Study of the potassium ion insertion of the electrodeposited electrochromic tungsten trioxide thin films

Various types of dynamic adjustable optical shutters have been proposed; they are called as “smart windows”. The electrochromic smart window utilizes the phenomenon of electrochromism. Electrochromism is the property of a material such that its color is changed by an electrochemical redox reaction. Numerous inorganic and organic electrochromic materials have been examined. During the color-bleach process, the redox reaction of the host material causes injection or ejection of both cation (or anion) and an electron (or hole). So it behaves as a mixed ion conductor and hence it has recently attracted interest in the field of solid state ionics. At present, several prototypes of electrochromic smart windows have been proposed and some of them are commercially available. The cathodic electrochromic oxides consist of n-type semiconductors such as TiO₂, V₂O₅, WO₃ and MoO₃. Among them, WO₃ has been intensively examined and used for most electrochromic devices. These materials are cathodically colored in blue. The electrochromic reaction is expressed by $$xA^ + + MO_y \left( {transparent} \right) + x e^ - \Leftrightarrow A_x MO_y \left( {blue} \right)\left( {A = H, Li, Na, K \ldots , MO_y = metal oxide} \right)$$ where the cation A⁺ and electron e^? are co-injected into the host oxide MO_y which results in the formation of the nonstiochiometric compound A_xMO_y. Here the electrodeposition method is used to deposite WO₃ films under by galvanostatic conditions. The parameters like deposition time, deposition temperature, electrolyte concentration, pH and bath temperature are optimized. The XRD results show the triclinic structure for the as-deposited film. The film shows the same structure after intercalation but the peak intensity is different. The tungsten trioxide thin films show the colour change during the intercalation and retrace the original colour. The diffusion coefficient for K⁺ ion is calculated by using the Randles-Servick equation. In this paper the electrochromic properties, the optical properties of the as deposited, ion intercalated and deintercalated WO₃ films and the diffusion coefficient values are presented.     

Numerical solution of the Navier-Stokes equations using a finite element method

A finite element algorithm for solving the Navier-Stokes equations is presented for the analysis of high-speed viscous flows. The algorithm uses triangular elements. The unsteady equations are integrated to steady state with a Runge-Kutta time-marching scheme. A postprocessing artificial dissipation term is introduced to stabilize the computations and to dampen dissipation errors. Numerical results are compared with the calculation of uniform flow on a rectangular region which encounters an embedded oblique shock. A shock/turbulent boundary layer problem is also solved and results are compared with experimental data. It is shown that the postprocessing smoothing term and boundary conditions similar to the finite difference method work well in the present numerical studies.     

Photo-fries reaction of 1-naphthyl cinnamate

The photo-Fries reaction of 1-naphthyl cinnamate afforded 2-cinnamoyl-1-naphthol. Likewise, 1-naphthylp-methyl-cinnamate gave 2-(p-methylcinnamoyl)-1-naphthol. The product chalcones were cyclised into the respective flavanones.     

Validation of a Stability Indicating LC Method for Amiodarone HCL and Related Substances

A simple, rapid and sensitive isocratic high performance liquid chromatographic (HPLC) method has been developed for the estimation of purity and quantitative determination of Amiodarone HCl active pharmaceutical ingredient (API).The method describes a quantitative estimation of five process related impurities of Amiodarone HCl with a resolution of more than or near to 3.0 between each impurity. These five known related substances are estimated by a simple, rapid and accurate reverse phase isocratic HPLC method. The method has been validated for the determination of assay and related substances in Amiodarone HCl API, using a C₈ column. The elution is carried out using a mobile phase consisting of water-methanol-acetic acid with a pH 5.8. For the quantitative determination of these relative substances, a relative response factors have been determined for all five related substances with respect to Amiodarone HCl. The precision (system precision, method precision and intermediated precision) is demonstrated for both the assay as well as related substances on six independent sample preparations. Accuracy of the method (recovery) is demonstrated for both Amiodarone and each of the five related substances. Specificity of the method is demonstrated by forced degradation study of Amiodarone HCl API under various stress conditions. The method is found to be stability indicating and useful for the analysis of assay and related substances of Amiodarone HCl API in a routine quality control laboratory and for the stability studies of drug substance.     

Attractive bridging interactions in dense polymer brushes in good solvent measured by atomic force microscopy

Using an atomic force microscope (AFM), we have investigated the interaction forces exerted by latex particles bearing densely grafted polymer brushes consisting of poly(N,N-dimethylacrylamide) (PDMA), poly(methoxyethylacrylamide) (PMEA), poly(N-isopropylacrylamide) (PNIPAM), and PMEA-b-PNIPAM in aqueous media (good solvent). The brushes were prepared by controlled surface-initiated atom transfer radical polymerization, and the hydrodynamic thicknesses were measured by dynamic light scattering. The molecular weight (Mn), grafting density (sigma), and polydispersity (PDI) of the brushes were determined by gel permeation chromatography and multiangle laser light scattering after cleaving the polymer from the latex surface by hydrolysis. Force profiles of PDMA (0.017 nm(-2) < or = sigma < or = 0.17 nm-2) and PMEA (sigma = 0.054 nm-2) brushes were purely repulsive upon compression, with forces increasing with Mn and a, as expected, due to excluded volume interactions. At a sufficiently low grafting density (sigma = 0.012 nm-2), PDMA exhibited a long-range exponentially increasing attractive force followed by repulsion upon further compression. The long-range attractive force is believed to be due to bridging between the free chain ends and the AFM tip. The PNIPAM brush exhibited a bridging force at a grafting density of 0.037 nm(-2), a value lower than the sigma needed to induce bridging in the PDMA brush. Bridging was therefore found to depend on grafting density as well as on the nature of the monomer. The grafting densities of these polymers were larger than those typically associated with bridging. Bridging interactions were used to confirm the presence of PNIPAM in a block copolymer PMEA-b-PNIPAMA brush given that the original PMEA homopolymer brush produced a purely repulsive force. The attractive force was first detected in the block copolymer brush at a separation that increased with the length of the PNIPAM block.     

Mixed-ligand cobalt(III) complexes derived from bis(dehydroacetato)ethylenediimine

Summary A hydroxocobalt(III) complex (1a), has been obtained by reaction of bis(dehydroacetato)ethylenediimine (H₂dhaen) with cobalt(II) hydroxide or acetate in the presence of air. Addition of a second complexing agent leads to the formation of a series of mixed-ligand complexes (2)-(26) having either the trans- or cis- configuration. In the cis- complexes, the quadridentate ligand dhaen adopts a nonplanar conformation. Configurations are distinguishable from characteristic differences in the electronic and n.m.r. spectra.