Bismuth oxide core-shell nanoparticle modified porous defect-rich carbon nitride material as well as preparation method and application thereof

Abstract

The invention relates to a bismuth oxide core-shell nanoparticle modified porous defect-rich carbon nitride material as well as a preparation method and application thereof. The method comprises the following steps: calcining urea in an air atmosphere to obtain the bismuth oxide core-shell nanoparticle modified porous defect-rich carbon nitride material; calcining in an atmosphere to obtain porous defect-rich carbon nitride; mixing an ethylene glycol liquid, a nitric acid solution, polyvinylpyrrolidone and the solid at room temperature to obtain a mixed solution, placing the mixed solution in a reaction kettle, carrying out water bath heating to generate a precipitate, filtering out the precipitate, and cleaning, drying and grinding the precipitate to obtain a powdery solid, the bismuth oxide core-shell nanoparticle modified porous defect-rich carbon nitride material is obtained. The material prepared by the invention is high in response capability to the sum.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of nanomaterial electrochemical sensing technology, in particular to a bismuth-bismuth oxide core-shell nanoparticle modified porous defect-rich carbon nitride material, a preparation method and applications thereof. BACKGROUND

[0002] Heavy metal pollution has become one of the global environmental problems, especially under the background of accelerating industrialization and urbanization, its threat to the ecological environment and human health is increasingly serious. Heavy metal ions (HMI) exist widely in water, soil and organisms, and the sources include cosmetics and their by-products, fertilizers, industrial emissions and household waste, etc. Because of the non-degradability and bioaccumulation of HMI, they can long-term enrichment in the organism and cause serious damage to the nervous, immune, reproductive and digestive systems. For example, lead ( ) can cause damage to the nervous system, and cadmium ( ) is closely related to kidney disease. Once these ions enter the environment, they can persist in nature for decades or even hundreds of years, are difficult to be biodegraded, and are enriched in the biosphere layer by layer, eventually affecting human health. Therefore, it is of great significance to establish a detection technology with high sensitivity and high selectivity to realize the accurate analysis of trace HMI (ppb level) in complex matrices such as blood, serum, saliva and water body, for environmental monitoring and public health safety.

[0003] Electrochemical detection technology has shown broad application prospects in the field of HMI analysis due to its high sensitivity, fast detection speed, simple operation, low cost and suitability for in-situ and real-time monitoring. By optimizing the composition and structure of the electrode material, the detection sensitivity of the electrochemical sensor can be effectively improved. At present, bismuth-based materials have become an important research direction for HMI electrochemical detection due to their excellent electrochemical performance, environmental friendliness and good complexation with heavy metal ions. In recent years, electrochemical sensors based on two-dimensional nanomaterials have attracted much attention due to their unique electronic structure and excellent electrocatalytic activity. Among them, graphitic carbon nitride ( ) is considered as a potential electrode modification material due to its semiconductor properties, good chemical stability and rich nitrogen active sites. However, the existing electrode material preparation methods and the electrode materials prepared by the methods have low response ability to and , i.e. low detection sensitivity, so it is necessary to design an electrode material and a preparation method to improve the sensitivity of the electrode material to the detection of heavy metal ions and . SUMMARY

[0004] Therefore, it is necessary to address the existing electrode material preparation methods and the effects of the prepared electrode materials on... and To address the issue of low responsiveness, this paper provides a method for preparing porous, defect-rich carbon nitride materials modified with bismuth oxide core-shell nanoparticles, along with their applications.

[0005] To solve the above problems, the present disclosure adopts the following technical solution: In a first aspect, this disclosure provides a method for preparing porous, defect-rich carbon nitride materials modified with bismuth oxide core-shell nanoparticles, comprising: Step 1: Calcining urea in air atmosphere, followed by grinding into granules to obtain graphitic carbon nitride. ; Step 2, in In the atmosphere, for Calcination yields porous, defect-rich carbon nitride. ; Step 3: At room temperature, combine ethylene glycol liquid, nitric acid solution, polyvinylpyrrolidone, solids and The mixture is then placed in a reaction vessel and heated in a water bath to generate a precipitate. The precipitate is filtered out, washed, dried, and ground to obtain a powder. Solid, namely, bismuth oxide core-shell nanoparticles modified into porous, defect-rich carbon nitride materials.

[0006] In a preferred embodiment, the heating rate of calcination in step 1 is 8~12℃ / min, and the holding temperature is 520~580℃. In a preferred embodiment, the calcination temperature in step 2 is set to 520~580℃, the calcination heating rate is 4.5~5.5℃ / min, and the calcination time is 3.5~4.5 h.

[0007] In a preferred embodiment, the nitric acid solution concentration is 0.9~1.1 mol / L, and polyvinylpyrrolidone and The weight ratio of the solids ranges from 1.58 to 1.72. The preferred weight ratio of the element to Bi is 0.44 to 0.47; the water bath heating is performed at 155 to 165°C for 15 to 17 hours.

[0008] In a preferred embodiment, step 4 is further included, which involves taking the powdered... The solid is dissolved in an aqueous ethanol solution with a concentration of 74%–76% to obtain... Solution, in solution The concentration is 4~6 mg / ml, using Solution preparation membrane.

[0009] In a preferred embodiment, the calcination heating rate in step 1 is 10℃ / min, the holding temperature is 550℃, and the holding time is 2h; the calcination temperature in step 2 is set to 550℃, the heating rate is 5℃ / min, and the calcination time is 4h; the concentration of the nitric acid solution is 1.0 mol / L, and the polyvinylpyrrolidone... solid and The weight ratio is 300:182:35; the water bath heating is performed at 160°C for 16 hours, and the drying is performed at 70°C for 12-24 hours; in step 4, the concentration of the ethanol-water solution is 75%. in solution The concentration is 5 mg / ml.

[0010] Secondly, this disclosure provides a bismuth oxide core-shell nanoparticle modified porous defect-rich carbon nitride material prepared using the preparation method of the bismuth oxide core-shell nanoparticle modified porous defect-rich carbon nitride material described in the first aspect.

[0011] Thirdly, this disclosure provides the application of bismuth oxide core-shell nanoparticle-modified porous defect-rich carbon nitride materials as described in the second aspect in the detection of lead and / or cadmium in water or soil.

[0012] Fourthly, this disclosure provides an electrochemical sensor, wherein the electrode material of the electrochemical sensor includes a bismuth oxide core-shell nanoparticle modified porous defect-rich carbon nitride material prepared by the preparation method of the bismuth oxide core-shell nanoparticle modified porous defect-rich carbon nitride material described in the first aspect.

[0013] The above describes a method for preparing porous, defect-rich carbon nitride material modified with bismuth oxide core-shell nanoparticles, and its applications. The method utilizes low-cost urea as a precursor in the synthesis. Secondary calcination of carbon nitride can effectively improve electron mobility and conductivity, thereby optimizing the electrocatalytic activity of electrode materials; hydrothermal method In having a ribbon-like structure In-situ surface growth was achieved Uniform surface modification of the material makes it difficult for bismuth oxide core-shell nanoparticles to accumulate, resulting in a high specific surface area that facilitates the exposure of catalytically active sites. It has outstanding lead-cadmium ion responsiveness, based on It can rapidly and stably detect lead and cadmium ions in water, soil, etc. Attached Figure Description

[0014] Figure 1This is a schematic flowchart of a method for preparing porous, defect-rich carbon nitride materials modified with bismuth oxide core-shell nanoparticles disclosed herein. Figure 2 for , Comparison chart of stripping current at different scales; Figure 3 For this disclosure , and SEM image; Figure 4 X-ray diffraction pattern; Figure 5 for Figure 4 A magnified view of a portion of the image; Figure 6 This is a Fourier transform infrared spectrum; Figure 7 This is an adsorption isotherm diagram; Figure 8 for , The 1s carbon spectrum of C in XPS; Figure 9 for , N 1s spectrum in XPS; Figure 10 for , Bi 4f spectrum of XPS; Figure 11 for , , , , For two heavy metal ions , Response comparison chart; Figure 12 for right , Current-potential curve; Figure 13 for right , A scatter plot showing the relationship between current and concentration; Figure 14 for Stability plot in multiple cycles; Figure 15 for In seawater , Current-potential curve; Figure 16 for In seawater , Scatter plot of current versus concentration. Detailed Implementation

[0015] The technical solutions of this disclosure will now be described in detail with reference to the accompanying drawings and preferred embodiments.

[0016] See Figure 1 This disclosure provides a method for preparing porous, defect-rich carbon nitride materials modified with bismuth oxide core-shell nanoparticles, comprising: Step 1: Calcining urea in air atmosphere, followed by grinding into granules to obtain graphitic carbon nitride. ; Step 2, in In the atmosphere, for Calcination yields porous, defect-rich carbon nitride. ; Step 3: At room temperature, combine ethylene glycol liquid, nitric acid solution, polyvinylpyrrolidone, solids and The mixture is then placed in a reaction vessel and heated in a water bath to generate a precipitate. The precipitate is filtered out, washed, dried, and ground to obtain a powder. Solid, namely, bismuth oxide core-shell nanoparticles modified into porous, defect-rich carbon nitride materials.

[0017] The bismuth oxide core-shell nanoparticle-modified porous defect-rich carbon nitride material is the electrode material prepared in this embodiment.

[0018] In this embodiment, step 1 specifically includes: A muffle furnace is used, with a heating rate of 8~12℃ / min, a holding temperature of 520~580℃, and a holding time of approximately 2 hours. Preferably, the heating rate is 10℃ / min, the holding temperature is 550℃, and the holding time is 2 hours, that is, heating to 550℃ and then holding at that temperature for 2 hours.

[0019] Specifically, urea is calcined in a muffle furnace under air atmosphere, heated to 550℃ at a heating rate of 10℃ / min and held at that temperature for 2 hours to obtain a yellow flocculent solid. This yellow flocculent solid is then ground into particles at room temperature under air atmosphere to obtain graphitic carbon nitride, denoted as […]. .

[0020] In this embodiment, step 2 specifically includes: Will The sample is calcined in a tube furnace at a temperature of 520–580°C, preferably 550°C; the heating rate is 4.5–5.5°C / min, preferably 5°C / min; and the calcination time is controlled within the range of 3.5–4.5 h, preferably 4 h. Nitrogen gas is required during the calcination process to prevent… Excessive oxidation. Step 2 yields porous, defect-rich carbon nitride. .

[0021] In this embodiment, step 3 specifically includes: The nitric acid solution concentration is 0.9-1.1 mol / L, preferably 1 mol / L. In one embodiment, polyvinylpyrrolidone, The weight ratio of the solids ranges from (59~61):(35.4~37.4), i.e., 1.58~1.72. Preferably, polyvinylpyrrolidone... solid and The weight ratio is 300:182:35.

[0022] In one specific embodiment, a 100 ppb Cd(II) and Pb(II) solution was used, with the bismuth loading fixed at 156 mg (precursor: Under the conditions of ), the results were evaluated by SWASV (square wave anodic stripping voltammetry). The effect of composite material ratio. With As the concentration increased from 30 mg to 70 mg, the stripping current gradually increased, indicating that more active sites are beneficial for ion enrichment and deposition; however, when... When the concentration was further increased to 110 mg, the current decreased instead, which may be due to agglomeration on the electrode surface, impaired electron transfer, or limited mass transport; see also Figure 2 The horizontal axis represents Add quality. The mass added is represented on the ordinate, with the current on the ordinate. Further, more specific experiments were conducted. The preferred content range is 68.7~73.4 mg. The preferred weight ratio of the compound to Bi is 0.44 to 0.47. In this embodiment, a composite ratio of approximately 0.45 (70 mg) was selected. (156 mg of Bi element).

[0023] Water bath heating produces a precipitate, which is the product. The product is filtered out of the solution, washed, dried, and then ground into powder. solid.

[0024] The water bath heating is performed at 155~165℃ for 15~17 hours, preferably at 160℃ for 16 hours.

[0025] Furthermore, it also includes step 4, which involves processing the powdered... solid configuration Solution, using Solution preparation membrane.

[0026] In this embodiment, step 4 specifically includes: Powder The solid is dissolved in an aqueous ethanol solution with a concentration of 74-76% to obtain... Solution, in solution The concentration is 4~6 mg / ml, preferably 5 mg / ml.

[0027] In one specific embodiment, steps 3 and 4 are as follows: At room temperature, add 0.364 g of [amount missing] to 50 mL of ethylene glycol. The solid was then mixed with 10 mL of 1 mol / L nitric acid and 0.6 g of polyvinylpyrrolidone (PVP). The mixture was stirred in two stages: first, for 5 min, mechanical stirring was used to initially mix the raw materials, preparing them for subsequent ultrasonic treatment; second, ultrasonic treatment was performed for 30 min to further enhance the mixing effect. After stirring, the mixture was poured into a 100 mL polytetrafluoroethylene autoclave and hydrothermally heated at 160℃ for 16 h. The product was then filtered, the filter residue was washed, and dried at 70℃ for 12–24 h. After drying, the residue was ground at room temperature in an air atmosphere to obtain a black powder. solid; Take 5 mg of powder The solid was dissolved in 1 ml of a solution consisting of 0.75 ml of ethanol and 0.25 ml of water, and dispersed evenly to prepare the following solution: A solution of 5 μl was applied to the Ø 3 mm surface of a polished and cleaned glassy carbon electrode (GCE). The solution was dried under an infrared lamp for 5 minutes to allow the material to form a uniform film on the GCE surface, thus obtaining the desired product. Membrane, also known as .

[0028] In this embodiment, a separate preparation was also made. , membrane, membrane, The membrane was tested and its performance was evaluated; see [link / reference]. Figures 3 to 16Understandably, the film formed on the electrode surface is used for heavy metal detection and testing.

[0029] Prepared alone The steps are as follows: Urea is placed in a muffle furnace and calcined in air atmosphere, heated to 550℃ at a heating rate of 10℃ / min and held at that temperature for 2 hours to obtain a yellow flocculent solid. This solid is then ground into granules to obtain graphitic carbon nitride, denoted as […]. .

[0030] Prepared alone The membrane preparation procedure is as follows: At room temperature, add 0.364 g of [unspecified ingredient] to 50 mL of ethylene glycol. The solid was then mixed with 10 mL of 1 mol / L nitric acid and 0.6 g of polyvinylpyrrolidone (PVP), stirred for 5 min, and sonicated for 30 min. The mixture was then poured into a 100 mL polytetrafluoroethylene autoclave and hydrothermally heated at 160 °C for 16 h. The product was filtered, the filter residue was washed, dried at 70 °C for 12–24 h, and ground to obtain a black powdery solid. 5 mg of the powder was then added to the mixture. Dissolve in 1 ml of a solution consisting of 0.75 ml of ethanol and 0.25 ml of water, disperse evenly, and prepare as follows: A solution of 5 μl was applied to the Ø 3 mm surface of a polished and cleaned glassy carbon electrode (GCE). The solution was dried under an infrared lamp for 5 minutes to allow the material to form a uniform film on the GCE surface, resulting in... Membrane, also known as .

[0031] Prepared alone The membrane preparation process is as follows: urea is placed in a muffle furnace and calcined in air atmosphere, heated to 550 °C at a heating rate of 10 °C / min and held at that temperature for 2 hours to obtain a yellow flocculent solid. This solid is then ground into particles to obtain graphitic carbon nitride, denoted as [missing information]. Place a crucible in a tube furnace, and add [the following ingredients] to the crucible near the outlet of the tube furnace. The solid was calcined for 4 hours under nitrogen protection at a temperature of 550℃ and a heating rate of 5℃ / min, ultimately yielding a bluish-yellow solid. ; 5 mg Dissolve in 1 ml of a solution consisting of 0.75 ml of ethanol and 0.25 ml of water, disperse evenly, and prepare as follows: A solution of 5 μl was applied to the Ø 3 mm surface of a polished and cleaned glassy carbon electrode (GCE). The solution was dried under an infrared lamp for 5 minutes to allow the material to form a uniform film on the GCE surface, resulting in... Membrane, also known as .

[0032] In this embodiment, In having a ribbon-like structure It grows in situ on the surface, exhibiting a checkerboard pattern, and exist The surface of the composite material is uniformly modified.

[0033] Please see Figure 3 , Figure 3 For the prepared , and The SEM image, where (a) corresponds to SEM image, (b) corresponding SEM image, (c) corresponding The SEM image shows... It appears as a small sphere, and It is ribbon-like, and at the same time You can see ribbon-like complex , Scattered growths surface.

[0034] Please see Figures 4-7 , Figure 4 X-ray diffraction (XRD) pattern, Figure 5 for Figure 4 of and The XRD pattern is magnified, with the horizontal axis representing 2θ, where θ is the Bragg angle, and the vertical axis representing the diffraction intensity. Figure 4 Example , , The X-ray diffraction curves of JCPDS are shown. JCPDS is an abbreviation for Joint Committee on Powder Diffraction Standards. Each substance corresponds to a unique "JCPDS card number". In this embodiment, the corresponding card number is "JCPDS #85-1329". "(012)", "(024)", "(100)" and "(002)" in the figure all represent crystal plane symbols. Figure 6 This is a Fourier transform infrared spectrum, with the horizontal axis representing wavenumber and the vertical axis representing transmittance. Figure 7 This is an adsorption isotherm plot of carbon nitride-based composite materials, used to characterize the material's specific surface area and pore structure. The horizontal axis, Volume, represents the adsorption volume (…). The vertical axis, Relative Pressure, represents the relative pressure. , 0~1, where P represents the actual pressure of the adsorbate during the adsorption process. (This represents the saturated vapor pressure of the adsorbate at the experimental temperature). The Surface area in the figure represents the specific surface area. ).

[0035] from Figure 6 As can be seen from this, 1253, 1325, 1425, 1460, 1573, 1643 It has an absorption peak at that point. , , , In 1253, 1325, 1425, 1460, 1573, 1643 The absorption peak at 812 is the absorption vibration peak of the CN and C=N bonds, while at 812... The absorption peak at that point is The characteristic breathing vibration pattern in the heptazine ring indicates that secondary calcination cannot alter the original... The skeleton also indicates , Successful synthesis. The XRD pattern (...) Figure 4 In ), , middle, and These correspond to their (100) and (002) crystal planes, respectively. The (100) crystal plane corresponds to the in-plane periodic repeating unit of the heptaazine ring, while the (002) crystal plane corresponds to the interlayer graphite phase stacking. This can be seen from the magnified XRD pattern ( Figure 5 It can be seen from ) The weakening of the (100) crystal plane peak is due to the in-plane periodic repeating unit defects of the heptaazine ring caused by secondary calcination, while the (002) crystal plane peak also decreases, proving that its interlayer stacking thickness is reduced, thus making The material was made into a thinner layer, and the successful synthesis of the material was confirmed by a combination of XRD and infrared analysis.

[0036] Adsorption-desorption test results are as follows Figure 7 As shown. Four materials ( , , , The pore size of these particles is mainly distributed in the mesoporous range of 10–50 nm. Compared to... , It has a higher specific surface area ( ), The smallest specific surface area ( ),and The specific surface area is between and Between. Therefore, it can be seen that secondary calcination promotes... The porous structure, with its higher specific surface area, typically means more adsorption sites, which helps to improve adsorption efficiency. Performance.

[0037] Figures 8 to 10 for and XPS (X-ray photoelectron spectroscopy) test images are used for analysis. and The surface chemical states and elemental composition are shown, with Binding Energy on the x-axis and Photoelectron Intensity on the y-axis. High-resolution C 1s XPS spectra (photoelectron energy spectra of the 1s orbitals of carbon) of the two materials are also shown. Figure 8 The peaks can be decomposed into three peaks at 284.8, 285.6, and 288.44 eV, which are attributed to the uncalibrated carbons in the aromatic ring, respectively. Hybridized carbon (N–C=N) and the group adjacent to the amino group .exist High-resolution N 1s spectrum Figure 9 In the photoelectron spectrum of the 1s orbital of nitrogen, the three characteristic peaks are located at 398.85, 399.85, and 401.07 eV, corresponding to the triazine ring, respectively. Hybrid nitrogen (C–N=C), bridged nitrogen ( ) and the skeletal amino nitrogen located at the boundary between the heptaazine unit and the hydrocarbon (H2N) (x = 1, 2). compared to, The N–C=N peak did not show a significant shift, while and The peaks underwent blue shifts of 0.21 eV and 0.38 eV, respectively, indicating that... and There are stronger interactions between them. Furthermore, see Table 1, which shows the peak area fitting results, it can be seen that... The proportion of the N–C=N peak in the middle increases, while The decrease in the proportion of [specific element] further supports the introduction of defects into carbon nitride during the secondary calcination process, thereby forming a defect-rich structure. Furthermore, in [the context of this process]... Bismuth was detected in the sample, and its Bi 4f spectrum ( Figure 10 The electron decomposes into four peaks. The binding energy is 162.76 eV. ) and 157.30 eV ( The peak spacing of ) was 5.3 eV, indicating that The system contains metallic bismuth. Additionally, two other peaks are observed at 164.56 eV and 159.25 eV, which can be attributed to... The Bi 4f5 / 2 and Bi 4f7 / 2 states indicate that It contains a certain amount .

[0038] Table 1 Figure 11 Prepared for this disclosure , , , , For two heavy metal ions ( , The response comparison graph shows that the vertical axis represents the current. It can be seen that... (Black pillar): It has the highest current and the strongest adsorption capacity. lowest; (Gray column): The current is approximately 4 μA, which is higher than that of other samples. The material has the best performance, for and It exhibits the strongest electrochemical response.

[0039] Figure 12 and Figure 13 For the prepared Performance graphs for the simultaneous detection of two heavy metal ions in 0.1M ABS at pH 6.0, where the material's effect on... The detection limit is as low as 0.53 ppb (S / N=3), with a linear range of 20–200 ppb. The detection limit is 0.31 ppb (S / N=3). Figure 12 for and Current-potential curve; the horizontal axis represents electrode potential (V vs. Ag / AgCl), and the vertical axis represents current (V / AgCl). ). Figure 13 This is a scatter plot showing the relationship between current and concentration, with the horizontal axis representing concentration (in ppb), indicating the concentration of current in the solution. and The content of; the vertical axis is the current (unit: ), which is the response current generated during the detection process. The corresponding linear fitting equation is , The corresponding linear fitting equation is , and Both represent current. The value represents the concentration, indicating that within a certain concentration range, the current and concentration have a linear relationship, and the ion concentration can be calculated from the current value using this equation; coefficient of determination , of ; The closer the value is to 1, the better the linear fit, meaning the more significant the linear relationship between ion concentration and current. of Closer to 1, its linear relationship is greater than better; testing line , of The detection limit indicates the lowest concentration of ions that can be reliably detected. The detection limit is lower, meaning that this detection method is more effective at detecting certain conditions. More sensitive, capable of detecting lower concentrations .

[0040] Figure 14 for The graph shows the stability test results of the material after multiple cycles. The horizontal axis, Number, indicates the test number, and the vertical axis represents the current. In six tests, the material exhibits good stability against both heavy metal ions, with particularly good stability against... The relative standard deviation (RSD) is 2.31%. The relative standard deviation (RSD) is 2.58%.

[0041] Figure 15 and Figure 16 Prepared for this disclosure Performance graph of the material under spiking gradient test in seawater. Figure 15 for and Current-potential curve; the horizontal axis represents electrode potential (Vvs. Ag / AgCl), and the vertical axis represents current (Current, ), Figure 16 This is a scatter plot showing the relationship between current and concentration, with the horizontal axis representing concentration (in ppb), indicating the concentration of current in the solution. and The content of; the vertical axis is the current (unit: This is the response current generated during the detection process. (Material resistance) The detection limit is as low as 0.53 ppb (S / N=3), with a linear range of 1–200 ppb. ,right The detection limit is 9.71 ppb (S / N=3), and the linear range is 1–200 ppb. This demonstrates its ability to directly measure two heavy metals in seawater, showcasing the material's potential for practical application in heavy metal detection in seawater.

[0042] This disclosure also provides a porous, defect-rich carbon nitride material modified with bismuth oxide core-shell nanoparticles, which is prepared by the above method.

[0043] This disclosure also provides an electrochemical sensor, wherein the electrode material of the electrochemical sensor comprises the bismuth oxide core-shell nanoparticle modified porous defect-rich carbon nitride material prepared by the above method. .

[0044] Specifically, the electrode material of the electrochemical sensor includes membrane.

[0045] This disclosure also provides an application, specifically the application of the bismuth oxide core-shell nanoparticle-modified porous defect-rich carbon nitride material in the detection of lead and / or cadmium in water / soil.

[0046] In particular, the water body mentioned is seawater, used for detecting lead ions in seawater ( The content of cadmium ions (Cd) in seawater is used to detect cadmium ions (Cd) in seawater. The content of ( ), which can be a percentage, mass, etc.

[0047] Specifically, in the detection of heavy metals, a film formed on the electrode surface is utilized; that is, the application specifically refers to... Application of membranes in the detection of lead and / or cadmium in water / soil.

[0048] This disclosure describes the synthesis of a product using low-cost urea as a precursor. Secondary calcination of carbon nitride can effectively improve electron mobility and conductivity, thereby optimizing the electrocatalytic activity of electrode materials; hydrothermal method In having a ribbon-like structure In-situ surface growth was achieved exist Uniform surface modification of the material makes it difficult for bismuth oxide core-shell nanoparticles to accumulate, resulting in a high specific surface area that facilitates the exposure of catalytically active sites. It exhibits outstanding lead-cadmium ion responsiveness, meaning it has strong responsiveness. It has the ability to rapidly detect lead and cadmium heavy metal ions in seawater and other sources, and the detection stability is good.

[0049] Specifically, porous, defect-rich carbon nitride ( The structure exhibits the following characteristics: (1) the reduced bandgap due to defect structure improves electron mobility, thereby optimizing the charge transfer process; (2) the ribbon-like two-dimensional porous structure provides a large specific surface area, which helps to enrich heavy metal ions and improve detection sensitivity. Furthermore, low-cost urea is used as a precursor for synthesis. This not only simplifies the manufacturing process but also increases the feasibility of practical applications for the sensor.

[0050] Utilizing porous, defect-rich carbon nitride ( The adsorption and enrichment of heavy metal ions by bismuth oxide core-shell nanoparticles with uniform surface modification in step 3 (…) It has a large specific surface area and is decorated with ribbon-like structures. The surface of the substrate serves as an active site for depositing heavy metal ions, further improving the performance of heavy metal ion detection and thus enhancing the detection signal. The substrate prepared in this disclosure... Combined Excellent electrocatalytic performance and Its large specific surface area and excellent ability to concentrate heavy metal ions enable efficient detection of various HMIs. Composite electrode materials exhibit superior performance in trace heavy metal detection: this composite material is effective under weakly acidic conditions. , The ions exhibit excellent detection sensitivity and selectivity, while maintaining stable detection performance in seawater environments. The preparation process disclosed herein is simple and provides new ideas for the development of green and low-cost sensing technologies.

[0051] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0052] The embodiments described above are merely illustrative of several implementations of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for preparing porous, defect-rich carbon nitride materials modified with bismuth oxide core-shell nanoparticles, characterized in that, include: Step 1: Calcining urea in air atmosphere, followed by grinding into granules to obtain graphitic carbon nitride. ； Step 2, in In this atmosphere, to conduct Calcination yields porous, defect-rich carbon nitride. ; Step 3: At room temperature, combine ethylene glycol liquid, nitric acid solution, polyvinylpyrrolidone, solids and The mixture is then placed in a reaction vessel and heated in a water bath to generate a precipitate. The precipitate is filtered out, washed, dried, and ground to obtain a powder. Solid, namely, bismuth oxide core-shell nanoparticles modified into porous, defect-rich carbon nitride materials.

2. The method for preparing a porous, defect-rich carbon nitride material modified with bismuth oxide core-shell nanoparticles according to claim 1, characterized in that, In step 1, the heating rate of calcination is 8~12℃ / min, and the holding temperature is 520~580℃.

3. The method for preparing a porous, defect-rich carbon nitride material modified with bismuth oxide core-shell nanoparticles according to claim 2, characterized in that, In step 2, the calcination temperature is set to 520~580℃, the heating rate is 4.5~5.5℃ / min, and the calcination time is 3.5~4.5 h.

4. The method for preparing a porous, defect-rich carbon nitride material modified with bismuth oxide core-shell nanoparticles according to claim 3, characterized in that, The nitric acid solution concentration is 0.9~1.1 mol / L, and polyvinylpyrrolidone and The weight ratio of the solids ranges from 1.58 to 1.

72. The preferred weight ratio of the element to Bi is 0.44 to 0.47; the water bath heating is performed at 155 to 165°C for 15 to 17 hours.

5. The method for preparing a porous, defect-rich carbon nitride material modified with bismuth oxide core-shell nanoparticles according to claim 4, characterized in that, It also includes step 4, which involves processing the powdered... The solid is dissolved in an aqueous ethanol solution with a concentration of 74%–76% to obtain... Solution, in solution The concentration is 4~6 mg / ml, using Solution preparation membrane.

6. The method for preparing a porous, defect-rich carbon nitride material modified with bismuth oxide core-shell nanoparticles according to claim 5, characterized in that, In step 1, the calcination heating rate is 10℃ / min, the holding temperature is 550℃, and the holding time is 2h; in step 2, the calcination temperature is set to 550℃, the heating rate is 5℃ / min, and the calcination time is 4h; the concentration of the nitric acid solution is 1.0 mol / L, and the polyvinylpyrrolidone... solid and The weight ratio is 300:182:35; the water bath heating is performed at 160°C for 16 hours, and the drying is performed at 70°C for 12-24 hours; in step 4, the concentration of the ethanol-water solution is 75%. in solution The concentration is 5 mg / ml.

7. A porous, defect-rich carbon nitride material modified with bismuth oxide core-shell nanoparticles, characterized in that, The bismuth oxide core-shell nanoparticle-modified porous defect-rich carbon nitride material is prepared using the preparation method of the bismuth oxide core-shell nanoparticle-modified porous defect-rich carbon nitride material as described in any one of claims 1 to 6.

8. The application of the bismuth oxide core-shell nanoparticles modified with porous, defect-rich carbon nitride materials as described in claim 7, characterized in that, The application is in the detection of lead and / or cadmium in water or soil.

9. The application of the bismuth oxide core-shell nanoparticles modified porous defect-rich carbon nitride material as described in claim 8, characterized in that, The water body is seawater.

10. An electrochemical sensor, characterized in that, The electrode material of the electrochemical sensor includes a bismuth oxide core-shell nanoparticle modified porous defect-rich carbon nitride material prepared by the preparation method of a bismuth oxide core-shell nanoparticle modified porous defect-rich carbon nitride material according to any one of claims 1 to 6.

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