Holmium ions-activated zinc-sulfo-boro-phosphate nanocomposites with silver nanoparticles sensitization

Abstract

Rare-earth ions (REIs)-doped oxide glasses and glass-ceramics (GCs) became promising for various photonic applications. However, the inherent small emission cross-section of the REIs-doped systems for practical applications need substantial enhancement. Despite some studies on holmium ion (Ho3+) luminescence from different hosts, the radiative properties of Ho3+ in zinc-sulfo-boro-phosphate GCs for the miniaturized and inexpensive lasers development remains deficient. In addition, the lasing potency of Ho3+-doped phosphate-based GC nanocomposites (GCNCs) with silver nanoparticles (Ag NPs) sensitization has not widely been explored. Thus, the structural, microstructural, impedance, optical and radiative properties of some Ag NPs and Ho3+ co-doped zinc-sulfo-boro-phosphate GCNCs were evaluated. Three series of samples with the composition of (40–x)P2O5–30B2O3–30ZnSO4–xHo2O3, where x = 0.0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0 mol%; (39.5–y)P2O5–30B2O3–30ZnSO4– 0.5Ho2O3–yAg nanopowder, where y = 0.6, 0.7, 0.8 and 0.9 mol%; and (39.5–z)P2O5– 30B2O3–30ZnSO4–0.5Ho2O3–zAgCl, where z = 0.6, 0.7, 0.8 and 0.9 mol% were prepared using melt-quenching method. Structural characteristics of the samples were determined using X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman, energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS) and density measurements. Microstructures of the samples were analyzed using high-resolution transmission electron microscope (HRTEM) and impedance spectroscopy (IS). Optical properties of the samples were measured using ultraviolet-visible-near infrared (UV-Vis-NIR) and photoluminescence (PL) spectroscopy. The XRD analyses of the as-quenched samples verified their GC nature. The observed increase and decrease in the samples density was attributed to the formation of more bridging oxygen (BO) and non-bridging oxygen (NBO), respectively. The density results of these GCs and GCNCs were supported by the FTIR, Raman and XPS spectral data analyses. The HRTEM images reconfirmed the GC nature of the samples and the existence of the Ag NPs within the network structure. The optical energy band gap, refractive index and Urbach energy were calculated from the UV absorption spectra to get the information about the local structural surroundings. The GC doped with 0.5 mol% of Ho2O3 exhibited the highest intensity of the red and green PL emissions. Furthermore, the GCNC doped with 0.8 mol% of Ag NPs (mean diameter of 20 nm) revealed the optimum PL intensity enhancement and strongest LSPR absorption band. The obtained larger values of the fluorescence branching ratio and emission cross-section compared to the existing state-of-the-art reports indicated the benefits of the studied samples for the construction of green and red wavelength lasers. A correlation between structural and optical properties was also established for the first time. The studied Ag NPs and Ho3+ co-doped phosphate-based GCNCs were asserted to be potential for the efficient photonic devices advancement. It is concluded that via the systematic composition optimization, these new types of GCNCs with customized lasing potency can be achieved.