This study synthesized and characterized composites of graphene oxide and TiO
(GO-TiO
). GO-TiO
thin films were deposited using the doctor blade technique. Subsequently, the thin films were ...sensitized with a natural dye extracted from a Colombian source (
). Thermogravimetric analysis, X-ray diffraction, Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance measurements were used for physico-chemical characterization. All the samples were polycrystalline in nature, and the diffraction signals corresponded to the TiO
anatase crystalline phase. Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) verified the synthesis of composite thin films, and the SEM analysis confirmed the TiO
films morphological modification after the process of GO incorporation and sensitization. XPS results suggested a possibility of appearance of titanium (III) through the formation of oxygen vacancies (O
). Furthermore, the optical results indicated that the presence of the natural sensitizer and GO improved the optical properties of TiO
in the visible range. Finally, the photocatalytic degradation of methylene blue was studied under visible irradiation in aqueous solution, and pseudo-first-order model was used to obtain kinetic information about photocatalytic degradation. These results indicated that the presence of GO has an important synergistic effect in conjunction with the natural sensitizer, reaching a photocatalytic yield of 33%.
Visual pH-sensing films containing curcumin (CR) and anthocyanins (ATH) were prepared as on-package indicator labels for nondestructively detecting fish freshness in real time. Fourier transform ...infrared spectroscopy analysis indicated that CR and ATH were successfully immobilized into the film-forming substrate based on starch, polyvinyl alcohol (SPVA) and glycerol. The incorporation of different natural dyes had no significant effect on moisture content, water solubility, water vapor permeability and thickness of colorimetric films. Results of color stability test illustrated that the composite films incorporated with CR were the most stable and the composite film incorporated with ATH was least stable at room temperature for 180 days. The colorimetric film without glycerol was found less sensitive to volatile ammonia. Based on the volatile amines released by fish, an application trial of five colorimetric films containing natural dyes was conducted in bighead carp (Hypophthalmichthys nobilis) at 4 °C. Results showed that the SPVA/glycerol film incorporated with CR and ATH at a ratio of 2:8 (v/v) could provide three different colors, which were assigned to the sign of freshness, medium freshness, and spoilage for packaged fish. Hence, this colorimetric film can be applied as a promising material of intelligent packaging for non-destructively monitoring the real-time freshness of fish products.
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•Five different films were incorporated with anthocyanins, curcumin and their mixed dyes.•Films respond via visible color change to volatiles in the package headspace.•SPVAG/ATH/CR film can discriminate fresh, medium fresh, and spoiled bighead carp.
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DSSC technology based on natural dyes still constitutes a tempting alternative to explore. Besides the ease of extraction, most natural dyes fulfill the characteristics to be applied as sensitizers. ...The presented results summarize the exploration of the features of several southern dyes, mostly coming from the Antarctic region. The explored pigments showed good absorption capacity within the visible region of the light spectra, and their molecules possess functional moieties to coordinate with the TiO2 semiconductor, oxidation potential value near 1 V and reduction potential near −0.8 V, adequate thermal stability, and low fluorescence emission.
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.
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The dyeing and finishing step represents a clear hotspot in the textile supply chain as the wet processing stages require significant amounts of water, energy, and chemicals. In order to tackle ...environmental issues, natural dyes are gaining attention from researchers as more sustainable alternatives to synthetic ones. This review discusses the topic of natural dyes, providing a description of their main features and differences compared to synthetic dyes, and encompasses a summary of recent research in the field of natural dyes with specific reference to the following areas of sustainable innovation: extraction techniques, the preparation of substrates, the mordanting process, and the dyeing process. The literature review showed that promising new technologies and techniques have been successfully employed to improve the performance and sustainability of natural dyeing processes, but several limitations such as the poor fastness properties of natural dyes, their low affinity with textiles substrates, difficulties in the reproducibility of shades, as well as other factors such as cost-effectiveness considerations, still prevent industry from adopting natural dyes on a larger scale and will require further research in order to expand their use beyond niche applications.
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Ecoprint is a technique for printing colors and shapes on fabric using natural materials. Ecoprint techniques have been introduced to junior high school students because they can capture the material ...and teacher's instructions independently, think critically and creatively. The purpose of the ecoprint introduction activity is to provide knowledge about ecoprint and students' skills in utilizing local potential through natural materials or plants around the school. The methods used are lectures, demonstrations, practice, and evaluation. The questionnaires and direct observations on ecoprint products were used as evaluations for this activity. Students have been able to print motifs and colors from leaves and flowers on a cloth to produce ecoprint products according to their respective creativity.
Azo dyes, including Tartrazine, Sunset Yellow, and Carmoisine, are added to foods to provide color, but they have no value with regard to nutrition, food preservation, or health benefits. Because of ...their availability, affordability, stability, and low cost, and because they provide intense coloration to the product without contributing unwanted flavors, the food industry often prefers to use synthetic azo dyes rather than natural colorants. Food dyes have been tested by regulatory agencies responsible for guaranteeing consumer safety. Nevertheless, the safety of these colorants remains controversial; they have been associated with adverse effects, particularly due to the reduction and cleavage of the azo bond. Here, we review the features, classification, regulation, toxicity, and alternatives to the use of azo dyes in food.
•The availability, affordability, stability and safety of azo dyes make them desirable for food use.•Tartrazine, Sunset Yellow or Carmoisine are the most widely used azo dyes due to their coloring capacity.•The safety of these artificial colorants is controversial due to possible adverse and toxic effects.•Further research on these dyes is needed to provide consistent data, alternatives to their use and safety.
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The most extensive textile export product and one of the nation's cultural legacies is batik cloth. However, regarding environmental quality, West Java's growing demand for batik production results ...in garbage contaminating the nearby waterways. The type of dye is where the harmful properties of batik waste originate. With descriptive qualitative methodologies and the Miles and Huberman model, this study intends to explain the various types of dyes used by SMEs producing batik in the batik centre region of the City and Tasikmalaya Regency and their impact for environmental health. The findings revealed that small and medium-sized enterprises (SMEs) engaged in the batik industry in Tasikmalaya City (Cipedes) utilized synthetic dyes such as indigosol, reactive Procion and Remazol, dispersion, and direct (mostly monoazo and diazo). In the meantime, batik artisans at the Tasikmalaya Batik Center (also known as Sukapura batik in Sukaraja) work with reactive Procion and Remazol (diazo), indigosol, jolawe fruit peel (Terminalia bellirica), soga jambal bark (Peltophorum pterocarpum), and tingi as natural dyes (Ceriops condolleana). The impact of used the different azo dyes can change the level of pH extremely, also improve the level of BOD, COD, TDS, and heavy metal such as chromium hexavalent ((Cr(VI)) in the waters
It is widely assumed that natural dyes in weaving degrade in quality when exposed to sunlight for an extended period. This indication is visible to the naked eye. There is currently no standard for ...evaluating the quality of natural dyes. The Boti tribe's weaving on Timor Island, East Nusa Tenggara Province, is one type of weaving that uses natural dyes. The dye is made from corn flour and a combination of "nobah" leaves and the bark of the "bauk ulu" tree (from the local language). White (from corn flour) and blue-black are the colors produced by dyeing the yarn. The purpose of this research is to examine the image quality of the Boti tribe's woven fabric. The parameters used were Means Square Error (MSE), Peak Signal to Noise (PSNR), and RGB values. The image of the weaving used as a reference is compared to the image of the sun-dried weaving. The image capture distance was 30 cm, and the cropped RGB image size was 423x623x3. The experimental method was used in the research. The drying time was one hour, and it was repeated every hour between 10:00 and 15:00 local time. The sun-dried images were photographed, and parameter comparisons were performed for analysis. The results demonstrated that the MSE and PSNR methods were effective in measuring the image quality of weaving dyed with natural dyes. The average value has changed by 8.42% for the R-value, 8.58% for the G value, and 9.68% for the B value. The average PSNR for RGB images is 9.44288 dB, and the MSE is 7477.52. For grayscale images, the average PSNR is 10.52 dB and the average MSE is 5832.06.
In this work, we report the synthesis of TiO2 photoelectrodes sensitized with different natural organic dyes extracted (using methanol) from spinach, raspberry and passion fruit for their application ...in Dye-Sensitized Solar Cells (DSSC). The effects of Lead Sulfide (PbS) NanoParticles (NPs) doping on the sensitized TiO2 photoelectrodes photovoltaic performance were mainly studied. Good absorption in the visible range (400–700 nm) was observed for natural dyes extracted from spinach and raspberry, observing characteristic peaks associated with chlorophylls, β-carotenes and phycoerythrin pigments. On the other hand, natural dye synthesized from passion fruit showed a poor absorption in this range concerning the previous mentioned sources. Cells using spinach and raspberry based dyes generally showed good Fill Factors (FF) higher than 55%, observing depreciable or negative influence of the PbS doping. Open-Circuit voltages (Voc), Short-Circuit current densities (Jsc) and Power Conversion Efficiencies (PCE) in the range of 0.35–0.55 V, 0.01–0.12 mA/cm2 and 0.002–0.03 % were respectively estimated.
•Natural organic dyes were synthesized from spinach, raspberry and passion fruit.•Spinach and raspberry dyes showed considerable optical absorption in visible range.•DSSCs presented high fill factors (>55 %) by using spinach and raspberry dyes.•PbS-NPs doping depreciably or negatively affected the photovoltaic performance.•Results suggest possible incompatibilities between PbS-NPs and natural dyes.
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