Synthesis of CsxWO3 nanoparticles and their NIR shielding properties

A simple two-step route is developed to fabricate hexagonal CsxWO3 nanoparticles. The core of this route is the preparation of the precursor by drying the mixture of WO3 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 CsxWO3 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 CsxWO3 nanoparticles without any further post-treatment. Furthermore, the film prepared from as-synthesized Cs0.32WO3 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 Cs0.32WO3 film while comparing with that of ordinary glass and commercial ITO glass (10 Ω □−1). Results revealed that the Cs0.32WO3 film showed superior performance than others.