Carbon quantum dot, preparation method, application in detection of flavonoid compounds and concentration detection method of flavonoid compounds

Abstract

The invention provides a carbon quantum dot, a preparation method, application in detection of flavonoid compounds and a concentration detection method of the flavonoid compounds. The carbon quantum dot provided by the invention has two excitation wavelengths of 313nm and 374nm. Wherein 313nm exciting light is used for irradiating the carbon quantum dots, and the intensity of 420nm fluorescence emitted by the carbon quantum dots is I313; the carbon quantum dots are irradiated with 374 nm exciting light, and the intensity of 420 nm fluorescence emitted by the carbon quantum dots is I374. The flavonoid compound can enable the carbon quantum dots to generate fluorescence quenching, and along with the increase of the concentration of the flavonoid compound, the reduction speeds of I313 and I374 are different, so that the concentration of the flavonoid compound is allowed to be detected by using I313 / I374.

Description

Technical Field

[0001] This invention relates to the field of flavonoid detection, and in particular to a carbon quantum dot, its preparation method, its application in flavonoid detection, and a method for detecting the concentration of flavonoids. Background Technology

[0002] Flavonoids are a class of polyphenolic compounds with wide applications in food science, medicine, and cosmetics. Among the many flavonoids, quercetin, rutin, morin, and kaempferol are renowned for their anti-inflammatory properties, showing great potential in the prevention and treatment of various chronic diseases. Specifically, these compounds have been shown to have therapeutic effects on cardiovascular diseases, and can prevent hypertension, protect the liver, and reduce the incidence of coronary heart disease. Furthermore, flavonoids possess strong free radical scavenging capabilities, inducing apoptosis in tumor cells while delaying the apoptosis process in normal tissue cells.

[0003] However, excessive intake of flavonoids may lead to gastrointestinal irritation and liver dysfunction, and disrupt hormone metabolism, causing endocrine disorders. Other studies have shown that long-term, high-dose flavonoid intake may overload the body's physiological systems, leading to the generation of reactive oxygen species (ROS) and ultimately DNA damage. Furthermore, different types of flavonoids exhibit significantly different pharmacological effects, and mixtures of flavonoids may produce more severe adverse reactions than single components. Therefore, identifying the concentration and type of flavonoids is of great importance. Summary of the Invention

[0004] Therefore, it is necessary to address the problem that existing technologies cannot effectively identify the concentration and components of flavonoids, and to provide a carbon quantum dot, its preparation method, its application in the detection of flavonoids, and a method for detecting the concentration of flavonoids.

[0005] The technical solution provided by this invention is as follows:

[0006] A method for preparing carbon quantum dots involves dissolving 5-aminoisophthalic acid and catechol in a solvent, and then heating and reacting them in a reaction vessel to obtain the carbon quantum dots.

[0007] In some embodiments of this application, the mass ratio of 5-aminoisophthalic acid to catechol is 1:1.

[0008] In some embodiments of this application, the reaction temperature of 5-aminoisophthalic acid and catechol is 180°C.

[0009] In some embodiments of this application, the reaction time of 5-aminoisophthalic acid and catechol is 8 hours.

[0010] In some embodiments of this application, the solvent is ethanol.

[0011] A carbon quantum dot is prepared using the aforementioned method for preparing carbon quantum dots.

[0012] An application of the aforementioned carbon quantum dots in the detection of flavonoids.

[0013] A method for detecting the concentration of flavonoids, comprising:

[0014] The carbon quantum dots were irradiated with 313nm excitation light, and the fluorescence intensity at 420nm emitted by the carbon quantum dots was obtained as i. 313 ;

[0015] The carbon quantum dots were irradiated with 374nm excitation light, and the fluorescence intensity at 420nm emitted by the carbon quantum dots was obtained as i. 374 ;

[0016] The carbon quantum dots are mixed with the test solution to form a mixture;

[0017] The mixture was irradiated with 313 nm excitation light to obtain a fluorescence intensity of I at 420 nm emitted by the carbon quantum dots. 313 ;

[0018] The mixture was irradiated with 374 nm excitation light to obtain a fluorescence intensity of I at 420 nm emitted by the carbon quantum dots. 374 ;

[0019] Based on I 313 / I 374 and i 313 / i 374 Determine the concentration of flavonoids in the test solution.

[0020] The application of HCA in the detection of flavonoids is based on the PLE spectroscopy of the aforementioned carbon quantum dots.

[0021] The application of LDA in the detection of flavonoids is based on the PLE spectroscopy of the aforementioned carbon quantum dots.

[0022] The beneficial effects of this invention are as follows:

[0023] The carbon quantum dots of this invention have two excitation wavelengths, 313 nm and 374 nm. Specifically, when the carbon quantum dots are irradiated with 313 nm excitation light, the fluorescence intensity emitted by the carbon quantum dots at 420 nm is I. 313 When the carbon quantum dots are irradiated with 374nm excitation light, the fluorescence intensity emitted by the carbon quantum dots at 420nm is I. 374 Flavonoids can quench the fluorescence of carbon quantum dots, and the fluorescence intensity increases with increasing flavonoid concentration. 313and I 374 The rate of decrease varies, thus allowing the use of I 313 / I 374 The concentration of flavonoids was detected.

[0024] Secondly, when carbon quantum dots and flavonoids are mixed, the fluorescence intensity decay rate at specific wavelengths in their PLE spectra changes with the specific type of flavonoid. Based on this characteristic, LDA and HCA can utilize the PLE spectra of the mixture of carbon quantum dots and flavonoids to detect and identify specific components of flavonoids and the concentration of each component. Attached Figure Description

[0025] Figure 1 This is a TEM image of carbon quantum dots in an embodiment of the present invention;

[0026] Figure 2 This is a particle size distribution diagram of carbon quantum dots in an embodiment of the present invention;

[0027] Figure 3 The image shows the AFM diagram of carbon quantum dots in an embodiment of the present invention.

[0028] Figure 4 The image shows the XRD pattern of carbon quantum dots in an embodiment of the present invention.

[0029] Figure 5 The image shown is an FT-IR image of carbon quantum dots in an embodiment of the present invention.

[0030] Figure 6 This is the full XPS spectrum of the carbon quantum dots in an embodiment of the present invention;

[0031] Figure 7 The high-resolution XPS spectrum of carbon quantum dots in this embodiment of the invention;

[0032] Figure 8 The UV-vis absorption spectrum, PL spectrum, and PLE spectrum of carbon quantum dots in this embodiment of the invention are shown below.

[0033] Figure 9 The PL spectra of carbon quantum dots under different wavelengths of excitation light in the embodiments of the present invention;

[0034] Figure 10 The EEM spectrum of carbon quantum dots in this embodiment of the invention;

[0035] Figure 11 Fluorescence stability test of carbon quantum dots in embodiments of the present invention Figure 1 ;

[0036] Figure 12 Fluorescence stability test of carbon quantum dots in embodiments of the present invention Figure 2 ;

[0037] Figure 13 This is a schematic diagram of the normalized fluorescence intensity of carbon quantum dots prepared at different reaction temperatures in the embodiments of the present invention;

[0038] Figure 14 This is a schematic diagram of the normalized fluorescence intensity of carbon quantum dots prepared at different reaction times in the embodiments of the present invention;

[0039] Figure 15 This is a schematic diagram of the normalized fluorescence intensity of carbon quantum dots prepared with different raw material ratios in the embodiments of the present invention;

[0040] Figure 16 This is a schematic diagram showing the ratio between the fluorescence intensity of carbon quantum dots after mixing with different substances and the fluorescence intensity before mixing in an embodiment of the present invention;

[0041] Figure 17 The PLE spectra and I of carbon quantum dots mixed with different concentrations of quercetin in the embodiments of the present invention are shown. 313 / I 374 The relationship curve between the concentration of quercetin and the concentration of quercetin;

[0042] Figure 18 The PLE spectra and I of carbon quantum dots mixed with different concentrations of rutin in the embodiments of the present invention are shown. 313 / I 374 The relationship curve between rutin concentration and rutin concentration;

[0043] Figure 19 The PLE spectra and I of carbon quantum dots and different concentrations of morin in the embodiments of the present invention are shown. 313 / I 374 The relationship curve between morin concentration and morin concentration;

[0044] Figure 20 The PLE spectra and I values ​​of carbon quantum dots mixed with different concentrations of kaempferol in the embodiments of the present invention are shown. 313 / I 374 The relationship curve between the concentration of kaempferol and the concentration of kaempferol;

[0045] Figure 21 The actual and theoretical UV-vis absorption spectra of quercetin and carbon quantum dots after mixing are shown in the embodiments of the present invention. The UV-vis absorption spectrum of quercetin, the PLE and PL spectra of carbon quantum dots, and the fluorescence lifetime decay curves before and after mixing quercetin and carbon quantum dots are also shown.

[0046] Figure 22 The actual and theoretical UV-vis absorption spectra of rutin and carbon quantum dots after mixing are shown in the embodiments of the present invention. The UV-vis absorption spectrum of rutin, the PLE and PL spectra of carbon quantum dots, and the fluorescence lifetime decay curves before and after mixing rutin and carbon quantum dots are also shown.

[0047] Figure 23 The actual and theoretical UV-vis absorption spectra of morin and carbon quantum dots after mixing are shown in the embodiments of the present invention. The UV-vis absorption spectrum of morin is shown in the figure. The PLE and PL spectra of carbon quantum dots are shown in the figure. The fluorescence lifetime decay curves of morin and carbon quantum dots before and after mixing are shown in the figure.

[0048] Figure 24 The actual and theoretical UV-vis absorption spectra of kaempferol and carbon quantum dots after mixing are shown in the embodiments of the present invention. The UV-vis absorption spectrum of kaempferol, the PLE and PL spectra of carbon quantum dots, and the fluorescence lifetime decay curves before and after mixing kaempferol and carbon quantum dots are also shown.

[0049] Figure 25 The fluorescence intensity attenuation rate at different wavelength positions in the PLE spectrum before and after mixing carbon quantum dots and flavonoids in this embodiment of the invention;

[0050] Figure 26 This is a schematic diagram of the LDA classification results for a mixture of carbon quantum dots and flavonoids in an embodiment of the present invention. Figure 1 ;

[0051] Figure 27 This is a schematic diagram of the LDA classification results for a mixture of carbon quantum dots and flavonoids in an embodiment of the present invention. Figure 2 ;

[0052] Figure 28 This is a schematic diagram illustrating the classification results of a mixture of carbon quantum dots and flavonoids using HCA in an embodiment of the present invention. Figure 1 ;

[0053] Figure 29 This is a schematic diagram illustrating the classification results of a mixture of carbon quantum dots and flavonoids using HCA in an embodiment of the present invention. Figure 2 . Detailed Implementation

[0054] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0055] Example:

[0056] This embodiment provides a carbon quantum dot preparation method comprising the following steps: dissolving 200 mg of 5-aminoisophthalic acid and 200 mg of catechol in 30 mL of ethanol, sonicating for 10 min, then transferring to a reaction vessel and reacting at 180 °C for 8 h. After the reaction is completed and cooled to room temperature, the reaction liquid is centrifuged at 8000 rpm for 10 min, filtered through a filter membrane with a pore diameter of 0.22 μm, then dialyzed through a dialysis membrane with a molecular weight cutoff of 1000 Da for 48 h, and finally evaporated under vacuum for 24 h to obtain the carbon quantum dots.

[0057] like Figure 1 and Figure 2 As shown, the carbon quantum dots prepared in this embodiment are generally spherical in shape, with an average diameter of approximately 4.6 nm and a lattice spacing of 0.21 nm. Figure 3 As shown, the height of the carbon quantum dots is approximately 2.6 nm. Figure 4 As shown, the diffraction peak 2θ of the carbon quantum dots is at 22°, matching the (002) crystal plane. Based on the above characterization, it can be confirmed that graphite nanocrystal nuclei exist in the carbon quantum dots, and the graphite nanocrystal nuclei follow the sp... 3 The arrangement of structural defects in hybrid carbon.

[0058] based on Figure 5 It can be seen that the hydrophilic groups on the surface of the carbon quantum dots have CO (1138cm) -1 -1369 cm -1 C=O (1704cm) -1 -NH / OH (3088cm) -1 -3576cm -1 These hydrophilic groups enable the carbon quantum dots to exhibit good dispersibility in water. Furthermore, the carbon quantum dots show good dispersibility at 1421 cm⁻¹. -1 and 1599 cm -1 The peak at that point corresponds to CN and C=C / C=N in the polyaromatic structure.

[0059] like Figure 6As shown, the peak corresponding to C 1s is located at 284.1 eV, the peak corresponding to N 1s is located at 398.4 eV, and the peak corresponding to O 1s is located at 531.6 eV. Calculations show that the carbon quantum dot contains 66.48% C, 6.12% N, and 27.4% O. Figure 7 As shown, in the C 1s spectrum, the peak at 283.47 eV corresponds to CC / C=C, the peak at 284.80 eV corresponds to CO / CN, and the peak at 287.83 eV corresponds to C=O / C=N; in the N 1s spectrum, the peak at 397.80 eV corresponds to pyridine nitrogen, and the peak at 398.81 eV corresponds to pyrrole nitrogen; in the O 1s spectrum, the peak at 530.26 eV corresponds to C=O, and the peak at 531.63 eV corresponds to CO.

[0060] like Figures 8-10 As shown, in the UV-vis absorption spectrum of the carbon quantum dots, there are two distinct peaks at 222 nm and 278 nm, corresponding to C=C, respectively. Transitions and C=O The absorption band between 300 nm and 390 nm corresponds to N-related surface states or defect bonds. Furthermore, the carbon quantum dots have one emission wavelength of 420 nm and two excitation wavelengths of 313 nm and 374 nm. When the carbon quantum dots are irradiated with 313 nm excitation light, the fluorescence intensity emitted by the carbon quantum dots at 420 nm is I. 313 When the carbon quantum dots are irradiated with 374nm excitation light, the fluorescence intensity emitted by the carbon quantum dots at 420nm is I. 374 .

[0061] like Figure 11 As shown, the fluorescence intensity of the carbon quantum dots remained almost unchanged after 24 hours of ultraviolet light irradiation. Similarly, the fluorescence intensity remained almost unchanged after 30 days of natural light irradiation. Even in a 2 mol / L NaCl solution, the fluorescence intensity of the carbon quantum dots showed almost no decay. Figure 12 As shown, the fluorescence intensity of the carbon quantum dots changes very little as the pH of the environment in which they are located increases from 4 to 10. In summary, the carbon quantum dots possess extremely high stability.

[0062] Building upon this, this embodiment further investigates the effect of different preparation conditions of carbon quantum dots on I 313 and I 374 The impact.

[0063] This embodiment first investigated the interaction between multiple carbon quantum dots obtained by reacting 200 mg of 5-aminoisophthalic acid and 200 mg of catechol at different reaction temperatures for 8 hours, focusing on I...313 and I 374 The differences. Specifically, for example... Figure 13 As shown, as the reaction temperature increases from 140℃ to 240℃, I 313 and I 374 Both showed a trend of first increasing and then decreasing, and under the condition of reaction temperature of 180℃, I 313 and I 374 Both reach their maximum values ​​simultaneously.

[0064] This embodiment also investigated the interaction between multiple carbon quantum dots obtained by reacting 200 mg of 5-aminoisophthalic acid and 200 mg of catechol at 180 °C for different times, targeting I. 313 and I 374 The differences. For example Figure 14 As shown, as the reaction time gradually increased from 2 hours to 12 hours, I 313 and I 374 All showed a trend of first increasing and then decreasing, and under the condition of a reaction time of 8 hours, I 313 and I 374 Both reach their maximum values ​​simultaneously.

[0065] Finally, this example investigated the interactions between multiple carbon quantum dots obtained from the reaction of 5-aminoisophthalic acid and catechol at different mass ratios at 180°C for 8 hours, targeting I. 313 and I 374 The differences. For example Figure 15 As shown, as the mass ratio of 5-aminoisophthalic acid to catechol gradually decreases from 3:1 to 1:3, I 313 and I 374 All showed a trend of first increasing and then decreasing. Among them, when the mass ratio of 5-aminoisophthalic acid to catechol was 1:1, I 313 and I 374 Both reach their maximum values ​​simultaneously. Specifically, when the mass ratio of 5-aminoisophthalic acid to catechol is 3:1, the mass of 5-aminoisophthalic acid is 600 mg and the mass of catechol is 200 mg; when the mass ratio of 5-aminoisophthalic acid to catechol is 2:1, the mass of 5-aminoisophthalic acid is 400 mg and the mass of catechol is 200 mg; when the mass ratio of 5-aminoisophthalic acid to catechol is 1:1, the mass of 5-aminoisophthalic acid is 200 mg and the mass of catechol is 200 mg; when the mass ratio of 5-aminoisophthalic acid to catechol is 1:2, the mass of 5-aminoisophthalic acid is 200 mg and the mass of catechol is 400 mg; and when the mass ratio of 5-aminoisophthalic acid to catechol is 1:3, the mass of 5-aminoisophthalic acid is 200 mg and the mass of catechol is 600 mg.

[0066] Based on this, in this embodiment, carbon quantum dots obtained under the conditions of a 1:1 mass ratio of 5-aminoisophthalic acid and catechol, a reaction temperature of 180°C, and a reaction time of 8 hours were finally selected for the detection of flavonoids.

[0067] Further as Figure 16 As shown, the carbon quantum dots are associated with L-serine, L-asparagine, L-alanine, L-tryptophan, L-proline, ciprofloxacin (CIP), chloramphenicol (CHL), benomyl, acetyl-K, hydroquinone (HQ), chlorogenic acid (CGA), salicylic acid (SA), resveratrol (Res), tannic acid (TA), proanthocyanidins (PC), and F. - CO3 2- ,Br - NO3 - I - Cl - PO4 3- SO4 2- K + Na + Mn 2+ Ca 2+ Ba 2+ Mg 2+ Cd 2+ Co 2+ Fe 2+ Fe 3+ Before and after mixing, I 313 and I 374 No significant changes were observed. However, before and after mixing the carbon quantum dots with flavonoids (quercetin, rutin, morin, and kaempferol), I... 313 and I 374 All values ​​decreased significantly. This confirms that the carbon quantum dots can be used to detect flavonoids and have good detection specificity for flavonoids. Furthermore, in this embodiment, the synthesis conditions of the carbon quantum dots were optimized, resulting in a higher detection specificity of the carbon quantum dots before mixing with flavonoids. 313 and I 374 The values ​​are relatively large, therefore, when carbon quantum dots are mixed with flavonoids, I 313 and I 374 It has a larger potential for reduction, thus providing a stronger detection capability for flavonoids.

[0068] Specifically, such as Figure 17As shown, when carbon quantum dots are specifically mixed with quercetin, as the concentration of quercetin increases, I... 313 and I 374 All gradually decrease, among which I 374 The speed is reduced faster, so I can be used. 313 / I 374 The concentration of quercetin was detected. Specifically, when the quercetin concentration was within the range of 0.075 μM–50 μM, I… 313 / I 374 It showed a good linear relationship with quercetin concentration (R0). 2 =0.99387), corresponding to a detection limit of 75 nM for quercetin concentration.

[0069] Further as Figures 18-20 As shown, similar to quercetin, when carbon quantum dots are mixed with rutin, morin, and kaempferol, respectively, they can all utilize I... 313 / I 374 To achieve the concentration detection of rutin, morin, and kaempferol.

[0070] Based on this, this embodiment provides a method for detecting the concentration of flavonoids, including the following steps:

[0071] Step 101: Irradiate the ethanol solution of the carbon quantum dots with 313nm excitation light, and obtain the fluorescence intensity of the carbon quantum dots at 420nm as i. 313 ;

[0072] Step 102: Irradiate the ethanol solution of the carbon quantum dots with 374nm excitation light, and obtain the fluorescence intensity of the carbon quantum dots at 420nm as i. 374 ;

[0073] Step 103: Mix the ethanol solution of the carbon quantum dots with the test solution to form a mixture;

[0074] Step 104: Irradiate the mixture with 313nm excitation light to obtain the 420nm fluorescence intensity of the carbon quantum dots as I. 313 ;

[0075] Step 105: Irradiate the mixture with 374nm excitation light to obtain the 420nm fluorescence intensity of the carbon quantum dots as I. 374 ;

[0076] Step 106: Based on I 313 / I374 and i 313 / i 374 Determine the concentration of flavonoids in the test solution.

[0077] like Figure 21 As shown, taking quercetin as an example, the actual UV-vis absorption spectrum of the mixture of carbon quantum dots and quercetin has a high degree of overlap with the theoretical UV-vis absorption spectrum, indicating that no new compounds are formed between carbon quantum dots and quercetin. Secondly, the UV-vis absorption spectrum of quercetin overlaps significantly with the PLE spectrum of carbon quantum dots, and also overlaps slightly with the PL spectrum of carbon quantum dots. Finally, when the excitation wavelength is 313 nm, the fluorescence lifetime of the mixture of carbon quantum dots and quercetin decreases from 5.66 ns to 5.33 ns; when the excitation wavelength is 374 nm, the fluorescence lifetime decreases from 5.36 ns to 5.15 ns. This confirms that the fluorescence quenching mechanism of carbon quantum dots by quercetin is a combination of internal filtering effect (IFE) and fluorescence resonance energy transfer (FRET), with IFE being the dominant mechanism. Figures 22-24 As shown, the characterization results of the carbon quantum dots mixed with rutin, morin, and kaempferol are as follows: Figure 21 Similarity. This confirms that quercetin, rutin, morin, and kaempferol exhibit largely the same fluorescence quenching mechanism in the carbon quantum dots.

[0078] Since quercetin, rutin, morin, and kaempferol have similar fluorescence quenching mechanisms for carbon quantum dots, and the concentrations of quercetin, rutin, morin, and kaempferol are all similar to I... 313 / I 374 There is a positive correlation, therefore, only through I 313 / I 374 Although the concentration of flavonoids can be quantitatively analyzed to some extent, it is not possible to effectively distinguish between quercetin, rutin, morin, and kaempferol.

[0079] based on Figures 17-20 It is known that quercetin, rutin, morin, and kaempferol have effects on I... 313 / I 374 The effects are quite similar, therefore, based solely on I... 313 / I 374 It is impossible to distinguish between quercetin, rutin, morin, and kaempferol.

[0080] However, as Figure 25 As shown, the fluorescence intensity decay rates at different wavelengths in the PLE spectrum of a mixture of carbon quantum dots and flavonoids differ, and the fluorescence intensity decay rate at a specific wavelength in the PLE spectrum also varies with the specific type of flavonoid. Figure 25 In the PLE spectrum, F1 corresponds to a wavelength of 313 nm, F2 to 335 nm, F3 to 360 nm, and F4 to 374 nm. The vertical axis is represented by (I0-I) / I0, where I0 is the fluorescence intensity at the corresponding wavelength in the PLE spectrum before mixing carbon quantum dots and flavonoids, and I is the fluorescence intensity at the corresponding wavelength in the PLE spectrum after mixing. The emission wavelength in the PLE spectrum is fixed at 420 nm.

[0081] Based on this, this embodiment prepared 5 mixtures of carbon quantum dots and quercetin, 5 mixtures of carbon quantum dots and rutin, 5 mixtures of carbon quantum dots and morin, and 5 mixtures of carbon quantum dots and kaempferol. In any of these mixtures, the total concentration of flavonoids was α. The PLE spectrum of each mixture was obtained, and then the fluorescence intensity corresponding to 313 nm and 335 nm in each PLE spectrum was acquired. Then, LDA (linear discriminant analysis) and HCA (hierarchical clustering analysis) were used to classify the mixtures based on the combination of fluorescence intensities corresponding to 313 nm and 335 nm.

[0082] like Figure 26 and Figure 28 As shown, when α is 25 μM, LDA and HCA can classify 20 mixtures well; when α is 50 μM, LDA and HCA can still classify 20 mixtures well; when α is 75 μM, LDA and HCA can still classify 20 mixtures well, with a classification accuracy of 100%.

[0083] In this embodiment, 35 mixed solutions of carbon quantum dots and flavonoids were prepared, with a total concentration of flavonoids of 100 μM in each mixed solution. Specifically, the concentrations of quercetin in five of the mixed solutions were as follows: 100 μM for 5 solutions; 80 μM for 5 solutions and 20 μM for 5 solutions; 60 μM for 5 solutions and 40 μM for 5 solutions; 50 μM for 5 solutions and 50 μM for 5 solutions; 40 μM for 5 solutions and 60 μM for 5 solutions; 20 μM for 5 solutions and 80 μM for 5 solutions; and 100 μM for 5 solutions. The PLE spectrum of each mixed solution was obtained again, and then the fluorescence intensity corresponding to 313 nm and 335 nm in each PLE spectrum was acquired. Then, LDA (linear discriminant analysis) and HCA (hierarchical cluster analysis) were used to classify the mixed solutions based on the combination of fluorescence intensities corresponding to 313 nm and 335 nm. For example... Figure 27 and Figure 29 As shown, LDA and HCA can classify 35 mixed solutions very well with a classification accuracy of 100%.

[0084] This confirms that LDA and HCA can be used to jointly identify the specific types of flavonoids in the test solution and the corresponding concentrations of different flavonoids.

[0085] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing carbon quantum dots, characterized in that, 5-Amino-isophthalic acid and catechol are dissolved in a solvent and then heated in a reaction vessel to obtain the carbon quantum dots.

2. The method for preparing carbon quantum dots according to claim 1, characterized in that, The mass ratio of 5-aminoisophthalic acid to catechol is 1:

1.

3. The method for preparing carbon quantum dots according to claim 1, characterized in that, The reaction temperature of 5-aminoisophthalic acid and catechol is 180℃.

4. The method for preparing carbon quantum dots according to claim 1, characterized in that, The reaction time for 5-aminoisophthalic acid and catechol is 8 hours.

5. The method for preparing carbon quantum dots according to claim 1, characterized in that, The solvent is ethanol.

6. A carbon quantum dot, characterized in that, The carbon quantum dots were prepared using the method described in any one of claims 1-5.

7. An application of carbon quantum dots as described in claim 6 in the detection of flavonoids.

8. A method for detecting the concentration of flavonoids, characterized in that, include: The carbon quantum dots as described in claim 6 are irradiated with 313nm excitation light, and the fluorescence intensity at 420nm emitted by the carbon quantum dots is obtained as i. 313 ; Irradiate the carbon quantum dots as described in claim 6 with 374nm excitation light, and obtain the fluorescence intensity of the carbon quantum dots at 420nm as i. 374 ; The carbon quantum dots as described in claim 6 are mixed with the test solution to form a mixture; The mixture was irradiated with 313 nm excitation light to obtain a fluorescence intensity of I at 420 nm emitted by the carbon quantum dots. 313 ; The mixture was irradiated with 374 nm excitation light to obtain a fluorescence intensity of I at 420 nm emitted by the carbon quantum dots. 374 ; Based on I 313 / I 374 and i 313 / i 374 Determine the concentration of flavonoids in the test solution.

9. The application of HCA in the detection of flavonoids, characterized in that, Based on the PLE spectrum of carbon quantum dots as described in claim 6.

10. The application of LDA in the detection of flavonoids, characterized in that, Based on the PLE spectrum of carbon quantum dots as described in claim 6.

Images