Tip-enhanced Raman Spectroscopy TERS

These observations were also interpreted as evidence for hot spots, proposing a generalized concept hot spots represent those small surface locations where both the electromagnetic and the resonance Raman part of surface enhancement are large. 

Tip-enhanced Raman spectroscopy (TERS) has been developed from the field of scanning near-field microscopy (SNOM), a field that is not directly related to SERS. Howevei one particular important concept of SNOM is also essential for the SERS process the near-field effect. It is common to both SNOM and the electromagnetic enhancement process of SERS and it is the heart of TERS. 

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Pettinger, B., Ren, B., Picardi, G., Schuster, R. and Ertl, G. (2005) Tip-Enhanced Raman spectroscopy (TERS) of malachite green isothiocyanate at Au(lll) bleaching behavior under the influence of high electromagnetic flelds./. Raman Spectrosc., 36, 541-550. 

For overcoming the limit of light microscopy and further improvement in spatial resolution, the implementation of scaiuiing near-held microscopy (SNOM) by means of a local illumination probe is an interesting approach [33-35]. The method is based on the held enhancement in the cavity between a sharp metal dp and the sample. In combination with Raman spectroscopy, this scanning probe technique is called tip-enhanced Raman spectroscopy (TERS) and enables high-resolution spatial microscopy with a lateral resolution of 50 nm [35]. Bouhelier [36] has reviewed advances in this held. 

Results will be split into various sections the first of which will be fundamentals of hot spots. This will include a summary of the most important developments in the theory of SERS hot spots for both the EM and CT enhancement mechanisms. The second section will cover developments in tip-enhanced Raman spectroscopy (TERS) which represents the idealized hot spot. Then some issues regarding hot spots and the single molecule will be tackled such as the magnitude of enhancement required for single-molecule detection, the effects of molecular orientation with respect to the hot spot as well as the possible influence of optical forces. Sections 4.4 and 4.5 will cover developments in the imaging and fabrication of SERS hot spots, respectively, which have important implications for theoretical modeling as well control of SERS hot spots. The chapter will conclude by summarizing some of the applications of SERS hot spots that have been recently reported. 

Idealized Hot Spot Control Tip-Enhanced Raman Spectroscopy (TERS)... 

It is appropriate to conclude this part of the chapter, before going on to review the literature on SE(R)RS of biomolecules at electrode surfaces, by briefly describing tip-enhanced Raman spectroscopy (TERS) since this rapidly developing technique offers the potential for studies at molecular resolution. In TERS a metal nanoparticle or metalized tip (usually Ag or Au) with an apex diameter of about 25 nm is illuminated by a laser as it is scanned across the surface (Figure 6.14). The tip is used to locally amplify and confine the electromagnetic field, in effect creating a local hotspot which can be scanned across the surface. The first examples of this approach were reported in 2000 [193-195]. Since then the approach has been... 

However, a-SNOM faces two fundamental difficulties (i) the power emitted from the aperture is usually on the order of nanoWatts, and too weak for collecting a spectrum with a short acquisition time (ii) its spatial resolution is limited to 50 nm in practice, and is insufficient for true nanoscale analysis [6]. In order to overcome these problems, alternatives have been developed during the past 10 years, namely, tip-enhanced Raman spectroscopy (TERS) [7, 8] (Figure 15.1b) and scattering SNOM (s-SNOM), which is mainly used in the IR spectral range (Figure 15.1c) [9]. In this chapter, we focus primarily on these two methods. 

Besides the effort put into the development of suitable SERS substrates, SERS shows great potential in combination with other techniques. Thus, e.g., tip-enhanced Raman spectroscopy (TERS) combines SERS with... 

Bohme, R. et al (2010) Biochemical imaging below the diffraction limit — probing cellular membrane related structures by Tip-Enhanced Raman Spectroscopy (TERS). J. Biophotonics, 3, 455-461. doi ... 

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