Temperature study of Raman, FT-IR and photoluminescence spectra of ZnPc thin layers on Si substrate

The temperature study of zinc phthalocyanine (ZnPc) thin layers deposited on (0 0 1) Si substrate using Raman, FT-IR absorption and photoluminescence (PL) methods are reported. The Raman scattering spectra of ZnPc layers were investigated in the spectral range 1250–1650 cm⁻¹ and in the temperature range 100–500 K. The changes of spectral parameters such as the band position, integrated intensity and full width at half maximum (FWHM) of selected Raman modes while heating and cooling processes have been determined. The fast decrease of the frequency and the intensity of these modes observed with the increase of the temperature above 420 K, can be probably caused by the change of crystalline form of ZnPc thin layer. The FT-IR measurements have been performed in the temperature range 98–523 K. Our study allowed us to estimate the orientation of the molecular plane similar to these of CuPc thin films deposited on Si substrate. The Raman spectra have been compared with FT-IR spectra of ZnPc molecules in KBr pellets and thin layers of ZnPc on (0 0 1) Si substrate. The PL spectra of ZnPc layers were measured in the spectral range 350–1200 nm and in the temperature range 13–320 K. With increasing temperature from 13 to 175 K we observed the increase of PL bands at 1.76 and 1.85 eV which disappear reaching temperature above 200 K.     

Analysis of Turbulent Noise Spectra of Electrochemical Reactions in Different Experimental Conditions

The Ershler–Randles impedance model is used to analyze the physical foundations of potentiostatic and galvanostatic spectra of turbulent noise of electrochemical redox reactions as a function of the frequency range of measurements and the electrode potential. On the whole, the theoretically calculated and experimentally measured spectra are in satisfactory agreement. A computer simulation of the dependence of characteristic frequencies on the electrode potential, reaction parameters, and experimental conditions is realized. The approach allows one to tentatively estimate the in-principle possibility of experimental realization of spectrum sections, which are located in different frequency ranges and contain information on the characteristic frequencies and kinetic parameters of the reaction under study, and to formulate conditions required for performing an experiment and extracting data on the process kinetics.     

Fabrication of Sol-Gel Optical Waveguide by Hot-Dip Coating Process

The TiO₂: Sb nanoscale thin films were deposited on glass substrates by the sol–gel dip-coating method. The influence of the dopant density on the structure and the phase transformation of the thin films were investigated by X-ray diffraction (XRD) and Raman spectra. From the results of XRD, the thin films were in a majority of anatase state. The results of Raman spectra indicated that the non-doped TiO₂ thin film composed of not only anatase but also brookite phase. Dopant Sb enhances the transformation of the TiO₂ from brookite to anatase phase. After doping proper amount of Sb, the thin films show more superhydrophilicity than the non-doped TiO₂ thin film as well. The crystal size of the TiO₂ : Sb is about 13.3–20 nm calculated from the XRD patterns.     

Spin state transitions in Langmuir–Blodgett films of recombinant cytochrome P450scc and adrenodoxin

Langmuir–Blodgett (LB) films of recombinant cytochrome P450scc, of P450scc–adrenodoxin (Adx) complex and alternated layers of Adx and P450scc have been obtained. Spectral properties of these proteins in thin films were investigated by UV–Vis absorption spectroscopy. It has been found that cytochrome P450scc exists in LB films only in low-spin state while before the deposition it was in high-spin state. The data suggest that transferring the hemoprotein or its complex with redox partner results in the modification of the spin state by a conformational transition. In order to investigate further the P450scc and Adx interaction, the mass density of the films formed from these molecules has been studied by nanogravimetric measurements. Comparative study between nanogravimetric and spectral characterisation was performed. The results indicate that the protein–protein interaction is disrupted, when the complex is organised in thin film.     

Revised vibrational band assignments for the experimental IR and Raman spectra of 2,3,4-trifluorobenzonitrile based on ab initio, DFT and normal coordinate calculations

In the present study, a systematic vibrational spectroscopic investigation for the experimental IR and Raman spectra of 2,3,4-trifluorobenzonitrile (TFB), aided by electronic structure calculations has been carried out. The electronic structure calculations – ab initio (RHF) and hybrid density functional methods (B3LYP) – have been performed with 6-31G* basis set. Molecular equilibrium geometries, electronic energies, IR intensities, harmonic vibrational frequencies, depolarization ratios and Raman activities have been computed. The results of the calculations have been used to simulate IR and Raman spectra for TFB that showed excellent agreement with the observed spectra. Potential energy distribution (PED) and normal mode analysis have also been performed. The assignments proposed based on the experimental IR and Raman spectra have been reviewed. A complete assignment of the observed spectra has been proposed.     

Near- and Mid-Infrared Spectroscopy of Sol-Gel Derived Ormosil Films for Photonics from Tetramethoxysilane and Trimethoxysilylpropylmethacrylate

Ormosil dipped thin films and cast films were prepared using tetramethoxysilane and trimethoxysilylpropylmethacrylate (TMSPM). Structural changes during thermally induced polymerisation of the organic groups were investigated using near- and mid-infrared (IR) spectroscopy. IR spectra of the ormosil dipped thin films, dried at 60°C, have shown that further heat-treatment of the films at 160°C leads to the free radical polymerisation of C=C bonds in TMSPM. In the mid-infrared spectra, the intensity of the band at around 3500 cm^–1, due to O–H bonds, increased with the progress of polymerisation of vinyl groups. Near-infrared spectra of the cast films showed that this increase in intensity of the O–H band is due to the increase of monomeric water molecules hydrogen bonded to silanols. We suggest that optical loss measurements must be made in a dry atmosphere or, with a cover coating to protect the ormosil from adsorption of water, to reduce this source of optical loss for waveguides based on TMSPM.     

UV-Visible and IR Spectroelectrochemical Studies of FeVO4 Sol-Gel Films for Electrochromic Applications

The sol-gel synthesis route, in combination with dip-coating deposition, was used for the preparation of FeVO₄ films. TEM measurements of Fe/V (1 : 1)-oxide films heated at 400°C reveal that the films consist of a triclinic FeVO₄-I and an orthorhombic FeVO₄-II phases with a grain size of up to 50 nm. The electrochromic properties of the films were tested in 1 M LiClO₄/propylene carbonate (PC) using various electrochemical techniques and in-situ UV-visible spectroelectrochemical measurements. The best compromise between the charge capacity per film thickness (Qd^–1 = –0.14 mC cm^–2 nm^–1), electrochemical stability (>1000 cycles) and optical modulation (T_vis = 0.15) was achieved in the potential range of 4.80 to 1.80 V vs. Li, which suggests that FeVO₄ films can be used as counter-electrodes in electrochromic devices.Extensive IR-spectroscopy studies of FeVO₄ films in charged/discharged states revealed the following spectra changes: (i) small charging (–0.01 mC cm^–2 nm^–1) leads to a variation in the intensity of all the vibrational bands without shifting their frequencies, (ii) higher chargings bring about the intensity and frequency changes of bridging V—O···Fe and V···O···Fe stretchings showing that vanadium, and probably also iron, are involved in the insertion/extraction processes, (iii) below 500 cm^–1 broad absorption appears due to the Li⁺—O modes, which also remained in the IR spectra of discharged (bleached) states revealing the irreversible lithiation, and (iv) charging to –0.30 and –0.50 mC cm^–2 nm^–1 leads to the amorphisation of the film structure.     

Performance evaluation of mapping and linear imaging FTIR microspectroscopy for the characterisation of paint cross sections

Different Fourier transform infrared microspectroscopic techniques, using attenuated total reflection (ATR) mode and single-element mercury–cadmium–telluride (MCT) detector (mapping) or multielement MCT detector (raster scanning), are compared with each other for the characterisation of inorganic compounds and organic substances in paint cross sections. All measurements have been performed on paint cross sections embedded in potassium bromide, a transparent salt in the mid-infrared region, in order to better identify the organic materials without the interference of the usual embedding resin. The limitations and advantages of the different techniques are presented in terms of spatial resolution, data quality and chemical information achieved. For all techniques, the chemical information obtained is found to be nearly identical. However, ATR mapping performed with a recently developed instrumentation shows the best results in terms of spectral quality and spatial resolution. In fact, thin organic layers (∼10 μm) have been not only identified but also accurately located. This paper also highlights the recent introduction of multielement detectors, which may represent a good compromise between mapping and imaging systems.     

DFT Calculation of the Structure of the Coordination Unit of Chlrophyll-Containing Proteins

In a DFT/B3LYP study (6-31G(d) basis set), the structure, IR spectra, and thermodynamic parameters of Mg-porphin-imidazole and Mg-khlorin-imidazole complexes, serving as models of the coordination unit of chlorophyll in proteins, have been calculated. When an axial ligand is added, the Mg atom goes out of the plane of the tetrapyrrole macrocycle, the deviation being 0.34 Å. The frequency of the out-of-plane vibrations of Mg in the complexes increased by 50 cm⁻¹, and the frequencies of the two in-plane vibrations decreased by 25 cm^{− 1}–30 cm⁻¹. IR vibrational spectra have been simulated.Original Russian Text Copyright © 2004 by M. D. Elkin, O. D. Ziganshina, K. V. Berezin, and V. V. Nechaev__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 1132–1135, November–December, 2004.     

Features of the mass spectra of hetisine bases with an OH group at C-14

The EI mass spectra of five hetisine bases with an OH group at C-14 have been investigated. The main directions of fragmentation are initiated by the cleavage of the C-14-C-20 bond. With the aid of measurements of the elementary compositions of the molecular and fragmentary ions and of a comparison of the B/E linked-scanning and metastable defocusing spectra, the mechanism of the formation of the key fragments has been established and alternative methods for the production of certain ions have been revealed.Institute of Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 82–89, January–February, 1992.     

Spectroscopic characterization of ambers and amber-like materials

Longitudinal acoustic (LA) phonon of Baltic, Dominican and Kuji ambers, amber-like rosin and synthetic acrylic resin has been investigated by means of Brillouin light scattering (BLS) at room temperature. We observed a pair of LA phonon peaks and a broad quasi-elastic scattering peak in backscattering spectra from ambers. The LA phonon frequencies were found to be 16.97–17.11 GHz for Baltic ambers, 17.23–17.68 GHz for Dominican ambers and 17.70–17.97 GHz for Kuji ambers, respectively. We would like to point out that the LA phonon frequency can be a good physical quantity to specify the amber-producing district. We also present a correlation between the BLS spectrum and infrared absorption spectrum of ambers and amber-like materials.     

Operating the pulsed discharged detector in both the electron-capture and photoionization modes within the same GC analysis

Summary Since the electron-capture detector (ECD) is highly selective, it is imperative to use a more universal ionization detector in conjunction with the ECD in order to detect non-capturing or weakly capturing compounds. Also in an EC study of weakly or moderately strong electron-capturing compounds, it is necessary to identify the EC peak of the compound by identifying the major component with an ionization detector. In this paper we have shown that the pulsed discharge detector can be interchanged between the EC and the helium ionization modes within 4–6 s. The application of this procedure has been illustrated with a mixture of alkane/alkene chlorocompounds. The interchange between EC and argon photoionization modes has also been investigated. The change from EC to argon photoionization also occurs in 4–6 s but the reverse process requires 9 s.     

Effective length of the alkyl chain and thermal behaviors of Langmuir–Blodgett films of octadecylammonium laurate, octadecylammonium octadecanoate and octadecylammonium tetracosanoate

Thermal behaviors of 11-layer Langmuir–Blodgett (LB) films of the double long-chain compounds of octadecylammonium laurate (ODALA), octadecylammonium octadecanoate (ODASA) and octadecylammonium tetracosanoate (ODATA) have been investigated by Fourier transform infrared spectroscopy. The temperature-dependent infrared spectra show that thermal stability of the three kinds of LB films depends upon the length of the hydrocarbon chain. The LB film of ODALA undergoes an order–disorder transition in the temperature range of 50–65 °C. In contrast, the ODATA LB film has the phase transition temperature range of 80–90 °C. Of particular interest is that both ODASA and ODATA LB films have nearly the same phase transition temperature range of 80–90 °C, indicating that the replacement between tetracosanoic acid and stearic acid has little effect on the thermal stability of the two compounds. The above observations suggest that the effective length of the alkyl chains, which is determined by the component with a shorter chain in the double long-chain compounds, has a dominant influence on the thermal stability. It is very likely that the whole chain of the shorter chain component such as octadecylamine in ODATA has contribution to the thermal stability while only the effective length of the longer alkyl chain component gives a significant effect.     

Steady-state and time-resolved studies of 2,7-carbazole-based conjugated polymers in solution and as thin films: determination of their solid state fluorescence quantum efficiencies

The UV–Vis absorption spectra and the luminescence properties of poly(N-octyl-2,7-carbazole) (POC) and poly(N-octyl-2,7-carbazole-alt-9,9-dioctyl-2,7-fluorene) PCF have been investigated in solution and in the solid state (thin films). No aggregate and/or excimer formation has been detected in these polymeric systems. From time-resolved fluorescence measurements in solution and in the solid state, the fluorescence efficiencies of the thin films have been estimated. It is found that the fluorescence efficiencies of these polycarbazoles in the solid state are quenched, as compared to those measured in fluid solutions, but remain relatively high (φ_F0.40), making them promising materials for electroluminescent devices.     

A novel amperometric sensor and chromatographic detector for determination of parathion

A novel amperometric sensor and chromatographic detector for determination of parathion has been fabricated from a multi-wall carbon nano-tube (MWCNT)/Nafion film-modified glassy-carbon electrode (GCE). The electrochemical response to parathion at the MWCNT/Nafion film electrode was investigated by cyclic voltammetry and linear sweep voltammetry. The redox current of parathion at the MWCNT/Nafion film electrode was significantly higher than that at the bare GCE, the MWCNT-modified GCE, and the Nafion-modified GCE. The results indicated that the MWCNT/Nafion film had an efficient electrocatalytic effect on the electrochemical response to parathion. The peak current was proportional to the concentration of parathion in the range 5.0×10^–9–2.0×10^–5 mol L^–1. The detection limit was 1.0×10^–9 mol L^–1 (after 120 s accumulation). In high-performance liquid chromatography with electrochemical detection (HPLC–ED) a stable and sensitive current response was obtained for parathion at the MWCNT/Nafion film electrode. The linear range for parathion was over four orders of magnitude and the detection limit was 6.0×10^–9 mol L^–1. Application of the method for determination of parathion in rice was satisfactory.     

Photoelectrochemical Behavior of Poly(3,4-ethylenedioxythiophene) in Acetonitrile Solutions during Cathodic Reduction of Oxygen

The photoelectrochemical behavior of a polymer electrode based on poly(3,4-ethylenedioxythiophene) (PEDT) is studied in acetonitrile solutions during the cathodic reduction of oxygen. The measurements are taken on PEDT films 490 nm thick deposited onto a platinum support in oxygen-saturated 0.1 M Bu₄NBF₄ solutions. The electrode was illuminated with a light of a wavelength 487 nm from a helium–cadmium laser in conditions of modulated illumination, and in doing so, the real and imaginary components of an alternating photocurrent were measured at different modulation frequencies. The peculiarity of the photoelectrochemical behavior of PEDT manifests itself in the emergence of an anodic photocurrent, which increases with a change in potential in the cathodic direction. At low modulation frequencies, the real and imaginary components are of the same sign, whereas at high modulation frequencies the components have opposite signs (photocurrent lags behind a change in the light intensity). The emergence of an anodic photocurrent is connected with the cathodic reduction of oxygen and the formation in a near-electrode layer of radical anion O^– ₂. Such a behavior of PEDT, which makes it different from other polymers of the thiophene series, is explained by different potentials of their anodic oxidation, to which a conductive state of the polymer is related.     

Thin film absorbers for visible,near-infrared,and short-wavelength infrared spectra

In this study, the refractive indices were determined for Al₂O₃ films deposited with ALD, and amorphous Mo-Si-N films deposited with reactive sputtering. The measurements were made by spectroscopic reflectometry, ellipsometry, gonioreflectometry, and double-beam transfer standard spectrometry. Based on the results, two thin film absorbers were designed and manufactured: one for wavelengths of 350…1000 nm, the other for wavelengths of 1200…2000 nm. The manufactured absorbers showed high absorption over their whole working spectra varying from 93.4 % at the minimum to 99.9 % at the maximum. One of the absorbers was applied to a MEMS thermopile detector with successful process integration.     

The vibrational spectra and structure of α-chloroacetic acid

Polarized mid-infrared spectra of single crystals as well as those of a highly oriented polycrystalline film of α-chloroacetic acid have been obtained. The fundamental frequencies have been assigned based on these spectra, the Raman spectrum of the solid acid and the infrared spectrum of α-chloroacetic acid-d₁ and assuming an oriented gas model of the crystal. The data are most consistent with a hydrogen bonded polymeric structure for α-chloroacetic acid.     

Emission characteristics of Cu in Dc voltage modulation applied glow discharge optical emission spectrometry.

In order to obtain the depth profile of a thin film, we investigated the emission characteristics of a voltage modulation glow discharge to optimize the modulation parameters (modulation voltage, offset voltage, and modulation frequency). In this study, a phase-sensitive detection method with a lock-in amplifier to the modulation technique led to a higher sensitivity and a larger signal-to-noise ratio in the emission analysis compared to the normal dc amplification method. Upon increasing the maximum voltage, the emission intensity of the Cu atomic line (CuI 239.34 nm) increased linearly at a modulation voltage of 400 V and an offset voltage of 300 V. On the other hand, the emission intensity was gradually reduced when a modulation frequency increased. It is advantageous for surface analysis that the voltage modulation technique gives a lower sputtering rate rather than the conventional dc discharge.     

Temporal fluctuations in the SERRS spectra of single iron–protoporphyrin IX molecule

Surface enhanced resonance Raman spectra of Fe–protoporphyrin IX, adsorbed on silver colloidal nanoparticles immobilized onto a polymer-coated glass slide have been investigated at very low concentrations. The spectra exhibit drastic temporal fluctuations on a time scale of seconds in both line frequency and intensity; such a trend suggesting that the single molecule limit is approached. Sequences of spectra have been analyzed in terms of an underlying continuum and of Raman peaks superimposed on this continuum. A statistical analysis of the spectrum intensity has allowed us to put into evidence that main contribution to the intensity fluctuations arises from the continuum. In addition, a high correlation between the total integrated intensity and the intensity detected at different Raman peaks has been revealed. Furthermore, the ratio between the intensity detected in correspondence of different FePP vibrational modes shows a temporal variability likely reflecting the intrinsic dynamics of the molecule. All these findings have been ascribed to a desorption–adsorption mechanism of the molecules at the silver surface.