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The optical extinction spectra of single gold nanoparticles stabilized by surfactant molecules are investigated using the spatial modulation spectroscopy technique. The experimental results are compared to computed spectra, focussing on the width of the surface plasmon resonance. It is shown to strongly vary from particle to particle, independently of their size and dielectric environment. This demonstrates the key role of the interface conditions on the width of the surface plasmon resonance for surfactant-stabilized metal nanoparticles. [ABSTRACT FROM AUTHOR]

The extinction spectrum of single silver nanoparticles with size ranging from 20 to 80 nm is investigated with the spatial modulation spectroscopy technique using either a tunable laser or a white lamp as the broadband source. Results are in good agreement with the prediction of the Mie theory, permitting to extract the nanoparticle size from the measured absolute value of the optical extinction cross-section. In contrast, the deduced refractive index of the nanoparticle environment and the reduction of the electron mean free path show a large dependence on the precise value of the bulk silver dielectric function. [ABSTRACT FROM AUTHOR]

Electron–lattice energy exchange is investigated in an ensemble of silver nanoparticles of mean diameter 9 nm and in a single 30-nm particle using a femtosecond pump–probe technique. The dependences of the measured transient transmission change and of the electron energy loss kinetics on the excitation amplitude are compared to the results of numerical simulations of nonequilibrium electron relaxation and of the two-temperature model. The good agreement between the theoretical and experimental data indicates that, for the studied low particle density samples, hot-electron cooling is dominated by electron–lattice coupling in a nanoparticle both for weak and large electron heating with a minor influence of their surrounding environment (glass or polymer matrix). [ABSTRACT FROM AUTHOR]

Effects of confinement on the electron-electron (e-e) and electron-phonon (e-ph) thermalization dynamics in noble metal clusters are calculated using simple approaches. The model predictions are compared with femtosecond pump-probe measurements which display an acceleration of the e-e and e-ph relaxation dynamics. The size-effects on the e-e relaxation dynamics are consistent with a model involving the surface-induced reduction of the screening efficiency of the Coulomb e-e interaction. With regard to the e-ph relaxation dynamics, this model yields too large time constants, pointing out deficiencies of the standard modelling of the e-ph energy exchanges in bulk metals. Analysis of these deficiencies shows that the bare e-ion interaction has to be involved in the transition matrix element describing the non-adiabatic e-ph energy exchanges. [ABSTRACT FROM AUTHOR]

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The effects of surface-induced lattice contraction on the size evolution of the surface plasmon resonance and of the electronic thermalization time in small silver clusters have been investigated in the framework of a mixed classical/quantum model. The increase of the conduction-electron density results in a blue-shift trend for decreasing cluster size. However this effect is counterbalanced by the increase of the dielectric function associated to the ionic-core background. Agreement with the blue-shift trend observed in experiment is recovered by introducing an inner surface skin of vanishing ionic-core polarizability having a thickness practically unchanged as compared to previous estimations. The influence of the lattice contraction on the electron dynamics is also discussed. It is shown that this influence is negligible as compared to the surface effects arising from the spillout and the inner skin of reduced ionic-core polarizability which are both responsible for a decrease of the electron thermalization time as the particle size decreases. [ABSTRACT FROM AUTHOR]

Femtosecond excitation and relaxation of nonequilibrium electrons are investigated in silver clusters using a two color pump-probe technique with resonant excitation of the surface plasmon resonance and off resonant probing. The excitation process is shown to be identical to that in metal films, and permits creation of a strongly athermal single electron excitation in a time scale shorter than the duration of the pulses (25-30 fs), in agreement with the free-electron absorption model. Following the time evolution of the nonequilibrium distribution yields information on the internal energy redistribution dynamics of the conduction electrons and of its modification by confinement in metal clusters. [ABSTRACT FROM AUTHOR]

The physical origin and the dynamics of the ultrafast optical nonlinear response of noble metal nanoparticles are analyzed around the surface plasmon resonance frequency using extension of the bulk metal electron kinetics and band structure models. The computed spectral and temporal responses are found to be in very good agreement with the measured ones in silver when taking into account the impact of electron excitation on both the interband absorption and electron optical scattering rate. A good reproduction of the strong excitation regime experimental results is also obtained in the case of gold, with a dominant contribution of the interband effect. [ABSTRACT FROM AUTHOR]

Abstract. Ultrafast modifications of the electron scattering rate due to selective heating of the free electron gas are investigated in silver nanoparticles embedded in a glass matrix. Measurements were performed using a two-color femtosecond pump-probe technique and probing the induced changes of the surface plasmon resonance width. The results show that ultrafast heating of the electron gas leads to a large transient increase of the probability of electron scattering off the nanoparticle surfaces, in agreement with a theoretical model. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Anaesthesia / Journal Canadien d'Anesthésie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)