Surface Tension of the 4-Methyl-2-Pentanone/Ethyl Benzoate Binary System in the Temperature Range from 278.15 to 308.15K

Surface tensions (σ) and densities (ρ) of 4-methyl-2-pentanone/ethyl benzoate binary mixtures have been measured over the entire composition range at 278.15, 288.15, 298.15, and 308.15 K. Values of the excess surface tensions (σ^E) and excess molar volumes (V^E) have been calculated. The σ^E and V^E values were fitted by to the Redlich–Kister polynomial equation and the A_k coefficients have been derived. The standard deviations between the calculated and the experimental excess properties have also been derived. The surface tension values have been further used to calculate the surface entropies (S^S) and surface enthalpies (H^S) per unit surface area. The lyophobicity (β) and the surface mole fractions (x₁^S) of the surfactant 4-methyl-2-pentanone have been derived using the extended Langmuir model. The obtained results are discussed from the viewpoint of the existence of specific interactions between unlike molecules in the bulk region and the surface.     

Investigation of the Electrochemical Reduction of Benzophenone in Aprotic Solvents Using the Method of Cyclic Voltammetry

The reduction of benzophenone (Bzph) in 3-pentanone (PEN), acetone (ACE), N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF), tetrahydrofuran (THF), acetonitrile (ACN) and dimethyl sulfoxide (DMSO) with n-tetrabutylammonium hexafluorophosphate (TBAPF₆) as background electrolyte was studied using the technique of cyclic voltammetry at the temperature of 263.15 K. The half-wave potentials (E _1/2) were extracted. The reduction of Bzph occurs in two successive one-electron steps to produce first the free radical anion Bzph⁻ and then the dianion Bzph²⁻. The results indicated that the radical anion Bzph⁻ is reoxidized to Bzph in all investigated solvent media whereas the dianion Bzph²⁻ is reoxidized to Bzph⁻ only in THF. The heterogeneous electron-transfer rate constants (k _s ) were evaluated by employing the electrochemical rate equation proposed by Nicholson. The rate of electron transfer for the Bzph/Bzph⁻ couple was found to be relatively slow in all investigated solvent media. Consequently, the electron-transfer processes can be recognized as quasi-reversible. The diffusion coefficients (D) of Bzph in the investigated solvent media have been calculated using the modified Randles-Sevcik equation. The effect of the physical and chemical properties of the solvent medium on the electrochemical behavior of Bzph has been examined.     

Conductivity Studies of <Emphasis Type="Italic">n</Emphasis>-Tetrabutylammonium Tetraphenylborate in 3-Pentanone in the Temperature Range from 283.15 to 329.15 K

The molar conductivities (Λ) of solutions of n-tetrabutylammonium tetraphenylborate (NBu₄BPh₄) in 3-pentanone have been measured in the temperature range from 283.15 to 329.15 K. The conductance data have been analyzed using the Lee-Wheaton conductivity equation with the distance parameter (a) set at Bjerrum’s pairing distance, and the limiting molar conductivities (Λ_o) and the association equilibrium constants (K _A) have been derived. The limiting ion conductivities (λ_±^o) have been evaluated according to the method of Krumgalz. The λ₊ ^o values have been compared with λ₊ ^o values calculated from the empirical equation of Gill. The thermodynamic functions, Gibbs energy (Δ G _A ^o), enthalpy (Δ H _A ^o) and entropy (Δ S _A ^o) for the process of ion-pair formation as well as the activation energy of the ionic movement (ΔH ^∗) have been evaluated. The obtained results are discussed in terms of ion-ion and ion-solvent interactions.     

Electrochemical Impedance Spectroscopy and Cyclic Voltammetry of <Emphasis Type="Italic">cis</Emphasis>-[Cr(bipy)<Subscript>2</Subscript>(SCN)<Subscript>2</Subscript>]I (where bipy: 2,2′-Bipyridine) in Polar Solvents

Cyclic voltammetric studies (CV) on the complex cis-bis(2,2′-bipyridine)bis(thiocyanate)chromium(III) iodide [Cr(bipy)₂(SCN)₂]I (where bipy: 2,2′-bipyridine, C₁₀H₈N₂) were recorded on platinum (Pt) and glassy carbon (GC) electrodes in either acetonitrile (ACN) or acetone (ACE) solvent media including n-tetrabutylammonium hexafluorophosphate (NBu₄PF₆) as supporting electrolyte, at scan rates (v) ranging from 0.05 to 0.12 V⋅s⁻¹. In addition, electrochemical impedance spectroscopic (EIS) measurements in the frequency (f) range from 0.1 Hz to 50 kHz were carried out on GC and Pt electrodes. The half-wave potential (E _1/2) of the redox couple Cr(III)/Cr(II) was determined as −0.84 V and −0.79 V (versus Ag/AgCl) in ACN and ACE, respectively. The heterogeneous electron transfer rate constant (k _s) corresponding to the couple Cr(III)/Cr(II) was found to be greater on GC compared to the Pt electrode. The nature of the solvent medium also affects the kinetics of the investigated couple, to be exact, k _s increases remarkably upon replacement of ACE by ACN. The EIS results indicate that the GC electrode is a better capacitor and provides the smaller charge transfer resistance in ACN.     

2-（1,3-Diphenylpropen-1,3-diolato）-1,3,2-（5-formylbenzo）dioxaborol： A ＇Whole-molecule Disorder＇ Crystal Structure

The boron atom in C22H15BO5 is O,O’-chelated by the anions in a tetrahedral geometry, with the planar five-and six-membered chelate rings being orthogonal to each other. The molecule lies on a two-fold rotation axis. The molecule is disordered with respect to another molecule in a 93:7 ratio; the treatment of the ‘whole-molecule disorder’ by employing a large number of restraints is described. Crystal data: C22H15BO5, monoclinic C2/c, a = 17.1804(5), b = 12.9409(4), c = 9.8842(3) , β = 124.832(2)o, V = 1803.82(9) 3 at –173 K.     

Nitrogen-doped multi-walled carbon nanotubes for paracetamol sensing

A novel sensor consisting of nitrogen-doped multi-walled carbon nanotubes was fabricated by means of chemical vapor deposition technique with decomposition of acetonitrile onto oxidized silicon wafer using ferrocene as catalyst. The electrochemical response of carbon nanotubes-based sensor towards oxidation of paracetamol to N-acetyl-p-quinone imine was investigated in phosphate buffer solution (pH 7.0) by means of standard electrochemical techniques. A quasi-reversible response for oxidation of paracetamol was identified on carbon nanotubes-based sensor with detection limit and sensitivity of 0.485 μM and 0.8406 A M^?1 cm^?2, respectively. It was found that the nitrogen doping in carbon nanotubes enhances the sensor's detection ability. Namely, electrochemical studies performed on film consisting of pristine carbon nanotubes reveal as well quasi-reversible response towards oxidation of paracetamol but nevertheless poorer detection ability and sensitivity (0.950 μM; 0.601 A M^?1 cm^?2). The findings strongly suggest the application of nitrogen-doped carbon nanotubes in biosensing.     

Nonlinear Filtering in Rieznnnnifln Manifolds

A general formulation of the nonlinear filtering problem inRiemanman manifolds is given by use of the strong solutionsof the stochastic differential equations for the state and observationprocesses in the orthonormal frame bundles of the state andobservation process manifolds, respectively. A general Bayesformula for the conditional expectation of smooth functionsof the state process is given. This is used to give a directderivation of the Zakai equation for the general problem underconsideration. An example is presented.     

Factorization of proper holomorphic maps on irreducible bounded symmetric domains of rank≥2

We obtain rigidity results on arbitrary proper holomorphic maps F from an irreducible bounded symmetric domain Ω of rank ≥2 into any complex space Z. After lifting to the normalization of the subvariety F (Ω) Z, we prove that F must be the canonical projection map to the quotient space of Ω by a finite group of automorphisms. The approach is along the line of the works of Mok and Tsai by considering radial limits of bounded holomorphic functions derived from F and proving that proper holomorphic maps between bounded symmetric domains preserve certain totally geodesic subdomains. In contrast to the previous works, in general we have to deal with multivalent holomorphic maps for which Fatou’s theorem cannot be applied directly. We bypass the difficulty by devising a limiting process for taking radial limits of correspondences arising from proper holomorphic maps and by elementary estimates allowing us to define distinct univalent branches of the underlying multivalent map on certain subsets. As a consequence of our rigidity result, with the exception of Type-IV domains, any proper holomorphic map f : Ω→ D of Ω onto a bounded convex domain D is necessarily a biholomorphism. In the exceptional case where Ω is a Type-IV domain, either f is a biholomorphism or it is a double cover branched over a totally geodesic submanifold which can be explicitly described.     

Electrochemical studies on novel films consisting of phosphorus-doped multi-walled carbon nanotubes

Ionics - Films consisting of phosphorus-doped multi-walled carbon nanotubes (further denoted as P-MWCNTs) were fabricated by means of chemical vapor deposition technique with decomposition of...