Tailored nanoscale structure of flame-made antimony doped tin oxides and their near-infrared shielding properties

Today's world is confronting mounting challenges and pressures from urbanization, industrial expansion, and the effects of climate change. These forces are fueling a surge in energy consumption, placing heavy demands on our limited resources. Buildings are a key contributor to this issue, as the need for cooling, heightened by heat from sunlight streaming through windows, emphasizes the critical importance of adopting energy-efficient solutions. Near-infrared (NIR) shielding glass, which blocks NIR radiation while allowing visible light transmission, is a promising approach for reducing cooling demands. Antimony-doped tin oxide (ATO) nanoparticles, known for their high thermal stability and electrical conductivity, offer a viable solution for NIR shielding due to their localized surface plasmon resonance (LSPR) effect. In this study, we systematically investigate the influence of the nanostructure, especially the crystal/particle diameter, on the NIR shielding performance of ATO nanoparticles synthesized via flame spray pyrolysis (FSP). Flame-made ATO nanoparticles ranging from around 5 to 35 nm were synthesized, characterized, and evaluated for their optical properties across the UV-VIS-NIR spectrum. The results reveal a strong dependence of NIR shielding performance on the crystal/particle diameter, with ATO nanoparticles averaging 20 nm demonstrating optimal NIR absorption while maintaining high visible light transmittance. X-ray photoelectron spectroscopy analysis indicates that the Sb⁵⁺/Sb³⁺ ion ratio plays a crucial role in modulating the free electron concentration and enhancing LSPR. Our findings demonstrate that precise engineering of the ATO crystal/particle diameter and composition by FSP can significantly enhance their optical performance, facilitating their application in energy-efficient smart glass technologies.