Silver Nanoclusters Tunable Visible Emission and Energy Transfer to Yb3+ Ions in Co-Doped GeO2-PbO Glasses for Photonic Applications

Abstract

This work investigates the optical properties of Yb³⁺ ions doped GeO₂-PbO glasses containing Ag nanoclusters (NCs), produced by the melt-quenching technique. The lack in the literature regarding the energy transfer (ET) between these species in these glasses motivated the present work. Tunable visible emission occurs from blue to orange depending on the Yb³⁺ concentration which affects the size of the Ag NCs, as observed by transmission electron microscopy. The ET mechanism from Ag NCs to Yb³⁺ ions (²F_7/2 → ²F_5/2) was attributed to the S₁→T₁ decay (spin-forbidden electronic transition between singlet-triplet states) and was corroborated by fast and slow lifetime decrease (at 550 nm) of Ag NCs and photoluminescence (PL) growth at 980 nm, for excitations at 355 and 405 nm. The sample with the highest Yb³⁺ concentration exhibits the highest PL growth under 355 nm excitation, whereas at 410 nm it is the sample with the lowest concentration. The restriction of Yb³⁺ ions to the growth of NCs is responsible for these effects. Thus, higher Yb³⁺ concentration forms smaller Ag NCs, whose excitation at 355 nm leads to more efficient ET to Yb³⁺ ions compared to 410 nm. These findings have potential applications in the visible to near-infrared regions, such as tunable CW laser sources and photovoltaic devices.

Keywords: germanate glasses; silver nanoclusters; tunable luminescence; ytterbium ions.