Europium induced point defects in SrSnO3-based perovskites employed as antibacterial agents

Abstract

The antibacterial activity of Eu3+-doped SrSnO3-type materials against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) bacteria is described. Two Eu3+-doped SrSnO3 perovskites - (SrEu)SnO3 and Sr(SnEu)O3 - were synthesised by a modified-Pechini method and characterised by XRD, FT-IR, FE-SEM, HR-STEM/EDX, BET, Photoluminescence (PL), UV-Vis, Q-band EPR and XPS to understand the impact of Eu doping on the materials’ properties. Structural characterisations indicated that the desired perovskite phase completely crystallised after calcination at 700 °C. Long and short-range structural changes were observed as a function of the site-doping with Eu and calcination temperature. Small specific surface area, which varied from 8.09 to 13.28 m2/g, was observed for the samples. Nonetheless, the formation of nanoparticles under 10 nm, clusters of nanoparticles> 100 nm, and nanorods with 100–600 nm × 10–50 nm (length × width) was evidenced. Eu3+ doping led to an increase of Sn2+ and oxygen vacancies in SrSnO3 lattice, playing an essential role in the antibacterial activity. Reduced Eu2+ species were also observed. The samples had activity below 5 % against Escherichia coli, whereas (SrEu)SnO3 displayed an efficiency of 100 % after 24 h against Staphylococcus aureus at a concentration of 1 mg/mL. Our results demonstrate that a specific chemical doping with Eu induces the formation of distinct point defect (Sn2+, Eu2+ and VO•) in the materials, which promoted a negative surface charge that seems to have improved the redox ability and, therefore, enhanced the biocide property.