Advanced Materials Letters

Silver nanoparticles (AgNPs) embedded double network (DN) nanocomposite hydrogels [of P(AM-co-HEMA) as second network and PVA-Borax as first network] were synthesized by in-situ reduction of silver nitrate using citric acid in presence of the fully swollen high strength DN hydrogels. The AgNPs embedded DN nanocomposites hydrogels (Ag-DNG) were characterized by FTIR, XRD and TEM analyses. Such Ag-DNG hydrogels were studied for their degree of swelling and swelling kinetics. They were also evaluated for their anti-bacterial characteristics using a Gram negative (Escherichia coli) and a Gram positive (Bacillus subtilis) bacteria. The XRD analysis revealed the presence of AgNPs in the DN nanocomposite hydrogels. The AgNPs were observed to be 20-50 nm in diameter as observed by TEM analysis. The degree of swelling of Ag-DNG hydrogels was lower than that of the virgin DN hydrogel which was because of the space of pores of the DN hydrogels occupied by AgNPs. The virgin DN hydrogels did not exhibit any antimicrobial property, whereas Ag-DNG hydrogels exhibited a significant amount of antibacterial activity towards gram positive and gram negative bacteria. Such AgNPs incorporated high strength DN nanocomposite hydrogels may find potential biomedical application.

In this work, we report the relationship between the electrical conductivity and nanoparticle effective surface area with functional properties of polymer-metal and polymer-clay nanocomposites. Conductivity of the nanocomposite strongly depends upon metal/clay nanoparticle size and concentration that ultimately dictate where the system percolates. Knowledge of percolation properties allows the design of functional nanocomposites for biomedical and sensors applications. Herein we report the successful production of three functional chitosan-metal/clay nanocomposites: a) chitosan-Ag films with antibacterial properties, b) chitosan-Au potentiometric sensor for detection of Cu ++ and c) chitosan-nanoclay potentiometric sensor for detection of NO3-. For all these applications the best functional performance of nanocomposites has been observed when NPs concentration increases and approaches the percolation threshold. The obtained relationship between electrical percolation threshold and functional properties of polymer nanocomposites is of primary importance in the design of high-performance applications.