Journal of Raman Spectroscopy

Parametric models can be a powerful means of modeling the Raman spectra of different classes of materials. Such calculations would be of significant help for both prediction and interpretation of the spectrocopic data of complex systems. The review discusses parametric models for the Raman intensity calculations with a particular emphasis on the bond polarizability model, its parameters and their transferability.

Multivariate analysis techniques for Raman imaging are outlined. The distributions of chemical components within tablets are revealed by factor analytic techniques. The information derived from the data analysis brings useful insight into building a mechanistic model for understanding complex phenomena studied by Raman imaging.

A review of performance of quantum computational methods is made in the prediction of purines and pyrimidine wavenumbers with a focus on density functional theoretical methods. B3LYP emerges as the functional of choice and predicts correct trends even with modest basis sets. Going ahead, taking solvent environment into account will be needed for improvement.

Two-dimensional correlation spectroscopy (2DCoS) has become a popular analytical tool applicable to a broad range of science problems. This review article provides a critical survey of recent protein studies using the 2DCoS Raman approach. Common misconceptions and potential pitfalls in the interpretation of 2D correlation data are also analyzed, and how some of the ‘artifacts’ of the 2DCoS approach in the reality turn into the strength of the method is demonstrated.

A cancerous cell line and a benign cell line were investigated by Raman spectroscopy. Applying supervised classification methods enabled a diagnosis routine with 99.11% acuracy. Special care was taken on the evaluation of the classification model in order to ensure an identification ability of the model. As a side effect it was possible to map the DNA/RNA distribution in the Raman images.

A review is presented on important developments published within the Journal of Raman Spectroscopy during 2008. This third overview again highlights advances in the field of research, provides readers of JRS with introductions to developments within the various sub-fields of Raman spectroscopy and reflects the trends of research of the Raman community.

Molecular structure of the sclerotic dentin in noncarious cervical lesions (NCCLs) including both the inorganic phase and organic phase has been investigated using Raman spectroscopy. It has been found that NCCL sclerotic dentin is hypermineralized with the mineral/matrix ratios 2–3 times higher than those of normal dentin, which is caused by both the increase of mineral content and decrease of organic matrix (collagen) content in the sclerotic dentin.

Raman spectra of metauranospinite complemented with infrared spectra were studied. Observed bands were assigned to the stretching and bending vibrations of (UO₂)²⁺ and (AsO₄)³⁻ units and of water molecules. UO bond lengths in uranyl and OH···O hydrogen bond lengths were calculated from the Raman and infrared spectra.

The number of Raman- and infrared-active modes of graphene and graphene layers is given. Wavenumbers of optically active modes are theoretically investigated as a function of number of layers within fifth-nearest-neighbor force-constant approach. The calculated results reproduce well the experimental data and clearly give the relation that ω_G = 1581.6 + 11/(1 + n^1.6).

Infrared spectra at 300 and 77 K and Raman spectra at 300 K of the valpromide (Vpd), N-substituted derivatives: N-ethylvalpromide (Etvpd), N-isopropylvalpromide (Ipvpd) and the N,N-disubstituted derivative: N,N-dimethylvalpromide (Dmvpd) with antiepileptic activity have been measured and analyzed with results derived from computational chemistry calculations. In agreement with theoretical predictions, experimental data indicate that while in the Etvpd, Dmvpd and Ipvpd there are four different conformational co-existing components Etvpd: TTCG⁺, TCCG⁻, TTTC, G⁺G⁺C G⁺; Dmvpd: TTCC, G⁻TTA⁺, G⁺A⁻TC, G⁺A⁻C A⁺; Ipvpd: TTCT, TCCT, TCCC, G⁻TTT, in the Vpd there are only three distinct stable conformations of C₁ symmetry group: TTC, TCT, G⁺G⁺T.

FT-Raman and FT-IR spectra of anilinium sulfate were recorded and analyzed. The surface-enhanced Raman scattering was recorded from a silver electrode. The vibrational wavenumbers of the title compound have been computed using the HF/6-31G* basis and compared with the experimental data. The presence of amino and sulfate group vibrations in the SERS spectrum reveal the interaction between amino and sulfate groups with the silver surface.

Raman spectra of pseudojohannite were studied and related to the mineral structure. Observed bands were assigned to the stretching and bending vibrations of (UO₂)²⁺ and (SO₄)²⁻ units and of water molecules.

Vibrational spectroscopic studies and calculations using density functional theory allowed the assignment of a number of normal modes of NLO crystal ethyl-3-(3, 4-dihydroxyphenyl)-2-propenoate. The nonlinear optical response was measured experimentally.

The photopolymerization in water of a carboxy-ended diacetylene chemisorbed onto gold and silver nanoparticles through the COOH group has been investigated by means of spectroscopic techniques. Raman spectra provided the more detailed information about the polymer form and the preferred conformation of the alkyl side chains.

The surface-enhanced Raman scattering technique explores sulfanilamide monolayers on the silver surface formed under different pH values. Spectral assignments were conducted based on BLYP/6-311G calculations. The fully protonated sulfanilamide on the surface adopted the direct adsorption of N¹³H₂, leading to benzene ring perpendicular and N⁷H₂ and S¹⁰O₂ near the surface, while the completely deprotonated sulfanilamide attached on the surface via N⁷H₂ with N¹³H₂ and S¹⁰O₂ away from the surface.

The vibrational properties of wild-type (b) and selenomethionine (SeMet) substituted (a) protein SOUL crystals have been investigated by Raman spectroscopy. The experimental Raman spectra of pure methionine (Met) and SeMet have been acquired and compared with the Raman intensities computed using ab initio calculations, in order to assign some Raman peaks identified as reliable markers revealing the replacement of Met with SeMet in SOUL protein. A quantitative evaluation of relative amount of SeMet replacement in the crystals of protein SOUL was achieved.

A method for indirect Raman microspectroscopy to measure stresses with a lateral resolution in the submicrometer range at a laboratory scale is proposed. The method encompasses the crystallization of an amorphous silicon layer by local laser annealing and its subsequent usage as a strain gage. Stresses in an aluminum thin film were determined as a function of temperature. In addition to the average stress, the stress distribution could be monitored.

Micro-Raman spectroscopy was used to investigate the hydration rate and bioactivity properties of a calcium silicate cement (wTC) and a phosphate-doped cement (wTC-TCP) in DPBS and HBSS solutions, at 37 °C. The latter showed a higher bioactivity in both media, suggesting that the phosphate dopant can act as nucleation agent accelerating the kinetics of apatite formation.

The temperature-induced line-shift of individual Raman lines in silicon carbide (SiC) was characterized in the temperature range of 3 to 112°C. The line-shift is linear with temperature and also depends on the scattering phonon wavenumber. Thermal calibration factors for various Raman lines in SiC are reported for application in the spectroscopic device characterization.

In this paper, we demonstrate the ability of portable Raman spectroscopy and spatially offset Raman spectroscopy (SORS) to rapidly identify real and fake ivory samples. Application of the SORS technique allows the interrogation of biomaterial samples through materials in which conventional Raman spectroscopic instrumentation cannot penetrate.

The mechanism of recrystallization in epitaxial GaN film, introduced by indentation technique, is probed by lattice dynamic studies using Raman spectroscopy. ‘Pop-in’ bursts in loading lines indicate nucleation of dislocations and climb of dislocations, setting in plastic motion of lattice atoms under stress field for the initiation of the recrystallization process. A planar defect migration mechanism that evolves with vacancy migration is considered as the rate-limiting factor for the dislocation dynamics initiating the recrystallization process in GaN.

Synthesis of Ti-PEG polymers and their transformation to nanocrystalline anatase TiO₂ at low temperature. This work presents (1) the chemical reactivity of PEG with Ti(OⁿBu)₄, (2) the isolation and identification of the titanium–PEG hybrid materials and (3) the mechanistic aspects involved in the formation of anatase NC-TiO₂

The Qⁿ speciation of binary cesium silicate glasses was studied by Raman spectroscopy. A method to extract the equilibrium constant from a set of Raman spectra is presented and the algorithm is given (Supplementary Information).

Brillouin scattering and heat capacity studies of bis(guanidinium)zirconium bis(nitrilotriacetate) hydrate were performed. The analysis of the acoustic anomalies revealed that the most pronounced anomalies at 290 K correspond to a second-order, displacive, cell-multiplying phase transition.

Raman spectra of brandholzite Mg[Sb(OH)₆]·6H₂O were studied, complemented with infrared spectra, and related to the structure of the mineral. Observed Raman and infrared bands are connected with O-H···O hydrogen bonds and their lengths 2.72, 2.79, 2.86, 2.88 and 3.0 Å (Raman) and 2.73, 2.83 and 3.07 Å (infrared).

The combined use of micro-Raman, FTIR, WDXRF, and microscopic examination enables us to investigate and determine pigments and decoration applied to a wood-based lacquer painting screen from the Tomb of Si-ma Jin-long, Shanxi Province, central China, made by Chinese craftsmen in the 5th century. Four major colors are successfully identified by spectroscopic analyses; besides, a preliminary discussion of the decoration is also presented.

Raman spectra of the liquid and solid methylcyclohexane and the infrared spectra of the gas and solid methylcyclohexane have been recorded, and the observed vibrational wavenumbers, depolarization ratios, and their intensities have been measured and compared with the corresponding predicted values and a full vibrational assignment has been made. The average ab initio predicted differences in energy between the more stable equatorial form and the less stable axial conformer are compared with a temperature-dependent study of the Raman liquid.

The effects of the electron-phonon coupling and π-electron confinement in linear carbon chains are interpreted on the basis of Raman wavenumbers, bond length alternation and electronic gap. The correlations among these quantities are shown on the basis of a tight-binding model. An intepration of experimental data and insights on the physical properties of polyynes are presented.

Using DFT modelling and multivariate curve resolution, pure component Raman spectra of the various protonated forms of HEDP were obtained and assigned. Evidence for strong hydrogen bonding at low pH in solution was also observed in the data set.

We provide direct visual evidence for chemical enhancement of surface-enhanced resonance Raman scattering via charge transfer at the Au₂₀–pyrazine–Au₂₀ junction. Charge difference densities reveal visually that there are five kinds of charge transfer.

The colour of red flashed medieval stained glasses and of their 19th century copies is obtained exploiting the surface plasmon resonance of copper nanoparticles. The comparison of their Raman signatures for different laser excitations in the light of previous model materials offers a way to retrieve some information on their production technology.

The complete assignment of the vibrational spectra of complex molecular crystals can be achieved by summing up pair wise interactions, as illustrated for nitrofurantoin anhydrous polymorphs.

The mechanisms of red lead degradation in a medieval Portuguese manuscript, Lorvão Apocalypse (1189), were studied by µ-Raman and µ-X-ray diffraction, and identified unequivocally, galena (PbS) as the degradation product of red lead. The presence of orpiment and its influence on the degradation mechanism was assessed.

The laser excitation wavelength is an important parameter in obtaining Raman spectra from drugs-of-abuse. This article compares the effect of near infrared wavelengths, 785 nm, using both benchtop and portable instrumentation and benchtop 1064 nm on the Raman spectra of seized drugs-of-abuse.

The SERS spectra of syringic and trans-coumaric acid chemically adsorbed onto silver colloids are reported. The formation of the silver complex at the nanostructure surface is supported by the results of density functional theory (DFT) calculations for the salts.

The experimental SERS spectra of pyridine on several metallic surfaces were compared to the transition metal complexes normal Raman and to the calculated Raman spectra of model clusters M₄(py) and M₄(α-pyridil), for M = Ag, Fe, Co or Ni. The complexes and calculated M₄(py) spectra are similar to the experimental SERS spectra, confirming the molecular adsorption of pyridine on the surface of the metallic electrodes, excluding the formation of adsorbed α-pyridil species.

Nine different extremely halophilic archaeal strains, which had been embedded in laboratory-made halite crystals in order to simulate evaporitic conditions, have been measured by FT-Raman spectroscopy at 1064 nm and dispersive micro Raman spectroscopy at 514.5 nm. The spectra showed prominent peaks at 1507, 1152 and 1002 cm⁻¹ which are attributed to haloarchaeal C₅₀ carotenoid compounds (mainly bacterioruberins).

Adsorption for 4-MBA molecules on TiO₂ NPs was studied mostly by SERS, as well as UV-vis, at different pH values as well as under different temperatures and concentrations. The results show that the 4-MBA are bonded to the TiO₂ simultaneously through the sulfur atoms and COO⁻ groups at neutral or alkaline pH, however, simply through the sulfur atom at acidic pH. The 4-MBA possess high adsorptive stability on TiO₂ at comparatively high temperature (150 °C), and concentration-dependent SERS experiments show that the saturated concentration for 4-MBA adsorbed on TiO₂ is about 10⁻³ M in natural case (pH = 6).

Confocal Raman microscopy has been applied to the detection of explosives and their precursors in situ on undyed natural and synthetic fibres as well as coloured textiles. Despite the presence of spectral bands arising from the natural and synthetic polymers and dyed textiles, the explosive substances could be identified by their characteristic Raman bands. Raman spectra of the explosives on clothing were readily obtained without sample preparation and with no alteration of the evidential material.

Polarized Raman spectroscopy is a powerful tool to investigate the structure of thin organic films. In the present study, diindenoperylene (DIP) thin films on (1 × 1)-rutile(110) were prepared via organic molecular beam deposition (OMBD). As a result, the coexistence of at least two DIP film structures is indicated because of the contribution of two Raman modes. Polarized Raman spectra used to characterize the actual orientation showed that the DIP molecules are predominantly present in the so-called σ-configuration (i.e. upright standing).

IR, Raman and SERS spectra of ethyl salicylate were recorded and analyzed. The vibrational wavenumbers of the title compound have been computed using the HF/6-31G* basis and compared with the experimental data. SERS studies suggest a flat orientation of the molecule at the metal surface. The presence of methyl modes in the SERS spectrum indicates the nearness of the methyl group to the metal surface.

Five miniatures by the so-called ‘Spanish Forger’, originally believed to be authentic medieval miniatures, were analysed by Raman microscopy and X-ray fluorescence. Many modern and synthetic pigments were identified along with traditional ones, a result which provides a firm scientific basis for believing that the miniatures are forgeries.

The composition of monolayers formed on silver from mixtures of 4-mercaptobenzoic acid (MBA) and four model aromatic thiols with strong base properties was analysed. Our investigations showed that among studied aromatic bases 4,6-diamino-2-mercaptopyrimidine is the most promising candidate for the formation of mixed monolayers with MBA.

The optical properties of focused ion beam-engraved, perfectly aligned and spatially controlled multi-quantum-well (MQW) InGaN/GaN nanopillars were investigated. Crystalline MQW nanopillars with a diameter of 30–95 nm and high aspect ratios (7:1–16:1) showed a maximum of three-fold enhancement in emission intensity per unit active area. A light-emitting contour map of Taiwan is drawn with a nanopillar structure to demonstrate the site control of the technique adopted in the present study. Raman scattering studies were used to characterize the newly created surfaces.

The infrared and Raman spectra of anhydrous lead oxalate (PbC₂O₄) were recorded and are discussed on the basis of its structural peculiarities and by comparison with the spectra of other metallic oxalates.

The molecular structure of methyl trifluoroacetate (CF₃C(O)OCH₃) has been determined in the gas phase from electron-diffraction data supplemented by ab initio (MP2) and DFT calculations using different basis sets. Experimental data revealed an anti conformation with a dihedral angle θ(CCOC) = 180°. The preference for the anti conformation was studied using the total energy scheme and the natural bond orbital (NBO) partition scheme.

Raman spectroscopy opens a new field in studying the kinetics of cement hydration which cannot be detected by traditional techniques of studying cement (XRD, FTIR). For the first time, stratlingite (C₂ASH₈) and C₃ASH₆ have been identified by Raman spectroscopy. The 3692 and 531 cm⁻¹ signals and 3639 cm⁻¹, respectively, can be assigned to these hydrated phases formed in MK-blended white cement paste.

Plasmon-tunable Ag-core Au-shell nanoparticles have been used to obtain SERS from single-walled nanotubes (SWNTs). By tuning the plasmon resonance close to the Raman excitation wavelength, we obtain significant enhancement in SERS of SWNTs.

Apomorphine (aporphine-10,11-diol) is a non-narcotic derivative of morphine and it is a potent short-acting dopamine agonist at D1 and D2 dopamine receptors, typically used in the treatment of patients with advanced Parkinson's disease. To identify the unknown vibrational spectrum of this compound, apomorphine bare salt and its commercial drug formulation (Apofin) were examined using Raman spectroscopy. Two strong characteristic Raman signals were found that could be used as marker bands: 1589 cm⁻¹ (stretching of the aromatic ring coupled with CH in-plane bending) and at 1302 cm⁻¹ (OH in-plane bending and CH₂ twisting and wagging vibrations).

The IR- and Raman spectra of copper phthalocyanine as well as isotopic shifts upon ¹⁵N substitution in CuPc were investigated. The symmetry of molecular vibrations was determined using polarized Raman spectra of oriented CuPc single crystal. Experimental studies were supported by quantum chemical computations using DFT calculations.

The temperature-dependent Raman spectra of ferroelectric Bi_4−xNd_xTi₃O₁₂ (x = 0, 0.5, 0.85) single crystals were recorded from 100 to 800 K. It was found that there is a critical Nd content x₀ between 0.5 and 0.85. A monoclinic distortion of orthorhombic structure occurs in Bi₄Ti₃O₁₂ crystals at temperatures below 200 K.

Folding of the Cp₂Mo(dmit) complex in various charge-transfer salts is investigated by Raman spectroscopy. Modifications of the electronic structure of the complex and vibrational modes due to folding are analyzed by DFT methods.

Raman and IR spectra of Bi₂W₂O₉, the m = 2 member of cation-deficient Aurivillius phase, have been measured. The results are compared with those obtained for Bi₂WO₆ and some m = 2 members of Aurivillius family of bismuth layered ferroelectrics.

The remnants of the polychromy of Saint Paul's church (16th century, Úbeda, Spain) have been studied using Raman microscopy in combination with SEM-EDX. The pictorial layers, pigments and preparation coatings, as well as degradation processes, were investigated in red (figure) and green areas.

From Raman and infrared spectra of 1,2-bis (trifluorosilyl) ethane (SiF₃CH₂CH₂SiF₃) in various phases and by DFT calculations with various basis sets, the conformers were identified and the spectra interpreted. The anti conformer with C_2h symmetry was 5.6 kJ mol⁻¹ more stable than the gauche conformer (C₂ symmetry) in the liquid, as observed in variable temperature Raman spectra.

This paper reports room-temperature IR and Raman studies and vibrational characteristics of amide and thiocyano groups of R-NH-CO-CH₂-SCN n-alkylamides of thiocyanoacetic acid (R = C₈H₁₇, C₉H₁₉, C₁₂H₂₅ and C₁₄H₂₉). Their molecular structure as well as experimental wavenumbers have been compared with those obtained from DFT chemical quantum calculations. The role of the hydrogen bonds in the stabilization of the structure has been analyzed.

In the present work, altarpieces of the 16th century, attributed to the Ferreirim Masters were analysed by micro-Raman spectroscopy. The preparation consists of chalk and gypsum and the palette was composed of lamp black, azurite, lead white, lead tin yellow (I), goethite, red lead, haematite and vermilion. Indigo was detected in one sample and lead carbonate, bassanite, anhydrite and a degradation product from massicot were found mainly in the panels subjected to high temperatures during a fire occurred in 1954.

A drawback of aspartame (E951) is its relatively low stability at high pH values and at high temperatures, thereby limiting its use. The changes observed in the very strong bands from the 1600–1300 cm⁻¹ spectral region, characteristic to the υ(CO) mode coupled with the NH bending mode, allows to establish the species present in the Raman and SERS solutions at different concentrations and pH values. According to the DFT calculations performed, E951 can give rise to an intramolecular hydrogen bonding network, with lengths in the same range as the hydrogen bonds in the peptide unit moieties.

Enhancements of resonant Raman scattering processes are observed in N-doped ZnO at room temperature. The greatly increased scattering intensity of the longitudinal optical (LO) phonon mainly arises from the defect-induced Raman scattering caused by N doping. The nature of the 1LO phonon at 578 cm⁻¹ is interpreted as a quasimode with mixed A₁ and E₁ symmetry because of the defects formed in the ZnO lattice. Furthermore, the previously neglected impurity-induced two-LO-phonon scattering process is clearly observed in N-doped ZnO.

The Raman spectra of the blue pigment as well as other materials in a blue, white and ‘gold’ 17th century Delft dish were analysed and compared to the blue pigment(s) used in a modern blue-and-white Delft dish, obtained from a tourist shop in Amsterdam in 2004.

The combination soft lithography and a meniscus force deposition technique enabled us to fabricate arrays of metal nanoparticle dimers of controlled morphology over a large area. Experimental results are compared with the results of Mie theory simulations. The presence of hot spots is confirmed through polarization studies and a 10⁹ Raman enhancement factor is measured.

FT-Raman and FT-IR spectra of 4-chloro-2-(3-chlorophenylcarbamoyl) phenyl acetate were recorded and analyzed. The vibrational wavenumbers of the title compound have been computed using the B3LYP/6-31G* basis and compared with the experimental data. The simultaneous IR and Raman activation of the CO stretching mode gives the charge transfer interaction through a π-conjugated path. The assignments of the normal modes are done by Potential Energy Distribution (PED) calculations.

The selective Raman features enable to discriminate between two seawater cultured pearl groups. The difference in the intensities of the CaCO₃ bands of Akoya and South seawater pearls provided a valuable clue for discrimination. The reproducible spectral collection for hard-surfaced and round pearl samples was achieved using the wide area illumination (WAI) scheme.