Search

Optically driving liquid crystal display (ODLCD) uses polarized light field to control the orientation of the liquid crystal, and the display content can be maintained without external electric field, with extremely low power consumption. However, it has a long rewriting time, which is difficult to achieve industrialization. In order to improve the rewriting performance, the influence of the rotational viscosity of the mixed system of azo-dyes (SD1, MR) and nematic liquid crystal (5CB) on the rewriting speed is investigated. The experimental results show that the electro-optical properties of SD1-5CB and MR-5CB have great changes after irradiation by polarized light, among which the SD1-5CB is the best to improve the performance. With the increase of SD1 concentration, the rotational viscosity of SD1-5CB decreases significantly due to the change of cis-trans isomerization of azo-dye, and the optimal doping concentration is 0.5 wt%. In this case, the rewriting time is shortened from 45 s to 11 s, which has the potential to broaden the application of ODLCD. [ABSTRACT FROM AUTHOR]

In the field of the microbial ecology of biofilms and activated sludges, it is widely accepted that the microstructure of the communities depends on the environmental factors. Nevertheless, due to their complexity, the exact mechanisms are still unknown. In this study, we applied a stepwise increase of an azo-dye concentration as a selective factor for adaptation towards biodegradation. The degrading biofilm was developed in a lab-scale sand biofilter. It functioned in a semi-continuous regime for 623 h. The concentration of the azo-dye amaranth was increased from 10 to 55 mg L−1. The effectiveness was 90% and the rate of amaranth elimination was 1.136 mg h−1. The fluorescence in-situ hybridisation (FISH) revealed zones with high activity of Pseudomonas sp. Also increasing importance of the unculturable Pseudomonas sp. and the relationships in the biofilm were found. At the final stage of the experiment, a decrease of the azoreductase activity and an increase of the catechol-1,2-dioxygenase activity were established in the depth of the biofilter. The obtained results were linked with different Pseudomonas microstructures (shown by FISH). The obtained data showed that the changes in the biofilm structure occurred accordingly to the biodegradation of the toxic compound and it included the development of cooperative microbial relationships in the key genus Pseudomonas. [ABSTRACT FROM AUTHOR]

This paper investigates the photoinduced change of refractive index in dye (methyl red, MR)-doped blue phase (DDBP) cells by illumination of a pump beam. Through excitation of light irradiation with proper photon energy, MR can transform from trans-state to cis-state and successively diffuse and anisotropically adsorb on the inner glass substrate of the DDBP cell along the direction perpendicular to the polarisation of the pump beam. The adsorbed MR molecules can effectively rotate the orientation of the liquid crystal (LC) molecules and thereby modulate the effective refractive index of the DDBP cell. The SEM images of the adsorbed regions of the illuminated DDBP samples were also taken for discussing the relation between the pump intensity and the photoinduced birefringence. [ABSTRACT FROM AUTHOR]

The novel oligomeric thin film structures with photochromic properties were obtained. They based on carbazole-containing oligomer as a matrix and azo-dye 4-((4-nitrophenyl)diazenyl)phenol as a photosensitive additive. Spectral, photoconductive, photovoltaic and information properties of films were investigated. It was shown, that all investigated film composites exhibit photoconductive and photovoltaic properties under light irradiation correspond to the azo-dye absorption region. The features of the photoconductive and photovoltaic properties of the investigated compositions, as well as the possible mechanisms of the photovoltaic effect and charge carriers photogeneration, were discussed. It was shown that the prepared composites can be used as reversible recording media. [ABSTRACT FROM AUTHOR]

Theoretical and experimental analysis of the rewriting time of liquid crystal (LC) optical rewritable (ORW) e-paper was conducted. The equations of rewriting time of alignment molecule SD1 film with and without interaction with LC based on diffusion model were derived, which shows that the rewriting time of LC ORW e-paper could be shortened by enlarging light intensity or decreasing azimuthal anchoring energy. The rewriting time of pure SD1 films and LC ORW cells was measured under different light intensities. And LC ORW cells with different azimuthal anchoring energy were prepared for rewriting time measurement. A good agreement between experimental and theoretical results was obtained, which indicates that using larger light intensity and making LC cell with smaller azimuthal anchoring energy, ORW rewriting time could be decreased to the amount suitable for practical use. [ABSTRACT FROM AUTHOR]

A sequential adsorption/photocatalytic regeneration process to remove tartrazine, an azo-dye in aqueous solution, has been investigated. The aim of this work was to compare the effectiveness of an adsorbent/photocatalyst composite – TiO2deposited onto activated carbon (AC) – and a simple mixture of powders of TiO2and AC in same proportion. The composite was an innovative material as the photocatalyst, TiO2, was deposited on the porous surface of a microporous-AC using metal-organic chemical vapour deposition in fluidized bed. The sequential process was composed of two-batch step cycles: every cycle alternated a step of adsorption and a step of photocatalytic oxidation under ultra-violet (365 nm), at 25°C and atmospheric pressure. Both steps, adsorption and photocatalytic oxidation, have been investigated during four cycles. For both materials, the cumulated amounts adsorbed during four cycles corresponded to nearly twice the maximum adsorption capacitiesqmaxproving the photocatalytic oxidation to regenerate the adsorbent. Concerning photocatalytic oxidation, the degree of mineralization was higher with the TiO2/AC composite: for each cycle, the value of the total organic carbon removal was 25% higher than that obtained with the mixture powder. These better photocatalytic performances involved better regeneration than higher adsorbed amounts for cycles 2, 3 and 4. Better performances with this promising material – TiO2deposited onto AC – compared with TiO2powder could be explained by the vicinity of photocatalytic and AC adsorption sites. [ABSTRACT FROM PUBLISHER]

Here, we report on the study of cationic amidoammonium calix[4]resorcinarenes1–5of various lipophilicity capable of binding acid–base indicator methyl orange (MO). We identified the contributions of macrocycle aggregation and conformational mobility in the binding of MO. The effective pKavalues of bound MO systematically decrease as the size and the packing density of the aggregates increase with an increase in calixresorcinarene lipophilicity. Consideration of a series of macrocycles clearly shows that large aggregates form most stable complexes, binding guests not on individual level but as aggregates. It was found that the most stable MO complex with5is formed due to electrostatic binding with ammonium groups of the macrocycle and incapsulation of MO in a hydrophobic layer of the aggregates. We have shown that competitive binding of MO and cationic surfactants by aggregates of5is suitable for visual/spectrophotometric detection of colourless anionic substrates. [ABSTRACT FROM AUTHOR]

New metal complexes of Co(II), Cu(II), Ni(II), Zn(II), Mn(II), Fe(III), Ru(III), UO2(II), and VO(II) with the Schiff base, 2-(5-((2-chlorophenyl)diazenyl)-2-hydroxy- benzylidene) hydrazine-carbothioamide (H2L) have been prepared and characterized by elemental and thermal analyses, FT-IR, UV–Vis, mass spectra, 1H-NMR, and ESR as well as conductivity and magnetic moments measurements. The IR spectra showed that the ligand acts as neutral tridentate, neutral bidentate or monobasic tridentate ligand. The geometries of metal complexes were either octahedral or square pyramidal. The ESR spectra of the solid copper(II) complexes indicated an axial symmetry type of a d(x2-y2) ground state with considerably ionic or covalent environment. The effect of the presence of an azo group on the biological activity of the ligand was investigated. The ligand and its complexes are biologically inactive due to the presence of azo group. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the related elements to view the free supplemental file. [ABSTRACT FROM AUTHOR]

This paper reports on the use of self-assembled monolayer films with azo-dye molecules for liquid crystal alignment. The film growth was monitored by absorption measurements and the thickness and morphology determined by atomic force microscopy. The dynamic photo-alignment data revealed that the orientation of the azo-groups is facilitated in the presence of the liquid crystal. These substrates induced strong anchoring of the E7 liquid crystal molecules, allowing their application in liquid crystal displays. The advantages of this system are the reversibility, where the active part of the device can be altered, and that any size or shape can easily be inscribed. Another important point is the absence of mechanical contact during the substrate preparation, making this process clean. [ABSTRACT FROM AUTHOR]

A highly stable ternary complex of copper(II) with 5-(4-nitrophenylazo) salicylic acid (NPAS) and 2,2'-Dipyridyl (Dp) in ethanol medium at room temperature gave a maximum absorption at 520 nm with a molar absorptivity 2.60×104 L mol-1 cm-1. This method was characterized by safety to the environment as there are no uses of hazardous solvents, which may harm our environment. The linear range for copper determination was 2.2-6.3 mg L-1. The method was sensitive, accurate, and tolerant to many foreign ions. All the reagents were stable under the working conditions. Moreover, the method was easy to perform for the determination of copper in pharmaceutical, biological, and water samples. [ABSTRACT FROM AUTHOR]

In this paper the nonlinear refractive index, n2, of an azo dye (Sudan III) doped nematic liquid crystal was measured at low laser power using closed aperture z-scan and moire deflectometry techniques. The positive sign indicates a self-focusing effect that accrued in the sample. The nonlinear refractive index n2 is in order of 10-6 cm2/W with z-scan method. This observation is found to be in good agreement with the moire deflectometry model. The optical response of the nematic liquid crystals was strongly enhanced by a small amount of dye impurities (Sudan III). Also the effect of external applied AC voltage on the nonlinear refractive is studied. [ABSTRACT FROM AUTHOR]

Photoinduced Anisotropy and All-Optical Poling are the result of two mechanisms, the angularly selective excitation of molecules (Angular Hole Burning) and the rotation of molecules during the excitation–relaxation cycle (Angular redistribution). In this paper we recall some previous results and we present two new experiments. The first one demonstrates the prime importance of reversible photoisomerization for angular redistribution: we compare dichroism and second harmonic generation, with photoisomerizable molecules and non photoisomerizable ones. The second experiment shows an example of the behavior of photoinduced anisotropy, in a liquid crystal azo-polymers: a 3D characterization of anisotropy is necessary. [ABSTRACT FROM AUTHOR]

4-(4 ′-Nitrophenylazo)-1-naphthol, a commercial azo-dye, was used as a side chain moiety for the preparation of six members of a new series of polymethacrylates, the poly(ω-[4-(4 ′-nitrophenylazo)-naphthalene-1-yloxy]alkyl methacrylate)s with 2, 4, 5, 6, 10, and 11 methylene units as spacer. A two-step synthesis gave the corresponding monomeric methacrylates, which were polymerized by a free radical polymerization using AIBN as initiator. The above polymethacrylates did not show any liquid crystallinity, however a side chain crystallization was observed for the last member of the polymer series. The UV/Vis spectroscopy showed that all polymers retained the optical properties of the azo-dye with a small hypsichromic shift and a decrease in intensity when moving from monomer to polymer. A copolymer of 6-methylene spacer monomeric ester with methyl methacrylate was also prepared, in order to study how copolymerization affected the properties of the corresponding homopolymer. [ABSTRACT FROM AUTHOR]