Synthesis, structural, linear/nonlinear optical properties, and radiation shielding potential of iron silicate (Fe2SiO4) nanoparticles for multi-functional applications

Abstract

In this study, Fe-doped SiO₂ nanoparticles (Fe–SiO₂ NPs) were synthesized using the sol-gel method to investigate their structural, and linear/nonlinear optical attributes as well as radiation shielding properties. The doping levels of Fe ranged from 0% to 12%. The X-ray diffraction (XRD) analysis confirmed the hexagonal structure of the SiO₂ matrix with the incorporation of a iron silicate cubic phase (Fe₂SiO₄) and minor peaks of monoclinic Fe₂O₃. With increasing Fe concentrations, the crystallite size increased from 39 nm to 48 nm, while lattice strain and dislocation density decreased. The optical measurements revealed a red shift in the absorption spectra with Fe doping, and the bandgap decreased from 5.65 eV for undoped SiO₂ to 5.26 eV for SOF-12. Nonlinear optical properties were significantly enhanced with Fe doping, as evidenced by the third-order nonlinear susceptibility (χ³) increased by more than double as Fe concentrations increased. Additionally, the nonlinear refractive index (n₂) exhibited a sharp increase with Fe content, indicating potential for nonlinear photonic applications. Radiation shielding assessments revealed a mass attenuation coefficient of 10.987 cm²/g at 0.015 MeV and a half-value layer of 3.36 cm at 1 MeV for the 12% Fe-doped sample (SOF-12), demonstrating superior lightweight shielding efficiency compared to conventional materials. These results demonstrate that Fe-doped SiO₂ NPs possess favorable structural and optical characteristics, making them promising candidates for applications in optoelectronics, radiation shielding, and photonic devices.