Application of zinc oxide quantum dot fluorescent sensor and detection of kaempferol

Abstract

The application belongs to the technical field of chemical analysis and detection, and discloses a zinc oxide quantum dot fluorescent sensor and application of the zinc oxide quantum dot fluorescent sensor in detection of kaempferol. The zinc oxide quantum dot fluorescent sensor is prepared by stirring zinc salt solution and lye uniformly, then adding amino silane and water to carry out sol-gel reaction to prepare a ZnO-QDs fluorescent probe solution; then, a substrate is immersed in the ZnO-QDs fluorescent probe solution to carry out incubation, and drying is carried out to obtain the zinc oxide quantum dot fluorescent sensor. S The zinc oxide quantum dot fluorescent sensor is applied to detection of kaempferol, can produce specific response with kaempferol, makes the fluorescence intensity of the ZnO-QD fluorescent probe gradually increase with the increase of the concentration of kaempferol, and can effectively exclude the interference of structural analogs such as quercetin and luteolin, so that the kaempferol in the sample can be accurately quantified; and the detection cost is low, the operation is convenient, the detection efficiency is high, the detection is green and safe, and the zinc oxide quantum dot fluorescent sensor is suitable for popularization and application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical analysis and detection, and particularly relates to a zinc oxide quantum dot fluorescent sensor and application of the zinc oxide quantum dot fluorescent sensor in detecting the content of kaempferol. BACKGROUND

[0002] Kaempferol is a common natural flavonoid, which is widely present in plants such as ginkgo, honeysuckle, chrysanthemum, green tea and grape. A large number of research results show that kaempferol has obvious antioxidant, anti-inflammatory, antibacterial, anticancer and antidiabetic activities, has potential application in the treatment of cardiovascular diseases, cancer, Parkinson's disease, rheumatoid arthritis and other diseases, and has been widely used in the pharmaceutical, food and cosmetic industries. Rapid detection of kaempferol in real samples has important practical significance.

[0003] Kaempferol exists in a complex system extracted from plants, usually in low content, and has many structural analogs such as quercetin and luteolin. Traditional detection methods for kaempferol usually include high-performance liquid chromatography, macroporous resin column chromatography and supercritical extraction. However, the detection involves high cost, long detection time, complex operation and requires professional personnel, which is not conducive to popularization. In addition, in the plant extract of kaempferol, there are usually structural analogs such as quercetin and luteolin, which interfere with the detection of kaempferol, further affecting the detection result of kaempferol. SUMMARY

[0004] The main purpose of the present application is to provide a new type of nano-effect fluorescent sensor and a method for high-sensitivity detection of kaempferol, which can realize rapid and accurate identification of kaempferol in complex matrices such as green tea, chrysanthemum, honeysuckle and flos lonicerae japonicae; and the preparation and detection method involved is simple, easy to operate, and suitable for popularization and application.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] A zinc oxide quantum dot fluorescent sensor, the preparation method thereof comprises the following steps:

[0007] The zinc salt solution and the alkali solution are stirred uniformly, then amino silane and water are added, and a sol-gel reaction is carried out, microfiltration is performed, and a ZnO-QDs fluorescent probe solution is obtained. The solution shows green fluorescence under the excitation of ultraviolet light, which indicates that zinc oxide particles are formed;

[0008] The substrate is incubated in the ZnO-QDs fluorescent probe solution, the probe solution is attached on the substrate to obtain a fluorescent substrate, and the zinc oxide quantum dot fluorescent sensor is obtained after drying.

[0009] In the above scheme, the zinc salt can be zinc acetate, zinc chloride or zinc nitrate, etc.; the solvent used in the zinc salt solution is an alcohol solvent, and specifically, methanol or ethanol, etc. can be selected.

[0010] In the above scheme, the base introduced in the lye is potassium hydroxide or sodium hydroxide, etc., and the solvent used is an alcohol solvent, and specifically, methanol or ethanol, etc. can be selected.

[0011] In the above scheme, the concentration of anhydrous zinc acetate in the zinc salt solution is 0.08-0.12 mol / L; the concentration of the base in the lye is 0.8-1.2 mol / L.

[0012] In the above scheme, the molar ratio of the introduced zinc salt to the base is 3.2-5:1.

[0013] In the above scheme, the amino silane can be 3-aminopropyl triethoxysilane (APTES), etc.

[0014] In the above scheme, the molar ratio of the introduced zinc salt to the amino silane is 1:0.5-2.

[0015] In the above scheme, the sol-gel reaction time is 0.5-2 h.

[0016] In the above scheme, the substrate can be paper-based, etc., and specifically, filter paper, etc. can be selected.

[0017] In the above scheme, the incubation time is 10-24 h.

[0018] In the above scheme, the drying treatment step uses room temperature, and the time is 3-10 min.

[0019] The zinc oxide quantum dot fluorescent sensor prepared according to the above scheme comprises zinc oxide fluorescent quantum dot particles distributed on a substrate.

[0020] The above zinc oxide quantum dot fluorescent sensor is applied to detect the content of kaempferol in a solution, and the specific steps include:

[0021] 1) Different standard concentrations of kaempferol solution are added dropwise to the zinc oxide quantum dot fluorescent substrate sensor, and under the irradiation of an ultraviolet lamp, the fluorescent image of the zinc oxide quantum dot fluorescent paper-based sensor after adding different kaempferol solutions is obtained (by means of shooting, etc.), and the RGB value of the fluorescent image is extracted;

[0022] 2) According to the corresponding relationship between the obtained RGB value and the standard concentration of kaempferol, a standard color chart based on the RGB value and the concentration of kaempferol is constructed;

[0023] 3) according to the steps of step 1), the fluorescence image and the corresponding RGB value of the zinc oxide quantum dot fluorescent paper-based sensor obtained after adding the solution to be detected are compared with the standard color chart to realize the concentration determination of the solution to be detected.

[0024] In the above scheme, the standard concentration is taken from 0 to 500 μg / mL.

[0025] In the above scheme, the fluorescence image is obtained after adding the kaempferol solution for 10 s.

[0026] Further, the fluorescence image is obtained after adding the kaempferol solution for 10-30 s.

[0027] In the above scheme, the wavelength of the ultraviolet lamp irradiation is 350-380 nm, preferably 365 nm.

[0028] Preferably, in order to ensure the detection accuracy, the kaempferol solution is added to the zinc oxide quantum dot fluorescent paper-based sensor at least three different positions in step 1) and step 3).

[0029] Further, the amount of kaempferol solution added each time in step 1) and step 3) is 6-10 μL, and the single drop amount is the same.

[0030] The present application provides a zinc oxide quantum dot fluorescent sensor for detecting the content of kaempferol in a solution substrate for the first time. After adding a solution containing kaempferol to the surface, the zinc oxide quantum dots can produce a specific response with kaempferol, induce fluorescence aggregation effect, and make ZnO-QD S The fluorescence intensity of the fluorescent probe gradually increases with the increase of the concentration of kaempferol, and the interference of structural similar substances such as quercetin and luteolin can be effectively excluded; the fluorescence image is taken under the ultraviolet lamp, the RGB value is extracted, the standard color chart based on the RGB value is constructed according to the corresponding relationship between the RGB value and the standard concentration, and the accurate quantification of kaempferol in the sample is realized.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] 1) The zinc oxide quantum dot fluorescent substrate sensor prepared by the present application has excellent specific response to kaempferol. The fluorescence photo under the ultraviolet lamp irradiation condition is directly obtained, then the RGB value is extracted to establish the standard color chart, and the rapid, high sensitivity and high accuracy detection of the concentration of kaempferol can be realized;

[0033] 2) The ZnO quantum dot fluorescent substrate sensor constructed by the present application has the advantages of lightness, portability, degradability, etc., and has the advantages of small sample amount, convenient sample addition, and can realize the effect of detecting multiple samples at a time, greatly shortening the detection time, and providing a new idea for the rapid and efficient detection of kaempferol;

[0034] 3) The detection method of the present application is low in detection cost, convenient to operate, fast, green and safe, and does not require large instruments, and is particularly suitable for food quality control of green tea, chrysanthemum, honeysuckle and the like, and is suitable for popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 Fluorescence image obtained by taking a photo of kaempferol samples of different concentrations obtained in Example 1 of the present application.

[0036] Figure 2 Fluorescence image obtained by taking a photo of different types of scented tea samples in Example 2 of the present application.

[0037] Figure 3 Visual detection standard color card of kaempferol of different concentrations in Example 2 of the present application.

[0038] Figure 4 RGB values extracted from the ZnO quantum dot fluorescence paper-based sensor for detecting kaempferol designed in Example 1 of the present application, combined with the chemometrics PLSR algorithm to fit the actual concentration and predicted concentration correlation curve of kaempferol.

[0039] Figure 5 RGB values extracted from the ZnO quantum dot fluorescence paper-based sensor for detecting kaempferol designed in Example 2 of the present application, combined with the chemometrics PLSR algorithm to fit the actual concentration and predicted concentration correlation curve of kaempferol in chrysanthemum, honeysuckle and flos lonicerae samples.

[0040] Figure 6 Detection of the content of kaempferol in chrysanthemum, honeysuckle and flos lonicerae by visual detection standard color card.

[0041] Figure 7 Results of the ZnO quantum dot fluorescence sensor obtained in Example 1 in response to kaempferol, quercetin and luteolin of the same concentration, respectively.

[0042] Figure 8 Scanning electron microscope image of the ZnO quantum dot fluorescence sensor obtained in Example 1 after reaction with kaempferol. DETAILED DESCRIPTION

[0043] The applicant will make a further detailed description of the present application in combination with specific examples, so that those skilled in the art can more clearly understand the present application. However, the following content should not be understood as limiting the scope of protection claimed by the claims of the present application.

[0044] The chemical reagents and solvents used in the examples are all of analytical purity. The stirring is carried out by a magnetic stirrer.

[0045] Example 1

[0046] A zinc oxide quantum dot fluorescent sensor and a method for detecting the content of kaempferol by using the same, the preparation and detection method comprising the following steps:

[0047] Zinc oxide quantum dot fluorescent sensor

[0048] (1) Synthesis of ZnO-QDs solution:

[0049] 80ml of zinc acetate methanol solution (zinc acetate is ultrasonically dispersed in methanol) with a concentration of 0.1mol / L and 60ml of potassium hydroxide methanol solution (potassium hydroxide is ultrasonically dispersed in methanol) with a concentration of 1.0mol / L are mixed uniformly (stirring for 2h), then 1mL of 3-aminopropyl triethoxysilane (APTES) and 2mL of pure water are added, and the sol-gel reaction is carried out for 1h; the obtained solution is micro-filtered by using a microporous filter membrane with a pore size of 0.22μm to obtain a ZnO-QDs fluorescent probe solution, which shows green fluorescence under the excitation of ultraviolet light, and finally stored in a refrigerator at 4℃ for standby;

[0050] (2) Construction of paper-based sensor:

[0051] The filter paper is incubated in the ZnO-QDs fluorescent probe solution for 12h, the probe solution is attached on the paper-based to obtain a fluorescent substrate, and the paper-based is naturally dried after being taken out; finally, the dried paper-based is cut into small round pieces with a size of 3mm×3mm for detection, and a ZnO-QDs fluorescent substrate sensor is obtained.

[0052] Detection of kaempferol content

[0053] 12 series of concentration gradients of kaempferol standard solution (6μL) with concentrations of 0, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, 300 and 500μg / mL are respectively dropped on the prepared ZnO-QDs fluorescent paper-based sensor to obtain detection test paper containing the sample to be tested; then the detection test paper of the sample to be tested is placed in a portable ultraviolet dark box for 10-30s, and under the irradiation of 365nm ultraviolet light, a fluorescence image is obtained by taking a photo by using a smart phone; the RGB value of the collected fluorescence image is extracted by using Photoshop software, and a standard color card based on the RGB value is constructed according to the corresponding relationship between the RGB value and the standard concentration of kaempferol;

[0054] The dropping and ultraviolet irradiation steps are repeated, the fluorescence photo of the ZnO-QDs fluorescent paper-based sensor after introducing 6μL of kaempferol solution with unknown concentration is determined, and it is compared with the standard color card to obtain the concentration value of the kaempferol solution.

[0055] Example 2

[0056] A method for detecting the content of kaempferol in flower tea (Honeysuckle, Honeysuckle, Hangzhou White Chrysanthemum) by using the zinc oxide quantum dot fluorescent sensor of embodiment 1, specifically comprising the following steps:

[0057] (1) Flower tea extraction

[0058] Honeysuckle pre-extraction: 1.00g of honeysuckle was weighed into a 15mL centrifuge tube, 10mL of 70% methanol water (V:V) was added, and after vortex mixing, it was extracted at 37℃ for 30min, then centrifuged at 8000r / min for 10min at room temperature, and the supernatant was filtered through a 0.22μm microporous filter membrane to obtain the honeysuckle extract;

[0059] Honeysuckle extraction: 1.00g of honeysuckle was weighed into a 15mL centrifuge tube, 10mL of 70% methanol water (V:V) was added, and after vortex mixing, it was extracted at 37℃ for 30min, then centrifuged at 8000r / min for 10min at room temperature, and the supernatant was filtered through a 0.22μm microporous filter membrane to obtain the honeysuckle extract;

[0060] Hangzhou White Chrysanthemum pretreatment process: 0.02g of Hangzhou White Chrysanthemum was weighed into a 15mL centrifuge tube, 10mL of 70% methanol water (V:V) was added, and after vortex mixing, it was extracted at 40℃ for 40min, then centrifuged at 8000r / min for 10min at room temperature, and the supernatant was filtered through a 0.22μm microporous filter membrane to obtain the chrysanthemum extract;

[0061] (2) Detection of kaempferol in flower tea:

[0062] A pipette was used to transfer 6μL of different groups of flower tea sample solutions to be detected onto the obtained zinc oxide quantum dot fluorescent sensor (preparation method same as embodiment 1), and the fluorescence photos after reaction (see Figure 2 ) were obtained, which were compared with the standard color card (see Figure 3 ) to obtain the concentration of kaempferol in the flower tea sample, and the specific comparison results are shown in Figure 5 .

[0063] Figure 6 The results of detecting the content of kaempferol in Hangzhou White Chrysanthemum, Honeysuckle and Honeysuckle by visual detection standard color card.

[0064] Figure 7 The results of the response of the zinc oxide quantum dot fluorescent sensor obtained in embodiment 1 to kaempferol and quercetin of the same concentration, respectively, can be seen that the zinc oxide quantum dot fluorescent sensor obtained in the present application can produce specific response with kaempferol, and quercetin and luteolin have basically no fluorescence enhancement effect.

[0065] Figure 8The scanning electron microscope image of the zinc oxide quantum dot fluorescent sensor obtained in Example 1 after reacting with kaempferol can be seen that a large amount of aggregation of zinc oxide quantum dots will be caused after the reaction.

[0066] Comparative Example 1

[0067] A method for detecting the content of kaempferol, the preparation and detection method are substantially the same as those of Example 1, the difference is that TGA-CdTe quantum dots, AgInS2 quantum dots, ZnS quantum dots, carbon dots and the like are respectively used instead of the zinc oxide quantum dots described in Example 1; the results show that the constructed fluorescent sensor cannot effectively exclude the interference of structural analogues such as quercetin and luteolin, and cannot realize the accurate measurement of the content of kaempferol.

[0068] The present application is not limited to the above-mentioned embodiments, and for those skilled in the art, a number of improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements are also considered to be within the scope of protection of the present application. The contents not described in detail in the specification belong to the prior art known to those skilled in the art.

Claims

1. A method for detecting the content of kaempferol in a solution by using a zinc oxide quantum dot fluorescent sensor, characterized in that, The specific steps include: 1) different standard concentrations of kaempferol solution are added dropwise to the zinc oxide quantum dot fluorescent substrate sensor, and under the irradiation of ultraviolet lamp, the fluorescence image of the zinc oxide quantum dot fluorescent paper-based sensor after adding different kaempferol solutions is obtained, and the RGB value of the fluorescence image is extracted; 2) according to the corresponding relationship between the obtained RGB value and the standard concentration of kaempferol, a standard color chart based on the RGB value and the concentration of kaempferol is constructed; 3) according to the steps described in step 1), the fluorescence image of the zinc oxide quantum dot fluorescent paper-based sensor obtained after adding the kaempferol solution to be detected and the corresponding RGB value are obtained, which are compared with the standard color chart to realize the concentration determination of the kaempferol solution to be detected; The preparation method of the zinc oxide quantum dot fluorescent sensor includes the following steps: 1) the zinc salt solution and the alkali solution are stirred uniformly, then the amino silane and water are added, and a sol-gel reaction is carried out, microfiltration is carried out, and a ZnO-QDs fluorescent probe solution is obtained; 2) the substrate is immersed in the ZnO-QDs fluorescent probe solution for incubation, and then dried to obtain the zinc oxide quantum dot fluorescent sensor; The amino silane is 3-aminopropyl triethoxysilane; The molar ratio of introduced zinc salt to alkali is 3.2-5:1; the molar ratio of introduced zinc salt to amino silane is 1:0.5-2.

2. The method of claim 1, wherein, The zinc salt is zinc acetate, zinc chloride or zinc nitrate; the solvent used for the zinc salt solution is an alcohol solvent.

3. The method of claim 1, wherein, The alkali introduced in the alkali solution is potassium hydroxide or sodium hydroxide, and an alcohol solvent is used.

4. The method of claim 1, wherein, The sol-gel reaction time is 0.5-2h.

5. The method of claim 1, wherein, The incubation time is 10-24h.

6. The method of claim 1, wherein, The standard concentration is taken from 0-500μg / mL.

7. The method of claim 1, wherein, The wavelength of the ultraviolet lamp irradiation is 350-380nm.

Images