Intrinsic luminescence centers in γ - and θ -alumina nanoparticles

Abstract

In this study, we investigate the photoluminescence (PL) properties of γ and θ -alumina nanoparticles synthesized by the chemical wet method followed by annealing. The obtained experimental results indicate the presence of some favorable near ultraviolet (NUV)-orange luminescent centers for usage in various luminescence applications, such as oxygen vacancies (F, F + 2 , F 2+ 2 , and F 2 centers), OH related defects, cation interstitial centers, and some new luminescence bands attributed to trapped-hole centers or donor-acceptor centers. The energy states of each defect are discussed in detail. The defects mentioned could alter the electronic structure by producing some energy states in the band gap that result in the optical absorption in the middle ultraviolet (MUV) region. Spectra show that photoionazation of F and F 2 centers plays a crucial role in providing either free electrons for the conduction band, or the photoconversions of aggregated oxygen vacancies into each other, or mobile electrons for electrons-holes recombination process by the Shockley-Read-Hall (SRH) mechanism.

Development of γ-Al2O3 with oxygen vacancies induced by amorphous structures for photocatalytic reduction of CO2

“…Meanwhile, a series of narrow bands are attributed to oxygen vacancies in different charge states. 29 Due to the oxygen vacancy defects, photogeneraterd electron-hole pairs can be efficiently separated on the surface of the sample Al-450. In brief, the results of the photocurrent response, electrochemical impedance and photoluminescence are consistent, which can illustrate the best electron transport performance and photogenerated electron-hole pair separation efficiency of Al-450.…”