A fluorescent carbon quantum dot and its preparation method and application in detecting aspartic acid

Abstract

The present invention belongs to the technical field of fluorescent carbon quantum dots, and in particular relates to a fluorescent carbon quantum dot, a preparation method thereof, and an application in the detection of aspartic acid. The preparation method of the fluorescent carbon quantum dot comprises the following steps: taking o-phenylenediamine and boric acid, adding them to ultrapure water, stirring evenly, heating and then cooling to obtain a brown-black solid; dissolving the brown-black solid in ultrapure water, centrifuging and obtaining the supernatant; the solution is placed in a dialysis bag, dialyzed to remove impurities, and a yellow solution, i.e., a fluorescent carbon quantum dot solution, is obtained. The carbon quantum dots prepared by the present invention are synthesized by a microwave-assisted method, have good stability, and are simple to synthesize. The high-efficiency fluorescent carbon quantum dots of this invention can be used as a fluorescent probe for quantitative measurement of aspartic acid.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorescent carbon quantum dots, and in particular relates to fluorescent carbon quantum dots, a preparation method thereof, and application thereof in detecting aspartic acid. Background Art

[0002] Aspartic acid (L-Asp) is an amino acid, also known as aspartic acid. It is one of the building blocks of proteins and a precursor for the synthesis of various amino acids, purines, and pyrimidines in the body. It has a protective effect on the myocardium and is one of the building blocks of proteins. It is also a precursor for the synthesis of various amino acids, purines, and pyrimidines in the body. In addition, aspartic acid participates in the ornithine cycle, promoting the production of urea from ammonia and carbon dioxide, reducing the amount of nitrogen and carbon dioxide in the blood, enhancing liver function, and reducing fatigue. However, excessive aspartic acid may affect brain function. Specifically, excessive aspartic acid may interfere with the normal function of neurotransmitters, affect information transmission between neurons, and may even negatively affect the brain's cognitive ability and learning and memory abilities. Due to the importance of L-Asp in living systems, its detection becomes particularly important.

[0003] To date, various methods have been used for the detection of L-Asp, including capillary electrophoresis, chromatography, and electrochemical methods. However, these methods are limited by high costs and cumbersome procedures. Therefore, there is an urgent need to develop a fast, sensitive, and low-cost sensor for the detection of L-Asp.

[0004] As a new type of nanomaterial, carbon quantum dots have the advantages of easy preparation, low cost, high water solubility and biocompatibility and are widely used in the quantitative detection of target substances. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention uses a microwave-assisted method to prepare carbon quantum dots with high efficiency and good fluorescence properties, and verifies that they can be used as a fluorescence detector for detecting aspartic acid.

[0006] The present invention is specifically achieved through the following technical solutions: a fluorescent carbon quantum dot, the preparation method comprises the following steps

[0007] Step 1: Add o-phenylenediamine and boric acid to ultrapure water, stir evenly, heat and then cool to obtain a brown-black solid

[0008] Step 2: Dissolve the brown-black solid in ultrapure water and centrifuge to obtain the supernatant; put the solution into a dialysis bag and dialyze to remove impurities to obtain a yellow solution, namely the fluorescent carbon quantum dot solution.

[0009] For the fluorescent carbon quantum dots mentioned above, in step 1, o-phenylenediamine: boric acid: ultrapure water = 0.2 g: 0.3: 10 ml.

[0010] In the above-mentioned fluorescent carbon quantum dots, in step 1, the pH value is 6.7.

[0011] For the above-mentioned fluorescent carbon quantum dots, in step 1, the heating temperature is 80-100° C., and the heating time is 25-120 min.

[0012] In the above-mentioned fluorescent carbon quantum dots, in step 2, the centrifugation is performed at 11000 rpm for 10 min. The specification of the dialysis bag is 500 Da.

[0013] For the above-mentioned fluorescent carbon quantum dots, in step 2, the ratio of the brown-black solid to ultrapure water is 1.4 g:20 mL.

[0014] The above-mentioned fluorescent carbon quantum dots are used as fluorescent probes in the detection of aspartic acid.

[0015] The above application method is as follows:

[0016] Step 1: Measure 3.2 ml of the solution to be tested containing aspartic acid, add 0.8 ml of a 5 mg / mL fluorescent carbon quantum dot solution according to any one of claims 1 to 6, mix well, and react for 10 minutes;

[0017] Step 2: Place the mixed solution obtained in step 1 into a fluorescence spectrometer, select 420 nm as the excitation wavelength, set the spectral range to 420-700 nm, and after obtaining the complete fluorescence spectrum, read the fluorescence intensity value F at 570 nm;

[0018] Step 3: Measure 3.2 ml of ultrapure water and add it to 0.8 ml of the above 5 mg / mL fluorescent carbon quantum dot solution. After mixing evenly, react for 10 minutes.

[0019] Step 4: Place the mixed solution obtained in step 3 into a fluorescence spectrometer, select 420 nm as the excitation wavelength, set the spectral range to 420-700 nm, and after obtaining the complete fluorescence spectrum, read the fluorescence intensity value F0 at 570 nm;

[0020] Step 5: Substitute the value of (F0-F) / F0 into the standard curve of fluorescent carbon quantum dots and calculate the aspartic acid concentration of the test solution.

[0021] For the above application, the method for drawing the standard curve of fluorescent carbon quantum dots is as follows: take 3.2 ml of standard aspartic acid solution of different concentrations, add 0.8 ml of the above-mentioned 5 mg / mL fluorescent carbon quantum dot solution thereto, mix evenly, and react for 10 minutes; the mixed solution is placed in a fluorescence spectrometer, 420 nm is selected as the excitation light wavelength, and the spectral range is set to 420-700 nm. After obtaining the complete fluorescence spectrum, the fluorescence intensity value F1 at 570 nm is read to draw the standard curve.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] The fluorescent carbon quantum dots prepared by the microwave-assisted method have efficient and stable fluorescence properties and are safe and non-toxic. Detection experiments have shown that the prepared carbon quantum dots can be used as a fluorescence probe for quantitative detection of aspartic acid, and are expected to become a fluorescent probe for detecting aspartic acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a transmission electron microscope image of the carbon quantum dots prepared in the present invention.

[0025] Figure 2 This is the X-ray diffraction pattern of the carbon quantum dots prepared in the present invention.

[0026] Figure 3 The optimal excitation spectrum and optimal emission spectrum of the carbon quantum dots prepared in the present invention are shown.

[0027] Figure 4 This is a graph showing the fluorescence intensity changes of the carbon quantum dots prepared in the present invention under different ions.

[0028] Figure 5 This is a graph showing the fluorescence intensity changes of the carbon quantum dots prepared in the present invention at different pH values.

[0029] Figure 6 This is a graph showing the fluorescence intensity changes of the carbon quantum dots prepared in the present invention under different salt ion concentrations.

[0030] Figure 7 This is a fluorescence spectrum diagram of the carbon quantum dots prepared in the present invention used as probes to detect aspartic acid at different concentrations.

[0031] Figure 8 The carbon quantum dots prepared for the present invention are used as a standard curve for detecting aspartic acid, wherein a is a standard curve for aspartic acid concentration of 0-15 μM, and b is a standard curve for aspartic acid concentration of 0-400 μM.

[0032] Specific implementation methods

[0033] The present invention is further described below by way of specific examples. The present invention is not limited to the examples, and slight variations are possible without departing from the scope of the examples.

[0034] Example 1 A fluorescent carbon quantum dot

[0035] The preparation method is as follows:

[0036] Step 1: Weigh 0.2 g of o-phenylenediamine and 0.3 g of boric acid separately for later use;

[0037] Step 2: Place the weighed drugs into a conical flask, add 10 ml of ultrapure water, stir and mix, and the pH value is 6.7;

[0038] Step 3: Place the above conical flask in a microwave oven and heat it for 25-120 minutes at a temperature of 80-100°C;

[0039] Step 4: Dissolve 1.4 g of the obtained brown-black solid in 20 ml of ultrapure water, centrifuge at 11,000 rpm for 10 min, and collect the supernatant;

[0040] Step 5: The obtained solution was placed in a 500Da dialysis bag and poured into 4L of ultrapure water for dialysis to remove unreacted precursors to obtain a brown-yellow solution, i.e., a fluorescent carbon quantum dot solution.

[0041] Example 2 Characterization of Fluorescent Carbon Quantum Dots

[0042] (1) Transmission electron microscopy: The carbon quantum dots prepared in Example 1 were characterized by transmission electron microscopy, and it was found that their size was about 2 nm (e.g. Figure 1 ).

[0043] (2) From the X-ray diffraction pattern of prepared carbon quantum dots (such as Figure 2 ) It can be seen that the carbon quantum dots have an obvious peak near 2θ=20°, which proves the existence of amorphous carbon in B-CDs.

[0044] (3) The optimal excitation wavelength and emission wavelength of the carbon quantum dot solution are 420 nm and 570 nm, respectively (e.g. Figure 3 ) and exhibits yellow fluorescence under 365nm ultraviolet light. Studies of its fluorescence spectra at different excitation wavelengths (400-480nm) revealed excitation-independent fluorescence emission, which is attributed to the uniform size distribution and surface defects of the synthesized carbon quantum dots.

[0045] (4) The study on the fluorescence stability of carbon quantum dots shows that the fluorescence intensity of carbon quantum dots was tested under different amino acids, different pH values and different salt ion strengths. Figure 4As shown in the results, the carbon quantum dots only have a quenching effect on aspartic acid in aqueous solutions of different amino acids, while other amino acids have almost no effect on the fluorescence intensity of the carbon quantum dots. This indicates that the carbon quantum dots can be used as a fluorescent probe for detecting aspartic acid. Figure 5 As shown in the figure, the effect of different pH values on the fluorescence intensity of carbon quantum dots. The results show that carbon quantum dots can maintain good fluorescence emission even in strong acid and strong base environments. The effect of different salt ion strengths (adding different concentrations of NaCl) on the fluorescence intensity of carbon quantum dots was further explored. It shows that the carbon quantum dot sample has good salt resistance and stability in salt solution (such as Figure 6 ).

[0046] Example 3 Application of fluorescent carbon quantum dots as fluorescent probes in the detection of aspartic acid

[0047] The method for drawing the standard curve of fluorescent carbon quantum dots is as follows:

[0048] Take 3.2 ml of standard aspartic acid solution of different concentrations, add 0.8 ml of 5 mg / mL fluorescent carbon quantum dot solution prepared in Example 1, mix well, and react for 10 minutes; put the mixed solution into the fluorescence spectrometer, select 420 nm as the excitation wavelength, set the spectral range to 420-700 nm, and after obtaining the complete fluorescence spectrum, read the fluorescence intensity value F1 at 570 nm and draw the standard curve. The spectrum should be as follows Figure 7 The standard curve is shown as Figure 8 The linear equations are: (F0-F) / F0=0.02117c[Asp]-0.01027(R2=0.99071)(0μM-11μM) and (F0-F) / F0=0.00134c[Asp]+0.20189(R2=0.99573)(11μM-400μM).

[0049] The steps for detecting aspartic acid using fluorescent carbon quantum dots are as follows:

[0050] Step 1: Take 3.2 ml of the solution to be tested, add 0.8 ml of 5 mg / mL carbon quantum dot solution fluorescent probe, mix well, and react for 10 minutes;

[0051] Step 2: Place the mixed solution obtained in step 1 into a fluorescence spectrometer, select 420 nm as the excitation wavelength, set the spectral range to 420-700 nm, and after obtaining the complete fluorescence spectrum, read the fluorescence intensity value F at 570 nm;

[0052] Step 3: Measure 3.2 ml of ultrapure water and add it to 0.8 ml of the 5 mg / mL carbon dot solution fluorescent probe. After mixing evenly, react for 10 minutes.

[0053] Step 4: Place the mixed solution obtained in step 3 into a fluorescence spectrometer, select 420 nm as the excitation wavelength, set the spectral range to 420-700 nm, and after obtaining the complete fluorescence spectrum, read the fluorescence intensity value F0 at 570 nm;

[0054] Step 5: Substitute the value of (F0-F) / F0 into the standard curve of fluorescent carbon quantum dots and calculate the aspartic acid concentration of the test solution.

[0055] In summary, the fluorescent carbon quantum dots prepared by microwave-assisted method in the present invention have efficient and stable fluorescence properties and are safe and non-toxic. Detection experiments show that the prepared carbon quantum dots can be used as fluorescent probes for quantitative detection of aspartic acid.

Claims

1. An application of fluorescent carbon quantum dots as fluorescent probes in detecting aspartic acid, characterized in that: The method for preparing fluorescent carbon quantum dots comprises the following steps: Step 1: Add o-phenylenediamine and boric acid to ultrapure water, stir evenly, heat in a microwave at 80-100°C for 25-120 minutes, and then cool to obtain a brown-black solid; Step 2: Dissolve the brown-black solid in ultrapure water and centrifuge to obtain the supernatant; put the solution into a dialysis bag and dialyze to remove impurities to obtain a yellow solution, namely the fluorescent carbon quantum dot solution.

2. The use according to claim 1, characterized in that In step 1, o-phenylenediamine: boric acid: ultrapure water = 0.2g:0.3g:10ml.

3. The use according to claim 1, characterized in that In step 1, the pH value is 6.

7.

4. The use according to claim 1, characterized in that In step 2, the centrifugation is performed at 11000 rpm for 10 min, and the specification of the dialysis bag is 500 Da.

5. The use according to claim 1, characterized in that In step 2, the ratio of brown-black solid to ultrapure water is 1.4 g:20 mL.

6. The use according to claim 1, characterized in that Here’s how: Step (1): 3.2 ml of the solution containing aspartic acid was measured, and 0.8 ml of 5 mg / mL fluorescent carbon quantum dot solution was added thereto. After mixing evenly, the mixture was reacted for 10 min. Step (2): Place the mixed solution obtained in step (1) into a fluorescence spectrometer, select 420 nm as the excitation wavelength, set the spectral range to 420-700 nm, and after obtaining a complete fluorescence spectrum, read the fluorescence intensity value F at 570 nm; Step (3): Measure 3.2 ml of ultrapure water and add it to 0.8 ml of 5 mg / mL fluorescent carbon quantum dot solution. After mixing evenly, react for 10 minutes. Step (4): Place the mixed solution obtained in step (3) into a fluorescence spectrometer, select 420 nm as the excitation wavelength, set the spectral range to 420-700 nm, and after obtaining a complete fluorescence spectrum, read the fluorescence intensity value F0 at 570 nm; Step (5): Substitute the value of (F0-F) / F0 into the standard curve of fluorescent carbon quantum dots and calculate the aspartic acid concentration of the test solution.

7. The use according to claim 6, characterized in that The method for drawing the standard curve of fluorescent carbon quantum dots is as follows: take 3.2 ml of standard aspartic acid solution of different concentrations, add 0.8 ml of 5 mg / mL fluorescent carbon quantum dot solution thereto, mix evenly, and react for 10 minutes; put the mixed solution into the fluorescence spectrometer, select 420 nm as the excitation light wavelength, set the spectral range to 420~700 nm, and after obtaining the complete fluorescence spectrum, read the fluorescence intensity value F1 at 570 nm to draw the standard curve.

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