MnO2@CDs composite material for visualizing detection of amoxicillin and preparation method thereof

Abstract

This invention provides a MnO2@CDs composite material for the visual detection of amoxicillin and its preparation method, relating to the field of analytical detection technology. The MnO2@CDs constructed in this invention can be used for both fluorescence and colorimetric detection of amoxicillin. Due to the resonant energy transfer between CDs and MnO2, the fluorescence of CDs is quenched. In the presence of AMO, MnO2 is degraded by AMO, releasing CDs, and its blue fluorescence is restored. In colorimetric detection, MnO2@CDs exhibit excellent oxidase-like properties, capable of oxidizing colorless TMB to yellow TMB. 2+ AMO has strong reducing properties and inhibits oxidation reactions. In the presence of AMO, it can promote the oxidation of TMB. 2+ When AMO is reduced to TMB, the solution color gradually changes from yellow to colorless as the AMO concentration increases, resulting in a vibrant color change and enabling the visual detection of AMO.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of analytical detection technology, and particularly relates to a MnO2@CDs composite material for visual detection of amoxicillin and a preparation method thereof. BACKGROUND

[0002] Amoxicillin (AMO) is a broad-spectrum antibiotic, belonging to semi-synthetic penicillin, which can be used for anti-infection treatment of different systems of human and animals, and is used as a feed additive for animal feeding in clinical medicine. Improper and excessive use of AMO can produce drug residues in various tissues and food, which poses a serious threat to human health, including allergic reactions and bacterial resistance to antibiotics. The increase of AMO residues has attracted global attention, and at present, in China, the European Union and North America, detection of AMO is a mandatory inspection item for animal food. Most countries have established the maximum residue limit of AMO. The European Union stipulates that the maximum limit of AMO and ampicillin in all animal food is 50 μg / kg, and the maximum limit in milk is 4 μg / kg. Therefore, AMO detection is a necessary means to ensure food safety and human health.

[0003] AMO can be quantitatively determined by traditional detection methods such as high performance liquid chromatography, kinetic spectrophotometry and electrochemical method. However, these methods are usually carried out in the laboratory, which requires expensive instruments, complex sample pretreatment and skilled technology, all of which are expensive and time-consuming. Therefore, it is urgent to develop a rapid, simple and highly selective AMO detection method. SUMMARY

[0004] The present application provides a MnO2@CDs composite material for visual detection of amoxicillin and a preparation method thereof, and the MnO2@CDs composite material provided by the present application can realize rapid, simple and accurate detection of AMO.

[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0006] The present application provides a MnO2@CDs composite material, which comprises hollow porous MnO2 spheres and carbon quantum dots loaded on the inner and outer surfaces of the hollow porous MnO2 spheres.

[0007] Preferably, the particle size of the hollow porous MnO2 spheres is 450-600 nm.

[0008] The present application provides a preparation method of the MnO2@CDs composite material described in the above scheme, which comprises the following steps: mixing hollow porous MnO2 spheres, carbon quantum dots and water, solid-liquid separation, drying the obtained solid to obtain the MnO2@CDs composite material.

[0009] The application provides application of the MnO2@CDs composite material as a probe in detection of amoxicillin.

[0010] The application provides a fluorescent detection method of amoxicillin, which comprises the following steps:

[0011] The MnO2@CDs composite material, the sample to be detected and water are mixed for reaction for more than 1 min, fluorescence detection is performed on the obtained mixed sample under excitation of a wavelength of 310 nm, the fluorescence intensity of the mixed sample at 450 nm is recorded, the concentration of amoxicillin in the sample to be detected is calculated according to a standard curve of amoxicillin concentration and fluorescence intensity at 450 nm.

[0012] The MnO2@CDs composite material is the MnO2@CDs composite material described in the above scheme or the MnO2@CDs composite material prepared by the preparation method described in the above scheme.

[0013] The application provides a colorimetric detection method of amoxicillin, which comprises the following steps:

[0014] The MnO2@CDs composite material, a 3,3',5,5'-tetramethylbenzidine solution, the sample to be detected, a buffer solution and water are mixed for reaction for more than 1 min, ultraviolet absorption detection is performed on the obtained mixed sample, the ultraviolet absorption value of the mixed sample at 450 nm is recorded, the concentration of amoxicillin in the sample to be detected is calculated according to a standard curve of amoxicillin concentration and ultraviolet absorption value at 450 nm, and the pH value of the buffer solution is 4.

[0015] The MnO2@CDs composite material is the MnO2@CDs composite material described in the above scheme or the MnO2@CDs composite material prepared by the preparation method described in the above scheme.

[0016] The application provides an intelligent detection method of amoxicillin based on an RGB analysis system, which comprises the following steps:

[0017] The MnO2@CDs composite material, the sample to be detected and water are mixed for reaction for more than 1 min to obtain a mixed sample; the mixed sample is photographed by using a mobile phone with an RGB analysis system, and three primary color values are read, the three primary colors include red, green and blue, wherein the red color value is represented by P R, the green color value is represented by P G, the blue color value is represented by P B, the sum of the three primary colors is represented by P T, P T = P R + P G + P B. R G B C C R G B ​​​​​​​, calculate the P of the mixed sample B The ratio of the sum of the three primary colors is denoted as Ratio, Ratio = P B / P C According to the standard curve of amoxicillin concentration and Ratio, the concentration of amoxicillin in the sample to be tested is calculated.

[0018] The MnO2@CDs composite material is the MnO2@CDs composite material described in the above scheme or prepared by the preparation method described in the above scheme.

[0019] The present application provides a fluorescent kit for detecting amoxicillin, comprising an aqueous solution of MnO2@CDs composite material; the MnO2@CDs composite material is the MnO2@CDs composite material described in the above scheme or prepared by the preparation method described in the above scheme.

[0020] The present application provides a colorimetric kit for detecting amoxicillin, comprising an aqueous solution of MnO2@CDs composite material, a 3,3',5,5'-tetramethylbenzidine solution and a buffer solution; the pH value of the buffer solution is 4; the MnO2@CDs composite material is the MnO2@CDs composite material described in the above scheme or prepared by the preparation method described in the above scheme.

[0021] The present application provides a semi-quantitative detection method for amoxicillin, comprising the following steps: wetting a dry test strip with an aqueous solution of MnO2@CDs composite material, adding a sample to be tested on the obtained wet test strip, comparing the fluorescence color of the test strip with a standard fluorescence card of known amoxicillin concentration, and obtaining the concentration of amoxicillin in the sample to be tested.

[0022] Alternatively, wetting a dry test strip with an aqueous solution of MnO2@CDs composite material, a 3,3',5,5'-tetramethylbenzidine solution, a buffer solution and water, adding a sample to be tested on the obtained wet test strip, comparing the color of the test strip with a standard colorimetric card of known amoxicillin concentration, and obtaining the concentration of amoxicillin in the sample to be tested; the pH value of the buffer solution is 4.

[0023] The MnO2@CDs composite material is the MnO2@CDs composite material described in the above scheme or prepared by the preparation method described in the above scheme.

[0024] The present application provides a MnO2@CDs composite material, comprising hollow porous MnO2 spheres and carbon quantum dots (CDs) loaded on the inner and outer surfaces of the hollow porous MnO2 spheres. Figure 1As shown, the MnO2@CDs constructed by the application can be used for fluorescence and colorimetric detection of amoxicillin at the same time, and the fluorescence of CDs is quenched due to the resonance energy transfer between CDs and MnO2. In the presence of antibiotic amoxicillin (AMO), MnO2 is degraded by AMO, and CDs are released, and the blue fluorescence of CDs is restored, and the fluorescence image of AMO can also be analyzed by a mobile phone based on an RGB analysis system. In colorimetric detection, MnO2@CDs has excellent oxidase-like properties, and can oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) into yellow TMB 2+ AMO has strong reducing property, which can inhibit the oxidation reaction, and in the presence of AMO, TMB 2+ can be reduced to TMB, and with the increase of AMO concentration, the color of the solution gradually changes from yellow to colorless, which causes a bright color change, and the colorimetric detection of AMO can be directly observed by naked eye, realizing the visual detection of AMO.

[0025] In AMO fluorescence detection, the fluorescence intensity linearly increases with the AMO concentration in the range of 0-0.045 μM, and the detection limit is 1 nM. In AMO colorimetric detection, the ultraviolet absorption value of the solution at 450 nm linearly decreases with the AMO concentration in the range of 0-0.09 μM, and the detection limit is 1.6 nM. The maximum limit of AMO in all animal food is 136.8 nM, and the maximum limit in milk is 10 nM according to the EU regulation. Therefore, the application of MnO2@CDs composite material as a probe can realize the sensitive detection of AMO, and has good selectivity and specificity for AMO fluorescence and colorimetric detection.

[0026] In addition, the application also constructs a standard fluorescence card and a standard colorimetric card for detecting amoxicillin, and the test strip is treated by the corresponding pretreatment solution, and after reacting with the AMO solution, the color of the test strip is compared with the standard colorimetric card and the standard fluorescence card, so that the concentration of AMO can be quickly obtained, thereby realizing the rapid semi-quantitative detection of AMO by colorimetric method and fluorescence method.

[0027] The application has great potential for sensitive, specific, convenient and rapid detection of AMO in complex environment.

[0028] In addition, vancomycin (VAN), flumequine (FLU), norfloxacin (NOR), ampicillin (AMP), erythromycin (EM), cephalexin (CEP), glutamic acid (GLU), melamine (MEI), cysteine (CYS), benzimidazole (DRB), urea (Urea) and potassium chloride (KCl) were used as potential interferents. The experimental results showed that MnO2@CDs had good selectivity for AMO fluorescence and colorimetric detection. When AMO and other interferents (such as VAN, FLU, NOR, AMP, EM, CEP, GLU, MEI, CYS, DRB, Urea, KCl) were added together, the experimental results showed that MnO2@CDs had good specificity for AMO fluorescence and colorimetric detection.

[0029] The present application detects the concentration of AMO in actual samples such as tap water, milk and serum. The experimental results show that the fluorescence recovery rate of AMO is between 88-115%, and the experimental standard deviation is between 0.08-4.3%, while the colorimetric recovery rate of AMO is between 85-108%, and the experimental standard deviation is between 0.31-7.4%, which is basically consistent with the added AMO concentration. Using HPLC method, the recovery rate of AMO is between 80-116%, and the experimental standard deviation is between 1.2-3.4%, which is equivalent to the two methods, indicating that the MnO2@CDs biosensor is suitable for AMO fluorescence and colorimetric detection in actual samples. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The present application is based on the principle of visual detection of amoxicillin based on MnO2@CDs composite material;

[0031] Figure 2 The characterization results of MnO2 and MnO2@CDS materials, wherein (A) SEM image, scale, 5 μm; (B) TEM image, scale, 0.2 μm; (C) Zeta image; (D) DLS image;

[0032] (E) XRD image, (F) X-ray energy spectrum analysis image of MnO2; (G) X-ray energy spectrum analysis image of MnO2@CDS;

[0033] Figure 3 The experimental results of amoxicillin fluorescence detection, wherein (A) feasibility, insert fluorescence image, (B) reaction time optimization results, (C) fluorescence spectrum image when different concentrations of amoxicillin are added,

[0034] (D) Linear relationship between amoxicillin concentration and fluorescence intensity, insert fluorescence image, wavelength λ = 450 nm;

[0035] Figure 4 The standard fluorescence card for amoxicillin detection;

[0036] Figure 5 are the results of amoxicillin colorimetric detection experiment, wherein, (A) feasibility, insert fluorescence chart, (B) reaction time optimization results, (C) when adding different concentrations of amoxicillin, ultraviolet absorption spectrum, (D) amoxicillin concentration and the linear relationship of ultraviolet absorption value corresponding, insert fluorescence chart, wavelength λ = 450nm;

[0037] Figure 6 is a standard color card for amoxicillin detection;

[0038] Figure 7 are the detection results of amoxicillin in natural water, milk and serum using fluorescence method and traditional liquid chromatography for comparison;

[0039] Figure 8 are the detection results of amoxicillin in natural water, milk and serum using colorimetric method and traditional liquid chromatography for comparison;

[0040] Figure 9 are the results of MnO2@CDs for amoxicillin fluorescence detection, (A) selectivity, insert fluorescence chart, (B) specificity, insert fluorescence chart, wavelength λ = 450nm;

[0041] Figure 10 are the results of MnO2@CDs for amoxicillin colorimetric detection, (A) selectivity, insert colorimetric chart, (B) specificity, insert colorimetric chart, wavelength λ = 450nm. DETAILED DESCRIPTION

[0042] The application provides a MnO2@CDs composite material, which comprises hollow porous MnO2 spheres and carbon quantum dots loaded on the inner and outer surfaces of the hollow porous MnO2 spheres.

[0043] In the application, the particle size of the hollow porous MnO2 spheres is preferably 450-600nm, and more preferably 480-550nm.

[0044] The application provides a preparation method of the MnO2@CDs composite material.

[0045] In the application, unless otherwise specified, all raw materials used are commercially available products which are well known in the art.

[0046] The application does not have special requirements for the preparation method of the hollow porous MnO2 balls, and a preparation method known in the art can be used. In the embodiments of the application, the preparation method of the hollow porous MnO2 balls is specifically as follows: 20 mL of ultrapure water (H2O), 25 mL of ethanol and 6 mL of ammonia water are sequentially added into a 100 mL beaker, and then ultrasonic mixing is performed for 10 min, 6 mL of tetraethyl orthosilicate is added into the above solution, and magnetic stirring is performed at room temperature for 2 h, and a milky white silica (SiO2) precipitate is generated. The obtained turbid solution is centrifuged at 5000 rpm for 5 min, the precipitate is washed with water for 3 times, the obtained precipitate is dried at 60℃, and SiO2 nanosphere powder is obtained; 7 mL of centrifuge tube A is taken, 0.075 g of potassium permanganate is weighed and dissolved in 5 mL of ultrapure water; 7 mL of centrifuge tube B is taken, 0.015 g of SiO2 nanosphere powder is weighed and dissolved in 5 mL of ultrapure water; the solutions in the two tubes A and B are mixed and ultrasonic mixing is performed for 20 min, and then the solution is left to stand at room temperature for 6 h. The solution after standing is centrifuged at 10000 rpm for 10 min to remove the supernatant, the obtained precipitate is soaked in a Na2CO3 solution (2M, 10 mL) for etching for 12 h, and finally the precipitate is centrifuged at 10000 rpm for 10 min, washed with water for 3 times, and finally dried in a 60℃ oven to obtain hollow porous MnO2 ball powder.

[0047] In the application, the particle size of the hollow porous MnO2 ball is preferably 450-600 nm, and more preferably 480-550 nm. The hollow porous MnO2 ball is used as a carrier in the application, the hollow porous structure has a large specific surface area and cavity, and can improve the loading efficiency of carbon quantum dots (CDs).

[0048] The application does not have special requirements for the source of the carbon quantum dots, and a method known in the art can be used for preparation. In the embodiments of the application, the preparation method of the carbon quantum dots is specifically as follows: 1 g of anhydrous citric acid, 0.5 mL of ethylenediamine and 30 mL of ultrapure water are sequentially added into a 50 mL beaker, the above mixed solution is stirred with a magnetic stirrer at room temperature for 1 h, and then transferred into a 40 mL stainless steel reaction kettle lined with polytetrafluoroethylene, heated at 200℃ for 24 h, the obtained product is cooled to room temperature, centrifuged at 10000 rpm for 10 min, the precipitate is discarded, the supernatant is dialyzed in a dialysis bag (with a molecular weight cut-off of 550 KDa) for 24 h, and the obtained CDs solution is stored in a refrigerator at 4℃ after dialysis. The CDs prepared by the above method exist in the form of a solution, which is convenient for subsequent application. The concentration of the CDs solution is 0.7 mg / mL, which is measured by a weighing method.

[0049] After the hollow porous MnO2 ball and the carbon quantum dots are obtained, the hollow porous MnO2 ball, the carbon quantum dots and water are mixed, solid-liquid separation is performed, the obtained solid is dried, and the MnO2@CDs composite material is obtained.

[0050] In the present application, the mass ratio of the hollow porous MnO2 ball and the carbon quantum dots is preferably 50:(5-10), and more preferably 50:(7-8).

[0051] The present application does not have special requirements for the amount of water, and the hollow porous MnO2 ball and the carbon quantum dots can be uniformly dispersed. In the present application, the mixing is preferably carried out under ultrasonic conditions, and the mixing time is preferably 1-3h, and more preferably 2h. In the present application, the mode of solid-liquid separation is preferably centrifugation, the rotation speed of the centrifugation is preferably 10000rpm, and the time of the centrifugation is preferably 8-12min. In the present application, the drying temperature is preferably 60℃, and the present application does not have special requirements for the drying time, and drying to the surface without water can be carried out.

[0052] The present application provides the application of the MnO2@CDs composite material as a probe in the detection of amoxicillin.

[0053] The present application provides a fluorescence detection method of amoxicillin, comprising the following steps:

[0054] The above-mentioned MnO2@CDs composite material, the sample to be tested and water are mixed for more than 1min, and the fluorescence intensity of the obtained mixed sample at 450nm is recorded under excitation at a wavelength of 310nm. According to the standard curve of the amoxicillin concentration and the fluorescence intensity at 450nm, the concentration of amoxicillin in the sample to be tested is calculated.

[0055] In the present application, the MnO2@CDs composite material is preferably used in the form of a MnO2@CDs composite material aqueous solution; the concentration of the MnO2@CDs composite material aqueous solution is preferably 5mg / mL. The sample to be tested is a solution; in the present application, the volume ratio of the MnO2@CDs composite material aqueous solution, the sample to be tested solution and water is preferably 1:1:18. In the examples of the present application, the volumes of the MnO2@CDs composite material aqueous solution, the sample to be tested solution and water are 10μL, 10μL and 180μL, respectively.

[0056] In the present application, the mixing reaction is preferably carried out at room temperature; and the mixing reaction time is preferably 1-5min.

[0057] Since CDs and MnO2 generate resonance energy transfer, the fluorescence of CDs is quenched. In the presence of AMO, MnO2 is degraded by AMO, and CDs are released, and the blue fluorescence of CDs is restored. The present application records the fluorescence intensity of the mixed sample at 450 nm by performing fluorescence detection on the obtained mixed sample, and the concentration of amoxicillin in the sample to be tested can be calculated according to the standard curve of amoxicillin concentration and fluorescence intensity at 450 nm.

[0058] In the present application, the method for obtaining the standard curve of amoxicillin concentration and fluorescence intensity at 450 nm preferably comprises the following steps:

[0059] Take 10 μL of MnO2@CDs composite aqueous solution (5 mg / mL) in a 200 μL centrifuge tube, add 5 μL of AMO aqueous solution with different known concentrations, add water to 200 μL, mix and incubate at room temperature for 1-5 min, use a fluorescence spectrophotometer to record the fluorescence spectrum of the incubated sample at 330-800 nm under an excitation wavelength of 310 nm, read the fluorescence value (F) at a wavelength of 450 nm, and draw a standard curve with the AMO concentration in the incubated sample as the abscissa and the fluorescence value (F) at a wavelength of 450 nm as the ordinate.

[0060] The present application provides a colorimetric detection method for amoxicillin, comprising the following steps:

[0061] Mix the above-mentioned MnO2@CDs composite material, 3,3',5,5'-tetramethylbenzidine solution, sample to be tested, buffer solution and water for more than 1 min, perform ultraviolet absorption detection on the obtained mixed sample, record the ultraviolet absorption value of the mixed sample at 450 nm, and calculate the concentration of amoxicillin in the sample to be tested according to the standard curve of amoxicillin concentration and ultraviolet absorption value at 450 nm; the pH value of the buffer solution is 4.

[0062] In the present application, the MnO2@CDs composite material is preferably used in the form of MnO2@CDs composite aqueous solution, the concentration of the 3,3',5,5'-tetramethylbenzidine aqueous solution is preferably 5 mM; the sample to be tested is a solution; the 3,3',5,5'-tetramethylbenzidine solution is preferably obtained by dissolving 3,3',5,5'-tetramethylbenzidine in dimethyl sulfoxide (DMSO); the concentration of the 3,3',5,5'-tetramethylbenzidine solution is preferably 5 mM; the buffer solution is preferably a NaAc-HAc buffer solution, and the pH value of the buffer solution is 4.

[0063] In the present application, the volume ratio of the MnO2@CDs composite aqueous solution, 3,3',5,5'-tetramethylbenzidine aqueous solution, buffer solution, sample to be tested and water is preferably 10:10:37:5:88; in the embodiments of the present application, the volumes of the MnO2@CDs composite aqueous solution, 3,3',5,5'-tetramethylbenzidine aqueous solution, buffer solution and sample to be tested are 10 μL, 10 μL, 37 μL, 5 μL and 88 μL, respectively.

[0064] In the present application, the mixing reaction is preferably carried out at room temperature, and the time of the mixing reaction is preferably 1-10 min. MnO2@CDs has excellent oxidase-like properties and can oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) to yellow TMB 2+ , AMO has strong reducing property and can inhibit oxidation, and in the presence of AMO, TMB 2+ can be reduced to TMB, and with the increase of AMO concentration, the color of the solution gradually changes from yellow to colorless, which causes a bright color change, and the colorimetric detection of AMO can be directly observed by the naked eye. Through ultraviolet absorption test, the ultraviolet absorption value of the mixed sample at 450 nm is recorded, and according to the standard curve of amoxicillin concentration and ultraviolet absorption value at 450 nm, the accurate concentration of amoxicillin in the sample to be tested can be obtained by calculation.

[0065] In the present application, the method for obtaining the standard curve of amoxicillin concentration and ultraviolet absorption value at 450 nm preferably comprises the following steps: mixing 10 μL of MnO2@CDs composite aqueous solution (5 mg / mL), 5 μL of series of AMO aqueous solution with known concentration, 10 μL of TMB solution (5 mM), 37 μL of HAc-NaAc buffer solution (0.1 M, pH 4) and 88 μL of H2O, and reacting for 10 min at room temperature. The ultraviolet absorption value of the mixed sample at 200-800 nm is recorded by using ultraviolet visible spectrophotometer, the ultraviolet absorption value (A) at wavelength 450 nm is read, the AMO concentration is taken as the abscissa, and the ultraviolet absorption value (A) at wavelength 450 nm is taken as the ordinate, and a standard curve is drawn.

[0066] The present application provides an intelligent amoxicillin detection method based on an RGB analysis system, which comprises the following steps:

[0067] The above-mentioned MnO2@CDs composite material, sample to be tested and water are mixed for more than 1 min to obtain a mixed sample; the mixed sample is photographed by using a mobile phone with an RGB analysis system, and the trichromatic color values are read, wherein the trichromatic color values include red color value, green color value and blue color value, the red color value is represented by P R , the green color value is represented by P GThis indicates that the blue color value is represented by P. B The sum of the three primary colors is represented by P. C Indicates: P C =P R +P G +P B Calculate P of the mixed sample. B The ratio of the total amount of the three primary colors to the total amount of the three primary colors is denoted as Ratio, and Ratio = P B / P C The concentration of amoxicillin in the sample was calculated based on the standard curve of amoxicillin concentration versus ratio.

[0068] In this invention, the MnO2@CDs composite material is preferably used in the form of an aqueous solution of the MnO2@CDs composite material, and the concentration of the aqueous solution of the MnO2@CDs composite material is preferably 5 mg / mL. The test sample is a solution; in this invention, the volume ratio of the aqueous solution of the MnO2@CDs composite material, the test sample solution, and water is preferably 1:1:18. In the embodiments of this invention, the volumes of the aqueous solution of the MnO2@CDs composite material, the test sample solution, and water are 10 μL, 10 μL, and 180 μL, respectively. In this invention, the mixing reaction is preferably carried out at room temperature, and the mixing reaction time is preferably 1–5 min.

[0069] After obtaining the mixed sample, the present invention uses a mobile phone equipped with an RGB analysis system to take a picture of the mixed sample, read the color values ​​of the three primary colors, and calculate the P of the mixed sample. B The ratio of the total amount of the three primary colors to the total amount of the three primary colors is denoted as Ratio, and Ratio = P B / P C The concentration of amoxicillin in the sample was calculated based on the standard curve of amoxicillin concentration versus ratio.

[0070] In this invention, the method for obtaining the standard curve of amoxicillin concentration versus ratio preferably includes the following steps: Take 10 μL of MnO2@CDs composite material aqueous solution (5 mg / mL) into a 200 μL centrifuge tube, add 5 μL of AMO aqueous solution of different known concentrations, add water to make up to 200 μL, mix well, and incubate at room temperature for 1–5 min. Take a picture of the obtained mixed sample using a mobile phone with an RGB analysis system, and read the three primary color values, where the three primary colors include red, green, and blue, and the red color value is represented by P... R The green color value is represented by P. G This indicates that the blue color value is represented by P. B The sum of the three primary colors is represented by P. C Indicates: P C =P R +PG +P B , calculate the P B of the mixed sample, denoted as Ratio, Ratio = P B / P C ; draw a standard curve with the AMO concentration in the mixed sample as the horizontal coordinate and the Ratio value as the vertical coordinate.

[0071] The application provides a fluorescent kit for detecting amoxicillin, comprising the aqueous solution of the MnO2@CDs composite material. In the application, the concentration of the aqueous solution of the MnO2@CDs composite material is preferably 5 mg / mL. In the application, the fluorescent kit preferably further comprises a standard fluorescent card with a known amoxicillin concentration.

[0072] The application also provides a semi-quantitative detection method for amoxicillin by using the fluorescent kit, comprising the following steps: wetting a dry test strip with the aqueous solution of the MnO2@CDs composite material, dropping the sample to be tested on the obtained wet test strip, comparing the fluorescent color of the test strip with the standard fluorescent card with a known amoxicillin concentration, and obtaining the concentration of amoxicillin in the sample to be tested.

[0073] The application does not have special requirements for the amount of the aqueous solution of the MnO2@CDs composite material, which can only wet the dry test strip. In the embodiments of the application, the volume is preferably 10 muL; the amount of the sample to be tested is preferably 10 muL.

[0074] The application treats the test strip with the corresponding pretreatment solution (aqueous solution of the MnO2@CDs composite material), reacts with the AMO solution for more than 1 min, compares the color of the test strip with the standard fluorescent card, and quickly obtains the AMO concentration, so as to realize the rapid semi-quantitative detection of AMO by the fluorescent method.

[0075] The application does not have special requirements for the obtaining method of the standard fluorescent card, which adopts the same treatment process as the actual detection sample, and the only difference is that the sample to be tested is replaced by an amoxicillin solution with a known concentration. In the embodiments of the application, the obtaining method of the standard fluorescent card is specifically as follows: soaking a dry water-absorbing test strip in a MnO2@CDs (5 mg / mL) solution for 1 min, taking out and laying the test strip, dropping 10 muL of AMO with different concentrations on the test strip, the final concentration of AMO is 0 nM, 3 nM, 5 nM, 10 nM, 15 nM, 20 nM, 25 nM, 30 nM, 35 nM, 40 nM, 45 nM, reacting for more than 1 min at room temperature, and obtaining the standard fluorescent card.

[0076] The application provides a colorimetric kit for detecting amoxicillin, comprising an aqueous solution of the MnO2@CDs composite material, a 3,3',5,5'-tetramethylbenzidine solution and a buffer solution; the buffer solution has a pH value of 4.

[0077] In the application, the aqueous solution of the MnO2@CDs composite material has a concentration of preferably 5 mg / mL; the 3,3',5,5'-tetramethylbenzidine solution has a concentration of preferably 5 mM, and the 3,3',5,5'-tetramethylbenzidine solution is preferably obtained by dissolving 3,3',5,5'-tetramethylbenzidine in dimethyl sulfoxide (DMSO); and the buffer solution is preferably a NaAc-HAc buffer solution, and the buffer solution has a pH value of 4.

[0078] The application provides a semi-quantitative detection method for amoxicillin by using the colorimetric kit described in the above scheme, comprising the following steps: wetting a dry test strip with an aqueous solution of the MnO2@CDs composite material, a 3,3',5,5'-tetramethylbenzidine solution, a buffer solution and water, dropping a sample to be detected on the obtained wet test strip, comparing the color of the test strip with a standard colorimetric card with a known concentration of amoxicillin, and obtaining the concentration of amoxicillin in the sample to be detected.

[0079] In the application, the aqueous solution of the MnO2@CDs composite material has a concentration of preferably 5 mg / mL; the 3,3',5,5'-tetramethylbenzidine solution has a concentration of preferably 5 mM, and the 3,3',5,5'-tetramethylbenzidine solution is preferably obtained by dissolving 3,3',5,5'-tetramethylbenzidine in dimethyl sulfoxide (DMSO); and the buffer solution is preferably a NaAc-HAc buffer solution, and the buffer solution has a pH value of 4.

[0080] The application does not have special requirements for the obtaining method of the standard colorimetric card, and the same processing procedure as the actual sample can be directly used, and the only difference is that the sample to be detected is replaced by an amoxicillin solution with a known concentration. In the examples of the application, the obtaining method of the standard colorimetric card is as follows: 10 μL of an aqueous solution of the MnO2@CDs composite material (5 mg / mL), 10 μL of a TMB solution (5 mM), 37 μL of an HAc-NaAc buffer solution (0.1 M, pH 4) and 93 μL of H2O are used to pretreat a dry test strip, then 10 μL of AMO with different concentrations is dropped on the water absorption paper, the final concentration of AMO is 0 nM, 5 nM, 15 nM, 25 nM, 35 nM, 45 nM, 55 nM, 65 nM, 75 nM, 80 nM and 90 nM, and the standard colorimetric card is prepared by reacting at room temperature for more than 1 min.

[0081] MnO2@CDs has excellent oxidase-like properties, which can oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) into yellow TMB 2+ AMO has strong reducing property, which can inhibit oxidation reaction, and in the presence of AMO, TMB 2+ can be reduced to TMB, and with the increase of AMO concentration, the color of the solution gradually changes from yellow to colorless, which causes a bright color change, and the colorimetric detection of AMO can be directly observed by naked eye, realizing the visual detection of AMO.

[0082] The test strip is treated with a corresponding pretreatment solution, and the color of the test strip is compared with a standard colorimetric card after reacting with the AMO solution for more than 1 min, so that the AMO concentration can be quickly obtained, thereby realizing the rapid semi-quantitative detection of AMO by colorimetry.

[0083] The MnO2@CDs composite material for visual detection of amoxicillin and the preparation method thereof provided by the present application will be described in detail below in combination with examples, but they cannot be understood as limiting the protection scope of the present application.

[0084] Example 1

[0085] (1) Preparation of hollow porous manganese dioxide (MnO2) spheres:

[0086] In a 100 mL beaker, 20 mL of ultrapure water (H2O), 25 mL of ethanol and 6 mL of ammonia water were sequentially added, and ultrasonic mixing was performed for 10 min. 6 mL of tetraethyl orthosilicate was added to the above solution, and magnetic stirring was performed at room temperature for 2 h, and a milky white silica (SiO2) precipitate was generated. The obtained turbid solution was centrifuged at 5000 rpm for 5 min, and the precipitate was washed with water for 3 times. The obtained precipitate was dried at 60°C to obtain SiO2 nanosphere powder. 7 mL of centrifuge tube A was taken, and 0.075 g of potassium permanganate was weighed and dissolved in 5 mL of ultrapure water. 7 mL of centrifuge tube B was taken, and 0.015 g of silica powder was weighed and dissolved in 5 mL of ultrapure water. The solutions in tubes A and B were mixed and ultrasonicated for 20 min, and then left to stand at room temperature for 6 h. The solution after standing was centrifuged at 10000 rpm for 10 min to remove the upper clear liquid, and the obtained precipitate was soaked in a Na2CO3 solution (2M, 10 mL) for etching for 12 h. Finally, the precipitate was centrifuged at 10000 rpm for 10 min, washed with water for 3 times, and finally dried in a 60°C oven to obtain hollow porous MnO2 sphere powder.

[0087] (2) Preparation of carbon quantum dots (CDs):

[0088] In a 50 mL beaker, anhydrous citric acid 1 g, ethylenediamine 0.5 mL and ultrapure water 30 mL were added successively, the above mixed solution was stirred at room temperature with a magnetic stirrer for 1 h, then transferred to a 40 mL inner lining of polytetrafluoroethylene stainless steel reaction kettle, heated at 200 °C for 24 h, the resulting product was cooled to room temperature, centrifuged at 10000 rpm for 10 min, the precipitate was discarded, the supernatant was dialyzed in a dialysis bag (molecular weight cut-off 550 KDa) for 24 h, after dialysis was completed, the obtained CDs solution was stored in a refrigerator at 4 °C. The concentration of the CDs solution was measured by weighing method to be 0.7 mg / mL.

[0089] (3) Synthesis of MnO2@CDs

[0090] Take 7 mL centrifuge tube, weigh 5 mg of hollow porous MnO2spheres powder, add 4 mL of ultrapure water and 1 mL of CDs solution (0.7 mg / mL), ultrasonic the above mixture for 2 h. Finally centrifuge at 10000 rpm for 10 min to obtain the precipitate, which is dried in an oven at 60 °C to obtain MnO2@CDs powder.

[0091] The morphology of MnO2and MnO2@CDs was characterized by SEM and TEM, and the results are shown in Figure 2 A and B. As can be seen from Figure 2 A and B, the SEM and TEM images of MnO2show that the material presents spherical shape, the particle size is about 500 nm, and the particles are uniformly dispersed. The SEM and TEM images of MnO2@CDs show that the material still presents spherical shape, the size is about 500 nm, and the particle dispersion is good. The experimental results show that the morphology of MnO2@CDs composite material formed after adding CDs does not change obviously. In order to further verify the successful preparation of the material, Zeta method was used for potential analysis, as shown in Figure 2 C, compared with MnO2spheres, the potential value of MnO2@CDs decreases from -28.25 mV to -49 mV, which proves that CDs are wrapped inside MnO2to form MnO2@CDs composite material. The particle size of the material was analyzed by DLS, as shown in Figure 2 D, the particle size of MnO2spheres and MnO2@CDs composite material is well coincided, about 500 ± 0.5 nm. The material structure was detected by X-ray diffraction (XRD) analysis, as shown in Figure 2 E, MnO2@CDs composite material shows similar diffraction peaks as MnO2, indicating that wrapping CDs in MnO2does not affect the original crystal structure of the material. The qualitative analysis of C, N and Mn elements in materials MnO2and MnO2@CDs was carried out by X-ray energy spectrum, as shown in Figure 2As shown in F and G, the elements of C, N, and Mn are uniformly distributed on the material. The above experimental results prove the successful preparation of MnO2 and MnO2@CDs materials.

[0092] Amoxicillin fluorescence detection experiment:

[0093] In the amoxicillin fluorescence detection experiment, 5 mg of MnO2@CDs was weighed and added to 1 mL of water to prepare a 5 mg / mL MnO2@CDs solution. 2.097 mg of amoxicillin was weighed and added to 1 mL of water to prepare a 5 mM amoxicillin solution. 10 μL of MnO2@CDs (5 mg / mL), 10 μL of amoxicillin (5 mM), and 180 μL of H2O were taken and reacted at room temperature for 5 min. Under an excitation wavelength of 310 nm, the fluorescence spectrum from 330 to 800 nm was recorded, and the fluorescence intensity at 450 nm was read.

[0094] As Figure 3 As shown in A, under an excitation wavelength of 310 nm, MnO2@CDs showed a weak fluorescence signal (black line a), and amoxicillin also showed a weak fluorescence signal (blue line b). When MnO2@CDs reacted with amoxicillin, the fluorescence signal was significantly enhanced (red line c). The above experimental results show that MnO2@CDs can be used for amoxicillin fluorescence detection.

[0095] To obtain the best fluorescence intensity, the present application optimizes the reaction time using the above steps, as Figure 3 As shown in B, at 0 min, the fluorescence intensity of MnO2@CDs for amoxicillin detection is low, and the corresponding fluorescence intensity rapidly increases after 1 min, and then remains unchanged, therefore, the present application selects 1 min as the reaction time.

[0096] Next, the present application evaluates the performance of MnO2@CDs for amoxicillin detection, as Figure 3 As shown in C, as the concentration of amoxicillin increases from 0 to 0.045 μM, the fluorescence of CDs gradually recovers, and the fluorescence intensity at 450 nm gradually increases, and the concentration of amoxicillin and the fluorescence signal intensity show a good linear relationship, and the detection lower limit is 1 nM (according to the 3 times deviation rule of the blank response), and the corresponding fluorescence image also gradually changes from dark to bright blue (as shown in D) as the concentration of amoxicillin increases. Figure 3

[0097] ​In the AMO fluorescence test paper detection experiment, the dry water absorption test paper strip was soaked in the MnO2@CDs (5 mg / mL) solution for 1 min, taken out and laid flat, 10 μL of different concentrations of AMO was added to the test paper strip, the final concentration of AMO was 0 nM, 3 nM, 5 nM, 10 nM, 15 nM, 20 nM, 25 nM, 30 nM, 35 nM, 40 nM, 45 nM, respectively, and reacted at room temperature for 5 min, and the fluorescence experiment color development result was as shown in Figure 4 .

[0098] Amoxicillin colorimetric detection test:

[0099] 1.202 mg of TMB was weighed, 1 mL of dimethyl sulfoxide (DMSO) was added, and a 5 mM TMB solution was prepared. 10 μL of MnO2@CDs (5 mg / mL), 5 μL of amoxicillin (5 mM), 10 μL of TMB solution (5 mM), 37 μL of HAc-NaAc buffer (0.1 M, pH 4) and 88 μL of H2O were incubated at 25°C for 10 min. The absorbance was detected at 450 nm.

[0100] As shown in Figure 5 A of FIG. 10, the TMB solution showed a low absorption peak at 450 nm, and the solution showed colorless Figure 5 A, a). The MnO2@CDs or AMO solution alone showed a low absorption peak at 450 nm, and showed colorless Figure 5 A, b and c). When TMB and AMO were added together, the solution showed a low absorption value at 450 nm, and showed colorless Figure 5 A, d). When MnO2@CDs and AMO were added together, the solution showed a low absorption value at 450 nm, and showed colorless Figure 5 A, e). When MnO2@CDs and TMB were added together, the solution showed a strong absorption peak at 450 nm, and showed bright yellow Figure 5 A, f), indicating that MnO2@CDs had oxidase-like activity. When MnO2@CDs, TMB and AMO were added together, the solution showed no significant absorption peak at 450 nm, and showed colorless Figure 5 A, g), which may be caused by the degradation of MnO2@CDs by AMO. The above experimental results prove that MnO2@CDs can be used for amoxicillin colorimetric detection.

[0101] To obtain the best AMO colorimetric detection time, the reaction time was optimized, and the absorption value of the TMB solution at 450 nm gradually decreased with the increase of the reaction time, reaching the minimum at 1 min, and then the ultraviolet absorption value changed little. Therefore, 1 min was selected as the optimal reaction time. Subsequently, the performance of MnO2@CDs for amoxicillin colorimetric detection was explored. With the increase of AMO concentration from 0 to 0.09 μM, the absorption value of the solution at 450 nm gradually decreased Figure 5 , and the AMO concentration showed a good linear relationship with the ultraviolet absorption value, with a detection limit of 1.6 nM (according to the 3-fold deviation rule for the blank response). Corresponding to the colorimetric image, with the increase of the AMO concentration, the test paper showed a multi-color change from yellow to colorless Figure 5 , indicating that the MnO2@CDs biosensor can be used for visual colorimetric detection of AMO.

[0102] The dried test paper strip was pretreated with 10 μL of MnO2@CDs (5 mg / mL), 10 μL of TMB solution (5 mM), 37 μL of HAc-NaAc buffer (0.1 M, pH 4), and 93 μL of H2O, and then 10 μL of different concentrations of AMO was added dropwise on the blotting paper. The final concentration of AMO was 0 nM, 5 nM, 15 nM, 25 nM, 35 nM, 45 nM, 55 nM, 65 nM, 75 nM, 80 nM, and 90 nM, respectively. After reaction at room temperature for 10 min, a colorimetric card was prepared, as shown in Figure 6 .

[0103] Comparison with large instruments:

[0104] (1) To explore the practicability of the MnO2@CDs fluorescent biosensor, the AMO concentration in tap water, milk, and serum was detected. Taking the actual sample tap water as an example, 10 μL of MnO2@CDs (5 mg / mL) was taken in a 200 μL centrifuge tube, a certain concentration of AMO was added, 5 μL of actual sample tap water was added, and water was added to 200 μL. After mixing, incubation was performed at room temperature for 5 min. Under the excitation wavelength of 310 nm, the fluorescence spectrum from 330 to 800 nm was recorded by a fluorescence spectrophotometer, and the fluorescence intensity at 450 nm was read.

[0105] As can be seen from Figure 7 , the recovery rate of AMO by fluorescence method was between 88 and 115%, and the experimental standard deviation was between 0.08 and 4.3%, which was basically consistent with the added AMO concentration. The corresponding sample color showed obvious changes. The recovery rate of AMO by HPLC method was between 80 and 107%, and the experimental standard deviation was between 1.3 and 2.5%, which was comparable to the two methods, indicating that the MnO2@CDs biosensor was suitable for fluorescence detection of AMO in actual samples.

[0106] (2) To investigate the practicability of MnO2@CDs colorimetric biosensor, the AMO concentration in tap water, milk and serum was detected. Taking the actual sample tap water as an example, 10 μL of MnO2@CDs (5 mg / mL) was taken in a 200 μL centrifuge tube, 10 μL of TMB (5 mM), 37 μL of NaAc-HAc (0.1 M) and 5 μL of actual sample tap water were added, a certain concentration of AMO was added, water was added to 150 μL, and after mixing, it was incubated at room temperature for 10 min. The ultraviolet absorption value of 200-800 nm was measured by ultraviolet visible spectrophotometer, and the ultraviolet absorption value at 450 nm was read. From Figure 8 It can be seen that the recovery rate of AMO is between 85-108%, and the experimental standard deviation is between 0.31-7.4%, which is basically consistent with the concentration of AMO added, and the corresponding sample color presents obvious change. The recovery rate of AMO is between 80-116% by HPLC method, and the experimental standard deviation is between 1.2-3.4%, which is equivalent to the two methods, indicating that the MnO2@CDs biosensor is suitable for colorimetric detection of AMO in actual samples.

[0107] Selectivity and specificity test:

[0108] (1) To evaluate the fluorescence detection selectivity of MnO2@CDs probe for AMO, vancomycin (VAN), flumequine (FLU), norfloxacin (NOR), ampicillin (AMP), erythromycin (EM), cephalexin (CEP), glutamic acid (GLU), melamine (MEI), cysteine (CYS), benzimidazole (DRB), urea (Urea) and potassium chloride (KCl) were used as potential interferents, replacing amoxicillin. Taking vancomycin as an example, the detection conditions are as follows: 10 μL of MnO2@CDs (5 mg / mL), 10 μL of vancomycin (25 mM) and 180 μL of H2O were reacted at room temperature for 5 min. At an excitation wavelength of 310 nm, the fluorescence spectrum of 330-800 nm was recorded, and the fluorescence intensity at 450 nm was read. Although the concentration of other interferents is 5 times higher than that of amoxicillin (AMO), the interferents only show weak fluorescence intensity, while AMO shows strong fluorescence signal (such as Figure 9 A), the experimental results show that MnO2@CDs has good selectivity for fluorescence detection of AMO.

[0109] When one of AMO and other interferents (such as VAN, FLU, NOR, AMP, EM, CEP, GLU, MEI, CYS, DRB, Urea, KCl) is detected. Taking vancomycin as an example, the detection conditions are as follows: 10 μL of MnO2@CDs (5 mg / mL), 10 μL of vancomycin (25 mM), 10 μL of amoxicillin (5 mM) and 170 μL of H2O are reacted at room temperature for 5 min. Under the excitation wavelength of 310 nm, the fluorescence spectrum of 330-800 nm is recorded, and the fluorescence intensity at 450 nm is read. The samples all show strong fluorescence signals, indicating that the influence of other interferents on the fluorescence detection of AMO is small, and the MnO2@CDs has good specificity for the fluorescence detection of AMO Figure 9 In the middle B).

[0110] (2) In order to evaluate the selectivity of the MnO2@CDs biosensor for the colorimetric detection of AMO, VAN, FLU, NOR, AMP, EM, CEP, GLU, MEI, CYS, DRB, Urea, KCl and other interferents are used to replace amoxicillin. Taking vancomycin as an example, the detection conditions are as follows: 10 μL of MnO2@CDs (5 mg / mL), 5 μL of vancomycin (25 mM), 10 μL of TMB solution (5 mM), 37 μL of HAc-NaAc buffer (0.1 M, pH 4) and 88 μL of H2O are incubated at 25°C for 10 min. The absorbance is detected at 450 nm. Although the concentration of other interferents is 2.5 times that of AMO, they all show high absorption values at 450 nm, only AMO shows low absorption value at 450 nm, indicating that the MnO2@CDs has good selectivity for the colorimetric detection of AMO Figure 10 In the middle A). When AMO is added with one interferent, taking vancomycin as an example, the detection conditions are as follows: 10 μL of MnO2@CDs (5 mg / mL), 5 μL of amoxicillin (5 mM), 5 μL of vancomycin (25 mM), 10 μL of TMB solution (5 mM), 37 μL of HAc-NaAc buffer (0.1 M, pH 4) and 83 μL of H2O are incubated at 25°C for 10 min. The absorbance is detected at 450 nm. The absorption values of the samples at 450 nm are all reduced, and compared with the blank control, they all show no color Figure 10 In the middle B), indicating that the influence of other interferents on the colorimetric detection of AMO is small, and the MnO2@CDs can be used for specific detection of AMO.

[0111] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled persons in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. Application of MnO2@CDs composite material as a probe in detection of amoxicillin, characterized in that, The preparation method of the MnO2@CDs composite material comprises the following steps: mixing hollow porous MnO2 balls, carbon quantum dots and water, solid-liquid separation, drying the obtained solid, and obtaining the MnO2@CDs composite material. The MnO2@CDs composite material comprises hollow porous MnO2 balls and carbon quantum dots CDs loaded on the inner and outer surfaces of the hollow porous MnO2 balls; wherein the CDs and the MnO2 produce resonance energy transfer, and the fluorescence of the CDs is quenched.

2. Use according to claim 1, characterized in that, The particle size of the hollow porous MnO2 ball is 450-600 nm.

3. A method for the fluorescence detection of amoxicillin, characterized in that, The method comprises the following steps: Mixing the MnO2@CDs composite material, the sample to be tested and water for reaction for more than 1 min, performing fluorescence detection on the obtained mixed sample under excitation of a 310 nm wavelength, recording the fluorescence intensity of the mixed sample at 450 nm, and calculating the concentration of amoxicillin in the sample to be tested according to a standard curve of amoxicillin concentration and fluorescence intensity at 450 nm; The MnO2@CDs composite material is the MnO2@CDs composite material used in the application of claim 1 or 2.

4. A colorimetric method for the detection of amoxicillin, characterized in that, The method comprises the following steps: Mixing the MnO2@CDs composite material, a 3,3',5,5'-tetramethylbenzidine solution, the sample to be tested, a buffer solution and water for reaction for more than 1 min, performing ultraviolet absorption detection on the obtained mixed sample, recording the ultraviolet absorption value of the mixed sample at 450 nm, and calculating the concentration of amoxicillin in the sample to be tested according to a standard curve of amoxicillin concentration and ultraviolet absorption value at 450 nm; the pH value of the buffer solution is 4; The MnO2@CDs composite material is the MnO2@CDs composite material used in the application of claim 1 or 2.

5. An amoxicillin intelligent detection method based on an RGB analysis system, characterized in that, The method comprises the following steps: MnO2@CDs composite material, the sample to be measured and water are mixed for reaction for more than 1 min to obtain a mixed sample; the mixed sample is photographed by using a mobile phone with an RGB analysis system, and the three primary color values are read, the three primary colors including red, green and blue, wherein the red color value is represented by R, the green color value is represented by G, the blue color value is represented by B, the sum of the three primary colors is represented by RGB, and the concentration of amoxicillin in the sample to be measured is calculated according to a standard curve of amoxicillin concentration and Ratio. P R P G P B P C P C P R P G P B P B P B / P C ; and the concentration of amoxicillin in the sample to be measured is calculated according to a standard curve of amoxicillin concentration and Ratio.​​​​​​​​​ The MnO2@CDs composite material is the MnO2@CDs composite material used in the application of claim 1 or 2.

6. A fluorescence kit for detecting amoxicillin, characterized by, The aqueous solution comprises the MnO2@CDs composite material; the MnO2@CDs composite material is the MnO2@CDs composite material used in the application of claim 1 or 2.

7. A colorimetric kit for the detection of amoxicillin, characterized in that, The aqueous solution comprises the MnO2@CDs composite material, a 3,3',5,5'-tetramethylbenzidine solution and a buffer solution; the pH value of the buffer solution is 4; the MnO2@CDs composite material is the MnO2@CDs composite material used in the application of claim 1 or 2.

8. A semi-quantitative method for the detection of amoxicillin, characterized in that, The method comprises the following steps: Dipping a dry test paper strip in an aqueous solution of the MnO2@CDs composite material, dropping the sample to be tested on the obtained wet test paper strip, comparing the fluorescence color of the test strip with a standard fluorescence card of a known amoxicillin concentration, and obtaining the concentration of amoxicillin in the sample to be tested; Or, dipping a dry test paper strip in an aqueous solution of the MnO2@CDs composite material, a 3,3',5,5'-tetramethylbenzidine solution, a buffer solution and water, dropping the sample to be tested on the obtained wet test paper strip, comparing the color of the test strip with a standard colorimetric card of a known amoxicillin concentration, and obtaining the concentration of amoxicillin in the sample to be tested; the pH value of the buffer solution is 4; The MnO2@CDs composite material is the MnO2@CDs composite material in the application of claim 1 or 2.

Images