Raman spectroscopy in the near infrared – a most capable method of vibrational spectroscopy

Raman spectroscopy has enjoyed a dramatic improvement during the last years: The interference by the fluorescence of impurities is virtually eliminated, the sample preparation is considerably easier as for infrared spectroscopy and many applications in routine analytics, quality control and process control in various branches of industry are now possible. It is shown that the up-to-date near-infrared Raman spectrometers now meet most demands for a modern analytical instrument concerning applicability, analytical information and convenience. It can be anticipated that Raman spectroscopy will catch up infrared spectroscopy, the current workhorse of vibrational spectroscopy.     

Influence of crystal size on the electron–phonon coupling in ZnO nanocrystals investigated by Raman spectroscopy

We have synthesized ZnO nanocrystals of different sizes (25–41 nm) using the sol–gel method and characterized them using different techniques such as: transmission electron microscopy (TEM) and X-ray diffraction (XRD). Raman spectra of different sizes of ZnO nanocrystals were recorded at two excitation wavelengths, 514 and 647 nm, in the spectral range 300–1200 cm⁻¹. The vibrational modes were assigned on the basis of group theory analysis. The influence of mean crystallite size on the strength of the electron–phonon coupling is experimentally estimated by the variation of relative intensities of second order Raman band and the first order Raman band for ZnO nanocrystals of different sizes. We found that the intensity ratio of the 2E₂ and 1E₂ Raman bands decreases almost linearly for both excitation wavelengths with decreasing crystallite size, which reveals that the Fröhlich interaction plays a dominant role in the electron–phonon coupling of the ZnO nanocrystals.     

Investigations of the hydrophobic and hydrophilic interactions in polymer–water systems by ATR FTIR and Raman spectroscopy

ATR FTIR and Raman spectra of polymers containing amide groups in the main chain and in the side chain and of the amide low-molecular-weight model compounds in water media were measured. The hydrophobic and hydrophilic interactions of the dissolved compounds with the neighboring water molecules are reflected in the wavenumbers of the CH₃ stretching and of the Amide I and II vibrations. The possibility of the existence of β-sheet-like structures in polypeptides surrounded by water molecules is also discussed.     

In situ surface-enhanced Raman spectroscopy in Li–O2 battery research

Surface-enhanced Raman spectroscopy (SERS) is a highly sensitive vibrational technique to obtain the structural information of chemical species on their surface and interface. In this short article, we briefly review the current research regarding the reaction mechanism and kinetics on the cathode surface of the Li–O₂ battery by in situ SERS observations, including reaction intermediates and products, influence of solvent, discharge/charge mechanisms, and mediation mechanism of redox mediators.     

The application of Fourier-transform Raman spectroscopy to the determination of conformation in poly(ε-caprolactam) chains

The Fourier-transform Raman spectra of various structural forms of poly(ε-caprolactam) have been obtained and the Raman bands characterizing planar and nonplanar conformation of the ε-caprolactam units have been defined. These bands have been used for the investigation of the conformational composition of ε-caprolactam sequences in several ε-caprolactam-butadiene block copolymers.     

“Surface-enhanced Raman spectroscopy studies of the passive layer formation in gold leaching from thiosulfate solutions in the presence of cupric ion”

Complementary electrochemical and spectroscopic techniques were used to characterize the behavior and composition of the passive layer formed at the gold surface in a thiosulfate electrolyte in the presence of cupric ions. Raman studies of three different cationic (calcium, ammonium, and sodium) thiosulfate leaching solutions revealed that the concentrations of thiosulfate, trithionate, sulfate, and tetrathionate remained constant in the bulk solution over a 3-h time period. The initial leaching current densities of these three systems were identical; however, significant differences in the open circuit potentials of these systems were observed. To provide additional information about the nature of the passive layer, gold nanorod array electrodes were fabricated and employed as substrates for studying the species present at the gold–thiosulfate interface using surface-enhanced Raman spectroscopy (SERS). The composition and behavior of the passive layer at the gold–thiosulfate interface greatly differed from those of the bulk solutions. The passive layer consisted primarily of elemental sulfur and sulfide-like species, with thiosulfate and its oxidation products, such as tri- and tetrathionates, as minority components. The nature of the cation (calcium, sodium, or ammonium) of the thiosulfate salt showed no significant effect on the composition of the passive layer at leaching times longer than 100 min. In addition, the presence of cupric ions also had no significant effect on the formation of the passive layer. However, copper is a much better oxidant than oxygen in gold–thiosulfate leaching reactions.     

Use of the Mass Spectrum–Compound Fragment Composition Database in the Determination of the Structure of Organic Compounds

A mass spectral database in which structural formulas are presented as nonisomorphic connected k-vertex fragments (2 k 7) is used for identifying the structure of organic compounds. It is shown with the example of a test sample of 13000 mass spectra of various organic compounds that up to half the fragments of an unknown analyte can be identified in 50% of cases. Relationships between the correctly and erroneously identified data are given.     

Applications of Fourier transform Raman spectroscopy in inorganic chemistry—a considered view

A sudy of a wide variety of coloured main group metal, transition metal coordination and transition metal organometallic complexes using Fourier transform Raman (FT-Raman) spectroscopy has demonstrated a high success rate (ca 50%) with good quality spectra obtained in short periods of time. It is suggested that FT-Raman spectroscopy should now be regarded as a routine spectroscopic tool for use in inorganic as well as organic research and teaching laboratories.     

Use of polyethylene glycol in the process of sol–gel encapsulation of Burkholderia cepacia lipase

Lipases from Burkholderia cepacia were encapsulated using polyethylene glycol (PEG, M _w 1500) at various concentrations (0.5–3.0 %, w/v) as an additive during the sol–gel immobilisation process. Matrixes immobilized in the presence and absences of additives were characterized by thermal analysis [thermogravimetric (TG) and differential scanning calorimetry (DSC)], scanning electron microscopy (SEM), enzymatic activity, and total activity recovery yield (Ya). The addition of PEG increased the activity values, with Ya just above 1.0 % (w/v) in the presence of PEG. The additional of 1.0 % (w/v) PEG increased enzyme activity from 33.98 to 89.91 U g^?1 and the values of recovery yield were 43.0–91.4 %, compared to values of the samples without PEG. PEG enhanced the thermal stability of the matrix structure in the temperature range 50–200 °C, as confirmed by TG and DSC analyses. This was influenced by the presence of water bound to the matrix. The SEM micrographs clearly showed an increase in the number of deposits on the material surface, producing matrices with greater porosity.     

A Raman spectroscopy study of cerium oxide in a cerium–5 wt.% lanthanum alloy

This paper describes a study of a cerium–5 wt.% lanthanum (Ce–5 wt.% La) alloy using Raman spectroscopy and X-ray diffraction (XRD). Examination of the alloy microstructure by optical microscopy and Raman spectroscopy revealed the presence of inclusions which were identified as cerium oxide (CeO₂). The study also highlighted the need to avoid excessive laser power during acquisition of the Raman spectra as this appeared to cause the oxidation of the region being analysed where previously no cerium oxide peak had been detected. The propensity of cerium to oxidise in air results in the formation of a CeO₂ layer on the surface of the alloy. Raman spectroscopy of the oxide layer formed on the alloy after exposure to air for 21 days found that the Raman peak denoting cerium oxide was seen at between 5 and 7 cm⁻¹ lower than the value for CeO₂ (465 cm⁻¹). This is attributed to a combination of a sub-stoichiometric oxide layer and the presence of La in the alloy.     

Structure of the hydration shell of 1,3-dimethyl-2-imidazolidinone according to FT—Raman spectroscopy

Russian Chemical Bulletin - The analysis of the shape of the ν(CO) vibrations of the isotropic Raman band for 1,3-dimethyl-2-imidazolidinone (1) in aqueous solutions and the calculations in...     

Probing the chemical reactivity of interfaces: Investigation on the interaction of dehydroindigo with Laponite by UV–vis,Raman and infrared spectroscopy

In this work, the interaction between dehydroindigo (an intermediary oxidized form of indigo) and Laponite clay was investigated. Dehydroindigo (DHI) has been detected when indigo is adsorbed by clay minerals, but it is relatively unstable and in the presence of water it turns back into indigo. It is, therefore, important to understand the factors that extend its stability and Laponite was chosen because the small aspect ratio implies in a large amount of silanol groups (SiOH) which would thus favor the DHI interaction through hydrogen bonding.A significant bathochromic shift (65 nm) of the DHI π®π* transition band in the visible region and changes in the relative intensities and position of the Raman bands at 1530, 1378 and 1167 cm⁻¹ assigned to ν(NCCN), δ(CN) and ν(CN) respectively, indicate that the interaction is stronger than expected for the van der Waals and polarization forces involved in the external surfaces interactions with the siloxane groups. It was also observed that DHI presents an enhanced photochemical stability when interacting with Laponite. These results indicate that hydrogen bonding between a DHI nitrogen atom and the −SiOH or MOH groups is mainly responsible for the behavior present in the DHI + Lap system.     

Minimum-uncertainty coherent states of the hyperbolic and trigonometric Rosen–Morse oscillators

A mixed supersymmetric-algebraic approach is employed to generate the minimum uncertainty coherent states of the hyperbolic and trigonometric Rosen–Morse oscillators. The method proposed produces the superpotentials, ground state eigenfunctions and associated eigenvalues as well as the Schrödinger equation in the factorized form amenable to direct treatment in the algebraic or supersymmetric scheme. In the standard approach the superpotentials are calculated by solution of the Riccati equation for the given form of potential energy function or by differentiation of the ground state eigenfunction. The procedure applied is general and permits derivation the exact analytical solutions and coherent states for the most important model oscillators employed in molecular quantum chemistry, coherent spectroscopy (femtochemistry) and coherent nonlinear optics.

     

The construction of the Gilmore–Perelomov coherent states for the Kratzer–Fues anharmonic oscillator with the use of the algebraic approach

By applying the algebraic approach and the displacement operator to the ground state, the unknown Gilmore–Perelomov coherent states for the rotating anharmonic Kratzer–Fues oscillator are constructed. In order to obtain the displacement operator the ladder operators have been applied. The deduced SU(1, 1) dynamical symmetry group associated with these operators enables us to construct this important class of the coherent states. Several important properties of these states are discussed. It is shown that the coherent states introduced are not orthogonal and form complete basis set in the Hilbert space. We have found that any vector of Hilbert space of the oscillator studied can be expressed in the coherent states basis set. It has been established that the coherent states satisfy the completeness relation. Also, we have proved that these coherent states do not possess temporal stability. The approach presented can be used to construct the coherent states for other anharmonic oscillators. The coherent states proposed can find applications in laser-matter interactions, in particular with regards to laser chemical processing, laser techniques, in micro-machinning and the patterning, coating and modification of chemical material surfaces.     

Use of Metal Ions for the Estimation of the Efficiency of Antibody–Antigen Interactions

The applicability of Co(II), Ni(II), Fe(III), and Cr(III) ion labels to the immunochemical determination of ribonuclease, Candida albicans, Trichophyton rubrum, and Phoma betaeantigens was studied. The catalytic waves of hydrogen evolution, which occur in transition metal solutions in the presence of protein compounds, were used as analytical signals. The maximum catalytic effect depends on the pH, buffer capacity, and nature of buffer solution and on the nature of antigen to be determined. A new procedure was proposed for the immunochemical determination of the ribonuclease antigen using Co(II) ions as a label. The conditions of the formation and degradation of the antibody–antigen immune complex were found. The linear analytical range for the ribonuclease antigen was 0.005–1.0 mg/mL.     

Growth substrate induced functional changes elucidated by FTIR and Raman spectroscopy in in–vitro cultured human keratinocytes

Non-invasive measurements of cellular function in in vitro cultured cell lines using vibrational spectroscopy require the use of spectroscopic substrates such as quartz, ZnSe and MirrIR etc. These substrates are generally dissimilar to the original in vivo extracellular environment of a given cell line and are often tolerated poorly by cultured cell lines resulting in morphological and functional changes in the cell. The present study demonstrates various correlations between vibrational spectroscopic analyses and biochemical analyses in the evaluation of the interaction of a normal human epithelial keratinocyte cell line (HaCaT) with MirrIR and quartz substrates coated with fibronectin, laminin and gelatin. The findings of this study suggest that there is a correlation between quantitative measurements of cellular proliferative capacity and viability and peak area ratios in FTIR spectra, with replicated differences in similar areas of the observed Raman spectra. Differences in the physiology of cells were observed between the two spectroscopic substrates coated in fibronectin and laminin, but little differences were observed when the cells were attached to gelatin-coated quartz and MirrIR slides. The correlations demonstrate the sensitivity of the spectroscopic techniques to evaluate the physiology of the system. Furthermore the study suggests that gelatin is a suitable coating for use in spectroscopic measurements of cellular function in human keratinocytes, as it provides a material that normalises the effect of substrate attachment on cellular physiology. This effect is likely to be cell-line dependent, and it is recommended that similar evaluations of this effect are performed for those combinations of spectroscopic substrate and cell lines that are to be used in individual experiments.     

Characterization of sol–gel process in the Y–Ba–Cu–O acetate–tartrate system using IR spectroscopy

Systematic investigation of sol–gel process in the Y–Ba–Cu–O acetate–tartrate system was performed using IR spectroscopy. Different values of synthesis parameters (temperature and duration of inorganic polymerization reactions, evaporation temperature and evaporation time during gelation) were used, and significant influence in some cases on superconducting characteristics of the oxide ceramics of composition YBa₂Cu₄O₈ was observed. Characterization by IR spectroscopy and thermogravimetric analysis, revealed the difference of local homogeneity in the precursor gels prepared under different evaporation regimes during gelation process. In addition, the explanation of the possible hydrolysis and condensation reactions in the sol state has been suggested.     

Molecular interactions in aqueous solutions of polyborates at different acidity based on the Raman spectroscopy data at 25°C

Investigation of aqueous solutions of polyborates LiB(OH)₄, Li₂B₄O₅(OH)₄, and LiB₅O₆(OH)₄ at different acidity has been performed by Raman spectroscopy at 25°C. The geometries and Raman vibrational frequencies of H₃BO₃ in aqueous phase were calculated at different basis sets, and verified the veracity. The calculated characteristic Raman shifts of B(OH)₃, B(OH)₄ ^?, B₃O₃(OH)₄ ^?, B₃O₃(OH)₅ ^2?, B₄O₅(OH)₄ ^2?, and B₅O₆(OH)₄ ^? were assigned to 880.0, 735.33, 599.06, 740.16, 551.67, and 521.04 cm^?1, respectively. Assignments of the bands were tentatively ascribed by comparing the calculated Raman spectrum. The chemical species distribution and the relevant molecular interaction mechanisms in the polyborates solutions were suggested.     

Operando UV-visible spectroscopy evidence of the reactions of iodide as redox mediator in Li–O2 batteries

We monitored by means of UV-visible spectroscopy the formation and consumption of triiodide ion (I₃⁻), generated when iodide ion (I⁻) is used as redox mediator in lithium–oxygen batteries. Results evidence the initial formation of I₃⁻ during oxidation, and its decomposition during reduction. Correlation of absorbance with capacity is consistent with the mediation of peroxide oxidation above 3 V. Decrease of I₃⁻ absorbance and the appearance of a peak at a wavelength of 410 nm after 14 hours at open circuit voltage revealed side reactions associated to electrolyte degradation leading to the formation of HOI. This work shows that UV-visible spectroscopy is a valuable tool for following reactions involved in the operation of lithium–oxygen batteries based in the absorbance of the species formed or consumed.