A functional polymer composite film, its preparation method and application

Abstract

This invention relates to the field of functional polymer materials technology, and discloses a functional polymer composite film, its preparation method, and its applications. The functional polymer composite film comprises a conjugated microporous polymer substrate and a conductive polymer functional layer. The conjugated microporous polymer substrate is a rigid framework with a three-dimensional interpenetrating network structure formed by polymerization of 4,4',4''-tris(carbazole-9-yl)triphenylamine as monomer. The conductive polymer functional layer is formed by polymerization of a metal-salen complex. The conductive polymer functional layer is anchored to the three-dimensional network framework and the interior of the micropores of the conjugated microporous polymer substrate through π-π stacking. This invention solves the problem of easy loss of active substances during alkaline activation and repeated use of traditional functional films. The composite film shows no significant current decay after multiple water washing cycles, is suitable for formaldehyde detection, exhibits high selectivity, strong anti-interference, good repeatability, and excellent long-cycle stability.

Description

Technical Field

[0001] This invention relates to the field of functional polymer materials technology, and in particular to a functional polymer composite film, its preparation method, and its application. Background Technology

[0002] With the rapid development of polymer materials science and modern analytical testing technology, functional polymer films, with their advantages of good film-forming properties, convenient processing, and adjustable functions, are increasingly widely used in key fields such as electrochemical sensors, optoelectronic devices, surface protection, industrial analysis, and smart packaging.

[0003] In the field of electrochemical sensing, the demand for rapid and accurate detection of toxic and harmful pollutants such as formaldehyde continues to increase. Nickel-based complexes, such as poly[Ni(salen)], are often used as core materials for sensing functional layers due to their excellent electrocatalytic oxidation activity for formaldehyde. However, current traditional polymer films and single nickel-based complex films suffer from many insurmountable technical defects in practical applications. Traditional polymer films, such as modified polyvinyl chloride (PVC) films, while possessing good film-forming properties, generally suffer from weak interfacial bonding, easy loss of active sites, and poor long-term stability when loading active functional molecules such as organometallic catalysts, making it impossible to maintain stable sensing performance. Single nickel-based complex films are difficult to deposit uniformly on electrode surfaces, resulting in a loose film structure and weak bonding with the substrate. During alkaline activation, the organic matrix is ​​prone to swelling or even detachment from the electrode surface, directly leading to a significant loss of loaded catalytic active centers. This, in turn, significantly reduces the film's sensitivity and response stability for formaldehyde detection, resulting in poor reproducibility of detection results. Meanwhile, traditional thin film materials have a small specific surface area, a limited number of catalytic active sites, weak resistance to interference from formaldehyde oxidation byproducts, and insufficient anti-pollution and anti-toxic properties, making it difficult to meet the requirements of high-sensitivity, high-selectivity, and high-stability sensing interfaces in practical scenarios such as industrial wastewater treatment and rapid indication of residual formaldehyde in food.

[0004] In summary, existing functional thin film materials cannot simultaneously achieve rigid framework support, stable nucleation site supply, robust active layer anchorage, and high-efficiency catalytic performance. Therefore, developing a novel functional polymer composite thin film material with stable structure, strong bonding, abundant active sites, and excellent detection performance has become a key technical problem that urgently needs to be solved in the fields of electrochemical sensing and functional polymer materials. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, one object of the present invention is to provide a functional polymer composite film.

[0006] The second objective of this invention is to provide a method for preparing such a functional polymer composite film.

[0007] The third objective of this invention is to provide an electrochemical sensor.

[0008] The fourth objective of this invention is to provide applications for this electrochemical sensor.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides a functional polymer composite film comprising a conjugated microporous polymer substrate and a conductive polymer functional layer; wherein the conjugated microporous polymer substrate is a rigid framework with a three-dimensional interpenetrating network structure formed by polymerization of 4,4',4''-tris(carbazole-9-yl)triphenylamine as a monomer; and the conductive polymer functional layer is formed by polymerization of a metal-salen complex. The conductive polymer functional layer is anchored to the three-dimensional network framework and micropores of the conjugated microporous polymer substrate through π-π stacking.

[0010] In some embodiments of the present invention, the functional polymer composite film is composed of a conjugated microporous polymer substrate and a conductive polymer functional layer; wherein, the conjugated microporous polymer substrate is formed by electropolymerization of 4,4',4''-tris(carbazole-9-yl)triphenylamine as a monomer; the conductive polymer functional layer is formed by electropolymerization of a metal-salen complex as a monomer; the conjugated microporous polymer substrate has a three-dimensional interpenetrating network structure; the conductive polymer functional layer is anchored to the three-dimensional network framework and the interior of the micropores of the conjugated microporous polymer substrate through π-π stacking.

[0011] In some embodiments of the present invention, the raw materials for preparing the metal-salen complex include: a salon ligand and a metal salt.

[0012] In some embodiments of the present invention, the salon ligand is selected from N,N'-bis(salicylicyl)ethylenediamine, N,N'-bis(salicylicyl)o-phenylenediamine or N,N'-bis(salicylicyl)cyclohexanediamine.

[0013] In some preferred embodiments of the present invention, the salon ligand is N,N'-bis(salicylyl)ethylenediamine.

[0014] In some embodiments of the present invention, the metal salt is selected from Ni(II) salt, Co(II) salt, Co(III) salt, Mn(III) salt or Cu(II) salt.

[0015] In some preferred embodiments of the present invention, the metal salt is a Ni(II) salt.

[0016] In some more preferred embodiments of the present invention, the metal salt is nickel acetate tetrahydrate (Ni(CH3COO)2·4H2O).

[0017] It should be noted that, in addition to Ni(II) salts, Co(II) salts, Co(III) salts, Mn(III) salts, and Cu(II) salts, the metal salts may also be selected from other metal salts that can coordinate with -OH or -N in the salon ligand. Among them, Ni(II) salts are particularly suitable because they can form highly reactive Ni under alkaline conditions. 2+ / Ni 3+ Redox pairs can efficiently catalyze the oxidation of formaldehyde to generate a measurable current, and have good selectivity. They are superior to other metal salts in the electrochemical detection of formaldehyde in food.

[0018] Specifically, the functional polymer composite film provided by this invention comprises a conjugated microporous polymer substrate with a three-dimensional interpenetrating network structure formed by polymerization of 4,4',4''-tris(carbazole-9-yl)triphenylamine as a monomer. This structure has the following characteristics: 1) high specific surface area, with the microporous structure providing a large number of active sites; 2) a rigid framework that can resist solvent swelling and mechanical stress; and 3) a π-conjugated system that provides a basis for π-π stacking. It also includes a conductive polymer functional layer polymerized with a metal-salen complex (such as Ni-salen) and anchored on the conjugated microporous polymer substrate. The conjugated aromatic ring structure of poly(4,4',4''-tris(carbazole-9-yl)triphenylamine) (PTCTA) has a strong π-π interaction with the conjugated structure in the metal-salen complex. This interaction causes the metal-salen complex to spontaneously anchor itself to the three-dimensional framework and micropores of PTCTA during polymerization, rather than through simple physical adsorption or surface coating. This anchoring effect achieves a tight molecular-level bond, with the conductive polymer uniformly distributed within the framework, exhibiting mechanical stability against detachment.

[0019] A second aspect of the present invention provides a method for preparing the functional polymer composite film described in the first aspect of the present invention, comprising the following steps: Under an inert atmosphere, the salon ligand and the metal salt are dissolved in an oxygen-free alcohol solvent and reacted to obtain a metal-salen complex. A conjugated microporous polymer-modified electrode was obtained by electropolymerization of 4,4',4''-tris(carbazole-9-yl)triphenylamine on a conductive substrate using a potentiostatic method. The electrode modified with the conjugated microporous polymer substrate was placed in an electrolyte containing the metal-salen complex, and a conductive polymer functional layer initially anchored to the conjugated microporous polymer substrate was formed by cyclic voltammetry electropolymerization to obtain a composite film precursor. The composite film precursor was placed in an alkaline solution for continuous cyclic voltammetric activation to obtain the functional polymer composite film.

[0020] In some embodiments of the present invention, the inert atmosphere includes nitrogen, helium, or argon.

[0021] In some embodiments of the present invention, the deoxygenation includes passing an inert gas into an alcohol solvent at 30-50°C for 25-35 minutes to remove oxygen.

[0022] In some embodiments of the present invention, the alcohol solvent includes ethanol.

[0023] In some embodiments of the present invention, the molar ratio of the salon ligand to the metal salt is (0.8-1.3):1.

[0024] In some preferred embodiments of the present invention, the molar ratio of the salon ligand to the metal salt is (1.0-1.2):1.

[0025] In some embodiments of the present invention, the solid-liquid ratio of the salon ligand to the alcohol solvent is (1.3-2.1) g: 100 mL.

[0026] In some preferred embodiments of the present invention, the solid-liquid ratio of the salon ligand to the alcohol solvent is (1.5-1.9) g: 100 mL.

[0027] In some embodiments of the present invention, the reaction temperature is 30-50°C and the time is 1-3 hours.

[0028] In some preferred embodiments of the present invention, the reaction temperature is 35-45°C and the time is 1.5-2.5h.

[0029] In some embodiments of the present invention, the reaction is further complicated by solid-liquid separation, collection of the solid phase, and recrystallization.

[0030] In some embodiments of the present invention, the conductive substrate includes a glassy carbon electrode.

[0031] In some embodiments of the present invention, the constant potential electropolymerization includes a three-electrode system, and the electrolyte includes dichloromethane (DCM) and acetonitrile (ACN) in a volume ratio of (3-5):1.

[0032] In some embodiments of the present invention, the electropolymerization electrolyte of the constant potential method further includes a co-electrolyte; the co-electrolyte includes tetrabutylammonium perchlorate.

[0033] In some embodiments of the present invention, the content of the co-electrolyte in the electropolymerization electrolyte by constant potential method is 0.08-0.12 mol / L.

[0034] In some embodiments of the present invention, the content of 4,4',4''-tris(carbazole-9-yl)triphenylamine in the electropolymerization electrolyte by constant potential method is 0.8-1.2 mmol / L.

[0035] In some preferred embodiments of the present invention, the content of 4,4',4''-tris(carbazole-9-yl)triphenylamine in the electropolymerization electrolyte by constant potential method is 0.9-1.1 mmol / L.

[0036] In some embodiments of the present invention, the potential of the constant potential electropolymerization is 0.8-1.4V and the time is 50-70s.

[0037] In some preferred embodiments of the present invention, the potential of the constant potential electropolymerization is 1.0-1.2V and the time is 55-65s.

[0038] Specifically, if the electropolymerization time is too short, the conjugated microporous polymer substrate will struggle to form a complete three-dimensional network structure covering the electrode surface. Furthermore, an excessively thin film will result in insufficient specific surface area, failing to provide adequate nucleation sites and anchoring points for subsequent electropolymerization of the metal-salen complex. This leads to a low loading of the conductive polymer functional layer, a small redox peak current in the composite film, and limited sensitivity. Conversely, if the electropolymerization time is too long, the conjugated microporous polymer substrate film will become too thick. While this further increases the specific surface area, the excessive thickness increases the resistance to electron transfer from the electrode surface to the active centers in the electrolyte, increasing charge transfer impedance. This, in turn, is detrimental to the output of the electrochemical signal and also leads to a decrease in the redox peak current. Therefore, it is necessary to strictly control the electropolymerization time for preparing the conjugated microporous polymer substrate.

[0039] In some embodiments of the present invention, after the electropolymerization by constant potential method is completed, a dedoping operation is further performed by applying a constant potential method at a potential of 0V for 20-40s.

[0040] In some embodiments of the present invention, the electrolyte used in the cyclic voltammetric electropolymerization includes acetonitrile.

[0041] In some embodiments of the present invention, the content of the metal-salen complex in the electrolyte is 4-6 mmol / L.

[0042] In some preferred embodiments of the present invention, the content of the metal-salen complex in the electrolyte is 4.5-5.5 mmol / L.

[0043] In some embodiments of the present invention, the electrolyte further includes a co-electrolyte; the co-electrolyte includes tetrabutylammonium hexafluorophosphate (TBAPF6).

[0044] In some embodiments of the present invention, the content of the auxiliary electrolyte in the electrolyte is 0.08-0.12 mol / L.

[0045] In some embodiments of the present invention, the potential of the cyclic voltammetric electropolymerization is -0.5~0.75V, the scan rate is 80-120mV / s, and the number of cycles is 3-10.

[0046] In some preferred embodiments of the present invention, the potential of the cyclic voltammetric electropolymerization is -0.5~0.75V, the scan rate is 90-110mV / s, and the number of cycles is 4-8.

[0047] In some embodiments of the present invention, after the cyclic voltammetric electropolymerization is completed, a washing operation with an alcohol solution is also included.

[0048] In some embodiments of the present invention, the concentration of the alkaline solution is 0.8-1.2 mol / L.

[0049] In some preferred embodiments of the present invention, the concentration of the alkaline solution is 0.9-1.1 mol / L.

[0050] In some embodiments of the present invention, the solute of the alkaline solution includes an alkali metal hydroxide.

[0051] In some preferred embodiments of the present invention, the solute of the alkaline solution includes at least one of potassium hydroxide and sodium hydroxide.

[0052] In some embodiments of the present invention, the activation potential is 0-0.85V, the scan rate is 150-250mV / s, and the number of cycles is greater than 600.

[0053] In some preferred embodiments of the present invention, the activation potential is 0-0.85V, the scan rate is 180-220mV / s, and the number of cycles is greater than 600.

[0054] A third aspect of the present invention provides an electrochemical sensor comprising an electrode substrate and a sensitive membrane modified on the surface of the electrode substrate, wherein the sensitive membrane is the functional polymer composite film described in the first aspect of the present invention.

[0055] The fourth aspect of the present invention provides the application of the electrochemical sensor described in the third aspect of the present invention in the detection of formaldehyde content.

[0056] In some embodiments of the invention, the application includes the real-time detection of residual formaldehyde in industrial wastewater, food packaging, or food.

[0057] Compared with the prior art, the beneficial effects of the present invention are: 1) The functional polymer composite film provided by the present invention adopts a conjugated microporous polymer rigid framework with a three-dimensional interpenetrating network structure. Its high specific surface area and microporous structure provide sufficient nucleation sites and anchoring points for the conductive polymer functional layer formed by the polymerization of metal-salen complexes, which greatly increases the loading of active material and makes it uniformly distributed. The conductive polymer functional layer is anchored to the three-dimensional network framework and micropores of the conjugated microporous polymer substrate through π-π stacking, which solves the problem that the active material is easy to fall off and be lost during alkaline activation and repeated use of traditional functional films. After multiple cycles of water washing, the current of the composite film remains basically stable with no significant attenuation. 2) The functional polymer composite film provided by this invention is suitable for the detection of formaldehyde at different concentrations. Due to the microporous confinement effect, it effectively isolates the poisoning effect of formaldehyde oxidation byproducts on the catalytic center. The composite film maintains high selectivity for formaldehyde even in the presence of interfering substances such as methanol and formic acid. It has good repeatability of formaldehyde detection and excellent long-term cycle stability, and is suitable for the real-time detection of formaldehyde content in complex matrices such as food. Attached Figure Description

[0058] Figure 1 The 1H NMR spectrum of the Ni-salen complex prepared in Example 1; Figure 2 The electropolymerization process of the Ni-salen complex on a bare glassy carbon electrode and the electroactivation process in KOH solution are shown in Comparative Example 1. Figure 3 A comparison of the electropolymerization processes of Ni-salen complexes on bare glassy carbon electrodes and conjugated microporous polymer substrates; Figure 4 This refers to the electroactivation process of the composite film precursor in KOH solution in Example 1; Figure 5 The FTIR spectra of the composite film precursor and the functional polymer composite film in Example 1 are shown below. Figure 6 XPS spectra of the composite film precursor and the functional polymer composite film in Example 1; Figure 7 SEM images of the conjugated microporous polymer substrate (a) in Example 1, the conductive polymer film precursor (b) and the conductive polymer film (c) in Comparative Example 1; Figure 8 Here are SEM images of the composite film precursor and the functional polymer composite film in Example 1; Figure 9 The image shows the EDS spectrum of the functional polymer composite film in Example 1. Figure 10 This is a comparison of the formaldehyde electrocatalytic performance of the conjugated microporous polymer substrate, the functional polymer composite film in Example 1, and the conductive polymer film in Comparative Example 1. Figure 11 The results of the cyclic water washing stability test of the conductive polymer film in Comparative Example 1 are shown. Figure 12 The results are from the cyclic water washing stability test of the functional polymer composite film in Example 1; Figure 13 The linear sweep voltammetric curve (a) and calibration curve (b) of the functional polymer composite film in Example 1 during the linear range test of high concentration formaldehyde are shown. Figure 14 The linear sweep voltammetric curve (a) and calibration curve (b) of the functional polymer composite film in Example 1 during the linear range test of low-concentration formaldehyde are shown. Figure 15 The results are the anti-interference performance test results of the functional polymer composite film in Example 1; Figure 16 The results of the reproducibility (a) and repeatability (b) evaluations of the functional polymer composite film in Example 1 are shown. Figure 17 The results are the long-cycle stability test results of the functional polymer composite film in Example 1; Figure 18 This is a photograph of the food sample purchased in the application example. Detailed Implementation

[0059] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the experimental or testing methods are conventional methods in the art.

[0060] Example 1 This embodiment prepares a functional polymer composite film, and the steps are as follows: S11. Add 100 mL of ethanol to a round-bottom flask and pass an inert gas through it at 40 °C for 30 min to remove oxygen, thus obtaining deoxygenated ethanol. S12. 1.717 g of N,N'-bis(salicylene)ethylenediamine and 1.592 g of nickel acetate tetrahydrate (molar ratio approximately 1:1) were dissolved in the above-mentioned deoxygenated ethanol and refluxed at 40 °C for 2 h under nitrogen protection. After the reaction was completed, the mixture was filtered to obtain an orange precipitate, which is the Ni-salen complex, denoted as [Ni(salen)]. The product was recrystallized in methanol and dried at room temperature, with a yield of 80%. S13. A three-electrode system is adopted, with a glassy carbon electrode (3mm) as the working electrode, a platinum wire as the counter electrode, and Ag / Ag... + As a reference electrode, a dichloromethane / acetonitrile mixed solution (4:1, v / v) containing 1 mmol / L 4,4',4''-tris(carbazole-9-yl)triphenylamine and 0.1 mol / L tetrabutylammonium perchlorate co-electrolyte was deposited at 1.1 V for 60 s using a potentiostatic method, followed by dedoping at 0 V for 30 s. Unpolymerized monomers were then washed to obtain a conjugated microporous polymer substrate modified electrode, denoted as PTCTA. S21. Using a conjugated microporous polymer-modified electrode as the working electrode, the electrode was placed in an acetonitrile electrolyte containing 5 mmol / L Ni-salen complex and 0.1 mol / L tetrabutylammonium hexafluorophosphate. Cyclic voltammetry was used to polymerize for 6 cycles in the potential range of -0.5 to 0.75 V at a scan rate of 100 mV / s. After polymerization, the electrode was washed with ethanol to obtain the composite film precursor. S31. The composite film precursor is placed in a 1 mol / L KOH solution, and continuous cyclic voltammetry scans are performed more than 600 times in the potential range of 0-0.85V at a scan rate of 200mV / s to make the redox peak nearly stable, thereby completing the activation of the film and obtaining a functional polymer composite film, denoted as PTCTA / poly[Ni(salen)].

[0061] Comparative Example 1 This comparative example prepares a conductive polymer film formed by electropolymerization of a Ni-salen complex, and the steps are as follows: 1) Using a bare glassy carbon electrode as the working electrode, the electrode was placed in an acetonitrile electrolyte containing 5 mmol / L Ni-salen complex (prepared in Example 1) and 0.1 mol / L tetrabutylammonium hexafluorophosphate. Cyclic voltammetry was used to polymerize for 6 cycles in the potential range of -0.5 to 0.75 V at a scan rate of 100 mV / s. After polymerization, the electrode was washed with ethanol to obtain a conductive polymer film precursor modified electrode. 2) The electrode modified with the precursor of the conductive polymer film was placed in a 1 mol / L KOH solution and subjected to continuous cyclic voltammetry scans for about 120 times in the potential range of 0-0.85V at a scan rate of 200mV / s to obtain the conductive polymer film, denoted as poly[Ni(salen)].

[0062] Characterization and performance testing 1. The Ni-salen complex prepared in Example 1 was characterized by nuclear magnetic resonance: Figure 1 The image shows the 1H NMR spectrum of the Ni-salen complex prepared in Example 1. Figure 1 It can be seen that the characteristic peak at 7.40 ppm in the spectrum belongs to the imine group (-CH=N-), and the characteristic peak at 3.44 ppm belongs to four aliphatic hydrogen atoms (ethylenediamine skeleton). The positions and intensities of the above characteristic peaks prove that the Ni-salen monomer molecule has the correct structure and the purity meets the requirements for electropolymerization.

[0063] 2. Analyze the electropolymerization process on the conjugated microporous polymer substrate in Example 1, the electroactivation process of the composite film precursor in KOH solution, and the electropolymerization process of the Ni-salen complex on the glassy carbon electrode in Comparative Example 1: Figure 2 The electropolymerization process of the Ni-salen complex on a bare glassy carbon electrode and the electroactivation process in KOH solution are shown in Comparative Example 1. Figure 2 (a) shows the entire electropolymerization process within the full potential window (-0.5~0.75V). As the number of cycles increases, the Ni-salen complex does indeed continuously polymerize and deposit on the electrode surface, and the film layer continuously thickens. Figure 2 (b) in Comparative Example 1 shows the electroactivation process of the film precursor in KOH solution. As the number of cyclic scans increases, the redox peak gradually increases and tends to stabilize, indicating that the film has been activated.

[0064] Figure 3 To compare the electropolymerization processes of Ni-salen complexes on bare glassy carbon electrodes and conjugated microporous polymer substrates, by Figure 3 It can be seen that, compared with the electropolymerization behavior of Ni-salen complexes on bare glassy carbon electrode (GCE) and conjugated microporous polymer substrate modified electrode (PTCTA), the polymerization current on PTCTA is significantly higher than that on bare glassy carbon electrode. This indicates that the rigid framework of conjugated microporous polymer provides more nucleation sites, which is beneficial to promoting the polymerization and efficient and uniform deposition of Ni-salen complexes.

[0065] Figure 4 The electroactivation process of the composite film precursor in KOH solution in Example 1 is described by... Figure 4 As the number of cycles increases, the redox peak gradually increases and tends to stabilize (600 times), indicating that the film is fully activated, the catalytic active center is fully formed, and the structure tends to be stable. Compared with the conductive polymer film in Comparative Example 1 (1.4 mA), the number of activation cycles (120 times) is greater, indicating that electrochemical oxidation is difficult, that is, the film is more stable, and the final activation current peak is larger (2.7 mA). This is because the extended π-conjugation interaction force of the conjugated microporous polymer PTCTA and the influence of the inherent microporous structure to provide deposition sites greatly increase the polymer loading of the Ni-salen complex and ensure stable deposition.

[0066] 3. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy were performed on the conjugated microporous polymer substrate, composite film precursor, functional polymer composite film in Example 1, and conductive polymer film precursor or conductive polymer film in Comparative Example 1. Figure 5 The images show the FTIR spectra of the composite film precursor and the functional polymer composite film in Example 1. Figure 5 (a) in the image is the overall infrared spectrum. Figure 5 (b) in the image is an amplified spectrum of the key functional group region in (a), derived from... Figure 5 It can be known that 1620cm -1 The presence of C=N stretching vibrations in the conductive polymer poly[Ni(salen)] on both sides, and the consistent presence of this peak before and after activation, indicates that some of the activated organic matrix remains adsorbed onto the surface with PTCTA through π-π interactions; 1300-1600 cm⁻¹ -1 The presence of aromatic ring skeletal vibrations, which remained unchanged before and after activation, indicates that activation did not affect the stability of the conjugated microporous polymer substrate. (1129 cm⁻¹) -1 and 722cm -1 The presence of CO stretching vibrations and Ni in the Ni-salen complex 2+ The stretching vibration of -O, the peak weakens after activation, indicating that Ni 2 + →Ni 3+ Oxidation leads to the breaking of coordination bonds, which proves the successful activation of nickel. That is, the activation process does not destroy the framework structure, but achieves the transformation of the valence state and coordination environment of the Ni active center, forming a highly efficient catalytic site.

[0067] Figure 6 The above are XPS spectra of the composite film precursor and the functional polymer composite film in Example 1. Figure 6 (a) in the spectrum represents the full spectrum. Figure 6 (b) in the image is the Ni 2p high-resolution spectrum of the composite thin film precursor. Figure 6(c) in the image represents the high-resolution Ni 2p spectrum of the functional polymer composite film, derived from... Figure 6 It can be seen that both the pre-activated composite film precursor and the activated functional polymer composite film contain C, N, O, and Ni elements. Compared with the initial valence state of Ni in the pre-activated precursor, a significant characteristic peak shift and a new peak appear after activation, confirming that Ni transforms from an inert valence state to a highly catalytically active valence state (Ni). 2+ / Ni 3+ This means that the activation of the catalytic site has been completed.

[0068] Figure 7 The images show SEM images of the conjugated microporous polymer substrate (a) in Example 1, the conductive polymer film precursor (b) in Comparative Example 1, and the conductive polymer film (c). Figure 7 It is known that the conjugated microporous polymer substrate exhibits a three-dimensional interpenetrating network microporous structure with a rough surface and large specific surface area, which can provide structural support for the rigid skeleton. The precursor of the conductive polymer film before activation is dense but has no obvious channels, and the active sites are not sufficiently exposed. After activation, the structure of the conductive polymer film is loose, uneven, and easy to fall off, resulting in poor stability.

[0069] Figure 8 Here are SEM images of the composite film precursor and the functional polymer composite film in Example 1, where... Figure 8 Images (a) and (c) in the figure are SEM images of the composite thin film precursor at different scales. Figure 8 Images (b) and (d) in the figure are SEM images of the functional polymer composite film at different scales, created by... Figure 8 It can be seen that before activation, the Ni-salen complex is uniformly distributed on the surface and inside of the PTCTA framework. The overall structure is continuous but not completely stable. After activation, the composite film still maintains the complete three-dimensional framework without cracking or falling off. The structure is more uniform and stable, proving that the PTCTA framework can effectively support and firmly anchor the functional layer.

[0070] Figure 9 The image shows the EDS spectrum of the functional polymer composite film in Example 1. Figure 9 (a) in the image is the EDS full spectrum. Figure 9 (b) in the diagram is the surface distribution map of element C. Figure 9 (c) in the diagram is the surface distribution map of element N. Figure 9 (d) in the diagram represents the surface distribution of element O. Figure 9 (e) in the diagram represents the surface distribution of Ni element, derived from... Figure 9 It can be seen that after activation, Ni elements are still uniformly present in the composite film, without agglomeration, segregation, or loss, indicating that the PTCTA framework can provide uniform nucleation sites, making the Ni catalytic centers highly dispersed and firmly anchored.

[0071] 4. Comparison of the responses of bare glassy carbon electrode (GCE), conjugated microporous polymer substrate (PTCTA) from Example 1, functional polymer composite film (PTCTA / poly[Ni(salen)]), and conductive polymer film (poly[Ni(salen)]) from Comparative Example 1 to formaldehyde (HCHO): A three-electrode system was used for testing. GCE, PTCTA-modified GCE, PTCTA / poly[Ni(salen)]-modified GCE, and poly[Ni(salen)]-modified GCE were used as working electrodes, respectively. Platinum wire was used as the counter electrode, and Ag / AgCl was used as the reference electrode. The test solution included a 1 mol / L KOH solution containing 0-5 mmol / L formaldehyde. Cyclic voltammetry was used at room temperature with a potential window of 0-0.85 V and a scan rate of 20-200 mV / s. The differences in the electrocatalytic response of each electrode to formaldehyde were compared. Figure 10 This example compares the formaldehyde electrocatalytic performance of the conjugated microporous polymer substrate, the functional polymer composite film, and the conductive polymer film in Comparative Example 1. Figure 10 (a) shows the cyclic voltammetry curves of GCE, PTCTA-modified GCE, PTCTA / poly[Ni(salen)]-modified GCE, and poly[Ni(salen)]-modified GCE in electrolytes with formaldehyde concentrations of 0 mmol / L and 1 mmol / L, at a scan rate of 100 mV / s. Figure 10 (b) shows the cyclic voltammetry curves of PTCTA / poly[Ni(salen)] modified GCE in electrolytes with formaldehyde concentrations of 0-5 mmol / L, at a scan rate of 100 mV / s. Figure 10 (c) shows the cyclic voltammetry curves of PTCTA / poly[Ni(salen)] modified GCE in an electrolyte with a formaldehyde concentration of 1 mmol / L, with a scan rate of 20-200 mV / s. Figure 10 In the figure, (d) represents the linear dependence of the peak current density of PTCTA / poly[Ni(salen)] modified GCE on the square root of the scan rate in an electrolyte with a formaldehyde concentration of 1 mmol / L. Figure 10It can be seen that the PTCTA / poly[Ni(salen)] modified electrode showed the largest increase in oxidation peak current after the addition of formaldehyde, indicating that the electrocatalytic performance is enhanced due to the synergistic effect between PTCTA and poly[Ni(salen)]. When the formaldehyde concentration gradually increased from 0 mmol / L to 5 mmol / L, the oxidation peak current increased accordingly with the increase of formaldehyde concentration, showing a good concentration dependence. This indicates that the functional polymer composite film has the potential electrochemical sensing capability for formaldehyde concentration. The peak current showed a good linear relationship with the square root of the scan rate, further proving that the formaldehyde oxidation on the PTCTA / poly[Ni(salen)] modified electrode is a diffusion-controlled process with excellent sensing kinetics.

[0072] 5. Comparison of the stability of the functional polymer composite film in Example 1 and the conductive polymer film in Comparative Example 1 under cyclic washing: A three-electrode system was used, with the functional polymer composite film modified electrode and the conductive polymer film modified electrode as working electrodes, respectively, platinum wire as the counter electrode, and Ag / AgCl as the reference electrode. Cyclic washing stability tests were performed in 1 mol / L KOH solution. First, a stable cyclic voltammetric curve was recorded in the 1 mol / L KOH solution to obtain the initial stable redox peak. Then, a certain concentration of formaldehyde was added to the solution, and after stirring evenly, the cyclic voltammetric curve of formaldehyde catalytic oxidation was tested. The electrode was removed and gently rinsed three times with deionized water to remove surface adsorbates and residual solution. The washed electrode was then placed back into fresh 1 mol / L KOH solution, and the cyclic voltammetric curve was recorded again to observe the peak current change. The formaldehyde addition detection-washing-blank detection cycle was repeated 3-4 times. Figure 11 The results of the cyclic water washing stability test of the conductive polymer film in Comparative Example 1 are shown below. Figure 11 In the figure, (a) and (c) represent the changes in the redox peaks after each formaldehyde washing test. Figure 11 (b) and (d) in the figure are cyclic voltammetric curves of formaldehyde detection in multiple tests; Figure 12 The results of the cyclic water washing stability test of the functional polymer composite film in Example 1 are shown below. Figure 12 In the figure, (a) and (c) represent the changes in the redox peaks after each formaldehyde washing test. Figure 12 Figures (b) and (d) show the cyclic voltammetry curves for multiple formaldehyde detections. Figure 11 and Figure 12It can be seen that after repeated water washing, the current of the conductive polymer film in Comparative Example 1 decreased significantly and the signal became unstable. However, after repeated water washing, the current of the functional polymer composite film in Example 1 remained basically stable with no significant decrease. This indicates that the rigid framework of PTCTA can provide highly stable nickel catalyst deposition sites and has a strong anchoring effect, solving the core problems of easy detachment and poor stability of the functional layer. At the same time, the microporous effect prevents the poisoning of the catalyst by formaldehyde oxidation byproducts, thus achieving the effect of real-time detection of formaldehyde at different concentrations.

[0073] 6. The functional polymer composite film in Example 1 was subjected to comprehensive performance testing. All tests were conducted using a three-electrode system, with PTCTA / poly[Ni(salen)] modified GCE as the working electrode, platinum wire as the counter electrode, and Ag / AgCl as the reference electrode. The test solution was 5 mL of 1 mol / L KOH solution, and the tests were carried out at room temperature. The details are as follows: 1) Linear range test of high concentration formaldehyde: The linear sweep voltammetry (LSV) method was used with a potential window of 0-0.85V and a scan rate of 50mV / s. First, the LSV curve of blank KOH solution was recorded. Then, 0.5mL of 50mmol / L formaldehyde standard solution was added one after another. After stirring evenly each time, the LSV curve was recorded and the oxidation peak current was read. Then, a calibration curve was plotted with formaldehyde concentration as the abscissa and peak current as the ordinate to obtain the sensitivity and linearity relationship. 2) Low concentration formaldehyde linear range test: The linear scanning voltammetry method was used with a potential window of 0-0.85V and a scan rate of 50mV / s. First, the LSV curve of the blank KOH solution was recorded. Then, 0.5mL of 1mmol / L formaldehyde standard solution was added one by one. After stirring evenly each time, the LSV curve was recorded. The calibration curve of the low concentration range was plotted to verify the low concentration detection performance. 3) Anti-interference performance test: The following interfering substances were added to 1 mol / L KOH solution respectively, and the electrocatalytic response was recorded: 10 mmol / L methanol, 100 mmol / L methanol, 10 mmol / L formic acid, 100 mmol / L formic acid, 10 mmol / L formaldehyde, and 100 mmol / L formaldehyde. The current response was compared to determine the selectivity of the functional polymer composite film for formaldehyde. 4) Repeatability test: Using the glassy carbon electrode modified with PTCTA / poly[Ni(salen)] as described in Example 1, formaldehyde of the same concentration was repeatedly tested multiple times, the current deviation was calculated, and the stability of the single electrode in multiple tests was evaluated. 5) Reproducibility test: Using the PTCTA / poly[Ni(salen)] modified glassy carbon electrode of Example 1, and multiple PTCTA / poly[Ni(salen)] modified glassy carbon electrodes prepared according to the method in Example 1, formaldehyde of the same concentration was detected, the current deviation was calculated, and the reproducibility between different electrodes was evaluated. 6) Long-term cycling stability test: PTCTA / poly[Ni(salen)] modified GCE was placed in 1 mol / L KOH solution and continuously cyclically scanned for 100 cycles at 0.4-0.85 V and 200 mV / s. The change of redox peak current in each cycle was recorded to evaluate the structural and performance stability of the electrode under continuous electrochemical scanning.

[0074] Figure 13 The linear sweep voltammetry curve (a) and calibration curve (b) of the functional polymer composite film in Example 1 during the linear range test of high-concentration formaldehyde are shown. Figure 14 The linear sweep voltammetry curve (a) and calibration curve (b) of the functional polymer composite film in Example 1 during the linear range test of low-concentration formaldehyde are shown. Figure 15 The results are the anti-interference performance test results of the functional polymer composite film in Example 1. Figure 16 The reproducibility (a) and repeatability (b) evaluation results of the functional polymer composite film in Example 1 are as follows. Figure 17 The results of the long-cycle stability test of the functional polymer composite film in Example 1 are from... Figures 13-17 It can be seen that the functional polymer composite film in Example 1 is suitable for the detection of formaldehyde at different concentrations. Based on the linear scanning voltammetric curve, the sensitivity can be calculated to be as high as 336.611 μA / mmol / L. It has high selectivity for formaldehyde, can resist interference from methanol and formic acid, has good repeatability in formaldehyde detection, and the signal is stable after 100 consecutive cycles. This indicates that the functional polymer composite film has a stable structure, good activity, and excellent long-cycle stability during long-term potential cycling.

[0075] Application examples To evaluate the applicability of the functional polymer composite film in Example 1 to the analysis of actual food samples, the formaldehyde content of chicken feet, shiitake mushrooms, and baby bok choy was tested using the scavenging method. All of these foods were purchased from local supermarkets. Figure 18 Here is a photograph of the food sample purchased in the application example: Take 5g of each of the above samples, soak them in deionized water for 3 days, filter and collect the filtrate. Perform chronoamperometry (CA) tests on the food samples at different standard formaldehyde concentrations (0 mmol / L, 0.5 mmol / L, 1 mmol / L, 1.5 mmol / L). A fixed working potential of 0-0.85V (vs Ag / AgCl) is applied to the electrode as the chronoamperometry measurement potential. After the current stabilizes into a linear curve, sample solutions of different standard formaldehyde concentrations are added sequentially. After each addition, wait 20-30s and record the change in current over time. The curve of current change over time is the chronoamperometry curve, which is used to analyze the relationship between formaldehyde concentration and current response.

[0076] Table 1 below shows the detection results of formaldehyde content in different foods in the application example (three tests). As can be seen from Table 1, the functional polymer composite film in Example 1 can resist the interference of soluble matrix components (such as sugars) in the physical sample. The matrix effect in formaldehyde detection is small, the recovery rate is 95.13%-105.33%, and the RSD is less than 6%, which meets the requirements of practical application.

[0077] Table 1. Detection results of formaldehyde content in different foods in application examples.

[0078] Where, recovery rate = average measurement value / amount added; RSD = standard deviation of multiple measurements / average measurement value.

Claims

1. A functional polymer composite film, characterized by, It includes a conjugated microporous polymer substrate and a conductive polymer functional layer; wherein, the conjugated microporous polymer substrate is a rigid framework with a three-dimensional interpenetrating network structure formed by polymerization of 4,4',4''-tris(carbazole-9-yl)triphenylamine as monomer; the conductive polymer functional layer is formed by polymerization of metal-salen complex; The conductive polymer functional layer is anchored to the three-dimensional network framework and the interior of the micropores of the conjugated microporous polymer substrate through π-π stacking. The functional polymer composite film is prepared by a method comprising the following steps: Under an inert atmosphere, the salon ligand and the metal salt are dissolved in an oxygen-free alcohol solvent and reacted to obtain a metal-salen complex. A conjugated microporous polymer-modified electrode was obtained by electropolymerization of 4,4',4''-tris(carbazole-9-yl)triphenylamine on a conductive substrate using a potentiostatic method. The electrode modified with the conjugated microporous polymer substrate was placed in an electrolyte containing the metal-salen complex, and a conductive polymer functional layer initially anchored to the conjugated microporous polymer substrate was formed by cyclic voltammetry electropolymerization to obtain a composite film precursor. The composite film precursor was placed in an alkaline solution for continuous cyclic voltammetric activation to obtain the functional polymer composite film.

2. The functional polymer composite film according to claim 1, characterized in that, The salen ligand is selected from N,N'-bis(salicylic acid)ethylenediamine, N,N'-bis(salicylic acid)o-phenylenediamine or N,N'-bis(salicylic acid)cyclohexanediamine; And / or, the metal salt is selected from Ni(II) salt, Co(II) salt, Co(III) salt, Mn(III) salt or Cu(II) salt.

3. The functional polymer composite film according to claim 1, characterized in that, The molar ratio of the salon ligand to the metal salt is (0.8-1.3):1; And / or, the reaction is carried out at a temperature of 30-50°C for 1-3 hours.

4. The functional polymer composite film according to claim 1, characterized in that, The content of the 4,4',4''-tris(carbazole-9-yl)triphenylamine in the electropolymerization electrolyte by constant potential method is 0.8-1.2 mmol / L; And / or, the potential for electropolymerization using the constant potential method is 0.8-1.4V, and the time is 50-70s.

5. The functional polymer composite film according to claim 1, characterized in that, The concentration of the metal-salen complex in the electrolyte is 4-6 mmol / L; And / or, the cyclic voltammetric electropolymerization has a potential of -0.5~0.75V, a scan rate of 80-120mV / s, and a cycle count of 3-10.

6. The functional polymer composite film according to claim 1, characterized in that, The concentration of the alkaline solution is 0.8-1.2 mol / L; And / or, the activation potential is 0-0.85V, the scan rate is 150-250mV / s, and the number of cycles is greater than 600.

7. An electrochemical sensor, characterized in that, It includes an electrode substrate and a sensitive film modified on the surface of the electrode substrate, wherein the sensitive film is a functional polymer composite film as described in any one of claims 1-6.

8. The application of the electrochemical sensor according to claim 7 in formaldehyde content detection.

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