Raman microspectroscopy

In principle, Raman microspectroscopy is attractive because the practical diffraction limit is on the order of the excitation wavelength, which is about 10-fold smaller for Raman spectroscopy with a visible laser than for mid-IR spectroscopy. It is therefore possible to focus visible laser light to much smaller spot sizes (400 nm in air and 240 nm with an oil immersion objective) than may be examined by mid-IR radiation. For various instrument-based reasons [4], charge-coupled device (CCD) Raman spectrometers have in practice proved to be far more successful for Raman microspectroscopy than ET-Raman spectrometers, and most instruments are based on this former concept. One further important instrumental advantage of the microscopes used for Raman microspectroscopy is their confocal design [5]. As the out-of-focus rays from an illuminated volume 

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Raman Microspectroscopy. Raman spectra of small soflds or small regions of soflds can be obtained at a spatial resolution of about 1 p.m usiag a Raman microprobe. A widespread appHcation is ia the characterization of materials. For example, the Raman microprobe is used to measure lattice strain ia semiconductors (30) and polymers (31,32), and to identify graphitic regions ia diamond films (33). The microprobe has long been employed to identify fluid iaclusions ia minerals (34), and is iacreasiagly popular for identification of iaclusions ia glass (qv) (35). 

Shimada, R., Kano, H. and Hamaguchi, H. (2006) Hyper-Raman microspectroscopy a new approach to completing vibrational spectral and imaging information under a microscope. Opt. Lett., 31, 320-322. 

Raman Microspectroscopy Study of Oscillatory Electrodeposition of Au at an Air/Liquid Interface... 

Figure 10 Polarized spectra obtained by Raman microspectroscopy of (A) the dragline silk of the spider Nephila edulis and (B) the cocoon silk of the silkworm Sarnia cynthia ricini. Adapted with permission from Rousseau et al. [63]. Copyright 2004 American Chemical Society.

Figures 21(a) and 21(b) show the SEM micrographs of the freeze-fractured cross-section of the film used in the construction of the bag. There are two distinct layers and possibly a third very much thinner tie layer. The outside layer is a layer of nominal thickness 13 pm. The inside layer is much thicker and is approximately 70 pm thick. At the interface between the outer and inner layers the apparent very thin tie layer is about 1 pm thick. This is too thin to be identified by FUR microscopy on a cross-section of the sample, since the technique is diffraction-limited, which means that layers of about 10 pm thickness or greater can only be readily identified [1]. The tie layer thickness is also probably too thin for fingerprinting by Raman microspectroscopy on a cross-section the lateral spatial resolution of Raman microspectroscopy is about 1-2 pm.

Hawi S.R., Rochanakij S., Adar F., Campbell W.B., Nithipatikom K., Detection of membrane-bound enzymes in cells using immunoassay and Raman microspectroscopy, Anal. Biochem. 1998 259 212-217. 

Rossle, M., Panine, P., Urban, V. S., and Riekel, C. (2004). Structural evolution of regenerated silk fibroin under shear Combined wide- and small-angle x-ray scattering experiments using synchrotron radiation. Biopolymers 74, 316-327. Rousseau, M. E., Lefevre, T., Beaulieu, L., Asakura, T., and Pezolet, M. (2004). Study of protein conformation and orientation in silkworm and spider silk fibres using Raman microspectroscopy. Biomacromolecules 5, 2247-2257. 

Similar work was performed by Maquelin et al.6 in 2000. They used con-focal Raman microspectroscopy to obtain spectra directly from microbial microcolonies on solid culture medium. The spectra were obtained after 6 h of culmring and were of most commonly encountered organisms. While depth studies showed varying quantitative levels of success, the qualitative (identification) of various bacterial strains was deemed a success. 

Wright of Advanced Micro Devices discusses the use of Raman microspectroscopy to measure the integrity of a film on semiconductor wafers during manufacture in US patent 6,509,201 and combined the results with other data for feed-forward process control [181]. Yield is improved by providing a tailored repair for each part. Hitachi has filed a Japanese patent application disclosing the use of Raman spectroscopy to determine the strain in silicon semiconductor substrates to aid manufacturing [182]. Raman spectroscopy has a well established place in the semiconductor industry for this and other applications [183]. 

Hilfiker et al. at Solvias used carbamazepine (CBZ) as a model compound to describe the use of Raman microscopy to characterize crystal forms, including during solvent evaporation experiments [228], The spectra were processed into clusters by spectral similarity. The authors note that all published and several new crystal forms were identified during the study. Solvias HTS uses a specific set of crystallization protocols that have tended to produce new polymorphs. Hilfiker notes that Raman microspectroscopy is an ideal analytical tool for high-throughput discrimination between crystal structures. [229], The ability to collect spectra directly and automatically in a microtiter plate with or without solvent and during evaporation is a major advantage over many other techniques. 

Raman microspectroscopy is readily performed on multiple locations inside each well. As in other instances, the results might not be representative of the whole sample because of the small sample volume probed. Polarization effects can be pronounced, but may be mitigated by averaging the results from additional locations. An alternative is rotating the sample, but this usually is not practical for multiwell plates. Both options increase analysis time. Such problems appear to be minimized when handling bulk powders [222,223,230], Several vendors sell systems preconfigured for automated analysis of microtiter plates and are typically integrated with optical microscopy. 

P. Heraud, J. BeardaU, D. McNaughton and B.R. Wood, In vivo prediction of the nutrient status of individual microalgal cells using Raman microspectroscopy, FEMS Microbiol. Lett, 275, 24—30 (2007). 

K. Y Noonan, M. Beshire, J. Darnell and K.A. Frederick, Qualitative and quantitative analysis of illicit drug mixtures on paper currency using Raman microspectroscopy, Appl Spectrosc., 59, 1493-1497 (2005). 

Abstract world class unconformity-related U deposits occur in the Proterozoic McArthur Basin (Northern Territory, Australia) and Athabasca Basin (Saskatchewan, Canada). Widespread pre-to post-ore silicifications in the vicinity of the deposits, allow proper observation of paragenetically well-characterized fluid inclusions. We used a combination of microthermometry, Raman microspectroscopy and Laser Induced Breakdown Spectroscopy (LIBS), to establish the physical-chemical characteristics of the main fluids having circulated at the time of U mineralization. The deduced salinities, cation ratios (Na/Ca, Na/Mg) and P-T conditions, led to the detailed characterization of a NaCI-rich brine, a CaCl2-rich brine and a low-salinity fluid, and to the identification of mixing processes that appear to be key factors for U mineralization. 

De Endredy, A.S. (1963) Estimation of free iron oxides in soils and clays by a photolytic method. Clay Min. Bull. 5 209-217 de Faria, D.L.A. Venancio Silva, S. de Oliveira, M.T. (1997) Raman Microspectroscopy of some iron oxides and oxyhydroxides. J. Raman Spectrosc. 28 873-878 De Grave, E. Vandenberghe, R.E. (1986) 57Fe Mossbauer effect study of well-crystallized goethite (a-FeOOH) Hyp. Interact. 28 643-646... 

G. Penel, G. Leroy, C. Rey, B. Sombret, J.P. Huvenne, E. Bres, Infrared and Raman microspectroscopy study of fluor-hydroxy- and hydroxy-apatite powders, J. Mater. Sci. Mater. Med. 8 (1997) 271-276. 

Notingher, L, and Hench, L. L. 2006. Raman microspectroscopy A noninvasive tool for studies of individual living cells in vitro. Exp. Rev. Med. Dev. 3 215-34. 

Petrov, G. L, Arora, R., Yakovlev, V. V., Wang, X., Sokolov, A. V., and Scully, M. O. 2007. Comparison of coherent and spontaneous Raman microspectroscopies for noninvasive detection of single bacterial endospores. Proc. Natl. Acad. Sci. USA 104 7776-79. 

Swain, R. J., and Stevens, M. M. 2007. Raman microspectroscopy for non-invasive biochemical analysis of single cells. Biochem. Soc. Pros. 35 544-49. 

Written by an international panel of experts, this volume begins with a comparison of nonlinear optical spectroscopy and x-ray crystallography. The text examines the use of multiphoton fluorescence to study chemical phenomena in the skin, the use of nonlinear optics to enhance traditional optical spectroscopy, and the multimodal approach, which incorporates several spectroscopic techniques in one instrument. Later chapters explore Raman microscopy, third-harmonic generation microscopy, and nonlinear Raman microspectroscopy. The text explores the promise of beam shaping and the use of a broadband laser pulse generated through continuum generation and an optical pulse shaper. 

Similar approaches were adopted by Ganikhanov (Chapter 5), who developed a state-of-the-art laser system, benefiting simultaneous third-harmonic and nonlinear Raman microscopy, and Yakovlev et al. (Chapter 6), who applied third-harmonic generation microscopy and nonlinear Raman microspectroscopy for biochemical analysis in microfluidic devices. 

Raman microspectroscopy [3] allows the observation of the transformation of a polyene structure to a carbon one. The formation of conjugate polyene units under the conditions of chemical dehydrochlorination of the polymer was confirmed by the presence of characteristic narrow peaks at 1,107 and 1,490 cm in the Raman spectra. The products obtained by thermal treatment at elevated temperatures are highly disordered sp -carbon materials, in which the porous structure has developed upon subsequent gasification (Fig. 4.3). 

A major advantage of Raman spectroscopy in the chemical characterization of pollen is its applicability in situ. The pollen grains in this study were investigated without prior purification or extraction procedures, which has been the case in most other investigations on pollen composition so far [45, 46, 57, 58]. Using Raman microspectroscopy on sections of snap-frozen samples, the chemical composition and very likely also their ultrastructure remain unaltered, and the co-localization of individual components could be studied in the context of pollen micromorphology, simultaneously in very short... 

Fourier transform infrared microspectroscopy (FTIR) and Raman microspectroscopy provide quantitative information about the chemical microstructure of heterogeneous solid foods (Cremer and Kaletunq, 2003 Piot et al., 2000 Thygesen et al., 2003) without sample destruction. 

Raman microspectroscopy results from coupling of an optical microscope to a Raman spectrometer. The high spatial resolution of the confocal Raman microspectrometry allows the characterization of the structure of food sample at a micrometer scale. The principle of this imaging technique is based on specific vibration bands as markers of Raman technique, which permit the reconstruction of spectral images by surface scanning on an area. 

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