Azo Dye Molecules Research Articles

Azo dyes degradation and mutagenicity evaluation with a combination of microbiological and oxidative discoloration treatments

This work evaluated the degradation of the Acid Blue 161 and Procion Red MX-5B dyes in a binary solution by the filamentous fungus Aspergillus terreus and the yeast Saccharomyces cerevisiae in systems with and without electrochemical oxidation as the pretreatment process. UV–Vis spectrophotometry, high-performance liquid chromatography with (HPLC), Fourier transform infrared (FT-IR) spectroscopy and Salmonella/microsome assay (Ames test) were applied towards the degradation analysis of the dyes. Adsorption tests with white clay immobilized on alginate were also conducted after the discoloration treatments to remove intermediate metabolites formed during the degradation of the dye molecules. The discoloration treatments led to the complete color removal of the solutions in all the systems tested. The clay demonstrated affinity for the metabolites formed after discoloration treatments, the removal rates were variable, but the all systems has proved efficient. The Salmonella/microsome assay (Ames test) with strains TA98 and TA100 in the absence and presence of exogenous metabolism (S9 microsomal system, Moltox) revealed that the initial molecules and by-products of the metabolism of the dyes were direct mutagens. The electrochemical/A. terreus/clay system was able to discolor the solutions and transform the direct mutagens into non-mutagenic compounds in addition to reducing the mutagenic potency of the pro-mutagens to the Salmonella strain TA100/S9, which demonstrates the high efficiency of this system with regard to discoloring and degrading azo dye molecules and their by-products. Therefore, this study showed that although not having standard treatment system for this type of pollutant, the combination of treatments can be considered promising. The use of electrochemical oxidation along with microbiological treatment may lead to the degradation and mineralization of these compounds, reducing or eliminating the environmental impact caused by the improper disposal of these dyes in aquatic environments.

Light-controllable Fano resonance in azo-dye-doped all-dielectric multilayer structure

Active modulation of Fano resonance by light is demonstrated for an all-dielectric multilayer system containing an azo-dye-doped layer. The sample studied consists of a polystyrene layer doped with disperse red 1 (azo dye) molecules, a polyvinyl alcohol layer, and a pure polystyrene layer. In a Kretschmann attenuated-total-reflection configuration, angle-scan reflection spectra of the sample were measured with blue probe light under blue light pumping. The Fano line shape was found to change systematically depending on the intensity of the pump light. Analyses based on electromagnetic calculations of the spectra and field distributions in the layers indicate that the Fano resonance observed is generated by coupling between a broad half-leaky guided mode supported by the azo-dye-doped layer and a sharp planar waveguide mode supported by the pure polystyrene layer. The systematic changes in the Fano line shape under pump light irradiation can be well understood by a systematic decrease in light absorption in the azo-dye-doped polystyrene layer; the decrease in light absorption is due to a decrease in the extinction coefficient of the layer arising from the photoisomerization of azo dye molecules.

Tri-phasic engineered wetland system for effective treatment of azo dye-based wastewater

Synthetic dyes are a major class of compounds used in the textile industry. The effluents released from these industries are carcinogenic and mutagenic in nature and pose potential threat to all life forms. Here, we designed a novel tri-phasic engineered flow through wetland system (TEWS) with three specific microenvironments (tri-phasic aquatic systems) integrated in a defined sequence to effectively treat azo dye-based textile wastewater. Tank 1 with free-floating and emergent aquatic macrophytes create anaerobic/anoxic microenvironments and facilitate reduction of the azo dye molecules. Tank 2 consists of submerged macrophytes which create an aerophilic microenvironment that direct the oxidation of carbon compounds along with nitrification. Tank 3 with free-floating plants and aquatic animals acts as filter feeder intended to remove suspended solids and colour, as well as residual carbon. The strategically designed TEWS attributes to 76%/87% of dye/chemical oxygen demand removal. The morphological toxicity test of plants and fishes illustrate the nontoxic nature of treated effluents. Thus, TEWS not only decolorizes the azo dye but also removes its toxic and mutagenic components.

Запись поляризационных голограмм в полимерных пленках с азокрасителями и азополимерами

Abstract Based on polymers with the addition of azo dyes as chromophores and azopolymers with the same covalently linked chromophores, recording media for polarization holography are created and their properties are studied when recording holograms of a plane wave front with parallel and perpendicular polarization of recording rays. It is found that the diffraction efficiency and the storage time of holograms are much longer in recording media with films of azo polymers in comparison with polymeric solid solutions of azo dyes. In the latter case, the energy of light is spent only for the trans – cis isomerization of azo dye molecules during exposure of holograms and the polymer chains do not undergo deformation with the formation of a surface relief in the polymer film. Therefore, it is preferable to use recording media based on solid solutions of azo dyes in dynamic polarization holography.

Highly dispersed conductive polypyrrole hydrogels as sensitive sensor for simultaneous determination of ascorbic acid, dopamine and uric acid

Conductive polymer hydrogels (CPHs) have exhibited great potential as advanced material for sensing. Here, a facile approach to 3D networked polypyrrole (PPy) hydrogel is reported. This strategy relies on the doping of the azo dye molecule Tartrazine during the synthesis of nanostructured conductive PPy hydrogel. The prepared PPy hydrogel can be highly dispersible in the mixed solvent of isopropanol/H2O (4/1). The unique 3D network nanostructure endow PPy hydrogels with high electric conductivity and effective interface area for enhanced sensing performance towards the simultaneous determination of ascorbic acid, dopamine and uric acid with respective lower detection limits of 1.283, 0.044 and 0.046μmolL−1. The as-designed electrochemical sensor also exhibited excellent stability and reproducibility.

Excited State Molecular Parameters Determined by Spectral Means

The possibility to characterize the electronic excited state of a spectrally active molecule based only on the solvatochromic study of electronic absorption spectra is demonstrated. The values of the regression coefficients given the contribution of universal interactions to the spectral shift and their theoretically established dependences on the solute molecule microscopic parameters are used. The values of the dipole moment, polarizability, and ionization potential in the ground electronic state of a spectrally active molecule are established by quantum mechanical methods. Two azo dye molecules are chosen in order to exemplify this method.

Green synthesis of aluminum-based metal organic framework for the removal of azo dye Acid Black 1 from aqueous media

Aluminum based metal-organic framework using a di-carboxylate linker succinic acid (Al-SA MOF), are synthesized in water with minimal generation of secondary pollutants. The physicochemical properties of Al-SA MOF were examined, followed by its utility for the adsorption of Acid Black 1 (AB1) in aqueous media. Influences of key parameters such as pH, contact time, initial AB1 concentration, temperature, and selectivity on the adsorption process were assessed. A series of adsorption mechanisms are proposed, which involve electrostatic, hydrogen bonding, and hydrophobic interactions. These findings suggest that Al-SA MOF is a potent candidate in removing complex azo dyes molecules from aqueous media.

Intramolecular charge transfer tuning of azo dyes: Spectroscopic characteristic and third-order nonlinear optical properties

Five novel azo dyes molecules with different intramolecular charge transfer (ICT) characters were synthesized and characterized. Their thermal stabilities were studied with thermogravimetric analysis (TGA). Their linear optical properties were investigated by Ultraviolet–visible (UV–Vis) and Fluorescence spectroscopy. △-Self-consistent-field density functional theoretical (SCF-DFT or simply △SCF) calculation and optical method were used to analyze the ICT strength of the azo Dyes 1, 2, 3, 4, 5, Disperse Red 1 (DR 1), DR 17 and DR 13. The fundamental gap, energy gaps (Eg) between HOMO and LUMO, optical gap falls down with the increase of the ICT strength. The third-order nonlinear optical (NLO) properties of azo dyes were investigated by Z-scan technique at the condition of 440 nm, 190 femtosecond, 20 Hz. The relationship between the third-order NLO properties and ICT character was discussed in detail. Going from dyes 1 → 2→3 → 4→5→DR 1→DR 17→DR 13, the Eg values decrease and the ICT strength increase. The third-order nonlinear susceptibility χ(3) and molecular second hyperpolarizability γ of the azo dyes are up to the order of 10−8 esu and 10−27 esu, respectively. The χ(3) and γ increase with the ICT strength. The Figures of Merit W » 1 and T « 1, meet the requirement of all-optical materials: W > 1 and T < 1. The results reveal that the studied azo dyes may be promising candidates for optical devices and this work may provide a reference for synthesis of organic optical materials.

Intravital molecular tagging velocimetry of cerebral blood flow using Evans Blue.

The effects of light-driven enhancement of Evans Blue dye complexes with blood plasma proteins were observed for the first time, both in vitro and in vivo. The possible background of the effect concerns the photochemical cis-trans isomerization of the azo dye molecules. The effect was induced in the solution with a red laser with a wavelength of 638 nm, which corresponds to the peak of the dye absorption. The lifetime of the enhanced fluorescence is approximately 1 second and enables its use as an optically tagged molecular flow tracer for blood flow velocity measurements. Utilizing the effect, we performed for the first time the intravital molecular tagging velocimetry of the blood velocity in blood vessels in a living animal. The results of the measurements of the blood flow velocities in the cerebral veins of a group of healthy mice are presented.

Optical manipulation of nematic colloids at the interfaces in azo-dye-doped liquid crystals.

This study demonstrates the optical manipulation of colloids dispersed in azo-dye-doped liquid crystals (DDLCs) where the accumulation occurs at the interfaces of the phase domains. We explain the mechanism related to the formation of the domains and the movement of the colloids in DDLCs with respect to the isomerization of azo-dye molecules via the illumination of laser beams. The colloids are dragged to the interfaces of the isotropic/nematic domain and the air bubble/isotropic domain by molecular interaction and Marangoni flows.

15.4: Optical Rewritable Liquid Crystal Displays without Front Polarizer

A front polarizer‐free optically rewritable (ORW) liquid crystal displays (LCDs) has been made via a hybrid alignment configuration with dye‐doped LCs. The hybrid structure consists of one optically active planar and one optically passive homeotropic alignment layer. The rewritability of the device is achieved by photo‐ reorienting the azo dye molecules in the active planar alignment layer. The dye doped in LCs function as a polarizer by following the LCs alignment via a guest‐host effect so that the front polarizer can be eliminated. This makes the device more compact and easier to operate for image erasing and rewriting. The image rewriting time only requires ~9.0s, which is determined by the exposure energy and LC parameters. The hybrid‐mode dye‐doped optically rewritable (DDORW) LCD devices could find applications in E‐paper, transparent display and various photonics devices.

Disclosing the synergistic mechanisms of azo dye degradation and bioelectricity generation in a microbial fuel cell

Microbial fuel cell (MFC) with cost-effective aerobic biocathode was developed for further treatment of azo dye intermediates into less harmful products in a single system. The fate of electrons in MFC for azo dye decolourisation and bioelectricity generation were explored via a series of studies including the effects of azo dye concentration, organic loading, external resistance and hydraulic retention time. The addition of low concentration of New Coccine (NC) (25 mg/L) improved 17% of the power density to 20.13 ± 0.37 W/m3. The internal resistance decreased from 50 to 32 Ω. As dye concentration increases, the decolourisation efficiency maintained over 90% (200 mg/L NC), whereas, power density dropped to 10.83 ± 1.21 W/m3. The increase of NC to higher concentration hindered the bioelectricity production, as both anode and azo dye molecules were competing for electrons. More electrons were utilized for decolourisation than bioelectricity generation as decolourisation efficiency improved, but power density dropped with the increase of organic loading. Lower external resistance allowed greater electron transfer, thus it enhanced the overall power performance. Higher power density (15.12 ± 1.12 W/m3) and normalized energy recovery (76 Wh/kg COD) were achieved at the lowest external resistance of 100 Ω. Both decolourisation and power performances were improved with 2 days HRT. The intermediate products from decolourisation and mineralization processes were identified, and the degradation pathway of NC has been proposed based on the UV–Vis, HPLC and GC–MS results.

Optical rewritable liquid crystal displays without a front polarizer.

A front polarizer-free optically rewritable (ORW) liquid crystal display (LCD) has been made via a hybrid alignment configuration with dye-doped LCs. The hybrid structure consists of one optically active planar and one optically passive homeotropic alignment layer. The rewritability of the device is achieved by photo-reorienting the azo dye molecules in the active planar alignment layer. The dye is doped in LCs to function as a polarizer by following the LCs' direction via a guest-host effect so that the front polarizer can be eliminated. This makes the device more compact and easier to operate for image erasing and rewriting. The image rewriting time only requires ∼9.0 s, which is determined by the exposure energy and LC parameters. The hybrid-mode dye-doped ORW LCD devices could find applications in E-paper, transparent display, and various photonics devices.

COMPARISON ON SOLAR PHOTOCATALYTIC DEGRADATION OF ORANGE G AND NEW COCCINE USING ZINC OXIDE AS CATALYST

The mineralization of azo dyes could be realized through solar photocatalytic degradation that is a green method where non-harmful end products are produced. The aim of this study was to investigate the mineralization of Orange G (OG) and New Coccine (NC) using ZnO as catalyst. The degradation of the azo dyes was conducted at different experimental conditions, and parameters such as effect of sunlight to the degradation rate, initial azo dye concentration, amounts of catalyst dosage, pH and effect of aeration to the decolorization of azo dye were investigated. Photocatalytic mineralization of the azo dyes was evaluated through the analysis of UV-Vis spectra, chemical oxygen demand (COD) and ion chromatography (IC) for residual ionic species analysis. The results showed that solar photocatalytic degradation using ZnO was effective for colour removal and the photodegradation rate followed Langmuir-Hinshelwood kinetic model. It was observed that the degradation rate of NC was higher than OG which may be due to the different number of sulphonate ions that are attached on to the azo dye molecule.

SORPTION OF RED FOOD COLORING POLYMERS WITH MOLECULAR IMPRINTS

Polymers with molecular imprints are used as modifiers of the surface of piezoelectric sensors, so it is necessary to study their sorption properties. Isotherms of sorption of synthetic dyes with polymers with molecular imprint and their comparison polymers are obtained. The type of sorption isotherm is characteristic for polymeric materials with micro- and mesopores. The maximum sorption capacity of polymers in relation to dyes is determined, the areas of the projection of the dye molecules on the surface of the sorbent are estimated. With the sorption of multiply charged anionic dye particles, the surface of the sorbent acquires a partial negative charge, which makes it difficult to sorbate as the surface concentration of the sorbate increases. The efficiency of sorption of azo dyes by polymers with molecular imprint from aqueous solutions depends on the amount of ionized sulfo groups in the azo dye molecule, their location in the benzene ring, the symmetry of the dye molecule. Sorption of azo dye by polymers with molecular prints is mainly due to the formation of hydrogen bonds between the sulphonic group of the dye and the hydroxyl group of the sorbent. The area of the projections of molecules on the surface of the modified polymer for all the dyes does not exceed the calculated values of the areas of the molecules, which indicates a loose filling of the sorbent surface and it is probable that the orientation of the dye molecules in the adsorption layer is close to perpendicular to the surface of the sorbent. The values of extraction rates and distribution coefficients are determined, the imprinting factor is calculated. The highest imprinting factor was obtained for the azo dye Ponso 4R. It has been established that polymers with molecular imprinting based on polyimide have better sorption ability with respect to target molecules than their comparison polymers.Forcitation:Zyablov A.N., Khalzova S.A., Selemenev V.F. Sorption of red food coloring polymers with molecular imprints. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 7. P. 42-47.

Optical control of plasmonic grating transmission by photoinduced anisotropy

Light transmission through subwavelength silver slit gratings coated with Langmuir–Blodgett films of an azo-dye compound was studied. While the coating was found to dramatically enhance the TM-polarized grating transmittance, it also enabled its low-intensity optical control: the photoinduced alignment of the azo-dye molecules yielded a significant (∼ 40 nm) shift of the extraordinary transmission peaks to shorter or longer wavelengths depending on the orientation of the induced optical axis with respect to the gratings.

Photoinduced Micropattern Alignment of Semiconductor Nanorods with Polarized Emission in a Liquid Crystal Polymer Matrix.

Photoalignment technology provides high alignment quality with an exceptional control over the local director of liquid crystals. Because of the reorientation ability of sulfonic azo dye molecules, they offer high azimuthal and polar anchoring energy with a low pretilt angle for the orientation of liquid crystals and liquid crystal composites. In this work, we make use of this approach to align thin film composites of light-emitting semiconductor nanorods dispersed in a liquid crystal polymer into both one-dimensional and two-dimensional microscale patterns. After unidirectional alignment, the patterns are fabricated by a second irradiation with different polarization azimuth and the employment of a photomask. Fluorescence micrographs reveal the nanorod pattern alignment in domain sizes down to 2 μm. Apart from demonstrating the possibility of controlling the orientation of anisotropic nanocrystals with strongly polarized emission on microscopic scale, our results are promising for the fabrication of complex nanostructures for photonic applications.

Polarization effects in light-tunable Fano resonance in metal-dielectric multilayer structures

A planar metal-dielectric multilayer structure containing a waveguide layer doped with azo-dye molecules exhibits a sharp Fano resonance that can be shifted by pump light irradiation owing to a photoinduced change of the refractive index of the waveguide layer by photoisomerization of the azo-dye molecules. Azo-dye-containing materials are polarization sensitive and the photoinduced shift of the Fano resonance is expected to depend on the pump polarization. Previous pump-probe attenuated-total-reflection measurements performed with a normal incidence of pump light exhibited intriguingly no dependence on the pump polarization. In this work, we extend our measurements to an oblique incidence, to optimize the overlap between the pump and probe polarizations, and we demonstrate a strong dependence on the pump polarization. To analyze the experimental results for both the normal and oblique pump conditions, we introduce phenomenological equations, based on the angular hole burning model of the photoisomerization of the azo-dye molecules. The equations allow us to describe the dependence of the refractive index changes in the waveguide layer on the pump angle and polarization. Using the equations, we could obtain good theoretical fits to the experimental data. The results of fitting suggest that the overlap between the pump and probe polarizations plays an important role in determining the amount of the photoinduced shift of the Fano resonance.

Hybrid structures based on quantum dots and graphene nanobelts

Luminescence and photoelectric properties of hybrid structures based on CdSe/ZnS quantum dots (QDs) and multilayer graphene have been investigated. A correlation between the luminescence quantum yield of QDs and their photoelectric properties in hybrid structures is established. It is shown that a decrease in the QD luminescence quantum yield due to adsorption of 1-(2-pyridylazo)-2-naphtol azo dye molecules onto the QD surface and a photoinduced increase in the QD luminescence quantum yield are accompanied by a symbate change in the hybrid structure photoconductivity.

Quantification of Adsorption of Azo Dye Molecules on Graphene Oxide Using Optical Spectroscopy

The presence of azo dye molecules in effluents is a source of water pollution and an environmental hazard. Thus, it is very important to separate out such dye molecules. We have investigated the use of graphene oxide (GO) for the purification of dye-contaminated water. The adsorption efficiency of GO in the degradation of azo dye molecules and the interaction mechanism has been estimated using Ultra Violet-Visible absorption spectroscopy. The charge on the dye molecules along with steric hinderance due to their molecular structure is understood to be detrimental in the adsorption and removal of such dyes. Spectroscopic studies suggest that GO can be used as a potential candidate for efficient removal of cationic azo-dye molecules by adsorption.