Effect of cobalt doping on structural,optical and redox properties cerium oxide nanoparticles

Cobalt-doped ceria nanoparticles were synthesized using the polyol method under co-precipitation hydrolysis. The structural, morphological, optical and redox properties were observed to investigate the influence of different concentration of cobalt ion doping on the prepared CeO₂ nanomaterials in terms of X-ray diffraction, field-emission transmission electron microscopy, thermogravimetric analysis, Fourier-transform infrared spectroscopy, UV/vis absorption spectroscopy and temperature program reduction techniques. The optical band gap energy was calculated from the optical absorption spectra for doped ceria nanoparticles, which have been found to be 2.68, 2.77, and 2.82 eV for the 2, 4, and 7 mol% Co ion-doped CeO₂ nanoparticles, respectively. As observed, the band gap energies increases as the doping Co ion concentrations increased, which could be due to significant increased oxygen vacancies with Co doping. The synergistic interaction between Co and CeO₂ was the main factor responsible for high catalytic activity of cobalt-doped CeO₂ model catalysts.     

Electrochemical Synthesis and Characterization of Electroactive Conducting Polypyrrole Polymers

Conducting/electroactive polypyrrole polymers are synthesized electrochemically on glassy carbon in various electrolytes (counterions). The polymers' electroactivity is measured using cyclic voltammetry. The electrolytes are chloride, nitrate, p-toluene sulfonate, dodecyl sulfate, and dodecylbenzenesulfonate of sodium and potassium ferrocyanide. It is found that the electrolyte (dopant) markedly affects the redox behavior of the polypyrrole films.     

X-ray study of Hg2Cl2Br2 and HgCl2HgBr2 reactions in solid state

The reactions (I) Hg₂Cl₂(s) + Br₂(g) and (II) HgCl₂(s) + HgBr₂(s) have been investigated by an X-ray method. Both the reactions yield two forms of the mixed halide HgClBr, designated as α-HgClBr and β-HgClBr. The cell parameters of the two are as follows:α-HgClBr: $\text{a = 6.196}\text{A}\text{?}$, $\text{b = 13.12}\text{A}\text{?}$, $\text{c = 4.37}\text{A}\text{?}$, z = 4, ? = 5.91 g/cm³. The powder pattern and cell parameters are similar to that of HgCl₂. Therefore it is probable that the chlorine atoms, in the linear halogenHghalogen molecules of HgCl₂ structure have been replaced by bromines, and since the radius of the bromine atom is larger than that of chlorine, the lattice is larger in this case.β-HgClBr: $\text{a = 6.78}\text{A}\text{?}$, $\text{b = 13.175}\text{A}\text{?}$, $\text{c = 4.17}\text{A}\text{?}$, z = 4, ? = 5.40. These parameters are the same as those reported in the literature for β-Hg(ClBr)₂, and its X-ray powder pattern is similar to HgCl₂. Therefore this phase also has linear halogenHghalogen molecules but the distribution of Cl and Br atoms is perhaps random.Heating the products (I) and (II) up to the melting point increases the amount of α phase and decreases the β phase, whereas crystallization increases the β phase. DTA study has supported the X-ray findings.     

Functionalization of medium-chain-length poly(3-hydroxyalkanoates) as amphiphilic material by graft copolymerization with glycerol 1,3-diglycerolate diacrylate and its mechanism

Glycerol 1,3-diglycerolate diacrylate (GDD) was graft copolymerized onto poly(3-hydroxyoctanoate-co-3-hydroxyhexanoate) P(3HO-co-3HHX) to render the latter more hydrophilic. Grafting of P(3HO-co-3HHX) backbone was performed using benzoyl peroxide as free radical initiator in homogenous acetone solution. The graft copolymer of P(3HO-co-3HHX)-g-GDD was characterized using spectroscopic and thermal methods. The presence of GDD monomer in the grafted P(3HO-co-3HHX) materials linked through covalent bond was indicated by spectroscopic analyses. Different parameters affecting the graft yield viz. monomer concentration, initiator concentration, temperature and reaction time were also investigated. Water uptake measurement showed that P(3HO-co-3HHX)-g-GDD copolymer became more hydrophilic as the GDD concentration in the copolymer increased. Introduction of hydroxyl groups via grafted GDD monomers improved the wettability and imparted amphiphilicity to the graft copolymer, thus potentially improving their facility for cellular interaction. Thermal stability of grafted copolymer reduced with increased grafting yield. The activation energy, E_a, for the graft copolymerization was calculated at ～ 51 kJ mol^?1. Mechanism of grafting reaction was also proposed.     

Chemoselective one-pot access to benzo[e]indole-4,5-diones and naphtho[2,1-b]thiophene-4,5-diones via copper-catalyzed oxidative [3 + 2] annulation of α-oxoketene N,S-acetals/β-ketothioamides with α-/β-naphthols

An operationally simple and efficient one-pot method for the synthesis of 1-aroyl (or alkanoyl)-2-thioalkyl-3-aryl (or alkyl)-3H-benzo[e]indole-4,5-diones and naphtho[2,1-b]thiophene-4,5-diones has been devised by copper-catalyzed cross-coupling of α-oxoketene N,S-acetals/β-ketothioamides with α-/β-naphthols in open air for the first time. The key to the success of this transformation is the room temperature oxidation of α-/β-naphthol to 1,2-naphthoquinone as a reactive species, which undergoes formal [3 + 2] annulation with α-oxoketene N,S-acetals/β-ketothioamides via cascade sequence of Michael addition/tautomerization/oxidation/cyclization/aromatization reactions, enabling addition of a pyrrole/thiophene ring onto naphthoquinone moiety. Further, benzo[e]indole-4,5-diones were transformed to pentacyclic fused phenazine derivatives under solvent-free conditions. Based on our experimental outcomes, a tentative mechanistic rationale for this chemoselective protocol is proposed, which is well validated and supported by the control experiments.     

Studies on Benzothiazolo‐asycyanino‐colorants Synthesis,Structural Correlation with UV Absorption Maxima and Bactericidal Potentiality

Fifteen new chromophoric chain β‐aryl substituted butadienyl‐benzothiazole asy‐cyanine colorants are synthesized by condensing substituted 3‐isopropylbenzothiazolium iodides and 4‐dimethylaminostyrylphenyl ketones using alkaline ethanolic DMF solution. The colorants show bathochromic shifts in comparison with unsubstituted analogues and styryl analogues but hypsochromic shifts when compared to 3‐methylbenzothiazolium analogues. The highly purified samples are screened in vitro against gram positive and gram negative microbes using Disc diffusion technique and found to be mildly active against some of them.     

High flow addition curing polyimides

A new series of high flow PMR-type addition curing polyimides was developed, which employed the substitution of 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (BTDB) for p-phenylenediamine (p-PDA) in a PMR-II formulation. These thermoset polyimides, designated as 12F resins, were prepared from BTDB and the dimethyl ester of 4,4′-(hexafluoroisopropylidene)-diphthalic acid (HFDE) with either nadic ester (NE) or p-aminostyrene (PAS) as the endcaps for addition curing. The 12F prepolymers displayed lower melting temperatures in DSC analysis, and higher melt flow in rheological studies than the corresponding PMR-II polyimides. Long-term isothermal aging studies showed that BTDB-based 12F resins exhibited comparable thermo-oxidative stability to p-PDA based PMR-II polyimides. The noncoplanar 2- and 2′-disubstituted biphenyldiamine (BTDB) not only lowered the melt viscosities of 12F prepolymers, but also retained reasonable thermal stability of the cured resins. The 12F polyimide resin with p-aminostyrene endcaps showed the best promise for long-term, high-temperature application at 343°C (650°F). © 1994 John Wiley & Sons, Inc.     

Some generalizations of Ekeland-type variational principle with applications to equilibrium problems and fixed point theory

In this paper, we introduce the concept of a Q$Q$-function defined on a quasi-metric space which generalizes the notion of a τ$\tau$-function and a w$w$-distance. We establish Ekeland-type variational principles in the setting of quasi-metric spaces with a Q$Q$-function. We also present an equilibrium version of the Ekeland-type variational principle in the setting of quasi-metric spaces with a Q$Q$-function. We prove some equivalences of our variational principles with Caristi–Kirk type fixed point theorems for multivalued maps, the Takahashi minimization theorem and some other related results. As applications of our results, we derive existence results for solutions of equilibrium problems and fixed point theorems for multivalued maps. We also extend the Nadler’s fixed point theorem for multivalued maps to a Q$Q$-function and in the setting of complete quasi-metric spaces. As a consequence, we prove the Banach contraction theorem for a Q$Q$-function and in the setting of complete quasi-metric spaces. The results of this paper extend and generalize many results appearing recently in the literature.