Structural and optical properties of nano-SiO₂ derived from the husk of some rice varieties and the effect of doping with Sm³⁺ ions

This article reports the synthesis and purification of nanosilica (SiO₂) derived from the husk of some rice varieties; Faro-44, Faro-46, Faro-52, Nerica-I, and Nerica-II. The husks were pretreated with H₂O and HCl. From the measurement results, Nerica-I rice husks produced the highest silica yield and best photophysical properties. Thus, the husks of Nerica-I rice were further pretreated with H₃PO₄ to additionally remove more mineral impurities and the derived nanosilica labeled nSiO₂ was selected to serve as a host matrix for doping with varying concentrations of Sm³⁺ions. The doped nanosilica (nSiO₂:xSm³⁺; x = 0.01, 0.05, and 0.1 molar ratios) maintained the amorphous structure of the undoped nanosilica, while the surface morphology as revealed by SEM and TEM indicates agglomerates of spherical nano-sized particles with average particle size measuring 21 nm. The Sm³⁺-doped nanosilica shows a large surface area measuring 198.0 m²/g. The photoluminescence excitation spectra show that near UV and blue LEDs can effectively be used as excitation sources to produce yellow and yellow-green emissions from Sm³⁺ ion-doped nSiO₂ suitable for display applications.