CN114062336A - Method for detecting herbicide killing intensity of pesticide based on nitrogen-doped carbon quantum dot fluorescence 'on-off-on' mode - Google Patents
Method for detecting herbicide killing intensity of pesticide based on nitrogen-doped carbon quantum dot fluorescence 'on-off-on' mode Download PDFInfo
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Abstract
The invention discloses a method for detecting the herbicide control intensity of pesticides based on a nitrogen-doped fluorescent carbon quantum dot fluorescent 'on-off-on' mode, wherein the nitrogen-doped fluorescent carbon quantum dot is convenient to synthesize, has good and stable fluorescent characteristics, and is Fe3+Can quench the fluorescence, has strong weed killing ability and Fe3+The specific binding enables the quenched fluorescence to recover within 1-2 min, so that the method can rapidly and specifically detect the weed control intensity, and can be used for detecting the weed control intensity in fruits, vegetables and water samples.
Description
Technical Field
The invention belongs to the technical field of organic matter detection, and particularly relates to a method for detecting the herbicide controlling strength of a pesticide by using a carbon quantum dot fluorescence 'on-off-on' method.
Background
Strong weed control, also known as 3-amino-1, 2, 4-triazole, is a non-selective chemical herbicide. Due to its strong solubility in water (the solubility in water at 25 ℃ is 280g/L), leaching may occur under certain conditions, such as sandy soil with low organic carbon content and high water level, resulting in polluted ground and surface water, and its volatility ratio is poor (the boiling point is 245 ℃), which easily causes strong weed killing to be enriched in water, causing serious pollution of water, and polluting plant food (fruits, vegetables) by using water as a medium. Excessive exposure to herbicides can cause damage to human alveoli and even thyroid and liver tumors, potentially posing a hazard to the environment and human health. Therefore, the method for detecting the herbicide controlling strength of the pesticide conveniently and quickly with high selectivity has great significance.
Since the carbon quantum dots are found for the first time in 2004 as a novel nano material, the carbon quantum dots attract a great deal of attention due to high chemical stability, good electrical conductivity and luminescence, and good biocompatibility. Carbon quantum dots are typically sp with a diameter of less than 10nm2/sp3/sp2-sp3A collection of hybrid carbonaceous entities with specific quantum confinement, edge effects. Carbon quantum dots have a single-layer or multi-layer graphene structure and thus generally have a graphene lattice with a large number of oxygen-containing functional groups on the surface, and are now generally defined as a class of carbon (primarily sp) molecules2) Core and surface passivation functional group core-shell type nanometer material. At present, the application of various dopants and the research progress of the surface functionalization of the carbon quantum dots improve the fluorescence performance of the carbon quantum dots, improve the chemical stability of the carbon quantum dots and enable the carbon quantum dots to have wider application prospects.
Disclosure of Invention
The invention aims to provide a method for sensitively and quickly detecting the herbicide controlling strength of a pesticide by using a carbon quantum dot fluorescence 'on-off-on' method.
The technical scheme adopted for solving the technical problems comprises the following steps:
1. mixing nitrogen-doped fluorescent carbon quantum dot aqueous solution and Fe3+Adding the solution into a centrifuge tube in sequence, and then using ultrapure water to fix the volume so that the concentration of the nitrogen-doped fluorescent carbon quantum dots in the obtained mixed solution A is 0.6-1.0 mu g/mL and Fe3+The concentration of (A) is 0.015-0.030 mmol/L, and the fluorescence intensity F of the obtained mixed solution A at 430nm is recorded under the excitation wavelength of 340nm0。
2. Doping nitrogen with fluorescenceCarbon quantum dot aqueous solution and Fe3+Adding the solution into a centrifuge tube in sequence, adding a weed control strong standard solution, and then fixing the volume with ultrapure water to obtain mixed liquid B in which the nitrogen is doped with fluorescent carbon quantum dots and Fe3+The concentration of the mixed solution B is the same as that in the step 1, after the mixed solution B is vibrated for 1-2 min, the fluorescence intensity F of the mixed solution B at 430nm, added with the standard solution with the herbicide controlling strength of different concentrations is recorded under the excitation wavelength of 340nm, and F-F is used0The ordinate represents the concentration of the herbicide controlling agent added, and the abscissa represents the concentration of the herbicide controlling agent added, and a standard curve of the fluorescence intensity varying with the concentration of the herbicide controlling agent is drawn.
3. And (3) when the sample to be tested for the weed control intensity is added according to the method in the step (2), the concentration of the weed control intensity in the sample to be tested for the weed control intensity can be calculated by contrasting the linear equation of the standard curve in the step (2) with the fluorescence intensity at the position of 430nm under the excitation wavelength of 340 nm.
The synthesis method of the nitrogen-doped fluorescent carbon quantum dot comprises the following steps: adding citric acid and urea into ultrapure water according to a mass ratio of 1:1, uniformly mixing, adding into a Teflon high-pressure reaction kettle, putting the Teflon high-pressure reaction kettle into a drying oven, keeping the temperature at 180 ℃ for 1h, naturally cooling to room temperature to obtain a nitrogen-doped fluorescent carbon quantum dot crude solution, adding the solution obtained through reaction into a 1kw dialysis bag, dialyzing the ultrapure water for 8-12 h to remove small molecular impurities, collecting the dialyzate, freeze-drying for 12-16 h to obtain blue nitrogen-doped fluorescent carbon quantum dot powder, and storing in a refrigerator at 4 ℃.
Fe as described above3+The solution is analytically pure FeCl3An aqueous solution.
The standard solution for controlling weed is a water solution with strong weed control.
The sample to be detected for the herbicide controlling strength is a fruit and vegetable or water sample. When the sample to be tested is a fruit and vegetable, adding the fruit and vegetable into a mixed solution of dichloromethane and acetic acid aqueous solution with the volume concentration of 1% in a volume ratio of 1:1 before testing, preferably controlling the adding amount of the fruit and vegetable in the mixed solution to be 20-30 g/100mL, crushing, homogenizing, performing centrifugal separation, discarding a lower dichloromethane layer, taking a supernatant, filtering with a 0.22 mu m microfiltration membrane, and taking an obtained filtrate as the sample to be tested.
The invention has the following beneficial effects:
the nitrogen-doped fluorescent carbon quantum dot is synthesized by a one-step hydrothermal method, is convenient to synthesize, has good fluorescent characteristic and water stability, and is Fe3+Can quench the fluorescence, has strong weed killing ability and Fe3+The quenched fluorescence is recovered within 1-2 min through specific binding, so that the method can quickly and specifically detect the weed control intensity, and can be used for detecting the weed control intensity in fruits, vegetables and water samples.
Drawings
FIG. 1 is a graph of the UV-VIS absorption spectrum of nitrogen-doped fluorescent carbon quantum dots.
FIG. 2 is a fluorescence spectrum of nitrogen-doped fluorescent carbon quantum dots at different excitation wavelengths.
FIG. 3 is a transmission electron microscope and high resolution transmission electron microscope image of nitrogen doped fluorescent carbon quantum dots.
Fig. 4 is a particle size distribution diagram of the nitrogen-doped fluorescent carbon quantum dots.
Fig. 5 is an X-ray diffraction pattern of nitrogen-doped fluorescent carbon quantum dots.
Fig. 6 is an X-ray photoelectron spectrum of nitrogen-doped fluorescent carbon quantum dots.
Fig. 7 is a fourier transform infrared spectrum of nitrogen-doped fluorescent carbon quantum dots.
FIG. 8 shows Fe in the presence of varying concentrations of herbicide3+And a fluorescence spectrum of the mixed solution of the nitrogen-doped fluorescent carbon quantum dots.
FIG. 9 is Fe3+And the linear relation graph of the fluorescence intensity of the mixed solution of the nitrogen-doped fluorescent carbon quantum dots at 430nm along with the change of the concentration of the herbicide controlling intensity.
FIG. 10 is Fe3+The anti-interference performance of the mixed solution of the nitrogen-doped fluorescent carbon quantum dots on strong weed control identification is improved.
Detailed Description
The invention will be further described in detail with reference to the following figures and examples, but the scope of the invention is not limited to these examples.
Example 1
1. Adding 2g of citric acid and 2g of urea into 20mL of ultrapure water, uniformly mixing, adding into a Teflon high-pressure reaction kettle, putting the Teflon high-pressure reaction kettle into an oven, and heating at 180 DEG CPerforming hydro-thermal synthesis for 1h, dialyzing the obtained dark-pine-stone green fluorescent carbon quantum dot solution with a 1kw dialysis bag for 12h, and freeze-drying to obtain blue nitrogen-doped fluorescent carbon quantum dot powder. As can be seen from fig. 1, an absorption peak is observed at 238nm in the uv-vis absorption spectrum of the obtained nitrogen-doped fluorescent carbon quantum dot, the peak is due to pi-pi transition of C ═ C bond of oxidized aromatic structure, and the absorption band at 332nm is due to surface carboxyl group, amino group and other groups passivating surface traps. When the excitation wavelength was changed from 310nm to 370nm, the fluorescence intensity of the nitrogen-doped fluorescent carbon quantum dot reached a maximum at 340nm and then further decreased, but the emission peak position was at 430nm, which hardly changed with the change in the excitation wavelength (see fig. 2), showing photoluminescence characteristics unrelated to excitation, which were the same as the reported carbon quantum dots. As can be seen from fig. 3, the obtained nitrogen-doped fluorescent carbon quantum dots are spherical particles with good dispersibility, the particle size range is 4-13 nm, the average particle size is 8nm (see fig. 4), and a high-resolution image shows that the nitrogen-doped fluorescent carbon quantum dots have a lattice spacing of 0.32nm, which also proves the X-ray diffraction pattern of the nitrogen-doped fluorescent carbon quantum dots (fig. 5). As shown in fig. 5, two peaks at 11.7 ° and 27.3 °, corresponding to the weaker peaks at lattice spacings of 0.75nm and 0.32nm, respectively, and 2 θ of 11.7 °, are due to the lattice spacing of graphite oxide, indicating that the nitrogen-doped fluorescent carbon quantum dots are partially oxidized during synthesis; the sharp high-intensity reflection at 27.3 ° is closer to the lattice spacing of graphene of 0.34nm, which indicates that the generated nitrogen-doped fluorescent carbon quantum dot has a graphene structure and proves the successful synthesis of the nitrogen-doped fluorescent carbon quantum dot. And analyzing the element composition and the chemical bond type in the synthesized nitrogen-doped fluorescent carbon quantum dot by adopting X-ray photoelectron spectroscopy. As shown in fig. 6, there are three major peaks at 284.6, 399.0 and 531.6eV corresponding to C1s, N1s and O1s, respectively, indicating successful incorporation of nitrogen atoms into the framework of carbon quantum dots by hydrothermal treatment. The doping concentration of nitrogen was found to be about 12.1% from the peak intensities of carbon, nitrogen and oxygen. The high resolution spectrum of C1s exhibits three major peaks, with the strongest peak at 284.6eV corresponding to the sp of the carbon atom2Conjugated two-dimensional skeleton structure, and two others at 288.1The peaks at 9eV and 286.10eV are attributed to C ═ O bonds and C-O/C-N bonds. The high resolution spectrum of N1s shows that the hybridization mode of nitrogen element is mainly represented by pyrrole nitrogen and graphite nitrogen. In addition, the functional group characterization of the nitrogen-doped carbon quantum dots was also performed by Fourier transform infrared spectroscopy (see FIG. 7), which is shown at 3150cm-1、1700cm-1、1584cm-1And 1399cm-1The position has 4 strong peaks which respectively represent stretching vibration of-OH, stretching vibration of C ═ O, stretching vibration of N-H and bending vibration of C-O-C, and the result shows that a large number of amino groups, hydroxyl groups and carboxyl groups exist on the surface of the nitrogen-doped fluorescent carbon quantum dot, so that the nitrogen-doped carbon quantum dot has the potential of becoming a fluorescent probe with good hydrophilicity.
Adding ultrapure water into the nitrogen-doped fluorescent carbon quantum dot powder to prepare a nitrogen-doped fluorescent carbon quantum dot solution with the concentration of 3 mug/mL; mu.L of 3. mu.g/mL fluorescent carbon quantum dot solution and 100. mu.L of 0.1mmol/L FeCl3The aqueous solution was sequentially added to a 1.5mL centrifuge tube, and then the total volume was adjusted to 400. mu.L with ultrapure water, and the fluorescence intensity F at 430nm was recorded at an excitation wavelength of 340nm0。
2. 100 mu L of 3 mu g/mL nitrogen-doped fluorescent carbon quantum dot solution and 100 mu L of 0.1mmol/L FeCl are sequentially added into a 1.5mL centrifuge tube3The total volume of the aqueous solution and 200 mul of the herbicidal strong aqueous solution with the concentration of 0.5, 1, 5, 10, 15, 20, 25, 30, 35, 40, 50, 60, 80 and 100 mug/mL respectively is 400 mul, the mixed solution is vibrated for 1min, and the fluorescence intensity F of the herbicidal strong added at 430nm is recorded under the excitation wavelength of 340nm, and F-F is used as the F-F0The ordinate represents the concentration of the herbicide controlling agent added, and the abscissa represents the concentration of the herbicide controlling agent added, and a standard curve of the fluorescence intensity varying with the concentration of the herbicide controlling agent is drawn.
As can be seen from FIG. 8, the addition of various concentrations of the herbicidally strong Fe3+The fluorescence light intensity of the nitrogen-doped fluorescence carbon-doped quantum dot mixed solution system is increased along with the increase of the concentration of the herbicide control intensity without red shift or blue shift, which shows that the herbicide control intensity can effectively recover Fe3+Fluorescence of the mixed solution system with the nitrogen-doped fluorescent carbon quantum dots. As can be seen from FIG. 9, the fluorescence intensity of the system is obviously changed along with the increase of the concentration of the herbicide in the system, which indicates that Fe3+The detection sensitivity of the system and the fluorescent carbon quantum dot mixed solution to the weed control is high. Constructing a standard curve for detecting the herbicidal strength, wherein when the concentration of the herbicidal strength is 0-40 mug/mL, the fluorescence intensity difference value and the concentration of the herbicidal strength are in a linear relation, the correlation coefficient is 0.9996, and the linear equation is as follows: y is 19.77318 x-2.9781, wherein y is the difference in fluorescence intensity (F-F)0) And x is the addition concentration of the herbicide. As can be seen in FIG. 9, F-F0The linear relationship with the concentration of the herbicide controlling is good. The lowest limit of detection was calculated using the formula for the lowest limit of detection, with a limit of detection (LOD of 3s/K, s being the standard deviation of the blank, K being the slope of the linear equation) of 0.183 μ g/mL (about 0.183mg/kg), which is lower than the limit of 0.5mg/kg in fruit specified in national standards.
3. Weighing 5g of fruits to be detected in a 50mL centrifuge tube, adding 10mL of dichloromethane and 10mL of acetic acid aqueous solution with the volume concentration of 1%, crushing, homogenizing, centrifuging for 15min at the rotating speed of 5000r/min, discarding the lower dichloromethane layer, taking 5mL of supernatant, filtering with a 0.22 mu m microfiltration membrane, and taking the obtained filtrate as a weed control strong sample to be detected. And (3) when the sample to be tested for the weed control intensity is added according to the method in the step (2), the concentration of the weed control intensity in the sample to be tested for the weed control intensity can be calculated by contrasting the linear equation of the standard curve in the step (2) with the fluorescence intensity at the position of 430nm under the excitation wavelength of 340 nm.
To demonstrate the beneficial effects of the present invention, Fe3+The mixed solution system with the nitrogen-doped fluorescent carbon quantum dots is used for testing the strong selectivity of the herbicide control, and the test conditions are as follows:
100 mu L of 3 mu g/mL nitrogen-doped fluorescent carbon quantum dot solution and 100 mu L of 0.1mmol/L FeCl are sequentially added into a 1.5mL centrifuge tube3Aqueous solution, 200 μ L of a 20 μ g/mL herbicidal composition, or 200 μ L of 1mmol/L interfering ion (such as K)+、Na+、Ca2+、Mg2+、Fe2+、Cu2+、SO4 2-、Cl-And HPO4 2-The amount of the interfering ions is 10 times of the amount of the iron ions) or 200 mul of 100 mug/mL other pesticides (such as mancozeb, phoxim and cypermethrin, the amount of the other pesticides is 5 times of the herbicide control), the total volume is 400 mul, the mixed solution is vibrated for 1min and then is excited at 340nm under the excitation wavelengthThe fluorescence intensity of the different interfering ions and pesticides added at 430nm was recorded.
As shown in FIG. 10, Fe was present only when the weed was strongly killed3+The fluorescence intensity of the mixed solution system with the nitrogen-doped fluorescent carbon quantum dots is obviously recovered. All other pesticides, interfering ions are not compatible with Fe3+Reacting with a nitrogen-doped fluorescent carbon quantum dot mixed solution system. These results indicate that other ions and other pesticides have little interference with the fluorescence value of the system, indicating quenched Fe3+The nitrogen-doped fluorescent carbon quantum dot mixed solution system has high selectivity for strong detection of target weed control.
Claims (7)
1. A method for detecting the herbicide control intensity of pesticides based on a nitrogen-doped fluorescent carbon quantum dot fluorescence 'on-off-on' mode is characterized by comprising the following steps:
(1) mixing nitrogen-doped fluorescent carbon quantum dot aqueous solution and Fe3+Adding the solution into a centrifuge tube in sequence, and then using ultrapure water to fix the volume so that the concentration of the nitrogen-doped fluorescent carbon quantum dots in the obtained mixed solution A is 0.6-1.0 mu g/mL and Fe3+The concentration of (A) is 0.015-0.030 mmol/L, and the fluorescence intensity F of the obtained mixed solution A at 430nm is recorded under the excitation wavelength of 340nm0；
(2) Mixing nitrogen-doped fluorescent carbon quantum dot aqueous solution and Fe3+Adding the solution into a centrifuge tube in sequence, adding a weed control strong standard solution, and then fixing the volume with ultrapure water to obtain mixed liquid B in which the nitrogen is doped with fluorescent carbon quantum dots and Fe3+The concentration of the mixed solution B is the same as that in the step (1), after the mixed solution B is vibrated for 1-2 min, the fluorescence intensity F of the mixed solution B at 430nm, added with the herbicide-killing strong standard solution with different concentrations is recorded under the excitation wavelength of 340nm, and F-F is used0The ordinate represents the concentration of the herbicide controlling intensity, the abscissa represents the concentration of the herbicide controlling intensity, and a standard curve of the fluorescence intensity changing along with the concentration of the herbicide controlling intensity is drawn;
(3) and (3) when the sample to be tested for the herbicidal strength is added according to the method in the step (2), the concentration of the herbicidal strength in the sample to be tested for the herbicidal strength can be calculated by contrasting the linear equation of the standard curve in the step (2) with the fluorescence intensity at the position of 430nm under the excitation wavelength of 340 nm.
2. The method for detecting the herbicidal strength of the pesticide based on the nitrogen-doped fluorescent carbon quantum dot fluorescent on-off-on mode as claimed in claim 1, wherein the synthetic method of the nitrogen-doped fluorescent carbon quantum dot comprises the following steps: adding citric acid and urea into ultrapure water according to a mass ratio of 1:1, uniformly mixing, adding into a Teflon high-pressure reaction kettle, putting the Teflon high-pressure reaction kettle into a drying oven, keeping the temperature at 180 ℃ for 1h, naturally cooling to room temperature to obtain a nitrogen-doped fluorescent carbon quantum dot crude solution, adding the solution obtained through reaction into a 1kw dialysis bag, dialyzing the ultrapure water for 8-12 h to remove small molecular impurities, collecting the dialyzate, freeze-drying for 12-16 h to obtain blue nitrogen-doped fluorescent carbon quantum dot powder, and storing in a refrigerator at 4 ℃.
3. The method for detecting the herbicidal strength of the pesticide according to claim 1 based on the nitrogen-doped fluorescent carbon quantum dot fluorescent "on-off-on" mode, wherein the method comprises the following steps: said Fe3+The solution is analytically pure FeCl3An aqueous solution.
4. The method for detecting the herbicidal strength of the pesticide according to claim 1 based on the nitrogen-doped fluorescent carbon quantum dot fluorescent "on-off-on" mode, wherein the method comprises the following steps: the standard solution for controlling weed intensity is an aqueous solution for controlling weed intensity.
5. The method for detecting the herbicidal strength of the pesticide according to claim 1 based on the nitrogen-doped fluorescent carbon quantum dot fluorescent "on-off-on" mode, wherein the method comprises the following steps: the sample to be detected for the herbicide controlling strength is a fruit and vegetable or water sample.
6. The method for detecting the herbicidal strength of the pesticide according to claim 5 based on the nitrogen-doped fluorescent carbon quantum dot fluorescent 'on-off-on' mode, wherein the method comprises the following steps: when the sample to be detected is the fruit and vegetable, before detection, the fruit and vegetable are added into a mixed solution of dichloromethane and acetic acid aqueous solution with the volume concentration of 1% in a volume ratio of 1:1, the mixed solution is crushed, homogenized and then centrifugally separated, a dichloromethane layer at the lower layer is discarded, supernatant is taken and filtered by a microfiltration membrane with the thickness of 0.22 mu m, and the obtained filtrate is used as the sample to be detected.
7. The method for detecting the herbicidal strength of the pesticide according to claim 6, which is based on the nitrogen-doped fluorescent carbon quantum dot fluorescent "on-off-on" mode, and is characterized in that: adding the fruits and vegetables into a mixed solution of dichloromethane and 1% by volume of acetic acid aqueous solution with the volume concentration of 1:1, and controlling the adding amount of the fruits and vegetables in the mixed solution to be 20-30 g/100 mL.
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| CN103965504A (en) * | 2014-05-13 | 2014-08-06 | 江苏联合化工有限公司 | Preparation method of rear earth doped core-shell type fluorescent imprinting polymer |
| AU2020103861A4 (en) * | 2020-05-19 | 2021-02-18 | Sichuan Agricultural University | Preparation of chicken feather nitrogen-doped carbon quantum dots based fluorescent probes and paraquat detection method |
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| CN103965504A (en) * | 2014-05-13 | 2014-08-06 | 江苏联合化工有限公司 | Preparation method of rear earth doped core-shell type fluorescent imprinting polymer |
| AU2020103861A4 (en) * | 2020-05-19 | 2021-02-18 | Sichuan Agricultural University | Preparation of chicken feather nitrogen-doped carbon quantum dots based fluorescent probes and paraquat detection method |
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| Title |
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| 邓祥意;冯雅丽;李浩然;杜竹玮;滕青;康金星;王洪君;: "基于氮掺杂碳量子点荧光猝灭效应检测Fe~(3+)", 分析化学, no. 10 * |
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