CN115820247A - Fluorescent detection material, preparation method thereof and Pb (II) detection method - Google Patents
Fluorescent detection material, preparation method thereof and Pb (II) detection method Download PDFInfo
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Abstract
The invention discloses a fluorescence detection material, a preparation method of the fluorescence detection material and a detection method of Pb (II). The fluorescent detection material includes a carbon dot and polyethyleneimine attached to the carbon dot. The preparation method comprises the following steps: (1) obtaining a first dispersion containing carbon dots; (2) Mixing the first dispersion liquid with a polyethyleneimine solution to obtain a second dispersion liquid; (3) And homogenizing the second dispersion liquid to obtain the fluorescence detection material. The preparation method of the fluorescence detection material is simple in process, convenient to control and low in generation cost, and through verification, the polyethyleneimine is doped on the carbon dots, so that the fluorescence quenching intensity of the fluorescence detection material during Pb (II) detection is remarkably improved compared with the fluorescence quenching intensity of the fluorescence detection material during Pb (II) detection by only using the carbon dots, the linear detection range, the sensitivity and the detection limit of Pb (II) are remarkably improved, the fluorescence detection material has excellent anti-interference capability, and the technical problem that trace Pb (II) in water is difficult to detect is effectively solved.
Description
Technical Field
The invention relates to Pb (II) (i.e. lead ions, pb) 2+ ) The technical field of detection, in particular to a fluorescent detection material, a preparation method thereof and a Pb (II) detection method.
Background
As a heavy metal pollutant, pb (II) has great harm to human health, and can cause a series of diseases such as nervous system disorder, limb weakness, anemia, diffuse brain injury, hypertensive encephalopathy, brain delay and the like, so that the technical requirement on detecting trace Pb (II) is higher and higher, and the detection of Pb (II) in water becomes one of the hot spots of research.
Fluorescence spectroscopy is of great interest because of its many advantages, such as simple operation, fast response time, high specificity and sensitivity, and high practicality. Carbon Dots (CDs) are a special fluorescent nano material, and have the characteristics of bright fluorescence, high light stability, good biocompatibility, excellent water solubility and the like. Therefore, the carbon dots are used as fluorescent probes and applied to the detection of Pb (II) in water, and the feasibility is high. However, the applicant finds in practice that the simple carbon dots cannot be applied to the detection of Pb (ii) in water due to the small degree of fluorescence change, poor interference resistance and the like.
Disclosure of Invention
The invention mainly aims to provide a fluorescence detection material, a preparation method thereof and a detection method of Pb (II) so as to solve the technical problems of insufficient fluorescence change degree and poor interference resistance in the prior art.
In order to achieve the above object, according to a first aspect of the present invention, there is provided a fluorescent detection material for detecting Pb (ii), wherein:
the fluorescent detection material for detecting Pb (II) comprises carbon dots and polyethyleneimine attached to the carbon dots.
In order to achieve the above object, according to a second aspect of the present invention, there is provided a method for preparing a fluorescent detection material for detecting Pb (ii), the method comprising:
the preparation method of the fluorescent detection material for detecting Pb (II) comprises the following steps:
(1) Obtaining a first dispersion containing carbon dots;
(2) Mixing the first dispersion liquid with a polyethyleneimine solution to obtain a second dispersion liquid;
(3) And homogenizing the second dispersion liquid to obtain the fluorescence detection material.
As a further development of the second aspect of the invention, the preparation of the first dispersion comprises the steps of:
(1) Obtaining reaction liquid, wherein the reaction liquid comprises L-cysteine, naOH and H 2 O 2 And water;
(2) And (4) thermally treating the reaction liquid to generate carbon dots.
As a further improvement of the second aspect of the present invention, the pH of the reaction solution is 9 to 10; l-cysteine and H in the reaction solution 2 O 2 In a molar ratio of 3: (2-5).
As a further development of the second aspect of the invention, the heat treatment is carried out in a sealed container; the heat treatment is carried out under continuous stirring; the heat treatment temperature is 90-110 ℃, and the heat treatment time is 10-16 h.
As a further improvement of the second aspect of the present invention, the method further comprises subjecting the precursor obtained by heat-treating the reaction solution to dialysis treatment to obtain a first dispersion.
As a further improvement of the second aspect of the invention, the dialysis treatment adopts a dialysis membrane with the molecular weight cut-off of 1000Da, and the dialysis time is 8-16 h.
As a further development of the second aspect of the invention, the step of homogenizing the second dispersion comprises sonication and heat treatment.
As a further improvement of the second aspect of the invention, the temperature of the heat treatment of the second dispersion is 50-70 ℃ and the time is 8-16 h; the heat treatment is carried out with continuous stirring.
In order to achieve the above object, according to a third aspect of the present invention, there is provided a method for detecting Pb (ii), the method comprising:
the method for detecting Pb (II) adopts the fluorescent detection material of the first aspect or the fluorescent detection material prepared by the preparation method of the second aspect.
The preparation method of the fluorescence detection material has the advantages of simple process, convenient control and low generation cost, and through verification, the polyethyleneimine is doped on the carbon dots, so that the fluorescence quenching intensity of the fluorescence detection material for detecting Pb (II) is obviously improved compared with the fluorescence quenching intensity of the fluorescence detection material for detecting Pb (II) by using pure carbon dots, the linear detection range, the sensitivity and the detection limit of Pb (II) are obviously improved, the fluorescence detection material has excellent anti-interference capability, the technical problem that trace Pb (II) in water is difficult to detect is effectively solved, and the fluorescence detection material has extremely strong practicability and is very suitable for popularization and use.
The invention is further described with reference to the following figures and detailed description. Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to assist in understanding the invention, and are included to explain the invention and their equivalents and not limit it unduly. In the drawings:
FIG. 1 shows different L-cysteines and H 2 O 2 The effect of the use of the obtained CDs-PEI is shown.
FIG. 2 is a graph showing the effect of using CDs-PEI obtained with different reaction solution heat treatment time.
FIG. 3 is a graph showing the effect of using CDs-PEI obtained at different reaction solution heat treatment temperatures.
FIG. 4 is a graph showing the effect of using CDs-PEI obtained at different concentrations of PEI solution.
FIG. 5 is a TEM and HR-TEM image of the CDs powder (inset).
FIG. 6 is a TEM and HR-TEM image of CDs-PEI powder (inset).
FIG. 7 is a particle size distribution diagram of CDs powder.
FIG. 8 is a particle size distribution diagram of CDs-PEI powder.
FIG. 9 is a Fourier transform infrared (FT-IR) spectrum of CDs powder and CDs-PEI powder.
FIG. 10 is an X-ray photoelectron spectroscopy (XPS) of CDs-PEI powder.
FIG. 11 shows CDs-PEI and CDs-PEI-Pb 2+ Fluorescence lifetime map of (1).
FIG. 12 is a graph showing the effect of CDs-PEI on the use of different pH's in a test environment.
FIG. 13 shows CDs-PEI and Pb 2+ And (3) a graph of the using effect of the CDs-PEI solution at different detection times.
FIG. 14 shows CDs-PEI with Pb 2+ And (3) a graph of the using effect of the CDs-PEI solution at different detection temperatures.
FIG. 15 is a graph comparing the effect of testing different metal ion solutions with the first dispersion.
FIG. 16 is a graph comparing the effect of CDs-PEI testing different metal ion solutions.
FIG. 17 shows the results of testing the interference resistance of CDs-PEI.
FIG. 18 shows that CDs-PEI tests different concentrations of Pb 2+ Fluorescence spectra in solution.
FIG. 19 shows the CDs-PEI test for different concentrations of Pb 2+ Degree of fluorescence quenching of the solution. .
FIG. 20 shows the degree of fluorescence quenching and Pb 2+ Linear fit curves between concentrations (0.5-200 μ M).
FIG. 21 shows the degree of fluorescence quenching and Pb 2+ Linear fit curves between concentrations (200-400 μ M).
Detailed Description
The present invention will now be described more fully hereinafter with reference to the accompanying drawings. Those skilled in the art will be able to implement the invention based on these teachings. Before the present invention is described in detail with reference to the accompanying drawings, it is to be noted that:
the technical solutions and features provided in the present invention in the respective sections including the following description may be combined with each other without conflict.
Moreover, the embodiments of the present invention described in the following description are generally only some embodiments of the present invention, and not all embodiments. Therefore, all other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative effort shall fall within the protection scope of the present invention.
With respect to terms and units in the present invention. The terms "comprising," "having," and any variations thereof in the description and claims of this invention and the related sections are intended to cover non-exclusive inclusions.
The embodiment of the preparation method of the fluorescent detection material for detecting Pb (II) comprises the following steps:
(1) Obtaining a first dispersion containing carbon dots (hereinafter referred to as CDs);
(2) Mixing the first dispersion liquid with a Polyethyleneimine (PEI) solution to obtain a second dispersion liquid;
(3) The second dispersion was homogenized to obtain a fluorescent detection material (hereinafter referred to as CDs-PEI), which includes carbon dots and polyethyleneimine attached to the carbon dots.
Therefore, the preparation method adopts a one-pot method, has simple process and can be produced in batch.
Wherein the step of homogenizing the second dispersion comprises heat treatment; to improve the homogenization effect, the heat treatment is preferably carried out under continuous stirring; it is further preferable that the second dispersion is subjected to ultrasonic treatment before the heat treatment, so that the heat treatment effect can be enhanced.
The temperature of the second dispersion liquid after heat treatment is 50-70 ℃, and can be but is not limited to any one of 50 ℃, 55 ℃, 60 ℃, 65 ℃ and 70 ℃, and the heat treatment time is 8-16 h, and can be but is not limited to any one of 8h, 10h, 12h, 14h and 16h.
The first dispersion can be obtained by dispersing a commercially available carbon dot in water, but is preferably prepared by the following method.
A preferred embodiment of the preparation of the first dispersion is a process comprising the steps of:
(1) Obtaining reaction liquid, wherein the reaction liquid comprises L-cysteine, naOH and H 2 O 2 And water;
(2) And (4) thermally treating the reaction liquid to generate carbon dots.
The pH of the reaction solution is 9 to 10, but is not limited to 9, 9.1, 9.3, 9.5, 9.8, or 10.
The heat treatment is carried out in a sealed vessel and under continuous stirring; the heat treatment temperature is 90-110 ℃, the heat treatment time can be 10-16 h, and the heat treatment time can be any one of 10h, 12h, 14h and 16h, but the heat treatment temperature is not limited to any one of 90 ℃, 95 ℃, 100 ℃, 105 ℃ and 110 ℃.
In order to improve the purity of the carbon point, the method further comprises the step of dialyzing a precursor obtained by heat treatment of the reaction solution to obtain a first dispersion solution; preferably, the dialysis treatment adopts a dialysis membrane with the molecular weight cutoff of 1000Da, and the dialysate is ultrapure water; the dialysis time is 8-16 h, but can be any one of 8h, 10h, 12h, 14h and 16h.
The first dispersion is freeze-dried to obtain the CDs powder, so that the concentration of the CDs in the first dispersion can be weighed and calculated.
The embodiment of the fluorescent detection material for detecting Pb (II) of the invention comprises CDs and Polyethyleneimine (PEI) attached to the CDs, and is prepared by the preparation method.
And (3) freeze-drying the fluorescence detection material to obtain CDs-PEI powder.
An embodiment of the method for detecting Pb (II) of the present invention is to use the above-mentioned fluorescent detection materialOr CDs-PEI powder obtained by freeze-drying a fluorescent detection material; in use, the fluorescence intensity of CDs-PEI and the fluorescence intensity of the mixture of CDs-PEI and the test solution are measured, passing Pb 2+ The linear relation between the concentration and the fluorescence quenching degree is converted to obtain Pb in the liquid to be detected 2+ And (4) concentration.
The advantageous effects of the present invention are illustrated by specific characterization and experiments as follows.
First on different L-cysteines and H 2 O 2 The molar ratio of the reaction solution, the heat treatment parameters of the reaction solution and the concentration of the PEI solution are compared to obtain the CDs-PEI. The other preparation parameters are as follows: the pH of the reaction solution was 9.5; 11.4mL of water, 3.3mL of NaOH (1M), 0.3635g of L-cysteine, H, in the reaction mixture 2 O 2 (30 wt%) was converted from a set ratio (3; the heat treatment temperature of the reaction solution is 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃ and 110 ℃, and the heat treatment time is 6h, 8h, 10h, 12h, 14h and 16h; the heat treatment temperature of the second dispersion liquid is 60 ℃, and the time is 12 hours; the volume of the PEI solution was 3.6. Mu.L at a concentration of 0mg/mL, 0.1mg/mL, 0.2mg/mL, 0.3mg/mL, 0.4mg/mL, 0.5mg/mL, 0.6mg/mL, 0.7mg/mL, 0.8mg/mL, 0.9mg/mL and 1mg/mL.
FIG. 1 shows different L-cysteines and H 2 O 2 The effect of the use of the obtained CDs-PEI is shown. FIG. 2 is a graph showing the effect of using CDs-PEI obtained with different heat treatment times of the reaction solution. FIG. 3 is a graph showing the effect of using CDs-PEI obtained at different reaction solution heat treatment temperatures. FIG. 4 is a graph showing the effect of using CDs-PEI obtained at different concentrations of PEI solution. In FIGS. 1-3, F 0 -F 1 To indicate the degree of quenching, F 0 Denotes the fluorescence intensity of CDs-PEI, F 1 Represent CDs-PEI and Pb 2+ Mixture of solutions (hereinafter, CDs-PEI-Pb used) 2+ Indicated) fluorescence intensity.
As can be seen from FIGS. 1-4, the optimal preparation process parameters for CDs-PEI are: l-cysteine and H 2 O 2 The molar ratio of (1) to (2) is 3, the heat treatment temperature of the reaction solution is 90 ℃, the heat treatment time is 12h, and the concentration of the PEI solution is 0.6mg/mL.
FIG. 5 is a TEM and HR-TEM image of the CDs powder (inset). FIG. 6 is a TEM and HR-TEM image of CDs-PEI powder (inset). FIG. 7 is a particle size distribution diagram of CDs powder. FIG. 8 is a particle size distribution diagram of CDs-PEI powder.
As shown in fig. 5-8, the CDs powder and the CDs-PEI powder both were spherical nanoparticulate and dispersed well; HR-TEM photographs showed well resolved lattice fringes with a lattice spacing of 0.21nm, corresponding to the (100) lattice plane of graphene carbon, indicating that the prepared CDs-PEI is composed of graphitic sp 2 Carbon cluster composition and good crystallization characteristics.
The nanoparticle size distribution histograms shown in fig. 7-8 were obtained by statistical analysis of the particle size of the nanospherical particles in the figure using Image J software. As shown in FIG. 7, the CDs powder has a particle size of 1.5-3.5 nm, a main distribution of 2.25-3.25 nm, and an average particle size of 2.54nm. As shown in FIG. 8, the CDs-PEI powder had a particle size of 1.5-5 nm, a predominant distribution of 2.75-3.75 nm, and an average particle size of 3.25nm.
FIG. 9 is a Fourier transform infrared (FT-IR) spectrum of CDs powder and CDs-PEI powder.
As shown in fig. 9, at 3424cm -1 And 1125cm -1 The characteristic absorption peaks at (A) are respectively attributed to the stretching vibration of N-H, O-H and C-O. The peak of C = O, C = C and C-N expansion and contraction vibration were each located at 1623cm -1 、1599cm -1 And 1406cm -1 Indicating that the material contains amide bonds. 606cm -1 The weak peak at (a) is the bending vibration of C-S. These results indicate successful modification of CDs by PEI.
FIG. 10 is an X-ray photoelectron spectroscopy (XPS) spectrum of a CDs-PEI powder.
As shown in fig. 10, the surface element contents of the CDs-PEI powder were respectively: 48.75% of C, 9.13% of N, 33.32% of O and 8.79% of S.
FIG. 11 shows CDs-PEI and CDs-PEI-Pb 2+ Fluorescence lifetime map of (1).
As shown in FIG. 11, fitting the fluorescence decay with a double exponential function resulted in a fluorescence lifetime of 6.85ns for CDs-PEI-Pb 2+ Has a fluorescence lifetime of 6.84ns; since the fluorescence lifetime hardly changes during the fluorescence quenching, the mechanism of fluorescence quenching may beIs considered to be a static quenching effect.
In the above characterization:
TEM and HRTEM adopt JEM-2100F transmission electron microscope; FT-IR adopts Fourier transform infrared spectrum of Perkin-Riemer of America; XPS uses an X' Pert PRO X-ray diffractometer (Saimer Feishel technologies, USA); fluorescence lifetime measurements were performed using an FLS1000 steady/transient fluorescence spectrometer (edinburgh, uk).
Secondly, the use effect of CDs-PEI under different test conditions is compared.
FIG. 12 is a graph showing the effect of CDs-PEI on the use of different pH's in a test environment. FIG. 13 shows CDs-PEI and Pb 2+ And (3) a graph of the using effect of the CDs-PEI solution at different detection times. FIG. 14 shows CDs-PEI with Pb 2+ And (3) a graph of the using effect of the CDs-PEI solution at different detection temperatures. Wherein CDs-PEI and Pb 2+ The pH of the solution was adjusted using BR buffer.
As can be seen from FIGS. 12-14, the optimum operating condition parameters for CDs-PEI are: pH =8, detection time 1min, detection temperature 20 ℃.
FIG. 15 is a graph comparing the effect of testing different metal ion solutions with the first dispersion. FIG. 16 is a graph comparing the effect of testing different metal ion solutions with CDs-PEI.
As shown in FIGS. 15-16, the first dispersion (i.e., CDs alone) is for Pb 2+ 、Hg 2+ And Co 2+ All have relatively obvious quenching effect, but the CDs-PEI only has Pb 2+ When the catalyst exists, obvious quenching occurs, so that after the PEI is introduced, the CDs-PEI has obviously more excellent selectivity, and Pb can be realized 2+ Specific recognition and detection.
FIG. 17 shows the results of testing the interference resistance of CDs-PEI. Wherein, when no interfering ion is contained, pb 2+ The volume of the solution is 200. Mu.L, and 200. Mu.L of water is used for replacing interfering ions; when containing interfering ions, pb 2+ The volume of the solution and the interfering ion solution were 200. Mu.L, respectively.
As shown in FIG. 17, pb 2+ When coexisting with interfering ions, CDs-PEI-Pb 2+ The fluorescence intensity of the interfering ions remains substantially constantSpecification of CDs-PEI for Pb 2+ The detection has good anti-interference capability and can be applied to the detection of actual samples.
Then, CDs-PEI was tested for Pb 2+ Was tested for sensitivity, linear range and practicality.
FIG. 18 shows that CDs-PEI tests different concentrations of Pb 2+ Fluorescence spectra in solution. FIG. 19 shows the CDs-PEI test for different concentrations of Pb 2+ Degree of fluorescence quenching of the solution. FIG. 20 shows the degree of fluorescence quenching and Pb 2+ Linear fit curves between concentrations (0.5-200 μ M). FIG. 21 shows the degree of fluorescence quenching and Pb 2+ Linear fit curves between concentrations (200-400 μ M).
As can be seen from FIG. 18, with Pb 2+ Increase in concentration of CDs-PEI-Pb 2+ Gradually decreases in fluorescence intensity.
As can be seen from FIG. 19, the degree of fluorescence quenching (F) 0 -F 1 ) With Pb 2+ The concentration of (A) shows a good linear relationship, and a two-stage linear relationship exists between the two.
As can be seen from FIGS. 20-21, when Pb, the reaction time is as high as Pb 2+ When the concentration is 0.5-200 mu M, the regression equation is y =841.82x +3655.9 2 =0.9980, when Pb 2+ When the concentration is 200-400 μ M, the regression equation is y =157.56x +138512 2 =0.9986; calculating Pb 2+ The detection limit of (2) is 0.270. Mu.M.
Selecting southwest traffic university campus lake water and laboratory tap water as actual samples, centrifuging for 10min, filtering with 0.45 μm filter membrane, and adding Pb with different concentrations into water sample 2+ (20. Mu. Mol/L, 100. Mu. Mol/L, 230. Mu. Mol/L), pb was tested using CDs-PEI and the regression equation described above 2+ The concentration of (c). Table 1 shows the CDs-PEI vs. Pb in actual water samples 2+ The detection result of (1).
TABLE 1
As can be seen from Table 1, pb 2+ The recovery rate of the product is within the range of 98.41-100.3 percent and is relative to the standardThe standard deviation (RSD) is less than 4.5 percent, which indicates that the CDs-PEI detects Pb in the actual water sample 2+ The accuracy is higher, and the method has great practical application value.
In the above fluorescence test, the volume of CDs-PEI was 400. Mu.L, and the solution to be tested (Pb) 2+ The volumes of the solution, the interfering ion solution and the water sample) are all 200 mu L, and before the test, BR buffer solution is adopted to fix the volume of the mixture of the CDs-PEI and the solution to be tested to 1.5mL, and then the fluorescence test is carried out; the pH value of the test environment refers to the pH value of 1.5mL of liquid to be tested in the cuvette; pb 2+ The concentration of (d) is 133. Mu.M at the time of quantification; the excitation wavelength of the fluorescence test was λ ex =410nm, and the slit for excitation and emission was 0.6nm.
The contents of the present invention have been explained above. Those skilled in the art will be able to implement the invention based on these teachings. All other embodiments, which can be derived by a person skilled in the art from the above description without inventive step, shall fall within the scope of protection of the present invention.
Claims (10)
1. A fluorescent detection material for detecting Pb (II), characterized in that: including carbon dots and polyethyleneimine attached to the carbon dots.
2. The preparation method of the fluorescent detection material for detecting Pb (II) comprises the following steps:
(1) Obtaining a first dispersion containing carbon dots;
(2) Mixing the first dispersion liquid with a polyethyleneimine solution to obtain a second dispersion liquid;
(3) And homogenizing the second dispersion liquid to obtain the fluorescence detection material.
3. The method of claim 2, wherein: the preparation of the first dispersion comprises the following steps:
(1) Obtaining reaction liquid, wherein the reaction liquid comprises L-cysteine, naOH and H 2 O 2 And water;
(2) And (4) thermally treating the reaction liquid to generate carbon dots.
4. The method of claim 3, wherein: the pH value of the reaction solution is 9-10; l-cysteine and H in the reaction solution 2 O 2 In a molar ratio of 3: (2-5).
5. The method of claim 3, wherein: the heat treatment is carried out in a sealed container; the heat treatment is carried out under continuous stirring; the heat treatment temperature is 90-110 ℃, and the heat treatment time is 10-16 h.
6. The method of claim 3, wherein: and performing dialysis treatment on the precursor obtained by heat treatment of the reaction solution to obtain a first dispersion solution.
7. The method of claim 6, wherein: the dialysis treatment adopts a dialysis membrane with the molecular weight cutoff of 1000Da, and the dialysis time is 8-16 h.
8. The method of claim 2, wherein: the step of homogenizing the second dispersion comprises sonication and heat treatment.
9. The method of claim 8, wherein: the temperature of the second dispersion liquid is 50-70 ℃ and the time is 8-16 h; the heat treatment is carried out with continuous stirring.
A method for detecting Pb (II), which is characterized in that: the fluorescent detecting material according to claim 1, or the fluorescent detecting material produced by the production method according to any one of claims 2 to 9.
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| CN102492724A (en) * | 2011-12-08 | 2012-06-13 | 天津大学 | Nanometer carbon quantum dot-polyethylenimine composite transgenic vector and preparation method and application thereof |
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| CN102492724A (en) * | 2011-12-08 | 2012-06-13 | 天津大学 | Nanometer carbon quantum dot-polyethylenimine composite transgenic vector and preparation method and application thereof |
| CN110564412A (en) * | 2019-08-12 | 2019-12-13 | 南京医科大学 | Preparation method of orange fluorescent emission PEI-CDs |
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