Catalytic Application of Silver Nanoparticles in Chitosan Hydrogel Prepared by a Facile Method

Abstract

In this research work, a simple method of silver nanoparticles’ self-synthesis in chitosan (CH) biopolymer hydrogels without utilizing a reducing agent is shown. The synthesized material was used as a catalyst in different reduction reactions. For this purpose, different amounts of CH powder were dissolved in acidic aqueous solutions and then crosslinked it with the formaldehyde solution to make a CH biopolymer hydrogel. Among all the prepared samples, a CH hydrogel prepared from a dense solution was found to be suitable for this study because of good mechanical stability. For the self-synthesis of silver nanoparticles inside hydrogel, it was immersed in an aqueous solution of AgNO3 (10 mM) for 3 days at room temperature. The color of the chitosan hydrogel changed to brown from transparent which indicated the successful formation of silver nanoparticles on CH hydrogel (Ag-CH). No reducing agent for conversion of the Ag1+ ions to nanoparticles in this whole synthesis method. Instrumental techniques such as FESEM, XRD and EDX analysis confirmed the successful preparation of Ag-CH. The Ag-CH was checked as a catalyst in the 2-nitrophenol (2-NP) and acridine orange (ArO) reduction reactions. Both reactions were carried out at high rate constants (2-NP = 0.260 min−1, ArO = 0.253 min−1) by using the Ag-CH hydrogel catalyst. In addition, we discussed the mechanism of action of the reducing agent, the effect of kapp on the two reduction reactions of Ag-CH and the recyclability.