Journal Description
Colorants
Colorants
is an international, peer-reviewed, open access journal on all aspects of coloring matters published quarterly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 31.1 days after submission; acceptance to publication is undertaken in 12.5 days (median values for papers published in this journal in the first half of 2024).
- Recognition of Reviewers: APC discount vouchers, optional signed peer review, and reviewer names published annually in the journal.
Latest Articles
Trade-Off Between Growth Regimes in Chlorella vulgaris: Impact on Carotenoid Production
Colorants 2024, 3(4), 282-297; https://doi.org/10.3390/colorants3040020 - 4 Nov 2024
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With the increasing awareness of socio-environmental issues, a global trend has emerged emphasizing the valorization of natural ingredients that promote health and well-being within sustainable production systems, such as microalgae-based carotenoids. Currently, little is understood about the correlation between biomass productivity and carotenoid
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With the increasing awareness of socio-environmental issues, a global trend has emerged emphasizing the valorization of natural ingredients that promote health and well-being within sustainable production systems, such as microalgae-based carotenoids. Currently, little is understood about the correlation between biomass productivity and carotenoid content, which is a fundamental parameter for facilitating the immediate expansion of microalgae bioprocesses and ensuring the availability and industrial viability of these compounds. In this context, this study aims to investigate the carotenoid profile of Chlorella vulgaris through growth curve experiments conducted under photoautotrophic and heterotrophic regimes. Additionally, a trade-off analysis was performed for the production of carotenoids from microalgae. Carotenoids were quantified using high-performance liquid chromatography coupled with diode array and mass spectrometry detectors (HPLC-PDA-MS/MS). The performance of kinetic phases and energy demands across growth regimes was assessed to provide insights into production trade-offs. The results indicated that a total of 22 different carotenoids were identified in all the extracts. The all-trans-lutein and all-trans-β-carotene were the majority compounds. The total carotenoid content of Chlorella vulgaris revealed significant differences in the kinetic phases of carotenoid production, indicating that carotenoid volumetric production is only viable if the cultures are conducted until the log and stationary phases, based on the function of the biomass volumetric production (weight.volume−1). Therefore, the best trade-off for the process was to provide photoautotrophic growth until the exponential phase (log). Under this condition, the maximum carotenoid and lutein content was 2921.70 µg.L−1, reaching a maximum cell biomass of 1.46 g.L−1. From an environmental/economic point of view, the energy demand was 7.74 kWh.L−1. Finally, the scientific advances achieved in this study provide a holistic view of the influence of the main cultivation methods on the production of microalgae carotenoids, suggesting a viable initial direction for different industrial applications.
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Open AccessArticle
Optical Characterization of Fluorescent Chitosan-Based Carbon Dots Embedded in Aqueous Natural Dye
by
Sthanley R. De Lima, Thiago V. Costa, Tácio T. S. Santos, Dora G. Felipe, Teófanes B. Serna, Acácio A. Andrade and Viviane Pilla
Colorants 2024, 3(4), 269-281; https://doi.org/10.3390/colorants3040019 - 21 Oct 2024
Abstract
(1) Background: This work evaluated the optical characterization of aqueous fluorescent chitosan-based carbon dots (or carbon nanoparticles CNPs) embedded in natural dye for potential functional packaging applications. Chitosan-based materials are nontoxic, biodegradable, biocompatible, bactericidal, and produced from renewable polymer sources. Anthocyanins are pigments
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(1) Background: This work evaluated the optical characterization of aqueous fluorescent chitosan-based carbon dots (or carbon nanoparticles CNPs) embedded in natural dye for potential functional packaging applications. Chitosan-based materials are nontoxic, biodegradable, biocompatible, bactericidal, and produced from renewable polymer sources. Anthocyanins are pigments of different colors with a large range of potential applications, such as in bioindicators and biomonitoring; (2) Methods: The CNPs were synthetized in aqueous solutions using chitosan as a carbon source. The natural dye was extracted from the leaves of Tradescantia pallida Purpurea in aqueous solutions. The fluorescence quantum efficiency (η) and fluorescence lifetime (τ) were determined using the mode-mismatched pump–probe thermal lens (TL) technique and time-resolved fluorescence lifetimes (TRFL) measurements, respectively; (3) Results: The η and τ were measured for CNPs embedded in natural dye solution at different concentrations (5.2, 12.09, and 21.57 mass percentage composition). The η and τ photophysical parameters obtained for CNPs embedded in natural dye were compared with those of other CNPs synthesized using different carbon sources, such as leaves, seeds, and protein; (4) Conclusions: Fluorescence spectra and time-resolved fluorescence measurements corroborate the TL results, and relatively high values of η were obtained for the CNP synthesized and embedded in natural dye.
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(This article belongs to the Special Issue Feature Papers in Colorant Chemistry)
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Open AccessPerspective
A Perspective on the Photofading of Organic Colorants
by
Anthony Harriman
Colorants 2024, 3(4), 263-268; https://doi.org/10.3390/colorants3040018 - 20 Oct 2024
Abstract
This perspective presents an account of the underlying features associated with the photofading of organic colorants. Photofading is commonly known to the scientific community as photodegradation or photooxidation, while in earlier times the more grandiose term “light fastness” was commonplace. This is a
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This perspective presents an account of the underlying features associated with the photofading of organic colorants. Photofading is commonly known to the scientific community as photodegradation or photooxidation, while in earlier times the more grandiose term “light fastness” was commonplace. This is a subject of immense diversity and significance, but there are many challenges to be faced when attempting mechanistic reasoning. The text is illustrated by descriptions of several systems taken from the scientific literature, together with anecdotes related to the principal researchers. The chemical challenges to be overcome in order to design photostable materials are outlined and reference is made to the natural world. It is stressed that the journal Colorants would welcome submissions in this field.
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Open AccessArticle
Sustainable Near-Infrared Reflective Blue Pigments: Recycled Aluminum from Can Seals for Cobalt Aluminates in Cool Coatings
by
Dienifer F. L. Horsth, Julia de O. Primo, Fauze J. Anaissi, Polona Umek and Carla Bittencourt
Colorants 2024, 3(4), 253-262; https://doi.org/10.3390/colorants3040017 - 11 Oct 2024
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Inorganic cool pigments are widely used as cooling agents in residential coatings due to their ability to achieve near-infrared reflectance. These coatings can be designed to exhibit a variety of colors independent of their reflectivity and absorption properties. Recent studies have highlighted the
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Inorganic cool pigments are widely used as cooling agents in residential coatings due to their ability to achieve near-infrared reflectance. These coatings can be designed to exhibit a variety of colors independent of their reflectivity and absorption properties. Recent studies have highlighted the development of novel near-infrared (NIR) blue pigments, with an increasing emphasis on environmentally sustainable options that demonstrate high NIR reflectivity. This trend highlights the importance of creating novel and eco-friendly NIR reflective blue pigments. This study presents the synthesis of cobalt aluminates with varying concentrations of coloring ions (Co2+), achieved through the recycling of aluminum can seals via chemical precipitation. The formation of the spinel phase was confirmed through X-ray diffraction (XRD), and a colorimetric analysis was performed in the CIEL*a*b* color space. The synthesized pigments exhibited high near-infrared solar reflectance, with R% values ranging from 34 to 54%, indicating their potential as energy-efficient color pigments for use in coatings.
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Open AccessArticle
Easy and Fast Obtention of ZnO by Thermal Decomposition of Zinc Acetate and Its Photocatalytic Properties over Rhodamine B Dye
by
Dalete Araujo de Souza, Pedro Hyug de Almeida da Silva, Francisco Paulino da Silva, Yonny Romaguera-Barcelay, Robson Dantas Ferreira, Edgar Alves Araujo Junior, José Fábio de Lima Nascimento, Fagner Ferreira da Costa, Litiko Lopes Takeno, Yurimiler Leyet Ruiz, Lianet Aguilera Dominguez, Walter Ricardo Brito and Francisco Xavier Nobre
Colorants 2024, 3(3), 229-252; https://doi.org/10.3390/colorants3030016 - 23 Sep 2024
Abstract
This study presents a simple, low-cost, and efficient route to obtain zinc oxide by adopting the thermal decomposition method of zinc acetate at 300 (Gr@ZnO_300), 400 (Gr@ZnO_400), 500 (Gr@ZnO_500), and 600 °C (Gr@ZnO_600) for 1 h. The diffraction patterns collected for the samples
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This study presents a simple, low-cost, and efficient route to obtain zinc oxide by adopting the thermal decomposition method of zinc acetate at 300 (Gr@ZnO_300), 400 (Gr@ZnO_400), 500 (Gr@ZnO_500), and 600 °C (Gr@ZnO_600) for 1 h. The diffraction patterns collected for the samples indicated the majority formation of the hexagonal phase (P63mc) for zinc oxide and residual amounts for graphitic carbon, which has a hexagonal structure of space group P63/mmc. The images collected by scanning electron microscopy (SEM) revealed the formation of sub-microcrystals with elongated rod-shaped morphology, with dimensions between 0.223 and 1.09 μm. The optical and colourimetric properties of the obtained materials indicate the presence of graphitic carbon in the samples, corroborating the analysis by XRD and Raman spectroscopy, with an optical bandgap close to 3.21 eV, and energies of the valence (EVB) and conduction (ECB) bands of 2.89 eV and −0.31 eV, respectively. The photocatalytic performance at 20 min of exposure time under UV light of all prepared samples in the decolourisation of rhodamine B (RhB) dye solutions follows the order Gr@ZnO_300 (95.6%) > Gr@ZnO_600 (92.8%) > Gr@ZnO_400 (84.0%) > Gr@ZnO_500 (78.1%), where the photocatalytic performance of Gr@ZnO_300 sample was 16.5 times more effective than the photolysis test. Moreover, the results confirmed that the best performance was archived at pH = 10, and the holes (h+) and superoxide (O2•−) radicals are the main species involved in the discolouration of RhB dye molecules in an aqueous medium. Finally, the reusability experiment shows high stability of the Gr@ZnO_300 sample as a solid photocatalyst and cycling capability, which obtained total discolouration of RhB of a solution under five cycling experiments of 60 min of exposure to UV light at room temperature.
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(This article belongs to the Special Issue Feature Papers in Colorant Chemistry)
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Open AccessArticle
A Multimode Detection Platform for Biothiols Using BODIPY Dye-Conjugated Gold Nanoparticles
by
Panangattukara Prabhakaran Praveen Kumar
Colorants 2024, 3(3), 214-228; https://doi.org/10.3390/colorants3030015 - 12 Aug 2024
Abstract
This study explored the synthesis and application of BODIPY-functionalized gold nanoparticles (AuNPs) for the sensitive detection of biothiols via an indicator displacement assay coupled with surface-enhanced Raman scattering (SERS) techniques, alongside their efficacy for in vitro cancer cell imaging. Moreover, the assay allowed
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This study explored the synthesis and application of BODIPY-functionalized gold nanoparticles (AuNPs) for the sensitive detection of biothiols via an indicator displacement assay coupled with surface-enhanced Raman scattering (SERS) techniques, alongside their efficacy for in vitro cancer cell imaging. Moreover, the assay allowed for the visible colorimetric detection of biothiols under normal and ultraviolet light conditions. The BODIPY (boron-dipyrromethene) fluorophores were strategically conjugated to the surface of gold nanoparticles, forming a robust nanohybrid that leverages the plasmonic properties of AuNPs for enhanced spectroscopic sensitivity. The detection mechanism exploited the displacement of the BODIPY indicator upon interaction with biothiols, triggering a measurable change in fluorescence and SERS signals. This dual-mode sensing approach provides high selectivity and sensitivity for biothiol detection, with detection limits reaching nanomolar concentrations using fluorescence and femtomolar concentration for cysteine using SERS. Furthermore, the BODIPY-AuNP complexes demonstrated excellent biocompatibility and photostability, facilitating their use in the fluorescence imaging of biothiol presence within cellular environments and highlighting their potential for diagnostic and therapeutic applications in biomedical research.
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(This article belongs to the Special Issue Feature Papers in Colorant Chemistry)
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Open AccessArticle
Synthesis and Characterization of Multifunctional Symmetrical Squaraine Dyes for Molecular Photovoltaics by Terminal Alkyl Chain Modifications
by
Kota Mori, Yuki Kurokawa and Shyam S. Pandey
Colorants 2024, 3(3), 198-213; https://doi.org/10.3390/colorants3030014 - 16 Jul 2024
Cited by 1
Abstract
Novel far-red sensitive symmetric squaraine (SQ) dyes with terminal alkyl chain modifications were designed, synthesized, and characterized, aiming towards imparting multifunctionalities such as photosensitization, dye aggregation prevention, and source of electrolyte components. The dye sensitizer SQ-80 with alkyl chain terminal modifications consisting of
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Novel far-red sensitive symmetric squaraine (SQ) dyes with terminal alkyl chain modifications were designed, synthesized, and characterized, aiming towards imparting multifunctionalities such as photosensitization, dye aggregation prevention, and source of electrolyte components. The dye sensitizer SQ-80 with alkyl chain terminal modifications consisting of 1-methylimidazolium iodide was designed and synthesized as a new dye sensitizer for DSSCs based on symmetric SQ-4 without any terminal modification used as reference. Upon adsorption on the mesoporous TiO2 surface, SQ-80 demonstrated reduced dye aggregation and stronger binding to the TiO2 surface, leading to enhanced durability of DSSCs. Apart from the most common photosensitization behavior, the newly designed dye demonstrated multifunctionalities such as aggregation prevention and electrolyte functionality, utilizing iodine-based redox electrolytes in the presence and absence of I2 and LiI additives. In the absence of LiI and I2, a mixture of SQ-77 with alkyl chain terminal modifications consisting of iodide and SQ-80 demonstrated a photoconversion efficiency of 1.54% under simulated solar irradiation, which was about six times higher compared with the reference dye SQ-4 (0.24%) (having no alkyl chain terminal modification).
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(This article belongs to the Special Issue Recent Progress on Functional Dyes and Their Applications)
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Open AccessArticle
Chromaticity of Gromwell, Cape jasmine Dyeing, and Effects of Zinc Oxide/Polyphenol Treatment with Copper Mordanting for UV Protection
by
Hye Jin Kim
Colorants 2024, 3(3), 175-197; https://doi.org/10.3390/colorants3030013 - 24 Jun 2024
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To protect skin from harmful ultraviolet (UV) radiation, there has been a resurgence in the use of natural dyes with metal mordants to reduce contamination by advanced chemicals. This study achieved natural dyeing in violet and yellow colors from Gromwell red roots and
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To protect skin from harmful ultraviolet (UV) radiation, there has been a resurgence in the use of natural dyes with metal mordants to reduce contamination by advanced chemicals. This study achieved natural dyeing in violet and yellow colors from Gromwell red roots and Cape jasmine seeds for UV-protective materials. The dyed fabrics were subjected to zinc oxide (ZnO) and polyphenol treatments, as well as copper post-mordanting. The SEM, TEM, and XRD tests showed that the ZnO nanoparticles, with hexagonal crystal structures, stuck to the fiber surfaces, and twisted strands resulted in the K/S reduction. First, this study found that the untreated cotton in violet, despite the highest K/S, faded the most intensely when exposed to UV. The color variation of untreated polyester was narrow, with little change in L, a*, and K/S. The color change of yellow-dyed samples treated with ZnO/polyphenol was not considerable in yellowness (b*: 28.838), while the violet fabrics displayed a significant decrease in K/S and an increase in b*. The combination of ZnO and polyphenol treatment improved UV absorption at 350 to 250 nm. Among the Cu-mordanted fabrics after ZnO/phenols treatment, the violet cotton turned reddish from blueish (negative to positive b*), with a hue change of 316° to 59° and the highest ΔE (25.90 ± 4.34) after UV exposure. In this study, the combination of ZnO/polyphenol with Cu-mordants allowed the Cape jasmine-dyed polyester to achieve a minimum ΔE as well as to keep its chroma and hue after UV exposure.
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Open AccessReview
Exploring the Role and Variability of 3d Transition Metal Complexes in Artistic Coloration through a Bottom-Up Scientific Approach
by
Alexandra Coia, Jackson Ruddick, Olivia Kuang and Li-Qiong Wang
Colorants 2024, 3(2), 152-174; https://doi.org/10.3390/colorants3020012 - 13 Jun 2024
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Transition metal complexes have historically played a pivotal role in creating vibrant pigments utilized across artistic mediums such as ceramics, paintings, and glass mosaics. Despite their extensive historical use, our understanding of the mechanisms governing transition metal complex behavior has predominantly emerged in
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Transition metal complexes have historically played a pivotal role in creating vibrant pigments utilized across artistic mediums such as ceramics, paintings, and glass mosaics. Despite their extensive historical use, our understanding of the mechanisms governing transition metal complex behavior has predominantly emerged in recent times, leaving numerous aspects of this process ripe for exploration. These complexes exhibit striking color variations under diverse conditions when employed in pigment formulations. This review utilizes a bottom-up scientific approach, spanning from microscopic to macroscopic scales, to unravel the molecular origins of the colors generated by transition metal complexes in pigments and ceramic glazes. Advanced spectroscopy techniques and computational chemistry play pivotal roles in this endeavor, highlighting the significance of understanding and utilizing analytical data effectively, with careful consideration of each technique’s specific application. Furthermore, this review investigates the influence of processing conditions on color variations, providing valuable insights for artists and manufacturers aiming to enhance the precision and quality of their creations while mitigating environmental impact.
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Open AccessArticle
Synthesis of Green Brucite [NixMg1−x(OH)2] by Incorporation of Nickel Ions in the Periclase Phase (MgO) Applied as Pigments
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Cássio Siqueira, Aline B. Schons, Patricia Appelt, Weslei D. Silva, Nayara Balaba, Mário A. A. Cunha and Fauze J. Anaissi
Colorants 2024, 3(2), 138-151; https://doi.org/10.3390/colorants3020011 - 20 May 2024
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Magnesium oxide is typically white and can be colorized with transition metal insertion by doping. We present the preparation of a green-colored hydroxide by the exchange of Mg2+ on the crystalline lattice with Ni2+ in MgO, using three nickel salts. MgO
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Magnesium oxide is typically white and can be colorized with transition metal insertion by doping. We present the preparation of a green-colored hydroxide by the exchange of Mg2+ on the crystalline lattice with Ni2+ in MgO, using three nickel salts. MgOst was prepared by the colloidal starch suspension method, using cassava starch. The oxides and hydroxides, before and after, were characterized by X-ray diffraction (XRD), and show that a phase change occurs: a transition from periclase (MgO) to brucite (Mg(OH)2) due to the incorporation of nickel ions from different salts (acetate, chloride, and nitrate), resulting in the solid solution [NixMg1−x(OH)2]. The FTIR spectrum corroborates the crystallographic structure identified through XRD patterns, confirming the formation of a crystal structure resembling brucite. The new samples present a green color, indicative of the incorporation of the Ni2+ ions. The antimicrobial activity of products resulting from the doping of magnesium oxide with nickel and the precursor MgOst was assessed through the minimum inhibitory concentration (MIC) test. The evaluation included three bacterial strains: Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), Salmonella gallinarum (ATCC 9184), and a yeast strain, Candida albicans (ATCC 10231). The obtained results were promising; the tested samples exhibited antimicrobial activity, with a MIC ranging from 0.312 to 0.625 μg.μL−1. The nickel compound, derived from the precursor chloride salt, demonstrated superior MIC activity. Notably, all tested samples displayed bactericidal activity against the S. aureus strain and exhibited a broad spectrum of inhibition, encompassing both Gram-positive and Gram-negative strains. Only the nickel compounds derived from precursors with acetate and nitrate anions demonstrated antimicrobial activity against C. albicans, exhibiting a fungistatic behavior. Based on the conducted studies, [NixMg1−x(OH)2] has emerged as a promising antimicrobial agent, suitable for applications requiring the delay or inhibition of bacterial growth.
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Open AccessEditorial
Colorants: Moving to the Next Stage
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Anthony Harriman
Colorants 2024, 3(2), 136-137; https://doi.org/10.3390/colorants3020010 - 14 May 2024
Abstract
As Editor-in-Chief of Colorants [ISSN: 2079-6447], I have watched the progressive growth of this journal and witnessed the expansion of topics way beyond the initial consideration [...]
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Open AccessArticle
Highly Stable Hybrid Pigments Prepared from Organic Chromophores and Fluorinated Hydrotalcites
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Magali Hernández, Carlos Felipe, Ariel Guzmán-Vargas, José Luis Rivera and Enrique Lima
Colorants 2024, 3(2), 125-135; https://doi.org/10.3390/colorants3020009 - 9 May 2024
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Structural hydroxide groups in layered magnesium–aluminum double hydroxides were partially replaced by fluoride ions. Fluorinated and fluorine-free materials were used as hosts for two dyes, carminic acid and hydroxyl naphthol blue, resulting in a hybrid pigment color palette. The pigments were produced by
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Structural hydroxide groups in layered magnesium–aluminum double hydroxides were partially replaced by fluoride ions. Fluorinated and fluorine-free materials were used as hosts for two dyes, carminic acid and hydroxyl naphthol blue, resulting in a hybrid pigment color palette. The pigments were produced by two ways, either incorporating chromophore during the synthesis of the layered double hydroxide or in a post-synthesis step through the memory effect of the LDHs. Additionally, the pigments were protected with a magnesium hydroxide phase to prevent the color from fading over time. The pigments were stable for periods as long as 10 years. The color properties of the pigments were significantly influenced by the host of dye since the presence of fluorine directly influences the acid–base properties of the layered double hydroxides. The pigments conferred their color to white cream in the preparation of colored creams. The colored creams acquired the color of the layered pigment.
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An Archaeometric Study of the Iron Age Ceramics from Quinta do Almaraz Archaeologic Site (8th to 5th Centuries BC)—Colour and Mineralogical Characterization
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Luis Filipe Vieira Ferreira, Ana Olaio, Manuel Francisco Costa Pereira and Isabel Luisa Ferreira Machado
Colorants 2024, 3(2), 111-124; https://doi.org/10.3390/colorants3020008 - 25 Apr 2024
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The ceramic pastes of ca. 31 samples recovered from the Almaraz archaeological site, located in the south bench of Tagus River, were studied in detail using XRF, micro-Raman and GSDR spectroscopies, as well as the XRD technique. The ceramic sherds could be grouped
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The ceramic pastes of ca. 31 samples recovered from the Almaraz archaeological site, located in the south bench of Tagus River, were studied in detail using XRF, micro-Raman and GSDR spectroscopies, as well as the XRD technique. The ceramic sherds could be grouped into six categories, red slip tableware, decorated tableware, yellow slip tableware, grey tableware, common tableware, and handmade pottery. Our studies of the mineralogic composition of the sherds’ body indicate all ceramics were produced locally, using siliceous clays in most cases and calcareous clays in a few ones. Micro-Raman and ground state diffuse reflectance absorption spectroscopy provided useful information regarding the materials used to produce the coloured ceramics: hematite and brookite for the red slip and decorated ceramics, jacobsite or carbon black for the black decoration or grey ceramics. For the yellow slip tableware, a simple engobe rich in yellow clay was used. XRF spectroscopic studies provided the elemental composition of all samples, and biplots of the potassium (K) versus calcium (Ca) contents, normalized to the silicon content of each ceramic paste, clearly show Pliocene and Miocene local clays sources were used to produce most ceramics. Only one sherd can be considered a Lisbon production.
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Open AccessArticle
Solid-State Luminescence with a Large Stokes Shift in Starch Functionalized with Low-Content ESIPT Dye
by
Emerson Colonetti, Lilian C. da Luz and Fabiano S. Rodembusch
Colorants 2024, 3(2), 99-110; https://doi.org/10.3390/colorants3020007 - 3 Apr 2024
Abstract
Herein, we present the preparation of solid-state photoactive starches with a large Stokes shift, along with the resulting materials. In this investigation, 2-(2′-hydroxyphenyl)benzazole derivatives responsive to intramolecular proton transfer in the excited state (ESIPT) were covalently bonded to the polymeric structure of starch
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Herein, we present the preparation of solid-state photoactive starches with a large Stokes shift, along with the resulting materials. In this investigation, 2-(2′-hydroxyphenyl)benzazole derivatives responsive to intramolecular proton transfer in the excited state (ESIPT) were covalently bonded to the polymeric structure of starch through a reaction involving an isothiocyanate group and the hydroxyl groups of starch. These compounds exhibit absorption at approximately 350 nm, which is related to fully spin- and symmetry-allowed π → π* electronic transitions, and solid-state fluorescence at approximately 500 nm, which features a significant separation between the absorption and emission maxima (~9000 cm−1). Due to the minimal use of fluorophores in functionalized starch preparation, this modification does not affect the original properties of the starch. Finally, photoactive starch-based films with significantly high transparency were successfully produced.
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(This article belongs to the Special Issue Feature Papers in Colorant Chemistry)
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Optical Investigation of 2-amino-7-isocyanofluorene, a Novel Blue-Emitting Solvatochromic Dye
by
Bence Kontra, Zoltán Mucsi, László Vanyorek and Miklós Nagy
Colorants 2024, 3(2), 86-98; https://doi.org/10.3390/colorants3020006 - 25 Mar 2024
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Smart solvatochromic isocyano-aminoarenes (ICAArs) have been gaining attention owing to their unique photophysical, antifungal and anticancer properties. Using a simple dehydration reaction with in situ-generated dichlorocarbene, we prepared 2-amino-7-isocyanofluorene (2,7-ICAF). We studied the effect of the longer polarization axis provided by the fluorene
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Smart solvatochromic isocyano-aminoarenes (ICAArs) have been gaining attention owing to their unique photophysical, antifungal and anticancer properties. Using a simple dehydration reaction with in situ-generated dichlorocarbene, we prepared 2-amino-7-isocyanofluorene (2,7-ICAF). We studied the effect of the longer polarization axis provided by the fluorene core on the spectral properties and we also compared it to those of the starting diamine. 2,7-ICAF shows a clear solvatochromic behavior close to the blue part (370–420 nm) of the visible spectrum. Quantum chemical calculations show internal charge transfer (ICT) between the donor amino and the electron-withdrawing isocyano groups. 2,7-ICAF has high molar absorptivity (ε = 15–18·103 M−1cm−1) and excellent quantum yield (Φf = 70–95%) in most solvents; however, its fluorescence is completely quenched in water. The high brightness (ε·Φf) and close to zero quantum yield in water may be favorable in biolabeling applications, where background fluorescence should be kept minimal. Overall, 2,7-ICAF shows enhanced photophysical properties compared to its previously investigated relative 4-amino-4′-isocyano-1,1′-biphenyl (4,4′-ICAB).
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Open AccessArticle
Decolorization and Detoxification of Industrial Wastewater Containing Indigo Carmine by Aspergillus niger AN400 in Sequential Reactors
by
Kelly Rodrigues, Alana M. X. de Sousa, Andreza D. O. dos Santos, Bárbara C. A. Barbosa, A. Rita Silva, Luciana Pereira and Glória M. M. Silva
Colorants 2024, 3(1), 73-85; https://doi.org/10.3390/colorants3010005 - 4 Mar 2024
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Effluents from the textile industry are an active problem in the sector and one of the world’s main environmental problems. The conventional treatments applied are not always efficient in terms of compliance with legislation, and, in many cases, the efficiency of treatment is
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Effluents from the textile industry are an active problem in the sector and one of the world’s main environmental problems. The conventional treatments applied are not always efficient in terms of compliance with legislation, and, in many cases, the efficiency of treatment is guaranteed by the enormous energy expenditure involved, camouflaging the momentary problem and not effectively treating it. In this work, batch reactors with immobilized biomass of Aspergillus niger AN400 were arranged in series for the treatment of real textile wastewater containing approximately 20 mg/L of indigo carmine. Sucrose was added as a co-substrate in concentrations of 1 g/L and 0.5 g/L, in the first and second reactors, respectively, over 19 cycles of 48 h. The highest decolorization rate in the system was (93 ± 4) %, with the largest amount removed in the first reactor (90 ± 6) %, occurring mainly by biological means. The production of aromatic by-products from the initial degradation of the dye molecule was reflected in the lower removal efficiency of dissolved organic matter: 52% in the first reactor, and 25% in the second reactor. The number of colonies of fungi was higher than that of bacteria, 2.24:1 and 2.44:1 in the first and second reactors, respectively. The treated effluent in the system showed less toxicity than the raw effluent, and this demonstrates the potential of this technology in the treatment of textile effluents containing indigo carmine.
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Open AccessReview
Azobenzene-Containing Schiff-Bases—Syntheses and Dyes Applications
by
Estelle Leonard, China Takeda and Takashiro Akitsu
Colorants 2024, 3(1), 53-72; https://doi.org/10.3390/colorants3010004 - 9 Feb 2024
Cited by 1
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Azo-Schiff bases contain an azo photochrome showing isomerization accompanying with color change, and an imine moiety (which can contribute to the metal complexation capability). The syntheses of these molecules will be described, and their dyes applications will be discussed, such as for fuel
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Azo-Schiff bases contain an azo photochrome showing isomerization accompanying with color change, and an imine moiety (which can contribute to the metal complexation capability). The syntheses of these molecules will be described, and their dyes applications will be discussed, such as for fuel cells, as photometric or colorimetric sensors. In addition, liquid crystals and their antibacterial efficiencies will also be discussed.
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Open AccessArticle
Development of a Carotenoid-Rich Microalgae Colorant by Microencapsulation
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Ana N. Nunes, Joana Monte, Soraya Rodríguez-Rojo, Isabel D. Nogueira, Luís F. Gouveia, Carla Brazinha and Ana A. Matias
Colorants 2024, 3(1), 39-52; https://doi.org/10.3390/colorants3010003 - 12 Jan 2024
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Dunaliella salina has been recognized as an excellent biomass source of carotenoid, which can be used as a natural orange coloring agent for food products. The most eco-friendly approach for extracting carotenoid is through supercritical carbon dioxide extraction, as it yields highly concentrated
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Dunaliella salina has been recognized as an excellent biomass source of carotenoid, which can be used as a natural orange coloring agent for food products. The most eco-friendly approach for extracting carotenoid is through supercritical carbon dioxide extraction, as it yields highly concentrated extracts while preventing pigment thermal degradation. However, there are limitations when a lipophilic extract is considered a food ingredient, in particular very difficult handling and low solubility in water-based products. The aim of this study was to develop a hydrosoluble form of a natural carotenoid-rich extract recovered from algae biomass within a biorefinery concept to be incorporated in aqueous-based food products. A two-step process was developed, starting with the emulsification of the supercritical extract into a mixture of maltodextrin and gum arabic, using soy lecithin as an emulsifier. The emulsification was followed by a spray-drying step. The impact of process variables on the encapsulation yield, efficiency, emulsion properties, and particle characteristics was studied. The resulting particles exhibited an intense orange color and good water dispersibility, facilitating uniform yellow coloring when incorporated into an aqueous-based product. Overall, spray-drying emulsions containing carotenoids derived from Dunaliella salina prove to be a promising strategy for the global market demand for natural colorants.
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Open AccessArticle
A Study on the Structure, Optical Properties and Cellular Localization of Novel 1,3-Benzothiazole-Substituted BODIPYs
by
Olga Kirkilessi, Christina Arapatzi, Heribert Reis, Vassiliki Kostourou, Kyriakos C. Prousis and Theodora Calogeropoulou
Colorants 2024, 3(1), 17-38; https://doi.org/10.3390/colorants3010002 - 31 Dec 2023
Cited by 1
Abstract
A library of seven novel 1,3-benzothiazole-substituted BODIPY derivatives with tunable optical properties was synthesized. The new fluorescent dyes exhibited bathochromically shifted absorptions (up to 670 nm) and emissions centered in the red and near-infrared spectral region (up to 677 nm) in comparison to
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A library of seven novel 1,3-benzothiazole-substituted BODIPY derivatives with tunable optical properties was synthesized. The new fluorescent dyes exhibited bathochromically shifted absorptions (up to 670 nm) and emissions centered in the red and near-infrared spectral region (up to 677 nm) in comparison to the parent compound 8-phenyl BODIPY (λabs: 499 nm, λemi: 508 nm). (TD)DFT calculations were performed to rationalize the spectroscopic properties of the new dyes. The cellular biodistribution of the new BODIPY dyes, their fluorescence stability and toxicity were investigated in both living and fixed fibroblasts using time-lapse fluorescent imaging and confocal microscopy. Six of the seven new dyes were photostable and non-toxic in vitro at 10 μM concentration. In addition, they efficiently stained the cell membrane, showing diffuse and dotty localization within the cell at low concentrations (1.0 and 0.1 μM). Specifically, dye TC498 was localized in vesicular structures in both live and fixed cells and could be used as a suitable marker in co-staining studies with other commonly used fluorescent probes.
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(This article belongs to the Special Issue Luminescent Small Molecules for Biochemistry)
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Open AccessReview
Bimetallic Fenton-like Catalysts in the Remediation of Dyes
by
Lydia R. Milam and Roy P. Planalp
Colorants 2024, 3(1), 1-16; https://doi.org/10.3390/colorants3010001 - 21 Dec 2023
Abstract
Remediation of organic dyes in natural waters is a significant environmental need under active study. This review analyzes bimetallic catalytic degradation systems that are based on the Fenton chemistry concept and that generate reactive oxygen species (ROS) as the agent of dye breakdown.
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Remediation of organic dyes in natural waters is a significant environmental need under active study. This review analyzes bimetallic catalytic degradation systems that are based on the Fenton chemistry concept and that generate reactive oxygen species (ROS) as the agent of dye breakdown. Recently developed advanced oxidation processes (AOPs) take advantage of bimetallic heterogeneous catalysts to facilitate rapid rates and full degradation. Catalysts based on two metals including iron, copper, molybdenum, cobalt and magnesium are discussed mechanistically as examples of effective radical ROS producers. The reactive oxygen species hydroxyl radical, superoxide radical, sulfate radical and singlet oxygen are discussed. System conditions for the best degradation are compared, with implementation techniques mentioned. The outlook for further studies of dye degradation is presented.
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(This article belongs to the Special Issue Feature Papers in Colorant Chemistry)
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Guest Editor: Anthony HarrimanDeadline: 31 December 2024