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