Ultrafast energy transfer in single nano-objects – ULTRASINGLE
Ultrafast energy transfer in individual nano-objects
The main objective of the ULTRASINGLE project is to contribute to a better understanding of energy transfer mechanisms occurring at the nanoscale, through the realization of time-resolved optical spectroscopy experiments on individual metal nano-objects and nanohybrids synthesized especially for the project, supplemented by numerical simulations allowing a quantitative interpretation of the measurements carried out.
General and specific objectives of the project
The modalities of energy transfer at the nanoscale differ markedly from those at the macroscopic scale, in particular because of the increased role played by the interfaces. The partial reflection of phonons at interfaces induces in particular thermal resistances which play a central role at the nanometric scale, and the transport of phonons also becomes ballistic at scales smaller than their mean free path. Understanding and mastering these mechanisms is crucial in many fields such as electronics and thermoelectricity, or to use nanoparticles for biological imaging and sensing. In this context, the ULTRASINGLE project pursues two specific objectives:<br />1) Understand and optimize the vibrational quality factors of nano-objects.<br />The achievement of this first objective requires in particular to better understand and minimize two distinct sources of vibrational damping: the acoustic radiation of nano-objects in their environment and the internal damping mechanisms related in particular to crystalline defects.<br />2) Study the modalities of internal thermal transfers in a nano-hybrid.<br /> This objective requires the synthesis of nano-hybrids made up of different metallic components, separated by a thin dielectric layer, and the realization of ultrafast optical spectroscopy experiments to selectively excite and probe the different constituents of the investigated nano-hybrids.
The objectives of the project are pursued by exploiting the unique and complementary expertise of the three partners in the fields of nano-object synthesis, optical spectroscopy and modeling of ultrafast processes involving nanoparticles. The project notably requires the performance of time-resolved optical spectroscopy measurements on individual nano-objects (synthesized especially for the project). This approach is based on the sudden excitation of a nanoparticle by a so-called pump light pulse, and the monitoring of the relaxation dynamics induced (internal thermalization, damped acoustic vibrations, cooling) through the transient modifications of the optical response of the studied nanoparticles, measured by a time-shifted probe pulse.
*The possibility of obtaining high vibrational quality factors for nano-objects supported on a substrate could be linked to radiative coupling phenomena between two distinct vibration modes of the nano-objects. This possibility had already been highlighted in previous work done at ILM and published in 2018, but its physical origin was not well understood at the time. *Many time-resolved optical spectroscopy experiments have been performed on individual gold nanodisks deposited on different solid substrates. They highlighted the very strong dependence of these dynamics on the properties (composition, thickness) of the substrates used, which had not been anticipated at the start of the project.
*The possibility of encapsulating a silver nanoparticle with a ultrathin silica shell (few nanometers thickness), highlighted in the project, has been demonstrated experimentally.
The synthesis of the nano-hybrids necessary to achieve objective 2) has been successfully carried out. This synthesis opens the way to the characterization of the heat transfer between two distinct metallic nanoparticles separated by a nanometric dielectric spacer, which would constitute a major result in the field of nanothermics.
Papers in peer-reviewed journals:
1. Electron and Lattice Heating Contribution to the Transient Optical Response of a Single Plasmonic Nano-Object; R. Rouxel, M. Diego, P. Maioli, N. Lascoux, F. Vialla, F. Rossella, F. Banfi, F. Vallée, N. Del Fatti et A. Crut;
The Journal of Physical Chemistry C 125, 23275-23286 (2021) doi.org/10.1021/acs.jpcc.1c06629 (Experimental and theoretical study of internal energy exchanges in an individual nano-object and of the associated transient optical response)
2. Substrate-supported nano-objects with High vibrational Quality Factors; A. Crut ;Journal of Applied Physics 131, 244301 (2022) doi.org/10.1063/5.0093585
(Elucidation of the conditions required to create weakly damped vibrational modes)
The modalities of nanoscale and macroscale energy transfer differ because of the increased role of interfaces and ballistic phonon transport in the former case, whose fundamental description is required in fields such as electronics, thermoelectricity, biological imaging or sensing. The proposed project aims at both optimizing the vibrational quality factors of metal nanoparticle-based nanoresonators (by determining and minimizing their intrinsic damping sources) and characterizing phonon transport in thin layers separating two distinct metallic components used as heater and thermometer, respectively. The consortium formed to reach these goals brings together three partners with complementary expertise: the synthesis of single-crystal gold nanoparticles and of metal-dielectric nano-hybrids, and their time-resolved optical spectroscopy at the single-particle level.
Project coordination
Aurelien CRUT (INSTITUT LUMIERE MATIERE)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
Partner
ILM INSTITUT LUMIERE MATIERE
NIMBE Nanosciences et innovation pour les matériaux, la biomédecine et l'énergie
ICMCB INSTITUT DE CHIMIE DE LA MATIERE CONDENSEE DE BORDEAUX
Help of the ANR 367,117 euros
Beginning and duration of the scientific project:
- 48 Months
