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Recent Progress on Functional Dyes and Their Applications

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A special issue of Colorants (ISSN 2079-6447).

Deadline for manuscript submissions: closed (31 December 2023) | Viewed by 24287

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Dr. Nadia Barbero

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Department of Chemistry, NIS Interdepartmental and INSTM Reference Centre, University of Torino, Via Giuria 7 and Via Quarello 15, 10100 Torino, Italy
Interests: synthesis and characterization of functional organic molecules and hybrid materials (organo-inorganic frameworks) for nonconventional and technological applications (nanotechnology, biotechnology, and photovoltaics)
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Dr. Carlotta Pontremoli

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Department of Chemistry, NIS Interdepartmental and INSTM Reference Centre, University of Torino, Via Giuria 7 and Via Quarello 15, 10100 Torino, Italy
Interests: mesoporous bioactive glasses; bone regeneration; cancer treatment; antimicrobial treatment; polymethine dyes; photodynamic therapy
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Dr. Simone Galliano

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Department of Chemistry, NIS Interdepartmental Center and INSTM Reference Centre, University of Torino, Via Pietro Giuria 7, 10125 Torino, Italy
Interests: dye-sensitized and thin film solar cells; functional organic (dyes and polymers) and hybrid materials (organo-inorganic frameworks) for technological applications

Special Issue Information

Dear Colleagues,

The rapid advances in material technology have brought to the definition of ‘functional dyes’ as attractive materials generating new functions that are e.g., changing their optical properties, converting energy, or recording information by external stimuli including light, temperature, pressure, pH, electric and magnetic field, etc.

As the result of considerable research efforts over the last few years, functional dyes have been applied as semiconductors, emitters and photosensitizers in optoelectronics and photovoltaics, optical and luminescent sensors for biological and environmental monitoring systems, and therapeutical agents for medical purposes.

Moreover, functional dyes have attracted growing interest as one of the most promising materials contributing to Sustainable Development Goals (SDGs 2030 Agenda for sustainable development).

In this context, the final aim of this Special Issue is to provide an overview of the most recent advances on functional dyes for high-technology and emerging applications such as dye-sensitized solar cells, photochromic materials, organic light emitting devices, organic semiconductors, hole-transporting materials, biological imaging, sensors, and photodynamic therapy.

In this respect, researchers working in this fascinating and avant-garde area are cordially invited to submit their original manuscripts relevant to the synthesis, fundamental studies, or applications of functional dyes.

Dr. Nadia Barbero
Dr. Carlotta Pontremoli
Dr. Simone Galliano
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Colorants is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

functional dyes
chromophores and fluorophores
near-infrared dyes
optical properties
photovoltaics
dye-sensitized solar cells
optoelectronics
photophysics, photochemistry and photobiology
bio-imaging and sensing
photodynamic therapy
phototermal therapy

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Published Papers (11 papers)

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Research

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16 pages, 2923 KiB

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 | Viewed by 912

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 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). Full article

(This article belongs to the Special Issue Recent Progress on Functional Dyes and Their Applications)

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20 pages, 3960 KiB

Open AccessArticle

Squaric Acid Core Substituted Unsymmetrical Squaraine Dyes for Dye-Sensitized Solar Cells: Effect of Electron Acceptors on Their Photovoltaic Performance

by Safalmani Pradhan, Yuki Kurokawa, Suraya Shaban and Shyam S. Pandey

Colorants 2023, 2(4), 654-673; https://doi.org/10.3390/colorants2040034 - 6 Nov 2023

Cited by 3 | Viewed by 1659

Abstract

The design and development of sensitizing dyes possessing wide-wavelength photon harvesting encompassing visible to near-infrared (NIR) wavelength regions are unavoidable for increasing the overall efficiency of dye-sensitized solar cells (DSSCs). In this study, three far-red-sensitive squaraine sensitizers were designed computationally, synthesized, and characterized, aiming towards their suitability as a potential sensitizer for DSSCs. It has been found that the incorporation of an electron acceptor moiety in the central squaraine core brought about a red shift in the absorption maximum (λ_max) and the emergence of a secondary absorption band in the blue region, thus broadening the photon-harvesting window. In addition, it also lowered the dye’s HOMO energy level enabling a facile regeneration of the photo-excited dye, which improved the photovoltaic performance of SQ-223, exhibiting a photoconversion efficiency (PCE) of 4.67%. Thereafter, to address the issue of wide-wavelength photon harvesting, DSSCs were fabricated by co-adsorbing two complementary dyes SQ-223 and D-131 in various molar ratios. The DSSC fabricated with D-131 and SQ-223 in 9:1 molar ratio displayed the best photovoltaic performance with a PCE of 5.81%, a significantly higher PCE when compared to corresponding individual dye-based DSSCs containing D-131 (3.94%) and SQ-223 (4.67%). Full article

(This article belongs to the Special Issue Recent Progress on Functional Dyes and Their Applications)

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14 pages, 4478 KiB

Open AccessArticle

Evaluation of Solar Conversion Efficiency in Dye-sensitized Solar Cells Using Natural Dyes Extracted from Alpinia purpurata and Alstroemeria Flower Petals as Novel Photosensitizers

by Leonardo Ricardo Bernardes da Conceição, Higor Oliveira da Cunha, Arcano Matheus Bragança Leite, Rajendran Suresh Babu, Sebastian Raja, Caue Ribeiro and Ana Lucia Ferreira de Barros

Colorants 2023, 2(4), 618-631; https://doi.org/10.3390/colorants2040032 - 10 Oct 2023

Cited by 12 | Viewed by 2070

Abstract

Herein, we evaluate the conversion efficiency of dye-sensitized solar cells (DSSCs) photosensitized using two different natural dyes extracted from Alpinia purpurata and Alstroemeria flower petals. The appreciable absorption capacity of the extracts in the visible light region was examined through absorption spectroscopy. The functional groups of the corresponding pigments were identified through Fourier transform spectroscopy (FTIR) technique thus indicating the presence of cyanidin 3-glycosides and piperine in the flowers of Alstroemeria and Alpinia purpurata. The extracted dyes were immobilized on TiO₂ on transparent conducting FTO glass, which were used as photoanode. The dye-coated TiO₂ photoanode, pt photocathode and iodide/triiodide redox electrolyte assembled into a cell module was illuminated by a light source intensity 100 mW/cm² to measure the photovoltaic conversion efficiency of DSSCs. The TiO₂ anode and Pt counter electrode surface roughness and morphological studies were evaluated using atomic force microscope (AFM) and field emission scanning electron microscopy (FESEM), respectively. Through the photoelectric characterizations, it was promising to verify that the solar conversion efficiency was calculated with the photovoltaic cell sensitized by Alstroemeria and Alpinia purpurata. This was achieved with a yield (η) of 1.74% and 0.65%, with an open-circuit voltage (V_oc) of 0.39 and 0.53 V, short-circuit current density (J_sc) of 2.04 and 0.49 mA/cm², fill factor (FF) of 0.35 and 0.40, and P_max of 0.280 and 0.100 mW/cm², respectively. The results are promising and demonstrate the importance of the search for new natural dyes to be used in organic solar cells for the development of devices that generate electricity in a sustainable way. Full article

(This article belongs to the Special Issue Recent Progress on Functional Dyes and Their Applications)

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10 pages, 1397 KiB

Open AccessArticle

Metal-Free Counter Electrodes for DSSCs Based on Nitrogen-Doped Reduced Graphene Oxide Materials

by Isolda Duerto, Clara Carrera, Daniel Barrios, Ana M. Benito, Wolfgang K. Maser, Belén Villacampa, Enrique García-Bordejé and María-Jesús Blesa

Colorants 2023, 2(2), 443-452; https://doi.org/10.3390/colorants2020020 - 16 Jun 2023

Cited by 2 | Viewed by 1516

Abstract

The importance of counter electrodes in Dye Sensitized Solar Cells (DSSCs) cannot be neglected as they enable the transfer of electrons across the outer circuit, thereby facilitating the reduction reaction of the I₃⁻/I⁻ redox electrolyte. However, the dissolution and deposition of the usual platinum layer on the counter electrode has resulted in contamination concerns. To address this issue, metal-free counter electrodes made of reduced graphene oxide (rGO) aerogels were developed and their catalytic performance towards I₃⁻ reduction was evaluated. The reduced graphene materials were characterized, and the fitting analysis of XPS revealed the presence of various nitrogen species, with the primary peaks attributed to pyridinic and pyrrolic nitrogen. The hydrothermal treatment of graphene oxide (GO) resulted in a higher graphitic character and the intensification of the contacts between graphene nanosheets, which should entail higher electrical conductivity, both in-plane and between rGO sheets. Additionally, the presence of nitrogen-provided active sites promoted the catalytic reduction of the electrolyte. Encouragingly, good charge transfer rates were observed between the counter electrode and the electrolyte in the assembled DSSCs, resulting in good photocurrents and exceptional stability over the course of nearly 1200 h after cell assembly. The results obtained suggest that these GO-based systems are promising candidates for developing metal-free counter electrodes for DSSC, supporting the interest of further study. Full article

(This article belongs to the Special Issue Recent Progress on Functional Dyes and Their Applications)

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15 pages, 4392 KiB

Open AccessArticle

Long-Alkyl Chain Functionalized Imidazo[1,5-a]pyridine Derivatives as Blue Emissive Dyes

by Gioele Colombo, Anita Cinco, G. Attilio Ardizzoia and Stefano Brenna

Colorants 2023, 2(2), 179-193; https://doi.org/10.3390/colorants2020012 - 10 Apr 2023

Cited by 5 | Viewed by 2162

Abstract

A series of boron difluoride compounds with 2-(imidazo[1,5-a]pyridin-3-yl)phenols bearing alkylic chains at the 1-position has been synthesized and characterized both with ¹H and ¹³C NMR and infrared spectroscopy. This series of compounds displayed blue emission in solution and in thin polymeric films, with interesting features like large Stokes shifts and good fluorescence quantum yields. Time-Dependent Density Functional Theory (TD-DFT) calculations allowed for the identification of the main electronic transitions as intra ligand transitions (¹ILT), as corroborated by the Natural Transition Orbitals (NTOs) shapes. Full article

(This article belongs to the Special Issue Recent Progress on Functional Dyes and Their Applications)

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24 pages, 5987 KiB

Open AccessArticle

Photocatalytic Properties of PbMoO₄ Nanocrystals against Cationic and Anionic Dyes in Several Experimental Conditions

by Francisco Nobre, Jairo Trindade, Marcus do Nascimento, Giancarlo Souza, Otoniel Mendes, Anderson Albuquerque, Júlio Sambrano, Paulo Couceiro, Walter Brito, Yurimiler Leyet Ruiz and José Milton De Matos

Colorants 2023, 2(1), 111-134; https://doi.org/10.3390/colorants2010008 - 5 Mar 2023

Cited by 2 | Viewed by 1990

Abstract

This paper reports easy and fast synthesis of PbMoO₄ nanocrystals by microwave-assisted hydrothermal (MH) method at different synthesis times (1, 10, 30 and 60 min) at 100 °C. X-ray diffraction, Rietveld refinement and Raman spectroscopy confirm all characteristics of diffraction peaks and active vibrational modes of the pure scheelite structure (tetragonal, I41/a) for all synthesized PbMoO₄ nanocrystals. The optical bandgap calculated directly from the samples is close to 3.5 eV. The images collected by scanning electron microscopy show particles with mean length from 159.90(8) nm to 303.02(3) nm with greater exposure of planes (111), (100), (011) and (110). The photocatalytic activity of PbMoO₄ nanocrystals against RhB and RBBR dyes resulted in successful degradation in short time intervals using ultraviolet light, where the best performance was achieved for the PbMoO₄-10 sample, which was 29.2 and 51.8 times more effective than photolysis. The contribution of oxidant species was monitored by radical scavengers, which confirms that holes (h⁺) are the main oxidative species in photodegradation of RhB and RBBR dyes, while reuse of the catalyst against RhB and RBBR dyes confirms high stability of the catalyst, although recycled four times. Full article

(This article belongs to the Special Issue Recent Progress on Functional Dyes and Their Applications)

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21 pages, 4253 KiB

Open AccessArticle

Mathematical Approach to Optimizing the Panchromatic Absorption of Natural Dye Combinations for Dye-Sensitized Solar Cells

by Noah B. Manz and Paul A. Fuierer

Colorants 2023, 2(1), 90-110; https://doi.org/10.3390/colorants2010007 - 2 Mar 2023

Cited by 2 | Viewed by 1991

Abstract

The goal of this work was to optimize the combination of natural dyes producing panchromatic absorption matched to the AM1.5 solar spectrum for use in dye sensitized solar cells (DSSCs). Six classes of dyes (Anthocyanins, Betalins, Chlorophyll, Xanthonoids, Curcuminoids and Phycobilins) were explored. UV-Vis data and radial basis function interpolation were used to model the absorbance of 2568 combinations, and three objective functions determined the most commensurable spectrum. TiO₂ anodes were sensitized with 42 dye combinations and IV measurements made on simple cells. The absorbance-optimized combination yielded an efficiency of only 0.41%, compared to 1.31% for a simple 1:1 molar ratio of Curcuminoids and α-Mangostin, which showed symbiotic effects. Our results indicate that panchromatic absorption alone is not sufficient to predict optimal DSSC performance, although the mathematical approach may have broader application. Full article

(This article belongs to the Special Issue Recent Progress on Functional Dyes and Their Applications)

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15 pages, 3427 KiB

Open AccessArticle

pH-Induced Orthogonal Photoresponse of trans-Chalcone Isomers and Related Compounds in Equilibria

by Jeonghee Kang, Ketevan Basilashvili, Barney Yoo and Jong I. Lee

Colorants 2023, 2(1), 58-72; https://doi.org/10.3390/colorants2010005 - 17 Feb 2023

Cited by 2 | Viewed by 2249

Abstract

Photoresponsive molecular devices can be a valuable tool to promote chemical changes in response to multiple signals, such as photons and pH, to deliver drugs or to detect physiological conditions in vivo. For example, trans-chalcones (Ct) from 4′-hydroxyflavylium (F1) and 7-hydroxyflavylium (F2) can undergo cis-trans isomerization by photoreaction into many different structures. The isomerization takes place at a slow rate in response to pH change; however, it can be done in seconds by photoreaction. In the investigation, as confirming the previous reports, 3-(2-hydroxy-phenyl)-1-(4-hydroxy-phenyl)-propenone, the trans-chalcone (Ct_F1) from F1, produces flavylium ions in pH = 1–4.5. Then, we further discovered that the flavylium quickly releases protons to yield the corresponding quinoidal base (A) in a solution of pH = 5.2 during irradiation with 350 nm. Meanwhile, the photolysis of 3-(2,4-dihydroxy-phenyl)-1-phenyl-propenone, the trans-chalcone (Ct_F2) from F2 at pH = 5.6, induces photoacid behavior by losing a proton from the trans-chalcone to generate Ct²⁻. The different outcomes of these nearly colorless chalcones under similar pH conditions and with the same photochemical conditions can be useful when yielding colored AH⁺, A, or Ct²⁻ in a mildly acidic pH environment with temporal and spatial control using photochemical means. Full article

(This article belongs to the Special Issue Recent Progress on Functional Dyes and Their Applications)

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9 pages, 2623 KiB

Open AccessArticle

N-Annulation of the BTI Rylene Imide Organic Building Block: Impact on the Optoelectronic Properties of π-Extended Molecular Structures

by José María Andrés Castán, Sana Abidi, Tatiana Ghanem, Saad Touihri, Philippe Blanchard, Gregory C. Welch, Yulian Zagranyarski, Julien Boixel, Bright Walker, Pierre Josse and Clément Cabanetos

Colorants 2023, 2(1), 22-30; https://doi.org/10.3390/colorants2010002 - 30 Dec 2022

Cited by 4 | Viewed by 2303

Abstract

Benzothioxanthene imide (BTI) has recently emerged as an interesting and promising block for organic electronics. In this contribution, we report on the impact of the N-annulation of the latter dye on the optoelectronic of π-extended molecular structures. To do so, the thiophene-diketopyrrolopyrrole was selected, as central π-conjugated core, and either end-capped with two BTIs or its N-annulated version, namely the TCI. While almost similar band gaps were measured for individual rylene imide dyes, significant differences were highlighted, and rationalized, on their π-extended counterparts. Full article

(This article belongs to the Special Issue Recent Progress on Functional Dyes and Their Applications)

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Review

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28 pages, 11012 KiB

Open AccessReview

N-Annulated Perylene Diimide Non-Fullerene Acceptors for Organic Photovoltaics

by Mahmoud E. Farahat and Gregory C. Welch

Colorants 2023, 2(1), 151-178; https://doi.org/10.3390/colorants2010011 - 21 Mar 2023

Cited by 12 | Viewed by 2647

Abstract

This work covers the development of non-fullerene acceptors for use in organic photovoltaics built using the N-annulated perylene diimide dye. The classic perylene diimide dye has been extensively used to construct non-fullerene acceptors, leading to device power conversion efficiencies of over 10%. Strong visible light absorption and deep frontier molecular energy levels have made such materials (both molecular and polymeric) near ideal for pairing with narrow-gap conjugated polymers in bulk-heterojunction active layers. The N-annulation of the dye provides an extra site for side-chain engineering and alters the electronic structure of the polycyclic aromatic core. In addition, N-annulation allows for selective bromination of the perylene core, leading to building blocks that are useful for the construction of large molecular frameworks using the atom-economical direct heteroarylation cross-coupling method. Herein, we detail a series of molecules developed by our team that are based on the N-annulated perylene diimide in the form of dimers with different cores (both electron-rich and electron-deficient); dimers with varied side chains; tetramers with varying geometries; and large, asymmetric molecules with internal energy cascades. The use of these molecules as non-fullerene acceptors in organic photovoltaic devices (binary and ternary blends, outdoor and indoor light applications, and spin-coated vs. slot-die-coated photoactive layers) is presented. Full article

(This article belongs to the Special Issue Recent Progress on Functional Dyes and Their Applications)

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14 pages, 1045 KiB

Open AccessReview

Alternative Sources of Natural Photosensitizers: Role of Algae in Dye-Sensitized Solar Cell

by Eddie Nahúm Armendáriz-Mireles, Carlos Adrián Calles-Arriaga, Wilian Pech-Rodríguez, Adalberto Castillo-Robles and Enrique Rocha-Rangel

Colorants 2023, 2(1), 137-150; https://doi.org/10.3390/colorants2010010 - 17 Mar 2023

Cited by 3 | Viewed by 2654

Abstract

In this paper, the potential of marine algae to act as sensitizers is systematically studied and presented. We aim to find a feasible financial strategy to enhance the global efficiency of dye-sensitized solar cells (DSSC). Algae are mainly composed of chlorophylls, carotenoids, flavonoids, and Betalains, which are essential pigments that confer unique characteristics that are required in natural sensitizers. Therefore, this review aims to unveil and understand the underlying mechanism between algae pigments and photoelectrodes and to conduct a comprehensive analysis to determine the effect of algae dye on light absorption efficiency and electron transport. The structural, morphological, optical, and electrochemical impedance properties are deeply analyzed, and we show the current opportunities for natural dyes to be used in energy technologies through DSSC. A comparison of several bibliographic sources dealing with DSSC based on algae provided a general overview of the improvements in factors such as the recombination times, the filling factor, and the Voc values. The contributions of this paper relate to the conversion efficiency and future applications in the DSSC field. Finally, this review exemplifies that the nature of the pigment affects the photophysical properties of the cell. Thus, this paper may contribute to future investigations of DSSC when choosing efficient natural dyes according to their optical and electronic properties. Therefore, this work provides the knowledge required to efficiently merge materials and dyes, in which photovoltaic energy systems’ reproducibility and scalability still represent a challenge. Lastly, this document discusses the natural pigments’ stability and the approaches to improve their chemical stability. Full article

(This article belongs to the Special Issue Recent Progress on Functional Dyes and Their Applications)

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