Synthesis of double D–A branched organic dyes employing indole and phenoxazine as donors for efficient DSSCs

Four novel metal-free organic sensitizers bearing double donor–acceptor (D–A) branches with indole and phenoxazine units as donors (SDD1–4) and cyanoacrylic acid as electron acceptor were synthesized and characterized for dye-sensitized solar cells (DSSCs). Dyes SDD1–3 were designed with indole as a donor and 1,4-phenylenebis(methylene), 1,4-butylene and 1,6-hexylene as a linker, respectively, while the dye SDD4 was designed with phenoxazine as a core donor. Their photophysical, electrochemical, and DSSCs characteristics were investigated. The results show that the architecture structure of the linkage affects the performance of the cells slightly. The DSSCs based on SDD4 shows much higher η than the DSSCs based on SDD1–3, which indicated that phenoxazine is a better donor than indole. Under standard global AM 1.5 solar condition (100 mW cm⁻²), the SDD4 dye-sensitized cell gave the highest η of 4.33% with chenodeoxycholic acid as a coadsorbent, reaching 82% of N719-based DSSCs.     

Amino acid‐functionalized ethyl cellulose: Synthesis,characterization, and gas permeation properties

Amino acid esters of ethyl cellulose [R′ = H ( 1 ), CH₃ ( 2 ), CH₂CH(CH₃)₂ ( 3 ), CH₂CONH₂ ( 4 ), CH₂OCH₂C₆H₅ ( 5 , 5′ ), CH₂CH₂CH₂CH₂NHOCOC(CH₃)₃ ( 6 )] were synthesized in moderate to quantitative yields (30–99%) by the reaction of t‐butoxycarbonyl (t‐Boc)‐protected amino acids or an activated ester derivative with hydroxy groups of ethyl cellulose [EC; degree of substitution (DS_Et), 2.69]. The amino acid functionalities displaying varied chemical nature, shape, and bulk were used, and bulk of the substituent on the α‐carbon of amino acids was elucidated to be of vital significance for the observed degree of incorporation (DS_Est). ¹H NMR spectra were used to determine the degree of incorporation of amino acid moiety (DS_Est), and almost complete substitution of the hydroxy protons was revealed in 1 , 2 , and 5′ . The onset temperatures of weight loss of 1 – 6 were 198–218 °C, indicating fair thermal stability. The glass transition temperatures of the derivatized polymers were 30–40 °C lower than that of EC (T_g 131 °C; cf. T_g of 1 – 6 , 93.5–103 °C). Free‐standing membranes of EC and its amino acid esters ( 1 , 2 , 5 , 5′ , and 6 ) were fabricated, and enhanced permselectivity for CO₂/N₂ and CO₂/CH₄ gas pairs was discerned, when compared with EC. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3986–3993, 2010     

Synthesis of functionalized p-dihydrobenzoquinones and p-benzoquinones based on [3+3] cyclizations of 1,3-bis-silyl enol ethers

Functionalized mono-protected p-dihydrobenzoquinones were prepared by [3+3] cyclization of 1,3-bis-silyl enol ethers with 2-acyloxy-3-(silyloxy)alk-2-en-1-ones. Deprotection and oxidation of the products afforded the corresponding p-benzoquinones.     

Polyurethane-TiO2 nanocomposite coatings from sunflower- oil-based amide diol as soft segment

Abstract

Vegetable oil based environmentally friendly polyurethane-TiO₂ nanocomposite coatings have been synthesized by using sunflower oil derived diol, toluene diisocyanate and TiO₂ nanoparticles. The chemical structure was confirmed by FTIR and NMR techniques while physico-chemical testing was carried out by standard laboratory methods. Physico-mechanical and anticorrosive tests of the coatings (in different corrosive media) have been investigated by standard methods. In addition to this the morphology and thermal stability behavior of the coatings have been carefully investigated by different techniques like XRD, TEM, TGA/DTG and DSC. The comparison of the performance of nanocomposites with the respective virgin polyurethane coatings reveals that the dispersion of nanoTiO₂ enhanced the mechanical, corrosion and thermal stability behavior of the polymer. The synthesized nanocomposites can be used safely upto 250–275?°C. These sunflower oil derived polyurethane nanocomposites can be used in the world of protective coatings, as an alternative of petroleum derived corrosion protective coating materials.     

Effect of alkyl chain length on chemical sensing of polydiacetylene and polydiacetylene/ZnO nanocomposites

Polydiacetylenes (PDAs) and PDA/ZnO nanocomposites based on the monomers 10,12-pentacosadiynoic acid (PCDA), 10,12-tricosadiynoic acid (TCDA), and 10,12-docosadiynedioic acid (DCDA) monomers have been investigated for chromatic chemical sensing of a number of organic liquids. Chromatic sensitivity is associated with the interaction of the organic liquid with the PDA side chain to give rise to the strain-induced blue to red colorimetric transition. Attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy demonstrated that in the PDA/ZnO nanocomposites, the PDA side chains form chelates with ZnO. The chromatic properties of PDAs and PDA/ZnO composites in organic liquids, to certain extent, depend on the side-chain length and the number of carboxylic head groups. Pure PDAs and PDA/ZnO nanocomposites in different organic liquids studied by Raman spectroscopy show that the chromatic selectivity of PDAs for certain organic liquids with respect to the blue to red phase transition is closely related to the side-chain structure of the PDAs. Moreover, the interactions are stronger with those PDAs where the blue to red transition is irreversible. Density functional theory (DFT) simulations show that the chromatic sensitivity of the PDAs toward a particular organic correlates with the C–C bond torsion angle of the PDA backbone.     

The Development of Highly Sensitive and Selective Immunosensor Based on Antibody Immobilized ZnO Nanorods for the Detection of D‐Dimer

ZnO nanorods were grown on gold coated glass substrate by low temperature aqueous chemical growth method. Scanning electron microscopy (SEM) and X‐ray diffraction (XRD) techniques were used for the characterization of ZnO nanorods. ZnO nanorods are highly dense, uniform, well aligned and perpendicular‐oriented to the substrate. ZnO nanorods exhibited good crystal quality. The well aligned ZnO nanorods were potentially used for the development of selective and sensitive immunosensor for the detection of D‐dimer by immobilizing antibody on stabilized lipid films. The ZnO nanorods based immunosensor responded to a wide range of D‐dimer concentrations with fast response time of ca. 20 s.     

Range formulation for a staring electro-optical and imaging system incorporating the effects of atmospheric transmission, focal plane 1/f noise and fixed pattern noise

To increase the detection range in staring FPAs, commonly the integration time T_i is increased, as the range is assumed to increase as one-fourth power of T_i, (T_i^1/4). It is shown here that the range dependence on T_i is weaker than T_i^1/4, because of the effect of atmosphere. Since the atmospheric transmission coefficient decreases with increasing range, the effect of increasing T_i on the range is considerably reduced. It is also shown that when detector 1/f noise dominates over other noise sources, the dependence of range on T_i is much weaker than T_i^1/4, having a logarithmic dependence Calculations have been done by integrating equations involving spectral functions—photon flux, atmospheric transmission coefficient, optics transmission coefficient and responsivity—over wavelength, in the spectral range from 8 μm to 12 μm. LOWTRAN2 has been used for spectral atmospheric transmission coefficients, for different conditions of ambient temperature (−30°C to 55°C) and relative humidity (50–85%). The range formulation also distinguishes between distant targets (point sources) and nearby targets (extended sources). The analysis is applicable for terrestrial imaging, where the temperature difference of the target and the background is small. The effect of fixed pattern noise (FPN) in mercury cadmium telluride (MCT) FPAs has also been considered by modeling FPN in terms of a composition variation in the MCT. It is seen that range, both in the point source and the extended source cases, is not a sensitive function of FPN.     

Gaussian-Random Ensembles of Pseudo-Hermitian Matrices

Attention has been brought to the possibility that statistical fluctuation properties of several complex spectra, or well-known number sequences, may display strong signatures that the Hamiltonian yielding them as eigenvalues is PT-symmetric (pseudo-Hermitian). We find that the random matrix theory of pseudo-Hermitian Hamiltonians gives rise to new universalities of level-spacing distributions other than those of GOE, GUE and GSE of Wigner and Dyson. We call the new proposals as Gaussian Pseudo-Orthogonal Ensemble and Gaussian Pseudo-Unitary Ensemble. We are also led to speculate that the enigmatic Riemann-zeros (1/2±it _n would rather correspond to some PT-symmetric (pseudo-Hermitian) Hamiltonian.     

Ion exchange test for microgram detection of mercaptans

A spot test for the detection of mercaptans is based on the reaction with sodium nitroprusside in the presence of an anion-exchange resin in OH^? form, to give a pink color on a resin bead surface.     

Positronium interactions in atomic physics

The role of positronium in the investigation of fundamental aspects of atomic physics is discussed. The recently developed technique of timed positronium beam production and the characterisation of the beam constituents in the energy range 7–41 eV are outlined. Examples of positronium atoms as probes in atomic scattering interactions are given.