Preparation method and application of fluorescent carbon dots

Abstract

The invention relates to a preparation method and application of fluorescent carbon dots, and belongs to the field of new materials. The invention provides a method for synthesizing the fluorescent carbon dots in one step through a microwave method by taking a traditional Chinese medicinal material common vladimiria root as a carbon source, and the method is simple, convenient, economical and environment-friendly. The prepared fluorescent carbon dots have excellent fluorescence performance, the maximum excitation wavelength is 360 nm, and the maximum emission wavelength is 465 nm. The novel fluorescent chemical sensor is developed by using the fluorescent carbon dots and is used for rapidly detecting Fe < 3 + > with high sensitivity and high selectivity, the linear range is 0.2-200 [mu] mol / L, and the detection limit is as low as 62nmol / L. The method shows good recovery rate and reproducibility in actual water sample detection, provides a simple, convenient and efficient new way for Fe < 3 + > detection, and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the field of new materials and relates to a preparation method of fluorescent carbon dots and applications thereof. Background Art

[0002] Metal ions are particularly important in our daily lives. 3+ It is one of the most important trace elements for animals, plants and humans. It plays an important role in the storage and transportation of oxygen to form human hemoglobin, signal transduction, catalysis and enzyme metabolism. Insufficient or excessive intake can lead to various problems such as liver damage, decreased immunity and hemochromatosis. 3+ The abnormal range of Fe is also one of the factors affecting many diseases such as anemia and Alzheimer's disease. 3+ It is closely related to the metabolic and photosynthetic processes of phytoplankton in aquatic environments, such as nitrate reduction, nitrogen fixation, and respiratory function. The World Health Organization (WHO) recommends that Fe 3+ The content of Fe should be lower than 0.3 mg / L, otherwise it will be regarded as a toxic metal. 3+ Sensitive and selective detection methods are essential. 3+ Research reports on detection methods include electrochemical methods, voltammetry, inductively coupled plasma mass spectrometry, chromatography, colorimetry, and atomic absorption spectrometry. However, these methods have the disadvantages of expensive instruments and equipment, cumbersome operating procedures, and high costs. Therefore, it is necessary to develop a fast, convenient, highly sensitive, and highly selective Fe 3+ The detection method is of great significance.

[0003] Nanomaterials refer to materials that are in the three-dimensional space of nanometer size (1-100nm) in at least one dimension, or materials composed of them as basic units. Among these materials, carbon dots (CDs) have attracted extensive attention due to their facile synthesis, low cost, adjustable surface functionalization, outstanding photostability, good biocompatibility, good hydrophilicity and environmental friendliness. The above excellent properties have led to their wide application in various fields, such as cell imaging, energy storage, heavy metal ion sensing, biomolecules, targeted drug delivery, solar cells and photocatalysis. So far, the synthesis of CDs mainly includes two methods: "top-down" and "bottom-up". The "top-down" synthesis strategy involves physical or chemical exfoliation from larger carbon sources to obtain CDs. The "bottom-up" synthesis technique uses small carbon sources to prepare CDs. Many previous studies used chemical reagents to synthesize CDs, which may cause environmental pollution and thus limit their practical applications. So far, a variety of natural plants have been used to prepare CDs. However, the low fluorescence quantum yield (QY) hinders their application in biological systems. Therefore, a facile, rapid, and environmentally friendly strategy to synthesize high quantum yield carbon dots is a key factor for their practical application. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a method for preparing fluorescent carbon dots and its application, especially Fe 3+ Application in detection.

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

[0006] The present invention provides a method for preparing fluorescent carbon dots, the steps of which are as follows:

[0007] S1: drying the Chinese herbal medicine Sichuan costusroot at a high temperature, and then crushing and sieving;

[0008] S2: Aucklandia lappa powder was mixed with ultrapure water, dispersed in a flask, and sonicated;

[0009] S3: placing in a microwave reactor, heating with microwaves for reaction, then filtering with a filter membrane and dialyzing with a dialysis bag, and drying to prepare the fluorescent carbon dots;

[0010] The mass volume ratio of the Sichuan costusroot powder to ultrapure water is 1-3:30 (g:mL);

[0011] The power of the microwave reactor is 600-1000W, and the microwave heating reaction is 6-10min;

[0012] The pore size of the filter membrane is 0.22 μm, the molecular weight cut-off of the dialysis bag is 1000 Da, and the dialysis time is 48-72 h;

[0013] The fluorescent carbon dots prepared by the method have a particle size of 4 to 8 nm;

[0014] The maximum excitation wavelength of the fluorescent carbon dots is 360 nm, and the maximum emission wavelength is 465 nm;

[0015] The fluorescent carbon dots are used to detect Fe 3+ Applications in

[0016] Fluorescent carbon dots for Fe detection 3+ The method is characterized in that:

[0017] S1: Add the fluorescent carbon dots to different Fe 3+ The fluorescence quenching reaction was carried out in a phosphate buffer solution with a concentration of 1.5 3+ The linear relationship between the concentrations of

[0018] S2: Add fluorescent carbon dots to Fe-containing 3+ A fluorescence quenching reaction is performed in the test environmental water body of phosphate buffer to obtain the fluorescence intensity;

[0019] S3: Calculate the Fe content in the environmental water to be tested through the standard curve 3+ concentration.

[0020] The beneficial effects of the present invention are:

[0021] In the present invention, the traditional Chinese medicine Sichuan costusroot is used as the carbon source, and a simple, economical and environmentally friendly synthesis method is adopted to synthesize carbon dots through a one-step microwave reaction. The maximum excitation and emission wavelengths of the carbon dots are located at 360nm and 465nm respectively. 3+ When introduced into the carbon dot solution, the fluorescence intensity of the carbon dots was quenched. Based on the carbon dots, a "closed-type" fluorescent chemical sensor was successfully established. The obtained fluorescent sensor showed simplicity, sensitivity and high selectivity. 3+ Fluorescence sensor, carbon dots in detecting Fe 3+ The carbon dots showed excellent performance with a linear range of 0.2-200 μmol / L and a detection limit of 62 nmol / L (3σ / k). 3+ The spiked recovery rate was 99.2% to 101.6%, and the relative standard deviation was 1.2% to 2.7%.

[0022] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0024] Figure 1 Synthesis process of carbon dots from Sichuan costusroot and detection of Fe 3+ Schematic diagram of the principle;

[0025] Figure 2 Transmission electron microscopy (TEM) image of carbon dots (A); histogram of carbon dot size distribution (B); X-ray photoelectron spectroscopy (XPS) image of carbon dots (C); high-resolution C1s spectrum of carbon dots XPS (D); emission spectrum of carbon dots (E); carbon dots and Fe 3+ Absorption spectrum and carbon dots fluorescence spectrum (FS) diagram (F);

[0026] Figure 3 For different concentrations of Fe 3+ Fluorescence quenching of carbon dots;

[0027] Figure 4 The influence of pH value. 0 (black curve) and I (red curve) represent the 3+ and Fe 3+ The fluorescence intensity of carbon dots in the presence of 0 -I) / I 0 (blue curve) indicates the addition of Fe 3+ The quenching efficiency after c(CDs):20mg / L; c(Fe 3+ ):20μmol / L; pH value: 4.4, 5.8, 6.2, 6.6, 7.0, 7.4, 8.0, 9.3;

[0028] Figure 5 The effect of reaction time. 0 (black curve) and I (red curve) represent the 3+ and Fe 3+ The fluorescence intensity of carbon dots in the presence of 0 -I) / I 0 (blue curve) indicates the addition of Fe 3+ The quenching efficiency after c(CDs):20mg / L; c(Fe 3+ ):20μmol / L; pH value: 6.2.

[0029] Figure 6 (A) Different concentrations of Fe 3+ Fluorescence emission spectra of carbon dots. (B) Standard curve. 0and I represent the 3+ and Fe 3+ Fluorescence intensity of carbon dots in the presence of; c(CDs): 20 mg / L; 0.1 mol / L phosphate buffer, pH 6.2.

[0030] Figure 7 Detection of Fe for carbon dots 3+ Selectivity with other anions or metal ions. 3+ The concentration of anions or other metal ions is 20μmol / L. 0.1mol / L phosphate buffer pH 6.2; excitation wavelength: 360nm; c(CDs): 20mg / L; I 0 and I represent the absence of Fe 3+ and Fe 3+ The fluorescence intensity of carbon dots in the presence of 0 -I) / I 0 Indicates the addition of Fe 3+ All histograms represent the quenching efficiency of the system in the presence of anions or other metal ions (I 0 -I) / I 0 . DETAILED DESCRIPTION

[0031] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0032] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0033] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0034] Example 1 Preparation of fluorescent carbon dots

[0035] 1. Instruments and Reagents

[0036] Fluorescence spectra were recorded on a Hitachi model F-2700FL fluorescence spectrophotometer (Japan). The size and morphology of carbon dots were analyzed using a TECNAI 10 transmission electron microscope (The Netherlands). UV-visible absorption spectra were acquired using a Hitachi U-2550 spectrophotometer (Japan). X-ray photoelectron spectra (XPS) of carbon dots were collected on a ThermoEscalab 250Xi X-ray photoelectron spectrometer (USA).

[0037] Sichuan costusroot, a traditional Chinese medicinal material, was purchased from Sichuan Longsen Chinese Medicine Co., Ltd. FeCl 3 、NaF、NaCl、KBr、KI、Na 2 CO 3 、Na 2 SO 4 AgNO 3 、BaCl 2 、ZnCl 2 、CoCl 2 、NiCl 2 MgCl 2 、MnCl 2 、Pb(NO 3 ) 2 , CuCl 2 All chemicals were provided by Shanghai Sinopharm Chemical Reagent Co., Ltd. All chemicals used were analytically pure and used directly without further purification. 0.1 mol / L phosphate buffer solutions of different pH values ​​were prepared using 0.2 mol / L NaH 2 PO 4 and 0.2 mol / LNa 2 HPO 4 The stock standard solutions were prepared in different proportions.

[0038] 2. Preparation of Fluorescent Carbon Dots

[0039] Fluorescent carbon dots were synthesized in one step by microwave method using traditional Chinese medicine Sichuan wood fragrance as carbon source. The traditional Chinese medicine Sichuan wood fragrance was dried at 105℃, and after drying, it was crushed and sieved through a 20-mesh sieve. 1.00g of Sichuan wood fragrance powder was weighed, dispersed in a 100mL round-bottom flask with 30mL ultrapure water, and placed in a microwave reactor after ultrasonic treatment for 10min. The microwave reactor power was adjusted to 1000W, and the microwave heating reaction was performed for 6min. When the solution changed from light yellow to dark brown, it indicated that the carbon dots had been successfully synthesized. After the reaction was complete, it was cooled to room temperature, centrifuged at 10000r / min for 15min to remove the large particles, and the supernatant was filtered with a 0.22μm filter membrane, the filtrate was collected and dialyzed with a dialysis bag (1000Da) for 72h to obtain a light yellow fluorescent carbon dot dispersion, and the light yellow fluorescent carbon dot solution was vacuum dried for 24h to obtain yellow fluorescent carbon dots. Finally, the carbon dots were dispersed in double distilled water to obtain a 0.4 g / L dispersion, which was stored in a refrigerator at 4°C for later use.

[0040] Example 2 Preparation of fluorescent carbon dots

[0041] Fluorescent carbon dots were synthesized in one step by microwave method using the Chinese herbal medicine Sichuan wood fragrance as carbon source. After the Chinese herbal medicine Sichuan wood fragrance was dried at 80°C, it was crushed and passed through a 60-mesh sieve. Weigh 2.00g of the Chinese herbal medicine Sichuan wood fragrance powder, disperse it in a 100mL round-bottom flask with 30mL ultrapure water, and place it in a microwave reactor after ultrasonic treatment for 10min. Adjust the microwave reactor power to 600W, and microwave heating reaction for 10min. When the solution changes from light yellow to dark brown, it indicates that the carbon dots have been successfully synthesized. After the reaction is complete, cool to room temperature, centrifuge at 10000r / min for 15min to remove the large particles, filter the supernatant with a 0.22μm filter membrane, collect the filtrate and dialyze it with a dialysis bag (1000Da) for 60h, and obtain a light yellow fluorescent carbon dot dispersion. Then, the light yellow fluorescent carbon dot solution is vacuum dried for 24h to obtain yellow fluorescent carbon dots. Finally, the carbon dots were dispersed in double distilled water to obtain a 0.4 g / L dispersion, which was stored in a refrigerator at 4°C for later use.

[0042] Example 3 Preparation of fluorescent carbon dots

[0043] Fluorescent carbon dots were synthesized in one step by microwave method using the Chinese herbal medicine Sichuan wood fragrance as carbon source. After the Chinese herbal medicine Sichuan wood fragrance was dried at a constant temperature of 40°C, it was crushed and passed through a 100-mesh sieve. 3.00 g of the Chinese herbal medicine Sichuan wood fragrance powder was weighed, dispersed in a 100 mL round-bottom flask with 30 mL of ultrapure water, and placed in a microwave reactor after ultrasonic treatment for 10 minutes. The microwave reactor power was adjusted to 800 W, and the microwave heating reaction was performed for 8 minutes. When the solution changed from light yellow to dark brown, it indicated that the carbon dots had been successfully synthesized. After the reaction was complete, it was cooled to room temperature, centrifuged at 10000 r / min for 15 minutes to remove the large particles, and the supernatant was filtered with a 0.22 μm filter membrane, the filtrate was collected and dialyzed with a dialysis bag (1000 Da) for 48 hours to obtain a light yellow fluorescent carbon dot dispersion, and then the light yellow fluorescent carbon dot solution was vacuum dried for 24 hours to obtain yellow fluorescent carbon dots. Finally, the carbon dots were dispersed in double distilled water to obtain a 0.4 g / L dispersion, which was stored in a refrigerator at 4°C for later use.

[0044] Example 4 Characterization of Fluorescent Carbon Dots

[0045] The structure and properties of the prepared carbon dots were characterized by fluorescence spectroscopy (FS), transmission electron microscopy (TEM), ultraviolet-visible absorption spectroscopy (UV-Vis) and X-ray photoelectron spectroscopy (XPS). Figure 2 (A) Transmission electron microscopy (TEM) images show that the carbon dots prepared from Sichuan woodruff are spherical or quasi-spherical, with uniform particles, good dispersion, and no agglomeration. Figure 2 From the carbon dot particle size distribution histogram (B), we can see that, through the statistics of 50 carbon dot particles, the carbon dot particle size is mainly distributed in the range of 4 to 8 nm, with an average particle size of 5.9 nm. Figure 2 From the X-ray photoelectron spectroscopy (XPS) image of carbon dots (C), it can be seen that characteristic peaks appear at 284.8eV and 532.5eV, indicating that the carbon dots mainly contain C and O elements. Figure 2 From the high-resolution C1s spectrum of the carbon dots in (D), it can be seen that the absorption peak of C1 is located at 284.74 eV, accounting for 48.79%, the absorption peak of C2 is located at 286.22 eV, accounting for 38.91%, the absorption peak of C3 is located at 287.75 eV, accounting for 10.54%, and the absorption peak of C4 is located at 288.86 eV, accounting for 1.76%. It can be seen that the surface of the carbon dots is rich in O functional groups. Figure 2 (E) is the emission spectrum of carbon dots at an excitation wavelength of 320nm to 390nm, with a maximum excitation wavelength of 360nm. Figure 2 (F) It can be seen that at the carbon dot concentration of 20 mg / L and Fe 3+ The concentration was 100 μmol / L, and the emission peak of carbon dots was located at 465 nm under the maximum excitation wavelength. 3+The characteristic absorption peaks of the carbon dots appear at 280nm and 290nm respectively. Taking quinine sulfate as the standard substance (fluorescence quantum yield is 54%), the fluorescence quantum yield of the carbon dots is 15%.

[0046] Example 5 Application of fluorescent carbon dots

[0047] 1. Carbon dots detect Fe 3+ Feasibility analysis

[0048] By adding different concentrations of Fe to the carbon dot solution with a concentration of 20 mg / L 3+ , studied the use of carbon dots to detect Fe 3 + feasibility, such as Figure 3 When Fe is added 3+ When Fe 3+ When the concentration of Fe is 2 μmol / L, 20 μmol / L and 200 μmol / L, the quenching efficiency is 17.6%, 66.4% and 93.6%, respectively. 3+ concentration, which shows that carbon dots can be used to detect Fe 3+ Feasibility characteristics.

[0049] 2. Optimization of pH conditions

[0050] To get better Fe 3+ Detection sensitivity, the detection conditions such as pH value were optimized, such as Figure 4 The effect of pH value of phosphate buffer solution on fluorescence quenching efficiency was studied in the range of 4.4-9.3. 0 -I) / I 0 It increases slightly from pH 4.4 to pH 6.2 and then decreases. 0 and I represent the addition of Fe 3+ Fluorescence intensity of carbon dots before and after; (I 0 -I) / I 0 Representatives join Fe 3+ Based on the above experimental results, pH 6.2 was finally used as the detection pH for Fe 3+ The optimal pH value.

[0051] 3. Optimization of reaction time conditions

[0052] In addition, the effect of reaction time on detection was studied, with a time span of 60 min, e.g. Figure 5 It is clearly seen that the fluorescence intensity of the carbon dots remains stable even after 60 min, which indicates that the carbon dots have excellent fluorescence stability. 3+After the addition of Fe, the fluorescence intensity of the carbon dots decreased immediately, and the fluorescence quenching efficiency reached the maximum when the reaction time was 2 min. In general, the quenching efficiency remained stable from 2 min to 60 min. 3+ After that, select Fe 3+ Perform quantitative testing.

[0053] 4.Fe 3+ Quantitative analysis

[0054] Under the optimal conditions obtained in the above study, as Fe 3+ With the increase of concentration, the fluorescence intensity of carbon dots gradually decreases ( Figure 6 A). Figure 6 B shows the relationship with Fe 3+ The concentration has a good linear correlation in the range of 0.20-200 μmol / L, and the linear equation can be expressed as (I 0 -I) / I=0.0872x+0.0672, the correlation coefficient is 0.9992, where I 0 -I is in the absence of Fe 3+ (I 0 ) and Fe 3+ The fluorescence intensity difference of (I) when present, x is Fe 3+ The concentration of Fe 3+ The detection limit of Fe was 62nmol / L (3σ / k), which is consistent with other literature reports on Fe 3+ Compared with the method (as shown in Table 1), this Fe 3+ The sensor has a good detection range and a low detection limit.

[0055] Table 1 Different Fe 3+ Comparison of detection methods

[0056]

[0057] 5. Carbon dots on Fe 3+ Selectivity of the test

[0058] As we all know, the selectivity of the proposed sensor is also very important in actual sample analysis. Since there are multiple ions in the actual sample, these ions may also cause the fluorescence intensity of the carbon dots to decrease, thus affecting the Fe 3+ To explore the effect of possible interfering species, several anions, such as F - , Cl - Br - ,I - , CO 3 2- 、SO 4 2-and some metal ions, including Ag + , Ba 2+ 、Zn 2+ 、Co 2+ 、Ni 2+ Mg 2+ , Mn 2+ , Pb 2+ , Cu 2+ , and the fluorescence spectrum was measured under 360nm excitation. Figure 7 As shown in the figure, it is clearly revealed that anions have no significant effect on the measurement. In addition, in the presence of carbon dots, the quenching efficiency of metal ions is almost less than 10%. Therefore, this method is effective for Fe 3+ The determination showed high selectivity.

[0059] 6. Interference Experiment

[0060] In order to explore the effects of other metal cations and anions on Fe 3+ Detect interference and keep Fe 3+ The concentration of F was constant at 20 μmol / L. - 、Ag + , Ba 2+ 、Zn 2+ The concentration of Br is 400 μmol / L; - , CO 3 2- 、Co 2+ 、Ni 2+ Mg 2+ The concentration of I- and SO 4 2 -、Mn 2+ , Pb 2+ , Cu 2+ The concentrations of 1 and 2 were 1200 μmol / L. As shown in Table 2, the quenching efficiency (I 0 -I) / I 0 It is still close to 66.4%, and the relative standard deviation (RSD) is 0.6%-2.5%. Obviously, the coexistence of other metal cations and anions does not interfere with the carbon dots to Fe 3+ Detection.

[0061] Table 2 Interference experiments at different concentrations

[0062]

[0063] 7.Fe 3+ Detection

[0064] Take 1 mL of 0.1 mol / L phosphate buffer (pH 6.2) and 200 μL of 0.4 g / L carbon dot solution, add appropriate amount of Fe 3+ The standard solution or sample solution was added and supplemented with double distilled water to a total volume of 4.0 mL. The mixed solution was thoroughly vortexed and reacted at room temperature for 2 min. The photomultiplier voltage of the fluorescence spectrophotometer was set to 400 V and the slit width to 5 nm. The fluorescence intensity was measured at room temperature and an excitation wavelength of 360 nm (the average of three measurements was taken). By comparing with the standard curve, Fe 3+ Content detection and analysis.

[0065] 8. Fe in actual water samples 3+ Detection

[0066] The actual water samples were collected from local steel plant wastewater, rivers and pharmaceutical wastewater, and ultrafiltration was performed using a 10KD ultrafiltration membrane. 1 mL of the actual water sample, 1 mL of 0.1 mol / L phosphate buffer (pH 6.2), and 200 μL of 0.4 g / L carbon dot solution were added to a test tube, and the final volume of the mixture was adjusted to 4.0 mL with double distilled water. The mixture was vortexed and reacted at room temperature for 2 min. Fe in the actual water sample 3+ The content was determined at an excitation wavelength of 360 nm. In order to obtain a satisfactory recovery rate, a recovery experiment was also carried out.

[0067] Practical application performance of carbon dots for Fe detection in steel plant wastewater, river and pharmaceutical wastewater 3+ First, Fe was measured in actual samples. 3+ Then 5μmol / L, 20μmol / L and 50μmol / L of Fe were added to the actual water samples. 3+ The results are shown in Table 3, with recoveries ranging from 99.2% to 101.6% and relative standard deviations (RSDs) ranging from 1.2% to 2.7%. These results indicate that carbon dots can be used for Fe 3+ The effectiveness of the test.

[0068] Table 3 Fe in wastewater from steel plants, rivers and pharmaceutical plants 3+ The measurement results.

[0069]

[0070] Using the traditional Chinese medicine Aucklandia lappa as the carbon source, carbon dots were prepared by microwave method, and a new type of fluorescent sensor was developed for rapid, highly sensitive and highly selective detection of Fe 3+ Based on Fe 3+ The fluorescence quenching effect of carbon dots demonstrates the detection of Fe in aqueous solution. 3+The linear range is 0.2-200 μmol / L and the detection limit is 62 nmol / L. This provides a simple and efficient method for synthesizing fluorescent carbon dots and achieves Fe 3+ Rapid detection of chlorinated carbon was achieved. In addition, the established method was validated by three real water samples and a satisfactory recovery rate was obtained. Cds from Aucklandia oxyphylla have many advantages, such as low cost, environmental protection, and excellent chemical and optical stability, which provide a potential avenue for the application of Cds in chemical sensing and environmental applications.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing fluorescent carbon dots, characterized in that: The steps are as follows: S1: drying the Chinese herbal medicine Sichuan costusroot at a high temperature, and then crushing and sieving; S2: Aucklandia lappa powder was mixed with ultrapure water, dispersed in a flask, and sonicated; S3: placing in a microwave reactor, heating with microwaves for reaction, then filtering with a filter membrane and dialyzing with a dialysis bag, and drying to prepare the fluorescent carbon dots.

2. The method for preparing fluorescent carbon dots according to claim 1, wherein: The mass volume ratio of the Sichuan costusroot powder to ultrapure water is 1-3:30 (g:mL).

3. The method for preparing fluorescent carbon dots according to claim 1, characterized in that: The power of the microwave reactor is 600-1000W, and the microwave heating reaction is 6-10 minutes.

4. The method for preparing fluorescent carbon dots according to claim 1, characterized in that: The pore size of the filter membrane is 0.22 μm, the molecular weight cutoff of the dialysis bag is 1000 Da, and the dialysis time is 48-72 h.

5. The fluorescent carbon dots prepared according to any one of claims 1 to 4, characterized in that: The particle size of the carbon dots is 4 to 8 nm.

6. The fluorescent carbon dot according to claim 5, characterized in that: The maximum excitation wavelength of the fluorescent carbon dots is 360 nm, and the maximum emission wavelength is 465 nm.

7. The fluorescent carbon dots according to claim 6 are used to detect Fe 3+ Application in.

8. Detection of Fe by Fluorescent Carbon Dots 3+ The method is characterized in that: S1: Add the fluorescent carbon dots to different Fe 3+ The fluorescence quenching reaction was carried out in a phosphate buffer solution with a concentration of 1.5 3+ The linear relationship between the concentrations of S2: Add fluorescent carbon dots to Fe-containing 3+ A fluorescence quenching reaction is performed in the test environmental water body of phosphate buffer to obtain the fluorescence intensity; S3: Calculate the Fe content in the environmental water to be tested through the standard curve 3+ concentration.

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