Azobenzene Dyes Research Articles

Synthesis of new azobenzene dyes clubbed with thiazolidinone moiety and their applications

Purpose The purpose of this paper is to synthesize some new azobenzene dyestuffs clubbed with thiazolidinone moiety and their solicitation in dyeing polyester fabrics representing their antibacterial evaluation. Design/methodology/approach Herein, the authors report the synthesis of new thiazolidinone moiety after the coupling of diazotized 4-aminoacetophenone with resorcinol. The newly synthesized dyes were characterized by IR, elemental analysis, mass spectroscopy and proton nuclear magnetic resonance (1H NMR) spectral studies. The characteristics of dyeing of these dyestuffs were evaluated at optimum conditions. Concurrent with dyeing of polyester fabric for synthesized dyes with their antibacterial activity was estimated. Antimicrobial activity of the dyed fabrics at different concentrations was evaluated against gram-positive and gram-negative bacteria. Findings Synthesized azobenzene dyestuffs clubbed with thiazolidinone dyes were applied on polyester fabrics. It was remarked that the modified dyes exhibited better colourfastness properties. Furthermore, the synthesized dyes revealed antimicrobial activity against gram-positive and gram-negative bacteria. Research limitations/implications The synthesized azobenzene dyes for polyester dyeing were not bore earlier. Practical implications The azobenzene dyes were accountable for giving improved colourfastness properties on polyester fabrics. Social implications The synthesized azobenzene derivatives are sensibly expensive and applicable dyes accompanied with good antimicrobial and anticancer activities. Originality/value A common process could be affording textiles of colour and antibacterial assets. The newly synthesized dyes containing thiazolidinone moieties with azobenzene coupler showed interesting disperse colourant for polyester with good antibacterial activity.

Strong Linearly Polarized Photoluminescence and Electroluminescence from Halide Perovskite/Azobenzene Dye Composite Film for Display Applications

AbstractPolarization emission from halide perovskite is expected to bring a lot of benefits for next‐generation displays, such as cost down, wide color gamut, and structure simplification. In this work, strong linearly polarized luminescence from emissive halide perovskites modulated by photoaligned azobenzene dye AD1 is demonstrated. The azobenzene dye functionalized halide perovskite thin films not only exhibit exceptionally high degree of polarization (DOP) of 86.2–93.1% for red, green, and blue emission, but also promise an improved environmental stability originating from the hydrophobic nature of the azobenzene dye. When these perovskite/AD1 composite films are applied in liquid crystal display panels to replace the conventional thick polarizer, the energy efficiency can be doubled and the color gamut can be extended to >120% NTSC. Furthermore, the AD1 functionalized strategy is successfully employed to generate linearly polarized electroluminescence from an inverted perovskite light‐emitting diode, showing a high DOP of 47%.

Direct observation and simultaneous use of linear and quadratic electro-optical effects

We report on the direct observation and simultaneous use of the linear and quadratic electro-optical effect and propose a method by which higher-order susceptibilities of electro-optical materials can be determined. The evaluation is based on the separation of the second- and third-order susceptibilities and the experimental technique uses a slot waveguide ring resonator fabricated in integrated photonic circuit technology, which is embedded by a guest-host polymer system consisting of the azobenzene dye Disperse Red 1 in a poly(methyl methacrylate) matrix as an active electro-optical material. The contribution of both effects on the electro-optical response under the influence of static and time-varying electrical fields is investigated. We show that the quadratic electro-optical effect has a significant influence on the overall electro-optical response even with acentric molecular orientated molecules. Our findings have important implications for developing electro-optical devices based on polymer-filled slot waveguides and give rise to advanced photonic circuits.

Thermal degradation of azobenzene dyes

Ten azobenzene dyes were tested for their thermal degradation products from ambient temperature to 800 °C using a thermogravimetric technique. Degradation products were analyzed at each 100 °C increment using gas chromatography-mass spectrometry. Products were identified based on their mass spectral data and their retention times. Thermal degradation from all dyes resulted in loss of the azo group as nitrogen gas and aromatic free radicals. Electron withdrawing groups enhance the dissociation of the phenyl nitrogen bond at the benzene moiety carrying the electron withdrawing group. On the other hand, electron donating groups inhibited the dissociation of the phenyl-N bond of the benzene moiety carrying the electron donating groups. The loss of nitrogen molecule from the dyes appeared to be taken place in a two-step rather than a one-step reaction in which the phenyl nitrogen bond of the phenyl group carrying the electron withdrawing group splits to form phenyl and azo phenyl radicals following by the loss of a nitrogen molecule and a new phenyl radical. This was also supported by calculating degradation reaction enthalpies and bond dissociation energies using density functional theory quantum mechanics.

Time-resolved photoluminescence and optical properties of a specific organic azo dye

The aim of this work is to measure the photoluminescence of the Disperse Blue 79 (DB 79) deposited as thin films and study its morphological properties by the mean of the Atomic Force Microscopy technique in order to apply it as an Organic Emitting Light Diode (OLED). The films were prepared by the mean of the home-made Physical Vapor Deposition apparatus in a high vacuum on BK7 glass substrates. The linear optical properties were studied by photoluminescence and decay time spectra. The photoluminescence was measured in a broad ranged from 25 to 300 K in a high vacuum, while the decay time technique was investigated to measure the studied sample’s life-time in real time. Obtained results confirm homogeneous morphology and good optical quality of investigated organic azobenzene dye. These results allow the DB 79 dye to be used for the first time in production of the Organic Light Emitting Diodes (OLEDs).

Controlling Self-Assembly with Light and Temperature.

Complexes between the anionic polyelectrolyte sodium polyacrylate (PA) and an oppositely charged divalent azobenzene dye are prepared in aqueous solution. Depending on the ratio between dye and polyelectrolyte stable aggregates with a well-defined spherical shape are observed. Upon exposure of these complexes to UV light, the trans → cis transition of the azobenzene is excited resulting in a better solubility of the dye and a dissolution of the complexes. The PA chains reassemble into well-defined aggregates when the dye is allowed to relax back into the trans isomer. Varying the temperature during this reformation step has a direct influence on the final size of the aggregates rendering temperature in an efficient way to easily change the size of the self-assemblies. Application of time-resolved small-angle neutron scattering (SANS) to study the structure formation reveals that the cis → trans isomerization is the rate-limiting step followed by a nucleation and growth process.

Dual Light and Temperature Responsive Micrometer-Sized Structural Color Actuators.

Externally induced color- and shape-changes in micrometer-sized objects are of great interest in novel application fields such as optofluidics and microrobotics. In this work, light and temperature responsive micrometer-sized structural color actuators based on cholesteric liquid-crystalline (CLC) polymer particles are presented. The particles are synthesized by suspension polymerization using a reactive CLC monomer mixture having a light responsive azobenzene dye. The particles exhibit anisotropic spot-like and arc-like reflective colored domains ranging from red to blue. Electron microscopy reveals a multidirectional asymmetric arrangement of the cholesteric layers in the particles and numerical simulations elucidate the anisotropic optical properties. Upon light exposure, the particles show reversible asymmetric shape deformations combined with structural color changes. When the temperature is increased above the liquid crystal-isotropic phase transition temperature of the particles, the deformation is followed by a reduction or disappearance of the reflection. Such dual light and temperature responsive structural color actuators are interesting for a variety of micrometer-sized devices.

The investigation of the dipole-dipole action direction and molecular space configuration effect during the dipole–dipole induced azobenzene supramolecular self-assembly

In order to study the effect of dipole-dipole action direction and molecular space configuration on supramolecular self-assembly of azobenzene, three azobenzene dye molecules N1 (" linear "), N2 (" L ") and N3 (" U ") were designed. First, the feasibility of molecular design is verified by theoretical calculations and then synthesized by experiments. By adjusting the direction of the molecular dipole moment and the spatial configuration of the molecule, the three dye molecules self-assemble to form supramolecular self-assemblers with different structures. The properties of three azobenzene dye molecules were studied by IR、NMR、 X-ray diffraction and UV–vis spectra. Theoretical calculation and experimental results show that the direction of dipole dipole interaction and molecular space configuration have important effects on the supramolecular self-assembly morphology of azobenzene.

Photo- and electrical-responsive liquid crystal smart dimmer for augmented reality displays.

A dual-stimuli polarizer-free dye-doped liquid crystal (LC) dimmer is demonstrated. The LC composition consists of photo-stable chiral agent, photosensitive azobenzene, and dichroic dye in a nematic host with positive dielectric anisotropy. Upon UV exposure, the LC directors and dye molecules turn from initially vertical alignment (high transmittance state) to twisted fingerprint structure (low transmittance state). The reversal process is accelerated by combining a longitudinal electric field to unwind the LC directors from twisted fingerprint to homeotropic state, and a red light to transform the cis azobenzene back to trans. This device can be used as a smart dimmer to enhance the ambient contrast ratio for augmented reality displays.

Metal ion chemosensors based on diaza-18-crown-6 coupling with azobenzene dye.

Novel naked-eye cation-selective chemosensors were developed from derivatives of diaza-18-crown-6 bearing one or two azobenzenes functionalized with o-acetic acid or p-nitro groups. The chromogenic acid and nitro derivatives exhibited solvatochromic effects with a majority of quinone-hydrazone tautomer in DMSO. The study of sensing properties of all molecules towards several metal ions showed that the one and two nitro-bearing N1 and N2 derivatives responded selectively to Cr3+ in MeCN with a color change from pink to colorless. They also showed selectivity for Hg2+ in DMSO with a color change from purple to light yellow. The detection limit of N1 and N2 that render visual difference to the naked eye are 0.21 ppm and 0.31 ppm for Cr3+ in MeCN, and 1.20 ppm and 1.00 ppm for Hg2+ in DMSO, while that obtained from 3σ method are 0.08 ppm and 0.03 ppm for Hg2+ in DMSO. These results demonstrate a potential use of p-nitro azobenzene diaza-18-crown-6 as naked-eye sensors, notably for Cr3+ that brings acute toxic to aquatic life.

An Untethered Magnetic‐ and Light‐Responsive Rotary Gripper: Shedding Light on Photoresponsive Liquid Crystal Actuators

AbstractHere, a remotely controlled dual magneto‐ and photoresponsive soft robotic gripper is reported, capable of loading, transport, rotation, and release of cargo. The untethered soft actuator consists of a magnetically responsive polydimethylsiloxane layer containing magnetic iron powder coated onto the central region of a light‐responsive liquid crystal polymer film hosting photochromic azobenzene dyes. Light is used to trigger the actuator to autonomously grab and pick up cargo with a high degree of control. Magnetic response is employed to conduct the locomotion as magnetic guidance, allowing the gripper to have both translational freedom and rotational freedom in its locomotion, differentiating the device from other soft robotic grippers. Control can be attained even in enclosed and/or confined spaces, through solely remote actuation. Through combined video, mechanical, and thermal analyses, the actuation mechanism of the light‐responsive liquid crystal network is investigated, shedding light on the decisive role of the temperature evolution in governing both rate of motion and deformation amplitude of the light‐responsive soft actuator.

ВЛИЯНИЕ ПРИРОДЫ ЗАМЕСТИТЕЛЯ В АЗОБЕНЗОЛЬНЫХ ХРОМОФОРАХ НА ДИФРАКЦИОННУЮ ЭФФЕКТИВНОСТЬ ПОЛЯРИЗАЦИОННЫХ ГОЛОГРАММ

The films of polymeric composites containing monomers of azobenzene dyes or azobenzene lateral groups chemically bonded to the main polymer chain demonstrate photoactive properties, and can be used in electrooptical light modulators and in recording media (RM) for polarization holography. Photoinduced optical anisotropy (PIA) appears under influence of linearly polarized light caused by the processes of trans-cis-izomerization of the azobenzene groups. This process is determining for application of the considered materials as RM for polarization holography. The films of polymeric polarization sensitive media based on a copolymer of styrene with nonyl methacrylate doped with azobenzene-type dyes with different electron-acceptor substituents are obtained in this work. In the films of copolymer the holograms of the plane wave front were registered for parallel and orthogonal orientations of polarization vectors of the object and reference light beams. Their photoelectrophysical, in particular photodielectric, and information properties are investigated. It was established, that when the mutual orientation of the recording beams changes from the orthogonal to parallel orientation the diffraction efficiency of the holograms increases in the case of using azo dye with the maximum number of auxochromic substituents in the molecule. The effect of the diffraction efficiency dependence on the chromophores structure is connected with the deepening of dye color. The photo-induced optical anisotropy in the films appears due to a change of the concentration ratio of trans- and cis-isomers of azobenzene dye fragments. This conclusion is confirmed by the photodielectric measurements data, namely, by the negative sign of the photodielectric effect, observed experimentally in the investigated thin film structures. It was shown, that investigated compositions can be used as information media for polarization holography.

Indicator Layers Based on Ethylene-Vinyl Acetate Copolymer (EVA) and Dicyanovinyl Azobenzene Dyes for Fast and Selective Evaluation of Vaporous Biogenic Amines.

The article presents naked-eye methods for fast, sensitive, and selective detection of isopentylamine and cadaverine vapours based on 4-N,N-dioctylamino-4′-dicyanovinylazobenzene (CR-528) and 4-N,N-dioctylamino-2′-nitro-4′-dicyanovinylazobenzene (CR-555) dyes immobilized in ethylene-vinyl acetate copolymer (EVA). The reaction of CR-528/EVA and CR-555/EVA indicator layers with isopentylamine vapours caused a vivid colour change from pink/purple to yellow/orange-yellow. Additionally, CR-555/EVA showed colour changes upon exposure to cadaverine. The colour changes were analysed by ultraviolet–visible (UV/VIS) molecular absorption spectroscopy for amine quantification, and the method was partially validated for the detection limit, sensitivity, and linear concentration range. The lowest detection limits were reached with CR-555/EVA indicator layers (0.41 ppm for isopentylamine and 1.80 ppm for cadaverine). The indicator layers based on EVA and dicyanovinyl azobenzene dyes complement the existing library of colorimetric probes for the detection of biogenic amines and show great potential for food quality control.

Synthesis of Azobenzene Dyes Mediated by CotA Laccase.

An eco-friendly protocol for the synthesis of azobenzene dyes by oxidative coupling of primary aromatic amines is reported. As efficient biocatalytic systems, CotA laccase and CotA laccase/ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)) enable the oxidation of various substituted anilines, in aqueous medium, ambient atmosphere and under mild reaction conditions of pH and temperature. A series of azobenzene dyes were prepared in good to excellent yields in an one-pot reaction. A mechanistic proposal for the formation of the azo derivatives is presented. Our strategy offers an alternative approach for the direct synthesis of azobenzene dyes, avoiding the harsh conditions generally required for most of the traditional synthetic methods.

QUERCETIN NANOPARTICLES REPRESSED LIVER AND BRAIN TOXICITIES INDUCED BY TARTRAZINE IN RATS

Tartrazine (TZ) is an azobenzene artificial yellow dye for foods, drugs, and cosmetics. Quercetin is member of the flavonoid family. The current study investigated the protective effect of quercetin nanoparticles (QNPs) against TZ. Male albino rats were divided into group1: control, group 2: TZ (50 mg/kg), group 3: QNPs (5 mg/kg), and group 4: QNPs+TZ. The results of the present study revealed that, the oral administration of TZ dye caused a significantly increased liver biomarkers. Also, a marked effect on lipid profile and blood parameters were shown. In addition TZ induced an elevation in the examined oxidative stress biomarkers and decrease in glutathione peroxidases and acetylcholine esterase. TZ diminished exploration and rearing in open field test as well as elevation in GABA content and apoptosis as well as changes in tissues by histopathological examination. In fact, the results showed good influence of QNPs in improving injuries associated with TZ administration.
 Keywords: Tartrazine Dye, Quercetin Nanoparticles, Liver-Brain injuries.

Optically transparent silica film with pH-sensing properties: Influence of chemical immobilization and presence of β-cyclodextrin on protolytic properties of alizarin yellow

A sol-gel synthetic rote was proposed for preparation of optically transparent silica films with covalently bonded azobenzene dye, alizarin yellow. Effect of chemical immobilization on protolytic properties of pH sensor moieties was studied using UV–vis spectroscopy. It was found that indicator dye attached to the silica framework through amide linkage retains the ability to respond on pH change by color transition. The response time of surface azobenzene groups evaluated from the kinetic studies in acidic and neutral medium consists of 10 and 5 min, correspondingly. Acid ionization constants of individual and grafted alizarin yellow were evaluated by spectrophotometric titration in phosphate buffer solutions. It was found that involving of indicator dye carboxylic group in covalent bonding with silica surface leads to the shift of pKa2 value, reflecting the dissociation of phenolic hydroxyl group, from 10.9 to 5.5. Influence of β-cyclodextrin on pH-sensing properties of individual and grafted alizarin yellow was evaluated by spectrophotometric titration in phosphate buffer solutions. Sensor material showed good reversibility, repeatability and long-term stability at immersion in aqueous solutions with pH in the range from 1 to 8.

Stable Immobilization of Size‐Controlled Bimetallic Nanoparticles in Photonic Crystal Fiber Microreactor

AbstractThe possibility of immobilizing ex situ‐synthesized colloidal bimetallic nanoparticles (NPs) of well‐defined characteristics inside hollow core photonic crystal fiber (HC‐PCF) microreactors is demonstrated. With the developed method, PtNi clusters remain strongly attached to the fiber core and can be used as active catalysts for the hydrogenation of an azobenzene dye. The study revealed that optical transmission exhibits a size‐dependent behavior, i.e., smaller NPs bring in less optical signal loss. Sufficient light transmission was achieved for all particle sizes. Furthermore, with these catalytic PCF microreactors, kinetic data can be obtained with a much lower amount of precious metals compared to a conventional batch reactor, opening a new pathway for in situ catalyst screening.

High Photoinduced Ordering and Controllable Photostability of Hydrophilic Azobenzene Material Based on Relative Humidity

Azobenzene materials provide an effective way for liquid crystal (LC) alignment besides traditional rubbing technology. A strong relationship between relative humidity (RH) and the photoalignment quality of hydrophilic azobenzene dye brilliant yellow (BY) has been investigated. Good photoalignment quality can only be ensured at about 40% RH or below. On the other hand, the photostability of the alignment layer is also influenced dramatically by RH. The rewritability can be guaranteed at extremely low RH (≤10%). It is gradually lost with increasing RH, and the alignment layer becomes photostable against further light exposure when at 40% RH or above. Therefore, the BY photoalignment layer can be tuned from rewritable to photostable by simply adjusting RH, and thus multistep photopatterned alignments can be obtained and reserved based on this method. Similar properties are also expected for other hydrophilic azobenzene photoalignment materials, where the specific RH values may vary correspondingly. The reason is due to the strong intermolecular interaction and J-aggregate formation of BY molecules with water insertion. Moreover, the lyotropic LC formed by J-aggregated BY molecules in aqueous solution is reported here.

Dynamical thermo-optical switching based on nematic liquid crystals doped with push–pull azobenzene dyes

Thermo-optical properties of push–pull azobenzene dyes doped nematic liquid crystals was investigated and experimentally demonstrated. The dynamical variations of transmission upon a CW Nd:YAG laser exposure at room temperature were determined by laser intensity, azobenzene dye concentration and sample temperature. Transmission behaviors at different temperatures were distinct, which resulted from oscillation transmittance performance of nematic liquid crystals with temperature variation and photoisomerization process of azobenzene dye. Our experimental results demonstrated that the dynamical thermo-optical change in azobenzene dye doped nematic liquid crystals could be a promising candidate for thermo-optical controller.

Design and Characterization of Dicyanovinyl Reactive Dyes for the Colorimetric Detection of Thiols and Biogenic Amines.

The synthesis of two new azobenzene dyes, namely CR-528 and CR-555, and their spectral properties in ethanol solution are described. The recognition of sulfur-containing analytes (2-mercaptoethanol (2-ME), sodium hydrosulfide (NaHS)), and biogenic amines (spermine, spermidine, ethanolamine) bestowed significant spectral changes with color changes from pink/purple to pale yellow/orange-yellow. The nitro acceptor group in the dicyanovinyl reactive dye contributes to higher sensitivity and lower detected analyte concentrations. The absorption maxima of both the dyes are at wavelengths compatible with low-cost light sources and detectors, making them excellent candidates for optical probes that are economic, simple to use, and do not require well-trained personnel.