RAIRS, reflection adsorption infrared spectroscopy

The growth of thiophene films on ice depends on both the structure of the ice and the deposition temperature. A specific adsorption state of thiophene on amorphous ice at 125 K is deduced from the distinct reflection-adsorption infrared spectroscopy (RAIRS) in the range between 700 and 900 cm <2001MI160>. 

A prerequisite for the development indicated above to occur, is a parallel development in instrumentation to facilitate both physical and chemical characterization. TEM and SPM based methods will continue to play a central role in this development, since they possess the required nanometer (and subnanometer) spatial resolution. Optical spectroscopy using reflection adsorption infrared spectroscopy (RAIRS), polarization modulation infrared adsorption reflection spectroscopy (PM-IRRAS), second harmonic generation (SFIG), sum frequency generation (SFG), various in situ X-ray absorption (XAFS) and X-ray diffraction spectroscopies (XRD), and maybe also surface enhanced Raman scattering (SERS), etc., will play an important role when characterizing adsorbates on catalyst surfaces under reaction conditions. Few other methods fulfill the requirements of being able to operate over a wide pressure gap (to several atmospheres) and to be nondestructive. 

We then designed model studies by adsorbing cinchonidine from CCU solution onto a polycrystalline platinum disk, and then rinsing the platinum surface with a solvent. The fate of the adsorbed cinchonidine was monitored by reflection-absorption infrared spectroscopy (RAIRS) that probes the adsorbed cinchonidine on the surface. By trying 54 different solvents, we are able to identify two broad trends (Figure 17) [66]. For the first trend, the cinchonidine initially adsorbed at the CCR-Pt interface is not easily removed by the second solvent such as cyclohexane, n-pentane, n-hexane, carbon tetrachloride, carbon disulfide, toluene, benzene, ethyl ether, chlorobenzene, and formamide. For the second trend, the initially established adsorption-desorption equilibrium at the CCR-Pt interface is obviously perturbed by flushing the system with another solvent such as dichloromethane, ethyl acetate, methanol, ethanol, and acetic acid. These trends can already explain the above-mentioned observations made by catalysis researchers, in the sense that the perturbation of initially established adsorption-desorption equilibrium is related to the nature of the solvent. 

Fig. 8.10 Reflection absorption infrared spectroscopy (RAIRS) spectra show that lateral interactions force CO to leave the twofold adsorption sites on palladium (IR frequency ca. 1920 cm-1) when NO is coadsorbed, and push it to the on top site (adsorption frequencies above 2000 cm-1). Adsorbed NO gives rise to the absorption peaks below 1800 cm-1. (Adapted from [35]).

The influence of pH and other factors on the reductive desorption and oxidative reformation of a hexadecanethiol SAM on a gold electrode was studied by reflection-absorption infrared spectroscopy (RAIRS) and cyclic voltammetry. At low pH the lack of solubility of desorbed molecules was problematic however, after three adsorption-desorption cycles the process was reproducible301. The reductive desorption in alkaline solution of an alkanethiol SAM on a single-crystal Au(l 11) electrode involves a one-electron process to yield a thiolate. Oxidative removal is a complicated process, involving up to eleven electrons per alkanethiol molecule302. 

In this paper, we focus on the structure and properties of PLL-g-PEG-modified surfaces as well as on the adsorption kinetics of PLL-g-PEG onto metal oxide surfaces. We present the results of surface investigations using reflection-absorption infrared spectroscopy (RAIRS), X-ray photoelectron spectroscopy (XPS), and time-of-flight sec-... 

Carbon monoxide on metals forms the best-studied adsorption system in vibrational spectroscopy. The strong dipole associated with the C-O bond makes this molecule a particularly easy one to study. Moreover, the C-0 stretch frequency is very informative about the direct environment of the molecule. The metal-carbon bond, however, falling at frequencies between 300 and 500 cm1, is more difficult to measure with infrared spectroscopy. First, its detection requires special optical parts made of Csl, but even with suitable equipment the peak may be invisible because of absorption by the catalyst support. In reflection experiments on single crystal surfaces the metal-carbon peak is difficult to obtain because of the low sensitivity of RAIRS at low frequencies [12,13], EELS, on the other hand, has no difficulty in detecting the metal-carbon bond, as we shall see later on. 

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