Microstructural aspects of the CePO₄:Tb³⁺ phosphor for luminescence sensing

Ceramic powders and thin films of cerium phosphate doped with trivalent terbium ions (CePO₄:Tb³⁺) were synthesized from liquid phases, and their microstructures were modulated to investigate the relationship between the structure and the luminescence switching property responsive to redox reactions. Aqueous KMnO₄ and L(+)-ascorbic acid solutions were used to evaluate the redox response of CePO₄:Tb³⁺, appearing as luminescence quenching and recovering, respectively. The particle shape and size of the powder samples depended on heat-treatment conditions, which had also a large influence on the switching property. As-prepared nanorod particles were more sensitive to the redox reactions than heat-treated larger spherical particles, indicating that the switching was governed by the surface state of the particles. The thickness of the thin-film samples was also an important factor to determine the response to the redox reactions. In any case, our results demonstrate that it is important to control the microstructure of the CePO₄:Tb³⁺ materials for their use in luminescence switching devices for the redox monitoring.