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

摘要

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 degrees 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 Ag-0 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 (lambda(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 (lambda(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.