Preparation of silver nanoparticles using different fractions of TEMPO-oxidized nanocellulose

Abstract

The aim of this study was to examine efficacy of different fractions of TEMPO-oxidized cellulose nanocrystals (TOCNs) as a reducing and capping agent of silver nanoparticles (AgNPs). Silver nanoparticles were prepared by thermal treatment of AgNO3 in aqueous suspensions of TOCN fractions. Three different nanocomposite materials based on different fractions of TOCNs and reduced in situ by TOCN silver nanoparticles were obtained. It was demonstrated that three fractions of TOCNs, characterised by varying water-solubility, degree of oxidation and viscosity, bind silver nanoparticles differently. The capping of anionic TOCNs fractions on the surface of nanoparticles was confirmed by zeta potential measurements, and therefore good stability of AgTOCNs nanoparticles was shown. The size and dispersion of AgNPs seems to be affected mainly by the viscosity of a given TOCN fraction. Water-soluble TOCN fractions yielded spherical AgNPs, while water-insoluble fractions contributed to the formation of nanoparticles characterised by diverse morphologies. The application of TEMPO-oxidized cellulose fractions for greener synthesis of silver nanoparticles is discussed. A mechanism including a polylol process is proposed as a possible means of silver cation reduction. The morphology and structural features of the TOCN nanocellulose-silver nanoparticle composites were assessed with the use of spectroscopic and microscopic techniques.