Chemical and morphological mechanisms of synthesizing rectangular cesium tungsten bronze nanosheets with broadened visible-light absorption and strong photoresponse property

Recently, nano-cesium tungsten bronze (Cs_xWO₃) is found to be a new candidate for the application in solar filter due to its high visible transmittance and excellent near-infrared shielding ability. However, a typical two-dimensional (2D) Cs_xWO₃ has not been reported since 2D nanomaterials have attracted great attention due to their fascinating properties, e.g., graphene. Herein, a novel synthesis system and related mechanisms are tried to develop for synthesizing 2D Cs_xWO₃ via hydrothermal method, which an original inspiration derived from the morphology control of sulfides. The results indicate that morphology modifier represents a new strategy in which thiourea and oleylamine interact synergistically rather than independently to synthesize 2D Cs_0.3WO₃. The more regular and larger the rectangular nanosheet, the broader and stronger the light absorption, the rectangular Cs_0.3WO₃ nanosheets with the maximum size are synthesized from thiourea, oleylamine and HCl concentrations of 4, 0.061 and 320 mmol/L, respectively, and exhibit a broad and strong absorption spectrum. The above nanosheet shows excellent instantaneous photo-thermal conversion property resulting in an obvious temperature increases from 20 °C to 88.5 °C when it was irradiated by 50 W halogen lamp for 10 s. Finally, both chemical reaction and morphological evolution in the synthesis processes are revealed.