|Monday, July 18|
Sampling and quantification in SERS immunoassays
* Christy Landes, Rice University, United States
Plasmonic nanoparticles support a localized surface plasmon resonance and large absorption cross section, allowing unmatched light absorption into confined areas. The ultrafast lifetime of the plasmon’s decay presents challenges harnessing the absorbed energy before it dissipates into heat. Hybridization of plasmonic nanomaterials with energy transfer acceptors such as semiconductors would enable subsequent reactions to harness the energy offered from plasmonic nanomaterials. While fully inorganic hybrids have been well-studied , hybridization of plasmons with polymer acceptors has had less attention. Plasmon damping in the scattering of individual gold nanorods upon the addition of a polyaniline shell will be discussed. Plasmon damping is a measure of energy transfer into the polymer. In this study, gold nanorod-polyaniline (AuNR-PANI) hybrids are investigated in different pH conditions to determine optimal conditions for the efficient transfer of energy from the plasmon to the PANI shell. Polyaniline has been shown to be sensitive to pH changes, transitioning from emeraldine salt to pernigraniline base as pH increases. By monitoring the modulation in the single particle resonance energy and linewidth resulting from changes in the refractive index and plasmon dynamics, respectively, we investigate the plasmon dynamics of single hybrids. Using a microfluidic cell on an inverted hyperspectral dark-field microscope, correlated single particle scattering spectra in acidic, neutral, and basic conditions is compared. As the pH varies, the PANI absorption spectra shift as a result of the change in protonation state. Broader line widths, indicating a faster plasmon decay time due to energy transfer, were seen in more acidic conditions due to a larger spectral overlap between the AuNR core resonance and PANI shell absorption.
Characteristics of the plasmon-induced reduction of CO2 with water over titania-interfaced gold-based catalysts
* Leila Hammoud, ICPEES (CNRS UMR 7515 / University of Strasbourg), France
Claire Strebler, ICPEES (CNRS UMR 7515 / University of Strasbourg), France
Valérie Keller, ICPEES (CNRS UMR 7515 / University of Strasbourg), France
Valérie Caps, ICPEES (CNRS UMR 7515 / University of Strasbourg), France
The gas phase photoreduction of CO2 with water can be achieved by plasmonic excitation of titania - interfaced gold nanoparticles (NPs) leading to the formation of methane. Methane production rates are however about 100 times lower than those obtained in semi-conductor (SC)-based processes. In this presentation, the effect of size and loading of the plasmonic NPs will be described. It will be shown how remarkably stable plasmon-induced methane production is, as compared with the SC-based process, how the hot carriers and heat generated upon decay of the localized surface plasmon resonance independently affect activity and selectivity, and how plasmon-derived methane production rates could be improved by one order of magnitude using this knowledge.
Core-shell gold-silver nanoparticles: Near-ultraviolet plasmon modes, sub-THz vibration modes, and acousto-plasmonic coupling
Tadele Orbula Otomalo, Le Mans University - France, France
Lorenzo Di Mario, Istituto di Struttura della Materia - CNR, Italy
Cyrille Hamon, Université Paris-Saclay, France
Doru Constantin, Université Paris-Saclay, France
Khanh-Van Do, CentraleSupélec - Université Paris-Saclay, France
Vincent Juvé, Le Mans University - France, France
Pascal Ruello, Le Mans University - France, France
Patrick O'Keeffe, Istituto di Struttura della Materia - CNR, Italy
Daniele Catone, Istituto di Struttura della Materia - CNR, Italy
Alessandra Paladini, Istituto di Struttura della Materia - CNR, Italy
* Bruno Palpant, CentraleSupélec - Université Paris-Saclay, France
Noble metal nanoparticles (NPs) exhibit localized plasmon resonance modes covering the visible and near-infrared spectral ranges. The NP size, shape, and composition influence the characteristics of these modes, but it is impossible to access strong resonances in the near-ultraviolet, although this would be potentially exploitable for many applications. Besides, shining plasmonic NPs with ultrashort laser pulses generates transient phenomena used in a wide range of fields. They originate from the ultrafast dynamics of the metal hot electron gas induced by multiphoton absorption. Our objectives are to measure, simulate and analyze the stationary and ultrafast transient optical response of bimetallic core-shell gold-silver nanoparticles. In addition, we aim at determining their vibrational modes in the sub-THz range. We first synthesize colloidal solutions of core-shell nanocuboids consisting of gold nanorods (48×16 nm²) coated with a silver shell with variable thickness (0 to 18 nm): AuNRs@Ag. Conventional UV-visible spectroscopy reveals that the NP dipolar transverse mode vanishes with increasing Ag-shell thickness, while higher-order modes grow in the near-ultraviolet. By carrying out broadband ultrafast transient absorption (TA) spectroscopy, we show that these higher-energy modes generate intense and sharp variations of the NP extinction. We break down the different contributions to this response and interpret its spectral profile by modeling the optical dynamics. In addition, we show that the TA signal reveals resonance modes hidden in its stationary counterpart. Furthermore, we analyze the time variation of the TA by fast Fourier transform, which reveals vibration modes from 15 to 150 GHz frequency. Simulations using the finite element method allow us to address this vibrational landscape. While bare AuNRs exhibit extensional and breathing modes, the AuNRs@Ag undergo complex motions, the amplitude and frequency of which depend on the Ag-shell thickness, as the silver load modifies the NP aspect ratio and mass. Moreover, varying the probe laser wavelength modifies the contribution of each vibrational mode to the TA spectra. This stems from the coupling of the different vibrations with the plasmon modes, as demonstrated by combining in simulations the NP elastic and optical properties simulations. To conclude, we have successfully explained the complex optical response of Ag-coated gold nanorods, both in the stationary and the transient regimes. The near-ultraviolet plasmon modes and sub-THz vibration modes of the core-shell NPs have been identified thanks to the support of our models. Furthermore, we have elucidated the role of acousto-plasmonic coupling in the transient absorption dynamics. The sharp spectral and temporal variations of the plasmon resonances in the near-UV may be exploited for photonic switching, ultrafast fluorescence control, near-field modulation for time-resolved sensing, and multiphotonic electron emission and photoluminescence in new spectral ranges. In addition, noble metal nanoparticles have often been proposed to be used as nanobalances by exploiting the load-dependence of their vibration mode frequencies. Our results suggest that, by probing the vibration properties in the spectral domains of different plasmon modes, we could quantitatively assess the relative deposition at the NP tips and sides.
Plasmonic gold particle assisted sorption behavior of porous materials
* Caroline Byun, LCMCP, Sorbonne university , France
Amélie Perot, LCMCP, Sorbonne university , France
Simon Delacroix, LPICM, Institut Polytechnique de Paris, France
Hajar Amyar, LCMCP, Sorbonne university , France
Aleix G. Güell, LPICM, Institut Polytechnique de Paris, France
Cedric Boissière, LCMCP, Sorbonne university , France
Marco Faustini, LCMCP, Sorbonne university , France
In this contribution, the thermal and optical behaviors of porous materials in which laser-driven local heating is induced by gold nanoparticle will be presented. To achieve this, bottom-up synthesis of plasmonic porous materials that combines gold nanoparticles and different types of porous materials (Oxides and Metal-Organic-Framework, MOF) were carried out. Then, in-situ measurement based on hyperspectral imaging microscopy was developed in order to follow the temperature-driven sorption behavior of porous plasmonic materials.