Understanding the photo-electrochemistry of metal-free di and tri substituted thiophene-based organic dyes in dye-sensitized solar cells using DFT/TD-DFT studies

Ionics - In this work, two 2, 5-disubstituted and three 2, 3, 5-trisubstituted thiophene-based organic dyes have been investigated using the density functional theory. Although substitution at the...     

Propagation of Polarized Light Through Azobenzene Polyester Films

When elliptically polarized light of appropriate wavelength corresponding to trans - cis - trans isomerisation process is incident on thin films of azobenzene polyesters, a helical structure is induced. We investigate the propagation of the exciting light beam (self-induced) as well as a probe light beam outside the absorption band through the polyester films. Investigations are carried out in one amorphous and one liquid crystalline polyester. We show that amorphous polyester after irradiation behaves like classical helical material.     

Multidimensional Persistence and Noise

In this paper, we study multidimensional persistence modules (Carlsson and Zomorodian in Discrete Comput Geom 42(1):71–93, 2009; Lesnick in Found Comput Math 15(3):613–650, 2015) via what we call tame functors and noise systems. A noise system leads to a pseudometric topology on the category of tame functors. We show how this pseudometric can be used to identify persistent features of compact multidimensional persistence modules. To count such features, we introduce the feature counting invariant and prove that assigning this invariant to compact tame functors is a 1-Lipschitz operation. For one-dimensional persistence, we explain how, by choosing an appropriate noise system, the feature counting invariant identifies the same persistent features as the classical barcode construction.     

Solution processed transition metal sulfides: application as counter electrodes in dye sensitized solar cells (DSCs)

A solution processed method for fabricating transition metal sulfides on fluorine doped tin oxide (FTO) as efficient counter electrodes in iodine/iodide based solar cells has been demonstrated. Conversion efficiencies of 7.01% and 6.50% were obtained for nickel and cobalt sulfides, respectively, comparable to the conventional thermally platinised FTO electrodes (7.32%). A comparable charge transfer resistance of Ni(3)S(2) and Co(8.4)S(8) to conventional Pt was found to be a key factor for such high efficiencies. Cyclic voltammetry, Kelvin probe microscopy, Electrochemical Impedance Spectroscopy, and Tafel polarization were performed to study the underlying reasons behind such efficient counter electrode performance.     

An asymptotic initial value method for second order singular perturbation problems of convection-diffusion type with a discontinuous source term

In this paper a numerical method is presented to solve singularly perturbed two points boundary value problems for second order ordinary differential equations consisting a discontinuous source term. First, in this method, an asymptotic expansion approximation of the solution of the boundary value problem is constructed using the basic ideas of a well known perturbation method WKB. Then some initial value problems and terminal value problems are constructed such that their solutions are the terms of this asymptotic expansion. These initial value problems are happened to be singularly perturbed problems and therefore fitted mesh method (Shishkin mesh) are used to solve these problems. Necessary error estimates are derived and examples provided to illustrate the method.     

Surface relief measurements in side-chain azobenzene polyesters with different substituents

Light-induced surface modification of a series of liquid-crystalline side-chain azobenzene polyesters which have the same main- and side-chain structure but eleven different substituents on the azobenzene is investigated. Using a transmission mask as well as single focused beams we show that the formation of the surface relief is dependent on the substituents. In both experiments irradiation with p-polarized light generates peaks for the CN, CF₃, CH₃ and F substituents, while for a Cl substituent valleys are observed. Also s-polarized light is found to produce surface deformations. An amorphous azobenzene polyester was included in the study for comparison. The results point to a mechanism of the surface relief phenomenon, in which the architecture of the polyesters plays a crucial role. Received: 11 September 2000 / Revised version: 4 December 2000 / Published online: 21 February 2001     

Approximation of derivative in a system of singularly perturbed convection-diffusion equations

In this paper, a numerical method for a weakly coupled system of two singularly perturbed convection-diffusion second order ordinary differential equations with a small parameter multiplying the highest derivative is presented. Parameter-uniform error bounds for the numerical solution and also to numerical derivative are established. Numerical results are provided to illustrate the theoretical results.     

Theory of photoinduced deformation of molecular films

Azobenzene-containing polymers exhibit strong surface-relief features when irradiated with polarized light. Currently proposed theories do not explain all the observed features. Here we propose a theory based on elastic deformation of the polymer due to interaction between dipoles ordered through polarized light irradiation. The effects are due to the presence of a boundary layer. The observation of both wells and humps dependent on the architecture of the polymer can be explained with the present theory. Received: 29 June 2001 / Revised version: 9 November 2001 / Published online: 17 January 2002     

Synthesis and analytical applications of sodium N-bromo-p-nitrobenzenesulfonamide

Sodium N-bromo-p-nitrobenzenesulfonamide (bromamine-N) is useful as an oxidizing titrant. The synthesis, composition and structure are reported. Direct titrations of ascorbic acid, glutathione, thioglycolic acid, methionine, sulfite and arsenite are described. The procedures are simple and rapid; errors are within ± 0.5%. The compound is a somewhat better titrant for those species than the chlorine analogs such as chloramine-T and chloramine-N.