Sum-frequency generation spectroscopy

This is a third-order nonlinear spectroscopic method that does not involve time delay. It consists of sending two coherent beams on a sample simultaneously one in the visible-UV region and the other one in the IR region and observing the photon that is emitted at the sum of their frequencies and is concomitant with the absorption of two photons, one in each of the two incident beams (72). The spectroscopic regions of the two incident beams are regions of transparency of the sample. The emitted photon requires absence of a centre of symmetry at molecular level to appear. It means that it practically does not appear in the bulk of a liquid, for instance, which is isotrope and consequently displays a centre of inversion in the average, but may appear on its surface, or at the interface between this liquid and another medium, where this centre of inversion disappears. It will consequently be most useful in the study of surfaces and interfaces, particularly the structures of the molecules thereon that can be deduced from the spectrum of these surfaces or interfaces (73). In many situations, it may be the unique tool to study liquid surfaces and interfaces and we shall see this in Ch. 9, which is devoted to liquid water-related examples. 

Beyond neat liquid water sum-frequency vibrational spectroscopy allowed the study of the alkyl chain conformation of surfactants such as dodecyl sulfate described in Ch. 9, that mediates the interfaces between water and CCI4 when the head group or the cations of these amphiphile molecules varied (77, 78). It also gave experimental evidence that the water surface favours the presence of anions rather than cations (79). This effect is at the origin of the oxidative power of sea water, which is ascribed to Cl anions positioned on surfaces of liquid-water droplets. It has also been applied to other H-bonded liquid water, such as methanol, where it could be demonstrated that the CH3 groups point away from the liquid at the interface with vapour (73). This is also the case for CH3 groups of acetic acid (80). Also the surface of liquid water could be shown (81) to be disrupted by even such a small amount as 0.3% of acetic acid, which does not ionize, even at this low 

We thus see that, as for the time-resolved nonlinear IR methods, sum-frequency vibrational spectroscopy is a valuable tool to convey information on H-bonds, particularly H-bonds at interfaces. 

Intramonomer bands other than are also sensitive to H-bonds, although in a much less spectacular way. This sensitivity proves to be most useful in chemistry and biology, and, as will be seen in the case of the H2O molecule, allows precise measurements of the number of H-bonds from which much structural and dynamic information can be obtained. It will prove useful to follow the development of the H-bond network of a macromolecule during hydration (Ch. 10). In physics and chemistry, the hypersensitive band ensures the 

These properties make IR spectroscopy certainly the most precise and powerful tool to observe H-bonds not only in physics but also in chemistry and biology. In its ID form, it requires a technique, conventional IR, which is a rontine technique, easy to implement in many set-ups. In its recent version of time-resolved spectroscopy, it is not presently a routine technique, but it has proved to be most informative. The particularly important effects H-bonds have on IR spectra require, however, some care and method during the analysis of these spectra, which is thus scarcely a routine analysis. We shall see that with a minimum of care and methodology it can nevertheless be nsed with no difficulty. 

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Vidal, F. and Tadjeddine, A. (2005) Sum-frequency generation spectroscopy of interfaces. Rep. Prog. Phys., 68, 1095-1127. 

Uosaki, K., Yano, T. and Nihonyanagi, S. (2004) Interfacial water structure at as-prepared and UV-rnduced hydrophilic Ti02 surfaces studied hy sum frequency generation spectroscopy and quartz crystal microhalance. J. Phys. Chem. B, 108, 19086-19088. 

Noguchi, H., Minowa, H., Tominaga, T., Gong, J. P., Osada, Y. and Uosaki, K. (2008) Interfacial water structure at polymer gel/quartz interfaces investigated by sum frequency generation spectroscopy. Phys. Chem. Chem. Phys., 10, 4987-4993. 

Backus EHG, Boim M. 2005. A quantitative comparison between reflection absorption infrared and sum-frequency generation spectroscopy. Chem Phys Lett 412 152-157. 

Lagutchev A, Hambir SA, Dlott DD. 2007. Nonresonant background suppression in broadband vibrational sum-frequency generation spectroscopy. J Phys Chem C 111 ... 

Lu GQ, Lagutchev A, Dlott DD, Wieckowski A. 2005. Quantitative vibrational sum-frequency generation spectroscopy of thin layer electrochemistry CO on a Pt electrode. Surf Sci 585 3-16. 

Henry, M.C., Wolf, L.K., and Messmer, M.C., In situ examination of the structure of model reversed-phase chromatographic interfaces by sum-frequency generation spectroscopy, J. Phys. Chem. B, 107, 2765, 2003. 

Kim et al. [22] have used vibrational sum-frequency generation spectroscopy (SFG) to characterize the surfaces of (3-HMX single crystals, as well as the interface between HMX and the copolymer Estane. SFG is a nonlinear vibrational spectroscopic technique, related to optical parametric amplification that selectively probes vibrational transitions at surfaces and interfaces. Compared with bulk HMX, the surface vibrational features are blueshifted and observed splittings are larger. The technique may have application to detection of explosive residues on surfaces. 

Kubota J, Domen K (2007) Study of the dynamics of surface molecules by time-resolved sum-frequency generation spectroscopy. Anal Bioanal Chem 388 17... 

Rupprechter G., Freund H.-J. (2001) Adsorbate-induced restructuring and pressure-dependent adsorption on metal nanoparticles studied by electron microscopy and sum frequency generation spectroscopy. Topics Catal 14 3... 

Rupprechter G (2001) Surface vibrational spectroscopy from ultrahigh vacuum to atmospheric pressure Adsorption and reactions on single crystals and nanoparticle model catalysts monitored by sum frequency generation spectroscopy. Phys Chem Chem Phys 3 4621... 

Rupprechter G, Dellwig T, Unterhalt H, Freund H-J (2001). CO adsorption on Ni(lOO) and Pt(l 11) studied by infrared-visible sum frequency generation spectroscopy design and application of an SFG-compatible UHV-high-pressure reaction cell. Top Catal, 15, 19... 

Ma, G., Liu, D., and Allen, H.C., Piperidine adsorption on hydrated a-alumina (0001) surface studied by vibrational sum frequency generation spectroscopy, Langmuir, 20, 11620, 2004. 

Chapter 1 summarizes methods for the stabilization of artificial lipid membranes. They include synthesis of new types of polymerizable lipids and polymerization of membranes. Creation and characterization of novel poly(lipid) membrane systems, as well as their functionalization for biotechnological applications, are also described. Chapter 2 addresses experimental studies on the design and characterization of lipopolymer-based monolayers at the air-water interface. Thermodynamic and structural data collected with X-ray and neutron reflectrometry, infrared reflection absorption spectroscopy, and sum frequency generation spectroscopy provide... 

Shultz M J, Schnitzer C, Simonelli D and Baldelli S 2000 Sum-frequency generation spectroscopy of the aqueous interface ionic and soluble molecular solutions Int. Rev. Rhys. Chem. 19 123-53... 

Ma G, Allen HC (2003) Surface studies of aqueous methanol solutions by vibhrational broad bandwidth sum frequency generation spectroscopy. J Phys Chem B 107 6343-6349 Maheshwari R, Sreeram KJ, Dhathathreyan A (2003) Surface energy of aqueous msolutions of Hofmeister electrolytes at air/liquid and solid/liquid interface. Chem Phys Lett 375 157-161 Marcus Y (1998) The properties of solvents. Wiley, Chichester... 

Zhang, D., Dougal, S.M., and Yeganeh, M.S. (2000) Effects of UV irradiation and plasma treatment on a polystyrene surface studied by IR-visible sum frequency generation spectroscopy. Langmuir, 16, 4528-4532. 

Aliaga, C. and Baldelli, S. (2007) Sum frequency generation spectroscopy of dicyanamide based room-temperature ionic liquidsorientation of the cation and the anion at the gas-liquid interface. J. Phys. Chem. B, 111, 9733-9740. 

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