This team of CentraleSupélec, investigating ultrafast optical and thermal exchanges at the nanoscale, belongs to both LPQM and Institut d'Alembert of the Ecole Normale Supérieure de Cachan and the CNRS.

Link to the ECP website of the group

Ultrafast plasmonics in metal nanoparticles

Noble metal nanoparticles offer remarkable optical properties linked with the plasmon  resonance phenomenon. Numerous developments are currently based on these properties, constituting the field of plasmonics. In order to better understand the physical processes involved, it appears relevant to study the dynamics of the optical response subsequent to the excitation of matter by a light pulse. This topic therefore relies on the development of modeling methods adapted to the different time scales involved and on the implementation of ultrafast laser spectroscopy techniques.

Photo-induced heat transfer at short time and space scales

In this theme we study the optical generation of heat and its transfer at both nanometer scale and ultrashort times, where the classical thermodynamics approaches are no longer valid. Beyond, it is possible to structure matter as to transform a thermal excitation into a coherent radiation. This can be achieved for instance by coupling the phonon-polariton phenomenon to a photonic cavity. This topic is developed in partnership with the EM2C laboratory.

Heat nanosources for chemistry and biology

Metal nanoparticles under visible electromagnetic radiation are able to act as nanoscale heat sources due to a series of internal energy exchanges. This conversion process can be employed in various fields, particularly for realizing optical, chemical or biological functions. One can then envisage materials or devices whose functionality is only activated and controlled by light. Within dedicated partnerships we jointly develop projects targeting biomedical applications (improvement of the adhesion of nanohybrid particles on cancer cells for nano-hyperthermia therapy, plasmonic liposomes for targeted drug delivery, intracellular DNA strand delivery triggered by nanoscale photothermal effect for gene therapy). Beyond, the high local electromagnetic field generated at the plasmon resonance of gold nanoparticles induces the effective ionization of water molecules around, which can be exploited for photodynamic therapy, in conjunction with the photothermal effect.

Ultrafast photo-induced modulation of the nanoparticle optical properties: photonic applications

Thanks to the localized plasmon resonance phenomenon, stemming from the interaction of an electromagnetic wave and the electrons confined in metal nanoparticles, one can efficiently and very quickly inject energy in the latter by light irradiation. From the series of the subsequent exchange and relaxation mechanisms the optical properties of the composite medium where these nanoparticles are spread are modified in a fast transient way. By playing together with these nanoscale photo-induced modifications and the processing of the composite medium in wavelength-scale structured devices (resonant cavity, photonic crystal), one may conceive optically controlled photonic functions.

Scientific partners

France: Énergétique Moléculaire et Macroscopique, Combustion (CNRS-ECP); Laboratoire de Chimie Physique (Orsay); Sciences et Ingénierie de la Matière Molle - Physico-chimie des Polymères et Milieux Divisés (ESPCI, Paris) ; UMR_S728  Université Denis Diderot (Paris 7) - Inserm; Photophysique et Photochimie Supramoléculaires et Macromoléculaires (ENS Cachan); Physicochimie des Electrolytes, Colloïdes et Sciences Analytiques (Paris).

International: Instituto de Optica, Madrid, Spain ; Univ. Sistan & Baluchestan, Iran.

Effective nanoscale photo-generation of reactive oxygen species

In partnership with the group of R. Pansu at PPSM laboratory in ENS de Cachan, we have demonstrated that in a gold nanorod irradiated by femtosecond light pulses a multiphotonic process enabled by the local field enhancement at the plasmon resonance generates efficiently a local plasma and reactive oxygen species, over a range of several micrometers (Fig. 1). This is very promising for local photodynamic therapy of cancer.

                 

Figure 1. Production of reactive oxygen species by a single gold nanorod irradiated by polarization-controlled femtosecond laser pulses tuned at the plasmon resonance, probed by a fluorescent molecule. From left to right: three different polarization directions. Scale bar: 1 µm.

Thermal metamaterials

On some materials at the nanoscale heat propagates as an electromagnetic surface wave called surface phonon polariton. The heat thus acquires coherence properties over distances up to and meter and it becomes possible to use the tools of nano-optics to change its propagation. By structuring the material at a sub-wavelength scale, one can then create a material whose thermal properties do not exist in nature. The development of simulation tools based solely on Maxwell's equations of electromagnetism has opened the opportunity to create passive materials with temperature inhomogeneities though at thermal equilibrium. This theme is developed in partnership with the team of S. Volz at EM2C laboratory.

                    

Figure 2. Median cross section of the distribution of heat around a silica thin film (black) with a photonic crystal cavity (top right of the film).

· ANR program Blanc 2013-2017, project Nan'Onsen: Heat nanosources for therapeutics, coordinator

· ANR-DGA program Astrid 2015-2017, project CALITREC: Cascade Laser In Tunable Robust Extended Cavity, partner

· C'Nano IdF, 2014-2016, project GoldHeat: Optical control of the permeability of liposomes by photothermal effect from gold nanoparticles, coordinator

· C'Nano IdF, 2014-2015, project IPERCHOS: Incidence Physiopathologique Et Réponse Cellulaire à l'Hyperthermie Optiquement Stimulée dans les nanoparticules d'or", partner

· Institut d'Alembert, 2014-2015, project LIGhTER: Light Induced thermal energy conversion of gold Nano rods applied to Gene THERapy, partner

· Labex LASIPS, 2015, project MorphoNano: Morphodynamique, nanoparticules d'or et enjeux de société", coordinator

· Labex LASIPS, 2015-2018, project NOPACH : "Photo-activated nano-objects for cell targetting and hyperthermia", coordinator

• Réponse optique ultrarapide de nanoparticules métalliques
• Propriétés thermo-optiques de milieux nanocomposites
• Transferts thermiques photo-induits aux petites échelles de temps et d'espace
• Nanosource de chaleur pour la chimie et la biologie
  
• Modulation photonique ultrarapide dans une cavité plasmonique