Synthesis of new dyes containing double tetrazole groups for sensitization of TiO<Subscript>2</Subscript> nanoparticles in dye-sensitized solar cells

Di(1H-tetrazol-5-yl)methane is employed as a new electron acceptor group in the synthesis of two metal-free organic dyes containing triphenylamine donor group. Dye-sensitized nanocrystalline TiO₂ solar cell (DSSC) applying these novel dyes is constructed for consideration of their photovoltaic properties. The electronic properties of the dyes are also considered with the aid of theoretical calculations. The DSSC constructed from 4-(2,2-di(1H-tetrazol-5-yl)vinyl)-N,N-diphenylaniline (T1) shows a short-circuit photocurrent density of 13.38 mA cm^?2, an open circuit voltage of 578 mV, and a fill factor of 0.54, with a resulted solar energy-to-electricity conversion efficiency of 4.18% under simulated 1 sun irradiation (100 mW cm^?2). This result reveals that the dye with the di(1H-tetrazol-5-yl)methane anchoring group injects more electrons to the conduction band of TiO₂ in comparison with its analogs with single tetrazole ring in their anchoring group. It is found that in spite of a red-shift of the absorption spectrum resulted from the lengthening of the molecule, the dye with two di(1H-tetrazol-5-yl)methane groups gives lower performance than the dye with a single electron acceptor.     

A new robust DEA model and super-efficiency measure

Applications of traditional data envelopments analysis (DEA) models require knowledge of crisp input and output data. However, the real-world problems often deal with imprecise or ambiguous data. In this paper, the problem of considering uncertainty in the equality constraints is analyzed and by using the equivalent form of CCR model, a suitable robust DEA model is derived in order to analyze the efficiency of decision-making units (DMUs) under the assumption of uncertainty in both input and output spaces. The new model based on the robust optimization approach is suggested. Using the proposed model, it is possible to evaluate the efficiency of the DMUs in the presence of uncertainty in a fewer steps compared to other models. In addition, using the new proposed robust DEA model and envelopment form of CCR model, two linear robust super-efficiency models for complete ranking of DMUs are proposed. Two different case studies of different contexts are taken as numerical examples in order to compare the proposed model with other approaches. The examples also illustrate various possible applications of new models.     

Asymptotic Behavior of Quasi-Autonomous Expansive Type Evolution Systems in a Hilbert Space

We introduce the notion of almost expansive sequences and curves and study their ergodic and asymptotic properties in a Hilbert space H. We apply our results to study the asymptotic behavior of solutions to the quasi-autonomous expansive type evolution system (du/dt)(t) + f(t) ∈ Au(t) on [0, ∞).     

From micelle supramolecular assemblies in selective solvents to isoporous membranes

The supramolecular assembly of PS-b-P4VP copolymer micelles induced by selective solvent mixtures was used to manufacture isoporous membranes. Micelle order in solution was confirmed by cryo-scanning electron microscopy in casting solutions, leading to ordered pore morphology. When dioxane, a solvent that interacts poorly with the micelle corona, was added to the solution, polymer-polymer segment contact was preferential, increasing the intermicelle contact. Immersion in water gave rise to asymmetric porous membranes with exceptional pore uniformity and high porosity. The introduction of a small number of carbon nanotubes to the casting solution improved the membrane stability and the reversibility of the gate response in the presence of different pH values.     

Fabrication of a nanostructure-based electrochemical sensor for simultaneous determination of N-acetylcysteine and acetaminophen

A carbon-paste electrode modified with 2,7-bis(ferrocenyl ethyl)fluoren-9-one (2,7-BF) and carbon nanotubes (CNTs) was used for the sensitive and selective voltammetric determination of N-acetylcysteine (NAC). The mediated oxidation of NAC at the modified electrode was investigated by cyclic voltammetry (CV). Also, the values of catalytic rate constant (k), and diffusion coefficient (D) for NAC were calculated. Differential pulse voltammetry (DPV) of NAC at the modified electrode exhibited two linear dynamic ranges with a detection limit (3σ) of 52.0 nmol L⁻¹. DPV was used for simultaneous determination of NAC and acetaminophen (AC) at the modified electrode, and quantitation of NAC and AC in some real samples by the standard addition method.     

Fabrication of a highly sensitive electrochemiluminescence lactate biosensor using ZnO nanoparticles decorated multiwalled carbon nanotubes

ZnO nanoparticles (nanoZnO) were decorated on multiwalled carbon nanotubes (MWCNTs) and then the prepared nano-hybrids, nanoZnO-MWCNTs, were immobilized on the surface of a glassy carbon electrode (GCE) to fabricate nanoZnO-MWCNTs modified GCE. The prepared electrode, GCE/nanoZnO-MWCNTs, showed excellent electrocatalytic activity towards luminol electrochemiluminescence (ECL) reaction. The electrode was then further modified with lactate oxidase and Nafion to fabricate a highly sensitive ECL lactate biosensor. Two linear dynamic ranges of 0.01-10 μmol L⁻¹ and 10-200 μmol L⁻¹ were obtained for lactate with the correlation coefficient better than 0.9996. The detection limit (S/N = 3) was 4 nmol L⁻¹ lactate. The relative standard deviation for repetitive measurements (n = 6) of 10 μmol L⁻¹ lactate was 1.5%. The fabrication reproducibility for five biosensors prepared and used in different days was 7.4%. The proposed ECL lactate biosensor was used for determination of lactate in human blood plasma samples with satisfactory results.     

Structural, theoretical and multinuclear NMR study of mercury(II) complexes with a new ambidentate phosphorus ylide

The reaction of the new ambidentate ylide, Ph₃PCHCOCH₂COOC₂H₅ (EAPPY), with HgX₂ (X = Cl, Br and I) in equimolar ratios using methanol as the solvent leads to binuclear complexes of the type [EAPPY·HgX₂]₂ (X = Cl (1), Br (2) and I (3)). Single crystal X-ray analysis reveals the presence of a centrosymmetric dimeric structure containing the ylide and HgX₂ (X = Br or I)_. The IR and NMR data of the product [(EAPPY)·HgCl₂]₂ (1), formed by the reaction of mercury(II) chloride with the same ylide, are similar to those of 2 and 3. Analytical data indicate a 1:1 stoichiometry between the ylide and Hg(II) halide in each of the three products. Theoretical studies indicate that the nature of the R group in ylides of the type Ph₃PCHCOR has a weak effect on the Hg-C(ylide) bond length in binuclear Hg₂L₂I₄ complexes.     

Enhanced electrochemiluminescence from luminol at multi-walled carbon nanotubes decorated with palladium nanoparticles: a novel route for the fabrication of an oxygen sensor and a glucose biosensor

Incorporation of palladium nanoparticles on the surface of multi-walled carbon nanotubes and modification of glassy carbon electrode with the prepared nano-hybrid material led to the fabrication of a novel electrode. The modified electrode showed attractive electrocatalytic activity and sensitizing effect on luminol-O(2) and luminol-H(2)O(2) electrochemiluminescence (ECL) reactions at neutral media. The sensitized luminol-O(2) and luminol-H(2)O(2) reactions were successfully applied for the ECL determination of dissolved O(2) and glucose, respectively. Under the optimal conditions for luminol-O(2) system, the ECL signal intensity of luminol was linear with the concentration of dissolved oxygen in the range between 0.08 and 0.94 mM (r=0.9996) and for luminol-H(2)O(2) system, the ECL signal intensity of luminol was linear with the concentration of glucose in the range between 0.1 and 1000 μM (r=0.9998). The limits of detection (S/N=3) for dissolved oxygen and glucose were 0.02 mM and 54 nM, respectively. The relative standard deviations (RSD) for repetitive measurements of 0.50 mM oxygen (n=10) and 10 μM glucose (n=30) were 3.5% and 0.3%, respectively. Also, under the optimal conditions for luminol-H(2)O(2) system, the ECL signal intensity of luminol was linear with the concentration of H(2)O(2) in the range between 1 nM and 0.45 mM (r=0.9997). The limit of detection (S/N=3) for H(2)O(2) detection was 0.5 nM and the relative standard deviation for repetitive measurements of 10 μM H(2)O(2) (n=10) was 0.8%.     

Selecting symmetric weights as a secondary goal in DEA cross-efficiency evaluation

In data envelopment analysis (DEA), the cross-efficiency evaluation method introduces a cross-efficiency matrix, in which the units are self and peer evaluated. A problem that possibly reduces the usefulness of the cross-efficiency evaluation method is that the cross-efficiency scores may not be unique due to the presence of alternate optima. So, it is recommended that secondary goals be introduced in cross-efficiency evaluation. In this paper we propose the symmetric weight assignment technique (SWAT) that does not affect feasibility and rewards decision making units (DMUs) that make a symmetric selection of weights. A numerical example is solved by our proposed method and its solution is compared with those of alternative approaches.     

Queues with Simultaneous Arrival of Customers and the Dependence Structure of the Waiting Times

Methodology and Computing in Applied Probability - We consider a queueing system where some customers decide to simultaneously wait in two queues, rather than in a single queue, to receive their...