CN111088032B - Preparation method of fluorescent polymer for simultaneously detecting trivalent chromium ions and hexavalent chromium ions - Google Patents
Preparation method of fluorescent polymer for simultaneously detecting trivalent chromium ions and hexavalent chromium ions Download PDFInfo
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Abstract
The invention discloses a preparation method of a fluorescent polymer for simultaneously detecting trivalent chromium ions and hexavalent chromium ions, which comprises the following steps: (1) Preparing a blue carbon point and a red carbon point, wherein the excitation wavelength of the blue carbon point is about 370nm, the emission wavelength is about 450nm, the excitation spectrum of the blue carbon point is completely overlapped with the absorption spectrum of hexavalent chromium ions, and the blue carbon point is quenched by the hexavalent chromium ions through an internal filtering effect; the excitation wavelength of the red carbon point is about 570nm, the emission wavelength is about 600nm, and the red carbon point can be quenched by trivalent chromium ions based on electron transfer; (2) coating blue carbon dots inside the silicon spheres; (3) And coating a fluorescent imprinting layer of trivalent chromium ions on the surface of the silicon sphere coated with the blue carbon dots, and finally forming a fluorescent polymer with a core-shell structure, wherein red carbon dots are doped in the fluorescent imprinting layer, and the fluorescent imprinting layer is of a mesoporous structure. The fluorescent polymer obtained by the method can be used for simultaneously detecting trivalent chromium ions and hexavalent chromium ions.
Description
Technical Field
The invention belongs to the technical field of detection methods, and particularly relates to a preparation method of a fluorescent polymer for simultaneously detecting trivalent chromium ions and hexavalent chromium ions.
Background
The metal ions exist in the environment in a plurality of ion forms, and the ion toxicity of different forms is different. Therefore, it is important to detect the metal ions in the environment, and to detect the ions in each form separately, except for the total amount of ions. Among the detection methods of a plurality of metal ions, the fluorescence detection method is widely applied due to the advantages of no need of expensive instruments, no need of complex sample pretreatment process, simple operation, high speed of the detection process and the like.
At present, the fluorescent detection of chromium ions is generally only carried out on ions of a certain form, such as hexavalent chromium or trivalent chromium, and few reports exist on a fluorescent method for simultaneously detecting chromium ions of two forms. Even though the document reports that hexavalent chromium and trivalent chromium can be detected simultaneously, the common practice is to firstly reduce hexavalent chromium to trivalent chromium for detection, or oxidize trivalent chromium to hexavalent chromium through potassium permanganate or hydrogen peroxide for detection, so that two chromium ion forms are not detected simultaneously in a true sense.
Disclosure of Invention
A first object of the present invention is to solve the above problems and to provide a method for preparing a fluorescent polymer for simultaneously detecting trivalent chromium ions and hexavalent chromium ions.
It is a second object of the present invention to provide a fluorescent polymer obtainable by the above method.
It is a third object of the present invention to provide the use of the above fluorescent polymers.
The aim of the invention is realized by the following technical scheme:
a method of preparing a fluorescent polymer for simultaneous detection of trivalent chromium ions and hexavalent chromium ions, the method comprising the steps of:
(1) Preparing a blue carbon point and a red carbon point, wherein the excitation wavelength of the blue carbon point is about 370nm, the emission wavelength is about 450nm, the excitation spectrum of the blue carbon point is completely overlapped with the absorption spectrum of hexavalent chromium ions, and the blue carbon point is quenched by the hexavalent chromium ions through an internal filtering effect; the excitation wavelength of the red carbon point is about 570nm, the emission wavelength is about 600nm, and the red carbon point can be quenched by trivalent chromium ions based on electron transfer;
(2) Coating blue carbon dots inside the silicon sphere;
(3) And coating a fluorescent imprinting layer of trivalent chromium ions on the surface of the silicon sphere coated with the blue carbon dots, and finally forming a fluorescent polymer with a core-shell structure, wherein red carbon dots are doped in the fluorescent imprinting layer, and the fluorescent imprinting layer is of a mesoporous structure.
Further, in the step (1), the preparation method of the blue carbon dots comprises the following steps: dissolving 1.2g of citric acid and 2.1mL of ethylenediamine in 80mL of water, placing the solution in a hydrothermal reaction kettle, reacting for 8 hours at 180 ℃ in an oven, taking out the solution, and dialyzing the solution to remove unreacted micromolecules to obtain a light yellow blue carbon dot solution;
the preparation method of the red carbon dots comprises the following steps: 2.8g of citric acid is dissolved in 50mL of formamide, the mixture is placed in a hydrothermal reaction kettle, the mixture is reacted for 8 hours at 180 ℃ in an oven, large particles are filtered out by a microporous filter membrane with 0.22 mu m after the mixture is taken out, small molecules are removed by dialysis, acetone is precipitated to obtain solid carbon dots, and then the solid carbon dots are redispersed in 50mL of water to obtain a red brown carbon dot solution.
Further, in the step (2), the blue carbon dots are coated inside the silicon spheres by an inverse microemulsion method, and the specific method is as follows: dispersing 1.8mL of triton-100 and 1.8mL of n-hexanol in 7.5mL of cyclohexane, then adding 500 mu L of the blue carbon dot solution obtained in the step (1), adding 60 mu L of 28wt% ammonia water, fully stirring to form microemulsion, adding 500 mu L of tetraethoxysilane, stirring at room temperature for reaction for 10 hours, adding acetone into the reaction solution after the reaction is finished to demulsifie, obtaining white flocculent precipitate, collecting the white flocculent precipitate, washing with ethanol and water for three times respectively, and drying in vacuum for standby.
In the step (3), the method for coating the trivalent chromium ion fluorescent imprinting layer on the surface of the silicon sphere comprises the following steps: 10mg of the blue carbon dot-coated silica spheres obtained in the step (2) were dispersed in 18mL of ultrapure water, and 1mL of the red carbon dot solution obtained in the step (1) and 0.1mmol of Cr were added 3+ Adding 0.8mL of 0.2mol/L cetyltrimethylammonium bromide solution into the mixed solution, adding 0.1mL of 0.2mol/L NaOH solution into the mixed solution, adding 200 mu L of ethyl orthosilicate, reacting the mixed solution in the dark at room temperature for 24 hours, collecting white precipitate, washing with ethanol/acetone mixed solution with the volume ratio of 8:2 to remove cetyltrimethylammonium bromide, and washing with 0.5mol/L EDTA solution to remove Cr 3+ Then cleaning with ultrapure water and vacuum drying for standby.
Fluorescent polymers obtained by any of the methods described above.
The fluorescent polymer is applied to detection of trivalent chromium ions and hexavalent chromium ions by a fluorescence spectrometry, and the fluorescent polymer realizes high-selectivity fluorescence detection of hexavalent chromium ions and trivalent chromium ions in blue and red excitation channels through an internal filtering effect and electron transfer respectively.
Further, the concentration of the fluorescent polymer in the sample to be detected is 60mg/L.
The invention has the following beneficial effects:
the preparation method of the fluorescent polymer for simultaneously detecting trivalent chromium ions and hexavalent chromium ions provided by the invention has the following advantages that the obtained fluorescent polymer is used for detecting trivalent chromium ions and hexavalent chromium ions:
(1) The fluorescence detection of chromium ions in two forms can be directly realized without the process of reducing hexavalent chromium to trivalent chromium or oxidizing trivalent chromium to hexavalent chromium;
(2) Two detection mechanisms are adopted to realize the detection of two chromium ions, and hexavalent chromium is detected based on the internal filtering effect of blue carbon dots and hexavalent chromium ions; detecting trivalent chromium ions based on the electron transfer effect of the red carbon dots and the trivalent chromium ions;
(3) The interference of other ions on detection is eliminated by adopting two different methods, and Co is eliminated by adopting a mode of coating blue carbon points inside a silicon sphere 2+ Interference to detection; method for eliminating Fe by adopting ion imprinting 3+ 、Ag + 、Pb 2+ 、Cu 2+ And the interference to trivalent chromium ion detection;
(4) The imprinting layer of chromium ions is of a mesoporous structure, so that the mass transfer resistance is reduced, and the detection sensitivity is improved;
(5) The simultaneous detection of chromium ions in two forms is realized by adopting two independent excitation channels of red and blue, the mutual interference is avoided, and the detection accuracy is high.
Drawings
FIG. 1 is a schematic diagram of a fluorescence sensing construction method for simultaneously detecting trivalent chromium and hexavalent chromium ions.
FIG. 2 is a fluorescent chart of the test for mutual interference of trivalent chromium ions and hexavalent chromium ions in example 2.
A in FIG. 3 is a fluorescence chart of example 4 for the test for eliminating interference with hexavalent chromium ions, and B is a fluorescence chart for the test for eliminating interference with trivalent chromium ions.
Detailed Description
The following description of the preferred embodiments of the present invention is provided for the purpose of illustration and explanation only and is not intended to limit the present invention.
The invention discloses a fluorescence sensing construction method for simultaneously detecting trivalent chromium ions and hexavalent chromium ions, which mainly comprises the following steps:
(1) Preparing a blue carbon point and a red carbon point, wherein the excitation wavelength of the blue carbon point is about 370nm, the emission wavelength is about 450nm, the excitation spectrum of the blue carbon point is completely overlapped with the absorption spectrum of hexavalent chromium ions, and the blue carbon point is quenched by the hexavalent chromium ions through an internal filtering effect; the excitation wavelength of the red carbon point is about 570nm, the emission wavelength is about 600nm, and the red carbon point can be quenched by trivalent chromium ions based on electron transfer;
(2) Coating blue carbon dots inside the silicon sphere;
(3) And coating a fluorescent imprinting layer of trivalent chromium ions on the surface of the silicon sphere coated with the blue carbon dots, and finally forming a fluorescent polymer with a core-shell structure, wherein red carbon dots are doped in the fluorescent imprinting layer, and the fluorescent imprinting layer is of a mesoporous structure.
The fluorescent polymer realizes high-selectivity fluorescent detection of hexavalent chromium ions and trivalent chromium ions in blue and red excitation channels through an internal filtering effect and electron transfer respectively.
The fluorescence spectrometer used in the following examples was F-7000 (Hitachi), all of which were commercially available.
Example 1
The preparation method of the fluorescent polymer comprises the following steps:
1. preparation of red carbon dots and blue carbon dots
(1) Blue carbon dot preparation: citric acid (1.2 g) +ethylenediamine (2.1 mL) was dissolved in 80mL water and placed in a hydrothermal reaction kettle and reacted in an oven at 180 ℃ for 8h. And taking out, and dialyzing to remove unreacted small molecules to obtain a pale yellow solution. The optimal excitation wavelength is 350nm, and the emission wavelength is 440nm.
(2) Preparation of red carbon dots: 2.8g of citric acid was dissolved in 50ml of formamide and placed in a hydrothermal reaction vessel and reacted in an oven at 180℃for 8 hours. The following treatment is carried out after the extraction: (1) filtering out large particles with a microporous filter membrane of 0.22 mu m, (2) dialyzing to remove small molecules, (3) precipitating acetone to obtain solid carbon dots, and then re-dispersing the solid carbon dots in 50mL of water to obtain brownish red liquid, wherein the optimal excitation wavelength is 570nm, and the emission wavelength is 600nm.
Description: the preparation method and raw materials of the red carbon dots and the blue carbon dots are not limited thereto, and may be prepared using other raw materials and methods, but the following points must be satisfied.
(1) The blue carbon point excitation peak has good coincidence with the absorption peak of hexavalent chromium ions, and the optimal excitation wavelength is about 370nm, so that the blue carbon point excitation peak can be quenched by hexavalent chromium ions through an internal filtering effect.
(2) The red carbon dot is capable of being quenched by trivalent chromium ions.
(3) The excitation wavelength of the red carbon dot cannot overlap with the excitation wavelength and the emission wavelength of the blue carbon dot, so that interference of two fluorescent intensities is avoided.
2. The blue carbon dots are coated in the silicon ball by an inverse microemulsion method
1.8mL of triton-100+1.8mL of n-hexanol was dispersed in 7.5mL of cyclohexane, then 500. Mu.L of the blue carbon dot solution was added, 60. Mu.L of 28wt% ammonia water was added, and the mixture was sufficiently stirred to form a microemulsion. After 500. Mu.L of ethyl orthosilicate was added, the reaction was maintained at room temperature with stirring for 10 hours. And after the reaction is finished, adding acetone into the reaction solution to demulsify, so as to obtain white flocculent precipitate. Collecting white flocculent precipitate, cleaning with ethanol and water for three times, and vacuum drying.
3. Trivalent chromium ion fluorescent imprinting layer coated on surface of silicon sphere
10mg of silicon spheres coated with blue carbon dots were dispersed in 18mL of ultrapure water, and a solution of 1mL of red carbon dots and 0.1mmol of Cr were added 3+ A mixed solution was prepared, 0.8mL of cetyltrimethylammonium bromide (CTAB) solution (0.2 mol/L) was added, 0.1mL of NaOH (0.2 mol/L) was added, 200. Mu.L of ethyl orthosilicate was added, and the mixed solution was reacted in the dark at room temperature for 24 hours. The white precipitate was collected and washed repeatedly with ethanol/acetone mixture (8:2, v/v) to remove CTAB.Repeated washing of 0.5mol/L EDTA solution to remove Cr 3+ Then cleaning with ultrapure water, and vacuum drying to obtain fluorescent polymer microspheres for later use.
Description:
(1) Functional monomers do not need to be added in the imprinting process, and functional groups on the surface of the red carbon dots are coordinated with trivalent chromium to perform imprinting, so that carbon dots are guaranteed to exist near each recognition site, the conversion efficiency from ion recognition to signal output is improved, and the sensitivity is improved
(2) CTAB is added in the imprinting process to form mesoporous channels and reduce mass transfer resistance.
Example 2
The mutual interference test of trivalent chromium ions and hexavalent chromium ions comprises the following steps:
(1) A solution of fluorescent polymer microspheres prepared in example 1 was prepared at a concentration of 60mg/L with PBS (pH=7.0) buffer solution.
(2) Taking 3900. Mu.L of the solution prepared in the step (1), adding 100. Mu.L of 400. Mu. Mol/L Cr 6+ The solution (final ion concentration is 10 mu mol/L) is mixed uniformly and then put into a fluorescence spectrometer to detect the fluorescence intensity under a blue excitation channel.
(3) Taking 3800 mu L of the solution prepared in the step (1), adding 100 mu L of 400 mu mol/L Cr 6+ Solution and 100. Mu.L of 400. Mu. Mol/L Cr 3+ The solution (the final ion concentration is 10 mu mol/L) is mixed uniformly and then put into a fluorescence spectrometer to detect the fluorescence intensity under a blue excitation channel. The results are shown in FIG. 2.
The detection result of the blue channel is: cr (Cr) 6+ The addition of (2) causes a significant decrease in fluorescence intensity in the blue channel, and Cr is added 3+ After that, will not be to Cr 6+ Is generated by the detection of (a).
The detection of the red channel uses a similar method as the blue channel. The results are shown in FIG. 2. The experimental results show that: cr (Cr) 3+ The addition of (2) caused a significant quenching of the fluorescence intensity in the red channel, the addition of Cr 6+ After that, will not be to Cr 3+ Is generated by the detection of (a).
Example 3
And detecting an actual water sample and adding a mark for recovery test. The water sample is the water of the near-Yi region, which is filtered by a 0.22 mu M microporous filter and stored in a refrigerator for use. The fluorescence detection method is compared with the ICP-MS detection method. When the fluorescence detection method is used, the fluorescent polymer microsphere of the example 1 is added into a water sample, and the concentration is 60mg/L. The method comprises the following steps:
(1) First, the ICP-MS is used for detecting the concentration of chromium ions in the water sample, and the existence of the chromium ions in the water sample is not detected. (total chromium content as determined by ICP-MS)
(2) Marking the water sample, and adding three Cr with different concentrations of 0.1, 1.0 and 5.0 mu mol/L 6+ . Three Cr 6+ The water sample was detected by ICP-MS and the blue channel of the fluorescence spectrometer, respectively. And calculating the standard adding recovery rate.
(3) Marking the water sample, and adding three Cr with different concentrations of 0.1, 1.0 and 5.0 mu mol/L 3+ . Three Cr 3+ The water sample was detected by ICP-MS and the red channel of the fluorescence spectrometer, respectively. And calculating the standard adding recovery rate.
(4) Marking the water sample and simultaneously adding Cr 6+ And Cr (V) 3+ The concentrations were 0.5. Mu. Mol/L. Cr is detected by a blue channel of a fluorescence spectrometer for the water sample 6+ Concentration, detection of Cr with Red channel 3+ Concentration, total chromium concentration was measured by ICP-MS. And calculating the standard adding recovery rate. The results of the measurements are shown in the following table.
As known from a labeling test, the fluorescence detection method has high accuracy and precision, and can detect Cr in a sample at the same time 6+ And Cr (V) 3+ 。
Example 4
The method for eliminating interference test comprises the following steps:
(1) A solution of fluorescent nanoparticle prepared in example 1 was prepared at a concentration of 60mg/L with a buffer solution of PBS (pH=7.0).
(2) Taking 3400 mu L of the solution prepared in the step (1), and adding 100 mu L of 400 mu mol/L Cr respectively 6+ 、Fe 3+ 、Fe 2 + 、Hg 2+ 、Cr 3+ 、Co 2+ And (3) uniformly mixing different ion solutions (the concentration of each ion is 10 mu mol/L), and then placing the mixed solution into a fluorescence spectrometer to detect the fluorescence intensity of the mixed solution under a blue excitation channel. The detection conditions are as follows: the excitation wavelength was 350nm, the slit was 2.5/2.5. The fluorescence intensity at 440nm was recorded, see FIG. 3A.
(3) Taking 3200 mu L of the solution prepared in the step (1), and adding 100 mu L of 400 mu mol/L of Cr respectively 6+ 、Fe 3+ 、Fe 2 + 、Hg 2+ 、Cr 3+ 、Co 2+ 、Ag + 、Al 3+ And (3) uniformly mixing different ion solutions (the concentration of each ion is 10 mu mol/L), standing for 10min, and then placing the mixed solution into a fluorescence spectrometer to detect the fluorescence intensity of the mixed solution under a red excitation channel. The detection conditions are as follows: excitation wavelength 580nm, slit 2.5/2.5, fluorescence intensity at 605nm was recorded, see B of fig. 3.
Experiments show that the interference on hexavalent chromium ions is eliminated through silicon ball coating, and the interference on trivalent chromium ions is eliminated through ion imprinting.
The foregoing description is only a preferred embodiment of the present invention, and the present invention is not limited thereto, but it is to be understood that modifications and equivalents of some of the technical features described in the foregoing embodiments may be made by those skilled in the art, although the present invention has been described in detail with reference to the foregoing embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. A method for preparing a fluorescent polymer for simultaneously detecting trivalent chromium ions and hexavalent chromium ions, the method comprising the steps of:
(1) Preparing a blue carbon point and a red carbon point, wherein the excitation wavelength of the blue carbon point is about 370nm, the emission wavelength is about 450nm, the excitation spectrum of the blue carbon point is completely overlapped with the absorption spectrum of hexavalent chromium ions, and the blue carbon point is quenched by the hexavalent chromium ions through an internal filtering effect; the excitation wavelength of the red carbon point is about 570nm, the emission wavelength is about 600nm, and the red carbon point can be quenched by trivalent chromium ions based on electron transfer;
(2) Coating blue carbon dots inside the silicon sphere;
(3) Coating a fluorescent imprinting layer of trivalent chromium ions on the surface of the silicon sphere coated with the blue carbon dots, and finally forming a fluorescent polymer with a core-shell structure, wherein red carbon dots are doped in the fluorescent imprinting layer, and the fluorescent imprinting layer is of a mesoporous structure; in the step (1), the preparation method of the blue carbon dots comprises the following steps: dissolving 1.2g of citric acid and 2.1mL of ethylenediamine in 80mL of water, placing the solution in a hydrothermal reaction kettle, reacting for 8 hours at 180 ℃ in an oven, taking out the solution, and dialyzing the solution to remove unreacted micromolecules to obtain a light yellow blue carbon dot solution;
the preparation method of the red carbon dots comprises the following steps: 2.8g of citric acid is dissolved in 50mL of formamide, the mixture is placed in a hydrothermal reaction kettle, the mixture is reacted for 8 hours at 180 ℃ in an oven, large particles are filtered out by a microporous filter membrane with 0.22 mu m after the mixture is taken out, small molecules are removed by dialysis, acetone is precipitated to obtain solid carbon dots, and then the solid carbon dots are redispersed in 50mL of water to obtain a red brown carbon dot solution.
2. The method for preparing the fluorescent polymer for simultaneously detecting trivalent chromium ions and hexavalent chromium ions according to claim 1, wherein in the step (2), blue carbon dots are coated inside the silicon spheres by an inverse microemulsion method, and the method is as follows: dispersing 1.8mL of triton-100 and 1.8mL of n-hexanol in 7.5mL of cyclohexane, then adding 500 mu L of the blue carbon dot solution obtained in the step (1), adding 60 mu L of 28wt% ammonia water, fully stirring to form microemulsion, adding 500 mu L of tetraethoxysilane, stirring at room temperature for reaction for 10 hours, adding acetone into the reaction solution after the reaction is finished to demulsifie, obtaining white flocculent precipitate, collecting the white flocculent precipitate, washing with ethanol and water for three times respectively, and drying in vacuum for standby.
3. The method for preparing a fluorescent polymer for simultaneously detecting trivalent chromium ions and hexavalent chromium ions according to claim 2, wherein in the step (3), the method for coating the surface of the silicon sphere with the trivalent chromium ion fluorescent imprinting layer is as follows: dispersing 10mg of the silicon spheres coated with the blue carbon dots obtained in the step (2) in 18mL of ultrapure water, adding a mixed solution consisting of 1mL of the red carbon dot solution obtained in the step (1) and 0.1mmol of Cr3+, adding 0.8mL of a 0.2mol/L cetyltrimethylammonium bromide solution, adding 0.1mL of a 0.2mol/L NaOH solution, adding 200 mu L of tetraethoxysilane, reacting the mixed solution in darkness at room temperature for 24 hours, collecting white precipitate, washing with an ethanol/acetone mixed solution with a volume ratio of 8:2 to remove cetyltrimethylammonium bromide, washing with 0.5mol/L EDTA solution to remove Cr3+, washing with ultrapure water, and vacuum drying for later use.
4. A fluorescent polymer obtainable by the process according to any one of claims 1 to 3.
5. The use of the fluorescent polymer according to claim 4 for detecting trivalent chromium ions and hexavalent chromium ions by fluorescence spectrometry, wherein the fluorescent polymer realizes high-selectivity fluorescence detection of hexavalent chromium ions and trivalent chromium ions in blue and red excitation channels through an inner filtering effect and electron transfer, respectively.
6. The use according to claim 5, wherein the concentration of the fluorescent polymer in the sample to be tested is 60mg/L.
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| CN114034673B (en) * | 2021-10-26 | 2023-03-31 | 华南农业大学 | Carbon dot-based molecular imprinting ratio fluorescent probe and preparation method and application thereof |
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