Effect of covalent organic framework modified graphene oxide on anticorrosion and self-healing properties of epoxy resin coatings

Improved Interfacial Interactions by Core-Shell CoFe2O4@SiO2 Composites to Enhance the Ability of Corrosion Resistance and Electromagnetic Wave Absorption

With the rapid development of science and technology, stealth and anti-corrosion activities in oceans have attracted widespread attention. This study successfully prepares CoFe2O4@SiO2 with a core-shell structure. This core-shell structure endows the CoFe2O4@SiO2 with good impedance matching and interfacial polarization. Thus, the CoFe2O4@SiO2 exhibits an excellent electromagnetic wave absorption performance with a minimum reflection loss of -45.16 dB. Moreover, the CoFe2O4@SiO2 exhibits an excellent dispersion ability in epoxy. The corrosion resistance of the CoFe2O4@SiO2/epoxy is enhanced. After 60 days of immersion, the low-frequency impedance modulus of the CoFe2O4@SiO2/epoxy is still >109 Ω cm2. The CoFe2O4@SiO2 realize the dual functions of stealth and anti-corrosion, which provide ideas for developing marine stealth applications.

Constructing dual-ligand Ce-MOF on graphene oxide modified with polydopamine endowing polyurethane coating with long-term smart anti-corrosion and mechanical robustness

Traditional mono-functional anti-corrosion coatings are unable to meet the long-term corrosion resistance requirements of metal materials, therefore developing multifunctional anti-corrosion coatings have broad application prospects. In this work, long-lasting anti-corrosion coatings with superhydrophobic and self-healing properties were successfully prepared by in-situ growth of dual-ligand cerium-based metal-organic framework (Ce-MOF) on the surface of graphene oxide (GO), followed by chemical modification with polydopamine (PDA), resulting in 5B level of adhesion and excellent mechanical robustness. The superhydrophobic surface, as the external armor of the coating, can effectively block the penetrating path of corrosive media. Meanwhile, the MOF structure formed by the coordination of 2-mercaptobenzimidazole (2-M) with cerium ions endows the coating with smart self-healing properties and long-lasting corrosion resistance. Electrochemical tests showed that the low-frequency impedance modulus value of the superhydrophobic coating still reached 3.82 × 108 Ω cm2 after 30 days salt immersion. Due to the formation of protective films and insoluble precipitates at the defect site by 2-M and cerium ions, the scratches on the coating were significantly reduced after 40 days salt spray experiment, demonstrating the self-healing ability of the coating. This multifunctional anti-corrosion coating provides a new approach for preparing coatings with long-term effective corrosion resistance.

Self-healing and corrosion-sensing multifunctional coatings containing pH-sensitive TiO2-based composites

Polyelectrolyte-encapsulated nanocontainers can effectively respond to changes of pH and thus control the on-demand release of corrosion inhibitors. A pH-responsive release system (Phen-Tpp@MTNs-PDDA) was developed based on the cationic polyelectrolyte poly dimethyl diallyl ammonium chloride (PDDA) encapsulated mesoporous TiO2 nanocontainers (MTNs) loaded with 1,10-phenanthroline (Phen) and tripolyphosphate ions (Tpp) corrosion inhibitors. The epoxy coating (EP) embedded with Phen-Tpp@MTNs-PDDA (Phen-Tpp@MTNs-PDDA/EP) demonstrates superior self-healing properties and confers long-term protection on the metal substrate through the cooperative effect of Phen and Tpp. Simultaneously, this hybrid coating is endowed with corrosion sensing capability based on the color development originating from the interaction of Phen and carbon steel. This self-healing and corrosion-sensing multifunctional coating provides an effective strategy for the corrosion protection of metals.

Covalent Organic Framework/Graphene Hybrids: Synthesis, Properties, and Applications

To address current energy crises and environmental concerns, it is imperative to develop and design versatile porous materials ideal for water purification and energy storage. The advent of covalent organic frameworks (COFs), a revolutionary terrain of porous materials, is underscored by their superlative features such as divinable structure, adjustable aperture, and high specific surface area. However, issues like inferior electric conductivity, inaccessible active sites impede mass transfer and poor processability of bulky COFs restrict their wider application. As a herculean stride forward, COF/graphene hybrids amalgamate the strengths of their constituent components and have in consequence, enticed significant scientific intrigue. Herein, the current progress on the structure and properties of graphene-based materials and COFs are systematically outlined. Then, synthetic strategies for preparing COF/graphene hybrids, including one-pot synthesis, ex situ synthesis, and in situ growth, are comprehensively reviewed. Afterward, the pivotal attributes of COF/graphene hybrids are dissected in conjunction with their multifaceted applications spanning adsorption, separation, catalysis, sensing, and energy storage. Finally, this review is concluded by elucidating prevailing challenges and gesturing toward prospective strides within the realm of COF/graphene hybrids research.

Biomimicking covalent organic frameworks nanocomposite coating for integrated enhanced anticorrosion and antifouling properties of a biodegradable magnesium stent

The utilization of biodegradable magnesium (Mg) alloys in the fabrication of temporary non-vascular stents is an innovative trend in biomedical engineering. However, the heterogeneous degradation profiles of these biomaterials, together with potential bacterial colonization that could precipitate infectious or stenotic complications, are critical obstacles precluding their widespread clinical application. In pursuit of overcoming these limitations, this study applies the principles of biomimicry, particularly the hydrophobic and anti-fouling characteristics of lotus leaves, to pioneer the creation of nanocomposite coatings. These coatings integrate poly-trimethylene carbonate (PTMC) with covalent organic frameworks (COFs), to modify the stent's surface property. The strategic design of the coating's topography, porosity, and self-polishing capabilities collectively aims to decelerate degradation processes and minimize biological adhesion. The protective qualities of the coatings were substantiated through rigorous testing in both in vitro dynamic bile tests and in vivo New Zealand rabbit choledochal models. Empirical findings from these trials confirmed that the implementation of COF-based nanocomposite coatings robustly fortifies Mg implantations, conferring heightened resistance to both biocorrosion and biofouling as well as improved biocompatibility within bodily environments. The outcomes of this research elucidate a comprehensive framework for the multifaceted strategies against stent corrosion and fouling, thereby charting a visionary pathway toward the systematic conception of a new class of reliable COF-derived surface modifications poised to amplify the efficacy of Mg-based stents. STATEMENT OF SIGNIFICANCE: Biodegradable magnesium (Mg) alloys are widely utilized in temporary stents, though their rapid degradation and susceptibility to bacterial infection pose significant challenges. Our research has developed a nanocomposite coating inspired by the lotus, integrating poly-trimethylene carbonate with covalent organic frameworks (COF). The coating achieved self-polishing property and optimal surface energy on the Mg substrate, which decelerates stent degradation and reduces biofilm formation. Comprehensive evaluations utilizing dynamic bile simulations and implantation in New Zealand rabbit choledochal models reveal that the coating improves the durability and longevity of the stent. The implications of these findings suggest the potential COF-based Mg alloy stent surface treatments and a leap forward in advancing stent performance and endurance in clinical applications.

Dual-template imprinted polymer electrochemical sensor for simultaneous determination of malathion and carbendazim using graphene quantum dots

Malathion (MAL) and carbendazim (CBZ) are organophosphate pesticides and fungicides, respectively. They are often used simultaneously in agriculture, and both have been shown to have harmful effects on humans and animals. Therefore, it is important to be able to measure both of these toxins simultaneously in order to assess their potential risks. This study aims to design a dual template electrochemical sensor using a cost-effective graphite-epoxy composite electrode (GECE) modified with molecularly imprinted polymers (MIPs) coated on graphene quantum dots (GQDs) for simultaneous detection of MAL and CBZ in real samples. GQDs were synthesized initially, and their surface was coated with MIPs that were formed using MAL and CBZ as the template molecules, ethylene glycol dimethyl acrylate as the cross-linker, and methacrylic acid as the functional monomer. The GQDs@MIP were characterized using Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, and X-ray scattering spectroscopy. Parameters affecting the sensor response, such as the percentage of GQDs@MIP in the fabricated electrode, the pH of the rebinding solution and analysis solution, and the incubation time, were optimized. The optimum pH values of the rebinding solution were verified using density functional theory (DFT) calculations. Under the optimized conditions, differential pulse voltammetry (DPV) response calibration curves of MAL and CBZ were generated, and the results showed that the sensor had a linear response to MAL in the range of 0.02-55.00 μM with a limit of detection (LOD) of 2 nM (S/N = 3) and to CBZ in the range of 0.02-45.00 μM with a low LOD of 1 nM (S/N = 3). The results also demonstrated the proposed sensor's long-term stability and anti-interference capability. The practical applicability of the fabricated electrode was evaluated for real sample analysis, and good recovery values were obtained.

Engineering Active-Site-Induced Homogeneous Growth of Polydopamine Nanocontainers on Loading-Enhanced Ultrathin Graphene for Smart Self-Healing Anticorrosion Coatings

Engineering nanocontainers with encapsulated inhibitors onto graphene has been an emerging technology for developing self-healing anticorrosion coatings. However, the loading contents of inhibitors are commonly limited by inhomogeneous nanostructures of graphene platforms. Here, we propose an activation-induced ultrathin graphene platform (UG-BP) with the homogeneous growth of polydopamine (PDA) nanocontainers encapsulated with benzotriazole (BTA). Ultrathin graphene prepared by catalytic exfoliation and etching activation provides an ideal platform with an ultrahigh specific surface area (1646.8 m²/g) and homogeneous active sites for the growth of PDA nanocontainers, which achieves a high loading content of inhibitors (40 wt %). The obtained UG-BP platform exhibits pH-sensitive corrosion inhibition effects due to its charged groups. The epoxy/UG-BP coating possesses integrated properties of enhanced mechanical properties (>94%), efficient pH-sensitive self-healing behaviors (98.5% healing efficiency over 7 days), and excellent anticorrosion performance (4.21 × 10⁹ Ω·cm² over 60 days), which stands out from previous related works. Moreover, the interfacial anticorrosion mechanism of UG-BP is revealed in detail, which can inhibit the oxidation of Fe²⁺ and promote the passivation of corrosion products by a dehydration process. This work provides a universal activation-induced strategy for developing loading-enhanced and tailor-made graphene platforms in extended smart systems and demonstrates a promising smart self-healing coating for advanced anticorrosion applications.

GO-functionalized MXene towards superior anti-corrosion coating

MXene flakes shows the great potential in corrosion protection area owing to their lamellar structure and remarkable mechanical features. However, these flakes are highly susceptible to oxidation, which results in their structure degradation and restrict their application in anti-corrosion field. Herein, graphene oxide (GO) was used to functionalize Ti₃C₂T_x MXene through TiOC bonding to fabricate GO-Ti₃C₂T_x nanosheets, which proved by Raman, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR). GO-Ti₃C₂T_x nanosheet inclusion into the epoxy coating and their corrosion performance in 3.5 wt.% NaCl solution with 5 MPa pressure was evaluated through electrochemical techniques including open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) along with salt spray. Results indicated that GO-Ti₃C₂T_x/EP presented superior anti-corrosion capability, the impedance modulus at low frequency (|Z|_{0.01 Hz}) was above 10⁸ Ω cm² after 8 days' immersion in 5 MPa environment, which was 2 orders of magnitude higher than that of the pure epoxy coating. Scanning electron microscope (SEM) and salt spray images demonstrated that the epoxy coating loaded with GO-Ti₃C₂T_x nanosheet could provide robust corrosion protection for Q235 steel via the physical barrier effect.

Design and enhanced anticorrosion performance of a Zn5Mo2O11·5H2O/h-BN nanocomposite with labyrinth of nanopores

Zinc molybdate (ZMO) is a safe and effective grafting material for anticorrosion. Herein, we reported the synthesis of ZMO/h-BN with the labyrinth of capillary pores owing to the in situ growth of ZMO on flake hexagonal boron nitride (h-BN) using the hydrothermal method. The special morphological structure provided a tortuous path for aggressive species to the steel substrate, which extended and blocked the transmission of aggressive species, enhancing the physical corrosion barrier performance. In addition, the capillary pores of ZMO contributed to the competitive adsorption of Cl^- in an electrolyte and reduced the diffusion of aggressive species, thus further delaying the corrosion process. Moreover, the capture of oxygen by forming a B-O bond with h-BN and the formation of a molybdate passive film are beneficial for the inhibition of cathodic and anodic reactions. As verified by electrochemical impedance spectroscopy (EIS), the anticorrosion performance of ZMO/h-BN coating increased by 49.58% and 130.72% compared with ZMO and epoxy resin (EP) coatings after immersing in a NaCl aqueous solution (3.50 wt%) for 72 h. This coating matrix provides an avenue for molybdate-based corrosion remediation.

Ionic modification of graphene nanosheets to improve anti-corrosive properties of organosilicon composite coatings†

Composite coatings with anti-corrosive properties were fabricated using quaternized silicone oil modified graphene oxide and silicone polymer. Quaternized silicone oil was successfully synthesized through copolymerization of octamethyl cyclotetrasiloxane (D4), chloropropylsilane and triethylamine. The quaternized silicone oil modified graphene oxide (M-GO) was characterized by using ¹H NMR, FT-IR, Small-angle X-ray scattering (SAXS), Thermogravimetry (TG) and Transmission electron microscopy (TEM). The results showed that the M-GO was formed successfully. The M-GO could be dispersed without aggregation in some organic solvents, and the concentration of M-GO could be up to 3 mg ml⁻¹. The M-GO-reinforced silicone composites exhibited obvious improvements in thermal stability, mechanical properties and especially anticorrosive properties with the highest E_corr (−121 mV) and the lowest I_corr (6.058 × 10⁻⁹ A cm⁻²), and the protection efficiency of the matrix could reach 99.97%. The anticorrosive mechanism of the fabricated composite coatings was investigated. This work provides a ready strategy for modification of GO and fabrication of high performance graphene-based silicone composite materials.

Silicone modified graphene oxide (M-GO) was readily and visually prepared. The M-GO-reinforced silicone composite coating exhibited obvious improvements in thermal stability, mechanical properties, especially anticorrosion.

Boosting Reactive Oxygen Species Generation by Regulating Excitonic Effects in Porphyrinic Covalent Organic Frameworks

Excitonic effects play a crucial role in determining the photocatalytic performance of polymer semiconductors, which has long been ignored. Herein, metal organic frameworks (MOFs, specially NH₂-MIL-125) modifying porphyrinic covalent organic frameworks (COFs, specially DhaTph) have been proven to be a suitable model to regulate excitonic effects. The photoluminescence measurements prove that DhaTph presents strong excitonic effects, which can generate ¹O₂ through an energy transfer process. Remarkably, the construction of the NH₂-MIL-125@DhaTph heterostructure can effectively facilitate the dissociation of excitons, resulting in distinct activation of O₂ to O₂^•- and •OH. Benefiting from the enhanced generation of reactive oxygen species, the NH₂-MIL-125@DhaTph composite exhibits a superior bactericidal effect and photocatalytic degradation performance. This work provides a deeper insight into the excitonic effects based on COFs during the photocatalytic process and opens a feasible avenue for the regulation of the excitonic effects in porphyrinic COFs.