Raman spectroscopy chemical structure analysis

In addition, any rational approach to peptide hormone and neurotransmitter design must ultimately depend on the application of physical-chemical principles of conformation and structure, the use of various spectroscopic methods (especially nuclear magnetic resonance, circular dlchrolsm, and Raman spectroscopies. X-ray analysis where possible, etc.), and an understanding of the nature of a hormone-receptor Interaction In physical-chemical terms. Here again the use of conformatlonally restricted peptide structures Is critical (, 2. Recently we have... 

Micro and chemical structural analysis, including porosity, bonding, coking X-ray diffraction (XRD) Nuclear magnetic resonance (NMR) Fourier-transform infrared (FTIR) Scanning electron microscopy (SEM) Transmission electron microscopy (TEM) Atomic force microscopy (AFM) Raman spectroscopy Small probe molecule volumetric and gravimetric adsorption... 

Unique applications employ both types of spectroscopies for structural analysis. The complementary nature of infrared and Raman effects can be seen in the structure determination of 1 1 hexafluoroisobutylene and vinylidene fluoride copolymer. This problem is virtually impossible to solve with other techniques. The two monomers can be linked in two ways during polymerization, by formation of head-to-tail (normal linking) or head-to-head linkages. By comparing infrared and Raman spectroscopic data, it was concluded that the polymers formed are indeed alternating in nature (66). It was additionally concluded that only head-to-tail linkages were observed. The proposed chemical structure is shown below. 

When my interest returned and we began researching the analytical applications of CD in the 70 s, I felt I had a head start. But there was so much that was new. A great deal had happened to CD over the years as it matured and expanded to include the far-UV the study of optical activity in excited state emissions, and in vibrational and Raman spectroscopy and the evolution of new empirical models applicable to the interpretation of the structural properties of macromolecules. Most important of all, perhaps, was the arrival of high tech electronics and materials which had brought CD instrumentation out of the dark ages. And now, ironically, almost 35 years after my introduction to CD, my special interest is the exploitation of chiral transition metal complexes as chirality induction reagents in chemical analysis. 

Fourier-Transform Infrared (FTIR) spectroscopy as well as Raman spectroscopy are well established as methods for structural analysis of compounds in solution or when adsorbed to surfaces or in any other state. Analysis of the spectra provides information of qualitative as well as of quantitative nature. Very recent developments, FTIR imaging spectroscopy as well as Raman mapping spectroscopy, provide important information leading to the development of novel materials. If applied under optical near-field conditions, these new technologies combine lateral resolution down to the size of nanoparticles with the high chemical selectivity of a FTIR or Raman spectrum. These techniques now help us obtain information on molecular order and molecular orientation and conformation [1],... 

IR, Raman, NMR, ESR, UPS, XPS, AES, EELS, SIMS) [1]. However, some industrial carbon materials such as amorphous carbon films and carbon black cannot be easily characterized from the local-structure point of view by these methods, because these materials usually take amorphous and complex structures. Recently, soft X-ray emission and absorption spectroscopy using highly brilliant synchrotron radiation [2] has been utilized to characterize various carbon materials, because information on both the occupied and unoccupied orbitals, which directly reflect the local structure and chemical states, can be provided from the high-resolution soft X-ray measurements. We have applied the soft X-ray spectroscopy to elucidate the local structure and chemical states of various carbon materials [3]. Additionally, we have successfully used the discrete variational (DV)-Xa method [4] for the soft X-ray spectroscopic analysis of the carbon materials, because the DV-Xa method can easily treat complex carbon cluster models, which should be considered for the structural analysis of amorphous carbon materials. 

Multinuclear NMR- ( C, Pt, T1), 1R-, Raman-spectroscopy. Electron Spectroscopy for Chemical Analysis (ESCA), X-ray, and Extended X-ray Absorption Fine Structure (EXAFS) studies confirm direct, short (2.60-2.64 A) Pt-Tl bonds. Figure 1. shows a typical ° T1 NMR spectrum of [(N C)5Pt-Tl( CN)] together with the structure determined by EXAFS. The spin-spin coupling pattern is consistent with 4 -h 1 - -1 equivalentligands (I = 1/2), respectively and one Pt nucleus (natural abundance 33.8%, 1=1 /2). The spectrum has been selected to illustrate the usefulness of T1 NMR spectroscopy in studies of the inorganic chemistry of thallium. The compounds are diamagnetic, and... 

In the study of minerals and other geological materials, Raman spectroscopy has been applied for chemical analysis and in studies of molecular and crystal structure, and of elastic and thermodynamic properties. A particularly important field for the application of Raman spectroscopy in chemical analysis is in the study of fluid inclusions in minerals, where the Raman microprobe has been developed to enable nondestructive in... 

The observation and understanding of SERS are clearly very important developments in the study of surface chemistry and surface physics. The combination of molecular information and extraordinary sensitivity provides a valuable probe of surface structure and behavior. Out of the broad study of SERS by both chemists and physicists have emerged several approaches to using SERS for chemical analysis. A common analytical situation involves preparation of a SERS active substrate by one of several methods, then exposure of the substrate to a liquid or gaseous sample. Subsequent Raman spectroscopy of the adsorbed layer provides the analytical signal, enhanced by whatever chemical or field enhancement is provided by the adsorbate-substrate interaction. The current and next section are not intended to address SERS substrates comprehensively, but several of analytical interest are described. 

The large signal enhancements often encountered with SERS have stimulated many investigations of analytical applications, examples of which are listed in Table 13.6. Many of these involve biological or environmental analysis, where low concentrations of analytes preclude the use of unenhanced or even resonance-enhanced Raman spectroscopy witout the added benefit of surface enhancement. Despite the great promise of a technique that increases Raman intensity by 10 or more, SERS has not yet resulted in widely used or routine analysis of real samples. SERS has been a very important and valuable probe of surface structure and has stimulated new discoveries about the behavior of metal-gas and metal-liquid interfaces, but its incursion into practical chemical analysis has been limited. It is worth considering why SERS has encountered formidable barriers to widespread analytical utility (2). 

In the study of the structure, i.e. the ionic composition of the investigated molten electrolyte, the physico-chemical analysis, based on the results of measurements of phase equilibrium, density, surface tension, viscosity, and electric conductivity of melts, combined with X-ray phase analysis and IR, respectively, Raman spectroscopy of quenched melts, is used. In the last two measurements, it may be assumed that the high temperature composition is at least qualitatively conserved after quenching. In the investigation of the structure of the electrolytes, the so-called chemical approach is used. 

There are few methods suitable for on-line chemical analysis of aerosol particles. Raman spectroscopy offers the possibility of identifying the chemical species in aerosol particles because the spectrum is specific to the molecular. structure of the material, especially to the vibrational and rotational modes of the molecules. Raman spectra have been obtained for individual micron-sized particles placed on surfaces, levitated optically or by an eiectrodynamic balance, or by monodisperse aerosols suspended in a flowing gas. A few measurements have also been made for chemically mixed and poly disperse aerosols. The Raman spectrum of a spherical particle differs from that of the bulk material because of morphology-dependent resonances that re.su It when the Raman scattered photons undergo Mie scattering in the particle. Methods have been developed for calculating the modified spectra (McNulty el al., 1980). 

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