Decolorization kinetics of the azo dye drimaren blue X3LR by laccase

Summary An extracellular Drimaren Blue X3LR decolorizing enzymatic activity was found in the crude filtrate of Funalia trogii grown by solid-state fermentation using wheat bran and soya bean waste. Decolorization of the azo dye Drimaren Blue X3LR by the crude filtrate and partially purified enzyme of Funalia trogii were investigated and compared. In the absence of additional redox mediator, maximum decolorization ratios of 81.33 % and 77.4 % were observed for Drimaren Blue X3LR using crude filtrate and partially purified enzyme respectively. Decolorization yield was found to be higher with crude enzyme preparations. Na₂S₂O₅ inhibited laccase and dye decolorizing enzyme activities but a significant peroxidase activity inhibition was not observed. Since the reaction was catalyzed in the absence of H₂O₂ as co-substrate, it could be concluded that this enzyme is not a peroxidase but may be a laccase.. The kinetic parameters of decolorization were calculated according to Michaelis constant (Km of 1.700 x 10^-5 mol dm^-3 and W_max = 8.02 x10^-7 mol dm^-3 sec^-1).     

Blue dye degradation in an aqueous medium by a combined photocatalytic and bacterial biodegradation process

This paper aimed at implementing a treatment system for polluted water with textile dyes, starting with a photocatalytic decomposition process using sunlight as a source of energy and continuing with a bacterial biodegradation process, in order to reach degradation percentages higher than those obtained using only one of the processes mentioned above. When water treatment with the dye in the combined system was over, an acute ecotoxicity test was performed to make sure that toxic metabolites were not produced due to biodegradation. Solophenyl Blue azoic dye, and Erionyl Blue and Terasil Blue anthraquinone dye-colored solutions were treated with the Pd/Al ₈₀ Ce ₁₀ Zr ₁₀ catalyst in a solar collector for the photocatalytic process. On the other hand, the waste dye, which was obtained from photocatalysis with a bacterial consortium from polluted areas by metals and hydrocarbons in aerobic conditions, was inoculated for biodegradation. Biodegradation was obtained for the dyes after both processes as 90.91% for the Solophenyl Blue azoic dye, and 87.80% and 87.94%, respectively, for the Erionyl Blue and Terasil Blue anthraquinone dyes. After the degradation processes, it was proven, via an ecotoxicity test with Daphnia magna , that toxic metabolites had not been produced.     

Molecular Design Rule of Phthalocyanine Dyes for Highly Efficient Near‐IR Performance in Dye‐Sensitized Solar Cells

A series of zinc–phthalocyanine sensitizers ( PcS16 – 18 ) with different adsorption sites have been designed and synthesized in order to investigate the dependence of adsorption‐site structures on the solar‐cell performances in zinc–phthalocyanine based dye‐sensitized solar cells. The change of adsorption site affected the electron injection efficiency from the photoexcited dye into the nanocrystalline TiO₂ semiconductor, as monitored by picosecond time‐resolved fluorescence spectroscopy. The zinc–phthalocyanine sensitizer PcS18 , possessing one carboxylic acid directly attached to the ZnPc ring and six 2,6‐diisopropylphenoxy units, showed a record power conversion efficiency value of 5.9 % when used as a light‐harvesting dye on a TiO₂ electrode under one simulated solar condition.     

Synthesis of two metabolites of 2,4-diamino-5(3,4,5-trimethoxybenzyl)-pyrimidines (Trimethoprim)

The synthesis of two metabolites M₃ and M₄ of 2,4-diamino-5-(3, 4, 5-trimethoxybenzyl)-pyrimidine (trimethoprim, 1 ) is reported. M₃ (trimethoprim 1-oxide) as well as the isomeric 3-oxide were prepared by oxidation of 1 with m-chloroperbenzoic acid. The structure of M₃ was finally established by x-ra analysis [4]. The metabolite M₄ [2, 4-diamino-5-(3-hydroxy-4, 5-dimethoxy-benzyl)-pyrimidine] was prepared by condensation of 3-benzyloxy-4, 5-dimethoxybenzaldehyde ( 2 ) with 3-methoxypropionitrile ( 3 ) and guanidine followed by hydrogenolysis of the intermediate 3-benzyloxy compound 4 .     

Lignin-degrading enzyme fromPhanerochaete chrysosporium

The extracellular fluid of ligninolytic cultures of the white-rot wooddestroying fungus,Phanerochaete chrysosporium Burds., contains an enzyme that degrades lignin model compounds as well as lignin itself (1). Like ligninolytic activity, the enzyme appears during idiophasic metabolism, which is triggered by nitrogen starvation. The enzyme has been purified to homogeneity by DEAE-Biogel A chromatography, as assessed by SDS polyacrylamide gel electrophoresis, isoelectric focusing, and gel filtration chromatography. These techniques also revealed a molecular weight of 42,000 daltons, and an isoelectric point of 3.4. The purified enzyme exhibits low substrate specificity. It is an oxygenase, but requires hydrogen peroxide for activity. The activity is optimum at 0.15 mM H₂O₂; at concentrations above 0.5 mM, H₂O₂is inhibitory. Model compound studies have shown that the enzyme catalyzes cleavage between Cα and Cß in compounds of the type aryl-CαHOH—CßHR-(R = -aryl or -O-aryl), and in the Cα-hydroxyl-bearing propyl side chains of lignin. This cleavage produces an aromatic aldehyde moiety from the Cα-portion, and a Cß-hydroxylated moiety from the Cα-portion. Cleavage between Cα and Cß in arylglycerol-Β-aryl ether structures leads indirectly to cleavage of the Β-aryl ether linkage, which is the most abundant intermonomer linkage in lignin. The Cß-hydroxyl oxygen comes from molecular oxygen, and not from H₂O₂, as determined by¹⁸O isotope studies. The pH optimum for these reactions is between 2.5 and 3.0; no activity is observed above pH 5. Formation of the expected aldehydes from spruce and birch lignins, and partial depolymerization of the lignins results from the action of the purified enzyme. In addition to Cα—Cß cleavage, the enzyme catalyzes aromatic alcohol oxidation, aryl methylene oxidation, hydroxylation at Cα and Cß in models containing a Cα—Cß double bond, intradiol cleavage in phenylglycol structures, and phenol oxidations.     

Photosensitization of Chinese hamster cells by water-soluble phthalocyanines

Abstract— Phthalocyanines are efficient photosensitizers of cultured mammalian cells and are considered for use in photodynamic therapy. The photobiological properties of chloroaluminum phthalocyanine sulfonate (AIPCS) were compared to those of the unsubstituted, water-insoluble derivative (AIPC). The development of photosensitization after addition of the dye into growth medium is ca. 8 times more rapid for AlPC than for AIPCS. Conversely, the loss of photosensitization when cells are incubated in a dye-free growth medium following a period of dye uptake, is also faster for AIPC. The dye uptake followed a kinetic behavior similar to the development of photosensitivity, but the loss of dye was too slow for both AlPC and AIPCS to explain loss of photosensitivity. When cells are incubated prior to illumination with AIPCS in phosphate buffered saline instead of growth medium, shorter time and smaller amount of dye are required to achieve the same level of photosensitization. The dependence of photosensitivity on dye concentration is linear for both AIPC and AIPCS. As already found for AIPC, photosensitization by the water-soluble derivative is also not enhanced in D₂O, suggesting that singlet oxygen is not involved in the cytotoxic response. Sodium salicylate, which was found to enhance the effect of AlPC was also effective with AIPCS. This effect is quite specific since the meta and para isomers had no effect. The metal atom complexed with the phthalocyanine ring is significant for the photobiological activity. Among the compounds tested, those containing Al or Zn are most active.     

Characterisation of selected hypnotic drugs and their metabolites using electrospray ionisation with ion trap mass spectrometry and with quadrupole time-of-flight mass spectrometry and their determination by liquid chromatography-electrospray ionisation-ion trap mass spectrometry

The electrospray ionisation-ion trap mass spectrometry (ESI-MSⁿ) of selected hypnotic drugs, i.e. zopiclone, zolpidem, flunitrazepam and their metabolites have been investigated. Sequential product ion fragmentation experiments (MSⁿ) have been performed in order to elucidate the degradation pathways for the [M+H]⁺ ions and their predominant fragment ions. These MSⁿ experiments show certain characteristic fragmentations in that functional groups are generally cleaved from the ring systems as neutral molecules such as H₂O, CO, CO₂, NO₂, amines and HF. When an aromatic entity is present in a drug molecule together with a nitrogen-containing saturated ring structure as with zopiclone and its N-desmethyl metabolite fragmentation initially occurs at the latter ring with the former being resistant to fragmentation. The structures of fragment ions proposed for ESI-MSⁿ can be supported by electrospray ionisation-quadrupole time-of-flight mass spectrometry (ESI-QTOF-MS).These molecules can be identified and determined in mixtures at low ng/ml concentrations by the application of liquid chromatography (LC)-ESI-MSⁿ which can be used for their analysis in saliva samples.This paper includes a tabulation of mass losses/signals at low m/z values for these hypnotic drugs and many others in recent publications which will be of value in the characterisation of drug metabolites of unknown structure and also natural product pharmaceuticals isolated from plants, etc.     

In Silico and in Vitro Physicochemical Screening of Rigidoporus sp. Crude Laccase-assisted Decolorization of Synthetic Dyes—Approaches for a Cost-effective Enzyme-based Remediation Methodology

The objective of this paper is to compare in silico data with wet lab physicochemical properties of crude laccase enzyme isolated from Rigidoporus sp. using wheat bran as solid substrate support towards dye decolorization. Molecular docking analysis of selected nine textile and non-textile dyes were performed using laccase from Rigidoporus lignosus as reference protein. Enzyme-based remediation methodology using crude enzyme enriched from solid state fermentation was applied to screen the effect of four influencing variables such as pH, temperature, dye concentration, and incubation time toward dye decolorization. The extracellular crude enzyme decolorized 69.8 % Acid Blue 113, 45.07 % Reactive Blue 19, 36.61 % Reactive Orange 122, 30.55 % Acid Red 88, 24.59 % Direct Blue 14, 18.48 % Reactive Black B, 16.49 % Reactive Blue RGB, and 11.66 % Acid Blue 9 at 100 mg/l dye concentration at their optimal pH at room temperature under static and dark conditions after 1 h of incubation without addition of any externally added mediators. Our wet lab studies approach, barring other factors, validate in silico for screening and ranking textile dyes based on their proximity to the T1 site. We are reporting for the first time a combinatorial approach involving in silico methods and wet lab-based crude laccase-mediated dye decolorization without any external mediators.     

THE PHOTOCHEMICAL PROPERTIES OF FLUOROALUMINUM PHTHALOCYANINE

Abstract Fluoride is known to inhibit the photodynamic activity of aluminum phthalocyanine in a variety of biological systems. In order to gain insight into this phenomenon, the effect of fluoride on the photophysical properties of free and albumin-bound chloroaluminum phthalocyanine sulfonate (AlPcS_n.) were studied. The association constant of NaF with AlPcS_n, in aqueous solution was measured as 500 ± 20 M^?1. This binding affects the photophysical properties of the dye: the absorption bands in the visible range are blue-shifted by 6–8 nm, and this effect is mirrored in the fluorescence emission spectrum. Human serum albumin significantly quenched the dye fluorescence independent of the presence of fluoride ion. The transient absorption spectrum of the excited dye triplet is unchanged by NaF, but the quantum yield for its generation is increased by 50%, with no decrease in its lifetime. Formation of fluoroaluminum phthalocyanine complexes was also observed in tetrabutylammonium fluoride-assisted solutions in wet acetonitrile. The fluoro-AlPcS_n, complex is a better photosensitizer for generation of singlet oxygen than the original dye-hydroxyl ion complex, as confirmed using the imidazole-N,N-dimethyl-4-nitrosoaniline method. On the other band, the fluoro-AlPcS_n. complex exhibits an intense inhibitory effect on photohemolysis of red blood cells (RBC) even after the cells are washed to remove free dye and fluoride prior to irradiation, indicating that once the dye is attached to the cellular site, the fluoride ligand is no longer prone to displacement (by hydroxyl ion, for example). Nonetheless, it is clear from the spectroscopic data that the new fluoro complex is an efficient sensitizer for photo-oxidation. Therefore, the reduced photodynamic action of the fluoro-AlPcS_n. complex on RBC (Ben-Hur et al., Photochem. Photobiol. 58 , 351–355, 1993) may result from a lowering of the efficiency of interaction of the fluorodye complex with sensitive cell target moieties.     

Variations in some extracellular enzyme activities during degradation of lignocellulose byPhanerochaete chrysosporium

The white-rot fungusPhanerochaete chrysosporium is able to degrade lignin only when its primary growth phase is completed. We have recently shown that the organism is able to establish new growth at 10–15 d intervals by recycling its own nitrogen (2). We have now further characterized this growth-rest cycle by measuring changes in extracellular protease, cellulase, and xylanase activities together with total extracellular protein during growth on different carbon sources.

1. WhenP. chrysosporium is grown on a N-limited glucose medium, the cessation of primary growth is closely connected to the increase in extracellular proteolytic activity. When the culture is not O₂-limited (2) it becomes ligninolytically active after about 2 d with a simultaneous decrease in proteolytic activity and an increase in extracellular protein. In O₂-limited cultures, the proteolytic activity remains on a high level for up to 6–7 d. During the second growth phase, the proteolytic activity again increases.
2. When P.chrysosporium is grown on a N-limited glucose medium supplemented with lignocellulosic materials the cellulase and xylanase activities are suppressed and the growth is again connected to an increase in extracellular proteolytic activity. Lignin is not degraded during the growth phases.
3. When P.chrysosporium is grown on a N-limited medium with lignocellulose as the only energy source, the growth phases are connected with increased cellulolytic, xylanolytic, and proteolytic activities. Again during the growth phase, lignin is not degraded. During the ligninolytic phase the level of measured extracellular enzyme activities decreases. A simultaneous increase in total extracellular protein seems to indicate that these enzymes are partly reused for synthesis of the ligninolytic system. Proteins associated with the ligninolytic system appear to be partly reused to synthesize the hydrolytic enzymes for the next growth phase.

     

Synthesis and characterization of functionalized silicon phthalocyanines for fabrication of self-assembled monolayers

Novel octasubstituted phthalocyanine derivatives XYSiPc(OR)₈ (X=alkyl, Y=alkoxy, R=alkane or alkene) were synthesized by reaction of alkoxy-substituted diiminoisoindolines with XSiCl₃ followed by quenching with an alcohol YOH. Three synthetic routes for adding anchoring groups to the phthalocyanines were explored: variation of the axial groups X and Y, or incorporation of vinyl groups around the periphery of the phthalocyanine ring. The latter approach yielded silicon and copper phthalocyanines with eight terminal vinyl groups, which reacted cleanly with thioacetic acid/AIBN to give products with eight protected terminal thiols.     

Photocatalytic reduction of azo dyes Naphthol Blue Black and Disperse Blue 79

Photocatalytic reduction of two textile azo dyes, Naphthol Blue Black (NBB) and Disperse Blue 79 (DB79) has been carried out in colloidal WO₃ and TiO₂ suspensions. Under bandgap excitation of the semiconductor colloids these dyes undergo irreversible reduction as they react with the trapped electrons. The quantum efficiency for the photocatalytic reduction of these dyes were 5.4% and 4.8% for NBB and DB79 respectively. The kinetics and mechanism of the interfacial charge transfer in these colloidal suspension has been elucidated with transient absorption spectroscopy. The reaction between the dye and trapped electrons is diffusion limited and occurs with rate constants of 1.1×10⁸ M⁻¹s⁻¹ and 4.0×10⁷ M⁻¹s⁻¹ for NBB and DB79 respectively.     

Methyloxy Substituted Heteroleptic Bis(phthalocyaninato) Yttrium Complexes: Density Functional Calculations

The effects of alkyloxy substituents attached to one phthalocyanine ligand of three heteroleptic bis(phthalocyaninato) yttrium complexes Y(Pc)[Pc(α‐OCH₃)₄] ( 1 ), Y(Pc)[Pc(α‐OCH₃)₈] ( 2 ), and Y(Pc)[Pc(β‐OCH₃)₈] ( 3 ), as well as their reduction products {Y(Pc)[Pc(α‐OCH₃)₄]}^? ( 4 ), {Y(Pc)[Pc(α‐OCH₃)₈]}^? ( 5 ), and {Y(Pc)[Pc(β‐OCH₃)₈]}^? ( 6 ) [H₂Pc(α‐OCH₃)₄=1,8,15,22‐tetrakis(methyloxy)phthalocyanine; H₂Pc(α‐OCH₃)₈=1,4,8,11,15,18,22,25‐octakis(methyloxy)phthalocyanine; H₂Pc(β‐OCH₃)₈=2,3,9,10,16,17,23,24‐octakis(methyloxy)phthalocyanine] are studied by DFT calculations. Good consistency is found between the calculated results and experimental data for the electronic absorption, IR, and Raman spectra of 1 and 3 . Introduction of electron‐donating methyloxy groups on one phthalocyanine ring of the heteroleptic double‐deckers induces structural deformation in both phthalocyanine ligands, electron transfer between the two phthalocyanine rings, changes in orbital energy and composition, shift of electronic absorption bands, and different vibrational modes of the unsubstituted and substituted phthalocyanine ligands in the IR and Raman spectra in comparison with the unsubstituted homoleptic counterpart Y(Pc)₂. The calculations reveal that incorporation of methyloxy substituents at the nonperipheral positions has greater influence on the structure and spectroscopic properties of bis(phthalocyaninato) yttrium double‐deckers than at the peripheral positions, which increases with increasing number of substituents. Nevertheless, the substituent effect of alkyloxy substituents at one phthalocyanine ligand of the double‐decker on the unsubstituted phthalocyanine ring and on the whole molecule and the importance of the position and number of alkyloxy substituents are discussed. In addition, the effect of reducing 1 – 3 to 4 – 6 on the structure and spectroscopic properties of the bis(phthalocyaninato) yttrium compounds is also discussed. This systemic DFT study is not only useful for understanding the structure and spectroscopic properties of bis(phthalocyaninato) rare earth metal complexes but also helpful in designing and preparing double‐deckers with tunable structure and properties.     

Enzymic demethylation of lignin model polymers

We have studied the demethylation of [O¹⁴CH₃]-polyguaiacol byPhanerochaete chrysosporium as a model for the fungal demethylation of lignin. Demethylating activity of whole-cell ligninolytic cultures was compared to demethylating activities of various oxygen-activating systems. Some of these systems demethylated polyguaiacol (e.g., Fenton’s reagent, rose bengal sensitized photolysis, and horseradish peroxidase + H₂O₂). Other systems did not (e.g., xanthine/xanthine oxidase). Even where oxygen-activating systems did demethylate polyguaiacol, we found no convincing evidence that these systems are used byPhanerochaete. We have detected in concentrated extracellular culture filtrates of ligninolyticPhanerochaete cultures an enzymatic activity that demethylates [O¹⁴CH₃]-polyguaiacol. The activity was stabilized greatly by concentrating culture filtrates by pressure dialysis (20,000 MW cutoff membrane). Concentrated enzyme preparations could be filter sterilized and stored at 4‡C for several days without extensive loss of activity. The methoxyl label released by our enzyme preparation was nongaseous (e.g., not¹⁴CO₂,¹⁴CO, or¹⁴CH₄), but volatile (e.g., CH₃OH or CH₂O). The amount of labeled methoxyl released by the enzyme preparation was about the same as that released by intact cultures. The enzyme preparation contained ∼50 Μg/mL of protein and had laccase activity against catechol or hydroquinone. Unsupplemented preparations lacked activity againsto-dianisidine, a dye used to assay peroxidase. However, when H₂O₂ was provided (0.8 mM),o-dianisidine was oxidized rapidly. This indicates that the preparation contained peroxidase, but lacked substrate levels of H₂O₂. Demethylation of polyguaiacol by the enzyme preparation was not stimulated by NADH, NADPH, FAD, or FMN. Demethylation was stimulated by >50% upon addition of H₂O₂ (0.5 mM). Concentrated culture filtrates ofPhanerochaete produced ethylene from methional, a reaction that has been used as an indicator of hydroxyl radical generating systems. However, the ethylene-generating activity and the demethylase activity in such preparations showed different purification and stability characteristics. Pure horseradish peroxidase and H₂O₂ demethylated polyguaiacol and produced ethylene from methional.Phanerochaete does produce H₂O₂, so our demethylase activity appears to be similar to a peroxidase, although we have not yet determined the identity of the methyl product of either enzyme preparation. We suspect that the demethylase operates by a freeradical mechanism, and that the methyl product released is likely to be methanol. Confirmation of these hypotheses provides the basis for our future work with this novel fungal enzyme system.     

Phanerochaete mutants with enhanced ligninolytic activity

In addition to lignin, the white rot fungusPhanerochaete chrysosporium has the ability to degrade a wide spectrum of recalcitrant organopollutants in soils and aqueous media. Most of the organic compounds are degraded under ligninolytic conditions with the involvement of the extracellular enzymes, lignin peroxidases, and manganese-dependent peroxidases, which are produced as secondary metabolites triggered by conditions of nutrient starvation (e.g., nitrogen limitation). The fungus and its enzymes can thus provide alternative technologies for bioremediation, biopulping, biobleaching, and other industrial applications. The efficiency and effectiveness of the fungus can be enhanced by increasing production and secretion of the important enzymes in large quantities and as primary metabolites under enriched conditions. One way this can be achieved is through isolation of mutants that are deregulated, or are hyperproducers or supersecretors of key enzymes under enriched conditions. Through UV-light and γ-ray mutagenesis, we have isolated a variety of mutants, some of which produce key enzymes of the ligninolytic system under high-nitrogen growth conditions. One of the mutants, 76UV, produced 272 U of lignin peroxidases enzyme activity/L after 9 d under high nitrogen (although the parent strain does not produce this enzyme under these conditions). The mutant and the parent strains produced up to 54 and 62 U/L, respectively, of the enzyme activity under lownitrogen growth conditions during this period. In some experiments, the mutant showed 281 U/L of enzyme activity under high nitrogen after 17 d.

     

Enzyme-Mediated Bacterial Biodegradation of an Azo Dye (C.I. Acid Blue 113): Reuse of Treated Dye Wastewater in Post-Tanning Operations

“Dyeing” is a common practice used to color the hides during the post-tanning operations in leather processing generating plenty of wastewater. The waste stream containing dye as pollutant is severely harmful to living beings. An azo dye (C.I. Acid Blue 113) has been biodegraded effectively by bacterial culture mediated with azoreductase enzyme to reduce the pollution load in the present investigation. The maximum rate of dye degradation was found to be 96?±?4 and 92?±?4 % for the initial concentrations of 100 and 200 mg/l, respectively. The enzyme activity was measured using NADH as a substrate. Fourier transform infrared spectroscopy (FT-IR) analysis was confirmed that the transformation of azo linkage could be transformed into N₂ or NH₃ or incorporated into complete biomass. Breaking down of dye molecules to various metabolites (such as aniline, naphthalene-1,4-diamine, 3-aminobenzenesulfonic acid, naphthalene-1-sulfonic acid, 8-aminonaphthalene-1-sulfonic acid, 5,8-diaminonaphthalene-1-sulfonic acid) was confirmed by gas chromatography and mass spectra (GC-MS) and mass (electrospray ionization (ESI)) spectra analysis. The treated wastewater could be reused for dyeing operation in the leather processing, and the properties of produced leather were evaluated by conventional methods that revealed to have improved dye penetration into the grain layer of experimental leather sample and resulted in high levelness of dyeing, which helps to obtain the desired smoothness and soft leather properties.     

Evaluation of Photocatalytic Activity by Dye Decomposition

A novel rapid evaluation method for the photocatalytic activity of TiO₂ thin films was developed. An organic dye with a polyvinyl alcohol (PVA) binder was spin coated on the TiO₂ thin film, and the decrease in the absorbance of the dye's absorption peak during UV light irradiation was measured. Acid Blue 9 (Brilliant Blue FCF; CI-42090) could be used as the probe, while Methylene Blue (CI-52015) was not applicable to this method because of the reversible color change after the UV irradiation was stopped. PVA has virtually no interaction with oxidizing radicals, therefore, it is regarded as a simple binder holding dye molecules in the coated dye-PVA film. It was found that the ambient humidity during the UV irradiation strongly accelerates the discoloration rate of the dye, probably due to the increase in the photogenerated oxidizing radicals on the TiO₂ surface. This dye discoloration could be explainedby the one-dimensional diffusion model with a first order reaction.     

Development of new dyeing photoinitiators based on benzylideneimidazopyridine dyes

Several dyes containing benzylideneimidazopyridine moiety (BIPDs) were synthesized and evaluated as photoinitiators for free‐radical polymerization induced with the visible emission of an argon‐ion laser. One method of dye structure change was applied in our study. The modification was based on the character of the substituent introduced into both the imidazopyridine skeleton and phenyl ring. Several different groups were tested including heavy atoms (? CI, ? Br) as well as electron‐accepting (? NO₂), and electron‐donating groups [? N(CH₃)₂, ? OCH₃]. Analysis of the dye properties demonstrated that there is a significant heavy atom effect on the photoinitiation ability of the novel dyes in both cases, for example, when a heavy atom is introduced into the phenyl ring as well as into the imidazopyridine part of the molecule. The introduction of an electron‐acceptor or electron‐donor group into the phenyl part of the dye caused a dramatic decrease in its photosensitivity. The type of applied counterion had no effect on the overall sensitivity of a dye. BIPDs are not particularly good photoinitiators. Further modification of the dye structure involved the elimination of the motion of a C?C bond by the coplanarization of the styrylium residue with other parts of the dye. This approach decreased the degree of branching of the dye, which stabilized the molecule in its excited state. The formed dye, quinoline[2,3‐b]‐2,3‐dihydro‐1H‐imidazo[1,2‐a]pyridinium bromide (QDIPB), exhibited dramatically enhanced sensitivity. QDIPB possessed broad structured spectra with a long‐wavelength part shifted to the blue as compared to other BIPD dyes. The change of the absorption spectra and its high photoinitiation ability makes QDIPB a good candidate for the photoinitiating system applied in dental restorative materials. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3048–3055, 2003     

Titania nanowires as substrates for sensing and photocatalysis of common textile industry effluents

Sensing and photocatalysis of textile industry effluents such as dyes using mesoporous anatase titania nanowires are discussed here. Spectroscopic investigations show that the titania nanowires preferentially sense cationic (e.g. Methylene Blue, Rhodamine B) over anionic (e.g. Orange G, Remazol Brilliant Blue R) dyes. The adsorbed dye concentration on titania nanowires increased with increase in nanowire dimensions and dye solution pH. Electrochemical sensing directly corroborated spectroscopic findings. Electrochemical detection sensitivity for Methylene Blue increased by more than two times in magnitude with tripling of nanowire average length. Photodegradation of Methylene Blue using titania nanowires is also more efficient than the commercial P25-TiO₂ nanopowders. Keeping illumination protocol and observation times constant, the Methylene Blue concentration in solution decreased by only 50% in case of P25-TiO₂ nanoparticles compared to a 100% decrease for titania nanowires. Photodegradation was also found to be function of exposure times and dye solution pH. Excellent sensing ability and photocatalytic activity of the titania nanowires is attributed to increased effective reaction area of the controlled nanostructured morphology.     

(M)‐ and (P)‐8‐[(1S,2R)‐2‐hydroxy‐1‐methyl‐2‐phenylethyl]‐8‐methyl‐8,9‐dihydro‐7H‐dinaphth[2,1‐c:1′,2′‐e]azepinium bromide solvates

The title compounds are diastereoisomers with antipodean axial chirality. The M isomer crystallizes as a (1/3) acetone solvate, C₃₂H₃₀NO⁺·Br^?·3C₃H₆O, while the P isomer crystallizes as a (1/1) di­chloro­methane solvate, C₃₂H₃₀NO⁺·Br^?·CH₂Cl₂. In each structure, O—H?Br hydrogen bonds link the cations and anions to give ion pairs. The seven‐membered azepinium ring adopts the usual twisted‐boat conformation and its ring strain causes a slight curvature of the plane of each naphthyl ring.