Thiochalcone substituted phthalocyanines for dye-sensitized solar cells: Relation of optical and electrochemical properties for cell performance

The new peripherally tetra-substituted metallophthalocyanines (MPcs, M=Zn, Co, Ni) bearing the chalcone, (E)-3-(4-hydroxyphenyl)-1-(thiophen-2-yl)prop-2-en-1-one, for dye-sensitized solar cells (DSSCs) were synthesized. FT-IR, ¹H NMR, ¹³C NMR, and UV–Vis spectroscopy techniques were utilized for characterization of all the MPcs. Electrochemical, optical and photovoltaic properties of all the MPcs as sensitizers were examined. Electrochemical studies reveal that while the ZnPc (4) and NiPc (6) give only Pc ring-based redox reactions, the CoPc (5) shows redox reactions based on both the central metal and the ring due to the metal 3d orbitals lying between the Pc HOMO and LUMO. The DSSC based on 5 gave the lowest power conversion efficiency (0.51%), perhaps due to the presence of a redox active central metal ion in the core of the complex, which results in a decrease electron transfer in the device. However, cells based on the other complexes including redox inactive central metal ions, which cannot reduce electron transfer, showed reasonable power conversion efficiencies of 1.27% and 1.11% for 4 and 6, respectively. The slight difference between the efficiencies can be attributed to higher molar extinction coefficient and narrower band gap of 4 than 6, which ensure a higher photocurrent and broader light absorption in the visible region.     

On the mean square average of special values of L-functions

Let χ be a Dirichlet character and L(s,χ) be its L-function. Using weighted averages of Gauss and Ramanujan sums, we find exact formulas involving Jordan?s and Euler?s totient function for the mean square average of L(1,χ) when χ ranges over all odd characters modulo k and L(2,χ) when χ ranges over all even characters modulo k. In principle, using our method, it is always possible to find the mean square average of L(r,χ) if χ and r?1 have the same parity and χ ranges over all odd (or even) characters modulo k, though the required calculations become formidable when r?3. Consequently, we see that for almost all odd characters modulo k, |L(1,χ)|<Φ(k), where Φ(x) is any function monotonically tending to infinity.     

On Dirichlet L-functions with periodic coefficients and Eisenstein series

We prove a Lipschitz type summation formula with periodic coefficients. Using this formula, representations of the values at positive integers of Dirichlet L-functions with periodic coefficients are obtained in terms of Bernoulli numbers and certain sums involving essentially the discrete Fourier transform of the periodic function forming the coefficients. The non-vanishing of these L-functions at s = 1 are then investigated. There are additional applications to the Fourier expansions of Eisenstein series over congruence subgroups of SL₂(\mathbbZ){SL_2(\mathbb{Z})} and derivatives of such Eisenstein series. Examples of a family of Eisenstein series with a high frequency of vanishing Fourier coefficients are given.     

Interface Conditions for a Phase Field Model with Anisotropic and Non-Local Interactions

An alternative formulation of the phase field method is utilized from an integral equation perspective. The technique allows one to derive macroscopic conditions at the interface from the microscopic potentials. Differential geometry and asymptotic analysis yield interface conditions, in arbitrary spatial dimension, for interactions that may include anisotropy as well as non-local potentials. The interface conditions can be expressed in various formulations, for example, in terms of the principal curvature directions of the interface, or the second order directional derivatives of the (signed) distance function and the Hessian of the surface tension.     

The effect of concrete slab–rockfill interface behavior on the earthquake performance of a CFR dam

Earthquake response of the concrete slab is mostly depended upon its conjunction with rockfill. This study aims to reveal the effect of concrete slab–rockfill interface behavior on the earthquake performance of a concrete-faced rockfill dam considering friction contact and welded contact. Friction contact is provided by using interface elements with five numbers of shear stiffness values. 2D finite element model of Torul concrete-faced rockfill dam is used for this purpose. Linear and materially non-linear time-history analyses considering dam–reservoir interaction are performed using ANSYS. Reservoir water is modeled using fluid finite elements by the Lagrangian approach. The Drucker–Prager model is preferred for concrete slab and rockfill in non-linear analyses. Horizontal component of 1992 Erzincan earthquake with peak ground acceleration of 0.515g is used in analyses. The maximum and minimum displacements and principal stresses are shown by the height of the concrete slab and earthquake performance of the dam is investigated considering different joint conditions for empty and full reservoir cases. In addition, potential damage situations of concrete slab are evaluated.     

Electrochemical Behavior and Electroanalytical Determination of Indole‐3‐Acetic Acid Phytohormone on a Boron‐Doped Diamond Electrode

In this work, a boron‐doped diamond (BDD) electrode was used for the electroanalytical determination of indole‐3‐acetic acid (IAA) phytohormone by square‐wave voltammetry. IAA yielded a well‐defined voltammetric response at +0.93 V (vs. Ag/AgCl) in Britton–Robinson buffer, pH 2.0. The process could be used to determine IAA in the concentration range of 5.0 to 50.0 µM (n=8, r=0.997), with a detection limit of 1.22 µM. The relative standard deviation of ten measurements was 2.09 % for 20.0 µM IAA. As an example, the practical applicability of BDD electrode was tested with the measurement of IAA in some plant seeds.