Method for self-sensitized detection of 2-chlorophenol based on eosin y-carbon nitride system

Abstract

The method for self-sensitization detection of 2-chlorophenol based on eosin Y-carbon nitride system relates to the application technology field of eosin Y-carbon nitride system in visual detection of 2-chlorophenol. The purpose of the present application is to solve the problems of how to improve the selective adsorption capacity of g-C3N4 to trace concentration 2-chlorophenol and realize visual super-sensitive detection of colorless 2-chlorophenol. Method: tetra bromo fluorescein disodium aqueous solution, silver modified carbon nitride nanosheet suspension and 2-chlorophenol aqueous solution are mixed, and the pH is adjusted to 3-9; the mixed solution is placed in a photocatalytic reactor, stirred and adsorbed for 1-30 min in the dark, 525 nm visible light is turned on, and after light irradiation, the filtrate is detected by ultraviolet visible spectrophotometer, and the visual detection of 2-chlorophenol in water based on single-atom silver modified carbon nitride nanosheet is completed. The method for self-sensitization detection of 2-chlorophenol based on eosin Y-carbon nitride system can be obtained.

Description

TECHNICAL FIELD

[0001] The application relates to the application of the eosin Y-carbon nitride system in the field of visual detection of 2-chlorophenol, in particular to a method for self-sensitization detection of 2-chlorophenol based on eosin Y-silver modified carbon nitride. BACKGROUND

[0002] A variety of fluorescent detection methods for environmental pollutants have been developed by using carbon nitride (g-C3N4) as a fluorescent response unit, but some pollutants, such as chlorophenol compounds, cannot be detected by the fluorescent method because they have no fluorescent response to g-C3N4. Chlorophenol compounds are a kind of chlorinated organic pollutants widely distributed in the world. Studies have shown that most chlorophenols have "three effects" (teratogenic, carcinogenic and mutagenic), genetic toxicity, biological enrichment and non-degradability, and have been listed as priority pollutants by various countries. Trace or even trace amounts of chlorophenol can cause harm to the ecosystem and human health, so rapid and ultra-sensitive detection of chlorophenol is of great significance to environmental monitoring and protection of the ecosystem and the public. Traditional chlorophenol detection methods mainly include gas chromatography, high performance liquid chromatography, capillary electrophoresis, electrochemical sensor method, molecular imprinting method, etc., but they have the disadvantages of complex pretreatment steps, high detection cost, long detection time, easy environmental interference and inability to be observed by naked eye, so it is urgent to develop new detection technology.

[0003] Dyes have a large light absorption coefficient and a wide absorption range, and can usually absorb light in the entire visible light region. They are a class of substances with rich colors. The excited state energy level of thioxanthene dyes such as eosin, fluorescein and rhodamine is mostly higher than that of semiconductor materials such as g-C3N4. Thioxanthene dyes are low in cost and have a wide range of visible light absorption, and are often used as photosensitizers for g-C3N4. In order to maintain the cycle of photocatalytic reaction, a sacrificial electron donor is needed to regenerate the dye molecules. Therefore, in the thioxanthene dye-g-C3N4 system, when there is no electron donor, the excited state electrons of thioxanthene dye will transfer to the conduction band of g-C3N4 under visible light excitation. The loss of electrons of the dye molecules may cause the sensitization discoloration of the dye itself. On the contrary, if other blocking agents are adsorbed on the surface of carbon nitride, the electron transfer between the dye and carbon nitride will be hindered, and the discoloration process will be blocked. Therefore, if the self-sensitization discoloration characteristics of the dye under light driving and the quantitative blocking effect of the detected substance on the discoloration are utilized, a new detection method based on dye sensitization can be developed.

[0004] Eosin Y (tetrabromofluorescein disodium), abbreviated as EY, as an acid red dye, has a suitable energy band structure and is often used as a photosensitizer of g-C3N4. Under visible light excitation, EY can sensitize g-C3N4, expand the visible light absorption of g-C3N4, and cause self-sensitization decolorization after losing electrons. If 2-chlorophenol (2-CP) can be competitively adsorbed on the surface of g-C3N4, the sensitization decolorization process can be blocked. A new self-sensitization detection method is established by using the quantitative relationship between the change in light absorption intensity of EY and the concentration of 2-CP. Two key problems need to be solved in this method, one is to improve the photoinduced electron transfer efficiency of the EY sensitization decolorization process, and the other is to improve the selective adsorption capacity of g-C3N4 to 2-CP. Based on this, since Ag can promote electron transfer and form a good coordination with Cl, dispersed Ag modified on g-C3N4 is expected to improve the detection ability of 2-CP. SUMMARY

[0005] The purpose of the present application is to solve the problems of how to improve the selective adsorption capacity of g-C3N4 to trace concentration 2-chlorophenol and realize visual ultra-sensitive detection of colorless 2-chlorophenol, and to provide a method for self-sensitization detection of 2-chlorophenol based on Eosin Y-carbon nitride system.

[0006] The method for self-sensitization detection of 2-chlorophenol based on Eosin Y-carbon nitride system is carried out according to the following steps:

[0007] The tetrabromofluorescein disodium aqueous solution, the silver modified carbon nitride nanosheet suspension and the 2-chlorophenol aqueous solution are mixed, and the pH is adjusted to 3-9 to obtain a mixed solution. The mixed solution is placed in a photocatalytic reactor, stirred and adsorbed for 1-30 min in the dark, then visible light with a wavelength of 525 nm is turned on, and after irradiation for 1-30 min, the filtrate is detected by a UV-visible spectrophotometer to complete the visual detection of 2-chlorophenol in water based on single-atom silver modified carbon nitride nanosheet.

[0008] The principle of the present application is as follows:

[0009] The present application selects 2-chlorophenol (2-CP) as the detected substrate, and introduces nanosilver on g-C3N4. On the one hand, it can promote the charge transfer between the dye and g-C3N4, and promote the oxidative decolorization of the dye. On the other hand, it can make 2-CP more accurately and efficiently adsorbed on g-C3N4 material through coordination with Ag. The introduction of dispersed nanosilver on CN improves the selective adsorption capacity of g-C3N4 to trace concentration 2-chlorophenol, and promotes the detection ability of EY sensitization efficiency to 2-CP.

[0010] The innovation point of the present application is as follows:

[0011] The application successfully establishes the sAg-CN-EY self-sensitization system for the visual detection of 2-CP for the first time, the system can effectively improve the color change degree of EY, and the interaction between the introduced Ag and 2-CP improves the selective adsorption, enrichment capacity of 2-CP, and then improves the selectivity and sensitivity of the detection of 2-CP.

[0012] The application has the following beneficial effects:

[0013] In the application, the nano Ag modified g-C3N4 nanosheet (sAg-CN) is first synthesized, when 2-CP does not exist in the system, the pink Eosin Y (EY) sensitizes sAg-CN under the visible light of 525 nm, which causes the self-sensitization of EY and the discoloration of EY, and the ultraviolet absorbance of EY is reduced; when 2-CP exists, the discoloration process can be blocked due to the enhanced selective adsorption of sAg-CN to 2-CP, and with the increase of the concentration of 2-CP, the ultraviolet visible absorbance (Abs) of EY is increased, therefore, the color of the system and the Abs of EY can be used to realize the visual, high-sensitivity and high-selectivity detection of 2-CP.

[0014] The application can obtain a method for self-sensitization detection of 2-chlorophenol based on the Eosin Y-carbon nitride system. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is the XPS Ag 3d spectrum of sAg-CN in Example 1;

[0016] Figure 2 It is the discoloring effect of sAg-CN on the EY solution in Example 1, A represents Dark, and B represents sAg-CN-EY;

[0017] Figure 3 It is the color response of the EY-sAg-CN detection system in Example 1 when different concentrations of 2-CP are added (with the gradual increase of the concentration of 2-CP, the color of EY gradually changes from white to light pink and then gradually changes to deep pink);

[0018] Figure 4 It is the ultraviolet visible absorption spectrum of EY in the EY-sAg-CN detection system in Example 1 when different concentrations of 2-CP are added;

[0019] Figure 5 It is the relationship between lg(C 2-CP ) and lg(η b ) in Example 1, A represents y=0.396x-0.235, R 2 =0.997, 10μg L -1 ~1mg L -1 ; B represents y=0.105x-0.806, R2 = 0.991, 1 ng L -1 ~ 10 pg L -1 ;

[0020] Figure 6 For the influence of the detection of 2-CP in Example 1 under the interference of other pollutants, the front histogram B represents the single other aromatic organic pollutants, and the rear histogram A represents the mixing of other aromatic organic pollutants in 2-CP. DETAILED DESCRIPTION

[0021] Embodiment I: This embodiment is based on the method for self-sensitizing detection of 2-chlorophenol by eosin Y-carbon nitride system, which is carried out according to the following steps:

[0022] The tetra bromide fluorescein disodium aqueous solution, the silver modified carbon nitride nanosheet suspension and the 2-chlorophenol aqueous solution are mixed, and the pH is adjusted to 3-9 to obtain a mixed solution; the mixed solution is placed in a photocatalytic reactor, first stirred and adsorbed for 1-30 min under no light, then a visible light with a wavelength of 525 nm is turned on, and after irradiation for 1-30 min, the filtrate is detected by a UV-visible spectrophotometer to complete the visual detection of 2-chlorophenol in water based on single-atom silver modified carbon nitride nanosheet.

[0023] Embodiment II: The difference between this embodiment and embodiment I is that the volume ratio of the tetra bromide fluorescein disodium aqueous solution, the silver modified carbon nitride nanosheet suspension and the 2-chlorophenol aqueous solution is (8-15):(2-5):1, the concentration of the tetra bromide fluorescein disodium aqueous solution is 3.3-20 mg / L, the concentration of the silver modified carbon nitride nanosheet suspension is 0.5-3.3 g / L, and the concentration of the 2-chlorophenol aqueous solution is 14 ng / L-14 mg / L.

[0024] The other steps are the same as those in embodiment I.

[0025] Embodiment III: The difference between this embodiment and embodiment I or II is that the tetra bromide fluorescein disodium aqueous solution is prepared according to the following steps: 0.001-0.01 g of tetra bromide fluorescein disodium powder is added to 300-500 mL of deionized water, and after mixing uniformly, a tetra bromide fluorescein disodium aqueous solution is obtained.

[0026] The other steps are the same as those in embodiment I or II.

[0027] Specific embodiment four: the difference between this embodiment and one of the specific embodiments one to three is that the silver modified g-C3N4 nanosheet suspension is prepared by the following steps: 0.05-2 g of silver modified g-C3N4 nanosheet powder is added to 100-600 mL of deionized water, and ultrasonic is performed under continuous stirring to obtain a silver modified g-C3N4 nanosheet suspension.

[0028] The other steps are the same as specific embodiments one to three.

[0029] Specific embodiment five: the difference between this embodiment and one of the specific embodiments one to four is that the 2-chlorophenol aqueous solution is prepared by the following steps: 2-chlorophenol powder is added to a 100 mL volumetric flask, 0.5 mL of methanol is first added, then deionized water is added to constant volume, and ultrasonic is performed under continuous stirring. After the 2-chlorophenol powder is completely dissolved, dilution is performed to obtain a 2-chlorophenol aqueous solution with a concentration of 14 ng / L-14 mg / L.

[0030] The other steps are the same as specific embodiments one to four.

[0031] Specific embodiment six: the difference between this embodiment and one of the specific embodiments one to five is that a 22 μm water phase filter membrane is used for filtration.

[0032] The other steps are the same as specific embodiments one to five.

[0033] Specific embodiment seven: the difference between this embodiment and one of the specific embodiments one to six is that the silver modified g-C3N4 nanosheet is prepared by the following steps:

[0034] Step one: melamine is added to deionized water, and stirring is performed at a temperature of 50-100 °C until complete dissolution to obtain solution A; cyanuric acid and silver nitrate are added to deionized water, and stirring is performed at a temperature of 50-100 °C until complete dissolution to obtain solution B; solution B is added to solution A under a temperature condition of 50-100 °C, and after uniform stirring, white granular material is obtained. Continue to heat and stir for 1-5 h, centrifuge after cooling, discard the supernatant, and the remaining white granular material is washed, dried, and ground;

[0035] Step two: under the protection of nitrogen, the ground powder in step one is heated to 450-550℃, and calcined at 450-550℃ for 2-6h, cooled, to obtain the once calcined porous carbon nitride; the once calcined porous carbon nitride is heated to 450-550℃ under the condition of air, and calcined at 450-550℃ for 2-6h, cooled, to obtain the twice calcined porous carbon nitride; the twice calcined porous carbon nitride is added into a nitric acid solution, stirred under reflux at 50-90℃ for 2-6h, cooled, centrifuged, the supernatant is discarded, and the remaining solid is washed and dried, to obtain silver modified carbon nitride nanosheets.

[0036] The other steps are the same as those in the first to sixth embodiments.

[0037] The eighth embodiment is different from one of the first to seventh embodiments in that the ratio of the mass of melamine to the volume of deionized water is (5-15)g:500mL, and the ratio of the mass of cyanuric acid, the mass of silver nitrate and the volume of deionized water is (2-6)g:(0.05-0.2)g:500mL.

[0038] The other steps are the same as those in the first to seventh embodiments.

[0039] The ninth embodiment is different from one of the first to eighth embodiments in that after cooling, the remaining white granular material is centrifuged at a speed of 4000r / min for 10min, the supernatant is discarded, and the remaining solid is sequentially washed with deionized water and anhydrous ethanol for 3-5 times, and then dried in a 60℃ oven and ground.

[0040] The other steps are the same as those in the first to eighth embodiments.

[0041] The tenth embodiment is different from one of the first to ninth embodiments in that in step two, the nitrogen gas is introduced at a rate of 50-200mL / min; the ground powder is heated to 450-550℃ at a heating rate of 0.5-5℃ / min; the once calcined porous carbon nitride is heated to 450-550℃ at a heating rate of 1-10℃ / min; the concentration of the nitric acid solution is 1-10mol / L; after cooling, the remaining solid is centrifuged at a speed of 4000r / min for 10min, the supernatant is discarded, and the remaining solid is sequentially washed with deionized water and anhydrous ethanol for 3-5 times, and then dried in a 60℃ oven.

[0042] The other steps are the same as those in the first to ninth embodiments.

[0043] The beneficial effects of the present application are verified by the following examples:

[0044] Example 1:

[0045] 1. The preparation method of silver-modified carbon nitride nanosheets is carried out according to the following steps:

[0046] Step 1: Add 10g of melamine to 500mL of deionized water and stir at 80℃ until completely dissolved to obtain solution A; add 4g of cyanuric acid and 0.111g of silver nitrate to 500mL of deionized water and stir at 80℃ until completely dissolved to obtain solution B; at 80℃, quickly add solution B to solution A and stir evenly to obtain white granules insoluble in water. Continue heating and stirring for 3 hours, cool, and centrifuge at 4000r / min for 10 minutes. Discard the supernatant. Wash the remaining white granules three times each with deionized water and anhydrous ethanol. After washing, dry in a 60℃ oven and grind.

[0047] Step Two: Under nitrogen protection (inlet rate 150 mL / min), the powder ground in Step One was placed in a covered ceramic boat, compacted, and then sealed with aluminum foil. It was then placed in a tube furnace and heated to 520°C at a rate of 1°C / min, and calcined at 520°C for 4 hours. After natural cooling to room temperature, porous carbon nitride was obtained after one calcination. The porous carbon nitride sample after one calcination was loosened, uncovered, wrapped in perforated aluminum foil, and placed back in the tube furnace. It was then heated to 520°C at a rate of 5°C / min under air conditions. The carbon nitride was calcined at 500℃ for 2 hours and then naturally cooled to room temperature to obtain porous carbon nitride after secondary calcination. The porous carbon nitride after secondary calcination was added to a 5 mol / L nitric acid solution and refluxed and stirred at 70℃ for 2 hours. After cooling, it was centrifuged at 4000 r / min for 10 minutes. The supernatant was discarded, and the remaining solid was washed three times each with deionized water and anhydrous ethanol. After washing, it was dried in an oven at 60℃ to obtain silver-modified carbon nitride nanosheets sAg-CN (CN represents g-C3N4).

[0048] X-ray photoelectron spectroscopy (XPS) was used to characterize the sAg-CN material. Figure 1 The XPS Ag 3d spectrum of sAg-CN in Example 1 is shown below; Figure 1 As shown, 374.1 eV and 368.1 eV in sAg-CN represent Ag, respectively. 0 The 3d3 / 2 and 3d1 / 2 values ​​indicate that this method successfully introduced Ag into g-C3N4.

[0049] 2. Visual detection of the 2-CP process based on the EY-sAg-CN system:

[0050] (1) Solution preparation:

[0051] Aqueous solution of tetrabromofluorescein disodium (EY, red powder) was prepared according to the following steps: 0.005 g of tetrabromofluorescein disodium powder was added to 500 mL of deionized water and mixed thoroughly to obtain a concentration of 10 mg / L. -1 A solution of tetrabromofluorescein disodium (pink).

[0052] A suspension of silver-modified carbon nitride nanosheets (sAg-CN) was prepared according to the following steps: 0.15 g of silver-modified carbon nitride nanosheet powder was added to 100 mL of deionized water, and the mixture was subjected to thorough sonication while continuously stirring to obtain a concentration of 1.5 g / L. -1 A white suspension of silver-modified carbon nitride nanosheets.

[0053] 2-Chlorophenol (2-CP) aqueous solution is prepared according to the following steps: 2-Chlorophenol powder is added to a 100mL volumetric flask, 0.5mL of methanol is added first, and then deionized water is added to make up to volume. While stirring continuously, the mixture is sonicated thoroughly until the 2-Chlorophenol powder is fully dissolved. Then, it is diluted to prepare 2-Chlorophenol aqueous solutions of different concentrations (14ng / L to 14mg / L).

[0054] (2) Detection process:

[0055] Take a 50mL weighing bottle and add 10mL of 10mg L to each. -1 Tetrabromofluorescein disodium aqueous solution, 3 mL 1.5 g L -1 A suspension of silver-modified carbon nitride nanosheets and 1 mL of 2-chlorophenol aqueous solutions of different concentrations were mixed, and the pH of the detection system was adjusted to 5 using 1 mL of dilute nitric acid solution. The resulting EY aqueous solution concentration was 6.67 mg / L. -1 The concentration of sAg-CN suspension was 0.3 g / L. -1 All weighing bottles to be tested were placed in the Pofilai multi-channel photocatalytic reactor. The mixture was stirred and adsorbed for 5 minutes in the absence of light. Then, visible light with a wavelength of 525 nm was turned on and the mixture was irradiated for 5 minutes. After filtration, the mixture was filtered using a 22 μm aqueous phase filter membrane. The filtrate was then detected using a UV-Vis spectrophotometer.

[0056] Figure 2 The decolorization effect of sAg-CN on EY solution in Example 1 is shown in Figure 1. A represents Dark and B represents sAg-CN-EY. Figure 3 The color response of adding different concentrations of 2-CP to the EY-sAg-CN detection system in Example 1; Figure 4 The UV-Vis absorption spectra of EY in the EY-sAg-CN detection system of Example 1 are shown below when different concentrations of 2-CP are added. sAg-CN with a nano-Ag loading of 2.5% was used as the optimal detection material. The decolorization process of EY sensitized by sAg-CN is as follows: Figure 2The dark adsorption experiment of sAg-CN on EY under no light condition was used as a control. The results showed that the decolorization effect of EY caused by the dark adsorption of sAg-CN on EY was not obvious, and the decolorization rate was not more than 0.02. Under the irradiation of 525 nm single-wavelength visible light, the absorption peak intensity of EY at 517 nm gradually decreased in the sensitized system in the presence of sAg-CN, and the color of EY solution gradually faded from pink to white. The decolorization rate was more than 0.94 at 5 min, and the decolorization rate was close to 1 at 9 min. The sensitized decolorization time of EY was shorter. It was thus shown that the sensitized system of EY-sAg-CN after the introduction of Ag had obvious decolorization effect on EY, and the detection time was 5 min. As the concentration of 2-CP in the system increased (1 ng L -1 →1 mg L -1 ), the blocking effect on sensitized decolorization was significantly enhanced. As shown in Figure 3 , the color of EY gradually changed from white to light pink to deep pink as the concentration of 2-CP in the system increased. As shown in Figure 4 , the absorption peak intensity of EY gradually increased as the concentration of 2-CP in the system increased.

[0057] Figure 5 For the relationship between lg(C 2-CP ) and lg(η b ) in Example 1, A represents y = 0.396x-0.235, R 2 = 0.997, 10 μg L -1 ~1 mg L -1 ; B represents y = 0.105x-0.806, R 2 = 0.991, 1 ng L -1 ~10 μg L -1 ; when the concentration of 2-CP was in the range of 1 ng L -1 ~1 mg L -1 , the logarithm of EY blocking rate lg(η b ) and the logarithm of 2-CP concentration lg[c] had different linear fitting equations in different concentration intervals, as shown in Figure 5 , when the concentration of 2-CP was in the range of 10 μg L -1 ~1 mg L -1 , the linear equation was lg(η b ) = 0.396lg[c]-0.235, and the linear correlation coefficient R 2 value was 0.997, when the concentration of 2-CP was in the range of 1 ng L -1 ~10 μg L -1The linear equation in the range is lg(η b ) = 0.105 lg[c] - 0.806, the linear correlation coefficient R 2 value is 0.991, the lowest quantitative limit is 1 ng L -1 (No. 9 bottle), the LOD is 0.35 ng L -1 . In addition, the visual semi-quantitative detection of 2-CP can be realized by EY color, and the lowest detection concentration that can be visually distinguished is 10 ng L -1 (No. 8 bottle), realizing the rapid visual detection of colorless 2-CP.

[0058] Where η b is the blocking rate of EY sensitized discoloration after adding 2-CP.

[0059] η b = (C b - C) / C0 * (1);

[0060] In the formula, η b represents the blocking rate of EY sensitized discoloration after adding 2-CP.

[0061] C b represents the concentration of EY in the detection system after adding 2-CP, with the unit of mg L -1 ;

[0062] C represents the concentration of EY after sensitized discoloration without 2-CP, with the unit of mg L -1 .

[0063] Figure 6 To implement the influence of the detection of 2-CP in Example 1 under the interference of other pollutants, the front column chart B represents the single other aromatic hydrocarbon organic pollutants, and the rear column chart A represents the 2-CP mixed with other aromatic hydrocarbon organic pollutants. Other aromatic hydrocarbon organic pollutants and chloride ions often coexist in actual environmental systems. In order to explore the selectivity of the EY-sAg-CN photosensitized detection system to the detection of 2-CP, Figure 6Several potential interfering substances, including phenanthrene, diphenyl (DIP), nitrobenzene (NIT), aniline (ANI), ethylbenzene (ETH), para-xylene (para-XYL), benzene (BEN), hydroquinone (HYD), benzene triol (BEN-tr) and chloride ion were added to sAg-CN to investigate their effects on the detection of 2-CP. The results showed that in the absence of 2-CP, the blocking rate of other coexisting interfering substances on EY was low, and EY appeared white, indicating that the photosensitization system had no obvious response to other interfering substances. However, in the presence of 2-CP, EY appeared pink, indicating that the detection system had an obvious selective response to 2-CP. On the other hand, when other organic pollutants and chloride ions were coexisting, the blocking rate of 2-CP detection did not change significantly, indicating that the detection of 2-CP was weakly affected by the coexistence of these interfering substances, and the environmental interference had little effect on the detection results of 2-CP. Therefore, this method achieved excellent selective detection of 2-CP.

Claims

1. A method for the self-sensitization detection of 2-chlorophenol based on the eosin γ-carbon nitride system, characterized in that... The detection method is performed according to the following steps: Aqueous solution of tetrabromofluorescein disodium, suspension of silver-modified carbon nitride nanosheets, and aqueous solution of 2-chlorophenol were mixed, and the pH was adjusted to 3-9 to obtain a mixed solution. The mixed solution was placed in a photocatalytic reactor, and the mixture was stirred and adsorbed for 1-30 min under no light conditions. Then, visible light at a wavelength of 525 nm was turned on and the solution was irradiated for 1-30 min. After filtration, the filtrate was detected using a UV-Vis spectrophotometer to complete the visualization detection of 2-chlorophenol in water based on single-atom silver-modified carbon nitride nanosheets.

2. The method for sensitizing 2-chlorophenol based on the eosin Y-carbon nitride system according to claim 1, characterized in that... The volume ratio of the tetrabromofluorescein disodium aqueous solution, the silver-modified carbon nitride nanosheet suspension, and the 2-chlorophenol aqueous solution is (8-15):(2-5):

1. The concentration of the tetrabromofluorescein disodium aqueous solution is 3.3-20 mg / L, the concentration of the silver-modified carbon nitride nanosheet suspension is 0.5-3.3 g / L, and the concentration of the 2-chlorophenol aqueous solution is 14 ng / L-14 mg / L.

3. The method for sensitizing 2-chlorophenol based on the eosin Y-carbon nitride system according to claim 1 or 2, characterized in that... The tetrabromofluorescein disodium aqueous solution is prepared according to the following steps: 0.001-0.01g of tetrabromofluorescein disodium powder is added to 300-500mL of deionized water and mixed evenly to obtain a tetrabromofluorescein disodium aqueous solution.

4. The method for sensitizing 2-chlorophenol based on the eosin Y-carbon nitride system according to claim 1 or 2, characterized in that... The silver-modified carbon nitride nanosheet suspension is prepared according to the following steps: 0.05-2g of silver-modified carbon nitride nanosheet powder is added to 100-600mL of deionized water, and sonicated while continuously stirring to obtain the silver-modified carbon nitride nanosheet suspension.

5. The method for sensitizing 2-chlorophenol based on the eosin Y-carbon nitride system according to claim 1 or 2, characterized in that... The 2-chlorophenol aqueous solution is prepared according to the following steps: 2-chlorophenol powder is added to a 100mL volumetric flask, 0.5mL of methanol is added first, and then deionized water is added to make up to volume. While stirring continuously, the mixture is sonicated until the 2-chlorophenol powder is fully dissolved. The solution is then diluted to obtain a 2-chlorophenol aqueous solution with a concentration of 14ng / L to 14mg / L.

6. The method for sensitizing 2-chlorophenol based on the eosin γ-carbon nitride system according to claim 1, characterized in that... Filtration was performed using a 22μm aqueous phase filter membrane.

7. The method for sensitizing 2-chlorophenol based on the eosin Y-carbon nitride system according to claim 4, characterized in that... The silver-modified carbon nitride nanosheets are prepared according to the following steps: Step 1: Add melamine to deionized water and stir at 50-100℃ until completely dissolved to obtain solution A; add cyanuric acid and silver nitrate to deionized water and stir at 50-100℃ until completely dissolved to obtain solution B; add solution B to solution A at 50-100℃ and stir until homogeneous to obtain white granules. Continue heating and stirring for 1-5 hours, cool, centrifuge, discard the supernatant, and wash, dry, and grind the remaining white granules. Step 2: Under nitrogen protection, the powder ground in Step 1 is heated to 450–550℃ and calcined at 450–550℃ for 2–6 hours, then cooled to obtain porous carbon nitride after one calcination. The porous carbon nitride after one calcination is then heated to 450–550℃ in air and calcined at 450–550℃ for 2–6 hours, then cooled to obtain porous carbon nitride after a second calcination. The porous carbon nitride after the second calcination is added to a nitric acid solution and refluxed and stirred at 50–90℃ for 2–6 hours. After cooling, it is centrifuged, the supernatant is discarded, and the remaining solid is washed and dried to obtain silver-modified carbon nitride nanosheets.

8. The method for sensitizing 2-chlorophenol based on the eosin γ-carbon nitride system according to claim 7, characterized in that... The mass ratio of melamine to deionized water is (5-15) g: 500 mL, and the mass ratio of cyanuric acid and silver nitrate to deionized water is (2-6) g: (0.05-0.2) g: 500 mL.

9. The method for sensitizing 2-chlorophenol based on the eosin γ-carbon nitride system according to claim 7, characterized in that... After cooling in step one, centrifuge at 4000 r / min for 10 min, discard the supernatant, and wash the remaining white particles 3 to 5 times each with deionized water and anhydrous ethanol. After washing, dry in a 60℃ oven and grind.

10. The method for sensitizing 2-chlorophenol based on the eosin Y-carbon nitride system according to claim 7, characterized in that... In step two, the nitrogen gas is introduced at a rate of 50–200 mL / min; the ground powder is heated to 450–550 °C at a heating rate of 0.5–5 °C / min; the porous carbon nitride after one calcination is heated to 450–550 °C at a heating rate of 1–10 °C / min; the concentration of the nitric acid solution is 1–10 mol / L; after cooling, the mixture is centrifuged at 4000 r / min for 10 min, the supernatant is discarded, and the remaining solid is washed 3–5 times each with deionized water and anhydrous ethanol, and then dried in an oven at 60 °C.

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