Light-activated Single Molecule SERS Substrates

这项拟议的研究将根据PI最近发现的一种效应开发高通量和可靠的SM-SERS基板：在纳米结构半导体上的金属纳米颗粒的光诱导电化学奥斯瓦尔德成熟(LIECOR)效应。LIECOR将被用于在纳米颗粒之间创造纳米级的间隙，这些纳米颗粒是巨大的电磁增强部位。拟议的努力旨在通过依赖三个关键特征来克服目前SERS的可靠性和低吞吐量问题：不含表面活性剂的纳米颗粒允许快速吸附分析物；拉曼激光在光谱采集开始时创建热点，以便在SERS之前允许在热点处最大限度地减少污染和氧化；LIECOR的自抑制特性产生均匀的分析结果。具体目标和如何实现这些目标如下。1)LIECOR的阐明和控制。可能的使能或驱动机制，如光导？以及？纳米光电池的形成？将在实验中进行测试。将研究半导体暗电导率和表面缺陷密度以及激光强度的影响。LIECOR微光点将采用共焦透射谱。特别是，LIECOR动力学将从一组激光强度级别的纳米粒子等离子体激元模式的光谱变化中实时监测。2)寻找表面增强的光学力是否加速了分子寻找热点的实验证据。在LIECOR完成后，将研究由于激光激发的突然变化(例如，开/关和偏振变化)引起的瞬时SERS。这种瞬变现象表明，在光学力的作用下，分子集中在热点附近。此外，还将进行毫秒分辨率的SM-SERS，以揭示纳米颗粒上的任何光学偏置表面扩散。3)展示了SM-SERS底物在生物光子学中的应用。SM-SERS底物将被用来在单分子水平上阐明光活性黄色蛋白在受体状态和信号状态之间的结构差异。4)利用金属纳米粒子电荷控制对阳离子或阴离子分子具有选择性的SERS衬底的开发。

CBET-0756791, KalkanThe proposed research will develop a high throughput and reliable SM-SERS substrate on the basis of an effect recently discovered by the PI: light-induced electrochemical Ostwald ripening (LIECOR) of metal nanoparticles on a nanotextured semiconductor. LIECOR will be exploited for the creation of nanoscopic gaps in between nanoparticles which are giant electromagnetic enhancement sites. The proposed effort aims at overcoming the current reliability and low throughput issues in SERS by relying on 3 key features: surfactant-free nanoparticles permitting quick analyte adsorption; creation of the hot spots by the Raman laser at the onset of the spectral acquisition so that minimum contamination and oxidation are allowed at the hot spots prior to SERS; self-inhibiting feature of LIECOR yielding uniformity. The specific goals targeted and how they will be addressed are as follows. 1) Elucidation and control of the LIECOR. Possible enabling or driving mechanisms like ?photoconductance? and ?formation of nano-photocells? will be tested experimentally. The impact of semiconductor dark conductivity and surface defect density, as well as laser intensity will be studied. Confocal transmission spectroscopy will be employed at the LIECOR micro-spot. In particular, LIECOR kinetics will be monitored real time from the spectral changes in nanoparticle plasmon modes for a set of laser intensity levels. 2) Searching for experimental evidence whether surface-enhanced optical forces expedite molecules find hot spots. Transient SERS due to sudden changes in laser excitation (e.g., on/off and change of polarization) will be explored (after the LIECOR is complete). Such transients suggest molecules concentrate around hot spots under the action of optical forces. In addition, millisecond-resolved SM-SERS will be carried out to reveal any optically-biased surface diffusion on the nanoparticles. 3) Demonstration of the utility of the SM-SERS substrates in biophotonics. The SM-SERS substrates will be employed to elucidate the difference in the structures of photo-active yellow protein between the receptor state and the signaling state at the single molecule level. 4) Development of SERS substrates, which are selective for cationic or anionic molecules by the control of metal nanoparticle charge.