Highly Efficient Near Infrared Photothermal Conversion Properties of Reduced Tungsten Oxide/Polyurethane Nanocomposites

Abstract

In this work, novel WO3-x/polyurethane (PU) nanocomposites were prepared by ball milling followed by stirring using a planetary mixer/de-aerator. The effects of phase transformation (WO3 → WO2.8 → WO2.72) and different weight fractions of tungsten oxide on the optical performance, photothermal conversion, and thermal properties of the prepared nanocomposites were examined. It was found that the nanocomposites exhibited strong photoabsorption in the entire near-infrared (NIR) region of 780–2500 nm and excellent photothermal conversion properties. This is because the particle size of WO3-x was greatly reduced by ball milling and they were well-dispersed in the polyurethane matrix. The higher concentration of oxygen vacancies in WO3-x contribute to the efficient absorption of NIR light and its conversion into thermal energy. In particular, WO2.72/PU nanocomposites showed strong NIR light absorption of ca. 92%, high photothermal conversion, and better thermal conductivity and absorptivity than other WO3/PU nanocomposites. Furthermore, when the nanocomposite with 7 wt % concentration of WO2.72 nanoparticles was irradiated with infrared light, the temperature of the nanocomposite increased rapidly and stabilized at 120 °C after 5 min. This temperature is 52 °C higher than that achieved by pure PU. These nanocomposites are suitable functional materials for solar collectors, smart coatings, and energy-saving applications.

Recent Advances in Tungsten-Oxide-Based Materials and Their Applications

“…FIGURE 1 | Photothermalconversion properties of WO 2.72 /PU nanocomposites by (A) UV-Vis-NIR transmittance spectra, (B) variation in the color observed for reduced tungsten oxide powder, and (C) the temperature difference WO 3 /PU, WO 2.8 /PU, and WO 2.72 /PU with 7 wt % as a function of time under infrared light irradiation. Reproduced with permission (Chala et al, 2017). Copyright 2017, MDPI.…”

“…The color changed from yellow to dark blue and to black for WO 3 , WO 3−x , and WC, respectively. The temperature T rapidly increased for WO 2.72 /PU, WO 2.8 /PU, WO 3 /PU, and pure PU to 58.9, 41.9, 30.9, and 9.9 • C after 30 s, respectively (see Figure 1C) (Chala et al, 2017). These results suggested that the WO 2.72 /PU nanocomposites exhibit a faster photothermal conversion rate than do WO 2.8 /PU, WO 3 /PU, and pure PU.…”

“…In our previous study, we demonstrated the photothermal conversion properties of WO 2.72 /polyurethane (PU) nanocomposites using a UV-Vis NIR spectrometer (Chala et al, 2017). The transmittance values of WO 2.72 /PU were found to be 75% in the visible region (400-780 nm).…”

One-Pot Synthesis of W-TiO2/SiO2 Catalysts for the Photodegradation of p-Nitrophenol

“…The W4f core levels of the XPS spectra are present in Figure 6(c). Each of them can be deconvoluted into two peaks, indicating the coexistence of W 6+ (BE = 35 1~35 5 eV for W4f 7/2 and BE = 37 5~38 2 eV for W4f 5/2) and W 5+ (BE = 34 2~34 4 eV for W4f 7/2 and BE = 36 8~37 0 eV for W4f 5/2) [35,36]. The Si2p core level of the XPS spectrum, Figure 6(d), shows only one symmetrical peak at 101~106 eV [37].…”

Ammonium Ion Intercalated Tungsten Oxide Nanorods with High Photothermal Conversion Efficiency and Low Cytotoxicity

“…Tungsten oxides (WO 3‐x ) have become promising materials in the field photothermal conversion because of their reduced tungsten states (W 5+ , W 4+ ) , . The number of reduced tungsten states increases with increment of the oxygen deficiencies, which has a huge impact on its photothermal conversion efficiency .…”