A Mild and Simple One‐pot Synthesis of 2‐Substituted Benzimidazole Derivatives Using DDQ as an Efficient Oxidant at Room Temperature

A series of 2‐substituted benzimidazoles were prepared through one‐pot reaction of o‐phenylenediamine with various aryl aldehydes in the presence of 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) in acetonitrile as solvent at room temperature. The reactions were smoothly preceded in excellent yields and short reaction times with an easy work‐up. The pure benzimidazoles as products were confirmed and characterized by physical and spectral data.     

Synthesis and Spectral Characteristics of Novel Fluorescent Dyes Based on Pyrimido[4,5‐d] [1,2,4]triazolo[4,3‐a]pyrimidine

Different derivatives of a novel heterocyclic system, i.e., pyrimido[4,5‐d] [1,2,4]triazolo[4,3‐a]pyrimidine, are synthesized in moderate‐to‐good yields. These compounds exhibit excellent photochromism upon photoirradiation. The photophysical characterizations of these new compounds were evaluated by UV/VIS absorption and fluorescence emission studies. The emission spectra in various solvents are also presented and discussed. The changes are due to the intramolecular H‐bonding of pyrimido‐triazolo‐pyrimidine with H₂O, and photoinduced electron and general solvent effect. These compounds display high fluorescence quantum yields and are reported as new fluorophores.     

Fabrication of a Nanostructure Based Electrochemical Sensor for Voltammetric Determination of Epinephrine,Uric Acid and Folic Acid

A carbon paste electrode (CPE) was modified by incorporation of graphene nano sheets and a ferrocene derivative. The modified electrode showed an excellent electrocatalytic effect on the oxidation of epinephrine. In phosphate buffer solution (PBS) of pH 7.0, the oxidation current increased linearly with concentration of epinephrine in the range of 0.05–550.0 µM and a detection limit (3σ) 27.0 nM was obtained for epinephrine. Then the modified electrode was used to determine epinephrine in an excess of uric acid and folic acid by SWV.     

Preparation of poly(2‐anilinoethanol) containing azobenzene group under electrical field and its liquid crystalline properties investigation

In this project, 2‐[N‐ethyl‐N‐[4‐[(4′‐nitrophenyl)azo]‐phenyl]amino]ethanol (Disperse Red‐I) was prepared by adding of (N‐ethyl‐2‐anilinoethanol) with the salt diazonium p‐nitroaniline. The main mesogenic liquid crystalline (LC) 2‐[N‐ethyl‐N‐[4‐[4′‐nitrophenyl)azo]‐phenyl]amino]ethyl‐3‐chloro propionate (Disperse Red‐II) was synthesized by reaction of disperse Red I and 3‐chloropropanoeic acid at the alkaline condition. Then 2‐anilinoethyl‐3‐chloropropionate‐{2‐[ethyl[4‐[(4′‐nitrophenyl)azo]phenyl]amino] ethanol}, (2AECP‐Red‐I) was prepared via reaction of disperse red‐II and 2‐anilinoethanol. On the other hand, poly 2‐anilinoethyl‐3‐chloropropionate‐{2‐[ethyl[4‐[(4′‐nitrophenyl)azo]phenyl]amino]ethanol} and poly(2AECP‐Red‐I) have been synthesized by polymerization of 2AECP‐Red‐I in two separate schemes. These include polymerization in the absence of electric field (EF) and polymerization under different EFs. A comparison of the results reveals that the polymer produced under electric field is more linear, regular in shape with high electrical conductivity, as well as good LC behavior with semectic texture. The resulted monomer and poly(2AECP‐Red‐I) are characterized by using Fourier transform infrared and ultraviolet–visible and were studied by thermogravimetric analysis and differential scanning calorimetry. Scanning electron microscopy images supported the formation of poly(2AECP‐Red‐I) and showed morphology feature and homogeneous structure on poly(2AECP‐Red‐I). Electrical conductivity of poly(2AECP‐Red‐I) has been studied by four‐point probe method. Copyright © 2014 John Wiley & Sons, Ltd.     

Density functional theory study of CO2 capture and storage promotion using manipulation of graphyne by 3d and 4d transition metals

In this work, the electronic and structural properties of 3d and 4d transition metal (TM)-decorated graphyne (GY) (TM-GY) toward CO₂ adsorption were studied using the D3-corrected density functional theory (DFT-D3) method. Then, CO₂ capture and storage (CCS) of the most stable structures were investigated. Results show that the most stable site for all TM decoration is the center of the 12-membered ring with various distances from carbon plane, and GY decorated with Ni and Zn from 3d and Zr and Cd from 4d TMs are also the most and the least stable, energetically with E_b of −5.834, −0.467, −6.181, and −0.963 eV, respectively. Evaluation of the adsorption behavior of CO₂ on TM-GY reveals that the strongest adsorption energies belong to Cr and Mo-GY (−1.502 and −1.117 eV, respectively), and for all 3d and 4d TMs, the horizontal direction of CO₂ is more stable, energetically. Increasing CO₂ molecules, step by step, on Cr and Mo-GY shows that they can hold 13 and 18 CO₂ molecules with average E_ads of −0.374 and −0.330 eV/CO₂ and corresponding CO₂ storage capacities of 47.66 and 54.10 wt%, respectively. These findings show that Cr and Mo-GY can be used in the future as suitable candidates for CCS applications.     

Postbuckling instability of nonlinear nanobeam with geometric imperfection embedded in elastic foundation

In this paper, the static instability of a nanobeam with geometrical imperfections that is embedded in elastic foundation is investigated. Size-dependent effect is included in the nonlinear model. It is argued that nonlocal parameter may render the nanobeam initially unstable. Static response is studied and the condition for instability is stated. The exact postbuckling solution for both the straight and curved nanobeam is presented. It is shown that the bifurcation diagram of a curved nanobeam with initial sinusoidal configuration is similar to that of a straight nanobeam in its nearest buckling mode. The results are verified with pervious relevant works on straight nanobeams and classical theory of curved beams and excellent agreement is shown.     

Relativistic symmetry of position-dependent mass particles in a Coulomb field including tensor interaction

The spatially-dependent mass Dirac equation is solved exactly for attractive scalar and repulsive vector Coulomb potentials,including a tensor interaction under the spin and pseudospin symmetric limits.Closed forms of the energy eigenvalue equation and wave functions are obtained for arbitrary spin-orbit quantum number κ.Some numerical results are also given,and the effect of tensor interaction on the bound states is presented.It is shown that tensor interaction removes the degeneracy between two states in the spin doublets.We also investigate the effects of the spatially-dependent mass on the bound states under spin symmetric limit conditions in the absence of tensor interaction.     

Analytical equations for oscillation amplitude of MOS Colpitts oscillator

New analytical equations are presented for amplitude analysis of metal–oxide–semiconductor (MOS) Colpitts oscillator. These equations are obtained from a large signal analysis that includes MOS operation in the saturation, triode and cutoff regions. The analysis is based on a reasonable estimation for the output voltage waveform. The estimated waveform must satisfy the nonlinear differential equations governing the circuit. The validity of the proposed method and the resulting equations has been verified through simulations using TSMC 0.18?µm complementary MOS process. The results are also compared with the other methods. Simulation results show high validity of the proposed equations.     

A Fast Adaptive Salt and Pepper Noise Reduction Method in Images

In this paper, an effective filtering method is proposed to remove impulse noise from images. In this two-stage method, detected noise-free pixels remain unchanged. Afterwards, a Gaussian filter with adaptive variances according to the image noise level is applied on the noisy pixels. Experimental results show that the proposed method outperforms recent impulse denoising methods in terms of PSNR, MAE, IEF, and SSIM. Moreover, the speed of the method is comparable with them, and it can be used effectively in real-time applications.