CN112129735A

CN112129735A - Preparation method and application of ZnCdSe QDs fluorescent probe

Info

Publication number: CN112129735A
Application number: CN202010937554.XA
Authority: CN
Inventors: 佘远斌; 孟清君; 付海燕; 周春松; 胡瑛
Original assignee: Shangyu Research Institute of ZJUT
Current assignee: Shangyu Research Institute of ZJUT
Priority date: 2020-09-08
Filing date: 2020-09-08
Publication date: 2020-12-25

Abstract

The invention discloses a preparation method and application of a ZnCdSe QDs fluorescent probe. Adding Pb into ZnCdSe QDs²⁺Resulting in quenching of fluorescence, and then adding a reagent capable of reacting with Pb to the detection system²⁺Specifically bound S^2‑So as to recover the fluorescence of ZnCdSe QDs and construct a turn-off-on detection system to realize S^2‑Qualitative and quantitative detection. Detecting the constructed 'turn-off-on' detection platform pair S by replacing metal ions and adding mineral water, green tea and coptis actual samples^2‑The specificity, the anti-interference performance and the standard adding recovery rate of the product,the results show that they are based on ZnCdSe QDs and Pb²⁺Detection system pair S^2‑Strong specificity, high anti-interference performance, high recovery rate in the range of 95.2-104.4%, and high recovery rate in S^2‑The method has a great application prospect in actual detection.

Description

Preparation method and application of ZnCdSe QDs fluorescent probe

Technical Field

The invention belongs to the technical field of fluorescence sensing, and particularly relates to a preparation method and application of a ZnCdSe QDs fluorescent probe.

Background

The sulfide is an important chemical raw material, and is widely applied to chemical industries such as rubber, chemical fertilizers, fireworks, papermaking, printing and dyeing, leather manufacturing and the like. However, sulfur ion is an anion which has toxic effect on organisms, sulfur reacts with oxidase and cytochrome in human bodies to influence the oxidation process of biological cells, and the exposure to a high-concentration sulfur ion environment can cause the organism tissues to be in an anoxic state, thereby finally threatening the life of the organisms. Therefore, it is very important to develop a detection method for rapidly determining the concentration of sulfur ions.

The fluorescence spectrum detection method has the advantages of high sensitivity, simplicity and low cost, and becomes an alternative method for the traditional detection methods such as Atomic Absorption Spectrometry (AAS), Atomic Emission Spectrometry (AES), cold atomic fluorescence spectrometry (CV-AFS), inductively coupled plasma-mass spectrometry (ICPMS) and Mass Spectrometry (MS) for detecting metal ions. In recent years, semiconductor nanocrystals (also called quantum dots, quantum dots) have been widely used for the detection of ions and biomolecular species due to their high quantum yield, broad and tunable excitation and emission spectra, high water solubility and biocompatibility, and simple synthesis methods. In the existing reports on the detection of heavy metals by quantum dots, the detection mode of fluorescence quenching (turn-off) is widely adopted. However, the factors that can trigger fluorescence quenching are manifold, so the specificity of the "turn-off" detection mode is poor, and even false positives can result. In view of the above problems, the present invention utilizes Pb²⁺Can cause the phenomenon of quenching of ZnCdSe QDs, and S^2-Can react with Pb²⁺The specific combination is carried out, so that the fluorescence of ZnCdSe QDs is recovered, thereby forming 'turn-off-on' mode detection and realizing the detection of S^2-And (4) carrying out quantitative detection.

Disclosure of Invention

The invention aims to disclose a preparation method and application of a ZnCdSe QDs fluorescent probe.

In order to achieve the purpose, the technical scheme of the invention is as follows: a preparation method of ZnCdSe QDs fluorescent probe comprises the following steps:

1) preparation of NaHSe precursor: weighing 1mol of selenium powder and 2-6 mol of NaBH₄Dissolving in water (the concentration can be any concentration, and the solution can be dissolved), placing the solution in a round-bottom flask, stirring for 30min under ice bath condition, and continuously introducing nitrogen gas in the process. The product was then transferred to a 2mL EP tube, sealed and stored in a refrigerator at 4 ℃ for later use.

2) Preparation of ZnCdSe QDs: weighing 1mol of ZnCl₂And 1-3 mol of NAC, dissolving in water (the concentration can be any concentration, and the solution can be dissolved), placing the mixed solution in a round-bottom flask, and stirring for 20min under the ice bath condition. Then, regulating the pH value of the mixture to 9-10 by using Tris-HCl buffer solution, and then injecting a proper amount of 0.04mol CdCl into the solution₂·2.5H₂O, then the mixed solution was kept under nitrogen and stirred for 20min under ice bath conditions. 0.1mol of NaHSe precursor prepared in step 1) was injected into the reaction, and then nitrogen was continuously introduced and stirred for 15min under ice bath conditions. And finally, transferring the mixed solution into a high-pressure kettle, and then placing the high-pressure kettle in an oven at the temperature of 180-220 ℃ for reaction for 40-60 min. Filtering the obtained product with a filter membrane with the particle size of 0.22 mu m, dialyzing with a dialysis bag with the specification of 3500D for 24h, and diluting 40 times as stock solution to be placed in a refrigerator for cold storage for later use.

Further, [ Se ] described in step 1)]:[NaBH₄]＝1:3～5。

The invention also relates to an application of the ZnCdSe QDs fluorescent probe prepared by the method in fluorescence detection, which is based on a 'turn-off-on' detection method and specifically comprises the following steps: adding a quencher into the ZnCdSe QDs fluorescent probe solution to quench the ZnCdSe QDs fluorescent probe solution, then adding the solution to be detected, detecting by using a fluorescence mode of a fluorescence spectrophotometer under the excitation wavelength of 340nm, recording a fluorescence emission spectrum within the range of 400-550 nm to obtain the fluorescence intensity, and obtaining the concentration of ions to be detected in the solution to be detected according to the fluorescence intensity.

The ions to be detected in the liquid to be detected are S^2-Correspondingly, the effective ion in the quencher is Pb²⁺。

The invention also relates to S based on the ZnCdSe QDs fluorescent probe^2-The detection system adopts the ZnCdSe QDs fluorescent probe prepared by the method and is added with Pb²⁺So that the fluorescence of the quantum dots is quenched.

Further, the concentration of the ZnCdSe QDs fluorescent probe is 3.6g/L, and the Pb is²⁺The concentration of (A) is 3 to 7 mu M.

The invention also relates to S based on the ZnCdSe QDs fluorescent probe^2-The method of (2) is a method of adding known S to the above-mentioned detection system^2-Detecting the concentration detection solution by using a fluorescence mode of a fluorescence spectrophotometer under the excitation wavelength of 340nm, recording the fluorescence emission spectrum in the range of 400-550 nm to obtain the fluorescence intensity, and constructing the S based on the ZnCdSe QDs fluorescence intensity^2-And detecting the model. During testing, S is added into the detection system^2-Detecting the liquid to be detected by using a fluorescence mode of a fluorescence spectrophotometer under the excitation wavelength of 340nm, recording a fluorescence emission spectrum within the range of 400-550 nm to obtain fluorescence intensity, and obtaining S according to the fluorescence intensity^2-S in the solution to be measured^2-The concentration of (c).

Compared with the prior art, the invention has the beneficial effects that:

(1) using simple fluorescent nano materials ZnCdSe QDs and Pb²⁺A turn-off-on detection platform is constructed, and S of a detection system is remarkably improved^2-The specificity of (A).

(2) The detection method is to S^2-The response range of (2) is between 0 and 20 mu M, and the linear correlation equation is (F)₀-F₁)/F₀The linear assay coefficient was 0.99503, calculated to have a limit of detection of 58.6nM, 0.05868C-0.02394.

Drawings

FIG. 1 shows the assay constructed according to the inventionPlatform detection S^2-Schematic diagram of (1).

FIG. 2 is a transmission electron microscope image of the ZnCdSe QDs fluorescent probe prepared by the present invention.

FIG. 3 is a Fourier transform mid-infrared spectrum of the detection system.

FIG. 4 shows that Pb is added into ZnCdSe QDs prepared by the present invention²⁺The latter ultraviolet characterization chart.

FIG. 5 is a graph showing the fluorescence lifetime of the detection system.

FIG. 6 is a graph showing the fluorescence quenching effect of various common metals on ZnCdSe QDs fluorescent probes prepared by the present invention.

FIG. 7 shows Pb²⁺To S^2-Specific map of (2).

FIG. 8 shows different Pb in the detection system²⁺Graph of the effect of the addition amount on the fluorescence recovery rate;

FIG. 9 shows a graph based on ZnCdSe QDs and Pb²⁺Detecting system for detecting different concentrations S^2-(0-20 mM) fluorescence spectrum.

FIG. 10 shows a graph based on ZnCdSe QDs and Pb²⁺Detecting system for detecting different concentrations S^2-(0-20 mM).

FIG. 11 is a pair S of detection systems constructed in accordance with the present invention^2-The specific detection result of (2).

Detailed Description

In order to better understand the present invention, the following examples are given for further illustration, but the scope of the present invention is not limited to the following examples.

In the following examples, the fluorescence intensity of a sample was measured using an F-7000 spectrofluorometer under the following conditions: the fluorescence intensity in the range of 400nm to 550nm was recorded at an optimum excitation wavelength of 340nm, and the volume of the sample solution system was determined to be 1 mL.

The quenching mechanism of this detection system was tested by UV spectroscopy (UV-1800PC UV-vis spectrometer (shanghai meida instruments ltd) and steady-state-transient fluorescence spectrometer (Edinburgh).

Example 1

The embodiment provides a preparation method of a ZnCdSe QDs fluorescent probe, which comprises the following specific steps:

1) preparation of NaHSe precursor: weighing 0.06g of selenium powder and 0.1135g of NaBH₄Dissolved in 7.5mL of ultrapure water, the solution was placed in a round bottom flask and stirred under ice bath conditions for 30min during which nitrogen was continuously purged to avoid oxidation of the reaction. The product was then transferred to a 2mL EP tube, sealed and stored in a refrigerator at 4 ℃ for later use.

2) Preparation of ZnCdSe QDs: 0.1363g of ZnCl were weighed out₂And 0.3264g NAC were dissolved in 40mL of ultrapure water, and the mixed solution was placed in a round-bottom flask and stirred under ice-bath conditions for 20 min. The pH of the mixture was then adjusted to 9.7 with 10mM Tris-HCl buffer, and CdCl (100. mu.L, 0.4M) was injected into the solution₂·2.5H₂O, then the mixed solution was kept under nitrogen and stirred for 20min under ice bath conditions. 1mL of NaHSe precursor solution was quickly injected into the reaction, followed by continued nitrogen sparge and stirring for 15min under ice bath conditions. Finally, the mixed solution was transferred to an autoclave and then placed in an oven at 200 ℃ to react for 50 min. Filtering the obtained product with a filter membrane with the particle size of 0.22 mu m, dialyzing with a dialysis bag with the specification of 3500D for 24h, and diluting 40 times as stock solution to be placed in a refrigerator for cold storage for later use.

Performing characterization analysis on the prepared ZnCdSe QDs fluorescent probe and a detection system:

1. TEM characterization of ZnCdSe QDs

The TEM (transverse electric field) representation result of ZnCdSe QDs is shown in figure 2, the average particle size of the quantum dots is about 3-4 nm, the quantum dots are uniformly dispersed in an aqueous solution, and the quantum dots have good water solubility.

2. Mid-infrared characterization

For ZnCdSe QDs, ZnCdSe QDs + Pb²⁺Detection system and ZnCdSe QDs + Pb²⁺+S^2-The detection system is characterized by FTIR to explore the rich functional groups on the surface. As shown in FIG. 3, a, b and c in the figure represent ZnCdSe QDs, ZnCdSe QDs + Pb, respectively²⁺And ZnCdSe QDs + Pb²⁺+S^2-The detection system, from the figure, it can be seen that the three detection systems are all at 3418cm^-1、1582cm^-1、1402cm^-1And 1357cm^-1The distinct absorption bands which are assigned to the O-H/N-H, C ═ C, C-N and COO functions, respectively, appear there. Due to ZnCdSe QDs + Pb²⁺And ZnCdSe QDs + Pb²⁺+S^2-The functional group contained in the system is basically identical to the functional group on the surface of ZnCdSe QDs, indicating Pb²⁺、S^2-Are not combined with functional groups on the surface of ZnCdSe QDs to form complexes.

3. Based on ZnCdSe QDs and Pb²⁺Ultraviolet characterization of the detection System of

ZnCdSe QDs added with Pb with different concentrations²⁺The fact that the rear UV spectrum remains substantially unchanged (FIG. 4) also indicates that the surface groups of ZnCdSe QDs do not react with Pb²⁺Combine to form a new complex.

4. Characterization of fluorescence lifetime

ZnCdSe QDs、ZnCdSe QDs+Pb²⁺And ZnCdSe QDs + Pb²⁺+S^2-Fluorescence lifetime characterization of the detection System FIG. 5 shows the addition of Pb²⁺The fluorescence lifetime of the post ZnCdSe QDs decreased from 30.47ns to 4.57ns, indicating the addition of Pb²⁺This then induces dynamic quenching of ZnCdSe QDs.

In conclusion, Pb can be presumed²⁺Electron transfer occurs with ZnCdSe QDs resulting in fluorescence quenching of the quantum dots. And ZnCdSe QDs + Pb²⁺+S^2-The fluorescence lifetime of (2) is 26.37ns, which is very close to that of ZnCdSe QDs. In addition, Pb can be clearly observed under visible light²⁺And S^2-A black precipitate formed immediately after mixing, which was presumed to be a poorly soluble substance PbS, and the mechanism is schematically shown in FIG. 1.

Example 2

1) preparation of NaHSe precursor: weighing 0.06g of selenium powder and 0.09g of NaBH₄Dissolved in 7.5mL of ultrapure water, the solution was placed in a round bottom flask and stirred under ice bath conditions for 30min during which nitrogen was continuously purged to avoid oxidation of the reaction. The product was then transferred to a 2mL EP tube, sealed and stored in a refrigerator at 4 ℃ for later use.

2) Preparation of ZnCdSe QDs: 0.1363g of ZnCl were weighed out₂And 0.1632g NAC were dissolved in 40mL of ultrapure water, and the mixed solution was placed in a round-bottom flask and stirred under ice-bath conditions for 20 min. The pH of the mixture was then adjusted to 9 with 10mM Tris-HCl buffer, and CdCl (100. mu.L, 0.4M) was injected into the solution₂·2.5H₂O, then the mixed solution was kept under nitrogen and stirred for 20min under ice bath conditions. 1mL NaHSe precursor solution was quickly injected into the reaction, followed by continued nitrogen introduction and stirring under ice bath conditions for 15 min. Finally, the mixed solution is transferred into an autoclave and then placed in an oven at 180 ℃ for reaction for 60 min. Filtering the obtained product with a filter membrane with the particle size of 0.22 mu m, dialyzing with a dialysis bag with the specification of 3500D for 24h, and diluting 40 times as stock solution to be placed in a refrigerator for cold storage for later use.

Example 3

1) preparation of NaHSe precursor: weighing 0.06g of selenium powder and 0.1419g of NaBH₄Dissolved in 7.5mL of ultrapure water, the solution was placed in a round bottom flask and stirred under ice bath conditions for 30min during which nitrogen was continuously purged to avoid oxidation of the reaction. The product was then transferred to a 2mL EP tube, sealed and stored in a refrigerator at 4 ℃ for later use.

2) Preparation of ZnCdSe QDs: 0.1363g of ZnCl were weighed out₂And 0.4896g NAC were dissolved in 40mL of ultrapure water, and the mixed solution was placed in a round-bottom flask and stirred under ice-bath conditions for 20 min. The pH of the mixture was then adjusted to 10 with Tris-HCl buffer at 10mM, and CdCl (100. mu.L, 0.4M) was injected into the solution₂·2.5H₂O, then the mixed solution was kept under nitrogen and stirred for 20min under ice bath conditions. 1mL NaHSe precursor solution was quickly injected into the reaction, followed by continued nitrogen introduction and stirring under ice bath conditions for 15 min. Finally, the mixed solution was transferred to an autoclave and then placed in an oven at 220 ℃ for reaction for 40 min. Filtering the obtained product with filter membrane with particle size of 0.22 μm, dialyzing with 3500D dialysis bag for 24 hr, and diluting 4And (5) putting the mixture as a stock solution in a refrigerator for cold storage and preservation for subsequent use.

Example 4

The present embodiment provides S^2-The specific detection method for the selection of the quencher in the detection system is as follows:

in order to select a proper quencher and explore the fluorescence quenching effect of various common metals on the ZnCdSe QDs fluorescent probe prepared by the invention, 100 mu L of ZnCdSe QDs stock solution prepared in example 2 and 400 mu L of Tris-HCl buffer solution with the concentration of 10mM are sequentially added into a quartz dish, and then 100 mu L of Tris-HCl buffer solution with the concentration of 10mM are respectively added into the quartz dish^-4Zn of M²⁺、Mn² ⁺、Ba²⁺、Al³⁺、K⁺、Mg²⁺、Fe²⁺、Na⁺、Cr⁶⁺、Cd²⁺、Ca²⁺、Fe³⁺、Cr³⁺、Co²⁺、Ni²⁺Solutions and concentrations of 5X 10^-5Pb of M²⁺、Hg²⁺、Ag⁺、Cu²⁺Adding ultrapure water into a quartz dish to a constant volume of 1mL, uniformly mixing the solution, reacting for 20min, detecting the fluorescence intensity of the corresponding system by using a fluorescence spectrophotometer, and repeating all experiments for three times. Rendering with F₁/F₀(F₁To detect the fluorescence intensity value of the system after the reaction is complete, F₀Initial fluorescence intensity value of ZnCdSe QDs) as ordinate, and various metal ions as abscissa, and the fluorescence quenching effect of various common metals on the ZnCdSe QDs fluorescent probe prepared by the invention is obtained (figure 6). Hg is shown in FIG. 6²⁺、Ag⁺、Cu²⁺And Pb²⁺All can cause ZnCdSe QDs fluorescence quenching. The invention further explores Hg²⁺、Ag⁺、Cu²⁺And Pb²⁺To S^2-The binding ability of (c).

mu.L of the ZnCdSe QDs stock solution prepared in example 2 and 400. mu.L of 10mM Tris-HCl buffer solution were sequentially added to a quartz dish, and then 100. mu.L of 5X 10mM Tris-HCl buffer solution was added to the quartz dish^-5Pb of M²⁺、Hg²⁺、Ag⁺And Cu² ⁺Dissolving in waterAdding ultrapure water into a quartz dish to a constant volume of 1mL, uniformly mixing the solution, reacting for 20min to completely quench the fluorescence of the quantum dots, and detecting the fluorescence intensity of the corresponding system by using a fluorescence spectrophotometer. Second, 50 μ L of 10 μ L of the extract was taken^-4Pb of M²⁺、Hg²⁺、Ag⁺、Cu²⁺Aqueous solution, S was added to each of the 4 samples^2-(200μL，10^-4M), adding 400 mu L of Tris-HCl buffer solution and 100 mu L of ZnCdSe QDs stock solution, finally fixing the volume to 1mL by using ultrapure water, detecting by using a fluorescence spectrophotometer after 20min, and repeating all experiments for three times. As shown in FIG. 7, in ZnCdSe QDs + Mⁿ⁺(Mⁿ⁺Representing heavy metal ion) is added with S^2-Then, only Pb²⁺The fluorescence intensity of the existing system can be recovered to 90 percent of the original fluorescence, while in Hg²⁺、Ag⁺And Cu²⁺In the existing systems, the fluorescence intensity is hardly recovered. In summary, the present invention selects Pb²⁺As S^2-Detecting the quencher in the system.

Example 6

The present embodiment provides S^2-Optimum Pb in detection System²⁺Selection of the amount to be added

Due to S^2-And Pb²⁺Has strong binding capacity, and can bind Pb through competition effect²⁺Is removed from the ZnCdSe QDs, so that the fluorescence intensity of the ZnCdSe QDs is restored. However if Pb in the system is detected²⁺Is too low, then the detection system is paired with S^2-The sensitivity of (2) can be reduced, and the detection requirement can not be met; if it is determined that Pb is present in the system²⁺Too high, the fluorescence intensity of ZnCdSe QDs will be difficult to recover. In order to make the catalyst based on ZnCdSe QDs and Pb²⁺The fluorescence intensity of the detection system is recovered to the maximum extent, and the research on Pb in the detection system is required²⁺The optimum amount of addition of (c). As shown in FIG. 8, Pb²⁺When the concentration is less than 5 mu M, the recovery rate of the fluorescence intensity of the quantum dots is gradually increased, and when the concentration is Pb, the recovery rate of the fluorescence intensity of the quantum dots is gradually increased²⁺At a concentration of more than 5. mu.M, the recovery rate of the fluorescence intensity of the quantum dot gradually decreases, and therefore, the optimum Pb is preferred²⁺The concentration was 5. mu.M.

Example 7

This example provides ZnCdSe QDs and Pb based²⁺Is the detection system S^2-The detection method is specifically as follows:

adding 20 μ L, 40 μ L, 60 μ L, 80 μ L, 100 μ L, 120 μ L, 140 μ L, 160 μ L, 180 μ L, 200 μ L into the cuvette respectively at a concentration of 10^-4S of M^2-Solution, then adding Pb to each sample²⁺(50μL，10^-4M), adding (10mM,400 mu L) Tris-HCl buffer solution and 100 mu L ZnCdSe QDs stock solution prepared in the example 2 into each sample, fixing the volume to 1mL with ultrapure water, mixing the solutions to be detected uniformly, fully reacting for 20min, detecting with a fluorescence spectrophotometer under the detection condition of 340nm excitation wavelength, and repeating the experiment for three times. The fluorescence spectrum and the linear fitting result of the reaction system were plotted as shown in fig. 9 and fig. 10, respectively. Then, the limit of detection of the detection system is 58.6nM according to the calculation formula LOD of limit of detection 3 σ/S (σ is linear slope, standard deviation of blank after repeated measurement of S).

Example 8

This example provides a ZnCdSe QDs and Pb based²⁺Is the detection system S^2-The specificity in the detection aspect is as follows:

in the first step, 100. mu.L of the ZnCdSe QDs stock solution prepared in example 2 and 400. mu.L of 10mM Tris-HCl buffer solution were sequentially added to a quartz dish, and then 100. mu.L of 5X 10mM Tris-HCl buffer solution was added to the quartz dish^-5Pb of M²⁺Adding ultrapure water into a quartz dish to a constant volume of 1mL, uniformly mixing the solution, reacting for 20min, and detecting the fluorescence intensity of a corresponding system by using a fluorescence spectrophotometer. Second, Pb is added²⁺(50μL，10^-4M) with 200. mu. L S, respectively^2-、Cl^-、I^-、SO₄ ^2-、SO₃ ^2-、HPO₄ ^-、NO₃ ^-、NO₂ ^-、F^-、Br^-、CO₃ ^2-、C₂O₄ ^2-、ClO^-、HCO₃ ^-、CH₃COO^-Mixing the aqueous solutions (wherein S^2-Has a concentration of 10^- ⁴M, the concentration of other anions is 10^-3M), then adding 400 mu L of LTris-HCl buffer solution and 100 mu L of ZnCdSe QDs stock solution respectively, finally fixing the volume to 1mL by using ultrapure water, detecting by using a fluorescence spectrophotometer after 20min, and repeating all experiments for three times. The results are shown in FIG. 11, except that S^2-Other anions with Pb²⁺Has a low competitive power for affinity, and cannot recover the fluorescence intensity of ZnCdSe QDs, so that the fluorescent dye is based on ZnCdSe QDs and Pb²⁺Detection system pair S^2-Has strong specificity.

Example 9

This example is based on ZnCdSe QDs and Pb²⁺Detecting S in the actual sample^2-The specific method comprises the following steps:

adding S in different concentrations to different complex matrices (mineral water, green tea and coptis) using standard addition methods^2-Investigation of different concentrations of S in complex matrices^2-(2. mu.M, 4. mu.M, 6. mu.M) recovery efficiency in the actual sample. The results are shown in Table 1, S in different practical samples^2-The recovery rate of (A) is in the range of 97.0-104.1%, and the Relative Standard Deviation (RSD) is not more than 10% (n is 3), which shows that the invention has great potential in practical application.

TABLE 1 mineral water, Green tea and Coptis chinensis samples for S^2-Recovery results of (2)

Claims

1. A preparation method of a ZnCdSe QDs fluorescent probe is characterized by comprising the following steps of:

1) preparation of NaHSe precursor: taking selenium powder and NaBH according to the molar ratio of 1: 2-6₄And dissolved in water and stirred for 30min under ice bath conditions, during which nitrogen was continuously introduced.

2) Preparation of ZnCdSe QDs: according to the molar ratio of 1:1 ℃3 in the proportion of ZnCl₂And NAC dissolved in water and stirred under ice bath conditions for 20 min. Then, regulating the pH value of the mixture to 9-10 by using Tris-HCl buffer solution, and then injecting a proper amount of CdCl into the solution₂·2.5H₂O, then the mixed solution was kept under nitrogen and stirred for 20min under ice bath conditions. Injecting a proper amount of NaHSe precursor prepared in the step 1) into the reaction, continuously introducing nitrogen under the ice bath condition and stirring for 15min, wherein [ Zn ]]:[Cd]:[Se]1:0.04: 0.1; and finally, transferring the mixed solution into a high-pressure kettle, and then placing the high-pressure kettle in an oven at the temperature of 180-220 ℃ for reaction for 40-60 min.

3) And filtering the obtained product by using a filter membrane with the particle size of 0.22 mu m, and dialyzing for 24h by using a dialysis bag with the specification of 3500D to obtain the ZnCdSe QDs fluorescent probe.

2. The method according to claim 1, wherein [ Se ] in step 1)]:[NaBH₄]＝1:3～5。

3. The application of the ZnCdSe QDs fluorescent probe prepared by the method of claim 1 in fluorescence detection is characterized in that a 'turn-off-on' detection method is adopted, and the method specifically comprises the following steps: adding a quencher into a ZnCdSe QDs fluorescent probe solution to quench the ZnCdSe QDs fluorescent probe solution, then adding a solution to be detected, detecting by using a fluorescence mode of a fluorescence spectrophotometer under the excitation wavelength of 340nm, recording a fluorescence emission spectrum within the range of 400-550 nm to obtain the fluorescence intensity, and obtaining the concentration of ions to be detected in the solution to be detected according to the fluorescence intensity;

4. S based on ZnCdSe QDs fluorescent probe^2-Characterized in that the detection system adopts Pb²⁺And ZnCdSe QDs fluorescent probes prepared by the method of claim 1, said ZnCdSe QDs fluorescent probes being fluorescence-quenched.

5. According to the rightThe detection system according to claim 4, wherein the concentration of the ZnCdSe QDs fluorescent probe is 3.6g/L, and the Pb is²⁺The concentration of (A) is 3 to 7 mu M.

6. S based on ZnCdSe QDs fluorescent probe^2-The detection method of (2), characterized in that it comprises adding S to the detection system according to claim 4^2-Detecting the liquid to be detected by using a fluorescence mode of a fluorescence spectrophotometer under the excitation wavelength of 340nm, recording a fluorescence emission spectrum within the range of 400-550 nm to obtain fluorescence intensity, and obtaining S according to the fluorescence intensity^2-S in the solution to be measured^2-The concentration of (c).