Understanding plasmon-enhanced electromagnetic hot spots for surface-enhanced spectroscopies

了解表面增强光谱的等离子体增强电磁热点

• 批准号: 1540927
• 负责人: Katherine Willets
• 金额: $ 28.58万
• 依托单位: Temple University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-01-16 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1540927&HistoricalAwards=false
• 关键词: Understanding; plasmon; enhanced; electromagnetic; hot

With this award, the Chemical Measurement and Imaging Program is funding the research of Katherine Willets at the University of Texas to develop new techniques to study the detailed structure of surfaces. These techniques will improve the functioning of a variety of chemical sensors, in particular a type based on a phenomenon known as surface-enhanced Raman scattering, or SERS. While SERS is an intensely promising sensing technology, its commercial utilization has been limited by problems that appear to be due to non-uniform surfaces that are not well-characterized or controlled. The current research seeks to improve the functioning of devices based on SERS technology by studying the signals that come from the surface when small particles of gold and silver are added. When molecules come into contact with surfaces treated with these small bits of gold and silver, the resulting SERS signal is enhanced, sometimes by more than a million-fold. The investigators are bringing a variety of analysis techniques to bear on this system in order to understand how this enhancement occurs and, more importantly, how it can be controlled. The work is having a broad impact on the development of new chemical sensing technologies. The long-term goal of the work is to develop new SERS probes that will have greater commercialization opportunities, thus exploiting the ease, portability and relative cheapness of this type of sensor. It is having a further broad impact on the training of the next generation of scientists through the involvement of students at all levels, including high school, in the research investigations.This project is focused on understanding how molecules interact with gold and silver nanoparticles that support localized surface plasmons in SERS. Excitation of plasmons leads to strongly enhanced electromagnetic fields at the surface of the nanoparticles, and by placing molecules into these enhanced fields at the surface, optical signals from the molecules can be increased. In particular, Raman scattering, which provides a molecular 'fingerprint' and is useful for a variety of chemical sensing applications, is strongly enhanced by these nanoparticles. Most work on understanding plasmons and SERS has focused on how excitation fields are enhanced by the nanoparticles, but has neglected the role of emission by the molecule, despite its importance in generating the measured signals. This project probes the role of the molecule interacting with plasmonic nanoparticles, in order to better understand the factors that lead to the strongest possible signals from molecular targets of interest. To more precisely understand how molecules couple to plasmonic nanoparticles, both spectral and spatial overlap between the molecules and the nanoparticles are being investigated. Electrogenerated chemiluminescence is used to probe plasmon-coupled emission in the absence of plasmon-enhanced optical excitation. Super-resolution optical imaging is also being used to probe how the location of molecules on the surface of plasmonic nanoparticles influences how and where the emission is coupled into the far-field with sub-10 nm resolution. A wavelength-resolved version of super-resolution imaging is used to achieve simultaneous spectral and spatial resolution in order to show how different Raman modes are coupled into the far-field via wavelength-dependent plasmon coupling. These studies will provide an improved understanding of how accounting for the molecule can potentially redefine the conventional picture of a 'hot spot' region of strongly enhanced local electromagnetic fields.

凭借该奖项，化学测量和成像计划正在资助德克萨斯大学 Katherine Willets 的研究，以开发研究表面详细结构的新技术。这些技术将改善各种化学传感器的功能，特别是基于表面增强拉曼散射（SERS）现象的类型。虽然 SERS 是一种非常有前途的传感技术，但其商业应用一直受到一些问题的限制，这些问题似乎是由于表面不均匀而导致的，这些问题没有得到很好的表征或控制。目前的研究旨在通过研究添加金和银小颗粒时来自表面的信号来改善基于 SERS 技术的设备的功能。当分子与经过这些小金银处理的表面接触时，产生的 SERS 信号会增强，有时增强超过一百万倍。研究人员正在将各种分析技术应用于该系统，以便了解这种增强是如何发生的，更重要的是，如何控制它。这项工作对新化学传感技术的开发产生了广泛的影响。这项工作的长期目标是开发新的 SERS 探针，该探针将具有更大的商业化机会，从而充分利用此类传感器的易用性、便携性和相对廉价性。通过让包括高中在内的各个级别的学生参与研究调查，它对下一代科学家的培训产生了更广泛的影响。该项目的重点是了解分子如何与支持的金和银纳米颗粒相互作用。 SERS 中的局域表面等离子体。等离子体激元的激发导致纳米粒子表面的电磁场强烈增强，并且通过将分子放入表面的这些增强的场中，可以增加来自分子的光信号。特别是，拉曼散射提供了分子“指纹”，可用于各种化学传感应用，这些纳米粒子大大增强了拉曼散射。大多数了解等离子体激元和 SERS 的工作都集中在纳米粒子如何增强激发场，但忽略了分子发射的作用，尽管它在生成测量信号方面很重要。该项目探讨了分子与等离子体纳米粒子相互作用的作用，以便更好地了解导致感兴趣的分子靶标产生最强信号的因素。为了更准确地了解分子如何与等离子体纳米颗粒耦合，正在研究分子和纳米颗粒之间的光谱和空间重叠。电生化学发光用于在没有等离子体增强光学激发的情况下探测等离子体耦合发射。超分辨率光学成像也被用来探测等离子体纳米颗粒表面分子的位置如何影响发射耦合到亚 10 nm 分辨率的远场的方式和位置。超分辨率成像的波长分辨版本用于同时实现光谱和空间分辨率，以显示不同的拉曼模式如何通过波长相关的等离子体耦合耦合到远场。 这些研究将更好地理解分子的解释如何可能重新定义强烈增强的局部电磁场“热点”区域的传统图像。

项目成果

Plasmon Heating Promotes Ligand Reorganization on Single Gold Nanorods

等离子激元加热促进单金纳米棒上的配体重组

• DOI: 10.1021/acs.jpclett.9b00079
• 发表时间: 2019-02
• 期刊: The Journal of Physical Chemistry Letters
• 作者: Cheng, Xiaoyu;Anthony, Taryn P.;West, Claire A.;Hu, Zhongwei;Sundaresan, Vignesh;McLeod, Aaron J.;Masiello, David J.;Willets, Katherine A.
• 通讯作者: Willets, Katherine A.