来源：ACS Publications
Energy consumption is one of the most important concerning issues of environmental problems especially the global warming phenomenon, with energy usage being the main cause. To reduce the energy used for cooling systems, development of material for smart buildings for near-infrared (NIR) protection is a challenge of material society. Metal oxides including tin oxide (SnO2) with an antimony (Sb) dopant are a candidate owing to their NIR shielding property. However, the upgrading of NIR absorption performance with rare-earth doping due to the specific property of rare-earth elements especially erbium (Er) shows strong absorption of the near-infrared region. This article synthesized Er/Sb-codoped SnO2 nanoparticles by sonochemical and thermal treatment processes at various Er dopant concentrations with a Sb dopant concentration stabilized at 5%. Crystallinity and morphology exhibited the tetragonal phase of SnO2 with a sphere-like nanostructure with an approximately average size of 10 nm. X-ray photoelectron spectroscopy was used to evaluate the chemical oxidation state of all elements, which verified the Er3+ and Sb5+ oxidation states of dopant ions, and oxygen vacancy observation led to the NIR absorption improvement.