Photoluminescence, structural and antibacterial properties of co-doped β-Ca3(PO4)2-type phosphates Ca8CuRE(PO4)7 (RE = Eu–Er)

Abstract

Novel Ca8CuRE (PO4)7 where RE3+ = Eu3+, Tb3+, Dy3+, Ho3+ and Er3+ were synthesized by a solid-state method in air. The structures of the samples were characterized by powder X-ray diffraction using Rietveld refinement to determine the occupation of crystal sites. The samples are found to have a centrosymmetric structure with space group R3¯c, as shown by dielectric measurements. These synthesized Ca8CuRE(PO4)7 samples have multifunctional properties. The Cu2+ ions provide antibacterial properties, while the rare earth elements ions exhibit luminescence properties, and the β-Ca3(PO4)2-type host is biocompatible. The photoluminescence properties of RE3+ ions were studied and compared with other simmilar Ca8MRE(PO4)7 phosphates, where M is a divalent metal. The photoluminescence intensity quenching in terms of energy transfer from RE3+ to Cu2+ is disscused. The bioactive properties were studied in relation to antibacterial activity against E. coli and S. aureus. All syntesized Ca8CuRE(PO4)7 samples demonstrate very high and stable inhibition of bacteria growth. The correlation between crystal structure and properties is discussed. By combining multiple approaches to the directional design of such materials, several important properties within a single chemical compound to achieve biovisualization and bioactive properties simultaneously can be combined.