Photoacoustics of core–shell nanospheres using comprehensive modeling and analytical solution approach

Abstract

Photoacoustic visualization of nanoparticles is capable of high contrast imaging at depth greater than that of traditional optical imaging techniques. Identifying the impact of various parameters on the photoacoustic signal is crucial in the design of effective medical imaging and diagnostics. Here, we develop a complete model of Fourier heat conduction incorporating the interfacial thermal resistance and photoacoustic equation for core-shell nanospheres in a fluid under nanosecond pulsed laser illumination. An analytical solution is obtained, elucidating the contribution of each region (core, shell, or the fluid) in the generation of the photoacoustic signal. The model reveals that the sharper the laser pulse temporal waveform is, the higher the sensitivity of the generated photoacoustic signal will be to the interfacial thermal resistance, and, thus, the higher the possibility of photoacoustic signal amplification will be using silica-coating. The comprehensive model and adopted analytical solution reveal the underlying physics of the photoacoustic signal generation form core-shell nanosphere systems.

Enhanced Heat Transfer with Metal-Dielectric Core-Shell Nanoparticles

“…As regards the nonlinear photoacoustic response of CSNPs, it may be analysed either by using the analytical approach of Calasso et al [91] in the linear regime, orby solving the finite difference time domain (FDTD) numerical scheme of Prost et al [11]. The frontier between the linear and non-linear regime corresponds to a laser fluence F 7 mJ/cm 2 , which for CSNP irradiated by femtosecond laser pulses with a wavelength in the vicinity of the surface plasmon resonance corresponds to a power P 20 W. Note that a recent study solved photoacoustic equation for silica-coated nanoparticles based on Fourier heat conduction model [42]. However, this work does not treat electron-phonon coupling processes, and addresses mainly long laser pulses (in the ns range).…”

“…[18,40], which are, however, restricted to static conditions only. Recent computational studies also investigated the photoacoustic response of silica coated gold nanospheres [41,42]. However, these works consider only one temperature to describe heat transfer in the coreshell nanoparticle, an approximation which is reasonable for nanosecond laser pulses, but is insufficient for femto and picosecond pulses.…”

Photoacoustic Response Optimization of Gold Nanorods in the Near-Infrared Region

“…The calculation results are compared with those in Refs. [19] and [35], as shown in Figure 3. It can be seen that the results of our model match with the results of the references.…”

“…Kumar et al [18] studied the effects of the arrangement, proportion, and thickness of Au and SiO2 in nanospheres on photoacoustic signals using the finite element method, providing an optimization strategy for practical application. Shahbazi et al [19] obtained the analytical solution for the photoacoustic response of core-shell nanospheres. On this basis, the effects of interface thermal resistance and the pulse laser waveform on photoacoustic signals of nanospheres are studied, and the proportion of photoacoustic signals generated by the shell and water layer is investigated.…”

Optothermal properties of plasmonic inorganic nanoparticles for photoacoustic applications

“…The time-resolved heat response of PNPs can be computationally simulated. For example, the response of Au nanoshells has been determined according to models which are related to the above description for light excitation with different pulse duration [ 62 , 63 ]. Besides theoretical descriptions of the photoinduced thermal processes, numerical simulations have been employed to study PNPs as photoacoustic signal generators [ 64 ].…”