School of Physical Sciences, The Open University, Walton Hall, MK7 6AA, Milton Keynes, United Kingdom.
Physical Chemistry, Institute of Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany.
J Chem Phys. 2020 Mar 31;152(12):124712. doi: 10.1063/1.5137898.
Laser illuminated gold nanoparticles (AuNPs) efficiently absorb light and heat up the surrounding medium, leading to versatile applications ranging from plasmonic catalysis to cancer photothermal therapy. Therefore, an in-depth understanding of the thermal, optical, and electron induced reaction pathways is required. Here, the electrophilic DNA nucleobase analog 5-Bromouracil (BrU) has been used as a model compound to study its decomposition in the vicinity of AuNPs illuminated with intense ns laser pulses under various conditions. The plasmonic response of the AuNPs and the concentration of BrU and resulting photoproducts have been tracked by ultraviolet and visible (UV-Vis) spectroscopy as a function of the irradiation time. A kinetic model has been developed to determine the reaction rates of two parallel fragmentation pathways of BrU, and their dependency on laser fluence and adsorption on the AuNP have been evaluated. In addition, the size and the electric field enhancement of the decomposed AuNPs have been determined by atomic force microscopy and finite domain time difference calculations, respectively. A minor influence of the direct photoreaction and a strong effect of the heating of the AuNPs have been revealed. However, due to the size reduction of the irradiated AuNPs, a trade-off between laser fluence and plasmonic response of the AuNPs has been observed. Hence, the decomposition of the AuNPs might be limiting the achievable temperatures under irradiation with several laser pulses. These findings need to be considered for an efficient design of catalytic plasmonic systems.
激光激发的金纳米粒子（AuNPs）高效地吸收光并使周围介质升温，从而实现了从等离子体催化到癌症光热治疗等多种应用。因此，需要深入了解热、光和电子诱导的反应途径。在这里，已将亲电 DNA 碱基类似物 5-溴尿嘧啶（BrU）用作模型化合物，以研究在各种条件下，用强纳秒激光脉冲照射 AuNPs 时，其在 AuNPs 附近的分解情况。通过紫外可见（UV-Vis）光谱跟踪 AuNPs 的等离子体响应以及 BrU 的浓度和产生的光产物，作为辐照时间的函数。已经开发了一个动力学模型来确定 BrU 的两种平行碎裂途径的反应速率，并评估了它们对激光强度和在 AuNP 上吸附的依赖性。此外，通过原子力显微镜和有限域时域差分计算分别确定了分解的 AuNPs 的尺寸和电场增强。结果表明，直接光反应的影响较小，AuNPs 的加热作用较强。然而，由于辐照 AuNPs 的尺寸减小，观察到激光强度与 AuNPs 的等离子体响应之间存在权衡。因此，AuNPs 的分解可能限制了在多次激光脉冲辐照下可达到的温度。在设计有效的等离子体催化系统时，需要考虑这些发现。
