A new issue of this journal has just
been published. To see abstracts of the papers it contains (with links through
to the full papers) click here:
Selected
papers from the latest issue:
A joint application of ATR-FTIR and SEM imaging with high spatial resolution: Identification and distribution of painting materials and their degradation products in paint cross sections
17 January 2013,
08:09:13
March 2013
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
A series of paint cross sections from an oil painting are studied by attenuated total reflection in conjunction with Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX). The imaging modes of both methods were employed to show their potential in the detection of various painting materials and their distribution in the paint cross sections. The goal of this work is to evaluate FTIR and SEM-EDX spectroscopy in order to understand the limitations and strengths of both approaches. It has been revealed that both techniques are complementary in the identification of pigments, extenders and binding media used by an artist. FTIR spectroscopy is also a powerful tool in the studies on degradation products that are formed due to ageing or deterioration of works of art. We attempted to identify such secondary products present in the paint cross section. Cadmium oxalate and a high concentration of zinc palmitate/stearate were detected for the first time with the use of ATR-FTIR imaging technique. These results can complement studies on the conservation issue and provide an insight into understanding the mechanisms of chemical processes that appear in art works.
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
A series of paint cross sections from an oil painting are studied by attenuated total reflection in conjunction with Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX). The imaging modes of both methods were employed to show their potential in the detection of various painting materials and their distribution in the paint cross sections. The goal of this work is to evaluate FTIR and SEM-EDX spectroscopy in order to understand the limitations and strengths of both approaches. It has been revealed that both techniques are complementary in the identification of pigments, extenders and binding media used by an artist. FTIR spectroscopy is also a powerful tool in the studies on degradation products that are formed due to ageing or deterioration of works of art. We attempted to identify such secondary products present in the paint cross section. Cadmium oxalate and a high concentration of zinc palmitate/stearate were detected for the first time with the use of ATR-FTIR imaging technique. These results can complement studies on the conservation issue and provide an insight into understanding the mechanisms of chemical processes that appear in art works.
Carbamazepine polymorphs: Theoretical and experimental vibrational spectroscopy studies
17 January 2013,
08:09:13
March 2013
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
This paper provides a detailed overview on vibrational spectroscopy studies on polymorphic forms of carbamazepine based on literature data followed by new experimental and theoretical results. Raman, FT-MIR and, for the first time, FT-FIR spectra of carbamazepine were measured and interpreted by means of the B3LYP/6-311++G** theoretical calculations combined with the potential energy distribution (PED) analysis. Theoretical spectra of single molecule and dimer were similar in the frequency range of aromatic rings vibrations, whereas bands representing motion of carboxamide group were shifted. Relatively good agreement was found between experimental and theoretical spectra. The PED analysis of the theoretical modes enabled a detailed assignment of most of the experimental bands. Marker bands were identified for carbamazepine polymorphic forms I, III and IV on the basis of Raman and IR measurements. FT-FIR and FT-MIR analyses were much more discriminative than Raman spectra in terms of polymorphs differentiation.
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
This paper provides a detailed overview on vibrational spectroscopy studies on polymorphic forms of carbamazepine based on literature data followed by new experimental and theoretical results. Raman, FT-MIR and, for the first time, FT-FIR spectra of carbamazepine were measured and interpreted by means of the B3LYP/6-311++G** theoretical calculations combined with the potential energy distribution (PED) analysis. Theoretical spectra of single molecule and dimer were similar in the frequency range of aromatic rings vibrations, whereas bands representing motion of carboxamide group were shifted. Relatively good agreement was found between experimental and theoretical spectra. The PED analysis of the theoretical modes enabled a detailed assignment of most of the experimental bands. Marker bands were identified for carbamazepine polymorphic forms I, III and IV on the basis of Raman and IR measurements. FT-FIR and FT-MIR analyses were much more discriminative than Raman spectra in terms of polymorphs differentiation.
A Raman study on the coordination sites and stability of the [Al(formamide)5]Cl3 complex
17 January 2013,
08:09:13
March 2013
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
Raman experiments of aluminum chloride and formamide (FA) solutions in different compositions and temperatures were carried out. Spectral changes provoked by the increase of the salt concentration were observed in different regions. The ν CO and ν CN modes of FA upon complexation were upshifted and suggest that the CONH hybrid (II) is stabilized by Al(III). Bands at 547 and 295cm−1, which are assigned to the ν AlO and ν AlN vibrations, respectively, evidence coordination through both O and N atoms of FA. The quantitative analysis performed at the carbonyl stretching region found 5 FA molecules around this cation, resulting in the formation of the [Al(FA)5]Cl3 complex. Its stability is maintained by whole studied concentration range and up to around 100°C. At higher temperatures, distortions in the FA shell begin occurring and a new component at 356cm−1 is then observed and assigned to the [AlCl4]− complex.
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
Raman experiments of aluminum chloride and formamide (FA) solutions in different compositions and temperatures were carried out. Spectral changes provoked by the increase of the salt concentration were observed in different regions. The ν CO and ν CN modes of FA upon complexation were upshifted and suggest that the CONH hybrid (II) is stabilized by Al(III). Bands at 547 and 295cm−1, which are assigned to the ν AlO and ν AlN vibrations, respectively, evidence coordination through both O and N atoms of FA. The quantitative analysis performed at the carbonyl stretching region found 5 FA molecules around this cation, resulting in the formation of the [Al(FA)5]Cl3 complex. Its stability is maintained by whole studied concentration range and up to around 100°C. At higher temperatures, distortions in the FA shell begin occurring and a new component at 356cm−1 is then observed and assigned to the [AlCl4]− complex.
A multivariate statistical analysis approach to highlight molecular processes in plant cell walls through ATR FT-IR microspectroscopy: The role of the α-expansin PhEXPA1 in Petunia hybrida
17 January 2013,
08:09:13
March 2013
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
Mid-infrared ATR FT-IR microspectroscopy is applied in conjunction with multivariate statistical analysis on petal samples of Petunia hybrida from wild-type and from two transgenic lines in which the PhEXPA1 expansin gene expression was down-regulated and up-regulated, respectively. New insights are given on the role of expansin in the rearrangement of the cell wall polymer network. Measurements are done without any previous sample treatment to preserve the native cell wall structure and natural biological variability. An original combination of data analysis techniques is proposed to highlight molecular processes in plant cells, based on an automated spectra selection procedure, Principal Component Analysis, Wilcoxon rank sum test and heat map data representation.
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
Mid-infrared ATR FT-IR microspectroscopy is applied in conjunction with multivariate statistical analysis on petal samples of Petunia hybrida from wild-type and from two transgenic lines in which the PhEXPA1 expansin gene expression was down-regulated and up-regulated, respectively. New insights are given on the role of expansin in the rearrangement of the cell wall polymer network. Measurements are done without any previous sample treatment to preserve the native cell wall structure and natural biological variability. An original combination of data analysis techniques is proposed to highlight molecular processes in plant cells, based on an automated spectra selection procedure, Principal Component Analysis, Wilcoxon rank sum test and heat map data representation.
Structural studies of copper-containing multicomponent glasses from the SiO2–P2O5–K2O–CaO–MgO system
17 January 2013,
08:09:13
March 2013
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
Multicomponent glasses from the SiO2–P2O5–K2O–MgO–CaO–CuO system acting as slow release fertilizers were synthesized by the melt-quenching technique. The influence of CuO and P2O5 addition on the structure of glasses was evaluated by FTIR, Raman, 31P, and 29Si MAS NMR spectroscopies. The studies showed that the Cu2+ ions displacing Ca2+ ions and Mg2+ ions in the structure of glass prefer to associate with the phosphorus Q1 species, forming the Q0 species with chemically stable POCu bonds. This is accompanied by the reduction of the degree of polymerization of the phospho-oxygen sub-network, with a simultaneous increased degree of polymerization of the silico-oxygen sub-network of the silicate–phosphate glasses.
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
Multicomponent glasses from the SiO2–P2O5–K2O–MgO–CaO–CuO system acting as slow release fertilizers were synthesized by the melt-quenching technique. The influence of CuO and P2O5 addition on the structure of glasses was evaluated by FTIR, Raman, 31P, and 29Si MAS NMR spectroscopies. The studies showed that the Cu2+ ions displacing Ca2+ ions and Mg2+ ions in the structure of glass prefer to associate with the phosphorus Q1 species, forming the Q0 species with chemically stable POCu bonds. This is accompanied by the reduction of the degree of polymerization of the phospho-oxygen sub-network, with a simultaneous increased degree of polymerization of the silico-oxygen sub-network of the silicate–phosphate glasses.
Investigation of medium range order in silicate glasses by infrared spectroscopy
17 January 2013,
08:09:13
March 2013
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
A new decomposition method of infrared spectra which takes into account the configurational and dynamical origins of the disorder allows retrieving structural information on short and medium range orders in potassium silicate glasses. The distribution of tetrahedral units, the occupation of cation sites, the ratio of SiO bond ionicities involving bridging and non bridging oxygen, and a measure of the impact of low frequency floppy modes on the high frequency dynamics are byproducts of the modeling process. The composition dependence of two vibrational modes clearly identified as spectral components signing medium range order, shows that the disruption of the silicate network follows selective schemes. The 3D silica like network completely disappears in glasses with K2O amounts greater than 11mol% and above this threshold a progressive appearance of 2D silicate sheets is evidenced.
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
A new decomposition method of infrared spectra which takes into account the configurational and dynamical origins of the disorder allows retrieving structural information on short and medium range orders in potassium silicate glasses. The distribution of tetrahedral units, the occupation of cation sites, the ratio of SiO bond ionicities involving bridging and non bridging oxygen, and a measure of the impact of low frequency floppy modes on the high frequency dynamics are byproducts of the modeling process. The composition dependence of two vibrational modes clearly identified as spectral components signing medium range order, shows that the disruption of the silicate network follows selective schemes. The 3D silica like network completely disappears in glasses with K2O amounts greater than 11mol% and above this threshold a progressive appearance of 2D silicate sheets is evidenced.
Temperature-dependent Raman spectroscopy studies of phase transformations in the K2WO4 and the MgMoO4 crystals
17 January 2013,
08:09:13
March 2013
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
Temperature-dependent Raman spectroscopy studies of K2WO4 and MgMoO4 polycrystals were performed in order to obtain information about vibrational and structural changes in these materials as a function of temperature. The stability of the monoclinic phase for both K2WO4 and MgMoO4 samples was assessed and our results indicated that this phase is stable in the 295–723K and 300–770K ranges for K2WO4 and MgMoO4, respectively. It was observed that both samples underwent two phase transformations above room temperature. The first phase transformations which occur at about 633K and 640K for K2WO4 and MgMoO4, respectively, is most likely connected with weak tilting and/or rotations of WO4/MoO4 tetrahedral units that lead to a disorder in the oxygen sublattice. Raman spectroscopy data also indicated that K2WO4 and MgMoO4 exhibited a first-order phase transition at around 723K and 770K, respectively, changing from monoclinic to hexagonal symmetry.
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
Temperature-dependent Raman spectroscopy studies of K2WO4 and MgMoO4 polycrystals were performed in order to obtain information about vibrational and structural changes in these materials as a function of temperature. The stability of the monoclinic phase for both K2WO4 and MgMoO4 samples was assessed and our results indicated that this phase is stable in the 295–723K and 300–770K ranges for K2WO4 and MgMoO4, respectively. It was observed that both samples underwent two phase transformations above room temperature. The first phase transformations which occur at about 633K and 640K for K2WO4 and MgMoO4, respectively, is most likely connected with weak tilting and/or rotations of WO4/MoO4 tetrahedral units that lead to a disorder in the oxygen sublattice. Raman spectroscopy data also indicated that K2WO4 and MgMoO4 exhibited a first-order phase transition at around 723K and 770K, respectively, changing from monoclinic to hexagonal symmetry.
Liquid phase dynamics of molten M2S2O7 (M=K, Cs): A temperature dependent Raman spectroscopic study
17 January 2013,
08:09:13
March 2013
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
The dynamics of M2S2O7 (M=K, Cs) pyrosulfate salts in the liquid state is investigated by steady-state Raman spectroscopic experiments performed at temperatures up to 600°C. The symmetric stretching modes of the S2O7 2− ions have been used as probes of the dynamics of these melts. Contrary to the most previous picosecond dynamics studies performed by means of Raman line profile analysis, we have employed in this work an approach that enables the extraction of valuable information concerning short-time dynamics by calculating time correlation functions of vibrational relaxation by fits in the frequency domain. The fitting method used enables the modeling of the real line profiles in a manner that is intermediate between Lorentzian and Gaussian by means of a function, which has an analytical counterpart in the time domain. The vibrational time correlation functions for both molten salts studied are rather adequately interpreted within the assumption of exponential modulation function concerning the environmental modulation in the context of Kubo–Rothschild approach and indicate that the system experiences an intermediate dynamical regime that gets only slower with increasing temperature. Continuous temperature dependence of the dephasing parameters is observed, while the temperature dependence of the dispersion parameter α indicates deviation from the simple liquid model and offers a complete picture of the way a complex liquid attains the condition of a simple one. The evolution of the dispersion parameter is indicative of the reduction of the coherence decay in the perturbation potential as a consequence of local short-lived aggregates. The experimental results are discussed in terms of theoretical models providing insight in the intermolecular coupling mechanisms.
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
The dynamics of M2S2O7 (M=K, Cs) pyrosulfate salts in the liquid state is investigated by steady-state Raman spectroscopic experiments performed at temperatures up to 600°C. The symmetric stretching modes of the S2O7 2− ions have been used as probes of the dynamics of these melts. Contrary to the most previous picosecond dynamics studies performed by means of Raman line profile analysis, we have employed in this work an approach that enables the extraction of valuable information concerning short-time dynamics by calculating time correlation functions of vibrational relaxation by fits in the frequency domain. The fitting method used enables the modeling of the real line profiles in a manner that is intermediate between Lorentzian and Gaussian by means of a function, which has an analytical counterpart in the time domain. The vibrational time correlation functions for both molten salts studied are rather adequately interpreted within the assumption of exponential modulation function concerning the environmental modulation in the context of Kubo–Rothschild approach and indicate that the system experiences an intermediate dynamical regime that gets only slower with increasing temperature. Continuous temperature dependence of the dephasing parameters is observed, while the temperature dependence of the dispersion parameter α indicates deviation from the simple liquid model and offers a complete picture of the way a complex liquid attains the condition of a simple one. The evolution of the dispersion parameter is indicative of the reduction of the coherence decay in the perturbation potential as a consequence of local short-lived aggregates. The experimental results are discussed in terms of theoretical models providing insight in the intermolecular coupling mechanisms.
A study of competitive molecular interaction effects on imprinting of molecularly imprinted polymers
17 January 2013,
08:09:13
March 2013
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
The work herein reports on an approach to obtain molecularly imprinted polymers (MIPs) for Atmer 129, an antistatic added to polyolefins and a previously non imprinted template with intra molecular H-bonding capability. The template–monomer interactions occurring in pre- and post-polymerization media were analyzed by FTIR and ATR-FTIR, respectively. After the prepolymerization study, the synthesis conditions were discussed and suitable porogens and potential template:monomer stoichiometries were suggested. The imprinting efficiency and selectivity of MIPs were evaluated in batch assays by HPLC or UPLC and compared with thermal behavior and morphological characteristics checked by Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM). The best results were obtained for MIPs synthesized at 60°C. A relation between imprinting effect and template shape recognition was suggested by selectivity studies. The major conclusion, which has been drawn from FTIR and DSC studies, is that independently of the H-bonding strength between Atmer 129 and monomer, the template started to crystallize out during the polymerization reaction, thus reducing the imprinting effect.
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
The work herein reports on an approach to obtain molecularly imprinted polymers (MIPs) for Atmer 129, an antistatic added to polyolefins and a previously non imprinted template with intra molecular H-bonding capability. The template–monomer interactions occurring in pre- and post-polymerization media were analyzed by FTIR and ATR-FTIR, respectively. After the prepolymerization study, the synthesis conditions were discussed and suitable porogens and potential template:monomer stoichiometries were suggested. The imprinting efficiency and selectivity of MIPs were evaluated in batch assays by HPLC or UPLC and compared with thermal behavior and morphological characteristics checked by Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM). The best results were obtained for MIPs synthesized at 60°C. A relation between imprinting effect and template shape recognition was suggested by selectivity studies. The major conclusion, which has been drawn from FTIR and DSC studies, is that independently of the H-bonding strength between Atmer 129 and monomer, the template started to crystallize out during the polymerization reaction, thus reducing the imprinting effect.
Highlights
► A study of inter- and intra-molecular interactions in pre- and post-polymerization complex was carried out by FTIR. ► A MIP was developed for a previously nonimprinted target, Atmer 129. ► Atmer 129 is able to form intra- and self-intermolecular H-bonding interactions. ► Atmer 129 started to crystallize out during the polymerization reaction. ► Selectivity results suggested that imprinting could be ascribed to shape recognition.Density functional theory studies on covalent functionalization of single-walled carbon nanotubes with benzenesulfonic acid
17 January 2013,
08:09:13
March 2013
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
The calculated Raman spectra of the covalently functionalized zigzag single-walled carbon nanotubes, f-(n,0)-SWCNTs (n =6–10), with benzenesulfonic acid showed that the radial breathing modes (RBMs) frequencies (ω RBM) of the sidewall functionalized tubes are red shifted in comparison with the frequencies of their non-functionalized counterparts, (n,0)-SWCNTs. It is also observed that this ω RBM red-shift is tube-diameter (d t) dependent, where almost no redshifts are observed for the (10,0)-SWCNT. Moreover, many new Raman bands, which results from the functional group, appear in the low energy region, ranging from 100 to 600cm−1. In the high frequency region, resulting from the functional group, the Raman spectra of the f-(n,0)-SWCNTs exhibited a few new peaks above the tangential bands of the SWCNTs (ranging from 1580 to 1650cm−1), which entirely belongs to the CC stretching, including bending deformation of the CCC bonds, and rock of CH in phenyl group of the benzenesulfonic acid as well as many new Raman peaks dispersed through spectrum. The calculated IR spectra also exhibited many new peaks through spectra of the f-(n,0)-SWCNT when comparing these with corresponding IR spectrum of the isolated nanotube. Furthermore, the calculated vertical singlet-singlet electronic transitions of the f-(n,0)-SWCNTs significantly altered in the optical structure of the nanotube and exhibited charge transfer states for both the functionalized (8,0)- and (12,0)-SWCNTs. The small distances among the calculated dipole-allowed and forbidden electronic energy levels also suggested an internal crossing (IC) processes.
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
The calculated Raman spectra of the covalently functionalized zigzag single-walled carbon nanotubes, f-(n,0)-SWCNTs (n =6–10), with benzenesulfonic acid showed that the radial breathing modes (RBMs) frequencies (ω RBM) of the sidewall functionalized tubes are red shifted in comparison with the frequencies of their non-functionalized counterparts, (n,0)-SWCNTs. It is also observed that this ω RBM red-shift is tube-diameter (d t) dependent, where almost no redshifts are observed for the (10,0)-SWCNT. Moreover, many new Raman bands, which results from the functional group, appear in the low energy region, ranging from 100 to 600cm−1. In the high frequency region, resulting from the functional group, the Raman spectra of the f-(n,0)-SWCNTs exhibited a few new peaks above the tangential bands of the SWCNTs (ranging from 1580 to 1650cm−1), which entirely belongs to the CC stretching, including bending deformation of the CCC bonds, and rock of CH in phenyl group of the benzenesulfonic acid as well as many new Raman peaks dispersed through spectrum. The calculated IR spectra also exhibited many new peaks through spectra of the f-(n,0)-SWCNT when comparing these with corresponding IR spectrum of the isolated nanotube. Furthermore, the calculated vertical singlet-singlet electronic transitions of the f-(n,0)-SWCNTs significantly altered in the optical structure of the nanotube and exhibited charge transfer states for both the functionalized (8,0)- and (12,0)-SWCNTs. The small distances among the calculated dipole-allowed and forbidden electronic energy levels also suggested an internal crossing (IC) processes.
Scanning angle Raman spectroscopy measurements of thin polymer films for thickness and composition analyses
17 January 2013,
08:09:13
March 2013
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
Scanning angle (SA) Raman spectroscopy was used to measure the thickness and composition of polystyrene films. A sapphire prism was optically coupled to a sapphire substrate on which 6–12% (w/v) polystyrene in toluene was spin coated. Raman spectra were collected as the incident angle of the p-polarized, 785-nm excitation laser was varied from 56 to 70°. These angles span above and below the critical angle for a sapphire/polystyrene interface. The thickness of the polystyrene film was determined using a calibration curve constructed by calculating the integrated optical energy density distribution as a function of incident angle, distance from the prism interface and polymer thickness. The calculations were used to determine the incident angle where waveguide modes are excited within the polymer film, which is the angle with the highest integrated optical energy density. The film thicknesses measured by SA Raman spectroscopy ranged from less than 400nm to 1.8μm. The average percent uncertainty in the SA Raman determinations for all films was 4%, and the measurements agreed with those obtained from optical interferometery within the experimental uncertainty for all but two films. For the 1270-nm and 580-nm polystyrene films, the SA Raman measurements overestimated the film thickness by 5 and 18%, respectively. The dependence of the calibration curve on excitation polarization and composition of the polymer and bulk layers was evaluated. This preliminary investigation demonstrates that scanning angle Raman spectroscopy is a versatile method applicable whenever the chemical composition and thickness of interfacial polymer layers needs to be measured.
Publication year: 2013
Source:Vibrational Spectroscopy, Volume 65
Scanning angle (SA) Raman spectroscopy was used to measure the thickness and composition of polystyrene films. A sapphire prism was optically coupled to a sapphire substrate on which 6–12% (w/v) polystyrene in toluene was spin coated. Raman spectra were collected as the incident angle of the p-polarized, 785-nm excitation laser was varied from 56 to 70°. These angles span above and below the critical angle for a sapphire/polystyrene interface. The thickness of the polystyrene film was determined using a calibration curve constructed by calculating the integrated optical energy density distribution as a function of incident angle, distance from the prism interface and polymer thickness. The calculations were used to determine the incident angle where waveguide modes are excited within the polymer film, which is the angle with the highest integrated optical energy density. The film thicknesses measured by SA Raman spectroscopy ranged from less than 400nm to 1.8μm. The average percent uncertainty in the SA Raman determinations for all films was 4%, and the measurements agreed with those obtained from optical interferometery within the experimental uncertainty for all but two films. For the 1270-nm and 580-nm polystyrene films, the SA Raman measurements overestimated the film thickness by 5 and 18%, respectively. The dependence of the calibration curve on excitation polarization and composition of the polymer and bulk layers was evaluated. This preliminary investigation demonstrates that scanning angle Raman spectroscopy is a versatile method applicable whenever the chemical composition and thickness of interfacial polymer layers needs to be measured.
No comments:
Post a Comment