Thermoresponsive polymer-stabilized silver nanoparticles

Silver nanoparticles (Ag NPs) stabilized by a thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAM), have been synthesized by the reduction of silver ions with NaBH4 in aqueous solutions. The obtained Ag NPs are very stable at room temperature due to the extended coil conformation of the PNIPAM chain at temperatures below its volume phase transition temperature (∼32 °C). At higher temperatures (such as 45 °C) above the phase transition of PNIPAM, only minute aggregation between Ag NPs was observed, showing that the collapsed PNIPAM chains still retain the ability to stabilize Ag NPs. The PNIPAM-stabilized Ag NPs were then characterized as a function of the thermal phase transition of PNIPAM by UV–vis spectroscopy, dynamic light scattering, transmission electron microscopy, and cyclic voltammeter. Consistent results were obtained showing that the phase transition of PNIPAM has some effect on the optical properties of Ag NPs. Switchable electrochemical response of the PNIPAM-stabilized Ag NPs triggered by temperature change was observed.

Thermo-responsive poly(N-isopropylacrylamide) (PNIPAM)-stabilized Ag nanoparticles (Ag NPs) were successfully synthesized by simply reducing the silver salt in the PNIPAM aqueous solution. The PNIPAM-stabilized Ag NPs show tunable optical properties, which is fully reversible dependence on the phase transition of PNIPAM. The Ag NPs only show electrochemically active when the PNIPAM chains collapse. These unique properties render PNIPAM-stabilized Ag NPs as potential electrode coating materials, of which the electrochemical properties could be switched by the environmental temperature.Figure optionsDownload as PowerPoint slide