W-CN-C photoelectric active material and preparation method thereof, and heavy metal ion self-energized sensor and preparation method thereof

Abstract

The invention relates to the technical field of heavy metal ion detection, in particular to a W-CN-C photoelectric active material and a preparation method thereof as well as a heavy metal ion self-energized sensor and a preparation method thereof. The preparation method comprises the following steps: carrying out mechanical ball-milling self-assembly on a nitrogen source and a carbon source to form an intermediate, and carrying out first calcination to obtain an mtCN material; dispersing the mtCN material in a mixed solvent, dropwise adding a Na2WO4. 2H2O solution under a heating condition, reacting, centrifuging, washing and drying to obtain a precursor; and calcining the precursor for the second time in the inert gas atmosphere to obtain the W-CN-C photoelectric active material. The PFC self-powered sensor for the heavy metal ions in the water body, provided by the invention, has the characteristics of relatively high detection sensitivity and stability, simpler instruments and equipment, low cost and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy metal ion detection, in particular to a W-CN-C photoelectric active material and a preparation method thereof, and a heavy metal ion self-powered sensor and a preparation method thereof. Background Art

[0002] With the rapid development of industrialization and urbanization, heavy metal ion pollution is becoming increasingly serious worldwide and has become one of the major environmental issues threatening global sustainable development (J.Cleaner Prod.2022,373,133780). Heavy metal ions are difficult to degrade, easily bioaccumulated, and highly toxic. They easily accumulate in aquatic environments, destroying the ecological balance of aquatic environments and entering the human body through the food chain, posing a serious threat to human health. At present, conventional quantitative methods for metal ions include atomic absorption spectroscopy and inductively coupled plasma mass spectrometry. These methods rely on precision instruments and skilled operators, and require complex sample pretreatment, which limits their practical application. Therefore, the development of fast, accurate, and economical heavy metal ion detection technology is of great practical significance for monitoring the heavy metal content in water bodies and protecting the ecological environment and human health. Summary of the Invention

[0003] In order to solve or partially solve the problems existing in the related art, the present invention provides a W-CN-C photoelectric active material and a preparation method thereof, and a heavy metal ion self-powered sensor and a preparation method thereof.

[0004] The present invention provides a method for preparing a W-CN-C photoelectric active material, which comprises:

[0005] Step a1), self-assembling a nitrogen source and a carbon source by mechanical ball milling to form an intermediate, and then calcining for the first time to obtain an mtCN material; the nitrogen source is melamine, urea or dicyandiamide, and the carbon source is glucose, chitosan or locust bean gum;

[0006] Step a2), dispersing the mtCN material in a mixed solvent, adding a Na2WO4·2H2O solution dropwise under heating conditions, and centrifuging, washing, and drying after the reaction to obtain a precursor; the mixed solvent is a mixed solvent of deionized water, anhydrous ethanol, and glycerol;

[0007] Step a3), calcining the precursor for the second time under an inert gas atmosphere to obtain a W-CN-C photoelectric active material.

[0008] Furthermore, in step a1), the mass ratio of the nitrogen source to the carbon source is (1000-4000): (2-100); and / or the temperature of the first calcination is 400-700°C, the heating rate is 2-5°C / min, and the calcination time is 2-6h.

[0009] Furthermore, in step a2), the concentration of the Na2WO4·2H2O solution is 0.05-0.2 mM, the mass volume ratio of the mtCN material to the Na2WO4·2H2O solution is 0.05-0.2 g:5 mL; the heating temperature is 80-95° C.; and / or,

[0010] In the step a3), the temperature of the second calcination is 400-600° C., the heating rate is 2-5° C. / min, and the calcination time is 1-4 hours.

[0011] The present invention also provides a W-CN-C photoelectric active material, which is prepared according to any one of the methods described above.

[0012] The present invention also provides a method for preparing a heavy metal ion self-powered sensor, which comprises:

[0013] Step b1), dispersing the W-CN-C photoelectric active material in deionized water, adding naphthol solution, and uniformly dispersing by ultrasonication to obtain a suspension;

[0014] Step b2), applying the suspension dropwise to the surface of ITO conductive glass to obtain a W-CN-C / ITO electrode;

[0015] Step b3), drop-coating the heavy metal ion aptamer solution on the surface of the W-CN-C / ITO electrode and incubating to obtain the apt / W-CN-C / ITO photoanode, i.e., the heavy metal ion self-powered sensor.

[0016] Furthermore, in step b1), the amount of naphthol solution used is 1 / 30 to 1 / 20 of deionized water, and the concentration of naphthol solution is 0.3-0.6 wt %; the concentration of W-CN-C photoelectric active material in the suspension is 1.0 to 5.0 mg / mL.

[0017] Furthermore, in step b2), the drop coating amount of the suspension is 90-120 μL / 1 cm 2 .

[0018] Furthermore, in step b3), the heavy metal ion aptamer solution is Cu 2+ Aptamer, Zn 2+ Aptamer or Pb 2 + aptamer solution;

[0019] The concentration of the heavy metal ion aptamer solution is 0.3-1.5 μM, and the amount of the heavy metal ion aptamer solution dropped is 8-12 μL / 1 cm 2 ;

[0020] The incubation time is 6 to 18 hours.

[0021] The present invention also provides a heavy metal ion self-powered sensor, which is prepared according to any one of the methods described above.

[0022] The present invention also provides an application of the above-mentioned heavy metal ion self-powered sensor in detecting heavy metal ions.

[0023] The technical solution provided by the present invention can have the following beneficial effects:

[0024] The W-CN-C photoelectrically active material and heavy metal ion self-powered sensor provided by the embodiments of the present invention have the following advantages:

[0025] 1) The carbon-rich structure significantly broadens the visible light absorption range of W-CN-C materials and enhances light utilization. 6+ / W 5+ The redox couple acts as an electron transport channel, accelerating the directional transfer of electrons. The synergistic effect of the two increases the open-circuit voltage of the PFC. Aptamers that specifically recognize heavy metal ions are introduced onto the surface of the photoanode, forming a sensing interface. The steric effect of the heavy metal ion-aptamer complex causes a change in the detection signal, resulting in a self-powered sensing system with high sensitivity and stability. By constructing a PFC with a high output signal using W-CN-C material as the photoanode, a highly sensitive and stable PFC self-powered sensing system for heavy metal ions can be developed.

[0026] 2) The present invention proposes a new strategy for coupling variable-valence transition metal ions with carbon-rich carbon nitride to prepare photoanode materials with wide spectral response, efficient charge transport and separation, and strong oxidation ability, providing a basis for constructing a highly sensitive and highly stable PFC self-powered sensing system.

[0027] 3) Compared with the traditional detection method that relies on large instruments, the PFC self-powered sensor for heavy metal ions in water proposed in this invention has the characteristics of higher detection sensitivity and stability, simpler instruments and equipment, and low cost.

[0028] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0030] Figure 1Transmission electron microscopy (TEM, a) and spherical aberration-corrected high-angle annular dark field-scanning transmission electron microscopy (AC HADDF-STEM, b) images of W-CN-C materials.

[0031] Figure 2 is the X-ray diffraction (XRD) pattern of the material, where a is CN, b is CN-C, c is W-CN, and d is W-CN-C.

[0032] Figure 3 This is the W 4f X-ray photoelectron spectroscopy (XPS) spectrum of the material, where a is W-CN and b is W-CN-C.

[0033] Figure 4 UV-visible diffuse reflectance spectra (DRS) of the materials, where a is CN, b is CN-C, c is W-CN, and d is W-CN-C.

[0034] Figure 5 Transient photocurrent response diagram of the photoanode material, where a is CN / ITO, b is CN-C / ITO, c is W-CN / ITO, and d is W-CN-C / ITO.

[0035] Figure 6 Linear sweep voltammetry (LSV) curves of the photoanode materials, where a is CN / ITO, b is CN-C / ITO, c is W-CN / ITO, and d is W-CN-C / ITO.

[0036] Figure 7 ΔE of different photoanode-based PFC self-powered systems ocp Figure, where a is CN / ITO, b is CN-C / ITO, c is W-CN / ITO, and d is W-CN-C / ITO.

[0037] Figure 8 E of different photoanode-based PFC self-powered sensing systems ocp -Time curve diagram, where a is ITO, b is W-CN-C / ITO, c is apt / W-CN-C / ITO, and d is Cu 2+ / apt / W-CN-C / ITO.

[0038] Figure 9 Detecting Cu for PFC self-powered sensing system 2+ E ocp Figure, where a is the detection of different concentrations of Cu 2+ The resulting E ocp -Time curve diagram, b is Cu 2+ Logarithm of concentration and E ocp Working curve diagram.

[0039] Figure 10 This is the detection performance diagram of the PFC self-powered sensor system connected to the multimeter, where a is different Cu 2+ The pictures taken under the concentration, b is the output voltage and Cu 2+ a is a nonlinear relationship graph of concentration, c is a linear relationship graph. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] The terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the invention. The singular forms "a," "the," and "the" used in this invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0042] It should be understood that although the terms "first", "second", "third", etc. may be used to describe various information in the present invention, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0043] Photocatalytic fuel cell (PFC) self-powered electrochemical sensor has the advantages of easy integration and miniaturization of detection devices, and can be used to develop on-site detection systems for heavy metal ions in environmental water bodies. It uses the open circuit voltage or power density generated by the spontaneous redox reaction at the two poles (anode and cathode) in the PFC as a detection signal. The interaction between the target and the electrode surface can cause a change in the detection signal, thereby realizing the detection of the target. The inventors of this application consider applying PFCs self-powered sensors to the detection of metal ions. The primary difficulty that needs to be overcome in the application is the design of photoanode materials with excellent photoelectric conversion efficiency. Therefore, the inventors designed active materials with high photoelectric conversion efficiency and stable response signals as photoanodes to develop highly sensitive and stable PFC self-powered sensing systems for heavy metal ions.

[0044] An embodiment of the present invention provides a method for preparing a W-CN-C photoelectric active material, which comprises:

[0045] Step a1), self-assembling a nitrogen source and a carbon source by mechanical ball milling to form an intermediate, and then calcining for the first time to obtain an mtCN material; the nitrogen source is melamine, urea or dicyandiamide, and the carbon source is glucose, chitosan or locust bean gum;

[0046] Step a2), dispersing the mtCN material in a mixed solvent, adding a Na2WO4·2H2O solution dropwise under heating conditions, and centrifuging, washing, and drying after the reaction to obtain a precursor; the mixed solvent is a mixed solvent of deionized water, anhydrous ethanol, and glycerol;

[0047] Step a3), calcining the precursor for the second time under an inert gas atmosphere to obtain a W-CN-C photoelectric active material.

[0048] In the above preparation method, step a1) is the step of preparing the porous carbonitride mtCN by ball milling and calcination. Specifically, the nitrogen source is selected from melamine, urea, or dicyandiamide, and the carbon source is selected from glucose, chitosan, or locust bean gum. The nitrogen source and carbon source are mixed by mechanical ball milling and self-assembled into an intermediate. The intermediate is then calcined. The high-temperature calcination decomposes the organic matter and forms a stable CN covalent bond network structure.

[0049] In this step, the mass ratio of the nitrogen source to the carbon source is preferably (1000-4000):(2-100); most preferably, the mass ratio of the nitrogen source to the carbon source is 100:1. The nitrogen source is most preferably melamine, and the carbon source is chitosan. The mechanical milling time is preferably 20-60 minutes, more preferably 30 minutes. The temperature of the first calcination is 400-700°C, the heating rate is 2-5°C / min, and the calcination time is 2-6 hours. More preferably, the temperature of the first calcination is 550°C, the heating rate is 2.5°C / min, and the calcination time is 4 hours.

[0050] Step a2) is a step for preparing a W-CN-C photoelectric active material precursor. Specifically, the mtCN material is first dispersed in a mixed solvent, which is composed of deionized water, anhydrous ethanol and glycerol, wherein ethanol and glycerol are used as reducing agents. The ratio of deionized water, ethanol and glycerol in the mixed solvent is preferably 1-3:0.5-1.5:1, more preferably 2:1-1.5:1. After uniform dispersion, Na2WO4·2H2O solution is added dropwise, and ethanol and glycerol are used as reducing agents to reduce WO4 2- W in 6+ Partially restored to W 5+ , forming W 6+ / W 5+The redox pair is beneficial to the storage and transmission of electrons, providing a precursor for W doping. After centrifugation and washing, the unadsorbed free WO4 2- Ions and solvent residues are removed to ensure the purity of the precursor, and the precursor is obtained after drying.

[0051] As a preferred embodiment of this step, the concentration of the Na2WO4·2H2O solution is 0.05-0.2 mM, and the mass-to-volume ratio of the mtCN material to the Na2WO4·2H2O solution is 0.05-0.2 g:5 mL. Most preferably, the concentration of the Na2WO4·2H2O solution is 0.1 mM, and the mass-to-volume ratio of the mtCN material to the Na2WO4·2H2O solution is 0.1 g:5 mL.

[0052] The heating temperature is preferably 80-95°C, most preferably 90°C. Heating is preferably performed in an oil bath. Furthermore, to ensure uniform W doping, this step is specifically as follows: the mtCN material is dispersed in a mixed solvent and stirred in an oil bath for 1-3 hours; the Na2WO4·2H2O solution is added dropwise and stirred in the oil bath for 6-9 hours; the mixture is then cooled, and the resulting reaction mixture is centrifuged, washed, and dried in sequence to obtain a precursor. Washing is preferably performed 1-3 times with water and 1-3 times with anhydrous ethanol respectively; drying is preferably performed under vacuum to prevent material agglomeration and maintain a porous structure.

[0053] Step a3) is to calcine the precursor to prepare W-CN-C photoelectric active material. 2- Restored to W 6+ or W 5+ , doped into the CN skeleton to form WC / N chemical bonds, construct W-CN-C, and improve the photoelectric performance. Calcination is carried out under inert protection to prevent the W species from being oxidized. The inert gas atmosphere can be an Ar atmosphere. In this step, the temperature of the second calcination is preferably 400-600°C, the heating rate is preferably 2-5°C / min, and the calcination time is preferably 1-4h. Most preferably, the temperature of the second calcination is 500°C, the heating rate is 5°C / min, and the calcination time is 2h.

[0054] The preparation method provided in this embodiment is intended to design W 6+ / W 5+ Doping carbon-rich carbon nitride (W-CN-C) photoelectric active materials, using it as a photoanode to construct a PFC with high output signal, thereby developing a highly sensitive and highly stable PFC self-powered sensing system for heavy metal ions. The carbon-rich structure significantly broadens the visible light absorption range of the W-CN-C material and enhances the light utilization efficiency. 6+ / W 5+The redox couple acts as an electron transport channel, accelerating directional electron transfer. The synergistic effect of the two increases the open-circuit voltage of the PFC. Aptamers that specifically recognize heavy metal ions are introduced onto the photoanode surface, forming a sensing interface. The steric effect of the heavy metal ion-aptamer complex causes a change in the detection signal, resulting in a self-powered sensing system with high sensitivity and stability.

[0055] Another embodiment of the present invention further provides a W-CN-C photoelectric active material, which is prepared by the method of the aforementioned embodiment. The specific implementation method is the same and will not be repeated here.

[0056] Another embodiment of the present invention provides a method for preparing a heavy metal ion self-powered sensor, comprising:

[0057] Step b1), dispersing the W-CN-C photoelectric active material in deionized water, adding naphthol solution, and uniformly dispersing by ultrasonication to obtain a suspension;

[0058] Step b2), applying the suspension dropwise to the surface of ITO conductive glass to obtain a W-CN-C / ITO electrode;

[0059] Step b3), drop-coating the heavy metal ion aptamer solution on the surface of the W-CN-C / ITO electrode and incubating to obtain the apt / W-CN-C / ITO photoanode, i.e., the heavy metal ion self-powered sensor.

[0060] In the above preparation method, step b1) is the step of uniformly dispersing the W-CN-C photoelectrically active material. In this step, ultrasonic dispersion is used to improve dispersion uniformity. The strong impact force generated by ultrasonic vibrations causes the W-CN-C particles to repeatedly interact with the solvent, thereby rapidly dispersing. Naphthol acts as a binder to stably fix the W-CN-C material to the electrode surface, preventing material shedding during testing. This step produces a stable and uniform suspension, facilitating subsequent electrode modification.

[0061] In this step, preferably, the amount of the naphthol solution used is 1 / 30 to 1 / 20 of the amount of deionized water, and the concentration of the naphthol solution is 0.3-0.6 wt %. More preferably, the amount of the naphthol solution used is 1 / 25 of the amount of deionized water, and the concentration of the naphthol solution is 0.5 wt %. The concentration of the W-CN-C photoelectrically active material in the resulting suspension is preferably 1.0 to 5.0 mg / mL, more preferably 1.0 mg / mL.

[0062] Step a2) is the step of forming a uniform W-CN-C active layer on the ITO surface by drop coating to ensure effective light absorption and charge transfer of the photoanode. ITO acts as a transparent conductive substrate, providing electron transport channels and supporting the active material. In this step, the drop coating amount of the suspension is preferably 90-120 μL / 1 cm2 , the most preferred is 100 μL / 1 cm 2 After the suspension is drop-coated, it is preferably dried with an infrared lamp. Infrared heat radiation promotes the rapid evaporation of deionized water and naphthol solvent, forming a dense and firmly bonded film, thus obtaining a W-CN-C / ITO electrode.

[0063] Step b3) is the step of dripping heavy metal ion aptamers on the surface of W-CN-C / ITO electrode to construct the dripping step of heavy metal ion aptamer solution. The heavy metal ion aptamer is fixed on the surface of W-CN-C to form an active interface that can recognize heavy metal ions. The aptamer selectively binds to the target heavy metal ion through the base sequence; after binding, it triggers the change of the electronic state of the W-CN-C surface, affecting the photocurrent signal. In this step, the heavy metal ion aptamer solution can be Cu 2+ Aptamer, Zn 2+ Aptamer or Pb 2 + Aptamer solution; specifically:

[0064] Cu 2+ The sequence of the aptamer can be 5'-ATC GCG ATA TTT TCT GTA GCG ATT CTT GTTTGAGCG CTC GGT ACG AAC AGA-3';

[0065] Zn 2+ The aptamer sequence number can be 5'-GCATC AGTTA GTCAT TACGC TTACG GCGGC TCTATCCTAACTGAT ATATT GTGAAGTCGT GTCCC-3';

[0066] Pb 2+ The aptamer sequence number may be ggTTggTgTggTTgg.

[0067] The concentration of the heavy metal ion aptamer solution is preferably 0.3-1.5 μM, more preferably 0.5-1.0 μM, and most preferably 0.8 μM; the amount of the heavy metal ion aptamer solution dropwise applied is preferably 8-12 μL / 1 cm 2 , the most preferred is 10 μL / 1 cm 2 The incubation can be carried out at room temperature, and the incubation time is preferably 6 to 18 hours, more preferably 10 to 15 hours, and most preferably 12 hours. After incubation, the steps of rinsing with a phosphate buffer solution and drying at room temperature are preferably included, ultimately obtaining a heavy metal ion self-powered sensor.

[0068] Another embodiment of the present invention further provides a heavy metal ion self-powered sensor, which is prepared according to the method of the above embodiment. The specific implementation is the same and will not be repeated here.

[0069] Another embodiment of the present invention further provides an application of the above-mentioned heavy metal ion self-powered sensor in detecting heavy metal ions. The application may specifically include:

[0070] Step c1), establish a standard curve

[0071] The heavy metal ion M n+ A standard droplet of known concentration is applied to the surface of the heavy metal ion self-powered sensor, and then dried, rinsed and aired to obtain a standard M n+ / apt / W-CN-C / ITO electrode;

[0072] According to the standard M n+ A standard PFC self-powered sensing system was constructed using the / apt / W-CN-C / ITO electrode as the working electrode, the Pt@C-modified glassy carbon electrode as the reference or counter electrode, and phosphate buffer as the electrolyte.

[0073] By testing the open circuit voltage-time curve of the standard PFC self-powered sensing system, the heavy metal ion concentration and E ocp The corresponding relationship is obtained, and then the standard curve of heavy metal ions is obtained;

[0074] Step c2), determining the heavy metal concentration of the test solution

[0075] The test liquid is applied to the surface of the heavy metal ion self-powered sensor, and then dried, rinsed and aired to obtain the test liquid. n+ / apt / W-CN-C / ITO electrode;

[0076] With the test M n+ A PFC self-powered sensing system was constructed using the / apt / W-CN-C / ITO electrode as the working electrode, a Pt@C-modified glassy carbon electrode as the reference electrode, and phosphate buffer as the electrolyte.

[0077] The open circuit voltage-time curve of the test PFC self-powered sensor system is tested, the open circuit voltage is brought into the standard curve of the heavy metal ions, and the concentration of the heavy metal ions in the test solution is calculated.

[0078] Preferably, in step c1), the heavy metal ion M in the standard solution n+ The concentration is preferably 1pM to 2500nM; the standard solution dosage is preferably 10 to 20μL / 1cm 2 The metal ion is preferably Cu 2+ 、Zn 2+ or Pb 2+ .

[0079] In step c2), the amount of the test solution to be applied is 10-20 μL / 1 cm2 .

[0080] In the above steps, the concentration of the phosphate buffer is preferably 0.1 M and the pH is 7.

[0081] The W-CN-C photoelectrically active material and heavy metal ion self-powered sensor provided by the embodiments of the present invention have the following advantages:

[0082] 1) The carbon-rich structure significantly broadens the visible light absorption range of W-CN-C materials and enhances light utilization. 6+ / W 5+ The redox couple acts as an electron transport channel, accelerating the directional transfer of electrons. The synergistic effect of the two increases the open-circuit voltage of the PFC. Aptamers that specifically recognize heavy metal ions are introduced onto the surface of the photoanode, forming a sensing interface. The steric effect of the heavy metal ion-aptamer complex causes a change in the detection signal, resulting in a self-powered sensing system with high sensitivity and stability. By constructing a PFC with a high output signal using W-CN-C material as the photoanode, a highly sensitive and stable PFC self-powered sensing system for heavy metal ions can be developed.

[0083] 2) The present invention proposes a new strategy for coupling variable-valence transition metal ions with carbon-rich carbon nitride to prepare photoanode materials with wide spectral response, efficient charge transport and separation, and strong oxidation ability, providing a basis for constructing a highly sensitive and highly stable PFC self-powered sensing system.

[0084] 3) Compared with the traditional detection method that relies on large instruments, the PFC self-powered sensor for heavy metal ions in water proposed in the present invention has the characteristics of higher detection sensitivity and stability, simpler instruments and equipment, and low cost.

[0085] The technical solution of the present invention will be further described below in conjunction with specific embodiments:

[0086] Comparative Example 1—Preparation of CN Material

[0087] Melamine (2 g) was placed in a muffle furnace, heated to 550°C at a heating rate of 2.5°C / min, and kept warm for 4 hours. After cooling, the sample was collected and ground into powder to obtain CN-bulk. CN-bulk (100 mg) was dispersed in a mixed solvent of deionized water (20 mL), anhydrous ethanol (10 mL) and glycerol (10 mL) and stirred in a 90°C oil bath for 9 hours. The cooled solution was centrifuged, washed three times with water and anhydrous ethanol each, and vacuum dried to obtain a precursor. The dried precursor (50 mg) was placed in a tubular furnace under an Ar atmosphere and heated to 500°C at a rate of 5°C / min and kept warm for 2 hours. After cooling, the sample was collected and recorded as CN.

[0088] Comparative Example 2—Preparation of CN-C Material

[0089] Melamine (2.0 g) and chitosan (20 mg) were mixed in a nylon ball mill and mechanically milled for 30 minutes to form a supramolecular intermediate. The intermediate powder was then calcined in a muffle furnace at 550°C at a heating rate of 2.5°C / min for 4 hours. mtCN was obtained after cooling. mtCN (100 mg) was dispersed in a mixture of deionized water (20 mL), anhydrous ethanol (10 mL), and glycerol (10 mL) and stirred in a 90°C oil bath for 9 hours. After cooling, the solution was centrifuged, washed three times with water and three times with anhydrous ethanol, and vacuum-dried to obtain the precursor. The dried precursor (50 mg) was heated to 500°C in a tube furnace under an Ar atmosphere at a rate of 5°C / min and held at that temperature for 2 hours. After cooling, a sample was collected and designated CN-C.

[0090] Comparative Example 3—Preparation of W-CN Material

[0091] Melamine (2 g) was placed in a muffle furnace and heated to 550°C at a rate of 2.5°C / min, where it was held for 4 hours. After cooling, the sample was collected and ground into a powder to produce CN-bulk. CN-bulk (100 mg) was dispersed in a mixed solvent of deionized water (20 mL), anhydrous ethanol (10 mL), and glycerol (10 mL) and stirred in a 90°C oil bath for 3 hours. Na2WO4·2H2O solution (0.1 mM, 5 mL) was added dropwise to the mixture, and stirring continued in a 90°C oil bath for 6 hours. The cooled solution was centrifuged, washed three times with water and alcohol, and vacuum dried to obtain the precursor. The dried precursor (50 mg) was placed in a tube furnace under an Ar atmosphere and heated to 500°C at a rate of 5°C / min, where it was held for 2 hours. After cooling, the sample was collected and designated W-CN.

[0092] Example 1 Preparation of W-CN-C Photoelectric Active Material

[0093] Melamine (2.0 g) and chitosan (20 mg) were mixed in a nylon ball mill and mechanically milled for 30 minutes to form an intermediate. The intermediate powder was then placed in a crucible and calcined in a muffle furnace at 550°C at a heating rate of 2.5°C / min for 4 hours. mtCN (100 mg) was dispersed in a mixture of deionized water (20 mL), anhydrous ethanol (10 mL), and glycerol (10 mL) and stirred in a 90°C oil bath for 3 hours. A 0.1 mM Na₂WO₄·2H₂O solution (5 mL) was added dropwise to the mixture, and stirring continued in a 90°C oil bath for 6 hours. After cooling, the solution was centrifuged, washed three times with water and three times with anhydrous ethanol, and dried under vacuum to obtain the precursor. The dried precursor (50 mg) was placed in a tube furnace under an Ar atmosphere and heated to 500°C at a rate of 5°C / min and held at that temperature for 2 h. After cooling, the sample was collected and recorded as W-CN-C.

[0094] Figure 1 Transmission electron microscopy (TEM, a) and spherical aberration-corrected high-angle annular dark field-scanning transmission electron microscopy (AC HADDF-STEM, b) images of the W-CN-C material. Figure 1a shows that the W-CN-C exhibits a flaky structure, and no particles of other W species are observed on the surface of the lamellae, suggesting that W may be doped in the form of ions. Figure 1b clearly shows a large number of bright spots. These isolated bright spots are atomically dispersed W sites, suggesting that W ions are dispersed as single atoms on the lamellae surface.

[0095] Figure 2 The X-ray diffraction (XRD) patterns of the materials, where a is CN, b is CN-C, c is W-CN, and d is W-CN-C. Compared with CN and W-CN, the peak intensities of the two peaks corresponding to the (100) and (002) planes of CN-C and W-CN-C are significantly reduced. And the (100) plane of CN-C and W-CN-C shifts to a small angle, indicating that the introduction of a carbon-rich structure leads to an increase in the distance between repeating units in the heptazine ring plane. Compared with CN and CN-C, the peak of (002) in W-CN and W-CN-C shifts slightly to a high angle, which indicates that W 6+ / W 5+ Doping reduces the interlayer spacing of the heptazine rings.

[0096] Figure 3 The W 4f X-ray photoelectron spectroscopy (XPS) spectra of the materials are shown in Figure 2, where a is W-CN and b is W-CN-C. The W 4f XPS spectra of W-CN and W-CN-C are fitted with four peaks, and the two peaks at 37.7eV and 35.2eV correspond to W 6+ 4f 5 / 2 and W 6+ 4f 7 / 2 The peaks at 36.6eV and 34.7eV correspond to W 5+ 4f 5 / 2 and W 5+ 4f 7 / 2 Orbital. Ethanol and glycerol act as reducing agents to convert WO4 2- W in 6+ Partially restored to W 5+ , forming W 6+ / W 5+ Redox pairs facilitate the storage and transport of electrons.

[0097] Figure 4 The UV-visible diffuse reflectance spectra (DRS) of the materials are shown in Figure 1, where a is CN, b is CN-C, c is W-CN, and d is W-CN-C. Compared with CN, the light absorption of W-CN in the UV region is significantly enhanced, while the absorption in the visible region is almost unchanged, indicating that W 6+ / W 5 + Doping can enhance the light utilization efficiency of W-CN in the ultraviolet region. Compared with CN, CN-C shows enhanced visible light utilization and a broadened absorption edge, which is related to the significant enhancement of the visible light absorption ability of CN-C by the carbon-rich structure. Compared with CN-C and W-CN, WCN-C shows a significantly improved ability to capture ultraviolet and visible light. The carbon-rich structure introduces and W 6+ / W 5+ Doping synergistically enhances the light utilization efficiency of W-CN-C.

[0098] Example 2—Preparation of modified ITO photoanode

[0099] The ITO conductive glass was ultrasonically cleaned in anhydrous ethanol for half an hour and then dried for later use.

[0100] A 1.0 mg / mL dispersion of W-CN-C (Example 1) was prepared using deionized water as the solvent. A 0.5 wt% naphthol solution (40 μL, 1 / 25 of the volume of deionized water) was added dropwise to the dispersion. The dispersion was then placed in an ultrasonicator for dispersion to obtain a stable and uniform suspension.

[0101] 100 μL of the suspension was transferred and applied to the ITO (fixed area of ​​1×1 cm 2 ) conductive glass surface and dried under infrared lamp for 30 minutes. The prepared electrode was named W-CN-C / ITO.

[0102] The same method was used, except that W-CN-C was replaced by the CN material, CN-C material and W-CN material prepared in Comparative Examples 1-3, respectively. The obtained electrodes were recorded as CN / ITO, CN-C / ITO and W-CN / ITO, respectively.

[0103] Use a pipette to remove Cu 2+ The aptamer solution (10 μL, 0.8 μM concentration, purchased from Sangon Biotech (Shanghai) Co., Ltd., sequence: 5'-ATC GCG ATA TTT TCT GTAGCG ATT CTT GTT TGAGCG CTCGGT ACG AAC AGA-3') was drop-coated onto the surface of the W-CN-C / ITO electrode and dried at room temperature for 12 h. The unanchored aptamer was rinsed with phosphate buffer and dried at room temperature. The prepared electrode was designated as apt / W-CN-C / ITO.

[0104] Take 10 μL Cu 2+ The solutions with concentrations of 0, 0.02, 0.05, 0.1, 0.3, 0.5, 0.8, 3, 10, 20, 40, 70, 120, 320, 520, 920, 1420, and 1920 nM were drop-coated on apt / W-CN-C / ITO (fixed area of ​​1 × 1 cm 2 ) on the electrode surface, dried naturally at room temperature, rinsed with phosphate buffer solution, and dried at room temperature. 2+ / apt / W-CN-C / ITO.

[0105]

Photoelectrochemical detection

[0106] Instrument: CHI660E electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd.)

[0107] The excitation light source was a 300W xenon lamp (PLS-SXE300, Beijing Perfect Light Technology Co., Ltd., wavelength range 320-780 nm). All electrochemical experiments were performed at room temperature in phosphate buffer (0.1 M, pH 7) without applying any bias voltage.

[0108] PFC self-powered sensing system: The modified ITO photoanode prepared in Example 2 was used as the working electrode, and a Pt@C dispersion (5 mg Pt@C dispersed in 500 μL water, 500 μL anhydrous ethanol, and 40 μL 5 wt% naphthol) was modified to a glassy carbon electrode (5 μL, Pt@C / GCE) as a reference or counter electrode to form a two-electrode system in a single quartz electrolytic cell.

[0109] Three-electrode system: The three-electrode system consists of the modified ITO photoanode prepared in Example 2 as the working electrode, a Pt wire counter electrode and a saturated Ag / AgCl reference electrode.

[0110] Test results:

[0111] Figure 5Figure 2 is the transient photocurrent response diagram of the photoanode material, where a is CN / ITO, b is CN-C / ITO, c is W-CN / ITO, and d is W-CN-C / ITO. In the three-electrode system, the photoelectric response ability of the prepared electrodes was investigated respectively. The current density difference (ΔI=I light -I dark , where I light and I dark represents the current density under light and darkness respectively) and is 0.080 μA cm -2 , 0.34μAcm -2 , 0.20μAcm -2 and 0.73 μA cm -2 , proving that the carbon-rich structure is related to W 6+ / W 5+ Doping synergistically enhances the charge separation efficiency of W-CN-C.

[0112] Figure 6 The linear sweep voltammetry (LSV) curves of the photoanode materials are shown in Figure 1, where a is CN / ITO, b is CN-C / ITO, c is W-CN / ITO, and d is W-CN-C / ITO. In a three-electrode system, the photocatalytic oxidation performance of the prepared electrodes was investigated. Compared with CN / ITO, CN-C / ITO, and W-CN / ITO, W-CN-C / ITO has the highest current density under continuous light irradiation, proving that W 6+ / W 5+ Doping and carbon-rich structure can synergistically enhance the photoelectric conversion efficiency of W-CN-C materials and improve the kinetics of water oxidation reaction, so that this material can be used as a photoanode to construct a PFC self-powered system.

[0113] Figure 7 ΔE of different photoanode-based PFC self-powered systems ocp Figure 1 shows a CN / ITO, b CN-C / ITO, c W-CN / ITO, and d W-CN-C / ITO. The results show that the E of the self-powered systems based on CN / ITO, CN-C / ITO, W-CN / ITO and W-CN-C / ITO photoanodes are ocp Difference (ΔE ocp =E ocp,light -E ocp,dark , where E ocp,light and E ocp,dark Represents E under light and dark respectively ocp ) are 0.18V, 0.22V, 0.20V and 0.25V respectively, indicating that the carbon-rich structure introduces and W 6+ / W 5+Doping can synergistically amplify the E of PFC ocp Detecting signals is beneficial to building a highly sensitive PFC self-powered sensing system.

[0114] Figure 8 E of different photoanode-based PFC self-powered sensing systems ocp -Time curve diagram, where a is ITO, b is W-CN-C / ITO, c is apt / W-CN-C / ITO, and d is Cu 2+ / apt / W-CN-C / ITO. Through π-π conjugated interaction, Cu 2+ The aptamer was anchored to the surface of ITO / W-CN-C photoanode to construct a Cu- 2+ Compared with W-CN-C / ITO, the E ocp The decrease (0.35 V) is attributed to the presence of non-conductive aptamer molecules on the surface of the photoanode, which hinders the transfer of electrons to ITO. 2+ After incubation, the E ocp The value is reduced to 0.26 V. The Cu 2+ -aptamer complex loaded on the surface of the photoanode further hinders the directional transmission of electrons and is not conducive to the catalytic oxidation of water molecules to produce O2. ocp As a detection signal to build a PFC self-powered sensing system for detecting Cu 2+ .

[0115] Example 3 - Application of self-powered sensor in detecting heavy metal ions

[0116] Different concentrations of Cu 2+ Incubate on the surface of the constructed apt / W-CN-C / ITO electrode to explore the self-powered sensing system for Cu 2+ detection performance.

[0117] 1. Add 10 μL Cu 2+ Standard droplets of known concentrations (0, 0.02, 0.05, 0.1, 0.3, 0.5, 0.8, 3, 10, 20, 40, 70, 120, 320, 520, 920, 1420, and 1920 nM) were applied to the surface of the electrode apt / W-CN-C / ITO prepared in Example 2, and then dried, rinsed with phosphate buffer solution, and air-dried to obtain standard Cu 2+ / apt / W-CN-C / ITO electrode;

[0118] 2. Based on the standard Cu 2+A standard PFC self-powered sensing system was constructed using a / apt / W-CN-C / ITO electrode as the working electrode, a Pt@C dispersion (5 mg Pt@C dispersed in 500 μL water, 500 μL anhydrous ethanol, and 40 μL 5 wt% naphthol) modified onto a glassy carbon electrode (5 μL, Pt@C / GCE) as the reference or counter electrode, and phosphate buffer (0.1 M, pH 7) as the electrolyte.

[0119] By testing the open circuit voltage-time curve of the standard PFC self-powered sensing system, Cu 2+ Concentration and E ocp The corresponding relationship is obtained, and then the standard curve of heavy metal ions is obtained.

[0120] Figure 9 Detecting Cu for standard PFC self-powered sensing system 2+ E ocp Figure, where a is the detection of different concentrations of Cu 2+ The resulting E ocp -Time curve diagram, b is the Cu 2+ Logarithm of concentration and E ocp Working curve diagram. Figure 9 As shown in a, with Cu 2+ With the increase of concentration (0~1920nM), the E ocp Gradually decrease. Cu 2+ The logarithm of concentration and E ocp There is a linear relationship, and the linear equation is y=-43.982x+246.946( Figure 9 b), linear correlation coefficient (R 2 ) was 0.9963, the linear range was 0.02-920 nM, and the detection limit (3S / N) was calculated to be 7 pM.

[0121] To further evaluate the constructed sensing system for detecting Cu 2+ The portability of the sensor system is studied by using a digital multimeter as the signal output device. 2+ Analyze performance. Connect a multimeter to test the open circuit voltage of the standard PFC self-powered sensor system. Figure 10 This is the detection performance diagram of the PFC self-powered sensor system connected to the multimeter, where a is different Cu 2+ Concentration of the photograph, Cu 2+ The concentrations of Cu are 0, 0.25, 1, 10, 30, 50, 70, 100 and 130 nM, and b is the output voltage and Cu 2+ The nonlinear relationship diagram of concentration is shown in Figure 2, and c is the linear relationship diagram. 2+ When the concentration increases from 0 to 130nM, the output voltage of the multimeter gradually decreases ( Figure 10a and b). There is a linear relationship between the logarithm of the concentration and the output voltage, and the linear equation is y=51.157x+196.610( Figure 10 c, R 2 =0.9766), the linear range was 0.25-130 nM, and the detection limit was 84 pM, indicating that the constructed sensing system can realize the detection of Cu 2 + Portable detection.

[0122] While various embodiments of the present invention have been described above, the above descriptions are intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or improvements to existing technologies, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a W-CN-C photoelectric active material, characterized in that: include: Step a1), self-assembling the nitrogen source and the carbon source by mechanical ball milling to form an intermediate, and then calcining for the first time to obtain the mtCN material; The nitrogen source is melamine, urea or dicyandiamide, and the carbon source is glucose, chitosan or locust bean gum; Step a2), dispersing the mtCN material in a mixed solvent, adding a Na2WO4·2H2O solution dropwise under heating conditions, and centrifuging, washing, and drying after the reaction to obtain a precursor; the mixed solvent is a mixed solvent of deionized water, anhydrous ethanol, and glycerol; Step a3), calcining the precursor for the second time under an inert gas atmosphere to obtain a W-CN-C photoelectric active material.

2. The preparation method according to claim 1, characterized in that In the step a1), the mass ratio of the nitrogen source to the carbon source is (1000-4000): (2-100); and / or the temperature of the first calcination is 400-700°C, the heating rate is 2-5°C / min, and the calcination time is 2-6h.

3. The preparation method according to claim 1, characterized in that In the step a2), the concentration of the Na2WO4·2H2O solution is 0.05-0.2 mM, the mass volume ratio of the mtCN material to the Na2WO4·2H2O solution is 0.05-0.2 g:5 mL; the heating temperature is 80-95° C.; and / or, In the step a3), the second calcination temperature is 400-600° C., the heating rate is 2-5° C. / min, and the calcination time is 1-4 hours.

4. A W-CN-C photoelectric active material, characterized in that It is prepared according to the method according to any one of claims 1 to 3.

5. A method for preparing a heavy metal ion self-powered sensor, characterized in that: include: Step b1), dispersing the W-CN-C photoelectric active material according to claim 4 in deionized water, adding the naphthol solution, and uniformly dispersing by ultrasonication to obtain a suspension; Step b2), applying the suspension dropwise to the surface of ITO conductive glass to obtain a W-CN-C / ITO electrode; Step b3), drop-coating the heavy metal ion aptamer solution on the surface of the W-CN-C / ITO electrode and incubating to obtain the apt / W-CN-C / ITO photoanode, i.e., the heavy metal ion self-powered sensor.

6. The preparation according to claim 5, characterized in that In the step b1), the amount of the naphthol solution is 1 / 30 to 1 / 20 of that of deionized water, and the concentration of the naphthol solution is 0.3-0.6 wt %; the concentration of the W-CN-C photoelectric active material in the suspension is 1.0 to 5.0 mg / mL.

7. The preparation method according to claim 5, characterized in that In step b2), the drop amount of the suspension is 90-120 μL / 1 cm 2 .

8. The preparation method according to claim 5, characterized in that In the step b3), the heavy metal ion aptamer solution is Cu 2+ Aptamer, Zn 2+ Aptamer or Pb 2+ aptamer solution; The concentration of the heavy metal ion aptamer solution is 0.3-1.5 μM, and the amount of the heavy metal ion aptamer solution dropped is 8-12 μL / 1 cm 2 ; The incubation time is 6 to 18 hours.

9. A heavy metal ion self-powered sensor, characterized in that: It is prepared according to the method according to any one of claims 5 to 8.

10. Use of the heavy metal ion self-powered sensor according to claim 9 and claim 1 in detecting heavy metal ions.

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