ZnO mesoscale nanoparticles photoluminescence obtained by green synthesis based on Beaucarnea gracilis

Zinc oxide (ZnO) has been extensively used in areas such as optoelectronics, solar cells, and photocatalysis, among others. Modifying the optical properties of ZnO through different processes can potentially improve the performance of devices based on this material. This work presents the biosynthesis of ZnO by Beaucarnea gracilis leaf extract. The natural extract was mixed with zinc nitrate hexahydrate, Zn(NO₃)₂·6H₂O resulting in a precipitate. Then the precipitate was calcined for 2 h at 400 °C, resulting in a yellowish-ZnO powder. Diffraction laser measurements showed a particle size average of 419 nm. The material exhibited high absorption in the UVA region with photoluminescence at 530 nm. Moreover, from the Tauc plot, a 2.7 eV band gap was obtained. Fourier Transform Infrared (FTIR) spectroscopy results confirmed the ZnO synthesis through 550 cm⁻¹ and 667 cm⁻¹ absorption peaks. To the best of our knowledge, this is the first time that ZnO has been synthesized by the endemic plant Beaucarnea gracilis. A major difference with conventional ZnO is significant reduction in the band gap from 3.3 eV to 2.7 eV. Moreover, the material exhibited photoluminescence at 530 nm by exposure to UV light which is attributed to oxygen vacancies. The increase in the optical absorbance in the UV–Visible region and the reduction in the optical band gap could enhance the performance in solar cells based on ZnO and in photocatalysis processes, allowing the use of visible light sources in addition to UV light.