Fibers microspectroscopy

Martoglio et al. (75, 16) and Jakes et al. (77) used microspectroscopy to find evidence of dyes, but the results were inconclusive due to the small sample size, and the lack of a comparative dye plant collection and associated spectra. Sibley and Jakes (18) researched the colored textiles of Etowah burial 57. Since it contained no iron, the iron-containing minerals that are thought of as ochre1 could not have been the source of the colorant. Furthermore, the researchers found organic bands in infrared spectra of these fibers that revealed not only the proteinaceous nature of the mineralized fibers, but also other bands that were attributed to dye. 

Microspectroscopy applies the identification power of infrared spectroscopy to the microscopic realm. Contaminants on printed circuit boards, blemishes in coatings, and other production defects can be isolated in situ and analyzed (see Electronics, coatings). Analysis of flaws that develop during use illuminates the method of failure. Microscopic samples, such as particulates filtered from air, can be analyzed individually. The forensic applications are many paint chips, single fibers, explosive residues, and inks on currency can all be identified nondestmctively (see Forensic chemistry). The structures of layered materials, such as laminated polymer films, are studied via microspectroscopy by cross-sectioning the materials and examining the individual layers edge on (47). 

Knshnan K (1988) Characterization of semiconductor silicon using the FT-TR microsampling techniques In Messerschmidt RG, Harthcock MA (eds) Infrared microspectroscopy theory and applications Marcel Dekker, New York, 139-151 Kuo MI, McClelland JF, Luo S, Chien PL, Walker RD, Hse CY (1988) Applications of infrared photoacoustic spectroscopy for wood samples Wood Fiber Sci 20 132-145 Lai Y-Z, Sarkanen KV (1975) Structrual variation in dehydrogenation polymers of comferyl alcohol Cellul Chem Technol 9 239-245... 

The applications that have been presented above are among the most innovative for SERS microspectroscopy, but others are stiU developing in very different fields, such as cultural heritage preservation and restoration. To this purpose, the SERS study is very important to identify organic dyes in fibers, paintings, and artistic enamels [49]. 

Fiber stress determination is of major importance for the modeling of composites and it is now weU established that Raman microspectroscopy, with its main advantage being its nondestructive nature, makes it possible in composites. First, Galiotis and Young demonstrated that Raman spectroscopy is an excellent method to follow the deformation of aramid and carbon fibers. This is a result of variation in the (stretching) vibrational wave number, as a consequence of the anharmonicity of the interatomic bonds. The relationship linking Raman wave number shifts (Av) to the tensile strain (Ae) is hnear, Av = TAe. 

Figure 9.26 and Figure 9.27 illustrate an example of using the FTIR microscope to identify a micro-sized particle. A contaminant particle is isolated, as shown in the micrograph (Figure 9.26). The twisted fiber is cotton. The particle attached to the fiber was examined with reflectance FTIR microspectroscopy. Figure 9.27 shows the IR spectrum of the particle and...

Figure 9.26 Micrograph of isolated particulate contamination (AM) and cotton fiber (C). (Reproduced with permission from H.J. Jumecki, Practical Guide to Infrared Microspectroscopy, Marcel Dekker, New York. 1995 Taylor Francis Group Ltd.)...

FTIR microspectroscopy (or FTIR microscopy or /r-FTIR) has been a conventional method for materials characterization since 1984, when Analect Instruments (now KVB) introduced a transmission microscope interfaced to its AQS FTIR [181]. Since then, FTIR microspectroscopy has developed into a greatly advanced tool for the analysis of thin films on a wide variety of snbstrates (including a single particle, cell, bacterium, or fiber) for scientific, industrial, and forensic applications [182-I9I]. Examples include oxide layers on technical Si wafers [192], organic films on Si (001) [193], organic [194-196]... 

The first question can almost always be answered by PLM, and often more specifically by FT-IR microspectroscopy, regardless of how httle fiber is available. The other four may often be more difficult. 

It was possible to trace the manufacturer of the fibers by an examination of their cross sections, which were made with difficulty, because of their brittle nature. Infrared microspectroscopy revealed that the fibers were photo-oxidized on the basis of a significant carbonyl absorption band of 1730 cm The fibers were... 

In principle, Raman spectroscopy is a microtechnique [161) since, for a given light flux of a laser source, the flux of Raman radiation is inversely proportional to the diameter of the laser-beam focus at the sample, i.e., an optimized Raman sample is a microsample. However, Raman microspectroscopy able to obtain spatially resolved vibrational spectra to ca. 1 pm spatial resolution and using a conventional optical microscope system has only recently been more widely appreciated. For Raman microspectroscopy both conventional [162] and FT-Raman spectrometers [ 163], [ 164] are employed, the latter being coupled by near-infrared fiber optics to the microscope. 

Applications of Raman microspectroscopy include the analysis of a wide variety of organic and inorganic materials, e.g., semiconductors, polymers, single fibers, molecular crystals, and minerals [165] - [168]. 

Figure 14.33 a) ATR spectra of single nylon carpet fiber untreated (top), treated (middle), and the result of spectral subtraction (bottom), b) Bicomponent fiber transmission spectrum (top), ATR spectrum of Nylon 6 sheath (middle), and difference spectrum of PET core (bottom).Reproduced with permission from Cho, L, et a ., "Single Fiber Analysis by Internal Reflection Infrared Microspectroscopy," iourna of Forensic Sciences 46 (2001), 1309-1314. Copyright 2001, ASTM International. 

Cho, L., et al. "Single Fiber Analysis by Internal Reflection Infrared Microspectroscopy." Journal cf Forensic Sciences 46 (2001), 1309-1314. 

PL Lang, JE Katon, JF O Keefe, DW Schiering. The Identification of fibers by infrared and Raman microspectroscopy. Microchem J 34 319-331, 1986. 

SP Bouffard, AJ Sommer, JE Katon, S Godber. Use of molecular microspectroscopy to characterize pigment-loaded polypropylene single fibers. Appl Spectrosc 48 1387-1393, 1994. 

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