ZnO QDs (at) ZIF-8 quantum dot fluorescent probe as well as preparation method and application thereof

Abstract

The invention discloses a ZnO QDs (at) ZIF-8 quantum dot fluorescent probe and a preparation method and application thereof.The preparation method comprises the steps that zinc acetate dihydrate is weighed according to the mass-to-volume ratio of 1: 100 g / mL, added into ethyl alcohol and subjected to ultrasonic treatment, and a solution A is obtained; according to the molar ratio of zinc acetate dihydrate to potassium hydroxide being 1: (1-2), potassium hydroxide is added into ethanol with the same volume and subjected to ultrasonic treatment, and a solution B is obtained; mixing the solution A and the solution B, uniformly stirring and standing to obtain a mixed solution; adding dimethylimidazole into the mixed solution in a stirring state, uniformly stirring, centrifuging, and washing to obtain the ZnO QDs (at) ZIF-8 quantum dot fluorescent probe. The molar ratio of the dimethylimidazole to the potassium hydroxide is (0.25-0.75): 1; the preparation process is simple and quick, the preparation cost can be reduced, a green low-pollution reagent is adopted in the preparation process, environment friendliness is achieved, the product sensitivity is high, and the response time is short.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, and relates to a ZnO QDs@ZIF-8 quantum dot fluorescence probe, and specifically relates to a ZnO QDs@ZIF-8 quantum dot fluorescence probe, a preparation method thereof, and an application thereof. Background Art

[0002] Copper ions (Cu 2+ ) play an irreplaceable role in many physiological processes, including the regulation of hemoglobin level, neuronal function, mitochondrial respiration, and cell metabolism. However, excessive intake of Cu 2+ will lead to protein denaturation and pathogenic states, and long-term exposure to high concentrations of Cu 2+ can cause neurodegenerative diseases such as Parkinson's disease, Menkes syndrome, Wilson's syndrome, and Alzheimer's disease. According to the recommendations of the World Health Organization, the concentration of Cu 2+ in drinking water should not exceed 1.3 mg / L (about 20 μM). Traditional methods for detecting copper ions include atomic absorption spectroscopy, gas chromatography-mass spectrometry (GC-MS), and inductively coupled plasma mass spectrometry (ICP-MS), but these require large and expensive instruments, increasing the cost and complexity of detection. Therefore, it is meaningful to develop a low-cost and simple-to-prepare fluorescence probe for rapid detection of copper ions.

[0003] ZIF-8 is a zeolitic imidazolate framework material. Due to the adsorption characteristics of ZIF-8 for cations, the adsorption of Cu 2+ is achieved through the complexation of its imidazole groups with Cu 2+ . The ZnO QDs@ZIF-8 quantum dot material is suitable for applications in fields such as water quality and food due to its non-toxic, environmentally friendly, easy availability of raw materials for preparation, and ability to be stored and detected at room temperature. However, currently, the mainstream ZnO QDs@ZIF-8 quantum dot materials are mostly prepared by methods such as sol-gel method, hydrothermal method, and thermal injection method. These methods have high energy consumption and long preparation time, which undoubtedly increases the cost of the material. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a ZnO QDs@ZIF-8 quantum dot fluorescence probe with rapid preparation and low cost, a preparation method thereof, and an application thereof. The probe has high sensitivity, short response time, and a simple, fast, and environmentally friendly preparation process.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions to achieve:

[0006] A preparation method of a ZnO QDs@ZIF-8 quantum dot fluorescence probe, comprising the following steps:

[0007] Step 1: Weigh zinc acetate dihydrate according to the mass-volume ratio of 1:100 g / mL, add it to ethanol, and perform ultrasonic treatment for 2 - 4 min to obtain solution A;

[0008] According to the molar ratio of zinc acetate dihydrate to potassium hydroxide of 1:(1 - 2), add potassium hydroxide to ethanol with the same volume as solution A and perform ultrasonic treatment for 2 - 4 min to obtain solution B;

[0009] Subsequently, mix solution A and solution B, stir evenly, and let it stand for 1 - 3 min to obtain a mixed solution;

[0010] Step 2: Add dimethylimidazole to the mixed solution prepared in Step 1 under stirring and continue stirring for 1 - 3 min, then perform centrifugation and washing to obtain the ZnO QDs@ZIF-8 quantum dot fluorescence probe;

[0011] Among them, the molar ratio of dimethylimidazole to potassium hydroxide is (0.25 - 0.75):1.

[0012] The present invention also has the following technical features:

[0013] Preferably, the ultrasonic power of the ultrasonic treatment in Step 1 is 300 - 500 W.

[0014] Preferably, the stirring in Step 1 and Step 2 is carried out using a magnetic stirrer at a rotation speed of 250 r / min.

[0015] Preferably, the centrifugation speed in Step 2 is 8000 r / min, and the centrifugation time is 3 - 5 min.

[0016] Preferably, the washing in Step 2 is carried out with ethanol for 3 - 5 times.

[0017] The present invention also protects a ZnO QDs@ZIF-8 quantum dot fluorescence probe prepared by the method as described above and its application in the detection of copper ions. The application method includes the following steps:

[0018] Step 1: Prepare a solution of the ZnO QDs@ZIF-8 quantum dot fluorescence probe with a concentration of 0.25 - 0.5 mg / mL using ethanol;

[0019] Step 2: Mix the solution prepared in Step 1 with the solution to be detected in an equal volume ratio and then perform spectral detection.

[0020] Compared with the prior art, the present invention has the following technical effects:

[0021] The present invention prepares a ZnO QDs@ZIF-8 quantum dot fluorescence probe by ultrasonic chemical method, shortening the reaction time to within 1 h. The preparation process is simple and fast, the raw materials for preparation are easy to obtain, which can greatly reduce the preparation cost. The preparation process uses green and low-pollution reagents, which is environmentally friendly;

[0022] The ZnO QDs@ZIF-8 quantum dot fluorescence probe prepared by the present invention has a good detection limit (LOD = 74 nM), which is lower than 20 μM proposed by the World Health Organization. And when the copper ion concentration is 20 μM, obvious fluorescence quenching can be observed with the naked eye. It has high sensitivity, short response time, and the material itself is non-toxic. It can be stored and detected at room temperature, and is suitable for the detection in the fields of water quality, food, etc. Description of the Drawings

[0023] Figure 1 It is the fluorescence change diagram of the ZnO QDs@ZIF-8 quantum dot fluorescence probe prepared in Examples 1 to 6 when adding copper ions with different concentrations;

[0024] Figure 2 It is the XRD diagram of the ZnO QDs@ZIF-8 quantum dot fluorescence probe prepared in Examples 1 to 6;

[0025] Figure 3 It is the ultraviolet-visible light spectrum diagram of the ZnO QDs@ZIF-8 quantum dot fluorescence probe prepared in Examples 1 to 6;

[0026] Figure 4 It is the ultraviolet-visible light Tauc diagram of the ZnO QDs@ZIF-8 quantum dot fluorescence probe prepared in Examples 1 to 6;

[0027] Figure 5 It is the fluorescence emission spectrum change diagram of the ZnO QDs@ZIF-8 quantum dot fluorescence probe prepared in Example 1 under the change of 0-15 μM copper ions;

[0028] Figure 6 It is the linear relationship diagram between (F0-F) / F0 and the copper ion concentration of the ZnO QDs@ZIF-8 quantum dot fluorescence probe prepared in Example 1 under the change of 0-15 μM copper ions;

[0029] Figure 7 It is the selectivity and anti-interference diagram of the ZnO QDs@ZIF-8 quantum dot fluorescence probe prepared in Example 1 in different ionic solutions;

[0030] Figure 8 It is the fluorescence diagram of different ionic solutions of the ZnO QDs@ZIF-8 quantum dot fluorescence probe prepared in Example 1 under the irradiation of a 295 nm ultraviolet lamp. Detailed Embodiments

[0031] The following further elaborates on the specific content of the present invention in conjunction with embodiments.

[0032] In the following embodiments, the purity of zinc acetate dihydrate used is greater than 99%, the purity of potassium hydroxide is greater than 85%, the purity of ethanol is greater than 99.7%, and the purity of dimethylimidazole is greater than 98%.

[0033] Example 1

[0034] This example provides a preparation method for a ZnO QDs@ZIF-8 quantum dot fluorescence probe, including the following steps:

[0035] Step 1: Weigh zinc acetate dihydrate according to a mass-to-volume ratio of 1:100 g / mL and add it to ethanol, then ultrasonically treat it at a power of 300 W for 3 min to obtain solution A;

[0036] According to a molar ratio of zinc acetate dihydrate to potassium hydroxide of 1:2, add potassium hydroxide to ethanol with the same volume as solution A and ultrasonically treat it at a power of 300 W for 3 min to obtain solution B;

[0037] Subsequently, mix solution A and solution B, stir at a rotation speed of 250 r / min for 1 min until uniform, and then let it stand for 1 min to obtain a mixed solution;

[0038] Step 2: Add dimethylimidazole to the mixed solution prepared in Step 1 under stirring and continuously stir at a rotation speed of 250 r / min for 1 min, then perform centrifugation at a rotation speed of 8000 r / min for 3 min, and then wash it with ethanol 3 times to obtain the ZnO QDs@ZIF-8 quantum dot fluorescence probe;

[0039] Among them, the molar ratio of dimethylimidazole to potassium hydroxide is 1.5:2.

[0040] Example 2

[0041] Example 2 is basically the same as Example 1, except that the molar ratios of zinc acetate dihydrate, potassium hydroxide, and dimethylimidazole are 1:2:1 in sequence.

[0042] Example 3

[0043] Example 3 is basically the same as Example 1, except that the molar ratios of zinc acetate dihydrate, potassium hydroxide, and dimethylimidazole are 1:2:0.5 in sequence.

[0044] Example 4

[0045] Example 4 is basically the same as Example 1, except that the molar ratios of zinc acetate dihydrate, potassium hydroxide, and dimethylimidazole are 1:1.5:1 in sequence.

[0046] Example 5

[0047] Example 5 is basically the same as Example 1, except that the molar ratios of zinc acetate dihydrate, potassium hydroxide, and dimethylimidazole are 1:1.5:0.5 in sequence.

[0048] Example 6

[0049] Example 6 is basically the same as Example 1, except that the molar ratios of zinc acetate dihydrate, potassium hydroxide, and dimethylimidazole are 1:1:0.5 in sequence.

[0050] Example 7

[0051] This example provides a preparation method of ZnO QDs@ZIF-8 quantum dot fluorescence probe, including the following steps:

[0052] Step 1: Weigh zinc acetate dihydrate in an ethanol solution at a mass-to-volume ratio of 1:100 g / mL and ultrasonically treat it for 2 min at a power of 400 W to obtain solution A;

[0053] Disperse potassium hydroxide in an equal volume of ethanol solution at a molar ratio of zinc acetate dihydrate to potassium hydroxide of 1:2 and ultrasonically treat it for 4 min at a power of 400 W to obtain solution B;

[0054] Subsequently, mix solution A and solution B, stir at a rotation speed of 250 r / min for 3 min until uniform, and let it stand for 3 min to obtain a mixed solution;

[0055] Step 2: Add dimethylimidazole to the mixed solution prepared in Step 1 under stirring and continuously stir for 3 min at a rotation speed of 250 r / min, then centrifuge at a rotation speed of 8000 r / min for 5 min, and then wash it 5 times with ethanol to obtain the ZnO QDs@ZIF-8 quantum dot fluorescence probe;

[0056] Among them, the molar ratio of dimethylimidazole to potassium hydroxide is 1:2.

[0057] Example 8

[0058] This example provides a preparation method of ZnO QDs@ZIF-8 quantum dot fluorescence probe, including the following steps:

[0059] Step 1: Disperse zinc acetate dihydrate in ethanol at a mass-to-volume ratio of 1:100 g / mL and ultrasonically treat it for 4 min at a power of 500 W to obtain solution A;

[0060] Disperse potassium hydroxide in ethanol of equal volume with a molar ratio of zinc acetate dihydrate to potassium hydroxide of 1:2 and ultrasonically treat it at a power of 500 W for 2 min to obtain solution B;

[0061] Subsequently, mix solution A and solution B, stir at a rotation speed of 250 r / min for 2 min until homogeneous, and let it stand for 2 min to obtain a mixed solution;

[0062] Step 2: Add dimethylimidazole to the mixed solution prepared in Step 1 under stirring and continuously stir for 2 min at a rotation speed of 250 r / min, then perform centrifugation at a centrifugation speed of 8000 r / min for 4 min, and then wash it 4 times with ethanol to obtain the ZnO QDs@ZIF-8 quantum dot fluorescence probe;

[0063] Among them, the molar ratio of dimethylimidazole to potassium hydroxide is 0.5:1.

[0064] Test and characterize the ZnO QDs@ZIF-8 fluorescence probe.

[0065] Figure 1 It is the fluorescence change diagram of the ZnO QDs@ZIF-8 quantum dot fluorescence probes prepared in Examples 1 to 6 when adding copper ions with different concentrations. Compared with other ratios, the sample with a ratio of 1:2:1.5 has a lower fluorescence intensity when the copper ion concentration is low. The ZnO QDs@ZIF-8 synthesized at this ratio has a higher sensitivity to Cu 2+ .

[0066] Figure 2 It is the XRD pattern of the ZnO QDs@ZIF-8 quantum dot fluorescence probes prepared in Examples 1 to 6. The X-ray diffraction pattern shows that the characteristic peaks of ZnO QDs@ZIF-8 are similar to those of ZIF-8, and its characteristic peaks appear at about 7.3°, 10.4°, 12.7° and 18.0° respectively, corresponding to the (110), (200), (211) and (222) crystal planes of ZIF-8. When the ratio of 2-mIm to KOH is low (for example, the molar ratio is 1:2:0.5 and 1:1.5:0.5), the crystallization of ZIF-8 is poor at this time and a broad peak will appear in the range of 30° to 40°. However, at high molar ratios (2-mIm:KOH≥0.5, such as 1:2:1.5, 1:1.5:1, 1:1:0.5), a ZIF-8 structure with better crystallization is shown. Therefore, on the premise of controlling the same ratio of ZnAc to KOH, the higher the addition amount of 2-mIm (in the range of 2-mIm:KOH = 0.25 to 0.75), the better the crystallization degree of ZnO QDs@ZIF-8. Due to the electron-donating property of the tertiary amine group in ZIF-8, it will react with Cu 2+Complexation occurs to improve the adsorption capacity of ZnO QDs@ZIF-8 for Cu 2+ , so ZnO QDs@ZIF-8 with good crystallinity has higher sensitivity to copper ions. Therefore, it can be seen from Figure 2 that the sensitivity of 1:2:1.5 is higher than that of 1:2:1 and higher than that of 1:2:0.5, and the sensitivity of 1:1.5:1 is higher than that of 1:1.5:0.5.

[0067] Figure 3 are the UV-visible spectra of the ZnO QDs@ZIF-8 quantum dot fluorescence probes prepared in Examples 1 to 6, which reflect the relationship between wavelength and absorbance of ZnAc:KOH:2-mIm at different molar ratios. The absorption of ZnO QDs@ZIF-8 occurs in the wavelength range of 290 - 350 nm, and the absorbance gradually decreases with the increase of the 2-mIm:KOH ratio. The band gap of a direct bandgap semiconductor can be obtained from the relationship diagram of (αhν) 2 and hν. As Figure 4 shows, when the molar ratio of 2-mIm exceeds 0.5, the band gap E g is between 3.4 and 3.6 eV. When the molar ratio of 2-mIm is equal to 0.5, the band gap is between 3.7 - 3.8 eV. The decrease in the band gap is due to the combination of ZnO QDs and ZIF-8.

[0068] Take 1 mL of the quantum dot probe solution with a concentration of 0.25 mg / mL prepared in Example 1 and mix it with 1 mL of aqueous solutions of copper ions with different concentrations. The copper ion concentration increases from 0 μM to 15 μM, and its fluorescence emission spectrum is tested. The change in the fluorescence emission spectrum is as Figure 5 shows. The excitation wavelength of ZnO QDs@ZIF-8 is 545 nm, and the fluorescence intensity gradually decreases with the increase of the copper ion concentration. The relationship diagram between (F0 - F) / F0 and the copper ion concentration in ZnO QDs@ZIF-8 is linearly fitted. The linear relationship is as Figure 6 shows. The obtained equation is y = 0.30463x + 0.00481, and R 2 = 0.99944. The LOD = 74 nM can be obtained by calculating 3σ / k.

[0069] Take 1 mL of the quantum dot probe solution with a concentration of 0.25 mg / mL prepared in Example 1 and perform fluorescence emission spectrum tests on 1 mL of aqueous solutions of different ions with a concentration of 20 μM. Among them, the cations are chloride salts, namely Ni 2+ , Mg 2+ , Cd 3+ , Ba 2+ , Al 3+ , K + , Fe3+ 、 Cu 2+ 、 Na + , where the anions are sodium salts, which are Cl - 、 CO3 2- 、 HCO3 - 、 NO3 - 、 SO4 2- 、 Ac - . The results are as Figure 7 shown. The green bar chart is the selectivity test result of ZnO QDs@ZIF-8. The fluorescence intensity in the solution with copper ions present is 7.4% of the fluorescence intensity of the blank group, showing obvious fluorescence quenching. For the quenching by the remaining ions, it is greater than that by copper ions. Therefore, ZnO QDs@ZIF-8 has good selectivity. The red bar chart is the anti-interference test result of ZnO QDs@ZIF-8. In the presence of the remaining ions, copper ions can obviously cause fluorescence quenching. Therefore, ZnO QDs@ZIF-8 has good anti-interference ability.

[0070] Figure 8 is the fluorescence image of the ZnO QDs@ZIF-8 quantum dot fluorescence probe prepared in Example 1 under the irradiation of a 295 nm ultraviolet lamp in different ionic solutions. Obvious fluorescence quenching occurred in the solution containing copper ions.

[0071] It should be noted that: The above examples are only used to illustrate the technical solutions of the present invention, rather than to limit it; Without departing from the concept of the present invention, the deductions or substitutions made by those skilled in the art all fall within the protection scope of the present invention.

Claims

1. A method for preparing a ZnO QDs@ZIF-8 quantum dot fluorescent probe, characterized in that: The following steps are involved: Step 1, weigh zinc acetate dihydrate at a mass volume ratio of 1:100 g / mL, add it to ethanol and ultrasonicate for 2 to 4 minutes to obtain solution A; According to the molar ratio of zinc acetate dihydrate to potassium hydroxide being 1:(1-2), potassium hydroxide is added to ethanol having an equal volume to solution A and ultrasonically treated for 2-4 minutes to obtain solution B; Then, solution A and solution B are mixed, stirred evenly and allowed to stand for 1 to 3 minutes to obtain a mixed solution; Step 2: Add dimethylimidazole to the mixed solution prepared in step 1 under stirring and continue stirring for 1 to 3 minutes, then centrifuge and wash to obtain a ZnO QDs@ZIF-8 quantum dot fluorescent probe; Wherein, the molar ratio of dimethylimidazole to potassium hydroxide is (0.25-0.75):

1.

2. The method for preparing the ZnO QDs@ZIF-8 quantum dot fluorescent probe according to claim 1, characterized in that: The ultrasonic power of the ultrasonic treatment described in step 1 is 300-500W.

3. The method for preparing the ZnO QDs@ZIF-8 quantum dot fluorescent probe according to claim 1, characterized in that: The stirring in step 1 and step 2 is carried out by using a magnetic stirrer at a speed of 250 r / min.

4. The method for preparing the ZnO QDs@ZIF-8 quantum dot fluorescent probe according to claim 1, characterized in that: The centrifugal speed described in step 2 is 8000r / min, and the centrifugal time is 3 to 5min.

5. The method for preparing the ZnO QDs@ZIF-8 quantum dot fluorescent probe according to claim 1, characterized in that: The washing described in step 2 is washing with ethanol 3 to 5 times.

6. A ZnO QDs@ZIF-8 quantum dot fluorescent probe prepared by the method according to any one of claims 1 to 5.

7. An application of the ZnO QDs@ZIF-8 quantum dot fluorescent probe in copper ion detection as claimed in claim 6, characterized in that: The following steps are involved: Step 1: Prepare a solution of ZnO QDs@ZIF-8 quantum dot fluorescent probe with ethanol to a concentration of 0.25-0.5 mg / mL; Step 2: Mix the solution prepared in step 1 with the solution to be detected in equal volume ratio and then perform spectral detection.

Images