Gasochromic properties of novel tungsten oxide thin films compounded with methyltrimethoxysilane (MTMS)

Abstract

Herein, thick tungsten–silicon films with long-term gasochromic performance were synthesized from methyltrimethoxysilane (MTMS) and tungsten oxide sols. Via the addition of MTMS, the thickness of WO₃/SiO₂ films was largely increased to nearly 3 μm without any cracks. Moreover, the transmittance difference between coloring and bleaching status reached over 97% in the near-infrared region. Different ratios of WO₃–MTMS compound films were prepared to confirm that the proper proportion of WO₃ : MTMS was 1 : 2, and WO₃–TEOS films were also prepared for comparisons. FT-IR and Raman spectra were obtained to characterize the structure of W–O and the existence of –CH₃ bonds. SEM and TEM images revealed the thickness of compound films and cross-links of the microstructure. The results showed that the WO₃–MTMS films exhibited a stable network with tungsten and silicon bonds, and the methyl group derived from MTMS hydrolysate played a positive role in gel and drying processes.