Metallic nanoparticles: new strategies of nanofabrication and characterization of their near-field thermal properties by nanoscale polymerization

Abstract : In this paper, new approaches of fabrication of metal NPs are presented. In particular, spatially controlled fabrication methods based on photodewetting or photochemical reduction processes and using a tightly-focused laser beam were developed. Secondly, we investigated the thermal properties of photoexcited GNPs using a recently developed approach of nanoscale chemical imaging based on thermo-polymerizable formulations. We used molecular thermo-probes to characterize the local heat profile in the vicinity of an isolated GNP under optical excitation. For this, we developed a set of thermopolymerizable formulations. Each one is characterized by a different and controlled polymerization temperature threshold (Tth), which can be adjusted by the weight percent of the initiator system. The resulting fingerprint of the temperature distribution around a single metal nanoparticle is imaged by AFM. In particular, we show the possibility of imaging the heat distribution with a spatial resolution better than 40 nm. By tuning the excitation wavelength, we show that the photo-induced heating of the temperature can be tuned according to the extinction spectrum. Finally, by using a set of thermopolymerizable solution characterized by different threshold temperatures to determine qualitatively the minimum of temperature reached around the nanoparticle.