A facile method to synthesize small-sized and superior crystalline Cs0.32WO3 nanoparticles for transparent NIR shielding coatings

Abstract

A simple one-step solvothermal route was developed to fabricate homogenous cesium tungsten bronze (Cs_0.32WO₃) nanoparticles, and an environmentally friendly aqueous solution was used to prepare transparent NIR shielding coatings. Based on the results, the addition of Cs⁺ ions promoted the formation of Cs₂WOCl₅ crystals, which inhibited the hydrolysis process of WCl₆ and limited the formation of hexagonal tunnels. Controlled formation of hexagonal tunnels is favorable for Cs⁺ ions that completely enter the hexagonal vacant tunnels to form the Cs_0.32WO₃ crystals. Via a controllable formation process, the superior crystalline Cs_0.32WO₃ nanoparticles with the primary particle size of 30–60 nm were synthesized at the low temperature of 200 °C and short time of 4 h without any other additives. Furthermore, the Cs_0.32WO₃ nanoparticles were well dispersed in the aqueous solution, and the as-prepared coating exhibited a high SETS value (0.72), which remained constant with an increase in the film thickness. Simulated solar irradiation experiments revealed that the as-prepared film cut off over about 91.6% of radiation. The simulated model of the real environment revealed that compared with the ordinary glass and commercial Cs_0.32WO₃, the as-prepared Cs_0.32WO₃ film showed superior NIR shielding performance for practical application.