Colorants

2 pages, 142 KiB

Open AccessEditorial

by Anthony Harriman

Colorants 2024, 3(2), 136-137; https://0-doi-org.brum.beds.ac.uk/10.3390/colorants3020010 - 14 May 2024

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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 [...] Full article

11 pages, 2511 KiB

Open AccessArticle

Highly Stable Hybrid Pigments Prepared from Organic Chromophores and Fluorinated Hydrotalcites

by Magali Hernández, Carlos Felipe, Ariel Guzmán-Vargas, José Luis Rivera and Enrique Lima

Colorants 2024, 3(2), 125-135; https://0-doi-org.brum.beds.ac.uk/10.3390/colorants3020009 - 9 May 2024

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Abstract

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 [...] Read more.

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. Full article

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14 pages, 2996 KiB

Open AccessArticle

An Archaeometric Study of the Iron Age Ceramics from Quinta do Almaraz Archaeologic Site (8th to 5th Centuries BC)—Colour and Mineralogical Characterization

by Luis Filipe Vieira Ferreira, Ana Olaio, Manuel Francisco Costa Pereira and Isabel Luisa Ferreira Machado

Colorants 2024, 3(2), 111-124; https://0-doi-org.brum.beds.ac.uk/10.3390/colorants3020008 - 25 Apr 2024

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Abstract

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 [...] Read more.

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. Full article

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12 pages, 2417 KiB

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://0-doi-org.brum.beds.ac.uk/10.3390/colorants3020007 - 3 Apr 2024

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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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Feature Papers in Colorant Chemistry)

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13 pages, 4752 KiB

Open AccessArticle

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://0-doi-org.brum.beds.ac.uk/10.3390/colorants3020006 - 25 Mar 2024

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Abstract

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 [...] Read more.

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 (Φ_f = 70–95%) in most solvents; however, its fluorescence is completely quenched in water. The high brightness (ε·Φ_f) 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). Full article

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Colorants, Volume 3, Issue 2 (June 2024) – 5 articles

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