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.
Highlights
The development of nanomaterials capable of effectively absorbing near-infrared (NIR) radiation with a broad working waveband has increasingly attracted attention from the viewpoint of energy economization for applications in photothermal therapy, solar collectors, smart windows, and optical filters [1,2,3]
WO3-x nanoparticles were prepared from pure WO3 via thermal reduction and, subsequently, novel WO3-x/PU nanocomposites were prepared using the WO3-x nanoparticles and PU by a simple stirred ball milling method
The particle size of the as-prepared nanocomposites was significantly reduced after ball milling
Summary
The development of nanomaterials capable of effectively absorbing near-infrared (NIR) radiation with a broad working waveband has increasingly attracted attention from the viewpoint of energy economization for applications in photothermal therapy, solar collectors, smart windows, and optical filters [1,2,3]. The process of converting light to heat involves absorption of photon energy of a specific wavelength by the photothermal material followed by conversion into thermal energy under optical illumination [8,9]. In this regard, plasmonic nanoparticles have received considerable attention in the past decade because of their novel and tunable localized surface plasmon resonance in the visible and NIR regions [10]. Gold is an expensive noble metal and the preparation of its nanostructures with NIR photothermal conversion properties usually requires accurate synthesis conditions or depositions process which is relatively expensive and limit its further application [20]. There is a need to develop a low-cost and simple method for the preparation of NIR-absorbing nanomaterials for photothermal applications
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