Heat confinement in prussian blue core-shell nanoparticles for photothermal action – HOTSPOT

The concept of “hot nano-spots” consists in the creation of a very localized heating in the corona of inorganic nanoparticles submitted under external stimuli in some particular conditions. This phenomenon permitting the assimilation of the nanoparticles to “hot nano-spots” in a cold environment has attracted a great deal of interest due to numerous advantages in a wide range of applications including biomedical area, catalysis, chemical and biological reactions and others. However, its direct proofs have not yet been provided and the rational design of nano-objects permitting to produce “hot nano-spots” has never been investigated. The aim of the HOTSPOT proposal consists in the design of smart photothermal agents with controlled heat transfer at the nanoscale to produce, demonstrate and control the “hot spot” effect. To achieve this aim, we focus on designing of Prussian Blue nanoparticles as photothermal nanoheater cores (under near infrared irradiation) enwrapped by an insulating silica shell with different thickness offering a modulable heat confinement at the nanoscale. The integrated temperature sensors will be used in order to provide the temperature detection during photothermal activation : (i) in the core of the nanoheater by Raman/IR spectroscopy of the temperature dependent ?(CN) vibration of the Prussian Blue nanoparticles, (ii) in the silica shell through the encapsulated in the pores ?-diketonate complexes of lanthanides as emissive self-referenced nanothermometers , and (iii) in the nanoscale corona at a variable distance from the nanoparticle surface by employing anchored to the surface NIR emissive ?-diketonate complexes. The heat transfer will be investigated by combining experiments and theoretical modeling in order to provide a temperature map at the nanoscale. We wish to validate the relevance of our concept by monitoring the interaction (melting) of a supported lipid bilayer mimicking the cell membrane with a single nanoparticle during the photothermal activation by using Atomic Force Microscopy coupled with fluorescent spectroscopy.