Raman reflection spectroscopy monolayers

Resonance Raman reflection spectroscopy of monolayers is possible, as illustrated in Fig. IV-14 for cetyl orange [157]. The polarized spectra obtained with an Ar ion laser allowed estimates of orientational changes in the cetyl orange molecules with a. 

Specular reflection spectroscopy has been actively used in in situ studies of the formation and optical behaviour of monolayer films on surfaces, and for detecting intermediates and products of heterogeneous chemical and electrochemical reactions. The vibrational spectra of the adsorbed species at electrode surfaces are obtained by surface-enhanced Raman scattering and infrared reflectance spectroscopies. Since the mid-1960s, modulated reflection spectroscopy techniques have been employed in elucidating the optical properties and band structure of solids. In the semiconductor electroreflectance, the reflectance change at the semiconductor surface caused by the perturbation of the dielectric properties of... 

Raman spectroscopy has provided information on catalytically active transition metal oxide species (e. g. V, Nb, Cr, Mo, W, and Re) present on the surface of different oxide supports (e.g. alumina, titania, zirconia, niobia, and silica). The structures of the surface metal oxide species were reflected in the terminal M=0 and bridging M-O-M vibrations. The location of the surface metal oxide species on the oxide supports was determined by monitoring the specific surface hydroxyls of the support that were being titrated. The surface coverage of the metal oxide species on the oxide supports could be quantitatively obtained, because at monolayer coverage all the reactive surface hydroxyls were titrated and additional metal oxide resulted in the formation of crystalline metal oxide particles. The nature of surface Lewis and Bronsted acid sites in supported metal oxide catalysts has been determined by adsorbing probe mole-... 

In contrast to the minimal activity in infrared reflection studies the technique of inelastic electron tunneling spectroscopy (IETS) recently has contributed a large amount of information on monolayer adsorption of organic molecules on smooth metal oxide surfaces,Q),aluminum oxide layers on evaporated aluminum. These results indicate that a variety of organic molecules with acidic hydrogens, such as carboxylic acids and phenols chemisorb on aluminum Oxide overlayers by proton dissociation - 1 — and that monolayer coverage can be attained quite repro-ducibly by solution doping techniques. - The IETS technique is sensitive to both infrared and Raman modes. — However, almost no examples exist in which Raman il and or infrared spectra have been taken for an adsorbate/substrate system for which IETS spectra have been observed. 

Ten years ago one would have predicted that Raman spectroscopy could never be used to study monolayer adsorption on metals because either (a) the sensitivity of the technique would be too low to permit detection of signals using a single reflection from a smooth metal surface, or (b) oxide supported metal surfaces are black if the metal loading is high and therefore the laser light would be absorbed. Both of the above objections have been shown to be faulty insofar as the technique has now been used to study absorption on silica-supported nickel (51, 52,53) and on single crystal nickel (54). Moreover in the special case of silver,... 

Numerous techniques have been employed to examine the monolayer structure of phospholipids at the air/water interface including surface tension, fluorescence, neutron and X-ray reflection, and IR and Raman spectroscopy. In contrast, very few techniques are suitable to examine monolayers at the oil/water interface. Surface tension and fluorescence microscopy [46-48] have shed some light on these buried monolayers, but most other surface techniques are hampered because of effects from the bulk liquids. Since VSFS is insensitive to the bulk, it is an excellent technique for probing these monolayers. 

R. A. Dluhy, S.M. Stephens, S. Widayatl and A.D. Williams, Vibrational Spectroscopy of Biophysical Monolayers. Applications of IR and Raman Spectroscopy to Biomembrane Model Systems at Interfaces, Spectrochim. Acta Part A51 (1995) 1413. (Review on biomembrane model systems studied by surface-sensitive vibrational spectroscopic methods. In particular the following methods are surveyed external reflectance IR spectroscopy, wave-guide Raman spectroscopy cmd SERS.)... 

Leverette, C.L. and Dluhy, R.A. (2000) A novel fiber-optic interface for unenhanced external reflection Raman spectroscopy of supported monolayers. Langmuir, 16, 3977-3983. 

In this chapter, electrochemical properties of ET proteins at electrode interfaces studied by spectroelectrochem-ical techniques are described. In situ spectroelectrochemical techniques at well-defined electrode surfaces are sufficiently selective and sensitive to distinguish not only steady state structures and oxidation states of adsorbed species but also dynamics of reactants, products, and intermediates at electrode surfaces on a monolayer level. The spectroelectrochemical techniques used in studies of ET proteins include IR reflection-absorption, potential-modulated UV-vis reflectance (electroreflectance), surface-enhanced Raman scattering (SERS) and surface plasmon resonance, total internal reflection fluorescence, (TIRE) and absorbance linear dichroism spectroscopies. 

The first in-situ X-ray diffraction (XRD) investigations of phase transitions of adsorbed monolayers and multilayers [6] and reconstmction of a metal surface [7,8] were also reported by Fleischmann and Mao. The phase transitions were reported for the underpotential deposition (upd) and overpotential deposition (opd) of thallium onto a roughened silver electrode surfaces (similar to those used in surface-enhanced Raman spectroscopy (SERS) using the reflection mode of collection), and for upd of lead onto gold and silver... 

Several techniques are usually employed to study the strain in QD layers. Raman spectroscopy and high-resolution X-ray diffraction, on the one hand, can be routinely used to address this issue, but the data obtained are averaged over the entire volume of the dots. High-resolution transmission electron microscopy (HRTEM), on the other hand, provides information at the monolayer scale, but the technique requires extensive sample preparation that may induce an extra relaxation owing to thin foil effects the data gathered are local and may not reflect the structure of the whole sample. Medium energy ion scattering (MEIS) appears as an alternative no preparation is needed. 

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