Surface-enhanced second harmonic

Chen C K, de Castro ARB and Shen Y R 1981 Surface enhanced second-harmonic generation Phys. Rev. Lett. 46 145-8... 

Shen, C. K., Heinz, T. H., Ricard, D. and Shen, Y. R. (1983) Surface-enhanced second-harmonic generation and Raman scattering. Rhys. Rev. B, 27, 1965-1979. 

Pipino ACR, Schatz GC, Van Duyne RP. Surface-enhanced second-harmonic diffraction experimental investigation of selective enhancement. Physical Review B 1996, 53, 4162 1169. 

Alternatively, various analytical methods based on SPR phenomenon have been developed, including surface plasmon field-enhanced Raman scattering (SERS) [7], surface plasmon field-enhanced fluorescence spectroscopy (SPFS) [8-11], surface enhanced second harmonic generation (SHG) [12], surface enhanced infrared absorption (SEIRA) [13], surface plasmon field-enhanced diffraction spectroscopy (SPDS) [14-18], Most of these methods take advantage of the greatly enhanced electromagnetic field of surface plasmon waves, in order to excite a chromophoric molecule, e.g., a Raman molecule or a fluorescent dye. Therefore, a better sensitivity is expected. 

Chen CK, de Castro ARB, Shen YR (1981) Surface-enhanced second-harmonic generation. Phys Rev Lett 46 145-148... 

SESHG Surface enhanced second harmonic generation... 

A. C. R. Pipino, G. C. Schatz and R. P. Van Duyne, Surface-enhanced second-harmonic diffraction ... 

Haller, K. L., Bumm, L. A., Altkorn, R. I., Zeman, E. J., Schatz, G. C., and Van Duyne, R. P. (1989] Spatially resolved surface enhanced second harmonic generation Theoretical and experimental evidence for electromagnetic enhancement in the near infrared on a laser microfabricated Pt surface,/. Chem. Phys., 90,1237-1252. 

Recently, Eisenthal and coworkers have developed time-resolved surface second harmonic techniques to probe dynamics of polar solvation and isomerization reactions occurring at liquid liquid, liquid air, and liquid solid interfaces [22]. As these experiments afford subpicosecond time resolution, they are analogous to ultrafast pump probe measurements. Specifically, they excite a dye molecule residing at the interface and follow its dynamics via the resonance enhance second harmonic signal. 

Antoine, R., Pellarin. M., Palpant, B., Broyer, M., Prevel, B., Perez, A., Gaietto, P.. Brevet, P.F.. Girault, H.H. Surface plasmon enhanced second harmonic response from gold clusters embedded in an alumina matrix.. 1. Appl. Phys. 84, 4532-4536 (1998)... 

M. Celebrano et al.. Mapping local held enhancements at nanos-tructured metal surfaces by second-harmonic generation induced in the near field. Journal of Microscopy, 229, 233-239 (2008). 

In recent years,3 4 however, there has been renewed interest in the study of the electrode/solution interface due in part to the development of new spectroscopic techniques such as surface-enhanced Raman spectroscopy,5-7 electrochemically modulated infrared reflectance spectroscopy and related techniques,8,9 second-harmonic generation,10-12 and others which give information about the identity and orientation of molecular species in the interfacial... 

There are different paths to achieving surface specificity. One can exploit optical susceptibilities and resonances that are nonzero only at the surface or only for the molecular species of interest adsorbed on the surface. Examples include the use of second-order nonlinear mixing processes such as second harmonic generation7-9 for which the nonlinear susceptibility tensor is nonzero only where inversion symmetry is broken. Spectroscopic techniques with very high selectivity for molecular resonances such as surface-enhanced infrared or Raman spectroscopy10-12 may also be used. 

In addition to the indirect experimental evidence coming from work function measurements, information about water orientation at metal surfaces is beginning to emerge from recent applications of a number of in situ vibrational spectroscopic techniques. Infrared reflection-absorption spectroscopy, surface-enhanced Raman scattering, and second harmonic generation have been used to investigate the structure of water at different metal surfaces, but the pictures emerging from all these studies are not always consistent, partially because of surface modification and chemical adsorption, which complicate the analysis. 

As discussed in Chapter 8, enhanced reactions of S02 at the interface have also been observed (Jayne et al., 1990). Surface second harmonic generation (SHG) experiments (Donaldson et al., 1995) subsequently identified a unique adsorbed S02 species at the air-water interface that may be involved in this enhanced reaction. Such SHG work on the uptake and reaction of N02 on water would clearly also be of value in understanding the kinetic anomalies. In addition, the use of sum frequency generation (SFG) spectroscopy, which in effect allows one to obtain the infrared spectrum of species present at interfaces, may shed some light on such reactions. 

Optical frequency up-conversion, or second harmonic generation (SHG), in nanostructured surfaces can be also considered as a kind of field enhance-menf [61]. In general, SHG efficiency is proportional to the square of nonlinear polarization ha (x [P (2second order susceptibility. For a nanostructured surface, the incident field is transformed to the local field given by Eq. 19, yielding ... 

Cdrift = diffuse reflectance infrared Fourier transform spectroscopy. sers = surface enhanced Raman scattering. eshg = second harmonic generation. 

The frequency dependence of SHG at simple metal surface has been the focus of a recent theoretical study of Liebsch [100]. Time-dependent density functional theory was used in these calculations. The results suggest that the perpendicular surface contribution to the second harmonic current is found to be significantly larger than had been assumed previously. He also concludes that for 2 a> close to the threshold for electron emission, the self-consistently screened nonlinear electronic response becomes resonantly enhanced, analogous to local field enhancement in the linear response near the bulk plasma frequency. 

Surface plasmon effects result in useful photothermal effects [73] and have been used to enhance the surface sensitivity of various spectroscopic measurements [74], including fluorescence, Raman scattering, and second-harmonic generation. 

Jordan P et al (2005) Surface-enhanced resonance Raman scattering in optical tweezers using co-axial second harmonic generation. Opt Express 13(11) 4148-4153... 

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