Preparation method of carbon quantum dot ratiometric fluorescent probe and method for detecting aureomycin

Abstract

The invention belongs to the technical field of aureomycin detection, and particularly relates to a preparation method of a carbon quantum dot ratiometric fluorescent probe and a method for detecting aureomycin. The method is based on the characteristic that aureomycin can enable a carbon quantum dot ratio fluorescent probe to correspondingly detect that the color of a system gradually changes from yellow to yellow green to dark blue to light purple to final dark purple under an ultraviolet lamp, and obvious changes occur. Detecting the fluorescence intensity change R425 / R515 of a mixed solution of a to-be-detected sample and D-CDs, and comparing with the standard curve to obtain the aureomycin content in the to-be-detected sample. Besides, a paper-based sensor containing the carbon quantum dot ratio fluorescent probe is prepared, a smart phone is used as a signal reader, carrying is convenient, on-site detection of aureomycin in a limited-resource environment can be achieved, and the detection method is simple, sensitive and efficient.

Description

Technical Field

[0001] The present invention belongs to the technical field of chlortetracycline detection, and particularly relates to a method for preparing a carbon quantum dot ratiometric fluorescent probe and a method for detecting chlortetracycline. Background Art

[0002] Chlortetracycline is one of the most widely used antibiotics for human health treatment and animal disease control. However, its overuse in animal husbandry has led to chlortetracycline residues in animal-derived foods such as meat, eggs, and milk. This residues then accumulate in the human body through the food chain, posing a serious threat to public health. Traditional methods for chlortetracycline residue detection primarily include microbiological methods, chromatography, and immunoassays. However, these methods suffer from limitations such as cumbersome pretreatment, time-consuming, and expensive procedures, and the requirement for specialized skills and personnel, making rapid detection difficult. Therefore, the simple, rapid, and accurate detection of chlortetracycline remains an urgent challenge.

[0003] Fluorescence analysis is considered a simple, rapid, sensitive, easy-to-use, and low-cost method using fluorescent materials (organic fluorescent dyes or fluorescent nanomaterials) as a signal platform. Carbon dots (CDs) stand out among numerous fluorescent nanomaterials due to their unique properties, including long fluorescence lifetime, large Stokes shift, and strong resistance to photobleaching. They have been widely used in fields such as food safety control. While CD-based fluorescence sensors play an important role in food safety testing, several challenges remain. Conventional single-emission fluorescence sensors rely on fluorescence enhancement and quenching to sense target analytes. This intensity-dependent sensing mode is susceptible to factors unrelated to the target analyte concentration. Ratiometric fluorescence sensors, with their built-in calibration feature, can reduce microenvironmental influences, making sensing more sensitive and reliable. Furthermore, visual detection methods based on naked-eye detection are attracting widespread attention. Ratiometric fluorescence sensors can provide different colors for identification, facilitating real-time visual monitoring on-site. Commercially available pH test strips and early pregnancy test strips are prime examples of this approach. Visual detection of ratiometric fluorescent probes has great development potential in environmental monitoring, food safety, clinical and field testing, and other fields.

[0004] Therefore, it is imperative to design a simple and rapid detection method in order to achieve rapid, online, real-time and visual detection of chlortetracycline. Summary of the Invention

[0005] This invention improves and supplements existing chlortetracycline detection technologies. It offers the advantages of safety, specificity, sensitivity, and simplicity, providing a fast and convenient chlortetracycline detection test strip. The test strip does not require complex reagents and equipment, allowing for minimal laboratory operation. The results are presented visually, providing intuitive and rapid results, enabling immediate detection and facilitating practical application.

[0006] In order to achieve the above object, the present invention specifically comprises the following steps:

[0007] (1) Preparation of dual-emission carbon quantum dot (D-CDs) fluorescent material: 2,5-diaminotoluene sulfate and ethylenediamine were dissolved in an aqueous solution, the pH was adjusted, and a hydrothermal reaction was performed. After cooling, the solution was centrifuged and dialyzed to obtain a dual-emission carbon quantum dot fluorescent material, which was recorded as D-CDs fluorescent material.

[0008] (2) Preparation of dual-emission carbon quantum dot detection test strips: Take the D-CDs fluorescent material prepared in step 1 and add it to water to obtain a suspension of D-CDs; then soak the hydrophilic filter paper in the suspension of D-CDs, take out the filter paper strips after soaking, and dry them to obtain dual-emission carbon quantum dot detection test strips.

[0009] (3) Using fluorescence spectroscopy at an excitation wavelength of 325 nm, record the fluorescence intensity R of the standard solution of chlortetracycline at different concentration gradients at emission wavelengths of 425 nm and 515 nm. 425 and R 515 ;

[0010] (4) Arrange and plot the experimental data obtained in step (3) using R 425 / R 515 The intensity ratio of chlortetracycline was used as the vertical axis and the chlortetracycline concentration was used as the horizontal axis to obtain the relationship between chlortetracycline concentration and R 425 / R 515 Linear equation for intensity ratio;

[0011] (5) Mix the sample solution to be tested with the D-CDs solution prepared in step (1); use fluorescence spectroscopy to excite at 325 nm to obtain the fluorescence intensity of the solution to be tested at 425 nm and 515 nm, and calculate R 425 / R 515 , substitute into the linear equation obtained in step (4) to calculate the content of chlortetracycline in the sample solution to be tested.

[0012] In the above-mentioned chlortetracycline detection method based on dual-emission carbon quantum dot ratiometric fluorescent probe, the dual-emission carbon quantum dot ratiometric fluorescent probe is prepared by the following method:

[0013] 1.5 g of 2,5-diaminotoluene sulfate and 2 mL of ethylenediamine were dissolved in water; after the solution was fully mixed, it was hydrothermally reacted at 180° C. for 10 hours; after the reaction was completed, it was cooled to room temperature, and the resulting solution was filtered and dialyzed to retain small molecules with a molecular weight of less than 3500 Da; and it was dried to obtain a carbon quantum dot ratiometric fluorescent probe powder.

[0014] In a specific embodiment, the concentration of the D-CDs solution in step (1) is 10 μg·mL -1 .

[0015] In a specific embodiment, the mixing ratio of the sample solution to be tested and the D-CDs solution in step (5) is 100:1.

[0016] In a specific embodiment, the concentration range of the standard solution of chlortetracycline with different concentration gradients is 0-143.16 ng mL -1 .

[0017] In a specific embodiment, the dialysis is performed by first filtering with a 0.22 μm filter membrane, and the filtrate is dialyzed in ultrapure water using a dialysis bag with a molecular weight cutoff of 3500 Da for 24 hours, and the water is refreshed every 6 hours to remove small molecules.

[0018] One of the purposes of the present invention is to provide a paper-based sensor for detecting chlortetracycline, which comprises immersing filter paper in an aqueous solution of a carbon quantum dot ratiometric fluorescent probe; incubating at room temperature for a period of time, and then drying to obtain the paper-based sensor for detecting chlortetracycline;

[0019] The filter paper can be cut into different shapes as required. Those skilled in the art should understand that the shape of the filter paper will not affect the test results. In a specific embodiment, the filter paper is cut into a circle with a diameter of 6 mm.

[0020] In a specific embodiment, the room temperature incubation is room temperature incubation for 10 minutes.

[0021] A second object of the present invention is to provide an application of the above-mentioned paper-based sensor for detecting chlortetracycline in a chlortetracycline detection method using a smartphone as a signal reader.

[0022] A third object of the present invention is to provide a method for detecting chlortetracycline using a smartphone as a signal reader, comprising the following steps:

[0023] (1) Add different concentrations of chlortetracycline standard solution to the surface of the paper-based sensor;

[0024] (2) Download and install the color scanning application (APP: Color Identifier) ​​on your smartphone;

[0025] (3) Use a color scanning application on a smartphone to record the fluorescence color of the paper-based sensor in step (1) under a 365nm ultraviolet lamp, and digitize and output the fluorescence color of the paper-based sensor to obtain RGB values; use R+G+B as the vertical coordinate and the concentration of chlortetracycline as the horizontal coordinate to obtain a linear equation of chlortetracycline concentration and R+G+B;

[0026] (4) Add the sample solution to be tested onto the surface of the paper-based sensor;

[0027] (5) Use a color scanning application on a smartphone to record the fluorescence color of the paper-based sensor in step (4) under a 365nm ultraviolet lamp, and digitize and output the fluorescence color of the paper-based sensor to obtain an RGB value; calculate R+G+B; substitute the value of R+G+B into the linear equation obtained in step (3) to calculate the content of chlortetracycline in the sample solution to be tested.

[0028] The above description of the amount of raw materials is only the amount used in laboratory operations, and is not an absolute limitation on the amount. Those skilled in the art should understand that in actual production, the amount can be adjusted according to the above ratio based on the production scale.

[0029] The method for detecting chlortetracycline of the present invention is applicable to matrix samples such as aqueous solutions, for example, water and milk; solid samples can be prepared in the form of aqueous solutions, or can be detected after filtering to remove water-insoluble components.

[0030] In the above steps (1) and (4), the amount of chloramphenicol standard solution or sample solution of different concentrations added to the paper-based sensor can be adjusted according to the size of the test paper used to prepare the paper-based sensor; in a specific embodiment of the present invention, the size of the test paper is a disc with a diameter of 6 mm, and the amount of chloramphenicol standard solution or sample solution of different concentrations added to the test paper is 200 μL / piece.

[0031] The principle of the preparation of carbon quantum dots and their detection of chlortetracycline provided by the present invention is to use the aromatic benzene ring structure and the functional groups rich in the surface of the carbon quantum dots as the specific recognition unit of chlortetracycline. When chlortetracycline is not added, the carbon quantum dots emit yellow fluorescence (λ em =515nm). After binding to chlortetracycline, the yellow fluorescence of the carbon quantum dots remained unchanged and the blue fluorescence gradually increased due to the aggregation-induced effect (λ em =425nm), producing a ratiometric fluorescence signal change based on the chlortetracycline content. Accordingly, the color of the detection system under UV light gradually changes from yellow to yellow-green to dark blue to light purple and finally to dark purple, a significant change.

[0032] Advantages of the technical solution of the present invention:

[0033] A carbon quantum dot ratiometric fluorescent probe was prepared via a one-step hydrothermal method. The carbon quantum dots maintain their inherent yellow fluorescence while specifically binding to chlortetracycline molecules to enhance the fluorescence at the blue emission point, producing a ratiometric fluorescent signal and a significant color gradient. This new fluorescent probe exhibits excellent physical and chemical stability and does not require complex carbon quantum dot modification. Ratiometric fluorescence detection of target molecules can be achieved using a single carbon quantum dot. Under ultraviolet light, the color of the carbon quantum dot solution can be observed to change significantly, gradually from yellow to yellow-green to dark blue to light purple, and finally to dark purple.

[0034] In addition, a portable, instrument-free paper-based sensor and smartphone-assisted sensing platform were developed for on-site visual detection of chlortetracycline. The developed paper-based sensor is easy to carry, low-cost, highly selective, and highly sensitive, and the detection signal can be read directly and easily by the naked eye. The smartphone serves as a simple answer analyzer, which is portable and easy to operate. When the concentration of chlortetracycline exceeds a certain level, a direct color change visible to the naked eye alerts the user, and further mobile phone-assisted image processing can provide quantitative analysis of chlortetracycline concentration. It can provide a powerful method for the qualitative identification and semi-quantitative analysis of chlortetracycline in the field and in resource-poor areas, showing great application potential in food safety monitoring. It not only provides a new strategy for ratiometric fluorescence and visual sensing of chlortetracycline, but also provides new insights into the development of efficient ratiometric fluorescence and visual sensing platforms, which are promising for many other on-site detection in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 TEM analysis and HRTEM images of carbon quantum dot ratiometric fluorescence probe;

[0036] Figure 2 X-ray photoelectron spectroscopy (XPS) patterns of D-CDs;

[0037] Figure 3 The specificity of carbon quantum dot ratiometric fluorescent probe for chlortetracycline;

[0038] Figure 4 Fluorescence spectra of the effects of different concentrations of chlortetracycline on the fluorescence intensity of D-CDs;

[0039] Figure 5 The linear equation for the detection of chlortetracycline by carbon quantum dot ratiometric fluorescence probe;

[0040] Figure 6 (A) Fluorescence image of the fluorescent test strip established in Example 1 according to different concentrations; (B) Linear equation for the detection of chlortetracycline based on the carbon quantum ratio fluorescence probe combined with a smartphone and a paper-based sensor. DETAILED DESCRIPTION

[0041] Unless otherwise specified, the terms used in the present invention generally have the meanings commonly understood by those skilled in the art.

[0042] The present invention will be further described in detail below with reference to specific examples and data. The following examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention in any way.

[0043] Example 1

[0044] A method for preparing a carbon quantum dot ratiometric fluorescent probe comprises the following steps:

[0045] 1.5 g of 2,5-diaminotoluene sulfate and 2 mL of ethylenediamine were weighed and dissolved in water. The solution was thoroughly mixed and transferred to a 25 mL Teflon-lined stainless steel autoclave. The reaction was carried out at 180°C for 10 hours. After cooling to room temperature, the resulting dark yellow solution was filtered through a 0.22 μm filter membrane and dialyzed against ultrapure water using a dialysis bag (molecular weight cutoff 3500 Da) for 24 hours, with the water refreshed every 6 hours to remove small molecules. Subsequently, the solution in the dialysis bag was evaporated and dried at 60°C to obtain a powder of the carbon quantum dot ratiometric fluorescent probe with a quantum yield of 10.81%.

[0046] Figure 1 Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) images of the carbon quantum dot ratiometric fluorescent probe (D-CDs) prepared by the above method. Figure 1 As shown in A, D-CDs are uniformly distributed nearly spherical nanoparticles. The particle size distribution histogram of D-CDs shows that the particle size distribution is 1.0-10.0 nm, with an average particle size of 2.0 nm. HRTEM image ( Figure 1 (bottom left corner of center A) shows that D-CDs have clear lattice fringes with a lattice spacing of approximately 0.21 nm, which is consistent with the (100) plane of graphitic carbon.

[0047] To further confirm the elemental composition and chemical bonding of D-CDs, X-ray photoelectron spectroscopy (XPS) measurements were performed. Figure 2 XPS graph of D-CDs, where A is the XPS full scan spectrum of D-CDs, B is the XPS spectrum of C1s, C is the XPS spectrum of N1s, D is the XPS spectrum of O1s, and E is the XPS spectrum of S2p;

[0048] Depend on Figure 2 It can be seen that the XPS full scan spectrum shows four obvious peaks at 171.97, 298.57, 399.17 and 535.87 eV, which are attributed to C1s, N1s, O1s and S2p. In the high-resolution spectrum ( Figure 2BE), the C1s band can be deconvoluted into three peaks at 284.7, 285.7 and 288.4 eV, corresponding to CC / C=C, CN / CO and C=O groups, respectively; in the N1s spectrum, the peaks at 399.9 and 401.5 eV correspond to NC and N--H groups; the O1s band at 531.2, 532.0 and 532.9 eV can be deconvoluted into three peaks, attributed to C=O and C-OH groups, respectively.

[0049] Example 2

[0050] A method for preparing a carbon quantum dot ratiometric fluorescent probe comprises the following steps:

[0051] 1.5 g of 2,5-diaminotoluene sulfate and 2 mL of ethylenediamine were weighed and dissolved in water. The solution was thoroughly mixed and transferred to a 25 mL Teflon-lined stainless steel autoclave. The reaction was carried out at 180°C for 10 hours. After cooling to room temperature, the resulting dark yellow solution was filtered through a 0.22 μm filter membrane and dialyzed against ultrapure water using a dialysis bag (molecular weight cutoff 3500 Da) for 24 hours, with the water being refreshed every 6 hours to remove small molecules. Subsequently, the solution in the dialysis bag was evaporated and dried at 60°C to obtain a powder of the carbon quantum dot ratiometric fluorescent probe.

[0052] Example 3

[0053] A method for detecting chlortetracycline, comprising the following steps:

[0054] (1) The carbon quantum dot ratiometric fluorescent probe prepared in Example 1 was prepared to a concentration of 10 μg·mL -1 The aqueous solution is D-CDs solution;

[0055] (2) Take the D-CDs solution prepared in step (1) and add different amounts of chlortetracycline to it to prepare standard solutions with different concentration gradients of chlortetracycline, where the concentration of chlortetracycline is 0-143.16 ng mL -1 ; After mixing evenly, incubate at room temperature for 60s;

[0056] (3) Fluorescence spectroscopy was used to record the emission spectra of chlortetracycline standard solutions with different concentration gradients under 325 nm excitation; the results are as follows: Figure 4 shown; from Figure 4 It can be seen that with the increase of chlortetracycline concentration, the fluorescence intensity of the D-CDs system at 515 nm did not change significantly (P>0.05), while the fluorescence intensity at 425 nm gradually increased.

[0057] (4) Arrange and plot the experimental data obtained using R 425 / R 515The intensity ratio is used as the ordinate and the CTC concentration is used as the abscissa to obtain the linear equation as follows: Figure 5 As shown, the linear relationship is Y = 0.1051x + 0.7128; the coefficient of determination is R 2 =0.998.

[0058] (5) The sample solution to be tested was mixed with the D-CDs solution prepared in step (1) in a ratio of 1:1 and incubated at room temperature for 60 seconds. The fluorescence intensity of the sample solution at 435 nm and 515 nm was obtained by fluorescence spectroscopy under excitation at 325 nm, and R was calculated. 425 / R 515 The intensity ratio of the chlortetracycline was compared with the standard curve obtained in step (4) to calculate the content of chlortetracycline in the sample solution to be tested.

[0059] The above method for detecting chlortetracycline has good stability and high reproducibility, with a detection limit of 1.29 ng mL -1 .

[0060] Specificity of carbon quantum dot ratiometric fluorescent probe for chlortetracycline:

[0061] The same concentration (60 ng·mL -1 ) were mixed with an equal volume of the D-CDs solution prepared in step (1), and after incubation at room temperature for 60 seconds, the emission spectrum of the mixture was recorded at an excitation wavelength of 325 nm using fluorescence spectroscopy. Figure 3 As shown, only chlortetracycline can cause the fluorescence intensity of the D-CDs system at 515 nm to change insignificantly, while the fluorescence intensity at 425 nm gradually increases.

[0062] Example 4

[0063] A method for detecting chlortetracycline based on a carbon quantum dot ratiometric fluorescence probe combined with a smartphone and a paper-based sensor, comprising the following steps:

[0064] (1) The carbon quantum dot ratiometric fluorescent probe prepared in Example 1 was prepared to a concentration of 10 μg·mL -1 aqueous solution;

[0065] (2) Cut the filter paper into a circle with a diameter of about 6 mm and then immerse it in the D-CDs (10 μg mL -1 ) solution; incubate at room temperature for 60 seconds, and then dry in air at room temperature to obtain a paper-based sensor for detecting chlortetracycline;

[0066] (3) Different concentrations (0-143.16 ng mL -1 ) is added to the surface of the circular paper-based sensor prepared in step (2); the amount of addition is 200 μL / piece of paper-based sensor;

[0067] (4) Observe the fluorescent color change of the circular paper-based sensor with the naked eye under ultraviolet light. Use the color scanning application (APP: Color Identifier) ​​downloaded from the App Store to digitize and output the fluorescent color of the paper-based sensor to obtain the RGB value; use the obtained experimental data (R+G+B) to organize and draw a graph to obtain the linear equation ( Figure 6 ), the linear relationship is Y = 0.57x + 426.69; the coefficient of determination is R 2 =0.9908.

[0068] (5) Add the sample solution to be tested to the surface of the paper-based sensor prepared in step (2); the addition amount is 200 μL / paper-based sensor; use a color scanning application on a smartphone to record the fluorescence color of the paper-based sensor under ultraviolet light, and digitize and output the fluorescence color of the paper-based sensor to obtain an RGB value; calculate R+G+B; substitute the value of R+G+B into the linear equation obtained in step (4) to calculate the content of chlortetracycline in the sample solution to be tested.

[0069] The above method has good stability and high repeatability in the detection of chlortetracycline, with a detection limit of 10.12 ng mL -1 .

[0070] In summary, the carbon quantum dot ratiometric fluorescent probe synthesized in this paper not only provides a new strategy for the ratiometric fluorescence and visual sensing of TC, but also provides new insights for the development of efficient ratiometric fluorescence and visual sensing platforms.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon quantum dot ratiometric fluorescent probe, characterized in that: The following steps are involved: 2,5-diaminotoluene sulfate and ethylenediamine are dissolved in an aqueous solution, the pH is adjusted, a hydrothermal reaction is carried out, and after cooling, centrifugation and dialysis are performed to obtain a dual-emission carbon quantum dot fluorescent material, namely a D-CDs fluorescent material solution.

2. The method for preparing a carbon quantum dot ratiometric fluorescent probe according to claim 1, wherein: 1.5 g of 2,5-diaminotoluene sulfate and 2 mL of ethylenediamine were dissolved in water; after the solution was fully mixed, it was hydrothermally reacted at 180° C. for 10 hours; after the reaction was completed, it was cooled to room temperature, and the resulting solution was filtered and dialyzed to retain small molecules with a molecular weight of less than 3500 Da; and it was dried to obtain a carbon quantum dot ratiometric fluorescent probe powder.

3. The method for preparing a carbon quantum dot ratiometric fluorescent probe according to claim 1, wherein: The concentration of the D-CDs solution is 10 μg·mL-1.

4. The method for preparing a carbon quantum dot ratiometric fluorescent probe according to claim 2, wherein: The dialysis was performed by first filtering with a 0.22 μm filter membrane, and the filtrate was dialyzed in ultrapure water using a dialysis bag with a molecular weight cut-off of 3500 Da for 24 hours, with the water being renewed every 6 hours to remove small molecules.

5. The method for preparing a carbon quantum dot ratiometric fluorescent probe according to claim 1 or 2, wherein: The filter paper is immersed in an aqueous solution prepared from the final product prepared in claim 1 or 2; after incubation at room temperature for a period of time, the paper-based sensor for detecting chlortetracycline is obtained by drying.

6. The method for preparing a carbon quantum dot ratiometric fluorescent probe according to claim 5, wherein: The room temperature incubation is room temperature incubation for 10 minutes.

7. A method for detecting chlortetracycline, characterized in that: The following steps are involved: Step (1), preparing the final product prepared in claim 1 or 2 into an aqueous solution with a concentration of 10 μg·mL-1, namely, a D-CDs solution; Step (2), preparing a dual-emission carbon quantum dot test strip: taking the D-CDs fluorescent material prepared in step 1 and adding it to water to obtain a D-CDs suspension; then soaking a hydrophilic filter paper in the D-CDs suspension, taking out the filter paper strip after soaking, and drying it to obtain a dual-emission carbon quantum dot test strip; Step (3), using fluorescence spectroscopy at an excitation wavelength of 325 nm, recording the fluorescence intensities R425 and R515 of the standard solutions of chlortetracycline at different concentration gradients at emission wavelengths of 425 nm and 515 nm; Step (4) arranging and plotting the experimental data obtained in step (3), using the intensity ratio of R425 / R515 as the ordinate and the chlortetracycline concentration as the abscissa, to obtain a linear equation of the chlortetracycline concentration and the R425 / R515 intensity ratio; Step (5) mixing the sample solution to be tested with the D-CDs solution prepared in step (1); Fluorescence spectroscopy was used to excite at 325 nm to obtain the fluorescence intensity of the test solution at 425 nm and 515 nm. R425 / R515 was calculated and substituted into the linear equation obtained in step (4) to calculate the content of chlortetracycline in the test sample solution.

8. A method for detecting chlortetracycline according to claim 7, characterized in that: In step (5), the mixing ratio of the sample solution to be tested and the D-CDs solution is 100:

1.

9. A method for detecting chlortetracycline according to claim 7, characterized in that: The concentration range of the standard solution of chlortetracycline with different concentration gradients is 0-143.16 ng mL-1.

10. A method for detecting chlortetracycline, characterized in that: The following steps are involved: Step (1), adding chlortetracycline standard solutions of different concentrations to the surface of the paper-based sensor obtained in claim 5; Step (2), using a color scanning application installed on a smartphone, namely, APP: Color Identifier, to record the fluorescence color of the paper-based sensor in step (1) under a 365nm ultraviolet lamp, and digitize and output the fluorescence color of the paper-based sensor to obtain an RGB value; using R+G+B as the vertical coordinate and the concentration of chlortetracycline as the horizontal coordinate, a linear equation of the chlortetracycline concentration and R+G+B is obtained; Step (3), adding the sample solution to be tested dropwise onto the surface of the paper-based sensor; Step (4), using a color scanning application on a smartphone to record the fluorescence color of the paper-based sensor in step (5) under a 365nm ultraviolet lamp, and digitizing and outputting the fluorescence color of the paper-based sensor to obtain an RGB value; calculating R+G+B; substituting the value of R+G+B into the linear equation obtained in step (4) to calculate the content of chlortetracycline in the sample solution to be tested.

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