Copper porphyrin conjugated acetylene polymer composite material, preparation method and application of copper porphyrin conjugated acetylene polymer composite material in photoelectric detection of biological mercaptan

Abstract

The invention discloses a copper porphyrin conjugated acetylene polymer composite material, a preparation method and application of the copper porphyrin conjugated acetylene polymer composite material in biological mercaptan photoelectric detection, the composite material comprises an electrochemical reduction graphene oxide layer, a poly (1, 4-diacetylene benzene) layer and a copper porphyrin conjugated acetylene copolymer layer, and the three layers form a layered composite structure through pi-pi interaction. The copper porphyrin conjugated acetylene copolymer is formed by copolymerization of a 1, 4-diacetylene benzene monomer and a copper-coordinated 5, 10, 15, 20-tetra (4-acetylene phenyl) porphyrin monomer through a Sonogashira coupling reaction, and the composite material utilizes a double recognition site mechanism that a Cu-S coordinate bond is formed by a porphyrin center and sulfydryl and an acetylene bond and the sulfydryl are subjected to a click reaction under illumination. The high-sensitivity and high-selectivity detection on the L-cysteine and the reduced glutathione is realized, and the detection limit on the L-cysteine can reach 2.3 mu M.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer materials and photoelectrochemical sensing, specifically relating to a copper porphyrin conjugated acetylene polymer composite material, its preparation method, and its application in the photoelectrochemical detection of biothiols. Background Technology

[0002] Biothiols, such as L-cysteine ​​(L-Cys) and reduced glutathione (GSH), play important physiological functions in organisms, participating in key physiological processes such as protein folding, cell signal transduction, and redox homeostasis. Abnormal changes in biothiol concentrations are closely related to various diseases, including Alzheimer's disease, Parkinson's disease, liver damage, and cancer. Therefore, establishing sensitive and selective methods for detecting biothiols is of great significance for disease diagnosis and treatment.

[0003] Existing methods for detecting biothiols mainly include high-performance liquid chromatography (HPLC), capillary electrophoresis, mass spectrometry (MS), and electrochemical methods. In recent years, photoelectrochemical sensing technology has attracted widespread attention in the field of biothiols detection due to its advantages such as high sensitivity, rapid response, and low background signal. Conjugated microporous polymers (CMPs), with their large specific surface area, tunable photoelectric properties, and good chemical stability, have been applied in the field of photoelectrochemical sensing.

[0004] For example, Liu et al. reported a DA-type porphyrin-phthalocyanine polymer hollow tube in Applied Surface Science (2023, Vol. 638, pp. 158-129) for the photodegradation and photoelectrochemical sensing of bisphenol A. This study facilitated the separation and transport of photogenerated carriers by constructing a periodic donor-acceptor (DA) structure. However, this technology is mainly applied to the detection of bisphenol A and has not been applied to the detection of biothiols.

[0005] Currently, existing technologies have the following shortcomings:

[0006] First, existing conjugated microporous polymer photoelectrochemical sensors are mainly for the detection of substances such as H2O2, glucose, and bisphenol A, and lack specific recognition mechanisms and highly sensitive detection methods for biothiol molecules.

[0007] Secondly, although metalloporphyrins have good coordination ability and photoelectric properties, there are few studies on introducing metalloporphyrins into conjugated acetylene polymer skeletons and using them for photoelectrochemical detection of biothiols. There is a lack of design ideas to achieve selective detection by utilizing the specific interaction between the metal center and the thiol group.

[0008] Third, the light absorption range of existing photoelectrochemical sensing materials is limited, and the separation and transmission efficiency of photogenerated carriers is not high, resulting in a weak photocurrent response and a need to improve detection sensitivity.

[0009] Therefore, there is an urgent need to develop a new type of photoelectrochemical sensing material that can achieve high sensitivity and high selectivity in the detection of biothiols. Summary of the Invention

[0010] To address the aforementioned problems in the existing technology, the purpose of this invention is to provide a copper porphyrin conjugated acetylene polymer composite material, its preparation method, and its application in the photoelectrochemical detection of biothiols, thereby solving the technical problems of low sensitivity, poor selectivity, and weak photocurrent response in the existing technology for biothiols detection.

[0011] To achieve the above objectives, the first aspect of the present invention provides a copper porphyrin conjugated acetylene polymer composite material, comprising an electrochemically reduced graphene oxide layer (ERGO), a poly(1,4-diacetylenebenzene) layer (PDEB), and a copper porphyrin conjugated acetylene copolymer layer [P(DEB-CuTP)], characterized in that:

[0012] The copper porphyrin conjugated acetylene copolymer layer [P(DEB-CuTP)] is copolymerized from 1,4-diethynylbenzene monomer and copper-coordinated 5,10,15,20-tetra(4-acetylenephenyl)porphyrin monomer via a Sonogashira coupling reaction. The copper-coordinated 5,10,15,20-tetra(4-acetylenephenyl)porphyrin monomer has Cu atoms coordinated to its central ring. 2+ ion;

[0013] The poly(1,4-diaethynylbenzene) layer (PDEB) is polymerized from 1,4-diaethynylbenzene monomers via a Sonogashira coupling reaction.

[0014] The electrochemically reduced graphene oxide layer (ERGO), the poly(1,4-diacetylenebenzene) layer (PDEB), and the copper porphyrin conjugated acetylene copolymer layer [P(DEB-CuTP)] are sequentially deposited on the surface of a conductive substrate, forming a layered composite structure through π-π interactions.

[0015] Preferably, the molar ratio of the 1,4-diethynylbenzene monomer to the copper-coordinated 5,10,15,20-tetra(4-ethynylphenyl)porphyrin monomer is (80-98):(2-20).

[0016] More preferably, the molar ratio of the 1,4-diethynylbenzene monomer to the copper-coordinated 5,10,15,20-tetra(4-ethynylphenyl)porphyrin monomer is (85-95):(5-15).

[0017] More preferably, the molar ratio of the 1,4-diethynylbenzene monomer to the copper-coordinated 5,10,15,20-tetra(4-ethynylphenyl)porphyrin monomer is 90:10.

[0018] Preferably, the thickness of the electrochemically reduced graphene oxide layer (ERGO) is 50-200 nm, the thickness of the poly(1,4-diacetylenebenzene) layer (PDEB) is 100-300 nm, and the thickness of the copper porphyrin conjugated acetylene copolymer layer [P(DEB-CuTP)] is 150-400 nm.

[0019] Preferably, the conductive substrate is any one of indium tin oxide (ITO) glass electrode, fluorine-doped tin oxide (FTO) glass electrode, gold electrode, or carbon-based electrode.

[0020] Preferably, the copper porphyrin conjugated acetylene polymer composite material has broad spectral absorption in the visible light region (400-800 nm), with the absorption edge red-shifted to 650-750 nm, and has three characteristic absorption peaks at 420-450 nm, 540-560 nm, and 620-650 nm.

[0021] A second aspect of the present invention provides a method for preparing the copper porphyrin conjugated acetylene polymer composite material, characterized by comprising the following steps:

[0022] (1) The graphene oxide dispersion was dropped onto the surface of the conductive substrate and reduced by electrochemical reduction at a voltage of -1.0 to -1.5V for 3-8 min to obtain the conductive substrate modified with electrochemically reduced graphene oxide layer (ERGO).

[0023] (2) The conductive substrate modified with electrochemically reduced graphene oxide (ERGO) obtained in step (1) is placed in a reaction solution containing 1,4-diacetylene monomer, catalyst and base, and reacted at 70-90℃ for 1-3 h to generate a poly(1,4-diacetylene) layer (PDEB) in situ on the surface of the electrochemically reduced graphene oxide layer;

[0024] (3) The modified electrode obtained in step (2) is placed in a mixed reaction solution containing 1,4-diethynbenzene monomer, copper-coordinated 5,10,15,20-tetra(4-ethynylphenyl)porphyrin monomer, catalyst and base, and reacted at 75-95℃ for 2-5 h. A copper porphyrin conjugated acetylene copolymer layer [P(DEB-CuTP)] is generated in situ on the surface of the poly(1,4-diethynbenzene) layer, and the electrode modified with copper porphyrin conjugated acetylene polymer composite material is obtained.

[0025] Preferably, in step (1), the concentration of the graphene oxide dispersion is 0.2-1.0 mg / mL, the voltage of the electrochemical reduction is -1.2 V, and the reduction time is 5 min.

[0026] Preferably, in steps (2) and (3), the catalyst is a combination of bis(triphenylphosphine)palladium dichloride [Pd(PPh3)2Cl2] and cuprous iodide (CuI), the base is triethylamine or N,N-diisopropylethylamine, and the solvent is at least one of dimethylformamide (DMF), tetrahydrofuran (THF) or toluene.

[0027] Preferably, in step (2), the concentration of the 1,4-diacetylenebenzene monomer is 1-5 mmol / L, the concentration of Pd(PPh3)2Cl2 is 0.05-0.2 mmol / L, the concentration of CuI is 0.1-0.4 mmol / L, the volume ratio of triethylamine is 5%-15%, the reaction temperature is 80℃, and the reaction time is 2 h.

[0028] Preferably, in step (3), the concentration of the 1,4-diethynylbenzene monomer is 2-8 mmol / L, the concentration of the copper-coordinated 5,10,15,20-tetra(4-ethynylphenyl)porphyrin monomer is 0.2-1.0 mmol / L, the molar ratio of the two is (85-95):(5-15), the concentration of Pd(PPh3)2Cl2 is 0.08-0.3 mmol / L, the concentration of CuI is 0.15-0.6 mmol / L, the volume ratio of triethylamine is 8%-20%, the reaction temperature is 85℃, and the reaction time is 3 h.

[0029] A third aspect of the present invention provides the application of the copper porphyrin conjugated acetylene polymer composite material in the preparation of a biothiol photoelectrochemical sensor.

[0030] Preferably, the biothiol is at least one of L-cysteine ​​(L-Cys), reduced glutathione (GSH), homocysteine ​​(Hcy), or cysteamine.

[0031] Preferably, the photoelectrochemical sensor has a detection linear range of 0.5-2000 μM for L-cysteine ​​and a detection limit of 1.5-3.0 μM; and a detection linear range of 2-2000 μM for reduced glutathione and a detection limit of 10-20 μM.

[0032] The beneficial effects of this invention are as follows:

[0033] Firstly, this invention introduces copper porphyrin structural units into a conjugated acetylene polymer backbone, utilizing the Cu coordinated on the porphyrin central ring. 2+The ions form Cu-S coordination bonds with the thiol (-SH) groups in the biothiol molecules. Simultaneously, the 1,3-diyne bonds in the copolymer can undergo click reactions with the thiol groups under light irradiation, forming a dual-recognition-site mechanism. This significantly improves the selective recognition ability and detection sensitivity of biothiols. Compared to existing sensing materials that rely on only a single recognition mechanism, the synergistic effect of the dual recognition sites in this invention achieves a detection limit of 2.3 μM for L-Cys and 15.3 μM for GSH, demonstrating significantly superior detection performance compared to existing technologies.

[0034] Secondly, this invention constructs a poly(1,4-diacetylenebenzene) layer (PDEB) and a copper porphyrin conjugated acetylene copolymer layer [P(DEB-CuTP)] sequentially on the surface of electrochemically reduced graphene oxide (ERGO). Utilizing the π-π interactions between the three layers to form a long-range conjugated structure, this effectively suppresses the recombination of photogenerated electron-hole pairs, accelerates electron transport speed, and increases the photocurrent response intensity of the composite material by 2.5-3.5 times. Compared to a single conjugated acetylene polymer, the layered composite structure of this invention significantly improves photoelectric conversion efficiency.

[0035] Third, the copper porphyrin unit introduced in this invention has a high extinction coefficient (ε>10). 5 M -1 cm -1 This significantly enhances the absorption of the composite material in the visible light region, with the absorption edge red-shifted to 650-750 nm, increasing the visible light utilization rate by 40%-60%. This broad spectral response characteristic allows the composite material to generate a stable photocurrent signal under normal visible light irradiation conditions, reducing detection costs and improving practicality.

[0036] Fourth, the preparation method of this invention is simple and easy to implement. A layered composite structure is constructed on the surface of a conductive substrate through layer-by-layer in-situ polymerization, without the need for complex pre-synthesis steps and post-processing. The preparation cycle is short (total reaction time does not exceed 8 hours), with good reproducibility, making it suitable for large-scale production. After being stored at room temperature for 3 months, the photocurrent response of the prepared composite material modified electrode can still maintain more than 90% of the initial value, demonstrating excellent stability.

[0037] Fifth, the copper porphyrin conjugated acetylene polymer composite material of this invention exhibits excellent selectivity for the detection of biothiols, with negligible responses to common interfering substances such as ascorbic acid (AA), uric acid (UA), glucose (Glu), and other amino acids, demonstrating strong anti-interference ability. This composite material has been successfully used for the detection of biothiols in human serum samples, with a recovery rate of 95%-105%, showing promising prospects for practical applications. Attached Figure Description

[0038] Figure 1This is a schematic diagram of the structure of the copper porphyrin conjugated acetylene polymer composite material of the present invention. It shows the sequential arrangement of the electrochemically reduced graphene oxide layer (ERGO), the poly(1,4-diacetylenebenzene) layer (PDEB), and the copper porphyrin conjugated acetylene copolymer layer [P(DEB-CuTP)].

[0039] Figure 2 The molecular structure of copper porphyrin conjugated acetylene copolymer [P(DEB-CuTP)] shows the conjugated polymer structure formed by the connection of 1,4-diethynylbenzene units and copper coordinated porphyrin units through acetylene bonds.

[0040] Figure 3 This is the ultraviolet-visible absorption spectrum of the composite material of the present invention. As can be seen from the figure, after introducing the copper porphyrin unit, the absorption of the composite material in the visible light region is significantly enhanced, and the absorption edge is red-shifted, indicating that the utilization rate of visible light is improved.

[0041] Figure 4 The figure shows a comparison of the photocurrent response of materials with different molecular structures. As can be seen from the figure, the photocurrent response intensity of the ERGO / PDEB / P(DEB-CuTP) composite material is significantly higher than that of ERGO / PDEB and P(DEB-CuTP) alone, indicating that the layered composite structure effectively improves the photoelectric conversion efficiency.

[0042] Figure 5 The photoelectric response characteristics of the composite material to L-cysteine ​​are shown. These are ERGO / PDEB / P(DEB-CuTP) and P(DEB-CuTP) as shown. 0.1 The photocurrent-time curves of the composite material in the presence of different concentrations of L-Cys (0-2000 μM) and the photocurrent-time curves of ERGO / PDEB in the presence of different concentrations of L-Cys are used to compare and illustrate the difference in response to L-Cys before and after the introduction of the copper porphyrin unit.

[0043] Figure 6 This paper compares the photoelectric response of the composite material to L-cysteine ​​and reduced glutathione. The figures show the photocurrent-time curves of the ERGO / PDEB / P(DEB-CuTP) composite material to L-Cys and GSH at different concentrations, and the linear fitting curves of the photocurrent change with L-Cys and GSH concentrations. Good linear relationships are observed in the low concentration range (0-500 μM) and the high concentration range (500-2000 μM), respectively. The figures show that the composite material has a higher response sensitivity to L-Cys than to GSH, which is related to the smaller molecular weight and lower steric hindrance of L-Cys. Detailed Implementation

[0044] The technical solution of the present invention will be clearly and completely described below through specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.

[0045] In this invention, unless otherwise stated, all reagents and raw materials used are commercially available or can be prepared by known methods.

[0046] Example 1: Preparation of copper porphyrin conjugated acetylene polymer composite material

[0047] Step 1: Preparation of copper-coordinated 5,10,15,20-tetra(4-ethynylphenyl)porphyrin (CuTPP)

[0048] 5,10,15,20-tetratetra(4-bromophenyl)porphyrin (H₂TBrPP, 500 mg, 0.58 mmol), trimethylsilylacetylene (TMSA, 800 μL, 5.8 mmol), bis(triphenylphosphine)palladium dichloride [Pd(PPh₃)₂Cl₂, 81 mg, 0.12 mmol], and cuprous iodide (CuI, 44 mg, 0.23 mmol) were dissolved in a mixed solution of 50 mL tetrahydrofuran (THF, analytical grade) and 10 mL triethylamine (analytical grade). The mixture was refluxed at 80 °C for 12 h under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, diluted with 100 mL dichloromethane, washed three times with saturated ammonium chloride solution, dried over anhydrous sodium sulfate, filtered, and the solvent was removed by rotary evaporation. The crude product was purified by silica gel column chromatography [eluent: dichloromethane / petroleum ether (volume ratio 3:1)] to give 5,10,15,20-tetrakis(4-trimethylsilylethynylphenyl)porphyrin (H2TPMSA) in 75% yield.

[0049] The H₂TPMSA (300 mg, 0.32 mmol) obtained above was dissolved in 30 mL of dichloromethane, and tetrabutylammonium fluoride (TBAF, 1.0 M tetrahydrofuran solution, 1.6 mL, 1.6 mmol, purchased from Energy Chemical) was added. The mixture was stirred at room temperature for 2 h. After the reaction was complete, 50 mL of water was added, and the mixture was extracted three times with dichloromethane (30 mL each time). The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the solvent was removed by rotary evaporation to give 5,10,15,20-tetra(4-ethynylphenyl)porphyrin (H₂TPP) in 92% yield.

[0050] H₂TPP (200 mg, 0.27 mmol) and copper acetate [Cu(OAc)₂·H₂O, 270 mg, 1.35 mmol] were dissolved in a mixed solution of 40 mL chloroform (analytical grade) and 10 mL methanol (analytical grade), and the mixture was refluxed at 80 °C for 6 h. After the reaction was completed, the mixture was cooled to room temperature, and the solvent was removed by rotary evaporation. The residue was purified by silica gel column chromatography [eluent: dichloromethane / methanol (v / v 98:2)] to give copper-coordinated 5,10,15,20-tetra(4-ethynylphenyl)porphyrin (CuTPP) as a purple-red powder, with a yield of 88%.

[0051] Step 2: Preparation of graphene oxide dispersion

[0052] Graphene oxide (GO) was prepared using a modified Hummers method. Graphite powder (2.0 g, 200 mesh), potassium sulfate (1.0 g, analytical grade), and phosphorus pentoxide (2.5 g, analytical grade) were added to 30 mL of concentrated sulfuric acid (98%, analytical grade) and stirred at 80 °C for 6 h. After cooling to room temperature, 200 mL of deionized water was slowly added for dilution. The mixture was filtered, and the filter cake was washed with deionized water until neutral. The cake was then vacuum dried at 60 °C for 12 h to obtain pre-oxidized graphite.

[0053] The pre-oxidized graphite (2.0 g) was added to concentrated sulfuric acid (46 mL) in an ice bath, and potassium permanganate (6.0 g, analytical grade) was slowly added, controlling the temperature to not exceed 20°C. After the addition was complete, the ice bath was removed, the temperature was raised to 35°C, and the mixture was stirred for 2 h. Then, 100 mL of deionized water was added, the temperature was raised to 98°C, and the mixture was stirred for another 15 min. After cooling to room temperature, 300 mL of deionized water and 15 mL of hydrogen peroxide (30%, analytical grade) were added to terminate the reaction. The mixture was bright yellow. The reaction mixture was centrifuged (8000 rpm, 10 min), the supernatant was discarded, and the precipitate was washed twice with 5% hydrochloric acid solution, and then repeatedly washed with deionized water until the pH was neutral. The resulting wet gel was freeze-dried under vacuum at room temperature for 48 h to obtain solid graphene oxide (GO).

[0054] Graphene oxide (50 mg) was dispersed in 50 mL of deionized water and sonicated for 2 h (power: 300 W, frequency: 40 kHz) to obtain a uniform dispersion of graphene oxide with a concentration of 1.0 mg / mL, which was brownish-yellow and stored at 4℃ for later use.

[0055] Step 3: Preparation of ITO electrode modified with electrochemically reduced graphene oxide (ERGO)

[0056] The indium tin oxide (ITO) glass electrode (size: 1.0 cm × 2.5 cm, sheet resistance: 10 Ω / m) was ultrasonically cleaned for 15 min in sequence with deionized water, acetone (analytical grade), and anhydrous ethanol (analytical grade), and then dried with nitrogen gas for later use.

[0057] 10 μL of graphene oxide dispersion (1.0 mg / mL) was dropped onto the clean conductive surface of an ITO electrode (effective area: 1.0 cm²). 2 The graphene oxide film was naturally dried at room temperature for 12 hours to form a uniform graphene oxide film.

[0058] Electrochemically reduced graphene oxide (ERGO) was prepared using an electrochemical reduction method. In a three-electrode system, an ITO electrode modified with graphene oxide was used as the working electrode, a platinum sheet electrode (size: 1.0 cm × 1.5 cm) was used as the counter electrode, and Ag / AgCl (saturated KCl solution) was used as the reference electrode. Electrochemical reduction was performed for 5 min in 0.1 M phosphate buffer solution (PBS, pH 7.4) under a constant voltage of -1.2 V (relative to the Ag / AgCl reference electrode). During the electrochemical reduction process, bubbles were generated in the solution, and the electrode surface gradually changed from brownish-yellow to black. After the electrochemical reduction was completed, the electrode was thoroughly rinsed with deionized water and dried with nitrogen to obtain the ERGO-modified ITO electrode. The morphology of ERGO was characterized using a scanning electron microscope (SEM, model: ZEISS Sigma 300, accelerating voltage: 5 kV). ERGO exhibited a wrinkled sheet-like structure with a thickness of approximately 100 nm.

[0059] Step 4: Prepare ITO electrode modified with ERGO / PDEB composite

[0060] 1,4-Diacetylenebenzene (DEB, 42 mg, 0.33 mmol), Pd(PPh3)2Cl2 (23 mg, 0.033 mmol), and CuI (13 mg, 0.066 mmol) were dissolved in a mixed solution of 10 mL DMF (analytical grade, purchased from Sigma-Aldrich) and 1 mL triethylamine, and sonicated for 5 min to ensure complete dissolution. An ERGO-modified ITO electrode (conductive side up) was immersed in the above reaction solution and reacted at 80 °C for 2 h under nitrogen protection. During the reaction, the solution color gradually changed from colorless to pale yellow, and the electrode surface color changed from black to dark gray. After the reaction, the electrode was removed and thoroughly rinsed with DMF, ethanol, and deionized water sequentially to remove unreacted monomers and catalysts. It was then dried under nitrogen to obtain the ERGO / PDEB composite-modified ITO electrode.

[0061] Fourier transform infrared spectrometer (FT-IR, model: Nicolet iS50, resolution: 4 cm⁻¹) was used. -1 PDEB was characterized at 2100 cm⁻¹. -1 An absorption peak for C≡C stretching vibration appears at 1600 cm⁻¹. -1 and 1500 cm -1 The presence of a benzene ring skeletal vibration absorption peak at the α-position confirms the successful synthesis of poly(1,4-diacetylene).

[0062] Step 5: Prepare ITO electrode modified with ERGO / PDEB / P(DEB-CuTP) composite material

[0063] like Figure 1-2 As shown, 1,4-diethynylbenzene (DEB, 63 mg, 0.50 mmol), the copper-coordinated 5,10,15,20-tetra(4-ethynylphenyl)porphyrin (CuTPP, 44 mg, 0.055 mmol, molar ratio 90:10) prepared in step 1, Pd(PPh3)2Cl2 (39 mg, 0.055 mmol), and CuI (21 mg, 0.11 mmol) were dissolved in a mixed solution of 12 mL DMF and 1.5 mL triethylamine, and sonicated for 10 min to ensure thorough mixing. The ITO electrode (conductive side up) modified with the ERGO / PDEB composite prepared in step 4 was immersed in the above mixed reaction solution and reacted at 85 °C for 3 h under nitrogen protection. During the reaction, the solution color gradually deepened from light red to deep purplish-red, and the electrode surface color changed from dark gray to purplish-black. After the reaction was complete, the electrode was removed and thoroughly rinsed with DMF, ethanol, and deionized water in sequence to remove unreacted monomers, catalysts, and solvents. It was then dried under nitrogen to obtain ERGO / PDEB / P(DEB-CuTP). 0.1 ITO electrode modified with composite material (subscript 0.1 indicates that the molar fraction of CuTPP is 10%).

[0064] The absorption spectrum of the composite material was determined using a UV-Vis spectrophotometer (model: Shimadzu UV-2600, wavelength range: 200-800 nm). Figure 3 As shown, ERGO / PDEB / P(DEB-CuTP) 0.1The composite material exhibits broad spectral absorption in the visible light region (400-800 nm), with three characteristic absorption peaks at 420 nm (Soret band), 540 nm, and 620 nm (Q band), which are characteristic absorptions of the porphyrin ring. Compared with PDEB and ERGO / PDEB, the introduction of CuTPP red-shifts the absorption edge of the composite material from 580 nm to 700 nm, significantly enhancing visible light absorption and indicating improved visible light utilization.

[0065] The elemental composition and chemical state of the composite material were analyzed using X-ray photoelectron spectroscopy (XPS, Thermo Scientific K-Alpha, monochromatic Al Kα rays, hν=1486.6 eV). The results showed that Cu 2p The binding energy is at 933.8 eV, Cu 2p The binding energy at 953.6 eV confirms that Cu 2+ The presence of the N 1s spectrum showed two peaks at 398.2 eV and 400.1 eV, corresponding to the pyrrole nitrogen on the porphyrin ring and the nitrogen coordinated with Cu, respectively, further confirming the successful introduction of the copper porphyrin unit.

[0066] Example 2: Photoelectrochemical performance testing of copper porphyrin conjugated acetylene polymer composite material

[0067] The photoelectrochemical performance of the composite-modified electrode was tested using an electrochemical workstation. The tests were conducted in a three-electrode system, with the composite-modified ITO electrode as the working electrode, a platinum sheet electrode as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte solution was 0.1 M PBS (pH 7.4). A 300 W xenon lamp (model: PLS-SXE300) was used as the light source, and visible light (λ>420 nm) was obtained through a 420 nm cutoff filter, with a light intensity of 100 mW / cm². 2 The illuminated area is 1.0 cm². 2 .

[0068] Under a 0 V bias voltage (relative to an Ag / AgCl reference electrode), electrodes modified with different materials were subjected to intermittent illumination (40 s in light and 40 s in dark), and photocurrent-time (It) curves were recorded. Under visible light illumination, the photocurrent density of the PDEB-modified electrode was approximately 14 μA / cm². 2 The photocurrent density of the ERGO / PDEB composite modified electrode is approximately 28 μA / cm². 2 ERGO / PDEB / P(DEB-CuTP) 0.1 The photocurrent density of the composite material-modified electrode reached 63 μA / cm². 2Compared to PDEB, ERGO / PDEB / P(DEB-CuTP) 0.1 The photocurrent density of the composite material was increased by approximately 4.5 times; compared with ERGO / PDEB, the photocurrent density was increased by approximately 2.25 times. This indicates that the introduction of ERGO and the copper porphyrin unit significantly enhanced the photocurrent response of the composite material.

[0069] The photocurrent response of the composite material under different bias voltages was further tested. At a bias voltage of -0.2 V (relative to the Ag / AgCl reference electrode), the ERGO / PDEB / P(DEB-CuTP) composite material... 0.1 The photocurrent density was the highest, reaching 65 μA / cm. 2 As the bias voltage increased from -0.2 V to 0.2 V, the photocurrent density gradually decreased. In subsequent biothiol detection experiments, a bias voltage of 0 V was selected as the optimal test condition to avoid the influence of the bias voltage on the detection results.

[0070] The charge transfer characteristics of the composite material were analyzed using electrochemical impedance spectroscopy (EIS). At open-circuit potential, in a frequency range of 1 Hz–100 kHz with an AC amplitude of 5 mV, the composite material was prepared in 0.1 M PBS (pH 7.4) containing 5 mM [Fe(CN)6]. 3- / 4- As a redox probe, ERGO / PDEB / P(DEB-CuTP) was used. Results showed that ERGO / PDEB / P(DEB-CuTP) 0.1 The charge transfer resistance (R) of composite materials ct The Ω is approximately 850Ω, significantly smaller than the R of PDEB. ct (Approximately 2300 Ω) and R of ERGO / PDEB ct (Approximately 1200 Ω), indicating that the layered composite structure effectively accelerates electron transport speed and reduces charge transfer resistance.

[0071] Example 3: Photoelectrochemical detection of L-cysteine ​​using ERGO / PDEB / P (DEB-CuTP) composite material

[0072] At 0 V bias voltage, visible light (λ>420 nm, light intensity 100 mW / cm²) 2 Under irradiation conditions, ERGO / PDEB / P(DEB-CuTP) was tested. 0.1 The photocurrent response of the composite material modified electrode to different concentrations of L-cysteine ​​(L-Cys, purchased from Sigma-Aldrich).

[0073] like Figure 5As shown, different volumes of L-Cys stock solution (10 mM) were added sequentially to the electrolytic cell in 0.1 M PBS (pH 7.4) solution, gradually increasing the final concentration of L-Cys from 0 to 2000 μM. After each addition of L-Cys, the mixture was stirred for 10 s to ensure uniform dispersion, and after standing for 2 min, photocurrent was measured. The results showed that the photocurrent intensity gradually decreased with increasing L-Cys concentration. When the L-Cys concentration increased from 0 to 2000 μM, the photocurrent density increased from 63 μA / cm². 2 Reduced to 18 μA / cm 2 The photocurrent decreased by approximately 71%.

[0074] In comparison, such as Figure 5 The response of the ERGO / PDEB-modified electrode (without the copper porphyrin unit) to L-Cys was also demonstrated. Under the same conditions, as the L-Cys concentration increased from 0 to 2000 μM, the photocurrent density increased from 28 μA / cm². 2 Reduced to 23 μA / cm 2 The photocurrent decreased by only about 18%. This comparative experiment fully demonstrates that the introduction of the copper porphyrin unit significantly improves the response sensitivity of the composite material to L-Cys.

[0075] like Figure 5 As shown, a linear fit was performed between the change in photocurrent (ΔI, defined as ΔI = I0 - I, where I0 is the photocurrent without L-Cys and I is the photocurrent after adding L-Cys) and the L-Cys concentration. For ERGO / PDEB / P (DEB-CuTP) 0.1 In the low concentration range (0.5-500 μM), the linear regression equation is ΔI (μA / cm). 2 )=0.043C L-Cys +45.77, correlation coefficient R 2 =0.993; In the high concentration range (500-2000 μM), the linear regression equation is ΔI (μA / cm). 2 )=0.016C L-Cys +0.016, correlation coefficient R 2 =0.991. Based on a signal-to-noise ratio (S / N) of 3, the limit of detection (LOD) for L-Cys is 2.27 μM.

[0076] This detection performance is superior to existing L-Cys detection sensors based on photoelectrochemical methods reported in the literature.

[0077] Example 4: Photoelectrochemical detection of reduced glutathione using ERGO / PDEB / P (DEB-CuTP) composite material

[0078] The ERGO / PDEB / P(DEB-CuTP) was tested using the same method as in Example 3. 0.1 The photocurrent response of the composite material modified electrode to reduced glutathione (GSH).

[0079] like Figure 6 As shown, in 0.1 M PBS (pH 7.4), different volumes of GSH stock solution (10 mM) were added sequentially to the electrolytic cell, gradually increasing the final GSH concentration from 0 to 2000 μM. With increasing GSH concentration, the photocurrent intensity gradually decreased, but the decrease was less than that of L-Cys. When the GSH concentration increased from 0 to 2000 μM, the photocurrent density increased from 63 μA / cm². 2 Reduced to 28 μA / cm 2 The photocurrent decreased by approximately 56%.

[0080] Then, a linear regression was performed on the change in photocurrent (ΔI) and GSH concentration. In the low concentration range (2-500 μM), the linear regression equation was ΔI (μA / cm²). 2 )=0.008C GSH +41.88, correlation coefficient R 2 =0.996; In the high concentration range (500-2000 μM), the linear regression equation is ΔI (μA / cm). 2 )=0.016C +49.92, correlation coefficient R 2 =0.993. Based on a signal-to-noise ratio (S / N) of 3, the limit of detection (LOD) for GSH is 15.32 μM.

[0081] ERGO / PDEB / P(DEB-CuTP 0.1 The composite material showed significantly higher response sensitivity to L-Cys than GSH. At low concentrations, the response slope to L-Cys (0.043 μA·cm⁻¹) was... -2 ·μM -1 ) is the slope of the response to GSH (0.008 μA·cm) -2 ·μM -1 The sensitivity difference is 5.4 times that of L-Cys. This difference in sensitivity may be related to the structure of the two biothiols. L-Cys is a simple amino acid with a small molecular weight and low steric hindrance; while GSH is a tripeptide composed of glutamic acid, cysteine, and glycine, with a larger molecular weight and higher steric hindrance. Therefore, during detection, L-Cys is more accessible and interacts with the copper porphyrin unit and alkyne bond structure in the composite material, exhibiting higher response sensitivity.

[0082] Example 5: Study on the interaction mechanism between biothiols and composite materials

[0083] To gain a deeper understanding of the interaction mechanism between biothiols and the ERGO / PDEB / P(DEB-CuTP) composite material, a series of characterization and comparative experiments were conducted.

[0084] 5.1 Formation of Cu-S Coordination Bonds

[0085] X-ray photoelectron spectroscopy (XPS) was used to analyze the changes in Cu 2p and S 2p spectra of the composite material before and after interaction with L-Cys. Before interaction with L-Cys, Cu 2p... The binding energy is 933.8 eV, corresponding to After reacting with 100 μM L-Cys for 30 min, Cu 2p The binding energy shifts by 0.5 eV to a lower energy level, reaching 933.3 eV, indicating an increase in the electron cloud density of Cu and the formation of Cu-S coordination bonds. Simultaneously, two new peaks appear in the S 2p spectrum at 163.2 eV and 164.4 eV, corresponding to S 2p... and S 2p This confirms that the sulfur atom in -SH is related to... Coordination occurred.

[0086] The formation process of Cu-S coordination bonds was monitored using ultraviolet-visible absorption spectroscopy. This was applied to Cu-S bonds containing ERGO / PDEB / P(DEB-CuTP). 0.1 L-Cys was added to the PBS solution of the composite material, and the absorption spectrum was measured every 5 minutes. The results showed that with increasing reaction time, the absorbance of the Soret band (420 nm) and Q band (540 nm, 620 nm) of the porphyrin gradually decreased, accompanied by a slight red shift (approximately 3-5 nm). This phenomenon indicates that the -SH group in L-Cys interacts with the porphyrin center. Coordination occurred, altering the electronic structure of the porphyrin ring and causing changes in the absorption spectrum.

[0087] 5.2 Click reaction of alkyne bond with -SH

[0088] Fourier transform infrared spectroscopy (FT-IR) was used to study the reaction of alkyne bonds with -SH under illumination. ERGO / PDEB / P(DEB-CuTP) was used as the catalyst. 0.1 The composite material was mixed with 100 μM L-Cys in 0.1 M PBS (pH 7.4) and subjected to visible light (λ>420 nm, light intensity 100 mW / cm²). 2 The reaction was carried out under irradiation for 30 min, then removed, thoroughly rinsed with deionized water, dried, and subjected to FT-IR analysis. The results showed that the C≡C stretching vibration absorption peak (2100 cm⁻¹) was observed after the reaction. -1The strength of ) decreased significantly, while at 2920 cm -1 and 2850 cm -1 Two new absorption peaks appeared at 1650 cm⁻¹, corresponding to CH stretching vibrations, indicating that some alkyne bonds underwent addition reactions. Furthermore, at 1650 cm⁻¹... -1 The presence of a C=C stretching vibration absorption peak nearby further confirms that the alkyne bond underwent a click reaction with -SH, generating a product containing a C=C bond.

[0089] To verify the promoting effect of light on the reaction, a comparative experiment was designed. ERGO / PDEB / P(DEB-CuTP) was used. 0.1 The composite material was reacted with 100 μM L-Cys in the dark for 30 min, and the change in photocurrent was measured. The results showed that the photocurrent decreased by only about 12% under dark conditions, while it decreased by about 38% under illumination. This comparative experiment indicates that illumination significantly promotes the reaction between the alkyne bond and -SH, which may be because the reactive oxygen free radicals generated by photoexcitation promote the click reaction.

[0090] 5.3 Synergistic effect of dual recognition sites

[0091] The interaction between biothiol molecules and composite materials involves two mechanisms: one is the porphyrin center. The composite material exhibits two key characteristics: first, it forms a Cu-S coordination bond with -SH; second, under light irradiation, the alkyne bond undergoes a click reaction with -SH. This synergistic effect of dual recognition sites significantly enhances the composite material's selective recognition ability for biothiols.

[0092] To verify the synergistic effect of the dual recognition sites, a copper-free base porphyrin conjugated acetylene copolymer [ERGO / PDEB / P(DEB-H2TP)] and an acetylene-free copper porphyrin polymer (prepared via oxidative coupling) were prepared, and their photocurrent response to L-Cys was tested. The results showed that ERGO / PDEB / P(DEB-H2TP) had a weak response to L-Cys, with a detection limit of approximately 18 μM; the detection limit of the acetylene-free copper porphyrin polymer was approximately 12 μM. Meanwhile, ERGO / PDEB / P(DEB-H2TP) showed a weaker response to L-Cys, with a detection limit of approximately 18 μM; while the detection limit of the acetylene-free copper porphyrin polymer was approximately 12 μM. 0.1 The detection limit of this material is 2.27 μM, which is significantly better than materials with a single recognition site. This fully demonstrates the importance of the synergistic effect of dual recognition sites in improving detection sensitivity.

[0093] When biothiols are combined with composite materials, the transport of photogenerated charge carriers is affected. On the one hand, the formation of Cu-S coordination bonds reduces the redox activity of the copper porphyrin unit, affecting the transport of photogenerated electrons; on the other hand, the click reaction between the alkyne bond and -SH disrupts the integrity of the conjugated system, increasing the resistance to electron transport. These two effects together lead to a significant reduction in photocurrent intensity, enabling highly sensitive detection of biothiols.

[0094] Example 6: Effect of copper porphyrin molar fraction on the photoelectrochemical properties of composite materials

[0095] To optimize the composition of the composite materials, a series of composite materials with different molar fractions of copper porphyrin were prepared, and the effect of the molar fraction of copper porphyrin on the photoelectrochemical performance was studied.

[0096] Following the method in Example 1, composite materials with copper porphyrin molar fractions of 0%, 5%, 10%, 15%, and 20% were prepared, respectively, and denoted as ERGO / PDEB / P(DEB-CuTP). x ), where x represents the mole fraction of copper porphyrin. The specific preparation conditions are as follows:

[0097] ERGO / PDEB (x=0%): Only 1,4-diethynylbenzene (DEB, 126 mg, 1.0 mmol) was used as the monomer, without the addition of CuTPP.

[0098] ERGO / PDEB / P(DEB-CuTP 0.05 DEB (120 mg, 0.95 mmol) and CuTPP (22 mg, 0.028 mmol) were used in a molar ratio of 95:5.

[0099] ERGO / PDEB / P(DEB-CuTP 0.10 DEB (113 mg, 0.90 mmol) and CuTPP (44 mg, 0.055 mmol) were administered in a molar ratio of 90:10.

[0100] ERGO / PDEB / P(DEB-CuTP 0.15 DEB (107 mg, 0.85 mmol) and CuTPP (66 mg, 0.083 mmol) were used in a molar ratio of 85:15.

[0101] ERGO / PDEB / P(DEB-CuTP 0.20 DEB (101 mg, 0.80 mmol) and CuTPP (88 mg, 0.11 mmol) were used in a molar ratio of 80:20.

[0102] The amounts of catalyst and base were adjusted accordingly based on the total molar amount of monomer, and other preparation conditions were the same as in Example 1.

[0103] The photocurrent response of composite materials with different copper porphyrin molar fractions was tested under 0 V bias and visible light irradiation conditions, and the results are summarized in Table 1.

[0104] Table 1. Photoelectrochemical properties of composite materials with different copper porphyrin molar fractions

[0105]

[0106] As shown in Table 1, the photocurrent density of the composite material first increases and then decreases with the increase of the copper porphyrin molar fraction, reaching a maximum of 63 μA / cm when the copper porphyrin molar fraction is 10%. 2 The response sensitivity and detection limit to L-Cys also showed a similar trend, reaching the optimal value at a copper porphyrin molar fraction of 10%.

[0107] When the molar fraction of copper porphyrin is too low (e.g., 5%), although the photocurrent density increases, the response sensitivity to L-Cys is low due to insufficient recognition sites. When the molar fraction of copper porphyrin is too high (e.g., 15% and 20%), although the number of recognition sites increases, excessive porphyrin units can disrupt the conjugated structure of the polymer, reducing electron transport efficiency and causing a decrease in both photocurrent density and response sensitivity. Therefore, the optimal molar fraction of copper porphyrin is 10%, which ensures sufficient recognition sites while maintaining good conjugated structure and electron transport performance.

[0108] Example 7: Selectivity study of composite materials for the detection of biothiols

[0109] To evaluate ERGO / PDEB / P(DEB-CuTP) 0.1 The selectivity of the composite material for the detection of biothiols was tested, and the photocurrent response of the composite material to various common interfering substances was also tested.

[0110] In 0.1 M PBS (pH 7.4), L-Cys (100 μM) and various common interfering substances, including ascorbic acid (AA, 200 μM), uric acid (UA, 200 μM), glucose (Glu, 500 μM), glycine (Gly, 200 μM), alanine (Ala, 200 μM), phenylalanine (Phe, 200 μM), tryptophan (Trp, 200 μM), tyrosine (Tyr, 200 μM), arginine (Arg, 200 μM), and lysine (Lys, 200 μM), were added to the electrolytic cell. The photocurrent response was tested under 0 V bias and visible light irradiation.

[0111] The results showed that ERGO / PDEB / P(DEB-CuTP) 0.1 The composite material showed a significant photocurrent response to L-Cys (100 μM), with a photocurrent reduction of approximately 42%. However, for other interfering substances at higher concentrations (200 μM or 500 μM), the photocurrent reduction was less than 8%, which was negligible. This indicates that the composite material has good selectivity for biothiols and strong anti-interference ability.

[0112] The results of the selectivity test can be explained in several ways: First, only biothiols contain -SH groups, which can interact with the porphyrin center. First, Cu-S coordination bonds are formed, while other interfering substances do not possess this structural feature. Second, under light irradiation, -SH can undergo click reactions with alkyne bonds, while carboxyl (-COOH), hydroxyl (-OH), amino (-NH2) and other groups have very low reactivity with alkyne bonds. Third, even if some interfering substances (such as AA and UA) have certain reducing properties, their influence on photocurrent is minimal due to the lack of specific interactions between them and the composite material.

[0113] The selectivity of the composite material to different biothiols was further tested. The photocurrent response of L-Cys, D-Cys, GSH, and homocysteine ​​(Hcy) was tested separately. The results showed that the composite material had almost the same response to L-Cys and D-Cys, indicating that it had no chiral selectivity; the response sensitivity to L-Cys was higher than that to GSH and Hcy, which is related to molecular size and steric hindrance.

[0114] Example 8: Reproducibility and stability study of composite materials

[0115] 8.1 Reproducibility Test

[0116] Using the same ERGO / PDEB / P (DEB-CuTP) 0.1 The composite material-modified electrode was used to continuously measure 100 μM L-Cys 20 times in 0.1 M PBS (pH 7.4) solution, with each measurement 3 min apart. The photocurrent response of the 20 measurements was basically consistent, with a relative standard deviation (RSD) of 4.3%, indicating that the composite material-modified electrode has good reproducibility.

[0117] In addition, five ERGO / PDEB / P(DEB-CuTP) molecules were prepared in parallel. 0.1 The photocurrent response of the composite material-modified electrode was measured under the same conditions in 100 μM L-Cys. The results showed that the relative standard deviation (RSD) of the photocurrent response of the five electrodes was 6.8%, indicating that the preparation method had good reproducibility and small batch-to-batch differences.

[0118] 8.2 Stability Test

[0119] ERGO / PDEB / P(DEB-CuTP) 0.1 The composite material-modified electrode was stored dry at room temperature, and its photocurrent response to 100 μM L-Cys was tested at regular intervals to assess its long-term stability. After one week of storage, the photocurrent response remained at 98% of its initial value; after one month, it remained at 95%; and after three months, it still remained at 92%. This indicates that the composite material-modified electrode has excellent long-term stability and is suitable for long-term storage and repeated use.

[0120] To further evaluate the stability of the composite material during use, the same electrode was reused 10 times in a 100 μM L-Cys solution. After each use, it was immersed in 0.1 M HCl solution (pH 2.0) for 5 min to remove the bound L-Cys, then thoroughly rinsed with deionized water, dried, and reused. The results showed that after 10 reuses, the photocurrent response still maintained 88% of the initial value, indicating that the composite material can be regenerated under acidic conditions and has a long service life.

[0121] Example 9: Application of composite materials in actual samples

[0122] To evaluate ERGO / PDEB / P(DEB-CuTP) 0.1 The potential of composite materials in actual sample testing was explored by determining the content of L-Cys and GSH in human serum samples using the standard addition method.

[0123] 9.1 Pretreatment of serum samples

[0124] Human serum samples were purchased from Beijing Solarbio Science & Technology Co., Ltd. 1 mL of serum sample was taken, 3 mL of anhydrous ethanol was added, and the mixture was thoroughly mixed. The mixture was incubated at 4°C for 30 min, then centrifuged at 8000 rpm for 10 min. The supernatant was collected, and the ethanol was removed by rotary evaporation. The residue was diluted to 5 mL with 0.1 M PBS (pH 7.4) to obtain the pretreated serum sample, which was stored at 4°C for later use.

[0125] 9.2 Determination by Standard Addition Method

[0126] Take 1 mL of pretreated serum sample, dilute it 10-fold with 0.1 M PBS (pH 7.4), and then add 0, 20, 50, and 100 μM L-Cys standard solutions, respectively. Test the photocurrent response under 0 V bias and visible light irradiation. Calculate the concentration of L-Cys in the serum sample based on the standard addition curve. Perform three parallel measurements; the results are shown in Table 2.

[0127] Table 2. Detection results of L-Cys and GSH in human serum samples (n=3)

[0128]

[0129] As shown in Table 2, the detection value of L-Cys in serum samples was 42.3 μM, and the detection value of GSH was 185.6 μM, which is consistent with the reported concentration range of biothiols in normal human serum (L-Cys: 30-200 μM, GSH: 100-300 μM) in the literature. The recovery rate of the standard addition method was 96.8%-103.8%, and the relative standard deviation (RSD) was less than 5%, indicating that the method has good accuracy and precision and is suitable for the detection of actual samples.

[0130] Example 10: Effect of different preparation conditions on the properties of composite materials

[0131] To further optimize the preparation conditions of the composite material, the effects of factors such as electrochemical reduction voltage, polymerization reaction temperature, and reaction time on the photoelectrochemical properties of the composite material were investigated.

[0132] 10.1 Effect of Electrochemical Reduction Voltage

[0133] ERGO was prepared using different electrochemical reduction voltages (-1.0 V, -1.2 V, -1.5 V, all with a reduction time of 5 min), and then ERGO / PDEB / P(DEB-CuTP) was prepared according to the method in Example 1. 0.1 Composite materials were used to test the photocurrent response.

[0134] The results showed that when the reduction voltage was -1.0 V, the reduction of graphene oxide was incomplete, resulting in low conductivity and a photocurrent density of only 38 μA / cm. 2 When the reduction voltage is -1.2 V, the reduction is relatively complete, and the photocurrent density reaches 63 μA / cm². 2 When the reduction voltage is -1.5 V, although the reduction is more complete, the excessively strong reduction conditions may cause partial damage to the graphene sheets, and the photocurrent density actually drops to 55 μA / cm. 2 Therefore, the optimal electrochemical reduction voltage is -1.2 V.

[0135] 10.2 Effect of Polymerization Temperature

[0136] In step 3, copper porphyrin conjugated acetylene copolymer layers were prepared using different reaction temperatures (75℃, 80℃, 85℃, 90℃, and 95℃, with a reaction time of 3 h for each temperature) and the photocurrent response to 100 μM L-Cys was tested.

[0137] The results showed that at a reaction temperature of 75℃, the polymerization rate was slow, the polymer layer was thin, and the photocurrent reduction was only 20%; at a reaction temperature of 85℃, the polymerization rate was moderate, and the photocurrent reduction reached 42%; at a reaction temperature of 95℃, although the polymerization rate increased, the excessively high temperature may lead to catalyst deactivation and polymer structural defects, and the photocurrent reduction actually decreased to 35%. Therefore, the optimal reaction temperature is 85℃.

[0138] 10.3 Effect of Polymerization Reaction Time

[0139] In step 3, copper porphyrin conjugated acetylene copolymer layers were prepared using different reaction times (1 h, 2 h, 3 h, 4 h, 5 h, all at a reaction temperature of 85 °C), and the photocurrent density and photocurrent response to 100 μM L-Cys were tested.

[0140] The results showed that as the reaction time increased, the polymer layer thickness gradually increased, and the photocurrent density first increased and then decreased. The highest photocurrent density (63 μA / cm²) was observed when the reaction time was 3 h. 2 The reaction time of 3 h resulted in the largest decrease in photocurrent of L-Cys (42%). When the reaction time was too short (1-2 h), the polymer layer was too thin, resulting in insufficient light absorption and recognition sites; when the reaction time was too long (4-5 h), the polymer layer was too thick, which may hinder light transmission and electron transport, thus reducing photoelectrochemical performance. Therefore, the optimal reaction time was 3 h.

[0141] Based on the above optimization experiments, the optimal preparation conditions were determined in this invention: the electrochemical reduction voltage was -1.2 V, the reduction time was 5 min; the polymerization temperature of the PDEB layer was 80℃, the reaction time was 2 h; the polymerization temperature of the P(DEB-CuTP) layer was 85℃, the reaction time was 3 h; and the molar fraction of copper porphyrin was 10%.

[0142] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A copper porphyrin conjugated acetylene polymer composite material, characterized in that, The product comprises an electrochemically reduced graphene oxide layer, a poly(1,4-diacetynylbenzene) layer, and a copper porphyrin conjugated acetylene copolymer layer. The copper porphyrin conjugated acetylene copolymer layer is copolymerized from a 1,4-diacetynylbenzene monomer and a copper-coordinated 5,10,15,20-tetra(4-acetynylphenyl)porphyrin monomer via a Sonogashira coupling reaction. The copper-coordinated 5,10,15,20-tetra(4-acetynylphenyl)porphyrin monomer has a central ring with [missing information - likely a specific structure or component]. Ions; the poly(1,4-diacetylenebenzene) layer is polymerized from 1,4-diacetylenebenzene monomers via a Sonogashira coupling reaction; the electrochemically reduced graphene oxide layer, the poly(1,4-diacetylenebenzene) layer, and the copper porphyrin conjugated acetylene copolymer layer are sequentially deposited on the surface of a conductive substrate, forming a layered composite structure through π-π interactions.

2. The copper porphyrin conjugated acetylene polymer composite material according to claim 1, characterized in that, The molar ratio of the 1,4-diethynylbenzene monomer to the copper-coordinated 5,10,15,20-tetra(4-ethynylphenyl)porphyrin monomer is (80-98):(2-20).

3. The copper porphyrin conjugated acetylene polymer composite material according to claim 1, characterized in that, The thickness of the electrochemically reduced graphene oxide layer is 50-200 nm, the thickness of the poly(1,4-diacetylenebenzene) layer is 100-300 nm, and the thickness of the copper porphyrin conjugated acetylene copolymer layer is 150-400 nm.

4. The copper porphyrin conjugated acetylene polymer composite material according to claim 1, characterized in that, The conductive substrate is any one of indium tin oxide glass electrode, fluorine-doped tin oxide glass electrode, gold electrode, or carbon-based electrode.

5. A method for preparing the copper porphyrin conjugated acetylene polymer composite material according to any one of claims 1-4, characterized in that, Includes the following steps: (1) The graphene oxide dispersion was dropped onto the surface of the conductive substrate and reduced by electrochemical reduction at a voltage of -1.0 to -1.5 V for 3-8 min to obtain the conductive substrate modified with electrochemically reduced graphene oxide layer. (2) The conductive substrate modified with electrochemically reduced graphene oxide layer obtained in step (1) is placed in a reaction solution containing 1,4-diacetylene monomer, catalyst and base, and reacted at 70-90℃ for 1-3 h to generate poly(1,4-diacetylene) layer in situ on the surface of electrochemically reduced graphene oxide layer. (3) The modified electrode obtained in step (2) is placed in a mixed reaction solution containing 1,4-diacetylenebenzene monomer, copper-coordinated 5,10,15,20-tetra(4-acetylenephenyl)porphyrin monomer, catalyst and base, and reacted at 75-95℃ for 2-5 h. A copper porphyrin conjugated acetylene copolymer layer is generated in situ on the surface of the poly(1,4-diacetylenebenzene) layer, and the electrode modified with copper porphyrin conjugated acetylene polymer composite material is obtained.

6. The preparation method according to claim 5, characterized in that, In step (1), the concentration of the graphene oxide dispersion is 0.2-1.0 mg / mL, the voltage of the electrochemical reduction is -1.2 V, and the reduction time is 5 min.

7. The preparation method according to claim 5, characterized in that, In steps (2) and (3), the catalyst is a combination of bis(triphenylphosphine)palladium dichloride and cuprous iodide, the base is triethylamine or N,N-diisopropylethylamine, and the solvent is at least one of dimethylformamide, tetrahydrofuran or toluene.

8. The preparation method according to claim 5, characterized in that, In step (3), the molar ratio of the 1,4-diethynylbenzene monomer to the copper-coordinated 5,10,15,20-tetra(4-ethynylphenyl)porphyrin monomer is (85-95):(5-15), the reaction temperature is 85℃, and the reaction time is 3 h.

9. The application of the copper porphyrin conjugated acetylene polymer composite material according to any one of claims 1-4 in the preparation of a biothiol photoelectrochemical sensor.

10. The application according to claim 9, characterized in that, The biothiol is at least one of L-cysteine, reduced glutathione, homocysteine, or cysteamine.

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