Nano Au enhanced upconversion in dichroic Nd3+:Au–antimony glass nanocomposites

Dichroic Nd3+:Au–antimony glass (K2O–B2O3–Sb2O3) nanocomposites (NCs) have been synthesized by single-step melt-quench thermochemical reduction process. The UV–Vis–NIR spectra show surface plasmon resonance (SPR) band of Au0 nanoparticles (NPs) and absorption peaks of Nd3+ ions. XRD and SAED results indicate growth of Au0 NPs along (200) plane. TEM image reveals elliptical Au0 NPs having sizes 12–21 nm (aspect ratio ∼1.2) responsible for the dichroic behavior. Photoluminescent upconversion under excitation at 805 nm exhibit two emission bands of Nd3+ ions at 540 (green) and 650 (red) nm due to 4G7/2 → 4I9/2 and 4G7/2 → 4I13/2 transitions respectively. Both bands undergo maximum 8 and 11 fold intensity enhancements respectively at 0.03 wt% Au0 (4.1 × 1018 atoms/cm3). Local field enhancement (LFE) induced by Au0 SPR and energy transfer (ET) from Au0 → Nd3+ is found to be responsible for enhancement while ET from Nd3+ → Au0 and optical re-absorption due to Au0 SPR for quenching.

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