Preparation method of red fluorescent carbon dots and application in detection of hypochlorite

Abstract

The present application relates to a kind of preparation method of red fluorescent carbon dots and application in detecting hypochlorite;Firstly, N,N'-(1,4-phenylene) bis(N-(4-aminophenyl) phenyl-1,4-diamine), tert-butyl hydroperoxide and hydrochloric acid are dispersed in ethanol, then the mixture is carbonized by solvothermal method, after separation and purification, the carbon dots of red fluorescent emission are obtained;The prepared red fluorescent carbon dots can be applied to the rapid detection of residual hypochlorite ions in utensils.Compared with prior art, the red fluorescent carbon dots in the present application have long emission wavelength, and the preparation method is simple, fast response (~10 seconds), high selectivity, wide applicable pH range (5-9), good reproducibility and other advantages, and has broad application prospect in rapid detection of residual hypochlorite in utensils.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation and application technology, and relates to a method for preparing red fluorescent carbon dots and their application in the detection of hypochlorite ions, specifically a method for preparing red fluorescent carbon dots and their application in detecting residual hypochlorite ions in detector dishes. Background Technology

[0002] hypochlorite anion (ClO) - Hypochlorous acid (HClO) and its protonated form possess strong oxidizing properties and are widely used in daily life and food hygiene as highly efficient, safe, and broad-spectrum bactericides. The most important pathway for hypochlorite disinfection is through hydrolysis at a specific pH to produce hypochlorous acid, which, in a strong oxidizing form, destroys cell membranes or cell walls, effectively killing bacteria, fungi, and other microorganisms. In recent years, hypochlorous acid disinfection has been studied and applied to the cleaning and disinfection of food processing equipment, including dairy plants, waterworks, fish and meat processing plants, and poultry farms. Appropriate concentrations of ClO... - It has a protective effect on human health; neutrophils in the human body can endogenously synthesize ClO. - To kill pathogens; while excessive levels of ClO - It can induce various chronic diseases, such as rheumatoid arthritis, neurodegenerative diseases, and atherosclerosis. Therefore, it is crucial to design and synthesize ClO with excellent selectivity and sensitivity. - Probes for detecting residual ClO in various food processing utensils - Rapid and accurate visual detection is of great significance.

[0003] Currently ClO - The main detection methods include titration, fluorescence, colorimetry, electrochemical methods, and liquid chromatography. Among these, fluorescence methods are advantageous for detecting residual hypochlorite due to their rapid response and high sensitivity. In recent years, many fluorescent probes have been developed for ClO₂. - Detection methods include detecting small organic molecules, fluorescent quantum dots, and gold and silver nanoclusters. However, these fluorescent probes suffer from drawbacks such as complex synthesis or purification processes and the use of heavy metal elements, limiting their further applications. Therefore, developing simple, safe, sensitive, and rapid ClO2-based fluorescent probes is crucial. - The detection probe is of great significance.

[0004] Fluorescent carbon dots, with their excellent optical properties, tunable spectra, good biocompatibility, and ease of functional group modification, are widely used in fluorescence imaging and detection. In recent years, methods for preparing fluorescent carbon dots have been continuously evolving, and simple and economical techniques for synthesizing different fluorescent carbon dots have been reported, enabling rapid responses to various metal ions and compounds without labeling. However, most currently detected carbon dots emit blue-green fluorescence, which may overlap with some interfering substances in the environment. Furthermore, the preparation reaction time and detection time are relatively long, and strict pH requirements exist. Therefore, developing fluorescent carbon dots that are easy to synthesize, emit red light, and respond rapidly, sensitively, and stably to ClO₂- residues in glassware is crucial. - The detection is of great significance.

[0005] Patent CN114199847A discloses a method for detecting hypochlorite using fluorescent carbon dots. The nitrogen-doped carbon dots synthesized in this method have excitation and emission wavelengths of 370 nm and 445 nm, respectively, falling within the ultraviolet and blue light regions. However, many substances in daily life exhibit blue fluorescence emission, which can easily interfere with the detection of hypochlorite in the sample under complex conditions. Furthermore, this patent provides a relatively simple model for hypochlorite detection and cannot address practical problems such as the detection of hypochlorite residues during food processing. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method for preparing red fluorescent carbon dots and their application in the detection of hypochlorite ions. This preparation method allows for the simple one-step synthesis of water-soluble red fluorescent carbon dots that provide rapid, sensitive, and specific identification and detection of hypochlorite ions, and its application in the rapid detection of residual hypochlorite ions in glass dishes.

[0007] The present invention is achieved using the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing red fluorescent carbon dots, comprising the following steps:

[0009] Step 1: Weigh N,N'-(1,4-phenylene)bis(N-(4-aminophenyl)benzene-1,4-diamine), tert-butylhydrogen peroxide and hydrochloric acid, dissolve them in ethanol, and (ultrasound) to obtain a mixture;

[0010] Step 2: Place the mixture obtained in Step 1 in an oven and heat it to react. After the reaction stops, let it stand and cool.

[0011] Step 3: Centrifuge the reaction solution obtained in Step 2, collect the supernatant and dialyze it to obtain a carbon dot solution;

[0012] Step 4: After vacuum drying the carbon dot solution obtained in Step 3, disperse it in ultrapure water, filter it to obtain a carbon dot solution that emits red fluorescence, namely the red fluorescent carbon dots.

[0013] Further, in step 1, the molar ratio of N,N'-(1,4-phenylene)bis(N-(4-aminophenyl)benzene-1,4-diamine), tert-butylhydrogen peroxide, and hydrochloric acid is 0.5-1.5:1:10.

[0014] In some embodiments, the molar ratio of N,N'-(1,4-phenylene)bis(N-(4-aminophenyl)benzene-1,4-diamine), tert-butyl hydroperoxide, and hydrochloric acid is 0.5:1:10, 1:1:10, or 1.5:1:10; and the amount of ethanol used is 25-35 mL.

[0015] Specifically, in some embodiments, the amount of N,N'-(1,4-phenylene)bis(N-(4-aminophenyl)phenyl-1,4-diamine) is 0.5-1.5 mM, the amount of tert-butyl hydroperoxide is 1 mM, the amount of hydrochloric acid is 10 mM, and the amount of ethanol is 30 mL.

[0016] Furthermore, in step 1, the mixture is sonicated until it is evenly dispersed.

[0017] Further, in step 2, the mixture obtained in step 1 is transferred to a reaction vessel and heated for reaction; the reaction vessel is a polytetrafluoroethylene (PTFE) reaction vessel. In some embodiments, the capacity of the PTFE reaction vessel is 50 mL.

[0018] Furthermore, in step 2, the heating temperature is 100-160℃, and the time is 1-4 hours. The room temperature mentioned in this invention is 25℃.

[0019] Furthermore, in step 3, the reaction solution is centrifuged to remove insoluble matter, the supernatant is collected and placed in a dialysis bag, and then dialyzed in ultrapure water to remove impurities; the reaction solution is a green solution.

[0020] Furthermore, the dialysis bag is a dialysis bag with a capacity of 500-1000 kDa.

[0021] Furthermore, in step 4, a 0.22μm filter membrane is used to remove large particle precipitates.

[0022] Secondly, the present invention provides a red fluorescent carbon dot obtained by the preparation method described above.

[0023] As a further explanation of the present invention, the optimal excitation wavelength and emission wavelength of the red fluorescent carbon dots are 588 nm and 612 nm, respectively, with an absolute fluorescence quantum yield of 17.4%. They exhibit red fluorescence under a 365 nm ultraviolet lamp.

[0024] Thirdly, the present invention provides an application of the red fluorescent carbon dot as a probe for residual hypochlorite ions in a detector dish.

[0025] Fourthly, the present invention provides a method for removing residual hypochlorite ions in the red fluorescent carbon dot detector dish, comprising the following steps:

[0026] S1: Different concentrations of ClO - The standard was mixed thoroughly with red fluorescent carbon dot solution to prepare ClO of different concentrations. - Standard reference material;

[0027] S2: Detect the fluorescence intensity of different standard references around 612 nm, and compare the obtained fluorescence intensity with ClO - A standard curve was plotted by linearly fitting the concentration.

[0028] S3: For residual ClO in the vessel - Concentration detection: Rinse the glassware thoroughly with ultrapure water and collect the solution to obtain the stock solution; mix the stock solution with red fluorescent carbon dot solution to obtain the test solution; measure and record the fluorescence intensity of the test solution at 612 nm, and combine with the standard curve obtained in S2 to obtain the ClO in the test solution and the stock solution. - Concentration, the residual ClO in the vessel is obtained according to the dilution factor. - concentration.

[0029] Furthermore, in step S1, ClO - The concentration range of the standard reference is 0-100 μM, namely 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 μM.

[0030] In some embodiments, the red fluorescent carbon dot solution in step S1 is an aqueous solution of 2 mg / mL red fluorescent carbon dots; ClO - The volume ratio of the standard to the red fluorescent carbon dot solution is 100:1.

[0031] As a further explanation of the present invention, the fluorescence intensity was measured using a fluorescence spectrophotometer with an excitation wavelength of 570 nm and fluorescence spectra collected in the range of 590-750 nm.

[0032] Further, in step S2, a fluorescence spectrometer is used to detect the fluorescence intensity of each standard reference solution at 612 nm under an excitation wavelength of 570 nm; the ratio of the fluorescence intensity of different standard reference solutions to the blank group at 612 nm is plotted on the ordinate. - Using the concentration as the x-axis, the fluorescence intensity and ClO were obtained. -Concentration relationship graph; furthermore, a good linear range between 0-50 μM was obtained, which served as a standard curve.

[0033] Furthermore, in step S3, the containers include, but are not limited to, food-related containers and equipment such as those used in dairy plants, waterworks, and fish and meat processing plants.

[0034] Further, in step S3, the amount of ultrapure water used is 20-50 mL. In some embodiments, the amount of ultrapure water used is 20 mL.

[0035] Further, in step S3, the concentration of red fluorescent carbon dots in the test solution is the same as the concentration of fluorescent carbon dots in the mixture from step S1. In some embodiments, the final concentration of both the red fluorescent carbon dots in the test solution and the fluorescent carbon dots in the mixture from step S1 is 20 μg / mL.

[0036] In some embodiments, the red fluorescent carbon dot solution in step S3 is an aqueous solution of 40 μg / mL red fluorescent carbon dots; the volume ratio of the stock solution to the red fluorescent carbon dot solution is 1:1.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. The red fluorescent carbon dots provided by this invention are water-dispersible and suitable for most everyday situations. They also exhibit good dispersibility over a wide pH range (pH 5-9) and have broad applicability.

[0039] 2. The red fluorescent carbon dots provided by this invention are easy to prepare by a one-step reaction, with an optimal excitation wavelength of 588 nm, an optimal emission wavelength of 612 nm, and an absolute fluorescence quantum yield of 17.4%.

[0040] 3. This invention utilizes the red fluorescent carbon dot as a fluorescent probe to detect residual ClO in a container. - The sensing detection was performed, and the fluorescence intensity at 612 nm was used as the ClO2 value. - The fluorescence response signal of carbon dots was used to construct the residual ClO in the vessel. - Detection methods.

[0041] 4. The red fluorescent carbon dots obtained in this invention are paired with ClO - It has selectivity, other common ions, such as Fe 3+ Fe 2+ Co 2+ Ni 2+ Cu 2+ Mg 2+ Mn 2+ Ca 2+ K + Cl -,Br - I - H2PO4 2- NO 2- NO 3- HCO3 2- S2O8 2- SO4 2- AcO - H2O2, IO4 - None of them could cause a significant change in the fluorescence signal of the carbon dot solution.

[0042] 5. The relative fluorescence intensity of the red fluorescent carbon dots obtained in this invention is similar to that of ClO. - It exhibits a good linear relationship between concentrations (0-50 μM) and can be used for ClO - The quantitative detection has a response time of approximately 10 seconds.

[0043] 6. The red fluorescent carbon dots in this invention can be directly used in ClO - The detection method has the advantages of simple synthesis method, rapid detection response, strong selectivity, high sensitivity and wide applicable pH range, and has good practical application value.

[0044] 7. This invention addresses the practical problem of detecting hypochlorite residues during food processing by constructing a relatively complete detection calculation model and method. It can not only quantitatively detect the concentration of residual ions, but also quickly and conveniently observe changes in red fluorescence directly with the human eye, thus having certain practical application value. Attached Figure Description

[0045] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0046] Figure 1 This is a schematic diagram illustrating the preparation method of red fluorescent carbon dots and its detection of hypochlorite in this invention.

[0047] Figure 2 These are transmission electron microscope (TEM) images and particle size distribution diagrams of the fluorescent carbon dots prepared in Example 2; Figure a is a TEM image, and Figure b is a particle size distribution diagram.

[0048] Figure 3 This is the infrared spectrum of the fluorescent carbon dots prepared in Example 2;

[0049] Figure 4 These are the X-ray photoelectron spectra of the fluorescent carbon dots prepared in Example 2 and the high-resolution photoelectron spectra of element C; wherein Figure a is the X-ray photoelectron spectrum and Figure b is the high-resolution photoelectron spectrum of element C.

[0050] Figure 5 This is the UV-Vis absorption spectrum of the fluorescent carbon dots prepared in Example 2;

[0051] Figure 6 This is the fluorescence excitation and emission spectrum of the fluorescent carbon dots prepared in Example 2;

[0052] Figure 7 This is a graph showing the absolute quantum yield of the fluorescent carbon dots prepared in Example 2;

[0053] Figure 8 This is a selectivity graph for hypochlorite detection of the carbon dot solution prepared in Example 2;

[0054] Figure 9 This is the fluorescence spectrum of the red fluorescent carbon dot solution in Example 6 after adding hypochlorite standard solutions of different concentrations;

[0055] Figure 10 This is a graph showing the relationship between the carbon dot solution prepared in Example 6 and the concentration of hypochlorite.

[0056] Figure 11 This is a linear relationship graph between the carbon dot solution prepared in Example 6 and the low concentration of hypochlorite;

[0057] Figure 12 This is a response time diagram of the carbon dot solution prepared in Example 7 to hypochlorous acid;

[0058] Figure 13 This is a comparison graph of the response of the carbon dot solution prepared in Example 8 to hypochlorite at different pH values;

[0059] Figure 14 This is a schematic diagram of the experiment using the carbon dot solution prepared in Example 9 to detect residual hypochlorite ions in the detector dish;

[0060] Figure 15 These are the fluorescence spectra of the carbon dot working solution prepared in Example 9 before and after mixing with the test solution;

[0061] Figure 16 The precipitation of the carbon dot solution prepared using o-phenylenediamine in Comparative Example 1 is shown.

[0062] Figure 17 The results show the selective detection of anions in the carbon dot solutions prepared using N,N'-(1,4-phenylene)bis(N-(4-aminophenyl)benzene-1,4-diamine) and the carbon dot solutions prepared using p-phenylenediamine in Comparative Example 2. Detailed Implementation

[0063] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0064] Example 1

[0065] A method for preparing red fluorescent carbon dots, as follows Figure 1 As shown, it includes the following steps:

[0066] (1) Weigh out N,N'-(1,4-phenylene)bis(N-(4-aminophenyl)phenyl-1,4-diamine), tert-butyl hydroperoxide and hydrochloric acid according to the proportion, dissolve them in ethanol, and sonicate to obtain a uniformly dispersed mixture; the molar ratio of N,N'-(1,4-phenylene)bis(N-(4-aminophenyl)phenyl-1,4-diamine), tert-butyl hydroperoxide and hydrochloric acid is 0.5:1:10, that is, the weighed N,N'-(1,4-phenylene)bis(N-(4-aminophenyl)phenyl-1,4-diamine), tert-butyl hydroperoxide and hydrochloric acid are 0.5mM:1mM:10mM respectively, and the volume of ethanol is 30mL;

[0067] (2) Transfer the above mixture to a reaction vessel and react at 130°C for 2 hours. After the reaction stops, let it stand and cool to room temperature, centrifuge to remove insoluble matter, collect the supernatant and put it into a 500kDa dialysis bag, and dialyze it in ultrapure water to remove impurities.

[0068] (3) After vacuum drying the carbon dot solution obtained in the previous step, redisperse it in ultrapure water and filter it with a 0.22μm filter membrane to remove large particle precipitates and obtain a carbon dot solution that emits red fluorescence.

[0069] (4) With Rhodamine B as a reference, its relative quantum yield is 2.9%.

[0070] Example 2

[0071] A method for preparing red fluorescent carbon dots includes the following steps:

[0072] (1) Weigh out N,N'-(1,4-phenylene)bis(N-(4-aminophenyl)phenyl-1,4-diamine), tert-butyl hydroperoxide and hydrochloric acid according to the proportion, dissolve them in ethanol, and sonicate to obtain a uniformly dispersed mixture; the molar ratio of N,N'-(1,4-phenylene)bis(N-(4-aminophenyl)phenyl-1,4-diamine), tert-butyl hydroperoxide and hydrochloric acid is 1:1:10, that is, the weighed N,N'-(1,4-phenylene)bis(N-(4-aminophenyl)phenyl-1,4-diamine), tert-butyl hydroperoxide and hydrochloric acid are 1mM:1mM:10mM respectively, and the volume of ethanol is 30mL;

[0073] (2) Transfer the above mixture to a reaction vessel and react at 130°C for 2 hours. After the reaction stops, let it stand and cool to room temperature, centrifuge to remove insoluble matter, collect the supernatant and put it into a 500kDa dialysis bag, and dialyze it in ultrapure water to remove impurities.

[0074] (3) After vacuum drying the carbon dot solution obtained in the previous step, redisperse it in ultrapure water and filter it with a 0.22μm filter membrane to remove large particle precipitates and obtain a carbon dot solution that emits red fluorescence.

[0075] (4) With Rhodamine B as a reference, its relative quantum yield is 14.3%.

[0076] Example 3

[0077] A method for preparing red fluorescent carbon dots includes the following steps:

[0078] (1) Weigh out N,N'-(1,4-phenylene)bis(N-(4-aminophenyl)phenyl-1,4-diamine), tert-butyl hydroperoxide and hydrochloric acid according to the proportion, dissolve them in ethanol, and sonicate to obtain a uniformly dispersed mixture; the molar ratio of N,N'-(1,4-phenylene)bis(N-(4-aminophenyl)phenyl-1,4-diamine), tert-butyl hydroperoxide and hydrochloric acid is 1.5:1:10, that is, the weighed N,N'-(1,4-phenylene)bis(N-(4-aminophenyl)phenyl-1,4-diamine), tert-butyl hydroperoxide and hydrochloric acid are 1.5mM:1mM:10mM respectively, and the volume of ethanol is 30mL;

[0079] (2) Transfer the above mixture to a reaction vessel and react at 130°C for 2 hours. After the reaction stops, let it stand and cool to room temperature, centrifuge to remove insoluble matter, collect the supernatant and put it into a 500kDa dialysis bag, and dialyze it in ultrapure water to remove impurities.

[0080] (3) After vacuum drying the carbon dot solution obtained in the previous step, redisperse it in ultrapure water and filter it with a 0.22μm filter membrane to remove large particle precipitates and obtain a carbon dot solution that emits red fluorescence.

[0081] (4) With Rhodamine B as a reference, its relative quantum yield is 4.2%.

[0082] Example 4

[0083] The red fluorescent carbon dots prepared in Example 2, which had a high quantum yield, were characterized, and the specific characterization results are as follows:

[0084] 1. The morphology of the red fluorescent carbon dots in Example 2 above was characterized by transmission electron microscopy, such as... Figure 2 As shown in a and b, the carbon dots are spherical with a size distribution range of 2.3-4.28 nm and have good dispersibility.

[0085] 2. The prepared carbon dots can be characterized by infrared spectroscopy (e.g., Figure 3 This carbon dot contains various chemical bonds and groups, such as C=O, NH, CN, C=C, and CO.

[0086] 3. Figure 4 To prepare the X-ray photoelectron spectrum of carbon dots, it can be seen from the figure that carbon dots contain three elements: C, N and O. The high-resolution electron spectrum of C element shows that the chemical bonds in carbon dots are mainly C / C=C, CO / CN and C=O, which is the same as the infrared test characterization results mentioned above.

[0087] 4. The carbon dots prepared in Example 2 were characterized by their spectroscopic properties: Figure 5 , Figure 6 The images show the absorption, excitation, and emission spectra of the prepared red fluorescent carbon dots. The UV-Vis absorption spectrum reveals that the characteristic absorption peaks of the prepared carbon dots are in the 560-620 nm range, with the maximum absorption peak at 591 nm. The excitation and emission spectra show that the optimal excitation of the fluorescent carbon dots is at 588 nm, corresponding to the point of strongest absorbance, while the maximum fluorescence emission is at 612 nm. Furthermore, studies of the fluorescence spectra at different excitation wavelengths (440-588 nm) revealed that the emission peaks of the carbon dots remained unchanged. Further… Figure 7 This indicates that the absolute quantum yield of the fluorescent carbon dot solution is 17.4%, which is comparable to the relative quantum yield calculated above using Rhodamine B as a reference.

[0088] Example 5

[0089] The fluorescent carbon dot solution prepared in Example 2 is effective against ClO₂ - The selective detection process involves the following steps:

[0090] (1) Prepare the fluorescent carbon dots into an aqueous solution with a concentration of 40 μg / mL for later use;

[0091] (2) Prepare standard solutions of various interfering substances with a concentration of 400 μM (Fe3+ Fe 2+ Co 2+ Ni 2+ Cu 2+ Mg 2+ Mn 2+ Ca 2+ K + Cl - ,Br - I - H2PO4 2- NO 2- NO 3- HCO3 2- H2PO4 2- S2O8 2- SO4 2- AcO - H2O2, KIO4, GSSH, ClO - )spare;

[0092] (3) Take 1 mL each of the prepared carbon dot solution and the interference standard solution, mix them evenly, and use a fluorescence spectrometer to detect the fluorescence intensity of the mixture at 612 nm and record it.

[0093] (4) Compare the fluorescence intensity of each group at 612 nm with the blank group, and calculate the A / A0 value (A is the fluorescence intensity at 612 nm after adding different interfering substances, and A0 is the fluorescence intensity at 612 nm of the blank control group). Figure 8 As shown, in the method provided by this invention, only hypochlorite ions have the greatest quenching effect on fluorescent carbon dots, indicating that the red fluorescent carbon dots on ClO - It has a high degree of selectivity.

[0094] Example 6

[0095] The fluorescent carbon dot solution prepared in Example 2 is effective against ClO₂ - The specific steps for sensitivity testing are as follows:

[0096] (1) Prepare the fluorescent carbon dots into an aqueous solution with a concentration of 2 mg / mL for later use;

[0097] (2) Weigh out different masses of sodium hypochlorite standard to prepare ClO2 solutions of different concentrations. - Standard reference solutions (0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 μM) are available for use;

[0098] (3) Take 2 mL of hypochlorite standard reference solutions of different concentrations, add 20 μL of carbon dot solution to each, mix well, and then test the fluorescence spectrum of each group. Figure 9As shown, relative to the blank group, with ClO - As the concentration increases, the fluorescence of the fluorescent carbon dots gradually quenches and the intensity gradually decreases.

[0099] (4) Further, by calculating the value of I / I0 (I represents the concentration of ClO added at different concentrations) - The fluorescence intensity after that, I0 is the same concentration of carbon dot solution without the addition of ClO - The fluorescence intensity was measured, and the I / I0 value was found to be related to ClO. - Concentration-related ( Figure 10 ). Figure 11 The (standard curve) shows the I / I0 value of the test solution and the ClO₂ value. - A good linear relationship exists between concentrations of 0-50 μM, with the linear equation being Y = -0.01131X + 1.101228 and a correlation coefficient R0. 2 =0.9955.

[0100] Example 7

[0101] The fluorescent carbon dot solution prepared in Example 2 is effective against ClO₂ - The response speed test steps are as follows:

[0102] (1) Prepare the fluorescent carbon dots into an aqueous solution with a concentration of 20 μg / mL for later use;

[0103] (2) Prepare ClO with a concentration of 1 mM - Solution for later use;

[0104] (3) Take 2 mL of the above carbon dot solution and add 20 μL of ClO - After solution preparation, the fluorescence intensity of the mixture at 612 nm was measured at different time points, and the carbon dot response was determined based on the F / F0 value (F represents the addition of ClO₂). - Fluorescence intensities at 612 nm at different time points after [following the initial fluorescence intensity of the carbon dot solution]. Figure 12 As shown, add ClO - After solution preparation, the fluorescence intensity of the solution decreased significantly after 10 seconds, demonstrating that the red fluorescent carbon dots prepared in this invention are effective for ClO₂. - Its rapid response capability has great application potential.

[0105] Example 8

[0106] The fluorescent carbon dot solution prepared in Example 2 is effective against ClO₂ - The response stability test is performed using the following steps:

[0107] (1) Prepare carbon dot solutions with a concentration of 20 μg / mL and adjust them to different pH values ​​(5, 6, 7, 8, 9);

[0108] (2) Prepare ClO with a concentration of 1 mM - Solution for later use;

[0109] (3) Take 2 mL of the above carbon dot solutions with different pH values, and add 20 μL of ClO - Before and after the solution was prepared, the fluorescence intensity of the mixture at 612 nm was recorded. From... Figure 13 It can be seen that the carbon dot solutions exhibit fluorescence properties in the pH range of 5-9, and all retain their fluorescein response to ClO₂. - Fast response performance and wide applicability.

[0110] Example 9

[0111] Residual ClO in sterilized utensils - Detection such as Figure 14 As shown, the specific steps are as follows:

[0112] (1) After the container has been sterilized with commercial disinfectant, rinse the cup wall with 20mL of ultrapure water to obtain the test solution;

[0113] (2) Prepare a carbon dot solution with a concentration of 40 μg / mL as the working solution;

[0114] (3) Take 1 mL each of the test solution and the working solution, mix them thoroughly, and then measure the fluorescence intensity of the mixture at 612 nm. Based on the fluorescence intensity and ClO2 mentioned above... - The concentration relationship can be used to calculate the ClO content in the mixture. - The ion concentration was further determined based on the dilution factor to obtain the residual ClO in the sterilized vessel. - Concentration. For example... Figure 15 As shown, after the detection solution collected from the re-rinsing and disinfecting vessel is mixed with the fluorescent carbon dot working solution, the fluorescence intensity of the working solution decreases. According to the calculation method in Example 6, the residual ClO in the vessel can be determined. - The concentration was 38.13 μM.

[0115] Comparative Example 1

[0116] The preparation method of this comparative example is basically the same as that of Example 2, except that N,N'-(1,4-phenylene)bis(N-(4-aminophenyl)phenyl-1,4-diamine) is replaced with o-phenylenediamine. In the subsequent dialysis purification step, the carbon dot solution obtained using o-phenylenediamine as a raw material will form a precipitate (e.g. Figure 16 As shown), ClO cannot be redispersed in neutral ultrapure water and is not suitable for subsequent aquatic environments. - The detection.

[0117] Comparative Example 2

[0118] The preparation method of this comparative example is basically the same as that of Example 2, except that N,N'-(1,4-phenylene)bis(N-(4-aminophenyl)phenyl-1,4-diamine) is replaced with p-phenylenediamine.

[0119] The selective detection of anions by the fluorescent carbon dot solution prepared in Comparative Example 2 is basically the same as that in Example 5, except that:

[0120] (1) Replace the interfering standard solution with I - SO4 2- AcO - CO3 2- ,S 2- ,PO4 3- Six common anionic solutions;

[0121] (2) The fluorescence intensity of the mixture of Comparative Example 2 at 609 nm was detected using a fluorescence spectrometer and recorded;

[0122] like Figure 17 As shown, the fluorescent carbon dot solution prepared in Comparative Example 2 reacts to CO3. 2- ,S 2- ,PO4 3- Plasma exhibits responsiveness and is easily interfered with by different anions, which is detrimental to the subsequent complex aquatic environment containing ClO. - The carbon dot solution prepared in Example 2 of this invention exhibits strong anti-interference properties and can be used for ClO4 detection. - Testing.

[0123] In summary, this invention provides a method for preparing red fluorescent carbon dots. The prepared red fluorescent carbon dots can be used to detect residual hypochlorite ions in tableware. It has the advantages of simple detection method, fast response (~10 seconds), high selectivity, wide applicable pH range (5-9), and good reproducibility. It has broad application prospects in the rapid detection of residual hypochlorite in tableware, such as various food-related tableware and packaging boxes.

[0124] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. Application of red fluorescent carbon dots as a fluorescent probe in rapid detection of residual hypochlorite in a container. The preparation method of the red fluorescent carbon dots comprises the following steps: Step 1: N,N'-(1,4-phenylene) bis(N-(4-aminophenyl) benzene-1,4-diamine), tert-butyl hydroperoxide and hydrochloric acid are weighed and dissolved in ethanol to obtain a mixed solution; Step 2: The mixed solution obtained in step 1 is heated for reaction, and after the reaction stops, it is cooled to obtain a reaction solution; Step 3: The reaction solution obtained in step 2 is centrifuged, and the supernatant is collected for dialysis to obtain a carbon dot solution; Step 4: The carbon dot solution obtained in step 3 is vacuum dried, dispersed in ultrapure water, filtered to obtain a carbon dot solution with red fluorescent emission, i.e. the red fluorescent carbon dots.

2. Use according to claim 1, characterized in that, In step 1, the molar ratio of N,N'-(1,4-phenylene) bis(N-(4-aminophenyl) benzene-1,4-diamine), tert-butyl hydroperoxide and hydrochloric acid is 0.5-1.5:1:

10.

3. Use according to claim 1, characterized in that, In step 2, the heating temperature is 100-160 ℃, and the time is 1-4 hours.

4. Use according to claim 1, characterized in that, In step 3, the dialysis uses a dialysis bag with a molecular weight of 500-1000 kDa.

5. The use according to claim 1, characterized in that, The optimal excitation wavelength and emission wavelength of the red fluorescent carbon dots are 588 nm and 612 nm, respectively, and they exhibit red fluorescence under a 365 nm ultraviolet lamp.

6. A method for detecting residual hypochlorite in a vessel using red fluorescent carbon dots, characterized in that, Comprise the following steps: S1: different concentrations of ClO - The standard was mixed with the red fluorescent carbon dot solution to prepare different concentrations of ClO - Standard control; S2: Detect the fluorescence intensity of different standard controls near 612 nm, and compare the obtained fluorescence intensity with ClO - The concentration linear fitting draws a standard curve graph; S3: For the residual ClO of the vessel - Concentration detection: the vessel was washed with ultrapure water and collected to obtain the stock solution; the stock solution was mixed with the red fluorescent carbon dot solution to obtain the test solution; the fluorescence intensity of the test solution at 612 nm was measured and recorded, combined with the standard curve obtained in S2, to obtain the residual ClO concentration in the test solution and the stock solution - Concentration detection: the vessel was washed with ultrapure water and collected to obtain the stock solution; the stock solution was mixed with the red fluorescent carbon dot solution to obtain the test solution; the fluorescence intensity of the test solution at 612 nm was measured and recorded, combined with the standard curve obtained in S2, to obtain the residual ClO concentration in the test solution and the stock solution - Concentration detection: the vessel was washed with ultrapure water and collected to obtain the stock solution; the stock solution was mixed with the red fluorescent carbon dot solution to obtain the test solution; the fluorescence intensity of the test solution at 612 nm was measured and recorded, combined with the standard curve obtained in S2, to obtain the residual ClO concentration in the test solution and the stock solution The red fluorescent carbon dots are prepared by the preparation method in claim 1.

7. The method of claim 6, wherein, In step S1, CIO - The concentration range of the standard control was 0-100 μM, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 μM, respectively.

8. The method of claim 6, wherein, In steps S2 and S3, the measurement of the fluorescence intensity uses a fluorescence spectrophotometer, the excitation wavelength is 570 nm, and the fluorescence spectrum in the range of 590-750 nm is collected.

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