Abstract:
Recent advances in nanotechnology have enabled the development of nanofertilizers that offer controlled nutrient release, improved plant uptake, and reduced environmental impact. Among these, silica nanoparticles (SiNPs) show great promise due to their unique nanoscale properties. Rice (Oryza sativa) is one of the major crops in Sri Lanka. Rice plants actively accumulate silicon (Si), which provides significant agronomic benefits. Within the plant, Si is deposited beneath the cuticle as a cuticle–Si double layer, primarily in the form of monosilicic acid absorbed from the soil. Rice hulls (RHs), an agricultural waste byproduct rich in amorphous silica, serve as a sustainable raw material for SiNP synthesis. However, existing methods for synthesizing SiNPs still require further optimization and characterization. Additionally, the precise effect of these SiNPs on rice cultivation as a nanofertilizer has not yet been discovered. Investigating cost-effective synthesis approaches and evaluating the effects of SiNPs on rice plant growth could contribute to more sustainable agriculture and enhanced rice production. The present study utilized RHs from three rice varieties (BG 359, BG 94, and BG 374/1) collected from paddy fields in the Ukuwela region of the Matale District. Among these, BG 359 exhibited the highest silica content. The SiNPs synthesized from the BG 359 RH variety were characterized using several analytical techniques. UV–Vis spectroscopy revealed absorption peaks in the 190–220 nm range, confirming the presence of pure silica through Si–O electronic transitions. Fourier-transform infrared (FTIR) spectroscopy identified key vibrational modes corresponding to Si–O–Si and O–Si–O bonds (~1100, ~650, and ~470 cm⁻ ¹), indicating the presence of an amorphous silica network. Scanning electron microscopy (SEM) revealed a porous, quasi-rod- shaped morphology with particle sizes ranging from 25 to 70 nm, further confirming the nanoscale structure of the synthesized SiNPs. The resulting SiNPs were then applied to rice seeds and plants to assess their effects on seed germination and growth. The findings demonstrated that SiNPs had a positive impact on both germination and the growth performance of Oryza sativa.
