Normal distribution profile for doping concentration in multilayer tunnel junction

In this paper, the effect of doping concentration and layer thickness on the performance of tunnel junctions (TJs) is studied. We investigate the behavior of single, double and triple layer structures of TJs. Triple layer structure shows better performance in comparison with the other structures and can reach the higher tunneling current besides lower voltage drop. Also, the behavior of the triple layer TJ with different doping concentration profiles is studied. We propose a new normal distribution profile for doping concentration in multilayer TJs which shows better performance in comparison with the linear and graded doping concentration profiles. The higher $\upalpha $ parameters in normal distribution enhance the device performance with increasing the smoothness of doping variations in the center and edge of the TJ. Finally, we examine different thicknesses of triple layer TJ in order to achieve the optimum structure.     

Modified-DBR-based semi-omnidirectional multilayer anti-reflection coating for tandem solar cells

In this paper, multilayer antireflection coatings are designed by modifying the thickness of two and three paired layer distributed Bragg reflector （DBR） structure. Our proposed DBR-based structures show antireflection behaviors, in spite of the reflection treatment in traditional DBR structures. Firstly, the proposed structures are designed to be equivalent to the theoretical ideal triple-layer （TL） antireflection coating （ARC）. Therefore, the problem of finding a suitable material for the middle layer of triple structure is solved. Simulation results show the significant equivalency for the reflectance of proposed structures to the ideal TL ARC at the same wavelengths and incident angles. Also, the design of the structure is changed in order to present the constant reflectance coefficient over a wide range of wavelengths. This structure enhances the omni-directionality of the multilayer ARC.     

Synthesis and characterization of poly (1‐vinyl‐3‐butylimidazolium‐co‐methyl methacrylate) gel polymer electrolytes for dye‐sensitized solar cells: Effect of structure and composition

Herein, three ionic liquid random copolymers (P) containing 1‐vinyl‐3‐butylimidazolium bromide (VBImBr) and methyl methacrylate (MMA) with various molar ratios were prepared using conventional free radical polymerization. Afterward, their corresponding chemically cross‐linked copolymers (XP) were formed similarly in the presence of polyethylene glycol dimethacrylate (PEGDMA). The synthesized copolymers were characterized using FT‐IR, ¹H NMR, and GPC. Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) results showed that the rigidity and thermal stability of the copolymers depended on the ionic liquid content as well as the degree of cross‐linking. Gel polymer electrolytes were then prepared via obtained copolymers in the presence of a constant amount of synthesized imidazolium‐based ionic liquid. Among the copolymers, the P3 with in feed VBImBr:MMA molar ratio of 70:30 and the cross‐linked 1%‐XP3 copolymer prepared with 1 mol% of PEGDMA exhibited the highest conductivity and diffusion coefficients for I₃^¯ and I^¯. The power conversion efficiency of the optimized linear and cross‐linked copolymers (P3 and 1%‐XP3) under the simulated AM 1.5 solar spectrum irradiation at 100 mW cm^?2 were 3.49 and 4.13% in the fabricated dye‐sensitized solar cells (DSSCs), respectively. The superior long‐term stability and high performance of the gel electrolyte containing 1%‐XP3 suggested it as commercial gel electrolyte for future DSSCs.     

A novel wire-type lead-selective electrode based on bis (1'-hydroxy-2'-acetonaphthone)-2,2'-diiminodiethylamine

The preparation of a lead-selective electrode based on bis(1'-hydroxy-2'-acetonaphthone)-2,2'-diiminodiethylamine (L) as sensing material is reported. The plasticized PVC membrane containing 30% PVC, 67% ortho-nitrophenyloctylether (NPOE) and 3% ionophore L was directly coated on a graphite rod. This electrode exhibits a nearly Nernstian slope of 27.8+/-0.2 mV decade(-1) over a concentration range 10(-6)-10(-2) M with a detection limit of 4.0 x 10(-7) M. The response time of the electrode was found to be <20 s. The potential of the sensor was independent on pH variations in the range 5-7. The selectivity of the electrode towards lead ions over Na+, K+, Ag+, Ca2+, Sr2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, La3+, Sm3+ and Er3+ ions was investigated. The prepared electrode was successfully used as an indicator for titration of a lead solution with a standard solution of EDTA. The applicability of the sensor for Pb2+ measurement in various synthetic and real samples has been also demonstrated.     

Complex Formation of 1,10-Dibenzyl-1,10-diaza-18-crown-6 with Ni2+, Cu2+, Ag+ and Cd2+ Metal Cations in Acetonitrile–dimethylformamide Binary Solutions

Conductance measurements are reported for nickel(II), cupper(II), silver(I) and cadmium(II), salts in acetonitrile (AN)–dimethylformamide (DMF) binary solvents containing macrocyclic ligand, 1,10-dibenzyl-1,10-diaza-18-crown-6 (DBDA18C6) at different temperatures. The changes in molar conductance caused by addition of DBDA18C6 to solutions were analyzed by non-linear least squares to give stability constants of 1:1 metal cation–DBDA18C6 complexes. The results show that the stabilities of the complexes are sensitive to solvent composition and in some cases the sequence of stabilities is changed with changing the composition of the mixed solvents. The values of thermodynamic quantities (ΔH°c and ΔS°c) for formation of DBDA18C6-Ni²⁺, DBDA18C6-Cu²⁺, DBDA18C6-Ag⁺ and DBDA18C6-Cd²⁺ complexes were obtained from temperature dependence of the stability constants and the results show that the values of ΔH°c and ΔS°c for these complexes are sensitive to the nature and composition of AN–DMF binary solutions, but they do not vary monotonically with the solvent composition.     

Ar ion milling of InSb for manufacturing single electron devices

Ar⁺ ion milling of InSb for manufacturing single electron devices was studied. It is shown that pyramidal structures (porous) are created on the (1 1 1) surface of InSb wafers by anisotropic etching. Also it was shown the axis of the pyramidal structure is a function of the angle of the Ar⁺ incident beam and does not depend on the energy of the beam. EDX measurement results show In_xO_y and Sb_xO_y were not created on the surface after milling process. FTIR measurement results show that the surface reflection was decreased and less than 0.3 V flat band voltage was seen in capacitance voltage measurement results. SEM images show that the etching has approximately vertical profile. Therefore the Ar⁺ milling technique can be used as a dry etching technique for manufacturing mesa and/or porous structures of InSb. Since the surface is porous and of near-pyramidal morphology, one can simulate the surface by a set of needles each of which is a nanometer-size capacitance (i.e. single electron device). We showed, the threshold voltage of this single electron device is 0.3 V approximately, and therefore it can be used for studying single-electron or Coulomb blockade effects.     

Tandem and transition metal-free synthesis of novel benzoimidazo-quinazoline as highly selective Hg<Superscript>2+</Superscript> sensors

A one-pot procedure for the synthesis of novel planar aza-heterocycles possessing good fluorescence potencies was described. These benzo-imidazopyrimido[4,5-b]quinolone derivatives came from the reaction of 2-chloroquinoline-3-carboxaldehydes and 2-aminobenzimidazole using K₂CO₃ in DMF. The fluorescence study of these conjugated systems was also considered, which revealed that they have highly selective sensing of mercury. Consequently, to investigate another aspect of the reaction, a three-component reaction was developed by adding malononitrile to the aforementioned starting materials in the presence of l-proline under reflux condition in H₂O/EtOH to provide amino-quinolin-3-yl-dihydrobenzo-imidazo-pyrimidine-3-carbonitriles in good yields.     

A new colorimetric assay for amylase based on starch-supported Cu/Au nanocluster peroxidase-like activity

In this paper, we present a new colorimetric technique as a novel assay for the easy and direct detection of α-amylase activity. This detection system utilizes the interaction of α-amylase with starch that is supporting copper/gold (Cu/Au) nanoclusters. The Cu/Au nanoclusters are synthesized using starch as a stabilizing agent at room temperature. These nanoclusters show robust peroxidase-like activity and are able to catalyze the oxidation of TMB (3,3,5,5-tetramethylbenzidine) in the presence of hydrogen peroxide (H₂O₂), leading to the generation of a blue-colored solution. The α-amylase detection mechanism is based on the digestion of the starch by α-amylase, which results in nanocluster aggregation, leading to increased nanoparticle size and thus decreased peroxidase-like activity of the Cu/Au NCs. Experiments showed that the gradual addition of α-amylase causes the peroxidase activity to decrease step by step in a linear fashion. Using this method, colorimetric sensing of α-amylase was achieved with a detection limit (LOD) of 0.04 U/mL and a linear range of 0.1–10 U/mL. This method is significantly selective for α-amylase and could be affordably and conveniently applied to the detection of α-amylase in blood serum.

Graphical Abstract

     

Preparation of chitosan–silica/PCL composite membrane as wound dressing with enhanced cell attachment

In the present study, the asymmetrical polycaprolactone membranes were synthesized using phase inversion method and modified by addition of Pluronic (F‐127) and sodium hydroxide treatment to improve the cell attachment. The chemical structure, physical properties and mechanical behavior of the membranes as well as cell attachment and proliferation on them were characterized and compared to determine the appropriate membrane used in wound dressing fabrication. Then, a composite membrane as wound dressing capable of drug controlled‐release was prepared composed of two merged layers: an asymmetrical poly(ε‐caprolactone) layer coated with a drug‐loaded chitosan – silica matrix. Drug release behavior and biocompatibility of the final system were evaluated. The results showed that the polycaprolactone modified membrane provides appropriate properties to expand fibroblast cell adhesion and proliferation. This in‐vitro study also showed that the controlled‐release composite wound dressing was developed with approximately 70% cumulative release rate, which provided a porous substrate to support skin cells. Copyright © 2017 John Wiley & Sons, Ltd.