CAREER: Plasmonic Nanocavities for Single Molecule Detection

用于单分子检测的等离子体纳米腔本提案描述了一个集成的研究，教育和推广计划，重点是等离子体纳米腔及其在单分子表面增强拉曼光谱（SERS）中的应用。所提出的等离子体纳米空腔，或金属纳米线（Ag）之间的微小间隙，是通过在垂直取向的第一层银纳米线上堆叠第二层平行银纳米线而形成的。初步研究表明，当顶部和底部纳米线之间的间隙缩小到几纳米或人类头发直径的千万分之一时，照明光可以聚焦到如此微小的纳米间隙中，光强度可提高10万倍。当分子被放置在这些等离子体纳米腔中时，它们的拉曼散射强度可以大大增强，因此甚至可以观察到单个分子信号。拉曼光谱代表了分子独特的振动信息，可用于分子的直接检测和鉴定。本研究旨在发展纳米线和纳米腔的纳米加工工艺，对这些等离子体纳米腔的特性和基本认识，并探索其在SERS中的应用。最终目标是展示基于SERS的强大单分子传感平台。该教育计划包括实施一项教育计划，旨在吸引俄亥俄州东北部的高能力学生到STEM（科学、技术、工程和数学）领域学习，并为已经在STEM领域学习的学生提供指导和研究机会。技术优势：银纳米线交叉条的独特之处在于：(1)纳米天线（即银纳米线）和纳米空腔集成在一个平台上，可以高效地将光聚焦到纳米尺度；(2)垂直腔体设计使得利用薄膜沉积技术以前所未有的精度制造纳米隙成为可能；(3)通过对纳米线施加电压，可以对这些纳米空腔中的分子进行电定位，从而为控制分子和纳米空腔提供了很大的灵活性。提出的研究将回答关于SERS增强机制的基本问题，并导致可重复的单分子传感器的发展。更广泛的影响：拟议中的研究有益于社会，因为单分子传感器可以找到从国土安全到医疗保健疾病诊断的无数应用。该职业规划的教育和推广部分包括为肯特州立大学（KSU）的中学后入学选择计划（PSEOP）学生制定指导研究体验计划；指导本科生做研究；创建一个名为？父母吗?晚上吗?高中生和他们的父母；通过让研究生参与多学科研究，加强研究生教育，并为研究生阶段的纳米/生物材料教学制定课程。KSU是俄亥俄州三大公立大学之一，超过80%的KSU学生是本科生；KSU主要为中低收入的本科生提供服务。这种不寻常的制度特征组合使KSU非常适合招收来自代表性不足的群体和/或弱势社区的学生，以从事科学和相关领域的职业。此次教育改革方案将直接影响到高丽大学科学及相关领域的女性和弱势群体的入学率、留任率和毕业率。

Plasmonic Nanocavities for Single Molecule DetectionThis proposal describes an integrated research, education and outreach plan with a focus on plasmonic nanocavities and their applications in single molecule surface enhanced Raman spectroscopy (SERS). The proposed plasmonic nanocavities, or the tiny gaps between metal nanowires (Ag), are formed by stacking a second layer of parallel Ag nanowires on top of a first layer of perpendicularly oriented Ag nanowires. Preliminary studies show that when the gaps between top and bottom nanowires are reduced to a few nanometers or ten millionth of the diameter of a human hair, illuminating light can be focused into such tiny nanogaps with up to 100000 times increase in light intensity. When molecules are placed inside these plasmonic nanocavities, their Raman scattering intensity can be largely enhanced so that even single molecule signals can be observed. The Raman spectra represent unique vibration information of molecules which can be used for direct detection and identification of the molecules. The proposed research aims at developing nanofabrication processes for nanowires and nanocavities, characterization and fundamental understanding of these plasmonic nanocavities, and exploring their applications in SERS. The ultimate goal is to demonstrate a robust single molecule sensing platform based on SERS. The education plan includes implementing an educational program aimed to attract high ability students in Northeast Ohio to majors in STEM (science, technology, engineering and mathematics) fields and to provide those students already in STEM fields with mentoring and research opportunities.Intellectual merit: The Ag nanowire crossbars are unique in three aspects: (1) nanoantennas (i.e. Ag nanowire) and nanocavities are integrated in single platform, making it highly efficient to focus light into nanometer scale; (2) the vertical cavity design makes it possible to fabricate nanogaps with unprecedented accuracy by using thin film deposition techniques; (3) Molecules within these nanocavities can be addressed electrically by applying voltages through these nanowires, providing great flexibility to control the molecules and nanocavities. The proposed research will answer fundamental questions about SERS enhancement mechanisms and lead to development of reproducible single molecule sensors. Broader impact: The proposed research benefits society because single molecule sensors can find myriad applications from homeland security to disease diagnostics for healthcare. The educational and outreach components of this career plan include developing of a guided research experience program for the Post Secondary Enrollment Option Program (PSEOP) students at Kent State University (KSU); mentoring undergraduates in research; creating an outreach program called ?Parent?s Night? for high school students and their parents; enhancing graduate education through involving graduate students in multidisciplinary research, and developing curriculum for teaching nano/biomaterials at the graduate level. KSU is one of three largest public universities in the state of Ohio, over 80% KSU students are undergraduates; and KSU primarily serves low- to middle-income undergraduates. This unusual combination of institutional traits makes KSU ideally suited to recruit students from under-represented groups and/or disadvantaged communities to pursue careers in science and related fields. The proposed educational plan will have a direct impact on improving enrollment, retention, and graduation rates of under-represented group members and women in science and related fields at KSU.