Exploring Gd³⁺-activated calcium-based host materials for phototherapy lamps: A comprehensive review

Apart from the use of sun therapy for the cure of many skin diseases and disorders of bygone days, nowadays artificial light sources of a narrowband (NB) ultraviolet-B (UV–B) have effectively revolutionized the treatment of such skin diseases. The crucial role of gadolinium (Gd³⁺) ions in calcium-based hosts lies in their narrowband emission spectrum, specifically at 311–315 nm, attributed to the ⁶P_7/2 to ⁸S_7/2 transition. Calcium-based materials, known for their chemical stability, facilitate Gd³⁺ embedding, enabling UV activation and express emission in the narrowband range. This emission spectrum is well-suited for skin treatments, aligning with the action spectrum of various skin diseases. Gd³⁺ activated host materials in fluorescent lamps are considered prime sources of NB-UVB emissions. Calcium-based host materials are proving to be popular environments for embedding of dopants for such emissions. Calcium-based phosphor materials are leading the research in phototherapy applications due to their strong UV-B emissions, especially when activated by Gd³⁺ ions. Applications of phosphor host materials of this nature are generally chemically and thermally stable, have a low synthesis temperature and which produce enhanced NB-UVB emissions specifically suited for phototherapy lamps. This paper is a review of calcium -based phosphor host materials in Gd³⁺ activated materials or through energy transfers from sensitized dopant ions for enhanced NB-UVB emissions that is pertinent for treatments of many skin diseases such as psoriasis, vitiligo, eczema, and many other skin conditions.