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

基本信息

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

项目摘要

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.

通过此奖项，化学测量和成像计划正在为德克萨斯大学的凯瑟琳·威利斯的研究提供资金，以开发新技术来研究表面的详细结构。这些技术将改善各种化学传感器的功能，尤其是基于称为表面增强的拉曼散射的现象或SER的现象。尽管SERS是一种非常有前途的传感技术，但其商业用途受到似乎由于不符合特征或控制的不均匀表面引起的问题的限制。当前的研究旨在通过研究添加金和银粒子时从表面出现的信号来改善基于SERS技术的设备的功能。当分子与这些小块的金和银处理的表面接触时，产生的SERS信号会增强，有时会增加一百万倍以上。研究人员正在为该系统带来各种分析技术，以了解这种增强是如何发生的，更重要的是，如何控制它。这项工作对新的化学传感技术的发展产生了广泛的影响。这项工作的长期目标是开发新的SERS探测器，这些探针将具有更大的商业化机会，从而利用这种类型的传感器的易移性，可移植性和相对便宜性。通过在包括高中在内的各个级别的学生参与研究调查，对下一代科学家的培训有进一步的广泛影响。该项目的重点是了解分子如何与支持SERS中局部表面等离子体的金纳米颗粒相互作用。等离子的激发导致纳米颗粒表面的电磁场强烈增强，并通过将分子放入表面上的这些增强的场中，可以增加分子的光信号。特别是，这些纳米颗粒强烈增强了拉曼散射，可提供分子“指纹”，可用于多种化学感测应用。大多数理解等离子体和SER的工作都集中在纳米颗粒增强激发场的方式上，但是尽管它在生成测量的信号方面很重要，但却忽略了该分子的发射作用。该项目探究了与等离子纳米颗粒相互作用的分子的作用，以便更好地理解导致感兴趣的分子靶标的最强信号的因素。为了更准确地了解分子对等离激元纳米颗粒的如何，正在研究分子和纳米颗粒之间的光谱和空间重叠。在没有等离子体增强的光学激发的情况下，使用电化化学发光来探测等离子体偶联的发射。超分辨率光学成像也用于探测等离激元纳米颗粒表面上分子的位置如何以低于10 nm的分辨率影响发射的方式和何处。超分辨率成像的波长分辨版本用于实现同时的光谱和空间分辨率，以显示如何通过依赖于波长的等离子体耦合将不同的拉曼模式耦合到远场。这些研究将对分子的计算如何有可能重新定义强烈增强局部电磁场的“热点”区域的常规图片有了深刻的了解。