Dyes and Pigments

Published by Elsevier
Online ISSN: 0143-7208
Publications
Article
Commercially available, near-infrared fluorescent squaraine dyes (Seta-635 and Seta-670) were covalently bound to antibodies and employed insurface enhanced immunoassay. From fluorescence intensity and lifetime changes determined for a surface which had been coated with silver nanoparticles as well as a non-coated glass surface, both labelled compounds exhibited a 15 to 20-fold enhancement of fluorescence on the silver coated surface compared to that achieved on the non-coated surface. In addition, the fluorescence lifetime changes drastically for both labels in the case of silver-coated surfaces. The fluorescence signal enhancement obtained for the two dyes was greater than that previously recorded for Rhodamine Red-X and AlexaFluor-647 labels.
 
Article
A high yield route to symmetric, conjugatable pentamethine carbocyanine dyes with far-red/near infrared (NIR) emission between 650 and 700 nm is reported. The dyes are prepared via condensation of indolium or benz[e]indolium inner salts with an alkyl carboxylic acid derivatized malonaldehyde dianil or alternatively in a one-pot reaction without isolation of the malonaldehyde intermediate. The fluorophores are water-soluble, have bright fluorescence emission, are easily prepared in good yield, and are promising candidates for use in a variety of biochemical and in vivo imaging applications.
 
Article
The R enantiomers of three, novel, 2D dipolar cations with 2,2′-bis(dimethylamino)-1,1′-binaphthalenyl electron donor groups connected to N-R-pyridinium acceptors were synthesised. The compounds displayed intense intramolecular charge-transfer bands in the visible region, the maximal energy of which decreased as R changed in the order Me > 2,4-dinitrophenyl > 2-pyrimidyl. Molecular quadratic nonlinear optical responses were determined for the chloride salts in methanol using femtosecond, hyper-Rayleigh scattering with 1300 and 800 nm lasers. The measured first hyperpolarizabilities βHRS were in the range 34–155 × 10−30 esu and increased at both wavelengths, showing the expected inverse relationship with respect to the charge-transfer energies. Single crystal X-ray structures were determined for the precursor compounds (R)-6,6′-dibromo-2,2′-bis(dimethylamino)-1,1′-binaphthalenyl and (R)-2,2′-bis(dimethylamino)-1,1′-binaphthalenyl-6,6′-dicarbaldehyde, revealing an average dihedral angle between the naphthalenyl units of 73°. Making the assumption that this angle was similar to that found in the chromophores studies in solution allowed the determination of two independent tensor components, βzzz and βzxx. For these molecules the greatest proportion of the total first hyperpolarizability lay along the charge-transfer axis (βzzz), but the “off-diagonal” βzxx values were still substantial (31–141 × 10−30 esu) and larger when compared with those determined by hyper-Rayleigh scattering for other 2D dipoles in the literature.
 
Article
A series of novel, substituted, pyrido[1,2-a]benzimidazole derivatives were synthesized using a novel tandem annulation reaction between 2-acylbenzimidazole derivatives and 4-bromobut-2-enoic esters under mild conditions. The compounds were characterized using IR, 1H NMR, 13C NMR and HRMS; the crystal structure of 2,7,8-trimethyl-3-ethoxycarbonyl-4-phenylpyrido[1,2-a]benzimidazole was determined as orthorhombic. The absorbance and fluorescence spectra of the pyrido[1,2-a]benzimidazoles were measured in dichloromethane; an intense absorption maxima was observed at 250 nm and emission maxima were noted at 460 nm. The absorption spectra and fluorescence characteristics of the pyrido[1,2-a]benzimidazole derivatives revealed that a phenyl and a methyl group attached to the pyrido[1,2-a]benzimidazole ring markedly influenced maximum emission.
 
Article
A series of new heterocyclic monoazo disperse dyes have been prepared by coupling 11-amino-13H-acenaphtho[1,2-e]pyridazino[3,2-b]quinazoline-13-one with various mono and di-N substituted derivatives of aniline. All the disperse dyes were characterized by their percentage yield, melting point, UV–visible spectroscopy, elemental analysis, infrared spectroscopy and dyeing performance on Nylon 66 and polyester fibres. The percentage dye bath exhaustion on different fibres have been found to be reasonably good and acceptable. The dyed fibres show fairly good to good fastness to light and very good to excellent fastness to washing, rubbing, perspiration and sublimation.
 
Article
A series of bis(1,2-dimethyl-3-indolizinyl)hetarylmethane dyes has been synthesised, where the hetaryl substituents are 2-benzoxazolyl, 2-benzothiazolyl, 1-methyl-2-benzimidazolyl, 4- and 2-pyridyl and 4-quinolyl.The interpretations of the 1H-NMR spectra supported the postulated structure of these dyes. The dependence of the electronic absorption spectra on the variation of the hetaryl substituents as well as on the pH* conditions of the water/methanol solvent mixture (halochromism) is discussed on the basis of PPP-CI and HMO calculations. Analogously to trihetarylmethane dyes described earlier1 a second-order perturbational effect could be shown to make the main contribution to the bathochromic shift on substituting the chromophoric di-indolizinylmonomethincyanine fragment at the central carbon atom. This effect was superimposed on the general first-order perturbational shift induced by the increased out-of-plane rotation of the chromophore on substitution with the bulky hetarenes.Lower dissociation constants K* and KR* in comparison with the di-indolylhetarylmethane series1 confirmed the calculated better delocalisation of the positive charge on the central carbon in the present system.
 
Article
In a sequence of reactions the activated thiocyanate derivative 2 was used to synthesize new Hansa Yellow dyestuffs embodying two heterocyclic moieties. The structure of the dyes was inferred from spectral and analytical data. Spectral behaviour of the dyes indicated that they existed essentially in the hydrazone form (5-C).Dyeings of the compounds on polyester were assessed with a view to evaluating the percentage reflectance of the dyed fibre at different wave-lengths in the visble region and the Kubelka-Munk equation was used to calculate the function of the dyed materials.
 
Article
1,4-Diethyl-1,2,3,4-tetrahydro-7-hydroxyquinoxalin-6-carboxaldehyde was synthesized and condensed with substituted active methylene compounds to obtain a series of novel coumarin compounds. Solutions of the dyes in various solvents exhibited an orange hue and brilliant fluorescence and displayed high thermal stability, as determined using thermogravimetric analysis. The dye having a heterocyclic benzimidazole ring as an electron withdrawing system was selected as a representative compound for comparison of its spectral characteristics with known analogues.
 
Article
The spectral-luminescent properties of a series of new cyanine dyes as possible probes for homogeneous assay of proteins have been studied. The fluorescent cyanine dyes development was based on the principle of “affinity-modifying group” with the use of benzothiazolo-4-[1,2,6-trimethylpyridinium] monomethine as template. It was shown that the cyanine dye P-5 can be used as a sensitive and specific fluorescent probe for the detection of BSA.
 
Article
Novel, metal-free and metallo(Cu, Co, Ni, Zn, Pb and Mn)phthalocyanine compounds were synthesized by exposure to microwave irradiation and the products purified. The newly prepared compounds were characterized using elemental analyses, IR, 1H/13C NMR, 1H–1H COSY measurements, MS, UV–vis spectroscopy and DTA/TG analysis. The electronic spectra exhibited an intense π → π* transition with characteristic Q and B bands of the phthalocyanine core, as expected. All decomposition products obtained from DTA/TG analysis were identified; it was found that the thermal stability of each phthalocyanine compound followed the order: MnPc < Metal-free < ZnPc < PbPc < CuPc < CoPc < NiPc.
 
Article
The synthesis of ansa-triazacarbocyanines 1 int he [n](1.3)-benzimidazolophan series is described. A new synthetic procedure for benzimidazole-2-on-hydrazones was developed, which presumably can be extended to other appropriate heterocyclic systems. UV/VIS and NMR spectra of the ansa-triazacarbocyanines 1 are discussed. Based on kinetic data of the thermal reverse reaction and on other evidence the reversible photobleaching (inverse photochromism) of 1 at low temperatures is attributed to photoisomerisation, analogous to the case of carbocyanines. The difference between the UV/VIS spectra of the ansa-series may be explained by the distortion of the benzimidazole-moiety by the ansa-bridge. This distortion may also be responsible for the differences in the activation parameters of the thermal reverse reaction of the photobleached products 1′. For 1,3-decamethylen-1,3-dihydro-2H-benzimidazole-2-one 20f the activation energy of the ring-flipping process was determined by dynamic NMR spectroscopy.ZusammenfassungCyanine haben in jüngerer Zeit als Laserfarbstoffe neu an Bedeutung gewonnen. Aus diesem Grunde hat auch das Interesse an der Photochemie dieser Farbstoffe zugenommen, denn die Bildung von Transienten
 
Article
The synthesis and basic spectroscopic properties of eight dichromophoric solvatochromic styrylpyridinium dyes are presented. The dyes were prepared by the condensation of propane 1,3-bis[4-methylpyridinium] dibromide with p-(N,N-dialkylamino)benzaldehydes. The synthesis of suitable substrates is presented as well. The dyes were characterized by 1H NMR spectroscopy and their purity with the use of thin-layer chromatography. The spectroscopic properties of the prepared dyes were determined in two organic solvents. The electronic absorption spectra of tested dyes demonstrate low sensitivity to the nature of the substituents introduced into the side aromatic rings. In contrast to this, the fluorescence band positions are affected by the structure of an electron donor and solvent polarity.
 
Article
Twenty, 1,3,3- trimethyl-2-[2-(2-Y-, 3- or 4-X-phenylamino)ethenyl]-3-H-indolium salts 1c–1z were synthesised and characterised by their spectroscopic properties (UV–VIS, IR and NMR), ionisation constants (pKa), and solvatochromic behaviour. The assigned 3-H-indolo-2-dimethinehemicyanine structure was proven on the basis of NMR data; the strong deshielding of the NH proton from the phenylamino moiety and of the N(1)CH3 protons from the 3-H-indole moiety (11.5–13.43 and 3.59–3.74 ppm, respectively) indicates partial positive charge at the nitrogen atoms of these groups. Such partial positive charge at both nitrogen atoms from the end of the trimethine chain is compatible with an electron delocalization through the cationic polymethine chain, which is characteristic of hemicyanine dyes. The positive charge at the mentioned NH group is also sustained by the obtained pKa values (8.05–9.37). The study concerning the solvatochromic behaviour revealed a small hypsochromic shift for all investigated dyes.
 
Article
A series of novel 6-(2-substituted-1,3,4-oxadiazol-5-yl)-2-phenylthieno[2,3-d]-pyrimidine fluorescent compounds were obtained by the condensation of 6-(2-methylthio-1,3,4-oxadiazol-5-yl)-2-phenylthieno[2,3-d]pyrimidine with appropriate secondary amines. The structures were characterized by IR, 1H NMR, mass, elemental analysis and UV–vis spectroscopy and the fluorescence characteristics were investigated in ethyl acetate and acetone by UV–vis absorption and emission spectra. The absorption spectra and fluorescence characteristics were correlated with substituents of the 6-(2-substituted-1,3,4-oxadiazol-5-yl)-2-phenylthieno[2,3-d]pyrimidine compounds and solvent polarity. The novel compounds also displayed intense blue to yellow-green fluorescence in ethyl acetate and acetone solutions.
 
Article
A series of 1,3,4-oxadiazole derivatives containing an imidazole unit were synthesized and characterized using 1H NMR, 13C NMR, mass spectrometry (or high-resolution mass spectrometry) and elemental analysis. The crystal structure of 2,5-bis(4-(1-n-butyl-4,5-diphenylimidazol-2-yl)phenyl)-1,3,4-oxadiazole was determined as monoclinic, space group C2/c type, using single crystal X-ray crystallography. For nine samples, UV–visible absorption coefficient (ɛ), maximum wavelength (λmax), fluorescence excitation wavelength (λex), fluorescence emission wavelength (λem), fluorescence quantum yield (ΦF), fluorescence lifetime (T) were measured in dichloromethane and in the solid state. For these selected compounds, thermogravimetric analysis was also employed and structure:optical behaviour characteristics were discussed.
 
Article
The 1,4-diketo-pyrrolo[3,4-c]-pyrroles' derivatives are easily synthesized in good yields upon exposure to microwave irradiation under solvent-free conditions and reaction times are considerably reduced.
 
Article
A clean, simple and efficient method for the synthesis of 3,3′-(arylmethylene)bis(2-hydroxynaphthalene-1,4-dione) derivatives has been developed which uses the reaction of 2-hydroxynaphthalene-1,4-dione and aromatic aldehydes in the presence of a catalytic amount of LiCl in aqueous media. To the best of our knowledge, this is the first report on such a synthesis of 3,3′-(arylmethylene)bis(2-hydroxynaphthalene-1,4-dione).
 
Article
Various primary amines react with 1,4-benzoquinone to form corresponding 2,5-bis(alkyl/arylamino)1,4-benzoquinone. The crystal structure of three such derivatives namely 2,5-bis(2-propylamino)1,4-benzoquinone, 2,5-bis(cyclohexylamino) 1,4-benzoquinone and 2,5-bis(3-methylanilino)1,4-benzoquinone is determined. The solid-state structure shows absence of intra-molecular hydrogen bonding between the carbonyl of the quinone unit with N–H of the amine group in these molecules. Each of these compounds shows a proton sensitive quasi-reversible redox couple. Analysis on the basis of torsion angle shows that conjugation of the OC–C–N frame has lesser contribution to the quasi-reversible cycle but the couple is effected by variation of the substituents on the nitrogen atom. The reaction of 1,4-naphthoquinone with primary amines also gives corresponding 2-amino-1,4-naphthoquinone derivatives. Two representative crystal structures of 2-amino-1,4-naphthoquinone derivatives are reported.
 
Article
1,4-Bis[N-(2-tolylsulphonylaminoethyl)]-1,4-diazacyclohexane bridged metal-free and metal phthalocyanine polymers were prepared. The metal-free phthalocyanine polymer was obtained by the reaction of 4,4′-[2,2′-(piperidine-1,4-diyldiethylene)di(tosylimino)]diphthalonitrile with hydroquinone. The chloride derivatives of Cu(I), Ni(II) and Co(II) were employed in order to synthesize the corresponding metal–phthalocyanine polymers. Zn(CH3CO2)2 was used for the preparation of the zincphthalocyanine polymer. For the preparation of the Co-containing polymer, ammonium molybdate had to be added as catalyst. The new polymers have been characterized by elemental analysis, IR, NMR, UV–VIS and DTA.
 
Article
Porphyrazines (M = H, Mg, Zn and Co) with a 2,3-dicyano-5-phenyl-5,6-dihydro-1,4-dithiin group fused to each pyrrole unit were synthesized and characterized starting with the corresponding unsaturated dicarbonitrile derivative. The voltammetric and spectroelectrochemical characterizations of the metallo-porphyrazines (M = 2H+, Mg2+, Zn2+ and Co2+) substituted with 2,3-dicyano-5-phenyl-5,6-dihydro-1,4-dithiin groups on peripheral positions are described. Cyclic voltammetry and differential pulse voltammetry studies showed that while metal-free, magnesium, and zinc porphyrazines represented well-defined one-electron ligand-based reductions and ligand-based one-electron oxidation couples, cobalt porphyrazine gave both metal-based and ligand-based reduction and oxidation couples. Assignments of the redox couples were confirmed by spectroelectrochemical measurements.
 
Article
Novel, photocrosslinkable, star-shaped molecules have been synthesized by attaching a tricyanopyrroline (TCP)-based chromophore to 6-(4-{1,1-bis-[4-(5-carboxy-pentyloxy)-phenyl]-ethyl}-phenoxy)-hexanoic acid. The chromophore 2-(3-cyano-4-(4-diethylamino-phenyl)-5-oxo-1-{4-[4-(3-oxo-3-phenyl-propenyl)-phenoxy]-butyl}-1,5-dihydro-pyrrol-2-ylidene)-malononitrile is a second-order nonlinear optical active compound and bears a chalcone moiety that is sensitive to UV light (λ = 320–350 nm) for 2π + 2π photocycloaddition. The resultant molecules exhibited good processability and showed 29–37 pm/V of the maximum electro-optic coefficient at 1300 nm.
 
Article
Oxa-thio bridged metal-free and metal phthalocyanine polymers were prepared. Metal-free phthalocyanine polymer (H2Pc) and metal phthalocyanine polymers (Ni, Cu, Co, Zn or Fe) carrying dithio-oxa bridged were synthesized from 3,3′-4,4′-tetracyanodiphenyl-1,5-dithiopenanyl-oxa-ether and hydroquinone or the corresponding anhydrous metal salts [NiCl2, CuCl, CoCl2, Zn(CH3CO2)2 or Fe(CO)5]. The model phthalocyanine compounds were characterized by IR, UV/VIS and DTA. The electrical conductivities of the phthalocyanines measured as gold sandwiches are about 10−10 Sm−1in vacuo and in air.
 
Article
Hetarylmalononitriles (thiazolylmalononitrile and benzothiazolylmalononitrile) were prepared by the coupling reaction of malononitrile with heterocyclic amines in nitrosyl sulfuric acid. 4-Hetarylazo-3,5-diaminopyrazole compounds were obtained by the reaction of hetarylmalononitriles with hydrazine hydrate (64%). Both compounds can react with arylazo- and hetarylazomalononitriles to give 3,6-di-(aryl or hetaryl)-azo-2,5,7-triaminopyrazolo[1,5-a]pyrimidine heterocyclic disazo dyes. These dyes were characterized by elemental and spectral analyses (IR, 1H NMR and mass). The solvatochromic behaviour in various solvents was evaluated.
 
Article
A series of new bis-1,8-naphthalimide derivatives has been synthesized and the FT-IR and UV/vis absorption characteristics discussed. Substituents effect on the IR spectral characteristics have been investigated. A new polyimide with a 1,8-naphthalimide unit main chain has been synthesized.
 
Article
Novel poly(propylenamine) first and second generation dendrimers in which the periphery was modified with 1,8-naphthalimide units were synthesized. Acetonitrile solutions of the materials were subjected to photophysical investigation to evaluate their capability to detect metal cations, by monitoring changes in their absorption and fluorescence spectra in the presence of Ag(+), Cu(2+), Co(2+), Ni(2+), Fe(3+) and Zn(2+). The potential of the dendrimers to detect metal ion pollutants was estimated.
 
Article
Photophysical properties of some 4-alkylamino-N-alkyl-1,8-naphthalimides and 3-bromo-4-alkylamino-N-alkyl-1,8-naphthalimides in ethanol solution have been investigated. It was demonstrated that the bromine atom in a C-3 position alters their properties. The bromine derivatives have a lower quantum yield of fluorescence owing to the influence of the bromine atom on the polarization of naphthalimide chromophoric system. On the other case, the photodegradation of these derivatives is higher and the reaction of photodegradation follows a pseudo first order.
 
Article
4-Alkylamino-N-alkyl-1,8-naphthalimides were prepared from 4-chloro-1,8-naphthalic anhydride and from 4-amino-1,8-naphthalimide. It was found that the amino nitrogen of 4-amino-N-alkyl-1,8-naphthalimides is nucleophilic enough to participate in nucleophilic displacement reactions without the need for added base, despite being a vinylogous amide. Bromination of 4-alkylamino-N-alkyl-1,8-naphthalimides using molecular bromine was found to occur in the absence of a Lewis acid catalyst, and to be regiospecific, yielding only the 3-bromo isomer. Extended reaction times and the use of excess bromine result in dealkylation of the 4-alkylamino substituent, but no polybromination of the naphthalimide ring system.
 
Article
This work describes the covalent grafting of 4-amino-1,8-naphthalimides, which are fluorescent dyes with very interesting optical properties, onto the walls of mesoporous molecular sieves. The mesoporous materials MCM-41 and SBA-15 were first treated with 3-aminopropyltriethoxysilane, generating amine-rich surfaces that were further reacted with 4-amino-1,8-naphthalic anhydride, resulting in yellow fluorescent solids. The success of the modification reactions was confirmed by elemental analysis, X-ray diffraction patterns, infrared spectroscopy, scanning electron microscopy and UV/visible and fluorescence spectroscopy. The emission spectra of the dye bound to MCM-41 was quite insensitive to solvent polarity, in contrast to dye-grafted SBA-15, which showed a high solvent sensitivity. These results suggest a tight fit of the dye molecules within the channels of MCM-41, leaving no room for the solvent molecules. In the case of SBA-15, the large pore size allows the invasion of the channels by solvent molecules, resulting in solvation of the encaged chromophore.
 
Article
The degradation of an azo dye Amido black 10B in aqueous solution by Fenton oxidation process has been investigated. The effects of different reaction parameters such as initial pH, the initial hydrogen peroxide concentration ([H2O2]0), the initial ferrous concentration ([Fe2+]0), the initial Amido black 10B concentration ([dye]0) and the temperature on the oxidative degradation of Amido black 10B have been assessed. The optimal reacting conditions were experimentally determined and it was found to be initial pH = 3.50, [H2O2]0 = 0.50 mM, [Fe2+]0 = 0.025 mM for [dye]0 = 50 mg/L at temperature = 25 °C. Under optimal conditions, 99.25% degradation efficiency of dye in aqueous solution was achieved after 60 min of reaction. The UV–vis spectral changes of Amido black 10B in aqueous solution during Fenton treatment process were studied. It was easier to destruct the azo linkage (–NN–) group than to destruct the aromatic rings of Amido black 10B by Fenton oxidation. The experimental results showed that the Fenton oxidation process was an effective process for the degradation of azo dye Amido black 10B at low H2O2 and Fe2+ concentrations.
 
Article
The photocatalytic degradation of two selected dye derivatives, chromotrope 2B (1) and amido black 10B (2), has been investigated in aqueous suspensions of titanium dioxide under a variety of conditions which is essential from an application point of view. The degradation was monitored by measuring the change in substrate concentration as a function of irradiation time employing UV spectroscopic analysis. In these studies, a number of byproducts are formed during the photooxidation process which can potentially be harmful to the environment, therefore, we have studied the mineralization of the pollutants by measuring the total organic carbon (TOC) as a function of irradiation time. The degradation of dyes were studied using different parameters such as types of TiO2, reaction pH, catalyst concentration, substrate concentration and in the presence of different electron acceptors such as hydrogen peroxide (H2O2), potassium bromate (KBrO3) and ammonium persulphate (NH4)2S2O8 besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient as compared with other photocatalysts. The dye derivative (1) was found to degrade faster as compared to the dye derivative (2).
 
Article
Pigment composites were obtained by adsorption of 9-aminoacridine and C.I. Mordant Red 11 onto silica supports which were both unmodified and also modified with N-2-(aminoethyl)-3-aminopropyltrimethoxysilane. The silica supports and pigment composites were characterised using particle size and polydispersity index, particle morphology and the presence of agglomerates, as well as sedimentation profile, water wettability and colorimetric parameters. The extent of silica surface coverage with each dye was determined on the basis of elemental analysis. The presence of functional groups on the silica support and the pigment composites was confirmed using FT-IR.
 
Article
The oxidative degradation of azo dye Reactive Orange 113 aqueous solution by H2O2/Fe2+ and ozone was investigated. The full decolorization is attained during the first minutes of oxidation process by H2O2/Fe2+ and ozone. The complete mineralization of aqueous solutions of Reactive Orange 113 dye cannot be achieved even under the optimal reaction conditions. Ozonation appeared more effective in comparison with Fenton's process. A tentative pathway for the oxidative degradation of Reactive Orange 113 dye were postulated.
 
Article
A dye acid red 114 (C.I. 23635) was photochemically removed by adding ferric ion (Fe3+), TiO2 particles, and H2O2 in the presence of the UV radiation. The removal rates of the acid red 114 (C.I. 23635) dye were 0.183, 0.210, and 0.233 mg/l/min when the concentrations of Fe3+ were 50, 100, and 130 mg/l. The removal rate of the dye increased from 0.173, through 0.200, 0.210 to 0.260 mg/l/min when the H2O2 concentrations were 10, 50, 100, and 150 mg/l, respectively. The removal rates were 0.200, 0.207, 0.210, 0.273, and 0.293 mg/l/min when the concentrations of TiO2 were 40, 60, 100, 500, and 1000 mg/l, respectively. The removal rate at pH 2.5 was higher than any other; pH 3.5, 5.5, and 8.5 and the photodegradation efficiency increased with the flow rate of air in the range from 1 to 10 l/min. From these results, relationships between the removal rate and the concentration of added Fe3+, H2O2, and TiO2 could be expressed as the following second-order equations, respectively, Rremoval=3×10−6 ×(CFe3+)2+5×10−5 ×(CFe3+)+0.1729; Rremoval=2×10−6 ×(CH2O2)2+2×10−3 ×(CH2O2)+0.1759; and Rremoval=−1×10−7 ×(CTiO2)2+2×10−4×(CTiO2)+0.1867.
 
Article
The aim of our research was to apply experimental design methodology in the optimization of photocatalytic degradation of azo dye (Reactive Red 120). The reactions were mathematically described as the function of parameters such as amount of TiO2 (X1), dye concentration (X2) and UV intensity (X3), and were modeled by the use of response surface methodology (RSM). These experiments were carried out as a central composite design (CCD) consisting of 20 experiments determined by the 23 full factorial designs with six axial points and six center points. The degradation of azo dye (RR120) followed an apparent first-order rate law in every pH condition. The results show that the responses of color removal (%) (Y1) in photocatalysis of dyes were significantly affected by the synergistic effect of linear term of UV intensity (X3) and the antagonistic effect of quadratic term of UV intensity (X32). Significant factors and synergistic effects for the TOC removal (%) (Y2) were the linear terms of TiO2 (X1), and UV intensity (X3). However, the quadratic terms of TiO2 (X12) and UV intensity (X32) had an antagonistic effect on Y2 responses. Canonical analysis indicates that the stationary point was a saddle point for Y1 response whereas a maximum point for Y2 response. The estimated ridge of maximum responses and optimal conditions for Y1 and Y2 using canonical analysis were 100% and 67.27%, respectively. The experimental values agreed with the predicted ones, indicating suitability of the model employed and the success of RSM in optimizing the conditions of photocatalysis.
 
Article
Decolorization of azo reactive dyes by ozone has been described by several authors. However, the efficiency of ozonation and the by-products produced by dye additives/impurities such as synthetic precursors, by-products, salts and dispersing agents in commercial azo dyes during the oxidative treatment have not been reported. To investigate the effects of such impurities on the ozonation process and on the formation of oxidation by-products, a commercially available azo reactive dye C.I. Reactive Red 120 was chosen as a model compound. Experiments were conducted in aqueous solutions of hydrolyzed C.I. Reactive Red 120 (200 mg/l) either with or without purification. Treatment efficiencies of purified and unpurified dye were evaluated in terms of COD, BOD28, absorbance and initial decolorization rates. Additionally, organic and inorganic anions were analyzed by HPIC. After 28 days of incubation the BOD28/COD ratio increased from 0.22 to 0.48 and from 0.05 to 0.26 for purified and unpurified C.I. Reactive Red 120, respectively, indicating an enhancement of biodegradable compounds in the ozonated solutions. The results also illustrate that the dye additives/impurities in commercial dyes affect the microbial activity as well as the biodegradability. It is therefore recommended that dyes should be purified before ozonation, if detailed information on the degradation processes and the resulting oxidation by-products are required.
 
Article
All three pigments crystallise in the triclinic system, space group P, and with one molecule in the unit cell so that all molecules have crystallographic Ci symmetry. The molecules exist in the bisketohydrazone tautomeric form. The intramolecular hydrogen bonding normally associated with this structural arrangement is observed, but there is no intermolecular hydrogen bonding. The molecules are not quite planar, but deviate from planarity by only a few degrees of torsional bond rotations. In each structure the molecules pack together in inclined interleaved stacks so that the ketohydrazonoarylamide groups lie above and below one another in antiparallel arrangements. The colour and technical performance of the pigments are discussed in relation to the structural details.
 
Article
This paper evaluates the Fenton process (involving oxidation and coagulation), ferric coagulation and H2O2/pyridine/Cu(II) system for the removal of color from a synthetic textile wastewater containing polyvinyl alcohol and a reactive dyestuff, Remazol Turquoise Blue G-133. Experiments were conducted to investigate the effects of operating variables such as pH, coagulant dose, polyelectrolyte type, H2O2 and Fe(II) concentrations, optimum pyridine and Cu(II) dosages on decolorization efficiency. Optimal operating conditions were experimentally determined. A decolorization efficiency of 96% was possible to achieve with Fenton's reagent at an optimum [Fe(II)]:[H2O2] molar ratio of 1.21:1. However, 27% of initial Fe(II) was still in the effluent which required further treatment. Optimum pH and coagulant dose were found to be 7 and 100–125 mg l−1, respectively, and the corresponding efficiency was ∼100%. Cationic polyelectrolyte was found to be the most suitable type and 2 mg l−1 of it enhanced the decolorization by 10% and 75% for filtered and nonfiltered samples, respectively. The maximum efficiency achieved by H2O2/pyridine/Cu(II) system was about 92% with a high initial reaction rate different from the H2O2/pyridine system which also led to 92% removal. However, the required H2O2 dosage was very high in this system with a low Cu(II).
 
Article
The interaction of acridine orange (C.I. Basic Orange 14) with bovine serum albumin and the subsequent sonodynamic damage to bovine serum albumin imparted by ultrasonic irradiation were studied. The quenching constant, binding constant and the binding site number were measured using fluorescence quenching. The distance of binding between the dye and the serum albumin was obtained according to Föster's nonradiative energy transfer theory. The effects of ultrasonic irradiation time, dye concentration, pH and ionic strength on bovine serum albumin were determined using UV–vis and fluorescence spectra; the extent of damage was enhanced by a increases in irradiation time, dye concentration and ionic strength, but was reduced by an increase in pH.
 
Article
A Brønsted-acidic task-specific ionic liquid, 1-methyl-3-propane sulfonic-imidazolium hydrosulfate ([MIMPS]HSO4), was employed as a catalyst for the synthesis of 14-alkyl- or aryl-14H-dibenzo[a,j]xanthenes via the one-pot condensation of β-naphthol with aliphatic or aromatic aldehydes. Various aliphatic and aromatic aldehydes were used in the reaction and in all cases the desired products were synthesized successfully. The novel synthesis method offers the advantages of high yields, short reaction times, simplicity and easy workup compared to the conventional method of syntheses. The catalyst could be recycled and reused five times without a noticeably decrease in its activity.
 
Article
Supercritical carbon dioxide is an alternative solvent that is considered for dry dyeing processes in the textile industry. The application of this process requires a study to determine the dye solubility in supercritical carbon dioxide. The solubility in supercritical carbon dioxide of a disperse dye at temperatures of 40, 60 and 80 °C and pressures from 100 to 350 bar was evaluated in a previous study. In the work described here, these solubility values have been correlated with fairly good accuracy using a model based on thermodynamic aspects and the use of equations of state. Physical properties and critical parameters of the solid have been estimated using different group contribution methods. The thermodynamic model has been developed by means of a program based on fitting the solid sublimation pressure and binary interaction parameter. The results obtained in the solubility correlation show that the choice of group contribution method is more important than the choice of equation of state.
 
Article
In this paper, the comparison of activated carbon fiber (ACF) felt and graphite cathode suggested H2O2 might effectively be electrogenerated from O2 reduction on the large surface area ACF felt cathode, this was more adaptive for electro-Fenton process. The removal of color and total organic carbon (TOC) from simulated dye wastewater containing Acid Red 14 (AR14) was experimentally investigated using electro-Fenton reaction with ACF cathode. After 360 min of electrolysis and under the operation conditions of 0.36 A current, 1 mM Fe2+ at pH 3, 70% TOC was removed as well as complete decolorization occurred. The effect of Fe2+ ion concentration and applied current were also studied in detail in the experimental runs.
 
Article
This paper evaluates the decolourisation of an azo dye Reactive Yellow 14 (RY14) by three advanced oxidation processes viz., solar/TiO2, solar/H2O2 and solar/H2O2/Fe2+ (photo-Fenton). The results showed that all the three processes could be effectively used for the decolourisation. The study on the effects of various experimental parameters such as pH, dye concentration, light intensity on the solar decolourisation revealed that these parameters influenced the removal rate. The photodecolourisation efficiencies with solar irradiation are comparable to UV irradiation. It is found that these three solar processes are viable techniques for the decolourisation of RY14.
 
Article
In order to develop a biotechnological solution to the disposal of waste pigment dispersions, the ability of azo dye-reducing Shewanella strain J18 143 cells to reduce model pigment dispersions was assessed. Resting cells were able to couple the oxidation of formate to the reduction of the azo/ketohydrazone chromophore in virtually insoluble pigmentary species. Pigments from the azoacetoacetanilide range and the azonaphthol range were used to investigate the effects of process parameters such as dispersion quality, addition of biocides, temperature and use of exogenous extracellular redox mediators. The physical impact of bioreduction on the pigment structure was also assessed. Pigments present in industrially manufactured dispersions were more readily reduced than those in powder form and the presence of a biocide in the dispersion did not affect the activity of cells of Shewanella strain J18 143. The initial pigment reduction rate increased with temperature up to 50 °C, but the higher temperatures had a detrimental effect on the long term activity of Shewanella strain J18 143. The reduction of the pigment dispersions was stimulated by the addition of the soluble electron shuttle anthraquinone-2,6-disulphonate. Particle sizing and environmental scanning electron microscopy showed that Shewanella strain J18 143 was able to degrade large pigment aggregates to produce individual pigment particles. GemSperse Orange EX5 was the pigment dispersion reduced to the corresponding amines most efficiently by Shewanella strain J18 143.
 
Article
The purpose of this study was to investigate the catalytic role of granular activated carbon (GAC) on the degradation and mineralization of two reactive azo dyes (C.I. Reactive Red 194 (RR194) and C.I. Reactive Yellow 145 (RY145) in aqueous solution by treatment with ozone. Decolourization of the aqueous solution, disappearance of the parent compound, COD and TOC removal were the main parameters investigated for this purpose. Formation of inorganic ions Cl−, SO42−, NH4+, NO3− and pH changes were also followed throughout ozonation of various systems. It was determined that ozone by itself is strong enough to decolorize these aqueous solutions contaminated by azo dyes and almost all COD disappeared by these treatments but efficient mineralization had not been achieved. The extent of TOC removal was about 25% when no granular activated carbon (GAC) had been used and this value was doubled in the presence of GAC. While the reactive hydroxyl radicals were formed on the surface of GAC, it was deduced that the main reactions of the organic species with these reactive radicals took place in the bulk of the solution. One other observation was that the mass ratio of GAC to organic substrate in the aqueous solution should have an optimum value for effective degradation of the organic substrates; excess GAC inhibits degradation reactions probably due to the adsorption of the organic species on the surface of GAC.
 
Article
A novel, efficient, one-pot, and solvent-free method for the preparation of aryl 14H-dibenzo[a,j]xanthene leuco-dye derivatives by condensation of 2-naphthol and substituted benzaldehydes is reported under thermal conditions. This method has the advantages of high yields, a cleaner reaction, simple methodology, convenient reaction times, easy workup and greener conditions.
 
Article
Novel metal-free and metal-containing (Zn, Ni, Cu) derivatives bearing eight 16-membered tetrathiamonoaza macrocycles in peripheral positions were synthesized and characterized by a combination of elemental analysis, UV–vis, FT-IR, NMR and MS spectral data. The metal-free phthalocyanine was synthesized by two different routes namely from 4,5-bis{[2-(1,4,10,13-tetrathia-7-azacyclohexadecan-7-yl)ethyl]thio}phthalonitrile and from 5,6-bis{[2-(1,4,10,13-tetrathia-7-azacyclohexadecan-7-yl)ethyl]thio}-1H-isoindole-1,3(2H)-diimine.
 
Article
The photodegradation of aqueous solutions of C.I. Reactive Orange 16 was investigated under UV irradiation. The degradation was studied by monitoring the change in absorption and relative intensity employing UV-spectroscopic and GC/MS analysis as functions of irradiation time. The rate of degradation of the dye was evaluated. The solution was completely decolorized after 100 min of photooxidation. The generated degradation products were detected by GC/MS. 6-Acetylamino-3-amino-naphthalene-2-sulfonic acid, N-(3,4-bis-hydroxymethyl-phenyl)-acetamide and phthalic acid were found during the degradation of C.I. Reactive Orange 16. The probable pathways for the formation of the degradation products were proposed. GC/MS analysis and degradation pathways demonstrated that naphthalene and benzene rings were observed during photooxidation.
 
Article
The photocatalytic oxidation of azo dye Acid Red 18 in water in the quartz labyrinth flow reactor with immobilized catalyst bed was investigated. A commercially available titanium dioxide (Aeroxide® P25, Degussa, Germany) was used as a photocatalyst. The influence of various factors, including reaction mixture flow rate, initial dye concentration and time of the irradiation on the photodegradation of model compound were examined. The reaction rate was affected by the circulation flow rate, particularly when the flow rate was low (i.e. 4.3 dm3/h). The decomposition rate of Acid Red 18 depended on the initial dye concentration. The rate constants calculated for dye concentrations of 10 and 30 mg/dm3 amounted to 0.228 and 0.176 h−1, respectively. Not only decolorization but also mineralization was effective in the proposed system. After a total fading of the dye solution, ca. 98% of TOC disappeared when the 10 mg/dm3 solution was applied and ca. 99% when 30 mg/dm3 was used. An important advantage of the photoreactor is that no separation of the catalyst is necessary and as a result the size of installation could be minimized and running costs decreased.
 
Article
In the present study, electrochemical degradation experiments were conducted to degrade a textile dye namely Reactive Blue 19 (RB-19). A laboratory scale bench-top reactor was used to investigate the effect of various operating parameters using titanium based dimensionally stable anode (DSA). The oxidation of RB-19 takes place in the bulk solution with electrolytically generated chlorine/hypochlorite. Increasing the initial pH and increasing the reaction temperature decreases the de-colorization efficiency. At the same time, increasing the chloride concentration and increasing the current density showed an increase in the color removal. The complete removal of color was achieved within a short period of electrolysis for different concentrations of RB-19. However, the removal of chemical oxygen demand (COD) and total organic carbon (TOC) was 55.8% and 15.6%, respectively, for 400 mg/L RB-19 with 1.5 g/L sodium chloride concentration. The intermediate compounds formed during the degradation were identified using a gas chromatography coupled with mass spectrometry (GC/MS). In the present study, no chlorinated organic compounds were detected during the course of electrolysis. The major compounds identified were benzene, 2-hydroxy, 4,4-napthaquinoine (C.I. Natural orange 6), 1-aminoanthraquinone (C.I. Diazo fast red AL), benzyl alcohol, benzaldehyde, benzoic acid, phthalic anhydride, phthalide, phthaldehyde and 1,3-indanone.
 
Article
Several, novel, 3′-, 5- and 3-substituted indolospirobenzopyrans were prepared and their reversible thermochromic equilibria were investigated by synthesising derivatives with appropriately placed “electronically” modifying substituents in both the indole and benzopyran rings as well as by synthesising structural variants that contained sterically hindering (with regard to spiropyran-opening ↔ closing) groups, within the spirocyclic ring-system. In addition, structural combinations of the above, involving the syntheses of sterically restricted and electronically biasing substituents were prepared and their effects upon the spiropyran ring-opening ↔ closing process investigated. The influence of these steric and electronic substituent effects on the relative quantities of the open- and closed-forms was established using 1H NMR at six temperature intervals (298, 320, 340, 360, 380 and 410 K). Further elucidation of the stereochemical conformation in these systems was undertaken using nuclear Overhauser enhancement (nOe) studies.
 
Top-cited authors
Narayanasami Kannan
  • Sundram Fasteners Limited
C. Namasivayam
  • Activated Carbons Manufacturing Consultant
D. Kavitha
Vimal Chandra Srivastava
  • Indian Institute of Technology Roorkee
Mohd Muneer
  • Aligarh Muslim University