Preparation method and application of carbon dots for dual-channel detection of pesticide carbendazim

Abstract

The invention discloses a preparation method of carbon dots for double-channel detection of pesticide carbendazim, which comprises the following steps: mixing a carbon source with acid water or aqueous alkali for reaction to obtain fluorescent carbon dots; and mixing the fluorescent carbon dots with a matrix for reaction to obtain the room-temperature phosphorescent carbon dots. The invention also discloses an application of the room-temperature phosphorescent carbon dot in two-channel detection of pesticide carbendazim. The room-temperature phosphorescent carbon dots prepared by the invention can interact with carbendazim in the presence of carbendazim, so that the distance between the room-temperature phosphorescent carbon dots and the carbendazim is short, and energy transfer or electron transfer between molecules can occur. The fluorescence intensity, the fluorescence wavelength, the phosphorescence intensity, the phosphorescence wavelength and the phosphorescence service life of the room-temperature phosphorescence carbon dots are changed, and the purpose of quantitatively detecting carbendazim through fluorescence and phosphorescence double channels is achieved. According to the method, the fluorescence and phosphorescence dual-channel sensing technology is used for ultrasensitively detecting the residual content of carbendazim in food and water environment for the first time, and compared with a traditional carbendazim detection method, the method has the advantages that the visualization effect is good, the accuracy and sensitivity are high, and the selectivity is good. And the requirements of batch preparation in industrial production are met, so that the method is extremely easy to practically popularize and apply.

Description

Technical Field

[0001] The invention belongs to the technical field of probe detection, and in particular relates to a preparation method and application of carbon dots for dual-channel detection of the pesticide carbendazim. Background Art

[0002] Carbendazim is a systemic broad-spectrum fungicide. It is mainly used to prevent and treat wheat fusarium head blight, rice sheath blight, cotton seedling damping-off and sweet potato yellow spot, as well as various diseases on field crops, vegetables, fruits and other crops caused by ascomycetes, deuteromycetes and basidiomycetes. It has a good effect on the prevention and treatment of diseases and insect pests caused by fungi. However, in actual production, the unscientific use of carbendazim not only leads to the accumulation of residues in agricultural products, but also causes problems such as the enhancement of pest resistance and environmental pollution. This process directly affects the quality and safety of agricultural products and greatly threatens human health. When people or livestock eat food containing high-dose carbendazim residues, acute poisoning incidents may occur, and the symptoms of poisoning include dizziness, nausea, vomiting, abdominal pain, etc. Although long-term consumption of agricultural and sideline products containing excessive carbendazim residues may not cause acute poisoning immediately, long-term low-dose exposure will also bring many hazards. For example, it can cause a decline in the function of the human immune system, making the human body more susceptible to disease; it can damage the liver and kidneys, affecting the normal metabolism and detoxification functions of these organs; and it can cause intestinal flora imbalance, leading to digestive disorders, diarrhea and other problems, and even increase the risk of secondary infection. It can be seen that the residues of carbendazim in agricultural products, soil and water bodies pose an extremely severe challenge to food safety, human health and environmental protection. At present, the commonly used methods for detecting carbendazim, such as gas chromatography, enzyme-linked immunosorbent assay, liquid chromatography-mass spectrometry, etc., are time-consuming, expensive equipment, and cumbersome sample preparation, which are difficult to meet the needs of rapid on-site screening and low-cost monitoring. Therefore, there is an urgent need for advanced sensing materials and efficient analytical detection technologies to overcome the difficulties faced by high-sensitivity detection of carbendazim residues in agricultural products and the environment. Summary of the invention

[0003] One of the purposes of the present invention is to provide a preparation method of carbon dots for dual-channel detection of the pesticide carbendazim, using cheap and readily available biomass and organic matter as carbon sources, designing and synthesizing dual-channel emission room temperature phosphorescent CDs, and utilizing different reaction raw materials, reaction time, and reaction temperature to achieve regulation of the fluorescence and phosphorescence emission intensity, wavelength, and lifetime of the CDs.

[0004] The second object of the present invention is to provide an application of the carbon dots, which induces changes in the fluorescence and phosphorescence intensity, wavelength and lifetime of the room temperature phosphorescent CDs probe through different interactions between carbendazim and room temperature phosphorescent CDs, thereby achieving highly sensitive and rapid spatiotemporal sensing of specific carbendazim.

[0005] The present invention provides a method for preparing carbon dots for dual-channel detection of the pesticide carbendazim, comprising the following steps:

[0006] S1. Add an acid aqueous solution or an alkaline aqueous solution to the carbon source and mix well to obtain a reaction solution;

[0007] S2. The reaction solution obtained in step S1 is transferred into a reactor, heated for reaction, and naturally cooled to room temperature after the reaction is complete. The reaction product is centrifuged, the supernatant is filtered, and the filtrate is placed in a dialysis bag and dialyzed in ultrapure water to obtain fluorescent carbon dots;

[0008] S3. The fluorescent carbon dots obtained in step S2 are mixed with the matrix and reacted for a preset time to obtain room temperature phosphorescent carbon dots.

[0009] Further, in step S1, the carbon source includes one or more of biomass, small organic molecules and polymer molecules;

[0010] The biomass includes watermelon, garlic, and orange;

[0011] The organic small molecules include ethylenediamine, citric acid, urea, acrylamide, and o-phenylenediamine;

[0012] The polymer molecules include polyvinyl alcohol, polyacrylic acid, polyacrylamide and polypropylene imine.

[0013] The acid aqueous solution includes one or more combinations of hydrochloric acid, hypochlorous acid, perchloric acid, hydrobromic acid, hypobromous acid, perbromic acid, iodic acid, hypoiodous acid, periodic acid, hydrofluoric acid, boric acid, nitric acid, nitrous acid, acetic acid, citric acid, sulfuric acid, hyposulfurous acid, carbonic acid, phosphoric acid, pyrophosphoric acid and hypophosphorous acid.

[0014] The alkaline aqueous solution includes one or more combinations of ammonia water, alkali metal or alkaline earth metal hydroxides, alkali metal or alkaline earth metal carbonates, alkali metal or alkaline earth metal monohydrogen carbonates, alkali metal or alkaline earth metal phosphates, alkali metal or alkaline earth metal monohydrogen phosphates, and alkali metal or alkaline earth metal dihydrogen phosphates.

[0015] The concentration of the acid aqueous solution or the alkaline aqueous solution is 0-1M; the molar ratio of the carbon source to the acid aqueous solution or the alkaline aqueous solution is 100:(1-10000).

[0016] Furthermore, in step S2, the reactor is any one of a microwave reactor, an ultrasonic reactor, a hydrothermal reactor and a muffle furnace.

[0017] The temperature of the heating reaction is 80° C. to 300° C., and the reaction time is 1 to 24 hours.

[0018] The centrifugal speed is 5000-12000 rpm, and the time is 0.1-1 h.

[0019] The pore size of the microporous filter membrane for filtration is 0.22-0.45 μm.

[0020] The molecular cutoff of the dialysis bag is 500 to 10,000 Da, and the dialysis time is 24 to 72 hours.

[0021] The obtained fluorescent carbon dots include blue fluorescent carbon dots, green fluorescent carbon dots, yellow fluorescent carbon dots and red fluorescent carbon dots; the emission wavelength of the fluorescent carbon dots is 350nm-800nm.

[0022] Furthermore, the molar ratio of the carbon source to the acid water or alkaline aqueous solution for preparing the blue fluorescent carbon dots is (100:1-20:1), the reaction time is 1-24h, and the reaction temperature is 80-250°C.

[0023] The molar ratio of the carbon source to the acid water or alkaline aqueous solution for preparing the green fluorescent carbon dots is (3:1-1:100), the reaction time is 1-24 hours, and the reaction temperature is 80-250°C.

[0024] The molar ratio of the carbon source to the acid water or alkaline aqueous solution for preparing the yellow fluorescent carbon dots is (100:1-1:20), the reaction time is 1-24 hours, and the reaction temperature is 100-300°C.

[0025] The molar ratio of the carbon source to the acid water or alkaline aqueous solution for preparing the red fluorescent carbon dots is (1:400-100:1), the reaction time is 1-24 hours, and the reaction temperature is 100-300°C.

[0026] Furthermore, in step S3, the molar ratio of the fluorescent carbon dots to the matrix is ​​1:(10-1000); the temperature of the mixed reaction of the fluorescent carbon dots and the matrix is ​​25°C-350°C, and the reaction time is 1-24h.

[0027] The matrix includes boric acid, phosphoric acid, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid, tetraethyl orthosilicate and inorganic salt.

[0028] The room temperature phosphorescent carbon dots have luminescent colors of blue, green, yellow, orange and red, and an emission wavelength of 350 to 800 nm.

[0029] Furthermore, the molar ratio of the fluorescent carbon dots to the matrix for preparing the blue room temperature phosphorescent carbon dots is (1:10 to 1:1000), the reaction time is 1 to 24 hours, and the reaction temperature is 25 to 300°C.

[0030] The molar ratio of the fluorescent carbon dots to the matrix for preparing the green room temperature phosphorescent carbon dots is (1:10-1:100), the reaction time is 1-24 hours, and the reaction temperature is 50-300°C.

[0031] The molar ratio of the fluorescent carbon dots to the matrix for preparing the yellow room temperature phosphorescent carbon dots is (1:20-1:400), the reaction time is 1-24 hours, and the reaction temperature is 25-300°C.

[0032] The molar ratio of the fluorescent carbon dots to the matrix for preparing the red room temperature phosphorescent carbon dots is (1:10-1:1000), the reaction time is 1-24 hours, and the reaction temperature is 50-300°C.

[0033] The present invention also provides an application of the carbon dots in dual-channel detection of the pesticide carbendazim, comprising the following steps:

[0034] a. dissolving the room temperature phosphorescent carbon dots in a buffer solution with a preset gradient pH, and testing the relationship between fluorescence intensity, fluorescence wavelength, phosphorescence wavelength, phosphorescence intensity, phosphorescence lifetime and buffer pH;

[0035] b. According to the relationship between the fluorescence intensity, fluorescence wavelength, phosphorescence wavelength, phosphorescence intensity, phosphorescence lifetime and buffer pH obtained in step a, a buffer with the optimal pH is selected as a solvent, and the wavelength dependence of the room temperature phosphorescent carbon dots is tested to obtain the excitation wavelength of the room temperature phosphorescent carbon dots at the optimal pH;

[0036] c. Using the optimal pH buffer obtained in step b as a solvent, according to the excitation wavelength of the room temperature phosphorescent carbon dots at the optimal pH, add carbendazim to set the concentration threshold, and test the maximum time required for the carbendazim reaction to be complete below the set concentration;

[0037] d. Using the buffer solution with the optimal pH obtained in step b as the solvent, the excitation wavelength of the room temperature phosphorescent carbon dots at the optimal pH, and the maximum time for the complete reaction obtained in step c, titrating carbendazim with a concentration gradient below the set concentration threshold to obtain the relationship between carbendazim concentration and fluorescence intensity and the relationship between carbendazim concentration and phosphorescence concentration;

[0038] e. Perform actual dual-channel detection of carbendazim according to the relationship between the carbendazim concentration and the fluorescence intensity or the carbendazim concentration and the phosphorescence concentration obtained in step d.

[0039] Furthermore, in step b, the pH of the buffer solution when the fluorescence and phosphorescence intensities are the highest is selected and the pH is taken as the optimal pH.

[0040] Principle of the present invention:

[0041] Carbendazim contains a benzimidazole ring, which has certain aromaticity and stability, and can form π-π stacking with other molecules containing large π bonds; the methyl carbamate group connected to the benzimidazole ring provides carbendazim with certain hydrophilicity and reactivity, and can form hydrogen bonds with other molecules containing hydroxyl or amino groups; in addition, the amino group in carbendazim can be protonated under certain conditions, carrying a positive charge, and undergoing electrostatic interactions with negatively charged molecules.

[0042] The carbon dots of the present invention can form π-π stacking and multiple hydrogen bonds with carbendazim, so that the distance between the two is relatively short, thereby having the opportunity to transfer energy or transfer electrons between molecules, so that the fluorescence wavelength, intensity, room temperature phosphorescence wavelength, intensity and lifetime of the carbon dots change.

[0043] Beneficial effects of the present invention:

[0044] (1) The room temperature phosphorescent CDs proposed in the present invention are synthesized by hydrothermal / microwave method using cheap, readily available, economical and green biomass raw materials and small molecule organic matter as carbon sources. The preparation process is green, environmentally friendly, low-cost and pollution-free.

[0045] (2) The present invention can obtain blue light, green light, yellow light, red light, near-infrared fluorescence and phosphorescence CDs materials by changing the reaction conditions (carbon source, substrate, pH value, reaction temperature, time, pressure, etc.), and the fluorescence and phosphorescence emission wavelengths thereof are between 350 and 800 nm, so that the fluorescence intensity, fluorescence wavelength, phosphorescence intensity, phosphorescence wavelength and phosphorescence life of CDs can be controlled and adjusted, and can be used to detect different carbendazims;

[0046] (3) The present invention proposes for the first time to detect carbendazim using carbon dots with dual-channel emission of fluorescence and room temperature phosphorescence. Through simple interactions (such as hydrogen bonding, electrostatic interaction, π-π stacking, etc.), the distance between carbendazim and carbon dots is relatively short, so that there is a chance for energy transfer or electron transfer between molecules. This causes the fluorescence wavelength, intensity, room temperature phosphorescence wavelength, intensity, and life span of the carbon dots to change accordingly, thereby achieving dual-channel multi-index detection of carbendazim and greatly improving the accuracy and sensitivity of detection. This type of room temperature phosphorescent CDs will provide a new technical basis for the rapid and accurate detection of carbendazim residues in agricultural products and the environment, and will greatly promote my country's innovation capabilities in carbendazim residue detection technology, and will be of great significance to food safety, human health and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a schematic diagram of the preparation process of room temperature fluorescent carbon dots in Example 1;

[0048] Figure 2 This is a phosphorescence photograph of the room temperature phosphorescent carbon dots prepared in Example 1;

[0049] Figure 3 The infrared spectrum of the room temperature phosphorescent carbon dots prepared in Example 2;

[0050] Figure 4 The phosphorescence spectrum of the room temperature phosphorescent carbon dots prepared in Example 3;

[0051] Figure 5 The fluorescence spectrum of the room temperature phosphorescent carbon dots prepared in Example 5;

[0052] Figure 6 Schematic diagram of the principle of dual-channel detection in Example 9;

[0053] Figure 7 is a graph showing changes in phosphorescence intensity and lifetime of room temperature phosphorescent carbon dots after adding carbendazim in Example 9;

[0054] Figure 8 This is a graph showing the change in fluorescence intensity of room temperature phosphorescent carbon dots after adding carbendazim in Example 10;

[0055] Fig. 9 This is the room temperature phosphorescent carbon dot spectrum after adding carbendazim in Example 11. DETAILED DESCRIPTION

[0056] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] Example 1

[0058] Add 2 mL 15 mM ethylenediamine and 5 g citric acid into a beaker containing 30 mL pure water and mix thoroughly.

[0059] like Figure 1 The preparation method of carbon dots was as follows: the mixed solution was transferred into a 50 mL polytetrafluoroethylene reactor, the reaction temperature was controlled at 180 °C, and the reaction time was 12 h;

[0060] After the reaction was completed, the mixture was naturally cooled to 30° C., the reaction solution was collected, and the blue fluorescent CDs were separated and purified.

[0061] The purified fluorescent CDs and 4 mL of 3 mM CaCl2 solution were placed in a polytetrafluoroethylene reactor, the reaction temperature was controlled at 280 °C, and the reaction time was 2 hours;

[0062] After the reaction, the mixture was naturally cooled to 30° C., and the obtained phosphorescent CDs were purified to obtain room temperature phosphorescent CDs with yellow phosphorescence and a lifetime of 10 s.

[0063] Figure 2 This is a phosphorescence photograph of room temperature phosphorescent CDs. It can be seen from the figure that after the 365nm ultraviolet lamp is turned off, its yellow phosphorescence can last for about 9 seconds.

[0064] Example 2

[0065] Accurately weigh 0.5g of o-phenylenediamine and 3mL of 2mM citric acid in 30mL of ultrapure water and mix thoroughly. Then transfer to a 30mL reactor, set the reaction temperature to 180℃, and the reaction time to 8h;

[0066] After the reaction, the mixture was naturally cooled to 30° C., the reaction solution was collected, and the red fluorescent CDs were separated and purified.

[0067] 1 mL of fluorescent CDs was mixed with 3 mL of 20% polyvinyl alcohol solution and stirred at room temperature for 4 hours. The solution was then dried at 60° C. for 1 hour to obtain red room temperature phosphorescent CDs.

[0068] Figure 3 This is the infrared spectrum of the CDs in Example 2. From the infrared spectrum, we can know that the surface of CDs contains a large number of hydroxyl groups and amino groups.

[0069] Example 3

[0070] 2 g of purple sweet potato was cut into pieces, mixed evenly with 30 mL of 50 mM sodium hydroxide solution, and then transferred to a 50 mL high-pressure reactor, the temperature was controlled at 180° C., and the reaction was carried out for 8 hours.

[0071] After the reaction was completed, the mixture was naturally cooled to room temperature, the reaction solution was collected, and the blue fluorescent CDs were obtained by separation and purification.

[0072] 2 mL of the obtained CDs and 4 mL of 10 mM phosphoric acid were dissolved in 14 mL of ultrapure water, and then transferred to a 100 mL round-bottom flask and reacted at 180° C. for 3 hours to obtain CDs with green room temperature phosphorescence.

[0073] Figure 4 This is the phosphorescence spectrum of the green room temperature phosphorescent CDs of Example 3. It can be seen from the figure that the optimal excitation wavelength of the phosphorescent CDs is 400nm, and the emission wavelength is 510nm.

[0074] Example 4

[0075] 2 g of wolfberry was mixed evenly with 30 mL of 10 mM sodium bicarbonate solution, and then transferred to a 50 mL high-pressure reactor, the temperature was controlled at 180° C., and the reaction was carried out for 8 hours.

[0076] After the reaction was completed, the mixture was naturally cooled to room temperature, the reaction solution was collected, and the blue fluorescent CDs were obtained by separation and purification.

[0077] 2 mL of the obtained CDs and 4 mL of 5 mM phosphoric acid were dissolved in 14 mL of ultrapure water, and then transferred to a 100 mL round-bottom flask and reacted at 180° C. for 3 hours to obtain CDs with yellow room temperature phosphorescence.

[0078] Example 5

[0079] Dissolve 2 ml of 10 mM urea and 3 ml of 15 mM phosphoric acid in a beaker containing 15 ml of ultrapure water and stir at room temperature for 30 min.

[0080] The mixed solution was placed in a microwave reactor and reacted for 5 minutes at a power of 700 W, and the obtained product was dissolved in 20 ml of ultrapure water. The liquid was then collected and filtered to purify to obtain blue fluorescent CDs.

[0081] 2 ml of fluorescent CDs were dissolved in 15 ml of ultrapure water, and then 2 ml of 15 mM tetraethyl orthosilicate and 0.5 ml of 5 mM ammonia water were added. The mixed solution was stirred at room temperature for 5 hours to obtain CDs with green room temperature phosphorescence.

[0082] Figure 5 : is the fluorescence spectrum of the fluorescent CDs in Example 5. It can be seen from the figure that the optimal excitation wavelength of CDs is 320nm, emitting blue fluorescence.

[0083] Example 6

[0084] Dissolve 0.5 g acrylamide and 3 ml 8 mM phosphoric acid in 20 ml ultrapure water and transfer the mixed solution to a beaker;

[0085] The mixed solution was placed in a microwave reactor and reacted at a power of 750 W for 10 minutes;

[0086] After the reaction was completed, the mixture was cooled to room temperature, the solid powder was dissolved in 20 ml of ultrapure water, the liquid was collected, and dialyzed for purification to obtain red fluorescent CDs.

[0087] 2 ml of red fluorescent CDs and 5 ml of 20% by mass polyvinyl pyrrolidone solution were stirred and reacted at room temperature for 5 hours, and the obtained liquid was naturally dried to obtain red room temperature phosphorescent CDs.

[0088] Example 7

[0089] Dissolve 0.1 g of o-phenylenediamine and 3 mL of 4 mM phosphoric acid in 20 mL of water, mix well, and stir at room temperature for 30 min;

[0090] The mixed solution was transferred to a beaker and then placed in a microwave reactor with the power set to 700 W and the reaction time set to 5 min;

[0091] After the reaction was completed, the mixture was cooled to room temperature, and the obtained reactant was dissolved in 20 ml of ultrapure water. The liquid was collected and purified by dialysis to obtain red fluorescent CDs.

[0092] Dissolve 2 ml of fluorescent CDs in 15 ml of water, then add 2 ml of 3 mM tetraethyl orthosilicate and 0.5 ml of 4 mM ammonia water, mix well, and stir the mixed solution at room temperature for 8 hours to obtain a red phosphorescent CDs solution.

[0093] Example 8

[0094] Dissolve 0.05g acrylamide, 0.1g ethylenediamine and 1g sodium phosphate in 30ml ultrapure water and stir to mix well; transfer the mixed solution to a 50ml high-pressure reactor, set the temperature to 200°C, and react for 12 hours;

[0095] After the reaction was completed, the mixture was cooled to room temperature, and the reaction solution was collected and separated and purified to obtain green fluorescent CDs;

[0096] Dissolve 5 ml of green fluorescent CDs in 20 ml of ultrapure water, add 3 g of boric acid, and stir thoroughly to mix;

[0097] The mixed solution was transferred to a 100 ml round-bottom flask and reacted at 180° C. for 5 hours to obtain a solid powder of yellow-green phosphorescent CDs.

[0098] Example 9

[0099] Using the room temperature phosphorescent CDs prepared in Example 1;

[0100] Use as Figure 6 The principle shown is: the large conjugated system on the surface of carbon dots forms π-π stacking with the benzene ring in the carbendazim molecule; the amino and hydroxyl groups on the surface of carbon dots form hydrogen bonds with the carbonyl groups in the carbendazim molecule, resulting in electron transfer between the two, and the fluorescence of carbon dots is quenched. The prepared yellow room temperature phosphorescent CDs are used for dual-channel detection of carbendazim, including the following steps:

[0101] The room temperature phosphorescent CDs were dissolved in buffer solutions of different pH values, and the buffer solution (pH = 7.4) with the highest fluorescence and phosphorescence intensities was selected by testing the changes in fluorescence / phosphorescence intensities.

[0102] In the buffer solution with the optimal pH = 7.4, the wavelength dependence of 450nm to 600nm was tested, and 500nm was found to be the optimal excitation wavelength;

[0103] Select pH=7.4 buffer solution as solvent and 500nm as excitation wavelength, add 20μM concentration of carbendazim, test the time required for reaction, and the time for complete reaction is 2min;

[0104] Under the above conditions, 0-10 μM carbendazim was titrated to test the changes in fluorescence intensity, fluorescence wavelength, phosphorescence intensity, phosphorescence wavelength, and phosphorescence lifetime.

[0105] Figure 7 The changes of room temperature phosphorescence of room temperature phosphorescent CDs before and after adding 10μM carbendazim. As can be seen from the figure, carbendazim can reduce the phosphorescence intensity of room temperature phosphorescent CDs and shorten their lifespan.

[0106] Example 10

[0107] Using the room temperature phosphorescent CDs prepared in Example 1;

[0108] The prepared yellow room temperature phosphorescent CDs are used for dual channel detection of carbendazim, comprising the following steps:

[0109] The room temperature phosphorescent CDs were dissolved in buffer solutions of different pH values, and the buffer solution (pH = 7.0) with the highest fluorescence and phosphorescence intensities was selected by testing the changes in fluorescence / phosphorescence intensities.

[0110] In the optimal buffer solution of pH=7.0, the wavelength dependence of 250nm to 350nm was tested, and 300nm was found to be the optimal excitation wavelength;

[0111] Select pH=7.0 buffer solution as solvent and 350nm as excitation wavelength, add 12μM concentration of carbendazim, test the time required for reaction, and the time for complete reaction is 1min;

[0112] Under the above conditions, 0-12 μM carbendazim was titrated to test the fluorescence intensity, fluorescence wavelength, phosphorescence intensity, phosphorescence wavelength, and phosphorescence lifetime.

[0113] Figure 8 This is the response of the blue fluorescence of CDs to carbendazim in Example 1. From the fluorescence response spectrum, it can be seen that as the concentration of carbendazim increases, the blue fluorescence intensity of CDs gradually decreases.

[0114] Embodiment 11

[0115] Using the room temperature phosphorescent CDs prepared in Example 8;

[0116] The prepared yellow-green room temperature phosphorescent CDs are used for dual-channel detection of carbendazim, comprising the following steps:

[0117] The room temperature phosphorescent CDs were dissolved in buffer solutions of different pH values, and the buffer solution (pH = 6.8) with the highest fluorescence and phosphorescence intensities was selected by testing the changes in fluorescence / phosphorescence intensities.

[0118] In the buffer solution with the best pH = 6.8, the wavelength dependence of 350nm to 450nm was tested, and 370nm was found to be the best excitation wavelength;

[0119] Select pH=6.8 buffer solution as solvent and 370nm as excitation wavelength, add 10μM concentration of carbendazim, test the time required for reaction, and the time for complete reaction is 1min;

[0120] Under the above conditions, 0-10 μM carbendazim was titrated to test the changes in fluorescence / phosphorescence intensity and lifetime.

[0121] Fig. 9 This is the response of the yellow-green phosphorescence of room temperature phosphorescent CDs to carbendazim. From the spectrum, it can be seen that the phosphorescence intensity of CDs gradually decreases with the increase of carbendazim concentration.

Claims

1. A method for preparing carbon dots for dual-channel detection of the pesticide carbendazim, characterized in that: The following steps are involved: S1. Add an acid aqueous solution or an alkaline aqueous solution to the carbon source and mix well to obtain a reaction solution; S2. The reaction solution obtained in step S1 is transferred into a reactor, heated for reaction, and naturally cooled to room temperature after the reaction is complete. The reaction product is centrifuged, the supernatant is filtered, and the filtrate is placed in a dialysis bag and dialyzed in ultrapure water to obtain fluorescent carbon dots; S3. The fluorescent carbon dots obtained in step S2 are mixed with the matrix and reacted for a preset time to obtain room temperature phosphorescent carbon dots.

2. The method for preparing carbon dots for dual-channel detection of the pesticide carbendazim according to claim 1, characterized in that: In step S1, the carbon source includes one or more of biomass, organic small molecules, and polymer molecules; biomass includes watermelon, garlic, and orange; organic small molecules include ethylenediamine, citric acid, urea, acrylamide, and o-phenylenediamine; polymer molecules include polyvinyl alcohol, polyacrylic acid, polyacrylamide, and polypropyleneimine.

3. The method for preparing carbon dots for dual-channel detection of the pesticide carbendazim according to claim 1, characterized in that: In step S1, the acid aqueous solution includes one or more combinations of hydrochloric acid, hypochlorous acid, perchloric acid, hydrobromic acid, hypobromic acid, perbromic acid, iodic acid, hypoiodous acid, periodic acid, hydrofluoric acid, boric acid, nitric acid, nitrous acid, acetic acid, citric acid, sulfuric acid, hyposulfurous acid, carbonic acid, phosphoric acid, pyrophosphoric acid and hypophosphorous acid; the alkaline aqueous solution includes one or more combinations of ammonia water, alkali metal or alkaline earth metal hydroxides, alkali metal or alkaline earth metal carbonates, alkali metal or alkaline earth metal monohydrogen carbonates, alkali metal or alkaline earth metal phosphates, alkali metal or alkaline earth metal monohydrogen phosphates, and alkali metal or alkaline earth metal dihydrogen phosphates; the concentration of the acid aqueous solution or the alkaline aqueous solution is 0 to 1M; and the molar ratio of the carbon source to the acid water or the alkaline aqueous solution is 100:(1 to 10000).

4. The method for preparing carbon dots for dual-channel detection of the pesticide carbendazim according to claim 1, characterized in that: In step S2, the reactor is any one of a microwave reactor, an ultrasonic reactor, a hydrothermal reactor and a muffle furnace; The heating reaction temperature is 80°C to 300°C, and the reaction time is 1 to 24 hours; The centrifugal speed is 5000-12000 rpm, and the time is 0.1-1h; The pore size of the microporous filter membrane is 0.22-0.45 μm; The molecular cutoff of the dialysis bag is 500 to 10,000 Da, and the dialysis time is 24 to 72 h; The obtained fluorescent carbon dots include blue fluorescent carbon dots, green fluorescent carbon dots, yellow fluorescent carbon dots and red fluorescent carbon dots; the emission wavelength of the fluorescent carbon dots is 350nm-800nm.

5. The method for preparing carbon dots for dual-channel detection of the pesticide carbendazim according to claim 4, characterized in that: In step S2, the molar ratio of the carbon source to the acid water or alkaline aqueous solution for preparing the blue fluorescent carbon dots is (100:1-20:1), the reaction time is 1-24h, and the reaction temperature is 80-250°C; The molar ratio of the carbon source to the acid water or alkaline aqueous solution for preparing the green fluorescent carbon dots is (3:1-1:100), the reaction time is 1-24 hours, and the reaction temperature is 80-250°C; The molar ratio of the carbon source to the acid water or alkaline aqueous solution for preparing the yellow fluorescent carbon dots is (100:1-1:20), the reaction time is 1-24 hours, and the reaction temperature is 100-300°C; The molar ratio of the carbon source to the acid water or alkaline aqueous solution for preparing the red fluorescent carbon dots is (1:400-100:1), the reaction time is 1-24 hours, and the reaction temperature is 100-300°C.

6. The method for preparing carbon dots for dual-channel detection of the pesticide carbendazim according to claim 1, characterized in that: In step S3, the molar ratio of the fluorescent carbon dots to the matrix is ​​1:(10-1000); the temperature of the mixed reaction of the fluorescent carbon dots and the matrix is ​​25°C-350°C, and the reaction time is 1-24h; The matrix includes boric acid, phosphoric acid, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid, tetraethyl orthosilicate and inorganic salt.

7. The method for preparing carbon dots for dual-channel detection of the pesticide carbendazim according to claim 1, characterized in that: In step S3, the luminescent colors of the obtained room temperature phosphorescent carbon dots are blue, green, yellow, orange and red, and the emission wavelength is 350 to 800 nm.

8. The method for preparing carbon dots for dual-channel detection of the pesticide carbendazim according to claim 7, characterized in that: In step S3, the molar ratio of the fluorescent carbon dots to the matrix for preparing the blue room temperature phosphorescent carbon dots is (1:10 to 1:1000), the reaction time is 1 to 24 hours, and the reaction temperature is 25 to 300° C.; The molar ratio of the fluorescent carbon dots to the matrix for preparing the green room temperature phosphorescent carbon dots is (1:10-1:100), the reaction time is 1-24 hours, and the reaction temperature is 50-300°C; The molar ratio of the fluorescent carbon dots to the matrix for preparing the yellow room temperature phosphorescent carbon dots is (1:20-1:400), the reaction time is 1-24 hours, and the reaction temperature is 25-300° C.; The molar ratio of the fluorescent carbon dots to the matrix for preparing the red room temperature phosphorescent carbon dots is (1:10-1:1000), the reaction time is 1-24 hours, and the reaction temperature is 50-300°C.

9. An application of the room temperature phosphorescent carbon dots obtained by the preparation method according to any one of claims 1 to 8 in dual-channel detection of the pesticide carbendazim, characterized in that: The following steps are involved: a. dissolving the room temperature phosphorescent carbon dots in a buffer solution with a preset gradient pH, and testing the relationship between fluorescence intensity, fluorescence wavelength, phosphorescence wavelength, phosphorescence intensity, phosphorescence lifetime and buffer pH; b. According to the relationship between the fluorescence intensity, fluorescence wavelength, phosphorescence wavelength, phosphorescence intensity, phosphorescence lifetime and buffer pH obtained in step a, a buffer with the optimal pH is selected as a solvent, and the wavelength dependence of the room temperature phosphorescent carbon dots is tested to obtain the excitation wavelength of the room temperature phosphorescent carbon dots at the optimal pH; c. Using the optimal pH buffer obtained in step b as a solvent, according to the excitation wavelength of the room temperature phosphorescent carbon dots at the optimal pH, add carbendazim to set the concentration threshold, and test the maximum time required for the carbendazim reaction to be complete below the set concentration; d. Using the buffer solution with the optimal pH obtained in step b as the solvent, the excitation wavelength of the room temperature phosphorescent carbon dots at the optimal pH, and the maximum time for the complete reaction obtained in step c, titrating carbendazim with a concentration gradient below the set concentration threshold to obtain the relationship between carbendazim concentration and fluorescence intensity and between carbendazim concentration and phosphorescence concentration; e. Perform actual dual-channel detection of carbendazim according to the relationship between the carbendazim concentration and the fluorescence intensity or the carbendazim concentration and the phosphorescence concentration obtained in step d.

10. The use according to claim 9, characterized in that: In step b, the pH of the buffer solution when the fluorescence and phosphorescence intensities are the highest is selected as the optimal pH.

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