Raman spectroscopic study on the formation of an adduct of acetonitrile with formamide

Raman spectra of binary mixtures of acetonitrile (ACN) and formamide (FA) in different compositions were obtained. The appearance of a new band at 2257 cm⁻¹, whose intensity shows large dependence on the FA concentration, is assigned to a FA–ACN adduct. This has been possible owing to the two H-bond donor sites of FA and the strong donor character of ACN, becoming the environment propitious for the donor–acceptor reaction. Quantitative measurements performed in the CN stretching region in the binary mixtures give a 1:1 stoichiometry in this adduct in the limit of infinite dilution. In the N–H stretching region of FA, the band at 3270 cm⁻¹ is assigned to (FA–FA)_n interactions, via hydrogen bonding.

The experimental evidence of the 1:1 FA–ACN adduct is presented for the first time using Raman spectroscopy. The results described here open new possibilities to study this adduct and to evaluate thermodynamics parameters of interest.     

Raman spectral changes of alcoholic zinc chloride solutions from liquid state to glassy state

Raman spectral changes associated with vitrification were measured for ZnCl₂·4OROH solutions (ROH=methanol, ethanol and 1-propanol). Solvated ZnCl₂ is the only major Zn-species in these solutions at room temperature while the dominant Zn-species stabilized in the glassy alcoholic solutions are ZnCl ₃ ^– , ZnCl ₄ ^2– and [Zn(MeOH)₆]²⁺ for the methanol solution, ZnCl₂ and ZnCl ₃ ^– for the ethanol solution and ZnCl₂ for the 1-propanol solution. Together with Raman data for aqueous ZnCl₂ solutions, the differences in the dominant Zn-species in the glassy alcoholic solutions are discussed in terms of the dielectric constants of solvents (water and alcohols).     

Determination of ratios of sulfate to bisulfate ions in aqueous solutions by Raman spectroscopy

Raman spectra are presented for aqueous ammonium bisulfate and zinc sulfate-sulfuric acid solutions over a wide range of concentration and from 20 to 85°C. The heights of the 980 cm ^–1 (primarily SO ₄ ^–2 ) and 1053 cm ^–1 (primarily HSO ₄ ^– ) bands are correlated with the pH of the solutions. The ratio of the species SO ₄ ^–2 and HSO ₄ ^– can be obtained from the ratio of scattering intensities at 980 and 1053 cm ^–1 . The H obtained from plots of the log of the concentration products versus 1/T is –37±5 kJ-mol ^–1 for ammonium bisulfate solutions and –48±4kJ-mol ^–1 for the ZnSO ₄ -H ₂ SO ₄ solutions. This compares to –22 kJ-mol ^–1 for the H of bisulfate ion dissociation as obtained from thermodynamic equilibrium constants.     

Molecular-level investigation on electrochemical interfaces by Raman spectroscopy

The structure and dynamics of electrode/liquid interfaces play an increasingly important role in electrochemistry. Raman spectroscopy is capable of providing detailed structural information at molecular level and new insight into the interfacial structure, adsorption, reaction, electrocatalysis and corro-sion. In this account we will summarize some progresses of surface Raman spectroscopy in the study of electrochemical interfaces, mainly based on our group's work, laying emphasis on the detection sensitivity, spectral resolution, time resolution and spatial resolution as well as the hyphenated technique.     

煤焦油的拉曼光谱表征和组分识别

用355 nm激光作为激发光源检测了煤焦油常温拉曼光谱;应用两种量子化学计算程序(Gaussian-DFT和ADF)模拟了占总量1%以上的15种煤焦油组分的拉曼光谱,模拟结果与实验光谱能较好匹配,并对振动模式进行了归属分析。研究表明,煤焦油组分主要由共轭六元环构成,其拉曼光谱特征谱带主要在1 660、1 420和1 265 cm^-1附近,当共轭六元环成链式结构时,1 420 cm^-1谱带特征明显;五元环嵌入共轭六元环链式结构会导致其拉曼光谱在1 265和1 660 cm^-1谱带相对强度增大;五元环、杂原子基团和甲基侧链依附在共轭六元环上,则对组分的拉曼光谱影响不显著。     

Intercalator-DNA interactions revealed by NIR surface-enhanced Raman spectroscopy

Using 1064 nm excited surface-enhanced Raman spectroscopy (SERS) a well known intercalator, ethidium bromide (EB), and a structurally related compound, 4-methyl-2,7-diamino-5,10-diphenyl-4,9-diazapyrenium hydrogensulfate (ADAP), have been studied. Concentration dependent SERS spectra of both aromatic species (1 × 10⁻⁷-5 × 10⁻⁵ M) indicated existence of dimeric associates at high concentration and an equilibrium shift towards monomers with a concentration decrease. Interactions of the intercalating molecules with DNA have been studied for various intercalator/DNA (base pair) molar ratios ranging from 10/1 to 1/10. In colloidal samples containing an intercalator in excess relative to DNA binding sites (from 10/1 to 2/1) enhancement of the Raman scattering gradually weakened, indicating a decrease in a number of free molecules adsorbed on the metal surface due to binding with DNA. At the drug/DNA ratios of 1/2 and 1/5 weaker but observable SERS bands indicated insertion of the drug molecules between the base pairs (intercalation strongly diminished interaction of the drug molecules with metal surface) as well as non-intercalative binding of the drug molecules able to stay in closer contact with a metal surface. A total intercalation of EB and ADAP molecules (intercalator/DNA of 1/7 and 1/10) resulted in almost complete loss of the SERS signal. Intensity of the SERS spectra of the intercalator/DNA complexes relative to the SERS intensity of the free intercalating molecules diminished to a lesser degree for ADAP/DNA than for EB/DNA. The obtained difference was attributed to a larger aromatic surface of the ADAP molecules which, although intercalated, could be positioned near the enhancing nanoparticles, unlike the smaller EB molecules which were deeply inserted within the DNA helix.     

Synthesis and characterization of zinc chloride containing poly(acrylic acid) hydrogel by gamma irradiation

In this study, the characterization of zinc chloride incorporated into a poly(acrylic acid) (PAAc) hydrogel prepared by gamma-ray irradiation was investigated. Zinc chloride powder with different concentrations was dissolved in the PAAc solution, and it was crosslinked with gamma-ray irradiation. The effects of various parameters such as zinc ion concentration and irradiation doses on characteristics of the hydrogel formed were investigated in detail for obtaining an antibacterial wound dressing.In addition, the gel content, pH-sensitive (pH 4 or 7) swelling ratio, and UV–vis absorption spectra of the zinc particles in the hydrogels were characterized. Moreover, antibacterial properties of these new materials against Staphylococcus aureus and Escherichia coli strains were observed on solid growth media. The antibacterial tests indicated that the zinc chloride containing PAAc hydrogels have good antibacterial activity.     

Theoretical investigation of the weak interactions of rare gas atoms with silver clusters by resonance Raman spectroscopy modeling

The interactions of rare gas atoms (Rg = Ar, Kr, and Xe) with small neutral and cationic silver clusters have been investigated by density functional methods and the effect of these weak interactions on the resonance Raman spectra of the complexes has been evaluated. The resonance Raman technique that depends on the properties of ground and excited state, seems deeply sensitive to the weak rare gas–metal cluster interactions, and the use of inert gases has been proven to be an excellent approach to recognize the ability of this technique to detect extremely weak interactions. In this work, for , and complexes the IR, normal and resonance Raman spectra have been calculated and the effect of rare gas–cluster stretching vibration ( ) on the pattern and the relative intensities of different spectra have been investigated. The resonance Raman spectra for the weakly interacted complexes (with the interaction energies less than ?2.0 kcal/mol) exhibit the vibration with the detectable intensity that its intensity increases by going from Ag₆–Ar to Ag₆–Xe complex. Moreover, the resonance Raman spectra (based on the excited state gradient approximation) for high intensity nearly degenerate excited states, proved the effect of accumulation of the excited state charge density on the relative intensity of vibration.     

Intradiffusion coefficients for perchlorate ions in zinc perchlorate and zinc chloride solutions at 25°C: Comparing transport properties of zinc chloride and zinc perchlorate systems

Intradiffusion coefficients for³⁶ClO ₄ ^– have been measured in solutions of zinc perchlorate of concentration 0.1 to 3 mol dm^–3 at 25°C by the diaphragm cell technique. In addition, intradiffusion coefficients for perchlorate ions in zinc chloride solutions have been measured over a concentration range at 25°C. The results confirm previous work on the effect of complexation on diffusion in zinc chloride solutions above a salt concentration of 0.1M. The present data, together with literature data for diffusion coefficients of the other species present in the zinc perchlorate electrolyte system, have enabled a simple analysis of the hydration around the zinc ions to be carried out. This indicates that the water diffusion data are consistent with the zinc ions having an effective hydration sphere of 11 (±2) water molecules. This is in keeping with values obtained for other simple divalent electrolytes using the same model. The model is extended here to allow analysis of water diffusion in zinc chloride solutions taking into account the presence of complexed chloro-zinc species. The experimental data are consistent with the effective hydration of the chloro-zinc complexes being independent of the number of chloride ligands and equal to 18±3 over a concentration range of 0 tol mol-dm^–3. This postulate is discussed in terms of its consequences on the water ligand dynamics for the complex equilibria.     

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.     

Interaction of tin (IV) chloride with sulfolane and between tin (IV) chloride and lithium chloride in sulfolane solution

Tin (IV) chloride reacts with sulfolane (S) to form a cis-octahedral adduct SnCl₄·S₂. Solutions of lithium chloride and tin (IV) chloride in sulfolane contain the complex ions SnCl ₅ ^– and SnCl ₆ ^2– at 11 and 21 mole ratios of constituents, respectively. The complexes are characterized by conductimetry and by Mössbauer, IR, and Raman spectroscopy.     

Effect of water vapor on the thermal decomposition process of zinc hydroxide chloride and crystal growth of zinc oxide

Thermal decomposition process of zinc hydroxide chloride (ZHC), Zn₅(OH)₈Cl₂·H₂O, prepared by a hydrothermal slow-cooling method has been investigated by simultaneous X-ray diffractometry and differential scanning calorimetry (XRD-DSC) and thermogravimetric-differential thermal analysis (TG-DTA) in a humidity-controlled atmosphere. ZHC was decomposed to ZnO through β-Zn(OH)Cl as the intermediate phase, leaving amorphous hydrated ZnCl₂. In humid N₂ with P_H2O=4.5 and 10 kPa, the hydrolysis of residual ZnCl₂ was accelerated and the theoretical amount of ZnO was obtained at lower temperatures than in dry N₂, whereas significant weight loss was caused by vaporization of residual ZnCl₂ in dry N₂. ZnO formed by calcinations in a stagnant air atmosphere had the same morphology of the original ZHC crystals and consisted of the c-axis oriented column-like particle arrays. On the other hand, preferred orientation of ZnO was inhibited in the case of calcinations in 100% water vapor. A detailed thermal decomposition process of ZHC and the effect of water vapor on the crystal growth of ZnO are discussed.     

Structure of solvated lithium and chloride ions in formamide

Structure of solvated lithium and chloride ions in formamide was investigated by means of X-ray diffraction at 25°C. Lithium ion has, on average, 5.4 formamide molecules as nearest neighbors with an Li⁺-O distance of 224 pm, while chloride ion is coordinated with 4.5 formamide molecules with the Cl^–···N distance of 327 pm. The amino group within a formamide molecule interacts with a chloride ion in the bifurcate manner through two hydrogen atoms.Session lecture, IX International Conference on Non-Aqueous Solutions, Pittsburgh, PA, August 1984.To whom correspondence should be addressed.     

有机银溶胶的吸收光谱和表面增强Raman光谱研究

研究了2-氨基苯并咪唑(BIMNH₂)、LiCl、NaOEt对Ag/EtOH溶胶吸收光谱和表面增强Raman散射(SERS)光谱的影响。结果表明,少量的吸附分子BIMNH₂、LiCl、NaOEt均能改变溶胶聚集状态,从而影响其吸收光谱和SERS效应。此外,Cl^-还可与Ag、BIMNH₂形成表面络合物而增强SERS效应。对Ag溶胶体系SERS光谱的溶剂效应也作了初步研究。     

Uranium-involving electrode processes in chloride melts: An x-ray absorption spectroscopy study

Products of anodic dissolution of uranium metal and the cathodic reduction of uranium(IV) ions in a molten eutectic mixture of lithium and potassium chlorides are studied at 450°C using x-ray absorption spectroscopy. It is shown that UCl ₆ ^3? — ions form in the melt as a result of the metal’s anodic dissolution, and the metal-ligand distance in the complex ion is 0.284 nm. No complex ions of another configuration are found to form. Cathodic reduction of the UCl ₆ ^2? — ions also yields the UCl ₆ ^3? — ions, with longer U-Cl bonds.     

Analysis by Raman and infrared spectroscopy combined with theoretical studies on the identification of plasticizer in PVC films

Raman and Fourier Transform infrared spectroscopy were used to study the vibrational spectra in commercial polyvinyl chloride (PVC) flexible films. In order to have insights of the PVC and the plasticizer structures, density functional theory calculations were conducted via B3LYP hybrid functional. The infrared and Raman calculations took into account geometry optimization of the PVC film, the plasticizer DEHA and the convolution of both. The convoluted spectra were then compared with the experimental data. Finally, the thermal stability of the PVC films was checked through one-hour thermal treatment of the samples comprising temperatures ranges from 50 to 200 °C.     

Resonance Raman spectroscopy of mass selected Al2 in an argon matrix

In an excitation range of 620–760 nm, resonance Raman spectra of aluminum dimers (Al₂) in an argon matrix have been obtained for the first time. Temperature annealing experiments were performed to remove Raman lines attributed site effects caused by the Al₂/Ar matrix. We observe a single fundamental at 293.3 (5) cm⁻¹ along with a progression up to 1149 (1) cm⁻¹. Taking successive differences of band centers we obtain spectroscopic constants for the ground state fundamental, ω_e=297.5 (5) cm⁻¹, the anharmonicity, ω_ex_e=1.68 (8) cm⁻¹. Our results are in close agreement with previous experimental results for Al₂ which designate the ground state as a ³Π_u state, and may be considered as confirmation of this assignment.     

Investigations of electrode surfaces in acetonitrile solutions using surface-enhanced Raman spectroscopy

The discovery of surface-enhanced Raman scattering (SERS) has resulted in a new tool for the elucidation of phenomena occurring at the electrode/solution interface. Our long term objective is to use this technology to identify species adsorbed at the electrode surface and to determine the dependence of the Raman intensity from these species on such variables as solvent, concentration, pH, electrode potential and laser exciting wavelength. The phenomenon is described in the introduction, to provide background for those not familiar with this topic. This is followed by a presentation of recent data from our laboratory, with a focus on nonaqueous solvents. Bands of the solvated Li⁺ and Na⁺ cations at the electrode surface are reported. Bands from trace H₂O (D₂O and HOD) and OH^– (OD^–) have been observed. At sufficiently negative potentials CN^– is generated from acetonitrile. Evidence is presented for the occurrence of photoelectrochemical reduction. Some preliminary results are given for propylene carbonate solvent which support this interpretation.Session lecture, IX International Conference on Non-Aqueous Solutions, Pittsburgh, PA, August 1984.     

Raman spectra of complexes of HCl with DMF with a strong quasisymmetric H-bond in solutions

Raman spectra of complexes of HCl with DMF with a strong quasisymmetric H-bond in solutions were obtained. The formation of these complexes is accompanied by significant changes in almost all the vibration frequencies and line intensities, the changes in Raman and IR spectra being similar in many features. A weak background scattering was found in the Raman spectra, which coincides in shape with the continuous absorption in IR spectra.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1593–1595, September, 1994.This work was supported by the Russian Foundation for Basic Research (Project No. 93-03-18856).