Spectroscopic assessment of the influence of copper loading and gamma-ray irradiation on calcium phosphate bio-relevant glasses

Calcium phosphate glasses containing copper possess antimicrobial properties and thus have attracted attention for biomedical applications such as tissue engineering [1]. Still, studies incorporating structural, thermal, and optical property evaluations in connection with the oxidation states of copper are scarce. In this work, a comprehensive evaluation was carried out on biologically relevant P2O5-CaO-Na2O-CuO glasses prepared with variable [CuO]/[Na2O] molar ratios by the melt-quenching technique [2]. A structural evaluation was first performed by X-ray diffraction to confirm amorphous nature and Fourier transform-infrared (FT-IR) spectroscopy to obtain information about phosphate network characteristics. The thermal properties were then assessed by dilatometry evaluating thermal expansion profiles, followed by differential scanning calorimetry (DSC) in the glass transition regime. The optical transmission from the ultraviolet (UV) to the near-infrared (NIR) region was then scrutinized in the context of solid-state physics through Tauc plots (optical band gap analysis) and Urbach plots (band tailing reflecting disorder). The optical appraisal was complemented by photoluminescence (PL) spectroscopy with emission decay analysis where appropriate. X-ray photoelectron spectroscopy (XPS) was ultimately employed to probe oxygen environments and perform Cu+/Cu2+ speciation for further connection with the evaluated properties. In a subsequent stage, the impact of gamma-ray irradiation was assessed for the various glasses through optical transmission and PL spectroscopy [3].