Periodic Reporting for period 1 - PLASMMONS (Plasmons and Mechanical Motions at the Nano-Scale Investigated with Frequency-Domain Experiments and Simulations)
Période du rapport: 2020-11-01 au 2022-10-31
Plasmons are oscillations of charge carriers in metallic nanostructures that confine light in the nanometer length-scale. Colloidal dispersions and self-assembled plasmonic nanoparticles can become an integral part of optoelectronics and light harvesting technologies like plasmonic solar cells, various types of sensors, and photocatalysts. The connection between the properties of plasmons and the static morphology of the metallic nanostructures (size, shape, spatial arrangement, chemical environment) has been studied over several decades. More recently the focus is on the effect of dynamical morphological changes on plasmons, as the ones induced with confined acoustic vibrations in the gigahertz (GHz) frequency range. Coupling between plasmonic and mechanical degrees of freedom paves the way for the so-called acousto-plasmonic devices, which can be utilized for various types of sensing and signal-processing applications.
For realistic applications, plasmonic nanostructures are synergistically combined with molecular ligands, polymers, or inorganic substrates, crystalline surfaces and nanomembranes. During this project, we have studied all these three types of hybrid plasmonic materials. More specifically, we studied:
1) Nanocomposites of plasmonic nanostructures embedded in polymers, which have a broad range of applications due to their temperature- and pressure-tunable mechanical and thermal properties, photothermal conversion and photo-actuation, the ability to employ a multifarious toolbox for nanofabrication, and their potential use in flexible devices.
2) Ligand-protected plasmonic nanoparticles. These are nanoparticles whose surface is decorated with molecules that drive self-assembly into ‘super-crystalline’ structures, i.e. colloidal crystals. An interesting aspect, examined during this project, is the ability of light and plasmons to energize the ligands and promote self-assembly.
3) Plasmonic nanostructures on surfaces and nanomembranes, which can be used as efficient sources of acoustic phonons (surface acoustic waves, SAW, and Lamb waves, respectively) for acoustoplasmonic devices. In future signal-processing devices, the high operational frequency needs to be combined with ultrasmall device size. Thus, plasmonics may offer new types of trasnducers between electromagnetic signals and acoustic phonons for timing, delaying or spectral filtering.
For all these systems, studies of acoustic phonons in plasmonic nanostructures are essential for heat management, mechanical properties, and optomechanics. The aim of this project is to elucidate the interaction between plasmons and mechanical motions in nanostructures using Brillouin Light Scattering (BLS) spectroscopy. More precisely, the objectives are: (1) to prepare and characterize plasmonic nanostructures, such as plasmonic nanorods dispersed in polymers and ligand-protected self-assembled plasmonic nanospheres, (2) to study their optical properties and identify the energy and symmetry of their plasmonic resonances, (3) to study their confined acoustic vibrations with BLS at various photon wavelengths, and (4) to study the interaction between plasmonic and mechanical resonances and understand how the plasmonic near-fields modify the selection rules for optomechanical coupling - the interaction giving rise to the BLS signal.
For realistic applications, plasmonic nanostructures are synergistically combined with molecular ligands, polymers, or inorganic substrates, crystalline surfaces and nanomembranes. During this project, we have studied all these three types of hybrid plasmonic materials. More specifically, we studied:
1) Nanocomposites of plasmonic nanostructures embedded in polymers, which have a broad range of applications due to their temperature- and pressure-tunable mechanical and thermal properties, photothermal conversion and photo-actuation, the ability to employ a multifarious toolbox for nanofabrication, and their potential use in flexible devices.
2) Ligand-protected plasmonic nanoparticles. These are nanoparticles whose surface is decorated with molecules that drive self-assembly into ‘super-crystalline’ structures, i.e. colloidal crystals. An interesting aspect, examined during this project, is the ability of light and plasmons to energize the ligands and promote self-assembly.
3) Plasmonic nanostructures on surfaces and nanomembranes, which can be used as efficient sources of acoustic phonons (surface acoustic waves, SAW, and Lamb waves, respectively) for acoustoplasmonic devices. In future signal-processing devices, the high operational frequency needs to be combined with ultrasmall device size. Thus, plasmonics may offer new types of trasnducers between electromagnetic signals and acoustic phonons for timing, delaying or spectral filtering.
For all these systems, studies of acoustic phonons in plasmonic nanostructures are essential for heat management, mechanical properties, and optomechanics. The aim of this project is to elucidate the interaction between plasmons and mechanical motions in nanostructures using Brillouin Light Scattering (BLS) spectroscopy. More precisely, the objectives are: (1) to prepare and characterize plasmonic nanostructures, such as plasmonic nanorods dispersed in polymers and ligand-protected self-assembled plasmonic nanospheres, (2) to study their optical properties and identify the energy and symmetry of their plasmonic resonances, (3) to study their confined acoustic vibrations with BLS at various photon wavelengths, and (4) to study the interaction between plasmonic and mechanical resonances and understand how the plasmonic near-fields modify the selection rules for optomechanical coupling - the interaction giving rise to the BLS signal.
The work performed during this project includes:
1) Synthesis and characterization: We have collaborated with nanofabrication laboratories to obtain gold nanorods in polymers and ligand-protected gold nanoparticles of various sizes, and to characterize them with electron microscopy, diffraction, optical absorption and BLS.
2) Multi-colored BLS: We used these different wavelengths to measure and compare BLS on- and off-resonance with the plasmons and to reveal plasmonic enhancement.
3) Pumped-BLS: We have developed the technique termed pumped-Brillouin light scattering (pumped-BLS) that combines femtosecond laser excitation with continuous wave BLS, for all-optical detection of non-thermal acoustic phonons. We have applied this technique to study the emission of acoustic phonons out of laser-excited metallic transducers on semiconducting surfaces.
4) Modelling plasmons, phonons and their interactions: We have developed finite-element-method (FEM) models using the commercially available COMSOL Multiphysics to study plasmons, confined acoustic vibrations/phonons, and optomechanical calculations based on the moving interface mechanism, the photoelastic effect and Drude-Lorentz modelling of the optical properties of metals.
5) Dissemination and exploitation: We have organized two mini Workshops at the Faculty of Physics of the Adam Mickiewicz University (AMU) as the host institution with the participation of theoreticians and experimentalists from various countries. The first was titled ‘Bosonic Excitations on Surfaces & Low-Dimensional Materials’. The second was titled ‘Plasmons and Vibrational Dynamics in Nanomaterials’. Moreover, we have delivered scientific presentations in international conferences like the APS, DPG, and EMRS.
Through dissemination actions, we have pursued and achieved international collaborations - including with researchers that hold European grants with complementary scope - such as: Prof. Shu Yang (University of Pennsylvania), Prof. Dr. Hab. Wiktor Lewandowski (University of Warsaw), Prof. Bahram Djafari Rouhani (University of Lille), Dr. Adnane Noual (University of Mohamed Premier), Prof. George Fytas (ERC AdG SmartPhon, Max Planck Institute for Polymer Research in Mainz, MPIP), Prof. Tanja Weil (MPIP) and the MSCA fellows Tommaso Marchesi D’Alvise and Clara Magdalena Saak, as well as Prof. Ralph Ernstorfer (ERC FLATLAND), the Humboldt fellow Dr. Tommaso Pincelli, and Professor Stephanie Reich (Free University of Berlin).
We estimate that we communicated our work to 40 scientists with EMRS 2021, 20 with APS March meeting in 2021, 20 with DPG 2021, 110 with Wombat 2022, nearly 50 scientists and students with a lecture in the University of Warsaw, 50 scientists with the two mini-workshops, while the social media attracted 80 followers or reactions from the general public. Finally, we made all the scientific articles available to the general public through the online repository of the Adam Mickiewicz University (https://repozytorium.amu.edu.pl(s’ouvre dans une nouvelle fenêtre)).
1) Synthesis and characterization: We have collaborated with nanofabrication laboratories to obtain gold nanorods in polymers and ligand-protected gold nanoparticles of various sizes, and to characterize them with electron microscopy, diffraction, optical absorption and BLS.
2) Multi-colored BLS: We used these different wavelengths to measure and compare BLS on- and off-resonance with the plasmons and to reveal plasmonic enhancement.
3) Pumped-BLS: We have developed the technique termed pumped-Brillouin light scattering (pumped-BLS) that combines femtosecond laser excitation with continuous wave BLS, for all-optical detection of non-thermal acoustic phonons. We have applied this technique to study the emission of acoustic phonons out of laser-excited metallic transducers on semiconducting surfaces.
4) Modelling plasmons, phonons and their interactions: We have developed finite-element-method (FEM) models using the commercially available COMSOL Multiphysics to study plasmons, confined acoustic vibrations/phonons, and optomechanical calculations based on the moving interface mechanism, the photoelastic effect and Drude-Lorentz modelling of the optical properties of metals.
5) Dissemination and exploitation: We have organized two mini Workshops at the Faculty of Physics of the Adam Mickiewicz University (AMU) as the host institution with the participation of theoreticians and experimentalists from various countries. The first was titled ‘Bosonic Excitations on Surfaces & Low-Dimensional Materials’. The second was titled ‘Plasmons and Vibrational Dynamics in Nanomaterials’. Moreover, we have delivered scientific presentations in international conferences like the APS, DPG, and EMRS.
Through dissemination actions, we have pursued and achieved international collaborations - including with researchers that hold European grants with complementary scope - such as: Prof. Shu Yang (University of Pennsylvania), Prof. Dr. Hab. Wiktor Lewandowski (University of Warsaw), Prof. Bahram Djafari Rouhani (University of Lille), Dr. Adnane Noual (University of Mohamed Premier), Prof. George Fytas (ERC AdG SmartPhon, Max Planck Institute for Polymer Research in Mainz, MPIP), Prof. Tanja Weil (MPIP) and the MSCA fellows Tommaso Marchesi D’Alvise and Clara Magdalena Saak, as well as Prof. Ralph Ernstorfer (ERC FLATLAND), the Humboldt fellow Dr. Tommaso Pincelli, and Professor Stephanie Reich (Free University of Berlin).
We estimate that we communicated our work to 40 scientists with EMRS 2021, 20 with APS March meeting in 2021, 20 with DPG 2021, 110 with Wombat 2022, nearly 50 scientists and students with a lecture in the University of Warsaw, 50 scientists with the two mini-workshops, while the social media attracted 80 followers or reactions from the general public. Finally, we made all the scientific articles available to the general public through the online repository of the Adam Mickiewicz University (https://repozytorium.amu.edu.pl(s’ouvre dans une nouvelle fenêtre)).
During this project we encountered several interesting findings: (1) we have studied the effect of laser irradiation on the self-assembly of colloidal nanoparticles, (2) we observed strong photon-energy-dependent BLS spectra and plasmonic enhancement for gold nanorods in polymers, (3) we studied light-to-motion conversion in a polymeric nanomembrane, and (4) we encountered unusual spectroscopic signatures for non-thermal acoustic phonons in metallic-semiconduting heterostructures using pumped-BLS. These studies pave the way for the use of Brillouin light scattering as a probe of acoustic phonons in nano- and meta-materials, which will also be able to extract information on the energy and symmetry of plasmonic near-fields. The fellowship ended with 5 publications in high impact journals (NanoLetters, ACS Nano, Advanced Materials), the initiation of a new research project that received funding from the National Science Centre of Poland, and various types of awards and distinctions such as the AMU Rektor’s first prize (twice) and the IDUB funding of the Adam Mickiewicz University.