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.

中文翻译：

---

纳秒级激光脉冲辐照金纳米颗粒的分子分解动力学—5-溴尿嘧啶案例研究

激光照射的金纳米颗粒（AuNP）有效吸收光线并加热周围的介质，从而导致了从等离子催化到癌症光热疗法的广泛应用。因此，需要对热，光和电子诱导的反应路径有深入的了解。在这里，亲电子DNA核碱基类似物5-溴尿嘧啶（BrU）已用作模型化合物，以研究在各种条件下用强ns激光脉冲照射的AuNP的分解。紫外线和可见光（UV-Vis）光谱已经追踪了AuNPs的等离子体响应以及BrU浓度和所产生的光产物随照射时间的变化。已开发出动力学模型来确定BrU的两个平行片段化途径的反应速率，并评估了它们对激光通量和在AuNP上的吸附的依赖性。此外，已分别通过原子力显微镜和有限域时差计算确定了分解后的AuNP的大小和电场增强。揭示了直接光反应的较小影响和AuNPs加热的强烈影响。然而，由于被辐射的AuNP的尺寸减小，已经观察到激光注量与AuNP的等离子体响应之间的权衡。因此，AuNPs的分解可能会限制几个激光脉冲照射下可达到的温度。这些发现需要考虑有效的催化等离子体系统的设计。分别通过原子力显微镜和有限域时差计算确定了分解后的AuNPs的大小和电场增强。揭示了直接光反应的较小影响和AuNP加热的强烈影响。然而，由于被辐射的AuNP的尺寸减小，已经观察到激光注量与AuNP的等离子体响应之间的权衡。因此，AuNPs的分解可能会限制几个激光脉冲照射下可达到的温度。为了有效设计催化等离子体系统，需要考虑这些发现。分别通过原子力显微镜和有限域时差计算确定了分解后的AuNPs的大小和电场增强。揭示了直接光反应的较小影响和AuNPs加热的强烈影响。然而，由于被辐射的AuNP的尺寸减小，已经观察到激光注量与AuNP的等离子体响应之间的权衡。因此，AuNPs的分解可能会限制几个激光脉冲照射下可达到的温度。为了有效设计催化等离子体系统，需要考虑这些发现。揭示了直接光反应的较小影响和AuNPs加热的强烈影响。然而，由于被辐射的AuNP的尺寸减小，已经观察到激光注量与AuNP的等离子体响应之间的权衡。因此，AuNPs的分解可能会限制几个激光脉冲照射下可达到的温度。为了有效设计催化等离子体系统，需要考虑这些发现。揭示了直接光反应的较小影响和AuNPs加热的强烈影响。然而，由于被辐射的AuNP的尺寸减小，已经观察到激光注量与AuNP的等离子体响应之间的权衡。因此，AuNPs的分解可能会限制几个激光脉冲照射下可达到的温度。这些发现需要考虑有效的催化等离子体系统的设计。