Screening of ultraviolet‐a and ultraviolet‐b radiation in marine green macroalgae (chlorophyta) 1.

11 November 2010

Abstract

Yttrium aluminum garnet (YAG) nanopowders doped with high neodymium (Nd) content (3 at.%) were synthesized by the sol–gel processing of (i) alkoxide precursors and (ii) metal chelates formed by complexing the cations with polyethylene glycol. A stoichiometric YAG composition was obtained following both procedures; however, the agglomeration of particles was significantly higher in glycolate synthesis, which shielded residual organics from oxidation (elemental analyses).

Distribution of Nd3+ ions in the YAG matrix, as shown by the absorption of pump energy and photoluminescence spectra of Nd:YAG ceramics, was more homogeneous in alkoxide-derived powders. The segregation of Nd centers in the glycolate-derived sample was supported by the precipitation of a crystalline Nd2O3 phase (X-ray diffraction) during sintering.

High-resolution absorption spectra (4I9/2(1)→4F9/2(1)) of the powders showed that a higher absorption cross-section of glycolate-derived powders is due to Nd3+–Nd3+ ion pairing, which leads to the quenching of photoluminescence. Owing to the better dispersion of optically active centers, the photoluminescence signal was found to be substantially enhanced in alkoxide-derived Nd:YAG ceramics.

Citation

Pescheck, F., Bischof, K. and Bilger, W., 2010. Screening of ultraviolet‐a and ultraviolet‐b radiation in marine green macroalgae (chlorophyta) 1. Journal of Phycology, 46(3), pp.444-455.

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