Hybrid Pigments Research Articles

A new method to prepare ‘Maya red’ pigment from sepiolite and Basic red 46

In the study, a new vacuum method was applied to prepare the hybrid pigments of sepiolite and Basic red 46 (XL-GRL). Various hybrid pigments respectively prepared by the vacuum method, solid method and liquid method were compared. The obtained products were respectively labeled as VM, SM and LM. The prepared pigments were then characterized and tested by X-ray diffraction, Fourier Transform infrared spectroscopy, scanning electron microscopy, and N2 physisorption method. The effects of the preparation methods on the structure, morphology, composition, chemical stability and thermal stability of the hybrid pigments were explored. The results indicated that XL-GRL was mainly adsorbed on the sepiolite via electrostatic attraction after heating at 150 °C. In addition, more XL-GRL molecules could be encapsulated in sepiolite channels in VM and exhibited the more stable performance than those in SM and LM in the chemical, thermal and color stability tests. Therefore, the vacuum method could effectively improve the stability of the hybrid pigments.

Studying dual active/barrier and self-healing reinforcing effects of the Neodymium (III)-Benzimidazole hybrid complex in the epoxy coating/mild steel system

The effectiveness of loading Neodymium (Nd)-Benzimidazole (Bi) complex pigment into the epoxy coating to achieve an effective active/barrier protective system has been studied. The Nd-Bi hybrid pigment chemical structure was analyzed by Fourier Transfer Infrared (FT-IR) analysis. The incorporation effect of Nd-Bi hybrid pigment on the physical properties and surface chemistry of epoxy coating films without and with Nd-Bi was examined by FT-IR, Thermogravimetric analysis (TGA/DTG) analysis, and contact angle measurements. From the results it was designated that the Nd-Bi incorporation into the epoxy coating has not negative influence on the coating stability under thermal condition, meaning that the curing process was kept unchanged. The influence of Nd-Bi pigment on the coating active/barrier inhibition mechanisms of the coating was evaluated by electrochemical impedance spectroscopy (EIS) analysis as well as salt spray test. The pigment impact on the coating interfacial adhesion in dry condition by pull-off test and the resistance against cathodic disbonding were studied. The obtained results from EIS, salt spray and cathodic delamination tests evidenced that the epoxy coating active/barrier inhibition performance in the presence of Nd-Bi pigment was significantly improved. The morphology and composition of the precipitated film in defect zone after 700 h exposure to salt spray test were studied by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) analyses. The SEM and EDS analyses results confirmed the film formation in the artificial defect zone.

Dressing protective clothing: stabilizing alizarin/halloysite hybrid pigment and beyond

The fading of organic dyes is a serious challenge for conservation of art works. Inspired by the ancient Maya blue pigment, a hybrid pigment of halloysite (Hal) and alizarin (AZ) was prepared by adsorption in aqueous solution. In addition, a layer of polyorganosilane (POS) is used to cover the surface of the hybrid pigment to enhance the chemical resistance and photostability. The hybrid pigments were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy and thermal analysis. The adsorption behavior of AZ onto Hal was investigated and optimized. AZ-Hal hybrid pigment was prepared at pH = 9. Chemical stability was checked by 1 mol/L HCl, 1 mol/L NaOH and ethanol attack. Photostability was evaluated by exposing the pigment to visible light for 360 h, which is equal to more than 28 years in a common museum. AZ molecules were adsorbed on the external and/or internal surface via physical adsorption and hydrogen bonds. The presence of POS in the hybrid pigment influences positively the chemical and light resistance. This may be due to the protective layer that isolates sensitive dyes and oxidising agents.

Characterization and Structure⁻Property Relationships of Organic⁻Inorganic Hybrid Composites Based on Aluminum⁻Magnesium Hydroxycarbonate and Azo Chromophore.

In this study, novel organic–inorganic composites were prepared by the complexation of dicarboxylic azo dye (AD) with aluminum–magnesium hydroxycarbonate (AlMg–LH). This procedure provides an effective method for the stabilization of dicarboxylic organic chromophores on an AlMg−LH host. The structures of the hybrid composites were examined by X-ray diffraction (XRD), secondary ion mass spectrometry (TOF-SIMS), 27-Al solid-state nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis (TGA) and scanning transmission electron microscopy (STEM). The TOF-SIMS method was applied to investigate the metal–dye interactions and to monitor the thermal stability of the organic–inorganic complexes. Secondary ion mass spectrometry confirmed the presence of a characteristic peak for C18H10O5N2Mg22+, indicating that both carboxylic groups interacted with AlMg−LH by forming complexes with two Mg2+ ions. Modification with hybrid pigments affected the crystal structure of the AlMg−LH mineral, as shown by the appearance of new peaks on the X-ray diffraction patterns. Adsorption of the dicarboxylic chromophore not only led to significantly enhanced solvent resistance but also improved the thermal and photostability of the hybrid pigments. We propose a possible arrangement of the azo dye in the inorganic matrix, as well as the presumed mechanism of stabilization.

Preparation of organic–inorganic hybrid methylene blue polymerized organosilane/sepiolite pigments with superhydrophobic and self-cleaning properties

Inspired by the self-cleaning and water-repellent properties of the lotus leaf in the natural world, a kind of organic–inorganic hybrid pigment with superhydrophobic properties was prepared by adsorption of cationic methylene blue (MB) azo dyes onto acid-treated sepiolite (SEP), and then a superhydrophobic functional group of polymerized organosilanes (POSs) obtained from hexadecyltrimethoxysilane (HDTMS) and tetraethoxysilane (TEOS) was introduced onto the composite pigments (MB/SEP). The excellent chemical, thermal and optical stability of MB@POS/SEP are due to the shielding effect caused by the chemical inertness of the POS sheet. Furthermore, the superhydrophobic MB@POS/SEP pigments show an extraordinary self-cleaning property, which is similar to the waterproof property of the lotus leaf and spider web. The superhydrophobicity is strongly linked to their chemical composition and morphology, which can be adjusted by varying the concentration of HDTMS and TEOS. This kind of superhydrophobic pigment can be applied in various fields, such as ceramics, building and daily necessities.

Carminic Acid Stabilized with Aluminum-Magnesium Hydroxycarbonate as New Colorant Reducing Flammability of Polymer Composites.

In this study, hybrid pigments based on carminic acid (CA) were synthesized and applied in polymer materials. Modification of aluminum-magnesium hydroxycarbonate (LH) with CA transformed the soluble chromophore into an organic-inorganic hybrid colorant. Secondary ion mass spectroscopy (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and UV-Vis spectroscopy were used to study the structure, composition, and morphology of the insoluble LH/CA colorant. Successful modification of the LH was confirmed by the presence of interactions between the LH matrix and molecules of CA. XPS analysis corroborated the presence of CA complexes with Mg2+ ions in the LH host. The batochromic shift in UV-Vis spectra of the organic-inorganic hybrid colorant was attributed to metal-dye interactions in the organic-inorganic hybrid colorants. Strong metal-dye interactions may also be responsible for the improved solvent resistance and chromostability of the modified LH. In comparison to uncolored ethylene-norbornene copolymer (EN), a modified EN sample containing LH/CA pigment showed lower heat release rate (HRR) and reduced total heat release (THR), providing the material with enhanced flame retardancy.

Characteristics of Hybrid Pigments Made from Alizarin Dye on a Mixed Oxide Host

This paper describes the fabrication of a new hybrid pigment made from 1,2-dihydroxyanthraquinone (alizarin) on a mixed oxide host (aluminum-magnesium hydroxycarbonate, LH). Various tools were applied to better understand the interactions between the organic (alizarin) and inorganic (LH) components, including ion mass spectroscopy (TOF-SIMS), 27-Aluminm solid-state nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). TOF-SIMS showed that modification of the LH had been successful and revealed the presence of characteristic ions C14H7O4Mg+ and C14H6O5Al−, suggesting interactions between the organic chromophore and both metal ions present in the mixed oxide host. Interactions were also observed between Al3+ ions and Alizarin molecules in 27Al NMR spectra, with a chemical shift detected in the case of the modified LH matrix. Any changes in color following reactions with Mg2+ and Al3+ ions were observed. Some of the physicochemical properties of alizarin, such as resistance to dissolution and color stability at elevated temperatures, were improved in comparison to the pure dye. This effect can be attributed to strong dye-LH interactions and the effective transformation of alizarin into an insoluble form. Moreover, the pigments exhibited higher thermal resistance and greater color stability in comparison to commercially available alizarin lakes (Alizarin Crimson).

Finding the Additives Incorporation Moment in Hybrid Natural Pigments Synthesis to Improve Bioresin Properties

Interest in applications of natural dye applications has increased because of their antibacterial properties and the possibility of extracting them from nature and residues. Using nanoclays as hosts to reinforce natural dye properties has been successfully demonstrated. However, no one has attempted to optimize the polymer matrix and hybrid pigment properties at the same time to ensure the best final properties for bio-composite applications. Using a statistical design for experiments, we propose the best combination of modifiers with the best nanoclay as the host of three natural dyes: chlorophyll, β-carotene, and betanine. Using the L9 Taguchi designs, we learned both the influence of the nanoclay structure, and the addition moment of surfactant, mordant salt, and silane modifiers. FTIR, XRD, DTG, integration sphere spectrophotometer, and UV-aging tests were used to characterize the hybrid pigments and epoxy bioresin composites. The degradation temperatures of the three natural dyes rose and the reinforcement of the stability of three natural dyes to UV–Vis radiation exposure was demonstrated, which avoided the migration of these dyes from bioresin to wet ribbing. Optimal results were obtained with hydrotalcite clay (calcined or not) by using surfactant and mordant before the natural dye, and before or after silane.

Aluminum-Magnesium Hydroxycarbonate/Azo Dye Hybrids as Novel Multifunctional Colorants for Elastomer Composites.

This study presents the preparation and characterization of new organic-inorganic pigments based on aluminum-magnesium hydroxycarbonate (LH) and azo dyes. Solvent resistance studies, XRD, SEM, and TGA confirmed the successful formation of hybrid pigments, which were characterized in terms of their physicochemical properties. The new hybrid pigments were applied in acrylonitrile-butadiene (NBR) and ethylene-propylene (EPM) rubber composites and cured with sulfur and peroxide curing systems, respectively. The mechanical properties, dispersion quality, and flame-retardant properties of the NBR/hybrid and EPM/hybrid pigment composites were determined by dynamic mechanical analysis (DMA), SEM, and microscale combustion calorimetry (MCC). Complex experimental investigations revealed that the layered nature of hybrid pigments could improve the barrier ability and flame retardancy of elastomer composites. In comparison to unmodified aluminum-magnesium hydroxycarbonate, the modified LH dye structures contributed to significantly decrease the heat release rate and the total heat release of the NBR and EPM composites, offering a new approach to imparting low flammability to elastomer materials.

New organic-inorganic hybrids as multifunctional additives to improve ethylene-norbornene (EN) composite stability

In this study, new multifunctional organic-inorganic pigments were synthesized by the complexation of carboxlic azo dyes (D1, D2) with aluminum-magnesium hydroxycarbonate (LH) and were applied as colorants in ethylene-norbornene copolymer (EN). The structures of the hybrid pigments were analyzed by X-ray diffraction (XRD), secondary ion mass spectrometry (TOF-SIMS), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). X-ray diffraction revealed that the hybrid pigments had developed new crystalline structures and showed the presence of additional peaks on their diffraction patterns. Moreover, TOF-SIMS confirmed that the modification had been successful, with the formation of dye-metal complexes embedded in the LH structure. The EN composites with hybrid pigments were subjected to accelerated UV aging. Alterations were monitored by Fourier transform infrared spectroscopy (FT-IR), spectrophotometry, differential scanning calorimetry (DSC) and mechanical tests. It was found that the EN composites containing hybrid pigments showed approximately 4 times higher tensile strength than both EN and an EN sample with unmodified LH under 250 h of UV irradiation. Adding 2 wt% of the multifunctional hybrid pigments to EN copolymer significantly enhanced the aging resistance and thermal stability of the resulting composites.

CoAl2O4/Kaoline Hybrid Pigment Prepared via Solid-Phase Method for Anticorrosion Application.

In this study, kaoline is incorporated to prepare CoAl2O4/kaoline hybrid pigments via traditional solid-state reaction, and the introduction of kaoline decreases the preparation temperature for formation of spinel CoAl2O4, and reduces the production cost of cobalt blue as well. More importantly, kaoline may participate in the crystallization of spinel CoAl2O4 during calcining process, and the hybrid pigments prepared using 8.1% Co3O4 and 81.5% kaoline features bright blue and good chemical resistance. Due to the synergistic effect between the sheet-like kaoline and the loaded CoAl2O4, the as-prepared CoAl2O4/kaoline hybrid pigments can be incorporated into epoxy paint system to obtain the high-performance blue anticorrosion coating, especially for acetic acid-salt fog corrosion.

Characterization and properties of new color-tunable hybrid pigments based on layered double hydroxides (LDH) and 1,2-dihydroxyanthraquinone dye

In this paper a novel, simple method for synthesis of lake pigments based on 1,2-dihydroxyanthraquinone dye and LDH carbonates was proposed. LDHs were modified with 1,2-dihydroxyanthraquinone, transforming the soluble dye into a new kind of hybrid lake. In result, the solvent resistance and photostability of the chromophore were improved, which may be attributed to strong dye–LDH interactions. TOF-SIMS technique was used for the first time to confirm the role of C14H7O4Mg+ and C14H6O5Al− ions in the formation of the hybrids. Alizarin lakes have been recognized as a new class of colorants which demonstrated good color characteristics and chemical stability.

New organic dye/anionic clay hybrid pigments: Preparation, optical properties and structural stability

Encapsulation and subsequent stabilization of organic dye into layered double hydroxides (LDHs) are investigated. Three commercialized dye molecules such as: acid orange 6, acid yellow 50 and acid green 25, were intercalated in Zn2-Al-LDH by co-precipitation method, analyzed by ICP and UV–Visible, and characterized by XRD at different temperatures. Functionalized organic molecules have been interleaved for the synthesized hybrid LDH materials. It is shown that the effect of encapsulation is revealed by the different interactions according to the molecule size and stacking of dye molecules. Thermal behavior of hybrid materials showed a clear enhancement of the structural stability in temperature over the chloride-Zn2Al LDH, indicating that the assembly may appear as a mutual benefit.

Optimal Synthesis of Environment-Friendly Iron Red Pigment from Natural Nanostructured Clay Minerals.

A series of environment-friendly clay minerals—α-Fe2O3 iron-red hybrid pigments—were prepared by a simple one-step hydrothermal reaction process using natural nanostructured silicate clay minerals as starting materials. The influence of structure, morphology and composition of different clay minerals on the structure, color properties, and stability of the pigments was studied comparatively by systematic structure characterizations with X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmittance electron microscope (TEM), X-ray fluorescence spectroscopy (XRF), X-ray photoelectron spectroscopy (XPS) and CIE-L*a*b* Colorimetric analyses. The results showed that the clay minerals act as green precipitants during the hydrothermal reaction to induce in-situ transformation of Fe(III) ions into Fe2O3 crystals. Meanwhile, they also act as the “micro-reactor” for forming Fe2O3 crystals and the supporter for inhibiting the aggregation of Fe2O3 nanoparticles. The color properties of iron-red hybrid pigments are closely related to the surface charges, surface silanol groups, and solid acid sites of clay minerals. The clay minerals with higher surface activity are more suitable to prepare iron-red pigments with better performance. The iron-red hybrid pigment derived from illite (ILL) clay showed the best red color performance with the color values of L* = 31.8, a* = 35.2, b* = 27.1, C* = 44.4 and h° = 37.6, and exhibited excellent stability in different chemical environments such as acid, alkaline, and also in high-temperature conditions.

Effects of different pH regulators on the color properties of attapulgite/BiVO4 hybrid pigment

Four different pH regulators including NaOH, Na2CO3, NaHCO3 and NH3·H2O were employed to prepare attapulgite doped bismuth yellow hybrid pigments by aqueous precipitation followed by an annealing process. Different hybrid pigments derived from different pH regulators had different color properties, and it might be related to the generated products in the process of adjusting pH, which further affected the phase compositions of the end hybrid pigments after being annealed. By contrast, the bismuth yellow hybrid pigments prepared using Na2CO3 as pH regulator exhibited the optimal color properties (L⁎ = 76.81, a⁎ = 4.64, b⁎ = 81.16, C⁎ = 81.29, and h° = 86.73). Interestingly, attapulgite provided the carrier for BiVO4 nanoparticles to inhibit the agglomeration, and the doping elements to improve its color properties as well. The as-prepared hybrid pigments are expected to be served as an eco-friendly and low-cost yellow colorant to replace the traditional and toxic ones.

Organic/inorganic hybrid pigments from flavylium cations and palygorskite

Abstract Features such as color, brightness and fluorescence are extremely important in applications of pigments. Hybrid materials inspired by the ancient Maya Blue pigment are a promising alternative to improve the properties and applicability of natural and synthetic dyes. In this work, we report the preparation, photophysical properties, and stability of several fluorescent hybrid pigments based on flavylium cations (FL) adsorbed on palygorskite (PAL). Five flavylium cations were investigated, viz., the 3′,4′,7-trimethoxyflavylium (FL1), 7-hydroxy-4′-methoxy-flavylium (FL2), 7-hydroxy-4-methylflavylium (FL3), 5,7-dihydroxy-4-methylflavylium (FL4) and 7-methoxy-4-methylflavylium (FL5) cations. Only FL1 and FL2, without a methyl substituent at the 4-position that could hinder inclusion in palygorskite channels, adsorbed strongly on PAL, producing fluorescent hybrid pigments with attractive colors. The spectroscopic and fluorescence properties of the FL1/PAL and FL2/PAL hybrid pigments were characterized. The color of the adsorbed dyes was somewhat more resistant to changes in external pH, photochemical stability was maintained and the thermal lability was markedly improved in the FL/PAL hybrid pigments, pointing to flavylium cations as promising chromophores for the development of fluorescent hybrid pigments with attractive colors.

When anthraquinone dyes meet pillared montmorillonite: Stability or fading upon exposure to light?

Hybrid pigments have attracted great interest due to their stability and physicochemical properties that can be used in paintings, artworks and in the field of cultural heritage. The study of new materials includes the search for new pigments by immobilization of the dyes in resistant substrates such clays minerals to get new colour fonts and materials with high stability. Organic-inorganic based lake pigments, at different pH, have been prepared. Ti- and Al-pillared montmorillonite were synthesized and loaded with carminic acid (CA) and alizarin (Aliz) organic dyes. The pillaring process was investigated by X-ray diffraction, textural analysis, transmission electronic microscopy and solid state nuclear magnetic resonance of 27Al. The interactions between the organic guest and the inorganic host were highlighted by infrared, 13C and 27Al solid state magnetic nuclear resonance and time resolved fluorescence spectroscopies. The spectra support complex formation between the chromophores and the inorganic matrix. The colours of the pigments prepared were pH dependent. Lake pigments based on Al-Pillared Mt were more stable under light than Ti-based hybrid, even in oil painting formulations.

Fabrication and characterization of zinc acetylacetonate/Urtica Dioica leaves extract complex as an effective organic/inorganic hybrid corrosion inhibitive pigment for mild steel protection in chloride solution

Zinc acetylacetonate is known as an inorganic anti-corrosive pigment with moderate corrosion inhibition performance in saline solutions due to slight solubility. In this study the zinc acetylacetonate pigment was modified by organic compounds existing in the extract of a green corrosion inhibitor. A series of hybrid organic/inorganic pigments based on zinc acetylacetonate and organic compounds of Urtica Dioica leaves extract (ZnAA-U.D) were synthesized in aqueous solutions. The effect of pH on the morphology and chemistry of the synthesized pigments were examined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), UV–Vis analysis, thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) techniques. Then, the inhibition effect of pigments in corrosion control of carbon steel in 3.5 wt.% NaCl solutions with pigments extracts were evaluated by visual observations, polarization test and SEM/-EDS analyses. Results revealed that the hybrid zinc acetylacetonate-Urtica Dioica pigment was successfully synthesized through chelation between the organic molecules of U.D extract, such as histamine, serotonin and caffeic acid, and inorganic part of zinc acetylacetonate (Zn2+). The lone pair electrons of heteroatoms existed in the structure of organic compounds of U.D extract could be shared with empty orbital of Zn2+ cations. It was also found that the pH of synthesis media remarkably influenced on the morphology, chemistry and corrosion inhibition properties of the pigment. According to the results the pigment synthesized at pH = 4 showed the highest solubility and corrosion inhibition properties. The hybrid pigment showed mixed corrosion inhibition properties and affected both anodic and cathodic reactions.

Corrosion inhibition properties of a green hybrid pigment based on Pr-Urtica Dioica plant extract

The main aim of this research is studying the corrosion inhibition properties of the combination of praseodymium nitrate (PrN) and Urtica Dioica (UrDi) on mild steel in sodium chloride solution. Fourier transform infrared (FT-IR), ultraviolet-visible (UV-Vis), thermogravimetric analysis/differential thermogravimetry (TGA/DTG) and X-ray photoelectron spectroscopy (XPS) results confirmed complex formation between Pr cations and UrDi (Pr-UrDi). Electrochemical results revealed that the Pr-UrDi hybrid complex had significant influence on the mild steel corrosion protection (by inhibition efficiency of ca. 94%) in NaCl solution.

Anti-corrosion performance of an epoxy ester coating filled with a new generation of hybrid green organic/inorganic inhibitive pigment; electrochemical and surface characterizations

In this study the effect of a hybrid organic/inorganic pigment based on zinc acetate-Cichorium intybus L. leaf extract on the corrosion protection properties of an epoxy ester coating were studied. Results of electrochemical impedance spectroscopy (EIS) revealed that the mild steel corrosion was significantly inhibited in the chloride solution in the presence of hybrid pigment extract. Results exhibited that with the increase in immersion time up to 24 h the corrosion inhibition efficiency significantly increased and reached the maximum value of 94%. Results obtained from the scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS) techniques confirmed the deposition of inhibitive films on the mild steel surface. Results showed that in the presence of hybrid pigment not only the barrier but also the active inhibition properties of the epoxy ester coating were effectively enhanced. The low frequency impedance value of the epoxy ester coating was increased in the presence of hybrid pigment, indicating the role of pigment on the coating barrier action enhancement. The increase in charge transfer resistance of the epoxy ester coating with artificial scratch depicted the active inhibition role of the hybrid pigment.