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Infrared adsorbed

Figure 8 Infrared adsorbance spectra of a phosphonate film on an aluminum oxide surface and of Zn-biphosphonate multilayer on gold (see figure on the left). Figure 8 Infrared adsorbance spectra of a phosphonate film on an aluminum oxide surface and of Zn-biphosphonate multilayer on gold (see figure on the left).
Figure 15 Normalized infrared adsorbance at the wave niunber 1380 cm for polycya-nurate films of different thickness for the nnmodified and the NEAP-modified sample. Figure 15 Normalized infrared adsorbance at the wave niunber 1380 cm for polycya-nurate films of different thickness for the nnmodified and the NEAP-modified sample.
The external reflection of infrared radiation can be used to characterize the thickness and orientation of adsorbates on metal surfaces. Buontempo and Rice [153-155] have recently extended this technique to molecules at dielectric surfaces, including Langmuir monolayers at the air-water interface. Analysis of the dichroic ratio, the ratio of reflectivity parallel to the plane of incidence (p-polarization) to that perpendicular to it (.r-polarization) allows evaluation of the molecular orientation in terms of a tilt angle and rotation around the backbone [153]. An example of the p-polarized reflection spectrum for stearyl alcohol is shown in Fig. IV-13. Unfortunately, quantitative analysis of the experimental measurements of the antisymmetric CH2 stretch for heneicosanol [153,155] stearly alcohol [154] and tetracosanoic [156] monolayers is made difflcult by the scatter in the IR peak heights. [Pg.127]

IRE Infrared emission [110] Infrared emission from a metal surface is affected in angular distribution by adsorbed species Orientation of adsorbed molecules... [Pg.314]

IR, FTIR Infrared absorption Transmission absorption Analysis state of adsorbed... [Pg.317]

The polymer concentration profile has been measured by small-angle neutron scattering from polymers adsorbed onto colloidal particles [70,71] or porous media [72] and from flat surfaces with neutron reflectivity [73] and optical reflectometry [74]. The fraction of segments bound to the solid surface is nicely revealed in NMR studies [75], infrared spectroscopy [76], and electron spin resonance [77]. An example of the concentration profile obtained by inverting neutron scattering measurements appears in Fig. XI-7, showing a typical surface volume fraction of 0.25 and layer thickness of 10-15 nm. The profile decays rapidly and monotonically but does not exhibit power-law scaling [70]. [Pg.402]

The importance of the particle levitation methods is that they allow the study of how a single particle responds to changes in environment. The infrared molecular spectroscopy of single particles is possible [253], as are photophysical studies using adsorbed or dissolved dyes. [Pg.526]

An interesting point is that infrared absorptions that are symmetry-forbidden and hence that do not appear in the spectrum of the gaseous molecule may appear when that molecule is adsorbed. Thus Sheppard and Yates [74] found that normally forbidden bands could be detected in the case of methane and hydrogen adsorbed on glass this meant that there was a decrease in molecular symmetry. In the case of the methane, it appeared from the band shapes that some reduction in rotational degrees of freedom had occurred. Figure XVII-16 shows the IR spectrum for a physisorbed H2 system, and Refs. 69 and 75 give the IR spectra for adsorbed N2 (on Ni) and O2 (in a zeolite), respectively. [Pg.584]

L. H. Little, Infrared Spectra of Adsorbed Molecules, Academic, New York, 1966. 68a. M. L. Hair, Infrared Spectroscopy in Surface Chemistry, Marcel Dekker, New... [Pg.596]

XI-1C) as well as alongside it. The infrared spectrum of CO2 adsorbed on 7-alumina suggests the presence of both physically and chemically adsorbed molecules [3]. [Pg.601]

Infrared Spectroscopy. The infrared spectroscopy of adsorbates has been studied for many years, especially for chemisorbed species (see Section XVIII-2C). In the case of physisorption, where the molecule remains intact, one is interested in how the molecular symmetry is altered on adsorption. Perhaps the conceptually simplest case is that of H2 on NaCl(lOO). Being homo-polar, Ha by itself has no allowed vibrational absorption (except for some weak collision-induced transitions) but when adsorbed, the reduced symmetry allows a vibrational spectrum to be observed. Fig. XVII-16 shows the infrared spectrum at 30 K for various degrees of monolayer coverage [96] (the adsorption is Langmuirian with half-coverage at about 10 atm). The bands labeled sf are for transitions of H2 on a smooth face and are from the 7 = 0 and J = 1 rotational states Q /fR) is assigned as a combination band. The bands labeled... [Pg.634]

Still another type of adsorption system is that in which either a proton transfer occurs between the adsorbent site and the adsorbate or a Lewis acid-base type of reaction occurs. An important group of solids having acid sites is that of the various silica-aluminas, widely used as cracking catalysts. The sites center on surface aluminum ions but could be either proton donor (Brpnsted acid) or Lewis acid in type. The type of site can be distinguished by infrared spectroscopy, since an adsorbed base, such as ammonia or pyridine, should be either in the ammonium or pyridinium ion form or in coordinated form. The type of data obtainable is illustrated in Fig. XVIII-20, which shows a portion of the infrared spectrum of pyridine adsorbed on a Mo(IV)-Al203 catalyst. In the presence of some surface water both Lewis and Brpnsted types of adsorbed pyridine are seen, as marked in the figure. Thus the features at 1450 and 1620 cm are attributed to pyridine bound to Lewis acid sites, while those at 1540... [Pg.718]

Studies to determine the nature of intermediate species have been made on a variety of transition metals, and especially on Pt, with emphasis on the Pt(lll) surface. Techniques such as TPD (temperature-programmed desorption), SIMS, NEXAFS (see Table VIII-1) and RAIRS (reflection absorption infrared spectroscopy) have been used, as well as all kinds of isotopic labeling (see Refs. 286 and 289). On Pt(III) the surface is covered with C2H3, ethylidyne, tightly bound to a three-fold hollow site, see Fig. XVIII-25, and Ref. 290. A current mechanism is that of the figure, in which ethylidyne acts as a kind of surface catalyst, allowing surface H atoms to add to a second, perhaps physically adsorbed layer of ethylene this is, in effect, a kind of Eley-Rideal mechanism. [Pg.733]

Consequently, m order for a vibrational mode to be observed in infrared-visible SFG, the molecule in its adsorbed state has to be both IR [(dp/dg,) 0] and Raman [ AaJAQ ) 0] active. [Pg.1294]

Yaroslavskii N G and Terenin A N 1949 Infrared absorption spectra of adsorbed molecules Dokl. Akad. Nauk 66 885-8... [Pg.1795]

Little L H 1966 Infrared Spectra of Adsorbed Species (New York Academic)... [Pg.1795]

Greenler R G 1966 Infrared study of adsorbed moleoules on metal surfaoes by refleotion teohniques J. Chem. P/rys. 44 310-15... [Pg.1796]

Floffmann F M 1983 Infrared refleotion-absorption speotrosoopy of adsorbed moleoules Surf. Sci. Rep. 3 107-92... [Pg.1796]

Dowrey A E and Maroott C 1982 A double-modulation Fourier transform infrared approaoh to studying adsorbates on metal surfaoes Appl. Spectrosc. 36 414-16... [Pg.1796]

Maiik i J and Trenary M 1989 infrared refieotion-absorption study of the adsorbate-substrate stretoh of CO on Pt (111) Surf. Sol. 214 L237-45... [Pg.1797]

Chabai Y J 1986 High-resoiution infrared speotrosoopy of adsorbates on semioonduotor surfaoes hydrogen on siiioon(IOO) and germanium(IOO) Surf. Sol. 168 594-608... [Pg.1797]

Monolayers of alkanetliiols adsorbed on gold, prepared by immersing tire substrate into solution, have been characterized by a large number of different surface analytical teclmiques. The lateral order in such layers has been investigated using electron [1431, helium [144, 1451 and x-ray [146, 1471 diffraction, as well as witli scanning probe microscopies [122, 1481. Infonnation about tire orientation of tire alkyl chains has been obtained by ellipsometry [149], infrared (IR) spectroscopy [150, 151] and NEXAFS [152]. [Pg.2624]

Allara D L and Nuzzo R G 1985 Spontaneously organized molecular assemblies. 2. Quantitative infrared spectroscopic determination of equilibrium structures of solution-adsorbed normal-alkanoic acids on an oxidized aluminum surface Langmuir 1 52-66... [Pg.2635]

Waldman D A, Kolb B U, McCarthy T J and Hsu S L 1988 Infrared study of adsorbed monolayers of poly(styrene-propylene sulphide) (PS-PPS) block copolymers Polym. Mater. Sc/. Eng. 59 326-33... [Pg.2641]

Beokerle J D, Casassa M P, Cavanagh R R, Heilweil E J and Stephenson J C 1990 Ultrafast infrared response of adsorbates on metal surfaoes vibrational lifetime of CO/Pt(111) Phys. Rev. Lett. 64 2090-3... [Pg.3050]

Whereas ATR spectroscopy is most commonly applied in obtaining infrared absorption spectra of opaque materials, reflection-absorption infrared spectroscopy (RAIRS) is usually used to obtain the absorption spectrum of a thin layer of material adsorbed on an opaque metal surface. An example would be carbon monoxide adsorbed on copper. The metal surface may be either in the form of a film or, of greaf imporfance in fhe sfudy of cafalysfs, one of fhe parficular crysfal faces of fhe mefal. [Pg.64]


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See also in sourсe #XX -- [ Pg.114 ]




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