Light-activated Single Molecule SERS Substrates

该研究将基于PI最近发现的一种效应：金属纳米颗粒在纳米纹理半导体上的光诱导电化学奥斯特瓦尔德成熟（LIECOR），开发一种高通量和可靠的SM-SERS衬底。LIECOR将被用于在纳米颗粒之间创造纳米级的间隙，这是巨大的电磁增强点。所提出的努力旨在克服目前SERS的可靠性和低通量问题，依靠3个关键特征：无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产生热点，以便在SERS之前在热点处允许最小的污染和氧化；LIECOR产生均匀性的自抑制特性。具体目标及其实现方式如下。1) LIECOR的阐明和控制。可能的启用或驱动机制，如光导？然后呢?纳米光电池的形成？将进行实验测试。研究了半导体暗电导率、表面缺陷密度以及激光强度的影响。共聚焦透射光谱学将用于LIECOR微点。特别是，LIECOR动力学将从纳米粒子等离子体模式的光谱变化中实时监测一组激光强度水平。2)寻找表面增强光力是否能加速分子找到热点的实验证据。在LIECOR完成后，将探索由于激光激发突然变化（如开/关和偏振变化）引起的瞬态SERS。这种瞬态表明分子在光力的作用下集中在热点周围。此外，将进行毫秒级分辨的SM-SERS，以揭示纳米颗粒上的任何光学偏态表面扩散。3) SM-SERS衬底在生物光子学中的应用。SM-SERS底物将在单分子水平上阐明光活性黄蛋白在受体状态和信号状态下的结构差异。4)通过控制金属纳米粒子的电荷来选择阳离子或阴离子分子的SERS底物的开发。

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.