Vibrational Spectra of Reference Material

The vibrational spectra of reference materials, notably the main components of soft tissue, are introduced in figure 3.1. In the IR spectrum (trace A) of the all-beta 

1439 (CH2) and 1735 cm (C=0). Additional Raman bands are assigned to the choline groups of hydrophilic lipid head groups (717 cm ) and to C=C groups in unsaturated fatty acid side chains (1267, 1657cm ). There are numerous bands of the aromatic system of cholesterol with the most intensive IR bands at 1053, 1364, 1376 and 1466cm (trace F) and the most intensive Raman bands at 427, 

1439 and 1672 cm (trace J). More comprehensive band assignments of biomolecules have been published in the Handbook of Vibrational Spectroscopy [32]. Taken together, these spectra demonstrate that they provide a sensitive fingerprint for each molecule, and that IR and Raman spectra complement each other to some extent. 

2852 and 2925 cm had decreased. The IR spectrum (trace C) was acquired from a consecutive tissue section that had been treated for 10 min with a drop of water. 

The overlay of the normahzed spectra indicated that lipid-associated bands near 1070, 1230, 1740, 2852 and 2925 cm had increased. In summary, the relative intensity ratios of Hpid to protein bands decreased in the order (C) (A) (B), consistent with the removal of Hpids by toluene and with the removal of proteins by water. Furthermore, the shapes of the amide bands changed, which was consistent with the secondary structure changes in proteins. 

---

The vibrational spectra of reference material are introduced in Figure 3.1, which belong to the main components of soft tissue. The IR spectrum (trace A) and Raman spectrum (F) of the all-beta protein concanavalin A are shown in Figure 3.1. IR bands due to the peptide backbone with P-sheet secondary structures are found at 3284 (amide A), 1636 (amide I), 1531 (amide II), and 1235 cm-i (amide III). Bands at 1403 (COO ) and 2963, 2874, 1455 cm- (CHg) are assigned to amino acid side chains. These bands are located in the Raman spectrum at similar positions at 1398 and 1449 cm . The Raman amide I band is centered at 1672 cm , the amide III band at 1238 cm , and the weak amide II band is not observed. Instead, other Raman bands of amino acids are identified at 759 and 1555 cm for Trp 621,1003, 1031, and 1208 cm for Phe 643, 829, and 853 cm for Tyr and 1126, 1317, and 1340 cm (CH2/CH3) for aliphatic amino acids. The IR spectrum (B) and Raman spectrum (G) of the all alpha protein bovine serum albumin show a number of differences. The amide bands... 

Because of their potential or real applications in various fields of technology, oligothiophenes (Th ) and polythiophene (PTh) have become the center of great interest in many laboratories ranging from chemical synthesis to device manufacturing [175,176]. The vibrational spectra of Th and PTh and of their innumerable functionalized derivatives have been recorded either for routine chemical characterization or for more detailed structural studies. Reference 42 provides a rather complete review of a few years of vibrational spectroscopy of these materials. 

The vibrational overtones and combinations of hydroxyl groups and thek associated molecular water occurring in the spectra of various gel siUca materials are summarized in Table 2 and discussed in References 3, 5, and 22. These peaks and bands found in the preparation of alkoxide-derived siUca gel monoliths are identical to those described for siUca gel powders (41). 

Figure 7 shows SNIFTIRS spectra for isoquinoline molecules adsorbed on mercury. The reference spectrum in each case was obtained at 0.0V vs. a SCE reference electrode at this potential the molecules are believed to be oriented flat on the metal surface. The vibrational frequencies of the band structure (positive values of absorbance) are easily assigned since they are essentially the same as those reported by Wait et al. (22) for pure isoquinoline. The differences in the spectra are that the bands for the adsorbed species exhibit blue shifting of 3-4 cm" relative to those of the neat material, and the relative intensities of the bands for the adsorbed species are markedly changed. 

M. Del Zoppo, C. Castiglioni, P. Zuliani and G. Zerbi, Molecular and electronic structure and nonlinear optics of polyconjugated materials from their vibrational spectra, in T. Skotheim (ed.), Handbook of Conducting Polymers, 2nd edn, Marcel Dekker, New York, 1998, and references cited therein. 

There are no comprehensive data files for CD spectra for standard reference materials (SRM) that compare with the exhaustive libraries which have been compiled for absorbance data in the electronic and vibrational spectroscopy ranges. Analysts are required to create their own CD spectral files using SRM prepared by the usual purveyors of fine chemicals. A significant problem with an SRM is that although it might meet the industry specifications for chemical purity, its enantiomeric purity is open to question. The few cases in which absolute enantiomeric purity might be assured involve natural products whose syntheses are under total enzymatic control. To prove 100% enantiomeric purity is beyond current capabilities. The problem is compounded even more with the risk that the material might racemize after its extraction from its natural environment. Therefore, it is not possible to assume absolute enantiomeric purity with firm conviction. 

After exposure to methane the IR spectra of manganese oxide showed absorption bands, which are characteristic of the C-H stretching vibrations (CHs 2962, 2872 cm CH2 2926, 2853 cm and CH 2890 cm ) [9]. The intensity of the C-H bands increased, if the exposure time to methane increased (Figs. 2,3). The intensity of the band at 1050 cm, which is assigned to V3(Si-0) of silica was used as an internal reference (Fig. 2). the intensity ratio for the CH2 and CH3 groups estimated for samples after 30 min reaction with methane, was found to be about five [10]. Thus XPS and FTIR surface analysis showed that carbonaceous material formed on the MnOx catalyst surface consists of CHx hydrocarbon deposits and manganese carbide species. 

A simple way to qualitatively interpret vibrational spectra is the fingerprint method of identifying materials. The fingerprint method includes spectrum comparison with a reference, and identification of characteristic bands in spectra. 

Vibrational Raman band intensities and frequencies are also dependent on temperature, applied pressure, and the intrinsic microstructure of the material. These second-order parameters may be extracted from measured spectra. Both X-ray diffraction lines and Raman bands from polycrystalline materials show increased broadening as the microcrystallite grain sizes decrease. In fact, for the hexagonal phase of BN, bandwidths vary linearly with the reciprocal grain size (13). Inherent stress in thin films is manifested in vibrational line shifts. Based on pressure-dependent measurements of vibrational frequencies in bulk solids, inherent stress and stress inhomogeneity can be determined in thin films. Since localized stress can influence the optical and electronic properties of a thin film, it appears to be an important parameter in film characterization studies. Vibrational features also exhibit temperature-dependent frequency shifts. Therefore, an independent measurement of temperature is sometimes necessary to deconvolute these effects. Reference to Figure 1 shows that the molecular temperature of a material may be determined from the Stokes/anti-Stokes... 

There is a series of polymers having a chemical structure — [(CHR) —O— which are derived as polyacetal resins, and are known as polyalkyene oxides or polyalkylene glycols. In the above structure, the polymer with R=H and M = 1 is polyoxymethylene, which is known as Delrin. This material is a high polymer of formaldehyde, which is terminated by an ether or ester function added to stabilize the final product. Other manufactured products include copolymers with ethylene oxide or propylene oxide. The IR and Raman spectra of polyoxymethylene are shown in Reference Spectrum 55. A strong peak at 1098 cm and a doublet at 936 and 900 cm in the IR spectrum are assigned to the C—O—C stretching vibration. It is not possible to determine if the sample is a homopolymer or copolymer from this spectrum. 

Before starting a new EC-SERS study, it is important to first obtain the normal Raman spectrum of the species in its original form, such as the pure hquid or solid. In addition, spectra should be collected for theexpected produces) of the electrode reaction to be studied. The Raman spectra of the molecules/materials in the solution to be measured during the in-situ study should then be recorded. These good-quality spectra will serve as references to compare with the surface Raman spectra. If the spectrum is too complex, an isotopic study will be very helpful for identifying the vibrational modes. Before the EC-SERS study, it is important to define the electrochemical behavior to obtain the characteristic potential for use in the in-situ EC-SERS study. 

In the introductory laboratory, the Raman spectroscopy of diamond and pearl, which is predominantly calcium carbonate, has been used to introduce the concept of the vibrational spectrum as a qualitative identifier [9]. The Raman spectra of the authentic gemstones are compared to the spectra of common costume jewelry substitutes, faux pearl and cubic zirconia, respectively. Synthetic calcium carbonate is used as a reference material for pearl. The pearl, faux pearl, and reference spectra are shown in Fig. 3. 

---