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Far-infrared investigation of kaolinite and halloysite intercalates using terahertz time-domain spectroscopy
30 October 2013,
21:17:54
Publication date: November
2013
Source:Vibrational Spectroscopy, Volume 69
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, Volume 69
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.
Vibrational spectroscopy of phthalocyanine and naphthalocyanine in sandwich-type (na)phthalocyaninato and porphyrinato rare earth complexes. Part 15: The IR characteristics of phthalocyanine in homoleptic tetrakis(phthalocyaninato) rare earth(III)-cadmium(II) quadruple-deckers
30 October 2013,
21:17:54
Publication date: November
2013
Source:Vibrational Spectroscopy, Volume 69
Author(s): Hong Shang , Hailong Wang , Wenjun Li , Jianzhuang Jiang
The infra-red (IR) spectroscopic data for a series of twelve sandwich-type homoleptic tetrakis[2,3,9,10,16,17,23,24-octa(octyloxy)phthalocyaninato] rare earth(III)-cadmium(II) quadruple-decker complexes [Pc(OC8H17)8]M[Pc(OC8H17)8]Cd[Pc(OC8H17)8]M[Pc(OC8H17)8] (M=Y, Pr–Yb except Pm) have been collected with resolution of 2cm−1 and their interpretation in terms tried by analogy with the IR characteristics of bis(phthalocyaninato) cerium double-decker [Pc(OC8H17)8]Ce[Pc(OC8H17)8] in which the macrocyclic ligands exist as the phthalocyanine dianion. Similar to the bis/tris(phthalocyaninato) rare earth sandwich counterparts, all the absorptions contributed primarily by or at least containing contribution from the vibrations of pyrrole or isoindole stretching, breathing or deformation or aza stretching in the IR spectra of these quadruple-decker compounds show dependent nature on the rare earth ionic size. The shift toward higher energy direction in the frequencies of these vibrations along with the decrease of the rare earth radii reveals the effective and increasing π–π interactions in these quadruple-decker sandwich compounds in the same order. Nevertheless, the decreased sensitivity of the frequencies of the above mentioned vibration modes in particular the weak absorption band due to the isoindole stretching at 1414–1416cm−1 for the quadruple-decker on rare earth metal size in comparison with corresponding band for bis(phthalocyaninato) rare earth counterparts indicates the relatively weaker π–π interaction in these quadruple-deckers than in the double-deckers.
Source:Vibrational Spectroscopy, Volume 69
Author(s): Hong Shang , Hailong Wang , Wenjun Li , Jianzhuang Jiang
The infra-red (IR) spectroscopic data for a series of twelve sandwich-type homoleptic tetrakis[2,3,9,10,16,17,23,24-octa(octyloxy)phthalocyaninato] rare earth(III)-cadmium(II) quadruple-decker complexes [Pc(OC8H17)8]M[Pc(OC8H17)8]Cd[Pc(OC8H17)8]M[Pc(OC8H17)8] (M=Y, Pr–Yb except Pm) have been collected with resolution of 2cm−1 and their interpretation in terms tried by analogy with the IR characteristics of bis(phthalocyaninato) cerium double-decker [Pc(OC8H17)8]Ce[Pc(OC8H17)8] in which the macrocyclic ligands exist as the phthalocyanine dianion. Similar to the bis/tris(phthalocyaninato) rare earth sandwich counterparts, all the absorptions contributed primarily by or at least containing contribution from the vibrations of pyrrole or isoindole stretching, breathing or deformation or aza stretching in the IR spectra of these quadruple-decker compounds show dependent nature on the rare earth ionic size. The shift toward higher energy direction in the frequencies of these vibrations along with the decrease of the rare earth radii reveals the effective and increasing π–π interactions in these quadruple-decker sandwich compounds in the same order. Nevertheless, the decreased sensitivity of the frequencies of the above mentioned vibration modes in particular the weak absorption band due to the isoindole stretching at 1414–1416cm−1 for the quadruple-decker on rare earth metal size in comparison with corresponding band for bis(phthalocyaninato) rare earth counterparts indicates the relatively weaker π–π interaction in these quadruple-deckers than in the double-deckers.
Raman spectroscopy analysis of pigments on Diego Velázquez paintings
30 October 2013,
21:17:54
Publication date: November
2013
Source:Vibrational Spectroscopy, Volume 69
Author(s): P.C. Gutiérrez-Neira , F. Agulló-Rueda , A. Climent-Font , C. Garrido
Raman micro-spectroscopy has been used for the identification of the pigments used by the Spanish painter Diego Velázquez (1599–1650), considered one of the greatest painters in art history. The set of cross-sectional samples studied belongs to paintings of the Museo del Prado collection and correspond to the three known periods of the artist's activity. We have obtained information on the chemical composition and crystal structure of the pigments used for various colours. The results are consistent with previous elemental composition determined by other analytical methods.
Source:Vibrational Spectroscopy, Volume 69
Author(s): P.C. Gutiérrez-Neira , F. Agulló-Rueda , A. Climent-Font , C. Garrido
Raman micro-spectroscopy has been used for the identification of the pigments used by the Spanish painter Diego Velázquez (1599–1650), considered one of the greatest painters in art history. The set of cross-sectional samples studied belongs to paintings of the Museo del Prado collection and correspond to the three known periods of the artist's activity. We have obtained information on the chemical composition and crystal structure of the pigments used for various colours. The results are consistent with previous elemental composition determined by other analytical methods.
Prediction of glycoprotein secondary structure using ATR-FTIR
30 October 2013,
21:17:54
Publication date: November
2013
Source:Vibrational Spectroscopy, Volume 69
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, Volume 69
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.
Structure and vibrational spectroscopy of the fenbufen–β-cyclodextrin inclusion complex
30 October 2013,
21:17:54
Publication date: November
2013
Source:Vibrational Spectroscopy, Volume 69
Author(s): Ferenc Billes , Antonio Hernanz , Hans Mikosch , Ioan Bratu
The structure and host–guest interactions in the inclusion complex (179 atoms) of β-cyclodextrin with fenbufen are studied. Fenbufen, the biphenyl derivative γ-oxo-(1,1′-biphenyl)-4-butanoic acid, is a widespread analgesic and non-steroidal anti-inflammatory drug. Its inclusion complex with β-cyclodextrin improves the oral bioavailability and entails fewer side-effects. Optimized molecular structures, atomic net charges and vibrational spectra have been computed for the host and guest molecules, as well as for the inclusion complex. The functional density theory with the B3LYP/3-21+G method/basis set has been applied. The calculated vibrational frequencies have not been scaled, and the simulated spectra have been compared with those obtained experimentally. The host–guest interactions have been investigated in detail.
Source:Vibrational Spectroscopy, Volume 69
Author(s): Ferenc Billes , Antonio Hernanz , Hans Mikosch , Ioan Bratu
The structure and host–guest interactions in the inclusion complex (179 atoms) of β-cyclodextrin with fenbufen are studied. Fenbufen, the biphenyl derivative γ-oxo-(1,1′-biphenyl)-4-butanoic acid, is a widespread analgesic and non-steroidal anti-inflammatory drug. Its inclusion complex with β-cyclodextrin improves the oral bioavailability and entails fewer side-effects. Optimized molecular structures, atomic net charges and vibrational spectra have been computed for the host and guest molecules, as well as for the inclusion complex. The functional density theory with the B3LYP/3-21+G method/basis set has been applied. The calculated vibrational frequencies have not been scaled, and the simulated spectra have been compared with those obtained experimentally. The host–guest interactions have been investigated in detail.
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
30 October 2013,
21:17:54
Publication date: November
2013
Source:Vibrational Spectroscopy, Volume 69
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 CH in-plane bending and CO 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 CH in-plane bending to shift lower and CO 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, Volume 69
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 CH in-plane bending and CO 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 CH in-plane bending to shift lower and CO 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.
Identification of the early postmortem metabolic state of porcine M. semimembranosus using Raman spectroscopy
30 October 2013,
21:17:54
Publication date: Available online 26
October 2013
Source:Vibrational Spectroscopy
Author(s): Rico Scheier , Jürgen Köhler , Heinar Schmidt
The metabolic conditions in the early postmortem muscle determine meat quality. Raman spectroscopy is shown to follow the early postmortem metabolism (0.5–10 h) of porcine M. semimembranosus (N = 10). To this end the Raman spectra, pH and lactate kinetics were measured in the laboratory. Raman difference spectra were utilized to identify the spectral changes and to assign them to metabolic and structural alterations in the pre-rigor (50 to 120min) and rigor (2 to 8.5 h) phases. In the Raman spectra, the decreasing pH was indicated by three signals assigned to phosphorylated metabolites and inorganic phosphate. Furthermore, the degradation of glycogen to lactate and a reduction of signal intensity of α-helical proteins were revealed. In the pre-rigor phase, degradation of phosphocreatine to creatine and reduction of oxy- to deoxymyoglobin was found. In the rigor phase, additionally, degradation of ATP to inosine monophosphate (IMP) was observed. Good agreement was achieved between measured and simulated Raman difference spectra. In the pre-rigor and rigor time frame, normal and deviating meat quality could be distinguished based on signals of phosphocreatine, ATP, IMP and α-helical proteins. This work provides a deeper understanding and the first semi-quantitative description of the early postmortem Raman spectra of meat which show potential for the non-invasive and early detection of the metabolic state of meat, and hence for the identification of deviating meat qualities.
Source:Vibrational Spectroscopy
Author(s): Rico Scheier , Jürgen Köhler , Heinar Schmidt
The metabolic conditions in the early postmortem muscle determine meat quality. Raman spectroscopy is shown to follow the early postmortem metabolism (0.5–10 h) of porcine M. semimembranosus (N = 10). To this end the Raman spectra, pH and lactate kinetics were measured in the laboratory. Raman difference spectra were utilized to identify the spectral changes and to assign them to metabolic and structural alterations in the pre-rigor (50 to 120min) and rigor (2 to 8.5 h) phases. In the Raman spectra, the decreasing pH was indicated by three signals assigned to phosphorylated metabolites and inorganic phosphate. Furthermore, the degradation of glycogen to lactate and a reduction of signal intensity of α-helical proteins were revealed. In the pre-rigor phase, degradation of phosphocreatine to creatine and reduction of oxy- to deoxymyoglobin was found. In the rigor phase, additionally, degradation of ATP to inosine monophosphate (IMP) was observed. Good agreement was achieved between measured and simulated Raman difference spectra. In the pre-rigor and rigor time frame, normal and deviating meat quality could be distinguished based on signals of phosphocreatine, ATP, IMP and α-helical proteins. This work provides a deeper understanding and the first semi-quantitative description of the early postmortem Raman spectra of meat which show potential for the non-invasive and early detection of the metabolic state of meat, and hence for the identification of deviating meat qualities.
Vibrational spectra and static vibrational contribution to first hyperpolarizability of naphthopyrans – A combined experimental and DFT study
30 October 2013,
21:17:54
Publication date: Available online 21
October 2013
Source:Vibrational Spectroscopy
Author(s): Kadali Chaitanya , Xue Hai Ju , B. Mark Heron , Christopher D. Gabbutt
Two pairs of isomeric photochromic naphthopyrans were investigated by FT-IR and FT-Raman spectroscopy and by Density Functional Theory (DFT) methods. The vibrational frequencies and contribution to first hyperpolarizabilities of the four naphthopyrans were determined at the B3LYP/6-31G (d, p) level. Comparison of the experimental and theoretical vibrational frequencies of the naphthopyrans was made. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA). These results show that the ratio between pure vibrational contribution to the electronic contribution of first hyperpolarizability ( β v / β e ) increases when the 4-methoxyphenyl groups in the symmetrical isomers is replaced by 4-morpholinophenyl and phenyl group resulting in an asymmetrically substituted isomer pair. At the static limit, the low vibrational frequency modes have dominating contributions to the vibrational dipole polarizability and first hyperpolarizability.
Source:Vibrational Spectroscopy
Author(s): Kadali Chaitanya , Xue Hai Ju , B. Mark Heron , Christopher D. Gabbutt
Two pairs of isomeric photochromic naphthopyrans were investigated by FT-IR and FT-Raman spectroscopy and by Density Functional Theory (DFT) methods. The vibrational frequencies and contribution to first hyperpolarizabilities of the four naphthopyrans were determined at the B3LYP/6-31G (d, p) level. Comparison of the experimental and theoretical vibrational frequencies of the naphthopyrans was made. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA). These results show that the ratio between pure vibrational contribution to the electronic contribution of first hyperpolarizability ( β v / β e ) increases when the 4-methoxyphenyl groups in the symmetrical isomers is replaced by 4-morpholinophenyl and phenyl group resulting in an asymmetrically substituted isomer pair. At the static limit, the low vibrational frequency modes have dominating contributions to the vibrational dipole polarizability and first hyperpolarizability.
Vibrational spectra of a ferrocenyl phosphine derivative chemisorbed on 3-aminopropylsilyl modified silica gel
30 October 2013,
21:17:54
Publication date: Available online 16
October 2013
Source:Vibrational Spectroscopy
Author(s): Vladimir Ivanovski , Miha Bukleski , Martyna Madalska , Evamarie Hey-Hawkins
Samples of silica gel dried at different temperatures, silica gel modified with 3-aminopropylsilyl (APS) and silica gel modified with APS and further with a ferrocenyl phosphine derivative were investigated by DRIFT, transmission FTIR and MicroRaman spectroscopy. The reaction between 3-aminopropyltrimethoxysilane (APTMS) and silica gel was mainly identified by the diminishing or vanishing intensity of the stretching band of the free OH groups in the silica gel. Further chemical reaction of the APS groups with a ferrocenyl phosphine derivative (suitable as ligand in homogeneous catalysis) was identified in the IR spectra by the appearance of the C=N stretching band of the formed Schiff base, and diminishing intensity of the δ(NH2) modes. According to the IR spectra the reaction of the ferrocenyl phosphine derivative with the APS-modified silica gel is almost quantitative. From the recorded IR and Raman spectra, conclusions concerning the substitution of APTMS methoxy groups during the chemisorption on silica gel were derived. Through deconvolution of the complex Raman band in the siloxy stretching region of the APS-modified silica gel, the newly formed siloxy bond was identified.
Source:Vibrational Spectroscopy
Author(s): Vladimir Ivanovski , Miha Bukleski , Martyna Madalska , Evamarie Hey-Hawkins
Samples of silica gel dried at different temperatures, silica gel modified with 3-aminopropylsilyl (APS) and silica gel modified with APS and further with a ferrocenyl phosphine derivative were investigated by DRIFT, transmission FTIR and MicroRaman spectroscopy. The reaction between 3-aminopropyltrimethoxysilane (APTMS) and silica gel was mainly identified by the diminishing or vanishing intensity of the stretching band of the free OH groups in the silica gel. Further chemical reaction of the APS groups with a ferrocenyl phosphine derivative (suitable as ligand in homogeneous catalysis) was identified in the IR spectra by the appearance of the C=N stretching band of the formed Schiff base, and diminishing intensity of the δ(NH2) modes. According to the IR spectra the reaction of the ferrocenyl phosphine derivative with the APS-modified silica gel is almost quantitative. From the recorded IR and Raman spectra, conclusions concerning the substitution of APTMS methoxy groups during the chemisorption on silica gel were derived. Through deconvolution of the complex Raman band in the siloxy stretching region of the APS-modified silica gel, the newly formed siloxy bond was identified.
Electric Field Standing Wave Effects in FT-IR Transflection Spectra of biological tissue sections: simulated models of experimental variability
30 October 2013,
21:17:54
Publication date: Available online 3 October
2013
Source:Vibrational Spectroscopy
Author(s): Tomasz P. Wrobel , Barbara Wajnchold , Hugh J. Byrne , Malgorzata Baranska
The so-called electric field standing wave effect (EFSW) has recently been demonstrated to significantly distort FT-IR spectra acquired in a transflection mode, both experimentally and in simulated models, bringing into question the appropriateness of the technique for sample characterization, particularly in the field of spectroscopy of biological materials. The predicted effects are most notable in the regime where the sample thickness is comparable to the source wavelength. In this work, the model is extended to sample thicknesses more representative of biological tissue sections and to include typical experimental factors which are demonstrated to reduce the predicted effects. These include integration over the range of incidence angles, varying degrees of coherence of the source and inhomogeneities in sample thickness. The latter was found to have the strongest effect on the spectral distortions and, with inhomogeneities as low as 10% of the sample thickness, the predicted distortions due to the standing wave effect are almost completely averaged out. As the majority of samples for biospectroscopy are prepared by cutting a cross section of tissue resulting in a high degree of thickness variation, this finding suggests that the standing wave effect should be a minor distortion in FT-IR spectroscopy of tissues. The study has important implications not only in optimization of protocols for future studies, but notably for the validity of the extensive studies which have been performed to date on tissue samples in the transflection geometry
Source:Vibrational Spectroscopy
Author(s): Tomasz P. Wrobel , Barbara Wajnchold , Hugh J. Byrne , Malgorzata Baranska
The so-called electric field standing wave effect (EFSW) has recently been demonstrated to significantly distort FT-IR spectra acquired in a transflection mode, both experimentally and in simulated models, bringing into question the appropriateness of the technique for sample characterization, particularly in the field of spectroscopy of biological materials. The predicted effects are most notable in the regime where the sample thickness is comparable to the source wavelength. In this work, the model is extended to sample thicknesses more representative of biological tissue sections and to include typical experimental factors which are demonstrated to reduce the predicted effects. These include integration over the range of incidence angles, varying degrees of coherence of the source and inhomogeneities in sample thickness. The latter was found to have the strongest effect on the spectral distortions and, with inhomogeneities as low as 10% of the sample thickness, the predicted distortions due to the standing wave effect are almost completely averaged out. As the majority of samples for biospectroscopy are prepared by cutting a cross section of tissue resulting in a high degree of thickness variation, this finding suggests that the standing wave effect should be a minor distortion in FT-IR spectroscopy of tissues. The study has important implications not only in optimization of protocols for future studies, but notably for the validity of the extensive studies which have been performed to date on tissue samples in the transflection geometry
Gamma ray induced changes on vibrational spectroscopic properties of strontium alumino-borosilicate glasses
30 October 2013,
21:17:54
Publication date: Available online 25
September 2013
Source:Vibrational Spectroscopy
Author(s): A. Rupesh Kumar , T.G.V.M. Rao , K. Neeraja , M. Rami Reddy , N. Veeraiah
The present investigation reports the effect of influence of aluminum ions on radiation damage of strontium borosilicate glasses studied by means of spectroscopic (viz., optical absorption (OA), infrared and Raman spectra). The composition of the glasses chosen for the study is 40SrO–xAl2O3–(15-x) B2O3–40SiO2(x=5, 7.5, 10), all in mol%. The glasses were synthesized by conventional melt quenching method. Later, the samples were exposed to gamma (γ) radiation dose of strengths 10 kGy and 30 kGy with a dose rate of 1.5Gy/s using 60Co as radiation source. The infrared spectra (IR), Raman spectra and optical absorption (OA) spectra of the samples were recorded at ambient temperature before and after irradiation. The OA spectra of the pre-irradiated samples do not exhibit any absorption bands in the UV–vis. regions and IR and Raman spectra exhibited conventional vibrational bands due to different borate, silicate AlO4 and AlO6 structural units. The OA spectra of post irradiated samples exhibited a broad absorption band in the wavelength region 600–750nm; it is attributed to electron trapped color centres. The intensity of this peak is observed to increase with increase of the γ-ray dose. Considerable changes in the intensities of various bands in the IR and Raman spectra were also observed. The changes were explained based on structural modifications taking place in the glass network due to γ-ray irradiation and finally it is concluded that the glasses mixed with 10.0 mol% of Al2O3 are relatively more radiation resistant.
Source:Vibrational Spectroscopy
Author(s): A. Rupesh Kumar , T.G.V.M. Rao , K. Neeraja , M. Rami Reddy , N. Veeraiah
The present investigation reports the effect of influence of aluminum ions on radiation damage of strontium borosilicate glasses studied by means of spectroscopic (viz., optical absorption (OA), infrared and Raman spectra). The composition of the glasses chosen for the study is 40SrO–xAl2O3–(15-x) B2O3–40SiO2(x=5, 7.5, 10), all in mol%. The glasses were synthesized by conventional melt quenching method. Later, the samples were exposed to gamma (γ) radiation dose of strengths 10 kGy and 30 kGy with a dose rate of 1.5Gy/s using 60Co as radiation source. The infrared spectra (IR), Raman spectra and optical absorption (OA) spectra of the samples were recorded at ambient temperature before and after irradiation. The OA spectra of the pre-irradiated samples do not exhibit any absorption bands in the UV–vis. regions and IR and Raman spectra exhibited conventional vibrational bands due to different borate, silicate AlO4 and AlO6 structural units. The OA spectra of post irradiated samples exhibited a broad absorption band in the wavelength region 600–750nm; it is attributed to electron trapped color centres. The intensity of this peak is observed to increase with increase of the γ-ray dose. Considerable changes in the intensities of various bands in the IR and Raman spectra were also observed. The changes were explained based on structural modifications taking place in the glass network due to γ-ray irradiation and finally it is concluded that the glasses mixed with 10.0 mol% of Al2O3 are relatively more radiation resistant.
