Nano violet tungsten oxide, also known as W18O49 or WO2.72, is a good raw material for producing NIR shielding material, i.e., near-infrared shielding material, such as WO2.72/polyurethane (PU) nanocomposites. According to the experts, among the non-stoichiometry tungsten oxides, monoclinic WO2.72 has received considerable interest due to its distinctive oxygen defect structure and intense near-infrared photoabsorption.
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For example, the experts demonstrated the photothermal conversion properties of WO2.72/PU nanocomposites using a UV-Vis NIR spectrometer. The transmittance values of WO2.72/PU were found to be 75% in the visible region (400–780 nm). Transmittance of the WO2.72/PU nanocomposites in the range of 780–2500 nm was very low (8%), which suggested that the WO2.72/PU nanocomposites exhibited stronger NIR absorption (92%) compared to other nanocomposites. This was because of the presence of free electrons or oxygen-vacancy-induced small polarons formed during the reduction process. In a word, the NIR shielding material of nano violet tungsten oxide has high visible light transmission and low near infrared light transmission. That is to say, such a material shields heat without affecting the daylighting.
