Mass Sensing, Strong Vibrational Coupling and Super-Resolution Imaging of Noble Metal Nanostructures

化学学部的大分子、超分子和纳米化学项目支持圣母大学的Gregory V. Hartland教授和他的团队创造出可以在室温下工作的超小、纳米级的质量天平。所有物体都会振动，振动频率取决于物体的大小和形状。对于纳米粒子来说，这些振动频率非常高，当两个粒子相互附着时，它们就会发生变化。利用这种效应，该项目有助于检测那些难以用传统技术检测到的颗粒。通过精确测量质量，研究人员能够识别诸如病毒之类的未知粒子。从这项研究中获得的基础知识也可以用于检测环境中的各种化学物质和颗粒。准确检测化学品和颗粒对于评估环境和生物危害的潜在风险非常重要。这项研究为圣母大学的研究生和本科生以及当地主要本科院校（PUIs）提供培训和教育。该项目还为埃尔克哈特社区学校的高中生和教师提供了研究经验。悬浮在空气中或放置在低密度基板上的金属纳米结构的振动模式具有非常高的质量因子，这使得它们的频率可以精确测量。哈特兰教授和他在圣母大学的团队获得了大分子、超分子和纳米化学项目的奖项，他们利用悬浮纳米结构来研究纳米结构的振动模式如何受到吸附质量的影响。他们还研究了不同纳米结构的振动模式之间的耦合，并对耦合纳米结构的振动运动进行了相干控制。这些实验是通过瞬态吸收显微镜实现的异步光学采样，双激光技术，避免使用机械延迟线来记录数据。测量结果允许直接确定大型不带电粒子的质量，这对传统的质谱仪来说是一个挑战。此外，利用超快中红外泵浦瞬态吸收显微镜对单金属纳米结构的等离子体共振进行了成像。这些实验产生了关于这些结构的等离子体模式形式的新信息，这对于理解作为表面增强光谱中心的场增强非常重要。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division supports Professor Gregory V. Hartland and his group at the University of Notre Dame to create ultra-small, nanometer-sized mass balances that can operate at room temperature. All objects vibrate and the vibration frequencies depend on the size and shape of the object. These vibration frequencies are very high for nanoparticles and they change when two particles are attached to each other. Using this effect, this project contributes to sensing particles whose sizes make them very difficult to detect with conventional techniques. By accurately measuring mass, the researchers are able to identify unknown particles such as viruses. The fundamental knowledge gained from this study can also enable the detection of a variety of chemicals and particles in the environment. The accurate detection of chemicals and particles is important for assessing potential risks from environmental and biological hazards. This research provides training and education to graduate and undergraduate students at the University of Notre Dame as well as from local primarily undergraduate institutions (PUIs). This project also provides research experience for high school students and teachers from Elkhart Community Schools. The vibrational modes of metal nanostructures suspended in air or placed on low density substrates have very high quality factors which allows their frequencies to be accurately measured. With this award from the Macromolecular, Supramolecular, and Nanochemistry Program, Professor Hartland and his group at the University of Notre Dame use suspended nanostructures to study how the vibrational modes of the nanostructures are affected by adsorbed mass. They also examine the coupling between the vibrational modes of different nanostructures, and coherently control the vibrational motion of coupled nanostructures. These experiments are performed by transient absorption microscopy implemented with asynchronous optical sampling, a dual laser technique that avoids the use of a mechanical delay line to record data. The results of the measurements allow the masses of large uncharged particles to be directly determined, which is a challenge for conventional mass spectrometers. In addition, ultrafast mid-infrared pump transient absorption microscopy is used to image the plasmon resonances of single metal nanostructures. These experiments generate new information about the form of the plasmon modes of these structures, which is important for understanding the field enhancements that are central to surface enhanced spectroscopies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.