CuO nanoparticles decorated on hydroxyapatite/ferrite magnetic support: photocatalysis, cytotoxicity, and antimicrobial response.

Photocatalysts supported in magnetic nanocomposites for application in environmental remediation processes have been evaluated for removing contaminants due to easy recovery and low toxicity to the ecosystem. In this work, copper oxide (CuO) nanoparticles with photocatalytic properties were decorated on magnetic support constituted by hydroxyapatite (HAP) and ferrite to achieve efficiency in contaminated water remediation under visible light irradiation. First, nanomaterials were obtained by precipitation route, allowing fast and straightforward synthesis. Then, CuO nanoparticles with 6 nm diameter were efficiently decorated on magnetic support (25 nm), showing a high ability to absorb visible light irradiation (bandgap) to promote electronic transition and charge separation. Under visible irradiation, CuO promotes the H2O2 reduction in the conduction band (BC) to form hydroxyl radicals (•OH), which are responsible for rhodamine B (RhB) dye degradation (> 90% in 60 min). Magnetic hysteresis assays confirmed the magnetic properties of HAP/ferrite support, which enabled the recovery and reuse of the magnetic photocatalyst efficiently up to 3 cycles. Due to low Cu2+ leaching after the photocatalytic application stage, cytotoxicity assay for the Allium cepa seeds did not exhibit abnormal cells other than those commonly found. Furthermore, the CuO-decorated nanoparticles showed bactericidal activity against S. aureus (Gram-positive) and E. coli (Gram-negative) microorganisms, being more significant for the first one. Thus, the developed nanocomposite of CuO nanoparticles decorated on the magnetic support surface showed to be a complete system for water remediation, acting in contaminant degradation under visible light irradiation and bactericidal control with environmentally friendly characteristics.Graphical abstract CuO nanoparticles decorated on hydroxyapatite/ferrite magnetic support acting as a photocatalytic and bactericidal system.

Potential of Nb2O5 nanofibers in photocatalytic degradation of organic pollutants.

Various photocatalytic nanomaterials for environmental remediation have been promoted due to the pollution caused by different organic pollutants. In this study, Nb2O5 nanofibers were obtained by electrospinning technique, presenting controlled crystallinity and high specific surface area to improve the photoactivity response. The structural characterization indicated Nb2O5 nanofibers with orthorhombic phase formation. The photoluminescence measurements showed different energy levels contributing to the electronic transition events. The nanofibers with a bandgap up to 3.6 eV were applied to photocatalysis of dyes (rhodamine B (RhB) or methylene blue (MB)) and fluoxetine (FLX), listed as an emergent pollutant. In the optimized condition (pH = 9), the RhB and MB photocatalysis was 59% and 93% more efficient than photolysis due to ζ = - 50 mV ± 5 for EtOH_550 sample increased interaction with MB (cationic) compared to RhB unprotonated (pKa = 3.7). Therefore, FLX (pKa = 10.7) was selected due to protonated form at pH = 9 and showed 68% ± 1 adsorption in 30 min for EtOH_550. The FLX photocatalytic degradation under UV light irradiation was up to 17% higher than the photolytic degradation. The formation of hydroxyl radicals in the photocatalytic system (EtOH_550) was proven by the Coumarine probe assay, corroborating with the greater amount of α-[2-(methylamino)ethyl]benzylalcohol (MAEB), a by-product obtained after FLX oxidation. Additionally, the material achieved specific catalytic activity for the different organic compounds (RhB, MB, or FLX). Therefore, Nb2O5 nanofibers were efficient for degrading three different pollutants under UV light, proving a viable alternative for environmental remediation.