Near-infrared absorbance properties of Cu 2−x S/SiO 2 nanoparticles and their PDMS-based composites

We synthesized different Cu 2−x S nanoparticles (CuS and Cu 1.8 S NPs) with localized surface plasmon resonance (LSPR) absorbance in the near infrared (NIR) region and applied a silica layer on the surface of Cu 2−x S nanoparticles (NPs) to achieve high photo-stability and dispersion stability. These plasmonic Cu 2−x S NPs have been much utilized as thermal shielding materials of energy-saving windows, due to shielding the ultraviolet (UV) and NIR regions, and transmitting the visible (Vis) region. However, this application is limited because Cu 2−x S NPs show photocatalyst properties that lead to the decomposition of organic matter, and dispersing these NPs into polymer films is difficult. Herein, silica coating successfully suppressed the generation of hydroxyl radicals on the surface of CuS NPs, which caused the photo-degradation of a polydimethylsiloxane (PDMS) polymer. Furthermore, a silica layer with the structure similar to that of PDMS provided the dispersion stability of CuS NPs. The achievement of good photo-stability and dispersion stability in the Cu 2−x S NPs was demonstrated by the thermal shielding effect using a simulated experiment. The temperature change of a box shielded with a CuS/SiO 2 –PDMS film (Δ T = 6.8 °C) was smaller than that when the box was shielded with common glass (Δ T = 12.7 °C) or a CuS–PDMS film (Δ T = 9.2 °C). This research introduces a new and reliable thermal shielding material.