LC/MS and LC/MS/MS based protocol for identification of dyes in historic textiles

Identification of dyes in historic textiles was until recently only based on reversed phase liquid chromatography and diode-array detection (RPLC–DAD). Although in the last years mass spectrometry (MS) is increasingly used as a detection system for liquid chromatography, most applications in the field are directed to identification of the molecular ions or in studies dedicated to degradation products which may be used as markers in RPLC–DAD. In the present work, an analytical protocol for the identification of dyes using RPLC/ESI/MS is presented. Atmospheric pressure electrospray ionization (ESI) was applied, in the negative ion monitoring mode. Both single stage and tandem MS (MS/MS) approaches were considered. An ion trap was used as mass analyzer. Experiments are based on the characterization of standards (natural dyes and/or dyed fibers) with the mass spectrometer sequentially working in the following modes: single MS/full scan, followed by plotting chromatograms through ion extraction (IEC) according to mass/charge ratios corresponding to molecular ions; single MS/selected ion monitoring (SIM) mode; tandem MS/single reaction monitoring (SRM) mode; tandem MS/multiple reactions monitoring (MRM) or product ion scanning modes. A faster chromatographic separation could be applied as MS detection readily balanced the selectivity of the analytical process. In a case study, 11 dyes from 3 biological sources were detected in a 0.5 mg historic sample.     

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.     

Synthesis and single-crystal X-ray diffraction analysis of new heterocyclic coloured materials. 3-Arylazo-8H-imidazo[1,2-b] pyrazolo[4,3-d]pyridazines

A simple synthetic strategy is described for the hitherto unreported 3-arylazo-8H-imidazo[1,2-b]pyrazolo[4,3-d]pyridazines 7 is described based on the reaction of 3-acetyl-4-cyano-1,5-diphenylpyrazole hydrazone 3 with the hydrazonoyl halides 1a-l. The structures of such dyes were confirmed by spectroscopic and X-ray crystallographic analyses. The mechanism of formation of such compounds was also discussed.     

Non‐covalent Versus Covalent Control of Self‐Assembly and Chirality of Nile Red‐modified Nucleoside and DNA

A DNA‐based covalent versus a non‐covalent approach is demonstrated to control the optical, chirooptical and higher order structures of Nile red ( Nr ) aggregation. Dynamic light scattering and TEM studies revealed that in aqueous media Nr ‐modified 2′‐deoxyuridine aggregates through the co‐operative effect of various non‐covalent interactions including the hydrogen bonding ability of the nucleoside and sugar moieties and the π‐stacking tendency of the highly hydrophobic dye. This results in the formation of optically active nanovesicles. A left‐handed helically twisted H‐type packing of the dye is observed in the bilayer of the vesicle as evidenced from the optical and chirooptical studies. On the other hand, a left‐handed helically twisted J‐type packing in vesicles was obtained from a non‐polar solvent (toluene). Even though the primary stacking interaction of the dye aggregates transformed from H→J while going from aqueous to non‐polar media, the induced supramolecular chirality of the aggregates remained the same (left‐handed). Circular dichroism studies of DNA that contained several synthetically incorporated and covalently attached Nr ‐modified nucleosides revealed the formation of helically stacked H‐aggregates of Nr but—in comparison to the noncovalent aggregates—an inversed chirality (right‐handed). This self‐assembly propensity difference can, in principle, be applied to other hydrophobic dyes and chromophores and thus open a DNA‐based approach to modulate the primary stacking interactions and supramolecular chirality of dye aggregates.     

Photo Catalytic Degradation of Azo Dyes over Mn2+ Doped TiO2 Catalyst under UV/Solar Light:An Insight to the Route of Electron Transfer in the Mixed Phase of Anatase and Rutile

Mn²⁺ ion was doped into the TiO₂ matrix and its photocatalytic activity was evaluated for the degradation of a mono azo dye methyl orange (MO) and a di‐azo dye brilliant yellow (BY) under UV/solar light. X‐ray diffraction results revealed the phase transformation from anatase to rutile due to the inclusion of Mn²⁺ ion into the TiO₂ matrix. All the doped catalysts showed a red shift in the band gap to the visible region. The degradation reaction of the dyes was found to be dependent on its structure. It was found that mono azo dye degrades faster than di azo dye under UV/solar light. The rate constant under identical conditions calculated for the degradation of MO is 2.4 times (under UV light) and 4.5 times (under solar light) higher compared to BY. Among the photocatalysts studied, Mn²⁺(0.06 at.%)‐TiO₂ showed higher activity under both UV and solar light illumination. The synergestic effect in the bicrystalline framework of anatase and rutile effectively suppresses the charge carrier recombination and enhances the photocatalytic activity. The degradation reaction was followed by UV‐visible spectroscopy and the photoproducts formed were analyzed by GC‐MS techniques.     

Magnetic solid‐phase extraction and ultrafast liquid chromatographic detection of Sudan dyes in red wines,juices, and mature vinegars

A nanocomposite of polystyrene‐coated magnetic nanoparticles was successfully synthesized and employed as adsorbent for magnetic solid‐phase extraction of four Sudan dyes (I, II III, and IV) in red wines, juices, and mature vinegars. The prepared magnetic nanoparticles with highly hydrophobic properties have excellent adsorption capacity for these lipophilic Sudan dyes. Extraction conditions were optimized. Experimental results showed that the recoveries of the four Sudan dyes were very satisfactory when 70 mg of polystyrene‐coated magnetic nanoparticles were used and the extraction could be completed within 20 min. It was proved that these magnetic nanoparticles can be reused after an easy washing process. By coupling the magnetic solid‐phase extraction with ultrafast liquid chromatography‐ultraviolet spectrometry, a rapid, green, effective, and sensitive method for the determination of Sudan dyes was developed. The LOD for Sudan I, Sudan II, Sudan III, and Sudan IV were 0.0039, 0.0063, 0.0057, and 0.017 ng/mL, respectively. Recoveries obtained by analyzing spiked water samples at three concentration levels (0.1, 1.0, and 10.0 ng/mL) were between 76.3 and 96.6%. The intra‐ and interday RSDs for the analytes were lower than 9.6%.     

新型D-π-A类敏化太阳电池染料及其应用

功能性有机染料在染料敏化太阳能电池领域具有重要的应用前景,电子给体、π共轭桥和电子受体（D-π-A）结构的染料是其中重要的组成类型.本文主要依据三苯胺和吲哚啉等取代苯胺为电子给体染料的结构设计,并结合本课题组的相关工作,综述了2008年以来此类D-π-A光敏染料的光电转换性能的研究进展.     

Influence of Solvent and Bridge Structure in Alkylthio‐Substituted Triphenylamine Dyes on the Photovoltaic Properties of Dye‐Sensitized Solar Cells

Three new triphenylamine dyes that contain alkylthio‐substituted thiophenes with a low bandgap as a π‐conjugated bridge unit were designed and synthesized for organic dye‐sensitized solar cells (DSSCs). The effects of the structural differences in terms of the position, number, and shape of the alkylthio substituents in the thiophene bridge on the photophysical properties of the dye and the photovoltaic performance of the DSSC were investigated. The introduction of an alkylthio substituent at the 3‐position of thiophene led to a decrease in the degree of redshift and the value of the molar extinction coefficient of the charge‐transfer band, and the substituent with a bridged structure led to a larger redshift than that of the open‐chain structure. The introduction of bulky and hydrophobic side chains decreased the short‐circuit photocurrent (J_sc), which was caused by the reduced amount of dye adsorbed on TiO₂. This resulted in a decrease in the overall conversion efficiency (η), even though it could improve the open‐circuit voltage (V_oc) due to the retardation of charge recombination. Furthermore, the change in solvents for TiO₂ sensitization had a critical effect on the performance of the resulting DSSCs due to the different amounts of dye adsorbed. Based on the optimized dye bath and molecular structure, the ethylene dithio‐substituted dye ( ATT3 ) showed a prominent solar‐to‐electricity conversion efficiency of 5.20 %.     

Polymethine dyes as spectral-fluorescent probes for biomacromolecules

It is known that polymethine dyes (PD) can form complexes with biomacromolecules, in which, as a rule, fluorescence buildup is observed. In addition, PD possess a unique property to form ordered aggregates of different types (dimers, H- and J-aggregates) both in the free state and on biomacromolecules as templates. This creates a basis for application of PD as spectral-fluorescent probes for biomacromolecules, which is a matter of this review. Besides, the review is devoted to studies of noncovalent interactions of PD with biomacromolecules: nucleic acids, proteins, and some others.