CDs / QDs (at) ZIF-8 probe, preparation method thereof and application of CDs / QDs (at) ZIF-8 probe in detection of tetracycline with three emission ratios

Abstract

The invention discloses a CDs / QDs (at) ZIF-8 probe, a preparation method of the CDs / QDs (at) ZIF-8 probe and application of the CDs / QDs (at) ZIF-8 probe to detection of tetracycline at three emission ratios, and belongs to the technical field of fluorescence sensing. The probe comprises ZIF-8 as well as a carbon dot and a cadmium telluride quantum dot which are encapsulated in the ZIF-8. The preparation method comprises the following steps: sequentially adding CDs and QDs into a 2-methylimidazole solution, uniformly mixing, dropwise adding a zinc salt solution, and reacting to obtain the CDs / QDs ZIF-8 probe. The probe can be used for performing three-emission-ratio fluorescent quantitative detection on tetracycline, and the detection limit is 14.2 nmol / L. The method is simple in synthesis steps and easy in condition control. The fluorescent color of the mixed solution of CDs / QDs ZIF-8 and tetracycline is changed from powder to green along with the increase of the concentration of tetracycline, the detection method is visual and rapid, the visualization effect is good, the detection gel can be prepared, the detection gel can be combined with a smartphone for use, and the method is simple, convenient to carry and convenient for field judgment.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorescence sensing, and specifically relates to a CDs / QDs@ZIF-8 probe and a preparation method thereof, and application thereof in triple emission ratio detection of tetracycline. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Tetracycline (TC), as a broad-spectrum antibiotic, is often used to prevent and treat animal infections due to its high antibacterial activity and low cost. In addition, it is used as a feed additive in animal husbandry to promote animal growth, which leads to excessive tetracycline residues in foods (such as pork, milk, and eggs). After tetracycline residues in food are absorbed by the human body, they can seriously cause gastrointestinal diseases, drug resistance, and liver damage. In order to protect human health, maximum residue limits (MRLs) of tetracycline in food have been established. The European Union and the US Food and Drug Administration set the MRLs of tetracycline in milk at 225nM and 676nM, respectively. Therefore, it is necessary to develop highly sensitive, selective, and portable sensing technologies for monitoring tetracycline residues.

[0004] Fluorescence sensing technology has simple and fast response detection capabilities and is currently a commonly used method for quantitative detection of tetracycline. The fluorescent probe developed for tetracycline sensing mainly relies on a single "fluorescence on" or "fluorescence off" response after interacting with tetracycline. For example, patent CN113866148A discloses a fluorescence sensing method for detecting tetracycline content based on the aggregation-induced emission effect. ZIF-8 interacts with tetracycline AIE molecules entering its framework, causing the aggregation effect of AIE molecules, thereby triggering a strong fluorescence signal. This method based on a single mode is easily interfered by other factors (such as instrument fluctuations), resulting in false positive results.

[0005] Therefore, designing integrated “on” and “off” ratio fluorescence sensors and developing multi-emission fluorescence sensing methods are of great significance in tetracycline detection, which not only expands the visual color change window and thus enhances visual discrimination ability, but also significantly improves sensitivity by utilizing multi-wavelength response. Summary of the invention

[0006] In order to overcome the deficiencies of the prior art, the object of the present invention is to provide a CDs / QDs@ZIF-8 probe and a preparation method thereof and its application in triple emission ratio detection of tetracycline. The CDs / QDs@ZIF-8 probe provided by the present invention can realize rapid, simple, sensitive and visual detection of tetracycline.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] In a first aspect of the present invention, a CDs / QDs@ZIF-8 probe is provided, wherein the CDs / QDs@ZIF-8 probe comprises a zeolite imidazolate framework ZIF-8 and carbon dots (CDs) and cadmium telluride quantum dots (QDs) encapsulated in the zeolite imidazolate framework ZIF-8.

[0009] The CDs / QDs@ZIF-8 probe provided by the present invention is a composite material, which is used to construct an integrated "on" and "off" multi-emission ratio fluorescence sensor for on-site detection of tetracycline. Tetracycline is a fluorescent responder, and the CDs / QDs@ZIF-8 solution is a multi-emission ratio fluorescence probe. The two specifically combine to obtain a fluorescence "on-off" mode. When the CDs / QDs@ZIF-8 probe contacts tetracycline, tetracycline quenches the blue fluorescence of CDs through an internal filtering effect, and ZIF-8 enhances the green fluorescence of tetracycline through fluorescence sensitization (Zn in the zeolite imidazolate framework (ZIF-8) 2+ The fluorescence of tetracycline can be amplified), and the red fluorescence of QDs remains basically unchanged, which is used as a reference signal. The ratio of the fluorescence intensity of tetracycline to the fluorescence intensity of CDs is used. 520 / F 427 The ratio of the fluorescence intensity of tetracycline to the fluorescence intensity of QDs is F 520 / F 618 The CDs / QDs@ZIF-8 probe has a built-in calibration effect, which can reduce the interference caused by the environment and instruments, solve the problems of long analysis time, complex sample pretreatment and the need for professionals in the existing tetracycline detection method, and realize the rapid, simple, sensitive and visual detection of tetracycline.

[0010] In some embodiments of the present invention, the particle size of the CDs / QDs@ZIF-8 probe is 100-150 nm.

[0011] In some embodiments of the present invention, the CDs / QDs@ZIF-8 probe has a blue fluorescence emission peak at a wavelength of 427nm and a red fluorescence emission peak at a wavelength of 618nm; the CDs / QDs@ZIF-8 probe produces a green fluorescence emission peak at a wavelength of 520nm for tetracycline.

[0012] The second aspect of the present invention provides a method for preparing the CDs / QDs@ZIF-8 probe, comprising the following steps:

[0013] The carbon dot solution, the cadmium telluride quantum dot solution and the 2-methylimidazole solution are mixed to obtain a mixed solution; the zinc salt solution is added dropwise to the mixed solution, and the mixture is stirred at room temperature for reaction. After the reaction is completed, a CDs / QDs@ZIF-8 probe is obtained.

[0014] In some embodiments of the present invention, the concentration of the carbon dot solution is 1.5-2 mg / mL, and the solvent is water; the concentration of the cadmium telluride quantum dot solution is 1.0-1.5 mg / mL, and the solvent is water; the concentration of the 2-methylimidazole solution is 1.5-2 mmol / mL, and the solvent is alcohol, preferably methanol; the concentration of the zinc salt solution is 0.5-0.7 mmol / mL, and the solvent is alcohol, preferably methanol;

[0015] The volume ratio of the carbon dot solution, the cadmium telluride quantum dot solution, the 2-methylimidazole solution and the zinc salt solution is (2.9-3.1):(1.9-2.1):(4.9-5.1):(1.9-2.1).

[0016] In some embodiments of the present invention, after the reaction is completed, the reaction product is obtained by centrifugation, and then washed and dried to obtain a CDs / QDs@ZIF-8 probe.

[0017] Preferably, the centrifugal speed is 10000-15000 rpm, and the time is 10-20 min.

[0018] Preferably, washing is performed with water.

[0019] Preferably, the drying is freeze drying, and the freeze drying time is 20-25 hours.

[0020] In some embodiments of the present invention, the particle size of the carbon dots is 3-5 nm, and the particle size of the cadmium telluride quantum dots is 4-7 nm.

[0021] In some embodiments of the present invention, the method for preparing carbon dots comprises the following steps:

[0022] L-cysteine ​​and citric acid are dissolved in water, mixed, evaporated and dried to obtain a syrupy substance; the syrupy substance is subjected to a hydrothermal reaction, cooled after the reaction is completed, and the reaction product is dispersed in water, and the pH is adjusted to neutral, centrifuged, and dialyzed to obtain carbon dots.

[0023] Preferably, the mass ratio of L-cysteine ​​to citric acid is 1:2, preferably (0.5-0.7g):(1-1.4g); the temperature of the evaporative drying is 70-90°C; the hydrothermal reaction has a reaction temperature of 200-250°C and a reaction time of 3-5h; the centrifugal speed is 10000-15000rpm and the time is 10-20min; the dialysis uses a dialysis membrane with a molecular weight cutoff of 300-500Da and a dialysis time of 24-30h.

[0024] In some embodiments of the present invention, the method for preparing cadmium telluride quantum dots comprises the following steps:

[0025] Tellurium powder and sodium borohydride are dissolved in water, and reacted under nitrogen protection to obtain a sodium hydrogen telluride solution; the sodium hydrogen telluride solution is added to an alkaline solution containing cadmium chloride and thioglycolic acid, and heated to react, and after the reaction is completed, the reaction product is precipitated and washed to obtain cadmium telluride quantum dots.

[0026] Preferably, the dosage ratio of the tellurium powder, sodium borohydride, cadmium chloride and thioglycolic acid is (70-100 mg):(140-200 mg):(2.9-3.1 mmol):(5.8-6.2 mmol); preferably, the mass ratio of the tellurium powder to sodium borohydride is 1:2, and the molar ratio of cadmium chloride to thioglycolic acid is 1:2; the heating reaction has a reaction temperature of 90-120°C and a reaction time of 30-40h.

[0027] The third aspect of the present invention provides an application of the CDs / QDs@ZIF-8 probe in the triple emission ratio detection of tetracycline.

[0028] A fourth aspect of the present invention provides a method for detecting tetracycline using a three-emission ratio, comprising the following steps:

[0029] The sample to be tested is added to the dispersion containing the CDs / QDs@ZIF-8 probe according to claim 1, excited at a wavelength of 360-365 nm, the fluorescence intensity values ​​at 427 nm, 520 nm and 618 nm are read and the fluorescence intensity ratio is calculated, and the obtained fluorescence intensity ratio is substituted into the standard curve to obtain the content of tetracycline in the sample to be tested;

[0030] The fluorescence intensity ratio is equal to the ratio of the fluorescence intensity at 520 nm to the fluorescence intensity at 427 nm plus the ratio of the fluorescence intensity at 520 nm to the fluorescence intensity at 618 nm.

[0031] CDs / QDs@ZIF-8 probe has a blue fluorescence emission peak at a wavelength of 427nm under excitation of 360-365nm wavelength, and QDs has a red fluorescence emission peak at a wavelength of 618nm. When tetracycline is detected, the ZIF-8 porous structure can achieve the enrichment of tetracycline. Under excitation of 360-365nm wavelength, CDs has a blue fluorescence at a wavelength of 427nm absorbed by tetracycline, and tetracycline produces green fluorescence at 520nm. The emission peak of red fluorescence of QDs at a wavelength of 618nm is not affected and remains essentially unchanged, so it is used as a reference signal. The CDs / QDs@ZIF-8 probe has a built-in calibration effect, which can reduce the interference caused by the environment and the instrument, and realize reliable quantitative analysis of the object to be measured. The fluorescence color of the mixed solution of CDs / QDs@ZIF-8 probe and tetracycline changes from pink to green as the concentration of tetracycline increases. The detection method is intuitive, rapid, and has good visualization effect. It can also prepare detection gel and be used in conjunction with a smartphone. It is simple and portable, making it convenient for on-site judgment.

[0032] In some embodiments of the present invention, in the dispersion, the concentration of the CDs / QDs@ZIF-8 probe is 1.8-2.2 mg / mL, and the solvent is water.

[0033] In some embodiments of the present invention, the method for preparing the standard curve comprises the following steps:

[0034] Tetracycline solution standards of different concentrations were added to the dispersion containing the CDs / QDs@ZIF-8 probe, respectively, and excited at a wavelength of 360-365 nm to obtain a fluorescence spectrum containing fluorescence intensities at 427 nm, 520 nm and 618 nm, and the fluorescence intensity ratio was calculated; a standard curve was drawn with tetracycline concentration as the horizontal axis and fluorescence intensity ratio as the vertical axis.

[0035] In some embodiments of the present invention, the samples to be tested include milk, pork, and lake water.

[0036] A fifth aspect of the present invention provides a tetracycline detection kit, comprising a hydrogel and the CDs / QDs@ZIF-8 probe, wherein the CDs / QDs@ZIF-8 probe is dispersed in the hydrogel.

[0037] In some embodiments of the present invention, the content of CDs / QDs@ZIF-8 probes in the hydrogel is 0.08-0.13 wt %.

[0038] In some embodiments of the present invention, the hydrogel is an agar hydrogel.

[0039] It should be noted that the tetracycline detection kit can be used in conjunction with a smart device (such as a mobile phone, a camera, etc.), and the concentration of tetracycline in the liquid sample to be tested can be calculated by taking a photo and extracting the RGB value through the smart device.

[0040] A sixth aspect of the present invention provides a method for rapid detection of tetracycline, the method comprising the following steps:

[0041] The sample to be tested is added to the tetracycline detection kit, excited at a wavelength of 360-365 nm, the color signal RGB value is extracted, the color signal ratio is calculated, and the obtained color signal ratio is brought into the standard curve to obtain the concentration of the liquid sample to be tested;

[0042] The color ratio is equal to the ratio of G to R plus the ratio of G to B.

[0043] In some embodiments of the present invention, the method for preparing the standard curve comprises the following steps:

[0044] Tetracycline solution standards of different concentrations are added to the tetracycline detection kit respectively, then excited at a wavelength of 360-365 nm, the color signal RGB value is extracted, and the color signal ratio is calculated; a standard curve is drawn with the tetracycline concentration as the horizontal coordinate and the color signal ratio as the vertical coordinate.

[0045] In some embodiments of the present invention, the samples to be tested include milk, pork, and lake water.

[0046] In some embodiments of the present invention, a smart device (such as a mobile phone, a camera, etc.) can be used to take photos and extract the RGB value of the color signal, which is simple to operate.

[0047] The beneficial effects of the present invention are:

[0048] The present invention uses ZIF-8, which is easy to prepare and has excellent biocompatibility, as a carrier to prepare CDs / QDs@ZIF-8 probes, and the synthesis conditions are simple and mild. The porous structure of ZIF-8 can achieve the enrichment of tetracycline, which will further enhance its sensing ability for target analytes. The present invention innovatively integrates the fluorescence "on" and "off" mechanisms into one, and designs a reference signal to develop a three-emission ratio fluorescence nanosensor with a built-in calibration effect, which can effectively reduce the interference caused by environmental and instrument fluctuations, and realize reliable quantitative analysis of the analyte.

[0049] The present invention loads CDs / QDs@ZIF-8 nanoprobes in hydrogel to prepare a portable hydrogel detection kit. The combination of this hydrogel detection kit and a smart phone not only reduces the detection cost and time, but also provides a new solution for on-site rapid qualitative identification and quantitative detection of tetracycline. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0051] Figure 1 Transmission electron microscopy images of CDs (A) and QDs (B) prepared in Example 1 of the present invention;

[0052] Figure 2 Transmission electron microscopy (A) and X-ray diffraction (B) images of the CDs / QDs@ZIF-8 probe prepared in Example 1 of the present invention;

[0053] Figure 3 This is the fluorescence emission diagram of the CDs / QDs@ZIF-8 probe prepared in Example 1 of the present invention;

[0054] Figure 4 The fluorescence spectrum (A) of the CDs / QDs@ZIF-8 probe after adding tetracycline solutions of different concentrations in Application Example 1 of the present invention, the color change diagram of the solution under 365nm ultraviolet light (B) and the fluorescence intensity ratio F 520 / F 427 +F 520 / F 618 Linear curve fitted with tetracycline concentration (C);

[0055] Figure 5 This is a graph showing the selective response of the CDs / QDs@ZIF-8 probe to tetracycline in Application Example 3 of the present invention;

[0056] Figure 6 The hydrogel photograph (A) after adding tetracycline solutions of different concentrations under 365nm ultraviolet light in Application Example 4 of the present invention and the linear curve (B) of color signal (G / R+G / B) and tetracycline concentration fitting;

[0057] Figure 7 (a) is a schematic diagram of the synthesis of CDs / QDs@ZIF-8 in Example 1 of the present invention, and (b) is a mechanism diagram of the CDs / QDs@ZIF-8 probe for tetracycline detection. DETAILED DESCRIPTION

[0058] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0059] Example 1: Preparation of CDs / QDs@ZIF-8 probe

[0060] Step 1: L-cysteine ​​(0.5 g) and citric acid (1 g) were dissolved in water to form a mixed solution, and the mixed solution was evaporated to dryness (80° C.) to obtain a syrupy substance, which was transferred to a reactor, subjected to a hydrothermal reaction at 200° C. for 3 h, cooled, and the reaction product was dispersed in water, and the pH was adjusted to neutral, and the reaction product was centrifuged (10000 rpm, 20 min) to remove large particles. The separated solution was dialyzed (dialysis was performed for 24 h using a dialysis bag with MWCO 300 Da) to obtain purified CDs, which were dissolved in water to obtain a CDs solution (1.5 mg / mL).

[0061] Step 2: Dissolve tellurium powder (80 mg) and sodium borohydride (160 mg) in 10 mL of water, react under nitrogen protection to obtain sodium hydrogen telluride (NaHTe) solution, add the NaHTe solution to an alkaline solution containing cadmium chloride (3 mmol) and thioacetic acid (6 mmol), react at high temperature (90°C, 30 h) to prepare QDs, precipitate and wash the QDs with ethanol to obtain purified QDs, and dissolve the purified QDs in water to obtain a QDs solution (1 mg / mL).

[0062] Step 3: Mix CDs solution (3 mL), QDs solution (2 mL) and 5 mL of 2-methylimidazole methanol solution (1.6 mmol / mL) to form a mixed solution, slowly add 2 mL of zinc nitrate methanol solution (0.5 mmol / mL) dropwise to the mixed solution, stir the reaction at room temperature (25°C, 3 h), centrifuge the reaction product (10000 rpm, 10 min), and wash with water to remove excess CDs, QDs and unreacted raw materials, and freeze-dry the separated solid material (24 h) to obtain CDs / QDs@ZIF-8 probe powder.

[0063] like Figure 1 As shown in the transmission electron microscope image A, the CDs prepared in this example are uniformly dispersed, with a particle size of about 3-5 nm. Figure 1 As shown in transmission electron microscopy image B, the QDs prepared in this example are uniformly dispersed in size, with a particle size of about 4-7 nm.

[0064] like Figure 2 As shown in the transmission electron microscope image A, the particle size of CDs / QDs@ZIF-8 prepared in this example is 100-150nm. Figure 2 As shown in the AX-ray diffraction pattern, the characteristic diffraction peaks of CDs / QDs@ZIF-8 are highly consistent with the diffraction peaks of standard ZIF-8, indicating that the structure of ZIF-8 does not change after loading CDs and QDs.

[0065] like Figure 3As shown, CDs / QDs@ZIF-8 showed characteristic fluorescence emission peaks of QDs (618 nm) and CDs (427 nm), respectively, which confirmed the successful preparation of CDs / QDs@ZIF-8.

[0066] Application example 1: Detection of different concentrations of tetracycline by CDs / QDs@ZIF-8

[0067] A series of tetracycline aqueous solutions with different concentrations were prepared. Tetracycline solutions with different concentrations (500 μL) were added to 500 μL CDs / QDs@ZIF-8 dispersion (2 mg / mL). The solutions were transferred to a fluorescence cuvette and tested in a fluorescence spectrophotometer. The fluorescence was excited at a wavelength of 360 nm and the fluorescence at 427 nm (F 427 )、520nm(F 520 ) and 618nm(F 618 The fluorescence intensity at the tetracycline concentration is the horizontal axis and the fluorescence intensity ratio (fluorescence intensity ratio = F 520 / F 427 +F 520 / F 618 , Note: F 427 is the fluorescence intensity at 427 nm, F 520 is the fluorescence intensity at 520 nm, F 618 The standard curve was drawn with (fluorescence intensity at 618 nm) as the ordinate.

[0068] The fluorescence emission spectra of CDs / QDs@ZIF-8 at different tetracycline concentrations in this example are shown in Figure 4 .like Figure 4 As shown in A, as the tetracycline content increased from 0 to 50 μM, the fluorescence of CDs / QDs@ZIF-8 at 427 nm gradually decreased, the fluorescence at 520 nm gradually increased, and the fluorescence at 618 nm remained basically unchanged. Figure 4 B shows that the detection solution has an obvious visible fluorescence change from pink to green under 365nm ultraviolet light. Figure 4 C is the fluorescence intensity ratio (F 520 / F 427 +F 520 / F 618 ) fitting straight line, indicating that the detection range of this method for tetracycline is 0.1-50μmol / L, and the detection limit is 14.2nmol / L, which has excellent detection effect.

[0069] Application Example 2: Detection of Tetracycline in Reagent Samples

[0070] Actual samples (500 μL) of lake water, pork or milk containing different spiked concentrations were added to 500 μL of CDs / QDs@ZIF-8 dispersion (2 mg / mL). The solution was transferred to a fluorescence cuvette and tested in a fluorescence spectrophotometer with an excitation wavelength of 360 nm and a recording wavelength of 427 nm (F 427 )、520nm(F 520 ) and 618nm(F 618 ) and calculated the fluorescence intensity ratio (fluorescence intensity ratio = F 520 / F 427 +F 520 / F 618 , Note: F 427 is the fluorescence intensity at 427 nm, F 520 is the fluorescence intensity at 520 nm, F 618 The fluorescence intensity at 618 nm is substituted into the standard curve to calculate the content of tetracycline in the liquid sample to be tested. The test data results are shown in Table 1.

[0071] The recovery of tetracycline was 91.70%-106.46%, and the relative standard deviation was less than 1.89%. The results showed that the ratio fluorescence sensing method has high accuracy and reliability and can be used for the analysis and detection of tetracycline in actual samples.

[0072] Table 1 Detection results of tetracycline in actual samples

[0073]

[0074] Application example 3: Selectivity of CDs / QDs@ZIF-8 for tetracycline detection

[0075] 500 μL of other kinds of antibiotics (penicillin (Pen), kanamycin sulfate (Kan), erythromycin (EM), vancomycin (Van), chloramphenicol (Chl) and bleomycin (BLM)), amino acids (glycine (Gly), tyrosine (Tyr), arginine (Arg), glutamic acid (Glu), methionine (Met), asparagine (Asn), phenylalanine (Phe)), other biomolecules (sucrose (Suc), glucose (Gluc), adenosine triphosphate (ATP), cholesterol (Cho), creatinine (Cre), adenosine (A), urea (Urea), collagen (Coll) and hyaluronic acid (HA)) and ions (Na + , K + Mg 2+ NH4 + 、NO3 - 、SO4 2- , Cl - and I- ) was added to 500 μL of CDs / QDs@ZIF-8 dispersion (2 mg / mL), the solution was transferred to a fluorescence cuvette, and the fluorescence was tested in a fluorescence spectrophotometer with an excitation wavelength of 360 nm and a recording of 427 nm (F 427 )、520nm(F 520 ) and 618nm(F 618 ) and calculated the fluorescence intensity ratio (fluorescence intensity ratio = F 520 / F 427 +F 520 / F 618 , Note: F 427 is the fluorescence intensity at 427 nm, F 520 is the fluorescence intensity at 520 nm, F 618 is the fluorescence intensity at 618 nm).

[0076] Test results such as Figure 5 As shown, the fluorescence intensity ratio of the system increased significantly only in the presence of tetracycline, and there was no obvious change in the absence of other types of substances, indicating that the sensing system has a high selectivity for tetracycline.

[0077] Application Example 4: Smartphone-Assisted Portable Hydrogel Detection of Tetracycline

[0078] Agarose (80 mg) was completely dissolved in boiling water (8 mL). 2 mL of CD / QDs@ZIF-8 dispersion (5 mg / mL) was added to the agarose solution and mixed thoroughly. The mixed solution (500 μL) was quickly dripped into the lid of a 5 mL centrifuge tube and cooled to form a hydrogel kit. A series of tetracycline aqueous solutions of different concentrations were prepared, and tetracycline solutions of different concentrations (100 μL) were added to the hydrogel for reaction. Photos were taken with a smartphone (HUAWEIP40) and the color signal RGB value was extracted. A standard curve was drawn with tetracycline concentration as the horizontal coordinate and color ratio (color ratio = G / R + G / B) as the vertical coordinate.

[0079] Test results such as Figure 6 As shown in A, the detection gel has an obvious visible fluorescence change from pink to green under 365nm ultraviolet light. Figure 6 B is the fitted straight line between the color ratio (G / R+G / B) and the tetracycline concentration, indicating that the detectable range of tetracycline for this detection gel method is 0.5–10.0 μmol / L, providing a portable and simple method for the detection of tetracycline.

[0080] Example 2: Preparation of CDs / QDs@ZIF-8 probe

[0081] The difference from Example 1 is that the concentration of the CDs solution is 2.0 mg / mL, the concentration of the QDs solution is 1.5 mg / mL, and the remaining steps are consistent with Example 1 to obtain CDs / QDs@ZIF-8 probe powder.

[0082] After testing, the particle size of CDs / QDs@ZIF-8 prepared in this embodiment is 100-150nm. The X-ray diffraction pattern shows that the characteristic diffraction peak of CDs / QDs@ZIF-8 is highly consistent with the diffraction peak of standard ZIF-8, indicating that the structure of ZIF-8 does not change after loading CDs and QDs. The CDs / QDs@ZIF-8 prepared in this embodiment shows the characteristic fluorescence emission peaks of QDs (618nm) and CDs (427nm), respectively, which confirms the successful preparation of CDs / QDs@ZIF-8.

[0083] When the CDs / QDs@ZIF-8 probe prepared in this example is used to detect tetracycline, the wavelength of 360 nm can be excited to obtain the 427 nm (F 427 )、520nm(F 520 ) and 618nm(F 618 ), which shows that it can be used to detect tetracycline.

[0084] Example 3: Preparation of CDs / QDs@ZIF-8 probe

[0085] The difference from Example 1 is that in step 1, a hydrothermal reaction is carried out at 250° C. for 3 h, and the remaining steps are consistent with those of Example 1 to obtain CDs / QDs@ZIF-8 probe powder.

[0086] After testing, the size of CDs prepared in this embodiment is uniformly dispersed, and the particle size is about 3-5nm. The particle size of CDs / QDs@ZIF-8 prepared in this embodiment is 100-150nm. The X-ray diffraction pattern shows that the characteristic diffraction peak of CDs / QDs@ZIF-8 is highly consistent with the diffraction peak of standard ZIF-8, indicating that the structure of ZIF-8 does not change after loading CDs and QDs. The CDs / QDs@ZIF-8 prepared in this embodiment shows the characteristic fluorescence emission peaks of QDs (618nm) and CDs (427nm), respectively, which confirms the successful preparation of CDs / QDs@ZIF-8.

[0087] When the CDs / QDs@ZIF-8 probe prepared in this example is used to detect tetracycline, the wavelength of 360 nm can be excited to obtain the 427 nm (F 427 )、520nm(F 520 ) and 618nm(F 618 ), which shows that it can be used to detect tetracycline.

[0088] Example 4: Preparation of CDs / QDs@ZIF-8 probe

[0089] The difference from Example 1 is that in step 2, the reaction is carried out at high temperature (120° C., 30 h) to prepare QDs, and the remaining steps are consistent with Example 1 to obtain CDs / QDs@ZIF-8 probe powder.

[0090] After testing, the QDs prepared in this embodiment are uniformly dispersed in size and have a particle size of about 4-7nm. The particle size of CDs / QDs@ZIF-8 prepared in this embodiment is 100-150nm. The X-ray diffraction pattern shows that the characteristic diffraction peaks of CDs / QDs@ZIF-8 are highly consistent with the diffraction peaks of standard ZIF-8, indicating that the structure of ZIF-8 does not change after loading CDs and QDs. The CDs / QDs@ZIF-8 prepared in this embodiment shows the characteristic fluorescence emission peaks of QDs (618nm) and CDs (427nm), respectively, which confirms the successful preparation of CDs / QDs@ZIF-8.

[0091] When the CDs / QDs@ZIF-8 probe prepared in this example is used to detect tetracycline, the wavelength of 360 nm can be excited to obtain the 427 nm (F 427 )、520nm(F 520 ) and 618nm(F 618 ), which shows that it can be used to detect tetracycline.

[0092] Example 5: Preparation of CDs / QDs@ZIF-8 probe

[0093] The difference from Example 1 is that in step 3, the reaction is stirred at room temperature (25° C., 5 h), and the remaining steps are consistent with Example 1 to obtain CDs / QDs@ZIF-8 probe powder.

[0094] After testing, the particle size of CDs / QDs@ZIF-8 prepared in this embodiment is 100-150nm. The X-ray diffraction pattern shows that the characteristic diffraction peak of CDs / QDs@ZIF-8 is highly consistent with the diffraction peak of standard ZIF-8, indicating that the structure of ZIF-8 does not change after loading CDs and QDs. The CDs / QDs@ZIF-8 prepared in this embodiment shows the characteristic fluorescence emission peaks of QDs (618nm) and CDs (427nm), respectively, which confirms the successful preparation of CDs / QDs@ZIF-8.

[0095] When the CDs / QDs@ZIF-8 probe prepared in this example is used to detect tetracycline, the wavelength of 360 nm can be excited to obtain the 427 nm (F 427)、520nm(F 520 ) and 618nm(F 618 ), which shows that it can be used to detect tetracycline.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A CDs / QDs@ZIF-8 probe, It is characterized in that The CDs / QDs@ZIF-8 probe comprises a zeolite imidazolate framework ZIF-8 and carbon dots and cadmium telluride quantum dots encapsulated in the zeolite imidazolate framework ZIF-8.

2. The CDs / QDs@ZIF-8 probe according to claim 1, It is characterized in that The particle size of the CDs / QDs@ZIF-8 probe is 100-150 nm; Preferably, the CDs / QDs@ZIF-8 probe has a blue fluorescence emission peak at a wavelength of 427 nm and a red fluorescence emission peak at a wavelength of 618 nm; the CDs / QDs@ZIF-8 probe produces a green fluorescence emission peak at a wavelength of 520 nm for tetracycline.

3. A method for preparing the CDs / QDs@ZIF-8 probe according to claim 1 or 2, It is characterized in that The steps include: The carbon dot solution, the cadmium telluride quantum dot solution and the 2-methylimidazole solution are mixed to obtain a mixed solution; the zinc salt solution is added dropwise to the mixed solution, and the mixture is stirred at room temperature for reaction. After the reaction is completed, a CDs / QDs@ZIF-8 probe is obtained.

4. The preparation method according to claim 3, It is characterized in that The concentration of the carbon dot solution is 1.5-2 mg / mL, and the solvent is water; the concentration of the cadmium telluride quantum dot solution is 1.0-1.5 mg / mL, and the solvent is water; the concentration of the 2-methylimidazole solution is 1.5-2 mmol / mL, and the solvent is alcohol, preferably methanol; the concentration of the zinc salt solution is 0.5-0.7 mmol / mL, and the solvent is alcohol, preferably methanol; The volume ratio of the carbon dot solution, the cadmium telluride quantum dot solution, the 2-methylimidazole solution and the zinc salt solution is (2.9-3.1):(1.9-2.1):(4.9-5.1):(1.9-2.1).

5. The preparation method according to claim 3, It is characterized in that After the reaction, the reaction product was obtained by centrifugation, washed and dried to obtain the CDs / QDs@ZIF-8 probe; Preferably, the centrifugal speed is 10000-15000 rpm, and the time is 10-20 min; Preferably, washing with water; Preferably, the drying is freeze drying, and the freeze drying time is 20-25 hours.

6. The preparation method according to claim 3, It is characterized in that The particle size of the carbon dots is 3-5 nm, and the particle size of the cadmium telluride quantum dots is 4-7 nm; Preferably, the method for preparing the carbon dots comprises the following steps: Dissolving L-cysteine ​​and citric acid in water, mixing, evaporating and drying to obtain a syrupy substance; subjecting the syrupy substance to a hydrothermal reaction, cooling after the reaction, dispersing the reaction product in water, adjusting the pH to neutral, centrifuging, and dialyzing to obtain carbon dots; Further preferably, the mass ratio of L-cysteine ​​to citric acid is 1:2, preferably (0.5-0.7g):(1-1.4g); the temperature of the evaporation drying is 70-90°C; the hydrothermal reaction, the reaction temperature is 200-250°C, the reaction time is 3-5h; the centrifugal speed is 10000-15000rpm, the time is 10-20min; the dialysis, the dialysis membrane has a molecular weight cutoff of 300-500Da, and the dialysis time is 24-30h; Preferably, the method for preparing cadmium telluride quantum dots comprises the following steps: Dissolving tellurium powder and sodium borohydride in water, reacting under nitrogen protection to obtain a sodium hydrogen telluride solution; adding the sodium hydrogen telluride solution to an alkaline solution containing cadmium chloride and thioglycolic acid, heating to react, and after the reaction is completed, precipitating and washing the reaction product to obtain cadmium telluride quantum dots; Further preferably, the dosage ratio of the tellurium powder, sodium borohydride, cadmium chloride and thioglycolic acid is (70-100 mg):(140-200 mg):(2.9-3.1 mmol):(5.8-6.2 mmol); preferably, the mass ratio of the tellurium powder to sodium borohydride is 1:2, and the molar ratio of cadmium chloride to thioglycolic acid is 1:2; the heating reaction has a reaction temperature of 90-120°C and a reaction time of 30-40h.

7. Use of the CDs / QDs@ZIF-8 probe according to claim 1 in triple emission ratio detection of tetracycline.

8. A method for detecting tetracycline by triple emission ratio, It is characterized in that The steps include: The sample to be tested is added to the dispersion containing the CDs / QDs@ZIF-8 probe according to claim 1, excited at a wavelength of 360-365 nm, the fluorescence intensity values ​​at 427 nm, 520 nm and 618 nm are read and the fluorescence intensity ratio is calculated, and the obtained fluorescence intensity ratio is substituted into the standard curve to obtain the content of tetracycline in the sample to be tested; The fluorescence intensity ratio is equal to the ratio of the fluorescence intensity at 520 nm to the fluorescence intensity at 427 nm plus the ratio of the fluorescence intensity at 520 nm to the fluorescence intensity at 618 nm; Preferably, in the dispersion, the concentration of CDs / QDs@ZIF-8 probe is 1.8-2.2 mg / mL, and the solvent is water; Preferably, the method for preparing the standard curve comprises the following steps: Tetracycline solution standards of different concentrations are added to the dispersion containing the CDs / QDs@ZIF-8 probe according to claim 1, respectively, and excited at a wavelength of 360-365 nm to obtain a fluorescence spectrum containing fluorescence intensities at 427 nm, 520 nm and 618 nm, and the fluorescence intensity ratio is calculated; a standard curve is drawn with the tetracycline concentration as the abscissa and the fluorescence intensity ratio as the ordinate; Preferably, the samples to be tested include milk, pork, and lake water.

9. A tetracycline detection kit, It is characterized in that It comprises a hydrogel and the CDs / QDs@ZIF-8 probe according to claim 1, wherein the CDs / QDs@ZIF-8 probe is dispersed in the hydrogel; Preferably, in the hydrogel, the content of CDs / QDs@ZIF-8 probes is 0.08-0.13 wt %.

10. A method for rapid detection of tetracycline, It is characterized in that The method comprises the following steps: adding the sample to be tested into the tetracycline detection kit according to claim 9, exciting with a wavelength of 360-365 nm, extracting the RGB value of the color signal, calculating the color ratio, substituting the obtained color ratio into the standard curve, and obtaining the content of tetracycline in the sample to be tested; The color ratio is equal to the ratio of G to R plus the ratio of G to B; Preferably, the method for preparing the standard curve comprises the following steps: Tetracycline solution standards of different concentrations are added to the tetracycline detection kit according to claim 9, respectively, and then excited at a wavelength of 360-365 nm, the RGB value of the color signal is extracted, and the color ratio is calculated; a standard curve is drawn with the tetracycline concentration as the horizontal axis and the color ratio as the vertical axis; Preferably, the samples to be tested include milk, pork, and lake water.

Images