1,1,3,3‐N,N,N′,N′‐Tetramethylguanidinium Trifluoroacetate Ionic Liquid–Promoted Efficient One‐Pot Synthesis of Trisubstituted Imidazoles

Trisubstituted imidazoles have been synthesized in very short reaction times with excellent yields in the presence of 1,1,3,3‐N,N,N′,N′‐tetramethylguanidinium trifluoroacetate as an ionic liquid at 100°C. The ionic liquid can be recycled for subsequent reactions without any appreciable loss of efficiency.     

Simultaneous derivatization and air‐assisted liquid–liquid microextraction of some parabens in personal care products and their determination by GC with flame ionization detection

A simultaneous derivatization/air‐assisted liquid–liquid microextraction technique has been developed for the sample pretreatment of some parabens in aqueous samples. The analytes were derivatized and extracted simultaneously by a fast reaction/extraction with butylchloroformate (derivatization agent/extraction solvent) from the aqueous samples and then analyzed by GC with flame ionization detection. The effect of catalyst type and volume, derivatization agent/extraction solvent volume, ionic strength of aqueous solution, pH, numbers of extraction, aqueous sample volume, etc. on the method efficiency was investigated. Calibration graphs were linear in the range of 2–5000 μg/L with squared correlation coefficients >0.990. Enhancement factors and enrichment factors ranged from 1535 to 1941 and 268 to 343, respectively. Detection limits were obtained in the range of 0.41–0.62 μg/L. The RSDs for the extraction and determination of 250 μg/L of each paraben were <4.9% (n = 6). In this method, the derivatization agent and extraction solvent were the same and there is no need for a dispersive solvent, which is common in a traditional dispersive liquid–liquid microextraction technique. Furthermore, the sample preparation time is very short.     

Zn/MCM-41-catalyzed unsymmetrical Hantzsch reaction and the evaluation of optical properties and anti-cancer activities of the polyhydroquinoline products

The three-component Hantzsch condensation of various aryl aldehydes, dimedone, and methyl 3-aminocrotonate was investigated in the presence of MCM-41-supported ZnNO3. The polyhydroquinoline products which were obtained under mild conditions and very easy workup were evaluated for anti-cancer activities against MCF-7, SK-BR-3, and HT-29 of breast and colon cancer cells. The fluorescence emission of some products was also studied and their optical parameters were reported.     

The Synthesis of Hetero-Halogenated Derivatives of Phloroglucide Analogues[1]

A short synthesis of the title compounds is reported. Most of the compounds prepared were found to be active against a number of pathogenic microorganisms in vitro.     

Alignment of carbon nanotubes in bulk epoxy matrix using a magnetic-assisted method: Solenoid magnetic field

Alignment of multi-walled carbon nanotubes (MWCNTs) in a bulk epoxy matrix was studied using a magnetic-assisted method. In this study, the applicability of solenoid magnetic field was compared to that of static magnetic field, which has recently been published. It has been found that solenoid magnetic field is able to provide better alignment of MWCNTs due to the uniform magnetic field along the axis of solenoid. Remarkable improvements were achieved in the mechanical properties of aligned MWCNT-reinforced epoxy composites. Alignment of MWCNTs was clearly observed in all regions of the composites by scanning electron microscopy and transmission electron microscopy.     

Unexpected relaxation dynamics of a self-avoiding polymer in cylindrical confinement

We report extensive simulations of the relaxation dynamics of a self-avoiding polymer confined inside a cylindrical pore. In particular, we concentrate on examining how confinement influences the scaling behavior of the global relaxation time of the chain, tau, with the chain length N and pore diameter D. An earlier scaling analysis based on the de Gennes blob picture led to tau approximately N(2)D(13). Our numerical effort that combines molecular dynamics and Monte Carlo simulations, however, consistently produces different tau results for N up to 2000. We argue that the previous scaling prediction is only asymptotically valid in the limit N"D(53)"1, which is currently inaccessible to computer simulations and, more interestingly, is also difficult to reach in experiments. Our results are thus relevant for the interpretation of recent experiments with DNA in nano- and microchannels.     

Elucidating the structure-dependent selectivity of CuZn towards methane and ethanol in CO2 electroreduction using tailored Cu/ZnO precatalysts

Understanding the catalyst compositional and structural features that control selectivity is of uttermost importance to target desired products in chemical reactions. In this joint experimental–computational work, we leverage tailored Cu/ZnO precatalysts as a material platform to identify the intrinsic features of methane-producing and ethanol-producing CuZn catalysts in the electrochemical CO₂ reduction reaction (CO₂RR). Specifically, we find that Cu@ZnO nanocrystals, where a central Cu domain is decorated with ZnO domains, and ZnO@Cu nanocrystals, where a central ZnO domain is decorated with Cu domains, evolve into Cu@CuZn core@shell catalysts that are selective for methane (∼52%) and ethanol (∼39%), respectively. Operando X-ray absorption spectroscopy and various microscopy methods evidence that a higher degree of surface alloying along with a higher concentration of metallic Zn improve the ethanol selectivity. Density functional theory explains that the combination of electronic and tandem effects accounts for such selectivity. These findings mark a step ahead towards understanding structure–property relationships in bimetallic catalysts for the CO₂RR and their rational tuning to increase selectivity towards target products, especially alcohols.

A higher degree of surface alloying and Zn concentration boosts the selectivity towards ethanol of CuZn catalysts in CO₂ electroreduction.     

Ultrasound‐assisted green synthesis of Cu‐based complexes of β‐cyclodextrin and their SOD‐like activity

A novel Cu–Zn β‐cyclodextrin (CuZn/β‐CD) model compound was synthesized under ultrasound irradiation to mimic the functionality of copper zinc superoxide dismutase (CuZnSOD). For comparison, Cu/β‐CD and Zn/β‐CD complexes were also synthesized via a sonochemical approach. The obtained complexes were characterized by FTIR, ICP‐OES, UV–vis and Scanning electron microscopy‐Energy dispersive X‐ray (SEM‐EDX) techniques. The SOD activity of the complexes was evaluated by a pyrogallol autoxidation method. These enzyme‐mimetic materials scavenge ambient free radicals, with the potential to provide significant antioxidant protection (scavenging ability > 70%).     

On construction of involutory MDS matrices from Vandermonde Matrices in GF(2 q )

Due to their remarkable application in many branches of applied mathematics such as combinatorics, coding theory, and cryptography, Vandermonde matrices have received a great amount of attention. Maximum distance separable (MDS) codes introduce MDS matrices which not only have applications in coding theory but also are of great importance in the design of block ciphers. Lacan and Fimes introduce a method for the construction of an MDS matrix from two Vandermonde matrices in the finite field. In this paper, we first suggest a method that makes an involutory MDS matrix from the Vandermonde matrices. Then we propose another method for the construction of 2 ⁿ × 2 ⁿ Hadamard MDS matrices in the finite field GF(2 ^q ). In addition to introducing this method, we present a direct method for the inversion of a special class of 2 ⁿ ?× 2 ⁿ Vandermonde matrices.