Enhanced Heat Transfer with Metal-Dielectric Core-Shell Nanoparticles

Abstract

Heat transfer from irradiated metallic nanoparticles is relevant to a broad array of applications ranging from water desalination to photoacoustics. The efficacy of such processes relies on the ability of these nanoparticles to absorb the pulsed illuminating light and to quickly transfer energy to the environment. Here we show that compared to homogeneous gold nanoparticles having the same size, gold-silica core-shell nanoparticles enable heat transfers to liquid water that are faster. We reach this conclusion by considering both analytical and numerical calculations. The key factor explaining enhanced heat transfer is the direct interfacial coupling between metal electrons and silica phonons. We discuss how to obtain fast heating of water in the vicinity of the particle and show that optimal conditions involve nanoparticles with thin silica shells irradiated by ultrafast laser pulses. Our findings should serve as guides for the optimization of thermoplasmonic applications of core-shell nanoparticles.

Electron–phonon effects on the photoacoustic response of gold core–silica shell nanoparticles: From the linear regime to nanocavitation

“…This interpretation is, at least qualitatively, consistent with time-resolved spectroscopy experiments demonstrating faster heat transfer for gold nanoparticles coated with thin silica shells and immersed in water as compared with bare gold nanoparticles [23]. Faster heat transfer is also found in two-temperature model simulations of heat transfer across gold nanoparticles embedded in very thin silica shell [24]. Facilitated heat transfer is, in this case, ascribed to electron-phonon processes taking place at the interface between gold and the silica shell.…”

“…1 and eq. 2, we have assumed uniform temperatures for both the electronic and metal phonon degrees of freedom, as we have already shown that heat diffusion inside the metal core has little effect on the nanoparticle thermal relaxation following the laser excitation [24].…”

“…The relative enhancement or deterioration of photoacoustic signal should be highly dependent on the shell thickness and also on the pulse duration pulse. Indeed, very thin silica shells and short pulse durations yield faster heat transfer to the environment [19,24]. By the way contrast, it is clear that thick shells should slow down heat transfer because of the low thermal conductivity of silica, resulting in photoacoustic decrease [21,25].…”

“…This one temperature description is a fair approximation for nanosecond pulses, but at sub picosecond time scales, electron-phonon processes neglected in the one temperature description become important. Indeed, we recently showed the role played by electron-phonon processes on the heating kinetics of colloidal gold-core silica shell nanoparticles [24]. In the context of nanoscale thermal transport, several experimental studies investigated heat transport at metal/dielectric interfaces, at picosecond time scales.…”

Continuous gas-phase synthesis of core–shell nanoparticles via surface segregation

“…Such attention to core-shell nanoparticles arises from the fact that they can exhibit enhanced physical and/or chemical properties. [1][2][3] Furthermore, core-shell particles with distinctly new properties compared to those of the constituent materials can be designed by tuning, for example, their size, shell thickness, and structures. [4][5][6][7] A large number of research projects are underway to fabricate highly functional core-shell materials for applications in various elds, including optoelectronic devices, 8,9 biomedical imaging, 10,11 catalysis, 12,13 and plasmonics.…”