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

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 (chi 3) 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.