Excess Molar Volumes and Viscosities for Binary Mixtures of 1-Alkoxypropan-2-ols with 1-Butanol, and 2-Butanol at 298.15 K and Atmospheric Pressure

Excess molar volumes Vm^E and kinematic viscosities v have been measured as a function of composition for binary mixtures of propylene glycol monomethyl ether （1-methoxy-2-propanol）, MeOCH2CH（OH）Me, propylene glycol monoethyl ether （1-ethoxy-2-propanol）, EtOCH2CH（OH）Me, propylene glycol monopropyl ether （1-propoxy-2-propanol）, PrOCH2CH（OH）Me, propylene glycol monobutyl ether （1-butoxy-2-propanol）, BuOCH2CH（OH）Me, and propylene glycol tert-butyl ether （1-tert-butoxy-2-propanol）, t-BuOCH2CH（OH）Me with 1-butanol, and 2-butanol, at 298.15 K and atmospheric pressure. The excess molar volumes are negative across the entire range of composition for all the systems with 1-butanol, and positive for the systems 2-butanol＋ 1-methoxy-2-propanol, and ＋1-propoxy-2-propanol, negative for the systems 2-butanol＋1-butoxy-2-propanol, and change sign for the systems 2-butanol＋ 1-ethoxy-2-propanol, and ＋ 1-tert-butoxy-2-propanol. From the experimental data, the deviation in dynamic viscosity η from ∑χiηi has been calculated. Both excess molar volumes and viscosity deviations have been correlated using a Redlich-Kister type polynomial equation by the method of least-squares for the estimation of the binary coefficients and the standard errors.     

High-pressure phase equilibria for the carbon dioxide–2-methyl-1-butanol,carbon dioxide–2-methyl-2-butanol,carbon dioxide–2-methyl-1-butanol–water,and carbon dioxide–2-methyl-2-butanol–water systems

High-pressure vapor–liquid equilibria for the binary carbon dioxide–2-methyl-1-butanol and carbon dioxide–2-methyl-2-butanol systems were measured at 313.2 K. The phase equilibrium apparatus used in this work is of the circulation type in which the coexisting phases are recirculated, on-line sampled, and analyzed. The critical pressure and corresponding mole fraction of carbon dioxide for the binary carbon dioxide–2-methyl-1-butanol system at 313.2 K were found to be 8.36 MPa and 0.980, respectively. The critical point of the binary carbon dioxide–2-methyl-2-butanol was also found 8.15 MPa and 0.970 mole fraction of carbon dioxide. In addition, the phase equilibria of the ternary carbon dioxide–2-methyl-1-butanol–water and carbon dioxide–2-methyl-2-butanol–water systems were measured at 313.2 K and several pressures. These ternary systems showed the liquid–liquid–vapor phase behavior over the range of pressure up to their critical point. The binary equilibrium data were all reasonably well correlated with the Redlich–Kwong (RK), Soave–Redlich–Kwong (SRK), Peng–Robinson (PR), and Patel–Teja (PT) equations of state with eight different mixing rules the van der Waals, Panagiotopoulos–Reid (P&R), and six Huron–Vidal type mixing rules with UNIQUAC parameters.     

NMR and Excess Volumes Studies in DMF–Alcohol Mixtures

Chemical shifts of the alcohol and DMF protons in DMF–alcohol mixtures with the mole fraction of alcohol are reported in order to study the hydrogen bond interaction present in the mixtures. The densities of DMF–methanol mixture at 22°C are also measured. Excess volumes and excess chemical shifts are correlated by the Redlich–Kister equation. The relation between excess volumes and excess chemical shifts in the mixtures is discussed. It is found that the maximum excess chemical shifts ^E(CHO-OH) and ^E(CH₃-OH) are positioned at about mole fraction methanol = 0.57 for the DMF–methanol system, as is V ^E. The results show that the NMR spectral method offers a valuable approach to similar future studies of interactions in mixtures.     

Excess Molar Volumes and Excess Partial Molar Volumes of Triethylene Glycol Monoethyl Ether–n-Alcohol Mixtures at 25°C

We have measured excess molar volumes V^E _m of binary mixtures of triethylene glycol monoethyl ether with methanol, ethanol, 1-propanol, 1-pentanol, and 1-hexanol over the full range of compositions at 25°C. The measurements were carried out with a continuous-dilution dilatometer. The excess molar volumes V^E _m are negative over the entire range of composition for the systems triethylene glycol monoethyl ether + methanol, + ethanol, and + 1-propanol and positive for the remaining systems, triethylene glycol monoethyl ether + 1-pentanol, and + 1-hexanol. The excess V^E _m increases in the positive direction with increasing chain length of the n-alcohol. The measured excess volumes have been compared to our previous published data with an effort to assess the effects of replacing methyl by ethyl groups and of inserting oxyethylene groups. The results have been used to estimate the excess partial molar volumes V^E _m,i of the components. The behavior of V^E _m and V^E _m,i with composition and the number of carbon atoms in the alcohol molecule is discussed.     

Excess Molar Volumes and Excess Partial Molar Volumes of Triethylene Glycol Monomethyl Ether–n-Alcohol Mixtures at 25°C

The excess molar volumes V ^E have been measured for binary mixtures of triethylene glycol monomethyl ether with methanol, ethanol, 1-propanol, 1-pentanol, and 1-hexanol as a function of composition using a continuous–dilution dilatometer at 25°C at atmosphere pressure. V ^E are negative over the entire range of composition for the systems triethylene glycol monomethyl ether + methanol, + ethanol, and + 1-propanol, and positive for the remaining systems, containing 1-pentanol and + 1-hexanol. V ^E increases in a positive direction with increasing carbon chain length of the n-alcohol. The excess partial molar volumes V _i ^E of the components were evaluated from the V ^E results. The behavior of V ^E and V _i ^E with composition and the number of carbon atoms in the alcohol molecule is discussed.     

Sol–Gel SiO2-ZrO2 Coatings for Optical Applications

SiO₂-ZrO₂ based nanostructured multilayers films have been prepared by sol–gel processing from metallorganic precursors by low temperature inorganic polymerization reactions. Simultaneous gelation of both precursors was realized. Homogeneous and transparent films were obtained at room temperature by dip- and spin-coating on glass and silicon wafer substrates. Samples with successively deposited layers (1–3 layers) and successive thermal treatments have been also studied. Each deposited layer was thermally treated for 1 h at 300°C. The coatings were characterized by XRD, spectroellipsometry (SE), UV-VIS spectroscopy and AFM methods. The influence of substrates, number of coatings and number of thermal treatments on the optical and structural properties of the films was established. The thickness of three deposited SiO₂-ZrO₂ layers is about 496 nm on glass substrates and 413 nm on the silicon wafer substrate. The films deposited on glass are more porous than those deposited on silicon. The properties of optical waveguide prepared from SiO₂-ZrO₂ layers on silicon substrates will be discussed.     

Excess Molar Volumes for Binary Mixtures of 1-Alkanol and 1-Alkene. III. The System 1-Hexanol + 1-Alkene at 25°C

Excess molar volumes, V ^E, are reported for binary mixtures of 1-hexanol with the homologous C₆, C₇, C₈, and C₁₀ 1-alkenes at 25°C. In this series of mixtures, the V ^E values vary as a function of mole fraction from positive–negative sigmoid shaped curves exhibiting a very small positive lobe in the dilute alkanol region for the shortest chain 1-alkene to positive values over the whole concentration range for the longer chain 1-alkene. The partial molar excess volumes, V _i ^E, were calculated for the components over the whole concentration range. The partial molar volume of 1-hexanol in the 1-hexene system shows a large and sharp minimum and in the 1-decene system is positive over the whole concentration range. The modified model [Treszczanowicz et al., J. Solution Chem. 31, 455 (2002) originally proposed by Treszczanowicz and Benson Fluid Phase Equilibr. 23, 117 (1985)] was used for the interpretation and prediction of the reported data. The model describes qualitatively the variation of V ^E with the length of the molecule and concentration as a result of superposition of the contributions of association, free volume, and nonspecific interactions.     

Polyaniline–MnO2 Composite Electrode for Electrochemical Supercapacitor

Russian Journal of Electrochemistry - Composite electroactive materials of polyaniline and manganese oxide (MnOx) are obtained via layer-by-layer potentiodynamic deposition of MnOx from MnSO4...     

TiO2–active carbon composites for wastewater photocatalysis

Titanium oxide–active carbon composites (TiO₂–AC) with photocatalytic activity were prepared by sol–gel method at low temperature. Titanium isopropoxide and active carbon were used as precursors, ethanol as solvent and HNO₃ as catalyst. The composition of the studied composites was accomplished by means of X-ray diffraction, and Fourier Transform-Infrared spectrometry. The rutile crystalline phase was present in all samples. In scanning electron microscopy images the TiO₂ aggregates existed either on the surface of the active carbon or heterogeneously dispersed over the whole catalyst matrix. The contact angle and point of zero charge measurements were applied to characterise the surface energy and surface charge. The photocatalytic activities of the TiO₂–AC composites were evaluated in the bleaching of methyl orange and methylene blue solution from ternary mixture of methyl orange, methylene blue and Triton X100. The double divisor ratio spectra derivative method (as a multivariable calibration method) was developed to overcome the spectral overlapping, for the simultaneous analysis of ternary mixture.     

Investigations on SnO2–TiO2 composite photoelectrodes for corrosion protection

Different compositions of SnO₂–TiO₂ composite electrode coatings were prepared on conducting ITO glass substrates and photoelectrochemical measurements were carried out on the coated substrates under illumination with ultraviolet light. Photopotential as well as polarization measurements were made on the samples to evaluate their performance with regard to application for cathodic protection of metals against corrosion. A composite electrode bearing SnO₂ and TiO₂ in a 1:1 molar ratio was found to exhibit the maximum photocurrent and a maximum lowering of potential under illumination when compared to the other compositions. A possibility of using a pure SnO₂ coating for cathodic protection of metals against corrosion under dark conditions was also explored.     

Preparation and electrocatalytic performance of Fe–N–C for electroreduction of H2O2

Fe–N–C catalysts were prepared through metal-assisted polymerization method. Effects of carbon treatment, Fe loading, nitrogen source, and calcination temperature on the catalytic performance of the Fe–N–C for H₂O₂ electroreduction were measured by voltammetry and chronoamperometry. The Fe–N–C catalyst shows optimal performance when prepared with pretreated active carbon, 0.2 wt.% Fe, paranitroaniline (4-NA) and one-time calcination. The Fe–N–C catalyst displayed good performance and stability for electroreduction of H₂O₂ in alkaline solution. An Al–H₂O₂ semi-fuel cell was set up with Fe–N–C catalyst as cathode and Al as anode. The cell exhibits an open-circuit voltage of 1.3 V and its power density reached 51.4 mW cm⁻² at 65 mA cm⁻².     

Molecular Nickel Thiolate Complexes for Electrochemical Reduction of CO2 to C1–3 Hydrocarbons

We report the unprecedented electrocatalytic activity of a series of molecular nickel thiolate complexes ( 1 – 5 ) in reducing CO₂ to C_1–3 hydrocarbons on carbon paper in pH-neutral aqueous solutions. Ni(mpo)₂ ( 3 , mpo=2-mercaptopyridyl-N-oxide), Ni(pyS)₃⁻ ( 4 , pyS=2-mercaptopyridine), and Ni(mp)₂⁻ ( 5 , mp=2-mercaptophenolate) were found to generate C₃ products from CO₂ for the first time in molecular complex. Compound 5 exhibits Faradaic efficiencies (FEs) of 10.6 %, 7.2 %, 8.2 % for C₁, C₂, C₃ hydrocarbons respectively at −1.0 V versus the reversible hydrogen electrode. Addition of CO to the system significantly promotes the FE_C1–C3 to 41.1 %, suggesting that a key Ni−CO intermediate is associated with catalysis. A variety of spectroscopies have been performed to show that the structures of nickel complexes remain intact during CO₂ reduction.     

Excess Molar Volumes and Liquid–Liquid Equilibria of the Ionic Liquid 1-Methyl-3Octyl-Imidazolium Tetrafluoroborate Mixed with Butan-1-ol and Pentan-1-ol

Experimental densities were measured for the system 1-methyl-3-octyl-imidazolium tetrafluoroborate [OMIM][BF₄] + butan-1-ol, + pentan-1-ol at 298.15 K and ambient pressure using a vibrating tube densimeter, taking into account the influence of the viscosity correction. Excess molar volumes V^E have been determined. V^E is quite small and negative in the alcohol-rich range of the mixture composition and positive in the alcohol-poor range. LLE data of [OMIM][BF₄] + pentan-1-ol have been measured using a laser light scattering cell for detecting cloud points at different compositions in the temperature range of 282–292 K. A miscibility gap with an upper critical solution temperature (UCST) of 292 K has been found.     

Nanocrystalline bioactive TiO2–chitosan impedimetric immunosensor for ochratoxin-A

Fourier transform infrared (FT-IR) and UV-visible spectroscopy were used to optimize TiO₂ concentration in chitosan (CS) to develop a sensitive CS/TiO₂ bioactive electrode. Electrochemical impedance spectroscopy (EIS) used to measure electro-activity of these bioactive electrodes associated with enhance oligosaccharide containing –CO groups from degradation of CS molecules. This matrix has free –NH₂ and –OH functional groups due to higher probability of hydrogen and covalent bonding between –OH group in CS molecules with Ti–O–Ti which supported immobilization of rabbit antibodies (IgGs) and proteins. Ochratoxin A (OTA) was detected and showed a linear response up to 10 ng/mL with CS/TiO₂ bio-electrode. The OTA detection sensitivity of 7.5 mM TiO₂ added CS bioactive electrode was four times higher than only CS.     

Ionic liquid–formulated hybrid solvents for CO2 capture

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Excess Molar Volumes for Binary Mixtures of 1-Alkanol and 1-Alkene. II. The System 1-Alkanol + 1-Octene at 15 and 35°C

Excess molar volumes V ^E measured at 15 and 35°C for the (1-propanol + 1-octene), (1-butanol + 1-octene), (1-octanol + 1-octene), and (1-decanol + 1-decene) systems are reported. These data and the measurements reported before at 25°C for this series of mixtures were used to calculate the excess molar isobaric thermal expansion A _p ^E = ( V ^E/ T)_p at 25°C. In the above series of mixtures the A _p ^E values change from positive over the whole concentration range in the systems formed by 1-propanol and 1-butanol, to positive-negative for longer chain alkanols, the positive values occurring in the alkene-rich region. For systems characterized by the sigmoid shape, the positive region of A _p ^E values decreases with increasing length of the 1-alkanol molecule. The modified model of associated mixtures proposed by Treszczanowicz and Benson predicts qualitatively the changes in the shape of the A _p ^E curves. The model allows interpretation of the above results as a balance between the contributions due to self-association of alkanol, nonspecific interactions, and free volume.     

Quantum dot–NBD–liposome luminescent probes for monitoring phospholipase A2 activity

In this paper we describe the fabrication and characterization of new liposome encapsulated quantum dot–fluorescence resonance energy transfer (FRET)-based probes for monitoring the enzymatic activity of phospholipase A_2. To fabricate the probes, luminescent CdSe/ZnS quantum dots capped with trioctylphosphine oxide (TOPO) ligands were incorporated into the lipid bilayer of unilamellar liposomes with an average diameter of approximately 100 nm. Incorporating TOPO capped quantum dots in liposomes enabled their use in aqueous solution while maintaining their hydrophobicity and excellent photophysical properties. The phospholipid bilayer was labeled with the fluorophore NBD C₆-HPC (2-(6-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)hexanoyl-1-hexa decanoyl-sn-glycero-3-phosphocholine). The luminescent quantum dots acted as FRET donors and the NBD dye molecules acted as FRET acceptors. The probe response was based on FRET interactions between the quantum dots and the NBD dye molecules. The NBD dye molecules were cleaved and released to the solution in the presence of the enzyme phospholipase A_2. This led to an increase of the luminescence of the quantum dots and to a corresponding decrease in the fluorescence of the NBD molecules, because of a decrease in FRET efficiency between the quantum dots and the NBD dye molecules. Because the quantum dots were not attached covalently to the phospholipids, they did not hinder the enzyme activity as a result of steric effects. The probes were able to detect amounts of phospholipase A₂ as low as 0.0075 U mL^?1 and to monitor enzyme activity in real time. The probes were also used to screen phospholipase A₂ inhibitors. For example, we found that the inhibition efficiency of MJ33 (1-hexadecyl-3-(trifluoroethyl)-sn-glycero-2-phosphomethanol) was higher than that of OBAA (3-(4-octadecyl)benzoylacrylic acid).     

Co–Cu–La catalysts for selective CO2 hydrogenation to higher hydrocarbons

Copper and lanthanum promoted cobalt catalysts for CO₂ hydrogenation to higher hydrocarbons are described. The catalysts were prepared by the self-propagating high-temperature synthesis followed by alkaline leaching. They are active in CO₂ hydrogenation at 200 °C under 10 bar pressure (CO₂ : H₂ = 1 : 3) with selectivity to C₂₊ alkanes up to 39%; no alkenes and alcohols are formed under these experimental conditions.