Electrospinning fabrication and characterization of poly(vinyl alcohol)/montmorillonite/silver hybrid nanofibers for antibacterial applications

Poly(vinyl alcohol) (PVA)/montmorillonite clay (MMT)/silver (Ag) nanoparticles have been electrospun for fabricating PVA/MMT/Ag nanofiber in aqueous solutions. Since PVA is a water-soluble and biocompatible polymer, it is one of the best materials for preparation of antibacterial nanofiber. MMT has been used as an inorganic filler to enhance properties of homopolymeric nanofiber. The PVA/MMT/Ag nanofiber diameter increases with increasing contents of MMT clay and Ag nanoparticles. In preservation test, the PVA/MMT/Ag nanofiber confirms an excellent antibacterial performance, elucidating for practical uses as a new preservative. Moreover, the PVA/MMT/Ag nanofiber shows improved thermal properties.     

Optical Emission and Raman Spectroscopy Studies of Reactivity of Low-Pressure Glow Discharges in Ar–O<Subscript>2</Subscript> and He–O<Subscript>2</Subscript> Gas Mixtures with Coked Catalysts

We demonstrate that low-pressure glow discharges in He–O₂ gas mixture are effective in removing carbonaceous surface layers from coked catalysts. These discharges contain a number of reactive species including O, O₃, and O₂*, and all these could contribute in the decoking process. However, an evolving understanding is that the O atoms in the discharge have a predominant role in this. A working hypothesis is that the O atoms react with the coke to form CO, CO₂ and other carbon complexes. Online measurements using emission spectra from O, H, and CO in the discharges are compared for the cases of He–O₂ and Ar–O₂ gas mixtures. Under the reported experimental conditions the estimated reactivity of the He–O₂ discharges is considerably higher compared with discharges in the Ar–O₂ gas mixture. Raman spectroscopy is used to confirm the removal of the coke from the surface of Pt/Alumina catalyst.     

Tributylammonium Halochromates/silica Gel:Simple Reagents for Oxidative Coupling of Thiols to Symmetrical Disulfides

New orange solid tributylammonium halochromates, (C₄H₉)₃N⁺CrO₃X^?, TBAXC (X=F, Cl) are easily synthesized by the reaction of tributylammonium fluoride and chloride with CrO₃ in a 1:1 molar ratio in the presence of HF and HCl. Tributylammonium halochromates(VI) are versatile reagent for the effective and selective oxidation of organic substrates. Silica gel supported TBAFC and TBACC are versatile reagents for the effective and selective oxidation of organic substrates, in particular, thiols, under mild conditions. Considerable improvements are observed in the presence of the absorbent, making the work‐up much more convenient.     

Pt/ZrO2:An Efficient Catalyst for Aerobic Oxidation of Toluene in Aqueous Solution

The heterogeneous oxidation of toluene in aqueous medium has been investigated. Artificially contaminated water with aromatic compound (toluene) was exposed to a simple platinized zirconia (1% Pt/ZrO₂) catalyst in the presence of molecular oxygen. This selective oxidation of toluene to benzyl alcohol, benzaldehyde and benzoic acid provides a step for removing toluene from wastewater or converting it into less harmful substances. Different parameters, e.g. the reaction time, temperature, pressure, the amount of catalyst and agitation, etc influenced the toluene conversion and selectivity. Typical batch reactor kinetic data were obtained and fitted to the classical Langmuir‐Hinshelwood model, Mars‐van Krevelen model as well as to the Eley‐Rideal model of heterogeneously catalyzed reactions. The Eley‐Rideal model was found to give a better fit. 1% Pt/ZrO₂ was observed to be the most active for oxidation of toluene at 333 K in oxygenated atmosphere [p(O₂) ca. 101 kPa] with a nominal stirring speed ≧900 r/min. It was found that catalytic oxidation may be an effective method for the removal of volatile organic compounds from aqueous solutions and comparable to other advanced oxidation processes.     

Separation/preconcentration and determination of vanadium with dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) and electrothermal atomic absorption spectrometry

A novel dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) for separation/preconcentration of ultra trace amount of vanadium and its determination with the electrothermal atomic absorption spectrometry (ETAAS) was developed. The DLLME-SFO behavior of vanadium (V) using N-benzoyl-N-phenylhydroxylamine (BPHA) as complexing agent was systematically investigated. The factors influencing the complex formation and extraction by DLLME-SFO method were optimized. Under the optimized conditions: 100 μL, 200 μL and 25 mL of extraction solvent (1-undecanol), disperser solvent (acetone) and sample volume, respectively, an enrichment factor of 184, a detection limit (based on 3S_b/m) of 7 ng L⁻¹ and a relative standard deviation of 4.6% (at 500 ng L⁻¹) were obtained. The calibration graph using the preconcentration system for vanadium was linear from 20 to 1000 ng L⁻¹ with a correlation coefficient of 0.9996. The method was successfully applied for the determination of vanadium in water and parsley.     

Fiber optic-linear array detection spectrophotometry in combination with dispersive liquid-liquid microextraction for preconcentration and determination of copper

In this research, simple, rapid and efficient method, dispersive liquid-liquid microextraction (DLLME) combined fiber optic -linear array detection spectrophotometry (FO-LADS) was developed using a cylindrical micro-cell for preconcentration and determination of Cu(II) in samples. DLLME and FO-LADS methods have good matching conditions for being combined since FO-LADS is a suitable method for the determination of analytes in low volume of the remained phase obtained after DLLME. Molar absorptivity of complex Cu with (4-benzylp iperidineditiocarbamate potassium salt) (BPDC) was determined as 2.75 × 10⁴ L mol^-1 cm^-1 at 7nmax = 436 nm. Under the optimum conditions the calibration graph was linear in the rage of 2–70 fug L^-1 with detection limit of 0.34 fug L^-1. The proposed procedure was successfully applied to the determination of Cu(II) in real water samples and human urine sample.     

Theoretical study on the reaction of hydrogen atoms with aniline

The reaction of aniline with hydrogen atom is investigated herein using the hybrid meta-DFT functional of BB1 K. Hydrogen atom is found to preferentially add at an ortho position. However, the fate of the o-(C₆H₅NH₂)H adduct is found to be solely the deactivation of the initial addition channel. The rate constant for the abstraction channel (C₆H₅NH₂ + H → C₆H₅NH + H₂) is fitted by the expression 1.10 × 10⁻¹¹ exp(−4,200/T) cm³ molecule⁻¹ s⁻¹. Our calculated rate constant for the abstraction channel agrees very well with the available experimental measurements. Satisfactory agreement is found between calculated and experimental measurements for the displacement channel (C₆H₅NH₂ + H → C₆H₆ + NH₂). Our detailed analysis for the corresponding displacements in toluene and phenol suggests that the three systems exhibit similar behavior with regard to the relative importance of abstraction and displacement channels.     

Melamine-(H_2SO_4)_3 and PVP-(H_2SO_4)_n as solid acids:Synthesis and application in the first mono-and di-nitration of bisphenol A and other phenols

Melamine and poly vinylpyrrolidone（PVP） reacted with neat sulfuric acid readily to form two new organic solid acids namely melamine-（H₂SO₄）₃ and PVP-（H₂SO₄）_n.These solid acids were used for the first nitration of bisphenol A as well as other phenols in the presence of NH₄NO₃.Mono- and di-nitro bisphenol A have been characterized with IR and ¹H NMR techniques.     

P-Dodecylbenzenesulfonic acid(DBSA),a Brфnsted acid-surfactant catalyst for Biginelli reaction in water and under solvent free conditions

We report herein the use of p-dodecylbenzenesulfonic acid(DBSA) as a catalyst for a one-pot Biginelli reaction to afford 3,4- dihydropyrimidinone derivatives in good to excellent yields.This reaction proceeds efficiently in water and under solvent free conditions.Comparisons of results indicate that although the yields are high and comparable for both methods,the reaction times are considerably shorter under solvent free conditions.     

Microwave assisted preparation of efficient activated carbon from grapevine rhytidome for the removal of methyl violet from aqueous solution

Grapevine rhytidome (the outer layer of bark on trunk), as an abundant and low-cost precursor, was used to prepare granular activated carbon with high surface area for the removal of methyl violet from aqueous solution. Microwave heating source was used to reduce the treatment time and energy consumption. To optimize the preparation, the effects of the different parameters, such as phosphoric acid concentration, acid/precursor weight ratio, impregnation time, microwave power, radiation time, and oven heating time on the ability of the samples for removal of methyl violet were studied. The obtained activated carbon was characterized by N₂ adsorption/desorption, SAXS, TEM and SEM methods. The adsorption of methyl violet onto the activated carbon was studied from both equilibrium and kinetic point of view and the results were compared with the commercial granular activated carbon. The rate of adsorption onto the prepared activated carbon was faster than commercial activated carbon. Different kinetic models were used to analyze the experimental kinetic data. The obtained activated carbon showed higher adsorption capacity (more than twice) for the adsorption of methyl violet in comparison with the commercial one. The equilibrium data were analyzed using different isotherm models. Adsorption was found to be maximum in the pH range 7-9.