Preparation method and application of nanocomposite coating for lead ion colorimetric detection

Abstract

This invention belongs to the field of environmental monitoring and nuclear pollution monitoring technology. Specifically, it discloses a method for preparing a nanocomposite coating for colorimetric detection of lead ions and its application. First, by optimizing the amount of dispersant PVP, reaction concentration, and temperature, uniformly sized silver nanoparticles (AgNPs) are prepared. Then, these nanoparticles are functionalized with thiol groups using a silane coupling agent. Finally, they are composited with a polyvinyl alcohol (PVA) solution to obtain a composite smart coating that combines color response and peelability. This coating has a detection limit of up to 3 mMol / L for lead ions, exhibiting good selectivity, stability, and hydrophilicity. Its elongation at break after film formation reaches 560%, providing a direct indication of lead contamination through color changes. Furthermore, the contaminant can be easily recovered by peeling off the film. This invention is suitable for rapid and visual detection and treatment of lead contamination at nuclear facilities.

Description

Technical Field

[0001] This invention relates to the field of environmental monitoring and nuclear pollution monitoring technology, specifically to a method for preparing a nanocomposite coating for lead ion colorimetric detection and its application. Background Technology

[0002] Lead has a wide range of applications in the nuclear industry, often used as reactor shielding material, nuclear waste container, and coolant material. While providing critical protection, it also poses a potential risk of contamination. During the operation, maintenance, or decommissioning of nuclear facilities, lead may be released in ionic form (Pb) due to equipment corrosion, wear, or accidents. 2 +) Leakage. Pb 2 Once released into the environment, lead contamination not only disrupts the ecological balance of soil and water bodies but also accumulates through the food chain, ultimately posing a serious threat to human health. Therefore, developing a technology capable of rapid, on-site detection and effective treatment of lead contamination in nuclear industry environments is of great significance.

[0003] Currently, the detection of lead ions mainly relies on laboratory analytical techniques such as atomic absorption spectrometry (AAS) and inductively coupled plasma mass spectrometry (ICP-MS). While these methods offer high detection accuracy, they have significant limitations: First, they require complex and expensive large-scale instruments and specialized operators, making them unsuitable for rapid, real-time monitoring at nuclear sites. Second, samples typically require complex pretreatment processes, taking anywhere from several hours to several days, hindering rapid response. Third, in complex nuclear environments, they are susceptible to interference from other metal ions, affecting the selectivity and accuracy of detection.

[0004] In terms of contamination treatment, wet spraying is currently commonly used to decontaminate residual radioactive aerosols or heavy metal contaminants on surfaces. However, conventional low-viscosity spray solutions are difficult to collect after settling, easily leading to the migration and secondary diffusion of contaminants. This not only limits decontamination efficiency but may also expand the contamination area. Therefore, there is an urgent need for a new technology that integrates rapid, highly selective detection with efficient and safe removal to address the lead contamination challenges faced in the nuclear industry environment. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for preparing a nanocomposite coating for colorimetric detection of lead ions and its application. The nanocomposite coating integrates the rapid colorimetric detection function of nano-silver with the peelable properties of polyvinyl alcohol, enabling highly selective and visual detection of lead ions. It can also safely and conveniently remove contaminants through mechanical peeling, making it particularly suitable for on-site monitoring and emergency treatment in special environments such as the nuclear industry, thus solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a nanocomposite coating for lead ion colorimetric detection, comprising the following steps:

[0007] S1. Preparation of silver nanoparticle colloid: Using silver nitrate as a precursor, polyvinylpyrrolidone (PVP) as a dispersant and sodium borohydride as a reducing agent, a reduction reaction was carried out under heating and stirring conditions to obtain silver nanoparticle colloid.

[0008] S2, Functionalized modified nano-silver: The pH of the nano-silver colloid obtained in step S1 is adjusted to acidic, a silane coupling agent is added, and the mixture is heated and stirred to carry out the reaction, thereby obtaining functionalized nano-silver with surface-grafted thiol groups.

[0009] S3. Preparation of PVA-based coating: Add polyvinyl alcohol (PVA) to deionized water, stir to dissolve, and form a uniform PVA aqueous solution;

[0010] S4. Preparation of Ag / PVA nanocomposite coating: The functionalized silver nanoparticles with surface grafted thiol groups obtained in step S2 are added to the PVA aqueous solution in step S3 and stirred and mixed evenly to obtain a gray, homogeneous Ag / PVA nanocomposite coating.

[0011] Preferably, in step S1, the mass ratio of polyvinylpyrrolidone (PVP) to silver nitrate is 1:0.5-2; the reaction concentration of silver nitrate is 0.05-0.5 mmol / L; and the temperature of the reduction reaction is 60-90°C.

[0012] Preferably, in step S1, the mass ratio of polyvinylpyrrolidone (PVP) to silver nitrate is 1:1; the reaction concentration of silver nitrate is 0.1 mmol / L; and the temperature of the reduction reaction is 80°C.

[0013] Preferably, in step S2, adjusting the pH of the nano-silver colloid to acidic specifically means adjusting the pH to 3.5–4.5; the amount of silane coupling agent added is 0.1%–0.5% of the total volume of the nano-silver colloid; and the reaction conditions are stirring at 60–80°C for 4–8 hours.

[0014] Preferably, the silane coupling agent is silane coupling agent KH580.

[0015] Preferably, in step S3, the polyvinyl alcohol is PVA-1788, with a degree of alcoholysis of 88% and a degree of polymerization of 1700, and its dosage is 8% to 12% of the total mass of the coating.

[0016] On the other hand, in order to achieve the above objectives, the present invention also provides the following technical solution: an Ag / PVA nanocomposite coating, characterized in that: the nanocomposite coating comprises a polyvinyl alcohol matrix and functionalized silver nanoparticles with thiol groups grafted onto their surfaces, uniformly dispersed therein.

[0017] On the other hand, in order to achieve the above objectives, the present invention also provides the following technical solution: the application of Ag / PVA nanocomposite coating in the preparation of a peelable membrane for lead ion detection and removal, characterized in that: the nanocomposite coating is coated on the surface of a substrate, dried into a film, and lead ions are visually detected by the color change of the film, and lead-containing pollutants are removed and recycled by peeling off the cured film.

[0018] Preferably, the visual detection of lead ions through membrane color change specifically includes: when the membrane comes into contact with lead ions, its color changes from gray to yellow, visually indicating lead contamination through color change; when Pb 2 At a concentration of 3 mmol / L, the color difference value ΔE can reach 10.67, which is sufficient for clear visual differentiation.

[0019] Preferably, the elongation at break of the membrane can reach 560%, and the nanocomposite coating has a stripping and removal efficiency of more than 96% for lead contaminants in a wide concentration range of 1 to 20 mmol / L.

[0020] The beneficial effects of this invention are:

[0021] 1) Rapid and intuitive detection: Utilizing the LSPR effect of nano-silver, Pb is detected through a visible color change (from gray to yellow). 2 Its rapid response requires no complex instruments, making it particularly suitable for on-site testing.

[0022] 2) High selectivity: AgNPs are modified by thiolization using KH580, utilizing the thiol group to react with Pb. 2 The specific strong interaction of + effectively avoids common metal ions (such as Cu) in the complex environment of the nuclear industry. 2+ Ca 2+ Mg 2+ Interference.

[0023] 3) Integrated Functions: Combining detection and decontamination functions, the material can not only act as a sensor to indicate pollution, but the PVA base film it forms also has excellent peelability (elongation at break can reach 560%), which can fix and remove pollutants like a "band-aid", fundamentally avoiding secondary pollution.

[0024] 4) Environmentally friendly and widely applicable: Using water as a solvent and PVA as a matrix, it is green and safe. The prepared coating has good hydrophilicity (contact angles on glass and stainless steel are approximately 62.5° and 65°, respectively) and stability (Zeta potential of approximately 45.7mV), and can effectively wet and adhere to the surfaces of various substrates, making it suitable for a wide range of applications. Attached Figure Description

[0025] Figure 1 A flowchart illustrating the preparation method of Ag / PVA nanocomposite coating for lead ion colorimetric detection provided in this embodiment of the invention;

[0026] Figure 2 For different Pb 2 + Color change gradient diagram at different concentrations (comparison of color charts corresponding to 1-5 mmol / L);

[0027] Figure 3 These are photographs showing the selective testing of different ions. (a) is the blank, and (b) is Cu. 2+ (c) represents Mg 2+ (d) represents Ca 2+ (e) represents Pb 2+ ;

[0028] Figure 4 SEM images of AgNPs at different relative PVP dosages: (a) SEM image of AgNPs at 1 μm with a relative dosage of 0; (a') SEM image of AgNPs at 500 nm with a relative dosage of 0; (b) SEM image of AgNPs at 1 μm with a relative dosage of 0.1; (b') SEM image of AgNPs at 500 nm with a relative dosage of 0.1; (c) SEM image of AgNPs at 1 μm with a relative dosage of 0.5; (c') SEM image of AgNPs at 500 nm with a relative dosage of 0.5; (d) SEM image of AgNPs at 1 μm with a relative dosage of 1; (d') SEM image of AgNPs at 500 nm with a relative dosage of 1.

[0029] Figure 5 The images show the TEM image, particle size distribution, and XRD pattern of AgNPs. (a) is 200 nm, (b) is 100 nm, (c) is the particle size distribution, and (d) is the XRD pattern of AgNPs.

[0030] Figure 6 The images show the FT-IR spectra of AgNPs and their modified forms. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Nanomaterials have shown great potential in the field of sensing due to their unique optical properties. Among them, silver nanoparticles (AgNPs) have attracted much attention due to their strong localized surface plasmon resonance (LSPR) effect; changes in their dispersion or aggregation state can lead to visible changes in solution color, offering possibilities for developing intuitive and rapid colorimetric sensors. Meanwhile, polyvinyl alcohol (PVA) materials, due to their good film-forming properties, water solubility, and peelability, have been used to prepare peelable membranes for immobilizing contaminants. However, no existing technology has yet found a method that combines Pb... 2 The combination of nano-silver with specific response function and PVA peelable membrane creates a smart composite material that can detect lead pollution in real time and with visualization, and can safely and conveniently remove pollutants through physical peeling.

[0033] Example 1

[0034] A method for preparing Ag / PVA nanocomposite coatings for colorimetric detection of lead ions, such as... Figure 1 As shown, it includes the following steps:

[0035] Step 1: Preparation of silver nanoparticle colloids: Using silver nitrate (AgNO3) as a precursor, polyvinylpyrrolidone (PVP) as a dispersant, and sodium borohydride (NaBH4) as a reducing agent, a reduction reaction is carried out under heating and stirring conditions to prepare uniformly dispersed and highly stable silver nanoparticle colloids. Preferably, the mass ratio of PVP to AgNO3 is 1:1, the AgNO3 concentration is 0.1 mmol / L, and the reaction temperature is 80℃. Under these conditions, silver nanoparticles with a particle size of approximately 6-12 nm and a uniform particle size distribution can be prepared.

[0036] Step 2: Thiol-functionalization modification of nano-silver: The pH of the obtained nano-silver colloid was adjusted to 4.0 with acetic acid, etc., and silane coupling agent KH580 was added. The mixture was stirred at 70°C for 6 hours. After hydrolysis of KH580, its thiol groups firmly bonded to the surface of the silver particles, thus successfully grafting Pb onto the surface of the nano-silver. 2 + It has a thiol (-SH) functional group with high affinity and selectivity.

[0037] Step 3: Preparation of PVA-based coating: Add 10% by mass of polyvinyl alcohol (PVA1788) powder to deionized water and stir at room temperature until completely dissolved to form a uniform, transparent PVA aqueous solution matrix with good film-forming properties.

[0038] Furthermore, the degree of polymerization and degree of alcoholysis of polyvinyl alcohol (PVA) are key factors affecting the final performance of composite coatings. Fully alcoholystolated PVA (such as PVA-124) forms a hard and brittle film that is easily broken upon peeling; low-polymerization-degree PVA (such as PVA-205) forms a film with poor cohesive strength and is easily brittle. Partially alcoholystolated, medium-polymerization-degree PVA (such as PVA-1788, 88% alcoholysis, 1700 degree of polymerization) achieves the best balance between film strength, flexibility, and peelability. The vinyl acetate residues in its molecular chain effectively disrupt the crystalline regions, giving the coating extremely high elasticity (elongation at break >500%), allowing it to be peeled off completely and continuously, which is the basis for convenient contaminant recovery. Therefore, this invention preferably uses PVA-1788 as the film-forming matrix.

[0039] Step 4: Preparation of Ag / PVA nanocomposite coating: The above-mentioned mercapto-modified nano-silver is mixed with PVA aqueous solution in a certain proportion and stirred at 60°C for 1 hour to make the functionalized nano-silver uniformly dispersed in the PVA matrix, and finally a gray, homogeneous Ag / PVA nanocomposite smart coating is obtained.

[0040] The Ag / PVA nanocomposite coating prepared in this invention and its application: This nanocomposite coating can be used to prepare peelable membranes, which are applied to the surface of a substrate and dried to form a film before use. When the membrane comes into contact with lead ions, its color changes from gray to yellow, indicating the presence of Pb in the analyte. 2 +Visualized and semi-quantitative detection of concentration. After the solvent evaporates and the membrane solidifies, the entire membrane can be completely peeled off by mechanical means, thereby achieving safe isolation and convenient recovery of pollutants. Compared with laboratory analysis techniques such as atomic absorption spectrometry (AAS) and inductively coupled plasma mass spectrometry (ICP-MS), this peelable intelligent decontamination coating can complete testing indoors and outdoors within minutes, requires no high technical skills from operators, is inexpensive, and integrates detection, fixation, peeling, and recovery.

[0041] Example 2

[0042] This invention uses polyvinyl alcohol as the matrix material to synthesize silver nanoparticles via chemical reduction. The surface is then functionalized with thiol groups using the silane coupling agent KH580. Finally, the nanoparticles are combined with a polyvinyl alcohol solution to prepare a smart composite material that combines lead ion colorimetric detection and peelable functionality. Water is used as the solvent, making the entire preparation process environmentally friendly and simple to operate.

[0043] The preparation of the Ag / PVA nanocomposite material of the present invention is based on obtaining 100 parts of composite coating; the preparation method of the Ag / PVA nanocomposite material includes the following steps:

[0044] S101: Preparation of nano-silver sol: Weigh 0.1-0.5 parts of silver nitrate, dissolve in 100 parts of deionized water, add polyvinylpyrrolidone dispersant with a mass ratio of 0.5:1 to 2:1 to silver nitrate, and stir and mix at 60-90℃; slowly add sodium borohydride solution as a reducing agent with a molar ratio of 1:11 to silver nitrate, react for 30-60 minutes, centrifuge and wash, and redisperse in water to obtain nano-silver sol;

[0045] S102: Thiol-functionalized modification of nano-silver: Take 100 parts of the above nano-silver sol, adjust the pH to 3.5-4.5 with acid, add 0.1-0.5 parts of silane coupling agent KH580, stir and react at 60-80℃ for 4-8 hours, and obtain thiolized nano-silver dispersion after centrifugation and washing.

[0046] S103: Preparation of PVA-based coating: Take 5-15 parts of polyvinyl alcohol P1788, add 85-95 parts of deionized water, stir at room temperature to 90℃ for 1-3 hours until completely dissolved, and obtain a uniform and transparent PVA solution.

[0047] S104: Preparation of Ag / PVA nanocomposite material: Take 100 parts of PVA solution, add 5-20 parts of mercapto-modified silver nano-dispersion, stir at 40-60℃ for 1-2 hours to mix evenly, and obtain a gray Ag / PVA nanocomposite coating; after the composite coating is allowed to stand for degassing for 12-24 hours, measure its viscosity, add deionized water as needed to adjust the viscosity to 200-5000 mPa·s, and seal and store in a cool place.

[0048] Example 3

[0049] A method for preparing Ag / PVA nanocomposite materials and its performance testing

[0050] 1. Preparation of silver nanoparticles (AgNPs)

[0051] In a 250 mL three-necked flask, add 100 mL of 0.1 mmol / L silver nitrate (AgNO3) solution, followed by polyvinylpyrrolidone (PVP, molecular weight 10000) at a mass ratio of 1:1 to AgNO3. Place the mixture in an 80 °C water bath and stir at 300 rpm for 10 minutes. Weigh out an equimolar amount of sodium borohydride (NaBH4) and dissolve it in 5 mL of ice water to prepare a reducing agent solution. Slowly add the NaBH4 solution dropwise to the three-necked flask using a constant pressure dropping funnel, controlling the dropping rate to approximately 1 drop / second. After the addition is complete, continue stirring at 80 °C for 30 minutes. After the reaction is complete, centrifuge and wash the resulting pale yellow solution three times (10000 rpm, 15 min), redisperse it in 100 mL of deionized water to obtain a concentrated AgNPs sol, which is then stored in a refrigerator at 4 °C protected from light.

[0052] 2. Thiol-functionalized modification of AgNPs

[0053] Take 100 mL of the prepared AgNPs sol and adjust the pH to 4.0 with acetic acid solution. Then add 0.2 mL (approximately 0.2% of the total volume) of silane coupling agent KH580, and place the mixture in a 70°C water bath, stirring at 400 rpm for 6 hours. The solution color changed from golden yellow to grayish white. After the reaction was complete, the solution was centrifuged and washed twice (12000 rpm, 20 min) to remove unreacted KH580. The precipitate was collected and redispersed in 50 mL of deionized water to obtain a concentrated solution of thiol-modified AgNPs.

[0054] 3. Formulation of PVA-based coatings

[0055] Weigh 10g of polyvinyl alcohol (PVA1788, degree of hydrolysis 87%–89%) powder and add it to 90g of deionized water. Stir at 500rpm for 1 hour at room temperature (25℃) until the PVA is completely swollen and dissolved, forming a clear, transparent, and homogeneous 10wt% PVA aqueous solution, which will serve as the coating matrix.

[0056] 4. Preparation of Ag / PVA nanocomposite smart coatings

[0057] Measure 100 mL of the above PVA-based coating and place it in a 150 mL beaker. While stirring, slowly add 20 mL of the thiol-modified AgNPs concentrate. Transfer the mixture to a 60°C water bath and stir continuously at 400 rpm for 1 hour to ensure that the silver nanoparticles are uniformly dispersed in the PVA matrix, finally obtaining a gray, homogeneous Ag / PVA nanocomposite coating.

[0058] 5. Performance Testing and Characterization

[0059] (1) Morphology and Structure Characterization: A small amount of unmodified AgNPs sol was dropped onto a silicon wafer, dried, and its morphology and dispersibility were observed using a scanning electron microscope (SEM). Figure 4 As shown, it can be observed that when the relative dosage is 1, the dispersion is uniform and there is no obvious agglomeration. A small amount is dropped onto a copper grid, and its particle size and distribution are observed using a transmission electron microscope (TEM). Figure 5 As shown in (a), (b), and (c), the results indicate that the AgNPs particle size is mainly distributed between 6 and 12 nm, and the dispersion is uniform. X-ray diffraction (XRD) analysis was performed, as shown... Figure 5 As shown in (d), typical diffraction peaks of silver were observed at 38.1° and 64.4°, confirming the successful preparation of well-crystallized AgNPs.

[0060] (2) Verification of modification effect: Fourier transform infrared spectroscopy (FT-IR) analysis was performed on AgNPs before and after modification, such as... Figure 6 As shown, the modified sample exhibited a distinct characteristic peak of thiol (-SH) stretching vibration in the wavenumber range of 600-700 cm⁻¹, confirming that KH580 had been successfully grafted onto the AgNPs surface.

[0061] (3) Colorimetric detection performance test: Lead acetate (Pb(CH3COO)2) powder was dissolved in deionized water to prepare Pb concentrations of 1, 2, 3, 4, and 5 mmol / L. 2 +Standard solutions, from left to right, correspond to... Figure 2 Take equal amounts of the modified AgNPs concentrate in cuvettes, and add different concentrations of Pb. 2 Add the solution and observe the color change. The results show that when Pb 2 When the concentration of Pb reaches 3 mmol / L, the solution exhibits a noticeable color change from grayish-white to yellow, which is visible to the naked eye. Scanning with a UV-Vis spectrophotometer revealed that as Pb... 2 As the concentration increases, the characteristic absorption peak of AgNPs near 400 nm gradually weakens and undergoes a red shift, further verifying its colorimetric detection capability.

[0062] (4) Selectivity test: Prepare a blank sample with a concentration of 50 mMol / L, Cu 2+ Mg 2+ Ca 2+ and Pb 2 +solution, respectively as follows Figure 3 (a)- Figure 3 (e) Equal volumes of the above ionic solution were added to equal volumes of the modified AgNPs concentrate. The results showed that only Pb 2 The + solution elicited a significant color reaction (turning yellow), while other ion solutions showed only slight color changes, demonstrating that the sensor is effective against Pb. 2 + It has high selectivity.

[0063] (5) Film Formation and Application Performance Testing of Composite Coatings: The prepared Ag / PVA composite coating was uniformly coated onto a clean glass plate and a 304 stainless steel plate, and dried at room temperature to form a film. Different concentrations (0, 1, 3, 5, 7 mmol / L) of Pb were prepared. 2 A solution was added dropwise to the membrane surface. After the liquid evaporated, the interaction between the membrane and Pb was observed. 2 + The contact area turns yellow, and the color intensity is similar to that of Pb. 2 The positive correlation with concentration indicates that it still possesses visual detection capabilities in its solid film state. A colorimeter was used to measure the color development area; when Pb... 2+ When the concentration is 3 mmol / L, the color difference value (ΔE) exceeds 10 (reaches 10.67), which meets the standard that can be clearly distinguished by the naked eye.

[0064] (6) Mechanical and Wetting Properties Tests: The composite coating was cast into a film, and after complete drying, it was cut into standard strips and subjected to tensile testing using a universal testing machine. The results showed that the elongation at break of the composite film reached 560%, proving its excellent flexibility and peelability. The initial contact angle of the film on the glass substrate was measured to be approximately 62.5° using a contact angle meter, and approximately 65° on the 304 stainless steel plate. The contact angle decreased rapidly within 60 seconds, indicating that it has good hydrophilicity and wettability, which is beneficial for spreading and adhesion on complex surfaces. The Zeta potential of the composite coating was measured to be +45.7mV using a Zeta potential meter, indicating that it has excellent storage stability and is not prone to agglomeration and sedimentation.

[0065] (7) Long-term stability test: The coating (25℃ group) stored for 6 months was recoated and its stability against 3mMol / LPb was tested. 2 The colorimetric response of the solution was observed, and compared with the initial sample, it was found that 3 mmol / L Pb could still be clearly distinguished by the naked eye. 2 + solution, for Pb 2 The selectivity for Cu2+ remained unchanged. + Ca2 + Interfering ions remained unresponsive. Further color difference analysis revealed a color difference value ΔE of 9.8 in the distinct color area, compared to the initial value (10.67), indicating a sensitivity retention rate of 91.8%. These experimental results demonstrate that the Ag / PVA nanocomposite coating prepared in this invention, after being stored at room temperature for 6 months, exhibited no significant attenuation in its core colorimetric detection function, maintaining a sensitivity retention rate exceeding 90%. This fully proves its excellent functional stability and meets the storage and usage requirements in practical applications.

[0066] (8) Stripping efficiency test under different lead contamination concentrations

[0067] Sample preparation: Fifteen clean 10cm×10cm 304 stainless steel plates were taken and divided into 5 groups, with 3 replicates in each group. 100μL of lead acetate solution with concentrations of 1, 3, 5, 10, and 20 mmol / L was uniformly coated onto each plate using a micropipette. The plates were then dried in a 60℃ oven for 30 minutes to simulate different degrees of lead contamination on the surface.

[0068] Coating and Film Formation: The Ag / PVA nanocomposite coating prepared in Example 3 was uniformly coated onto the surface of the contaminated substrate, with the wet film thickness controlled at 500 μm. The coating was dried at room temperature (25°C) for 24 hours to form a complete and continuous composite film.

[0069] Peeling and Detection: Carefully peel the cured film 180 degrees from the edge of the substrate, ensuring the entire film is removed intact. Gently wipe the surface of the substrate three times with a lint-free cloth moistened with deionized water to collect any possible residual contaminants. Digest the lint-free cloth in deionized water. Quantify the lead content in the digestion solution using inductively coupled plasma mass spectrometry (ICP-MS). Experimental results show that the Ag / PVA nanocomposite coating prepared in this invention achieves a lead contaminant removal efficiency of over 96% within a wide concentration range of 1–20 mMol / L. This demonstrates that the material not only enables visual detection of lead contamination but also efficiently and reliably removes contaminants through a simple physical peeling operation, achieving an integration of detection and decontamination functions and effectively avoiding the risk of secondary contamination.

[0070] Comparison of different PVA models in Example 1

[0071] Equal amounts of PVA-1788 (degree of polymerization 1700, degree of hydrolysis 88%), VA-124 (degree of polymerization 2400, degree of hydrolysis 98.5%), and PVA-205 (degree of polymerization 500, degree of hydrolysis 88%) were prepared using the same procedures as in Example 1. The results showed that the PVA-124 composite film was hard and brittle after formation. During tensile testing, its elongation at break was extremely low (<50%), and it easily broke when attempted to peel from the glass substrate, making large-area complete peeling impossible. The PVA-205 composite film was too soft and sticky after formation, with poor cohesive strength. During peeling, the film easily tore and produced debris, making complete peeling impossible, and its mechanical strength was insufficient to fix contaminants. In contrast, the PVA-1788 composite film was flexible, with a high elongation at break (560%), allowing for complete, large-area peeling without residue. This comparison demonstrates the absolute advantage of PVA-1788 in terms of peelability, and its unique combination of polymerization degree and alcoholysis degree is the key to realizing the "convenient recycling" function of this invention.

[0072] Comparison of different PVA dosages in Example 2

[0073] Except for changing the amount of polyvinyl alcohol (PVA1788) (set to 5wt%, 8wt%, 12wt%, and 15wt%, respectively), the other preparation steps are exactly the same as in Example 3.

[0074] The performance comparison results show that the 5wt% PVA control group solution was too dilute, resulting in poor film formation. After drying, it formed a discontinuous and defective film, which could not effectively encapsulate the nano-silver sensor and was severely fragmented during peeling. In contrast, the 8wt% and 12wt% PVA control groups produced films with good film properties, exhibiting a continuous and uniform film. The peeling force was moderate, allowing for both firm adhesion to the substrate and easy, complete peeling, demonstrating excellent overall performance. The 15wt% PVA control group solution had excessive viscosity, making coating difficult. The resulting film was too thick, requiring excessive peeling force, easily breaking at the peeling edges, and leaving a small amount of colloid residue on the substrate. Therefore, it can be concluded that the PVA dosage significantly affects the film-forming properties and peelability of the coating. This invention determines that 8%–12% is the optimal dosage range for PVA1788, within which a balance between detection and peeling performance can be achieved.

[0075] Comparative Example 3: Effect of different reaction temperatures on the preparation of AgNPs

[0076] Except for setting the reaction temperatures sequentially to 20℃, 40℃, 60℃, 80℃, and 100℃, the remaining steps were the same as in "Preparation of Nano Silver Sol" in Example 3. Macroscopic observation and UV-Vis spectral analysis revealed that when the temperature was below 80℃, the product stability was poor, and it was prone to agglomeration and sedimentation or the appearance of multiple absorption peaks. When the temperature was 80℃, the product solution was stable, and the UV-Vis spectrum showed a single, sharp characteristic absorption peak near 400nm, indicating that the AgNPs prepared at this temperature had uniform particle size and the best dispersibility.

[0077] Comparative Example 4: Effect of different PVP dosages on AgNP preparation

[0078] Except for setting the mass ratio of PVP to AgNO3 to 1:0, 1:0.1, 1:0.5, and 1:1 respectively, the remaining steps were the same as in "Preparation of Nano Silver Sol" in Example 3. SEM observation revealed that when the PVP dosage was 0, 0.1, and 0.5, AgNPs exhibited severe agglomeration and uneven particle size distribution; when the mass ratio of PVP to AgNO3 was 1:1, AgNPs showed the best dispersibility and uniform particle size distribution.

[0079] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0080] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0081] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0082] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the preparation of a nanocomposite coating for colorimetric detection of lead ions, characterized by, Includes the following steps: S1. Preparation of nano-silver colloid: Using silver nitrate as a precursor, polyvinylpyrrolidone (PVP) as a dispersant, and sodium borohydride as a reducing agent, a reduction reaction is carried out under heating and stirring conditions to obtain nano-silver colloid; the mass ratio of PVP to silver nitrate is 1:1; the reaction concentration of silver nitrate is 0.1 mmol / L; and the temperature of the reduction reaction is 80℃. S2, Functionalized modified nano-silver: The pH of the nano-silver colloid obtained in step S1 is adjusted to acidic, a silane coupling agent is added, and the mixture is heated and stirred to carry out the reaction, thereby obtaining functionalized nano-silver with surface-grafted thiol groups. S3. Preparation of PVA-based coating: Add polyvinyl alcohol (PVA) to deionized water, stir to dissolve, and form a homogeneous PVA aqueous solution; the polyvinyl alcohol is PVA-1788, and its amount is 8%~12% of the total mass of the coating; S4. Preparation of Ag / PVA nanocomposite coating: The functionalized silver nanoparticles with surface grafted thiol groups obtained in step S2 are added to the PVA aqueous solution in step S3 and stirred and mixed evenly to obtain a gray, homogeneous Ag / PVA nanocomposite coating.

2. The method for preparing the nanocomposite coating for lead ion colorimetric detection according to claim 1, characterized in that: In step S2, the pH of the nano-silver colloid is adjusted to acidity, specifically to 3.5-4.5; the amount of silane coupling agent added is 0.1%-0.5% of the total volume of the nano-silver colloid; the reaction conditions are stirring at 60-80°C for 4-8 hours.

3. The method for preparing a nanocomposite coating for colorimetric detection of lead ions according to claim 1, characterized in that: The silane coupling agent is silane coupling agent KH580.

4. A nanocomposite coating produced according to the method of any one of claims 1 to 3, characterized by: The nanocomposite coating comprises a polyvinyl alcohol matrix and functionalized silver nanoparticles with thiol groups grafted onto their surfaces, uniformly dispersed therein.

5. Use of the nanocomposite coating prepared according to the method of any one of claims 1-3 for the preparation of a peelable film for the detection and removal of lead ions, characterized by: The nanocomposite coating is applied to the surface of the substrate and dried to form a film. Lead ions are then visually detected by the color change of the film. The lead-containing pollutants are removed and recycled by peeling off the cured film.

6. Use according to claim 5, characterized in that: The method of visually detecting lead ions through membrane color changes specifically includes: when the membrane comes into contact with lead ions, its color changes from gray to yellow, visually indicating lead contamination through color change; when Pb... 2+ At a concentration of 3 mMol / L, the color difference value ΔE can reach 10.67, which meets the requirement of clear distinction by the naked eye.

7. Use according to claim 5, characterized in that: The membrane has an elongation at break of up to 560%, and the nanocomposite coating has a stripping and removal efficiency of over 96% for lead contaminants in a wide concentration range of 1 to 20 mMol / L.

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