Here, we report shifts of the linewidth of a plasmon enhanced whispering gallery mode (WGM) of a glass microsphere cavity due to binding of single sub-kDa molecules. The observed linewidth of the WGM can either increase or decrease upon binding of single molecules depending on the location of their binding sites. The linewidth shifts arise due to the change in the unresolved frequency splitting of standing wave modes (SWMs). These SWMs are formed due to the scattering from the gold nanoparticles attached to the WGM. Monitoring the WGM linewidth provides a robust method for sensing single molecules over prolonged time periods as the linewidth is unaffected by changes in the host refractive index due to drifts in temperature, pressure, or change in the concentration of buffers.

中文翻译：

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使用光学回音壁模式进行单分子检测的有效线宽偏移

在这里，我们报告了由于单个 sub-kDa 分子的结合导致的玻璃微球腔的等离子体增强回音壁模式 (WGM) 的线宽的变化。观察到的 WGM 线宽可以根据单个分子的结合位点的位置增加或减少。由于驻波模式 (SWM) 的未解析频率分裂的变化，会出现线宽偏移。这些 SWM 是由于附着在 WGM 上的金纳米粒子的散射而形成的。监测 WGM 线宽提供了一种在较长时间内检测单个分子的稳健方法，因为线宽不受由于温度、压力或缓冲液浓度变化引起的宿主折射率变化的影响。