Multimodal luminescence and energy transfer mechanism in a narrowband UVB emitting phosphor system towards futuristic phototherapeutic devices

Abstract

This investigation presents the synthesis and advanced spectroscopic characterization of Gd³⁺-activated CaMgSi₂O₆ phosphors, synthesized via a high-temperature modified solid-state reaction method, tailored for narrowband ultraviolet B (UVB) phototherapeutic applications. The strategic incorporation of Gd³⁺ ions into the CaMgSi₂O₆ host lattice yields intense, sharp emission at 314 nm, attributed to the ⁶P_7/2 → ⁸S_7/2 intra-configurational transition under 275 nm excitation. Photoluminescence (PL) studies reveal five distinct 4f–4f and 4f–5d transitions, with the optimized composition, Ca_0.95MgSi₂O₆:0.05Gd³⁺, demonstrating superior emission intensity ideal for treating dermatological conditions such as psoriasis. X-ray diffraction (XRD) analysis confirms a monoclinic crystal structure (space group C2/c), corroborated by alignment with the International Centre for Diffraction Data (ICDD, #01-075-0945), validating successful Gd³⁺ integration into the host matrix. Field-emission scanning electron microscopy (FESEM) reveals refined surface morphologies, with average particle sizes of 0.433 μm (pure) and 0.36 μm (x = 0.05 mol). Fourier transform infrared (FTIR) spectroscopy verifies the structural integrity of the silicate matrix, while Diffuse reflectance spectroscopy (DRS) indicates a narrowed bandgap upon Gd³⁺ activation. Temperature-dependent PL (TDPL) and time-resolved PL (TRPL) analyses elucidate exceptional thermal stability and efficient radiative energy transfer dynamics, respectively. These attributes position Gd³⁺-activated CaMgSi₂O₆ as a highly promising candidate for next-generation, precise, and portable phototherapy devices, advancing dermatological treatment efficacy.