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Plasma-Mediated Nanocavitation and Photothermal Effects in Ultrafast Laser Irradiation of Gold Nanorods in Water
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DOI：10.1021/jp312475h.png)
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Abstract
En 中文
We present a theoretical and experimental study that reveals the physical mechanism underlying the response of an in-resonance gold nanorod (AuNR) in water to a near-infrared ultrafast laser pulse. Results reveal the presence of two different regimes of interaction, depending on the irradiation fluence. For fluences below 3 mJ/cm(2), AuNRs are in the so-called absorption regime and are shown to strongly absorb energy, leading to a fast temperature increase revealed by the onset of characteristic mechanical vibration of the structure. In situ measurement demonstrates a permanent deformation of the AuNRs occurring for fluences over 100 mu J/cm(2). In the absorption regime, we show the formation of a nanoscale plasma around the structure, dominated by a photothermal emission from the AuNR, and the generation of a pressure wave. However, no cavitation occurs under the deformation threshold fluence (100 mu J/cm(2)). For fluences over 3 mJ/cm(2), in the near-field regime, the energy transfer is dominated by the enhanced near-field around the particle that directly ionizes and heats a nanoplasma in the surrounding water. We theoretically show that bubbles with diameters approximate to 490 nm can be generated in this near-field regime for an incident fluence of 200 mJ/cm(2). In situ optical characterization of the produced bubbles supports this result and shows that bubbles with diameters approximate to 200-600 nm can be generated for fluences ranging 100-400 mJ/cm(2). Important shielding of the laser-nanostructure interaction by the surrounding plasma is shown to decrease considerably the near-field enhancement, the energy absorption, and the diameter of the generated bubbles and may explain the smaller bubbles generated around in-resonance 10 x 41 nm(2) AuNRs when compared to off-resonance 25 X 60 nm(2) AuNRs and 100 nm AuNPs.
Keywords:
MIE SCATTERING
THERAPY PPTT
NANOPARTICLES
RESONANCE
SURFACE
CELLS
CARCINOMA
BUBBLES
ENERGY
AGENTS
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