Kumar, N. LakshmanN. LakshmanKumarPandiyan, V.V.PandiyanVimalraj, V.V.VimalrajAbisheik, T.T.AbisheikChinnasamy, SuryaSuryaChinnasamySadeq, Abdellatif M.Abdellatif M.SadeqRajabathar, Jothi RamalingamJothi RamalingamRajabatharArun ThirumuruganRaja, AnnamalaiAnnamalaiRajaAhn, Young-HoYoung-HoAhnBalu, KrishnakumarKrishnakumarBalu2026-07-072026-07-072026-09OPTICAL MATERIALS, 177, 118190 (2026). https://doi.org/10.1016/j.optmat.2026.1181900925-34671873-1252https://hdl.handle.net/20.500.12740/24624The unrestricted discharge of azo dyes into water bodies poses serious environmental and health concerns due to their chemical stability and resistance to conventional treatment methods. Photocatalysis offers an effective and sustainable approach for their degradation. Among semiconductor photocatalysts, ZnO is attractive because of its low cost and eco-friendly nature;" however, its wide band gap (similar to 3.37 eV) and rapid electron-hole recombination restrict visible-light activity. In this study, europium (Eu)-doped ZnO nanoparticles were synthesized via a co-precipitation method to enhance photocatalytic performance. The prepared materials were comprehensively characterized using XRD, FT-IR, UV-DRS, Raman, PL, FE-SEM, XPS, and HR-TEM analyses. Photocatalytic activity was evaluated using Reactive Red 120 (RR 120) under UV-C irradiation and natural sunlight under optimized conditions of 30 mg catalyst dosage in 100 mL of 50 ppm RR 120 solution at pH 7. Under these conditions, 1.0 wt% Eu-doped ZnO achieved nearly 100% degradation within 80 min under UV-C light with an apparent rate constant of 0.04322 min(-1), which is approximately 79 times higher than that of pristine ZnO (0.000549 min(-1)). Under sunlight irradiation, complete degradation was achieved within 120 min with a rate constant of 0.03668 min(-1), significantly outperforming undoped ZnO. The catalyst retained over 90% of its initial efficiency after four successive cycles, indicating good stability and reusability. Parameter optimization, along with scavenger and GC-MS analyses, confirmed that hydroxyl and superoxide radicals play dominant roles in the degradation mechanism. In addition, Eu-doped ZnO exhibited strong antibacterial activity against both Gram-positive and Gram-negative bacterial strains. These findings demonstrate the dual functionality of Eu-doped ZnO as an efficient photocatalyst and antimicrobial material, highlighting its potential for wastewater treatment and environmental remediation applications."PhotocatalysisEu-ZnOAzo dyesEnvironmental remediationAntibacterial activityArticulohttps://doi.org/10.1016/j.optmat.2026.118190