Jackson Daniel J, Dawes Brian A, Kamenetska Maria
Department of Chemistry, Boston University, Boston, Massachusetts 02215, United States.
Department of Physics, Boston University, Boston, Massachusetts 02215, United States.
J Phys Chem Lett. 2023 Mar 23;14(11):2830-2836. doi: 10.1021/acs.jpclett.3c00088. Epub 2023 Mar 13.
Single molecule force spectroscopy using optical tweezers (OT) has enabled nanoresolved measurements of dynamic biological processes but not of synthetic molecular mechanisms. Standard OT probes made from silica or polystyrene are incompatible with trapping in organic solvents for solution phase chemistry or with force-detected absorption spectroscopies. Here, we demonstrate optical trapping of gold nanoparticles in both aqueous and organic conditions using a custom OT and darkfield instrument which can uniquely measure force and scattering spectra of single gold nanoparticles (Au NPs) simultaneously. Our work reveals that standard models of trapping developed for aqueous conditions cannot account for the trends observed in different media here. We determine that higher pushing forces mitigate the increase in trapping force in higher index organic solvents and lead to axial displacement of the particle which can be controlled through trap intensity. This work develops a new model framework incorporating axial forces for understanding nanoparticle dynamics in an optical trap. These results establish the combined darkfield OT with Au NPs as an effective OT probe for single molecule and single particle spectroscopy experiments, with three-dimensional nanoscale control over NP location.
使用光镊（OT）的单分子力谱技术能够对动态生物过程进行纳米级分辨测量，但无法用于合成分子机制的测量。由二氧化硅或聚苯乙烯制成的标准OT探针，不适用于在有机溶剂中进行溶液相化学捕获，也不适用于力检测吸收光谱。在此，我们展示了使用定制的OT和暗场仪器在水性和有机条件下对金纳米颗粒进行光捕获，该仪器能够同时独特地测量单个金纳米颗粒（Au NPs）的力和散射光谱。我们的研究表明，为水性条件开发的标准捕获模型无法解释在此不同介质中观察到的趋势。我们确定，更高的推力会减轻在高折射率有机溶剂中捕获力的增加，并导致颗粒的轴向位移，这可以通过捕获强度来控制。这项工作开发了一个新的模型框架，纳入轴向力以理解光阱中纳米颗粒的动力学。这些结果确立了结合暗场OT和Au NPs作为单分子和单粒子光谱实验的有效OT探针，能够对NP位置进行三维纳米级控制。
