Isomorphous Substitution of Metallic Elements for Zeolite Y in the Aqueous Solution

The substitutions of Ti, Fe and Zr into zeolite Y in the aqueous solutions of (NH4)2TiF6, (NH4)3ZrF7 and (NH4)3FeF6 were systematically Investigated. It was found that Ai atoms in the framework can be replaced by some metallic elements and the extent of substitution depends on the M/A1 ratio of the solution. The maximum allowable M/A1 ratio of the aqueous solution Is related with the radius of the M atom and the stability constant of the MFnm- complex. The substituted zeolite samples with crystallinity greater than 80% were characterized by means of XRD, IR, DTA, TPR and NH3-TPD measurements. The incorporation of Ti, Fe and Zr into the zeolite leads to an increase in the unit cell parameter, a lowering of thermal stability and a red shift of the asymmetric stretching frequency. The extent of these changes is apparently related with the ionic radius of the metallic element and the degree of substitution. The results of various characterization methods show that the het-eroatoms are readily Introduced int     

A Gold Electrode QCM Study on the Self-Assembling Process of Thioglycollic Acid in Aqueous Solution

Quartzcrystalmicrobalance(QCM)iswellknownasanexcellenttoolforthestudyofchemicaland/orphysicalprocessesonthesolidsurfaceaccompaniedbymasschangedowntoananogramlevell.Inaddition,itiswellestablishedthatathiol-containingcompoundisabletoadsorbonsomesubstrates(e.g.,An,Cu,andCd)toformaself-assembledmonolayerbythewell-knownchemicalreactionofthethiolgroupwiththesubstrate2.Tothebestofourknowledge,therearenoreportsontheself-assemblingprocessesofalkanethiolcompoundsinaqueoussolutionswithQCMteclmique.In…     

Interaction Between Ranitidine Hydrochloride and Bovine Serum Albumin in Aqueous Solution

The interaction between ranitidine hydrochloride (RAN) and bovine serum albumin (BSA) in aqueous solution was investigated by means of fluorescence, synchronous fluorescence, and UV-Vis spectroscopy. The fluorescence of BSA was quenched remarkably by RAN and the quenching mechanism was concluded to be static quenching. The binding constants K and the number of binding sites n were calculated at three different temperatures. The RAN–BSA binding distance was determined to be less than 8 nm, suggesting that energy transfer may occur from BSA to RAN. The interaction process is spontaneous. Based on the obtained thermodynamic parameters, electrostatic forces may play a major role in this process. In addition, the effect of RAN on the conformation of BSA was analyzed using synchronous fluorescence spectra.     

Calorimetry to Evaluate Inclusion Mechanism in the Complexation Between 2-hydroxypropyl-β-cyclodextrin and Barbiturates in Aqueous Solution

Two different types (structures) of inclusion complexes with a 1:1 stoichiometry between barbiturates and 2-hydroxypropyl-β-cyclodextrin (HPCyD) were realized in aqueous solution using isothermal titration calorimetry and molecular dynamics simulation. The first type of complex with a higher association constant was entropy driven and the substituent R ₂ was inserted into the HPCyD cavity by hydrophobic interaction. The barbituric acid ring contributed to the second type of complex, which was characterized by large negative values of ΔH and small positive ΔS reflecting van der Waals interaction and/or hydrogen bonding formation between the hetero atoms in the barbituric acid ring and the secondary hydroxyl groups of HPCyD. This revised version was published online in July 2006 with corrections to the Cover Date.     

Aqueous Solutions of Colloidal Ruthenium: the Radiation–Chemical Preparation and Optical Absorption

The radiation-chemical reduction of Ru(III) is studied in aqueous RuCl₃ solutions containing isopropyl alcohol. In the presence of sodium polyacrylate, the stable sols of metal are formed with spherical particles 4–8 nm in diameter. The optical spectrum of nanoparticles is characterized by an increasing absorption in the UV spectral region with no maximum (₂₀₀ = 7.2 × 1030 l mol^–1 cm^–1). The colloids of ruthenium in an aqueous solution are stable in the open air.     

γ-Radiation-Initiated Polymerization of Acrylonitrile in Aqueous Solution and in Emulsion

The γ-radiation-initiated polymerization of acrylonitrile (AN) at 25[ddot] C has been studied, both in aqueous solution and in emulsion, at dose rates between 70 and 175 krad/hr. The effect of added emulsifier, sodium lauryl sulfate (SLS), on reaction rates, R_p, and on polymer molecular weight, M_n, has been investigated. G (monomer polymerized) values ranged from 7,500 in aqueous solution to 20,000 in bulk to 45,000 in emulsion, all based on the total energy absorbed. In the aqueous solution polymerization, where R_p is approximately first order in initial monomer concentration over the range 0.15 ± [AN]_o ± 1.06 moles/liter, addition of SLS increases R_p but does not influence the order of the reaction with respect to [AN]_o. In the emulsion system at 70 krad/hr and at a phase volume ratio AN/H₂O of 1/2, (PR = 1/2), R_p varies as [SLS]^0.1 over the concentration range 0.01 ± [SLS] ± 2.5± wt/vol of aqueous phase. At the same PR value, and at 80 krad/hr, M_n of the polymer (measured by viscometry in dimethylformamide solution) is effectively independent of [SLS] in the range of 0.01 ± [SLS] ± 10± wt/vol of aqueous phase. Initial R_p values are either independent of PR in the range 1/3 ± PR ± 1/1 or exhibit an insensitive and unsystematic dependence thereon. Based on measurements at 70 and at 175 krad/hr, the intensity exponent of R_p at PR = 1/2 is approximately 0.4.     

Structure of the β-Cyclodextrin·p-Hydroxybenzaldehyde Inclusion Complex in Aqueous Solution and in the Crystalline State

-Cyclodextrin (-CD) and p-hydroxybenzaldehyde (p-HB) were studied by ¹H-NMR in deuterated aqueous solution and the stoichiometry of the resulting complex (1:1) was determined by the continuous variation method. Inclusion of p-HB in -CD was confirmed by the observation of NMR shifts for the inside H5 protons of the -CD cavity. In the solid state X-ray analysis was carried out and revealed the detailed structure of the inclusion complex. Two -CDs cocrystallize with four p-HB and 9.45 water molecules[2(C₆H₁₀O₅)^7·4C₇H₆O_2·9.45H₂O] in the triclinic space group P1 with unit cell parameters: a = 15.262(2), b = 15.728(1), c = 16.350(1) Å, = 92.67(1)°, = 96.97(1)°, = 103.31(1)°. The anisotropic refinement of 1973 atomic parameters converged at an R-factor = 0.066 for 10157 data with F_o ² > 2 (F_o ²). The 2:4 stoichiometry for the -CD inclusion complex with p-HB in the crystalline state is different from that obtained in solution. -CD forms dimers stabilized by direct O2(m)₁O3(m)₁·O2(n)₂O3(n)₂ hydrogen bonds (intradimer) and by indirect O6(m)₁·O6(n)₂ hydrogen bonds with one or two bridging water molecules joined in between (interdimer). These dimers are stacked like coins in a roll constructing infinite channels where the p-HB molecules are included. The p-HB molecules direct their polar CHO and OH groups into the nonpolar -CD cavities and are hydrogen bonded to each other, yielding infinite, antiparallel chains. In addition, crystals of the complex were also investigated with thermogravimetry, vibrational spectroscopy (FTIR), and ¹³C CP-MAS NMR spectroscopy. The results obtained enabled us to structurally characterize the -CD inclusion complex with p-HB.     

Electrophoretic Mobilities of the Isotopes of Chloride and Bromide Ions in Aqueous Solution at 25 °C and Infinite Dilution

The electrophoretic mobilities of a few halide isotopes in aqueous solution have been evaluated at 25 °C and infinite dilution by analyzing a combination of data obtained by capillary electrophoresis (CE) and conductance data extracted from the literature. The effect of the temperature on the electrophoretic mobility has been thoroughly re-investigated to give the following temperature dependence for the chloride ion at 25 °C: 1.565%/ °C in 5×10⁻³ mol⋅L⁻¹ sodium chromate + 3×10⁻³ mol⋅L⁻¹ sodium borate buffer. The precise determination of the electrophoretic mobility of chloride and bromide ions, including the evaluation of their associated uncertainties, has been performed from conductance data spanning over 75 years. The electrophoretic mobilities are found to be −(79.124±0.020)×10⁻⁹ m²⋅V⁻¹⋅s⁻¹ for Cl⁻ and −(80.99±0.04)×10⁻⁹ m²⋅V⁻¹⋅s⁻¹ for Br⁻. Thanks to the precise determination of the temperature contribution and the re-evaluation of conductance data, the following values have been found for ³⁵Cl⁻, ³⁷Cl⁻, ⁷⁹Br⁻, and ⁸¹Br⁻ (in 10⁻⁹ m²⋅V⁻¹⋅s⁻¹): −(79.18±0.02), −(78.95±0.06), −(81.04±0.04), and −(80.94±0.04).     

Synthesis and Spectroscopic Characterizations of an Insulinomimetic Peroxovanadate Complex in Aqueous Solution

The reaction system of diperoxooxalatovanadate {K_3 [VO (O_2)_2-(C_2O_4)]·H_2O, bpV(Oxa)} and imidazole was studied in anaqueous solution by 1D multinuclear (~1H, ~(13)C and ~(51)V) NMR,2D NMR diffusion ordered spectroscopy (DOSY), and variabletemperature NMR techniques. It was shown that DOSY was auseful tool for the study of a mixture. All of the ~1H and ~(13)CNMR signals of the peroxovanadate (V) complexes were as-     

Adsorption and Aggregation Behavior in Aqueous Solution of Tetrasiloxane-based Carboxylate Surfactants via “Thiol-ene” Photochemical Reaction

Anionic silicone surfactants have long been a neglected field. In this paper three anionic silicone surfactants were synthesized first time from dichloromethylvinylsilane through hydrolysis-condensation, “thiol-ene” photo- chemical and then salting reaction. The critical aggregate concentration (CAC), surface tension, minimum surface area per surfactant molecule and surface pressure at CAC were studied by both surface tension and electrical conductivity. The results showed that they had significant surface activity at the gas/liquid interface and were capable to reduce the surface tension of water to approximately 20 mN m⁻¹. The results of transmission electron microscopy showed that the three silicone surfactants self-assembled into spherical aggregates of uniform size in aqueous solution above the CAC. The dynamic light scattering results demonstrated that the size of the aggregates was determined to be in the range from 60 to 300 nm at 0.05 mol L⁻¹ and the order of the size of the aggregates is (Me₃SiO)₃SiCO₂Li<(Me₃SiO)₃SiCO₂Na<(Me₃SiO)₃SiCO₂K.     

The Dependence of the PdCl 4 2− /Pd0 Electrode Potential on the Dispersity of Metallic Palladium

It was found that metastable equilibrium in the heterogeneous reaction

Investigation on the Electrochemical Polymerization of Catechol by Means of Rotating Ring—disk Electrode

The electrolysis of catechol was studied in the pH values of 1 to 10. The results from the rotating ring-disk electrode (RRDE) experiments show that at low pH values,the electrochemical polymerization of catechol was performed by one step,and at higher pH values,the electrochemical polymerization of catechol was carried out by two steps,i.e.oxidation of catechol and followed by polymerization.The intermediates generated at the disk were detected at the ring electrode in the ring potential region of -0.2 to 0 V(vs.Ag/AgCl).One of reasons for the decrease in the ratio of ir to id with increasing the ring potential is caused by formation of positively charged intermediates at the disk electrode.This ratio increases with increasing the rotation rate of the RRDE,which indicates that the intermediates are not stable.A shielding effect during polymerization of catechol was observed when the ring potential was set at 0.1 V (vs.Ag/AgCl).The electron spin resonance(ESR) of polycatechol show that polycatechol possesses unpaired electrons.The images of polycatechol films synthesized at differentconditions are described.     

Investigation of Electrochemical Charging Behaviors of“Naked” Gold Nanoparticles Ensembles in Aqueous Media

Gold nanoparticles were imnoobilized onto the electrode surface by simple self-assembly technique.Interestingly,the ensembles of these nanoparticles exhibit quantized charging behaviors in aqueous solution.Possible mechanism for such behaviors was proposed.     

Thermodynamic Data for the Complex Formation of Alkylamines and Their Hydrochlorides with α-Cyclodextrin in Aqueous Solution

The formation of complexes between α-cyclodextrin and n-alkylamines and their hydrochlorides has been studied in aqueous solution using calorimetric titrations. All alkylamines form stronger complexes than the corresponding hydrochlorides. The values of the reaction enthalpies are smaller for the alkylamine hydrochlorides compared with the alkylamines. By increasing the number of methylene groups, these differences become smaller. In addition, the reaction enthalpies for protonation of the alkylamines and their complexes with α-cyclodextrin have been measured. The heat of protonation of these complexes is always smaller compared with the alkylamines. Due to the protonation and the formation of a strong solvation shell around the ammonium group the interactions with α-cyclodextrins are weakened. From a thermodynamic cycle using all measured reactions, it can be concluded that the aggregation of the alkylamines with long alkyl chains (heptyl-, octyl-, and nonylamine) has an influence on the values of the reaction enthalpies and entropies for the protonated form only.This revised version was published online in July 2005 with a corrected issue number.     

Studies of the Atrazine Aqueous Suspension Stability in the Presence of an Anionic Polymer—Influences of Polymer Molecular Weight and Solution pH

The influence of the molecular weight of sodium salt of styrene/methacrylic acid (SSMA) copolymers and solution pH value (range of 3–11) on the stability of the atrazine suspension was studied. SSMA with different molecular weights was synthesized by emulsion polymerization. Adsorption, zeta potential measurements, microscopy, and suspension stability measurements were carried out. The obtained results indicate that the adsorption of SSMA on the surfaces of atrazine particles decreases with the increase of the molecular weight, and the hydrogen bonding is the main adsorption force. The presence of SSMA improves the stability of the atrazine suspension. The stability of the atrazine suspension decreases with the increase of the molecular weight of SSMA. On the other hand, the stability of the atrazine suspension with SSMA increases firstly and then decreases with the increase in solution pH in the range of 3–11.     

Thermodynamic and 13C NMR Studies of the Inclusion Complexes of α- and β-Cyclodextrins with Cyano- and Nitrophenols in Aqueous Solution

Equilibrium constants for the formation of 1 : 1 inclusioncomplexes of -cyclodextrin (-CD) with neutral and anionic phenol derivatives (3- and 4-cyanophenols and 3- and 4-nitrophenols) have been evaluated at 5, 12, 25, and 35 °C by means of spectrophotometry. Similarly, the equilibrium constants have been determined for the inclusion complexes of-cyclodextrin (-CD) with the phenols. Enthalpy and entropy changes for the formationof the inclusion complexes have been estimated from the temperature dependences of theequilibrium constants. With -CD, the enthalpy andentropy changes for the anionic species have been found to be more negative than those for the neutral ones, except for 4-cyanophenol, suggesting that the inclusion complexes of the anionic species are more rigid than those of the neutral species. From analyses of chemical shift differences in ¹³C NMR spectra of 3- and 4-cyanophenolsand 3- and 4-nitrophenols in aqueous solutions with and without CDs, a nitro ora cyano group has been found to be first bound to the - and -CD cavities.     

Standard Enthalpies of Formation of β-Aminobutyric Acid and Products of Its Dissociation in Aqueous Solution

Russian Journal of Physical Chemistry A - Heats of dissolution of β-aminobutyric acid in water and aqueous solutions of potassium hydroxide at 298.15 K are measured via direct calorimetry....     

Removal of Disperse Dyes from Aqueous Solution Using Sawdust and BDTDA‐Sawdust

The adsorption of two disperse dyes, disperse blue 56 and disperse red from aqueous solution onto sawdust (SD) and benzyldimethyltetradecyl ammonium (BDTDA) treated sawdust has been studied. The effect of initial concentration of dyes, pH, and contact time has been studied. The pH had a considerable influence on adsorption and optimum pH for adsorption of disperse dyes is found to be in the range of 2–3. The experimental data were analyzed using Langmuir and Freundlich adsorption isotherm equations. The experimental data were fitted well to pseudo first order kinetic model with R²>0.99. The results indicate that sawdust modified with surfactant can be employed as a low cost alternative to commercial activated carbon for the removal of disperse dyes.     

Spontaneous Vesicle Formation in Mixed Aqueous Solution of Poly-tailed Cationic and Anionic Surfactants

Spontaneous vesicles from the mixed queous solution of poly-talied cationic surfactant PTA and anionic surfactant AOT are firstly obtained.Vesicle formation and characterizations are demonstrated by negative-staining TEM and dynamic light scattering.A monodisperse vesicle system is obtained with a polydispersity of 0.082.Ultrasonication can promote the vesicle formation,Mechanism of vesicle formation is discussed from the viewpoint of molecular interaction.