针尖增强拉曼散射 (TERS)

显微拉曼已经成为分析微米级材料的一个重要工具。HORIBA Scientific拉曼显微镜具有独特的共焦性能和高空间分辨率,从而将远场光学分辨率推向极限,通常可以达到亚微米级别的分辨率。

近场光学拉曼分析与原子力显微镜(AFM)联用可以分析更小尺度的材料。这种联用系统可以用于TERS研究,实现真正的纳米拉曼,使空间分辨率小于100nm

TERS方法是基于拉曼、表面增强拉曼散射(SERS)以及AFM的联用。利用纳米尺度的胶体颗粒或粗糙金属衬底的表面等离子体共振,SERS可以探测到百万分之一(ppm)数量级的化学样品,因而长期以来一直被用于增强微弱的拉曼信号。TERS的增强原理和SERS相同,但是TERS是使用金属包覆的AFM针尖作为触角来增强与针尖接触区域样品的拉曼信号。由于AFM针尖是纳米尺度的,所以可以获得纳米尺度范围的局域增强。通过区分TERS和常规拉曼散射(针尖离开样品),可以获得直径<100nm区域内的拉曼信息。

虽然TERS效应还没有被完全理解,但是它已经引起了极大的关注,因为它可以获取纳米分辨率上的化学图像。LabRAM 纳米拉曼平台与最先进的AFM联用,再加上HORIBA久负盛名的拉曼专业技术,可以放心地进行TERS探索性实验。

TERS已经应用于很多不同的领域,它突破了共焦拉曼仪器以前所受到的微米级别光学衍射极限限制,开启了显微分析和成像的新局面。

点击此处查看典型的Raman-AFMTERS应用实例。

Therefore near-field spontaneous Raman of non-resonant molecules is close to impossible even with the best possible optics and detection hardware.

Surface-Enhanced Raman Scattering has flourished in the past 30 years as it brought the promise of single molecule detection with Raman, through the use of surface plasmon resonance effects. Tip-Enhanced Raman Scattering essentially takes advantage of the same effect, but the SPM probe tip is the enhancing surface promoting Raman scattering only from a nanoscale area.

Successful TERS measurement usually involves properly crafted probe-tips, which must be coated with a rough noble-metal layer in order to allow coupling of light into surface plasmons. Proper excitation wavelength selection to match possible sample resonance and probe-tip peak plasmon coupling efficiency also helps generate extremely high enhancement of the local Raman signal so that when scanning the probe, spatial resolution in the order of 10nm can be achieved and best resolution of 2nm has been reported using HORIBA equipment.

Over the years, HORIBA Scientific has developed an optimized optical, mechanical and software SPM coupling platform to provide the best possible light collection efficiency with the ability to easily align the Raman laser on the SPM tip for efficient and stable TERS imaging. HORIBA Scientific leadership and innovation in Raman spectroscopy lets you approach this novel technique with confidence, focusing on sample measurement, trusting the equipment is optimized for this purpose.

TERS is being explored for many different application areas, and opens up new possibilities in nanoscale chemical analysis and imaging.

硅样品拉曼信号的TERS增强,通过仔细的偏振控制实现远场抑制