Azo Linkage Research Articles

Treatment of azo dye wastewater by the self-flocculating marine bacterium Aliiglaciecola lipolytica

Microorganisms with capacity to degrade and separate azo dyes from water are potential in developing eco-friendly and cost-effective method for azo wastewatertreatment, challenged for large volume, toxicity and high salinity. Marine bacterium Aliiglaciecola lipolytica (A. lipolytica) was examined to decolorize Congo Red (CR), a typical azo dye in sythesized water. The results showed that the bacterium could achieve aerobic decolorization (more than 90%) and self-flocculation under wide conditions (temperature 25–35°C, initial CR concentration 25–100 mg L−1, salinity 0–20 g L−1, pH 5–6, glucose concentration 4–8 g L−1, and (NH4)2SO4 concentration 1–2 g L−1). It was proved that the dyes were firstly adsorbed onto cells by extracellular polymeric substances (EPS), and about 46% of them were then degraded. This degradation process was through co-metabolism with the glucose and also mediated by azoreductase and intracellular laccase. The azo linkage (-N=N-), the chromophore groups (C-N) and sulfonate groups (−SO3) were cleaved; then the naphthalene rings were decomposed, which made CR into smaller molecules. The bacterium secreted many EPS, especially protein-like and humic acid substances in tightly bound EPS (TB-EPS), which could decrease electrostatic force and increase hydrophobicity of cell surface contributed to dye adsorption and cell self-flocculation. It was stressed that self-flocculation marine bacterium A. lipolytica could provide a promising technique for azo dye wastewater treatment.

DFT study of azo linkage effect on homoaromatization of some 1,4-dihydropryridines

1,4-dihydropryridine derivatives revealed various biological activities and pharmacological properties such as antiviral, antibacterial and anti-inflammatory activities. In this research, density functional theory (DFT) calculations at the B3LYP level are used to optimize the geometry of the compounds. In this study, we were interested in evaluation of homoaromaticity of the selected compounds using nucleus independent chemical shifts NICS(0), NICS(0.5), NICS(1), NICS(1.5) and NICS(2), bond lengths, bond angles and HOMO-LUMO gap.

Azo functionalized polystyrene supported Copper nanoparticles: An economical and highly efficient catalyst for A[formula omitted] and KA[formula omitted] coupling reaction under microwave irradiation

The combination of polymeric support and metal nanoparticles were always leading towards better catalytic systems. Herein, we report Cu supported on azo functionalized polystyrene. The synthesized catalyst was characterized by (SEM, HR-TEM, EDX, RAMAN, XPS, and IR). Active Cu species stabilized by azo linkages present in the polymer matrices is responsible for the catalytic activity. We enrolled in the catalyst in A3 (aldehyde, amine, and acetylene) and KA2 (cyclic ketone, amine, acetylene) coupling reaction. Synthesized catalyst performs much better under microwave irradiation as compared to the conventional method. The better activity of the catalyst may be due to the presence of azo linkages which stabilized the copper nanoparticles in polymer matrices. We achieved 98% yield in both the coupling reactions and time ranges between 15–20 min. We synthesized six derivatives of tetra substituted propargylamine and twenty two derivatives of propargylamines by utilizing optimized conditions. Furthermore, the synthesized catalyst and the reaction conditions were environmentally friendly. In the reusability scan, we found that catalyst was reuse more than seven times with a slight loss in its activity.

A family of azoquinoline derivatives: Effect of the substituent at azo linkage on thermal cis-trans isomerization based on an experimental and computational approach

The subject of the research is a series of azo-dyes based on the quinoline structure, which are practically omitted as materials which use photoinduced optical anisotropy for applications. The work presents the kinetics of thermal cis-trans isomerization reaction of 5-azo-8-hydroxy-2-methylquinoline and 5,5'-((1E,1′E)-[1,1′-biphenyl]-4,4′-diylbis(diazene-2,1-diyl))bis(2-methylquinolin-8-ol) compounds. The impact of the structure of the substituent at the azo linkage on the cis-trans isomerization kinetics was investigated experimentally and theoretically using the UV–Vis spectroscopy and the density-functional theory (DFT). The kinetics of the dark-return of the cis-to trans-isomer of azoquinolines was investigated after UV-irradiation. It was found that attaching the nitro substituent to the azoquinolines structure retards the photoisomerization process in comparison to the other substituents (i.e. F, Cl, Br, N atoms or CH3, OH, COOH, OCH3 groups). The calculated rate constants were in qualitative agreement with the experimental values. To the best of our knowledge, the cis-trans isomerization kinetics for azoquinolines has not been studied yet.

Ni foam-supported azo linkage cobalt phthalocyanine as an efficient electrocatalyst for oxygen evolution reaction

Oxygen evolution reaction (OER) is a multiple electron transfer process with a high activation barrier. Designing low cost, easily synthesizable catalysts with less overpotential and high intrinsic activity towards OER is of prime importance. The present work utilizes an organic macrocycle to decrease the overpotential for oxygen evolution reaction. The cobalt phthalocyanine polymer is synthesized via azo linkage by a diazotization method. The synthesized cobalt phthalocyanine is characterized by spectroscopic and analytical techniques. The cobalt phthalocyanine polymer-coated Ni foam is used as an OER catalyst that exhibits a lesser overpotential of 370 mV (±2 mV) at the current density of 10 mA cm−2. Surprisingly, the mixing of synthesized cobalt phthalocyanine polymer with the benchmark catalyst IrO2 results in an excellent OER activity with a decrease in overpotential up to 304 mV (±1 mV). To the best of our knowledge, it is the best value reported so far for organic macrocycle-based OER catalysts. In addition, at the current density of 50 mA cm−2, the overpotential for OER at MPc-modified Ni electrode was 450 mV (±2 mV). The performance of the macrocycle-modified electrode is comparable with some of the advanced OER catalysts reported previously.

Photoswitchable Bent-Core Nematic Liquid Crystals with Methylated Azobenzene Wing Exhibiting Optic-Field-Enhanced Fréedericksz Transition Effect

We have investigated two new series of unsymmetrical four-ring bent-core molecules with methylated azobenzene wings exhibiting nematic mesophase. The difference between the two series was in the relative position of the methyl (−CH3) substituent with respect to the azo (−N═N−) linkage in the molecule. Single-crystal X-ray diffraction analysis unravels significant insights into the spatial molecular arrangement and molecular stacking interactions of these bent-core systems. The materials were able to show photoswitching behavior and photomasking effect in the liquid-crystalline state via nematic to isotropic (order to disorder) transition when illuminated with UV light. In solid state, the materials exhibit photochromism upon UV light exposure. One of the representative compounds (2/12) was studied to observe the optically enhanced Freedericksz transition (FT) effect stimulated by UV light intensity. A prototype of phase grating has also been devised based upon the observed FT-enhanced effect that has a pr...

Multianalyte azo dye as an on-site assay kit for colorimetric detection of Hg2+ions and electrochemical sensing of Zn2+ ions.

A new tailor-made colorimetric chemosensor, (E)-1-(benzo[d]thiazol-2-yl)-3-(pyridin-3-yldiazenyl)naphthalen-2-ol (1), containing benzothiazole and pyridine moieties connected through an azo (-N=N-) linkage has been designed and synthesized. The synthesized chemosensor displayed an eye-catching color change upon binding to acetate [AcO-;colorless to russet] and mercury (II) [Hg2+;colorless to greenish blue] ions in 9:1 (v/v) aqueous CH3CN (pH7.0 HEPES buffer).The mechanism of interaction between the chemosensor and the Hg2+/AcO- ions has been confirmed by 1H NMR titration experiments. Moreover, the colorimetric chemosensor 1 displayed potential in-field applications as on-site assay kit and detection of Hg2+ ions in real water samples. Importantly chemosensor 1 gave selective electrochemical response towards Zn2+ ions, enabling simple azo-dye 1 as multichannel chemosensor for colorimetric detection of Hg2+ ions and electrochemical detection of Zn2+ ions.

Triptycene based fluorescent polymers with azo motif pendants: Effect of alkyl chain on fluorescence, morphology and picric acid sensing

A design and synthesis of three unique triptycene based polymers containing azo linkages in the side chain of polymer backbone is being reported herein for the first time. These triptycene based azo-polymers (TBAPs) have high solubility in common organic solvents due to the presence of pendent alkyl chains as well as triptycene motifs. TBAPs are well characterized by GPC, TGA, 1H NMR, FTIR, PXRD, FESEM, UV and fluorescence spectroscopy. Polymers with azo-linkages are generally non-fluorescent. However, TBAPs are fluorescent in nature which makes them unique. It was observed that TBAP3 having the longest pendent alkyl chain is most fluorescent when compared with TBAP1 and TBAP2 (which have smaller pendent alkyl chains). Furthermore, TBAPs have been applied for the detection of trace quantities of PA in THF. The binding constants of TBAPs with PA are in the order of 105 M−1 and the PA can be detected even in nanomolar concentrations. It was observed that TBAP1 having the smallest pendent alkyl chain has the highest binding affinity for PA relative to TBAP2 and TBAP3 (having longer pendent alkyl chains). Further, the effect of the chain length on the supramolecular assembly of these polymers was observed using FESEM. The size of domains present in polymer films was found to increase with increasing chain length of alkyl group.

Synthesis, Characterization, and Electrical and Thermal Stability of Semiconducting π-Conjugated Polyazomethines Containing a Tetraphenylthiophene-Oxazole Unit

A series of polyazomethines (PAM-01, PAM-02, PAM-03) containing various amounts of tetraphenylthiophene-oxazole (TPTP-o) moieties were produced by the polycondensation of a diamine precursor (TPTP-o) with equimolar proportions of two aromatic dialdehydes [isophthalaldehyde (1,3 IPA) and terephthalaldehyde (1,4 TPA)]. The TPTP-o precursor was successfully synthesized in three steps. The synthesized TPTP-o and the polymers (PAM-01, PAM-02, PAM-03) were characterized by ultraviolet–visible (UV–Vis) spectroscopy, FT-IR spectroscopy, x-ray diffraction (XRD), 1H-NMR, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. The effects of the TPTP-o units in the PAM on the insertion with azo linkages were studied with respect to conductivity and thermal stability. The room-temperature DC electrical conductivity of the PAM films was found to range from 9.59 × 10−7 S/cm to 9.73 × 10−7 S/cm. UV absorption at 342 nm confirmed the formation of azo (–C=N–) linkages in the polymer, which is helpful for electron conductivity throughout the polymer network. All three PAMs had a glass transition temperature (Tg) between 260°C and 267°C, and T10% thermal degradation values of thermally stable polyazomethines were in the range of 517–530°C. All three PAMs showed moderate solubility in organic solvents and inherent viscosity of between 0.31 dL/g and 0.35 dL/g. The XRD study indicated that all three PAMs were amorphous in nature, with a broad peak in the vicinity of 20°.

Cooperative catalytic performance of bimetallic Ni-Au nanocatalyst for highly efficient hydrogenation of nitroaromatics and corresponding mechanism insight

HNO3-modified carbon black supported Ni-Au bimetallic nanocatalysts (HCB-Ni-Au) with different Ni/Au molar ratio were synthesized for hydrogenation of nitroaromatics. The synergistic effect between bimetallic nanoparticles and HCB, Ni and Au nanoparticles improved the catalytic efficiency. The reaction mechanism and pathway investigation exhibited that nitroaromatics were reduced by cleavage of NO bond and azo linkage (NN) and uptake of H from NiH and AuH bonds. Density functional theory theoretical calculation showed 4-nitrophenol (4-NP) with higher free energy was easier to be catalyzed. The activation of enthalpy for MO was 65.7 kcal mol−1, which displayed the highest catalytic rate of 2.1055 min−1. Meanwhile, the reaction rate of 4-NP hydrogenation catalyzed by HCB-Ni6-Au1 reached 1.9617 min−1, which was 15 and 38 times higher than that of Ni and Au monometallic nanocatalyst, respectively. HCB-Ni6-Au1 with good structural stability could be well reused and applied in tap, distilled, river, and lake water samples.

Study of the Corrosion Inhibitive Effect and Adsorption Process of Two Azo-Aldehydes on Carbon Steel in 1 M H2SO4

Two aromatic aldehydes with azo linkage (AS1 and AS2) were assessed for their inhibitive effect on carbon steel corrosion in 1 M H2SO4. The inhibition efficiency was studied by gravimetric and electrochemical analysis. The effects of concentration and temperature on the inhibition efficiency have also been studied. The obtained results showed that both of the used compounds can be considered as efficient carbon steel corrosion inhibitors. The compound which has methyl group in its structure (AS2) has higher inhibition efficiency (93.11% with 0.2 mM at 303 K by electrochemical analysis) than the one with cyano group (AS1). The adsorption isotherms of the inhibitors were studied; it was found that the adsorption of the two compounds obeys Langmuir isotherm. The studied inhibitors are mixed type inhibitors and adsorbed onto the surface of the carbon steel by a physisorption process. SEM and AFM techniques were used to study the effect of the aggressive solution on the morphology of the metal surface in the absence and presence of the used inhibitors.

Tetraphenylthiophene–thiazole-based π-conjugated polyazomethines: synthesis, characterization and gas sensing application

2,5-Bis(4-(2-aminothiazole) phenyl)-3 and 4-diphenyltetraphenyl thiophene (TPTPThDA) are fine processed in three steps. A series of polyazomethines containing thiophene–thiazole unit have been incorporated by the polycondensation of a new diamine, i.e. TPTPThDA, with proportionate of aromatic dialdehydes. The impact of insertion of thiazole entity in the polyazomethine matrix with the azo linkages having dialdehydes [isophthalaldehyde (1,3 IPA) and terephthalaldehyde (1,4 TPA)], on conductivity and gas sensing properties, has been studied. In all polyazomethines synthesized (PAM-01 to PAM-05), the preeminent in terms of conductivity and gas sensing properties has been established to be the PAM-03 containing polyazomethine matrix composition of 1,3 IPA and 1,4 TPA with thiophene–thiazole unit. After the infusion with the dialdehyde comonomers, an inflation of the molecular weight and the polyazomethines films were highly selective towards H2S gas at 35 °C with great sensitivity and acceptable selectivity. Along this, all polyazomethines have Tg in the range of 257–260 °C and T10% value of all thermally stable polyazomethines in air and nitrogen was in between of 458–545 °C and 527–601 °C, respectively. The polymer backbone contains rigid framework expect PAM-05, and due to this, they show less solubility in organic solvents. XRD study confirms that all the polyazomethines are amorphous in nature having broad peak in the range of 20°. The UV at 342 nm shows that there is a formation of imine (–C=N–) linkages in the polymer matrix which is helpful for the conduction of electron throughout. The band gap energy of PAM-3 is found as 3.63 eV.

Remarkable diversification of bacterial azoreductases: primary sequences, structures, substrates, physiological roles, and biotechnological applications.

Azoreductases reductively cleave azo linkages by using NAD(P)H as an electron donor. The enzymes are widely found in bacteria and act on numerous azo dyes, which allow various unique applications. This review describes primary amino acid sequences, structures, substrates, physiological roles, and biotechnological applications of bacterial azoreductases to discuss their remarkable diversification. According to primary sequences, azoreductases were classified phylogenetically into four main clades. Most members of clades I-III are flavoproteins, whereas clade IV members include flavin-free azoreductases. Clades I and II prefer NADPH and NADH, respectively, as electron donors, whereas other members generally use both. Several enzymes formed no clades; moreover, some bacteria produce azoreductases with longer primary structures than those hitherto identified, which implies further diversification of bacterial azoreductases. The crystal structures commonly reveal the Rossmann folds; however, ternary structures are moderately varied with different quaternary conformation. Although physiological roles are obscure, several azoreductases have been shown to act on metabolites such as flavins, quinones, and metal ions more efficiently than on azo dyes. Considering that many homologs exclusively act on these metabolites, it is possible that azoreductases are actually side activities of versatile reductases that act on various substrates with different specificities. In parallel, this idea raises the possibility that homologous enzymes, even if these are already defined as other types of reductases, widely harbor azoreductase activities. Although azoreductases for which their genes have been identified are not abundant, it may be simple to identify azoreductases of biotechnological importance that have novel substrate specificities.

Impact of the proportionation of dialkoxy chain length on the mesophase behaviour of Schiff base/ester liquid crystals; experimental and theoretical study

ABSTRACTNew non-symmetrical homologues series of Schiff base/ester series, 4-alkoxyphenylimino-4ʹ-phenyl-4ʹ’-alkoxybenzoates, have two terminal alkoxy groups (Im/n), were synthesised and investigated for their mesophase behaviour. Where the number of carbon in the alkoxy chains attached to the phenylimino and benzoate moieties named m and n respectively. The newly Schiff base structures were confirmed via elemental analyses IR, and NMR spectroscopy. Mesomorphic properties were investigated by differential scanning calorimetry and polarised light microscopy. All investigated compounds proved to be dimorphic exhibits semictic A and nematic phases with high stability. The present Schiff base groups and the previously prepared 4-alkoxyphenylazo-4ʹ-phenyl-4ʹ’-alkoxybenzoates were compared and results revealed that the replacement the azo linkage by phenylimino group change the mesophase stability and the type of the phase depending up on the length of alkoxy – chain m that attached to the phenylimino mesogenic part. Furthermore, we have performed density functional theory theoretical calculations to confirm the experimental data and the results are in consistent with the experimental investigation.

C3N5: A Low Bandgap Semiconductor Containing an Azo-Linked Carbon Nitride Framework for Photocatalytic, Photovoltaic and Adsorbent Applications.

Modification of carbon nitride based polymeric 2D materials for tailoring their optical, electronic and chemical properties for various applications has gained significant interest. The present report demonstrates the synthesis of a novel modified carbon nitride framework with a remarkable 3:5 C:N stoichiometry (C3N5) and an electronic bandgap of 1.76 eV, by thermal deammoniation of the melem hydrazine precursor. Characterization revealed that in the C3N5 polymer, two s-heptazine units are bridged together with azo linkage, which constitutes an entirely new and different bonding fashion from g-C3N4 where three heptazine units are linked together with tertiary nitrogen. Extended conjugation due to overlap of azo nitrogens and increased electron density on heptazine nucleus due to the aromatic π network of heptazine units lead to an upward shift of the valence band maximum resulting in bandgap reduction down to 1.76 eV. XRD, He-ion imaging, HR-TEM, EELS, PL, fluorescence lifetime imaging, Raman, FTIR, TGA, KPFM, XPS, NMR and EPR clearly show that the properties of C3N5 are distinct from pristine carbon nitride (g-C3N4). When used as an electron transport layer (ETL) in MAPbBr3 based halide perovskite solar cells, C3N5 outperformed g-C3N4, in particular generating an open circuit photovoltage as high as 1.3 V, while C3N5 blended with MA xFA1- xPb(I0.85Br0.15)3 perovskite active layer achieved a photoconversion efficiency (PCE) up to 16.7%. C3N5 was also shown to be an effective visible light sensitizer for TiO2 photoanodes in photoelectrochemical water splitting. Because of its electron-rich character, the C3N5 material displayed instantaneous adsorption of methylene blue from aqueous solution reaching complete equilibrium within 10 min, which is significantly faster than pristine g-C3N4 and other carbon based materials. C3N5 coupled with plasmonic silver nanocubes promotes plasmon-exciton coinduced surface catalytic reactions reaching completion at much low laser intensity (1.0 mW) than g-C3N4, which showed sluggish performance even at high laser power (10.0 mW). The relatively narrow bandgap and 2D structure of C3N5 make it an interesting air-stable and temperature-resistant semiconductor for optoelectronic applications while its electron-rich character and intrasheet cavity make it an attractive supramolecular adsorbent for environmental applications.

Facile fabrication of Amberlite XAD-16 with dipicolylamine for remediation of industrial wastewater containing lead and copper: Isotherm, kinetics, thermodynamics and selectivity studies

A new chelating resin was synthesized for the selective removal of potentially toxic Pb (II) and Cu (II) by the functionalization of a ligand dipicolylamine on the Amberlite XAD-16 resin through azo (NN) linkage. Physicochemical parameters of the synthesized XAD-DP resin were characterized by using FT-IR, TGA-DTA, SEM, 13C NMR, BET analysis and point zero charge studies. It showed good reusability (55 cycles) and high stability. The optimum experimental variables for sorption/desorption of metal ions were systematically investigated by batch method. The maximum sorption for Pb (II) and Cu (II) were observed at pH 5.6 at the equilibrium time of 60 and 150 min, respectively with a resin dosage of 0.1 g and desorbed quantitatively by using 5 mL of 2 M HCl. Among five studied isotherm models, the maximum adsorption capacities were 166.67 and 36.63 mg g−1 for Pb (II) and Cu (II) respectively at 308 K in accordance with the Langmuir isotherm model. The sorption kinetics and thermodynamic studies revealed that adsorption of Pb (II) and Cu (II) followed pseudo-second-order kinetics with endothermic and spontaneous behaviour. In addition, XAD-DP shows the preferential adsorption for Pb (II) and Cu (II), respectively in competitive metal ion environment. The applicability of the synthesized resin was explored through batch studies in industrial effluents resulting in >97.9% removal efficiency for Pb (II) and Cu (II) in battery manufacturing industries and 100% removal from thermal power plants effluents.

Heterogeneous activation of peroxymonosulfate using Mn-Fe layered double hydroxide: Performance and mechanism for organic pollutant degradation

On account of high oxidation ability of sulfate radical-based advanced oxidation processes (AOPs), the eco-friendly catalysts for peroxymonosulfate (PMS) activation have received considerable attentions. Previous studies mainly focused on Cobalt-based catalyst due to its high activation efficiency, such as Co3O4/MnO2 and FeCo-layered double hydroxide (LDH), whereas Cobalt-based catalyst usually has serious risk to environment. To avoid this risk, MnFe-LDH was primarily synthesized in this research by simple co-precipitation and subsequently utilized as an effective catalyst for peroxymonosulfate (PMS) activation to degrade organic pollutants. The experimental results demonstrated that MnFe-LDH with a lower dosage (0.20 g/L) could efficiently activate PMS to achieve 97.56% removal of target organic pollutants Acid Orange 7 (AO7). The AO7 degradation process followed the pseudo-first-order kinetic well with an activation energy of 21.32 kJ/mol. The intrinsic influencing mechanism was also investigated. The quenching experiment and electron spin resonance (ESR) indicated that sulfate and hydroxyl radicals were produced by the effective activation of PMS by MnFe-LDH, resulting in a high rate of decolorization. The possible AO7 removal pathway in the constructed MnFe-LDH/PMS system was presented on the basis of UV–vis spectrum analysis and GC–MS, which suggested that the AO7 degradation was firstly initiated by breaking azo linkages, then generated phenyl and naphthalene intermediates and finally presented as ring-opening products. This effective MnFe-LDH/PMS system showed great application potential in the purification of wastewater contaminated by refractory organic pollutants.

Conventional and microwave-irradiated synthesis of new bischalcone derivatives

A series of 12 novel methyl- and halogen-substituted bischalcones containing an azo linkage was synthesized by a Claisen–Schmidt condensation between ( E)-1-{4-[(4-acetyl-2-hydroxyphenyl)diazenyl]phenyl}ethanone and various araldehydes using microwave irradiation and conventional procedures and the results were compared.

Anthracene-based azo dyes for photo-induced proton-coupled electron transfer.

Herein, we report a new donor-acceptor system for photo-induced proton-coupled electron transfer (PCET) that leverages an azo linkage as the proton-sensitive component and anthracene as a photo-trigger. Electrochemistry shows a change in the reduction potential with addition of acid. However, photochemistry is invariant to the absence or presence of acid. The anthracene and phenol/4-methoxyphenyl moieties of the azo dyes are highly conjugated, likely mitigating photo-induced charge transfer, despite sufficient driving force.

A novel method for oxidative degradation of metanil yellow azo dye by hexacyanoferrate(III) ions.

In the present work, the degradation of metanil yellow, an azo dye, by hexacyanoferrate(III) ions (oxidant) in the aqueous alkaline medium has been investigated by kinetic-spectrophotometric method at λmax 435nm of the reaction mixture. The effect of various parameters such as the concentration of dye, oxidant, and solution pH on the reaction rate has been determined. The results show that the rate of degradation increases linearly with the increase in concentrations of oxidant and dye at optimum pH of 9.0 and constant temperature of 40±0.1°C. Thermodynamic parameters such as energy of activation, enthalpy of activation, entropy of activation, and energy of formation have been calculated by studying the reaction rate at four different temperatures, that is, 40-55°C. Based on the experimental results, a plausible reaction mechanism involving complex formation has been proposed and a rate law has been derived. UV-Vis and LC-MS methods of analysis of degradation products show the formation of simpler and less hazardous degradation products. PRACTITIONER POINTS: It is also observed that the time required for azo dye degradation by the present method is about ten times less than the reported methods. Thus degradation of azo linkage and formation of simple and less hazardous products (efficient degradation of dye) makes it a novel method.