Method for detecting coumaphos based on carbon quantum dot-iron ion solution system

Abstract

The invention discloses a method for detecting coumaphos based on a carbon quantum dot-iron ion solution system, which comprises the following steps: dissolving lotus seed powder in deionized water, carrying out ultrasonic treatment until solids are completely dissolved, adding a passivator, uniformly mixing to obtain a uniform solution, carrying out pyrolytic reaction on the uniform solution, and naturally cooling to obtain a brown solution; centrifuging the obtained dark brown solution to remove large-particle precipitates, performing suction filtration by using a filter membrane with the pore diameter of 0.22 mu m to obtain a carbon quantum dot solution, performing rotary evaporation on the obtained carbon quantum dot solution to obtain a concentrated solution, and finally performing freeze drying on the concentrated solution to obtain powdery carbon quantum dots. The blue light-emitting carbon quantum dot synthesized by the invention realizes fluorescence'closing-opening 'integrated detection of iron ion quenching-coumaphos recovery for the first time, coumaphos can be quickly and sensitively detected on site, quantitative analysis is realized, and the application of the fluorescent carbon quantum dot in the field of pesticide residue detection is expanded.

Description

Technical Field

[0001] This invention belongs to the field of carbon nanomaterial synthesis and fly phosphonate pesticide residue detection technology, specifically involving a method for detecting fly phosphonate based on a carbon quantum dot-iron ion solution system. Background Technology

[0003] Among numerous pesticides, phosmet, a highly toxic organophosphate insecticide and acaricide, is prone to residue and accumulation in agricultural products due to its strong chemical stability and resistance to degradation. The Chinese national standard (GB 2763-2021) sets strict limits on phosmet residues in food (e.g., 0.05 mg / kg). Therefore, there is an urgent practical need to develop a specific detection method for phosmet that meets the requirements of this standard and is suitable for rapid on-site screening.

[0004] Currently, detection methods based on fluorescent probes have shown great potential in the field of pesticide residue analysis due to their advantages such as high sensitivity, rapid response, and ease of operation. Among them, carbon quantum dots (CDs), as an emerging fluorescent nanomaterial, are considered an ideal fluorescence sensing platform due to their excellent water solubility, tunable luminescence properties, low toxicity, and good biocompatibility. In the synthesis of CDs, the hydrothermal method is widely used because of its simple process, mild conditions, and ease of large-scale production. In recent years, using biomass waste as a carbon source to prepare CDs has become a cost-effective and environmentally friendly strategy.

[0005] Patent document CN2021113377754 discloses a method for preparing fluorescent carbon quantum dots from *Alternanthera philoxeroides* and detecting tartrazine. The preparation process includes the following steps: weighing *Alternanthera philoxeroides* powder and thiourea in a beaker at a 1:1 mass ratio, adding water and stirring, then transferring to a reaction vessel; placing in an oven and reacting at a set temperature; after the reaction is complete, naturally cooling to room temperature, filtering to obtain a carbon quantum dot solution, dialyzing, rotary evaporating, and drying to obtain carbon quantum dot powder. The prepared fluorescent carbon quantum dots for detecting tartrazine are of the "turn-off" type, possessing advantages such as high sensitivity, strong stability, good selectivity, and low cost, and can be used as a convenient and accurate rapid detection method for tartrazine. However, this patent document only relates to the preparation of carbon quantum dots based on *Alternanthera philoxeroides* and their application in detecting tartrazine, and does not involve the synthesis of carbon quantum dots using biomass lotus seeds as a carbon source or the fluorescent detection of the pesticide phosmet.

[0006] Applying biomass-based CDs directly to the specific detection of fly toxic phosphorus in complex matrices still faces some challenges. First, unmodified CDs often lack specific recognition ability for target analytes and are easily affected by coexisting substances. Second, their fluorescence properties (such as quantum yield and stability) directly affect the sensitivity and reliability of detection. Furthermore, how to achieve high-performance preparation and specific functionalization of CDs through simple processes is the key to improving their sensing application value.

[0007] Existing technologies indicate that the optical properties of fluorescence discs (CDs) and their interactions with target materials are highly dependent on the chemical composition of their carbon source precursors and the surface modification during synthesis. Lotus seeds, as a biomass raw material rich in protein and starch, naturally contain nitrogen, oxygen, and other heteroatoms, which facilitate intrinsic doping during carbonization, thereby optimizing the electronic structure and fluorescence properties of CDs. Furthermore, post-treatment of CDs with suitable surface-modifying passivating agents can further passivate surface defects and introduce specific functional groups, thereby modulating their fluorescence behavior and interactions with metal ions or organic molecules. This provides a possibility for constructing fluorescence sensing systems.

[0008] This invention synthesizes carbon quantum dots (LS-MEA-CDs) using biomass lotus seeds as the carbon source via a one-step hydrothermal method and then functionalizes them with the passivating agent ethanolamine. To detect phosmet pesticide residues, a fluorescence "off-on" detection method was designed. The detection principle involves first quenching the fluorescence of the carbon quantum dots with iron ions, then introducing phosmet to bind with the iron ions, achieving specific fluorescence recovery. This method achieves excellent sensitivity and specificity in phosmet detection, providing a novel and efficient method for on-site pesticide residue detection. Currently, there are no related reports in this area. Summary of the Invention

[0009] The technical problem solved by this invention is to provide a method for detecting fly toxic phosphorus based on a carbon quantum dot-iron ion solution system. This method first uses iron ions to quench the fluorescence of carbon quantum dots, and then introduces fly toxic phosphorus to bind with iron ions to achieve specific fluorescence recovery, thereby achieving high sensitivity and specificity in the detection of fly toxic phosphorus.

[0010] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for detecting fly toxic phosphorus based on a carbon quantum dot-iron ion solution system, the specific steps of which are as follows: Step S1, Preparation of carbon quantum dots: Carbon quantum dots are prepared by hydrothermal reaction at 60~220℃ using biomass lotus seed powder and passivating agent as raw materials, wherein the passivating agent is one or more of diethylamine, ethanolamine, polyethyleneimine or polyethylene glycol. Step S2, Construction of the standard curve: In a series of centrifuge tubes, first add 0.50 mL of Tris-HCl buffer solution (pH 7.4), 4 μL of 6.12 mg / mL carbon quantum dot solution, and 35 μL of 5 mg / mL iron ion solution, respectively. Then, add phosmet standard solution in increasing concentrations sequentially. Dilute to 4.00 mL with ultrapure water, shake well, and scan the fluorescence emission spectrum at an excitation wavelength of 350 nm. Record the fluorescence intensity at 435 nm. The fluorescence intensity at 435 nm in the mixed system without phosmet standard solution is recorded as F1, and the fluorescence intensity at 435 nm with phosmet standard solution is recorded as F2. Calculate the F2-F1 value. The linear regression equation is Q = 293.17 + 10.25 × (F2-F1), R0 = 293.17 + 10.25 × (F2-F1). 2 =0.997, where Q is the concentration of phosmet, the linear range is 12.5~150 μg / L, the limit of detection is 1.55 μg / L, and the limit of quantitation is 5.15 μg / L; Step S3, detection of phosphatidylcholine concentration in the phosphatidylcholine-containing test solution: First, add 0.50 mL of Tris-HCl buffer solution (pH=7.4), 4 μL of carbon quantum dot solution (6.12 mg / mL), and 35 μL of iron ion solution (5 mg / mL) to a centrifuge tube. Then, add the phosphatidylcholine-containing test solution and dilute to 4.00 mL with ultrapure water. Shake well and scan the fluorescence emission spectrum at an excitation wavelength of 350 nm. Record the fluorescence intensity at an emission wavelength of 435 nm. The fluorescence intensity at an emission wavelength of 435 nm in the mixed system without the phosphatidylcholine-containing test solution is recorded as F1, and the fluorescence intensity at an emission wavelength of 435 nm with the phosphatidylcholine-containing test solution is recorded as F2. Calculate the F2-F1 value and calculate the phosphatidylcholine concentration in the phosphatidylcholine-containing test solution based on the linear regression equation.

[0011] Preferably, the specific preparation process of the carbon quantum dots is as follows: dissolve the biomass lotus seed powder in deionized water and sonicate until the solid is completely dissolved, then add a passivating agent and mix evenly to obtain a homogeneous solution. Transfer the homogeneous solution to a hydrothermal reactor and pyrolyze it at 60~220℃ for 2~8h. After the reaction is completed, cool naturally to obtain a brown solution. Centrifuge the obtained dark brown solution to remove large particle precipitates and filter it through a filter membrane with a pore size of 0.22μm to obtain a carbon quantum dot solution. Rotary evaporate the obtained carbon quantum dot solution to obtain a concentrated solution. Finally, freeze-dry the concentrated solution to obtain powdered carbon quantum dots.

[0012] Preferably, the carbon quantum dot-iron ion solution system formed by the carbon quantum dots and iron ions can selectively detect fly phosphonates among interfering substances, wherein the interfering substances are one or more of the following: azoxystrobin, dichlorvos, fenvalerate, chlorpyrifos, imidacloprid, carbofuran, phoxim, fenthion, isoprocarb, parathion, phosmet, methamidophos, iprodione, terbufos, trichlorfon, carbendazim, or methyl parathion.

[0013] Preferably, the ratio of lotus seed powder, deionized water and passivating agent is 0.3g:9~10mL:0.2~0.8mL.

[0014] Preferably, the freeze-drying temperature is -50°C.

[0015] Preferably, the specific preparation steps of the carbon quantum dots are as follows: 0.3g of biomass lotus seed powder is dissolved in 10mL of deionized water and sonicated until the solid is completely dissolved. Then, 0.8mL of passivating agent ethanolamine is added and mixed evenly to obtain a homogeneous solution. The homogeneous solution is transferred to a hydrothermal reactor and pyrolyzed at 200℃ for 4h. After the reaction is completed, it is naturally cooled to obtain a brown solution. The obtained dark brown solution is centrifuged to remove large particle precipitates and then filtered through a filter membrane with a pore size of 0.22μm to obtain a carbon quantum dot solution. The obtained carbon quantum dot solution is rotary evaporated to obtain a concentrated solution. Finally, the concentrated solution is freeze-dried at -50℃ to obtain powdered carbon quantum dots.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The synthesis process of this invention is simple. Carbon quantum dots with stable fluorescence properties can be obtained in one hydrothermal step without the need for multi-step modification or noble metal doping.

[0017] 2. This invention is the first to use biomass lotus seeds as a carbon source, which is inexpensive and achieves efficient conversion of biomass resources.

[0018] 3. In this invention, passivating agents such as ethanolamine are added to modify CDs. The quantum yield of the optimized LS-MEA-CDs is increased by 2.6 times compared with the unmodified ones, and the fluorescence intensity remains stable within 6 months.

[0019] 4. This invention is the first to achieve integrated detection of fluorescence "off-on" by iron ion quenching and fly toxic phosphorus recovery, which can avoid false negative results and has significant anti-interference ability.

[0020] 5. The solution system composed of blue luminescent carbon quantum dots synthesized in this invention and iron ions can rapidly and sensitively detect fly toxic phosphorus, realize on-site quantitative analysis, and expand the application of fluorescent carbon quantum dots in the field of pesticide residue detection. Attached Figure Description

[0021] Figure 1This is a transmission electron microscope image of the carbon quantum dots prepared in Example 1.

[0022] Figure 2 This is the Fourier transform infrared spectrum of the carbon quantum dots prepared in Example 1.

[0023] Figure 3 These are the optimal excitation and emission spectra of the carbon quantum dots prepared in Example 1.

[0024] Figure 4 The images show fluorescence spectra of the carbon quantum dot solution prepared in Example 1 with the addition of iron ion solutions of different concentrations.

[0025] Figure 5 The fluorescence spectra are obtained by adding different concentrations of fly venom phosphorus solution to the carbon quantum dot-iron ion solution system prepared in Example 1.

[0026] Figure 6 This is the standard working curve for detecting fly toxic phosphorus in the carbon quantum dot-iron ion solution system prepared in Example 1.

[0027] Figure 7 This describes the selectivity of carbon quantum dots prepared in Example 1 for common metal ions.

[0028] Figure 8 This describes the selectivity of the carbon quantum dot-iron ion solution system prepared in Example 1 for different organophosphorus pesticides. Detailed Implementation

[0029] The following examples further illustrate the above-described content of the present invention, but it should not be construed as limiting the scope of the subject matter of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Example 1

[0030] 0.3g of biomass lotus seed powder was dissolved in 10mL of deionized water and sonicated until the solid was completely dissolved. Then, 0.2mL of passivating agent ethanolamine was added and mixed thoroughly to obtain a homogeneous solution. The homogeneous solution was transferred to a hydrothermal reactor and pyrolyzed at 200℃ for 4 hours. After the reaction, it was allowed to cool naturally to obtain a brown solution. The brown solution was centrifuged to remove large precipitates and then filtered through a 0.22μm filter membrane to obtain a carbon quantum dot solution. The obtained carbon quantum dot solution was rotary evaporated to obtain a concentrated solution. Finally, the concentrated solution was freeze-dried at -50℃ to obtain powdered blue luminescent carbon quantum dots. The obtained carbon quantum dots were prepared into a blue luminescent carbon quantum dot solution and diluted to 4mL in a cuvette. The absorption and fluorescence spectra of the solution were measured using a UV-Vis spectrophotometer and a fluorescence spectrophotometer. The UV-Vis absorption spectrum, fluorescence excitation spectrum, and emission spectrum of the carbon quantum dots are shown below. Figure 3As shown in the figure, the ultraviolet absorption peak at 350 nm in the near-ultraviolet region is consistent with the fluorescence excitation peak. The fluorescence emission peak is in the 435 nm region, showing strong downconversion fluorescence characteristics. Example 2

[0031] 0.3 g of biomass lotus seed powder was dissolved in 10 mL of deionized water and sonicated until the solid was completely dissolved. Then, 0.4 mL of passivating agent ethanolamine was added and mixed thoroughly to obtain a homogeneous solution. The homogeneous solution was transferred to a hydrothermal reactor and pyrolyzed at 200 °C for 4 h. After the reaction was completed, it was naturally cooled to obtain a brown solution. The brown solution was centrifuged to remove large particles of precipitate and then filtered through a 0.22 μm pore size filter membrane to obtain a carbon quantum dot solution. The obtained carbon quantum dot solution was rotary evaporated to obtain a concentrated solution. Finally, the concentrated solution was freeze-dried at -50 °C to obtain powdered blue luminescent carbon quantum dots. The obtained carbon quantum dots were prepared into a blue luminescent carbon quantum dot solution and diluted to a volume of 4 mL in a cuvette. Example 3

[0032] 0.3 g of biomass lotus seed powder was dissolved in 10 mL of deionized water and sonicated until the solid was completely dissolved. Then, 0.6 mL of passivating agent ethanolamine was added and mixed thoroughly to obtain a homogeneous solution. The homogeneous solution was transferred to a hydrothermal reactor and pyrolyzed at 200 °C for 4 h. After the reaction was completed, the solution was allowed to cool naturally to obtain a brown solution. The brown solution was centrifuged to remove large precipitates and then filtered through a 0.22 μm pore size filter membrane to obtain a carbon quantum dot solution. The carbon quantum dot solution was then subjected to rotary evaporation to obtain a concentrated solution. Finally, the concentrated solution was freeze-dried at -50 °C to obtain powdered blue luminescent carbon quantum dots. The obtained carbon quantum dots were prepared into a blue luminescent carbon quantum dot solution and diluted to a volume of 4 mL in a cuvette. Example 4

[0033] 0.3 g of biomass lotus seed powder was dissolved in 10 mL of deionized water and sonicated until the solid was completely dissolved. Then, 0.8 mL of passivating agent ethanolamine was added and mixed thoroughly to obtain a homogeneous solution. The homogeneous solution was transferred to a hydrothermal reactor and pyrolyzed at 200 °C for 4 h. After the reaction was completed, the solution was allowed to cool naturally to obtain a brown solution. The brown solution was centrifuged to remove large precipitates and then filtered through a 0.22 μm pore size filter membrane to obtain a carbon quantum dot solution. The carbon quantum dot solution was then subjected to rotary evaporation to obtain a concentrated solution. Finally, the concentrated solution was freeze-dried at -50 °C to obtain powdered blue luminescent carbon quantum dots. The obtained carbon quantum dots were prepared into a blue luminescent carbon quantum dot solution and diluted to a volume of 4 mL in a cuvette. Example 5

[0034] Using 350 nm as the excitation wavelength, the concentration of 11 mg / mL was measured. -1Fluorescence spectra of carbon quantum dot solutions with different concentrations of iron ion solutions added (e.g.) Figure 4 As shown in the figure, the intrinsic fluorescence emission intensity of the blue luminescent carbon quantum dots gradually decreases with the increase of iron ion concentration, but does not change its maximum emission wavelength, indicating the feasibility of using the blue luminescent carbon quantum dots as a reliable fluorescent nanoprobe for the quantitative detection of metallic iron ions. Example 6

[0035] Using 350 nm as the excitation wavelength, the concentration of 4.65 mg / mL was measured. -1 Fluorescence spectra of carbon quantum dot solutions with different concentrations of phosmet solution added (e.g.) Figure 5 As shown in the figure, the fluorescence emission intensity of the blue luminescent carbon quantum dot-iron ion solution gradually increases with the increase of the concentration of phosphatidylcholine, indicating the feasibility of using the blue luminescent carbon quantum dots as a reliable fluorescent nanoprobe for the quantitative detection of phosphatidylcholine. Example 7

[0036] Plotting the standard curve: In a series of centrifuge tubes, first add 0.50 mL of Tris-HCl buffer solution (pH 7.4), 4 μL of 6.12 mg / mL carbon quantum dot solution, and 35 μL of 5 mg / mL iron ion solution, respectively. Then, add phosmet standard solution in increasing concentrations sequentially. Dilute to 4.00 mL with ultrapure water, shake well, and scan the fluorescence emission spectrum at 350 nm excitation wavelength. Record the fluorescence intensity at 435 nm. The fluorescence intensity at 435 nm in the mixed system without phosmet standard solution is recorded as F1, and the fluorescence intensity at 435 nm with phosmet standard solution is recorded as F2. Calculate the F2-F1 value. The linear regression equation is Q = 293.17 + 10.25 × (F2-F1), R0 = 293.17 + 10.25 × (F2-F1). 2 =0.997, where Q is the concentration of phosmet, the linear range is 12.5~150 μg / L, the limit of detection is 1.55 μg / L, and the limit of quantitation is 5.15 μg / L; Detection of phosphatidylcholine concentration in the test solution: Add 0.50 mL of pH 7.4 Tris-HCl buffer solution, 4 μL of 6.12 mg / mL carbon quantum dot solution, and 35 μL of 5 mg / mL iron ion solution to a centrifuge tube. Then add the phosphatidylcholine test solution and dilute to 4.00 mL with ultrapure water. Shake well. Scan the fluorescence emission spectrum at 350 nm excitation wavelength and record the fluorescence intensity at 435 nm. Record the fluorescence intensity at 435 nm in the mixed system without the phosphatidylcholine test solution as F1, and the fluorescence intensity at 435 nm with the phosphatidylcholine test solution as F2. Calculate the F2-F1 value and obtain the phosphatidylcholine concentration in the test solution based on a linear regression equation. Example 8

[0037] In a series of centrifuge tubes, 0.50 mL of Tris-HCl buffer solution (pH 7.4) and 6 μL of 6.12 mg / mL carbon quantum dot solution were added, followed by the addition of iron ions and other common metal ions of the same concentration. The solutions were then diluted to 4.00 mL with purified water and shaken well. The fluorescence emission spectra were scanned at an excitation wavelength of 350 nm, and the fluorescence intensity at an emission wavelength of 435 nm was recorded. Figure 7 As shown, the different letters above the horizontal line represent statistically significant differences (p<0.05, one-way ANOVA of the graphety test). Carbon quantum dots show almost no significant fluorescence quenching reaction to other common metal ions such as manganese, chromium, aluminum, nickel, calcium, potassium, copper, cobalt, magnesium, cadmium, lead, silver, and barium. Therefore, iron ions were chosen as the intermediate to turn off fluorescence in the method for determining fly phosphonate, and this indicates that the iron ion determination method provided by this invention has high selectivity. Figure 7 As shown. Example 9

[0038] In a series of centrifuge tubes, 0.50 mL of Tris-HCl buffer solution (pH 7.4), 4 μL of carbon quantum dot solution (6.12 mg / mL), and 35 μL of iron ion solution (5 mg / mL) were added respectively. Then, the same concentrations of phosmet and other similar organophosphorus pesticides were added, and the volumes were adjusted to 4.00 mL with purified water and mixed well. The fluorescence emission spectra were scanned at an excitation wavelength of 350 nm, and the fluorescence intensity at an emission wavelength of 435 nm was recorded. Figure 8 As shown, different letters above the horizontal line indicate statistically significant differences (p<0.05, one-way ANOVA of the graphety test). Carbon quantum dots showed almost no significant fluorescence recovery response to other organophosphorus pesticides and common pesticides such as pyraclostrobin, dichlorvos, fenvalerate, chlorpyrifos, imidacloprid, carbofuran, phoxim, fenthion, isoprocarb, parathion, phosmet, methamidophos, iprodione, terbufos, trichlorfon, carbendazim, and methyl parathion. This indicates that the fly toxic phosphorus determination method provided by this invention has high selectivity. Figure 8 As shown.

[0039] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Various changes and modifications can be made to the present invention without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for detecting fly toxic phosphorus based on a carbon quantum dot-iron ion solution system, characterized in that... The specific steps are as follows: Step S1, Preparation of carbon quantum dots: Carbon quantum dots are prepared by hydrothermal reaction at 60~220℃ using biomass lotus seed powder and passivating agent as raw materials, wherein the passivating agent is one or more of diethylamine, ethanolamine, polyethyleneimine or polyethylene glycol. Step S2, Construction of the standard curve: In a series of centrifuge tubes, first add 0.50 mL of Tris-HCl buffer solution (pH 7.4), 4 μL of 6.12 mg / mL carbon quantum dot solution, and 35 μL of 5 mg / mL iron ion solution, respectively. Then, add phosmet standard solution in increasing concentrations sequentially. Dilute to 4.00 mL with ultrapure water, shake well, and scan the fluorescence emission spectrum at an excitation wavelength of 350 nm. Record the fluorescence intensity at 435 nm. The fluorescence intensity at 435 nm in the mixed system without phosmet standard solution is recorded as F1, and the fluorescence intensity at 435 nm with phosmet standard solution is recorded as F2. Calculate the F2-F1 value. The linear regression equation is Q = 293.17 + 10.25 × (F2-F1), R0 = 293.17 + 10.25 × (F2-F1). 2 =0.997, where Q is the concentration of phosmet, the linear range is 12.5~150 μg / L, the limit of detection is 1.55 μg / L, and the limit of quantitation is 5.15 μg / L; Step S3, detection of phosphatidylcholine concentration in the phosphatidylcholine-containing test solution: First, add 0.50 mL of Tris-HCl buffer solution (pH=7.4), 4 μL of carbon quantum dot solution (6.12 mg / mL), and 35 μL of iron ion solution (5 mg / mL) to a centrifuge tube. Then, add the phosphatidylcholine-containing test solution and dilute to 4.00 mL with ultrapure water. Shake well and scan the fluorescence emission spectrum at an excitation wavelength of 350 nm. Record the fluorescence intensity at an emission wavelength of 435 nm. The fluorescence intensity at an emission wavelength of 435 nm in the mixed system without the phosphatidylcholine-containing test solution is recorded as F1, and the fluorescence intensity at an emission wavelength of 435 nm with the phosphatidylcholine-containing test solution is recorded as F2. Calculate the F2-F1 value and calculate the phosphatidylcholine concentration in the phosphatidylcholine-containing test solution based on the linear regression equation.

2. The method for detecting fly toxic phosphorus based on a carbon quantum dot-iron ion solution system according to claim 1, characterized in that: The carbon quantum dot-iron ion solution system formed by the carbon quantum dots and iron ions can selectively detect fly phosphonates among interfering substances, wherein the interfering substances are one or more of the following: azoxystrobin, dichlorvos, fenvalerate, chlorpyrifos, imidacloprid, carbofuran, phoxim, fenthion, isoprocarb, parathion, phosmet, methamidophos, iprodione, terbufos, trichlorfon, carbendazim, or methyl parathion.

3. The method for detecting fly toxic phosphorus based on a carbon quantum dot-iron ion solution system according to claim 1, characterized in that... The specific preparation process of the carbon quantum dots is as follows: dissolve the biomass lotus seed powder in deionized water and sonicate until the solid is completely dissolved. Then add a passivating agent and mix evenly to obtain a homogeneous solution. Transfer the homogeneous solution to a hydrothermal reactor and pyrolyze it at 60~220℃ for 2~8h. After the reaction is completed, cool naturally to obtain a brown solution. Centrifuge the obtained dark brown solution to remove large particle precipitates and filter it through a filter membrane with a pore size of 0.22μm to obtain a carbon quantum dot solution. Rotary evaporate the obtained carbon quantum dot solution to obtain a concentrated solution. Finally, freeze-dry the concentrated solution to obtain powdered carbon quantum dots.

4. The method for detecting fly toxic phosphorus based on a carbon quantum dot-iron ion solution system according to claim 3, characterized in that: The ratio of lotus seed powder, deionized water and passivating agent is 0.3g:9~10mL:0.2~0.8mL.

5. The method for detecting fly toxic phosphorus based on a carbon quantum dot-iron ion solution system according to claim 3, characterized in that: The freeze-drying temperature is -50℃.

6. The method for detecting fly toxic phosphorus based on a carbon quantum dot-iron ion solution system according to claim 1, characterized in that... The specific preparation steps of the carbon quantum dots are as follows: 0.3g of biomass lotus seed powder is dissolved in 10mL of deionized water and sonicated until the solid is completely dissolved. Then, 0.8mL of passivating agent ethanolamine is added and mixed evenly to obtain a homogeneous solution. The homogeneous solution is transferred to a hydrothermal reactor and pyrolyzed at 200℃ for 4h. After the reaction is completed, it is naturally cooled to obtain a brown solution. The obtained dark brown solution is centrifuged to remove large particle precipitates and then filtered through a filter membrane with a pore size of 0.22μm to obtain a carbon quantum dot solution. The obtained carbon quantum dot solution is rotary evaporated to obtain a concentrated solution. Finally, the concentrated solution is freeze-dried at -50℃ to obtain powdered carbon quantum dots.

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