P-aminoazobenzene Research Articles

Studies on the Adsorption of p-Aminoazobenzene onto Kaolinite

As one of the most important soil components, kaolinite plays an important role in transport and fixation of organic pollutants in soils. P-Aminoazobenzene (PAAB) is a sort of the carcinogenic aromatic amine which is commonly used as the intermediates of azo dyes. It can cause mutations and cancer of aquatic biota as well as humans. In this study, adsorption of PAAB on kaolinite in aqueous solution under different pHs, temperature and ionic strength was examined. Adsorption kinetic experiments indicated that the adsorption of PAAB on kaolinite at pH 1.4 and 4.0 followed the Elovich kinetics. The adsorption isotherm of PAAB onto kaolinite was well described by the Langmuir model, with an adsorption capacity of 2.2 mg/g at pH 1.4 and 1.43mg/g at pH 4.0. Adsorption of PAAB increased with decreasing solution pH and ionic strength. The negative free energy change (� G) after adsorption indicated that the adsorption process is a spontaneous process. The enthalpy change (� H) at pH 1.4 and 4.0 was -6.93 and -4.72 kJ/mol, respectively, suggesting that PAAB adsorption was an exothermal process and the physical adsorption predominated in the adsorption of PAAB on kaolinite. The adsorption affinity of PAAB for kaolinite surface was attributed to the electrostatic attractive and van der Waals' forces.

Heterogeneous photo catalytic degradation of anionic and cationic dyes over TiO 2 and TiO 2 doped with Mo 6+ ions under solar light: Correlation of dye structure and its adsorptive tendency on the degradation rate

Degradation of synthetic dyes like Methyl Orange (MO), p-amino azo benzene (PAAB), Congo Red (CR), Brilliant Yellow (BY), Rhodamine-B (RB) and Methylene Blue (MB) under solar light were carried out using TiO 2 doped with Mo 6+ ions. The rate constant for the degradation of anionic dyes MO, PAAB, CR and BY was high at pH 5.6, while for cationic dyes the highest rate constant was obtained in the alkaline pH 8.0. These differences can be accounted to their adsorption capacity on the catalyst surface at different pH conditions. Among the photocatalyst used, Mo 6+ (0.06%)–TiO 2 showed enhanced activity due to the effective separation of charge carriers.

Study on the nonlinear optical properties of three azo dyes by Z-scan measurements

The nonlinear optical properties of p-aminoazobenzene (PAAB), methyl orange (MO) and p-dimethylamino benzene arsenic acid (PDBAA) were investigated by a single beam Z-scan technique, respectively. Their solution samples all exhibited large nonlinear refractive indices under the excitation of a 633 nm laser. Among the three azo dyes, PDBAA showed the largest value of nonlinear refractive index. Moreover, the process of nonlinear refraction induced by the laser thermal effect was also analyzed in this paper.

Fluorescence Study on the Interaction of Bovine Serum Albumin with P-Aminoazobenzene

In this paper, the interaction between p-aminoazobenzene (PAAB) and BSA was investigated mainly by fluorescence quenching spectra, circular dichroism (CD) and three-dimensional fluorescence spectra under simulative physiological conditions. It was proved that the fluorescence quenching of BSA by PAAB was mainly a result of the formation of a PAAB-BSA complex. The modified Stern-Volmer quenching constant K(a) and the corresponding thermodynamic parameters DeltaH, DeltaG and DeltaS at different temperatures were calculated. The results indicated that van der Waals interactions and hydrogen bonds were the predominant intermolecular forces in stabilizing the complex. The distance r=4.33 nm between the donor (BSA) and acceptor (PAAB) was obtained according to Förster's non-radioactive energy transfer theory. The synchronous fluorescence, CD and three-dimensional fluorescence spectral results showed that the hydrophobicity of amino acid residues increased and the losing of alpha-helix content (from 63.57 to 51.83%) in the presence of PAAB. These revealed that the microenvironment and conformation of BSA were changed in the binding reaction.

Ruthenium(III) – catalyzed oxidative cleavage of p-aminoazobenzene by chloramine-B in alkaline medium and uncatalyzed reaction in acid medium: spectrophotometric kinetic and mechanistic study

p-Aminoazobenzene (PAAB) is one of the important monoazo dyes and its oxidation kinetic study is of much use in understanding the mechanistic profile of PAAB in redox reactions. Consequently, the kinetics of oxidation of PAAB by sodium N-chlorobenzenesulfonamide or chloramine-B (CAB) in HClO4 medium and in NaOH medium catalyzed by ruthenium(III) chloride (RuIII) have been investigated at 298 K. U.v.–vis spectrophotometry was used as a basic analytical approach in this study. Under an identical set of experimental conditions, the reactions of PAAB–CAB in HClO4 medium were facile, but the reactions became too slow to be studied in alkaline medium and hence ruthenium(III) chloride has been used as a catalyst in alkaline medium. The stoichiometry (1:2) and oxidation products (nitrosobenzene and p-nitrosoaniline) are the same in both media, but the kinetic and mechanistic patterns were found to be different. The experimental rate laws obtained are: − d[CAB]/dt = k [CAB]0 [PAAB]0 [H+] in acid medium and − d[CAB]0/dt = k [CAB]0 [PAAB]0[OH−]x[RuIII]y in alkaline medium, where x and y are less than unity. The reaction was examined with reference to changes in (a) concentration of benzenesulfonamide, (b) concentration of added neutral salts, (c) ionic strength, (d) dielectric permitivity and (e) solvent isotope effect. The reaction was also studied at different temperatures and the overall activation parameters have been evaluated. The oxidation reaction fails to induce the polymerization of added acrylonitrile. C6H4SO2NHCl and C6H4SO2NCl− have been postulated as the reactive oxidizing species in acidic and alkaline media, respectively. It was found that the reactions are nearly 20 times faster in acid medium in comparison with alkaline medium. It was also observed that ruthenium(III) was an efficient catalyst for the facile oxidation of PAAB by CAB in alkaline medium by making the reaction go twelve-fold faster than the uncatalyzed reactions. The catalytic constant (KC) has been calculated at different temperatures and the values of activation parameters with respect to ruthenium(III) have also been evaluated in alkaline medium. The observed results have been explained by plausible mechanisms and the relative rate laws have been deduced.

SERS-measured and DFT-calculated vibrational spectra of p-Aminoazobenzene

P-Aminoazobenzene (PAAB) is one of the 24 kinds of carcinogenic azo dyes that the European Union forbids but it does not yet have an official method to detect PAAB. This paper experimentally observes the Normal Raman Spectrum (NRS) and infrared absorption spectrum of PAAB and presents theoretical vibrational spectra calculated from a density functional theory (DFT) method on the basis of B3LYP with 6–31 basis set. The calculated results show very good agreement with the experimentally observed IR and Raman frequencies. We also report the SERS spectra of PAAB adsorbed on silver and copper layers, which offer a sensitive but simple method to detect PAAB. Finally, the possible adsorbed states of PAAB on the silver and copper layers are discussed.

Oriented Attachment-Based Assembly of Dendritic Silver Nanostructures at Room Temperature

How particles aggregate into an interesting dendritic structure has been the object of research for many years because of its importance in understanding physical processes involved and in designing novel materials. In this work, we for the first time describe an oriented attachment-based assembly mechanism for formation of different types of dendritic silver nanostructures at room temperature. It is found that the concentration of both AgNO(3) and p-aminoazobenzene (PA) molecules has a significant effect on the formation and growth of these novel nanostructures. Characterization by transmission electron microscopy (TEM) clearly shows that the dendritic silver nanostructures can be obtained through the preferential oriented growth along a crystallographically special direction. Interestingly, we observe that the oriented attachment at room temperature can also take place between relatively large single-crystalline silver particles with a diameter range from 20 to 60 nm, which may provide a new possibility for the design of novel metal nanostructures by using large metal nanoparticles as building blocks at room temperature. Moreover, a surface-enhanced Raman scattering (SERS) technique is used to investigate the role of PA molecules during the growth of the dendritic silver nanostructures.

Contact sensitization to disperse dyes in children.

From January 1996 to December 2000, 1098 children, including 667 subjects with suspected allergic contact dermatitis and 431 patients with atopic dermatitis (AD), were patch tested with seven disperse dyes: disperse blue 124 (DB124), disperse blue 106 (DB106), disperse red 1 (DR1), disperse yellow 3 (DY3), disperse orange 3 (DO3), p-aminoazobenzene (PAAB), and p-dimethylaminoazobenzene (PDAAB). Of these, 51 patients (4.6%; 34 girls and 17 boys) proved sensitized to disperse dyes. AD or history of AD was present in 30 patients (59%). The most common sensitizer was DY3 (17 patients), followed by DO3 (15 patients), and DB124 (14 patients). Among dye-positive patients, about 12% were sensitized to disperse dyes alone and only 14% reacted to para-phenylenediamine. In disperse dye-sensitive children not affected by AD, the feet, axillae, and groin appeared to be the most common localizations, whereas in those with AD, involvement of the face and the flexural areas of the limbs was more common. In conclusion, our study showed that in children with suspected contact sensitization, disperse dyes should be regarded as potential triggering allergens.

Experimental study on skin sensitization potencies and cross-reactivities of hair-dye-related chemicals in guinea pigs.

In screening patch testing of hairdressers with occupational contact dermatitis, multiple positive reactions to hair dye-related chemicals, such as p-phenylenediamine (PPD), p-toluenediamine x 2HCl (PTD) and p-aminophenol (PAP), a fabric dye p-aminoazobenzene (PAB), and a tar dye Sudan III, were frequently encountered. To investigate individual skin sensitization potency and the cross-reactivities among above chemicals, a guinea pig maximization test with the above 5 chemicals was performed. In each group, 6 animals were induced with one of the chemicals at 0.1% concentration by intradermal injection and at 1.0% by topical application. The animals were challenged with all 5 chemicals in concentrations of dilution by 10 from 0.1% to 0.001%. Under the conditions of 0.1% challenges, similar sensitization potencies were observed in PPD (6/6), PTD (6/6), PAP (5/6) and PAB (6/6) groups, but no positive reactions were elicited in the Sudan III group. The cross-reactivities to PPD were confirmed in the animals challenged with PTD (6/6), PAP (6/6), PAB (6/6) and Sudan III (3/6). In the PTD-induced group, positive responses to cross-challenges were elicited by PPD (5/6), PAP (3/6), PAB (5/6) and Sudan III (1/6). The cross-reactivities to PAP were observed only with PPD (2/5) and PAB (5/5). PAB-induced animals responded only to PPD (1/6). The results indicate that all these chemicals except Sudan III are strong sensitizers. Their cross-reactivities are different in sensitized conditions, respectively. The cross-reactivities to PPD were higher than those to PTD, PAP and PAB.

Cross‐sensitizations between azo dyes and para‐amino compound

Combined sensitizations to different azo dyes, probably based both on true cross-sensitization and on simultaneous positive reactions, have frequently been described. However, since azo dyes are included in the standard series in a minority of countries, the case studies considered comprise, with few exceptions, a small number of subjects. The aim of our study was to investigate cross-reactions between different azo dyes and para-amino compounds in azo-dye-sensitive subjects, to study the clinical aspects of azo dye dermatitis, to assess the relevance of sensitization to azo dyes, and to relate the pattern of cross-sensitizations to the chemical structure of the different dyes. Out of 6203 consecutively tested patients, 236 were sensitized to at least 1 of 6 azo compounds employed as textile dyes, included in our standard series. 107 subjects reacted to Disperse Orange 3 (DO3), 104 to Disperse Blue 124 (DB124), 76 to p-aminoazobenzene (PAB), 67 to Disperse Red 1 (DR1), 42 to Disperse Yellow 3 (DY3), and 31 to p-dimethylaminoazobenzene (PDAAB). Co-sensitizations to para-phenylenediamine were present in most subjects sensitized to DO3 (66%) and PAAB (75%), in 27% and 36% of DR1 and DY3-sensitive subjects, and only in 16% of subjects sensitized to DB124. Apart from the hands and the face, the neck and the axillae were the most frequently involved skin sites. Whereas the involvement of flexural areas was mainly connected with sensitization to DB124, in patients with hand dermatitis and in those working as hairdressers, sensitization to DO3 and PAAB was more frequent. Moreover, in the former patient group, a history of textile dye allergy was most frequently obtained. Out of 33 patients tested with an additional textile dye series, only 5 subjects reacted to anthraquinone dyes. Cross-sensitizations between azo dyes and para-amino compounds can partially be explained on the basis of structural affinities.

Properties of mixed aqueous solutions of perfluorooctanoate with poly(N‐vinylpyrrolidone)

AbstractAqueous mixtures of ammonium perfluorooctanoate (C8FN) and poly(N‐vinylpyrrolidone) (PVP) were characterized by measuring the surface tension, conductivity and solubilization. Sodium perfluorooctanoate was also used for comparison. The critical micelle concentration (c. m. c.) of C8FN was found to be 30 mmol L‐1. The dependence of the surface tension on the surfactant concentration could be successfully described by the surface condensation based on the Langmuir‐type adsorption. The cross‐sectional molecular area of the C8FN oriented perpendicular on the surface is estimated at 19.8Å2. The addition of PVP increases the molecular area, suggesting an interaction between C8FN and PVP on the surface. The solubilization of p‐aminoazobenzene (PAAB) in these systems shows a synergetic effect in the low‐concentration range of C8FN and PVP. Changes in the absorption spectra of PAAB indicated the interaction between C8FN and PVP.

SERS and resonance Raman studies of p-aminoazobenzene on gold and silver electrodes

Surface-enhanced Raman scattering (SERS) spectra and cyclic voltammetry were used to detect the products of the oxidation and reduction of p-aminoazobenzene (PAAB) on roughened gold and silver electrodes in acidic and neutral solutions. The results indicated that oligomerization products are formed during the oxidation of PAAB on a gold electrode. We identified these products as oligomers formed by CN coupling of the PAAB cation radicals. The same products are formed on a silver electrode at a lower potential as the result of a photoelectrochemical reaction. The measurements carried out in the negative potential range proved that PAAB undergoes irreversible reduction in acidic media and reversible reduction to hydrazobenzene in neutral media.

Oxidative polymerization of p-aminoazobenzene in acetonitrile : A new electroactive polymer

The oxidative polymerisation of p-aminoazobenzene (PAAB) on glassy carbon in acetonitrile was studied by cyclic voltammetry, the potential step method, and SEM and FT-IR spectroscopy. The presence of a base-like pyridine was found to be essential for the polymerization process. The prepared polymer (poly( p-aminoazobenzene), abbreviated as poly-PAAB) films of thicknesses up to several (μm were found to be very stable and insoluble in aqueous solutions and in common organic solvents, except dimethyl formamide and tetrahydrofuran. The films are electroactive in acidic solutions but electroinactive in acetonitrile. The electroactivity of these films is attributed to a proton + electron addition/elimination reaction at -NH- sites. The capacitive current contribution in the potential region where the films are electroactive is larger than is usually observed for the conventional polyaniline films. The concentration of the electroactive sites in poly-PAAB was found to be about twenty times lower than that of polyaniline while the diffusion coefficient for the charge transport process within the films was found to be four times lower. The azo groups presented in the films were found to be reduced irreversibly in acetonitrile and aqueous acidic solutions. The prolonged reduction of the azo groups was found to lead to the loss of the electroactivity and the slow degradation of the films.

SORPTION OF DISPERSE DYES BY POLYESTER/POLYETHER BLOCK COPOLYMER FILMS

Poly (tetramethylene terephthalate) (4GT)-poly (tetramethylene oxide) (PTMO) block copolymer films were either annealed at various temperatures ranging from 130-190°C or drawn at 25°C with the draw ratios ranging from 1.0-7.0. These films were dyed at 80°C with C. I. Disperse Yellow 7 (Y-7) and p-Aminoazobenzene (PAAB). The equilibrium dye sorption (Mo) of Y-7 and PAAB by the annealed films increased with an increase in the crystallinity (Cv). Mo of Y-7 by the drawn films increased during drawing; similarly the Cv values of the drawn films slightly increased with draw ratios (λ). The change in Mo of these disperse dyes was analyzed in terms of the mosaic-block dyeing model by use of fine structural data of the block copolymer films. It was suggested that the change in Mo with increasing Cv depended on the dyeability of amorphous side region between the crystalline cores located parallel to the molecular axis. In the case of the drawn films, the increase in Mo of Y-7 with λ is ascribed to the increase in the fraction of inter-fibrilar tie chains in the side region; these chains would have a strong affinity particularly to a long rodlike dye molecule such as Y-7. The increase in Ms is probably associated with the orientation of the amorphous chain in the side region.

Equilibrium disperse dye sorption by drawn polypropylene films

AbstractIsotactic polypropylene (PP) films drawn at various temperatures ranging from 100 to 155°C have been dyed at 80°C with p‐aminoazobenzene (PAAB) or C.I. Disperse Yellow 7 (Y‐7). The equilibrium dye sorption (M0) of PAAB obtained for these films decreased with an increase in draw ratio (λ) of the films. The M0 values of Y‐7, however, increased with increasing in λ similarly the crystallinities of these films increased slightly with draw ratios. By use of fine structural data of these films, the change in M0 of Y‐7 for drawn PP films were analyzed in terms of a mosaic‐block structural model. The increase in M0 with increasing in λ was thus ascribed to enhanced sorption by the amorphous side region between crystalline cores located parallelly in the direction to the molecular axis. The side regions of the drawn systems become rich in interfibrillar tie chains in a higher range of λ. The side region seem to have a strong affinity particularly to a long rodlike dye molecule such as Y‐7; this feature is probably associated with the amount of the amorphous chains having extended chain conformation, the fraction of which increases during drawing.

OBSERVED CONCENTRATION DISTRIBUTION IN REPEATED LAMINATE AND DIFFUSION COEFFICIENTS

Concentration distributions of p-aminoazobenzene (PAAB) were measured by the use of repeated laminates and compared with those predicted by the theoretical treatment1). Film rolls composed of two different component films were used in the measurements.Over all diffusion coefficients Dov through the repeated laminates were calculated either from the observed concentration distributions in both component films or from that in one component film by employing the methods described previously1). Both agreed well with each other.With known Dov together with D through the partner component film, a method of calculation of diffusion coefficient D through a component film in a given repeated laminate was presented.In repeated laminates composed of nylon 6 with polypropyrene (Pp) or cellophane (Ce), values of D for PAAB through Pp and Ce were estimated using the method.

CONCENTRATION DEPENDENCE OF DIFFUSION COEFFICIENT OF DISPERSE DYE IN POLYVINYLACETATE

A sublimative desorption study of model disperse dyes, p-nitroaniline (PNA), p-amino-azobenzene (PAAB) in polyvinylacetate has been carried out with dye content from 0.01 to 0.25 in g-dye/g-polymer. The desorption temperature ranged from 80 to 130°C. The apparent diffusion coefficients of these dyes increased linearly with an increase in dye concentration; diffusion of PNA showed much stronger concentration dependence than that of PAAB. These features of dye diffusivity could be explained quantitatively in terms of Fujita's free volume theory of diffusion. On the other hand, increasing dye concentration had an effect on lowering the glass transition temperature (Tg) of the colored polymer. Both depression of Tg and increase in dye diffusivity with dye concentration were considered as resulting from the same functional increase in fractional free volume in polymer-dye mixture with increasing dye content.

Degradation of p-Aminoazobenzene byBacillus subtilis

p-Aminoazobenzene (PAAB) was degradated byBacillus subtilis. Both aniline and p-phenylenediamine as degradative compounds from PAAB were identified by thin layer chromatographic-, and high performance liquid chromatographic-methods. This fact suggests that the first degradative reaction of PAAB byB. subtilis is reductive fission of azo bond in PAAB.

SUBLIMATION DESORPTION OF DYE FROM FILM ROLL

A roll of nylon 6 film dyed with p-aminoazobenzene (PAAB) was heated at 120°C in a vacuum (5×10-3 Torr) for 10_??_20 hrs and from the concentration distribution of PAAB obtained, diffusion coefficient D of the dye in nylon in the absence of water was calculated by means of Sekido and Matsui1) (M method).D was also determined by measuring the rate of sublimation from a single layer of the dyed nylon film (S method).From these results following conclusions were obtained:(1) When the specimen was dyed so long that the dye concentration attained equilibrium value, D values from both methods were in good accordance.(2) Even when the dyeing was not attained the equilibrium, the D value obtained by M method was equal to that obtained in (1).

Water Insouble Dyes Containing s-Triazine Ring. I

p-Aminoazobenze ne, 4-amino-1, 1'-azonaphthalene, 1-amino-4-cyclohexyl-aminoanthraquinone, and 1-amino-4-hydroxyanthraquinone, respectively, is made to react with cyanuric chloride to give a dichloro-s-triazine type pigment, (F=residual group of the pigment). Reaction of this with monoethanolamine, diethanolamine, N, N-diethylethyl-enediamine, and ethylenimine, respectively yielded dyes with general formula, where R=H or R'; R'=-CH2CHZOH, -CH2CH2N(C2H5)2 or The dyeing properties of these pigments with substituent groups, such as -N(CH2CH2OH)2 and -NHCH2CH2OH were considerably selective, and Nylon. Vinylon and acetate fibers were dyed well, but cotton, rayon. Tetron and acrylonitrile type fibers were not dyed by these pigments. The basic pigments having a substituent group, -NHCH2CH2N(C2H5)2, showed the characteristics of basic pigment and had less selective property, they dye silk well, and the dyeing properties to rayon, wool and acrylonitrile type fibers was increased, while that of to Nylon, Vinylon and acetate fibers decreased. The quarternary salt also showed the same dyeing property. The products containing ethyle-nimino group as substituent had a charcteristic of reactive or polymerizable pigment, they were fixed on cotton by a mere heating at 110-30°c without condensation agent such as alkali, and the dyed materials were fast against the extraction test with pyridine.