COME-ON

COME-ON aims at demonstrating controlled light-induced organization of individual nano-sized objects using photomechanically active azo-derivative molecules. Indeed, the cis-trans photoisomerization of such molecules is known to produce huge average mass-transport effects in polymeric hosts. However, these properties have yet never been exploited to initiate and spatially control any light-driven motion of nano-objects. Our main goal is to investigate at the molecular scale the requirements to convey nanoparticles (NPs) by light and to ultimately control the direction of the NPs displacement in order to be able to consider in the longer term the realization of “on-demand” NP assemblies. The project musters 2 partners coming from 3 different research institutes and showing complementary competences in pluridisciplinary domains : - Local probe microscopy techniques for the characterization of photoinduced movements at the molecular and at the NP scale : Scanning Tunneling Microscopy (STM) : Partner 1, CEA Saclay DSM-IRAMIS ; Optical Microscopy coupled to shear force measurements (SNOM-SFM, Partner 2 Condensed Matter Physics Lab, CNRS at Ecole Polytechnique) and Atomic Force Microscopy (AFM, Partners 1 et 3 : PPSM laboratory at ENS Cachan). - Ensemble characterization techniques such as confocal fluorescence microscopy (Partner 3) - Photophysics (Partner 1) and photochemistry (Partner 3) of photochromic molecules and materials. - Chemical synthesis and surface functionalisation, which should implies both partners 2 and 3. Two configurations will be studied for the investigation of photoinduced NPs movements : NPs incorporated in a photoactive matrix and NPs dispersed on a surface. Before considering photoinduced NPs movements, we will study molecular photoisomerisation dynamics in order to understand in detail the relations between the structure of the molecules and its photomechanical properties in a given environment. Particular effort will be dedicated to molecules and NPs functionalization towards first avoiding any aggregation effects and second, optimizing azos-NPs interactions. The NPs photoinduced movements will be characterized in-situ and in real time at different scales : from the molecule scale to the NP scale to the scale of the distance travelled by the NP. For this purpose, we will make use of different microscopy techniques enabling either ensemble or individual characterization measurements : confocal microscopy, near-field optical microscopy coupled to shear-force detection (SNOM-SFM), atomic force microscopy (AFM) and scanning tunneling microscopy (STM). Two types of nanoparticles will be considered depending on the characterization tools : luminescent nanoparticles (Quantum Dots or silica NP bearing luminescent entities) and metallic nanoparticles (Gold).