Antimicrobial and Photocatalytic Properties under Visible Blue LED Light of Silver Phosphate Supported on Biogenic...

In this study, we report the synthesis of silver phosphate supported on a phase mixture of Analcime and Pitiglianoite zeolites. The hybrid materials were obtained with AgP amounts of 25% (AgP_ZLT_25), 50% (AgP_ZLT_50), 75% (AgP_ZLT_75), and 95% (AgP_ZLT_95) relative to the ZLT mass. Structural characterization by X-ray diffraction (XRD) and structural refinement by the Rietveld method revealed that ZLT is composed of 71.02 ± 0.54% Analcime and 28.98 ± 0.47% Pitiglianoite zeolite. The percentage of AgP in the mixture, also quantified by the Rietveld method, resulted in values of 7.99 ± 0.46, 36.70 ± 4.84, 67.50 ± 5.06, and 93.74 ± 3.15% for the samples AgP_ZLT_25, AgP_ZLT_50, AgP_ZLT_75, and AgP_ZLT_95, respectively. Vibrational characterization by Raman and infrared (IR) spectroscopy revealed the presence of the main active vibrational modes of silver phosphate, silicate, and aluminate groups, in both pure and hybrid materials. The E _gap values revealed that ZLT effectively absorbs in the ultraviolet region, with E _gap equal to 3.65 eV. While the hybrid materials exhibited a decrease in the E _gap value, specifically between 3.63 eV (AgP_ZLT_25) and 2.35 eV (AgP_ZLT_95), in consequence of the contributions of the electronic transitions of AgP (E _gap = 2.35 eV). The photocatalytic performance of the materials prepared in the photodegradation of RhB dye in an aqueous medium under exposure to LED-simulated visible light resulted in dye discoloration percentages of 97.07% for the AgP_ZLT_95 sample and 93.56% for the AgP_ZLT_75 sample. Furthermore, analysis of the rate constant (k _app) and half-life of the reactions (t _1/2) revealed that the AgP_ZLT_95 catalyst was approximately 1,391.5 times more efficient compared to photolysis, exhibiting superior activity in the generation of superoxide radicals and vacancies. Additionally, it was found that zeolite acts as a sacrificial material, reducing the photocorrosion process of silver phosphate. Hybrid materials, as well as AgP, exhibited high antimicrobial activity, resulting in a minimum inhibitory concentration (MIC) of 0.01562 mg mL^-1 for the bacteria Staphylococcus aureus and Escherichia coli, while for the fungi Candida parapsilosis and Candida albicans, the MIC was 0.03125 mg mL^-1, as a result of redox processes involving reactive oxygen species (ROS), as well as silver-ion activity and [AgO₄] and [PO₄] clusters in the cell wall and internal structures of microorganisms.