Preparation of blue-emitting carbon dots from malus hallings and their application in the detection of iron ions in liquor

Abstract

The application provides a preparation method of a blue fluorescent carbon dot of Rosa roxburghii tratt, which comprises the step of subjecting Rosa roxburghii tratt original juice to a hydrothermal reaction. The application also provides an application of the blue fluorescent carbon dot of Rosa roxburghii tratt in detecting iron ions in liquor. The blue fluorescent carbon dot is synthesized by using Rosa roxburghii tratt as raw material and by using one-step hydrothermal reaction, the raw material is derived from nature, is green and non-toxic, and the synthesis method is simple, convenient and environmentally friendly, and the pretreatment process is simple and easy to implement; the blue fluorescent carbon dot obtained by the application has excellent structure and fluorescence advantages, and the unique and special response of the blue fluorescent carbon dot to fluorescence quenching of the blue fluorescent carbon dot is not interfered by other heavy metal components, and the blue fluorescent carbon dot is especially suitable for Fe 3+ quantitative detection in liquor, and the operation is simple, fast in response, fast in determination speed, and accurate in determination result, and the blue fluorescent carbon dot is conducive to wide promotion in the field of liquor metal ion detection. 3+ ​

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of iron ion detection in Baijiu, and particularly relates to a preparation method of golden pear blue fluorescent carbon dots and application of the carbon dots in iron ion detection in Baijiu. BACKGROUND

[0002] Baijiu, as a traditional fermented food in China, has a long history and a wide distribution of industry, and has formed a basic pattern of eight major flavor types supplemented by four major flavor types (Maotai flavor, Luzhou flavor, Qingxiang flavor, and rice flavor). However, due to the use of raw materials, utensils, production, storage, transportation process, and environmental pollution, Baijiu inevitably contacts metal materials during brewing and storage. Some iron utensils such as iron boilers, Baijiu fermentation tanks, wine burning equipment, wine receiving containers, and wine storage containers are prone to corrosion, which leads to fluctuations in the content of Fe 3+ in Baijiu, and further affects the taste and flavor of Baijiu.

[0003] At present, the conventional detection method of Fe 3+ includes atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), and electrochemical method, but all of them inevitably have the disadvantages of high price, complicated pretreatment process, and harsh conditions, which greatly limit their application. Therefore, it is necessary to study and develop a simple, low-cost, and sensitive method to realize the rapid detection of Fe 3+ in the brewing process of Baijiu, which is of great significance for the quality control and traceability of the brewing process of Baijiu.

[0004] Carbon dots (CDs) are a new type of carbon-based nanoparticles, which are often applied in the fields of chemical analysis, biological sensing, and biological imaging due to their excellent biocompatibility, water solubility, low toxicity, and stability. Compared with traditional analysis methods, the fluorescent probe based on CDs has more obvious advantages in the analysis of Baijiu flavor substances and the detection of harmful substances, and is a very potential and hot detection method at present. For example, the patent document with the publication number CN113267478A discloses a method for detecting the content of total organic acid in Baijiu based on red fluorescent carbon quantum dots, and the patent document with the publication number CN108794475B discloses a fluorescent carbon dot for sensing alcohol, a preparation method thereof, and application thereof.

[0005] At present, some studies have shown that specific CDs can realize the quantitative detection of Fe 3+ . For example, the patent document with the publication number CN117903792A discloses a biomass fluorescent carbon dot and application thereof in the detection of iron ions, but like other existing CDs, it also has the disadvantage of low sensitivity in the detection of Fe 3+The detection can only be limited to the relatively simple metal ion aqueous solution, and the application in the solid fermentation product medium such as liquor has not been seen, and the reason is that the solid fermentation substrate of liquor is very complex, when the existing CDs are used for detecting iron ions, some components in liquor will interfere with the detection result. Therefore, it is of great significance to develop a CDs fluorescent probe which is not affected by the components of liquor and apply it to the quantitative detection of Fe 3+ in liquor. SUMMARY

[0006] In order to overcome the shortcomings of the prior art, the present application provides a preparation method and application of golden pear blue fluorescent carbon dots, which solves the technical problem that the existing fluorescent carbon dots cannot be applied to the quantitative detection of iron ions in liquor.

[0007] The technical scheme adopted by the present application to solve its technical problems is:

[0008] The present application first provides a preparation method of golden pear blue fluorescent carbon dots, which comprises the step of hydrothermal reaction of golden pear original juice.

[0009] Further, the reaction temperature of the hydrothermal reaction is 160-200 DEG C, and the reaction time is 5-10h.

[0010] In some embodiments, the hydrothermal reaction further comprises the steps of centrifugation, filter membrane filtration, dialysis and vacuum freeze-drying after the hydrothermal reaction.

[0011] Further, the centrifugal rate of the centrifugation is 9000-11000r / min, and the centrifugation time is 8-12min.

[0012] Further, the filter membrane used in the filter membrane filtration is a 0.20-0.25um microporous filter membrane.

[0013] Further, the molecular weight cut-off of the dialysis bag used in the dialysis is 800-1200Da, and the dialysis time is 20-28h.

[0014] Further, the brownish powder is obtained after the vacuum freeze-drying step.

[0015] The present application also provides an application of the golden pear blue fluorescent carbon dots in the detection of iron ions in liquor.

[0016] Further, the application method of detecting iron ions in liquor is:

[0017] (1) draw a standard working curve: add a certain amount of golden thorny pear blue fluorescent carbon dots in ethanol solution, then add different amounts of iron ion solution, measure the fluorescence intensity of each solution under the excitation wavelength of 355nm and the emission wavelength of 453nm using a fluorescence spectrometer, record the fluorescence emission spectrum, obtain the relationship between the fluorescence quenching efficiency and the concentration of iron ion, and draw a standard working curve;

[0018] (2) detecting the content of iron ion in the actual liquor sample: adding golden thorny pear blue fluorescent carbon dots into the liquor sample to be tested, detecting the fluorescence intensity at 453nm by fluorescence spectrometer, and calculating the content of iron ion in the liquor sample according to the standard working curve obtained in step (1).

[0019] Further, the final concentration of the golden thorny pear blue fluorescent carbon dots after adding the iron ion solution in step (1) is 50-200 μg / mL.

[0020] The positive effects of the present application are as follows:

[0021] Firstly, the present application uses golden thorny pear as raw material, and synthesizes blue fluorescent carbon dots by one-step hydrothermal reaction, which is derived from nature, green and non-toxic, and the synthesis method is simple and environmental friendly, and the pretreatment process is simple and easy to operate.

[0022] Secondly, the blue light-emitting carbon dots obtained by the present application have excellent structure and fluorescence advantages, and the rich phenolic hydroxyl groups and fluorescence characteristics make the Fe 3+ The blue fluorescent carbon dots have a unique and specific response to the fluorescence quenching of the blue fluorescent carbon dots, and are not interfered by other heavy metals and other components, and are especially suitable for the quantitative detection of Fe 3+ in liquor.

[0023] In addition, the present application can quench the fluorescence of the blue fluorescent carbon dots by Fe 3+ , and the content of Fe 3+ can be obtained by quantifying the quenching effect, which is simple and easy to operate, fast in response and determination speed, accurate in determination result, and conducive to the wide promotion in the field of liquor metal ion detection. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a preparation process schematic diagram of golden thorny pear blue fluorescent carbon dots;

[0025] Figure 2 is a morphology structure characterization of golden thorny pear blue fluorescent carbon dots, wherein a is a TEM diagram of golden thorny pear blue fluorescent carbon dots; b is a particle size distribution diagram of golden thorny pear blue fluorescent carbon dots; c is a Fourier transform infrared spectrum diagram of golden thorny pear blue fluorescent carbon dots;

[0026] Figure 3Fig. 1 is a fluorescence performance characterization of the blue fluorescent carbon dots of the golden thorn pear, wherein a is a fluorescence excitation, emission spectrum and ultraviolet-visible absorption spectrum of the blue fluorescent carbon dots of the golden thorn pear; and b is an excitation-emission spectrum of the blue fluorescent carbon dots of the golden thorn pear under different excitation wavelengths;

[0027] Figure 4 Fig. 4 is a detection specificity and standard curve of the blue fluorescent carbon dots of the golden thorn pear on Fe 3+ , wherein a is a fluorescence intensity change graph of the blue fluorescent carbon dots of the golden thorn pear under the same concentration and different metal ions; b is a fluorescence intensity graph of the blue fluorescent carbon dots of the golden thorn pear under different Fe 3+ concentrations; c is a fluorescence intensity signal column chart of the blue fluorescent carbon dots of the golden thorn pear with the addition of Fe 3+ and other interfering metal ions; and d is a standard curve graph of the blue fluorescent carbon dots of the golden thorn pear as a fluorescence probe for detecting Fe 3+ ;

[0028] Figure 5 Fig. 5 is a standard addition recovery rate of the blue fluorescent carbon dots of the golden thorn pear for detecting Fe 3+ in four kinds of liquor with different flavors, wherein a corresponds to the liquor with Maotai flavor, b corresponds to the liquor with strong aroma, c corresponds to the liquor with clear aroma, and d corresponds to the liquor with rice aroma. DETAILED DESCRIPTION

[0029] With reference to Figure 1 , the present application provides a preparation method of blue fluorescent carbon dots of the golden thorn pear, which comprises the following steps performed in sequence:

[0030] Step S1. Preparation of the golden thorn pear original juice

[0031] The fresh golden thorn pear is washed and the inedible part is removed, and then is crushed by a juicer, and the residue is filtered to obtain the golden thorn pear original juice.

[0032] Step S2. Hydrothermal reaction of the golden thorn pear original juice

[0033] 15-35 mL of the golden thorn pear original juice is added into a high-pressure kettle with polytetrafluoroethylene as the inner lining, and then is placed into a muffle furnace for hydrothermal reaction at 160-200℃ for 5-10 h. If the reaction temperature is lower than 160℃ or the reaction time is lower than 5 h, the carbon dots are not easy to form, and if the reaction temperature is higher than 200℃ or the reaction time is higher than 10 h, the surface groups of the carbon dots will change, and the detection effect on Fe 3+ is poor.

[0034] Step S3. Purification

[0035] After the hydrothermal reaction, the obtained brown solution was cooled to room temperature naturally, centrifuged at a speed of 9000-11000 r / min for 8-12 min, then further purified by a 0.20-0.25 μm microporous filter membrane, the purified solution was dialyzed in a dialysis bag with a molecular weight cut-off of 800-1200 Da for 20-28 h, and vacuum freeze-dried to obtain a brownish powder, which was the pure J-CDs, and stored at 4 ℃ for standby.

[0036] In the following, only certain exemplary embodiments are described simply. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present application. Therefore, the drawings and the description are considered to be exemplary in nature rather than limiting.

[0037] Example 1 Preparation of J-CDs

[0038] The present application provides a method for preparing J-CDs, which comprises the following steps in sequence:

[0039] Step S1. Preparation of J-CDs

[0040] The J-CDs were prepared by the following steps in sequence:

[0041] Step S2. Hydrothermal reaction of J-CDs

[0042] 20 mL of the J-CDs were added into a high-pressure kettle with a polytetrafluoroethylene lining, and then placed in a muffle furnace for hydrothermal reaction at 180 ℃ for 8 h.

[0043] Step S3. Purification

[0044] After the hydrothermal reaction, the obtained brown solution was cooled to room temperature naturally, centrifuged at a speed of 9000-11000 r / min for 8-12 min, then further purified by a 0.20-0.25 μm microporous filter membrane, the purified solution was dialyzed in a dialysis bag with a molecular weight cut-off of 800-1200 Da for 20-28 h, and vacuum freeze-dried to obtain a brownish powder, which was the pure J-CDs, and stored at 4 ℃ for standby.

[0045] Example 2 Characterization of J-CDs

[0046] The morphology of J-CDs was characterized by transmission electron microscopy (TEM). Figure 2 a is the TEM image of J-CDs prepared in Example 1, from Figure 2It can be seen that the blue fluorescent carbon dots of Malus halliana are approximately spherical and elliptical particle structures with good dispersibility, and the particle size distribution is a single dispersion of nanoparticles. Figure 2 It can be seen that the particle size distribution range is 1.75-4.0 nm, and the average particle size is about 2.75 nm, which proves that the blue fluorescent carbon dots of Malus halliana are successfully synthesized. Figure 2 It can be seen that the blue fluorescent carbon dots of Malus halliana have a characteristic absorption peak at 3200-3500 cm -1 A wide band is observed, which proves that there may be a characteristic absorption peak of N-H / O-H in the skeleton.

[0047] Figure 3 The fluorescence excitation, emission spectrum and UV-Vis absorption spectrum of the blue fluorescent carbon dots of Malus halliana are shown in Figure a. It can be seen from the figure that the optimal excitation and emission wavelengths of the blue fluorescent carbon dots of Malus halliana are 355 nm and 453 nm, respectively. In the UV-Vis absorption spectrum, there is a shoulder peak at 270-300 nm, which can be attributed to the π-π* transition of C=C bond; at the same time, the J-CDs have a shoulder peak in the range of 350-375 nm, which is attributed to the n-π* transition of C–O and C–N band.

[0048] Figure 3 The excitation-emission spectrum of the blue fluorescent carbon dots of Malus halliana under different excitation wavelengths is shown in Figure b. When the excitation wavelength changes between 320 and 460 nm, the emission center red shifts from 448 to 530 nm, which indicates that the PL emission of J-CDs is related to the change of PL excitation wavelength, and the change of the latter may be related to factors such as surface edge defects, quantum confinement effect, aromatic sp2 bond, etc.

[0049] In order to study the fluorescence stability of the blue fluorescent carbon dots of Malus halliana, the fluorescence intensity of the blue fluorescent carbon dots of Malus halliana in Example 1 was tested under different metal ions and different iron ion intensities. As shown in Figure Figure 4 a, in the ethanol solution with a concentration of 2400 μM and an ethanol volume fraction of 53% of different metal ions, the blue fluorescent carbon dots of Malus halliana only have a quenching effect on Fe 3+ , and other metal ions have little effect on the fluorescence intensity of the blue fluorescent carbon dots of Malus halliana, which indicates that the blue fluorescent carbon dots of Malus halliana have high specificity for recognizing iron ions in ethanol solution, and the blue fluorescent carbon dots of Malus halliana can be used as a fluorescence probe for detecting iron ions in liquor. In order to further investigate the influence of other metal ions on the detection of Fe 3+ by the blue fluorescent carbon dots of Malus halliana in liquor, as shown in Figure Figure 4 c, when other metal ions exist in the ethanol solution, Fe 3 +The back gold thorny pear blue fluorescent carbon dots all show obvious fluorescence quenching effect, and the quenching degree is extremely small, which shows that the gold thorny pear blue fluorescent carbon dots of Example 1 have strong metal ion anti-interference ability, and can detect iron ions in a complex and changeable liquor environment.

[0050] Example 3 Application of gold thorny pear blue fluorescent carbon dots in detecting iron ions in liquor

[0051] Example 3 of the present application provides an application of gold thorny pear blue fluorescent carbon dots in detecting iron ions in liquor, comprising:

[0052] (1) Draw a standard working curve: add a certain amount of gold thorny pear blue fluorescent carbon dots to an ethanol solution, and then add different amounts of iron ion solution, so that the final concentration of the gold thorny pear blue fluorescent carbon dots is 120 μg / mL, and the final concentration of the iron ions is 0.5 μM, 20 μM, 40 μM, 60 μM, 80 μM, 100 μM, 120 μM, 140 μM, 200 μM, 300 μM, 400 μM, 500 μM, 600 μM, 700 μM, 800 μM, 900 μM, 1000 μM, incubate at room temperature for 10 min, excite with 355 nm light, and measure the fluorescence intensity of each solution at 453 nm using a fluorescence spectrometer, record the fluorescence emission spectrum, and obtain the relationship between the fluorescence quenching efficiency (ΔF / F0) and the concentration of iron ions, and draw a standard working curve, wherein ΔF=F0-F, F0 represents the fluorescence emission intensity without adding iron ion solution, and F represents the fluorescence emission intensity after adding different amounts of iron ion solution;

[0053] Figure 4 ( Figure 4 b, 4d) shows that as the concentration of iron ions increases, the fluorescence intensity of the solution decreases, and when the concentration of iron ions is between 0.5-140 μM, a good linear relationship is shown, and the linear equation is ΔF / F0=0.00208x+0.0204, R 2 =0.9978, wherein x is the concentration of iron ions; this shows that the gold thorny pear blue fluorescent carbon dots of the present application have high sensitivity in detecting iron ions.

[0054] (2) Detection of iron ion content in liquor samples: a certain amount of golden pear blue fluorescent carbon dots was added to liquor samples of four types of flavor, including Maotai flavor, strong flavor, clear flavor and rice flavor, wherein the final concentration of the golden pear blue fluorescent carbon dots was 120 μg / mL, three different brands of Maotai flavor liquor were recorded as LTJ, LJ and MHJ, three different brands of strong flavor liquor were recorded as NZDQ, MZL and YXJ, three different brands of clear flavor liquor were recorded as HX, NLS and PZJ, and three different brands of rice flavor liquor were recorded as NGX, SHJ and WJT, the fluorescence intensity at 453 nm was detected by a fluorescence spectrometer, and the content of iron ions in the liquor samples was calculated according to the standard working curve obtained in step (1) and recorded as the original content;

[0055] Then different standard amounts of iron ion solution (the final concentration of iron ions was 35 μM, 65 μM, 100 μM and 120 μM, respectively) were added to the above-mentioned liquor sample system to be tested, and the final volume was 5 mL. The fluorescence intensity of the system at 453 nm was measured, and the total measured amount of iron ions was obtained according to the standard working curve, and the recovery rate was calculated as total measured amount / (original content + standard addition amount). The detection results are shown in Table 1. Figure 5 As shown in Table 1, the results show that the Fe 3+ content of the original liquor samples of different brands and different flavors tested is 0, and the Fe 3+ addition recovery rate of the Maotai flavor, strong flavor, clear flavor and rice flavor liquor of different brands tested is between 84-108.81%, and the RSD (relative standard deviation) is between 0.89-5.34%, indicating that the golden pear blue fluorescent carbon dots of the present application can be used for high-sensitivity quantitative detection of Fe 3+ in four main flavor liquors in China.

[0056] Example 4

[0057] The present application provides a preparation method of golden pear blue fluorescent carbon dots, which comprises the following steps in sequence:

[0058] Step S1. Preparation of golden pear juice

[0059] The golden pear fruit is washed, the inedible part is removed, then it is crushed with a juicer, and the filtrate is obtained by filtering the residue to obtain the golden pear juice.

[0060] Step S2. Hydrothermal reaction of golden pear juice

[0061] 15 mL of the golden pear juice is added to a high-pressure kettle with polytetrafluoroethylene as the inner liner, and then it is placed in a muffle furnace for hydrothermal reaction at 160℃ for 10 h.

[0062] Step S3. Separation and purification

[0063] After the hydrothermal reaction, the brown solution was cooled to room temperature naturally, centrifuged at a speed of 9000 r / min for 8 min, then further purified by a 0.20 μm microporous filter membrane, the purified solution was dialyzed in a dialysis bag with a molecular weight cut-off of 800 Da for 20 h, and vacuum freeze-dried to obtain a brownish powder, which was the pure blue fluorescent carbon dots of Rosa roxburghii Tratt, which was stored at 4℃ for standby.

[0064] Example 5

[0065] The embodiment 5 of the present application provides a preparation method of blue fluorescent carbon dots of Rosa roxburghii Tratt, which comprises the following steps in sequence:

[0066] Step S1. Preparation of Rosa roxburghii Tratt original juice

[0067] The fresh fruit of Rosa roxburghii Tratt was washed, the inedible part was removed, then crushed by a juicer, and the residue was filtered to obtain the original juice of Rosa roxburghii Tratt.

[0068] Step S2. Hydrothermal reaction of the original juice of Rosa roxburghii Tratt

[0069] 35 mL of the original juice of Rosa roxburghii Tratt was added to a high-pressure kettle with polytetrafluoroethylene as the inner liner, and then placed in a muffle furnace for hydrothermal reaction at 200℃ for 5 h.

[0070] Step S3. Separation and purification

[0071] After the hydrothermal reaction, the brown solution was cooled to room temperature naturally, centrifuged at a speed of 11000 r / min for 12 min, then further purified by a 0.25 μm microporous filter membrane, the purified solution was dialyzed in a dialysis bag with a molecular weight cut-off of 1200 Da for 28 h, and vacuum freeze-dried to obtain a brownish powder, which was the pure blue fluorescent carbon dots of Rosa roxburghii Tratt, which was stored at 4℃ for standby.

[0072] Example 6

[0073] The embodiment 6 of the present application provides a preparation method of blue fluorescent carbon dots of Rosa roxburghii Tratt, which comprises the following steps in sequence:

[0074] Step S1. Preparation of Rosa roxburghii Tratt original juice

[0075] The fresh fruit of Rosa roxburghii Tratt was washed, the inedible part was removed, then crushed by a juicer, and the residue was filtered to obtain the original juice of Rosa roxburghii Tratt.

[0076] Step S2. Hydrothermal reaction of the original juice of Rosa roxburghii Tratt

[0077] 20 mL of the original juice of Rosa roxburghii Tratt was added to a high-pressure kettle with polytetrafluoroethylene as the inner liner, and then placed in a muffle furnace for hydrothermal reaction at 185℃ for 7 h.

[0078] Step S3. Isolation and purification

[0079] After the hydrothermal reaction, the obtained brown solution was centrifuged at a speed of 10000 r / min for 11 min, then purified by a 0.23 μm microporous filter membrane, and the purified solution was dialyzed in a dialysis bag with a molecular weight cut-off of 1100 Da for 25 h, and vacuum freeze-dried to obtain a pure brownish powder of the golden pear blue fluorescent carbon dots, which was stored at 4°C for standby.

[0080] The above only describes the preferred embodiments of the present application, and it should be understood that the above description of the embodiments is only used to help understand the method of the present application and its core idea, and is not used to limit the protection scope of the present application, and any modification, equivalent replacement, etc. within the idea and principle of the present application should be included in the protection scope of the present application.

Claims

1. Use of a Malus hallings golden blue fluorescent carbon dot, characterized in that: The blue fluorescent carbon dots of Malus hallings are used for detecting the content of iron ions in liquor, and the preparation method of the blue fluorescent carbon dots of Malus hallings comprises the following steps: Fresh Malus hallings fruits are washed, inedible parts are removed, and then the fruits are crushed by a juicer, and the residue is filtered to obtain Malus hallings original juice; The Malus hallings original juice is subjected to hydrothermal reaction; The excitation and emission wavelengths of the blue fluorescent carbon dots of Malus hallings are 355 nm and 453 nm, respectively. The reaction temperature of the hydrothermal reaction is 160-200 DEG C, and the reaction time is 5-10 h.

2. The application of the golden pear blue fluorescent carbon dots according to claim 1, characterized in that: The hydrothermal reaction further comprises the steps of centrifugation, filter membrane filtration, dialysis and vacuum freeze drying.

3. The application of the golden pear blue fluorescent carbon dots according to claim 2, characterized in that: The centrifugal speed of the centrifugation is 9000-11000 r / min, and the centrifugal time is 8-12 min.

4. The application of the golden pear blue fluorescent carbon dots according to claim 2, characterized in that: The filter membrane used in the filter membrane filtration is a 0.20-0.25 μm microporous filter membrane.

5. The application of the golden pear blue fluorescent carbon dots according to claim 2, characterized in that: The dialysis bag used in the dialysis has a molecular weight cut-off of 800-1200 Da, and the dialysis time is 20-28 h.

6. The application of the golden pear blue fluorescent carbon dots according to claim 2, characterized in that: The vacuum freeze drying step obtains brownish powder, which is the blue fluorescent carbon dots of Malus hallings.

7. The application of the golden pear blue fluorescent carbon dots according to claim 1, characterized in that, The content detection method of the iron ions comprises the following steps: (1) a standard working curve is drawn: a certain amount of the blue fluorescent carbon dots of Malus hallings is added into an ethanol solution, different amounts of iron ion solution are added, a fluorescence spectrometer is used to measure the fluorescence intensity of each solution under the excitation wavelength of 355 nm and the emission wavelength of 453 nm, the fluorescence emission spectrum is recorded, the relationship between the fluorescence quenching efficiency and the concentration of the iron ions is obtained, and the standard working curve is drawn; (2) the content of the iron ions in an actual liquor sample is detected: the blue fluorescent carbon dots of Malus hallings are added into the liquor sample to be detected, the fluorescence intensity at 453 nm is detected by using a fluorescence spectrometer, and the content of the iron ions in the liquor sample is calculated according to the standard working curve obtained in step (1).

8. The application of the golden pear blue fluorescent carbon dots according to claim 7, characterized in that: The final concentration of the blue fluorescent carbon dots of Malus hallings after the addition of the iron ion solution in step (1) is 50-200 μg / mL.

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