A fluorescent detection material and its preparation method and application

Abstract

The present invention provides a fluorescent detection material and its preparation method and application. The preparation method of the fluorescent detection material of the present invention combines molecular imprinting technology with fluorescent detection and nanotechnology, and constructs a multifunctional detection material integrating specificity and fluorescent detection by combining nano core-shell materials with highly sensitive fluorescent indication technology; specifically, on the basis of synthesizing CdTe quantum dots, the surface of CdTe QDs is modified with silicon dioxide to obtain CdTe quantum dots with surface modified SiO2; then, using benzidine as a template molecule, the fluorescent detection material is prepared using surface molecular imprinting technology; at the same time, the prepared MIPs-CdTe QDs@SiO2 is used as an identification and detection element to construct a molecular imprinting fluorescent sensor, and a rapid detection of benzidine in drinking water sources is established; the fluorescent detection material prepared by the present invention has the characteristics of high efficiency, rapidity, specificity, sensitivity and easy operation.

Description

Technical Field

[0001] The invention relates to the technical field of detection materials for non-volatile pollutants in drinking water sources, and in particular to a fluorescent detection material and a preparation method and application thereof. Background Art

[0002] Benzidine is a typical representative of non-volatile pollutants in drinking water sources. Benzidine and its salts can cause contact dermatitis, damage the liver and kidneys, and cause hemorrhagic cystitis and bladder cancer when they come into contact with the skin or enter the body. They are identified as Class 1 carcinogens by the World Health Organization's International Agency for Research on Cancer (IARC). As long as the concentration reaches 6.7μg / L, there is a risk of cancer to the human body. Therefore, it is included in the list of priority monitoring pollutants internationally. The standard limit of benzidine is stipulated as 0.2μg / L in the "Surface Water Environmental Quality Standard" (GB 3838-2002).

[0003] Since the concentration of non-volatile pollutants in drinking water sources is very low, in order to ensure the sensitivity of detection, it is generally combined with sample pretreatment and chromatographic separation to separate and enrich the target molecules for determination. In current research, online detection methods cannot meet the high-sensitivity determination of trace non-volatile pollutants. How to quickly and efficiently detect the content of non-volatile pollutants in drinking water sources has become a hot issue affecting human health and water environment safety. It is urgent to invent a detection method with high sensitivity and strong specificity.

[0004] Quantum dots (QDs) are composed of 100-1000 atoms or molecules with a diameter between 1-10nm. Also known as colloidal semiconductor nanomaterials, QDs have a particle size of less than 10nm in each dimension of three-dimensional space, which is prone to quantum confinement effect. This effect gives QDs superior fluorescence properties and optical stability. QDs materials can be used to detect pollutants in water, but current QDs materials have poor selectivity for benzidine in water. Summary of the invention

[0005] In view of this, the present invention proposes a fluorescent detection material and a preparation method and application thereof to solve or partially solve the technical problems existing in the prior art.

[0006] In a first aspect, the present invention provides a method for preparing a fluorescent detection material, comprising the following steps:

[0007] Add cadmium salt and N-acetyl-L-cysteine ​​to water, adjust the pH to 10-11, then add sodium borohydride and telluride, mix and react at 90-110° C. to obtain CdTe quantum dots;

[0008] Add CdTe quantum dots into water, then add alcohol solvent, stir, add silicon source and ammonia water, and react in the dark to obtain CdTe quantum dots with surface modified SiO2;

[0009] Adding benzidine to an alcohol solvent and stirring to obtain a benzidine solution;

[0010] The CdTe quantum dots with surface modified SiO2 are added into water, and then benzidine solution is added, and then ammonia water is added, stirred, and then 3-aminotriethoxysilane and silicon source are added dropwise. The reaction is carried out in the dark, and the reaction product is washed with an alcohol solvent, centrifuged and dried to obtain a fluorescent detection material.

[0011] Preferably, in the method for preparing the fluorescent detection material, the cadmium salt includes at least one of cadmium chloride, cadmium sulfate and cadmium nitrate.

[0012] Preferably, in the method for preparing the fluorescent detection material, the telluride includes at least one of potassium tellurite and sodium tellurite.

[0013] Preferably, in the method for preparing the fluorescent detection material, the silicon source includes at least one of tetraethyl orthosilicate, methyl orthosilicate, silicon tetrachloride and silicon tetrafluoride.

[0014] Preferably, the preparation method of the fluorescent detection material is to add cadmium salt and N-acetyl-L-cysteine ​​to water, adjust the pH to 10-11, then add sodium borohydride and telluride, mix and react at 90-110°C, then extract with an alcohol solvent, centrifuge and dry to obtain CdTe quantum dots;

[0015] CdTe quantum dots are added into water, and then an alcohol solvent is added, and after stirring, a silicon source and ammonia water are added. After the reaction is protected from light, the reaction product is washed with an alcohol solvent, centrifuged, and dried to obtain CdTe quantum dots with surface modified SiO2.

[0016] Preferably, in the method for preparing the fluorescent detection material, in the step of preparing CdTe quantum dots, the mass ratio of cadmium salt, N-acetyl-L-cysteine, water, sodium borohydride, and telluride is (0.1-0.3):(0.2-0.4):(90-110):(0.1-0.3):(0.005-0.02);

[0017] In the step of preparing CdTe quantum dots with surface modified SiO2, the mass volume ratio of CdTe quantum dots, water, alcohol solvent, silicon source, and ammonia water is (40-60) mg: (1-3) mL: (5-15) mL: (200-300) μL: (200-300) μL;

[0018] In the step of adding SiO2 surface-modified CdTe quantum dots to water, then adding benzidine solution, adding ammonia water, stirring, and then dropwise adding 3-aminotriethoxysilane and a silicon source, the mass volume ratio of SiO2 surface-modified CdTe quantum dots, water, ammonia water, 3-aminotriethoxysilane, and silicon source is (80-120) mg: (20-40) mL: (1-3) mL: (500-700) μL: (700-900) μL;

[0019] The benzidine solution is obtained by adding benzidine to an alcohol solvent and stirring. Specifically, 0.5 to 2 mmol of benzidine is added to 80 to 120 mL of an alcohol solvent and stirred to obtain the benzidine solution.

[0020] Preferably, the preparation method of the fluorescent detection material comprises adding CdTe quantum dots with surface modified SiO2 into water, then adding benzidine solution, then adding ammonia water, stirring, then dropwise adding 3-aminotriethoxysilane and a silicon source, reacting in the dark, washing the reaction product with an alcohol solvent, drying after centrifugation, then washing with methanol-potassium hydroxide eluent until no benzidine can be detected in the supernatant, then washing with an alcohol solvent, and drying to obtain the fluorescent detection material.

[0021] Preferably, in the method for preparing the fluorescent detection material, the alcohol solvent includes at least one of ethanol, methanol, glycerol and ethylene glycol.

[0022] In a second aspect, the present invention further provides a fluorescence detection material, which is prepared by the preparation method.

[0023] In a third aspect, the present invention also provides an application of the fluorescent detection material in detecting benzidine in water.

[0024] The fluorescent detection material and its preparation method and application of the present invention have the following beneficial effects compared with the prior art:

[0025] The preparation method of the fluorescent detection material of the present invention combines molecular imprinting technology with fluorescent detection and nanotechnology, and constructs a multifunctional detection material integrating specificity and fluorescent detection by combining nano core-shell materials with highly sensitive fluorescent indication technology. Specifically, on the basis of synthesizing CdTe quantum dots, the surface of CdTe QDs is modified with silicon dioxide to obtain CdTe quantum dots with surface modified SiO2. Then, benzidine is used as a template molecule to prepare the fluorescent detection material by using surface molecular imprinting technology. At the same time, a molecular imprinting fluorescent sensor is constructed using the prepared MIPs-CdTe QDs@SiO2 as an identification and detection element, and a rapid detection of benzidine in a drinking water source is established. The fluorescent detection material prepared by the present invention has the characteristics of high efficiency, rapidity, specificity, sensitivity and easy operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 This is a schematic diagram of the preparation principle of the fluorescent detection material of the present invention;

[0028] Figures 2-3 The transmission electron microscope images of the CdTe quantum dots prepared in Example 1 at different magnifications;

[0029] Figure 4 The fluorescence spectrum of MIPs CdTe-QDs@SiO2 changes with the increase of benzidine concentration;

[0030] Figure 5 The fluorescence spectrum of NIPs-CdTe QDs@SiO2 changes with the increase of benzidine concentration;

[0031] Figure 6 The changes of Stern-Volmer values ​​of MIPs-CdTe QDs@SiO2 and NIPs-CdTe QDs@SiO2 to benzidine at different times;

[0032] Figure 7 is the quenching constant of MIPs-CdTe QDs@SiO2 and NIPs-CdTe QDs@SiO2 to benzidine and its structural similarities. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The present invention provides a method for preparing a fluorescent detection material, comprising the following steps:

[0035] S1, adding cadmium salt and N-acetyl-L-cysteine ​​to water, adjusting the pH to 10-11, then adding sodium borohydride and telluride, mixing and reacting at 90-110° C. to obtain CdTe quantum dots;

[0036] S2, adding CdTe quantum dots to water, then adding alcohol solvent, stirring, adding silicon source and ammonia water, and reacting in the dark to obtain CdTe quantum dots with surface modified SiO2;

[0037] S3, adding benzidine to an alcohol solvent and stirring to obtain a benzidine solution;

[0038] S4. Add CdTe quantum dots with surface modified SiO2 into water, then add benzidine solution, then add ammonia water, stir, then drop 3-aminotriethoxysilane and silicon source, react in the dark, wash the reaction product with alcohol solvent, centrifuge and dry to obtain fluorescent detection material.

[0039] It should be noted that the surface of quantum dots is easily affected by environmental conditions, so functional modification of the surface of quantum dots is the key to preparing fluorescent detection materials. Silica can provide chemical and physical protection of the surface, and has good dispersibility and biocompatibility, so it is a commonly used quantum dot surface modification material. Silicon sources such as tetraethyl orthosilicate (TEOS) are the most commonly used silanization agents and are widely used in various quantum dot modification systems, so TEOS is selected as the raw material for quantum dot silanization modification. However, the silicon-modified fluorescent detection material lacks selectivity in the recognition of the target. Therefore, in order to improve the selectivity of QDs fluorescence detection, molecularly imprinted polymers (MIPs) with specific recognition ability are introduced into the sensor, that is, the selectivity of the fluorescent detection material is improved by forming MIPs on the surface of quantum dots. Surface imprinting is a method of synthesizing MIPs with a larger specific surface area, recognition sites mainly on the surface, and faster adsorption and recognition speed formed on the surface of a specific carrier by chemical methods. In most studies, 3-aminotriethoxysilane (APTES) was used as the functional monomer and TEOS as the cross-linking agent. Under the action of ammonia water (NH3·H2O), template molecules were added to synthesize imprinted polymers through self-assembly. Finally, the template molecules were washed away, leaving specific recognition sites on the surface of quantum dots.

[0040] Specifically, the preparation method of the fluorescent detection material of the present application is to modify the surface of CdTe QDs with silicon dioxide (SiO2) on the basis of synthesizing CdTe quantum dots (i.e., CdTe QDs) to obtain CdTe quantum dots with surface modified with SiO2 (i.e., CdTe QDs@SiO2); then, using benzidine as a template molecule, the surface molecular imprinting technology is used to prepare the fluorescent detection material (i.e., MIPs-CdTe QDs@SiO2); at the same time, a molecular imprinting fluorescence sensor is constructed using the prepared MIPs-CdTe QDs@SiO2 as an identification and detection element to establish a rapid detection of benzidine in drinking water sources.

[0041] In some embodiments, the cadmium salt includes at least one of cadmium chloride, cadmium sulfate, and cadmium nitrate.

[0042] In some embodiments, the telluride includes at least one of potassium tellurite and sodium tellurite.

[0043] In some embodiments, the silicon source includes at least one of tetraethyl orthosilicate, methyl orthosilicate, silicon tetrachloride, and silicon tetrafluoride.

[0044] In some embodiments, cadmium salt and N-acetyl-L-cysteine ​​are added to water, the pH is adjusted to 10-11, and then sodium borohydride and telluride are added, mixed and reacted at 90-110°C, and then purified and extracted using an alcohol solvent, centrifuged and dried to obtain CdTe quantum dots.

[0045] In the above embodiment, the mixture is reacted at 90-110° C., and then purified and extracted using an alcohol solvent, and dried after centrifugation to obtain CdTe quantum dots. Specifically, an alcohol solvent is added to the product after the reaction, and the alcohol solvent changes the polarity of the product after the reaction, thereby causing the generated quantum dots to aggregate, and then centrifugation is performed to obtain CdTe quantum dots.

[0046] In some embodiments, CdTe quantum dots are added to water, and then an alcohol solvent is added. After stirring, a silicon source and ammonia water are added. After the reaction is protected from light, the reaction product is washed with an alcohol solvent, centrifuged, and dried to obtain CdTe quantum dots with surface modified SiO2.

[0047] In some embodiments, in the step of preparing CdTe quantum dots, the mass ratio of cadmium salt, N-acetyl-L-cysteine, water, sodium borohydride, and telluride is (0.1-0.3):(0.2-0.4):(90-110):(0.1-0.3):(0.005-0.02).

[0048] In some embodiments, in the step of preparing CdTe quantum dots with surface modified SiO2, the mass volume ratio of CdTe quantum dots, water, alcohol solvent, silicon source, and ammonia water is (40-60) mg: (1-3) mL: (5-15) mL: (200-300) μL: (200-300) μL.

[0049] In some embodiments, in the step of adding SiO2 surface-modified CdTe quantum dots to water, then adding benzidine solution, adding ammonia water, stirring, and then dropwise adding 3-aminotriethoxysilane and a silicon source, the mass volume ratio of SiO2 surface-modified CdTe quantum dots, water, ammonia water, 3-aminotriethoxysilane, and silicon source is (80-120) mg: (20-40) mL: (1-3) mL: (500-700) μL: (700-900) μL.

[0050] In some embodiments, benzidine is added to an alcohol solvent and stirred to obtain a benzidine solution. Specifically, 0.5 to 2 mmol of benzidine is added to 80 to 120 mL of an alcohol solvent and stirred to obtain a benzidine solution.

[0051] In some embodiments, CdTe quantum dots with surface modified SiO2 are added to water, and then a benzidine solution is added, and then ammonia water is added and stirred, and then 3-aminotriethoxysilane and a silicon source are added dropwise. The reaction is carried out in the dark, and the reaction product is washed with an alcohol solvent, dried after centrifugation, and then washed with methanol-potassium hydroxide eluent until no benzidine is detected in the supernatant. The supernatant is then washed with an alcohol solvent and dried to obtain a fluorescent detection material.

[0052] Specifically, in the above embodiment, the method for preparing the methanol-potassium hydroxide eluent is: dissolving potassium hydroxide solution and methanol to obtain an eluent, and different concentrations are commonly used; in the present application, the method for preparing the methanol-potassium hydroxide eluent is: first prepare a 0.1 mol / L KOH aqueous solution, and then dissolve the KOH aqueous solution and methanol in a volume ratio of 1:1.

[0053] In some embodiments, the alcohol solvent includes at least one of ethanol, methanol, glycerol, and ethylene glycol.

[0054] Specifically, the preparation principle of the fluorescent detection material of the present application is: at a temperature of 90 to 110°C, cadmium salt (such as CdCl2), N-acetyl-L-cysteine ​​(NAC), sodium borohydride (NaBH4), and telluride (such as K2TeO3) are used as raw materials to synthesize CdTe quantum dots by a one-step method; then, a silicon source (such as tetraethyl orthosilicate TEOS) is used to modify a layer of SiO2 protective shell on the surface of the CdTe quantum dots under certain conditions to obtain CdTe QDs@SiO2; using CdTe QDs@SiO2 as a carrier, under the action of functional monomer 3-aminotriethoxysilane (APTES) and crosslinking agent TEOS, NH3·H2O is used as a catalyst, and a template molecule benzidine (C 12 H 12 N2), self-assemble to synthesize imprinted polymers; then wash the product repeatedly with CH3OH-KOH eluent to wash away the template molecule benzidine, and finally leave specific three-dimensional hole recognition sites on the surface of quantum dots. When these sites encounter benzidine again, they can produce specific binding to detect benzidine.

[0055] Specifically, Figure 1 A schematic diagram showing the preparation principle of the fluorescent detection material of the present application is shown.

[0056] The present application combines molecular imprinting technology with fluorescence detection and nanotechnology, and combines nano core-shell materials with highly sensitive fluorescence indication technology to construct a multifunctional fluorescence detection material that integrates specificity and fluorescence detection; the fluorescence detection material prepared in the present application has good stability and dispersibility in aqueous solution, with a size of about 4 nm, uniform dispersion, and no agglomeration; the fluorescence detection material prepared in the present application has the characteristics of high efficiency, rapidity, specificity, sensitivity, and easy operation.

[0057] Based on the same inventive concept, an embodiment of the present application also provides a fluorescence detection material, which is prepared using the above-mentioned preparation method.

[0058] Based on the same inventive concept, an embodiment of the present application also provides an application of the above-mentioned fluorescent detection material in detecting benzidine in water.

[0059] The present application aims at the very low concentration of non-volatile pollutants (benzidine) in drinking water sources. On the basis of synthesizing CdTeQDs, the surface of CdTe QDs is modified with SiO2, and then the MIPs-CdTe QDs@SiO2 composite material is prepared by surface molecular imprinting technology. The molecular imprinting polymer is organically combined with fluorescence detection and nanotechnology to provide a fluorescent detection material with high sensitivity and strong specificity for detecting benzidine in drinking water sources.

[0060] The following further illustrates the preparation method of the fluorescent detection material of the present application with specific examples. This section further illustrates the content of the present invention in conjunction with specific examples, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0061] Example 1

[0062] The present invention provides a method for preparing CdTe quantum dots, comprising the following steps:

[0063] S1. Add 10 ml of 0.1 M CdCl2 solution and 0.25 g of N-acetyl-L-cysteine ​​to 100 mL of deionized water, mix well, adjust the pH to 10 with NaOH aqueous solution, then add 0.15 g of NaBH4 and 2.5 ml of 0.02 M K2TeO3 solution, mix well, stir and react at 100 ° C for 1 h, cool to room temperature, add 2 times the volume of anhydrous ethanol to the reaction mixture, mix well, centrifuge and extract, and vacuum dry to obtain CdTe quantum dots.

[0064] Figures 2-3The transmission electron microscope images of the CdTe quantum dots prepared in Example 1 at different magnifications are shown; the CdTe quantum dots have good stability and dispersibility in aqueous solution, are approximately spherical, have a size of about 4 nm, are evenly dispersed, and have no agglomeration.

[0065] Example 2

[0066] The present invention provides a method for preparing a fluorescent detection material, comprising the following steps:

[0067] S1. Prepare CdTe quantum dots according to the method in Example 1. Dissolve 50 mg of CdTe quantum dots in 2 mL of deionized water, add 10 mL of anhydrous ethanol, mix well, stir at 30°C, then drop 250 μL of tetraethyl orthosilicate (TEOS), and then add 250 μL of NH3·H2O solution (using commercially available ammonia water with a mass fraction of 25-28%), react in the dark for 1 day, and after the reaction is completed, wash the reaction product with anhydrous ethanol, centrifuge, and vacuum dry to obtain CdTe quantum dots with SiO2 surface modified (CdTeQDs@SiO2);

[0068] S2, adding 1 mmol of benzidine to 100 mL of anhydrous ethanol, and dissolving by ultrasonication to obtain a benzidine solution;

[0069] S3. Dissolve 100 mg of surface-modified SiO2 CdTe quantum dots (CdTe QDs@SiO2) in 30 mL of deionized water, add the benzidine solution in step S2 and mix and stir, then add 2 mL of NH3·H2O, add 600 μL of 3-aminotriethoxysilane (APTES) and 800 μL of tetraethyl orthosilicate (TEOS) dropwise under stirring, and react in the dark for 1 day. After the reaction is completed, wash the reaction product with anhydrous ethanol, and then repeatedly wash with CH3OH-KOH eluent until no benzidine can be detected in the supernatant, then wash with anhydrous ethanol, and dry to obtain the fluorescent detection material (MIPs-CdTe QDs@SiO2).

[0070] Comparative Example 1

[0071] This comparative example provides a method for preparing a non-imprinted polymer fluorescent detection material, comprising the following steps:

[0072] S1. Prepare CdTe quantum dots according to the method in Example 1. Dissolve 50 mg of CdTe quantum dots in 2 mL of deionized water, add 10 mL of anhydrous ethanol, mix well, stir at 30°C, then drop 250 μL of tetraethyl orthosilicate (TEOS), then add 250 μL of NH3·H2O solution, react in the dark for 1 day, and after the reaction is completed, wash the reaction product with anhydrous ethanol, centrifuge, and vacuum dry to obtain CdTe quantum dots with SiO2 surface modified (CdTe QDs@SiO2);

[0073] S2. Dissolve 100 mg of CdTe quantum dots with SiO2 surface modified (CdTe QDs@SiO2) in 30 mL of deionized water, add 100 mL of anhydrous ethanol and mix and stir, then add 2 mL of NH3·H2O, add 600 μL of 3-aminotriethoxysilane (APTES) and 800 μL of tetraethyl orthosilicate (TEOS) dropwise under stirring, and react in the dark for 1 day. After the reaction is completed, wash the reaction product with anhydrous ethanol, then repeatedly wash with CH3OH-KOH eluent, then wash with anhydrous ethanol, and dry to obtain a non-imprinted polymer (NIPs-CdTe QDs@SiO2), which is the fluorescence detection material.

[0074] Performance Testing

[0075] (1) Fluorescence detection experiment of benzidine

[0076] At room temperature, a certain amount of MIPs-CdTeQDs@SiO2 prepared in Example 2 and NIPs-CdTe QDs@SiO2 prepared in Comparative Example 1 were dissolved in ultrapure water by ultrasonic oscillation to obtain 20 mg / L imprinted and non-imprinted solutions, respectively.

[0077] Accurately add 2 mL of 20 mg / L MIPs-CdTe QDs@SiO2 solution into 7 10 mL centrifuge tubes, and then add 5 mL of benzidine standard solution with concentrations of 1, 5, 10, 20, 40, 70, and 100 μg / L, respectively. After ultrasonic dispersion, place the tubes in a shaker and shake them at 25 ° C and 240 r / min for 1 hour. Take an appropriate amount of solution into a cuvette for fluorescence detection.

[0078] Kinetics: In 7 10mL centrifuge tubes, accurately add 2mL of 20mg / L MIPs-CdTe QDs@SiO2 solution and 5mL of 100μg / L benzidine standard solution. After ultrasonic dispersion, put them into a shaker and oscillate at 25℃ and 240r / min. Take out a centrifuge tube at 1, 5, 10, 20, 30, 45, and 60min respectively, and take an appropriate amount of solution into a cuvette for fluorescence detection.

[0079] Control experiment: According to the above method, except that MIPs-CdTe QDs@SiO2 was replaced by non-imprinted polymer NIPs-CdTe QDs@SiO2, other conditions remained unchanged and a control experiment of the same group was performed.

[0080] Based on the fluorescence quenching effect between CdTe QDs@SiO2 and template molecules, MIPs-CdTe QDs@SiO2 was used as a fluorescence sensitive material to detect different concentrations of benzidine. The relationship between the fluorescence intensity of MIPs-CdTe QDs@SiO2 and the concentration of template molecules (benzidine) can be expressed by the Stern-Volmer equation:

[0081] F0 / F=1+K SV [C]

[0082] In the above equation, F0 and F represent the fluorescence intensity of QDs@SiO2-MIPs before and after adding benzidine, K SV is the Stern-Volmer constant, and C is the concentration of added benzidine.

[0083] Figure 4 The fluorescence spectrum of MIPs CdTe-QDs@SiO2 changes with the increase of benzidine concentration; Figure 5 The fluorescence spectrum of NIPs-CdTe QDs@SiO2 changes with the increase of benzidine concentration.

[0084] from Figure 4 It can be seen that the fluorescence intensity of CdTe QDs@SiO2-MIPs gradually decreases with the increase of benzidine concentration from 1 to 100 μg / L, and there is a linear correlation with a correlation coefficient of 0.996 and K SV,MIP 8597M -1 .from Figure 5 As can be seen from the figure, the fluorescence intensity of NIPs-CdTe QDs@SiO2 also decreases with the increase of benzidine concentration, and also shows a linear correlation relationship, but compared with MIPs-CdTe QDs@SiO2, its decrease is smaller, the correlation coefficient is 0.995, and K SV,NIP 2363M -1 The index for evaluating the selectivity of imprinted polymers is the imprinting factor, also known as K SV,MIP With K SV,NIP The ratio of the two. It can be calculated that the imprinting factor of MIPs-CdTe QDs@SiO2 is 3.64, which indicates that MIPs-CdTe QDs@SiO2 has good selectivity for benzidine.

[0085] Figure 6Changes of Stern-Volmer values ​​of MIPs-CdTe QDs@SiO2 and NIPs-CdTe QDs@SiO2 to benzidine at different times.

[0086] Depend on Figure 6 It can be seen that during the adsorption time from 0 to 30 minutes, the fluorescence intensity of MIPs-CdTe QDs@SiO2 decreased to the maximum, that is, the F0 / F-1 value was the largest. Then, as the adsorption time increased, the F0 / F-1 value did not change much, indicating that the specific adsorption was completed within 30 minutes. However, the F0 / F-1 result of NIPs-CdTe QDs@SiO2 did not change significantly with the extension of time. This shows that NIPs-CdTe QDs@SiO2 does not have specific selection for benzidine. In summary, this study used 30 minutes as the fluorescence detection time.

[0087] (2) Specificity verification

[0088] In order to test the specificity of MIPs-CdTe QDs@SiO2 for the detection of benzidine, several interfering substances with similar structures to benzidine were selected, such as diphenyl ether (C6H5)2O, 3,3'-dichlorobenzidine (C 12 H 10 C l2 N2) for specificity verification. Although these two substances are similar in structure to benzidine,

[0089] The quenching constant of MIPs-CdTeQDs@SiO2 is different. Figure 7 is the quenching constant of MIPs-CdTe QDs@SiO2 and NIPs-CdTe QDs@SiO2 to benzidine and its structural similarities.

[0090] from Figure 7 It can be seen that the fluorescence quenching constant of MIPs-CdTe QDs@SiO2 for benzidine is the largest, and is significantly larger than the other two structural analogs. In addition, the quenching constants of NIPs-CdTe QDs@SiO2 for the three substances are almost the same, because the preparation process of NIPs-CdTe QDs@SiO2 does not use benzidine and its structural analogs as templates, and has no specific selectivity for these three substances. In the process of preparing MIPs-CdTe QDs@SiO2 in this application, due to the use of benzidine as a template molecule, a specific three-dimensional recognition space is generated in the hole site. Therefore, these sites can specifically combine with the structure of benzidine, causing fluorescence quenching. Structural analogs have different shapes and molecular weights, and cannot completely bind to the recognition site, so they cannot be specifically recognized. Therefore, MIPs-CdTe QDs@SiO2 has specific selectivity for benzidine.

[0091] (3) Rapid detection of benzidine in drinking water sources

[0092] Water samples were collected from three drinking water sources, and analyzed according to this method. Low-concentration mixed standard solution (5μg / L benzidine standard solution) was added for spike analysis. The results showed that no benzidine was detected in the water samples from the three different water sources, and the corresponding low-concentration spiked recoveries of benzidine were 92%, 94%, and 91%, respectively. The results show that this method is suitable for the rapid detection of benzidine in drinking water sources.

[0093] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a fluorescent detection material, characterized in that: The following steps are involved: Add cadmium salt and N-acetyl-L-cysteine ​​to water, adjust the pH to 10-11, then add sodium borohydride and telluride, mix and react at 90-110° C., then extract with an alcohol solvent, centrifuge and dry to obtain CdTe quantum dots; Add CdTe quantum dots to water, then add alcohol solvent, stir, add silicon source and ammonia water, react in the dark, wash the reaction product with alcohol solvent, centrifuge, and dry to obtain CdTe quantum dots with SiO2 modified on the surface; Adding benzidine to an alcohol solvent and stirring to obtain a benzidine solution; The CdTe quantum dots with surface modified SiO2 are added to water, and then a benzidine solution is added, and then ammonia water is added, stirred, and then 3-aminotriethoxysilane and a silicon source are added dropwise, and the reaction is carried out in the dark, and the reaction product is washed with an alcohol solvent, centrifuged and dried to obtain a fluorescent detection material; The silicon source includes at least one of tetraethyl orthosilicate, methyl orthosilicate, silicon tetrachloride, and silicon tetrafluoride; In the step of preparing CdTe quantum dots, the mass ratio of cadmium salt, N-acetyl-L-cysteine, water, sodium borohydride, and telluride is (0.1-0.3):(0.2-0.4):(90-110):(0.1-0.3):(0.005-0.02); In the step of preparing CdTe quantum dots with surface modified SiO2, the mass volume ratio of CdTe quantum dots, water, alcohol solvent, silicon source, and ammonia water is (40-60) mg: (1-3) mL: (5-15) mL: (200-300) μL: (200-300) μL; In the step of adding SiO2 surface-modified CdTe quantum dots to water, then adding benzidine solution, adding ammonia water, stirring, and then dropwise adding 3-aminotriethoxysilane and a silicon source, the mass volume ratio of SiO2 surface-modified CdTe quantum dots, water, ammonia water, 3-aminotriethoxysilane, and silicon source is (80-120) mg: (20-40) mL: (1-3) mL: (500-700) μL: (700-900) μL; The benzidine solution is obtained by adding benzidine to an alcohol solvent and stirring. Specifically, 0.5 to 2 mmol of benzidine is added to 80 to 120 mL of an alcohol solvent and stirred to obtain the benzidine solution.

2. The method for preparing the fluorescence detection material according to claim 1, characterized in that: The cadmium salt includes at least one of cadmium chloride, cadmium sulfate and cadmium nitrate.

3. The method for preparing the fluorescent detection material according to claim 1, characterized in that: The telluride includes at least one of potassium tellurite and sodium tellurite.

4. The method for preparing the fluorescent detection material according to claim 1, characterized in that: The CdTe quantum dots with surface modified SiO2 are added into water, and then benzidine solution is added, and then ammonia water is added, stirred, and then 3-aminotriethoxysilane and silicon source are added dropwise, and the reaction is carried out in the dark. The reaction product is washed with an alcohol solvent, dried after centrifugation, and then washed with methanol-potassium hydroxide eluent until benzidine cannot be detected in the supernatant, and then washed with an alcohol solvent and dried to obtain a fluorescent detection material.

5. The method for preparing the fluorescent detection material according to any one of claims 1 to 4, characterized in that: The alcohol solvent includes at least one of ethanol, methanol, glycerol and ethylene glycol.

6. A fluorescence detection material, characterized in that: The preparation method is as described in any one of claims 1 to 5.

7. Use of the fluorescent detection material as claimed in claim 6 in detecting benzidine in water.

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