Effect of MnO2 and α-Fe2O3 on organic binders degradation investigated by Raman spectroscopy

Vibrational spectroscopy and GC–MS were used to investigate the effect of MnO₂ and α-Fe₂O₃ on the degradation of methyl linoleate and vegetal and animal fatty. The metal oxides are among the most employed pigments in rock art paintings, whereas the organic compounds were used to mimic organic binders potentially used in such paintings.Both oxides were very effective in the catalytic oxidation of the organic substrates and light had no significant effect, qualitatively or quantitatively, on the final products. In the case of methyl linoleate without metal oxide, the effect of light (visible) was investigated and it was demonstrated that the samples kept in the dark produced relatively less oxidation products, although the main products were the same (hexanal, methyl 9-oxononanoate and methyl octanoate). In the presence of MnO₂ and α-Fe₂O₃ methyl 9-oxononanoate was the main product, followed by hexanal. The spectral patterns of the oxidation products were different for manganese and iron oxide and GC–MS demonstrated that more compounds are formed in the former than with α-Fe₂O₃. Vegetal and animal fatty presented the same behavior that methyl linoleate did.The results here reported indicated that the two pigments considered actively contribute to fat degradation and the presence of inorganic pigments is the main factor to take into account when organic binders degradation in rock art paintings are investigated.     

Use of the Gerchberg–Saxton algorithm in optimal coherent anti-Stokes Raman spectroscopy

We are utilizing recent advances in ultrafast laser technology and recent discoveries in optimal shaping of laser pulses to significantly enhance the stand-off detection of explosives via control of molecular processes at the quantum level. Optimal dynamic detection of explosives is a method whereby the selectivity and sensitivity of any of a number of nonlinear spectroscopic methods are enhanced using optimal shaping of ultrafast laser pulses. We have recently investigated the Gerchberg–Saxton algorithm as a method to very quickly estimate the optimal spectral phase for a given analyte from its spontaneous Raman spectrum and the ultrafast laser pulse spectrum. Results for obtaining selective coherent anti-Stokes Raman spectra (CARS) for an analyte in a mixture, while suppressing the CARS signals from the other mixture components, are compared for the Gerchberg–Saxton method versus previously obtained results from closed-loop machine-learning optimization using evolutionary strategies.     

Influence of the synthesis parameters on the thermal behavior of some ZnO–starch composites

Ten ZnO–starch composites were synthesized using a simple precipitation methodology. The IR spectroscopy and XRD investigations reveal the presence of amorphous starch and crystalline ZnO. The obtained composites present a spherical morphology, 5–8 spheres being interconnected into aggregates. The thermal analysis demonstrates that starch decomposition and ZnO thermally induced nucleation and crystal growth depending on the synthesis parameters such as starch processing (dissolution or gelatinization), reaction temperature (80, 90, and 100 °C), reaction time (15 min or 6 h), and applied treatments (heating or ultrasound irradiation).     

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.     

Influence of the spin acceleration time on the properties of ZnO:Ga thin films deposited by sol–gel method

Journal of Sol-Gel Science and Technology - A detailed study of the structural, morphological, optical, and electrical properties of the spin-coated Ga-doped ZnO (GZO) films in which these...     

Influence of electron irradiation on the properties of α-aluminum hydride polymorph

Russian Chemical Bulletin - Changes in dielectric properties and thermal stability of the alpha-aluminum hydride polymorph (α-AlH3) after irradiation with electrons with an energy of 7 MeV...     

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.     

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.     

Gauging away the electron–electron interaction by the local phase of complex wave functions in two-electron systems

The electron–electron interaction is eliminated in the expectation values of the electronic Hamiltonian for two-electron systems. The part of the Hamiltonian referring to the repulsive interaction is gauged away by the local phase of the complex wave functions, much like a gauge field transformation, thereby leading to a one-electron Hamiltonian. Despite the appearance of complex wave functions, the expectation values of the total momentum operator vanish and Löwdin’s criterion holds for the stationary states.     

Influence of heat treatment on the size of sodium lignosulfonate particles in water—ethanol media

Russian Chemical Bulletin - Dynamic light scattering and size exclusion chromatography were used to investigate the size of sodium lignosulfonate particles in water—ethanol media and the...     

Influence of stereoelectronic effects on the 1JC─F spin–spin coupling constant in fluorinated heterocyclic compounds

The Perlin effect and its analog for fluorinated compounds (the fluorine Perlin-like effect) manifest on one-bond C─H (C─F for the fluorine Perlin-like effect) spin–spin coupling constants (SSCCs) in six-membered rings. These effects can be useful to probe the stereochemistry (axial or equatorial) of the C─H and C─F bonds, respectively. The origin of these effects has been debatable in the literature as being due to hyperconjugative interactions, dipolar effects, and induced current density. Accordingly, a variety of model compounds has been used to probe such effects since the cyclohexanone carbonyl group and the endocyclic heteroatom lone pairs play different roles on the above-mentioned effects. Thus, the ¹J_C─F SSCC in fluorinated lactams and lactones were theoretically studied to gain further insight on the nature of the fluorine Perlin-like effect. In addition, because the intramolecular α-effect has recently gained attention for its importance in the reactivity and stereoelectronic interactions in peroxide compounds, some fluorinated 1,2-dioxanes and 1,2-dithianes were studied to evaluate the role of the α-effect on the behavior of ¹J_C─F SSCCs. Differently from fluorinated ketones and ethers, the fluorine Perlin-like effect in the amides and esters cannot be explained by hyperconjugative or dipolar interactions alone, because the resonance in these groups affect the ¹J_C─F values. The O─O and S─S-containing systems exhibit a strong fluorine Perlin-like effect, but unlike the α-effect, this behavior cannot be explained neither by hyperconjugation nor by dipolar interactions alone; the spatial proximity of the C─F and O─O/S─S bonds is proposed to affect the magnitude of the ¹J_C─F SSCC.     

Investigation on the photo-induced de-oxygenation process of myoglobin in aqueous solution by use of fluorescence spectroscopy

A photo-induced de-oxygenation process of myoglobin (Mb) in aqueous solution was investigated by use of fluorescence spectroscopy. The spectra are characterized by the fluorescence intensity declining gradually after each scan,and the decay of fluorescence intensity being significant in each scan,which is assigned to the release of oxygen from the opening of the heme-pockets induced by illumination. More illumination will cause more release of oxygen; if the temperature of an Mb solution is increased when it is illuminated,the rate of de-oxygenation will be higher. It was found that ligand-oxygen in Fe-porphyrin could be removed from Mb by nitrogen. This indicates that the interac-tion between oxy-Mb and other different gases can be tested by the method of fluorescence spectros-copy. In addition,fluorescence spectroscopy can be employed to probe the energy transfer between Fe-porphyrin and tryptophan or tyrosine in Mb molecules.     

Adsorbate-adsorbent and adsorbate-adsorbate interactions in CO overlayers adsorbed on α-Cr203 as investigated by infrared spectroscopy

CO is adsorbed at 298 K only on the (0001) faces of polycrystaltine αCr₂0₃ with the appearance of a single i.r. peak whose frequency shifts from 2185 (θ ≈ 0) to 2170 cm^-1 (θ_max). This shift is due to the building up of adsorbate-adsorbate interactions (dynamic and static). The dipole--dipole (dynamic) interaction has been measured by means of the diluted isotopic method and can be explained in terms of CO oscillators adsorbed on identical sites and with their axes parallel. This suggests that the (0001) face is fiat and that the Cr³⁺-CO bond, although mainly σ in character, has some participation of the d-π^* orbitals, The adsorption of CO causes distinct perturbations in the i.r, spectrum of the α-Cr₂O₃ (intensity erosions in the multiphonon and fundamental regions): this is ascribed to changes in the anharmonieity and force constants ofsurface vibrations. Attempts to detect the Me-CO stretching and bending vibrations in the low frequency range of the spectrum (700--200 cm ^-1) have been unsuccessful; the reasons for this negative result are discussed.     

Influence of variation in the silicon content on the silicon precipitation in the Al–Si binary system

Ti-based amorphous alloys produced by ultra-rapid melt cooling represent an excellent option as biomaterials because of their mechanical properties and corrosion resistance. However, complete elimination of toxic elements is affecting the glass-forming ability and amorphous structure could be obtained only for thin ribbons or powders that are subsequently processed by powder metallurgy. Amorphous ribbons of special Ti₄₂Zr₄₀Ta₃Si₁₅ alloy, which is completely free of any toxic element, were produced by melt spinning, and the thermostability of resulting material was investigated in order to estimate its ability for further heat processing. Isochronal differential scanning calorimetry (DSC) was used to determine transformation points such as glass transition temperature T _g or crystallization temperature T _x. The activation energy for crystallization of amorphous phase was calculated based on Kissinger method, using heating rates ranging between 5 and 20 °C min^?1. Amorphous structure of resulting ribbon was evidenced by means of X-rays diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). It was determined that amorphous Ti₄₂Zr₄₀Ta₃Si₁₅ alloy has a high activation energy for crystallization, similar to other Ti-based amorphous alloys, which provides good thermal stability for subsequent processing, especially by means of powder metallurgy techniques.     

Influence of calcination temperature on the photocatalytic property of Fe–Cu–ZnO/graphene under visible light irradiation

Fe–Cu–ZnO/graphene composites are prepared by sol-gel method. The influence of the calcination temperature on the catalytic performance of Fe–Cu–ZnO/graphene composites has been studied and their physicochemical properties are characterized via X-ray diffraction (XRD), fourier transform infrared spectrometer (FTIR), scanning electron microscopy (SEM), thermogravimetry-differential scanning calorimetry (TG-DSC) and UV-Vis diffuse reflectance spectra (UV–Vis–DRS). The results show that Fe–Cu–ZnO/graphene composite calcined at 400°C exhibits the highest photocatalytic activity and the degradation rate of dark green dye in aqueous medium achieves 99.28% under exposure of visible light irradiation. The zinc species in the catalyst calcined at 400°C are all converted to the hexagonal wurtzite structures, and Cu²⁺ and Fe³⁺ are substituted ions in Zn²⁺ sites or incorporated into interstitial sites in the ZnO lattice which broaden the spectral response range to visible light. Meanwhile, the electrical properties of graphene are excellent which contribute to the enhanced charge carrier separation, extended light absorption, and increased surface hydroxyl groups. In addition, the catalyst is found to be relatively high reusable.     

Catalysis of the Suzuki–Miyaura coupling reaction in water by heteroannular cyclopalladated ferrocenylimine complexes

Catalytic studies on the air- and moisture-stable triphenylphosphine (PPh₃) adducts of heteroannular cyclopalladated ferrocenylimines [PdCl{C₅H₄FeC₅H₄CHRN=CHC₄H₃X}(Ph₃P)] (R = H, CH₃; X = S, O) indicate that they are all effective catalysts for the Suzuki–Miyaura coupling reaction of activated aryl bromides with phenylboronic acid in water under air atmosphere. Typically, using 1 mol‰ of catalyst in the presence of 1.2 equivalents of K₃PO₄ as base in water at 100 °C provided the corresponding biaryls in good to excellent yields. Meanwhile, the structure of [PdCl{C₅H₄FeC₅H₄CH(CH₃)N=CHC₄H₃S}(PPh₃)] has been established by the single-crystal X-ray diffraction technique. According to the crystal structure, the palladium atom is bound to the unsubstituted Cp ring, showing the four-coordinate structure typical of palladium complexes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.