|Gold nanoparticles for plasmonics and nano-medicine|
Leader: Sylvie Marguet
Participants: Aurélie Habert, Jérôme Caron (Master-2), Mohammad Khaywah (Post-doc)
Summary: This theme aims to take advantage of the enhancement of the light-matter interaction in gold nanohybrids made of gold nanoparticles with a morphology optimized to generate light, heat or charge carriers, depending on the targeted application. This research is carried out in collaboration with several expert academic research laboratories (see below) in order to discover unexpected properties. It is part of the themes developed by two CNRS Research Groups: the GdR Or-Nano and the GdR PMSE (Molecular Plasmonics and Enhanced Spectroscopies).
Plasmonics is a growing discipline at the interface between physics, chemistry and biology due to promising applications in key areas such as energy, environment and health. Gold nanoparticles (Au-NPs) concentrate incident light in an extremely small volume on their surface thanks to their plasmon resonance. In nanohybrid structures (Au-NP/molecular adsorbate or semiconductor NP), this nanoantenna effect is used to enhance several kinds of linear and non-linear phenomena. The confinement of the electromagnetic field around colloidal NPs (crystalline and not rough) is stronger than that of NPs made by nanolithography. The relaxation of the plasmon occurs according to ultra-fast competitive relaxation pathways, the relative importance of which depends on the morphology of the NP, its environment and the irradiation mode (continuous or pulsed ns,ps,fs). Thus, AuNPs can behave as nano-sources of light, heat or hot carriers and their morphology is a key parameter for this. Au-NPs also have high potential as contrast agents for medical imaging: photoacoustic imaging, dark field scattering, multi-photonic luminescence, high frequency ultrasound, quantitative phase contrast, or computed tomography. In the field of therapy, the generation of heat (Thermal PhotoTherapy, PTT) and more recently of R.O.S. (reactive oxygen species) from Au-NPs alone is an original way still little explored to treat tumors, especially in the absence of oxygen when the conventional PDT with photosensitizers in the excited triplet state (porphyrin type) cannot work (PDT: PhotoDynamic Therapy with singlet oxygen).
Some of our Au-NPs are only produced in a few laboratories: perfectly spherical spheres 8-220nm, rods with an ultra-small diameter of 6 nm, wires, cubes, stars, octahedrons, plates from 100nm to 1µm (either hexagonal, triangular or disk) of various lengths and thicknesses. Some of them are very interesting, for example: spheres and cubes deposited on a gold film are used for different types of microscopy in the gap, triangular plates are sensitive and promising biosensors for photoacoustic imaging,plates can spontaneously self-assemble in 1D columnar aggregates or 2D metasurfaces. Atomically flat, they are also promising for the FIB fabrication of monocrystalline patterns, not otherwise accessible.
Our efforts are focused on colloidal synthesis and self-assembly of high quality gold nanoparticles of various sizes and shapes. Protocols are developed to disperse them uniformly on various substrates, coat them with a layer of silica of variable thickness 3-30nm (Au@SiO2) and replace the surfactant attached to their surface by other more appropriate molecules, depending on the application. Electromagnetic "hot spots" are prepared by self-assembly (1D, 2D and 3D), see fig.
Funded Collaborations (past and present) :
“SINAPSE” (2019-2021) ANR : Silicon Carbide NanoProbes and optical Signal Enhancement for intracellular transport investigation in 3D cultures of neurons
“HEPPROS” (2018-2020) Plan Cancer : Highly Efficient Plasmonic Production of Reactive Oxygene Species for Photodynamic Therapy:
“HAPPLE” (2013-2017) ANR : Hybrid Anisotropic Plasmon-Photonics for Light Emission:
“COSSMET” (2014-2015) DIM Nano-K :
Publications : up-to-date list.
"From plasmon-induced luminescence enhancement in gold nanorods to plasmon-induced luminescence turn-off: a way to control reshaping"
“Near-Field Localization of Single Au Cubes, a Predictive Group Theory Scheme.”
“Fano Transparency in Rounded Nanocube Dimers Induced by Gap Plasmon Coupling”,
“Two-photon luminescence of single colloidal gold nanorods: revealing the origin of plasmon relaxation in small nanocrystals”,
“Engineering the emission of light from a scanning tunneling microscope using the plasmonic modes of a nanoparticle."
“An Electrically Excited Nanoscale Light Source with Active Angular Control of the Emitted Light”
“Mapping the Electromagnetic Near-Field Enhancements of Gold Nanocubes”.
“Spatial Confinement of Electromagnetic Hot and Cold Spots in Gold Nanocubes”.