Influence of the temperature-dependent dielectric constant on the photoacoustic effect of gold nanospheres,Physical Chemistry Chemical Physics

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Influence of the temperature-dependent dielectric constant on the photoacoustic effect of gold nanospheres
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2022-11-21 , DOI: 10.1039/d2cp03866h
Jian-Ping Sun _{1,

2} , Ya-Tao Ren _{1,

2,

3} , Ren-Xi Gao ₄ , Bao-Hai Gao _{1,

2} , Ming-Jian He _{1,

2} , Hong Qi _{1,

2}

Affiliation

Photoacoustic imaging techniques with gold nanoparticles as contrast agents have received a great deal of attention. The photoacoustic response of gold nanoparticles strongly depends on the far-field optical properties, which essentially depend on the dielectric constant of the material. The dielectric constant of gold not only varies with wavelength but is also affected by temperature. However, the effect of the temperature dependence of the dielectric constant on gold nanoparticles’ photoacoustic response has not been fully investigated. In this work, the Drude–Lorentz model and Mie theory are used to calculate the dielectric constant and absorption efficiency of gold nanospheres in aqueous solution, respectively. Then, the finite element method is used to simulate the heat transfer process of gold nanospheres and surrounding water. Finally, the one-dimensional velocity–stress equation is solved by the finite-difference time-domain method to obtain the photoacoustic response of gold nanospheres. The results show that under the irradiation of a high-fluence nanosecond pulse laser, ignoring the temperature dependence of the dielectric constant will lead to large errors in the photothermal response and the nonlinear photoacoustic signals (it can even exceed 20% and 30%). The relative error of the photothermal and photoacoustic response caused by ignoring the temperature-dependent dielectric constant is determined from both the temperature dependence of absorption efficiency and the maximum temperature increase of gold nanospheres. This work provides a new perspective for the photothermal and photoacoustic effects of gold nanospheres, which is meaningful for the development of high-resolution photoacoustic detectors and nano/microscale temperature measurement techniques.

中文翻译：

温度相关介电常数对金纳米球光声效应的影响

以金纳米粒子作为造影剂的光声成像技术受到了广泛关注。金纳米粒子的光声响应在很大程度上取决于远场光学特性，而远场光学特性主要取决于材料的介电常数。金的介电常数不仅随波长变化，而且还受温度影响。然而，介电常数的温度依赖性对金纳米粒子的光声响应的影响尚未得到充分研究。在这项工作中，Drude-Lorentz 模型和 Mie 理论分别用于计算金纳米球在水溶液中的介电常数和吸收效率。然后，采用有限元法模拟金纳米球与周围水的传热过程。最后，通过时域有限差分法求解一维速度-应力方程，得到金纳米球的光声响应。结果表明，在高通量纳秒脉冲激光照射下，忽略介电常数的温度依赖性会导致光热响应和非线性光声信号出现较大误差（甚至超过20%和30%）。由忽略温度依赖性介电常数引起的光热和光声响应的相对误差由吸收效率的温度依赖性和金纳米球的最大温度增加决定。这项工作为金纳米球的光热和光声效应提供了新的视角，

更新日期：2022-11-21

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