Department of Chemistry, Yale University, 350 Edwards St., New Haven, Connecticut 06520, USA.
J Chem Phys. 2018 Apr 14;148(14):144201. doi: 10.1063/1.5017853.
Measuring absorption spectra of single molecules presents a fundamental challenge for standard transmission-based instruments because of the inherently low signal relative to the large background of the excitation source. Here we demonstrate a new approach for performing absorption spectroscopy in solution using a force measurement to read out optical excitation at the nanoscale. The photoinduced force between model chromophores and an optically trapped gold nanoshell has been measured in water at room temperature. This photoinduced force is characterized as a function of wavelength to yield the force spectrum, which is shown to be correlated to the absorption spectrum for four model systems. The instrument constructed for these measurements combines an optical tweezer with frequency domain absorption spectroscopy over the 400-800 nm range. These measurements provide proof-of-principle experiments for force-detected nanoscale spectroscopies that operate under ambient chemical conditions.
测量单分子的吸收光谱对基于传统透射的仪器来说是一个基本的挑战，因为相对于激发光源的大背景信号，其固有信号非常低。在此，我们展示了一种新的方法，用于在溶液中进行吸收光谱学研究，使用力测量在纳米尺度上读取光激发。在室温下的水中，已经测量了模型发色团与光学捕获的金纳米壳之间的光致力。该光致力被表征为波长的函数，以产生力谱，对于四个模型系统，该力谱被证明与吸收光谱相关。为了进行这些测量，我们将光学镊子与 400-800nm 范围内的频域吸收光谱学相结合。这些测量为在环境化学条件下工作的力探测纳米尺度光谱学提供了原理验证实验。
