Syntheses, Properties, and Applications of Organic Dyes and Pigments

A special issue of Coatings (ISSN 2079-6412). This special issue belongs to the section "Corrosion, Wear and Erosion".

Deadline for manuscript submissions: closed (20 December 2023) | Viewed by 11153

Special Issue Editor

Special Issue Information

Dear Colleagues,

Today, our world is surrounded by natural and synthetic colored molecules, termed colorants, characterized by mobile electrons (pi-electrons) that can be excited by visible light and then emit radiation in the visible range of the spectrum (400–700 nm).

Recent literature is full of publications on the synthesis and characterization of new dyes (porphyrins, phthalocyanines, and so on) and pigments. The aim of this Special Issue is to present research papers that renew the recent discoveries in the field of dyes and pigments. Organic and inorganic dyes will be presented for visible and near infrared regions, and their use in medical applications, such as cancer phototherapy and biomedical analysis, capture and storage of solar energy, optical images and color laser marking for security documents, will be exemplified, too. Last but not least, some of the materials for cultural heritage conservation will be addressed. Although this problem cannot be entirely solved in the field of application, the collection of articles in this Special Issue will be helpful for researchers, academics and industrial agents. Contributions as original articles and review articles are encouraged, covering different areas of application.

Prof. Dr. Rodica Mariana Ion
Guest Editor

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Keywords

  • Functional dyes and pigments
  • Medical dyes
  • Biomedical applications
  • Photodynamic therapy
  • Natural dyes
  • Dyes for solar cells
  • Hair dyes
  • Textile dyes
  • Inorganic colorants
  • Organic semiconductors
  • Solar cells
  • Nonlinear optical dyes
  • Laser dyes
  • Pigments and coatings for cultural heritage

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Related Special Issue

Published Papers (4 papers)

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Research

18 pages, 10421 KiB  
Article
Non-Invasive Characterisation of the Wall Paintings in the Byzantine Church of Palazzo Simi (Bari, Italy) and Digital Photogrammetric Survey for a Pigment Mapping
by Giovanna Fioretti, Gioacchino Tempesta, Salvatore Capotorto and Giacomo Eramo
Coatings 2023, 13(6), 996; https://doi.org/10.3390/coatings13060996 - 26 May 2023
Cited by 1 | Viewed by 1396
Abstract
The paper illustrates the results of a non-invasive characterisation of pigments and their mixtures in the pictorial surfaces of the wall paintings (10th century) found in the Byzantine church of Palazzo Simi in Bari (Italy). The investigation techniques included portable digital polarised microscopy, [...] Read more.
The paper illustrates the results of a non-invasive characterisation of pigments and their mixtures in the pictorial surfaces of the wall paintings (10th century) found in the Byzantine church of Palazzo Simi in Bari (Italy). The investigation techniques included portable digital polarised microscopy, fibre optic reflectance spectroscopy (FORS) and X-ray fluorescence spectroscopy (XRF). Data comparison supported the recognition of red and yellow ochres, green earth, vine black, minium and Egyptian blue. The presence of some pigment mixtures demonstrated the recurrence of specific technical expedient used by local medieval artists in order to simulate more expensive pigments, which enabled contribution to the understanding of the valuable artistic tradition of the Apulian Middle Age. Both for purposes of conservation and fruition of the site, which is not always accessible, and due to the complexity in taking suitable photographs for the representation of results, the latter was performed on orthophotos extracted from a digital photogrammetric 3D model of the whole archaeological site. By means of chromatic overlapped layers, an interactive compositional map of the pictorial surfaces was produced. Full article
(This article belongs to the Special Issue Syntheses, Properties, and Applications of Organic Dyes and Pigments)
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19 pages, 7671 KiB  
Article
A Multi-Analytical Investigation of Roman Frescoes from Rapoltu Mare (Romania)
by Rodica-Mariana Ion, Marius Gheorghe Barbu, Andrei Gonciar, Gabriel Vasilievici, Anca Irina Gheboianu, Sofia Slamnoiu-Teodorescu, Madalina Elena David, Lorena Iancu and Ramona Marina Grigorescu
Coatings 2022, 12(4), 530; https://doi.org/10.3390/coatings12040530 - 14 Apr 2022
Cited by 7 | Viewed by 2898
Abstract
(1) Background: Due to the precarious situation of many monuments or archeological sites, analytical investigations are necessary to obtain information about the used materials, as well as to identify the most appropriate solutions for their conservation/restoration. This paper addresses the characterization of mural [...] Read more.
(1) Background: Due to the precarious situation of many monuments or archeological sites, analytical investigations are necessary to obtain information about the used materials, as well as to identify the most appropriate solutions for their conservation/restoration. This paper addresses the characterization of mural painting fragments collected during the excavation in 2018 in Rapoltu Mare (La vie), Deva. (2) Methods: Specific analytical techniques were used, as follows: X-ray diffractometry (XRD), wavelength dispersive X-ray fluorescence (WDXRF), optical microscopy (OM), zoom microscopy and scanning electron microscopy (SEM), spectroscopic techniques (UV–Vis, FTIR, Raman), porosity and thermal analysis, all of which provide information about the structure, chemical composition, morphology and topography of pigments and their deterioration as well. (3) Results: Up to seven different pigments were identified: Egyptian blue, carbon, calcite, gypsum, hematite, goethite and green earth. Egyptian Blue is identified in all the other color areas, except the white area: in the green zone (as degradation product with beeswax) and in the red zone (in mixture with ochre) too. In addition, carbon and beeswax were highlighted as toner and binder for pigments, respectively. In the presence of the organic beeswax binding environment, the Egyptian blue pigment particles darkened or turned yellow significantly, changing the blue to a greenish color. It is also possible to identify wollastonite (CaSiO3) in the blue pigment, which indicates that the temperature used in the manufacturing of Egyptian blue was higher than 950 °C from thermal analysis. The presence of apatite, hematite and gypsum deposits in the Hunedoara region certifies that these pigments could have been of local origin, as demonstrated by the presence of analytically identified elements (Fe, P, S, Ca). (4) Conclusions: The analytical techniques used for such investigations have highlighted the main pigments used in Roman times for various Roman murals. Full article
(This article belongs to the Special Issue Syntheses, Properties, and Applications of Organic Dyes and Pigments)
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15 pages, 3825 KiB  
Article
Research on Interface Modification and Thermal Insulation/Anticorrosive Properties of Vacuum Ceramic Bead Coating
by Jin Gao, Taiyang Zhu, Zhi Zhang, Yuan Kong and Xin Zhang
Coatings 2022, 12(3), 304; https://doi.org/10.3390/coatings12030304 - 24 Feb 2022
Cited by 3 | Viewed by 2734
Abstract
The thermal insulation effect of the coating was closely related to the content of the thermal insulation filler, but too much filler would cause interfacial compatibility problems of various substances in the coating, micro-defects in the coating, and affect the anti–corrosion performance of [...] Read more.
The thermal insulation effect of the coating was closely related to the content of the thermal insulation filler, but too much filler would cause interfacial compatibility problems of various substances in the coating, micro-defects in the coating, and affect the anti–corrosion performance of the coating. Therefore, solving the interface problem was the key to preparing a coating with heat insulation and anticorrosion functions. In this study, organic–inorganic hybrid polymer was used to modify the surface of vacuum ceramic microbeads, and epoxy–silicone resin was used as the film–forming material to prepare a heat-insulating and anticorrosive coating that can withstand 200 °C. The SEM morphology showed that the interface compatibility of the vacuum ceramic beads modified by the organic–inorganic hybrid agent and the film-forming material were improved, the dispersibility was significantly improved, and the beads were tightly arranged; the thermal conductivity of the coating reached 0.1587 W/(m·K), which decreased by 50% after adding 20% ceramic beads, ANSYS finite element simulation showed that the coating has good thermal insulation performance; after the coating underwent a thermal aging test at 200 °C for 600 h, the microstructure was dense, and the low-frequency impedance modulus was still around 109 Ω·cm2. There was no obvious defect in the microstructure after the alternating cold and heat test for 600 h; the low-frequency impedance modulus was still above 108 Ω·cm2, and the low-frequency impedance modulus of the coating was 1010 Ω·cm2 after the 130d immersion test, indicating that the coating had good heat resistance and anti-corrosion performance. Full article
(This article belongs to the Special Issue Syntheses, Properties, and Applications of Organic Dyes and Pigments)
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12 pages, 1380 KiB  
Article
Push-Pull Heterocyclic Dyes Based on Pyrrole and Thiophene: Synthesis and Evaluation of Their Optical, Redox and Photovoltaic Properties
by Sara S. M. Fernandes, Maria Cidália R. Castro, Dzmitry Ivanou, Adélio Mendes and Maria Manuela M. Raposo
Coatings 2022, 12(1), 34; https://doi.org/10.3390/coatings12010034 - 28 Dec 2021
Cited by 14 | Viewed by 2304
Abstract
Three heterocyclic dyes were synthesized having in mind the changes in the photovoltaic, optical and redox properties by functionalization of 5-aryl-thieno[3,2-b]thiophene, 5-arylthiophene and bis-methylpyrrolylthiophene π-bridges with different donor, acceptor/anchoring groups. Knoevenagel condensation of the aldehyde precursors with 2-cyanoacetic acid was [...] Read more.
Three heterocyclic dyes were synthesized having in mind the changes in the photovoltaic, optical and redox properties by functionalization of 5-aryl-thieno[3,2-b]thiophene, 5-arylthiophene and bis-methylpyrrolylthiophene π-bridges with different donor, acceptor/anchoring groups. Knoevenagel condensation of the aldehyde precursors with 2-cyanoacetic acid was used to prepare the donor-acceptor functionalized heterocyclic molecules. These organic metal-free dyes are constituted by thieno[3,2-b]thiophene, arylthiophene, bis-methylpyrrolylthiophene, spacers and one or two cyanoacetic acid acceptor groups and different electron donor groups (alkoxyl, and pyrrole electron-rich heterocycle). The evaluation of the redox, optical and photovoltaic properties of these compounds indicate that 5-aryl-thieno[3,2-b]thiophene-based dye functionalized with an ethoxyl electron donor and a cyanoacetic acid electron acceptor group/anchoring moiety displays as sensitizer for DSSCs the best conversion efficiency (2.21%). It is mainly assigned to the higher molar extinction coefficient, long π-conjugation of the heterocyclic system, higher oxidation potential and strong electron donating capacity of the ethoxyl group compared to the pirrolyl moiety. Full article
(This article belongs to the Special Issue Syntheses, Properties, and Applications of Organic Dyes and Pigments)
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