Synthesis of CDs / GO-PBA nanocomposite probe and detection method of salmonella

Abstract

The application discloses a CDs / GO-PBA nanocomposite probe synthesis and a Salmonella detection method. The method comprises the following steps: hydrothermal carbonization of mannose and histidine to obtain a pseudo-glycopeptide carbon dot, and then reaction of 3-aminophenylboronic acid and graphene oxide to obtain boronated modified graphene oxide GO-PBA. CDs are loaded on the GO-PBA sheet layer by forming a borate ester bond between the hydroxyl group and the boronic acid group, and CDs / GO-PBA with quenched fluorescence is obtained. The CDs / GO-PBA is added into a Salmonella typhimurium bacterial suspension, and after the CDs bind to the Salmonella typhimurium through the lectin-sugar interaction, the dynamic borate ester bond is broken, the CDs are separated from the graphene surface, and the fluorescence is restored. The concentration of the Salmonella typhimurium is detected by measuring the fluorescence intensity through a fluorescence spectrometer. The method can quickly and quantitatively detect the Salmonella typhimurium, and has good sensitivity and a wide detection range.

Description

TECHNICAL FIELD

[0001] The application relates to the field of pathogenic microorganism detection, in particular to a synthesis method of CDs / GO-PBA nanocomposites and application thereof in detection of Salmonella. BACKGROUND

[0002] Salmonella is a bacillary gram-negative zoonosis pathogen, has a wide host spectrum, and can cause gastrointestinal diseases in humans and animals, symptoms of which are light to enteritis and heavy to septicemia. It is one of the most common pathogens causing outbreaks of food poisoning and in vivo infection, is easy to contaminate food such as meat, eggs and milk, has strong transmissibility, is difficult to prevent and control, has the characteristics of wide prevalence, and causes great threat to human life and health. Therefore, it is urgent to develop an efficient, rapid and sensitive Salmonella detection method.

[0003] At present, the fluorescence method for detecting Salmonella has great advantages, and is more convenient and rapid than bacterial culture method and enzyme-linked immunosorbent technology. However, the existing technology needs to use antibodies, aptamers and phages as recognition probes for detection of target objects, the recognition probes are expensive and have poor stability, the carbon dots synthesized by sugar and amino acid simulate the sugar peptide structure, have stable performance, are low in price, and have a simple synthesis method, which is beneficial to cost reduction and mass production. In addition, the carbon dots have fluorescence resistance to light bleaching, have good signal stability and high reproducibility. According to the recognition ability and fluorescence characteristics of the pseudo-sugar peptide carbon dots to Salmonella, the GO can stably quench the fluorescence of the CDs through fluorescence resonance energy transfer (FRET), and when the bacteria are combined with the CDs, the carbon dots will leave the surface of the GO, so that the fluorescence is recovered, and the method can directly detect Salmonella. Therefore, a fluorescence recovery type detection method for rapidly and accurately detecting Salmonella is established. SUMMARY

[0004] In order to overcome the above-mentioned deficiencies in the prior art, the purpose of the present application is to provide a synthesis method of a fluorescent CDs / GO-PBA nanocomposite probe and application thereof in detection of Salmonella.

[0005] The purpose of the present application is to overcome the deficiencies in the prior art, the method grafts the pseudo-sugar peptide CDs with Salmonella recognition performance on the GO-PBA to prepare the fluorescent sensing probe, and then uses the fluorescence method to detect Salmonella.

[0006] The preparation method adopts mannose and histidine as raw materials, and prepares the pseudo glycopeptide carbon dots through hydrothermal carbonization; 3-aminophenylboronic acid is added to GO, and GO-PBA is synthesized under the condition of heating and stirring; then the carbon dots and GO-PBA are coupled to form the CDs / GO-PBA nanocomposite material through a dynamic boronic ester bond. The solution of the nanocomposite material is added to a salmonella liquid and incubated for a period of time, centrifuged, and the fluorescence intensity of the supernatant is measured, and the concentration of salmonella can be judged according to the fluorescence intensity within a certain range.

[0007] The object of the application is achieved at least by one of the following technical solutions.

[0008] The application provides a synthesis method of the CDs / GO-PBA nanocomposite material, which comprises the following steps:

[0009] (1) mannose and histidine are added to water, mixed uniformly, and subjected to hydrothermal reaction under heating, a filtrate is obtained by filtration, and the filtrate is subjected to dialysis to obtain a pseudo glycopeptide carbon dot solution;

[0010] (2) 3-aminophenylboronic acid is added to a GO solution, and subjected to reaction under heating and stirring to obtain a reaction liquid, and the reaction liquid is centrifuged to remove unreacted 3-aminophenylboronic acid, thereby obtaining a GO-PBA solution;

[0011] (3) the pseudo glycopeptide carbon dot solution is added to the GO-PBA solution in step (2), and subjected to stirring reaction, and then the solution is centrifuged (to remove unreacted carbon dot solution), thereby obtaining a CDs / GO-PBA nanocomposite material solution;

[0012] Further, the preparation of the mannose / histidine solution in step (1) comprises: mannose and histidine are added to water, mixed uniformly, and the mannose / histidine solution is obtained; in the mannose / histidine solution, the mass ratio of mannose to histidine is 1-7, and the concentration is 30-100 mg / mL.

[0013] Preferably, the stirring in step (1) is magnetic stirring.

[0014] Further, the temperature of the hydrothermal reaction in step (1) is 150-230 DEG C, and the hydrothermal reaction time is 3-12 h; the dialysis bag used for dialysis has a molecular weight cut-off of 500-1000 Da; the dialysis time is 3-7 days; and the concentration of the carbon dot solution is 0.5-1 mg / mL.

[0015] Preferably, the centrifugation rate in step (1) is 10000-14000 rpm, and the centrifugation time is 1-10 min.

[0016] Further, the concentration of the GO solution in step (2) is 0.3-0.5 mg / mL; the mass ratio of 3-aminobenzoic acid to the GO solution is 3:1-7:1; the heating reaction temperature is 60-80 DEG C, and the heating reaction time is 2-3 h.

[0017] Further, the concentration of the GO-PBA solution in step (3) is 0.3-0.5 mg / mL, the pH is 7.8-8.2, and the volume ratio of the pseudo-glycopeptide carbon dot solution to the GO-PBA solution is 0.2-0.25.

[0018] Further, the reaction temperature in step (3) is 20-30 DEG C, and the reaction time is 20-40 min.

[0019] The application provides a CDs / GO-PBA nanocomposite material synthesis method composed of the above steps.

[0020] The application provides application of the synthesized CDs / GO-PBA nanocomposite material in fluorescent detection of Salmonella, which comprises the following steps:

[0021] The solution of the CDs / GO-PBA nanocomposite material is added into Salmonella liquid, and then incubated at 37 DEG C under oscillation, the supernatant is obtained by centrifugation, and then the Salmonella is detected by fluorescence method, and the concentration of the Salmonella is determined according to the fluorescence intensity.

[0022] The application provides application of the synthesized fluorescent CDs / GO-PBA nanocomposite probe in detection of Salmonella, which does not rely on specific antibodies, aptamers and bacteriophages which are expensive and poor in stability, but utilizes the mannose residues on the surface of CDs to recognize Salmonella through lectin-sugar interaction, and has the characteristics of low cost, easy preparation and stability; the CDs are modified on the surface of GO-PBA through borate ester bonds, and the fluorescence is quenched due to fluorescence resonance energy transfer (FRET); in the presence of target bacteria, the Salmonella combines with the carbon dots to cause the borate ester bonds between the CDs and the GO-PBA to break, the CDs fall off from the surface of the GO-PBA, and the fluorescence is recovered. The added amount of the CDs / GO-PBA nanocomposite material is 300-500 muL, and 10 4 ~10 7 CFU / mL of Salmonella can be detected. The diol structure of the pseudo-glycopeptide carbon dots can specifically recognize Salmonella, GO is a stable fluorescence quencher, the recovery type fluorescent probe is constructed to improve the detection sensitivity, and in addition, the detection can be completed within 1 hour by using a fluorescence spectrometer. Therefore, the constructed fluorescent probe can quickly and highly sensitively detect the content of Salmonella in food samples.

[0023] The fluorescent sensor composed of the CDs / GO-PBA nanocomposite material can quickly and highly sensitively detect Salmonella.

[0024] The application provides a method for detecting Salmonella by using a fluorescent CDs / GO-PBA nanocomposite probe.

[0025] Compared with the prior art, the application has the following advantages:

[0026] (1) The synthesis method of the CDs / GO-PBA nanocomposite material provided by the application uses mannose and histidine as raw materials to synthesize carbon dots, and the raw materials are widely available, low in cost, safe and non-toxic, and stable in performance.

[0027] (2) The prepared pseudo-glycopeptide CDs are used as recognition elements, which are low in cost, easy to prepare, and stable in fluorescent properties, and do not depend on specific antibodies, aptamers and bacteriophages which are expensive and poor in stability.

[0028] (3) The GO is boronated and modified, and then mixed with the pseudo-glycopeptide carbon dots to combine the pseudo-glycopeptide carbon dots through a dynamic borate ester bond, so that a fluorescence recovery type probe is constructed, and the stability and sensitivity of detection are improved.

[0029] (4) The preparation method provided by the application is simple in process and low in energy consumption, and is conducive to large-scale industrial production.

[0030] (5) The CDs / GO-PBA nanocomposite material synthesized by the application has a detection range of 10 4 ~ 10 7 CFU / mL for Salmonella, and has the characteristics of high sensitivity, rapid detection, easy to carry and stability, and can be applied to the detection of Salmonella in food samples. DETAILED DESCRIPTION

[0031] Figure 1 is a particle size diagram of the pseudo-glycopeptide carbon dots obtained in Example 2.

[0032] Figure 2 is a diagram of the change of the fluorescence intensity with the concentration of Salmonella.

[0033] Figure 3 is a scanning electron microscope diagram of the incubation of the CDs / GO-PBA with Salmonella in Example 2. DETAILED DESCRIPTION

[0034] The following further describes the specific implementation of the present application with examples, but the implementation and protection of the present application are not limited thereto. It should be noted that if the following process is not specifically described in detail, it can be implemented or understood by referring to the prior art. If the reagent or instrument used is not marked with the manufacturer, it is considered to be a conventional product that can be obtained by commercial purchase.

[0035] Example 1

[0036] A synthesis method of CDs / GO-PBA nanocomposites, comprising the following steps:

[0037] (1) 0.2 g of mannose and 0.2 g of histidine were added to 15 mL of water, and stirred by magnetic stirring to obtain a mannose / histidine solution. The mannose / histidine solution was placed in a muffle furnace and heated to 150℃ for hydrothermal reaction, and the hydrothermal reaction time was 3 h. After the reaction, the filtrate was obtained by filtration, the filter membrane pore size was 0.45 μm, and the supernatant was placed in a dialysis bag with a molecular weight of 1000 Da for dialysis, and the dialysis time was 3 d to obtain a pseudo-glycopeptide carbon dot solution;

[0038] (2) 15 mg of 3-aminobenzoic acid was added to 5 mL of GO solution (0.3 mg / mL) and stirred uniformly, and then placed in a water bath at 60℃ and 500 rpm for 3 h. The unreacted 3-aminobenzoic acid was removed by centrifugation to obtain GO-PBA;

[0039] (3) 1 mL of the pseudo-glycopeptide carbon dot solution (0.5 mg / mL) of step (1) was added to 5 mL of the GO-PBA solution (0.3 mg / mL) of step (2), stirred uniformly, and the pH was adjusted to 7.8. Then it was placed in a water bath at a temperature of 25℃ for 20 min, and after centrifugation, a CDs / GO-PBA nanocomposite solution was obtained.

[0040] The application of the CDs / GO-PBA nanocomposite in the fluorescence detection of Salmonella, comprising:

[0041] 300 μL of the CDs / GO-PBA solution was added to the sample solution to be detected, and the Salmonella was detected by fluorescence method, and the concentration of the Salmonella was determined according to the fluorescence intensity.

[0042] A series of concentration gradient Salmonella solutions were prepared, and the concentration range of the Salmonella solution was 10 4 ~ 10 7 CFU / mL, which was divided into five groups, i.e. 10 4 , 5×10 4 , 10 5 , 10 6 and 10 7CFU / mL; CDs / GO-PBA solution was added to the above solution, and detection was performed using fluorescence. The detection range of the fluorescence sensor in Example 1 is 10. 5 ~10 7 CFU / mL.

[0043] Example 2

[0044] A method for synthesizing CDs / GO-PBA nanocomposite materials includes the following steps:

[0045] (1) Add 0.7g mannose and 0.1g histidine to 30mL of water, stir magnetically until homogeneous, and obtain a mannose / histidine solution; place the mannose / histidine solution in a muffle furnace and heat to 190℃ for hydrothermal reaction for 9h. After the reaction, filter and collect the filtrate. The filter membrane has a pore size of 0.22μm. Place the supernatant in a dialysis bag with a molecular weight of 500Da and dialyze for 7d to obtain a glycopeptide carbon dot solution.

[0046] (2) Add 25 mg of 3-aminophenylboronic acid to 8 mL of GO solution (0.5 mg / mL), stir well, and then put it into a water bath and react at 70 °C and 600 rpm for 3 h. Centrifuge to remove unreacted 3-aminophenylboronic acid to obtain GO-PBA.

[0047] (3) Add the 2 mL of glycopeptide carbon dot solution (0.5 mg / mL) described in step (1) to the 8 mL of GO-PBA solution (0.5 mg / mL) described in step (2), stir evenly, adjust the pH to 8.0, and then put it into a water bath and react at 25°C for 30 min. After centrifugation, the CDs / GO-PBA nanocomposite solution is obtained.

[0048] The application of the CDs / GO-PBA nanocomposite material in the fluorescent detection of Salmonella includes:

[0049] Add 500 μL of CDs / GO-PBA solution to the sample solution to be tested, and detect Salmonella by fluorescence method. The concentration of Salmonella is determined based on the fluorescence intensity.

[0050] Figure 1 The particle size distribution of carbon dots in glycopeptides is shown below. Figure 1 As can be seen above, the average particle size of the carbon dots is 4.75 nm.

[0051] Figure 2 The SEM image shows the co-culture of CDs / GO-PBA and Salmonella. It can be seen that a large number of Salmonella appeared on the surface of the CDs / GO-PBA sheets, indicating that Salmonella was adsorbed by CDs / GO-PBA during the detection process.

[0052] The concentration of the prepared Salmonella solution ranges from 10 4 ~ 10 7 CFU / mL; the fluorescent recovery probe is added to the above solution, and the fluorescent method is used for detection. Figure 3 The relationship between the concentration of Salmonella obtained by the fluorescent method and the fluorescence intensity is shown in the following figure: Figure 3 As can be seen from the figure, the fluorescence intensity increases with the increase of the concentration of Salmonella, and the linear range is 10 4 ~ 10 7 CFU / mL.

[0053] Example 3

[0054] A synthesis method of a CDs / GO-PBA nanocomposite material, comprising the following steps:

[0055] (1) 0.7 g of mannose and 0.1 g of histidine are added to 45 mL of water, and are uniformly mixed by magnetic stirring to obtain a mannose / histidine solution; the mannose / histidine solution is placed in a muffle furnace and heated to 170℃ for hydrothermal reaction, and the hydrothermal reaction time is 6 h. After the reaction, the filtrate is obtained by filtration, the pore size of the filter membrane is 0.22 μm, and the supernatant is placed in a dialysis bag with a molecular weight of 500 Da for dialysis, and the dialysis time is 4 d to obtain a pseudo-glycopeptide carbon dot solution;

[0056] (2) 20 mg of 3-aminobenzoic acid is added to 10 mL of GO solution (0.4 mg / mL) and stirred uniformly, and then it is placed in a water bath at 80℃ and 550 rpm for 3 h, and the unreacted 3-aminobenzoic acid is removed by centrifugation to obtain GO-PBA;

[0057] (3) 2 mL of the pseudo-glycopeptide carbon dot solution (0.5 mg / mL) of step (1) is added to 10 mL of the GO-PBA solution (0.4 mg / mL) of step (2), and is stirred uniformly, and the pH is adjusted to 8.2, and then it is placed in a water bath at a temperature of 25℃ for 40 min, and a CDs / GO-PBA nanocomposite material solution is obtained after centrifugation.

[0058] The application of the CDs / GO-PBA nanocomposite material in the fluorescent detection of Salmonella, comprising:

[0059] 300 μL of the CDs / GO-PBA solution is added to a sample solution to be detected, and the Salmonella is detected by the fluorescent method, and the concentration of the Salmonella is determined according to the size of the fluorescence intensity.

[0060] A series of concentration gradient Salmonella solutions are prepared, and the concentration of the Salmonella solution ranges from 10 4 ~ 107 CFU / mL, divided into five groups, 10 4 , 5x10 4 , 10 5 , 10 6 and 10 7 CFU / mL; the CDs / GO-PBA solution is added to the above solution, and the fluorescence method is used for detection. The detection range of the fluorescence sensor of Example 1 is 5x10 4 ~ 10 7 CFU / mL.

[0061] Example 4

[0062] A synthesis method of a CDs / GO-PBA nanocomposite material, comprising the following steps:

[0063] (1) 0.9g of mannose and 0.3g of histidine are added to 30mL of water, magnetically stirred, mixed uniformly to obtain a mannose / histidine solution; the mannose / histidine solution is placed in a muffle furnace and heated to 210℃ for hydrothermal reaction, and the hydrothermal reaction time is 9h. After the reaction, the filtrate is filtered with a filter membrane with a pore size of 0.22μm, and the supernatant is placed in a dialysis bag with a molecular weight of 500Da for dialysis, and the dialysis time is 5d, to obtain a pseudo-glycopeptide carbon dot solution;

[0064] (2) 25mg of 3-aminobenzoic acid is added to 10mL of GO solution (0.5mg / mL), stirred uniformly, and then placed in a water bath at 70℃ and 650rpm for 2h, and the unreacted 3-aminobenzoic acid is removed by centrifugation to obtain GO-PBA;

[0065] (3) 2mL of the pseudo-glycopeptide carbon dot solution (0.5mg / mL) of step (1) is added to 10mL of the GO-PBA solution (0.5mg / mL) of step (2), stirred uniformly, and the pH is adjusted to 8.0, and then placed in a water bath at a temperature of 20℃ for 30min, and after centrifugation, a CDs / GO-PBA nanocomposite material solution is obtained.

[0066] The application of the CDs / GO-PBA nanocomposite material in fluorescence detection of Salmonella, comprising:

[0067] 300μL of the CDs / GO-PBA solution is added to the sample solution to be detected, and the Salmonella is detected by fluorescence method, and the concentration of the Salmonella is determined according to the fluorescence intensity.

[0068] A series of concentration gradient Salmonella solutions are prepared, and the concentration range of the Salmonella solution is 10 4 ~ 10 7CFU / mL, 5x10 4 CFU / mL, 10 4 CFU / mL, 10 5 CFU / mL, 10 6 CFU / mL and 10 7 CFU / mL; the CDs / GO-PBA solution was added to the above solution, and the fluorescence method was used for detection. The detection range of the fluorescence sensor of Example 4 was 10 5 CFU / mL to 10 7 CFU / mL.

[0069] Example 5

[0070] A synthesis method of a CDs / GO-PBA nanocomposite material, comprising the following steps:

[0071] (1) 1.4 g of mannose and 0.2 g of histidine were added to 60 mL of water, and were uniformly mixed by magnetic stirring to obtain a mannose / histidine solution; the mannose / histidine solution was placed in a muffle furnace and was heated to 230°C for hydrothermal reaction, and the hydrothermal reaction time was 12 h. After the reaction, the filtrate was obtained by filtration, the filter membrane pore size was 0.22 μm, and the supernatant was placed in a dialysis bag with a molecular weight of 500 Da for dialysis, and the dialysis time was 6 d to obtain a pseudo-glycopeptide carbon dot solution;

[0072] (2) 30 mg of 3-aminobenzoic acid was added to 10 mL of a GO solution (0.5 mg / mL) and was uniformly stirred, and then was placed in a water bath at 70°C and 700 rpm for 2.5 h, and unreacted 3-aminobenzoic acid was removed by centrifugation to obtain GO-PBA;

[0073] (3) 3 mL of the pseudo-glycopeptide carbon dot solution (0.5 mg / mL) of step (1) was added to 10 mL of the GO-PBA solution (0.5 mg / mL) of step (2), and was uniformly stirred, and the pH was adjusted to 8.0, and then was placed in a water bath at 30°C for 30 min, and after centrifugation, a CDs / GO-PBA nanocomposite material solution was obtained.

[0074] The application of the CDs / GO-PBA nanocomposite material in fluorescence detection of Salmonella, comprising:

[0075] 300 μL of the CDs / GO-PBA solution was added to a sample solution to be detected, and the Salmonella was detected by a fluorescence method, and the concentration of the Salmonella was determined according to the fluorescence intensity.

[0076] A series of concentration gradient Salmonella solutions were prepared, and the concentration range of the Salmonella solution was 10 4 CFU / mL, 5x10 7 CFU / mL, 104 , 5 x 10 4 , 10 5 , 10 6 and 10 7 CFU / mL; CDs / GO-PBA solution was added to the above solution and detected by fluorescence method. The detection range of the fluorescence sensor of Example 5 was 10 5 ~ 10 7 CFU / mL.

[0077] The above examples are only the preferred embodiments of the present application, and are used to explain the present application, but not to limit the present application. The changes, replacements, modifications, etc. made by those skilled in the art without departing from the spirit and essence of the present application shall all belong to the protection scope of the present application.

Claims

1. A method for synthesizing CDs / GO-PBA nanocomposites, characterized in that, The method comprises the following steps: (1) dissolving mannose and histidine in pure water, mixing uniformly to obtain a mannose / histidine solution, and performing hydrothermal reaction under heating, and filtering the solution through a filter membrane after cooling, and dialyzing the filtrate to obtain a pseudo-glycopeptide carbon dot solution; (2) adding 3-aminobenzoic acid into a GO solution, heating and stirring intensively, and then centrifuging to wash away unreacted 3-aminobenzoic acid to obtain a boronic acid functionalized graphene oxide (GO-PBA) solution; (3) adding the pseudo-glycopeptide carbon dot solution in step (1) into the GO-PBA solution, stirring and reacting, and then centrifuging to remove unreacted carbon dots to obtain a solution of the CDs / GO-PBA nanocomposite.

2. The method of synthesis of CDs / GO-PBA nanocomposite according to claim 1, wherein, In step (1), the preparation of the mannose / histidine solution comprises: the mass ratio of mannose to histidine is 1-7, and the concentration is 30-100 mg / mL.

3. The method of synthesis of CDs / GO-PBA nanocomposite according to claim 1, wherein, In step (1), the temperature of the hydrothermal reaction is 150-230 ℃, the time of the hydrothermal reaction is 3-12 h, the pore size of the filter membrane is 0.2-0.5 μm, the molecular weight cut-off of the dialysis bag used for dialysis is 500-1000 Da, and the time of dialysis is 3-7 d.

4. The method of synthesis of CDs / GO-PBA nanocomposite according to claim 1, wherein, In step (2), the concentration of the GO solution is 0.3-0.5 mg / mL, the mass ratio of 3-aminobenzoic acid to the GO solution is 3-7, the heating temperature is 60-80 ℃, the heating time is 2-3 h, and the stirring speed is 500-700 rpm.

5. The method of synthesis of CDs / GO-PBA nanocomposite according to claim 1, wherein, In step (3), the concentration of the GO-PBA solution is 0.3-0.5 mg / mL, the pH is 7.8-8.2, and the volume ratio of the pseudo-glycopeptide carbon dot solution to the GO-PBA solution is 0.2-0.

25.

6. The method of synthesis of CDs / GO-PBA nanocomposite according to claim 1, wherein, In step (3), the reaction temperature is 20-30 ℃, and the reaction time is 20-40 min.

7. A CDs / GO-PBA nanocomposite prepared by the synthetic method of any one of claims 1-6.

8. Use of the CDs / GO-PBA nanocomposite of claim 7 in fluorescent detection of Salmonella for purposes other than disease diagnosis and treatment.

9. Use according to claim 8, characterized in that, The method comprises the following steps: The solution of the CDs / GO-PBA nanocomposite is added into a Salmonella suspension, and incubated at 37 ℃ under oscillation, and the supernatant is taken by centrifugation, and the concentration of Salmonella is calculated according to the fluorescence intensity.

10. Use of the CDs / GO-PBA nanocomposite of claim 9 in the fluorescent detection of Salmonella, characterized by, The material does not rely on specific antibodies, aptamers and phages and the like which are expensive and poor in stability, but utilizes the mannose residues on the surface of CDs to recognize Salmonella through lectin-sugar interaction, and has the characteristics of low cost, easy preparation and stability; the CDs are modified on the surface of GO-PBA through borate ester bond, and the fluorescence is quenched due to fluorescence resonance energy transfer (FRET); in the presence of target bacteria, the combination of Salmonella and carbon dots causes the borate ester bond between CDs and GO-PBA to break, and the CDs fall off from the surface of GO-PBA, and the fluorescence is recovered; the added amount of the solution of the CDs / GO-PBA nanocomposite is 300 ~ 500 μL; the concentration of Salmonella in the Salmonella bacterial suspension is 10 4 ~ 10 7 CFU / mL.

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