Novel one-pot solvothermal synthesis and phase-transition mechanism of hexagonal Cs_xWO₃ nanocrystals with superior near-infrared shielding property for energy-efficient windows

The controllable one-pot synthesis of hexagonal Cs_xWO₃ nanocrystals without post heat-treatment remains a great challenge in the field of nanocrystal materials. In this study, a facile one-pot method for controllable synthesis of Cs_xWO₃ nanocrystals was proposed using stable and relatively cheap ammonium metatungstate and cesium carbonate as starting materials. The reducibility of tartaric acid, tartaric acid with chloroplatinic acid was studied, and the possible synthetic mechanisms of Cs_xWO₃ nanocrystals with different crystalline phases were discussed in detail. The results indicate that tartaric acid chloroplatinic acid can promote the formation of the maximum W⁵⁺ ions in the hexagonal Cs_xWO₃ nanocrystals. When the solid content in the dispersion reached 6 wt%, ordinary glass with the coating demonstrated the average visible light transmittance of 71.76% and the average near-infrared shielding ratio of 85.64%. This work is of great significance for synthesizing low-cost hexagonal Cs_xWO₃ nanocrystals without post heat-treatment and promoting the development of energy-efficient windows.