Nano composite filler of core-shell structure based on microenvironment fluorescence response, preparation and application in intelligent anticorrosive coating

Abstract

The invention discloses a core-shell structure nano composite filler based on microenvironment fluorescence response as well as a preparation method and application thereof. The nano composite filler sequentially comprises a functional nanoparticle core, a middle layer and an MOFs shell layer with a dual-fluorescence effect from inside to outside, the functional nanoparticle core is selected from materials with electromagnetic shielding, phase change heat storage or metal corrosion inhibition functions; the middle layer is selected from polydopamine or polyamino silane; the MOFs shell layer with the dual fluorescent effect is composed of a fluorescent MOFs material and a fluorescent agent loaded on the fluorescent MOFs material and can be used for preparing an intelligent anti-corrosion early warning coating, and therefore the technical problems that a traditional intelligent anti-corrosion coating is poor in designability and single in function are solved.

Description

Technical Field

[0001] The present invention belongs to the field of metal anti-corrosion coating materials, and more specifically, relates to a nano-composite filler with a core-shell structure based on microenvironment fluorescence response and applied to an intelligent anti-corrosion coating. Background Art

[0002] Metal materials are commonly exposed to corrosion in natural environments and industrial applications, a process that significantly shortens the material's service life. Among existing protective technologies, organic coatings, with their excellent isolation properties, have become the mainstream solution for preventing metals from coming into contact with corrosive media. However, traditional organic coatings are susceptible to environmental factors, resulting in microcracks, pinholes, structural defects, and mechanical damage during transportation. Therefore, the development of intelligent protection systems with autonomous damage monitoring and self-repair capabilities has become a key technical direction urgently awaiting breakthroughs in the field of corrosion protection.

[0003] On the one hand, coating damage will significantly accelerate the corrosion rate of the metal substrate. By establishing a real-time monitoring and early warning mechanism to track the material degradation process, it is not only possible to timely grasp the corrosion dynamics characteristics, but also to provide a scientific basis for formulating precise maintenance strategies, thereby effectively extending the service life of the coating. On the other hand, self-repairing intelligent protective coatings can achieve microcrack closure and barrier function reconstruction based on intrinsic and extrinsic response mechanisms. Through the self-warning-self-repair dual-function synergistic mechanism, the system can not only achieve corrosion microenvironment regulation and early failure signal tracing, but also actively inhibit the electrochemical corrosion process before human intervention, thereby significantly improving the comprehensive protection efficiency and full life cycle protection capabilities of the protective coating system.

[0004] Metal-Organic Frameworks (MOFs) have become the core material system for the design of a new generation of intelligent protective coatings due to their ultra-high specific surface area, programmable pore topology, and unique nano-confinement effect. Current research focuses on the development of the basic functions of MOFs as nanoscale corrosion inhibitor carriers (typical representatives include patented technologies such as CN112552789A and CN112457696A), and the realization of self-repair functions of corrosion micro-areas through physical encapsulation strategies. However, this type of technical route fails to effectively integrate the intrinsic advantages of MOFs, such as their multi-scale interface regulation capabilities, environmental response characteristics, and catalytic conversion activity, resulting in significant technical bottlenecks in the synergistic enhancement of multi-level protection systems such as gradient release, intelligent early warning, and cathodic protection.

[0005] Fluorescence-responsive MOFs inherit the structural advantages of traditional framework materials and exhibit unique photophysical properties and multi-level energy transfer mechanisms. A typical technology, as shown in patent CN114716879A, constructs a dual-mode damage-corrosion monitoring system based on dual-color fluorescence conversion by implanting fluorescent MOFs with metal ion recognition capabilities as intelligent sensing units into the coating matrix. The core of this technology is that when the coating is only physically damaged, the MOFs contact the infiltrating medium, triggering a first fluorescence emission; when corrosion extends to the metal substrate, the metal ions released from the corroded microregions coordinate with the MOFs to drive fluorescence conversion, forming a second characteristic emission peak. The introduction of this dual-color fluorescence system can promptly detect coating damage and indicate the damage status of the coating. However, the aforementioned methods cannot spontaneously delay metal corrosion, and most current intelligent coatings have bottlenecks such as limited functionality and poor designability. Summary of the Invention

[0006] In response to the above defects or improvement needs of the existing technology, the present invention provides a nano-composite filler with a core-shell structure based on microenvironment fluorescence response for application in intelligent anti-corrosion coatings, thereby solving the technical problems of weak designability and single function bottlenecks of traditional intelligent anti-corrosion coatings.

[0007] To achieve the above objectives, according to one aspect of the present invention, a nanocomposite filler with a core-shell structure based on microenvironment fluorescence response is provided, which comprises, from the inside out, a functional nanoparticle core, an intermediate layer, and a MOFs shell layer with a dual fluorescence effect; the functional nanoparticle core is selected from a material with electromagnetic shielding, phase change heat storage or metal corrosion inhibition functions; the intermediate layer is selected from polydopamine or polyaminosilane; the MOFs shell layer with a dual fluorescence effect is composed of a fluorescent MOFs material and a fluorescent agent loaded on the fluorescent MOFs material; the first fluorescence effect of the MOFs shell layer with a dual fluorescence effect is generated by the fluorescent MOFs material, and the second fluorescence effect is generated by the fluorescent agent.

[0008] Preferably, the material having electromagnetic shielding function is selected from one or more of Fe3O4, Ni, Co, and Fe-Ni alloy;

[0009] Preferably, the material having phase change heat storage function is selected from one or more of lauric acid, palmitic acid, and stearic acid;

[0010] Preferably, the material having metal corrosion inhibition function is selected from one or more of Na2MoO4, Na3PO4, and 2-mercaptobenzimidazole.

[0011] Preferably, the fluorescent MOFs material is selected from Zr-MOF, Zn-MOF or In-MOF; the fluorescent agent is selected from rhodamine B, cadmium sulfide quantum dots or carbon quantum dots.

[0012] Preferably, the particle size of the nanocomposite filler is 100-500 nm; the particle size of the functional nanoparticles is 30-300 nm; the thickness of the intermediate layer is 10-50 nm; and the thickness of the MOFs shell with dual fluorescence effect is 50-200 nm.

[0013] According to another aspect of the present invention, a method for preparing the core-shell nanocomposite filler based on microenvironment fluorescence response is provided, comprising the following steps:

[0014] (1) dispersing the functional nanoparticles in tris(hydroxymethylaminomethane) hydrochloride buffer, then adding dopamine to react, thereby obtaining polydopamine-coated functional nanoparticles; or dispersing the functional nanoparticles in deionized water, adding toluene or ethanol, then adding aminosilane, and heating under reflux to react, thereby obtaining polyaminosilane-coated functional nanoparticles;

[0015] (2) The polydopamine-coated functional nanoparticles or polyaminosilane-coated functional nanoparticles obtained in step (1) and the MOFs material with dual fluorescence effect are added into a solvent and dissolved, and then transferred into a reactor for reaction to obtain the core-shell structure nanocomposite filler.

[0016] Preferably, the reaction temperature in the reactor is 80-120° C., and the reaction time is 12-120 h.

[0017] According to another aspect of the present invention, an intelligent anti-corrosion warning coating is provided, comprising the aforementioned nanocomposite filler with a core-shell structure based on microenvironment fluorescence response and an organic resin material with hydrophobic properties.

[0018] Preferably, the hydrophobic organic resin material is one or more of epoxy resin, fluorocarbon resin or acrylic resin; in the intelligent anti-corrosion warning coating, the mass fraction of the nano-composite filler is 0.1wt% to 5wt%.

[0019] According to another aspect of the present invention, an application of the intelligent anti-corrosion warning coating is provided, wherein the intelligent anti-corrosion warning coating is coated on a metal substrate.

[0020] Preferably, the metal substrate is an aluminum single-substance substrate, an aluminum alloy substrate, a copper single-substance substrate, a copper alloy substrate, a zinc single-substance substrate, a zinc alloy substrate, an iron single-substance substrate, or an iron alloy substrate.

[0021] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0022] (1) The present invention uses a nanocomposite filler composed of a functional nano core, a polydopamine or polyaminosilane intermediate layer, and a MOF shell with a fluorescent effect. The nanocomposite filler has customizable properties. According to needs, nanocomposite fillers with different functions such as electromagnetic shielding, phase change heat storage, or metal corrosion inhibition can be customized. It can also be expanded according to actual application requirements. It has strong designability and can achieve customization of coating functions. It also has multiple functions such as photothermal self-healing and damage / corrosion graded visual warning.

[0023] (2) The intermediate layer of the core-shell structured nanocomposite filler selected by the present invention is polydopamine or polyaminosilane, which has unique surface universal growth characteristics and is easy to coat on the surface of various nanoparticles. At the same time, the catechol functional groups rich in the molecular structure of polydopamine and the amino groups contained in polyaminosilane have excellent metal ion coordination capabilities, which can effectively promote the heterogeneous nucleation and growth process of the MOFs layer and realize the construction of the core-shell structure of the nanocomposite filler. In addition, polydopamine has excellent photothermal response performance. When the coating is locally irradiated with near-infrared light, the nanofiller contains polydopamine, causing the coating to heat up locally, soften and flow, thereby filling the damaged area of ​​the coating and realizing the photothermal self-healing function of the coating.

[0024] (3) The MOF shell of the core-shell nanofiller selected in the present invention has a dual-mode fluorescence response mechanism: when the coating is slightly physically damaged, the MOF shell of the nanocomposite filler with dual fluorescence effect contacts the corrosive medium, stimulating the fluorescent agent to produce a first characteristic fluorescence; when the coating is deeply damaged and the metal substrate corrodes, the metal ion concentration or pH value of the microenvironment at the damaged location changes, and the metal ions in the environment interact with the fluorescent MOF material, causing the fluorescence emission behavior to change, inducing the fluorescent MOF shell to stimulate the second characteristic fluorescence. This dual-mode fluorescence response corresponds to the coating micro-damage and metal substrate corrosion, respectively, realizing a corrosion graded visual early warning system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The scanning electron micrographs of Fe3O4, Fe3O4@PDA and Fe3O4@PDA@Zr-MOF-RhB prepared in Example 1 (corresponding to Figure 1 (a), (b), (c)).

[0026] Figure 2 Transmission electron micrographs of Fe3O4, Fe3O4@PDA and Fe3O4@PDA@Zr-MOF-RhB prepared in Example 1 (corresponding to Figure 2 (a), (b) and (c) to (d)).

[0027] Figure 3Under 365nm ultraviolet light irradiation, the Fe3O4@PDA@Zr-MOF-RhB nanofiller prepared in Example 1 was dispersed in deionized water and Al-containing 3+ Fluorescence image in aqueous solution.

[0028] Figure 4 The fluorescence micrographs of the aluminum-based coating samples with pre-made scratches of different depths in Example 2 after continuous immersion for 12 hours in a 3.5wt% NaCl simulated corrosion environment (corresponding to Figure 3 (a), (b)).

[0029] Figure 5 Shielding effect and dielectric constant of Fe3O4, Zr-MOF-RhB and Fe3O4@PDA@Zr-MOF-RhB in Example 1 in the X-band, where (a) is the shielding effect in the X-band; (b) is the dielectric constant.

[0030] Figure 6 Electrochemical impedance spectroscopy characteristics of the smart anti-corrosion coating sample developed in Example 2 immersed in a 3.5wt% NaCl simulated corrosion environment.

[0031] Figure 7 These are microscopic morphologies of scratches on the pre-scratched aluminum-based coating sample in Example 2 before and after near-infrared light irradiation, where (a) is before irradiation; (b) is after irradiation. DETAILED DESCRIPTION

[0032] In order to clearly explain the technical purpose, innovative solutions and core advantages of the present invention, the following will systematically analyze the technical solutions in combination with typical embodiments and drawings. It should be noted that the embodiments are all illustrative examples, and their technical parameters and implementation paths are not intended to be limiting interpretations of the scope of protection of the present invention. It is worth noting that the functional modules involved in each embodiment (including but not limited to electromagnetic shielding, self-warning, photothermal response, etc.) can achieve collaborative configuration and functional coupling across embodiments in the absence of principle conflicts.

[0033] The present invention provides a method for preparing a nanocomposite filler with a core-shell structure based on microenvironment fluorescence response:

[0034] (1) dispersing the functional nanoparticles in Tris buffer, then adding dopamine to react, thereby obtaining polydopamine-coated functional nanoparticles; or dispersing the functional nanoparticles in anhydrous toluene, adding aminosilane, and heating under reflux to react, thereby obtaining polyaminosilane-coated functional nanoparticles;

[0035] (2) The polydopamine-coated functional nanoparticles or polyaminosilane-coated functional nanoparticles obtained in step (1) and the MOFs material with a fluorescent effect are added to a solvent for dissolution, and then transferred to an autoclave for reaction to obtain the core-shell structured nanocomposite filler.

[0036] In some embodiments, in step (1), the material having electromagnetic shielding function is selected from one or more of Fe3O4, Ni, Co, and Fe-Ni alloy; the material having phase change heat storage function is selected from one or more of lauric acid, palmitic acid, and stearic acid; and the material having metal corrosion inhibition function is selected from one or more of Na2MoO4, Na3PO4, and 2-mercaptobenzimidazole. The particle size is nanoscale, ranging from 30 to 300 nm. The preparation methods thereof are respectively the corresponding general methods for synthesizing nanoparticles.

[0037] In step (1), the thickness of the intermediate layer is about 10 to 50 nm. When the intermediate layer is polydopamine, its preparation method is as follows: the functional nanoparticles and dopamine hydrochloride are mixed in a certain mass ratio, dissolved in a certain volume of Tris solution, stirred for several hours, washed, purified and vacuum dried to obtain the corresponding nanoparticles with a PDA layer; when the intermediate layer is polyaminosilane, its preparation method is as follows: the functional nanoparticles are dispersed in anhydrous toluene, stirred evenly, and then aminosilane is added dropwise, and refluxed at 80 to 120°C for 12 to 15 hours.

[0038] The shell of the core-shell nanocomposite filler in step (2) is a metal ion or pH-responsive fluorescent MOF, and the resulting nanocomposite filler has a particle size of approximately 100 to 500 nm. The general preparation method is to uniformly mix the nanoparticles with the surface-modified intermediate layer with a metal salt, an organic ligand, and a fluorescent agent in a specific molar ratio, transfer the mixture to a closed reactor, and react at a specific temperature for a specific time to successfully construct the core-shell nanocomposite filler. After washing, purification, and vacuum drying, the corresponding core-shell nanocomposite filler is obtained.

[0039] The present invention discloses an application of a nanocomposite filler with a core-shell structure based on microenvironment fluorescence response for an intelligent anti-corrosion warning coating, comprising the nanocomposite filler with the core-shell structure and a polymer hydrophobic resin. The intelligent anti-corrosion coating has multiple functions including customized performance (electromagnetic shielding, phase change heat storage or metal corrosion inhibition), photothermal self-healing and damage / corrosion graded visual warning.

[0040] The method comprises the following steps: S1 compounding the core-shell structured nanocomposite filler with a hydrophobic polymer resin, and performing a metal substrate surface coating and curing process to prepare a multifunctional anti-corrosion warning coating.

[0041] The intelligent anti-corrosion warning coating prepared in step S1 is prepared by the following method: the core-shell structured nanocomposite filler prepared in steps (1) and (2) is dispersed in acetone, ultrasonicated for 20 to 30 minutes, and after adding epoxy resin, mechanically stirred for 60 to 90 minutes, then a curing agent is added, stirred for 10 minutes, and the coating is evenly coated on the surface of the metal substrate using an applicator. After curing at room temperature for 12 to 48 hours, an intelligent anti-corrosion coating is successfully prepared that integrates customized performance (electromagnetic shielding, phase change heat storage or metal corrosion inhibition), photothermal self-healing and damage / corrosion graded visual warning functions.

[0042] In the coating of step S1, the mass proportion of the core-shell structured nanocomposite filler is 0.1% to 5%, and the mass proportion of the curing agent is 15% to 35%.

[0043] The metal matrix in step S1 includes aluminum and its alloys, copper and its alloys, zinc and its alloys, or iron and its alloys.

[0044] In step S1, the core-shell structured nanocomposite filler can be uniformly deposited on the surface of the metal substrate by using a blade coating, spin coating or spray coating process, and the film thickness can be controlled in the range of 10 to 100 μm.

[0045] The above method can be used to prepare an intelligent anti-corrosion warning coating, which can have multiple functions such as customized performance (electromagnetic shielding, phase change heat storage or metal corrosion inhibition), photothermal self-healing and damage / corrosion graded visual warning. The functional nanoparticles in the nanofiller structure customize the electromagnetic shielding, phase change heat storage and metal corrosion inhibition functions of the coating. The polydopamine or polyaminosilane intermediate layer of the nanofiller structure has excellent photothermal response performance. When irradiated with near-infrared light, the coating is locally heated, softened and flowed, filling the damaged area and realizing the photothermal self-healing function of the coating. The MOFs shell with dual fluorescence effect in the nanofiller structure has a dual-mode fluorescence response mechanism to metal ions or pH: when the coating is micro-damaged, the first characteristic fluorescence is excited; when the coating is deeply damaged or the metal substrate is corroded, the second characteristic fluorescence is excited; the dual-mode fluorescence response corresponds to the micro-damage of the coating and the corrosion of the metal substrate, forming a graded visual warning system. The intelligent coating developed by the present invention breaks through the bottleneck of the single function of traditional anti-corrosion coatings, and the process route is simple and controllable. It shows good industrial application potential in the field of equipment protection in harsh environments such as marine engineering, aerospace, etc.

[0046] Example 1

[0047] A method for preparing a nanocomposite filler with a core-shell structure based on microenvironment fluorescence response comprises the following steps:

[0048] (1) Synthesis of Fe3O4 nanoparticles: 2.4 g of FeCl3·6H2O and 0.982 g of FeCl2·4H2O were dissolved in 10 mL of deionized water with vigorous stirring at 80°C under a N2 atmosphere. Subsequently, 5 mL of ammonium hydroxide was added. After 30 min, 3 mL of oleic acid was added and the mixture was stored at 80°C for 1.5 h. The obtained magnetite nanoparticles were washed with water and methanol until neutral. Subsequently, 0.5 g of magnetite nanoparticles were added to 12 mL of water containing 10 mg of SDS and sonicated in an ice-water bath for 10 min to obtain a microemulsion. A styrene emulsion was prepared using 5 mL of styrene, 50 mg of SDS, 40 mL of water, and 0.033 mL of tetradecane. The microemulsion and 5 mg of KPS were mixed and stirred at 500-600 rpm in a N2 atmosphere for 30 min. 10 mL of styrene emulsion was added to the mixture and kept in an 80 °C water bath for 20 h. The mixture was collected with a magnet and washed three times with deionized water and dispersed in 10 mL of H2O for further use.

[0049] (2) 200 μL of Fe3O4 nanoparticles were dispersed in 40 mL of Tris buffer (pH = 8.5), and then 10 mg of dopamine was added to achieve the desired PDA layer thickness. After 8 h of reaction, the product (Fe3O4@PDA) was collected by magnet and stored in 1 mL of H2O.

[0050] (3) 0.54 mmol ZrOCl2·8H2O, 0.74 mmol 2,5-dihydroxyterephthalic acid, 0.1 mmol rhodamine B (RhB) and the Fe3O4@PDA obtained above were added to 15 mL N,N-dimethylformamide, and after ultrasonic dissolution, the mixture was transferred to a 50 mL autoclave and crystallized at 80 °C for 12 h. The mixture was cooled to room temperature, washed with DMF and ethanol, and dried in vacuum at 60 °C for 12 h. The prepared metal Al 3+ MOFs shell / Fe3O4 core nanomaterials (Fe3O4@PDA@Zr-MOF-RhB) responding to dual fluorescence effect, its microscopic morphology is as follows Figure 1 、 Figure 2 As shown in the figure, it can be seen that the synthesized Fe3O4@PDA and Fe3O4@PDA@Zr-MOF@RhB materials have obvious core-shell structure, proving that the material synthesis is successful. Figure 3 Under 365nm ultraviolet light, Fe3O4@PDA@Zr-MOF-RhB in Example 1 was respectively 3+ It can be seen that in deionized water, Fe3O4@PDA@Zr-MOF-RhB exhibits yellow fluorescence. 3+ In aqueous solution, it exhibits blue-green fluorescence.

[0051] Figure 5 For the shielding effect and dielectric constant of the nanofiller in Example 1 at X-band, the electromagnetic shielding performance of the Fe3O4@PDA@Zr-MOF-RhB nanofiller endowed by the Fe3O4 nanoparticle core was shown.

[0052] Example 2

[0053] A preparation method of a smart anticorrosion early warning coating, comprising the following steps:

[0054] Take 0.07 g of Fe3O4@PDA@Zr-MOF-RhB prepared in Example 1 and disperse it in a small amount of acetone, ultrasonic for 30 min, then add 5 g of epoxy resin (EP), mechanically stir for 90 min, then add 1 g of curing agent, stir for 10 min, then use a film applicator to coat the coating on the surface of aluminum (10 mm x 10 mm x 4 mm), and cure at room temperature for 72 h to obtain a smart coating. The thickness of the coating after curing is 20 μm. Use a blade to make scratch defects with a depth of less than 5 μm and more than 20 μm on the surface of the epoxy resin coating added with Fe3O4@PDA@Zr-MOF-RhB nanofiller, and then perform immersion experiment in 3.5wt% NaCl solution.

[0055] Figure 4 The optical photograph of the aluminum sample with scratches in Example 2 after immersion in 3.5wt% NaCl solution. It can be seen from the fluorescence microscope that after immersion in 3.5wt% NaCl solution for 12 h, the scratch part of the metal surface coating presents a color change visible to the naked eye, the shallow scratch part appears yellow fluorescence, and the deep scratch part appears blue fluorescence. This phenomenon shows that the shallow scratch part of the metal does not corrode, Fe3O4@PDA@Zr-MOF-RhB produces yellow fluorescence after contacting with the corrosion medium; the deep scratch part of the metal substrate corrodes, the metal produces Al 3+ , blue fluorescence after contacting with the filler, and at the same time, it shows that the prepared smart anticorrosion coating can realize timely and long-acting self-warning of coating damage / metal corrosion.

[0056] Figure 6 The AC impedance spectrum of the coating in Example 2, from the figure it can be seen that the capacitive arc radius of the epoxy resin added with Fe3O4@PDA@Zr-MOF-RhB is obviously larger than that of pure epoxy resin, which shows that the addition of nanofiller also effectively improves the anticorrosion performance of the coating.

[0057] Figure 7 The SEM images of the coating with scratches in Example 2 before and after near-infrared light irradiation, from the figure it can be seen that after near-infrared laser irradiation, the scratch depth and width of the coating are obviously reduced, which proves that the coating has good photo-thermal self-healing function.

[0058] Example 3

[0059] A preparation method of an intelligent anticorrosion early warning coating, comprising the following steps:

[0060] (1) 2.4 g of FeCl3-6H2O and 0.982 g of FeCl2-4H2O were dissolved in 10 mL of deionized water under stirring at 80°C under N2atmosphere. Then 5 mL of ammonium hydroxide was added, and after 30 min, 3 mL of oleic acid was added, and it was stored at 80°C for 1.5 h. The obtained magnetite nanoparticles were washed to neutral with water and methanol. Then, 0.5 g of the magnetite nanoparticles was added to 12 mL of water containing 10 mg of SDS, and was treated with ultrasonic in an ice-water bath for 10 min to obtain a microemulsion. A styrene emulsion was prepared using 5 mL of styrene, 50 mg of SDS, 40 mL of water, and 0.033 mL of tetradecane. The microemulsion and 5 mg of KPS were mixed, and stirred at a speed of 500-600 rpm under N2atmosphere for 30 min, 10 mL of the styrene emulsion was added to the mixture, and was kept in a water bath at 80°C for 20 h, and was collected with a magnet and washed with deionized water for 3 times, and was dispersed in 10 mL of H2O for further use.

[0061] (2) 200 μL of Fe3O4nanoparticles were dispersed in 40 mL of Tris buffer (pH = 8.5), and then 10 mg of dopamine was added to achieve the desired PDA layer thickness. After 8 h of reaction, the product (Fe3O4@PDA) was collected by a magnet and stored in 1 mL of H2O.

[0062] (3) 0.15 mmol of InCl3-4H2O, 0.05 mmol of 2,2'-dipyridyl-5,5' dicarboxylic acid, and 0.011 mmol of NaOH were dissolved in a mixed solution of 4 mL of CH3CN and 4 mL of H2O, and the obtained Fe3O4@PDA was added. Then the mixture was transferred to a 25 mL autoclave, and was reacted at 120°C for 120 h, and was cooled to room temperature, and was washed with deionized water for 3 times, and was dried in a vacuum drying box at 50°C for 12 h. A pH-responsive fluorescent MOFs shell / Fe3O4core nanomaterial (Fe3O4@PDA@In-MOF) was prepared.

[0063] (4) 0.05g Fe3O4@PDA@In-MOF was dispersed in a small amount of acetone and ultrasonicated for 30min. Then, 5g epoxy resin was added and mechanically stirred for 90min. Then, 1g curing agent was added and stirred for 10min. The coating was coated on the surface of carbon steel (10mm×10mm×4mm) using a film applicator and cured at room temperature for 72h to obtain a smart coating. The coating thickness after curing was 20μm. A blade was used to create scratch defects with a depth of less than 5μm and more than 20μm on the surface of the epoxy resin coating with Fe3O4@PDA@In-MOF nanofiller, and then an immersion experiment was carried out in 3.5wt% NaCl solution. After immersion for 12h, the coating with Fe3O4@PDA@In-MOF added showed visible color changes at different scratch depths. Blue fluorescence appeared at the shallower scratches and green fluorescence appeared at the deeper scratches. The metal in the shallower scratches did not corrode, and Fe3O4@PDA@In-MOF produced blue fluorescence in contact with the corrosive medium. The deeper scratches corroded, and the cathode oxygen reduction reaction produced OH. - , the local pH value increases, causing Fe3O4@PDA@In-MOF to produce green fluorescence, which can provide early warning of coating damage and metal corrosion based on the different fluorescence colors.

[0064] Example 4

[0065] A method for preparing an intelligent anti-corrosion early warning coating comprises the following steps:

[0066] (1) 2.4 g of FeCl3·6H2O and 0.982 g of FeCl2·4H2O were dissolved in 10 mL of deionized water with vigorous stirring at 80°C under N2 atmosphere. Subsequently, 5 mL of ammonium hydroxide was added. After 30 min, 3 mL of oleic acid was added and the mixture was stored at 80°C for 1.5 h. The obtained magnetite nanoparticles were washed with water and methanol until neutral. Subsequently, 0.5 g of magnetite nanoparticles were added to 12 mL of water containing 10 mg of SDS and treated with ultrasound in an ice-water bath for 10 min to obtain a microemulsion. A styrene emulsion was prepared using 5 mL of styrene, 50 mg of SDS, 40 mL of water and 0.033 mL of tetradecane. The microemulsion was mixed with 5 mg of KPS and stirred at 500-600 rpm under N2 atmosphere for 30 min. 10 mL of styrene emulsion was added to the mixture and kept in an 80°C water bath for 20 h. The mixture was collected with a magnet and washed three times with deionized water and dispersed in 10 mL of H2O for further use.

[0067] (2) 200 μL of Fe3O4 nanoparticles were dispersed in 40 mL of Tris buffer (pH = 8.5), and then 10 mg of dopamine was added to achieve the desired PDA layer thickness. After 8 h of reaction, the product (Fe3O4@PDA) was collected by magnet and stored in 1 mL of H2O.

[0068] (3) 0.987mmol Zn(NO3)2·6H2O was dissolved in 20mL deionized water, 7.904mmol 2-methylimidazole was dissolved in 20mL deionized water, and ultrasonically mixed. Then 2mL CdS quantum dots / 10mL carbon dot solution was added to the mixed solution, and the Fe3O4@PDA obtained above was added. The obtained mixed solution was placed in a polytetrafluoroethylene reactor and reacted at 60℃ for 2h. After cooling to room temperature, the product was washed with deionized water 3 times and then placed in a vacuum drying oven at 50℃ for 12h to prepare metal Cu 2+ Responsive fluorescent MOFs shell / Fe3O4 core nanomaterials (Fe3O4@PDA@Zn-MOF).

[0069] (4) 0.06g Fe3O4@PDA@Zn-MOF was dispersed in a small amount of acetone and ultrasonicated for 30min. Then, 5g epoxy resin was added and mechanically stirred for 90min. Then, 1g curing agent was added and stirred for 10min. The coating was coated on a copper surface (10mm×10mm×4mm) using a film applicator and cured at room temperature for 72h to obtain a smart coating. The coating thickness after curing was 20μm. A blade was used to create scratch defects with a depth of less than 5μm and more than 20μm on the surface of the epoxy resin coating with Fe3O4@PDA@Zn-MOF nanofiller, and then an immersion experiment was carried out in 3.5wt% NaCl solution. After immersion for 6h, the coating with Fe3O4@PDA@Zn-MOF added showed visible color changes at different scratch depths. The shallower scratches showed orange fluorescence, and the deeper scratches showed purple fluorescence. In the shallower scratches, copper did not corrode, and the metal organic framework material produced orange fluorescence in contact with the environmental medium. In the deeper scratches, Fe3O4@PDA@Zn-MOF and Cu produced by copper corrosion produced orange fluorescence. 2+ The reaction produces purple fluorescence, which can provide early warning of coating damage and metal corrosion based on the different fluorescence colors.

[0070] Example 5

[0071] A method for preparing a microenvironment-responsive fluorescent MOFs shell / functional nanocore composite filler-added intelligent anti-corrosion coating comprises the following steps:

[0072] (1) 2.4 g of FeCl3·6H2O and 0.982 g of FeCl2·4H2O were dissolved in 10 mL of deionized water with vigorous stirring at 80°C under N2 atmosphere. Subsequently, 5 mL of ammonium hydroxide was added. After 30 min, 3 mL of oleic acid was added and the mixture was stored at 80°C for 1.5 h. The obtained magnetite nanoparticles were washed with water and methanol until neutral. Subsequently, 0.5 g of magnetite nanoparticles were added to 12 mL of water containing 10 mg of SDS and treated with ultrasound in an ice-water bath for 10 min to obtain a microemulsion. A styrene emulsion was prepared using 5 mL of styrene, 50 mg of SDS, 40 mL of water and 0.033 mL of tetradecane. The microemulsion was mixed with 5 mg of KPS and stirred at 500-600 rpm in N2 atmosphere for 30 min. 10 mL of styrene emulsion was added to the mixture and kept in an 80°C water bath for 20 h. The mixture was collected with a magnet and washed three times with deionized water and ethanol. The mixture was dispersed in 10 mL of deionized water for further use.

[0073] (2) 200 μL of Fe3O4 nanoparticles were dispersed in 40 mL of anhydrous toluene, and then 2 mL of aminosilane was added to achieve the desired APTS layer thickness. After 12 h of reaction, the product (Fe3O4@APTS) was collected by magnet and stored in 1 mL of anhydrous toluene.

[0074] (3) 0.987mmol Zn(NO3)2·6H2O was dissolved in 20mL deionized water, 7.904mmol 2-methylimidazole was dissolved in 20mL deionized water, and ultrasonically mixed. Then 2mL CdS quantum dots were added to the mixed solution, and the Fe3O4@APTS obtained above was added. The obtained mixed solution was placed in a polytetrafluoroethylene reactor and reacted at 60℃ for 2h. After cooling to room temperature, the product was washed with deionized water three times and then placed in a vacuum drying oven at 50℃ for 12h to prepare metal Cu 2+ MOFs shell / Fe3O4 core nanomaterials responsive to dual fluorescence effects (Fe3O4@APTS@Zn-MOF).

[0075] (4) 0.06g Fe3O4@APTS@Zn-MOF was dispersed in a small amount of acetone and ultrasonicated for 30min. Then, 5g epoxy resin was added and mechanically stirred for 90min. Then, 1g curing agent was added and stirred for 10min. The coating was coated on a copper surface (10mm×10mm×4mm) using a film applicator and cured at room temperature for 72h to obtain a smart coating. The coating thickness after curing was 20μm. A blade was used to create scratch defects with a depth of less than 5μm and more than 20μm on the surface of the epoxy resin coating with Fe3O4@APTS@Zn-MOF nanofiller, and then an immersion experiment was carried out in 3.5wt% NaCl solution. After immersion for 6h, the coating with Fe3O4@APTS@Zn-MOF added showed visible color changes at different scratch depths. The shallower scratches showed orange fluorescence, and the deeper scratches showed purple fluorescence. In the shallower scratches, copper did not corrode, and the metal organic framework material produced orange fluorescence in contact with the environmental medium. In the deeper scratches, Fe3O4@APTS@Zn-MOF and Cu produced by copper corrosion produced orange fluorescence. 2+ The reaction produces purple fluorescence, which can provide early warning of coating damage and metal corrosion based on the different fluorescence colors.

[0076] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A nanocomposite filler with a core-shell structure based on microenvironment fluorescence response, characterized in that: From the inside out, they are a functional nanoparticle core, an intermediate layer, and a MOFs shell with a dual fluorescence effect; the functional nanoparticle core is selected from a material with electromagnetic shielding, phase change heat storage or metal corrosion inhibition functions; the intermediate layer is selected from polydopamine or polyaminosilane; the MOFs shell with a dual fluorescence effect is composed of a fluorescent MOFs material and a fluorescent agent loaded on the fluorescent MOFs material; the first fluorescence effect of the MOFs shell with a dual fluorescence effect is generated by the fluorescent MOFs material, and the second fluorescence effect is generated by the fluorescent agent.

2. The nanocomposite filler with a core-shell structure based on microenvironment fluorescence response according to claim 1, characterized in that: The material with electromagnetic shielding function is selected from one or more of Fe3O4, Ni, Co, and Fe-Ni alloy; the material with phase change heat storage function is selected from one or more of lauric acid, palmitic acid, and stearic acid; the material with metal corrosion inhibition function is selected from one or more of Na2MoO4, Na3PO4, and 2-mercaptobenzimidazole.

3. The nanocomposite filler with a core-shell structure based on microenvironment fluorescence response according to claim 1, characterized in that: The fluorescent MOFs material is selected from Zr-MOF, Zn-MOF or In-MOF; the fluorescent agent is selected from rhodamine B, cadmium sulfide quantum dots or carbon quantum dots.

4. The nanocomposite filler with a core-shell structure based on microenvironment fluorescence response according to claim 1, characterized in that: The particle size of the nanocomposite filler is 100-500 nm; the particle size of the functional nanoparticles is 30-300 nm; the thickness of the intermediate layer is 10-50 nm; and the thickness of the MOFs shell layer with dual fluorescence effect is 50-200 nm.

5. The method for preparing a nanocomposite filler with a core-shell structure based on microenvironment fluorescence response according to any one of claims 1 to 4, characterized in that: The steps include: (1) dispersing the functional nanoparticles in tris(hydroxymethylaminomethane) hydrochloride buffer, then adding dopamine to react, thereby obtaining polydopamine-coated functional nanoparticles; or dispersing the functional nanoparticles in deionized water, adding toluene or ethanol, then adding aminosilane, and heating under reflux to react, thereby obtaining polyaminosilane-coated functional nanoparticles; (2) The polydopamine-coated functional nanoparticles or polyaminosilane-coated functional nanoparticles obtained in step (1) and the MOFs material with dual fluorescence effect are added into a solvent and dissolved, and then transferred into a reactor for reaction to obtain the core-shell structure nanocomposite filler.

6. The method for preparing a nanocomposite filler with a core-shell structure based on microenvironment fluorescence response according to claim 5, characterized in that: The reaction temperature in the reactor is 80-120° C., and the reaction time is 12-120 h.

7. An intelligent anti-corrosion warning coating, characterized in that: The invention comprises a nano composite filler with a core-shell structure based on microenvironment fluorescence response as described in any one of claims 1 to 4 and an organic resin material with hydrophobic properties.

8. The intelligent anti-corrosion early warning coating according to claim 7, characterized in that: The hydrophobic organic resin material is one or more of epoxy resin, fluorocarbon resin or acrylic resin; in the intelligent anti-corrosion warning coating, the mass fraction of the nano-composite filler is 0.1wt% to 5wt%.

9. The use of an intelligent anti-corrosion early warning coating according to any one of claims 7 to 8, characterized in that: The intelligent anti-corrosion warning coating is coated on a metal substrate.

10. The use of an intelligent anti-corrosion early warning coating according to claim 9, wherein the metal substrate is an aluminum single-substance substrate, an aluminum alloy substrate, a copper single-substance substrate, a copper alloy substrate, a zinc single-substance substrate, a zinc alloy substrate, an iron single-substance substrate, or an iron alloy substrate.

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