室温下微弱振动信号的单分子定位检测

Acoustic vibrations are central to communication in our daily lives, but also form the basis of many technologies such as radar, sonar, seismography, or ultrasound medical imaging. The main advantage of acoustic waves is their faculty to propagate in media that absorb or scatter electromagnetic waves. Detection of extremely weak vibrations is the basis for development of smaller, faster and more sensitive devices, but also the key of new sciences. In this project, we will use a single molecule as an acoustic probe to detect the weak acoustic vibration around the molecule based on its small size and sensitivity to its local environment. It is known that the enhancement factor of fluorescence or Raman signal strongly depends on the distance between the molecule and the surface. We propose to detect the distance variation by monitoring the fluorescence or Raman signal of the molecule, and thus get the information of the vibration. The molecule works as a “microphone” to “listen” the sound around it. Such microphone is so small that can be used to detect vibrations in a specific location at nanometer scale and sensitive enough to detect quantum states of nano-oscillators and would open new avenues for high-resolution acoustic microscopy.

声波振动检测不仅是人们日常交流必不可少的一部分，也是雷达、声纳、地震仪、B超等现代技术的核心基础，在军事、医学、建筑等领域起到不可或缺的作用。微弱声波振动信号的检测不仅是开发高效、灵敏、微型化器件的基础，也是取得重大科学突破的关键。最近报道的“引力波”就是对极其微弱振动信号的成功检测。本项目拟利用单分子的极小尺寸和对周围环境的敏感性，以单个小分子为探针，以表面增强荧光或拉曼信号对分子与表面间距的高度依赖为基础，通过分子荧光或拉曼信号增强幅度的变化，监测分子到表面距离的变化，从而探测分子周围环境中微弱的振动信息，在室温条件下实现“单分子麦克风”。这种单分子麦克风同时具有高空间分辨率和高灵敏度，可以在亚纳米尺度上检测微弱的振动信号，甚至可以读取纳米振子的量子信息，有望进一步发展高分辨声学显微技术，对材料内部或生命组织内部的相互作用过程进行定位研究。

本项目以实现室温下微弱振动信号的单分子检测为研究目标，项目执行期内首先考察了有机小分子、聚合物、量子点、钙钛矿等多种高效发光材料的发光特性，特别是光稳定性，筛选最优材料和条件作为探针分子。最终选定以结晶紫和金纳米棒作为探针体系，组建单分子振动检测体系，通过优化光路设计和体系，实现单个分子荧光强度的长时间稳定检测，以石英晶体音叉作为模拟振动源，为体系提供固定振动频率为32k的微弱振动信号，实时监测采集分子荧光强度信息，利用傅立叶变换提取分子荧光强度扰动信息，可清晰看到分子荧光在32k Hz频率处有周期性波动，实现了振动信号的单分子检测，经表征检测灵敏度可达皮米量级。并进一步通过理论模型计算，推算在该体系下振动检测的极限灵敏度可达飞米量级。本项目实现了室温下利用分子光谱技术实现振动信号的高灵敏检测，不仅有望用于地质勘测、地质灾害监测、建筑物监测等领域，也为进一步发展高分辨声学显微镜奠定基础。