Control of Silver Nano-particle Nucleation and Synthesis with Nanocelluloses: Applications in Paper-based Sensing and Anti-microbial Activity

The synthesis of silver nanoparticles (AgNPs) has drawn significant research interest due to their unique and well-defined physical-chemical properties. Developing a feasible chemical method to synthesize silver nanoparticles using sustainable, renewable, and environmentally friendly materials is very important for environmental safely. In this work, a new route for the synthesis of silver nanoparticles (AgNPs) by using sustainable, renewable and environmentally friendly cellulose nanocrystals (CNCs) is described. Moreover, in this study the utilization of cellulose-AgNPs materials in sensing and antibacterial applications was investigated. The influence of the surface charge of cellulose nanocrystals on the rate of nucleation, growth, stabilization and size distribution of AgNPs was investigated. CNCs produced by sulfuric acid hydrolysis followed by partial desulfation and CNC produced by hydrochloric acid (HCl) hydrolysis followed by different levels of carboxylation by TEMPO-mediated oxidation were used to elucidate the effects of sulfate ester and of carboxyl groups on the silver nanoparticle synthesis process. The results shed light on the mechanistic aspects related to synthesis, control of nucleation, and stabilization of AgNP in a sustainable way, and highlight the potential of CNCs in metal nanoparticle synthesis. The fundamental knowledge of controlled nucleation of plasmonic silver nanoparticles by cellulose was applied to demonstrate a new plasmonic sensing mechanism for qualitative detection of proteins on paper. In contrast to conventional paper-based diagnostic devices that use the cellulosic component as a support structure, the proposed method takes advantage of cellulose as a nucleation controller during silver nanoparticle formation. Reduction of silver ions interacting competitively with the nucleation controlling cellulosic surface and the suppressing effect of protiens on reduction (via complexation) resulted in silver nanoparticles whose size–shape dependent plasmonic properties quantitatively reflected the concentration of protein on paper. In addition, aerogels prepared from aqueous dispersions of anionic and cationic cellulose nanofibrils (CNFs) were investigated as solid supports for enzymes and silver nanoparticles to elicit a sustained antibacterial effect. The antibacterial activity of CNF aerogels loaded with silver nanoparticles (AgNP) after in situ synthesis via UV reduction was tested against gram-negative and gram-positive bacteria. The results were compared with CNFs aerogels carrying antibacterial lysozyme.