Department of Mechanical Engineering, University of Minnesota, Twin Cities, Minneapolis, MN, 55455, USA.
Department of Biomedical Engineering, University of Minnesota, Twin Cities, Minneapolis, MN, 55455, USA.
Sci Rep. 2021 Jan 13;11(1):898. doi: 10.1038/s41598-020-79393-w.
Laser heating of gold nanospheres (GNS) is increasingly prevalent in biomedical applications due to tunable optical properties that determine heating efficiency. Although many geometric parameters (i.e. size, morphology) can affect optical properties of individual GNS and their heating, no specific studies of how GNS aggregation affects heating have been carried out. We posit here that aggregation, which can occur within some biological systems, will significantly impact the optical and therefore heating properties of GNS. To address this, we employed discrete dipole approximation (DDA) simulations, Ultraviolet-Visible spectroscopy (UV-Vis) and laser calorimetry on GNS primary particles with diameters (5, 16, 30 nm) and their aggregates that contain 2 to 30 GNS particles. DDA shows that aggregation can reduce the extinction cross-section on a per particle basis by 17-28%. Experimental measurement by UV-Vis and laser calorimetry on aggregates also show up to a 25% reduction in extinction coefficient and significantly lower heating (~ 10%) compared to dispersed GNS. In addition, comparison of select aggregates shows even larger extinction cross section drops in sparse vs. dense aggregates. This work shows that GNS aggregation can change optical properties and reduce heating and provides a new framework for exploring this effect during laser heating of nanomaterial solutions.
由于可调谐的光学性质决定了加热效率，金纳米球（GNS）的激光加热在生物医学应用中越来越普遍。尽管许多几何参数（例如尺寸、形态）会影响单个 GNS 的光学性质及其加热效果，但尚未对 GNS 聚集如何影响加热进行专门研究。我们假设，在某些生物系统中可能发生的聚集，将显著影响 GNS 的光学性质，从而影响其加热效果。为了解决这个问题，我们采用了离散偶极子近似（DDA）模拟、紫外可见光谱（UV-Vis）和激光量热法，研究了直径为（5、16、30nm）的 GNS 原颗粒及其包含 2 至 30 个 GNS 颗粒的聚集体。DDA 表明，聚集可使每个颗粒的消光截面减少 17-28%。通过 UV-Vis 和激光量热法对聚集体的实验测量也表明，与分散的 GNS 相比，聚集体的消光系数降低了 25%，加热效果显著降低（约 10%）。此外，对选定聚集体的比较表明，在稀疏聚集体和密集聚集体中，消光截面的降幅更大。这项工作表明，GNS 聚集会改变光学性质并降低加热效果，并为在纳米材料溶液的激光加热过程中探索这种效应提供了新的框架。
