Abstract

IR transmission and visible photoluminescence (PL) were studied in raw nanoporous aluminum oxyhydroxide (NOA) and in samples after thermal treatment at different temperatures. Structural and chemical modifications of the NOA sample were related to the water content and adsorption/desorption process at the surface. The differences observed in the FTIR spectra in vacuum and after ageing of the samples can be explained by the effects of molecular water and OH− groups on the stability of the low-temperature phases of NOA. A considerable increase in PL intensity and spectrum expansion to longer wavelengths were observed in all NOA samples after water desorption. This was accompanied by strong changes in the PL decay kinetics. Quenching of the fast luminescent decay and low-energy transitions in aged samples were observed after ageing of the samples. Partial passivation of the NOA surface and defective sites under ambient conditions is discussed.

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