Infrared spectroscopy silicates

The setting reaction of dental silicate cement was not understood until 1970. An early opinion, that of Steenbock (quoted by Voelker, 1916a,b), was that setting was due to the formation of calcium and aluminium phosphates. Later, Ray (1934) attributed setting to the gelation of silicic acid, and this became the received opinion (Skinner Phillips, 1960). Wilson Batchelor (1968) disagreed and concluded from a study of the acid solubility that the dental silicate cement matrix could not be composed of silica gel but instead could be a silico-phosphate gel. However, infrared spectroscopy failed to detect the presence of P-O-Si and P-O-P bonds (Wilson Mesley, 1968). 

Koretsky, E. M., Sverjensky, D. A., and Sahai, N. (1998). A model of surface site types on oxide and silicate minerals based on crystal chemistry— implications for site types and densities, multisite adsorption, surface infrared-spectroscopy, and dissolution kinetics. Amer. J. Sci. 298, 349-438. 

McNicol et al. (49) used luminescence and Raman spectroscopy to study structural and chemical aspects of gel growth of A and faujasite-type crystals. Their results are consistent with a solid-phase transformation of the solid amorphous network into zeolite crystals. Beard (50) used infrared spectroscopy to determine the size and structure of silicate species in solution in relationship to zeolite crystallization. 

Although the use of water as a solvent is usually avoided in infrared spectroscopy, it can be used to obtain spectra of the dissolved substance in the ranges 930-1580 and 1750-2930 cm-1. The silicate solutions were run as... 

Poly(vinyl acetate). The dielectric and mechanical spectra of hybrids produced by mixing a poly (vinyl acetate)—THF solution with TEOS, followed by the addition of HC1 have been investigated (45). Mixtures were made which were believed to be 0, 5, 10,15, and 20 wt °/o Si02, respectively. These composites were transparent and Fourier transform infrared spectroscopy (ftir) revealed hydrogen bonding between the silicate network and carbonyl units of the poly(vinyl acetate) (PVAc). No shift in the T of the composites from that of the pure PVAc was observed. Similady, the activation... 

Total soil carbon was determinated by elemental analysis with an automatic analyzer (CHNS 932, Lego). FOURIER transform infrared spectroscopy (IFS 66, Bruker) was used for analysis of the main soil components clay, feldspar, silicate, carbonate, and sulfate. This method is based on the application of a multi-step iterative spectra exhaustion method in which the soil spectrum is decremented by a small fraction of the spectrum of the most probable component [HOBERT et al., 1993]. 

Infrared spectroscopy is used to detect most organic material and some inorganic materials such as iron, silicates, carbonates, and sulfates. The technique uses the absorbance of the infrared light frequencies to detect the nature of chemical bonds present. 

With improved possibilities for infrared spectroscopy, broad extinction bands around 9.7 pm and 18 pm have been detected, which were ascribed to the stretching (Woolf Ney 1969) and bending (Treffers Cohen 1974) modes in the SiC>4 tetrahedron forming the building block of silicates, because they correspond to known absorption bands seen in all terrestrial silicates. These bands are also seen in the emission from dust shells around O-rich stars. This gave the first observational hints on the mineralogy of the silicate dust. The smooth, structureless nature of the bands indicated that the silicates in the ISM and in circumstellar dust shells are amorphous. 

From infrared spectroscopy it is very difficult to obtain the composition of the amorphous silicates. This is because the spectral signature observed is a combination of grain composition, shape, size, and structure, making it difficult to isolate the pure amorphous silicate signal. This, in combination with the relatively small spectral changes caused by the composition of the silicates, makes it hard to get a definitive answer in most cases. In the case of interstellar dust we have a unique opportunity the grains are very small and (almost) all silicates are amorphous. 

Both the anhydrous, porous IDPs and Tempel 1 appear to have a higher crystalline to amorphous silicate ratio than is inferred from infrared spectroscopy of interstellar or most circumstellar grains. This could simply be a result of grain alteration in interstellar space, with radiation processing converting crystalline silicates to amorphous silicates. 

Both the analysis of Comet Wild 2 dust particles (Brownlee et al. 2006) and infrared spectroscopy of dust particles from comets Halley, Hale-Bopp, and Tempel 1 (Lisse et al. 2006) have shown that crystalline silicates are common constituents of comets. The presence of crystalline silicates in comets indicates that the crystallization of amorphous interstellar silicates occurred in the comet-forming region... 

Surface analytical techniques. A variety of spectroscopic methods have been used to characterize the nature of adsorbed species at the solid-water interface in natural and experimental systems (Brown et al, 1999). Surface spectroscopy techniques such as extended X-ray absorption fine structure spectroscopy (EXAFS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) have been used to characterize complexes of fission products, thorium, uranium, plutonium, and uranium sorbed onto silicates, goethite, clays, and microbes (Chisholm-Brause et al, 1992, 1994 Dent et al, 1992 Combes et al, 1992 Bargar et al, 2000 Brown and Sturchio, 2002). A recent overview of the theory and applications of synchrotron radiation to the analysis of the surfaces of soils, amorphous materials, rocks, and organic matter in low-temperature geochemistry and environmental science can be found in Fenter et al (2002). 

Infrared spectroscopy can also be used incisively to identify the six main varieties of asbestos fibers. Specific absorption bands in the infrared spectrum can be associated with the asbestos fibers, first in the 3600 3700 cm-1 range (specific hydroxyl bands) and, second, in the ranges 600—800 and 900 1200 cm-1 (specific absorption bands for various silicate minerals (10)). 

Zeolites containing phosphorus in the tetrahedral site in the framework have been synthesized. Phosphorus incorporation in a variety of structural types of zeolite frameworks has been achieved analcime, phillipsite, chabazite, Type A zeolite, Type L zeolite, and Type B ( ) zeolite. The syntheses and properties of some of the new aluminosilicophos-phate zeolites are described. The synthesis technique involves gel crystallization where incorporation of phosphorus is accomplished by controlled copolymerization and coprecipitation of all the framework component oxides, aluminate, silicate, and phosphate, into a relatively homogeneous gel phase. Subsequent crystallization of the gel is carried out at temperatures in the region of 80° to 210°C. Proof and mechanism of framework substitution of phosphorus is based on electron microprobe analysis, infrared spectroscopy, and other characterization. 

The object of this study was to apply mid-infrared spectroscopy to zeolite structural problems with the ultimate hope of using infrared, a relatively rapid and readily available analytical method, as a tool to characterize the framework structure and perhaps to detect the presence of the polyhedral building units present in zeolite frameworks. The mid-infrared region of the spectrum was used (1300 to 200 cm"1) since that region contains the fundamental vibrations of the framework (Si,Al) 04 tetrahedra and should reflect the framework structure. Infrared data in similar spectral regions have been published for many mineral zeolites (30) and a few synthetic zeolites (23, 49, 50). There is an extensive literature on infrared spectra of silica, silicates, and aluminosilicates (17). However, no systematic study of the infrared characteristics of zeolite frameworks as related to their crystal structure has appeared. 

It is likely that further applicationsi of sophisticated instrumentation to analysis of silicates will appear in future literature. In addition to ESCA, SIPS, X-ray spectroscopy, laser Raman and dispersive infrared spectroscopy, newer techniques such as Fourier transform infrared and photoacoustic spectroscopy may be used as tools to characterize silicate structure. 

Chemical modifications by derivitizing the surfaces of mineral fiber silicates have revealed alterations in reactivity in in vitro cell toxicity studies, suggesting a multifactorial character of particle/cell interactions [171]. In addition, the adsorption of bovine serum albumin onto asbestos fibers has been shown by infrared spectroscopy and NMR to be mediated by O—H—N hydrogen bonds [172]. In view of the various hypotheses put forward in the bulk biochemical studies and the apparent surface-oriented origins of these reactions, it is important to examine the features of the silicate/cell interfaces and surfaces. Herein we present a typical case of the interaction between a related alumino-silicate (i.e., cummingtonite) and bioorganic cell interaction. 

Williams et al. (1966u) have identified various phospholipids isolated from human red cells. Thin-layer chromatography and infrared spectroscopy were used to identify and confirm the phospholipids in each fraction eluted from silicic acid columns. The identification and establishment of the purity of the isolated phospholipids by these methods had been described earlier by Kuchmak and Dugan (1963) and Williams et al. (1966b). 

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