Missions

One of the main goals of UV plasmonics is to detect the adsorption of molecules of interest, such as DNA and proteins, on a metal nanostructure, with a higher sensitivity than in the visible range. It is promising to assemble nanoparticles (NPs) in order to shift the plasmonic resonance, change their vibrational modes and improve their sensitivity. In this project, we design colloidal active metasurfaces
composed of assembled plasmonic bimetallic nanorods, in which external stimuli adjust the distance between the NPs and modulate the temporal and spectral variation of the near-UV optical response.
Exposing plasmonic NPs to ultrashort laser pulses produces a series of transient phenomena, including ultrafast dynamics of the plasmon modes (LSPR) as well as the activation of vibration modes. Noble metal NPs have often been proposed to be used as nanobalances by exploiting the load-dependence of their vibration mode frequencies. In preliminary works, we have shown that bimetallic silver-coated gold nanorods are promising for LSPR sensing as well as nanobalances in the near-UV region. While these effects have been predominantly studied on individual NPs, exploring the ultrafast properties of NP assemblies beyond a few particles remains a novel area for both numerical and experimental approaches.
We expect to modulate the temporal and spectral variation of the optical response in the near UV by adjusting plasmonic coupling in the metasurface. We will leverage our expertise in synthesizing and assembling NPs in solution. Specifically, we will focus on assembling nanorods, utilizing their elongated shape to form 2D layered phases (metasurfaces) through excluded-volume interactions. The optical properties of the NP assemblies will be assessed, by the post-doctoral researcher, by conventional spectrophotometry and numerical modeling. The dynamics of the optical response will be measured by broadband pump-probe transient absorption spectroscopy and simulated.6 The ultimate goal is to design plasmonic sensors in the UV spectral region, which could detect NPs loads by a dual optical readout, based on plasmon and acoustic vibration frequency shifts.

Activités

-teamwork
-pump-probe transient absorption spectroscopy measurements
-spectral modeling
-communication of results (conferences, article writing)

Compétences

The candidate must have a background in nanophysics (plasmonics, optics, condensed matter). Excellent communication skills (written and oral) in English are expected. Knowledge of French is not mandatory. The candidate's research experience must not exceed 4 years after their PhD.

Contexte de travail

The LuMIn Laboratory (Light, Matter, and Interfaces) is a research unit (FRE2036) established on January 1, 2020, under the supervision of Université Paris-Saclay, ENS Paris-Saclay, CNRS (INSIS), and CentraleSupélec.
The Laboratoire de Physique des Solides (LPS) is a joint research unit (UMR 8502) affiliated with Université Paris-Saclay and CNRS. It is part of the CNRS Institute of Physics and the 28th section of the National Council of Universities. LPS is also a member of the Fédération Friedel-Jacquinot, a coordinating structure for physics research on the Moulon plateau in Orsay (Île-de-France).

Contraintes et risques

Laser-related risks