ACS Nano. 2020 Aug 25;14(8):9408-9422. doi: 10.1021/acsnano.0c05215. Epub 2020 Aug 12.
Photoacoustic (PA) imaging is an emerging imaging modality whereby pulsed laser illumination generates pressure transients that are detectable using conventional ultrasound. Plasmonic nanoparticles such as gold nanorods and nanostars are often used as PA contrast agents. The thermoelastic expansion model best describes the PA response from plasmonic nanoparticles: Light absorption causes a small increase in temperature leading to thermoelastic expansion. The conversion of optical energy into pressure waves () is dependent on several features: (i) the absorption coefficient (μ), (ii) the thermal expansion coefficient (β), (iii) specific heat capacity () of the absorbing material, (iv) speed of sound in the medium (c), and (v) the illumination fluence (). Controlling the geometry, composition, coatings, and solvents around plasmonic nanostructures can help tune these variables to generate the optimum PA signal. The thermoelastic expansion model is not limited to plasmonic structures and holds true for all absorbing molecules. Here, we focus on ways to engineer these variables to enhance the PA response from plasmonic nanoparticles.
光声（PA）成像是一种新兴的成像方式，通过脉冲激光照射产生可通过传统超声检测到的压力瞬变。等离子体纳米粒子（如金纳米棒和纳米星）通常用作 PA 造影剂。热弹性膨胀模型最好地描述了等离子体纳米粒子的 PA 响应：光吸收导致温度略有升高，从而导致热弹性膨胀。将光能量转换为压力波（）取决于几个因素：（i）吸收系数（μ），（ii）热膨胀系数（β），（iii）吸收材料的比热容（），（iv）介质中的声速（c）和（v）光强度（）。控制等离子体纳米结构周围的几何形状、组成、涂层和溶剂可以帮助调整这些变量以产生最佳的 PA 信号。热弹性膨胀模型不仅限于等离子体结构，对所有吸收分子都适用。在这里，我们专注于设计这些变量的方法，以增强等离子体纳米粒子的 PA 响应。
