Exploiting thermally driven processes in thin-polymer films and on metal particle surfaces.

Abstract

Temperature variations play a pivotal role in deciding the path of many biological and physical processes, yet only few available probes allow measuring these fluctuations at the micro- and nano-scale accurately. In this work, we aim to develop new strategies to map thermal variations in thin polymer films. This acquired knowledge will subsequently allow us to drive chemical reactions using locally generated heat by magnetic nanoparticles with high spatial resolution. A thermal probe was thus developed through complexing poly (phenylene ethynylene) fluorescent-based conjugated polyelectrolyte (PPE-CO₂) with polyvinylpyrrolidone-co-vinyl acetate (PVP-VA). When testing the temperature response in PVP-VA solution, a relative maximum sensitivity of 2.35percent was obtained. The polymer complex was then spun cast onto quartz slides and imaged using a DSLR camera at different temperatures between 20.0 °C and 60.0 °C. Finally, these images were analyzed using the ImageJ software to study the change in color upon increasing the temperature. Building on the previous work, iron-oxide magnetic nanoparticles were complexed with gold nanoparticles via a multi-layer coating method. The heat generated by the magnetic nanoparticles when placed in an alternating magnetic field is transferred to the gold nanoparticle surface where heat-dependent reduction reaction of resazurin, a weakly fluorescent molecule, to a highly fluorescent resorufin is monitored. This level of spatial heat control will allow us to locally catalyze chemical reactions and release reactive oxygen species intracellularly with surgical spatial control.