Biomass doped carbon dots as well as preparation method and application thereof

Abstract

The invention discloses biomass doped carbon dots as well as a preparation method and application thereof. The novel biomass-doped carbon dots are synthesized by taking pomegranate peel powder as a carbon source and 2-hydroxy-3-naphthoic acid as a dopant and adopting a one-step hydrothermal method, selective detection of the acid dropping glyphosate in the soil is realized, and the prepared carbon dots have good selective identification on the acid dropping glyphosate and can be used for detecting the acid dropping glyphosate in the soil. And the method can be effectively applied to acid dropping and glyphosate detection under different soil conditions. The preparation method of the prepared carbon dots is simple and easy to implement, low in cost, high in sensitivity and excellent in selectivity, can be widely applied to detection of acid dropping glyphosate in various soil environments, and has good practical application value and social value. The invention lays a theoretical foundation for practical development of novel doped carbon dots, and also provides a new idea and enlightenment for subsequent research in related fields.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of carbon quantum dots, and particularly relates to a biomass-doped carbon dot and a preparation method and application thereof. BACKGROUND

[0002] Some herbicides and pesticides, such as ammonium glufosinate, tribenuron, glyphosate, etc., are widely used in agriculture at present, but these herbicides cannot be completely utilized, and are thus left in the soil in large amounts. These residual herbicides are extremely easy to be enriched through the food chain, and finally endanger human health, threaten the life safety and the quality of life. Traditional detection methods have many drawbacks, while biomass carbon dots (CDs) have the characteristics of green environmental protection and simple preparation, and can also be made into high-tech materials from agricultural waste, achieving green development. Making high-tech materials from agricultural waste by using resource recycling is the concept of green development, which is of great help to environmental protection and sustainable agricultural development. For biomass resources, it opens up a new way of resource utilization, and realizes the recycling of resources. SUMMARY

[0003] The application aims to provide a biomass-doped carbon dot and a preparation method and application thereof. The application synthesizes a new type of doped CDs by using a one-step hydrothermal method with pomegranate peel powder as a carbon source and 2-hydroxy-3-naphthoic acid as a dopant, and uses the CDs to selectively detect glyphosate in soil.

[0004] To achieve the above-mentioned application purposes, the application adopts the following technical solutions:

[0005] The application provides a preparation method of a biomass-doped carbon dot, which comprises the following steps:

[0006] (1) drying, crushing and sieving fruit peels to obtain fruit peel powder;

[0007] (2) doping the fruit peel powder with a dopant, and then adding ultrapure water to perform a heating reaction;

[0008] (3) filtering the product after the reaction with an ultrafiltration membrane to obtain biomass-doped carbon dots.

[0009] Further, the fruit peels in the step (1) are pomegranate peels.

[0010] Further, the dopant in the step (2) is 2-hydroxy-3-naphthoic acid.

[0011] Further, the mass ratio of the fruit peel powder to the dopant is 1:1-2.

[0012] Further, the heating temperature in the step (2) is 180-200 DEG C, and the heating time is 6-8 h.

[0013] Further, the mass ratio of the total mass of the fruit peel powder and the dopant in step (2) to the mass of ultrapure water is about 30-40:1.

[0014] Further, the ultrafiltration membrane in step (3) is selected from 0.45 μm and 0.22 μm filter membranes.

[0015] The application further provides the biomass-doped carbon dots prepared by the preparation method.

[0016] The application provides application of the biomass-doped carbon dots in detection of herbicides in soil.

[0017] Further, the herbicide is glyphosate.

[0018] Further, the detection step is as follows: the dried and sieved soil sample is filtered using ultrapure water, 3 mL of the obtained filtrate is added into a cuvette, then 25 μL of the biomass-doped carbon dots is added, a capillary tube is used for stirring, after the mixture is fully mixed, fluorescence detection is performed under visible light or an ultraviolet lamp at 365 nm, and the reaction change of the filtrate of different soil samples is observed; if the solution reaction presents orange red under visible light or the solution reaction presents green under the ultraviolet lamp, it indicates that the soil sample contains herbicides.

[0019] Compared with the prior art, the application has the following advantages and beneficial effects:

[0020] The application prepares a new type of biomass-doped carbon dots by using pomegranate peel powder as a carbon source and 2-hydroxy-3-naphthalene carboxylic acid as a dopant through one-step hydrothermal synthesis, and realizes selective detection of glyphosate in soil, and the prepared carbon dots have good recognition performance for glyphosate and can be effectively applied to detection of glyphosate in different soil environments. The carbon dots prepared by the application have the advantages of simple and easy preparation, low cost, high sensitivity, excellent selectivity, wide application in detection of glyphosate in various soil environments, good practical application value and social value. The application lays a theoretical foundation for practical development of new doped carbon dots and provides a new idea and inspiration for subsequent research in related fields. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a preparation diagram of the doped CDs.

[0022] Figure 2 It is a TEM morphology diagram of the doped CDs.

[0023] Figure 3 It is an infrared spectrum diagram of the doped CDs.

[0024] Figure 4 XPS spectra of doped CDs.

[0025] Figure 5 UV, excitation and emission spectra of doped CDs.

[0026] Figure 6 Emission spectra of doped CDs under different excitation.

[0027] Figure 7 Selectivity of doped CDs to different herbicides.

[0028] Figure 8 Anti-interference of doped CDs to different pesticides.

[0029] Figure 9 Anti-interference of doped CDs to different metal ions.

[0030] Figure 10 Anti-interference of doped CDs to different anions.

[0031] Figure 11 Fluorescence titration and linear relationship of doped CDs.

[0032] Figure 12 Reaction of doped CDs with GLY under the influence of different pH.

[0033] Figure 13 Reaction of doped CDs with GLY.

[0034] Figure 14 Changes of two mixtures of doped CDs and GLY under visible light and ultraviolet light.

[0035] Figure 15 Fluorescence lifetime of doped CDs.

[0036] Figure 16 Reaction of doped CDs with GAY in different soils.

[0037] Figure 17 Reaction of doped CDs with GAY in different soils under different light. DETAILED DESCRIPTION

[0038] The technical solutions of the present application will be further described in detail in combination with the following specific examples.

[0039] In the following examples, unless otherwise specified, the experimental methods used are conventional methods, and the materials, reagents, etc. used can be purchased from biological or chemical reagent companies.

[0040] Example 1: Preparation of a new type of doped CDs

[0041] The CDs in this experiment were prepared using a hydrothermal method. Figure 1 The specific steps are as follows:

[0042] The pomegranate peel used in this experiment was obtained by peeling the outer skin of fresh pomegranates purchased from the market before consumption. After being air-dried, the peel was ground into powder and passed through a 200-mesh sieve to obtain pomegranate peel powder. 150 mg of pomegranate peel powder and an equal amount of 2-hydroxy-3-naphthoic acid were accurately weighed and poured into 50 mL polytetrafluoroethylene lined containers. 10 mL of ultrapure water was then added. The containers were placed in a high-pressure reactor, the lid was tightened, and the reactor was heated in a constant-temperature drying oven at 180°C for 6 hours. After the reaction was completed, the mixture was cooled to room temperature and then filtered through disposable filter membranes of 0.45 μm and 0.22 μm, respectively, to obtain the CDs-doped solution, which was stored in a refrigerator at 4°C for later use.

[0043] Example 2: Confirmatory Test

[0044] I. Experimental Procedure

[0045] 1. Selectivity of pesticides

[0046] To test the single-target recognition ability of CDs for pesticides, the experimental procedure was as follows: First, 3 mL of ultrapure water was added to a cuvette as a base solution. Then, 25 μL of CD solution was precisely added to the solution using a pipette. Next, 25 μL of different pesticide solutions, such as glyphosate, 2-methyl-4-chlorothiazide, bensulfuron-methyl, cyhalofop-butyl, acetochlor, fluoxastrobin, chlorpyrifos, and clodinafop-propargyl, were added to the mixture using a spotting capillary. After the mixture was fully mixed, fluorescence spectroscopy was measured and analyzed.

[0047] 2. Interference Experiment

[0048] To further investigate the specific selectivity of CDs for particular targets, other substances that may be present in the soil, such as metal ions (Al), were added to the CDs. 3+ Ca 2+ Cd 2+ Co 2+ Cr 3+ Fe 2+ Fe 3+ K + Mg 2+ Na + Cu 2+ Mn 2+ Ni 2+ Pb 2 + Zn 2+ ), anion (CH3COO) - CO32-, P2O7 4-, Br - , Cl - , F - , HCO3 - , I - , NO2 - , PO4 3- , SCN - ), pesticides (glyphosate, chlorpyrifos, avermectin, chlorfluazuron, chlorfluazuron, methomyl) were tested by fluorescence, and possible fluorescence changes were recorded and analyzed.

[0049] 3. Fluorescence titration

[0050] In order to understand the selectivity of CDs and target objects, fluorescence titration experiments were carried out. The experimental steps are as follows: first, dissolve 25 μL of CDs solution in 3 mL of ultrapure water as the initial solution. Then, according to the preset gradient of the target object concentration, start from 4 μL, and add the target object solution to the above solution by 4 μL each time, mix well and immediately measure the fluorescence intensity, and continue to add the target object solution until the fluorescence of carbon quantum dots no longer changes. Through the experimental steps and data recording, the complex interaction between the two can be understood.

[0051] 4. Analysis of recognition mechanism

[0052] The recognition mechanism mainly involves the recognition processes of inner filter effect, fluorescence resonance energy transfer (FRET) and photoinduced electron transfer (PET). This experiment mainly shows that the reaction between doped CDs and glyphosate occurs by observing the color change of the solution under visible light and ultraviolet light. Combined with literature and fluorescence lifetime changes, the recognition mechanism is determined.

[0053] II. Experimental results

[0054] 1. Structural characterization of carbon dots

[0055] According to the steps in Example 1, a doped CDs solution was prepared, then concentrated, dialyzed for 24 h, and copper mesh was used as a sample carrier to observe the morphology of CDs by transmission electron microscopy. The results are shown in Figure 2 From the figure, it can be seen that the CDs prepared in Example 1 are spherical in shape, with a diameter of less than 10 nm, and the overall structure is relatively regular, and the dispersion in aqueous solution is relatively uniform.

[0056] The infrared spectrum test adopts potassium bromide tabletting method, and the Fourier infrared spectrometer is used for testing, and the results are as follows Figure 3The main absorption peaks in the infrared spectrum are as follows: the broad absorption peak at 3403 cm-1 is O-H stretching motion, the absorption peak at 2898 cm-1 is C-H anti-symmetric stretching motion of alkane, the absorption peak at 1712 cm-1 is C=O stretching vibration of carboxylic acid, the absorption peaks at 1616 cm-1 and 1512 cm-1 are C=C stretching vibration of aromatic hydrocarbon, the absorption peak at 1399 cm-1 is C-O stretching vibration of carboxylic acid, and the absorption peak at 1033 cm-1 is C-O stretching vibration of phenol.

[0057] In order to further study the surface functional groups, chemical composition and elemental state of the doped CDs, X-ray photoelectron spectroscopy was used to test the doped CDs. The results are shown in Figure 4 Figure 2. As shown in Figure 2, three peaks were found at 284.8, 398.8 and 531.3 eV, which were attributed to C1s, N1s and O1s, respectively. The C 1s spectrum can be resolved into C=C / C-C at 284.8 eV and 283.4 eV. The N 1s spectrum also has two peaks at 398.3 eV and 400.5 eV, which are attributed to C-N=C and C-NHx, respectively. The peak at 531.3 eV is attributed to C=O in the O1s spectrum.

[0058] In addition, the ultraviolet-visible absorption spectrum, excitation spectrum and emission spectrum of the CDs were studied in detail. The results are shown in Figure 5 Figure 3. As shown in Figure 3, there are two obvious ultraviolet absorption peaks at 245 nm and 271 nm, which are attributed to the π→π* transition of C=C or the n→π* transition of C=O in the sample. The maximum excitation of the CDs is 378 nm, and the maximum emission wavelength has two peaks at 412 nm and 520 nm.

[0059] As shown in Figure 6 Figure 4, the fluorescence performance of the CDs was tested under different excitation wavelengths of Ex 300 nm-400 nm, and it can be observed that the fluorescence peak of the CDs shifts, showing the dependence of the excitation wavelength. Since the two peaks of the CDs change, 520 nm / 412 nm is selected as the modeling index for detecting glyphosate.

[0060] 2. Selectivity to pesticides

[0061] In this experiment, the interaction between the doped carbon dots and pesticides was tested, and it was found that the CDs exhibit the strongest fluorescence emission at 412 nm and 520 nm. However, it is worth noting that when in contact with glyphosate, the fluorescence intensity of the CDs significantly decreases at 412 nm, while it significantly increases at 520 nm, and other herbicides do not have a significant effect on the fluorescence of the carbon dots. This proves that the CDs have a high selective recognition ability for glyphosate under the condition that no fluorescence is detected for the pesticide.

[0062] To confirm the unique selective recognition ability of CDs to glyphosate, an interference experiment was designed and performed. The experiment was designed as follows: 25 μL of herbicide was added to 3 mL of water for one measurement, and 25 μL of CDs was added after stirring for one measurement, and the change in the two peak values in the fluorescence graph was observed. As shown in FIG. 6, the ratio of CDs plus herbicide to herbicide alone at 412 nm and 520 nm was 1.2, and it can be clearly seen from the graph that the carbon dots have unique recognition for glyphosate. Figure 7 The ratio of CDs plus herbicide to herbicide alone at 412 nm and 520 nm was 1.2, and it can be clearly seen from the graph that the carbon dots have unique recognition for glyphosate.

[0063] 3. Interference experiment

[0064] To further prove the unique recognition of CDs, the following experiment was designed: 3 mL of ultrapure water was added to a cuvette, 25 μL of CDs was added, and then different pesticides were added to determine whether the CDs would have a significant fluorescence reaction with the pesticides. As shown in FIG. 7, the doped CDs did not have a significant fluorescence reaction with the pesticides. Figure 8 The doped CDs did not have a significant fluorescence reaction with the pesticides.

[0065] To confirm whether CDs will only react with glyphosate in soil, the following experiment was designed: 3 mL of ultrapure water was added to a cuvette, 25 μL of CDs was added, and then different metal ions were added to determine whether the CDs would react with these metal ions. As shown in FIG. 8, the doped CDs did not have a significant reaction with the metal ions. Figure 9 The doped CDs did not have a significant reaction with the metal ions.

[0066] To ensure that CDs can stably react with glyphosate in different anion environments, the following experiment was designed: 3 mL of ultrapure water was added to a cuvette, followed by the addition of 100 μL of anion, and then CDs and glyphosate were added to observe whether the CDs could react with glyphosate in different anion environments, as shown in FIG. 9. Figure 10 As shown in FIG. 9, the anion had no effect on the recognition of CDs for glyphosate.

[0067] 4. Fluorescence titration

[0068] To explore the interaction between CDs and glyphosate, a fluorescence titration test was performed to detect the response of CDs to glyphosate. 3 mL of ultrapure water was prepared and placed in a cuvette, 25 μL of CDs was added for fluorescence testing, and then 4 μL of glyphosate was added each time.

[0069] From the fluorescence titration curve shown in FIG. 10, it can be seen that the fluorescence intensity of CDs increased with the increase of glyphosate, and the fluorescence intensity of CDs reached a maximum when the concentration of glyphosate was 0.2 mM. Figure 11It can be seen that with the drop of acid glyphosate, the peak of carbon dots at 412 nm gradually decreased, while the peak at 520 nm first decreased and then gradually increased until the fluorescence intensity no longer changed. According to the titration results, referring to existing research, the concentration of acid glyphosate and the fluorescence intensity of doped CDs showed a linear relationship, and the linear regression equation was obtained: y = 1173x + 0.97 (R2 = 0.990), where the concentration x unit is μL / mL, and the detection limit is calculated according to formula 3σ / k as 1.8 × 10-4μL / mL.

[0070] 5, pH effect

[0071] In order to evaluate the effect of CDs in different pH (1-14) environment, fluorescence test was carried out. First, 3 mL of solution with a certain pH was added to the cuvette as the base solution, then 25 μL of CDs solution was accurately added to the solution with a pipette, and the test was carried out after stirring for 1 min with a sample capillary. The fluorescence change of doped CDs at different pH, as shown in Figure 12 , the values in the figure are the ratios at 412 nm and 520 nm under different pH, the larger the ratio, the stronger the reaction, from the information in the figure, it can be concluded that the fluorescence intensity ratio gradually increases from pH 1-4. The fluorescence intensity ratio from pH 4-8 is not significant, close to the test value without buffer solution, which is conducive to application. But the fluorescence intensity ratio gradually decreases from pH 8-12, and gradually increases from pH 12-14.

[0072] 6, identification mechanism analysis

[0073] As Figure 13 , the CDs in the fluorescence diagram show a decrease in peak at 412 nm and an increase in peak at 520 nm, indicating that CDs have reacted with acid glyphosate. As Figure 14 , CDs appear to change from light orange yellow to orange red under sunlight. Under the irradiation of ultraviolet lamp, the originally light blue carbon dots change to green after reacting with acid glyphosate, which reveals that the CDs can react with acid glyphosate. Figure 15 The fluorescence lifetime decay curves of CDs and CDs-GLY system are shown, the results show that the fluorescence lifetime of CDs is 2.27 ns (τ0), and the fluorescence lifetime of CDs-GLY system is 3.01 ns (τ), the ratio of τ / τ0 is about 1.33, which also indicates that the fluorescence is enhanced after adding acid glyphosate to the CDs solution. According to existing research, the reason for fluorescence enhancement is mainly because of the realization of aggregation induced enhancement (AIE) approach. In this mechanism, acid glyphosate reacts with the groups on the surface of CDs, causing changes in surface charge, leading to changes in radiant energy, resulting in fluorescence enhancement.

[0074] Example 3: Application of novel doped CDs in soil

[0075] In order to apply the research results to the actual sample detection, we selected several types of soil including roadside soil sample 1 (holly root soil), farmland soil samples 2-4 (corn black soil, wheat light yellow soil, and wheat gray yellow soil) for processing. First, the soil samples were air-dried, then ground through a 200 mesh sieve, and 5 grams of soil sample was added to 20 milliliters of ultrapure water and filtered through a funnel. The filtrate was collected and detected. Under visible light and ultraviolet light (365 nm), the identification performance of different soil sample filtrates was observed and analyzed in detail, and the use effect of carbon dots in actual samples and the interaction relationship with pesticides were evaluated.

[0076] In this test, four different soil samples were filtered, and their aqueous solutions were used instead of ultrapure water for experiments. The purpose was to test whether CDs could react with glyphosate in different soil environments. 3 mL of soil filtrate from different sources was added to a cuvette, 25 μL of CDs was added first, and then glyphosate was added. It was observed whether CDs could react with glyphosate in different soil environments. As shown in Figure 16 CDs could react with glyphosate in different soil environments.

[0077] In order to further determine the application in soil, as shown in Figure 17 CDs could react with glyphosate in different soil filtrates under daylight or ultraviolet light. CDs presented orange yellow under daylight and orange red after reacting with glyphosate, and under ultraviolet light, the near light blue fluorescence changed to green fluorescence. This indicates that the CDs can be applied in soil samples.

[0078] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, for those skilled in the art, the technical solutions recorded in the foregoing examples can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions claimed by the present application.

Claims

1. A method for preparing biomass-doped carbon dots, characterized in that, Includes the following steps: (1) The fruit peel is dried, crushed and sieved to obtain fruit peel powder; (2) After mixing the fruit peel powder with the adulterants, add ultrapure water and heat to react; (3) The product after the reaction was filtered by ultrafiltration membrane to obtain biomass-doped carbon dots.

2. The preparation method according to claim 1, characterized in that, The fruit peel used in step (1) is pomegranate peel.

3. The preparation method according to claim 1, characterized in that, The dopant in step (2) is 2-hydroxy-3-naphthoic acid.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the fruit peel powder to the adulterant is 1:1-2.

5. The preparation method according to claim 1, characterized in that, The heating temperature in step (2) is 180℃-200℃, and the heating time is 6h-8h.

6. The preparation method according to claim 1, characterized in that, The total mass ratio of fruit peel powder and adulterants in step (2) to the mass ratio of ultrapure water is approximately 30-40:

1.

7. The preparation method according to claim 1, characterized in that, The ultrafiltration membranes used in step (3) are 0.45μm and 0.22μm membranes.

8. The biomass-doped carbon dots prepared by the method of claim 1, characterized in that, The diameter of the bio-doped carbon dots is less than 10 nm.

9. The application of the biomass-doped carbon dots as described in claim 8 in the detection of herbicides in soil.

10. The application according to claim 9, characterized in that, The herbicide is glyphosate-trimethoate.

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