Environmentally friendly in situ synthesis of gold nanoparticles mediated by thermoresponsive Chitosan-g-PNIPAM copolymer

The ability of polymers to encapsulate active compounds and provide colloidal stability make polymer-protected inorganic nanoparticles highly promising for use in biomedical fields. Inspired by this requirement, the basic purpose of this research is to develop, characterize, and evaluate chitosan- g -poly( N -isopropylacrylamide) (Chit- g -PNIPAM)/gold nanoparticles (AuNPs) composite colloids. This study's originality lies in the one-pot, in situ synthesis of AuNPs mediated by the Chit- g -PNIPAM copolymer, being of hybrid biological-synthetic nature, in aqueous solution without the use of any further reducing agents. The composite nanostructure preparation involves a two-step mechanism: a) ion exchange/chelate generation using HAuCl 4 salt, followed by b) the chemical reduction of gold ions (Au 3+ ) and in situ synthesis of AuNPs. Dynamic light scattering analysis (DLS) and UV–Vis spectroscopy methods were employed to examine the kinetics of Chit- g -PNIPAM/AuNPs nanoparticulate composite structures synthesis in conjunction with reaction temperature and amine group/gold ([N]/[Au]) molar ratio. The morphology and size of the formed hybrid organic-inorganic particles is elucidated by scanning transmission electron microscopy. Furthermore, the thermoresponsive properties of obtained smart nanoparticulate colloids were confirmed by UV–Vis and DLS experiments. • In-situ synthesis of AuNPs mediated by Chit- g -PNIPAM copolymer as reducing agent. • AuNPs formation is correlated with the [N]/[Au] molar ratio and temperature. • Chit- g -PNIPAM/AuNPs composite nanostructures exhibited thermoresponsive properties. • Chit- g -PNIPAM/AuNPs thermoresponsive nanostructures are stable for at least 30 days.