Simple and efficient synthesis of N-alkyl and N-aryl succinimides in hot water

A new, simple synthesis of succinimides is described. The reactions were carried out under the ultimate green conditions excluding both catalyst and organic solvent by applying simple stirring at 100?°C. A wide variety of N-susbstituted succinimides have been prepared in high yields by using succinic acid and primary amines in hot water. Yield of N-alkyl substituted succinimides were found to be higher than those of N-aryl substituted succinimides.     

Fabrication of an Electrochemical E. coli Biosensor in Biowells Using Bimetallic Nanoparticle‐Labelled Antibodies

An electrochemical biosensor was developed for the determination of Escherichia coli (E. coli) in water. For this purpose, silver‐gold core‐shell (Ag@Au) bioconjugates and anti‐E. coli modified PS‐microwells were designed in a sandwich‐type format in order to obtain higher sensitivity and selectivity. Ag@Au bimetallic nanoparticles were synthesized by co‐reduction method. The core‐shell formation was analyzed by using UV‐Vis spectroscopy and transmission electron microscopy. Biotin labeled anti‐E. coli antibodies were coupled with Ag@Au nanoparticles to form bioconjugates. The electrochemical immunosensor was prepared by immobilizing anti‐E. coli on polystyrene (PS)‐microwells via chemical bonding. These modified microwells were identified with X‐ray photoelectron spectroscopy and surface enhanced Raman spectroscopy. E. coli was sandwiched between Ag@Au bioconjugates and anti‐E. coli on PS‐microwells at different concentrations. The relationship between the E. coli concentration and stripping current of gold ions (Au³⁺) were investigated by square wave anodic stripping voltammetry at pencil graphite electrode. The proposed method can provide some advantages such as lower detection limit and shorter detection time. The electrochemical response for the immunosensor was linear with the concentration of the E. coli in the range of 10¹ and 10⁵ cfu/mL with a limit of detection 3 cfu/mL. The procedure maintains good sensitivity and repeatability and also offers utility in the fields of environmental monitoring and clinical diagnosis.     

Tailoring Electrochemical CO2 Reduction on Copper by Reactive Ionic Liquid and Native Hydrogen Bond Donors

Electrochemical CO₂ reduction (CO₂RR) on copper (Cu) shows promise for higher-value products beyond CO. However, challenges such as the limited CO₂ solubility, high overpotentials, and the competing hydrogen evolution reaction (HER) in aqueous electrolytes hinder the practical realization. We propose a functionalized ionic liquid (IL) which generates ion-CO₂ adducts and a hydrogen bond donor (HBD) upon CO₂ absorption to modulate CO₂RR on Cu in a non-aqueous electrolyte. As revealed by transient voltammetry, electrochemical impedance spectroscopy (EIS), and in situ surface-enhanced Raman spectroscopy (SERS) complemented with image charge augmented quantum-mechanical/molecular mechanics (IC-QM/MM) computations, a unique microenvironment is constructed. In this microenvironment, the catalytic activity is primarily governed by the IL and HBD concentrations; former controlling the double layer thickness and the latter modulating the local proton availability. This translates to ample CO₂ availability, reduced overpotential, and suppressed HER where C₄ products are obtained. This study deepens the understanding of electrolyte effects in CO₂RR and the role of IL ions towards electrocatalytic microenvironment design.     

Effect of trace metals on reactive crystallization of gypsum

The effect of Fe²⁺, Fe³⁺, and Cr³⁺ ions on crystallization of calcium sulfate dihydrate (gypsum) produced by the reaction between calcium hydroxide suspension and sulphuric acid solution was investigated at 3.5 pH and 65°C in the absence and presence of 2500 ppm citric acid concentration. Crystal size distributions, filtration rates, and morphology of gypsum were determined and discussed as a function of ion concentration. Average particle size of gypsum was not affected significantly by the presence of Fe²⁺, Fe³⁺, and Cr³⁺ ions individually. Variation of gypsum morphology depending on ion concentration affected the filtration characteristics. The presence of Fe³⁺ or Cr³⁺ ions besides 2500 ppm citric acid influenced both average particle size and filtration characteristics. The effect of citric acid on gypsum morphology was suppressed at high Fe³⁺ and Cr³⁺ ion concentrations. The change of morphology is related to the complex formation between Fe³⁺ or Cr³⁺ ions and citric acid at high ion concentrations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of fuel choice on conductivity and morphological properties of samarium doped ceria electrolytes for IT-SOFC

The present investigation is emphasized on the effect of various combustion agents on the crystal properties, surface microstructure, and oxygen ion conductivity of 20% mole-Sm doped ceria (Ce_0.80Sm_0.20O_1.90/SDC20) ceramics as solid electrolyte for IT-SOFCs. The most widely used combustion agents for engineering ceramic production as ethylene glycol, diethylene glycol, triethylene glycol, L-alanine, L-valine, glycine, citric acid monohydrate, urea, and EDTA-citric acid were compared in terms of SDC20 properties. X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and electrochemical impedance spectroscopy (EIS) were used to determine the microstructure properties, crystal structure and ionic conductivity of SDC20 powder. XRD pattern of the ceramics revealed the formation of single-phase fluorite structure. According to the results of electrochemical analysis, the maximum total ionic conductivity was observed in SDC20 electrolyte synthesized using triethylene glycol as the fuel among all the synthesized electrolytes (5.72 x 10^–2 S.cm^–1).     

Effect of the Amount of Polysorbate 80 and Oregano Essential Oil on the Emulsion Stability and Characterization Properties of Sodium Alginate Microcapsules

Essential oils have a high volatility that leads to evaporation and loss of their pharmacological effect when exposed to the environment. The objectives of the present work were to prepare microcapsules with oregano essential oil by extrusion using sodium alginate as a shell material and non-ionic surfactant polysorbate 80 as an emulsifier to stabilize the emulsion. The present study was aimed to evaluate the physical parameters of microcapsules and to compare the influence of the amount of emulsifier and the essential oil-to-emulsifier ratio on the capsules’ physical parameters and encapsulation efficiency; to our knowledge, the existing research had not yet revealed whether unstable emulsion affects the encapsulation efficiency of oregano essential oil. This study showed that increasing the emulsifier amount in the formulation significantly influenced encapsulation efficiency and particle size. Moreover, increasing the emulsion stability positively influenced the encapsulation efficiency. The emulsion creaming index depended on the emulsifier amount in the formulation: the highest creaming index (%) was obtained with the highest amount of polysorbate 80. However, the essential oil-to-polysorbate 80 ratio and essential oil amount did not affect the hardness of the microcapsules (p > 0.05). In conclusion, the obtained results could be promising information for production of microcapsules. Despite the fact that microencapsulation of essential oils is a promising and extremely attractive application area for the pharmaceutical industry, further basic research needs to be carried out.     

Hybrid HDMR method with an optimized hybridity parameter in multivariate function representation

High Dimensional Model Representation (HDMR) based methods are used to generate an approximation for a given multivariate function in terms of less variate functions. This paper focuses on Hybrid HDMR which is composed of Plain HDMR and Logarithmic HDMR. The Plain HDMR method works well for representing multivariate functions having additive nature. If the function under consideration has a multiplicative nature, then the Logarithmic HDMR method produces better approximation. Hybrid HDMR method aims to successfully represent a multivariate function having neither purely additive nor purely multiplicative nature under a hybridity parameter. The performance of the Hybrid HDMR method strongly depends on the value of this hybridity parameter because this parameter manages the contribution level of Plain and Logarithmic HDMR expansions. The main purpose of this work is to optimize the hybridity parameter to get the best approximations. Fluctuationlessness Approximation Theorem is used in this optimization process and in evaluating the multiple integrals appearing in HDMR based methods. A number of numerical implementations are given at the end of the paper to show the performance of our proposed method.     

Development and Validation of an RP-HPLC Method for Determination of Valganciclovir in Human Serum and Tablets

This paper describes the validation of an isocratic high-performance liquid chromatographic method for the assay of valganciclovir in raw materials, tablets and human serum samples. Valganciclovir and fluvastatin (internal standard) were well separated using a reversed phase column and a mobile phase consisting of a mixture of acetonitrile:methanol:KH₂PO₄ (0.02 M) (40:20:40; v/v/v) (at pH 5.0). The mobile phase was pumped at 1.0 mL min⁻¹ flow rate and valganciclovir was detected by diode-array detection at 255 nm. The retention times for valganciclovir and fluvastatin were 3.41 and 5.60 min, respectively. A linear response (r > 0.999) was observed in the range of 10–30,000 ng mL⁻¹ in mobile phase and serum. The limit of detection and limit of quantification were found as 2.95 and 9.82 ng mL⁻¹ in mobile phase and 1.73 and 5.77 ng mL⁻¹ in human serum samples, respectively. Validation parameters as precision, accuracy, selectivity, reproducibility and system suitability tests were also determined. The method can be used for valganciclovir assay of tablets and human serum samples as the method separates valganciclovir from tablet excipients and endogenous substances.

     

Barrier properties of polylactic acid/layered silicate nanocomposites for food contact applications

Polylactic acid/layered silicate nanocomposite films were prepared by solution casting technique. Four types of organo modified montmorillonite and an unmodified bentonite were used as inorganic fillers. The structural characterizations were done by FTIR/ATR and dispersion of the layered silicates was determined by XRD. XRD results showed that the prepared nanocomposites showed flocculated, intercalated and exfoliated structure. The highest crystallinity degree obtained was 28. Overall migration tests were studied with food simulants included distilled water, 3% acetic acid, 95% ethanol. The migration values of all the prepared films were found to be below the allowed limit (10 mg/dm²). The best result in oxygen gas transmission and water vapor transmission rates were 233.4 cm³ mm/m² day MPa and 98.3 g/m² day, respectively. Consequently the oxygen barrier property has increased by 34% and water vapor barrier property increment was 65% when compared to pure PLA film.     

The Antifungal Activity of Erica manipuliflora Salisb. Extracts and Secondary Metabolite: Ursolic Acid

Moscow University Chemistry Bulletin - Erica manipuliflora Salisb. and Erica arborea L. are common species in the seaside areas in Turkey. The aerial parts of Erica manipuliflora and Erica arborea,...