Interest in the production of sustainable textile products has led to the consideration of natural dyes as environmentally friendly alternatives to synthetic dyes, the latter of which are typically neither biodegradable nor renewable. Recently, extracts from coffee husk have been examined for textile coloration and found to function best on wool and silk fabrics using metal-based mordants. The present research was designed to examine extracts of coffee husk (Coffea arabica L.) and avocado pits (Persea americana Mill.) for use in dyeing organic cotton at shade depths comparable to or above those reported for applying dyes in coffee extracts to protein fibers. The approach developed was also designed to eliminate the need for a metal mordant for natural dye uptake on cotton, further reducing adverse environmental impact. This work included determining the pH and mordant levels required to optimize dye uptake. The dyed cotton fabrics were characterized for colorimetric properties using the CIELAB system, where the K/S values were 2.9 at pH 5.08 (without adjustment), 3.8 at pH 7, and 4.4 at pH 11 using avocado extract, and providing better results than metal mordants at pH 5 and 7. As for color fastness, the best ratings were 4 on a scale of 1 - 5, and UPF testing gave a value of 50+ which can be categorized as excellent. Thus, the use of avocado extract as a biomordant for coffee-based dyes has made possible an allnatural fiber/mordant/dye combination involving cotton textiles having K/S values comparable to those on protein fibers.

Indigo is a widely used colorant available from natural and synthetic origin. It is practically insoluble in water. Indigo can reach aquatic sediments through wastewater discharges from dyeing processes, terrestrial compartments from the treatment sludges used as biosolids and dyed textiles disposed in landfills. The aim of this work was to chemically characterize a commercial natural indigo dye from Isatis tinctoria (woad) and, evaluate its toxicity using a sediment organism (Parhyale hawaiensis) in an acute test (96 h) and the soil dwelling invertebrate Enchytraeus crypticus in a chronic assay (21 days). These organisms are model organisms and representative of the environmental compartments where dye's destination is expected. Also, the toxicity of natural indigo was evaluated under the conditions in which it is applied to textiles. Specifically, water column invertebrate Daphnia similis was used to test indigo in its leuco form along with the salts used for its generation. The composition of the test sample was 91 % indigo, 4 % indirubin and 5 % of other components including flavonoids. The sample was toxic to P. hawaienis (LC50 309 g kg- 1) and inhibited the reproduction of E. crypticus at concentrations 5.06 and 7.59 g kg- 1 in dry soil. The leuco form of indigo was acutely toxic to Daphnia similis at concentrations 0.2 and 1 g L- 1. The data of this study can be used to guide other indigo toxicity studies and provide information that can be used in preliminary risk assessment evaluations of environmental compartments, such as aquatic sediments and indigo contaminated soils.

Natural dyes are gaining interest as a more ecological approach to textile coloration, as well as for slow fashion and the bioeconomy. The use of local raw materials is a way of valuing small producers and recovering traditional knowledge. In this context, the current investigation was developed to study the use of lignocellulose-based Stryphnodendron adstringens (Mart.) Coville (known as "barbatim & atilde;o") bark extract, from a native tree in Brazil, as a natural dye for textile dyeing. Physical-chemical analyses were performed on the reddish-brown extract, the results of which showed an acidic pH and the likely presence of condensed tannins and flavanols. The optimised dyeing process was evaluated by a 23 factorial design. The fabrics dyed under optimised conditions were evaluated for colour fastness to laundering, rubbing, light and perspiration, and obtained good colour fastness ratings in most of these tests. Wastewaters from dyeings were characterised by physicochemical analyses. Because of the high turbidity and high biochemical oxygen demand and chemical oxygen demand levels, as well as the amount of residual metal ions from dyeing with mordants, the need for wastewater pretreatment was evident. Based on this research, S. adstringens extracts have significant potential for textile coloration.

Dye-sensitized solar cell (DSSC, DSC, DYSC, or Grätzel cell) are a semiconductor photovoltaic device that directly converts solar radiation into electric current. In contrast to conventional systems in which the semiconductor takes on both the task of absorbing light and transporting charge carriers, the two functions are separated in the DSSCs. The light is absorbed by a sensitizer, which is anchored to the surface of a broadband semiconductor. A typical DSSC consists of a mesoporous photoanode with a dye-sensitized titanium dioxide (TiO2) film, an electrolyte containing iodide/triiodide (I-1/I3-1) redox couple, and a counter electrode with platinum (Pt) catalyst. Upon the absorption of light energy, a photo-excited electron is injected from the excited state of the dye into the conduction band of the TiO2. However, the immobilization of the adsorbing dye molecules onto the surface of semiconducting metal oxide nanoparticles is crucial for initiating an electrical current, via the injection of electrons, which collectively act as the working electrode of a DSSC. Herein we report the synthesis, characterization, and evaluation of the compound 5-(4-octyloxyphenyl)tetrazole (LTz-5) as dye co-adsorbente to DSSCs. This dye was incorporated in DSSCs as a co-sensitizer with different other dyes (HD-2, HD-14, and MH-13), to evaluate the effect of interaction between dye and co-adsorbent on the energy conversion efficiency (%η). The energy conversion efficiency of the DSSC was 8.78 % from HD-2 – LTz-5 (4.9 % increase compared to CDCA), 9.20 % from HD-14 – LTz-5 (0.66 % increase compared to CDCA), and 5.01 % from MH-13 – LTz-5 (1.0 % reduction compared to CDCA). The latter results suggest that steric effects restrict the anchoring ability of the tetrazole groups, by hindering their approach to TiO2 surface and by restricting the coplanarity of the system.

Emodin is an anthraquinone secondary metabolite produced by several species of plants and fungi. Emodin is known for its pharmacological versatility, and, in the textile industry, for its good dyeing properties. However, its use in the textile industry can result in the formation and disposal of large volumes of wastewater. Emodin mutagenicity has been shown in bacteria and in human cells, but little is known about its possible toxic, genotoxic, or mutagenic effects in aquatic organisms. We have evaluated the eco/genotoxicity of emodin to aquatic organisms. Emodin was toxic to Daphnia similis (EC50 = 130 mu g L-1) and zebrafish embryos (LC50 = 25 mu g L-1). No toxicity was observed for Raphidocelis subcapitata, Ceriodaphnia dubia, or Parhyale hawaiensis. Additional biochemistry/molecular studies are needed to elucidate the toxic/mutagenic pathways of emodin in aquatic organisms. The PNEC value for emodin was 0.025 mu g L-1. In addition to mutagenicity in the Salmonella/ microsome assay, emodin was mutagenic in the micronucleus assay in the amphipod P. hawaiensis. Among the anthraquinone dyes tested to date, natural or synthetic, emodin was the most toxic to aquatic species.

Traditional textile dyeing processes usually require large quantities of water and energy and generate wastewater that can be harmful to the environment. Dyeing in supercritical carbon dioxide (sc-CO2) media is promising in textile coloration due especially to it providing a waterless process and eliminating the need for an energy intensive drying step. The natural anthraquinone emodin showed promising results for dyeing different fibres through sc-CO2 process. However, emodin is mutagenic. The aim of this study was to develop non-mutagenic derivatives of emodin that can be applied to textiles using sc-CO2. Emodin structure was modified incorporating acryloyl groups, which are considered suitable for decreasing potential for DNA intercalation, and thus mutagenicity. The presence of acryloyl groups would also enable atmospheric plasma induced bonding with fibres. Molecular modelling studies showed that emodin derivatives became less planar with increasing number of attached acryloyl groups, making intercalation unlikely. The derivatives produced were tested to assess mutagenicity in vitro (Salmonella/microsome assay, TA1537, 10% S9) and in vivo (micronucleus test in hemocytes of aquatic crustacean). We found that emodin can be derivatised using acryloyl chlorides to give mono- and di-acrylate esters suitable for dyeing polyester fibres in sc-CO2. However, the new dyes presented mutagenicity for both in vitro and in vivo. Although the derivatives provided greenish-yellow alternatives to emodin for dyeing synthetic fibres, they do not appear to be viable alternatives from the point of view of preserving human and environmental health. Plasma bonding studies are underway.

The concept of sustainability has gained prominence in recent years, enhancing the need to develop products that are less harmful to the environment. Dyes are used by various industrial sectors and have a lot of market value; they are used on a large scale mainly by the textile industry that uses large volumes of water and is one of the main contributors to the contamination of water bodies. Some natural compounds, especially anthraquinones are re-emerging as possible alternatives to synthetic dyes, some of which are known for their toxic and/or mutagenic effects. The BioColour project (https://biocolour.fi/) which is interested in promoting the development of new alternative molecules to synthetic dyes, provided us highly purified anthraquinone dyes dermocybin and dermorubin (>98% purity) extracted from a specie of fungus Cortinarius sanguineus. Dyes were tested for their acute and chronic toxicity using different aquatic organisms. Dermorubin was not toxic to any of the organisms tested for the highest test concentration of 1 mg L−1 and it was the most promising dye. Dermocybin was toxic to Daphnia similis (EC50 = 0.51 mg L−1), Ceriodaphnia dubia (IC10 = 0.13 mg L−1) and Danio rerio embryos (extrapolated LC50 = 2.44 mg L−1). A safety limit, i.e, predicted no-effect concentration (PNEC) of 0.0026 mg L−1 was derived based on the toxicity of dermocybin. The PNEC value can be used to provide hazard information for future application in commercial dyeing processes. Then, we compared the toxicity of dermocybin and dermorubin with ecotoxicity data available in the literature on other anthraquinone dyes of natural and synthetic origin. Some natural dyes can be as toxic as synthetic ones, or more toxic when chronic effects are considered. Despite natural dyes being used since centuries past, there are few ecotoxicological studies available. This study is designed to help develop a more comprehensive understanding of their toxicological properties.

The use of photoprotection products is indispensable today, due to the potential harmful effects of ultraviolet (UV) rays. Textiles are a natural barrier against UV radiation and can be made more effective by applying UV blockers. The present study investigates the photoprotection properties arising from dyeing cotton fabric with pomegranate peel extract. The extract was characterized by TPC, TFC, THT, color, pH, HPLC-UV and including its antiradical activity. The dyed fabric samples were evaluated for color, color fastness to light, rubbing, washing and sweating, along with a determination of SEM, EDS, ATR-FTIR, and UPF properties. The chemical analyses of the P. granatum peel aqueous extract by HPLC-UV indicated the presence of ellagic acid, punicalagin and punicalin derivatives. The extract showed antiradical activity (11.1 +/- 0.4 CI50 (mg L-1) which is consistent with a high amount of total phenols 307 +/- 26 (mg GAE/g extract), total flavonoids 150.3 +/- 2.3 (mg RE/g extract), and condensed tannins 632.6 +/- 84.1 (mg TAE/g extract). The dyed fabric samples showed yellowish colors and good color fastness ratings. The evaluation of the Ultraviolet Protection Factor (UPF) indicated mostly values from 15 to 24, equivalent to the category of good to very good photoprotection. Bearing in mind that ZnO is often used in combination with other UV-blockers to enhance the coverage of sunscreens, an aspect of this study involved determining the UPF of the pomegranate extract mixed with ZnO. In this case, ZnO addition did not significantly enhance the UPF of the dyed cotton fabric.

The present study involved characterizing the physicochemical, dyeing, UV-protective, and antibacterial properties of pomegranate peels extract on woven cotton fabric. As a point of departure, the extract itself was characterized using methods such as SEM, TG, DSC, ATR-FTIR, and UV–Vis analyses. ATR-FTIR and UV–Vis spectra were consistent with the presence of polyphenolic compounds that provide a basis for defining the observed coloristic properties of the extract. Coloristic measurements on cotton indicated that mostly yellow to brown colors with good to excellent wash, light, rubbing, and perspiration fastness were obtained. The best results were obtained when the peel extract was used to dye cotton in the presence of Fe (II) and without the need to adjust its pH of 4.06. This dyeing also gave a K/S value (color strength) upwards of 10.3, which is significantly more than values previously reported for peel extracts. In view of continuing interest in identifying natural colorants having dual properties on textiles, fabric samples dyed with the extract were also evaluated for their UV protection and antibacterial properties. UV protection testing indicated that most of the samples gave a UPF value of 15–24, which is equivalent to the category of good photoprotection. However, the dyed fabric did not exhibit antibacterial activity when tested against Gram-positive and Gram-negative bacteria, probably due to deep dye penetration into cotton fibers.

The search for waterless dyeing technologies led to the use of liquid (supercritical) carbon dioxide as a medium for dyeing synthetic fibers with the disperse dye family. The structural similarities between certain plant-based dyes and synthetic disperse dyes led us to explore textile dyeing with natural dyes in liquid carbon dioxide. In our initial studies, we found that anthraquinone dyes (e.g. Dermocybin and Emodin) extracted from mushrooms dyed polyester and nylon fibers in liquid carbon dioxide in 30 min. Our work has now been extended to plant extracts containing madder, weld, woad, or logwood, and to aliphatic polyenes (e.g. betacarotene and lycopene), all at 0.5-1.0% (weight of dye/weight of fabric; (w/w)) shade depths. The best results (dye uptake levels) from the former group of dyes were obtained using madder and logwood, with weld giving no dye uptake. To enhance color depths from weld, we treated a weld extract with amylase enzyme solution, to enhance solubility in carbon dioxide by cleaving off the glucose group(s). As anticipated, enzyme treatment led to a canary yellow shade on polyester at 1% (w/w). Regarding the aliphatic polyenes, results showed better dye uptake on polyester at 3500 psi and 110 degrees C, giving a red shade from lycopene at 1% (w/w). Coloristic data obtained are reported in this paper.

The design of hair dyes having environmentally benign characteristics in addition to very good durability to washing and UV light is of importance to overcome the limitations of conventional permanent hair dyes in the marketplace. As a step toward meeting this vision, we synthesized anionic azo dyes having a built-in C4, C8, or C12 alkyl chain and evaluated their hair dyeing and toxicological properties. As anticipated, the dyes increased in hydrophobicity (SlogP) with the increase in alkyl chain length. Based on prior technology, it is known that certain anionic textile dyes possessing a C12 group exhibit high affinity for wool fibers during rigorous washing in the commercial milling process. In the present study, the dye containing the C8 chain displayed the greatest uptake and the most promise as a potential permanent hair dye. Further, dyes containing a C4 or C8 carbon chain were found to be nontoxic <= 100 mg L-1 using the crustaceans Daphnia similis and Parhyale hawaiensis as test organisms. The dye containing a C12 carbon chain provided an EC50 of 57.4 mg L-1 using D. similis, but it was nontoxic <= 100 mg L-1 to P. hawaiensis. All dyes were nontoxic using the algae Raphidocelis subcapitata, and none of the dyes exhibited mutagenicity toward the strains used.

The molecular, spectroscopic, and excited state properties of synthetic dyes for fiber-based outdoor materials continue to be of commercial interest. Early developments in this area were reported in the 1980s, when the need for dyes for polyester (PET)-based automobile interiors gave rise to commercially viable nitrodiphenylamine yellow, anthraquinone red and blue, and azo red dyes. To augment that initial knowledge base, the present study involved the use of experimental and theoretical methods to help establish the molecular structures and excited state properties of some more recent dyes for producing photostable colors on PET fibers. Having completed the characterization of present-day scarlet, blue, and yellow disperse dyes for PET-based fibers used outdoors, our attention turned to commercially available red and violet dyes. In this regard, HPLC analysis showed that the red product was a mixture containing four components, while the violet product contained only one component. Results from H-1 NMR, HRMS, and single crystal X-ray diffraction analyses indicated that the principal components were dyes having a 1-amino-4-hydroxyanthraquinone base structure. The presence of an -OH group alpha to an anthraquinone C=O moiety provides for intramolecular H-bonding and a subsequent opportunity for intramolecular proton transfer in the excited state - as a photostabilizing mechanism. Further, for both dyes, results from the analysis of Frontier HOMO and LUMO isosurfaces indicated strong HOMO-LUMO overlap without molecular gaps and were consistent with strong excited state energy dissipation in a non-destructive way. (C) 2021 Elsevier B.V. All rights reserved.

As a part of an ongoing interest in identifying environmentally friendly alternatives to synthetic dyes and in using liquid CO2 as a waterless medium for applying the resulting colorants to textiles, our attention turned to yellow-to-red biocolorants produced by Cortinarius sanguineus fungus. The three principal target anthraquinone colorants (emodin, dermocybin, and dermorubin) were isolated from the fungal bodies using a liquid–liquid separation method and characterized using 700 MHz NMR and high-resolution mass spectral analyses. Following structure confirmations, the three colorants were examined for dyeing synthetic polyester (PET) textile fibers in supercritical CO2. We found that all three biocolorants were suitable for dyeing PET fibers using this technology, and our attention then turned to determining their toxicological properties. As emodin has shown mutagenic potential in previous studies, we concentrated our present toxicity studies on dermocybin and dermorubin. Both colorants were non-mutagenic, presented low cellular toxicity, and did not induce skin sensitization. Taken together, our results indicate that dermocybin and dermorubin possess the technical and toxicological properties needed for consideration as synthetic dye alternatives under conditions that are free of wastewater production.

The ability to add value to waste materials from industrial operations has come to the attention of the wood processing industry, with reports, for example, of extracts from the bark tree conveying colour and UV protection to textile fibres. The objective of the present work was to expand our developments in this arena by using Copaifera langsdorffii Desf. bark extract as a natural dye for textile dyeing. A complete 2³-statistical experimental design and the central point was elaborated. The results showed that the optimal dyeing conditions were 98 °C, for 60 min, using undiluted bark extract. The dyed fabric was analysed by a spectrophotometer using the CIELAB system for evaluation of the colour strength. The results showed a K/S value of 5.78, and the dyed fabric had good colour fastness to rubbing and washing.

Two new organic dyes (SD-1 and SD-2) featured with donor-pi-acceptor architecture were synthesized and applied to dye-sensitized solar cells (DSSCs). In these sensitizers, an azo bridge pi-spacer is used to link the phenyl tetrazole acceptor with 2-naphthol donors. To amplify the pull-push effect, the nitro group was connected to the electron acceptor group. The effect of the position of the nitro group and the tetrazole group linked to the benzene ring on the photophysical, electrochemical, and photovoltaic prop-erties of sensitizers are investigated in detail. They all show intense UV-Vis absorptions around 400 nm and 510 nm. The co-sensitizations of SD-1 and SD-2 with ruthenium complex HD-2 are further evaluated and the co-sensitization results were compared with DCA. Co-sensitization of HD-2 with SD-2 was more efficient than found for co-sensitization with DCA (5.6% higher). Moreover, the influences of molecular geometry on charge recombination and photovoltaic performance of DSSCs were systematically investi-gated by incident photon to current efficiency (IPCE) spectra and electrochemical impedance spectroscopy (EIS) investigations. (C) 2021 Elsevier B.V. All rights reserved.

As a new approach to permanent/oxidative hair dyes, we demonstrated that certain monoazo dyes containing substituents that enable diffusion into hair fibers and subsequent chelation/complexation using benign metal ions (Al3+ and Fe3+), rather than a harsh oxidant and strong alkali, merit consideration in this application area. This is important, because billions of individuals worldwide color their hair using permanent hair dye products that can contain aromatic amines and phenols that display genotoxicity and/or skin sensitization (e.g., para-phenylenediamine, PPD). Herein, our work is extended to an examination of the toxicological properties and durability of metallizable monoazo dyes, in comparison to a commercially used permanent hair dye product. Results from the Salmonella/microsome mutagenicity assay and from acute toxicity tests using aquatic test organisms (Daphnia similis, 48-h and Parhyale hawaiensis, 96-h) indicated that the proposed dyes were significantly less toxic than the top-eight permanent hair dye precursors utilized annually. Regarding durability, monoazo dye chelation in situ led to a higher degree of resistance to removal by washing than a commercial permanent hair dye. Taken together, these results further demonstrate the potential of the dyes as sustainable alternatives to conventional permanent hair dyes.