In the last 30 to 40 years, various new types of carbon materials have been engineered for multip... more In the last 30 to 40 years, various new types of carbon materials have been engineered for multiple industrial uses. It is now well-known that the Raman spectrum is sensitive to the structure, even though the spectrum is rather uncomplicated. Because Raman spectroscopy now has a reputation for providing good information, potential users of Raman equipment can request information on the quality of their sample. However, they are often not able to define clearly what they mean by “quality.” If they are growing diamond films, they may or may not want interstitial sp2 carbon to glue polycrystalline diamond together. If they are growing hard diamond-like carbon (DLC) films, they may want to correlate the spectral characteristics with physical characteristics of the film. In this column, I explain how the Raman characteristics can aid in characterization of carbon materials.
In a follow-up to my February 2020 column, I started a more systematic study of extractables and ... more In a follow-up to my February 2020 column, I started a more systematic study of extractables and leachables. Following a suggestion from Mark Witkowski of the FDA, I looked at three sets of centrifuge vials that were exposed to the following liquids in an effort to evaluate the potential of Raman microscopy to identify compounds exiting in polymers under particular conditions: saline, phosphate buffer, water, saline treatment at 100 0C, phosphate buffer treatment at 100 0C, water treatment at 100 0C, ethanol, chloroform, pH 5, and pH 9. Although all containers were made of polypropylene (PP), they didn’t behave similarly. Compounds that were extracted from PP vials from different manufacturers were not always the same. Although the number of spectral types that are recorded is large, this article focuses on a few whose interpretation is interesting. The goal was to figure out when it makes sense to employ Raman microscopy for such identification. The characteristics considered were ...
The microsphere formation mechanism of bis(NR-amido-L-phenylalanine) 1,1-cyclobutanedicarboxylate... more The microsphere formation mechanism of bis(NR-amido-L-phenylalanine) 1,1-cyclobutanedicarboxylate, whose self-assembly was triggered by protonation of its carboxylic groups, was investigated by Raman microscopy. An image of the Raman intensity contour map, Raman imaging, shows that water is excluded from the core during the L-phenylalanine dicarboxylate aggregation. In situ Raman microscopic studies on the size and morphological changes of microspheres indicates that osmotic pressure on the sphere, generated by water exclusion from the sphere's core, controls the final assembled structure and morphology.
Microscopic strain distributions in varying thicknesses of polysilicon layers deposited as bridge... more Microscopic strain distributions in varying thicknesses of polysilicon layers deposited as bridges over silicon substrates were determined by high resolution micro-Raman spectroscopy. In particular, we mapped the dependence of the first order Raman spectrum as a function of the position across polysilicon bridges (approximately 550 × 230 /xm2), over tunnels etched in the silicon substrate. Shifts in Raman band frequencies as a function of position on the bridge structures were observed to be dependent upon the thickness of the membrane layer (between 1 and 3 /xm) as well as the annealing conditions. Assuming a simplified uni-axial stress parallel to the surface, the effective tensile stress at the center of the bridge of thickness 2.5 /xm is reduced by annealing from 2.5 GPa to 0.18 GPa.
In this month’s column, I review the band assignments of a protein spectrum, pointing out why it ... more In this month’s column, I review the band assignments of a protein spectrum, pointing out why it can be useful to know the band assignments when attempting to use the Raman spectra to understand the functionality of proteins. In fact, the American Chemical Society (ACS) has just issued a virtual issue of Journal of Physical Chemistry entitled “Protein Crowding and Stability,” discussing how the protein conformation impacts its biological functionality. I address how the Raman spectra can help with the determination of protein structure.
By now, it is well known that Raman spectroscopy has the potential to be used for a variety of an... more By now, it is well known that Raman spectroscopy has the potential to be used for a variety of analytical applications, and that the hurdles to using the technique 30–40 years ago have been largely overcome. However, a remaining impediment to exploiting the technology is that very few analysts have the ability to know what they are looking at. Even if there is experience in infrared (IR) spectroscopy, which looks at similar molecular vibrations, making the Raman measurements and interpreting the results will be quite different. There are databases and searching programs that can aid the analyst, but using these resources effectively also requires a learning curve. What I am going to try to do in this article is provide some advice for dealing with those situations where the searching program does not provide a definitive result.
... Fran Adar,* ... See ref Ma. define. -8 -9 -10 -I1 -12 Flgure 4. MO energy levels by IEH metho... more ... Fran Adar,* ... See ref Ma. define. -8 -9 -10 -I1 -12 Flgure 4. MO energy levels by IEH method for model compounds re-sembling: (a) ferrocytochrome b5; (b) oxyhemoglobin; (c) ferricyto-chrome b5; (d) deoxyhemoglobin; (e) methemoglobin. ...
Raman microspectroscopy was used to characterize normal and malignant hepatocytes in both culture... more Raman microspectroscopy was used to characterize normal and malignant hepatocytes in both cultured cells and human liver tissues. Consistent spectral changes were observed, including intensity increases at 1040 and 1083 cm-' with malignancy. A loss of intensity at 1241 cm-' was also observed in cancer cells, but was obscured in tissues by the overlap of a 1253 cm-' band, thought to originate from heme proteins. Normal liver tissue also differed from both the malignant tumor and its accompanying cirrhotic tissue at 1182 cm-'. These results demonstrate the potential usefulness of Raman spectroscopy in clinical diagnosis, and investigations into the source of the observed spectral changes will provide information on the underlying mechanisms of carcinogenesis.
A method using confocal Raman microspectroscopy for the detection of cellular proteins in single ... more A method using confocal Raman microspectroscopy for the detection of cellular proteins in single intact cells was developed. Two approaches were used to improve the detection of these cellular components. First, compounds with high Raman scattering were investigated for potential use as Raman labels. Raman labels were conjugated to either biomolecules or biotin and used as markers in the detection of cellular enzymes and receptors. Second, silver colloids were used to increase the surface-enhanced Raman scatter (SERS) of these Raman labels. Cresyl violet and dimethylaminoazobenzene are Raman labels that provide very sensitive SERS detection by a confocal Raman microscope with a HeNe laser at wavelength of 632.8 nm. The detection of 12-lipoxygenase and cyclooxygenase-1 in single bovine coronary artery endothelial cells and the binding of angiotensin II to its receptors in zona glomerulosa cells was demonstrated.
wo main categories of optical detectors are used in analytical instruments: single channel and mu... more wo main categories of optical detectors are used in analytical instruments: single channel and multichannel. Single-channel detectors have just one element that accepts light through the exit slit of a monochromator. An instrument containing a single-channel detector produces a spectrum by rotating the monochromator grating and recording one data point for each grating position. In contrast, multichannel detectors collect many data points simultaneously without moving a grating or any other part of the spectrograph. This allows much more efficient data collection than for their singlechannel counterparts, as large amounts of spectral data can be collected in a single exposure. The most popular multichannel detectors are chargecoupled devices (CCDs) made of silicon with several thousand elements, or pixels, arranged in a rectangle. Scientific-grade CCDs exhibit high responsivity from the near-ultraviolet to the near-infrared (NIR) region of the spectrum—200 nm to 1.1 μm. At longer wa...
Carotenoids serve multiple uses in biological systems ranging from visual pigments to antioxidant... more Carotenoids serve multiple uses in biological systems ranging from visual pigments to antioxidants. Because the resonance Raman spectrum varies with subtle chemical changes on the functional side groups, the spectra of carotenoids have been used for identification and characterization. This installment of “Molecular Spectroscopy Workbench” summarizes the spectroscopy of these materials and why it can be useful when studying them. Carotenoids—Their Resonance Raman Spectra and How They Can Be Helpful in Characterizing a Number of Biological Systems Molecular Spectroscopy Workbench
Over the past 5 years our Raman business has seen continually accelerating growth. The biggest co... more Over the past 5 years our Raman business has seen continually accelerating growth. The biggest component to this growth is in the pharmaceutical industry. Several factors contribute to this success. It is generally now known that it is easy to record a Raman spectrum, and that the information derived complements that of XRD (X-ray diffraction) and FTIR (Fourier Transform Infrared Spectroscopy). The spectral resolution at 1 μm is far greater than either of these techniques. And spectra can be recorded inside of glass and plastic containers. Of greatest interest is the differentiation between the various solid state forms, and distribution of the APIs (Active Pharmaceutical Ingredients) in final products. All of these issues are discussed in this article, with illustrative examples. Introduction With the revolution and evolution of Raman instrumentation over the past 10-12 years, the Raman market has been growing at an accelerated pace. Consequently we get more and more requests to pr...
The Raman spectrum of an anodically prepared 700Anative oxide film of Hg0.7 Cd0.3 Te has been mea... more The Raman spectrum of an anodically prepared 700Anative oxide film of Hg0.7 Cd0.3 Te has been measured on the Raman micro-probe. In order to model the native oxide this spectrum was compared to the spectra of oxide particles (mixed in the ratio determined to be present in the films) that had been sintered under vacuum. The spectra of the oxides indicate an amorphous phase and represents a lowest order approximation to the structure of the native oxide film. The Raman microprobe data conplements that of XPS and Auger which assign oxidation states of +2, +2 and +4 to Hg, Cd, and Te respectively but which provide no information on intermediate or long range order. The identification of an amorphous phase in the oxides is also consistent with the known glass former property of TeO2 and the tendency of HgO and CdO to be glass modifiers. The Raman technique is unique in its ability to differentiate between Cd/Hg TeO3 and a mixture of CdO/HgO and TeO2.
ABSTRACT For the first time, in situ Raman and FTIR measurements have been carried out on a singl... more ABSTRACT For the first time, in situ Raman and FTIR measurements have been carried out on a single bench-top instrument to characterize an alumina-supported palladium during the catalytic DeNOx reaction. While IR spectroscopy gives access to dedicated information on the NOx adsorbed species, Raman spectroscopy is highly sensitive to the molecular structure modifications of the active phase and allows us to characterize the adsorbed species as well as their bonds with the support. The ability to monitor the very same reaction via both techniques in a quasi-simultaneous approach provides full and complementary vibrational information giving a better insight into the catalytic reaction.
In the last 30 to 40 years, various new types of carbon materials have been engineered for multip... more In the last 30 to 40 years, various new types of carbon materials have been engineered for multiple industrial uses. It is now well-known that the Raman spectrum is sensitive to the structure, even though the spectrum is rather uncomplicated. Because Raman spectroscopy now has a reputation for providing good information, potential users of Raman equipment can request information on the quality of their sample. However, they are often not able to define clearly what they mean by “quality.” If they are growing diamond films, they may or may not want interstitial sp2 carbon to glue polycrystalline diamond together. If they are growing hard diamond-like carbon (DLC) films, they may want to correlate the spectral characteristics with physical characteristics of the film. In this column, I explain how the Raman characteristics can aid in characterization of carbon materials.
In a follow-up to my February 2020 column, I started a more systematic study of extractables and ... more In a follow-up to my February 2020 column, I started a more systematic study of extractables and leachables. Following a suggestion from Mark Witkowski of the FDA, I looked at three sets of centrifuge vials that were exposed to the following liquids in an effort to evaluate the potential of Raman microscopy to identify compounds exiting in polymers under particular conditions: saline, phosphate buffer, water, saline treatment at 100 0C, phosphate buffer treatment at 100 0C, water treatment at 100 0C, ethanol, chloroform, pH 5, and pH 9. Although all containers were made of polypropylene (PP), they didn’t behave similarly. Compounds that were extracted from PP vials from different manufacturers were not always the same. Although the number of spectral types that are recorded is large, this article focuses on a few whose interpretation is interesting. The goal was to figure out when it makes sense to employ Raman microscopy for such identification. The characteristics considered were ...
The microsphere formation mechanism of bis(NR-amido-L-phenylalanine) 1,1-cyclobutanedicarboxylate... more The microsphere formation mechanism of bis(NR-amido-L-phenylalanine) 1,1-cyclobutanedicarboxylate, whose self-assembly was triggered by protonation of its carboxylic groups, was investigated by Raman microscopy. An image of the Raman intensity contour map, Raman imaging, shows that water is excluded from the core during the L-phenylalanine dicarboxylate aggregation. In situ Raman microscopic studies on the size and morphological changes of microspheres indicates that osmotic pressure on the sphere, generated by water exclusion from the sphere's core, controls the final assembled structure and morphology.
Microscopic strain distributions in varying thicknesses of polysilicon layers deposited as bridge... more Microscopic strain distributions in varying thicknesses of polysilicon layers deposited as bridges over silicon substrates were determined by high resolution micro-Raman spectroscopy. In particular, we mapped the dependence of the first order Raman spectrum as a function of the position across polysilicon bridges (approximately 550 × 230 /xm2), over tunnels etched in the silicon substrate. Shifts in Raman band frequencies as a function of position on the bridge structures were observed to be dependent upon the thickness of the membrane layer (between 1 and 3 /xm) as well as the annealing conditions. Assuming a simplified uni-axial stress parallel to the surface, the effective tensile stress at the center of the bridge of thickness 2.5 /xm is reduced by annealing from 2.5 GPa to 0.18 GPa.
In this month’s column, I review the band assignments of a protein spectrum, pointing out why it ... more In this month’s column, I review the band assignments of a protein spectrum, pointing out why it can be useful to know the band assignments when attempting to use the Raman spectra to understand the functionality of proteins. In fact, the American Chemical Society (ACS) has just issued a virtual issue of Journal of Physical Chemistry entitled “Protein Crowding and Stability,” discussing how the protein conformation impacts its biological functionality. I address how the Raman spectra can help with the determination of protein structure.
By now, it is well known that Raman spectroscopy has the potential to be used for a variety of an... more By now, it is well known that Raman spectroscopy has the potential to be used for a variety of analytical applications, and that the hurdles to using the technique 30–40 years ago have been largely overcome. However, a remaining impediment to exploiting the technology is that very few analysts have the ability to know what they are looking at. Even if there is experience in infrared (IR) spectroscopy, which looks at similar molecular vibrations, making the Raman measurements and interpreting the results will be quite different. There are databases and searching programs that can aid the analyst, but using these resources effectively also requires a learning curve. What I am going to try to do in this article is provide some advice for dealing with those situations where the searching program does not provide a definitive result.
... Fran Adar,* ... See ref Ma. define. -8 -9 -10 -I1 -12 Flgure 4. MO energy levels by IEH metho... more ... Fran Adar,* ... See ref Ma. define. -8 -9 -10 -I1 -12 Flgure 4. MO energy levels by IEH method for model compounds re-sembling: (a) ferrocytochrome b5; (b) oxyhemoglobin; (c) ferricyto-chrome b5; (d) deoxyhemoglobin; (e) methemoglobin. ...
Raman microspectroscopy was used to characterize normal and malignant hepatocytes in both culture... more Raman microspectroscopy was used to characterize normal and malignant hepatocytes in both cultured cells and human liver tissues. Consistent spectral changes were observed, including intensity increases at 1040 and 1083 cm-' with malignancy. A loss of intensity at 1241 cm-' was also observed in cancer cells, but was obscured in tissues by the overlap of a 1253 cm-' band, thought to originate from heme proteins. Normal liver tissue also differed from both the malignant tumor and its accompanying cirrhotic tissue at 1182 cm-'. These results demonstrate the potential usefulness of Raman spectroscopy in clinical diagnosis, and investigations into the source of the observed spectral changes will provide information on the underlying mechanisms of carcinogenesis.
A method using confocal Raman microspectroscopy for the detection of cellular proteins in single ... more A method using confocal Raman microspectroscopy for the detection of cellular proteins in single intact cells was developed. Two approaches were used to improve the detection of these cellular components. First, compounds with high Raman scattering were investigated for potential use as Raman labels. Raman labels were conjugated to either biomolecules or biotin and used as markers in the detection of cellular enzymes and receptors. Second, silver colloids were used to increase the surface-enhanced Raman scatter (SERS) of these Raman labels. Cresyl violet and dimethylaminoazobenzene are Raman labels that provide very sensitive SERS detection by a confocal Raman microscope with a HeNe laser at wavelength of 632.8 nm. The detection of 12-lipoxygenase and cyclooxygenase-1 in single bovine coronary artery endothelial cells and the binding of angiotensin II to its receptors in zona glomerulosa cells was demonstrated.
wo main categories of optical detectors are used in analytical instruments: single channel and mu... more wo main categories of optical detectors are used in analytical instruments: single channel and multichannel. Single-channel detectors have just one element that accepts light through the exit slit of a monochromator. An instrument containing a single-channel detector produces a spectrum by rotating the monochromator grating and recording one data point for each grating position. In contrast, multichannel detectors collect many data points simultaneously without moving a grating or any other part of the spectrograph. This allows much more efficient data collection than for their singlechannel counterparts, as large amounts of spectral data can be collected in a single exposure. The most popular multichannel detectors are chargecoupled devices (CCDs) made of silicon with several thousand elements, or pixels, arranged in a rectangle. Scientific-grade CCDs exhibit high responsivity from the near-ultraviolet to the near-infrared (NIR) region of the spectrum—200 nm to 1.1 μm. At longer wa...
Carotenoids serve multiple uses in biological systems ranging from visual pigments to antioxidant... more Carotenoids serve multiple uses in biological systems ranging from visual pigments to antioxidants. Because the resonance Raman spectrum varies with subtle chemical changes on the functional side groups, the spectra of carotenoids have been used for identification and characterization. This installment of “Molecular Spectroscopy Workbench” summarizes the spectroscopy of these materials and why it can be useful when studying them. Carotenoids—Their Resonance Raman Spectra and How They Can Be Helpful in Characterizing a Number of Biological Systems Molecular Spectroscopy Workbench
Over the past 5 years our Raman business has seen continually accelerating growth. The biggest co... more Over the past 5 years our Raman business has seen continually accelerating growth. The biggest component to this growth is in the pharmaceutical industry. Several factors contribute to this success. It is generally now known that it is easy to record a Raman spectrum, and that the information derived complements that of XRD (X-ray diffraction) and FTIR (Fourier Transform Infrared Spectroscopy). The spectral resolution at 1 μm is far greater than either of these techniques. And spectra can be recorded inside of glass and plastic containers. Of greatest interest is the differentiation between the various solid state forms, and distribution of the APIs (Active Pharmaceutical Ingredients) in final products. All of these issues are discussed in this article, with illustrative examples. Introduction With the revolution and evolution of Raman instrumentation over the past 10-12 years, the Raman market has been growing at an accelerated pace. Consequently we get more and more requests to pr...
The Raman spectrum of an anodically prepared 700Anative oxide film of Hg0.7 Cd0.3 Te has been mea... more The Raman spectrum of an anodically prepared 700Anative oxide film of Hg0.7 Cd0.3 Te has been measured on the Raman micro-probe. In order to model the native oxide this spectrum was compared to the spectra of oxide particles (mixed in the ratio determined to be present in the films) that had been sintered under vacuum. The spectra of the oxides indicate an amorphous phase and represents a lowest order approximation to the structure of the native oxide film. The Raman microprobe data conplements that of XPS and Auger which assign oxidation states of +2, +2 and +4 to Hg, Cd, and Te respectively but which provide no information on intermediate or long range order. The identification of an amorphous phase in the oxides is also consistent with the known glass former property of TeO2 and the tendency of HgO and CdO to be glass modifiers. The Raman technique is unique in its ability to differentiate between Cd/Hg TeO3 and a mixture of CdO/HgO and TeO2.
ABSTRACT For the first time, in situ Raman and FTIR measurements have been carried out on a singl... more ABSTRACT For the first time, in situ Raman and FTIR measurements have been carried out on a single bench-top instrument to characterize an alumina-supported palladium during the catalytic DeNOx reaction. While IR spectroscopy gives access to dedicated information on the NOx adsorbed species, Raman spectroscopy is highly sensitive to the molecular structure modifications of the active phase and allows us to characterize the adsorbed species as well as their bonds with the support. The ability to monitor the very same reaction via both techniques in a quasi-simultaneous approach provides full and complementary vibrational information giving a better insight into the catalytic reaction.
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