Quantum dot@zif-8 composite material, and preparation method and application thereof

Abstract

This invention proposes a quantum dot@ZIF-8 composite material, its preparation method, and its applications, belonging to the field of functional nanomaterials and fluorescence sensing analysis and detection technology. This invention involves mixing CdTe quantum dots (CdTe QDs) with red fluorescence emission and carbon quantum dots (C QDs) with blue fluorescence emission in a specific ratio, followed by in-situ self-assembly growth of ZIF-8, resulting in a quantum dot@ZIF-8 composite material with dual fluorescence signal emission. The quantum dot@ZIF-8 nanocomposite material prepared by this method not only possesses the fluorescence properties of quantum dots but also largely retains the original structure and properties of ZIF-8, making it a simple and effective method for preparing composite materials with excellent fluorescence performance. This quantum dot@ZIF-8 composite material can be used to prepare ratiometric fluorescence sensing probes for the visual detection of glucose with high sensitivity.

Description

Technical Field

[0001] This invention belongs to the field of functional nanomaterials and fluorescence sensing analysis and detection technology, and particularly relates to a quantum dot@ZIF-8 composite material, its preparation method and application. Background Technology

[0002] Glucose plays a vital role in life processes, and persistently high levels of glucose in the body can cause many endocrine and metabolic diseases, such as diabetes. As a chronic disease, diabetes often leads to various complications, including retinopathy, blindness, heart disease, kidney failure, and stroke. Strict blood glucose control, maintaining blood glucose levels within the normal range, can delay the onset and progression of diabetes-related complications and improve the survival rate of diabetic patients. Therefore, continuous blood glucose monitoring is crucial for the management of diabetes. Furthermore, abnormally elevated glucose levels in urine may also indicate some kidney diseases. Therefore, developing glucose analysis tools with high sensitivity, high selectivity, and low cost is of great significance for human health monitoring.

[0003] Fluorescence analysis technology has attracted much attention due to its high sensitivity, intuitive detection, simplicity, fast response, and low cost. However, most fluorescent materials often have only a single fluorescence emission wavelength, and the constructed single-emission sensing system is easily affected by many factors unrelated to the analyte, such as instrument deviation and environmental fluctuations. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a quantum dot@ZIF-8 composite material, its preparation method, and its applications.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] One of the technical solutions of the present invention:

[0007] A method for preparing quantum dot@ZIF-8 composite material involves mixing CdTe quantum dots with red fluorescence emission and carbon quantum dots with blue fluorescence emission, followed by in-situ self-assembly growth of ZIF-8 to obtain the quantum dot@ZIF-8 composite material.

[0008] Furthermore, the synthesis method of the CdTe quantum dots with red fluorescence emission is as follows: Cadmium nitrate tetrahydrate and trisodium citrate are dissolved in water, mercaptopropionic acid is added, and then an alkaline solution is added to adjust the pH to alkaline. Sodium tellurite and potassium borohydride are added, and the reaction is carried out under reflux in an oil bath. After the reaction is completed, the mixture is naturally cooled to room temperature, precipitated with isopropanol, washed, and dried to obtain CdTe quantum dots with red fluorescence emission.

[0009] Furthermore, the molar ratio of cadmium nitrate tetrahydrate, trisodium citrate, sodium tellurite, and potassium borohydride is 3.8:6.8:1:9;

[0010] The reflux reaction in the oil bath is carried out at a temperature of 105°C for 12-16 hours. This temperature is sufficient to ensure that the liquid in the reaction vessel can evaporate and reflux without wasting resources. If the reaction time is too short, the generated cadmium telluride will not be red fluorescent. Within the reaction time of 12-16 hours specified in this invention, CdTe quantum dots emitting red fluorescence are obtained.

[0011] Furthermore, the method for synthesizing the carbon quantum dots with blue fluorescence emission is as follows: citric acid and tris(hydroxymethyl)aminomethane are dissolved in water and subjected to a hydrothermal reaction. After the hydrothermal reaction is completed, the mixture is removed after natural cooling and filtered to obtain a carbon quantum dot (CQDs) dispersion.

[0012] Furthermore, the molar ratio of citric acid to tris(hydroxymethyl)aminomethane is 1:1;

[0013] The hydrothermal reaction was carried out at a temperature of 200°C for 6 hours.

[0014] Furthermore, the method for in-situ self-assembly growth of ZIF-8 to obtain quantum dot@ZIF-8 composite material is as follows: Zinc acetate is dissolved in water and labeled as the first solution; 2-methylimidazole and hexadecyltrimethylammonium bromide (CTAB) are dissolved in water, the CQDs dispersion and the CdTe quantum dots are added, and the mixture is sonicated and then stirred, labeled as the second solution; the first solution is poured into the second solution, and the mixture is stirred evenly at room temperature. After the reaction is completed, the precipitate is collected by centrifugation, washed, and dried to obtain the quantum dot@ZIF-8 composite material.

[0015] Furthermore, the mass ratio of zinc acetate to 2-methylimidazole is 0.3:1.059.

[0016] Furthermore, the mass-to-volume ratio of the CdTe quantum dots to the CQDs dispersion is (40-90) mg:0.8 mL. This invention investigated the effect of changing the mass of CdTe quantum dots on the sensitivity and detection limit of the quantum dot@ZIF-8 composite material by fixing the amount of CdTe quantum dots. It was found that changing the amount of CdTe quantum dots does not affect the fundamental properties of the quantum dot@ZIF-8 composite material, but it does have a certain impact on the sensitivity and detection limit. When the mass-to-volume ratio of CdTe quantum dots to CQDs dispersion is 90 mg:0.8 mL, the detection limit is 0.061 mM; when the mass-to-volume ratio is 40 mg:0.8 mL, the detection limit is 0.011 mM.

[0017] Furthermore, the preparation method of the quantum dot@ZIF-8 composite material is as follows:

[0018] (1) Synthesis of carbon quantum dots (C QDs) with blue fluorescence emission: 1.054 g (0.005 mol) of citric acid and 0.609 g (0.005 mol) of tris(hydroxymethyl)aminomethane were dissolved in 10 mL of ultrapure water and then transferred to a 25 mL hydrothermal reactor. The mixture was heated at 200 °C for 6 h. After natural cooling, the mixture was removed and filtered three times through a 0.22 μm microporous organic filter membrane to obtain a C QDs dispersion.

[0019] (2) Synthesis of cadmium telluride quantum dots (CdTe QDs) with red fluorescence emission: 118 mg (0.38 mmol) of cadmium nitrate tetrahydrate and 200 mg (0.68 mmol) of trisodium citrate were dissolved in 50 mL of ultrapure water and ultrasonically stirred. After dissolution, 55 μL of mercaptopropionic acid was added and mixed thoroughly. The solution changed from clear and transparent to milky white. Then, sodium hydroxide solution (0.1 M) was added to adjust the pH of the solution to 10.5, and the solution became clear. Subsequently, 22.2 mg (0.1 mmol) of sodium tellurite and 50 mg (0.9 mmol) of potassium borohydride were added, and the solution was refluxed in an oil bath at 105 °C for 12-16 h, so that the colorless solution slowly turned red. The liquid after reaction was naturally cooled to room temperature, precipitated with the same volume of isopropanol, washed three times with isopropanol, and dried to obtain CdTe QDs powder.

[0020] (3) Preparation of quantum dot@ZIF-8 composite material:

[0021] 300 mg of zinc acetate was weighed and dissolved in 5 mL of ultrapure water, labeled as the first solution; 1.059 g of 2-methylimidazole and 1 mg of hexadecyltrimethylammonium bromide (CTAB) were weighed and dissolved in 4.2 mL of ultrapure water, and then 0.8 mL of CQDs dispersion and 40-90 mg of CdTe QDs powder were added. The mixture was sonicated for 30 min and then stirred for 30 min, labeled as the second solution; the first solution was poured into the second solution and stirred at room temperature for 2 h. After the reaction was completed, the sample was collected by centrifugation, washed several times alternately with water and ethanol, and dried under vacuum at 60 °C to obtain the quantum dot@ZIF-8 composite material.

[0022] To avoid the adverse effects described in the background art, this invention introduces two fluorescence emission signals into the design of the fluorescence sensing system, establishing a ratiometric fluorescence sensing system. It simultaneously monitors the intensity of both emission wavelengths and calculates and calibrates the intensity ratio for analyte quantification. Compared to single-emission fluorescence sensors, the ratiometric fluorescence sensor of this invention achieves internal self-calibration by integrating two fluorescence emissions into a single system, eliminating signal fluctuations caused by changes in the background environment and providing more accurate and reliable quantitative information. Furthermore, changes in the intensity ratio of the two fluorescence signals lead to changes in the fluorescence color of the sensing system, which can be directly observed with the naked eye under ultraviolet light. Therefore, the novel functional nanomaterial with dual emission wavelengths used as a ratiometric fluorescence sensing probe in this invention is beneficial for developing a more reliable, convenient, and low-cost visual sensing and analysis mode.

[0023] Furthermore, the zeolite imidazole ester framework (ZIF-8) is a typical metal-organic framework (MOF) material with many advantages, including high porosity, large specific surface area, tunable pore size, and good stability. The quantum dot@ZIF-8 composite material not only possesses the advantages of ratiometric fluorescence sensors but also largely retains the performance of the original MOF framework. Due to the adsorption properties of ZIF-8, the generated H2O2 accumulates in the pores, resulting in a high local concentration, which effectively quenches the fluorescence of CdTe QDs in the quantum dot@ZIF-8, thus improving the sensing and analytical performance.

[0024] The second technical solution of the present invention:

[0025] The present invention also provides a ratiometric fluorescent probe prepared from the quantum dot@ZIF-8 composite material prepared by the above method.

[0026] The third technical solution of the present invention:

[0027] Application of a quantum dot@ZIF-8 composite material prepared according to the above method in the preparation of a ratiometric fluorescence sensor.

[0028] The fourth technical solution of the present invention:

[0029] The present invention also provides the application of the quantum dot@ZIF-8 composite material prepared according to the above method or the above ratiometric fluorescent probe in glucose detection, and the present invention can realize the visual detection of glucose.

[0030] This invention synthesizes carbon quantum dots (CQDs) with blue fluorescence emission and cadmium telluride quantum dots (CdTeQDs) with red fluorescence emission. These two materials are then thoroughly mixed in a specific ratio and in-situ self-assembled to grow ZIF-8, resulting in a quantum dot@ZIF-8 composite material with dual fluorescence emission signals. The prepared quantum dot@ZIF-8 composite material is used as a fluorescent probe to form a ratiometric fluorescence sensing system with glucose oxidase (GOx). After reacting a glucose sample with this sensing system for a period of time, the fluorescence signal can be directly observed with the naked eye under a handheld 365nm UV flashlight, or the fluorescence spectrum can be measured using a fluorescence spectrophotometer. The fluorescence intensity is determined based on the ratio of the fluorescence intensity at the maximum emission wavelength of the two quantum dots (F...). C / F CdTe To accurately quantify.

[0031] Compared with the prior art, the present invention has the following advantages and technical effects:

[0032] This invention prepares a quantum dot@ZIF-8 composite material with dual fluorescence emission wavelengths. This composite material possesses both the fluorescence properties of quantum dots and the structural advantages of ZIF-8 materials, enabling the fabrication of high-performance fluorescent sensing probes. The synthesis method of this composite material is simple and the conditions are mild.

[0033] This invention utilizes a ratiometric fluorescence sensing system based on quantum dot@ZIF-8 composite material for glucose detection, effectively avoiding the drawbacks of single-emission fluorescence signals being susceptible to instrument and environmental factors. The response signals to different glucose concentrations can be directly observed with the naked eye using a handheld 365nm flashlight, making detection more intuitive and convenient. It exhibits good selectivity for glucose, effectively avoiding interference from similar substances.

[0034] The ratiometric fluorescence sensing platform constructed based on quantum dot@ZIF-8 composite material has a large wavelength difference of 215nm at the strongest emission point of the two peaks. This can effectively avoid the interference between the two emission peaks of the probe and is more conducive to its application in detection.

[0035] This invention combines a hybrid quantum dot system with ZIF-8, which has many advantages such as high porosity and large specific surface area. Combining the advantages of both is beneficial to improving the analytical performance of the sensing system (detection limit is 0.011 mM).

[0036] The amounts of each substance in this invention are reasonably selected, and the optimal reaction ratios and reaction conditions are obtained through detailed comparison, analysis and optimization during the experiment. The ratioographic fluorescent probe based on quantum dot@ZIF-8 composite material obtained by the reaction has the best performance. Attached Figure Description

[0037] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0038] Figure 1 For the morphology and elemental composition characterization of the quantum dot@ZIF-8 composite material in Example 1, (A) is a transmission electron microscope (TEM) image of carbon quantum dots (CQDs); (B) is a TEM image of cadmium telluride quantum dots (CdTe QDs); (C) is a TEM image of the quantum dot@ZIF-8 composite material; (D)-(K) are TEM elemental distribution mapping diagrams of the quantum dot@ZIF-8 composite material.

[0039] Figure 2 For the structural characterization of the quantum dot@ZIF-8 composite material in Example 1, (A) is the X-ray diffraction (XRD) data of ZIF-8 and quantum dot@ZIF-8 composite material, and (B) is the infrared absorption spectrum of ZIF-8 and quantum dot@ZIF-8 composite material.

[0040] Figure 3 For the property characterization of the quantum dot@ZIF-8 composite material in Example 1, (A) is the Zeta potential data before and after the quantum dots and ZIF-8 are combined, (B) is the fluorescence spectrum before and after the quantum dots and ZIF-8 are combined, and the inset is a photograph of the quantum dots, ZIF-8 and the composite material under a 365nm ultraviolet lamp.

[0041] Figure 4 The fluorescence signal response of the ratiometric fluorescence sensing system based on the quantum dot@ZIF-8 composite material of Example 1 to glucose samples of different concentrations is shown in Figure (A). The ratio of fluorescence intensity at the maximum emission wavelength of C QDs to CdTe QDs in Figure (F) is used as the criterion. C / F CdTe The standard working curve (B) was plotted with glucose concentration on the x-axis and glucose concentration on the y-axis. The inset is a photograph of the corresponding sample test system under a 365nm UV lamp.

[0042] Figure 5 The effects of reaction temperature (A), reaction time (B), and GOx enzyme concentration (C) on F C / F CdTe The effect of the UV light is shown in the illustration, which is a photograph of the corresponding sample test system under a 365nm UV lamp.

[0043] Figure 6 The selective test results of the ratiometric fluorescence sensing system based on the quantum dot@ZIF-8 composite material of Example 1 are shown in the inset, which is a photograph of the corresponding sample test system under a 365nm ultraviolet lamp.

[0044] Figure 7The fluorescence signal response of the carbon quantum dot (C QDs) fluorescence sensing system alone in Example 1 to glucose samples of different concentrations;

[0045] Figure 8 The fluorescence signal response of the fluorescence sensing system of cadmium telluride quantum dots (CdTe QDs) alone in Example 1 to glucose samples of different concentrations is shown in Figure (A). The standard working curve (B) is plotted with the fluorescence intensity at the maximum emission wavelength of CdTe QDs in Figure (A) as the ordinate and the logarithm of glucose concentration as the abscissa.

[0046] Figure 9 The fluorescence signal response of the ZIF-8 fluorescence sensing system alone to glucose samples of different concentrations;

[0047] Figure 10 The effect of different reflux times on the fluorescence signal of CdTe QDs in Example 1 and Comparative Examples 1-3. Detailed Implementation

[0048] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0049] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0050] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0051] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0052] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0053] In this embodiment of the invention, room temperature refers to 25±2℃.

[0054] All raw materials used in the embodiments of this invention were obtained through commercial purchase.

[0055] The technical solution of the present invention will be further illustrated by the following embodiments.

[0056] Example 1

[0057] (1) Synthesis of carbon quantum dots (C QDs) with blue fluorescence emission: 1.054 g (0.005 mol) of citric acid and 0.609 g (0.005 mol) of tris(hydroxymethyl)aminomethane were dissolved in 10 mL of ultrapure water and then transferred to a 25 mL hydrothermal reactor. The mixture was heated at 200 °C for 6 h. After natural cooling, the mixture was removed and filtered three times through a 0.22 μm microporous organic filter membrane to obtain a C QDs dispersion.

[0058] (2) Synthesis of cadmium telluride quantum dots (CdTe QDs) with red fluorescence emission: 118 mg (0.38 mmol) of cadmium nitrate tetrahydrate and 200 mg (0.68 mmol) of trisodium citrate were dissolved in 50 mL of ultrapure water and ultrasonically stirred. After dissolution, 55 μL of mercaptopropionic acid was added and mixed thoroughly. The solution changed from clear and transparent to milky white. Then, sodium hydroxide solution (0.1 M) was added to adjust the pH of the solution to 10.5, and the solution became clear. Subsequently, 22.2 mg (0.1 mmol) of sodium tellurite and 50 mg (0.9 mmol) of potassium borohydride were added, and the solution was refluxed in an oil bath at 105 °C for 12 h, so that the colorless solution slowly turned red. The liquid after reaction was naturally cooled to room temperature, precipitated with the same volume of isopropanol, washed three times with isopropanol, and dried to obtain CdTe QDs powder with red fluorescence emission.

[0059] (3) Preparation of quantum dot@ZIF-8 composite material:

[0060] 300 mg of zinc acetate was dissolved in 5 mL of ultrapure water and labeled as solution one. 1.059 g of 2-methylimidazole and 1 mg of hexadecyltrimethylammonium bromide (CTAB) were dissolved in 4.2 mL of ultrapure water. Then, 0.8 mL of CQDs dispersion and 40 mg of red fluorescent CdTe QDs powder were added to this solution. The mixture was sonicated for 30 min and then stirred for another 30 min, labeled as solution two. Solution one was poured into solution two and stirred at room temperature for 2 h. After the reaction was complete, the sample was collected by centrifugation, washed three times alternately with water and ethanol, and dried under vacuum at 60 °C to obtain the quantum dot@ZIF-8 composite material.

[0061] Preparation of the ratiometric fluorescence sensing system: The quantum dot@ZIF-8 composite material obtained above was prepared into a 1 mg / mL dispersion with water. 100 μL of this dispersion was mixed thoroughly with 30 μL of glucose oxidase (GOx, 30 U / mL) and 170 μL of Tris-HCl buffer (0.01 M, pH = 7.4) to form the ratiometric fluorescence sensing system. 50 μL of glucose sample was added and thoroughly mixed with the system. The optimal response signal was obtained by reacting at 55 °C for 75 min.

[0062] Plotting the standard working curve: Prepare a series of glucose standard solutions with concentrations (0, 0.1mM, 0.5mM, 0.8mM, 1.0mM, 2.0mM, 5.0mM, 8.0mM, 10mM, 20mM); mix 50μL of each glucose standard solution with the fluorescence sensing system thoroughly and react at 55℃ for 75min; observe the fluorescence color response of the system with the naked eye under a 365nm UV lamp and take photos with a smartphone; test the fluorescence emission spectrum (excitation wavelength 365nm) using an F-7000 fluorescence spectrophotometer, record the intensity at the maximum fluorescence emission wavelength of C QDs and CdTe QDs respectively, and calculate the ratio, denoted as F. C / F CdTe Using this ratio as the ordinate and glucose concentration as the abscissa, a standard working curve was plotted, yielding the linear regression equation y = 2.5016x + 6.3289, with a correlation coefficient R0. 2 =0.9993, linear range 0.1-20mM.

[0063] Selectivity test of the fluorescence sensing system: The fluorescence sensing system was reacted with 50 μL of solutions of glucose, maltose, lactose, urea, sucrose, and fructose of the same concentration for the same amount of time, and its fluorescence spectrum was measured under the same conditions. The F-value was calculated. C / F CdTe .

[0064] Figure 1 For the morphology and elemental composition characterization of the quantum dot@ZIF-8 composite material in Example 1, (A) is a transmission electron microscope (TEM) image of carbon quantum dots (CQDs); (B) is a TEM image of cadmium telluride quantum dots (CdTe QDs); (C) is a TEM image of the quantum dot@ZIF-8 composite material; (D)-(K) are TEM elemental distribution mapping diagrams of the quantum dot@ZIF-8 composite material. Figure 1It can be seen that both C QDs and CdTe QDs have uniform particle size and good dispersion, proving that both quantum dots were successfully prepared. The uniform distribution of the two quantum dot components in ZIF-8 can be observed in the quantum dot@ZIF-8 composite material, proving the successful preparation of the quantum dot@ZIF-8 composite structure.

[0065] Figure 2 The structure characterization of the quantum dot@ZIF-8 composite material in Example 1 is shown in (A), which is the X-ray diffraction (XRD) data of ZIF-8 and the quantum dot@ZIF-8 composite material, and (B) is the infrared absorption spectrum of ZIF-8 and the quantum dot@ZIF-8 composite material. It can be seen that the XRD and infrared spectrum data of ZIF-8 did not change significantly before and after the composite, which proves that the composite with quantum dots does not have a significant impact on the structural composition of ZIF-8. The composite material inherits the structural performance advantages of ZIF-8.

[0066] Figure 3 For the characterization of the quantum dot@ZIF-8 composite material in Example 1, (A) shows the zeta potential data before and after the quantum dots and ZIF-8 are combined, and (B) shows the fluorescence spectra before and after the quantum dots and ZIF-8 are combined. The inset shows photographs of the quantum dots, ZIF-8, and composite material under a 365nm UV lamp. It can be seen that the zeta potentials of individual C QDs and CdTe QDs are negative, while ZIF-8 is positive. The zeta potential of the composite material is positive, proving the successful combination of quantum dots and ZIF-8, and the quantum dot@ZIF-8 composite material was successfully prepared. From the fluorescence spectrum, it can be seen that individual C QDs have a fluorescence emission peak at 405nm, and blue fluorescence can be observed under a 365nm lamp. Individual CdTe... The quantum dots (QDs) exhibit a fluorescence emission peak at 620 nm and show red fluorescence under a 365 nm light. By combining these two types of quantum dots with non-fluorescent ZIF-8, a quantum dot@ZIF-8 composite material with both fluorescence emission wavelengths is obtained, exhibiting pinkish-purple fluorescence under a 365 nm light. This demonstrates the successful synthesis of a quantum dot@ZIF-8 composite material with dual-wavelength emission, which can be used to construct a visualized ratiometric fluorescence sensing system.

[0067] Figure 4 (A) shows the fluorescence signal response of the ratiometric fluorescence sensing system based on the quantum dot@ZIF-8 composite material of Example 1 to glucose samples of different concentrations; (B) shows the fluorescence intensity ratio (F) of C QDs and CdTe QDs at the maximum emission wavelength. C / F CdTeUsing F as the ordinate and glucose concentration as the abscissa, a standard working curve was plotted. The inset shows a photograph of the corresponding sample test system under a 365nm UV lamp. It can be seen that as the glucose concentration in the system increases, the red fluorescence signal attributed to CdTeQDs gradually weakens, while the blue fluorescence signal attributed to CQDs gradually strengthens. The system fluorescence signal (F) C / F CdTe It exhibits a good linear relationship with glucose concentration in the range of 0.1–20 mM, with a detection limit of 0.011 mM.

[0068] Figure 5 The effect of reaction temperature (A), reaction time (B), and enzyme concentration (C) on the fluorescence signal F of the system. C / F CdTe The illustration shows the corresponding sample test system under a 365nm UV lamp. It can be seen that the best analytical performance can be obtained by reacting at 55℃ for 75 min with 30U / mL glucose oxidase (GOx).

[0069] Figure 6 The figure shows the selectivity test results of the ratiometric fluorescence sensing system based on the quantum dot@ZIF-8 composite material in Example 1. The inset is a photograph of the corresponding sample test system under a 365nm ultraviolet lamp. It can be seen that the ratiometric fluorescence sensing system based on the quantum dot@ZIF-8 composite material has good selectivity and anti-interference ability for glucose detection.

[0070] The C QDs in Example 1 were diluted 500 times. 50 μL of the diluted C QDs solution was thoroughly mixed with 50 μL of water, 50 μL of glucose sample (different concentrations), 30 μL of GOx, and 170 μL of Tris-HCl buffer, and reacted at 55 °C for 75 min. The fluorescence color response of the system was observed with the naked eye under a 365 nm UV lamp, and photos were taken with a smartphone. The fluorescence emission spectrum (excitation wavelength 365 nm) was tested using an F-7000 fluorescence spectrophotometer. Figure 7 The inset shows the fluorescence signal response of the fluorescence sensing system based on carbon quantum dots (CQDs) in Example 1 to glucose samples of different concentrations. The image shows a photograph of the sample under a 365 nm UV lamp. It can be seen that the CQDs show almost no fluorescence signal response to glucose.

[0071] The CdTe QDs from Example 1 were prepared into a 1 mg / mL dispersion with water. 50 μL of this dispersion was mixed thoroughly with 50 μL of water, 50 μL of glucose sample (different concentrations), 30 μL of GOx, and 170 μL of Tris-HCl buffer, and reacted at 55 °C for 75 min. The fluorescence color response of the system was observed with the naked eye under a 365 nm UV lamp, and photos were taken with a smartphone. The fluorescence emission spectrum (excitation wavelength 365 nm) was measured using an F-7000 fluorescence spectrophotometer. Figure 8 Figure (A) shows the fluorescence signal response of the fluorescence sensing system using cadmium telluride quantum dots (CdTe QDs) alone to glucose samples of different concentrations. A standard working curve (B) was plotted with the fluorescence intensity at the maximum emission wavelength of the CdTe QDs as the ordinate and the logarithm of the glucose concentration as the abscissa. This demonstrates that the ratiometric signal response of the fluorescence system mainly originates from the signal changes of the CdTe QDs.

[0072] Preparation of ZIF-8 material: 300 mg of zinc acetate was dissolved in 5 mL of ultrapure water and labeled as solution one; 1.059 g of 2-methylimidazole and 1 mg of hexadecyltrimethylammonium bromide (CTAB) were dissolved in 5 mL of ultrapure water and labeled as solution two; solution one was poured into solution two and stirred at room temperature for 2 h. After the reaction was complete, the sample was collected by centrifugation, washed three times alternately with water and ethanol, dried under vacuum at 60 °C, and ground to obtain ZIF-8 solid powder. The solid powder was dispersed in water to form a dispersion of 1 mg / mL. 100 μL of this dispersion was mixed thoroughly with 50 μL of glucose sample (different concentrations), 30 μL of GOx, and 170 μL of Tris-HCl buffer and reacted at 55 °C for 75 min; the fluorescence color response of the system was observed with the naked eye under a 365 nm UV lamp and photographed with a smartphone; the fluorescence emission spectrum (excitation wavelength 365 nm) was measured using an F-7000 fluorescence spectrophotometer. The fluorescence signal response of this single ZIF-8 fluorescence sensing system to glucose samples of different concentrations is shown in the figure. Figure 9 It can be seen that ZIF-8 alone has almost no fluorescence signal and no obvious signal response to the addition of glucose.

[0073] Example 2

[0074] Same as Example 1, except that in step (2) when preparing cadmium telluride quantum dots, the reflux time in the oil bath at 105°C is 16h.

[0075] A sensor was fabricated using the quantum dot@ZIF-8 composite material prepared in this embodiment, following the same preparation method and performance testing method as in Example 1. Testing showed that the performance of the sensor prepared in this embodiment was not significantly different from that in Example 1.

[0076] Example 3

[0077] Same as Example 1, except that the mass-to-volume ratio of CdTe quantum dots to C QDs dispersion was 90 mg: 0.8 mL when preparing the quantum dot@ZIF-8 composite material.

[0078] The preparation and detection methods of the ratiometric fluorescence sensing system are the same as in Example 1, and the detection limit is 0.061 mM.

[0079] Comparative Example 1

[0080] Synthesis of cadmium telluride quantum dots (CdTe QDs) exhibiting green fluorescence emission: 118 mg (0.38 mmol) of cadmium nitrate tetrahydrate and 200 mg (0.68 mmol) of trisodium citrate were dissolved in 50 mL of ultrapure water and ultrasonically stirred. After dissolution, 55 μL of mercaptopropionic acid was added and mixed thoroughly, causing the solution to change from clear and transparent to milky white. Then, sodium hydroxide solution (0.1 M) was added to adjust the pH of the solution to 10.5, and the solution became clear. Subsequently, 22.2 mg (0.1 mmol) of sodium tellurite and 50 mg (0.9 mmol) of potassium borohydride were added, and the mixture was refluxed in an oil bath at 105 °C for 2 h. The reacted liquid was allowed to cool naturally to room temperature, precipitated with an equal volume of isopropanol, washed three times with isopropanol, and dried to obtain CdTe QDs powder exhibiting green fluorescence emission. Figure 10 ).

[0081] Comparative Example 2

[0082] Synthesis of cadmium telluride quantum dots (CdTe QDs) exhibiting orange-yellow fluorescence emission: 118 mg (0.38 mmol) of cadmium nitrate tetrahydrate and 200 mg (0.68 mmol) of trisodium citrate were dissolved in 50 mL of ultrapure water and ultrasonically stirred. After dissolution, 55 μL of mercaptopropionic acid was added and mixed thoroughly, causing the solution to change from clear and transparent to milky white. Then, sodium hydroxide solution (0.1 M) was added to adjust the pH of the solution to 10.5, and the solution became clear. Subsequently, 22.2 mg (0.1 mmol) of sodium tellurite and 50 mg (0.9 mmol) of potassium borohydride were added, and the mixture was refluxed in an oil bath at 105 °C for 6 h. The reacted liquid was allowed to cool naturally to room temperature, precipitated with an equal volume of isopropanol, washed three times with isopropanol, and dried to obtain CdTe QDs powder with orange-yellow fluorescence emission. Figure 10 ).

[0083] Comparative Example 3

[0084] Synthesis of cadmium telluride quantum dots (CdTe QDs) exhibiting orange fluorescence emission: 118 mg (0.38 mmol) of cadmium nitrate tetrahydrate and 200 mg (0.68 mmol) of trisodium citrate were dissolved in 50 mL of ultrapure water and ultrasonically stirred. After dissolution, 55 μL of mercaptopropionic acid was added and mixed thoroughly, causing the solution to change from clear and transparent to milky white. Then, sodium hydroxide solution (0.1 M) was added to adjust the pH of the solution to 10.5, and the solution became clear. Subsequently, 22.2 mg (0.1 mmol) of sodium tellurite and 50 mg (0.9 mmol) of potassium borohydride were added, and the mixture was refluxed in an oil bath at 105 °C for 8 h. The reacted liquid was naturally cooled to room temperature, precipitated with an equal volume of isopropanol, washed three times with isopropanol, and dried to obtain CdTe QDs powder exhibiting orange fluorescence emission. Figure 10 ).

[0085] Based on the above, this invention provides a quantum dot @ZIF-8 composite material, its preparation method, and its applications. This quantum dot @ZIF-8 composite material can be used to prepare ratiometric fluorescent sensing probes for the visual detection of glucose. This invention involves mixing CdTe quantum dots (CdTe QDs) with red fluorescence emission and carbon quantum dots (C QDs) with blue fluorescence emission in a specific ratio, followed by in-situ self-assembly growth of ZIF-8 to obtain a quantum dot @ZIF-8 composite material with dual fluorescence signal emission. The quantum dot @ZIF-8 nanocomposite material prepared by this method not only possesses the fluorescence properties of quantum dots but also largely retains the original structure and properties of ZIF-8, making it a simple and effective method for preparing composite materials with excellent fluorescence properties.

[0086] This composite material was used as a fluorescent probe to form a ratiometric fluorescence sensing system with glucose oxidase (GOx). The target analyte, glucose, is oxidized under GOx catalysis to produce hydrogen peroxide (H2O2), resulting in a red fluorescence signal (F) from the CdTe QDs. CdTe The fluorescence signal of CQDs (F) weakens, while the blue fluorescence signal of CQDs (F) decreases. C The ratio of the two (F) is enhanced. C / F CdTe The system exhibits a good linear relationship with glucose concentration. Furthermore, the fluorescence color of the system changes from pink to purple and then to blue under 365nm ultraviolet light irradiation. This phenomenon can be directly observed with the naked eye, thus enabling convenient and visual detection of glucose.

[0087] Therefore, the quantum dot@ZIF-8 composite material synthesized in this invention can be used as a high-performance ratiometric fluorescent probe to construct a convenient and efficient ratiometric fluorescence sensing method, effectively reducing interference caused by environmental changes and instrument fluctuations, and making the results stable and reliable.

[0088] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. Application of quantum dot@ZIF-8 composite material in glucose detection, characterized in that, The preparation method of the quantum dot@ZIF-8 composite material includes the following steps: mixing CdTe quantum dots with red fluorescence emission with carbon quantum dots with blue fluorescence emission, and then growing ZIF-8 in situ by self-assembly to obtain the quantum dot@ZIF-8 composite material. The ratiometric fluorescence sensing platform constructed based on the quantum dot@ZIF-8 composite material has a wavelength difference of 215 nm at the point of strongest emission. The synthesis method of the CdTe quantum dots with red fluorescence emission is as follows: Cadmium nitrate tetrahydrate and trisodium citrate are dissolved in water, mercaptopropionic acid is added, and then the pH is adjusted to alkaline by adding alkaline solution. Sodium tellurite and potassium borohydride are added, and the reaction is carried out under reflux at 105 °C for 12-16 h in an oil bath. After the reaction is completed, the mixture is naturally cooled to room temperature, precipitated with isopropanol, washed, and dried to obtain CdTe quantum dots with red fluorescence emission. The molar ratio of cadmium nitrate tetrahydrate, trisodium citrate, sodium tellurite, and potassium borohydride is 3.8:6.8:1:

9. The method for synthesizing the carbon quantum dots with blue fluorescence emission is as follows: citric acid and tris(hydroxymethyl)aminomethane are dissolved in water and subjected to a hydrothermal reaction at 200 °C for 6 h. After the hydrothermal reaction is completed, the mixture is taken out after natural cooling and filtered to obtain a dispersion containing carbon quantum dots with blue fluorescence emission. The molar ratio of citric acid to tris(hydroxymethyl)aminomethane is 1:

1. The method for in-situ self-assembly growth of ZIF-8 to obtain quantum dot@ZIF-8 composite material is as follows: Zinc acetate is dissolved in water and labeled as the first solution; 2-methylimidazole and hexadecyltrimethylammonium bromide are dissolved in water, and the dispersion containing carbon quantum dots with blue fluorescence emission and the CdTe quantum dots are added, ultrasonicated and then stirred, labeled as the second solution; the first solution is poured into the second solution, stirred evenly at room temperature, and after the reaction is completed, the precipitate is collected by centrifugation, washed, and dried to obtain the quantum dot@ZIF-8 composite material. The mass-to-volume ratio of CdTe quantum dots to the dispersion containing carbon quantum dots with blue fluorescence emission is (40-90) mg:0.8 mL, and the mass ratio of zinc acetate to 2-methylimidazole is 0.3:1.059.

Images