Fading Of Dyes Research Articles

Transparent tissue in solid state for solvent-free and antifade 3D imaging

Optical clearing with high-refractive-index (high-n) reagents is essential for 3D tissue imaging. However, the current liquid-based clearing condition and dye environment suffer from solvent evaporation and photobleaching, causing difficulties in maintaining the tissue optical and fluorescent features. Here, using the Gladstone-Dale equation [(n−1)/density=constant] as a design concept, we develop a solid (solvent-free) high-n acrylamide-based copolymer to embed mouse and human tissues for clearing and imaging. In the solid state, the fluorescent dye-labeled tissue matrices are filled and packed with the high-n copolymer, minimizing scattering in in-depth imaging and dye fading. This transparent, liquid-free condition provides a friendly tissue and cellular environment to facilitate high/super-resolution 3D imaging, preservation, transfer, and sharing among laboratories to investigate the morphologies of interest in experimental and clinical conditions.

Digital Unfading of Chromogenic Film Informed by Its Spectral Densities

A material-based approach for the digital restoration of chromogenic photographic and film materials affected by dye fading is proposed. Through a digital reconstruction of the original optical properties, the proposed restoration methodology approximates the original color appearance in a non-subjective manner, thus improving the results compared to conventional RGB tonal re-adjustment of the film scan both in terms of quality and presumed faithfulness to original appearance. In order to do so, the degree of fading is derived from neutral black parts of the film’s image content, and the knowledge of the film material’s spectral densities is used to digitally reconstruct the colors corresponding to the material’s original dye concentrations and render them in an RGB space. For a comparison, results from conventional re-grading were adjusted to render them most similar—and thus comparable—to the results of the proposed spectrally informed digital unfading. The restored images obtained through spectrally informed unfading were deemed clearly superior in terms of color subtlety, color faithfulness and coherence.

Hydroxypropyltrimethyl Ammonium Chloride Chitosan Nanoparticles Coatings for Reinforcement and Concomitant Inhibition of Anionic Water-Sensitive Dyes Migration on Fragile Paper Documents.

The fragile paper is treated to improve the stability and appearance of the paper artifact, such as washing, lining, deacidification, and reinforcement. During the above treatments, paper documents inevitably make contact with water directly, leading to the appearance change, stability decrease, and migration or fading of anionic water-sensitive dyes, which are seriously harmful to information security. Herein, Hydroxypropyltrimethyl ammonium chloride chitosan (HACC) nanoparticles were employed for the reinforcement and concomitant inhibition of anionic water-sensitive dye migration on fragile paper. HACC nanoparticles were prepared through physical ball grinding method and characterized via LPSA, SEM, TEM, XRD and FTIR. To evaluate the protective potential of HACC nanoparticles coating, the chemical and mechanical properties of coated and uncoated papers were evaluated after dry heat and hygrothermal accelerated aging. Additionally, good color stability of anionic water-sensitive dyes was observed on the paper coated with HACC nanoparticles after lining technology. Finally, the interaction mechanism between the anionic water-sensitive dyes and HACC nanoparticles was analyzed using an ultraviolet spectrophotometer and FTIR. The as-proposed technique can provide technical support to improve the mechanical properties of fragile paper and enhance the anionic water-sensitive dyes stability in the aqueous phase.

Multifunctional Liquid‐Free Ionic Conductive Elastomer Fabricated by Liquid Metal Induced Polymerization

AbstractNovel liquid‐free ionic conductive elastomers are fabricated by the polymerization of acrylic acid (AA) in polymerizable deep eutectic solvent (PDES). Liquid metal (LM) nanodroplets are used to initiate and further cross‐link polyacrylic acid (PAA) chains into a liquid‐free polymeric network without any extra initiators and cross‐linkers. The resulting liquid‐free ionic conductive elastomers exhibit high transparency (94.1%), ultra‐stretchability (2600%), and autonomous self‐healing. Spin trapping electron paramagnetic resonance and dye fading experiments reveal the generation of free radicals. UV–visible spectrometry and viscosity tests demonstrate the cross‐linking effect of Ga3+. The gelation time is much shorter than that of the conventional ammonium persulfate thermal initiation process. Furthermore, this liquid‐free polymer material is intrinsically resistant to freezing and drying, enabling it to operate under harsh conditions. In consideration of transparency, self‐healing, ultra‐stretchability, moldability, and sensory features, the resulting elastomeric conductor may hold promise for industrial applications in wearable devices, force mapping, and flexible electroluminescent devices.

The Body Was There

The Body Was There Shakarean Hutchinson (bio) Click for larger view View full resolution Photo by Patty O'Hearn Kickham [End Page 102] Six months later she was pregnant. The curves of her hips opened up; her breasts grew heavy. The blue cotton dress, the dye fading into something lighter and unhappy, whispered the secrets of her changing body to those who made it their business to know what was happening with the women on Bilkens Farm. [End Page 103] Patty was one of those women. She'd been born on Bilkens Farm sometime during the 1820s, when Bilkens's father still ran the plantation. Her weathered face showed the signs of years of rice work, and her hands were nearly permanently callused and chafed. She kept a watch on all the young girls, particularly those who were married off on Marriage Day. During the day, as she directed the cutting of the rice stalks into large piles waiting to be stripped of their grains, she studied all the women slaves that came into her view. Young girl. Teenaged girl. Woman. After a woman's gray hair grew in and the lines in her face settled deep into her face, Patty knew she could stop watching them. But until that point, Patty diligently monitored the women's midsections for any signs of growth, their swollen feet. She even sniffed around the fields and the cabins at night for the acidic smell of bile held in the heated South Carolina air. For Patty, her mission, her main job on Bilkens Farm, was to catch every single pregnancy. She hadn't missed one yet. Tenah was easy to spot. She worked at the rice fields with Patty and an old woman named Mitilde, who didn't need monitoring. Mitilde was the elder of the plantation, the one the rest of the slaves listened to first, forging a respect Bilkens himself didn't have with the rest of the people. She was trusted by the Bilkens family. And it was Mitilde whom Patty went to first when she saw that Tenah wasn't as stick thin as she had been. When Tenah's body formed more of a shape. When Tenah looked less like the teenaged girl waiting for her name to be called during Marriage Day and more like a woman. It could be just her filling out, Mitilde had said. But Patty was never wrong. Mitilde nodded and went to the women in the kitchen and asked them to brew the tea. She handed them a Carolina jessamine already in full bloom, its petals opened out, the tips slightly downward. The kitchen women didn't need an explanation. They brewed the pale brown tea, poured it into a gray porcelain coffee mug with a chip on the top rim, and handed the drink to Mitilde, who gave it to Patty. Who stood outside Tenah and Grafton's cabin just before dawn, the heat of the mug warming her hands in the cool of predawn. Patty looked over her shoulder every so often, making sure one of the overseers or Bilkens himself hadn't found her standing outside the cabins and not getting herself ready for the day of work. She watched the sun as it slowly inched up over the horizon. Her right foot tapped against the splitting wood step. She knew she would be expected to be at her position by the time the sun offered sufficient light in the sky. She didn't want to have to hustle to get there. [End Page 104] The door to the cabin squeaked open, and Tenah stood in the doorway. She was wearing her blue dress that was starting to fade more into the idea of blue. She took a step back inside when she saw Patty standing just beyond the stairs, looking up toward the sun. She didn't like Patty all that much. She was nosy, impatient, and bossy, and Tenah didn't understand why she was in charge of the rice stalks, work that needed time management. There were already Bilkens and the overseers and even Mitilde. She would never share it, but in Tenah's opinion, there didn...

Improved garment longevity and reduced microfibre release are important sustainability benefits of laundering in colder and quicker washing machine cycles

The global impact of laundering clothing is significant, with high levels of water, energy use, and pollution associated with this consumer care process. In this research, the impacts of washing temperature and washing time on garment colour loss (dye fading), colour transfer (dye staining), and microfibre release were evaluated using retail consumer clothing. Significantly greater colour loss and greater colour transfer were observed for a 40 °C, 85 min wash cycle compared to a cold-quick (25 °C; 30 min) cycle. Desorbing dyes were found to mainly be reactive dyes. From fundamental kinetic studies, it was observed that significant increases in both rate of dye desorption and total dye desorption occurred when increasing from 20 °C to 40 °C, but the difference in dye release between 40 °C and 60 °C was not as significant; the same kinetic trends were observed for dye transfer. Microfibre release was significantly greater for the 40 °C, 85 min cycle in comparison with the cold-quick cycle, and this effect continued with further washes. These results mean that reducing time and temperature in laundry could have a significant impact in terms of extended garment longevity and reduced dye and microfibre liberation into the environment, in addition to energy savings.

Dressing protective clothing: stabilizing alizarin/halloysite hybrid pigment and beyond

The fading of organic dyes is a serious challenge for conservation of art works. Inspired by the ancient Maya blue pigment, a hybrid pigment of halloysite (Hal) and alizarin (AZ) was prepared by adsorption in aqueous solution. In addition, a layer of polyorganosilane (POS) is used to cover the surface of the hybrid pigment to enhance the chemical resistance and photostability. The hybrid pigments were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy and thermal analysis. The adsorption behavior of AZ onto Hal was investigated and optimized. AZ-Hal hybrid pigment was prepared at pH = 9. Chemical stability was checked by 1 mol/L HCl, 1 mol/L NaOH and ethanol attack. Photostability was evaluated by exposing the pigment to visible light for 360 h, which is equal to more than 28 years in a common museum. AZ molecules were adsorbed on the external and/or internal surface via physical adsorption and hydrogen bonds. The presence of POS in the hybrid pigment influences positively the chemical and light resistance. This may be due to the protective layer that isolates sensitive dyes and oxidising agents.

The Pivotal Role of Student Labor in the Clarke Historical Library's Moving Image Access and Preservation Project

The Pivotal Role of Student Labor in the Clarke Historical Library's Moving Image Access and Preservation Project Marian J. Matyn (bio) and Tressa Graves (bio) INTRODUCTION TO THE CLARKE, ITS INSTITUTIONAL CONTEXT, AND ITS HOLDINGS The Clarke is both a historical library and archives.1 It is one of the major archives and historical libraries in the state of Michigan and the only one in the northern Lower Peninsula. Its major collecting focus is Michigan history, children's literature, and Central Michigan University (CMU) archives. While the primary-source collections include a wide variety of formats, moving image film constitutes only a small part of the overall collection. Of the nearly 8,000 cubic feet of archival collections in the Clarke stacks, approximately 110 cubic feet are 8mm and 16mm films (450,000 linear feet total). Summary Information on AV Materials in the Clarke Most of the Clarke's films are 16mm acetate film stock, although there is also a small number of 8mm films. The majority of the Clarke's film materials are a part of the Channel 9 & 10 News Collection, 1950s–1980s. Channel 9 & 10 was and remains the main TV news station for the thirty-five counties in the northern Lower Peninsula of Michigan, the entire Upper Peninsula, and parts of Canada. The initial estimate was that the Channel 9 & 10 Collection totaled approximately three thousand reels of film shelved in seventy cubic feet of archival shelving in variously sized containers. These films are the only extant copies of the station's news production from the period. Other films in the Clarke's collection, mostly with a Michigan or CMU focus, are distributed throughout numerous paper-based archival collections and total an additional 20,500 linear feet. [End Page 27] Identification of Significant Subsections of the AV Collection and Their Challenges The main issues faced are lack of description, lack of donor forms, and some level of physical deterioration. No particular series or subseries is in worse condition than another. One CMU film, Football Scrimmage (September 1950), has significant acetate decay and a strong vinegar odor. Seventeen reels of the Channel 9 & 10 News Collection are fused together in a solid mass, an issue known as blocking, thus leaving the films unviewable and unidentifiable. Several Channel 9 & 10 News clips have color dye fading and are now magenta hued. The Clarke has inadequate funds for conservation or digitization of these few films that are badly deteriorated. In the case of Football Scrimmage, it is possible that we will be able to find a CMU alum who will be willing to pay for digitization of the film. Not knowing what is on the blocked films makes it hard to find donors. Many small manuscript-focused archives with film collections are unaware that the International Federation of Film Archives (FIAF) exists and is willing to help them locate other archives better able to care for their film.2 Staff Context of the Archives and Identification of the Authors/Project Leaders The Clarke has six full-time staff members and student employees, none of whom is trained or educated in film access and preservation. Until 2011, archivist Marian Matyn was a lone arranger archivist. Although there are now two archivists, moving images are not part of the newer archivist's responsibility. Matyn and undergraduate student Tressa Graves began the project in 2012 to identify, rehouse, preserve, and make accessible the archival film collections. Neither Matyn nor Graves was a film specialist when the project began, although Graves had interned during summer 2012 at the Alaska Film Archives at the University of Alaska Fairbanks. When planning the project, Matyn and Graves lacked established backgrounds, education, and extensive experience with film. Prior to the film preservation and access project, only very basic archival housing and description were completed for films. Significantly, the Clarke is the first university archives in Michigan to embark on a film access and preservation project. The Henry Ford, located 152 miles southeast of CMU, was the first Michigan cultural heritage institution to initiate a film preservation project. The Clarke was the second institution in the state to do so, closely followed by Michigan State University (MSU...

Micellar rate effects on the kinetics of nitrophenol violet anion reaction with HO– ion: Comparing Piszkiewicz's, Berezin's, and Pseudophase Ion-Exchange models

Triphenylmethine dyes are often used as the probes for studying the properties of micellar media and other organized solutions and the influence of the latter on the kinetics of the reactions. The reports by different authors are mainly devoted to the study of the accelerated alkaline fading of cationic triphenylmethine dyes, Ct+, in micelles of cationic surfactants, whereas the presence of anionic surfactants strongly decelerates the reaction Ct+ + HO– → carbinol. At the same time, the anionic dyes interact with hydroxide ion much more slowly even in cationic surfactant micelles. For instance, as shown by Grunwald and Duynstee as early as 1959, for a sulfonephthalein dye bromophenol blue anion, BPB2−, the reaction occurs so slowly that it is impossible to determine the rate constant. Hence, all the regularities of the nucleophilic attack of the hydroxide ion in cationic micelles were until now studied using cationic dyes. Therefore, it seemed to be significant to find an anionic triphenylmethine dye electrophilic enough to examine the rate of its reaction with alkali in the presence of cationic surfactants. As such a dye, we used another sulfonephthalein dye, nitrophenol violet, NPV (3,3′-dinitrophenolsulfonephtalein), which meet the above condition. Indeed, it was possible not only to (quantitatively) describe the decelerating effect of cationic micelles on the reaction NPV2− + HO−, but also utilize it for comparing the most popular Piszkiewicz's, Berezin's, and Pseudophase Ion-Exchange models of micellar kinetics in CTAB and CTAOH solutions. Zwitter-ionic, non-ionic, and anionic surfactants were used as well. The obtained results allow generalizing the concept of micellar effects on the kinetics of nucleophilic attack and validating the above-mentioned theories. Also, the results demonstrate the usefulness of the dye NPV for studying of the nucleophilic attack in systems with positively charged colloidal particles. For instance, in addition to the electrostatic deceleration of the reaction between two anions on lowering the polarity of the medium it was shown that the cationic head groups in the Stern layer display a “diverting” influence on the HO– ion.

Characterisation and photocatalytic assessment of TiO2 nano-polymorphs: Influence of crystallite size and influence of thermal treatment on paint coatings and dye fading kinetics

A study on the thermal effects on TiO2 rutile and anatase nano-powders was undertaken and displayed some unusual photoactivity and crystal structure properties. Rutile nano-particles with different crystallite sizes were characterised and the possible effect on activity were investigated. One of the rutile samples appeared to have trace amounts of anatase and was annealed at high temperatures at 1172 K and 1272 K to highlight the thermodynamic stability phenomenon of titania. Parallel to this study, anatase nano-particles were investigated before and after being annealed up to 1022 K. For all the samples used in this work, characterisation was undertaken using micro-Raman microscopy/XRD and Scanning Electron Microscopy (SEM) while photoactivity assessment was made by measuring and monitoring the photodegradation of a mixture of dye methyl-orange (MeO) and nano-powders under UV-light for 3h30 min in suspension. The study revealed that rutile nano-powder samples were thermodynamically stable even at very high temperatures and poorly active but with an unusual photoactive feature. Concerning the anatase samples; SEM investigation revealed a questioning size growth as the samples showed a different particle size depending on the temperature of thermal treatment. It revealed that annealing at 672 K seemed to be a key temperature as the particles change from a polyhedral structure to a two-dimensional structure showing a platelet like shape. The photocatalytic studies of the anatase nano-particles showed a very high activity especially before annealing. This highlighted the fact that the anatase phase can subsist at high temperatures such as 1022 K and exhibit a persistence in photoactivity even though it has decreased significantly after 672 K. SEM analysis was in accordance with the photoactivity investigation. Nevertheless, the most interesting feature of the results emanates from the reaction order study and rate constant analysis taken from the kinetic shape of the graph of the degradation of MeO as a function of the irradiation time for the different particle sized rutile nanoparticles. Here a zero-order reaction was determined and as a consequence raised questions about the theory of the mechanism of the activities of titania in terms of surface chemistry, surface area dependence and photoactivity. For example, for the nano-rutiles the sample with a 25 nm crystallite size was the most active and the sample with the smallest crystallite size (15 nm) was the least active and yet was found to contain trace levels of nano-anatase. This effect was also substantiated by UV absorption and weathering studies on doped isocyanate-acrylic paint films. UV analysis clearly shows that the absorptivity of the nanoparticles plays a role and correlates with the photoactivity. The 15 nm particles have decreased absorptivity in the near UV and hence decreased activity.

Trametes villosa Lignin Peroxidase (TvLiP): Genetic and Molecular Characterization.

White-rot basidiomycetes are the organisms that decompose lignin most efficiently, and Trametes villosa is a promising species for ligninolytic enzyme production. There are several publications on T. villosa applications for lignin degradation regarding the expression and secretion of laccase and manganese peroxidase (MnP) but no reports on the identification and characterization of lignin peroxidase (LiP), a relevant enzyme for the efficient breakdown of lignin. The object of this study was to identify and partially characterize, for the first time, gDNA, mRNA, and the corresponding lignin peroxidase (TvLiP) protein from T. villosa strain CCMB561 from the Brazilian semiarid region. The presence of ligninolytic enzymes produced by this strain grown in inducer media was qualitatively and quantitatively analyzed by spectrophotometry, qPCR, and dye fading using Remazol Brilliant Blue R. The spectrophotometric analysis showed that LiP activity was higher than that of MnP. The greatest LiP expression as measured by qPCR occurred on the 7th day, and the ABSA medium (agar, sugarcane bagasse, and ammonium sulfate) was the best that favored LiP expression. The amplification of the TvLiP gene median region covering approximately 50% of the T. versicolor LPGIV gene (87% identity); the presence of Trp199, Leu115, Asp193, Trp199, and Ala203 in the translated amplicon of the T. villosa mRNA; and the close phylogenetic relationship between TvLiP and T. versicolor LiP all indicate that the target enzyme is a lignin peroxidase. Therefore, T. villosa CCMB561 has great potential for use as a LiP, MnP, and Lac producer for industrial applications.

6‐Pyridinium benzo[a]phenazine‐5‐oxide derivatives as visible photosensitisers for polymerisation

Several 6‐pyridinium benzo[a]phenazine‐5‐oxide derivatives have been synthesised and characterised by proton nuclear magnetic resonance spectroscopy and mass spectrometry. The spectroscopic and electrochemical properties of these dyes were examined. The dyes were used as reducible sensitisers for selected electron donors (phenylthioacetic acid, phenoxyacetic acid, N‐phenylglycine, and ethyl 4‐N,N‐dimethylaminobenzoate) and as oxidisable sensitisers for electron acceptors (onium and N‐alkoxypyridinium salts). These photoredox pairs were found to be effective visible‐wavelength photoinitiators for the free radical polymerisation of trimethylolpropane triacrylate under visible light. The cationic photopolymerisation of cyclohexene oxide by the studied dyes and the onium salt photoredox pairs was ineffective. The obtained results are discussed on the basis of both free energy change for electron transfer to or from the benzo[a]phenazine dyes and the photochemical properties of the dyes, particularly their photobleaching. The proposed mechanism of dye fading is supported by density functional theory calculations and spectroscopic characterisation of the radical cation of the dye.

Correction to: How complexing with a small number of transition metal ions can prevent dye fading

Correction to: How complexing with a small number of transition metal ions can prevent dye fading

Kinetics of Fading of Some Triphenylmethane Dyes: Effects of Electric Charge, Substituent, and Aqueous Binary Mixtures of Dimethyl Sulfoxide and 2‐Propanol

ABSTRACTThe rate constants of alkaline fading of a number of triphenylmethane (TPM) dyes including methyl green (ME2+), brilliant green (BG+), fuchsin acid (FA2−), and bromophenol blue (BPB2−) were obtained in aqueous binary mixtures of 2‐propanol (protic solvent) and dimethyl sulfoxide (DMSO) (aprotic solvent) at different temperatures. It was observed that the reaction rate constants of BG+ and ME2+ increased and those of FA2− and BPB2− decreased with an increase in weight percentages of aqueous 2‐propanol and DMSO binary mixtures. 2‐Propanol and DMSO interact with the used TPM molecules through hydrogen bonding and ion–dipole interaction, respectively, in addition to their hydrophobic interaction with TPM dyes. The fundamental rate constants of a fading reaction in these solutions were obtained by the SESMORTAC model. Also, the effect of electric charge and substituent groups of a number of TPM dyes on their alkaline fading rate was studied.

How complexing with a small number of transition metal ions can prevent dye fading

In an earlier study of the effect of transition metal ions on the production of singlet oxygen by dyes it was found that four ions, namely Cu(2+), Ni(2+), Co(2+) and Co(3+) suppress singlet oxygen production altogether, provided the dyes are made ligands in coordination complexes of the ions. By this the fading half-life of the dyes is prolonged by at least 1000 times. This article is a mechanistic interpretation of the observed phenomena as well as an appreciation of their practical consequences. Enclosing the dyes together with the operative ions in coordination complexes circumnavigates the spin prohibition that separates the triplet excited state of the dye from its ground state. It does so by replacing the spin-forbidden step with two faster steps. The first is the transition of the highest energy electron of the excited state to a transient ionic state, the second is the transition from the ionic state to the ground state of the dye. The second transition is spin forbidden, but it is powerfully accelerated by the heavy-atom-effect of the ionic nucleus. This makes it possible to design colorants that are virtually fade-proof.

Colour Fading of Textile Fabric by Plasma Treatment

Colour fading of a reactive dye (C.I. Reactive Blue 19) dyed textile fabric was performed by atmospheric pressure plasma (APP) treatment with the use of plasma jet. Under the APP treatment condition of treatment time = 5 sec/mm; ignition power = 160 W; oxygen concentration = 1%; jet distance = 3 mm, significant colour-fading effect was achieved. For comparison purpose, the reactive dye dyed textile fabric was subjected to conventional enzymatic colour-fading process. Experimental results revealed that the APP-induced colour-fading effect was comparable with conventional enzymatic colour-fading process.

Effects of Low-Oxygen Environments in the Light Fading of Six Dyes Present in the Autochrome Color Screen

Because the dyes present in the autochrome color screen are extremely sensitive to light, autochromes are commonly not displayed. The authors investigated the effectiveness of low-oxygen environments in delaying the fading of dyes used in the autochrome process—Tartrazine, Erythrosine B, Rose Bengal, Patent Blue, Crystal Violet, and Flexo Blue. Samples of these colorants were subjected to accelerated light fading in both atmospheric and nearanoxic conditions. The low-oxygen environment was achieved by purging a glass tube with argon gas prior to sealing, maintained with oxygen scavengers, and monitored with indicators capable of detecting oxygen levels above 0.1%. Significant increases in color stability of the dyes were observed in this environment, but a complete halt to the fading process was not achieved.

Improvement of light fastness of natural dye: effect of ultraviolet absorbers containing benzotriazolyl moiety on the photofading of red carthamin

While the contribution of ultraviolet absorbers to synthetic dyes has been investigated by several workers, there have been few studies pertaining to the use of functional ultraviolet absorbers as a means of improving the light fastness of natural dyes. In this paper, numerous potential ultraviolet absorbers were prepared to prolong the life of natural dye carthamin. The effects of these compounds in reducing photofading were examined on a polymer substrate. The use of commercial ultraviolet absorbers was not necessarily useful in improving the light fastness of the colour. However, benzophenone‐type ultraviolet absorbers containing a built‐in ultraviolet absorber moiety markedly retarded the photofading rate. It is proposed that 2,2′,4,4′‐tetrahydroxy‐5‐methylbenzotriazolylbenzophenone and its derivatives may be used as effective stabilisers in the fading of natural dyes.

An Approach to the Photostabilization of Dyes: The Effects of Multifunctional Stabilizers on the Light Fastness of Acid Dye

Numerous potential triazine-stabilizers were synthesized to prolong the life of an azo dye. The effect of these compounds in reducing photofading was examined in cellulose acetate film. The simple use of UV absorbers or radical scavengers was not necessarily useful in improving the light fastness of the dye. The triazine-stabilizers containing a number of different types of stabilizing fragments, however, markedly suppressed the photofading of the dye. It was proposed that nickel complexes of multifunctional triazine-stabilizers may be used as effective stabilizers in the fading of dyes.

Vibrational spectroscopy to study degradation of natural dyes. Assessment of oxygen-free cassette for safe exposition of artefacts

An important issue connected with conservation chemistry is how to improve the storage and exposure conditions in order to suppress the fading and degradation of dyes and other components of paintings. Although the oxygen-free exposure cassettes are commonly known in museums, there is still lack of information in the literature about the effect of anoxic conditions on the degradation of dyes. This study is an attempt to start a database formation on the dyes degradation. Five commercial dyes (indigo, dragon's blood, curcumin, madder, carminic acid) were submitted to accelerated ageing by exposure to intensive light in the visible range in both oxygen-free (anoxia) and -rich conditions. Degradation of the samples was investigated by several analytical techniques (attenuated total reflectance infrared spectroscopy, Raman spectroscopy, reflectance UV-Vis spectroscopy, X-ray fluorescence spectroscopy and optical microscopy). The conclusions are based on the estimators (derived from the determination of colour differences from Vis spectra and from the changes in FTIR and Raman vibrational bands intensity). According to them, only indigo, dragon's blood and curcumin show greater stability in anoxic conditions in comparison with oxygen-rich ones while madder, carminic acid undergo greater degradation.