Size-Dependent Electron–Phonon Coupling in Monocrystalline Gold Nanoparticles

Abstract

Hot electrons in metal nanoparticles thermalize with the lattice via electron−phonon coupling. Size dependency is controversially discussed in literature. Here we investigate poly-and monocrystalline gold nanoparticles via transient absorption spectroscopy. As reported earlier, electron−phonon coupling in polycrystalline particles is not size-dependent. However, we clearly observe a size-dependent electron−phonon coupling in monocrystalline particles. Larger monocrystalline particles show slower electron−phonon coupling due to the decreasing effect of electron-surface scattering, with electron−phonon coupling constants approaching the values reported for bulk gold. In polycrystalline particles, size dependencies are outweighed by effective electron scattering at grain boundaries. Linear absorption spectra indicate that plasmon damping is also enhanced in polycrystalline particles by grain boundaries.

Role of Solvent in Electron‐Phonon Relaxation Dynamics in Core‐Shell Au−SiO2 Nanoparticles

“…Intrinsic electron-phonon coupling time has been evaluated from the extrapolated y intercept of the plot of electron-phonon relaxation time against pump energy. [62] A similar trend of relaxation times for both the values has been observed.…”

Atomic-Level Structure Determines Electron–Phonon Scattering Rates in 2-D Polar Metal Heterostructures

“…We attribute the increased electron–phonon scattering rates in 2-D alloy heterostructures to increased structural disorder. An acceleration of electron–phonon scattering with increasing density of defects occurs in graphene, noble metal nanoparticles, and thin films. − The importance of the metal phonon modes in determining the early time dynamics is also suggested by the presence of oscillatory features observed in the transient absorption data. In 2-D alloys, a prominent oscillation is observed in the time-domain data.…”

Electron and Lattice Heating Contributions to the Transient Optical Response of a Single Plasmonic Nano-Object

“…Measured signals were quantitatively compared with complete calculations based on eqs 2 and 3 performed with ∆Teq= 6.5 K, close to the experimental values for the investigated ND (Figure 4). The global agreement between experimental and simulated signals was found to be optimal for an electron-lattice energy transfer time of τe-L≈ 800 fs at weak excitation, a value slightly smaller than the one measured on large diameter colloidal gold nanoparticles 9 , possibly as a result of polycrystallinity effects 48 (the increase of this time constant for strong excitation, 49,53 illustrated in Figure S6 of the Supporting Information, is predicted by the numerical model). This initial analysis also showed that the agreement between measured and simulated time-resolved signals (in particular in terms of amplitudes) could be significantly improved in some cases by comparing experimental measurements with time-resolved signals simulated using a slightly different (within < 15 nm) λpr value.…”

“…The average measured values of pump and probe pulse durations (about 1 ps and 200 fs) were considered in the modeling, for computing the time-dependent excitation of the electron gas and for convoluting the computed Δσ ext ( t ), respectively. A 500 fs time constant was assumed for the electron gas thermalization by electron–electron interactions in gold, while the electron-to-lattice energy transfer time (∼1 ps in gold in the weak-excitation regime ,, ) was left as a free parameter, as its value for nanoparticles produced by electron beam lithography may be affected by the presence of crystalline defects. , The ND thermal cooling induced by heat propagation in the substrate, investigated in detail in a recent study, was neglected here as it occurs on time scales of about 500 ps for 20 nm thick NDs, much longer than the <10 ps ones investigated here.…”