Studying Surface Chemistry beyond the Diffraction Limit: 10 Years of TERS

Abstract

The use of an illuminated scanning probe tip to greatly enhance Raman scattering from the sample underneath the tip is one of the most intriguing developments in optical spectroscopy, and the steeply increasing number of publications per year shows that chemists, physicists and biologists alike recognize the importance and great potential of this technique. With tip-enhanced Raman spectroscopy (TERS), one of the main goals in surface science has been achieved, namely the combination of scanning probe microscopy and optical spectroscopy such as Raman spectroscopy. Important here is the use of the tip as an optical antenna to substantially increase the emitted radiation and to simultaneously improve the optical resolution much beyond the Abbe diffraction limit. This permits the correlation of topographic and chemical information of the same surface region. The synergy of detailed insight in morphology and the chemical nature of the target species facilitates data interpretation significantly and enables characterization of interfaces at the nanometer scale. A wide variety of substrates and sample molecules have been studied with TERS since the first publication of tip-enhanced Raman spectra, and the technique has reached a first level of maturity on its 10th birthday, with TERS applications extending into various research fields from surface chemistry over biology to nanoscale physics.

Tip-enhanced Raman scattering—Targeting structure-specific surface characterization for biomedical samples

“…From theoretical considerations, the enhancement of the Raman scattering signal due to EM field is then in the range of~5-30 nm. Consequently, if the tip-sample distance increases, the enhancement decreases considerably [12]. The EM field enhancement can be attributed to two prominent effects: (1) lightning rod effect and (2) surface plasmons [13,14].…”

Microspectroscopy as applied to the study of wood molecular structure

“…It seems that Raman microspectroscopy at present offers the best combination of spatial and spectral resolution, with information obtainable at the sub-cell wall level for all three major wood cell wall polymers. The spatial resolution can be driven below the diffraction limit by tip enhanced Raman microscopy (Domke and Pettinger 2010;Stadler et al 2010). …”

Methods for Vectorial Analysis and Imaging in High-Resolution Laser Microscopy

“…Undoubtedly, one of the most recent scientific challenges in optical imaging is the achievement of very high spatial resolutions that might reach the so-called nanoscopic scale and ultimately go beyond the diffraction limit (Betzig and Trautman, 1992;Domke and Pettinger, 2010;Durant et al, 2006;Dyba and Hell, 2002;Gramotnev and Bozhevolnyi, 2010;Hayazawa et al, 2002;Novotny and Hecht, 2006;Westphal et al, 2008; and many others not listed). The importance of such a challenge is clear in the disciplines of chemical, biological, and physical interest where imaging of details comparable to or even smaller than the optical wavelengths is crucial to the understanding of the phenomena occurring at that spatial level and, in this regard, optical systems combining laser techniques with microscopy realized with lenses of high numerical aperture (NA) can successfully meet the challenge (Cheng et al, 2002;Denk et al, 1990;Dorn et al, 2003;Dyba and Hell, 2002;Freudiger et al, 2008;Kino and Corle, 1997;Masters and So, 2008;Novotny and Hecht, 2006;Pawley, 2006;Van de Nes et al, 2006;Volkmer et al, 2001;Westphal et al, 2008;Zipfel et al, 2003;Zumbusch et al, 1999).…”