Hybrid Pigments Research Articles

Fabrication of multifunctional hybrid pigment for color cosmetics based on chitosan-modified palygorskite and sappanwood extract

Consumer perception and market demand have driven the replacement of synthetic colorants with naturally derived alternatives in the cosmetic industry. This study describes a facile way to prepare durable inorganic-organic hybrid pigment with advanced biocompatibility, antibacterial and hydrophobic properties tailored for color cosmetics by initial modification of palygorskite with chitosan to anchor sappanwood dye extract and subsequently coating with amino-modified silicone oil (ASO). The hybrid pigments were characterized by transmittance electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and the Brunauer–Emmett–Teller method. The results indicated that the sappanwood dye was loaded on chitosan-modified palygorskite via hydrogen bonding and electrostatic interaction. Furthermore, the chitosan-palygorskite/sappanwood hybrid pigment exhibited enhanced biocompatibility and color stability on exposure to different heating temperatures and UVA radiation after subsequent hydrophobic modification with amino-modified silicone oil. Moreover, facial foundation cosmetics based on the chitosan-palygorskite/sappanwood@ASO composites exhibited excellent brightening and skin color corrective effect on human volunteers without any adverse response. And no significant difference was observed in 12 out of 14 sensory evaluation indexes in the comparison of this hybrid pigment-based makeup with two commercially available products. This study provides a new route to stabilize natural botanical colorant for cosmetic use by chitosan-modified clay minerals.

Advancing Chlorophyll Photostability: Dual Physicochemical Protection via Ce-Doped Hydrotalcite Organic-Inorganic Hybrid Pigments.

In pursuit of enhancing the photostability of chlorophyll, a novel organic-inorganic hybrid pigment has been synthesized via a supramolecular intercalation assembly method, incorporating cerium-ion-doped hydrotalcite as the host matrix and chlorophyll as the intercalated guest molecule. This innovative pigment amalgamates the vivid coloration properties of organic dyes with the robust stability characteristic of inorganic substances. Determined from the detailed investigation of the structural evolution of chlorophyll during photodegradation, the dual physicochemical protection mechanism is critical to the advancement of chlorophyll photostability. It leverages the oxygen barrier attributes of the hydrotalcite's laminate structure and the ultraviolet light absorption and scattering capabilities of CeO2 nanoparticles formed in situ. Furthermore, Ce-doping introduces a redox cycle between Ce4+ and Ce3+ ions, which serves as a chemical defense by neutralizing reactive oxygen species that emerge during chlorophyll degradation. This multifaceted approach results in a substantial enhancement of photostability, with the hybrid pigment containing 0.3 Ce doped content, demonstrating a mere 5.90% alteration in reflectance at the 635 nm peak after 250 h of UV-accelerated aging. This breakthrough provides a dual physicochemical protective strategy that not only significantly prolongs the lifespan of chlorophyll pigments but also holds potential for broadening their application scope in various industries, including plastics and coatings, where color fastness and durability are paramount.

Hybrid sol-gel silane composite coating reinforced with a hybrid organic/inorganic inhibitive pigment: Synthesis, characterization, and electrochemical properties

This work aims to develop environmentally friendly silane coating reinforced with a hybrid pigment to protect mild steel against corrosion in a saline environment. Fourier-transform infrared (FT-IR) spectroscopy, contact angle (CA) measurement, field emission scanning electron microscopy (FE-SEM), and energy dispersive spectroscopy (EDS) were used to study the coating structure and its protective mechanisms. The presence of hybrid pigment led to the conversion of more Si–OH groups into Si–O–Si groups during condensation process increasing the cross-linking density of silane; the enhanced cross-linking yields the coating with lower defects and stronger adhesion to substrate and so improved barrier and anti-corrosion properties. The EIS test showed that the charge transfer resistance (Rct) for the sample coated with hybrid sol-gel silane increases up to 40 % for all immersion times after the incorporation of the hybrid pigment into the coating matrix. The polarization test showed that the corrosion current density (icorr) value decreases from 1.40 to 0.56 μA/cm2 after 120 h of exposure to the saline solution when the hybrid pigment is added to the coating matrix. These results demonstrate the inhibitive action of the hybrid pigment enhancing the protective performance of the sol-gel silane coating.

Improved anticorrosive performance of epoxy coating by introducing a one-pot synthesised nano-ceria embedded lamellar polyaniline/kaolinite hybrid

This study presents an innovative and uncomplicated approach to produce ceria-decorated lamellar polyaniline utilising interfacial oxidative polymerisation, with ceric ammonium nitrate as both the aniline oxidiser and the ceria precursor. The study found that a 1 % weight of active polyaniline/ceria hybrid provides better corrosion protection. The addition of barrier kaolinite further enhances the protective properties of the hybrid. The study also proposes a mechanism for the synergistic function of ceria, polyaniline, and kaolinite in achieving better protective performance of the coating in harsh saline environments. The EIS results indicate that the cPAni_K/epoxy material shows a high |Z|0.01Hz value of 5.59 × 1010 and two months of continuous exposure, the charge transfer resistance maintained at 2.14 × 109 Ω cm2. EIS results exhibited the durability of the coating in the harsh saline media. Corrosion rate shows that cPAni_K embedded epoxy displays the corrosion rate of the eight-order lower than that of the pristine epoxy coat. This newly developed active/passive hybrid pigment is eco-friendly and suitable for preventing corrosion in marine environments.

Highly Stable Hybrid Pigments Prepared from Organic Chromophores and Fluorinated Hydrotalcites

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.

Efficiency of Anti-Corrosion Protective Coatings Based on Graphene Oxides Functionalised with Green Inhibitors

Mild steel (MS) is commonly used for infrastructure and machinery due to its various engineering properties and benefits, but they are highly prone to corrosion. For decades, organic polymeric coatings are widely applied to protect metallic systems against corrosion. Besides the physical barrier, the organic coatings have been manipulated by adding anti-corrosion pigments or corrosion inhibitors, such as red-lead or chromate to enhance protection. However, these conventional anticorrosive pigments have been substituted because of their toxicity and environmental problems. Recent studies have been consequently conducted to develop environmentally safe and green alternatives obtained from natural products.In the framework of this study, a novel green hybrid pigment nano-pigment based on graphene oxide (GO) and an organic natural inhibitor was prepared and included in a Polyvinyl Butyral (PVB) coating. The protective properties of PVB coatings without and with the addition of GO and f-GO on steel in 3.5wt% NaCl solution were studied by electrochemical methods.The new pigment functionalised GO (f-GO) is not only able to be an outstanding barrier, but it can also store a considerable amount of corrosion inhibitors and release them, when necessary, on the protective coating system. GO was functionalised with the green inhibitor in aqueous phase and the compound obtained was characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermo gravimetric analysis (TGA), ultraviolet-visible spectroscopy (UV-Vis) and atomic force microscopy (AFM).FT-IR and UV-Vis spectroscopy results indicated that the organic compound effectively reduced GO into f-GO and PVB/f-GO composite coatings showed 100 times higher anticorrosion resistance than PVB/GO and neat PVB. Figure 1

Superstable cellulose-supported clay-based methylene blue hybrid pigment encapsulated with porous TiO2: Processing by adsorption strategy

Organic dyes have limited industrial use due to their poor stability and resistance to harsh environmental conditions. By using inorganic materials, adsorption of organic dyes can be used to synthesize a highly stable pigment material in hybrid structure. A simple, rapid and controllable method to prepare stable hybrid pigment by adsorption of methylene blue (MB) on ethyl cellulose (EC) modified montmorillonite (Mt) was investigated. The effects of different ratios of EC, initial concentration, adsorbent dosage, time and pH on the adsorption of MB on EC:Mt were investigated. MB adsorption conformed to the Langmuir isotherm (R2 = 0.99) model according to the equilibrium test results and to the pseudo-second-order kinetic model (R2 = 1.00) in the results of the time experiments. EC:Mt-MB was coated with a layer of TiO2 to increase the stability of the hybrid pigment. Thermodynamic calculations show that MB adsorption was spontaneous and endothermic. The characterizations of the synthesized composites were performed by SEM, FT-IR, XRD, UV-DRS, TGA/DTG and zeta potential analyzes. EC:Mt-MB@TiO2 pigment showed excellent chemical stability in acidic, alkaline and ethanol medium, together with UV resistance much higher than EC:Mt-MB hybrid pigment.

Mechanochemical preparation of low cost kaolinite-based BiVO4 hybrid pigments with high near infrared reflectance

For accelerate construction of the energy and resource-saving and environmental-friendly society, cleaner preparation of low-cost and high-performance colorful near-infrared reflective inorganic pigments with the decorative function is indispensable to reduce the hazards of urban heat island and simultaneously beautify the appearance of the buildings. Due to the non-toxicity, good chemical stability and narrow band gap, BiVO4 has been becoming a promising environment-friendly yellow inorganic pigments among the conventional heavy metals-containing inorganic pigments. In this study, the low-cost and brilliant kaolinite-based BiVO4 hybrid pigments were fabricated by cleaner mechanochemical method based on cheap and abundant kaolinite using crystal water of the hydrated metal salts as trace solvent, which could effectively promote the interaction of the involved components at the molecular level during grinding and then decreased the mass transfer resistance for the formation of monoclinic scheelite BiVO4 in the following calcination. The obtained hybrid pigments at the optimal preparation conditions exhibited brilliant color properties (D65-10°, L * = 83.45 ± 0.08, a * = 4.17 ± 0.08, b * = 88.59 ± 0.17), high near-infrared reflectance of 86.22%, infrared solar reflectance of 88.14% and high emissivity of 0.9369 in the waveband of 8–13 μm. Furthermore, the hybrid pigments could be used for coloring epoxy resin with high emissivity of 0.8782 in 8–13 μm. Therefore, the brilliant and low-cost kaolinite-based bismuth yellow hybrid pigments have the enormous potential to be served as colorful functional nanofillers for cooling roofing materials.

Raw Smectite from the Guarapuava–Parana–Brasil Saturated with Copper Ions and Its Properties

In this study, raw smectite (Sm), from the Guarapuava–Parana–Brasil region, was saturated with copper ions (Cu-Sm) by ion exchange and the samples Sm and Cu-Sm were used in crystal violet (CV) adsorption and applied as an antimicrobial and antifungal hybrid pigment. Samples (Sm and Cu-Sm) were used to remove crystal violet (CV) dye from aqueous media, simulating wastewater. Samples after use as adsorbents were characterized and named smectite/adsorbed dye (Sm/Dye) and copper smectite/adsorbed dye (Cu-Sm/Dye); and they were applied as hybrid pigments with antimicrobial action. The Sm and Cu-Sm were characterized by X-ray diffractometry (XRD), energy dispersive X-ray fluorescence (EDXRF), vibrational spectroscopy (FTIR), Zeta potential (ζ), scanning electron microscopy (SEM), and colorimetry (CIE L*a*b*), enabling the identification of the presence of intercalated copper ions and on the smectite surface. The adsorption assays were carried out to evaluate the effects of initial dye concentration and contact time. Tests for application as a hybrid pigment showed good compatibility with commercial white paint being applied on plaster blocks and later photoaging and chemical stability tests were performed in acid and basic environments, both were discussed by colorimetry (CIE L*a*b*), thus being able to relate it to the color variation (∆E). The samples (Sm, Cu-Sm, Sm/Dye, and Cu-Sm/Dye) were dispersed in white paint at 10% and 20% (% w/w) to evaluate the ability to inhibit different microorganisms. The modification with copper ions promoted an increase in the adsorptive capacity relative to the raw smectite and provided antibacterial and antifungal action to the hybrid pigment against Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Candida albicans. The Cu-Sm and Cu-Sm/Dye samples showed excellent results against all studied microorganisms and reveal successful materials that can be used in environments that require microbiological protection.

Nigella sativa extract phytochemicals: Effective green/bio-active anti-corrosion agent for steel protection in saline media

This research aims to develop a low-VOC silane (sol-gel) coating functionally protected by novel non-toxic metal-organic networks (MONs) based on extracted Nigella sativa bio-molecules/Zinc nitrate. The effectiveness of the silane coating containing the MONs pigment was investigated via electrochemical (i.e., EIS) and accelerated (i.e., salt spray) corrosion experiments. Based on the electrochemical tests' results in the solution phase, an efficiency of 67.8% and a mixed-type corrosion mitigation mechanism were obtained for the hybrid pigment to protect the mild steel against the NaCl media. Moreover, adding the synthesized MONs into the silane coating matrix dramatically increased its protection performance. Fourier-transform infrared spectroscopy (FT-IR) results revealed that the coating’s curing index is affected after the MONs pigment’s inclusion in the silane matrix. The change in the coating curing index increases the silane film crosslinking density, improving coating adhesion to the metallic substrate and then enhancing its anti-corrosion protection performance. The electrochemical tests were employed in the presence of artificial defects to study the active protection performance of the silane layer. Results indicated that the active anti-corrosion protection performance of the silane coating was significantly improved after employing the synthesized MONs in its structure. Adsorbing the inhibitive species in the scratched region of the silane coating and fabricating the inhibitive film at this region is the main protection mechanism, which was illustrated via SEM/EDS analysis.

Characterization of calcined red soil applied in the removal of methylene blue dye from wastewater to produce a hybrid pigment

AbstractWe obtained natural red soil (RS), rich in iron, from the region of Palotina in the state of Paraná, Brazil. The RS sample was purified by suspension in water and sieved to remove plant particulates. It was then treated thermally at 800°C to remove organic volatiles; this sample was called RS800. The samples were characterized using X-ray diffraction, X-ray fluorescence, infrared and electronic spectroscopy, ζ-potential analysis and scanning electron microscopy. Colorimetric studies were performed according to the CIEL*a*b* system. Tests have shown that RS800 has the ability to remove methylene blue (MB) dye from wastewater. Thus, it was used as an adsorbent at various temperatures (25, 35, 45°C). According to the Langmuir model, the maximum adsorption capacity (qmax) was 23.256 mg g–1 (25°C). Unexpectedly, increasing temperature reduced qmax to 21.659 mg g–1 at 35°C and to 21.186 mg g–1 at 45°C. Therefore, RS800 must be used at room temperature (25°C), making its application in large-scale wastewater treatment feasible. After using RS800 as an adsorbent, the solids were filtered, dried, pulverized, and used as hybrid pigments in commercial white paints. Pigmented paints were used to paint a plaster specimen and colorimetric measurement was performed. These paints were tested for colour stability in acidic and alkaline environments. The results indicate that RS800 is efficient in the treatment of water contaminated with cationic dyes and can be reused as a hybrid pigment.

Ecological hybrid pigments with improved thermal, light, and chemical stability based on purpurin dye and different minerals for applications in polymer materials

A facile and cost-effective route was developed for the production of high-performance hybrid pigments by the stabilization of the natural red dye (purpurin) on mineral supports. For the first time, hydrotalcite (LDH), sepiolite (SEP), and aluminum-magnesium hydroxycarbonate (LH30) with different chemical compositions and structures were used as inorganic supports for purpurin. The physico-chemical properties of the prepared pigments were characterized by time-of-flight secondary ion mass spectrometry (ToF-SIMS), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), color measurements, release kinetic experiments, and thermogravimetric analysis (TGA). Purpurin molecules were confirmed to have been successfully incorporated into the inorganic supports via interactions between the purpurin chromophore and Mg2+, Zn2+ and/or Al3+ ions from the mineral host. The interactions resulted in hybrid pigments with higher thermal stability and lower tendency to migrate, without changing the morphology of the minerals. The hybrid pigments were applied as new colorants for ethylene-norbornene copolymer. The polymer composites were subjected to long-term UV irradiation followed by color and mechanical measurements. The results suggest that purpurin-based hybrid pigments can act as durable and effective colorants. This work provides a novel approach for preparing stable and multifunctional hybrid pigments based on natural dyes and mineral supports.

In-situ construction of Cr2O3@ATO hybrid pigment towards synergetic enhancement of visible light-infrared-radar compatible stealth

Multiband compatible stealth engineering with controllable visible light-infrared (VIS-IR) features and radar wave absorption is urgently needed to improve the survivability of advanced military equipment. Cr2O3 has good visible light stealth performance under green background, but it is lack of IR and radar multi-band stealth properties. Herein, a core-shelled Cr2O3@stannic antimony oxide (ATO) structure was developed to enhance the IR-radar compatible stealth properties of Cr2O3 by in-situ precipitation method, concurrently maintaining its visible light stealth property. The morphology, conductivity, and infrared stealth properties of the Cr2O3@ATO hybrids were influenced by the calcination temperature, and the IR and radar stealth performance were tunable by ATO content. The lowest emissivity of Cr2O3@ATO pigments is 0.852, reduced by 10% than pure Cr2O3. The Cr2O3@ATO filled silicone resin coatings possessed good thermal stability and IR stealth stability. Benefiting from the enhanced interfacial polarization and conductive loss, the Cr2O3@ATO exhibited an effective absorption bandwidth of 2 GHz in the X band, with respect to pure Cr2O3 without radar absorption property. The Cr2O3@ATO structure opens an avenue for advanced VIS-IR-Radar compatible stealth materials.

A bifunctional epoxy coating doped by cerium (III)-8-hydroxyquinoline: Early self-reporting and stimuli-responsive inhibition on corrosion of Al substrate

Recently, anti-corrosion coatings with auto-inhibition and self-reporting on their premature flaws are becoming more and more attractive. In this work, we engineered a cerium nitrate/8-hydroxyquinoline (Ce-HQ) hybrid pigment to endow epoxy coatings with corrosion self-inhibiting and fluorescent self-reporting performances via molecule design. The Ce-HQ pigments were synthesized by physical mixture and then dispersed into the commercial epoxy coating. Once the epoxy coating gets degraded, the underneath aluminum alloy matrix may corrode to produce Al3+ ions, which can compete with Ce3+ ions in the Ce-HQ complex, and then chelate with dissociative 8-HQ to form fluorescent Al-HQ complex, due to the higher bonding strength of Al3+ with 8-HQ than Ce3+ ions. Thus, not only the responsive releasing of Ce3+ ions and 8-HQ can inhibit the underlying Al alloy, but the newly formed Al-HQ complex could indicate the location and severity of coating flaws through fluorescent emission under UV light. Electrochemical impedance evidenced that the composite epoxy coating containing 1 % mass Ce-HQ presents high corrosion resistance even after 504 h of salt spray test, showing 90 % corrosion refraining efficiency. This work may enlighten an approach to developing self-healing and self-diagnosis coating for premature corroded Al alloy beneath coatings via reactive release and fluorescent visualization.

Coordinated water stabilizes indigo-sepiolite hybrid pigments: Evidence from acid modification

Sepiolite can form stable hybrid pigments by immobilizing organic dyes in its microporous structure. Previous investigations demonstrated that the micropores and coordinated water might be responsible for the exceptional color and stability of indigo-sepiolite hybrid pigments. This work reveals the roles of coordinated water in forming hybrid pigments by acid modification. Raw sepiolite was modified by nitric acid at different conditions before use. Then a series of indigo-sepiolite pigments were prepared by indigo and acid-modified sepiolite. Their microstructures were characterized and analyzed by X-ray diffraction, Fourier transform infrared, transmission electron microscopy, and N2 adsorption-desorption. The color properties of hybrid pigments were evaluated by reflectance spectra and CIE color parameters. Investigations into the chemical stability of pigments were conducted using concentrated HNO3 and dimethyl sulfoxide. In addition, the photostability of pigments exposed to simulated 30-year illumination in a typical museum was studied. Acid modification of sepiolite contributed to a larger specific surface area and pore volume. However, acid modification resulted in worse color properties and stability due to the removal of coordinated water bonded with octahedral Mg2+. These findings confirmed that coordinated water molecules were the key to stabilizing indigo-sepiolite hybrid pigments by forming hydrogen bonds.

Twin-screw extrusion synthesis of low-cost cobalt ferrite ceramic pigments using natural mixed-dimensional palygorskite clay

Due to the disadvantages of traditional solid-phase and liquid-phase methods for preparation of mixed metal oxide ceramic pigments, it is indispensable to develop a green, clean, low-cost and continuous preparation technology. In this study, the low-cost and high-performance cobalt ferrite ceramic pigments were facilely prepared based on natural mixed-dimensional palygorskite clay by a continuous mechanochemical method using twin-screw extrusion. The incorporation of the mixed-dimensional palygorskite clay effectively improved the agglomeration of pigment nanoparticles and decreased the production cost. The hybrid pigments presented the optimal color properties (L* = 17.16, a* = 1.07, b* = 3.58 and C* = 3.74) when the cobalt ferrite content, calcination temperature and time were 60 wt%, 1100 °C and 90 min, respectively. Furthermore, the as-prepared hybrid pigments exhibited excellent chemical and thermal stability and biocompatibility, the mass tone and hiding power of the hybrid pigments were superior to the commercial cobalt black pigments, thus the obtained hybrid pigments could be served as an eco-friendly underglaze pigment for coloring of ceramic embryo body with good color saturation. Beyond all doubt, this study will provide a promising strategy for continuous cleaner preparation of low-cost cobalt ferrite ceramic pigments.

Facile color regulation of organic/inorganic hybrid pigments combining with palygorskite and CoNi layered double hydroxides

Maya blue or Maya blue-like pigments are famous for their vivid colors and good environmental stability, but their colors are dependent on the natural or synthetic organic dyes, thus the color system is not complete due to the limited types of organic dyes. In this study, the novel and multicolor organic/inorganic hybrid pigments with the controlled colors were facilely fabricated by wet-method adsorption of cationic dyes using palygorskite followed by one-step loading and intercalation of CoNi layered double hydroxides (CoNi LDHs) with anionic dyes. The colors, compositions, and morphologies of hybrid pigments were analyzed by combining with different characterization techniques. The results indicated that the colors of hybrid pigments were determined with the colors of the involved cationic dyes, anionic dyes and CoNi LDHs, which could be accurately designed by adjusting the colors and contents of cationic and anionic dyes. What's more, the samples loaded with the sensing dye of methyl orange exhibited intelligent behavior at different pH values (2.5–5.5). Incorporation of palygorskite and CoNi LDHs obviously enhanced the thermal stability of the organic dyes. Based on the synergistic effects between organic and inorganic compositions of hybrid pigments, incorporation of hybrid pigments enhanced the mechanical properties of chitosan composite film with the desired color, and thus the as-prepared hybrid pigments could be served as promising colorant and reinforced materials for coloring and reinforcing of polymeric packing materials.

Evaluation of the aminosilane and colloidal silica treated red iron oxide pigment effects in styrene acrylic and polyurethane dispersion

PurposeThis study aims to perform the surface treatment of synthetic α-Fe2O3 red iron oxide pigment with hydrolysate 3-aminopropyl silane (A) and colloidal silica (CS) and investigate the effects of surface-treated pigment on the styrene acrylic (SA) emulsion and polyurethane (PU) dispersion.Design/methodology/approachFor this purpose, firstly red iron oxide particles were modified with A and CS separately in an aqueous medium. After isolation of the modified iron oxide were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). Moreover, the degree of the dispersion stability of the modified pigment in coatings with SA emulsion and PU dispersion was investigated by using an oscillation rheometer. Loss (G''), storage (G') modulus, loss factor [tan(δ)] and yield stress (τ0) values were determined by performing amplitude and frequency sweep tests.FindingsThe τ0 in SA coatings decreases with the amount of used A and increases with the amount of used CS. The τ0 decreases as the amount of used A and CS in PU coatings increases. The use of CS on red iron oxide pigments causes storage modulus to increase in SA coatings at low angular frequencies, while it causes a decrease in PU coatings.Originality/valueTo the best of the authors’ knowledge, for the first time, the suspended state of the iron oxide hybrid pigment formed with CS in the coating was investigated rheologically in this study.

Organic-Inorganic Hybrid Pigments Based on Bentonite: Strategies to Stabilize the Quinoidal Base Form of Anthocyanin.

Anthocyanins are one of the natural pigments that humanity has employed the most and can substitute synthetic food dyes, which are considered toxic. They are responsible for most purple, blue, and red pigment nuances in tubers, fruits, and flowers. However, they have some limitations in light, pH, oxygen, and temperature conditions. Combining biomolecules and inorganic materials such as clay minerals can help to reverse these limitations. The present work aims to produce materials obtained using cetyltrimethylammonium bromide in bentonite clay for incorporation and photostabilization of anthocyanin dye. Characterizations showed that the organic molecules were intercalated between the clay mineral layers, and the dye was successfully incorporated at a different pH. Visible light-driven photostability tests were performed with 200 h of irradiation, confirming that the organic-inorganic matrices were efficient enough to stabilize the quinoidal base form of anthocyanin. The pigment prepared at pH 10 was three-fold more stable than pH 4, showing that the increase in the synthesis pH promotes more stable colors, probably due to the stronger intermolecular interaction obtained under these conditions. Therefore, organobentonite hybrids allow to stabilize the fragile color coming from the quinoidal base form of anthocyanin dyes.

Synthesis of a novel environmentally friendly hybrid pigment for effective corrosion control of mild steel

This work aims to synthesize a novel environmentally friendly organic/inorganic hybrid pigment, based on sodium lignosulfonate and zinc acetate, to improve the anti-corrosion protection performance of the mild steel in 3.5 wt% NaCl solution. Open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy tests were employed to evaluate the anti-corrosion protection performance of the steel substrate after using the inhibitive pigment in saline solution. Moreover, scanning electron microscope equipped with energy dispersive spectroscopy, Fourier transform-infrared spectroscopy, ultraviolet-visible spectroscopy (UV–Vis), inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction patterns, and contact angle tests were used to evaluate the synthesized pigment's structure and inhibition mechanism. Based on the ICP-OES and UV–Vis results, the amount of the lignosulfonate molecules and Zn2+ cations releasing from the structure of the inhibitive pigments after 24 h immersion in saline solution is about 160 and 68 ppm, respectively. The electrochemical test results illustrated that the polarization resistance of the steel substrate improved from 4.53 kΩ.cm2 to 22.5 kΩ.cm2 after adding the inhibitive pigment to the saline solution. The production of the inhibitive film on the surface of the steel substrate is the main reason for this improvement.