Confocal micro-Raman spectroscopy

Recent progress in confocal micro Raman spectroscopy has made it possible to investigate chromosomes and whole single living cells (Puppels et al., 1990, 1991). A spatial resolution of less than 1 )im was obtained. Different Raman spectra have been recorded of the cytoplasm and the cell nucleus. The spectrum of the nucleus consists of lines attributed to DNA and protein vibrations, strongly ressembling the spectra of isolated chromatin. The search for left-handed Z form DNA in metaphase chromosomes is in progress. 

The stress distribution in HOD films was studied in Ref. [353] by polarized confocal micro-Raman spectroscopy using a 514.5-nm Ar ion laser. The process conditions for the HOD films are listed in Table H.4, and the SEM image is shown in Figure 11.44. This paper is so comprehensive, and includes a number of relevant references so that the readers are recommended to read it to know the details of the experimental and analysis techniques. The results obtained are listed below ... 

Composition profiles generated by interdiffusion in the concentrated regime between polyphenylene oxide-polystyrene blend pairs were experimentally determined by two techniques. Three-point bending moment measurements over a convenient temperature range (dynamic mechanical analysis (DMA)) were used to determine interphase composition profiles. Confocal micro-Raman spectroscopy was also used to measure local compositions along a direction which was perpendicular to the original interface. The study included some limiting cases to test accuracy, precision and flexibility of the DMA method. 4 refs. 

Santini A, Miletic V (2008) Comparison of the hybrid layer formed by Silorane adhesive, one-step self-etch and etch and rinse systems using confocal micro-Raman spectroscopy and SEM. J Dent 36 683-691... 

Vibrational spectroscopic methods have higher sensitivity toward water molecules especially at a low vapor pressure. Confocal micro-Raman spectroscopy is a noninva-sive, nondestructive technique with a high spatial resolution of micrometers, higher than that of the NMR techniques. With Raman spectroscopy, the chemical composition of membranes can be obtained, which is a major advantage over scattering techniques. Micro-Raman spectroscopy hence can be a powerful tool for the direct, simultaneous measurement of the chemical compositions in PEMs and the water content. ... 

The Raman techniques combined with AEM microscopic imaging, as for instance TERS (tip-enhanced Raman scattering) spectroscopy [27], allow to analyze surface nanostructures beyond the diffraction limit, but the cost of the instrumental apparatus is not affordable for any research laboratory. Therefore, in this chapter, the results obtained with those techniques will not be presented, though they increased Raman enhancement factors by up to lO, with the possibility of single-molecule detection. Conversely, confocal micro-Raman apparatus is affordable to every research group allowing SERS investigations with more comparable results. 

A clever way to minimize the unwanted background from the cover plate or the environment is combining laser tweezers and confocal Raman spectroscopy (LTRS) [73, 74], While the single cells are levitated well off the surface and held in the focus of the laser beam the Raman spectral patterns of these cells are recorded with high sensitivity. Another appealing fact is the usage of one laser for both Raman excitation and optical trapping to keep the instrumental efforts as low as possible. Additionally the trapped cells can also be micro-manipulated and moved from one place to another, e.g., from the native matrix to a clean collection chamber. 

No.9, 1997,p.2067-75 STUDY OF THE CONFORMATIONS OF POLY(EPSILON-CAPROLACTAM) AND POLY(EPSILON-CAPROLACTAM)-POLYBUTADIENE BLOCK COPOLYMERS BY FTIR SPECTROSCOPY WITH PHOTOACOUSTIC DETECTION AND BY MICRO-RAMAN CONFOCAL SPECTROSCOPY Schmidt P Fernandez M R Pastor J M Roda J Czech Republic,Academy of Sciences ... 

FTIR spectroscopy with photoacoustic detection and micro-Raman confocal spectroscopy were used to study the conformations of poIy(epsilon caprolactam) and poly(epsilon-caprolactam)-polybutadiene block copolymers. In the block copolymers prepared by anionic polymerisation, the fraction of the planar conformation of poly(epsilon-caprolactam) chains decreased with increasing polybutadiene content. In the surface layers formed by rapid saw cutting and in the islands formed by microtome cutting, the content of the planar conformation was lowered. This was substantially increased by water treatment, especially at elevated temperatures. 15 refs. 

The laser radiation can be focused to a diameter of the order of a few multiples of its wavelength. Therefore, even by using the normal entrance optics of the spectrometer one can investigate Raman spectra of micro samples. However, in order to be able to exactly adjust the area from which the Raman spectrum is taken, common microscopes, able to adjust the sample by observation with visible light are modified for the excitation and observation of Raman spectra. Such microscopes may even allow confocal observation with 3-dimensional spatial resolution. It must be remembered that the optical conductance of microscopes is quite small, therefore much longer observation times are needed for Raman spectroscopy of micro samples. This cannot be compensated by a... 

The interaction between zinc oxide and stearic acid in a medium suitable to simulate a vulcanized system has been investigated [65] experimentally using vibrational spectroscopic technique. Confocal Raman micro spectroscopy revealed that at ambient temperature both components are phase-separated in the form of microcrystals. When the reaction temperature (SO C and above) is reached only zinc oxide is present in the form of particles while the stearic acid melts and gets molecularly dispersed within the rahher matrix. The analysis points to a core-shell structure of the reacting system stearic acid diffuses to the surface of zinc oxide domains causing the shrinkage of the zinc oxide core and the formation of a shell of increasing thickness made of zinc stearate. 

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