Chemical Structure Of Dyes Research Articles

Natural dyes as sensitizers for dye-sensitized solar cells

The dye-sensitized solar cells (DSSCs) have been fabricated by using a series of natural dyes extracted from euonymus japonicus and purple plants. The optical characteristics and chemical structure of dyes were investigated by UV-visible spectroscopy and Fourier infrared spectroscopy. It is found that the absorption of sunlight and bonding performance to TiO2electrode of dyes had significantly effects on the conversion efficiency of solar cells. The results show the cells using blueberry as sensitizer achieved best conversion efficiency of 0.218%, attributed to its strong absorption and excellent bonding to the TiO2electrode, correspondingly, the short-circuit photocurrent density ([Formula: see text] and open-circuit voltage ([Formula: see text] were 1.3[Formula: see text]mA/cm2and 430[Formula: see text]mV, respectively.

Influence of Titanium Dioxide Preparation Method on Photocatalytic Degradation of Organic Dyes

Titanium catalysts (TiO2) were synthesized by three different methods. Their photocatalytic activity was validated through photodegradation of Reactive Red 45 (RR45) azo dye and Acid Blue 25 (AB25) anthraquinone dye in an aqueous solution under UV irradiation. TiO2 photocatalysts were characterized by FTIR, XRD and SEM. Photosensitivity and TiO2 activity range were characterized by UV/Vis spectroscopy. Photocatalytic validation has been made by way of determining the degree of RR45 and AB25 removal. TOC was determined as a measure of the mineralization of RR45 and AB25 by photocatalysis. The stability of TiO2 catalysts and a possibility of using them in consecutive photocatalysis cycles have also been studied. The results show that the photocatalytic efficiency depends on the crystal structure of TiO2. The size of crystallites depends on synthesis conditions. From the results of photocatalytic efficiency it is concluded that the chemical interaction between a catalyst and a dye strongly depends on the dye chemical structure.

PCA-spectroscopy study of common salt effect on solubility of direct dye

PurposeThis work aims to explain the effect of common salt on absorbance spectra and solubility of textile direct dyes, which is important in analysing and reusing wastewater of dyeing process.Design/methodology/approachSeveral textile dyes such as Direct red 243, Direct yellow 86 and Direct blue 201 solutions with and without NaCl salt were used to study the effect of common salt on solubility of textile direct dyes. Several methods such as derivative spectrophotometry, principal component analysis and colorimetric techniques were used to analyse the absorbance spectra of dye solution.FindingsThe obtained results indicate that the effect of common salt on absorbance spectra and solubility of textile direct dye depends on the chemical structure of dyes. The NaCl salt significantly affects the solubility of Direct red 243 (red dye) and Direct yellow 86 (yellow dye) which have Azo compounds containing four SO3 functional groups. But the NaCl salt does not change the solubility of Direct blue 201 (Blue dye) which has Azo compound containing two SO3 functional groups. Also, the NaCl salt decreases the accuracy of dye concentration prediction.Practical implicationsDuring reusing wastewater of dyeing process, the amount of dyes has been evaluated via absorbance spectra of dye solution.Originality/valueThis work explains the effect of common salt on solubility of textile direct dyes and the accuracy of dyes concentration prediction.

Azo dyes degradation using TiO2-Pt/graphene oxide and TiO2-Pt/reduced graphene oxide photocatalysts under UV and natural sunlight irradiation

The photocatalytic degradation of azo dyes with different structures (amaranth, sunset yellow and tartrazine) using TiO2-Pt nanoparticles (TPt), TiO2-Pt/graphene oxide (TPt-GO) and TiO2-Pt/reduced graphene oxide (TPt-rGO) composites were investigated in the presence of UV and natural sunlight irradiation. The composites were prepared by a combined chemical-thermal method and characterized by Transmission Electron Microscopy (TEM), X-ray powder diffraction (XRD), Infrared (FTIR) and UV–Vis spectroscopy. The modification of TiO2-Pt with graphene oxide shifted its optical absorption edge towards the visible region and increased its photocatalytic activity under UV and natural sunlight irradiation. The efficiency of catalysts on azo dyes degradation (in similar conditions) reached high values (above 99%) under sunlight conditions, proving the remarkable photocatalytic activities of obtained composites. TPt-GO nanocomposite exhibited higher photoactivity than TPt or TPt-rGO, demonstrating degradation efficiencies of 99.56% for amaranth, 99.15% for sunset yellow and 96.23% for tartrazine. The dye photodegradation process follows a pseudo-first-order kinetic with respect to the Langmuir-Hinshelwood reaction mechanism. A direct dependence between azo dyes degradation rate and chemical structure of dyes has been observed.

Oxyethylene chain length affects the physicochemical properties of sugar-based anionic surfactants with phosphates groups

In this study we prepared a series of novel sugar based anionic-polyoxyethylene stearyl ether surfactants through reactions of propylene glycol dextrin with oxirane-containing polyoxyethylene stearyl ethers and phosphorus oxychloride. These surfactants, which contain polyoxyethylene chains and sodium phosphonate groups as hydrophilic moieties, exhibited surface activities superior to those of traditional surfactants containing only one nonpolar or hydrophobic moiety and one polar head unit. The critical micelle concentration (cmc), surface excess concentration at the surface (Γcmc) and standard free energy of micellization per mole (ΔGm°) of these surfactants decreased upon increasing the length of their polyoxyethylene chain. In addition, we used UV–vis spectroscopy to study the interactions of dyes with these sugar based anionic surfactants in solution, the results shows that the interaction of the dye and surfactant molecules and the type of dye–surfactant aggregate formed will depend upon chemical structure of dye and surfactant.

Chromonic liquid crystals formed by CI Acid Red 266 and related structures

Chromonic liquid crystals are currently receiving increased attention because they have applications in a wide range of products. In this study, we have compared the chromonic mesophase behaviour of four azo dyes with similar chemical structures. Our objective is to determine if there is an obvious link between mesophase formation and dye chemical structure. Orange G does not form mesophases over the concentration range examined (saturated solution > ~20–30 wt%). The other three compounds all form nematic (N) and hexagonal (H) mesophases, but over very different concentration ranges. X-ray diffraction shows that the ordered Edicol Sunset Yellow (ESY) aggregates present in the mesophases have a single molecule cross section, while those of CI Acid Red have a cross section equivalent to six to eight molecules, probably organised in a ‘water-filled pipes’ structure. NMR quadrupole splittings of 2H2O demonstrate that water binding to the aggregates is similar to that found for surfactant lyotropic mesophases. The sodium (23Na) quadrupole splittings for Orange II and CI Acid Red are similar to the values found for surfactant hexagonal phases, suggesting that most sodium ions are ‘bound’ to the aggregates. This is unlike the behaviour of ESY where only one of the two sodium ions is bound.

Effect of dye chemical structure on the efficiency of photoassisted electrochemical degradation using a cathode containing carbon nanotubes and a Ti/RuO2 anode

In this research, photoassisted electrochemical degradation of 13 commercial dyes with various chemical structures and substituent groups was investigated using a cathode containing carbon nanotubes (CNTs) and a titanium/ruthenium oxide (Ti/RuO2) anode. The inner and outer diameters of the CNTs and their stabilization on carbon paper support were confirmed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. All experiments were carried out in identical operating conditions using a recirculation system under ultraviolet (UV) light irradiation. The dyes with electron-releasing groups (e.g., amino, hydroxyl, and acetamido) were more degraded than those containing electron-withdrawing groups (e.g., sulfo, sulfonyl, and halo) due to inductive and/or resonance effects. Moreover, the obtained results reveal that the degradation process follows pseudo-first-order kinetics, and the degradation efficiency was evaluated as the electrical energy per order.

Dye Decolourization of the Remazol Dye in Textile Effluent by Using<i> Bambusa he</i><i>terostachya</i>

Enlargement of textile industry in Malaysia is swiftly growing as it plays vital role in human evolution by providing cloths. Industrialization in textile fields plays main part in colouring of fabric as it gives environmental concerns associated with textile effluent. The usages of dyestuff make textile effluent difficult to biodegrade as the complexity of chemical structures of dyes. The diversity of forestry creates nature plant such as bamboo which is used as mediator in dye decolorize of textile effluent. As sustainable resolution can reduce environmental system destruction, the effectiveness and competency of bambusa heterostachya has been investigated to analyze the potential in decolorize of textile effluent. The result exhibited good dye decolourization rate of 70 - 80 % in less than 72 hours with influence studies.

The effect of dye chemical structure on adsorption on activated carbon: a comparative study

The effect of the molecular structure of dyes Eriochrome Black T and Bromophenol Blue on their adsorption on the surface of activated carbon manufactured from locally available biosorbent has been studied. Batch experiments were performed to investigate factors that may affect the adsorption process. The effect of stirring rate was investigated in the range 0–240 rpm, with an initial concentration of 4–100 mg/l and a stirring time of 0–400 min. The mechanism and rate of adsorption were investigated for both dyes using pseudo‐first‐order, pseudo‐second‐order, intraparticle diffusion, and liquid film diffusion models. The monolayer adsorption capacities for Eriochrome Black T and Bromophenol Blue were found to be 36.5 and 39.68 mg/g respectively. The difference in dye uptake was attributed to the presence of the electron‐withdrawing bromine group in Bromophenol Blue. Results showed that the Langmuir isotherm best fitted the adsorption of the two dyes on the prepared activated carbon. The pseudo‐second‐order model best fitted the experimental data, and liquid film diffusion and intraparticle diffusion were the controlling adsorption mechanisms.

Structure-based model for light-harvesting properties of nucleic acid nanostructures.

Programmed self-assembly of DNA enables the rational design of megadalton-scale macromolecular assemblies with sub-nanometer scale precision. These assemblies can be programmed to serve as structural scaffolds for secondary chromophore molecules with light-harvesting properties. Like in natural systems, the local and global spatial organization of these synthetic scaffolded chromophore systems plays a crucial role in their emergent excitonic and optical properties. Previously, we introduced a computational model to predict the large-scale 3D solution structure and flexibility of nucleic acid nanostructures programmed using the principle of scaffolded DNA origami. Here, we use Förster resonance energy transfer theory to simulate the temporal dynamics of dye excitation and energy transfer accounting both for overall DNA nanostructure architecture as well as atomic-level DNA and dye chemical structure and composition. Results are used to calculate emergent optical properties including effective absorption cross-section, absorption and emission spectra and total power transferred to a biomimetic reaction center in an existing seven-helix double stranded DNA-based antenna. This structure-based computational framework enables the efficient in silico evaluation of nucleic acid nanostructures for diverse light-harvesting and photonic applications.

Photocatalytic effect of TiO2and the effect of dopants on degradation of brilliant green

Abstract Photocatalysis speeds up the photoreaction in the presence of a catalyst. TiO2 has low toxicity, less resistance and less corrosion and has semiconductor properties. Its strong oxidative potential of the positive holes oxidizes water to create hydroxyl radicals. Moreover, TiO2 has been proven to be a tremendous photocatalyst compound by which many organic substrates have been shown to be oxidatively degraded under UV irradiation. In this research the photocatalytic effect of TiO2 on degradation of Brilliant Green (BG) was studied. In conjunction the effect of dopants such as Zn and Cu on photocatalysis of TiO2 were also studied. Structural and morphological properties of TiO2 were characterized by SEM and XRD. From this research the initial concentration of sample, pH of samples, chemical structure of dyes and catalyst loading were most valuable parameters for dye degradation. TiO2 showed excellent result on degradation of BG compared with doped TiO2. 99% degradation was obtained in presence of TiO2, followed by TiO2/Zn for 87% and TiO2/Cu for 46%. TiO2 doped with transition metals can increase or decrease photocatalytic degradation of dyes.

Influence of dye type and salinity on aerobic decolorization of azo dyes by microbial consortium and the community dynamics

In this research, aerobic decolorization of different azo dyes by a microbial community was studied. The results showed that more than 80% of four azo dyes (100 mg/L) could be aerobically decolorized by the microbial consortium, however, the time needed was obviously different. Kinetic data indicated that the processes were well described by zero-order kinetics, and the chemical structures of dyes had obvious influence on decolorization rates. On the other hand, effects of salinity on decolorization were also investigated. There was still 40% dye removal for Acid Brilliant Red GR when the salinity increased to 250 g/L. And the microbial community structures with different salinity were detected by PCR-DGGE. It was shown that the same two bacteria were dominant in all decolorization systems, and some typical halophilic microorganisms were found under higher-salt conditions.

Dye removal from colored textile wastewater using acrylic grafted nanomembrane

In this paper, the dye removal ability of the acrylic grafted polysulfone nanomembrane using ultraviolet radiation was studied to remove dyes from colored textile wastewater. Acrylic acid was used to modify polysulfone ultrafiltration membrane. The effect of different operating parameters such as pressure, salt concentration and chemical structure of dyes was evaluated. Data indicated that the photografted membrane has acceptable performance both in terms of flux and rejection. The dye rejection and hydraulic permeability were 86–99.9% and 7.6 L m − 2 h − 1 bar − 1 , respectively. It was found that the rejection of dyes decreased with salt concentration due to a decrease of the Donnan effect. Also, the low molecular weight dyes and highly charged dyes were more sensitive in the presence of salts. Addition of 80 mM Na 2SO 4 in dye solution decreased the dye rejection more than 15%. The rejection enhancement for all cases was negligible by increasing driving pressure from 1 to 4 bar. Dyes with low charger were more sensitive to operating pressure than that of dyes with higher charges. All findings supported that acrylic grafted nanomembrane is potentially capable to separate dyes from colored textile effluent.

Inaccurate chemical structures of dyes and fluorochromes found in the literature can be problematic for teaching and research

Representations of the chemical structures of dyes and fluorochromes often are used to illustrate staining mechanisms and histochemical reactions. Unfortunately, inaccurate chemical structures sometimes are used, which results in problems for teaching and research in histochemistry. We comment here on published examples of inadequate chemical drawing and modeling. In particular, omission of hydrogen atoms can lead to misleading hydrogen-bonding interactions, and inaccurate drawing and modeling procedures result in a variety of implausible molecular structures. The examples and arguments given here are easily intelligible for non-chemists and could be used as part of a training approach to help avoid publication of misleading or puzzling dye structures and molecular models for illustrating biological staining and histochemical studies.

Influence of Solution Composition and Chemical Structure of Dye on Removal of Organic Dye by DC Diaphragm Discharge in Water solutions

AbstractThe process of organic dye removal from various water solutions containing organic dyes and inorganic additives by the DC diaphragm discharge has been studied in so called “negative part” of this. The concentration of treated dye decreases almost exponentially to constant residual value. The final dye concentration reached approximately 20% of the initial value after 10 minutes of the treatment of the Direct Red 79 dye solution. The dye de-coloration was affected by the dye structure. The azo and diazo compounds have been degraded significantly faster to be compared to thiazine compounds. The degradation process requires an optimal adjustment of the initial solution conductivity. The optimum conductivity of approximately 600 μS⋅cm

Activated Carbon Produced from Waste Wood Pallets: Adsorption of Three Classes of Dyes

Activated carbon was derived from waste wood pallets in Hong Kong via phosphoric acid activation and applied to adsorption of basic dye (methylene blue), acid dyes (acid blue 25 and acid red 151), and reactive dye (reactive red 23). The results showed that respective adjustment in phosphoric acid concentration, impregnation ratio, activation temperature, and activation time could maximize the surface area and pore volume of activated carbon. An increase of impregnation ratio or activation temperature significantly influenced the pore size distribution by expanding the porous structure and creating more macropores than micropores. The characterization of the carbon surface chemistry using Fourier-transform infrared (FTIR) spectroscopy, however, revealed a decrease in the amount of several functional groups with increasing activation temperature. The physical properties (surface area and pore volume) of the wood waste-derived activated carbon (using 36% phosphoric acid with an impregnation ratio of 1.5 at an activation temperature of 550°C for 1.5 h) were comparable to those of commercial activated carbon (Calgon F400). The contrasting pH effects on the adsorption of different classes of dyes signified the importance of both electrostatic interaction and chemical adsorption, which correlated to pH-dependent dissociation of surface functional groups. It is noteworthy that the physical properties of activated carbon were insufficient to account for the observed dye adsorption behavior, whereas the surface chemistry of activated carbon and the nature and chemical structure of dyes were more important. The fast kinetics and high capacity of dye adsorption of wood waste-derived activated carbon suggest that production of activated carbon from different types of wood waste should merit further investigation.

Implication of mycelium-associated laccase from Irpex lacteus in the decolorization of synthetic dyes

The white rot fungus Irpex lacteus is able to decolorize such synthetic dyes as Reactive Orange 16 and Remazol Brilliant Blue R. Here, we demonstrate that this type of dye decolorization is mainly related to a laccase-like enzyme activity associated with fungal mycelium. In its bound form, the enzyme detected showed a pH optimum of 3.0 for the oxidation of ABTS, DMP and guaiacol, and a pH of 7.0 for syringaldazine. The highest enzymatic activity was obtained with ABTS as substrate. Enzyme activity was fully inhibited with 50 mM NaN 3. Depending on the chemical structure of dyes, redox mediators had a positive effect on the dye decolorization by fungal mycelium. Enzyme isolated from fungal mycelium was able to decolorize synthetic dyes in vitro.

UV-induced photocatalytic degradation of azo dyes by organic-capped ZnO nanocrystals immobilized onto substrates

ZnO nanocrystals (mean particle size: 6nm) with different surface organic coating and commercial ZnO powder (mean particle size: 200nm) have been immobilized onto transparent substrates and comparatively examined as photocatalysts for the UV-induced degradation of two azo dyes, Methyl Red and Methyl Orange, in water. The effects of the pH, of the catalyst surface status, and of the dye chemical structure on the course of the photocatalysis are discussed. Reasonable degradation pathways for both target molecules are proposed on the basis of the structural identification of several by-products. The results demonstrate that surfactant-capped ZnO nanocrystals exhibit more versatile performances than those of conventional ZnO-based photocatalysts, because the surface organic coating makes the oxide resistant to photocorrosion and to pH changes. Surface-protected ZnO nanocrystals can be regarded as a valuable alternative to standard TiO2 photocatalysts.

Photocatalytic degradation of azo dyes by organic-capped anatase TiO2 nanocrystals immobilized onto substrates

The UV-induced photocatalytic degradation of two azo dyes, Methyl Red and Methyl Orange, has been carried out in aqueous media in the presence of oleic acid (OLEA)- and tri-n-octylphosphine oxide (TOPO)-capped anatase TiO2 nanocrystal powders (mean particle size: 6nm) deposited onto a quartz substrate. The progress of photodegradation was followed by combining UV–vis absorption measurements with HPLC–MS analysis. The abatement efficiency for the two organic compounds was compared with that obtained with commercial TiO2 P25 Degussa by evaluating a few significant variables, such as the dye chemical structure, pH of the solution, and catalyst surface status. Identification of several by-products by HPLC–MS analysis has allowed to propose a reasonable degradation pathway for both target molecules. Significantly, although all titania catalysts were effective in removing both parent dyes and their related derivatives, the degradation rate by the OLEA-capped TiO2 nanocrystals was double as that obtained with both its TOPO-capped analogous and TiO2 P25 Degussa. It is suggested that efficient catalysis strictly depends on microscopic mechanisms that occur at the catalyst surface, basically involving specific dye adsorption and local density of terminal OH moieties.

STRESSED POLYMERS CHANGE COLOR

LIGHT-EMITTING POLYMER blends that respond to stresses and strains by changing their hue have potential uses ranging from early internal failure sensors to antitampering films for packaging, according to the polymer scientists who developed the materials at Case Western Reserve University, Cleveland. Associate professor Christoph Weder and graduate student Brent R. Crenshaw prepared blends of conventional polymers such as linear low-density polyethylene and a series of highly photoluminescent dyes { Chem. Mater. , 15 , 4717 (2003)}. dyes serve as integral sensors, Weder says. They allow a material's mechanical deformation to be traced through a change in its fluorescence—for example, from red to green. Under UV light, the effect is readily seen by the naked eye. The phenomenon relies on phase separation of small aggregates of the cyano-oligo( p -phenylene vinylene) dye molecules in the polymer matrix. The phase behavior of the blend is controlled by varying the dye's chemical structure, the blend co...