Analysis of Photoacoustic Response from Gold–Silver Alloy Nanoparticles Irradiated by Short Pulsed Laser in Water

Abstract

In this paper, we perform a finite element (FE)-based numerical analysis to calculate the photoacoustic (PA) signal generated by spherical gold-silver (Au-Ag) alloy nanoparticles (NPs). These spherical particles are size-controlled and monodispersed, with tunable plasmonic resonance wavelength via change of the alloy composition. This enables their use in photoacoustic imaging as a contrast agent. This theoretical framework self consistently solves the electromagnetic, thermodynamic and transient acoustic pressure physics using a multiphysics coupling approach. We model our system as an optically heterogeneous medium irradiated by a nanosecond laser pulse in the tissue therapeutic optical window (NIR irradiation, with wavelength of 800 nm). We calculate the photoacoustic signal generated by the photo-thermal expansion of both the particle and its surrounding medium. The results show the impact of the gold molar fraction (GMF) of Au-Ag alloy NPs on the PA signal for different NP sizes. We show that significantly stronger PA signals are achieved using Au-Ag alloy NPs (GMF = 0.55) in comparison with pure AuNPs (GMF = 1) and pure AgNPs (GMF = 0) of the same size and shape.

Formation Mechanism of Laser-Synthesized Iron-Manganese Alloy Nanoparticles, Manganese Oxide Nanosheets and Nanofibers

“…Alloy particles are generally synthesized through five techniques, including molecular beams (e.g., laser evaporation or ion/magnetron sputtering), chemical reduction, thermal decomposition of transition-metal complexes, and electrochemical synthesis. [1] These methods often need either expensive vacuum equipment for alloy prepared for various applications, such as construction of magnetic LAL-FeNi alloy nanostrand-polymer films for shielding radio frequency electromagnetic waves, [17] AgAu nanoparticles for reducing reproductive toxicity [18] and photoacoustic imaging, [19] AuFe nanoparticles as multimodal contrast agents for SERS-MRI-CT multiplexing, [20] catalysis, and electrocatalysis using PtAu, [3,21] PtCo, [22] and PtPb [23] particles.…”

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

“…Several experimental and computational efforts have been undertaken to quantify and elucidate some of the physics of the pulsed laser irradiation of nanospheres [5][6][7][8][9][10][11] . However, the impact of many physical parameters on the PA signal has not been fully investigated, and the full description of the underlying physics is currently lacking.…”

“…They particularly focused on the temperature dependency of water thermal expansion coefficients and resulting PA deviations from the point-absorber model of Calasso et al 12 . Hatef et al analyzed the PA signal of gold-silver alloy nanospheres using the commercial multiphysics package (COMSOL) 9 . Both groups, however, did not consider the silica-coating of the nanospheres, or model the interfacial thermal resistance 10 at the gold-water interface, which can have a significant impact on the PA signal, as our model demonstrates.…”

Photoacoustic and Magnetic Resonance Imaging Bimodal Contrast Agent Displaying Amplified Photoacoustic Signal

“…To further investigate the underlying mechanism of PA signal‐amplifying effect by IO nanoparticles, COMSOL, a commercial software based on finite element method has been adopted. Previous simulations studied the influence of nanoparticle morphology, coating, material, and laser energy configurations on either photothermal or PA signals. Two sets of inbuilt computational models are commonly utilized by researchers: 1) stress‐pressure model, which computes the light distribution, heat generation, thermal expansion, and pressure generation; 2) thermal‐pressure or heat‐pressure model, which computes only the heat and acoustic functions.…”