Preparation of Silver Nanoparticles Deposited on TEMPO-Oxidized Cellulose Nanofibers

Silver nanoparticles (AgNPs) were synthesized by a chemical method in which cellulose nanofibers (CNFs) extracted from pineapple leaves served as a stabilizing and reducing agent. In this study, pineapple leaves were oxidized by the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation with sodium hypochlorite (NaClO) to obtain CNFs. After the oxidation, the transformation from hydroxyl groups to carboxylate groups of cellulose was confirmed by Fourier-transform infrared spectroscopy (FTIR), and TEMPO-oxidized CNFs with a higher carboxylate content were obtained. Then, TEMPO-oxidized CNFs with a carboxylate content of 2.49 mmol/g and non-oxidized CNFs with a carboxylate content of 0.68 mmol/g were used as a reducing agent to synthesize AgNPs. The formation of AgNPs was confirmed by color changes of the Ag solutions from white to yellow. Furthermore, AgNPs with an average diameter of 76.5 ± 22.15 nm were obtained when TEMPO-oxidized CNFs were used as a reducing agent, while non-oxidized CNFs generated AgNPs with a larger particle size of 181.2 ± 66.16 nm. This suggested that the TEMPO-oxidized CNFs could be used as a stabilizing and reducing agent for the synthesis of AgNPs with smaller diameters.