|Tuesday, July 19|
Gold nanoparticles and plasmonics: lets make the electrons dance!
* Olivier Pluchery, Sorbonne University - Institut des NanoSciences de Paris, France
Gold nanoparticles are famous for their ruby-red color due to the localized surface plasmon resonance. This color is the visible manifestation of an intimate coupling between an optical wave and the electrons, that takes place at the nanometer scale well below the diffraction limit. This dance of electrons occurs at a very high tempo set by the optical frequency (1015 Hz). The resonance is the visible sign of local electric field amplification that has been scrutinized for two decades and used for biosensing, for controlling photothermal effects, or for innovative thermo-therapies. This talk will first review the fundaments of plasmonics with a didactic approach, and also highlights a few of these applications.1-4 When the tempo of the electron dance is slowed down to zero, phenomena are described by electrostatics, a domain where local charges play a crucial role. These charges may enhance chemical reactivity or they create Schottky contacts between a metal particle and a semiconducting layer. Gold nanoparticles are versatile nano-objects that allow investigating fundamental questions linked to this local charge reorganization. In particular we will discuss one key property of surfaces using the concept of work function (WF). WF is clearly defined for a pure material with a planar and infinite interface but becomes unclear when surfaces are rough, when they accommodate local charges or when they are functionalized with molecules. Indeed, molecules induce charge transfer and dipolar moments. All these effects greatly influence the nanoscale chemistry and also the electric transport behavior at scales below 5 nm. The second part of the talk will show how local charges are measured and discuss consequences in nanoelectronics and chemical reactivity.5-7 Finally, combining these two tempo help understand key aspects of the recent topic of hot-electron physics.8 Plasmonic structures are able to concentrate the optical electromagnetic field and act as hot carrier sources. We will review some fascinating recent results related to hot electrons. References 1. Pluchery, O.; Bryche, J.-F., Plasmonics: An Introduction. World Scientific Publishing: London, 2022; p 340. 2. Dileseigres, A. S.; Prado, Y.; Pluchery, O., How to Use Localized Surface Plasmon for Monitoring the Adsorption of Thiol Molecules on Gold Nanoparticles? Nanomaterials 2022, 12 (2), 292. 3. Pluchery, O.; Schaming, D.; Remita, H. Patent: Packaging with two-color visual effect for decoration or identification. WO2017013373A1. 27-Jan-2017, 2017. 4. Snegir, S.; Huhn, T.; Boneberg, J.; Haus, S.; Pluchery, O.; Scheer, E., Ultraviolet Deactivation of Silane-Functionalized Surfaces: A Scalable Approach for Patterned Nanoparticle Assembly. J. Phys. Chem. C 2020, 124 (35), 19259-19266. 5. Zhang, Y.; Kang, J.; Pluchery, O.; Caillard, L.; Chabal, Y. J.; Wang, L.-W.; Sanz, J. F.; Salmeron, M., Nanoimaging of Organic Charge Retention Effects: Implications for Nonvolatile Memory, Neuromorphic Computing, and High Dielectric Breakdown Devices. ACS Applied Nano Materials 2019, 2 (8), 4711-4716. 6. Pluchery, O.; Caillard, L.; Dollfus, P.; Chabal, Y. J., Gold nanoparticles on functionalized silicon substrate under Coulomb blockade regime: an experimental and theoretical investigation. J. Phys. Chem. B 2018, 122 (2), 897-903. 7. Zhang, Y.; Pluchery, O.; Caillard, L.; Lamic-Humblot, A.-F.; Casale, S.; Chabal, Y. J.; Salmeron, M., Sensing the Charge State of Single Gold Nanoparticles via Work Function Measurements. Nano Letters 2015, 15 (1), 51-55. 8. Halas, N. J., Spiers Memorial Lecture Introductory lecture: Hot-electron science and microscopic processes in plasmonics and catalysis. Faraday Discussions 2019, 214 (0), 13-33.