闪烁表面增强拉曼散射的观测与分析
Summary
该协议描述了由于在银色表面上使用幂定律的单个分子的随机游走而引起的表面增强拉曼散射的分析。
Abstract
从一个单一的分子在银 nanoaggregate 结, 闪烁的表面增强拉曼散射 (SERS) 观察。本文介绍了如何制备 SERS 活性银 nanoaggregate, 在显微图像中记录某些闪烁点的视频, 并分析闪烁的统计数据。在这个分析中, 幂律再现了明亮事件相对于其持续时间的概率分布。黑暗事件的概率分布由幂律和指数函数拟合。幂定律的参数代表了光明和黑暗状态的分子行为。随机游走模型和分子在整个银色表面的速度可以估计。即使使用平均值、自相关函数和超分辨率 SERS 成像, 也难以估计。在未来, 幂律分析应与频谱成像相结合, 因为这种分析方法不能单独证实闪烁的起源。
Introduction
表面增强拉曼散射 (SERS) 是高灵敏度的拉曼光谱从一个高贵的金属表面。由于拉曼光谱提供了基于尖峰位置的分子结构的详细信息, 通过分子中官能团的振动模式, 可以研究金属表面上的单个分子的信息使用 SERS1,2,3。从银 nanoaggregate 与吸附在分子水平, 一个闪烁的信号被 观察1,2,3,45,7,8,9,10,11,12,13,14,15, 16, 频谱波动1,2,3,4,5,67,8, 9,10,11,12,13,14。眨眼可以由一个单一的分子, 随机进出一个增强电磁 (EM) 领域在一个纳米银 nanoaggregate 交界处。因此, 闪烁被认为是分子检测的简单证据, 与使用 SERS 强度的泊松分布和双分析物2、3、17的技术相比。然而, 闪烁和波动频谱的详细机制, 可能强烈依赖于分子行为在 Ag 表面, 仍然是有争议的。
在先前的研究中, 用自相关函数分析了闪烁的 SERS, 它可以计算在增强的 EM 场中进出的分子的扩散系数和浓度12,13,14.此外, 一个标准化的标准偏差评分, 代表了不稳定性的总强度, 是从信号的时间剖面的15。然而, 这些分析方法可能是基于一些分子的行为。相比之下, 在一个超分辨率成像的闪烁 SERS, 分子行为在增强 EM 领域可以识别16。但是, 这些技术只能在增强的 EM 域中获得这些参数。单个分子在广泛范围内的随机行为 (例如, 在闪烁的 SERS 中) 可以表示为幂定律, 而不是平均4,5,6,7,8 ,9,10,11, 类似于单个半导体量子点 (数字)18,19中闪烁的荧光。通过使用幂律分析4、5、6、7、8、91011, 分子行为可以估计在明亮状态 (在增强的 EM 领域) 和黑暗状态10;那是, 分子的行为在整个银色表面可以估计。
对于此技术, 银胶体粒子使用4,5,6,,8,9,10,11。这些粒子显示各种局部的表面等离子共振 (LSPR) 波段, 强烈影响增强的电磁场时, 他们是在一定的波长兴奋。因此, SERS 活性银纳米粒子存在于胶体悬浮液中, 并能立即获得一些数据。在简单的纳米结构的情况下, 有特定的大小, 形状和安排, LSPR 依赖的 SERS 闪烁可以隐藏其他依赖性7;也就是说, 如果使用了 LSPR 的好的或坏的纳米结构, 则参数将是恒定的, 因此其他的依赖将被隐藏。幂律分析已被用于发现从银胶体粒子的各种依赖的闪光 SERS, 4,5,6,7,89,10,11。
Protocol
Representative Results
Discussion
从银 nanoaggregate 结, SERS 被发射。因此, 我们需要准备粒子而不是胶体纳米粒子, 这是被柠檬酸阴离子覆盖。银聚合体是由添加多聚 l-赖氨酸所产生的盐析效应形成的, 它具有-NH3+ , 是来自氯化钠的 SERS、Na+阳离子的来源, 如补充材料的图 S2所示。此外, 为了照亮宽区的许多斑点, 不聚焦的激光光束是通过一个不附着在显微镜上的透镜, 相对于样品表面, 以30°的角度?…
Disclosures
The authors have nothing to disclose.
Acknowledgements
作者感谢 Prof. y Ozaki (Kwansei 学院大学) 和 Dr. (国家高等工业科技研究院) 对这项工作进行了卓有成效的讨论。这项工作得到了教育、文化、体育、科学和技术部 (No. 16K05671) 的 KAKENHI (补助金) 的支持。
Materials
| Silver nitrate, 99.8% | Wako | 194-00832 | |
| Trisodium citrate dihydrate, 99. % | Wako | 191-01785 | |
| Poly-L-lysine aqueous solution, 0.1% | Sigma-Aldrich | P8920 | |
| 3,3'-disulfopropylthiacyanine triethylamine | Hayashibara Biochemical Laboratories | NK-2703 | a kind of thiacyanine dyes |
| 3,3'-diethyl-5,5'-dichloro-9-methylthiacarbocyanine iodine salt | Hayashibara Biochemical Laboratories | SMP-9 | a kind of thiacarobocyanine dyes |
| Sodium chloride, 99.5% | Wako | 191-01665 | |
| Dimroth condenser | Iwaki | 61-9722-22 | perchased from AS ONE |
| Magnetic stirrer | Corning | DC-420D | |
| Oil bath | Advantech | OS-220 | |
| Glass plate | Matsunami | S-1112 | Microscope slide |
| Blower | Hozan | Z-288 | Air duster |
| Liquid blocker pen | Daido Sangyo | LIQUID BLOCKER (Super Pap Pen). Ready-to-use hydrophobic barrier pen designed for immunohistochemistry applications | |
| Inverted microscope | Olympus | IX-70 | |
| Objective lens | Olympus | LCPlanFl 60× | NA 0.7 |
| Dark field condenser | Olympus | U-DCD | NA 0.8–0.92 |
| Cooled digital CCD camera | Hamamatsu | ORCA-AG | controlled by software Aqua Cosmos |
| Software for the cooled digital CCD camera | Hamamatsu | AquaCosmos | used for also derivation of the time-profiles from the blinking spots in the video |
| Color CCD camera | ELMO | TNC-C920 | not used for analysis |
| DPSS laser | RGB laser system | NovaPro532-75 | λ = 532 nm; 60 mW (corresponds to a power density of 600 W/cm2) |
| Interference filter | Semrock | LL01-532-12.5 | |
| Long pass filter | Semrock | BLP01-532R-25 | |
| Software for the distinguishment and counting of the bright/dark events | home-maid | programmed by C++ | |
| Software for the fitting by a power law | LightStone | Origin6.1 |
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