3D ordered macro–mesoporous indium doped Al2O3

Abstract

Three-dimensional ordered macro–mesoporous (3DOMM) Al₂O₃ and In doped Al₂O₃ have been successfully synthesized via a dual-templating approach with a colloidal crystal template and surfactant block copolymers. The samples were characterized using X-ray diffraction (XRD), N₂ adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-visible (UV-vis) and photoluminescence (PL) spectroscopy. The results indicate that the indium dopants are dispersed well within the mesoporous framework, and the incorporation of indium could efficiently promote the optical properties of the composite. The as-synthesized 3DOMM structures have a large surface area (>200 m² g⁻¹), and the luminescence intensity of 3DOMM In doped Al₂O₃ with an In/Al molar ratio of 7% (3DOMM 7In–MAl) is two times higher than that of 3DOMM Al₂O₃ (3DOMM MAl). Further theoretical calculations, based on first-principle density functional theory (DFT), demonstrate that In doping facilitates the formation of oxygen vacancies, and the hybridization of oxygen vacancy defect states and In 5s, 5p states induce some hybrid states below the conduction band edge. The blue shift of absorption edges of 3DOMM 7In–MAl compared to pure 3DOMM MAl could be attributed to the electron transfer from oxygen vacancies to In atoms.