CN116656351B - Preparation method and application of alcohol-soluble fluorescent carbon dots for detecting iron ions in organic phase - Google Patents
Preparation method and application of alcohol-soluble fluorescent carbon dots for detecting iron ions in organic phase Download PDFInfo
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims abstract description 132
- 229910052742 iron Inorganic materials 0.000 title claims abstract description 122
- -1 iron ions Chemical class 0.000 title claims abstract description 120
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 56
- 239000012074 organic phase Substances 0.000 title claims abstract description 44
- 238000002360 preparation method Methods 0.000 title claims abstract description 38
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 93
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 93
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 46
- 239000003960 organic solvent Substances 0.000 claims abstract description 28
- MCGBIXXDQFWVDW-UHFFFAOYSA-N 4,5-dihydro-1h-pyrazole Chemical compound C1CC=NN1 MCGBIXXDQFWVDW-UHFFFAOYSA-N 0.000 claims abstract description 17
- QAIPRVGONGVQAS-UHFFFAOYSA-N cis-caffeic acid Natural products OC(=O)C=CC1=CC=C(O)C(O)=C1 QAIPRVGONGVQAS-UHFFFAOYSA-N 0.000 claims abstract description 17
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 17
- 238000001914 filtration Methods 0.000 claims abstract description 8
- 239000007787 solid Substances 0.000 claims abstract description 8
- 238000001816 cooling Methods 0.000 claims abstract description 4
- 238000003756 stirring Methods 0.000 claims abstract description 4
- 239000000243 solution Substances 0.000 claims description 118
- 239000012086 standard solution Substances 0.000 claims description 56
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical compound CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 claims description 26
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 26
- 238000000034 method Methods 0.000 claims description 26
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 claims description 25
- 238000002156 mixing Methods 0.000 claims description 19
- 239000012490 blank solution Substances 0.000 claims description 16
- 230000005284 excitation Effects 0.000 claims description 15
- 239000011259 mixed solution Substances 0.000 claims description 15
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- 238000001514 detection method Methods 0.000 abstract description 34
- 239000002904 solvent Substances 0.000 abstract description 9
- 238000010791 quenching Methods 0.000 abstract description 4
- 230000000171 quenching effect Effects 0.000 abstract description 3
- 230000007547 defect Effects 0.000 abstract description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 abstract description 2
- 239000002994 raw material Substances 0.000 abstract description 2
- 239000006184 cosolvent Substances 0.000 abstract 1
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 26
- 238000006862 quantum yield reaction Methods 0.000 description 18
- 238000004458 analytical method Methods 0.000 description 8
- 229910021645 metal ion Inorganic materials 0.000 description 8
- QIVBCDIJIAJPQS-VIFPVBQESA-N L-tryptophane Chemical compound C1=CC=C2C(C[C@H](N)C(O)=O)=CNC2=C1 QIVBCDIJIAJPQS-VIFPVBQESA-N 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 238000009616 inductively coupled plasma Methods 0.000 description 5
- 230000035945 sensitivity Effects 0.000 description 5
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- 231100000331 toxic Toxicity 0.000 description 4
- 230000002588 toxic effect Effects 0.000 description 4
- 239000002699 waste material Substances 0.000 description 4
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
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- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 description 1
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 1
- PTFCDOFLOPIGGS-UHFFFAOYSA-N Zinc dication Chemical compound [Zn+2] PTFCDOFLOPIGGS-UHFFFAOYSA-N 0.000 description 1
- DGEZNRSVGBDHLK-UHFFFAOYSA-N [1,10]phenanthroline Chemical compound C1=CN=C2C3=NC=CC=C3C=CC2=C1 DGEZNRSVGBDHLK-UHFFFAOYSA-N 0.000 description 1
- 238000002835 absorbance Methods 0.000 description 1
- WDJHALXBUFZDSR-UHFFFAOYSA-M acetoacetate Chemical compound CC(=O)CC([O-])=O WDJHALXBUFZDSR-UHFFFAOYSA-M 0.000 description 1
- 238000001479 atomic absorption spectroscopy Methods 0.000 description 1
- 238000012742 biochemical analysis Methods 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 229910001431 copper ion Inorganic materials 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000029087 digestion Effects 0.000 description 1
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- 150000002500 ions Chemical class 0.000 description 1
- 231100000053 low toxicity Toxicity 0.000 description 1
- 238000004020 luminiscence type Methods 0.000 description 1
- 229910001425 magnesium ion Inorganic materials 0.000 description 1
- 238000000120 microwave digestion Methods 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000020477 pH reduction Effects 0.000 description 1
- 238000005424 photoluminescence Methods 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- IFGCUJZIWBUILZ-UHFFFAOYSA-N sodium 2-[[2-[[hydroxy-(3,4,5-trihydroxy-6-methyloxan-2-yl)oxyphosphoryl]amino]-4-methylpentanoyl]amino]-3-(1H-indol-3-yl)propanoic acid Chemical compound [Na+].C=1NC2=CC=CC=C2C=1CC(C(O)=O)NC(=O)C(CC(C)C)NP(O)(=O)OC1OC(C)C(O)C(O)C1O IFGCUJZIWBUILZ-UHFFFAOYSA-N 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
- 238000002798 spectrophotometry method Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000004627 transmission electron microscopy Methods 0.000 description 1
- 229960004799 tryptophan Drugs 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
- C09K11/65—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing carbon
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- B82—NANOTECHNOLOGY
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- G01N21/6428—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes"
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- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
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Abstract
The invention relates to a preparation method and application of an alcohol-soluble fluorescent carbon dot for detecting iron ions in an organic phase. Firstly, adding 3, 4-dihydroxycinnamic acid and absolute ethyl alcohol, uniformly stirring, performing hydrothermal reaction, and naturally cooling to room temperature to obtain a solution; filtering the obtained solution, dialyzing and purifying by using absolute ethyl alcohol, and distilling under reduced pressure to obtain an alcohol-soluble fluorescent carbon dot solid. According to the invention, absolute ethyl alcohol is used as a solvent for the first time, 3, 4-dihydroxycinnamic acid is used as a raw material, and alcohol-soluble fluorescent carbon dots are prepared through hydrothermal reaction, so that the detection of iron ions in an organic phase is realized. The surface of the fluorescent carbon dot can provide hydroxyl functional groups to realize coordination with iron ions and lead to fluorescent quenching of the carbon dot; compared with the defects that the water-soluble carbon point and the organic solvent are difficult to dissolve or certain cosolvent is needed to be added, the alcohol-soluble fluorescent carbon point has more convenience and practicability when being used for detecting iron ions in the organic phase.
Description
Technical Field
The invention belongs to the technical field of fluorescent carbon dots, and particularly relates to a preparation method and application of an alcohol-soluble fluorescent carbon dot for detecting iron ions in an organic phase.
Background
The exceeding of the iron ion impurities can seriously affect the stability and effectiveness of some organic reagents. Meanwhile, in some chemical synthesis processes, the detection of the iron ion content in an organic phase is used as an important investigation index. The commonly used iron ion detection method mainly comprises a phenanthroline spectrophotometry, an atomic absorption spectrometry, an inductively coupled plasma emission spectrometry and the like. However, these methods are mostly suitable for aqueous systems, which require relatively complex pretreatment steps for the determination of iron ions in organic phase systems. The digestion, roasting and other processes of the sample during pretreatment easily cause the loss of the object to be detected, and the discharged toxic and harmful waste is not beneficial to environmental protection.
In recent years, carbon dots have been attracting attention as a novel carbon fluorescent nanomaterial because of its low cost, low toxicity, easy preparation, easy modification, and strong fluorescence stability. In the field of biochemical analysis, metal ion detection based on fluorescent carbon dots has shown great potential for application. However, most of these carbon points for metal ion detection are water-soluble carbon points, and it is difficult to directly use them for detection applications of iron ions in an organic phase system. Therefore, for the detection of iron ions in organic solvents, further research is needed to find an organic phase iron ion detection method which is simple to operate, environment-friendly, low in cost and high in sensitivity, and has good application value.
Disclosure of Invention
The method aims at solving the problems that the iron ion determination step in an organic phase system is complex, the object to be detected is easy to lose in the determination process, toxic and harmful waste is discharged to pollute the environment, and the like in the prior art, and the existing method for detecting the iron ion by utilizing the carbon point is difficult to directly use in the determination of the iron ion in the organic phase system. The invention aims to provide a preparation method and application of an alcohol-soluble fluorescent carbon dot for detecting iron ions in an organic phase, which can be used for detecting iron ions in various organic solvents.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the invention provides a preparation method of an alcohol-soluble fluorescent carbon dot for detecting iron ions in an organic phase, which comprises the steps of adding 3, 4-dihydroxycinnamic acid and absolute ethyl alcohol into a container, uniformly stirring, performing hydrothermal reaction, and naturally cooling to room temperature to obtain a solution; filtering the obtained solution, dialyzing and purifying by using absolute ethyl alcohol, and distilling under reduced pressure to obtain an alcohol-soluble fluorescent carbon dot solid.
Preferably, the volume ratio of the mass of the 3, 4-dihydroxycinnamic acid to the absolute ethanol is 1.4g-2.2g:20mL; the hydrothermal reaction condition is that the temperature is raised to 180-220 ℃ at the heating rate of 10 ℃/min, and the reaction is carried out for 2-10 h after the target temperature is reached.
Preferably, the volume ratio of the mass of the 3, 4-dihydroxycinnamic acid to the absolute ethanol is 1.8g:20mL; the hydrothermal reaction condition is that the temperature is raised to 200 ℃ at a heating rate of 10 ℃/min, and the reaction is carried out for 6 hours after the target temperature is reached; filtering with 0.22 μm organic filter membrane; the dialysis purification time is 48 hours; the cut-off molecular weight of the dialysis bag is 100-500Da.
The invention provides an alcohol-soluble fluorescent carbon dot, which is prepared by adopting the preparation method.
The invention provides application of the alcohol-soluble fluorescent carbon dots obtained by the preparation method in detecting iron ions in an organic phase.
Preferably, the organic solvent in the organic phase is absolute ethanol, methanol, acetonitrile, dichloromethane, or acetyl ethyl ester.
Preferably, the method comprises the step of detecting the iron ions by a fluorescence method.
Preferably, the step of detecting iron ions by a fluorescence method comprises the following steps:
(1) Dissolving the alcohol-soluble fluorescent carbon dot solid by absolute ethyl alcohol to prepare an alcohol-soluble fluorescent carbon dot solution with the final concentration of 51-85 mug/mL;
(2) Preparation of standard solution: preparing iron ion-containing solutions with different concentration gradients by using an organic solvent, and respectively adding alcohol-soluble fluorescent carbon dot solutions to obtain the final concentration of iron ions of 1.00 multiplied by 10 -6 mol/L-50.0×10 -6 mixing the standard solution with mol/L, and reacting for 1h at room temperature; wherein the concentration of alcohol-soluble fluorescent carbon points in each standard solution is the same;
measuring the fluorescence intensity of the standard solution at 360nm by using a fluorescence spectrophotometer under the condition of an excitation wavelength of 260nm, and marking as Fn, wherein n is the number of the standard solution, and n is an integer;
(3) Preparation of a blank solution: adding only an organic solvent into an alcohol-soluble fluorescent carbon dot solution, uniformly mixing the solution, reacting for 1h at room temperature, and measuring the fluorescence intensity of the solution at 360nm under the excitation wavelength of 260nm, wherein the fluorescence intensity is marked as F0;
(4) The relative fluorescence intensity of the standard solution was calculated: F0/Fn to obtain a linear relation between the final concentration of the iron ions in the standard solution and the relative fluorescence intensity of the standard solution;
(5) Measurement of the solution to be measured: adding a solution to be detected into the alcohol-soluble fluorescent carbon dot solution to obtain a mixed solution to be detected, uniformly mixing, reacting for 1h at room temperature, and measuring the fluorescence intensity of the mixed solution at 360nm under the condition of an excitation wavelength of 260 nm; and (3) obtaining the concentration of iron ions in the solution to be detected according to the linear relation obtained in the step (4).
Preferably, the final concentration of the alcohol-soluble fluorescent carbon dot solution in the step (1) is 85 mug/mL; the mixing volume ratio of the solution containing iron ions to the alcohol-soluble fluorescent carbon dot solution in each standard solution in the step (2) is 1:9, adding the same volume of the alcohol-soluble fluorescent carbon dot solution into each standard solution; the organic solvent is absolute ethanol, methanol, acetonitrile, methylene dichloride or acetyl ethyl ester.
Preferably, the concentration of the alcohol-soluble fluorescent carbon dots in the blank solution in the step (3) is the same as that of the alcohol-soluble fluorescent carbon dots in the standard solution; the concentration of the alcohol-soluble fluorescent carbon points in the mixed solution to be detected in the step (5) is the same as that of the alcohol-soluble fluorescent carbon points in the standard solution; the volumes of the standard solution, the blank solution and the solution to be tested are the same.
The beneficial effects are that:
according to the invention, absolute ethyl alcohol is used as a solvent for the first time, 3, 4-dihydroxycinnamic acid is used as a raw material to prepare alcohol-soluble fluorescent carbon dots through hydrothermal reaction, and the alcohol-soluble fluorescent carbon dots are utilized to realize detection of iron ions in an organic phase. On one hand, the surface of the fluorescent carbon dot can provide hydroxyl functional groups to coordinate with iron ions and lead to fluorescent quenching of the carbon dot; on the other hand, the alcohol-soluble carbon point can be mutually dissolved with most organic solvents and maintain good fluorescence luminescence performance, and compared with the defect that the water-soluble carbon point and the organic solvents are difficult to mutually dissolve or certain auxiliary solvents are required to be added, the alcohol-soluble fluorescence carbon point has more convenience and practicability when being used for detecting iron ions in the organic phase.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. Wherein:
FIG. 1 is a Transmission Electron Microscope (TEM) image of alcohol-soluble fluorescent carbon dots obtained in example 1.
FIG. 2 is a graph showing fluorescence emission spectra of alcohol-soluble fluorescent carbon dots obtained in example 1.
FIG. 3 is a graph of the concentration optimization of alcohol-soluble fluorescent carbon dots in example 6.
FIG. 4 is a linear range of iron ions detected in the absolute ethanol solution of example 6.
Wherein the abscissa is the final concentration of iron ions in the standard solution, as in FIGS. 5-8 below.
FIG. 5 is a linear range of iron ions detected in methanol solution in example 7.
FIG. 6 is a linear range of the detection of iron ions in acetonitrile solution of example 8.
FIG. 7 is a linear range of iron ions detected in methylene chloride solution in example 9.
FIG. 8 is a linear range of iron ions detected in an acetoacetate solution in example 10.
FIG. 9 is a diagram showing the detection of iron ions in an absolute ethanol solution in comparative example 1.
FIG. 10 is a graph showing the effect of the acetone solution of comparative example 2 on the fluorescence emission intensity of alcohol-soluble fluorescent carbon dots.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which are derived by a person skilled in the art based on the embodiments of the invention, fall within the scope of protection of the invention.
The present invention will be described in detail with reference to examples. It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
Aiming at the problems that the iron ion determination step is complex, the object to be detected is easy to lose in the determination process, toxic and harmful waste is discharged to pollute the environment, and the existing carbon point detection method is difficult to directly use for determining the iron ion in the organic phase system, the invention provides a preparation method of alcohol-soluble fluorescent carbon point for detecting the iron ion in the organic phase, 3, 4-dihydroxycinnamic acid and absolute ethyl alcohol are added into a reaction kettle, the reaction kettle is uniformly stirred, hydrothermal reaction is carried out, and then the reaction product is naturally cooled to room temperature, so that yellow transparent clear solution is obtained; filtering the obtained solution, dialyzing and purifying with absolute ethyl alcohol, distilling under reduced pressure to obtain alcohol-soluble fluorescent carbon dot solid, and storing in a drying tank in dark place.
In the preferred embodiment of the invention, the volume ratio of the mass of the 3, 4-dihydroxycinnamic acid to the absolute ethanol is 1.4g-2.2g:20mL (e.g., 1.4g:20mL, 1.6g:20mL, 1.8g:20mL, 2.0g:20mL, or 2.2g:20 mL).
In a preferred embodiment of the present invention, the hydrothermal reaction is carried out at a temperature of from 2h to 10h (e.g., 2h, 4h, 6h, 8h or 10 h) after heating to 180 ℃ -220 ℃ (e.g., 180 ℃, 200 ℃ or 220 ℃) at a heating rate of 10 ℃/min.
In a preferred embodiment of the invention, the volume ratio of the mass of the 3, 4-dihydroxycinnamic acid to the absolute ethanol is 1.8g:20mL. The hydrothermal reaction conditions were such that the reaction was carried out at a temperature rising rate of 10℃per minute to 200℃and then at that temperature for 6 hours. Under the condition, the fluorescence quantum yield of the alcohol-soluble fluorescent carbon dots prepared by the method is highest, and can reach 13.78% by taking L-tryptophan (the fluorescence quantum yield is 14%) as a reference.
In the preferred embodiment of the invention, a 0.22 μm organic filter membrane is used for filtration; the dialysis purification time is 48 hours; the cut-off molecular weight of the dialysis bag is 100-500Da. The purification steps are simple and convenient, and the operation is easy.
The invention also provides application of the alcohol-soluble fluorescent carbon dots in detecting iron ions in the organic phase.
In a preferred embodiment of the invention, the organic phase is the organic solvent absolute ethanol, methanol, acetonitrile, dichloromethane, or acetyl ethyl ester.
Among common organic solvents, some solvents cannot be used for detection in the method, such as acetone, when the mixed volume ratio of the alcohol-soluble fluorescent carbon dot solution to the acetone solution is 39: at 1 (the volume ratio of the acetone solution to the mixed solution is 2.5%), the fluorescence of about 70% of alcohol-soluble carbon points can be quenched.
In a preferred embodiment of the invention, the method comprises the step of detecting iron ions by a fluorescence method.
In a preferred embodiment of the invention, the step of detecting iron ions by a fluorescence method comprises the following steps:
(1) Dissolving the alcohol-soluble fluorescent carbon dot solid with absolute ethyl alcohol to prepare an alcohol-soluble fluorescent carbon dot solution with the final concentration of 51-85 mug/mL;
(2) Preparation of standard solution: preparing iron ion-containing solutions with different concentration gradients by using an organic solvent, taking the iron ion-containing solutions with the same volume and different concentration gradients, and respectively adding alcohol-soluble fluorescent carbon dot solutions with the same volume to obtain the final concentration of the iron ions of 1.00 multiplied by 10 -6 mol/L-50.0×10 -6 Several (e.g., 1.00X 10) of standard solutions in mol/L -6 mol/L、2.50×10 -6 mol/L、5.00×10 -6 mol/L、10.0×10 -6 mol/L、20.0×10 -6 mol/L、30.0×10 -6 mol/L、40.0×10 -6 mol/L and 50.0X10 -6 mol/L), mixing uniformly, and reacting for 1h at room temperature; wherein the concentration of alcohol-soluble fluorescent carbon points in each standard solution is the same;
measuring the fluorescence intensity of the standard solution at 360nm by using a fluorescence spectrophotometer under the condition of an excitation wavelength of 260nm, and recording as Fn, wherein n is the number of the standard solution, and n is an integer (for example, n is 1,2,3,4,5,6,7 or 8);
(3) Preparation of a blank solution: adding only an organic solvent into an alcohol-soluble fluorescent carbon dot solution, uniformly mixing the solution, reacting for 1h at room temperature, and measuring the fluorescence intensity of the solution at 360nm under the excitation wavelength of 260nm, wherein the fluorescence intensity is marked as F0;
(4) The relative fluorescence intensity of the standard solution was calculated: F0/Fn to obtain a linear relation between the final concentration of the iron ions in the standard solution and the relative fluorescence intensity of the standard solution;
(5) Measurement of the solution to be measured: adding a solution to be detected into the alcohol-soluble fluorescent carbon dot solution to obtain a mixed solution to be detected, uniformly mixing, reacting for 1h at room temperature, and measuring the fluorescence intensity of the mixed solution at 360nm under the condition of an excitation wavelength of 260 nm; and (3) obtaining the concentration of iron ions in the solution to be detected according to the linear relation obtained in the step (4).
The alcohol-soluble fluorescent carbon dots prepared by the method are used for detecting the iron ions in the organic phase, so that complicated pretreatment steps in the traditional detection method can be avoided, and meanwhile, the loss of a sample to be detected is reduced. For example, when conventional detection methods are used to determine iron ions in an organic phase, it is often necessary to pretreat the sample by microwave digestion, acidification, or evaporation, and the emissions from the treatment and detection processes are not environmentally friendly. In addition, the excessive pretreatment steps, the adhesion of combustion ash to the container wall in the measurement process and the like are easy to cause the loss of the sample to be measured. The method utilizes a fluorescence analysis method, and can realize the specificity and sensitivity detection of trace iron ions by detecting the change of the fluorescence emission intensity of carbon dots by only directly mixing the organic solvent to be detected with the carbon dots. The method is simple to operate, low in cost, environment-friendly, free from toxic and harmful wastes, and applicable to iron ion detection in various organic phases.
In a preferred embodiment of the present invention, the final concentration of the alcohol-soluble fluorescent carbon dot solution in step (1) is 85. Mu.g/mL; the mixing volume ratio of the solution containing iron ions to the solution of the alcohol-soluble fluorescent carbon dots in the step (2) is 1:9, a step of performing the process; the organic solvent is absolute ethanol, methanol, acetonitrile, methylene dichloride or acetyl ethyl ester.
According to the invention, the mixing volume ratio of the alcohol-soluble fluorescent carbon dot solution and the organic solvent containing iron ions is specifically optimized to be 9:1 (the volume ratio of the organic solvent to the mixed solution is 10%), so that the sensitivity can be ensured, a wider linear range can be provided, and the practicability is stronger.
1) The influence of the organic solvent on the fluorescence emission intensity of the alcohol-soluble fluorescent carbon dots is reduced. The initial fluorescence intensity (F0) of the alcohol-soluble fluorescent carbon dots is affected by the physicochemical properties of the added organic solvent and is related to the added volume of the organic solvent. Therefore, to ensure the detection sensitivity, the volume of the organic solvent to be added needs to be optimized.
2) In order to obtain a linear range that is easy to handle and to determine in practical applications. The content of iron ions in the actual organic phase to-be-measured sample is usually micro-level or trace level, the too small volume ratio of the organic solvent to the mixed solution can cause the too large dilution factor of the sample, and the sample may need to be subjected to pretreatment such as enrichment concentration during actual measurement, and the solubility of the iron ions in different organic solvents also needs to be considered. Therefore, to ensure the practicality of the detection method, the volume of the organic solvent to be added needs to be optimized.
In the preferred embodiment of the invention, the concentration of the alcohol-soluble fluorescent carbon dots in the blank solution in the step (3) is the same as that in the standard solution; the concentration of the alcohol-soluble fluorescent carbon points in the mixed solution to be detected in the step (5) is the same as that of the alcohol-soluble fluorescent carbon points in the standard solution; the volumes of the standard solution, the blank solution and the solution to be tested are the same.
The preparation method and application of the alcohol-soluble fluorescent carbon dot for detecting iron ions in an organic phase are described in detail below by means of specific examples.
Example 1 preparation of alcohol-soluble fluorescent carbon dots 1
Adding 1.8g of 3, 4-dihydroxycinnamic acid and 20mL of absolute ethyl alcohol into a polytetrafluoroethylene reaction kettle, uniformly stirring, heating to 200 ℃ at a heating rate of 10 ℃/min, maintaining the temperature for 6 hours for reaction, and naturally cooling to room temperature to obtain a yellow transparent clear solution. Filtering the obtained solution with 0.22 μm organic filter membrane, dialyzing with absolute ethanol for 48 hr (dialysis bag cut-off molecular weight: 100-500 Da), distilling under reduced pressure to obtain alcohol-soluble fluorescent carbon dot solid, and storing in a drying tank in dark place.
Transmission Electron Microscope (TEM) analysis:
transmission Electron Microscopy (TEM) analysis was performed on the alcohol-soluble fluorescent carbon dots obtained in example 1, as shown in FIG. 1. As can be seen from FIG. 1, the alcohol-soluble fluorescent carbon dots are in the form of monodisperse uniform particles with a particle size of 4-7nm.
Fluorescence emission spectrometry:
fluorescence emission spectroscopy was performed on the alcohol-soluble fluorescent carbon dots obtained in example 1, as shown in FIG. 2. As can be seen from FIG. 2, the maximum excitation wavelength of the alcohol-soluble fluorescent carbon dots is 260nm, and the maximum emission wavelength is 360nm.
Fluorescence quantum yield analysis:
l-tryptophan was used as a reference (fluorescence quantum yield 14.0%). The fluorescence quantum yield was calculated to be 13.78% ± 0.25% according to the formula:
wherein Φ is the quantum yield, F is the photoluminescence intensity, A is the absorbance, η is the refractive index of the solvent (η Water and its preparation method ＝1.3330,η Absolute ethyl alcohol = 1.3618), subscript x represents the alcohol-soluble fluorescent carbon dot, subscript R represents the reference L-tryptophan, and the same applies below.
Example 2 preparation of alcohol-soluble fluorescent carbon dots 2
The preparation method of the alcohol-soluble carbon point for detecting iron ions in the organic phase in this example is different from that in example 1 only in that:
the dosage of the 3, 4-dihydroxycinnamic acid is 1.4g, the volume of the absolute ethyl alcohol is 20mL, the hydrothermal reaction is carried out after the temperature is raised to 180 ℃, the reaction is carried out for 6 hours at the temperature, and the interception molecular weight of the dialysis bag is 100-500Da. Fluorescence quantum yield analysis:
l-tryptophan was used as a reference (fluorescence quantum yield 14.0%). The fluorescence quantum yield was 9.04% + -0.96% calculated according to the formula.
EXAMPLE 3 preparation of alcohol-soluble fluorescent carbon dots 3
The preparation method of the alcohol-soluble carbon point for detecting iron ions in the organic phase in this example is different from that in example 1 only in that:
the dosage of the 3, 4-dihydroxycinnamic acid is 1.8g, the volume of the absolute ethyl alcohol is 20mL, the hydrothermal reaction is carried out after the temperature is raised to 200 ℃, the reaction is carried out for 2 hours at the temperature, and the interception molecular weight of the dialysis bag is 100-500Da. Fluorescence quantum yield analysis:
l-tryptophan was used as a reference (fluorescence quantum yield 14.0%). The fluorescence quantum yield was 11.46% + -0.83% calculated according to the formula.
EXAMPLE 4 preparation of alcohol-soluble fluorescent carbon dots 4
The preparation method of the alcohol-soluble carbon point for detecting iron ions in the organic phase in this example is different from that in example 1 only in that:
the dosage of the 3, 4-dihydroxycinnamic acid is 1.8g, the volume of the absolute ethyl alcohol is 20mL, the hydrothermal reaction is carried out after the temperature is raised to 200 ℃, the reaction is carried out for 4 hours at the temperature, and the interception molecular weight of the dialysis bag is 100-500Da. Fluorescence quantum yield analysis:
l-tryptophan was used as a reference (fluorescence quantum yield 14.0%). The fluorescence quantum yield was calculated to be 12.38% ± 0.19% according to the formula.
EXAMPLE 5 preparation of alcohol-soluble fluorescent carbon dots 5
The preparation method of the alcohol-soluble carbon point for detecting iron ions in the organic phase in this example is different from that in example 1 only in that:
the dosage of the 3, 4-dihydroxycinnamic acid is 2.0g, the volume of the absolute ethyl alcohol is 20mL, the hydrothermal reaction is carried out after the temperature is raised to 180 ℃, the reaction is carried out for 6 hours at the temperature, and the interception molecular weight of the dialysis bag is 100-500Da. Fluorescence quantum yield analysis:
l-tryptophan was used as a reference (fluorescence quantum yield 14.0%). The fluorescence quantum yield was 9.86% ± 0.94% calculated according to the formula.
Example 6 application of alcohol-soluble fluorescent carbon dots in detection of iron ions (iron ion-absolute ethanol solution) in organic phase
(1) The alcohol-soluble fluorescent carbon dots obtained in example 1 were dissolved with absolute ethanol. In order to avoid the influence of fluorescence self-quenching caused by the excessive concentration of carbon dots on analysis and detection results, the fluorescence emission intensities of carbon dots with different concentrations at the maximum emission wavelength are examined, and the results are shown in fig. 3. As can be seen from FIG. 3, the alcohol-soluble fluorescent carbon dot solution has higher fluorescence emission intensity in the concentration range of 51-85 mug/mL. The concentration of the alcohol-soluble fluorescent carbon dot solution corresponding to the maximum fluorescence emission intensity is selected in the experiment, and the alcohol-soluble fluorescent carbon dot solution with the final concentration of 85 mug/mL is prepared.
(2) Preparation of standard solution: taking 180 mu L of 8 parts of the alcohol-soluble fluorescent carbon dot solution obtained in the step (1), and respectively adding 20 mu L of iron ions with the concentration of 1.00 multiplied by 10 in sequence -5 mol/L、2.50×10 -5 mol/L、5.00×10 -5 mol/L、10.0×10 - 5 mol/L、20.0×10 -5 mol/L、30.0×10 -5 mol/L、40.0×10 -5 mol/L、50.0×10 -5 The final concentration of Fe ion in the absolute ethanol solution is 1.00-50.0X10 -6 The standard solution of mol/L (the concentration of fluorescent carbon points in the standard solution is the same and the concentration of iron ions is gradually increased), and the mixture is uniformly mixed and then reacted for 1h at room temperature.
The fluorescence intensities of 8 parts of the standard solutions at 360nm were measured by a fluorescence spectrophotometer at an excitation wavelength of 260nm, and were designated Fn (n is 1,2,3,4,5,6,7, 8).
(3) Preparation of a blank solution: 180 mu L of the alcohol-soluble fluorescent carbon dot solution obtained in the step (1) is taken, 20 mu L of absolute ethyl alcohol solution is added, the mixture is uniformly mixed and then reacted for 1h at room temperature, and the fluorescence intensity of the mixture at 360nm is measured under the condition of an excitation wavelength of 260nm and is marked as F0.
(4) The relative fluorescence intensities (F0/Fn) of the alcohol-soluble fluorescent carbon dot solutions (standard solutions) to which iron ions of different concentrations were added were calculated.
As a result, as shown in FIG. 4, the relative fluorescence intensity (F0/Fn) of the standard solution increased with increasing iron ion concentration, and was 1.00-50.0X10 at the final iron ion concentration -6 Has good linear relation in the mol/L concentration range, R 2 = 0.9924, the detection limit is calculated to be 0.23×10 -6 mol/L。
Example 7 use of alcohol-soluble fluorescent carbon dots in detection of iron ions (iron ion-methanol solution) in organic phase
The application of the alcohol-soluble fluorescent carbon dots in detecting iron ions in the organic phase in this experimental example is different from that in example 6 only in that:
preparation of standard solution in step (2): step (1) of taking 180. Mu.L8 parts of the obtained alcohol-soluble fluorescent carbon dot solution are added with 20 mu L of iron ions with the concentration of 1.00 multiplied by 10 in sequence -5 mol/L、2.50×10 -5 mol/L、5.00×10 -5 mol/L、10.0×10 -5 mol/L、20.0×10 -5 mol/L、30.0×10 -5 mol/L、40.0×10 -5 mol/L、50.0×10 -5 The final concentration of iron ions obtained by the mol/L iron ion-methanol solution is 1.00-50.0X10 respectively -6 The standard solution of mol/L is mixed uniformly and then reacted for 1h at room temperature.
Preparing a blank solution in the step (3): and (3) adding 20 mu L of methanol solution into the alcohol-soluble fluorescent carbon dot solution obtained in the step (1), uniformly mixing, and reacting for 1h at room temperature.
As a result, as shown in FIG. 5, the relative fluorescence intensity (F0/Fn) of the standard solution increased with increasing iron ion concentration, and was 1.00-50.0X10 at the final iron ion concentration -6 Has good linear relation in the mol/L concentration range, R 2 = 0.9906, the detection limit is calculated to be 0.51×10 -6 mol/L。
Example 8 use of alcohol-soluble fluorescent carbon dots in detection of iron ions (iron ion-acetonitrile solution) in organic phase
The application of the alcohol-soluble fluorescent carbon dots in detecting iron ions in the organic phase in this experimental example is different from that in example 6 only in that:
preparation of standard solution in step (2): taking 180 mu L of 8 parts of the alcohol-soluble fluorescent carbon dot solution obtained in the step (1), and respectively adding 20 mu L of iron ions with the concentration of 1.00 multiplied by 10 in sequence -5 mol/L、2.50×10 -5 mol/L、5.00×10 -5 mol/L、10.0×10 -5 mol/L、20.0×10 -5 mol/L、30.0×10 -5 mol/L、40.0×10 -5 mol/L、50.0×10 -5 The final concentration of iron ions obtained by the mol/L iron ion-acetonitrile solution is 1.00-50.0X10 respectively -6 The standard solution of mol/L is mixed uniformly and then reacted for 1h at room temperature.
Preparing a blank solution in the step (3): and (3) adding 20 mu L of acetonitrile solution into the alcohol-soluble fluorescent carbon dot solution obtained in the step (1), uniformly mixing, and reacting for 1h at room temperature.
The results are shown in FIG. 6, relative to the standard solutionThe fluorescence intensity (F0/Fn) increases with increasing concentration of iron ions and is in the range of 1.00 to 50.0X10 at the final concentration of iron ions -6 Has good linear relation in the mol/L concentration range, R 2 = 0.9810, the detection limit is calculated to be 0.20×10 -6 mol/L。
Example 9 use of alcohol-soluble fluorescent carbon dots in detection of iron ions in organic phase (iron ion-dichloromethane solution)
The application of the alcohol-soluble fluorescent carbon dots in detecting iron ions in the organic phase in this experimental example is different from that in example 6 only in that:
preparation of standard solution in step (2): taking 180 mu L of 8 parts of the alcohol-soluble fluorescent carbon dot solution obtained in the step (1), and respectively adding 20 mu L of iron ions with the concentration of 1.00 multiplied by 10 in sequence -5 mol/L、2.50×10 -5 mol/L、5.00×10 -5 mol/L、10.0×10 -5 mol/L、20.0×10 -5 mol/L、30.0×10 -5 mol/L、40.0×10 -5 mol/L、50.0×10 -5 The final concentration of iron ions obtained by the solution of iron ions and methylene dichloride in mol/L is 1.00 to 50.0X10 respectively -6 The standard solution of mol/L is mixed uniformly and then reacted for 1h at room temperature.
Preparing a blank solution in the step (3): and (3) adding 20 mu L of dichloromethane solution into the alcohol-soluble fluorescent carbon dot solution obtained in the step (1), uniformly mixing, and reacting for 1h at room temperature.
As a result, as shown in FIG. 7, the relative fluorescence intensity (F0/Fn) of the standard solution increased with increasing iron ion concentration, and was 1.00-40.0X10 at the final iron ion concentration -6 Has good linear relation in the mol/L concentration range, R 2 = 0.9935, the detection limit is calculated to be 0.37×10 -6 mol/L。
Example 10 use of alcohol-soluble fluorescent carbon dots in detection of iron ions (iron ion-acetyl ethyl ester solution) in organic phase
The application of the alcohol-soluble fluorescent carbon dots in detecting iron ions in the organic phase in this experimental example is different from that in example 6 only in that:
preparation of standard solution in step (2): taking 180 mu L of 8 parts of the alcohol-soluble fluorescent carbon dot solution obtained in the step (1), and respectively adding 20 mu L of iron ions with the concentration of 1.00 in sequence×10 -5 mol/L、2.50×10 -5 mol/L、5.00×10 -5 mol/L、10.0×10 -5 mol/L、20.0×10 -5 mol/L、30.0×10 -5 mol/L、40.0×10 -5 mol/L、50.0×10 -5 The final concentration of iron ions obtained by mol/L of the iron ion-acetyl ethyl ester solution is 1.00 to 50.0X10 respectively -6 The standard solution of mol/L is mixed uniformly and then reacted for 1h at room temperature.
Preparing a blank solution in the step (3): and (3) adding 20 mu L of ethyl acetate solution into the alcohol-soluble fluorescent carbon dot solution obtained in the step (1), uniformly mixing, and reacting for 1h at room temperature.
As a result, as shown in FIG. 8, the relative fluorescence intensity (F0/Fn) of the standard solution increased with increasing iron ion concentration, and was 1.00-40.0X10 at the final iron ion concentration -6 Has good linear relation in the mol/L concentration range, R 2 = 0.9902, the detection limit is calculated to be 0.38x10 -6 mol/L。
Comparative example 1 Selective identification detection of iron ions by alcohol-soluble fluorescent carbon dots
The method of example 6 was used to detect the selectivity of the alcohol-soluble fluorescent carbon sites for iron ions in the organic phase as follows:
(1) The alcohol-soluble fluorescent carbon dots obtained in example 1 were dissolved in absolute ethanol to prepare an alcohol-soluble fluorescent carbon dot solution having a final concentration of 85. Mu.g/mL.
(2) Preparation of metal ion solution: taking 180 mu L of 6 parts of the alcohol-soluble fluorescent carbon dot solution obtained in the step (1), and adding 20 mu L of 100.0X10 g of the solution respectively -5 The final concentration of the metal ion-ethanol solution of the mol/L is 100.0X10 -6 The metal ion-ethanol solution with mol/L is evenly mixed and then reacts for 1h at room temperature. The method is characterized in that common metal ion impurities in an organic phase are selected to carry out an iron ion selective identification detection test, and metal ion solutions are respectively iron ions, copper ions, calcium ions, magnesium ions, zinc ions and sodium ions.
(3) Preparation of a blank solution: 180 mu L of the alcohol-soluble fluorescent carbon dot solution obtained in the step (1) is taken, 20 mu L of absolute ethyl alcohol solution is added, and the mixture is uniformly mixed and then reacted for 1h at room temperature.
(4) The fluorescence intensity of the above 6 parts of metal ion solution at 360nm is measured by using a fluorescence spectrophotometer under the condition of an excitation wavelength of 260nm, and the relative fluorescence intensity of the alcohol-soluble fluorescent carbon dot solution added with different metal ions is calculated.
As a result, as can be seen in FIG. 8, at 100.0X10 -6 In the mol/L of different metal ions-ethanol solution, only iron ions can effectively quench fluorescence of carbon dots under the test condition of the method, and other metal ions have no obvious quenching effect, so that the method has stronger specific recognition performance on the iron ions.
Comparative example 2 Effect of acetone solvent on fluorescence emission intensity of alcohol-soluble fluorescent carbon dots
The influence of the acetone solvent on the fluorescence emission intensity of the alcohol-soluble fluorescent carbon dots is examined, and the specific steps are as follows:
(1) The alcohol-soluble fluorescent carbon dots obtained in example 1 were dissolved in absolute ethanol to prepare an alcohol-soluble fluorescent carbon dot solution having a final concentration of 85. Mu.g/mL.
(2) Preparation of different volumes of acetone and carbon dot mixed solution: 399.5, 399.0, 395.0, 390.0 and 360.0. Mu.L of the alcohol-soluble fluorescent carbon dot solution obtained in the step (1) were respectively taken, 0.5, 1.0, 5.0, 10 and 40. Mu.L of acetone solution were added thereto, and the mixture was uniformly mixed and reacted at room temperature for 1 hour.
(3) Preparation of a blank solution: 399.5, 399.0, 395.0, 390.0 and 360.0. Mu.L of the alcohol-soluble fluorescent carbon dot solution obtained in the step (1) are taken respectively, 0.5, 1.0, 5.0, 10 and 40. Mu.L of absolute ethanol solution are added, and the mixture is reacted for 1 hour at room temperature after being uniformly mixed.
(4) The fluorescence intensity of the above 5 parts of mixed solution of acetone and carbon dots at 360nm is measured by using a fluorescence spectrophotometer under the condition of an excitation wavelength of 260nm, and the relative fluorescence intensity of the alcohol-soluble fluorescent carbon dot solution added with different volumes of acetone is calculated.
As shown in FIG. 10, the addition of the acetone solvent quenches the fluorescence emission of the alcohol-soluble fluorescent carbon dots, and quenches the fluorescence of about 70% of the alcohol-soluble carbon dots when the acetone solution accounts for 2.5% of the volume ratio of the mixed solution, which indicates that the method is not suitable for measuring the concentration of iron ions in the acetone solvent.
Comparative example 3 comparative comparison with inductively coupled plasma emission spectrometer (ICP) measurement results
The concentration of iron ions in the labeled absolute ethanol sample was determined by the method of example 6 and compared to the measurement results of an inductively coupled plasma emission spectrometer.
Taking 180 mu L of 3 parts of the alcohol-soluble fluorescent carbon dot solution obtained in the step (1), and respectively adding 20 mu L of iron ions with the concentration of 1.00 multiplied by 10 in sequence -5 mol/L、1.50×10 -5 mol/L、3.00×10 -5 The final concentration of the iron ions obtained by the solution to be detected of the mol/L iron ion-ethanol solution is 1.00 multiplied by 10 respectively -6 mol/L、1.50×10 -6 mol/L、3.00×10 -6 Adding the standard solutions 1,2 and 3 in mol/L, uniformly mixing, reacting for 1h at room temperature, and measuring the fluorescence intensity at 360nm under the condition of an excitation wavelength of 260 nm; and (3) calculating the concentration of the iron ions in the labeling solution according to the linear relation obtained in the step (4), and calculating the average labeling recovery rate and the relative standard deviation.
The concentration of iron ions in the above-mentioned labeled solution was measured by ICP method, and the average labeled recovery and the relative standard deviation were calculated and compared with the detection results of the present method, and the results are shown in table 1 below.
TABLE 1
As shown in the results of the table 1, compared with the prior art, the invention has higher sensitivity and accuracy and has certain practical value.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. 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 (7)
1. The application of the alcohol-soluble fluorescent carbon dot in detecting iron ions in an organic phase is characterized in that the preparation method of the alcohol-soluble fluorescent carbon dot comprises the following steps:
adding 3, 4-dihydroxycinnamic acid and absolute ethyl alcohol into a container, uniformly stirring, performing hydrothermal reaction, and naturally cooling to room temperature to obtain a solution; the volume ratio of the mass of the 3, 4-dihydroxycinnamic acid to the absolute ethanol is 1.4g-2.2g:20mL; the hydrothermal reaction condition is that the temperature is raised to 180-220 ℃, and after the target temperature is reached, the reaction is 2h-10 h;
filtering the obtained solution, dialyzing and purifying by using absolute ethyl alcohol, and distilling under reduced pressure to obtain an alcohol-soluble fluorescent carbon dot solid;
the organic solvent in the organic phase is absolute ethanol, methanol, acetonitrile, dichloromethane or acetyl ethyl ester.
2. The use according to claim 1, wherein the hydrothermal reaction conditions are elevated at an elevated temperature rate of 10 ℃/min.
3. The use according to claim 1, wherein the ratio of the mass of 3, 4-dihydroxycinnamic acid to the volume of absolute ethanol is 1.8g:20mL;
the hydrothermal reaction condition is that the temperature is raised to 200 ℃ at a heating rate of 10 ℃/min, and after the target temperature is reached, the reaction is carried out 6h; filtering with 0.22 μm organic filter membrane;
the dialysis purification time was 48h; the cut-off molecular weight of the dialysis bag is 100-500Da.
4. The use according to claim 1, comprising the step of detecting iron ions by fluorescence.
5. The method of claim 4, wherein the step of detecting the iron ions by fluorescence comprises:
(1) Dissolving the alcohol-soluble fluorescent carbon dot solid by absolute ethyl alcohol to prepare an alcohol-soluble fluorescent carbon dot solution with the final concentration of 51-85 mug/mL;
(2) Preparation of standard solution: by usingPreparing iron ion-containing solutions with different concentration gradients by using an organic solvent, and respectively adding alcohol-soluble fluorescent carbon dot solutions to obtain the final concentration of iron ions of 1.00 multiplied by 10 -6 mol/L-50.0×10 -6 mixing the standard solution with mol/L, and reacting at room temperature for 1h; wherein the concentration of alcohol-soluble fluorescent carbon points in each standard solution is the same;
using a fluorescence spectrophotometer to measure the fluorescence intensity of the standard solution at 360nm under the condition of an excitation wavelength of 260nm, and marking as Fn, n being the number of the standard solution and n being an integer;
(3) Preparation of a blank solution: adding only an organic solvent into the alcohol-soluble fluorescent carbon dot solution, uniformly mixing the solution, reacting at room temperature for 1h, and measuring the fluorescence intensity of the solution at 360nm under the condition of an excitation wavelength of 260nm, wherein the fluorescence intensity is marked as F0;
(4) The relative fluorescence intensity of the standard solution was calculated: F0/Fn to obtain a linear relation between the final concentration of the iron ions in the standard solution and the relative fluorescence intensity of the standard solution;
(5) Measurement of the solution to be measured: adding a solution to be detected into the alcohol-soluble fluorescent carbon dot solution to obtain a mixed solution to be detected, uniformly mixing, reacting for 1h at room temperature, and measuring the fluorescence intensity of the mixed solution at a position of 360nm under the condition of an excitation wavelength of 260 nm; and (3) obtaining the concentration of iron ions in the solution to be detected according to the linear relation obtained in the step (4).
6. The use according to claim 5, wherein the final concentration of the alcohol-soluble fluorescent carbon dot solution of step (1) is 85 μg/mL;
the mixing volume ratio of the solution containing iron ions to the alcohol-soluble fluorescent carbon dot solution in each standard solution in the step (2) is 1:9, adding the same volume of the alcohol-soluble fluorescent carbon dot solution into each standard solution;
the organic solvent is absolute ethanol, methanol, acetonitrile, dichloromethane or acetyl ethyl ester.
7. The use according to claim 5, wherein the concentration of alcohol-soluble fluorescent carbon dots in the blank solution of step (3) is the same as the concentration of alcohol-soluble fluorescent carbon dots in the standard solution;
the concentration of the alcohol-soluble fluorescent carbon points in the mixed solution to be detected in the step (5) is the same as that of the alcohol-soluble fluorescent carbon points in the standard solution;
the volumes of the standard solution, the blank solution and the solution to be tested are the same.
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