Enhanced IR and UV Shielding Performance of Leucoxene-CuS Composite-Based Paint Coatings

Abstract

The increasing energy consumption of heating and cooling systems underscores the need for advanced materials that improve the thermal insulation of building envelopes, particularly windows. This study develops and characterizes a novel paint coating for glass that integrates UV-reflective and IR-responsive optical properties. The coating is based on a composite of leucoxene, a natural TiO₂-rich mineral that acts as a UV-reflective component, and copper sulfide (CuS) nanoparticles, synthesized via co-precipitation, which serve as potent IR absorenhanbers. Composites with varying CuS-to-leucoxene weight ratios (1:9 to 5:5) were systematically analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The composites were incorporated into an acrylic paint matrix and applied onto glass substrates. Optical characterization using UV–Vis–NIR spectroscopy indicated that increasing CuS content led to reduced diffuse reflectance, while higher leucoxene content contributed to improved UV reflectance. Thermal gradient behavior, evaluated under controlled IR irradiation, revealed that the 5:5 CuS-to-leucoxene composite exhibited the largest measured surface-to-interior temperature gradient, achieving a temperature difference (ΔT) of approximately 47 °C between the coated surface and the interior. Notably, the 1:9 composition demonstrated comparable performance with a lower filler content, indicating a more cost-effective alternative. These results demonstrate the potential of leucoxene–CuS composites as tunable and functional coatings for energy-efficient window and building applications.