Green synthesis and enhanced photocatalytic activity of ZnSe nanoparticles capped with Artemisia herba-alba and calligonum plants extracts

This study reports, for the first time, the green synthesis of zinc selenide (ZnSe) nanoparticles (NPs) capped with Artemisia herba-alba and Calligonum extracts, benchmarked against conventional L-cysteine-capped ZnSe. Using plant extracts as natural capping agents provides an eco-friendly strategy to tailor the surface chemistry and photocatalytic behavior of ZnSe NPs. The NPs were synthesized hydrothermally and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), UV–Vis spectroscopy, and photoluminescence (PL), and then evaluated for methylene blue (MB) degradation under UV irradiation. XRD revealed mixed cubic and wurtzite phases with crystallite sizes ranging from 5.6 to 7.7 nm, while the PL analysis suggested more effective charge separation in plant-extract-capped ZnSe. Photocatalytic tests demonstrated that Calligonum-capped ZnSe achieved ~ 40% MB degradation after 180 min, outperforming Artemisia-capped ZnSe (28%) and showing comparable performance to L-cysteine-capped ZnSe (38%). Kinetic analysis further revealed that Artemisia-capped ZnSe exhibited the highest rate constant, indicating superior intrinsic photocatalytic activity. The enhanced performance of plant-capped ZnSe was attributed to phytochemical-induced defect states that promote charge separation and reactive oxygen species generation. These findings establish Artemisia and Calligonum extracts as sustainable capping agents, offering a low-cost, environmentally friendly route for designing ZnSe nanocatalysts with significant potential in wastewater treatment and environmental remediation.