Polydiacetylene-coated gold nanoparticles as a novel plasmonic thermosensor based on the phase transition of the outer shell

We report the synthesis of a core-shell nanostructure formed by a gold nanosphere surrounded by an external layer of poly(10,12-pentacosadiynoic acid). The gold core provides intense SERS signaling, whereas the polymer shell ensures structure stability. We introduce the concept of temperature response induced by phase-transition, as opposed to current plasmonic thermosensors based on surface adsorption of low molecular weight reporters. The behavior of the core-shell nanostructure has been investigated by Variable Temperature SERS (VT-SERS) measurements in the range of 150 – 400 K. The polymer shell is initially in the blue form and converts into the stable red one starting from 290 K. This transition produces temperature effects on the position and the Full Width at Half Height (FWHH) of the ν(–C=C–) peak that are suitable for temperature monitoring. VT-SERS measurements are proved to be useful for studying the behavior of ultrathin polymer films.