Tailoring of the optical and magnetic properties of ZnO nanoparticles using selective Si doping

Zinc oxide (ZnO) nanoparticles (NPs) have attracted interest in various optoelectronic applications such as solar cells, photodetectors, and display technologies owing to their remarkable properties as an optoelectronic material. This study mainly focuses on the optical and magnetic properties of pure and Si-doped ZnO NPs synthesized via the sol–gel method. The wurtzite hexagonal phase has an average crystallite size of ~ 12–14 nm, confirmed from X-ray diffraction (XRD) analysis. Fourier-transform infrared (FTIR) spectroscopy identified a distinct absorption peak at 680 cm⁻ 1 , indicative of Zn–O–Si bond formation. The significant excitonic absorption peak of Si-doped ZnO NPs appears in the UV wavelength range with a redshift. The optical bandgap reduction from 3.24 eV for pure to 3.01 eV for 3 mol% Si-doped ZnO NPs with enhanced transparency makes it an attractive candidate for optoelectronic applications. Morphological assessments using scanning electron microscopy (SEM) confirm particle aggregation behaviour, and transmission electron microscopy (TEM) reveals nearly spherical nanoparticles measuring a size of ~ 8–13 nm. Due to Si 4+ doping, defect-mediated mechanisms contribute to exhibiting ferromagnetism with the highest saturation magnetization (M s ) of 0.23 emu/g for 3 mol% Si-doped ZnO NPs. The reduced band gap and significantly enhanced saturation magnetization highlight the pivotal role of selected Si doping in tailoring the optical and magnetic properties of ZnO NPs, thereby enhancing their potential for applications in ultraviolet photodetectors, spintronic, and nanoscale optoelectronic devices.