyrolytic decomposition of tungstate-based inorganic-organic hybrid nanobelts

The paper described a novel approach toward WO3 nanocrystals by pyrolytically decomposing tungstate-based inorganic-organic hybrid nanobelts in air at 500-600 °C for 2 h. The above-mentioned hybrid nanobelts were derived via a reaction of layered H2W2O7·xH2O and n-octylamine in a reverse-micelle-like medium (H2W2O7·xH2O/n-octylamine/heptane). The as-obtained WO3 nanocrystals and their intermediate products were characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM & FE-SEM), thermoanalysis (TG-DSC), Fourier-transform infrared spectra (FT/IR), UV-vis absorption and X-ray photoelectron spectroscopy (XPS). The as-obtained WO3 nanocrystals had an apparent size of 20-50 nm, and took on a loose-aggregate-like morphology. The WO3 nanocrystals derived via the pyrolytic decomposition process were almost separated from each other and could be redispersed readily, while the WO3 nanocrystals obtained by the conventional acid-precipitation process tightly agglomerated into large particles with apparent sizes of several micrometers, without redispersibility even under an intense sonication treatment.