OP: Super-resolution imaging of plasmon-molecule interactions

光学显微镜，比如几乎每所高中都有的用来观察细胞的显微镜，在空间分辨率上有固有的限制。它们无法分辨两个距离比可见光波长更近的物体，可见光波长约为500纳米，约为人类头发直径的1/100。最近，超分辨率显微镜已经开发出来，可以分辨只有10纳米间隔的单个分子。超分辨率显微镜在成像荧光染料靠近其他分子（如蛋白质）时取得了巨大的成功，但当分子靠近金属纳米结构时，它就麻烦了。当分子与金属中松散的电子相互作用时，问题就出现了，这会模糊它的位置。在天普大学化学系大分子、超分子和纳米化学项目的支持下，Willets教授正在研究荧光分子与金属纳米颗粒的相互作用。Willets教授和她的学生们正在开发能够更好地确定荧光分子位置的方案。该项目可以为产生更高保真度的超分辨率图像铺平道路，这可能有助于推进用于生物传感、纳米医学和太阳能转换的纳米技术。这项工作还为研究生和本科生提供了培训机会，促进了国家科学队伍的发展。此外，Willets实验室还积极参与费城市中心Freire特许学校九年级的科学课程，帮助学生培养对科学探索和发现的欣赏。Willets教授和她的学生们一起工作，用荧光标记的DNA在特定的位置使金纳米棒和纳米球功能化。然后使用超分辨率成像和偏振分辨显微镜的组合来跟踪荧光分子的位置和方向如何影响荧光分子的定位精度。在超分辨率成像中，单个荧光分子通过将其衍射极限发射拟合到模型函数（如二维高斯函数）来定位其空间位置，其精度优于10 nm。然而，荧光发射器与纳米结构的等离子体模式之间的耦合影响了定位精度，导致荧光分子的计算位置偏离其真实位置。理论模型提供了单个分子相对于等离子体纳米结构的位置和取向如何影响定位误差的见解。通过创建定义明确的有机等离子体混合纳米颗粒，该团队正在开发新的分析工具来提取隐藏在荧光图像中的信息，以提高超分辨率图像与实际纳米结构特性之间的一致性。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。

Optical microscopes, such as those found in almost every high school to look at cells, have an inherent limit to their spatial resolution. They cannot resolve two objects that are closer to each other than the wavelength of light, which for visible colors is about 500 nm, or about 1/100 the diameter of a human hair. Recently super-resolution microscopes have been developed that can resolve individual molecules that are only 10 nm apart. Super-resolution microscopy has had tremendous success when imaging fluorescent dyes near other molecules, such as proteins, but it has trouble when the molecule is located near a metal nanostructure. The problem arises when the molecule interacts with the loosely held electrons in the metal, which blurs its location. With support from the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Willets at Temple University is studying the interaction of fluorescent molecules with metal nanoparticles. Professor Willets and her students are developing protocols that can better pinpoint the location of the fluorescent molecule. The project could pave the way to producing higher fidelity super-resolution images, which may help to advance nanotechnologies for biosensing, nanomedicine, and solar energy conversion. The work also provides training opportunities for graduate and undergraduate students, furthering the development of the Nation's scientific workforce. In addition, the Willets lab is actively engaged with the 9th grade science classes at Freire Charter School in downtown Philadelphia, helping the students to foster an appreciation for scientific exploration and discovery.Working alongside her students, Professor Willets is functionalizing gold nanorods and nanospheres at specific sites with fluorescently-labeled DNA. A combination of super-resolution imaging and polarization-resolved microscopy is then used to track how the position and orientation of the fluorescent molecules impacts the localization precision of the fluorescent molecule. In super-resolution imaging, single fluorescent molecules are localized by fitting their diffraction-limited emission to a model function, such as a two-dimensional Gaussian, to localize their spatial position with better than 10 nm precision. However, coupling between the fluorescent emitter and the plasmon modes of the nanostructure impacts the localization accuracy, resulting in the calculated position of the fluorescent molecule being shifted from its true position. Theoretical modeling provides insight into how the position and orientation of a single molecule relative to the plasmonic nanostructure affects the localization error. By creating well-defined hybrid organic-plasmonic nanoparticles, the team is developing new analysis tools to extract information hidden in the fluorescence images to improve agreement between the super-resolved images and the actual nanostructure properties.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.