Influence of Silver on Formation of Biphasic Calcium Phosphates by Solution Combustion for Potential Antibacterial and Photocatalytic Applications

Abstract— Silver-doped calcium phosphate powders were synthesized by solution combustion synthesis. X-ray powder diffraction confirmed the phase composition, demonstrating the influence of silver on the formation of hydroxyapatite (HAP) and tricalcium phosphate (β-TCP). Specifically, increasing silver concentration led to a decrease in HAP and an increase in the β-TCP phase. Rietveld refinement analysis revealed a corresponding increase in β-TCP crystallite size (from 62 to 98 nm) with higher silver concentrations, suggesting the incorporation of silver into the β-TCP lattice. Silver phosphate was observed only at an Ag/(Ag + Ca) cationic ratio of 0.12. Scanning electron microscopy (SEM) revealed aggregates formed during combustion, while transmission electron microscopy (TEM) showed Ag nanoparticles supported on the calcium phosphate. Antimicrobial assays demonstrated activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria for the powders with Ag/(Ag + Ca) ratios of 0.12 and 0.09. Additionally, potential photocatalytic activity was assessed via methylene blue (MB) degradation under sunlight. UV-Vis spectroscopy revealed significant MB degradation after 4 h of sunlight exposure, with the blue solution becoming transparent. These results indicate that the synthesized powders are promising for use in antimicrobial and photocatalytic applications.