Fourier transform monolayer studies

Amcau D, Ozanam F, Allongue P, Chazalviel J-N (2008) The titration of carboxyl-terminated mono-layers revisited in situ calibrated fourier transform infrared study of well-defined monolayers on silicon. Langmuir 24 9440-9448... 

Microphonic Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) has emerged as a useful tool for characterizing fractions of a monolayer of organic species adsorbed on opaque, high surface area samples. Such a study of calcined and sulfided hydrodesulfurization catalysts will be discussed. 

When the development of dedicated i rared spectrometers for surface studies started some ten years ago, some of them were designed as more or less complete ellipsometers, which in principle are insensitive to the ambient gas phase molecules. Fedyk et al. detected CO adsorbed on an evaporated Cu film at 4 torr, while Golden et al. reported work at 100 torr. More recently, Burrows et used a Fourier transform spectrometer and the polarizer approach above to study the reaction-rate oscillations in the oxidation of CO on a large Pt polycrystalline foil at pressures up to one atmosphere. With this rapid FTIR spectrometer they obtained a time resolution of 0.6 s at a sensitivity of 5% of a full CO monolayer. 

Organic Monolayer Studies Using Fourier Transform Infrared Reflection Spectroscopy... 

Fourier-transformed infrared spectroscopy (FT1R), either in the transmission mode(70), the grazing incidence reflection (GI) mode(7,5) or the attenuated total reflection (ATR) mode(7,2), has been the most widely used experimental tool for the characterization and structure determination of SA monolayers. GI-IR is especially useful in determining the molecular orientation in the film structures because it senses only the vibrational component perpendicular to the substrate surface(7,5). Polarized ATR-IR can also be used to study molecular orientation(7,77). McKeigue and Gula-ri(72) have used ATR-IR to quantitatively study the adsorption of the surfactant Aerosol-OT. 

A consistent description of the structure of alkanethiol monolayers on gold has emerged from an array of spectroscopic and diffraction studies. X-ray photoelectron spectroscopic (XPS) studies support the presence of anisotropically chemisorbed alkanethiolates on gold [24-29]. Ellipsometric measurements [24-27, 30], capacitance studies [30] and XPS measurements [31] confirm monolayer film thickness. Fourier transform infrared external reflective spectroscopy (FTIR-ERS) shows that the chains tilt at about 30° off the surface normal, and the plane containing the carbon backbone is twisted out of the plane of tilt by about 50° [25-27, 30, 32, 33]. 

A study with the hydrophobic signal peptide of coli lambda phage in phospholipid monolayers, showed a preference for pC helical conformation when the peptide was inserted into the lipid phase (18), However, interaction with the lipid surface without insertion induced the peptide to adopt the -structure ), These observations, obtained with circular dichroism and Fourier transform-infrared (FT-IR) data, provide the first direct evidence for interconversions between various conformational... 

Grazing-angle Fourier transform infrared (FTIR) spectra of monolayers of BDDAP-C-HMTCAQ, BDDAP-C-BHTCNQ, and TDDOP-C-HETCNQ, have been measured, and reported previously [19-21, 23]. The C-H stretch bands are well resolved, even for a single monolayer, and a broad structure at about 3500 cm- is seen for "fresh" samples, but disappears for samples older than about 60 days this may be water trapped between the LB film layer and the aluminum layer, but the identification is not certain. Further studies are planned. 

Leufgen et al. [82] reported the investigation of a template-assembled synthetic protein (TASP) conformation and its orientation in self-assembled monolayers (SAM) by means of TOF-SIMS. In this study, both the presence and molecular orientation of the TASP molecule can be monitored by TOF-SIMS, and furthermore, the influence of self-assembly protocols on the TASP molecular surface orientation can be studied by TOF-SIMS, although Fourier transform infrared spectroscopy (FTIR) and surface plasmon resonance (SPR) fail in this case. 

In this study, the layered structure of the organotiichlorosilane monolayer with a vinyl end group was constructed by the Langmuir method and its structure was analyzed by X-ray reflectivity (XR), Brewster angle Fourier transform infrared (B-FT-IR) spectroscopic measurements (14), electron diffraction (ED) and scanning force microscopic (SFM) observations. Furthermore, the domain height of the (NTS/FOETS) mixed monolayer surface with phase-separated structure was controlled by the combined method of Langmuir and chemisorption methods. 

The recrystallization of S-layer proteins at phosphatidylethanolamine monolayers on aqueous subphases was also studied on a mesoscopic scale by dual label fluorescence microscopy and Fourier-Transform-Infra-Red spectroscopy (FTIR) [87], It was shown that the phase state of the lipid exerts a marked influence on the protein crystallization. When the surface monolayer was in the phase separated state between the fluid and crystalline phases, the S-layer protein was preferentially absorbed at the boundary line between the two coexisting phases and crystallization proceeded underneath the crystalline phase. Crystal growth was much slower under the fluid lipid and the entire interface was overgrown only after prolonged protein incubation. In turn, as indicated by characteristic frequency shifts of the methylene stretch vibrations on the hpids, protein crystallization affected the order of the alkane chains and drove the fluid lipid into a state of higher order. It was also found that the protein did not interpenetrate the lipid monolayer as confirmed by X-ray reflectivity studies [85]. 

SAMs of allgrlphosphonic acids (butylphosphonic acid, octylphosphonic acid, undecylphosphonic acid and octadecylphosphonic acid) on native niekel oxide allow substrates to be functionalized easily. Monolayer formation has been investigated by diffuse reflectance Fourier transform infrared spectroscopy, non-contact mode atomic force microscopy, contact angle measurements and matrix-assisted laser desorption ionization mass spectrometry. Cyclic voltammetry and electrochemical impedance spectroscopy studies showed that the monolayer increased surface resistance to oxidation. 

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