# Atmosphere-dependent synthesis and crystallization behavior of silica nanoparticles derived from rice husk biomass

## TL;DR

This paper shows how silica nanoparticles can be made from rice husk waste using eco-friendly methods, and how their structure can be controlled through thermal treatment.

## Contribution

The study demonstrates a scalable, green synthesis of silica nanoparticles from rice husk and reveals atmosphere-dependent crystallization behavior.

## Key findings

- Silica nanoparticles with diameters of 20-37 nm were successfully synthesized from rice husk biomass.
- Thermal treatment at 1000 °C transformed amorphous silica into crystalline cristobalite-type structures.
- The process offers a sustainable route for waste valorization and functional nanoparticle production.

## Abstract

This work on sustainable nanomaterials focuses on their green synthesis methods using cheap and renewable precursors. In this study, silica nanoparticles (SiO2 NPs) were prepared from agro-waste biomass rice husk through an environmentally safe extraction process. Three controlled ashing conditions were used to determine the effect of the processing atmosphere on the end-product SiO2 NPs. Besides offering a reliable route to silica recovery, this process allowed one to control the phase and structure of the final nanostructures. The formation of high-purity SiO2 NPs was confirmed through characterization with the assistance of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field-emission-scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM) and zeta potential measurements. The as-synthesized nanoparticles exhibited a predominantly amorphous nature, with particle diameters ranging from 20 to 37 nm, and consisted of aggregated spherical grains. Post-synthesis thermal treatment at 1000 °C effectively induced a clear amorphous-to-crystalline phase change in the silica structure. This reaction caused the emergence of cristobalite-type silica, confirming that the structural stage and consequent morphology can be accurately engineered by the thermal treatment of the green-synthesised NPs. This study extensively highlights the enormous potential of rice husk biomass as a dual-use feedstock for waste valorization and the scalable production of SiO2 NPs, which can be further utilized for phase-associated functional applications.

This work on sustainable nanomaterials focuses on their green synthesis methods using cheap and renewable precursors.