Synthesis of semiconductor ZnO nanoparticles using Citrus microcarpa extract and the influence of concentration on their optical properties

•ZnO nanoparticles were synthetized using Citrus microcarpa extract.•Molecules in the extract act as stabilizers preventing agglomeration.•XRD pattern showed a hexagonal Wurtzite phase.•All nanoparticles were achieved more than 98% of degradation under solar light. In this work, ZnO semiconductor nanoparticles were synthesized by using different concentrations of Citrus microcarpa extract 1%, 2%, and 4% w/v (weight/volume), which have organic contents that act as stabilizers in the green synthesis of nanoparticles. The obtained nanoparticles were characterized by several techniques, such as FT-IR, UV-vis, XRD, PL, SEM-EDS, TEM-SAED, and XPS. The FTIR results showed the characteristic vibrations of the extract together with the Zn-O bond ubicated at 480 cm−1; the band gap values decreased as extract concentration increased, obtained 3.03, 2.94, and 2.89 eV for 1%, 2%, and 4% w/v, respectively; XRD and XPS corroborate the formation of ZnO, with a wurtzite phase without impurities as revealed by XRD; PL exhibited a narrow UV emission band and a broader emission band in the visible region; TEM indicates for all product synthesis a quasi-spherical morphology with a decrease in average sizes as the percentage of extract increased being 39.7, 16.8, and 13.1 nm for 1%, 2%, and 4%, respectively. Finally, the photocatalytic activity of the nanoparticles was evaluated by the degradation of Methylene Blue (MB), Methyl Orange (MO), and Rhodamine B (RB) under UV and solar light. The ZnO semiconductor nanoparticles synthesized using 4% extract concentration achieved a 90% degradation of MB during the first 40 and 30 min under UV and solar light, respectively. Additionally, synthesis reached more than 98% of degradation under solar light. [Display omitted]