Interaction between graphite oxide and Congo red in aqueous media

Interaction between graphite oxide and Congo red, a diazo dye containing NH₂ and SO₃ functional groups, was studied using UV–vis, FTIR, capillary electrophoresis and potentiometric methods. UV–vis experiments managed to elicit a colorful set of reactions, which were dependent on the sonication of solution. It was established that the molecules of Congo red after sonication are able to penetrate through the hydration shell and extract the protons attached to the functional groups on the surface of graphite oxide. Interaction between the graphite oxide particles and Congo red molecules is suggested to stabilize the aqueous suspensions of single-layer graphite oxide sheets. Potentiometric titration data show that the Congo red molecules adsorbed on the surface of graphite oxide are able to prevent the penetration of OH⁻ ions to reach the acidic functional groups inside the graphite oxide stacks. Electrostatic repulsion among these functional groups is quite high. Ionization of the graphite oxide colloidal particles with adsorbed Congo red molecules leads to the significant changes in their conformation.     

配合物Co(2-mpac)2(H2O)2的晶体结构与热稳定性

以2-甲基-5-羧基吡嗪为配体合成了标题化合物,并利用元素分析、红外光谱、单晶X-射线衍射以及热重分析对配合物进行了表征.晶体学数据:三斜晶系,P-1空间群,a=5.1068(7)(A),b=6.3725(8)(A),c=12.2900(16)(A),α=103.5740(10)°,β=91.057(2)°,γ=108...     

Colloidal stability of gadolinium-doped ceria powder in aqueous and non-aqueous media

In this work the colloidal behaviour of Ce_0.9Gd_0.1O_2?δ powder in aqueous and non-aqueous media (ethanol) is studied. Commercial powder was characterised by particle size distribution, specific surface area measurements, X-ray diffraction and scanning electron microscopy. Diluted suspensions were characterised by particle size distribution and zeta potential, using dynamic light scattering and laser Doppler velocimetry principles, respectively. The solubility of the powder in water as a function of pH was analysed by inductively coupled plasma atomic emission spectrometry. Colloidal stability was studied as a function of pH, type and concentration of dispersants (polyacrylic-based deflocculant in water and a phosphate ester in ethanol). The time stability of the suspensions was analysed by multiple light scattering. The most stable suspension was obtained with a phosphate ester content of 2.0 wt% in ethanol. Finally, preliminary coatings have been obtained by dip coating using concentrated suspensions, which could be accessible to industrial scale so that they can be used as interlayers in solid oxide fuel cells.     

配合物Ni（bacbh）2（Py）2的合成、晶体结构及热稳定性

以苯亚甲基苯乙酮-4-氯苯甲酰腙为配体,水热合成了一个镍的单核配合物Ni(bacbh)2(Py)2(bacbh:苯亚甲基苯乙酮-4-氯苯甲酰腙;Py:吡啶),并利用元素分析、红外光谱、X射线单晶衍射及热失重分析对配合物进行了表征。该配合物为单斜晶系,空间群为P2(1)/n,晶胞学数据:a=1.344 3(6)nm,b=2.471 7(12)nm,c=1.465 1(7)nm,β=98.47°,V=4.815(4)nm3,Z=4,μ=0.561 mm-1,Dc=1.292 mg/m3,F(000)=1 944,最终偏离因子[I>2sigma(I)]R1=0.038 6,wR2=0.096 1(all data),GOF=1.007(CCDC:840865)。     

Electrochemical oxidation of terbium(III) in aqueous media: influence of supporting electrolyte on oxidation potential and stability

Journal of Applied Electrochemistry - Apart from the generally dominant trivalent oxidation state, several lanthanides can occur in divalent or tetravalent states as well. Changing the valence...     

Functional polymers. LIII. Photochemical behavior of 2(2-hydroxyphenyl)2H-benzotriazole derivatives

Summary The absorption spectra of 2 [2-hydroxy-5-(meth) acryloxyphenyl] 2H-benzotriazoles, their homoand copolymers were studied. The immediate environment (next monomer units in copolymers) determine the details of the spectral characteristics. Copolymers are more efficient in photostabilizing poly-cis-1, 4-butadiene-1, 3 in solution than the monomer or the homopolymer.Functional Polymers LII., S.J. Li, S.K. Fu, O. Vogl; Monatshefte für Chemie, in press     

Functional polymers. LVI. Photochemical behavior of 2(2-hydroxyphenyl)2H-benzotriazole derivatives

Summary Introduction of a second benzotriazole unit into 2(2-hydroxyphenyl)2H-benzotriazole structures causes a significant hyperchromic effect on the absorption spectra, the addition of a second hydrogen bonding hydroxyl group causes a small bathochromic shift, but a significant effect on the fluorescence spectrum.Functional Polymers. LV., Y.C. Jiang, S.K. Wu, A. Sustic, F. Xi, and O. Vogl, Polymer Bulletin 20, 161 (1988)     

Functional polymers. LV. Photochemical behavior of 2(2-hydroxyphenyl)2H-benzotriazole derivatives

Summary Polymerizable 2(2-hydroxyphenyl)2H-benzotriazole ultraviolet absorbers have the normal hydrogen bonded maximum at 340 nm. When more than one ortho-hydroxy group capable of hygen bonding is present in the molecule the extinction coefficient increases dramatically; the fluorescence spectra are also affected. It is expected that these compounds are very effective ultraviolet stabilizers.Functional Polymers. LIV., G.S. Dai, S.K. Wu, A. Sustic, F. Xi, and O. Vogl, Polymer Bulletin 20, 67 (1988)     

Functional polymers. LIV. Photochemical behavior of 2(2-hydroxyphenyl)2H-benzotriazole derivatives

Summary The absorption spectra of 2(2-hydroxyphenyl)2H-benzotriazoles derivatives substituted with electron-donating and withdrawing groups in various positions on the phenyl ring allowed to estimate the relative stability of the hydrogen-bonded structures as evidenced by the 340 nm/300 nm ratio.Photodegradation studies of poly-cis-1,4-butadiene-1,3 with and without 2(2-hydroxyphenyl) benzotriazole absorbers with various substituents show that compounds with R=H are better photostabilizers than those with RH.Functional Polymers LIII., R.X. Liu, S.K. Wu, S.J. Li, F. Xi, O. Vogl; Polymer Bulletin 20, 59 (1988)     

Kinetics and stability of a chromobacterium viscosum lipase in reversed micellar and aqueous media

The lipolytic activity of Chromobacterium viscosum lipase B (EC 3.1.1.3.; triacylglycerol hydrolase) solubilized both in water and AOT/isooctane reversed micelles has been investigated using triolein as a substrate. The influence of relevant parameters in the catalytic activity such as temperature, pH, surfactant and substrate concentrations, and water content was tested and compared in both media. A study of stability of the lipase was carried out, with particular reference to the influence of pH. Three major effects of the encapsulation of the lipase in the micelles were observed: increased activity (up to 7 times higher than in water), greater stability, specially at pH 7, and higher resistance to thermal deactivation.     

High luminescent brightness and thermal stability of red emitting Li3Ba2Y3(WO4)8:Eu3+ phosphor

A series of Li₃Ba₂Y_3−x(WO₄)₈:xEu³⁺ (x=0.1, 1, 1.5, 2 and 2.8) phosphors were synthesized by a high temperature solid-state reaction method. Under the excitation of near ultraviolet (NUV) light, the as-prepared phosphor exhibits intense red luminescence originating from the characteristic transitions of Eu³⁺ ions, which is 1.8 times as strong as the commercial Y₂O₂S:Eu³⁺ phosphor. The optimal doping concentration of Eu³⁺ ions here is confirmed as x=1.5. The electric dipole-quadrupole (D-Q) interaction is deduced to be responsible for concentration quenching of Eu³⁺ ions in the Li₃Ba₂Y₃(WO₄)₈ phosphor. The analysis of optical transition and Huang-Rhys factor reveals a weak electron-phonon coupling interaction. The temperature-dependent emission spectra also indicate that the as-prepared Li₃Ba₂Y₃(WO₄)₈:Eu³⁺ phosphor has better thermal stability than that of the commercial Y₂O₂S:Eu³⁺ phosphor. Therefore, our results show that the as-prepared Li₃Ba₂Y₃(WO₄)₈:Eu³⁺ phosphor is a promising candidate as red emitting component for white light emitting diodes (LEDs).     

Sericite-chalcocite mineral particle interactions and hetero-aggregation (sliming) mechanism in aqueous media

Attractive particle interactions which lead to hetero-aggregation or “sliming” of gangue and valuable mineral particles are encountered in a number of hydrometallurgical and flotation processes. Sliming leads to poor recovery of the valuable, hydrophobic minerals and high recovery of hydrophilic gangue particles in flotation concentrates. In the present work, the influence of interfacial chemistry and dispersion conditions on particle interactions which underpin the mechanism of hetero-aggregation between sericite and chalcocite particles was investigated in the pH range 5-9 at 23 °C. Hetero-aggregation is shown to occur under aqueous dispersion conditions where the fluid shear rate was high and the individual chalcocite and sericite particles were negatively charged, as shown by the electrokinetic potential data. Continuous flow particulate adsorption and rheological studies revealed that the hetero-aggregation behaviour was strongly pH and oxidative environment dependant. Sliming was greater at lower than higher pH and under air saturation than N₂ gas purge. The unexpected hetero-aggregation is ascribed to chalcocite (Cu(I)₂S) surface oxidation and dissolution which accentuated with decreasing pH and Cu (II) ion hydrolysis effect. Specific adsorption of Cu (II) complexes onto the mix minerals’ surfaces had a striking impact on the interfacial chemistry, reflecting significantly enhanced dispersion shear yield stress. The attractive particles’ interactions are believed to be due to a combination of Cu(II)-mediated mechanisms including: electrostatic-charge patch attraction, van der Waals attraction, adsorbed ion-particle bridging, surface nucleation and cementation. Sliming mitigation was demonstrated by the use of N₂ gas and higher pH, as evidenced by markedly lower sericite-chalcocite dispersion shear yield stress and greatly reduced particulate adsorption behaviour.     

Complex system of poly(methacrylic acid) with poly(vinylpyrrolidone) in aqueous media

Two‐component polymer solutions [i.e., poly(methacrylic acid) (PMAA) and poly(vinylpyrrolidone) (PVP)] were prepared through solution polymerization. The complex system PMAA/PVP was obtained through the mixing of a PMAA solution and a PVP solution in different volume ratios at certain concentrations. The properties of the component solutions and the complex system were investigated with transmittance, surface tension, and viscosity measurements. The results showed that the properties of the complex system were related not only to the ratio of PMAA to PVP but also to the concentration of the PMAA and PVP solutions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2280–2286, 2005     

Poly(vinyl chloride) thermal stability. I. Evaluation by melt rheology

Capillary rheometry is used to characterize the thermal stability of poly(vinyl chloride). By isothermally extruding the polymer melt at constant shear rate, apparent viscosity–time relationships are obtained having three distinct regions: (1) obtainment of equilibrium viscosity, (2) constant viscosity, and (3) rapidly changing viscosity. During regions 2 and 3 the polymer extrudate gradually changes in color from water clear to black. These characteristic regions are related to the temperature of extrusion by Arrhenius plots. An activation energy of 40 kcal./g.-mole was calculated for the decomposition of PVC. Infrared spectroscopy, thermal gravimetric analysis, and intrinsic viscosity experiments are used to corroborate the results of the melt flow data.     

Corrosion and mechanical behavior of fusion bonded epoxy (FBE) in aqueous media

In recent years there have been many reported cases of corrosion failure in cement concrete pipelines. In the majority of cases, the failures have been attributed to rebar corrosion which is caused by the permeability of chloride from low resistivity soil and subsequent attack on a passive layer on an iron bar in the structure. As a possible alternative to cementitious materials, some organic coatings based on olefin, vinyl or epoxy-based polymers have been considered. However, due to a paucity of data on the behavior of these coatings in aqueous media— particularly product water—the possibility of their application in water transmission systems in the Kingdom has not been fully exploited. This paper deals with the studies carried out on the corrosion and mechanical behavior of fusion bonded epoxy (FBE) coating on steel in aqueous media which include product water, distilled water and saline water. The mechanical testings on coating include adhesion, bending and cathodic disbondment testings. The corrosion studies include immersion testing under static and dynamic conditions, autoclave tests and accelerated (salt-fog) tests. The analysis of results indicates chemical inertness of FBE coating in either of the aforementioned water used during testing, good adhesion and no damage to the coating during bending. Cathodic disbondment tests indicate that FBE coating sustains under cathodic protection (CP) conditions. In general, the results of mechanical and corrosion tests indicate that FBE is a promising material for internal coating on steel in water transmission systems.     

2-（3-羟基苯基）[60]富勒烯吡咯烷衍生物的合成及热稳定性

利用甘氨酸和3-羟基苯甲醛与C60发生1,3-偶极环加成反应,合成分离得到了2-(3-羟基苯基)[60]富勒烯吡咯烷,用UV-Vis、1H-NMR、FT-IR、MS等测试手段表征了产物的结构,并通过单因素方法,探讨了反应条件对产物产率的影响,得到最佳工艺条件:反应物摩尔比1∶3∶6,温度95℃,反应时间18h,产物的产率可达75%(以消耗的C60计)。利用差热分析仪测试了产物的热稳定性,结果表明,产物在空气中具有良好的热稳定性。     

Formation of mesoglobules in aqueous media from thermo-sensitive poly(ethoxytriethyleneglycol acrylate)

A series of six poly(ethoxytriethyleneglycol acrylate) (PETEGA) homopolymers were synthesized by atom transfer radical polymerization, reversible addition-fragmentation transfer polymerization, and anionic polymerization in order to cover a molecular weight range from 7,000 to 40,000 Da. The polymers exhibited a lower critical solution temperature (LCST) behavior in water, which was observed by the occurrence of a cloud point (CP) at around 35 °C. The transmittance of visible light versus temperature dependence overlapped during the cooling and the heating cycles, showing almost a complete lack of hysteresis. Moreover, instead of the occurrence of an uncontrolled macroscopic phase separation, stable colloidal aggregates (mesoglobules) of narrow distribution in particle size were formed in water at temperatures above the LCST of PETEGA at 1 g L⁻¹ solutions. The dimensions of the mesoglobules ranged from 91 to 235 nm, and particle size was not influenced by the molecular weight of PETEGA. Temperature changes caused considerable variations of the mesoglobules dimensions, which were smaller at higher temperatures. The addition of an anionic surfactant simultaneously increased the CP values by 4–6 °C and lowered the dimensions of the mesoglobules.     

Photochemical reactions of antioxidant sesamol in aqueous solution

Antioxidant intermediate radicals generated by continuous ultraviolet (UV) and pulsed UV laser irradiation of sesamol in aqueous solutions were investigated. Radical species with the intensity ratio of 1∶4∶6∶4∶1 were observed by using continuous wave electron paramagnetic resonance (EPR) with continuous UV irradiation. The radical was also observed after the irradiation. To observe the intermediate radical right after the excitation, Fourier transform EPR (FT EPR) was used. Trace amounts of the same radical were also detected by FT EPR with pulsed UV laser. Based on the hyperfine coupling constant (2.3 G) and g-value (2.0048), together with FT EPR results, this radical was found to be a benzoquinone anion radical. The radical might have been produced via multistep reactions of the excited sesamol in aqueous solution, and it was stable for at least several minutes. In addition to the benzoquinone radical, the formation and dynamics of the sesamolyl radical were investigated by using FT EPR. FT EPR showed the detailed behavior of the radical. Characterization of the intermediate is important to evaluate the antioxidant sesamol. Part of these results was presented at the 90th American Oil Chemists’ Society Annual Meeting & Expo, Orlando, FL, May 1999.