Synthesis of CsxWO3 nanoparticles and their NIR shielding properties

A simple two-step route is developed to fabricate hexagonal Cs x WO 3 nanoparticles . The core of this route is the preparation of the precursor by drying the mixture of WO 3 sol and CsCl , which leads to a higher Cs/W (0.32) ratio at low temperature in a short time. During reaction, oleic acid, used as a solvent, can be adsorbed on the surface of Cs x WO 3 nanoparticles, which results in small particle size (20 nm × 10 nm) and mild agglomeration. In addition, oleic acid also plays a role as a reducing agent in forming Cs x WO 3 nanoparticles without any further post-treatment. Furthermore, the film prepared from as-synthesized Cs 0.32 WO 3 nanoparticles shows excellent NIR-shielding properties (approximately 99% of the near-infrared radiation is cut off over a wavelength range of 780–2600 nm and the visible-light transmittance at 465 nm is 78.9%) when covering on an ordinary sheet of glass. A model which simulates the real environment is applied to evaluate heat-shielding performance of the Cs 0.32 WO 3 film while comparing with that of ordinary glass and commercial ITO glass (10 Ω □ −1 ). Results revealed that the Cs 0.32 WO 3 film showed superior performance than others.