A Study of Intermediate for Synthesis of Cs_0.3WO₃ with Near-Infrared Photothermal Response

Nanoscale tungsten bronze can convert near-infrared light into thermal energy. For a chemical synthesis, intermediate products and processes are potentially positive or negative to an end product. In this study, (NH4)2SO4 was added into the hydrothermal system of WO3, CsCl, CH3CH2CHO, and NH3·H2O to increase the Cs/W ratio in solution. An intermediate, Cs1.1W1.65O5.5, was isolated. Subsequently, it was confirmed via a kinetics experiment conducted for different times. The results of the NH3·H2O and NH4COOCH3 system indicate there are two influence factors that influence the formation of Cs1.1W1.65O5.5: the leaching out of W and imine reactions. A low leaching out rate induces a high Cs/W ratio and low-concentration W in solution, leading to the formation of Cs1.1W1.65O5.5. The imine reaction decreasing CH3CH2CHO restrains the reduction in Cs1.1W1.65O5.5. The increase in CH3CH2COO− with the reduction reaction results in both the micron-size sticks and nano-size equiaxial particles in powder