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24 pages, 6128 KiB

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

Viewed by 453

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 [...] Read more.

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 (E_VB) and conduction (E_CB) 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. Full article

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

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15 pages, 5236 KiB

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

Viewed by 626

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 [...] Read more.

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. Full article

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

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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://doi.org/10.3390/colorants3020007 - 3 Apr 2024

Viewed by 967

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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11 pages, 4875 KiB

Open AccessArticle

Synthesis of High Near-Infrared Reflective Black Pigment Based on YMn₂O₅

by Kazuki Yamaguchi, Satoru Mochizuki, Yudai Nagato, Takuro Morimoto and Toshiyuki Masui

Colorants 2023, 2(4), 705-715; https://doi.org/10.3390/colorants2040036 - 6 Dec 2023

Cited by 1 | Viewed by 1381

Abstract

Y(Mn_0.95M_0.05)₂O₅ (M = Al, Fe, Ga, Ti, and Zr) samples were synthesized via a sol–gel method using citric acid to find a new near-infrared (NIR) reflective black pigment. Among these samples, the optical reflectance of Y(Mn [...] Read more.

Y(Mn_0.95M_0.05)₂O₅ (M = Al, Fe, Ga, Ti, and Zr) samples were synthesized via a sol–gel method using citric acid to find a new near-infrared (NIR) reflective black pigment. Among these samples, the optical reflectance of Y(Mn_0.95Fe_0.05)₂O₅ and Y(Mn_0.95Ga_0.05)₂O₅ in the near-infrared region was found to be larger than that of YMn₂O₅. Then, the concentration of the dopant (Fe or Ga) was changed between 0 and 15%, and the resulting UV–Vis–NIR reflectance spectra were measured. As a result, the optical reflectance of the Fe-doped samples decreased in the near-infrared region, while that of the Ga-doped samples increased. Accordingly, Y(Mn_1−xGa_x)₂O₅ (0 ≤ x ≤ 0.20) samples were synthesized, and the crystal structure, particle size, optical properties, and color of the samples were characterized. The single-phase samples were obtained in the composition range of 0 ≤ x ≤ 0.15, and the lattice volume decreased with increasing Ga³⁺ concentration. Optical absorption below 850 nm was attributed to the charge transfer transition between O_2p and Mn_3d orbitals, and the absorption wavelength of Y(Mn_1−xGa_x)₂O₅ shifted to the shorter wavelength side as the Ga³⁺ content increased, because of the decrease in the Mn³⁺ concentration. Although the sample color became slightly reddish black by the Ga³⁺ doping, the solar reflectance in the near-infrared region reached 47.6% at the composition of Y(Mn_0.85Ga_0.15)₂O₅. Furthermore, this NIR reflectance value was higher than those of the commercially available products (R < 45%). Full article

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

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13 pages, 9116 KiB

Open AccessArticle

Repurposing the Strontium Ranelate Antiosteoporotic Drug as a New Outstanding Biocompatible Blue Dye

by Luca M. Sihn, Erick L. Bastos, Marcelo Nakamura, Mayara K. Uchiyama and Henrique E. Toma

Colorants 2023, 2(3), 578-590; https://doi.org/10.3390/colorants2030029 - 13 Sep 2023

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Abstract

Blue dyes are relatively uncommon in nature, and a novel dithiophene dye (RanB) is reported in this paper. This dye is derived from an old anti-osteoporotic drug and is a metal ion complexing agent, displaying a planar molecular structure, with two sets of [...] Read more.

Blue dyes are relatively uncommon in nature, and a novel dithiophene dye (RanB) is reported in this paper. This dye is derived from an old anti-osteoporotic drug and is a metal ion complexing agent, displaying a planar molecular structure, with two sets of carboxylate, isonitrile, thiophene, and iminodiacetate groups. The blue color originates from a strong absorption peak at 648 nm, accompanied by an unusual fluorescence at 555 nm, with higher energy compared to the main absorption band. RanB forms complexes with lanthanoid ions through the iminodiacetate groups and serves as an effective sensitizer for Tb³⁺ ions, heightening their emission and improving their use as luminescent agents. Its photo-physical properties and the interaction with Tb³⁺ have been investigated using absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopy, along with computational methods (ZINDO/S and DFT). The RanB toxicity in human umbilical vein endothelial cells has also been tested, showing a lack of toxicity, holding promising prospects for application as a luminescent and coloring agent in pharmaceuticals and food. Full article

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

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13 pages, 1764 KiB

Open AccessArticle

Adsorption Process of Methyl Orange Dye onto Zinc Hydroxide Nitrate: Kinetic and Thermodynamic Studies

by Daiane Amaral de Ramos Nogueira, Tânia Marina Palhano Zanela, Monielly Viomar Machado, Carlos Alberto Policiano Almeida and Rafael Marangoni

Colorants 2023, 2(3), 565-577; https://doi.org/10.3390/colorants2030028 - 6 Sep 2023

Cited by 2 | Viewed by 1351

Abstract

Zinc hydroxide nitrate (ZHN) was used as an anionic adsorbent for the removal of methyl orange (MO) dye from aqueous solutions. ZHN was characterized via X-ray diffraction (XRD) and infrared spectroscopy (FTIR) techniques. Investigations were carried out to see how the adsorption of [...] Read more.

Zinc hydroxide nitrate (ZHN) was used as an anionic adsorbent for the removal of methyl orange (MO) dye from aqueous solutions. ZHN was characterized via X-ray diffraction (XRD) and infrared spectroscopy (FTIR) techniques. Investigations were carried out to see how the adsorption of MO was affected by factors such as initial MO concentration, contact time and temperature. Adsorption isotherms were analyzed using the Langmuir and Freundlich equations, with the first one being the better result for the equilibrium data. Adsorption kinetics was studied through applying pseudo-first and pseudo-second-order kinetic models, and the experimental data were better fitted to the pseudo-second-order model. The activation energy was determined using the Arrhenius equation to be 105.45 kJ mol⁻¹, revealing the chemical nature of the adsorption process. The thermodynamic parameters were also determined, showing the adsorption of MO onto ZHN to be a non-spontaneous and exothermic process. The experimental results showed ZHN as a potential adsorbent with adsorption capacity for removing anionic dyes from water medium. Full article

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

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13 pages, 4946 KiB

Open AccessArticle

Enhanced Dyeing of Polypropylene Using Fluorine–Oxygen Gas Mixtures

by Masanari Namie, Jae-Ho Kim and Susumu Yonezawa

Colorants 2023, 2(3), 552-564; https://doi.org/10.3390/colorants2030027 - 31 Aug 2023

Viewed by 1477

Abstract

Surface fluorination with pure F₂ gas can easily make the surface on PP (polypropylene) hydrophobic, and it causes limited dyeability, as reported in a previous paper. In this study, to produce a more hydrophilic surface, surface fluorination of PP was performed at [...] Read more.

Surface fluorination with pure F₂ gas can easily make the surface on PP (polypropylene) hydrophobic, and it causes limited dyeability, as reported in a previous paper. In this study, to produce a more hydrophilic surface, surface fluorination of PP was performed at 25 °C, total gas pressure of 13.3 kPa, and reaction time of 1 h using F₂ and O₂ mixtures with different proportions of F₂ gas. The surface roughness of the fluorinated PP samples was about 1.5 times higher than that of the untreated sample (5 nm). Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy (XPS) results showed that the PP-derived bonds (-C-C- and -CH_x) decreased because they were converted into polar groups (-C–O, -CHF-, and -CF_x), which increased the surface electronegativity of the PP. The variation in the F₂ gas proportion in the gas mixture significantly affected the hydrophilicity and surface composition of the PP. At F₂ gas proportions of <70%, the hydrophilicity of the fluorinated PP samples was increased. Notably, the hydrophilic and negatively charged PP surface enhanced the dyeing of the polymer with basic methylene blue (MB). In contrast, at F₂ gas proportions of >90%, the PP surface became hydrophobic owing to increased numbers of hydrophobic -CF₃ bonds. Thus, enhanced PP dyeing can be controlled based on the composition of the F₂ and O₂ gas mixture. Full article

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

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Review

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16 pages, 5529 KiB

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

Viewed by 1041

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. [...] Read more.

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. Full article

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

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