论文标题
了解纳米结构的近场光声学的时空分辨率
Understanding the Spatiotemporal Resolution of Near-Field Photoacoustics from Nanostructures
论文作者
论文摘要
了解纳米级光声产生的机制是开发更有效的光声设备和代理的关键。与已经在成像中充分使用的远场光声效应不同，近场轮廓会导致复杂的波 - 组织相互作用，但研究不足。在这里，我们表明，近场光声波的时空轮廓可以通过激光脉冲，各向异性和纳米颗粒（S）空间排列来塑造。以金纳米棒为例，我们发现短轴中的近场光声振幅比长轴强约75％，并且各向异性空间分布会在距离纳米诺罗德表面〜50 nm处的各向同性球波收敛。我们通过用断裂的对称性将各向同性的各向同性排列各向异性来进一步扩展到非对称金纳米结构，以实现在声学波长内的精确控制的近场光声“焦点”。
Understanding the mechanism of photoacoustic generation at the nano-scale is key to developing more efficient photoacoustic devices and agents. Unlike the far-field photoacoustic effect that has been well employed in imaging, the near-field profile leads to a complex wave-tissue interaction but is under-studied. Here we show that the spatiotemporal profile of the near-field photoacoustic waves can be shaped by laser pulses, anisotropy, and nanoparticle(s) spatial arrangement. Using a gold nanorod as an example, we discovered that the near-field photoacoustic amplitude in the short axis is ~75% stronger than the long axis, and the anisotropic spatial distribution converges to an isotropic spherical wave at ~50 nm away from the nanorod's surface. We further extend the model to asymmetric gold nanostructures by arranging isotropic nanospheres anisotropically with broken symmetry to achieve a precisely controlled near-field photoacoustic "focus" largely within an acoustic wavelength.
