Enhanced photoluminescence up and downconversions of Sm3+ ions by Ag nanoparticles in chloroborosilicate glass nanocomposites

Abstract

A Sm³⁺ doped Ag-chloroborosilicate glass nanocomposite has been synthesized in a dielectric glass matrix SiO₂–B₂O₃–Al₂O₃–K₂O–BaCl₂ (CBS) by a single-step melt-quenching technique involving selective thermochemical reduction by a reducing agent. The T_g has been found to be 630–633 °C as obtained by dilatometry and differential scanning calorimetry. The colourless nanocomposite was heat treated according to a pre-designed heat treatment protocol. X-ray diffraction patterns show the emergence of nanocrystalline phases of BaCl₂ and Ag⁰ after certain heat treatments. Study of the microstructure of the crystallized samples by field emission scanning electron microscopy and transmission electron microscopy reveals the presence of a polycrystalline phase of BaCl₂. The refractive index was found to be 1.5987 at 632.8 nm. UV-Vis absorption spectra shows absorption bands at around 400 nm which arises due to the surface plasmon resonance of Ag nanoparticles (NPs). The band gets widened with increasing crystallization of the glass matrix. Photoluminescence spectra (λ_ex = 447 nm) shows enhanced downconversion of the frequency which varies with heat treatment duration. The extent of the enhancement was found to be dependent on the size of Ag NPs. Also the effect of matrix crystallization on the emission intensity is evident. Enhanced frequency upconversion (λ_ex = 949 nm) was found to take place only when the matrix becomes crystallized. This happened due to the formation of low-phonon energy BaCl₂ nanocrystals and thereby decreasing the non-radiative emission probabilities. These optical properties means the nanocomposite has potential for various nanophotonic applications.