Synthesis of silver nanoparticles by using rice husk extracts prepared with acid–alkali pretreatment extraction process

Abstract

Phenolic acids are the major bioactive compounds responsible for the reducing properties of rice husk. This study quantified the phenolic acid profile, total phenolic content (TPC), reducing power, and ferric-reducing antioxidant power (FRAP) of rice husk extracts ameliorated with acid–alkali pretreatment extraction (AAPE) process. The AAPE rice husk extract exhibited higher phenolic content (TPC: 3428 mg gallic acid equivalent (GAE)/100 g husk) and possessed stronger reducing properties (FRAP of 1433 mM FeSO4/g husk) than the rice husk extract with hot water extraction (TPC: 33 mg GAE/100 g husk, FRAP: 12 mM FeSO4/g husk). A green synthesis process for preparing silver nanoparticles (AgNPs diameter approximately 19 nm) with stable dispersion was obtained, and a conceptual model using caffeic acids as protective agents in synthesized AgNPs was conducted. The recycling of rice husk not only reduces the pollution from the use of chemical reducing agents and dispersants but also enhances the value-addition of the husk.