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papers from the latest issue:
Synthesis and mesomorphic investigation of calamitic liquid crystalline system ethyl-[4-(4′-decyloxy)benzoyloxy]-benzoate (4-EDBB): A temperature dependent micro-Raman study and DFT calculations
19 September 2013,
08:36:11
Publication date: Available online 18
September 2013
Source:Vibrational Spectroscopy
Author(s): Rajib Nandi , K. Vikram , Sachin Kumar Singh , Bachcha Singh , Ranjan K. Singh
A new liquid crystalline material containing diester linking group Ethyl-[4-(4′-decyloxy)benzoyloxy]-benzoate (4-EDBB) was synthesized. The phase transition temperatures were noted by Differential Scanning Calorimetry (DSC), the texture pattern were observed by polarizing optical microscopy (POM) and temperature dependent Raman study was employed to observe the transitions as well as to understand the molecular rearrangement during phase transition. The transitions were observed with all the three techniques but the Raman signature of crystal → Smectic A transition is many fold and more precise and accurate. The correlation between intermolecular interaction and phase behaviour has been discussed using temperature dependence Raman data of C-H in-plane bending and C=O stretching vibrations. With the help of DFT method the possible dimers of 4-EDBB were optimized and the rotational isomers were also investigated. There exists weak hydrogen bonds at room temperature, which breaks as the temperature is increased causing the C-H in-plane bending to shift lower and C=O stretching vibrations to shift higher. The discussion of the temperature dependent Raman data reveals that at crystal → Smectic A transition as a result of intra-molecular rotation the molecules transform from trans- to cis- conformer.
Source:Vibrational Spectroscopy
Author(s): Rajib Nandi , K. Vikram , Sachin Kumar Singh , Bachcha Singh , Ranjan K. Singh
A new liquid crystalline material containing diester linking group Ethyl-[4-(4′-decyloxy)benzoyloxy]-benzoate (4-EDBB) was synthesized. The phase transition temperatures were noted by Differential Scanning Calorimetry (DSC), the texture pattern were observed by polarizing optical microscopy (POM) and temperature dependent Raman study was employed to observe the transitions as well as to understand the molecular rearrangement during phase transition. The transitions were observed with all the three techniques but the Raman signature of crystal → Smectic A transition is many fold and more precise and accurate. The correlation between intermolecular interaction and phase behaviour has been discussed using temperature dependence Raman data of C-H in-plane bending and C=O stretching vibrations. With the help of DFT method the possible dimers of 4-EDBB were optimized and the rotational isomers were also investigated. There exists weak hydrogen bonds at room temperature, which breaks as the temperature is increased causing the C-H in-plane bending to shift lower and C=O stretching vibrations to shift higher. The discussion of the temperature dependent Raman data reveals that at crystal → Smectic A transition as a result of intra-molecular rotation the molecules transform from trans- to cis- conformer.
Far-infrared investigation of kaolinite and halloysite intercalates using terahertz time-domain spectroscopy
19 September 2013,
08:36:11
Publication date: Available online 18
September 2013
Source:Vibrational Spectroscopy
Author(s): D. Zich , T. Zacher , J. Darmo , V. Szöcs , D. Lorenc , M. Janek
Two clay minerals from the kaolin group, namely well-ordered kaolinite and poorly-ordered halloysite, were investigated by terahertz time-domain spectroscopy (THz-TDS). Both clay samples were used for preparation of their respective intercalates using dimethyl sulfoxide (DMSO) and potassium acetate (KAc) with water. The intercalates were also characterized by X-ray powder diffraction and Fourier transform infrared spectroscopy. The dielectric behaviour of clay samples was investigated in the far-infrared region of 0.2–2.7THz corresponding to about 6.7–89.9cm−1. The frequency dependence of the power absorption coefficient revealed clear absorption bands for DMSO intercalates but not for KAc with water. For kaolinite - DMSO intercalate a distinct doublet at 1.70THz (56.6cm−1) and 1.88THz (62.6cm−1), and for halloysite - DMSO intercalate a single broad band centred around 1.72THz (57.3cm−1) were found. These bands are reported for the first time in this type of intercalation substances and indicate the application potential of THz time-domain spectroscopy for use in the investigation and detection of chemical behaviour of molecular species introduced into the interlayer space of layered substances such as clays and clay minerals. Additionally, the qualitative characteristics of observed bands of DMSO intercalates in the THz region reasonably resembled the structural order/disorder of used kaolinite and halloysite samples.
Source:Vibrational Spectroscopy
Author(s): D. Zich , T. Zacher , J. Darmo , V. Szöcs , D. Lorenc , M. Janek
Two clay minerals from the kaolin group, namely well-ordered kaolinite and poorly-ordered halloysite, were investigated by terahertz time-domain spectroscopy (THz-TDS). Both clay samples were used for preparation of their respective intercalates using dimethyl sulfoxide (DMSO) and potassium acetate (KAc) with water. The intercalates were also characterized by X-ray powder diffraction and Fourier transform infrared spectroscopy. The dielectric behaviour of clay samples was investigated in the far-infrared region of 0.2–2.7THz corresponding to about 6.7–89.9cm−1. The frequency dependence of the power absorption coefficient revealed clear absorption bands for DMSO intercalates but not for KAc with water. For kaolinite - DMSO intercalate a distinct doublet at 1.70THz (56.6cm−1) and 1.88THz (62.6cm−1), and for halloysite - DMSO intercalate a single broad band centred around 1.72THz (57.3cm−1) were found. These bands are reported for the first time in this type of intercalation substances and indicate the application potential of THz time-domain spectroscopy for use in the investigation and detection of chemical behaviour of molecular species introduced into the interlayer space of layered substances such as clays and clay minerals. Additionally, the qualitative characteristics of observed bands of DMSO intercalates in the THz region reasonably resembled the structural order/disorder of used kaolinite and halloysite samples.
Prediction of Glycoprotein Secondary Structure using ATR-FTIR
19 September 2013,
08:36:11
Publication date: Available online 17
September 2013
Source:Vibrational Spectroscopy
Author(s): S.P. Lewis , A.T. Lewis , P.D. Lewis
Glycoproteins are important biomolecules with a diverse array of structural and signaling functions in biology. Determination of glycoprotein secondary structure is becoming increasingly important in aiding the understanding of how these molecules function in biological environments and disease. Furthermore, glycoproteins such as mucins are being evaluated in various nano-engineering processes that require knowledge of how the underlying secondary structure might alter in different target environments. We have developed an analytical procedure for predicting the secondary structures of glycoprotein using ATR-FTIR on dry film. Using Bovine submaxillary mucin (BSM) as a glycoprotein model, we determined the additive infrared spectral pattern of acetyl amino sugars and amino acids that could contribute to the absorbance in the Amide I band of BSM through empirical data. We show through subtraction of these spectra how the absorbance pattern of the protein backbone can be determined in order to predict glycoprotein secondary structure. The analysis predicted a predominant pattern of random coil, beta sheet and beta turn secondary structure for BSM after carbohydrate and amino acid spectral subtraction in agreement with other methods. Our relatively simple approach can be applied to predict secondary structure in other glycoproteins.
Source:Vibrational Spectroscopy
Author(s): S.P. Lewis , A.T. Lewis , P.D. Lewis
Glycoproteins are important biomolecules with a diverse array of structural and signaling functions in biology. Determination of glycoprotein secondary structure is becoming increasingly important in aiding the understanding of how these molecules function in biological environments and disease. Furthermore, glycoproteins such as mucins are being evaluated in various nano-engineering processes that require knowledge of how the underlying secondary structure might alter in different target environments. We have developed an analytical procedure for predicting the secondary structures of glycoprotein using ATR-FTIR on dry film. Using Bovine submaxillary mucin (BSM) as a glycoprotein model, we determined the additive infrared spectral pattern of acetyl amino sugars and amino acids that could contribute to the absorbance in the Amide I band of BSM through empirical data. We show through subtraction of these spectra how the absorbance pattern of the protein backbone can be determined in order to predict glycoprotein secondary structure. The analysis predicted a predominant pattern of random coil, beta sheet and beta turn secondary structure for BSM after carbohydrate and amino acid spectral subtraction in agreement with other methods. Our relatively simple approach can be applied to predict secondary structure in other glycoproteins.
Micro-Raman mapping on an anatase TiO2 single crystal with a large percentage of reactive (001) facets
19 September 2013,
08:36:11
Publication date: Available online 4
September 2013
Source:Vibrational Spectroscopy
Author(s): Guang Zeng , Kai-Kai Li , Hua-Gui Yang , Yun-Hong Zhang
After it has been successfully synthesized in 2008, so far, no Raman investigations on the micro-sized anatase TiO2 single crystal which has a large percentage of the reactive (001) facets have been conducted to the best of our knowledge. In the present work, this unique anatase TiO2 single crystal was investigated by noninvasive and nondestructive Raman mapping technique. Raman images of both non-polarized and polarized measurements showed that the Raman features of the crystal varied with measurement position. The differences among the Raman spectra measured on different crystal facets were believed to result from the orientations and the symmetry rules. Whereas the differences among those measured at different points of the same crystal facet under the same measurement condition were supposed to indicate the defects of the crystal structure, such as oxygen vacancies, local lattice disorder etc. Furthermore, the appearance of the two second order Raman peaks of 803 and 918cm−1 as well as the blue-shift of 395cm−1 peak implies the anharmonicity of the crystal structure, which is also probably caused by the crystal defects. Our results provide useful information about the structure of this unique anatase TiO2 material, and could be complementary to those that acquired by other characterization techniques.
Source:Vibrational Spectroscopy
Author(s): Guang Zeng , Kai-Kai Li , Hua-Gui Yang , Yun-Hong Zhang
After it has been successfully synthesized in 2008, so far, no Raman investigations on the micro-sized anatase TiO2 single crystal which has a large percentage of the reactive (001) facets have been conducted to the best of our knowledge. In the present work, this unique anatase TiO2 single crystal was investigated by noninvasive and nondestructive Raman mapping technique. Raman images of both non-polarized and polarized measurements showed that the Raman features of the crystal varied with measurement position. The differences among the Raman spectra measured on different crystal facets were believed to result from the orientations and the symmetry rules. Whereas the differences among those measured at different points of the same crystal facet under the same measurement condition were supposed to indicate the defects of the crystal structure, such as oxygen vacancies, local lattice disorder etc. Furthermore, the appearance of the two second order Raman peaks of 803 and 918cm−1 as well as the blue-shift of 395cm−1 peak implies the anharmonicity of the crystal structure, which is also probably caused by the crystal defects. Our results provide useful information about the structure of this unique anatase TiO2 material, and could be complementary to those that acquired by other characterization techniques.
Vibrational spectroscopic study of poly(dimethylsiloxane)-ZnO nanocomposites
19 September 2013,
08:36:11
Publication date: September
2013
Source:Vibrational Spectroscopy, Volume 68
Author(s): L. Bistričić , V. Borjanović , L. Mikac , V. Dananić
A series of poly(dimethylsiloxane)-zinc oxide (PDMS-ZnO) nanocomposites having different concentrations of ZnO nanoparticles (0, 1, 5, 10 and 20wt%) have been prepared. Raman and FTIR-ATR spectroscopic analysis was performed in order to determine the interaction between the ZnO nanoparticles and PDMS polymer matrix. Density functional theory (DFT) using the (B3-LYP)/6-311++G(2df,2p) method was used to investigate the vibrational spectra of PDMS. A complete vibrational assignment is supported by the normal coordinate analysis, calculated Raman activities as well as IR intensities. The presence of ZnO nanoparticles in PDMS gives rise to significant differences in relative intensities of the characteristic vibrational bands with respect to the cross-linked polymer. The changes in relative intensities of Raman bands, as well as swelling measurements, were used to explain the effect of ZnO nanoparticles on the cross-linked structure of PDMS nanocomposites. It is established that ZnO nanoparticles influence the cross-linking density of the polymer matrix.
Source:Vibrational Spectroscopy, Volume 68
Author(s): L. Bistričić , V. Borjanović , L. Mikac , V. Dananić
A series of poly(dimethylsiloxane)-zinc oxide (PDMS-ZnO) nanocomposites having different concentrations of ZnO nanoparticles (0, 1, 5, 10 and 20wt%) have been prepared. Raman and FTIR-ATR spectroscopic analysis was performed in order to determine the interaction between the ZnO nanoparticles and PDMS polymer matrix. Density functional theory (DFT) using the (B3-LYP)/6-311++G(2df,2p) method was used to investigate the vibrational spectra of PDMS. A complete vibrational assignment is supported by the normal coordinate analysis, calculated Raman activities as well as IR intensities. The presence of ZnO nanoparticles in PDMS gives rise to significant differences in relative intensities of the characteristic vibrational bands with respect to the cross-linked polymer. The changes in relative intensities of Raman bands, as well as swelling measurements, were used to explain the effect of ZnO nanoparticles on the cross-linked structure of PDMS nanocomposites. It is established that ZnO nanoparticles influence the cross-linking density of the polymer matrix.
Spectroscopic analysis of pigments and inks in manuscripts: I. Byzantine and post-Byzantine manuscripts (10–18th century)
19 September 2013,
08:36:11
Publication date: September
2013
Source:Vibrational Spectroscopy, Volume 68
Author(s): Irena Nastova , Orhideja Grupče , Biljana Minčeva-Šukarova , Melih Ozcatal , Lenče Mojsoska
Pigments and inks used in six Byzantine manuscripts (covering the period from 10th to 15th century) and one 18th century post-Byzantine manuscript have been analyzed, using micro-Raman spectroscopy, ATR-FT-infrared spectroscopy and SEM–EDS. Micro-Raman spectroscopy allowed fast and in situ analysis of majority of pigments and inks used, except for the purple-red organic pigment, brown-purple ink and metallic pigments (silver and gold). The nature of the organic purple-red pigment and organic purple ink was revealed applying ATR-FTIR. In the analysis of the metallic pigment (silver and gold) as well as additional technique in characterizing organic purple-red dye and ink, SEM–EDS was used. Varieties of inks were used in the manuscripts. Gold and silver inks were used for capital letters and for emphasizing certain paragraphs. Red ink was identified as madder in illuminated manuscripts and as vermilion in simple texts. Gall ink was identified as black-brown ink in most of the manuscripts. In 18th century manuscript logwood was identified while in the 12th century manuscript, goethite was used as ink. The analysis of the pigments and inks revealed that over the course of 5 centuries, the pigments used for decoration in Byzantine manuscripts remained similar and traditional (mineral and organic), with pronounced variations in the 18th century post-Byzantine manuscript.
Source:Vibrational Spectroscopy, Volume 68
Author(s): Irena Nastova , Orhideja Grupče , Biljana Minčeva-Šukarova , Melih Ozcatal , Lenče Mojsoska
Pigments and inks used in six Byzantine manuscripts (covering the period from 10th to 15th century) and one 18th century post-Byzantine manuscript have been analyzed, using micro-Raman spectroscopy, ATR-FT-infrared spectroscopy and SEM–EDS. Micro-Raman spectroscopy allowed fast and in situ analysis of majority of pigments and inks used, except for the purple-red organic pigment, brown-purple ink and metallic pigments (silver and gold). The nature of the organic purple-red pigment and organic purple ink was revealed applying ATR-FTIR. In the analysis of the metallic pigment (silver and gold) as well as additional technique in characterizing organic purple-red dye and ink, SEM–EDS was used. Varieties of inks were used in the manuscripts. Gold and silver inks were used for capital letters and for emphasizing certain paragraphs. Red ink was identified as madder in illuminated manuscripts and as vermilion in simple texts. Gall ink was identified as black-brown ink in most of the manuscripts. In 18th century manuscript logwood was identified while in the 12th century manuscript, goethite was used as ink. The analysis of the pigments and inks revealed that over the course of 5 centuries, the pigments used for decoration in Byzantine manuscripts remained similar and traditional (mineral and organic), with pronounced variations in the 18th century post-Byzantine manuscript.
Temperature dependence of the microstructure of 1-butyl-3-methylimidazolium tetrafluoroborate in aqueous solution
19 September 2013,
08:36:11
Publication date: September
2013
Source:Vibrational Spectroscopy, Volume 68
Author(s): Huiyong Wang , Jianji Wang , Lamei Zhang
Many applications of ionic liquids (ILs) are closely related with their microstructure in mixtures. For example, morphology and pore size of the MCM-41 prepared in aqueous ILs are greatly dependent on the aggregation behavior of the ILs in water. Therefore, the study on the microstructure of ILs in aqueous solutions is of great importance. In this work, 1H NMR, dynamic light scattering and attenuated total reflection infrared spectroscopy have been used to investigate the temperature effect on the structures of aqueous 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]) solutions. It was shown that the size of the IL aggregates becomes larger with decreasing temperature. When the system temperature is below the upper critical solution temperature (UCST) of the binary mixture at about 4°C, the aggregate size of the IL is larger than 1000nm. Additionally, the two-dimensional IR results reveal that at low IL concentrations, H2O can interact with [BF4]− prior to the CH groups of the imidazolium ring, whereas cation and anion of the IL tend to form aggregate at high IL concentrations. With the decrease of temperature, the interactions between cation and anion of the IL become stronger, but those between the IL and water become weaker, thereby resulting in the growth of the aggregate of cation with anion of the IL. This result may give a reasonable explanation for the origin of the UCST behavior of aqueous [C4mim][BF4] solution.
Source:Vibrational Spectroscopy, Volume 68
Author(s): Huiyong Wang , Jianji Wang , Lamei Zhang
Many applications of ionic liquids (ILs) are closely related with their microstructure in mixtures. For example, morphology and pore size of the MCM-41 prepared in aqueous ILs are greatly dependent on the aggregation behavior of the ILs in water. Therefore, the study on the microstructure of ILs in aqueous solutions is of great importance. In this work, 1H NMR, dynamic light scattering and attenuated total reflection infrared spectroscopy have been used to investigate the temperature effect on the structures of aqueous 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]) solutions. It was shown that the size of the IL aggregates becomes larger with decreasing temperature. When the system temperature is below the upper critical solution temperature (UCST) of the binary mixture at about 4°C, the aggregate size of the IL is larger than 1000nm. Additionally, the two-dimensional IR results reveal that at low IL concentrations, H2O can interact with [BF4]− prior to the CH groups of the imidazolium ring, whereas cation and anion of the IL tend to form aggregate at high IL concentrations. With the decrease of temperature, the interactions between cation and anion of the IL become stronger, but those between the IL and water become weaker, thereby resulting in the growth of the aggregate of cation with anion of the IL. This result may give a reasonable explanation for the origin of the UCST behavior of aqueous [C4mim][BF4] solution.
Label free non-invasive imaging of topically applied actives in reconstructed human epidermis by confocal Raman spectroscopy
19 September 2013,
08:36:11
Publication date: September
2013
Source:Vibrational Spectroscopy, Volume 68
Author(s): Franziska D. Fleischli , Stephanie Mathes , Christian Adlhart
Raman spectroscopy has become a versatile tool for the in vivo characterization of skin. Here we describe use of Raman spectroscopy for high resolution optical cross sectioning to resolve skin constituents and administered drugs at the cellular level. Percutaneous penetration is typically studied using permeation cells with biopsies of animals or human skin. Although this technique provides valuable clinical data, little insight is gained in the microstructure of drug penetration (intercellular or transcellular) or in the mode of action of applied vehicles or penetration enhancers. Therefore, a Raman microspectroscopic method was combined with a confocal scanning setup to image the microstructure of commercially available skin models (SkinEthic®) and the spatial distribution of penetrated actives. The models’ microstructure was scanned without any special treatment or environment such as cutting, staining, freezing, or application of vacuum. The non-invasive Raman images reveal the layered structure of stratum corneum. This in particular for lipids while water tends to be more evenly distributed. When penetration of the hydrophilic active glycerol and the lipophilic octyl methoxycinnamate, OMC, was studied, a strong correlation between the local distribution of skin constituents and the hydrophilic/lipophilic character of the active was observed.
Source:Vibrational Spectroscopy, Volume 68
Author(s): Franziska D. Fleischli , Stephanie Mathes , Christian Adlhart
Raman spectroscopy has become a versatile tool for the in vivo characterization of skin. Here we describe use of Raman spectroscopy for high resolution optical cross sectioning to resolve skin constituents and administered drugs at the cellular level. Percutaneous penetration is typically studied using permeation cells with biopsies of animals or human skin. Although this technique provides valuable clinical data, little insight is gained in the microstructure of drug penetration (intercellular or transcellular) or in the mode of action of applied vehicles or penetration enhancers. Therefore, a Raman microspectroscopic method was combined with a confocal scanning setup to image the microstructure of commercially available skin models (SkinEthic®) and the spatial distribution of penetrated actives. The models’ microstructure was scanned without any special treatment or environment such as cutting, staining, freezing, or application of vacuum. The non-invasive Raman images reveal the layered structure of stratum corneum. This in particular for lipids while water tends to be more evenly distributed. When penetration of the hydrophilic active glycerol and the lipophilic octyl methoxycinnamate, OMC, was studied, a strong correlation between the local distribution of skin constituents and the hydrophilic/lipophilic character of the active was observed.
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