Synthesis and vibrational spectroscopic characterisation of synthetic hydrozincite and smithsonite

Hydrozincite and smithsonite were synthesised by controlling the partial pressure of CO₂. Previous crystallographic studies concluded that the structure of hydrozincite was a simple one. However both Raman and infrared spectroscopy show that this conclusion is questionable. Multiple bands are observed in both the Raman and infrared spectra in the (CO₃)²⁻ antisymmetric stretching and bending regions of hydrozincite showing that the symmetry of the carbonate anion is reduced and in all probability the carbonate anions are not equivalent in the hydrozincite structure. Multiple OH stretching vibrations centred in both the Raman and infrared spectra show that the OH units in the hydrozincite structure are non-equivalent. The Raman spectrum of synthetic smithsonite is a simple spectrum characteristic of carbonate with Raman bands observed at 1408, 1092 and 730 cm⁻¹.     

Synthesis and vibrational spectroscopic characterisation of nickel containing aurichalcite

Raman spectroscopy complimented with supplementary infrared spectroscopy has been used to characterise a synthetic nickel substituted aurichalcite a zinc/nickel hydroxy carbonate, (Zn²⁺, Cu²⁺, Ni²⁺)₅(CO₃)₂(OH)₆. XRD patterns show high orientation and indicate the presence of some minor impurities. The diffraction patterns for the Ni-aurichalcite are well correlated with the standard reference patterns. EDAX analyses indicate variations in chemical composition of Zn/Ni ratios of ∼20:1. The symmetry of the carbonate anion in aurichalcite is C_s and is composition dependent. This symmetry reduction results in multiple bands in both the symmetric stretching and bending regions. The intense band for the Ni-aurichalcite at 1070 cm⁻¹ is assigned to the ν₁(CO₃)²⁻ symmetric stretching mode. Three Raman bands assigned to the ν₃(CO₃)²⁻ antisymmetric stretching modes are observed for Ni-aurichalcite at 1372, 1480 and 1543 cm⁻¹. Multiple Raman bands are observed in the regions from 800 to 850 cm⁻¹ and 720 to 750 cm⁻¹, and are attributed to ν₂ and ν₄ bending modes confirming the reduction of the carbonate anion symmetry in the aurichalcite structure. This research proves that nickel containing aurichalcites can be synthesised in the laboratory thus mimicing the natural nickel containing aurichalcites.     

Infrared and Raman spectroscopic investigation of crosslinked polystyrenes and radiation‐grafted films

The crosslinking of functionalized polystyrene resins is often of critical importance in determining resin properties and performance in the application of these materials as membranes and supports. In this investigation model systems are developed for quantifying the infrared and Raman spectroscopic properties of copolymers based on poly(styrene‐co‐divinylbenzene). Analytical curves appropriate for the quantification of para‐ and metasubstituted species and pendant double bonds are reported, and corrections to previously reported spectroscopic assignments and analytical methods are made. The usefulness of these two analytical methods in characterizing radiation‐grafted films and commercial copolymers is compared, and typical characterization results are given. The relative concentrations of the species found in the grafted films are quite different from their concentrations in the grafting solution, and empirical relationships between the two are developed. In addition, the graft composition varies as a function of the base polymer film thickness and type and the penetration depth in the grafted film. Radiation‐grafted films are more highly crosslinked in their near surface regions, and thinner films are more extensively crosslinked. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 59–75, 2004     

Nondestructive analysis of ancient Egyptian funerary relics by Raman spectroscopic techniques

The non-destructive Raman spectroscopic analysis of a range of ancient Egyptian funerary artefacts has been undertaken with a view to establish the identification of the pigment composition and nature of the interaction with the substrate. The specimens date from the New Kingdom to the Graeco-Roman period, ca. 3900-1800 years b.p. In this study a comparison has also been effected between the near-infrared and red excitation wavelengths for the characterisation of these materials. A particular problem for Raman analysis of these artefacts was found in the application of resin or organic compounds to the surface or substrata, as colourants or to aid adhesion of the pigments, and degradation of the resins with burial environment and exposure has resulted in large fluorescent backgrounds. Nevertheless, useful information has been obtained which assists in the interpretation of the construction of some of the artefacts.     

Rietveld refinement and vibrational spectroscopic study of alunite from el Gnater, central Tunisia

The crystal structure of alunite (K_0.72,Na_0.28) Al₃(SO₄)₂(OH)₆ from El Gnater, central Tunisia, is refined by the Rietveld method. Raman and infrared data of this mineral are also given in order to provide some further information about the mineralogy and chemistry of this alunite. The crystal system is trigonal, space group R $ \bar 3 The crystal structure of alunite (K_0.72,Na_0.28) Al₃(SO₄)₂(OH)₆ from El Gnater, central Tunisia, is refined by the Rietveld method. Raman and infrared data of this mineral are also given in order to provide some further information about the mineralogy and chemistry of this alunite. The crystal system is trigonal, space group R m, with a = 6.9834(4) ? and c = 17.0899(11) ?. Final Rietveld refinement converges to R _p = 0.16, R _wp = 0.16, and R _Bragg = 0.07. In the alkalic site, the occupancy of potassium and sodium is refined to 72 and 28%, respectively. The Raman and infrared spectra are investigated in order to improve previous assignments of the observed frequencies, especially for tetrahedral and octahedral vibration and OH group, which are discussed on the basis of unit-cell group analysis and by comparison with previously observed wavenumbers of natrojarosite and synthetic alunite. The text was submitted by the authors in English.     

Investigation of selectively substituted monosaccharides by the method of vibrational spectroscopy and X-ray analysis

The influence of steric factors on the formation of vibrational spectra of carbohydrates was illustrated by the example of selectively substituted monosaccharides. We consider compounds in which the difference and similarity of vibrational spectra are largely determined by the difference and similarity of the geometry of their molecular base (the molecule's skeleton). At the same time, in the case of selectively substituted nitrates of methyl-β- -glucopyranoside, the skeletal bases of which are identical, with differences in the localization site of volumetric substituents and their total number, or in rotational isomers (conformations) of the lateral nitrate groups, their Fourier Raman spectra are different over a wide spectral range. It is concluded that steric factors and the position of volumetric substituents of hydroxyls produce an exceptionally important effect on the formation of vibrational spectra of carbohydrates.     

Investigation of patinas formed on Chinese bronzes using modern multianalytical techniques

This paper presents an integrated study on nine natural Chinese bronze patinas without causing any damage to the bronze substrates, employing five modern analytical techniques including X‐ray diffraction (XRD), Fourier transform infrared (FT‐IR) and Raman spectroscopy, inductively coupled plasma atomic emission spectroscopy (ICP‐AES), and inductively coupled plasma mass spectrometry (ICP‐MS). Two artificial Chinese bronze patinas were also investigated by the same techniques for comparative purposes. As a result, XRD determined the chemical compositions of all selected samples and showed that the primary compound was malachite in natural soil environment under the general situation. Meanwhile, some interesting corrosion products such as gerhardtite and free copper were also observed. Three groups were classified according to the XRD results in order to provide a deeper insight into their spectroscopic characterization. Spectroscopic data of these patinas from FT‐IR and Raman spectroscopy are shown and interpreted in detail. ICP‐AES and ICP‐MS analyses provided valuable quantitative information, and made the study of the patinas more profound. Furthermore, all analytical results indicated that bronze patinas are extremely complex by virtue of the storage environment and their substrate alloys. The natural samples were rather heterogeneous and the artificial samples, especially the sample formed in the laboratory, were rather homogeneous of which the chemical constituents could be well defined. Copyright © 2007 John Wiley & Sons, Ltd.     

Application of vibrational spectroscopy techniques for material identification from fire debris

The primary goal of this research is to demonstrate the use of vibrational spectroscopy techniques as a tool for the identification of materials post fire. This paper discusses the use micro-Raman spectroscopy and ATR-FTIR to identify materials found in fire debris. The polymeric materials under study were high density and low density polyethylene (HDPE and LDPE), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA) and cotton. These are commonly materials found in households around the world, their identification from the debris provides useful forensic information on the spatial distribution of fuels in a fire compartment, thus allowing for accurate analysis and modelling. Earlier work has established Raman spectroscopy to be a very good tool for material identification post fire. The addition of ATR-FTIR spectroscopy as a technique in developing this novel tool for identification of materials post fire has established vibrational spectroscopy in the area of fire investigation. This study indicated that the limitations associated with Raman spectroscopy in post fire identification, could be made insignificant by the strengths of ATR-FTIR spectroscopy and vice versa. To further establish the validity of this identification process principal component analysis was used to discriminate between the spectrum of the burnt materials and an error analysis computed. Both techniques demonstrated that identification could be done with very minimal confusion between the materials studied.     

高灰煤中矿物质及碳结构的振动光谱分析

利用傅里叶变换红外光谱(FT-IR)、拉曼光谱和X射线衍射(XRD),分析了广西合山煤(GX)和平顶山煤(PD)及其酸洗煤的矿物质组分和碳结构。FT-IR谱图显示,GX和PD原煤的高岭石含量最为丰富,其次是石英和方解石,由二阶导数红外谱图发现,煤中还存在云母、蛇纹石、石膏和碱性长石。此外,从FT-IR谱图出现的三个层间水OH伸缩振动峰(3 695、3 651和3 619 cm^-1)判断煤中高岭石的结晶度不高。酸洗煤的FT-IR和XRD分别显示出清晰的芳香C=C官能团峰(1 600 cm^-1)和微晶碳(002)衍射峰;原煤的FT-IR和XRD都表明,矿物质完全掩盖了碳的信息。尽管如此,原煤及酸洗煤的拉曼谱图显示出清晰的缺陷碳峰(D峰)和石墨碳峰(G峰),而矿物质的信息完全被信号更强的碳峰掩盖。酸洗处理对煤的碳结构有较弱的影响,酸洗煤的碳结构有序度略低于原煤。     

Vibrational Spectroscopic and Mechanical Investigation of Carbon Nanotube-Reinforced Styrene-Butadiene Rubbers

This paper reports investigations carried out on elastomeric matrices based on a styrene-butadiene copolymer filled with multiwall carbon nanotubes. Stress-strain measurements of the composites demonstrate that carbon nanotubes bring significantly improvements in the mechanical properties with regard to the pure polymer. Raman spectroscopy, which is one of the most extensively employed methods for the characterization of carbon materials, has been applied for the analysis of the dependence of the Raman spectra on the nanotube content and on application of an uniaxial deformation. The results reveal a negligible stress transfer suggesting a weak interface between the tubes and the polymer chains.     

Investigation of silicate mineral sanidine by vibrational and NMR spectroscopic methods

Sanidine, a variety of feldspar minerals has been investigated through optical absorption, vibrational (IR and Raman), EPR and NMR spectroscopic techniques. The principal reflections occurring at the d-spacings, 3.2892, 3.2431, 2.9022 and 2.6041 Å confirm the presence of sanidine structure in the mineral. Sanidine shows five prominent characteristic infrared absorption bands in the region 1200–950, 770–720, 590–540 and 650–640 cm⁻¹. The Raman spectrum shows the strongest band at 512 cm⁻¹ characteristic of the feldspar structure, which contains four membered rings of tetrahedra. The UV–vis–NIR absorption spectrum had strong absorption features at 6757, 5780 and 5181 cm⁻¹ due to the combination of fundamental OH– stretching. The bands at 11236 and 8196 cm⁻¹and the strong, well-defined band at (30303 cm⁻¹ attest the presence of Fe²⁺ and Fe³⁺, respectively, in the sample. The signals at g = 4.3 and 3.7 are interpreted in terms of Fe³⁺ at two distinct tetrahedral positions Tl and T2 of the monoclinic crystal structure The ²⁹Si NMR spectrum shows two peaks at −97 and −101 ppm corresponding to T2 and T1, respectively, and one peak in ²⁷Al NMR for Al(IV).     

UV-Raman and NMR spectroscopic studies on the crystallization of zeolite A and a new synthetic route

UV-Raman and NMR spectroscopy, combined with other techniques, have been used to characterize crystallization of zeolite A. In situ UV-Raman spectroscopy shows that the starting gel for crystallization of zeolite A contains a lot of four-ring (4R) building units and the appearance of six-ring (6R) building blocks is the signal for crystal formation. (29)Si NMR spectroscopy results suggest that the starting gel is double four-ring (D4R) rich and during crystallization of zeolite A both α and β cages appear. (27)Al NMR spectroscopy results indicate the absence of Al (2Si) species in the starting gel, suggesting the absence of single 4R building units in the starting gel. Furthermore, composition analysis of both solid and liquid samples shows that the solid rather than liquid phase predominates for the crystallization of zeolite A. Therefore, it is proposed that the crystallization of zeolite A mainly occurs in the solid phase by self-assembly or rearrangement starting from the zeolite building units mainly consisting of D4R. The essential role of D4R is directly confirmed by successful conversion from a solution of D4R to zeolite A in the presence of NaCl, and the importance of solid phase is reasonably demonstrated by the successful synthesis of zeolite A from a dry aluminosilicate gel. By considering that the solid phase has a major contribution to crystallization, a novel route was designed to synthesizing zeolite A from the raw materials water glass (Na(2)SiO(3) in aqueous solution) and NaAlO(2), without additional water and NaOH; this route not only simplifies synthetic procedures, but reduces water consumption.     

Experimental and calculated vibrational spectra and structure of Ziegler-Natta catalyst precursor: 50/1 comilled MgCl2-TiCl4

The vibrational Infrared and Raman Spectra of a MgCl₂-TiCl₄ Ziegler-Natta catalyst precursor with a 50/1 MgCl₂/TiCl₄ ratio have been recorded. The Raman spectrum of this catalyst precursor, in the range 50-500 cm⁻¹, shows clear scattering lines which can be assigned to the complex MgCl₂-TiCl₄, well separated from those of the initial species. Analogous, but less clear signals can be found in the infrared spectrum. Vibrational symmetry analysis and quantum chemical calculations of suitable models of MgCl₂-TiCl₄ complex have been made for the interpretation of the experimentally recorded spectra. The observed spectroscopic signals can be explained in terms of the existence of only one type of MgCl₂-TiCl₄ complex where the TiCl₄ molecules are complexed on the MgCl₂ along the (110) lateral cuts in a local C_2v symmetry with the Ti atoms in an octahedral coordination.     

Raman spectroscopic study of magnetite (FeFe2O4): a new assignment for the vibrational spectrum

A detailed Raman study on natural magnetite has been carried out. Raman spectra show four out of the five predicted Raman bands located at 668, 538, 306, and 193 rcm⁻¹. The location of the fifth, unobserved phonon mode, is inferred from spectra of other ferrites at 450-490 rcm⁻¹. Polarized experiments on an oriented single crystal provide a new interpretation of the Raman spectrum with the following assignment for symmetries of the observed modes: A_1g for 668 rcm⁻¹, E_g for 306 rcm⁻¹, and T_2g for 538, 193, and 450-490 rcm⁻¹. The results are compared with those of the earlier Raman studies and possible explanations for the discrepancies are suggested. Some of the inconsistencies can be resolved by considering the effect of oxidation of magnetite during the Raman experiments.     

Analysis of biosensors by chemically specific optical techniques. Chemiluminescence-imaging and infrared spectroscopic mapping ellipsometry

The standard methods currently used to read out microarrays are fluorescent and chemiluminesent imaging techniques. These methods require labeling of a component with a marker and, usually, only the concentration of the marker molecule is detected. A label-free imaging method that also enables quantitative spectroscopic analysis of the composition and component interaction would be of great advantage. In this article it is shown for the first time that IR mapping ellipsometry enables label-free imaging of a biochip before and after incubation with peptide solution. The measurements prove that IR ellipsometry is a sensitive tool for laterally resolved identification of the different materials and determination of the composition of a biochip. The lateral resolution required was achieved by using radiation from an infrared synchrotron beamline.      

Thermal decomposition of humboldtine: A high resolution thermogravimetric and hot stage Raman spectroscopic study

Evidence for the existence of primitive life forms such as lichens and fungi can be based upon the formation of oxalates. These oxalates form as a film like deposit on rocks and other host matrices. Humboldtine as the natural iron(II) oxalate mineral is a classic example. Thermogravimetry coupled to evolved gas mass spectrometry shows dehydration takes place in two steps at 130 and 141°C. Loss of the oxalate as carbon dioxide occurs at 312 and 332°C. Dehydration is readily followed by Raman microscopy in combination with a thermal stage and is observed by the loss of intensity of the OH stretching vibration at 3318 cm^-1. The application of infrared emission spectroscopy supports the results of the TG-MS. Three Raman bands are observed at 1470, 1465 and 1432 cm^-1 attributed the CO symmetric stretching mode. The observation of the three bands supports the concept of multiple iron(II) oxalate phases. The significance of this work rests with the ability of Raman spectroscopy to identify iron(II) oxalate which often occurs as a film on a host rock.This revised version was published online in November 2005 with corrections to the Cover Date.     

Quantum chemical calculation of vibrational spectra of large molecules--Raman and IR spectra for Buckminsterfullerene

In this work we demonstrate how different modern quantum chemical methods can be efficiently combined and applied for the calculation of the vibrational modes and spectra of large molecules. We are aiming at harmonic force fields, and infrared as well as Raman intensities within the double harmonic approximation, because consideration of higher order terms is only feasible for small molecules. In particular, density functional methods have evolved to a powerful quantum chemical tool for the determination of the electronic structure of molecules in the last decade. Underlying theoretical concepts for the calculation of intensities are reviewed, emphasizing necessary approximations and formal aspects of the introduced quantities, which are often not explicated in detail in elementary treatments of this topic. It is shown how complex quantum chemistry program packages can be interfaced to new programs in order to calculate IR and Raman spectra. The advantages of numerical differentiation of analytical gradients, dipole moments, and static, as well as dynamic polarizabilities, are pointed out. We carefully investigate the influence of the basis set size on polarizabilities and their spatial derivatives. This leads us to the construction of a hybrid basis set, which is equally well suited for the calculation of vibrational frequencies and Raman intensities. The efficiency is demonstrated for the highly symmetric C(60), for which we present the first all-electron density functional calculation of its Raman spectrum.     

Mössbauer, vibrational spectroscopic and solution X-ray diffraction studies of the structure of iron(III) complexes formed with indole-3-alkanoic acids in acidic aqueous solutions

The chemical reactions between iron(III) and indole-3-acetic (IAA), -propionic (IPA), and -butyric (IBA) acids were studied in acidic aqueous solutions. The motivation of this work was that IAA is one of the most powerful natural plant-growth-regulating substances (phytohormones of the auxin series). Mössbauer spectra of the frozen aqueous solutions of iron(III) with indole-3-alkanoic acids as ligands (L), showed parallel reactions between Fe³⁺ and the ligands. Partly, it resulted in a complex formation which precipitated in aqueous solution and partly, in a redox process with iron(II) and the oxidised indole-3-alkanoic acids as products. The Mössbauer parameters of the Fe²⁺ species suggested a hexaaquo coordination environment. The chemical composition and coordination structure of the precipitated complexes were investigated using elemental analysis, Mössbauer spectroscopy, Fourier transform infrared (FTIR) and Raman spectroscopic techniques. The complexes were soluble in some organic solvents. So, Mössbauer, FTIR and solution X-ray diffraction measurements were carried out on the solution of complexes in acetone, hexadeutero acetone and methanol, respectively. The data obtained supported the existence of the μ-dihydroxo-bridging structure of the dimer: [L₂Fe<(OH)₂>FeL₂] (where L is indole-3-propionate, -acetate or -butyrate).     

Towards identification of traditional European and indigenous Australian paint binders using pyrolysis gas chromatography mass spectrometry

We report a pyrolysis GC–MS method capable of analysing Indigenous Australian and European binders typically used in the manufacture of culturally important painted works. Eleven different traditional European binders and ten different Indigenous Australian binders were examined. The method allows discrimination between highly complex and impure lipid, resin, polysaccharide, wax, and protein-based binders. Each was found to have characteristic pyrolysis products that were unique to the binder material, demonstrating the potential for differentiation of these binders on Australian Aboriginal artworks towards identification and conservation of cultural heritage.     

Conformational analysis of 2-oxo(thio)-1,3,2-dioxaphosphorinanes with a P-H bond from vibrational spectroscopic data

The steric structure of four 2-hydro-2-oxo(thio)-1,3,2-dioxaphosphorinane (DOP) molecules has been studied by means of Raman and IR spectroscopy. A characteristic feature of these compounds is the presence of a hydrogen atom as a "light" exocyclic substituent whose vibration is not mixed with the vibrations of the molecular skeleton.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center, Russian Academy of Sciences, 420083 Kazan, Tatarstan, Russia. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 12, pp. 2725–2730, December, 1992.