CN114813672A - Method for detecting concentration of white spirit ethanol by using red light carbon quantum dot fluorescent probe - Google Patents
Method for detecting concentration of white spirit ethanol by using red light carbon quantum dot fluorescent probe Download PDFInfo
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- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 title claims abstract description 142
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 96
- 239000007850 fluorescent dye Substances 0.000 title claims abstract description 49
- 238000000034 method Methods 0.000 title claims abstract description 31
- 239000000243 solution Substances 0.000 claims abstract description 87
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 39
- IDGUHHHQCWSQLU-UHFFFAOYSA-N ethanol;hydrate Chemical compound O.CCO IDGUHHHQCWSQLU-UHFFFAOYSA-N 0.000 claims abstract description 30
- 238000002189 fluorescence spectrum Methods 0.000 claims abstract description 14
- 239000011259 mixed solution Substances 0.000 claims abstract description 14
- 238000002156 mixing Methods 0.000 claims abstract description 10
- 238000001514 detection method Methods 0.000 claims abstract description 7
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- CBCKQZAAMUWICA-UHFFFAOYSA-N 1,4-phenylenediamine Chemical compound NC1=CC=C(N)C=C1 CBCKQZAAMUWICA-UHFFFAOYSA-N 0.000 claims description 11
- 238000007865 diluting Methods 0.000 claims description 5
- 239000007864 aqueous solution Substances 0.000 claims description 3
- -1 polytetrafluoroethylene Polymers 0.000 claims description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 3
- 238000003756 stirring Methods 0.000 claims description 3
- 238000005303 weighing Methods 0.000 claims description 3
- 230000001476 alcoholic effect Effects 0.000 abstract description 12
- 239000003513 alkali Substances 0.000 abstract description 2
- 235000019441 ethanol Nutrition 0.000 description 48
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 28
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 27
- 239000004310 lactic acid Substances 0.000 description 14
- 235000014655 lactic acid Nutrition 0.000 description 14
- 239000000654 additive Substances 0.000 description 12
- BJEPYKJPYRNKOW-REOHCLBHSA-N (S)-malic acid Chemical compound OC(=O)[C@@H](O)CC(O)=O BJEPYKJPYRNKOW-REOHCLBHSA-N 0.000 description 10
- BJEPYKJPYRNKOW-UHFFFAOYSA-N alpha-hydroxysuccinic acid Natural products OC(=O)C(O)CC(O)=O BJEPYKJPYRNKOW-UHFFFAOYSA-N 0.000 description 10
- 230000005284 excitation Effects 0.000 description 10
- 239000001630 malic acid Substances 0.000 description 10
- 235000011090 malic acid Nutrition 0.000 description 10
- 235000011054 acetic acid Nutrition 0.000 description 9
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 6
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 6
- 239000000523 sample Substances 0.000 description 6
- 235000015165 citric acid Nutrition 0.000 description 5
- 229910021642 ultra pure water Inorganic materials 0.000 description 5
- 239000012498 ultrapure water Substances 0.000 description 5
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 4
- 230000000996 additive effect Effects 0.000 description 4
- 239000000796 flavoring agent Substances 0.000 description 4
- PHTQWCKDNZKARW-UHFFFAOYSA-N isoamylol Chemical compound CC(C)CCO PHTQWCKDNZKARW-UHFFFAOYSA-N 0.000 description 4
- ZXEKIIBDNHEJCQ-UHFFFAOYSA-N isobutanol Chemical compound CC(C)CO ZXEKIIBDNHEJCQ-UHFFFAOYSA-N 0.000 description 4
- 238000010791 quenching Methods 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 239000012452 mother liquor Substances 0.000 description 3
- PXRKCOCTEMYUEG-UHFFFAOYSA-N 5-aminoisoindole-1,3-dione Chemical compound NC1=CC=C2C(=O)NC(=O)C2=C1 PXRKCOCTEMYUEG-UHFFFAOYSA-N 0.000 description 2
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 2
- DHKHKXVYLBGOIT-UHFFFAOYSA-N acetaldehyde Diethyl Acetal Natural products CCOC(C)OCC DHKHKXVYLBGOIT-UHFFFAOYSA-N 0.000 description 2
- 125000002777 acetyl group Chemical class [H]C([H])([H])C(*)=O 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 2
- 239000007853 buffer solution Substances 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- HYBBIBNJHNGZAN-UHFFFAOYSA-N furfural Chemical compound O=CC1=CC=CO1 HYBBIBNJHNGZAN-UHFFFAOYSA-N 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- ZNJHFNUEQDVFCJ-UHFFFAOYSA-M sodium;2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid;hydroxide Chemical compound [OH-].[Na+].OCCN1CCN(CCS(O)(=O)=O)CC1 ZNJHFNUEQDVFCJ-UHFFFAOYSA-M 0.000 description 2
- 239000012085 test solution Substances 0.000 description 2
- 239000011787 zinc oxide Substances 0.000 description 2
- 235000014692 zinc oxide Nutrition 0.000 description 2
- WRMNZCZEMHIOCP-UHFFFAOYSA-N 2-phenylethanol Chemical compound OCCC1=CC=CC=C1 WRMNZCZEMHIOCP-UHFFFAOYSA-N 0.000 description 1
- 241000227425 Pieris rapae crucivora Species 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
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- 230000000694 effects Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 238000001027 hydrothermal synthesis Methods 0.000 description 1
- 238000004811 liquid chromatography Methods 0.000 description 1
- 238000004020 luminiscence type Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000010413 mother solution Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000010561 standard procedure Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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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
- 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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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- 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
- G01N21/6428—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes"
- G01N2021/6432—Quenching
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Abstract
A method for detecting the concentration of white spirit ethanol by using a high-water-solubility red light carbon quantum dot fluorescent probe belongs to the technical field of fluorescent probes. Mixing red light carbon quantum dot solution with 0-100% ethanol-water solution, measuring fluorescence emission spectrum of the mixed solution, and establishing a relation curve of fluorescence emission peak fluorescence intensity-ethanol concentration; and mixing the red light carbon quantum dot solution with white spirit with unknown ethanol concentration, adding sodium hydroxide with final concentration of 10-20 mM, measuring the fluorescence emission spectrum of the solution, substituting the emission peak fluorescence intensity value into a relation curve of fluorescence emission peak fluorescence intensity-ethanol concentration, and calculating to obtain the white spirit concentration, thereby realizing the detection of the white spirit ethanol concentration. After the pH value of the white spirit is compensated by adding alkali, the reaction system can be restored to the same fluorescence intensity in an ethanol-water system, and the fluorescent probe can be used for accurately detecting the alcoholic strength of the white spirit.
Description
Technical Field
The invention belongs to the technical field of fluorescent probes, and particularly relates to a method for detecting the concentration of white spirit ethanol by using a high-water-solubility red light carbon quantum dot fluorescent probe.
Background
Chinese white spirit is popular with consumers all over the world due to long history and unique process. The alcohol content is the volume percentage of the alcohol content in the liquor, is an important index for identifying the liquor quality, and is also one of the main bases for consumers to buy the liquor. As a qualified white spirit, the alcohol content of the mark must be very accurate. However, some illegal merchants sometimes have large deviations in their identified alcohol content. Therefore, the quality of the white spirit can be preliminarily evaluated by measuring the content of the ethanol in the white spirit. In order to standardize the quality of white spirit in the market, China has issued a series of standard methods for detecting the alcoholic strength of the white spirit, such as: a bottle method, an alcohol method, a gas chromatography method, a digital densitometer method, and the like. However, these methods are complicated and time-consuming. Therefore, there is an urgent need to develop a simple, sensitive and efficient method for detecting the alcohol content of white spirit.
Carbon Quantum Dots (CQDs) have been discovered since 2000 and have been a hot point of research due to their excellent stability, low cost and good biocompatibility [1] . Carbon quantum dots are used in various fields, for example: solar cell, capacitor, sensing detection and biological application [2-6] And so, researchers have tried to synthesize carbon quantum dots having different emission wavelengths using various raw materials and methods. However, under the irradiation of ultraviolet light, the emission wavelength of the carbon quantum dot is mostly located in the blue or green light region, which limits the practical application of the carbon quantum dot. Therefore, the development of a cheap, environment-friendly and simple method for preparing red carbon quantum dots is urgently needed.
The foregoing invention [7] P-phenylenediamine (PPD) and Citric Acid (CA) are selected as raw materials to synthesize a carbon quantum dot with red luminescence property, and when the carbon quantum dot is applied to detection of ethanol concentration in an ethanol-water system, the carbon quantum dot shows good linear response. However, when the method is further used for detecting the ethanol concentration in the actual white spirit, the following results are found: when the concentration of ethanol in the ethanol-water system is the same as that of ethanol in the white spirit, the fluorescence emission intensity of the carbon quantum dots in the ethanol-water system is different (obviously lower). By investigating the white spiritThe influence of various additives and pH values on the fluorescence intensity of the carbon quantum dots is found as follows: this quenching of fluorescence of carbon quantum dots is mainly caused by the acidity in wine: the fluorescence intensity is significantly reduced with decreasing pH. That is, the pH of the actual white spirit is lower than that of the ethanol-water solution with the same concentration. Therefore, after the pH value of the liquor is adjusted and controlled to be compensated, the alcohol content of the actual liquor can be accurately detected by the fluorescent carbon quantum dots.
Disclosure of Invention
The invention provides a method for detecting the concentration of white spirit ethanol by using a high-water-solubility red light carbon quantum dot fluorescent probe. The carbon quantum dot is directly prepared by taking p-phenylenediamine (PPD) and Citric Acid (CA) as raw materials through a one-step hydrothermal method under the conditions of high temperature and high pressure, the optimal excitation wavelength of the carbon quantum dot is 500nm, the emission wavelength is 620nm, and the carbon quantum dot emits red light under the irradiation of an ultraviolet lamp (365 nm); further, the carbon quantum dots are used for detecting the alcoholic strength of the white spirit. We observed that: when the concentration of ethanol in the ethanol-water system is the same as that of ethanol in the white spirit, the fluorescence intensity of the carbon quantum dots is obviously lower. To explain the difference in quenching property, we examined the effect of various additives in white spirit on the fluorescence intensity of carbon quantum dots, and the results show that: the fluorescence intensity of the carbon quantum dots can be quenched by lactic acid, acetic acid and malic acid, and the fluorescence intensity of the carbon quantum dots is not influenced by other common white spirit additives. Moreover, when the pH value of the solution is artificially changed, the fluorescence intensity of the carbon quantum dots is changed; further, the lower the pH of the solution, the more the fluorescence intensity of the carbon quantum dot is quenched. Further, after the pH value of the white spirit is compensated by adding alkali, the fluorescence intensity of the carbon quantum dots is gradually enhanced and can be restored to the fluorescence intensity in the same ethanol-water system. The results show that: the carbon quantum dots can be used as fluorescent probes for accurately detecting the alcoholic strength of the white spirit by compensating and regulating the pH value of the white spirit.
The invention relates to a method for detecting the concentration of alcohol in white spirit by using a red light carbon quantum dot fluorescent probe with high water solubility, which comprises the following steps:
(1) weighing 0.01-0.03 g of p-phenylenediamine, dissolving the p-phenylenediamine in 10mL of water, adding 8-15 mL of 1mM citric acid aqueous solution after fully dissolving, and stirring at room temperature for 8-15 min; transferring the reaction solution into a high-pressure reaction kettle with a polytetrafluoroethylene inner container, and reacting for 8-15 h at 170-190 ℃ to obtain a red light carbon quantum dot solution;
(2) diluting the red light carbon quantum dot solution obtained in the step (1) by 50-150 times with water, and mixing with an ethanol-water solution with the ethanol concentration of 0% -100%; the total volume of the mixed solution is 1000 mu L, wherein the volume of the diluted red light carbon quantum dot solution is 5-20 mu L, and the balance is ethanol-water solution; then measuring the fluorescence emission spectrum of the mixed solution, and establishing a relation curve of fluorescence emission peak fluorescence intensity-ethanol concentration;
(3) diluting the red light carbon quantum dot solution obtained in the step (1) by 50-150 times with water, and mixing with white spirit with unknown ethanol concentration; the total volume of the mixed solution is 1000 mu L, wherein the volume of the diluted red light carbon quantum dot solution is 5-20 mu L, and the balance is white spirit; and (3) adding sodium hydroxide with the final concentration of 10-20 mM into the mixed solution, measuring the fluorescence emission spectrum of the solution, substituting the emission peak fluorescence intensity value into the relation curve of the fluorescence emission peak fluorescence intensity-ethanol concentration established in the step (2), and calculating to obtain the concentration of the white spirit, thereby realizing the detection of the concentration of the white spirit ethanol.
Drawings
FIG. 1 is a linear relation graph of fluorescence intensity difference of fluorescence emission peak of a fluorescent probe solution with ethanol concentration (0-100%) in ethanol-water solution and white spirit under 500nm excitation.
FIG. 2 is a point line graph showing that the fluorescence intensity of the fluorescence emission peak of a fluorescent probe solution in ultrapure water changes with the concentration (10-50 mM) of a common additive for fen-flavor liquor under the excitation of 500 nm.
FIG. 3 shows fluorescence emission spectra of a fluorescent probe solution in ultrapure water under 500nm excitation, as a function of the concentrations of lactic acid, malic acid and acetic acid (10-50 mM).
FIG. 4 is a point line graph showing that fluorescence intensity of fluorescence emission peak of a fluorescent probe solution in ultrapure water varies with different concentrations of lactic acid, malic acid and acetic acid (10-50 mM) under 500nm excitation.
FIG. 5 shows fluorescence emission spectra of fluorescent probe solutions as a function of pH under 500nm excitation.
FIG. 6 is a point line graph showing the change of fluorescence intensity of fluorescence emission peak of a fluorescent probe solution with pH under the excitation of 500 nm.
FIG. 7 is a linear relationship graph of fluorescence intensity of a fluorescence emission peak of a low-concentration fluorescent probe solution with the change of ethanol concentration (0-100%) in an ethanol-water solution under the excitation of 500 nm.
FIG. 8 is a fluorescence emission spectrum of a fluorescent probe solution in fen-flavor liquor under 500nm excitation, which varies with the concentration of sodium hydroxide.
FIG. 9 is a point line graph showing the variation of fluorescence intensity of fluorescence emission peak of fluorescent probe solution in fen-flavor Chinese liquor with the concentration of sodium hydroxide under the excitation of 500 nm.
Table 1 comparison table of pH values of ethanol-water solutions and white spirit with different alcoholic strength.
Table 2 shows the results of the evaluation of the alcohol content of the commercial fen-flavor liquor by using the fluorescent probe solution.
And 3, comparing the result of detecting the alcoholic strength of the unknown white spirit by adopting the fluorescent probe solution with the result of the traditional method.
As shown in FIG. 1, when the ethanol concentration in the ethanol-water system is the same as that in the white spirit, the fluorescence enhancement amplitude of the carbon quantum dot fluorescence emission peak is different, and the difference is probably caused by the additive in the white spirit. As shown in fig. 2, when the carbon quantum dots and the different kinds of additives are mixed, the fluorescence intensity of the carbon quantum dots is not affected by the other white spirit additives except that the lactic acid can quench the fluorescence intensity of the carbon quantum dots. However, the residual acids (malic acid, lactic acid) also affect the fluorescence of the carbon quantum dots. In addition, when the pH of the solution is changed, the fluorescence intensity of the carbon quantum dot is changed, and the lower the fluorescence intensity of the carbon quantum dot as the pH of the solution is decreased. Meanwhile, the pH value of the white spirit is lower than that of the ethanol-water solution with the same concentration. The results indicate that the pH value may be a main factor causing the difference of the fluorescence intensity of the carbon quantum dots in the two systems. By compensating the pH value of the white spirit, the fluorescence intensity of the carbon quantum dots is gradually enhanced and is restored to the fluorescence emission intensity in a pure ethanol-water system. The results show that: by compensating the pH value, the carbon quantum dots can be used as a fluorescent probe for detecting the alcoholic strength of the white spirit.
Detailed Description
The following examples further illustrate the present invention, but the present invention is not limited to these examples.
P-phenylenediamine, citric acid, malic acid, lactic acid, acetal, methanol, ethyl acetate, 1-propanol, lactic acid, n-butanol, isobutanol, isoamyl alcohol, which are used in the present invention, were purchased from Shanghai Allantin reagent company. The anhydrous ethanol is purchased from Shandong Yuwang and New materials under heaven Limited, the Xinghuacun, the Daqu raw wine, the Beijing Erguotou and the Chinese white spirit are purchased from local supermarkets, the sodium hydroxide is purchased from the national medicine group chemical reagent Limited, the acetic acid is purchased from the Beijing chemical plant, and the deionized ultrapure water is used in the whole experimental process.
Example 1:
preparation of red light carbon quantum dot fluorescent probe solution [7] The method specifically comprises the following steps: weighing 0.02g of p-phenylenediamine, dissolving the p-phenylenediamine in 10mL of water, adding 10mL of 1mM citric acid aqueous solution after fully dissolving, and stirring for 10min at room temperature; and then transferring the reaction solution into a high-pressure reaction kettle with a polytetrafluoroethylene inner container, and reacting for 10 hours at 180 ℃ to obtain the red light carbon quantum dot fluorescent probe solution.
Fluorescent response of the fluorescent probe solution to ethanol-water solution and ethanol in white spirit: adding absolute ethyl alcohol into deionized ultrapure water, respectively preparing ethanol-water mixed solutions with different concentrations (the volume concentrations of the ethanol are respectively 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100%), then adding 950 mu L of the ethanol-water mixed solution with different concentrations and 50 mu L of the red light carbon quantum dot fluorescent probe solution into a cuvette, and measuring the fluorescence emission spectrogram of the solution after fully and uniformly mixing.
Preparing white spirit with different concentrations (the volume concentration of the ethanol is respectively 26.5%, 50.35%, 63%, 73%, 83% and 93%) by diluting and increasing the concentration of the ethanol, then adding 950 mu L of the white spirit with different concentrations and 50 mu L of red light carbon quantum dot fluorescent probe solution into a cuvette, and measuring the fluorescence emission spectrogram of the solution after fully and uniformly mixing.
By plotting the difference of the fluorescence intensity of two systems of carbon quantum dots (F-F) 0 ，F 0 Representing the fluorescence intensity of a fluorescence emission peak in a fluorescence emission spectrum before adding the ethanol/white spirit; f represents the fluorescence intensity of the fluorescence emission peak in the fluorescence emission spectrum after adding ethanol/white spirit) and the ethanol concentration (figure 1). It can be obviously seen that when the ethanol-water system and the white spirit have the same ethanol concentration, the fluorescence intensity of the carbon quantum dots has larger difference.
Example 2:
preparing a series of ethanol-water mixed solutions (42%, 53%, 56%, 65.8%) with the same concentration as the alcohol content of the Chinese liquor, and respectively detecting the pH values of the ethanol-water solution and the Chinese liquor. The results are shown in Table 1. The results show that: the pH value of the white spirit is lower than that of the ethanol-water solution with the same concentration.
Table 1: and comparing the pH values of the ethanol-water solution and the white spirit with different alcoholic strength.
Example 3:
influence of additives in the white spirit on the fluorescence intensity of the fluorescent probe solution: respectively preparing 1.0M liquor additive mother liquor (2-phenethyl alcohol, methanol, 1-propanol, n-butanol, isobutanol, isoamyl alcohol, acetal, furfural, ethyl acetate and lactic acid, wherein the solvent is water); the red light carbon quantum dot fluorescent probe solution prepared in example 1 was diluted 100 times with water and divided into multiple portions (each portion was 1.0mL), and different volumes and different types of white spirit additive mother liquor were added to each portion of the diluted solution so that the final concentrations of the white spirit additives were 10, 20, 30, 40, and 50mM, respectively. Then, the fluorescence emission spectrum of the solution was recorded using a fluorescence spectrometer. As shown in FIG. 2, the fluorescence intensity of the carbon quantum dots is not greatly affected by other white spirit additives except that the lactic acid can quench the fluorescence intensity of the carbon quantum dots.
Example 4:
influence of common acids on fluorescence intensity of fluorescent probe solutions: respectively preparing lactic acid, acetic acid and malic acid mother liquor (1.0M) with the same concentration; 990 μ L of 53% ethanol-water mixed solution and 10 μ L of red light carbon quantum dot fluorescent probe solution (the red light carbon quantum dot fluorescent probe solution prepared in example 1 was diluted 100 times with water) were mixed to prepare a test solution, and lactic acid, acetic acid, and malic acid mother solutions of different volumes were added dropwise to the above multiple test solutions to make final concentrations 10, 20, 30, 40, and 50mM, respectively. And measuring the fluorescence emission spectrogram of the solution after fully and uniformly mixing. As shown in the experimental results of fig. 3: the fluorescence intensity of the fluorescence emission peak of the carbon quantum dot gradually weakens with the increase of the concentrations of lactic acid (panel a), acetic acid (panel b) and malic acid (panel c). Meanwhile, by drawing a relation graph (figure 4) of the fluorescence intensity of the carbon quantum dot fluorescence emission peak of the system and the concentrations of lactic acid, acetic acid and malic acid, the following can be obviously seen: lactic acid, acetic acid and malic acid can quench the fluorescence intensity of the carbon quantum dots.
Example 5:
influence of pH on fluorescence intensity of fluorescent probe solution: preparing HEPES-NaOH buffer solutions with pH values of 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 9, 9.5 and 10 respectively. 900 μ L of HEPES-NaOH buffer solutions with different pH values and 100 μ L of red light carbon quantum dot fluorescent probe solution (the red light carbon quantum dot fluorescent probe solution prepared in example 1 is diluted by 10 times with water) are added into a cuvette, and after the solutions are sufficiently mixed, the fluorescence emission spectrograms of the solutions are measured. FIG. 5 shows that the fluorescence intensity of the fluorescence emission peak of the carbon quantum dot is closely related to the pH value, and the fluorescence intensity of the fluorescence emission peak of the carbon quantum dot gradually increases with the increase of the pH value. Meanwhile, by drawing a relation graph (fig. 6) between the fluorescence intensity of the fluorescence emission peak of the carbon quantum dot and the pH value, it can be clearly seen that the lower the pH value is, the weaker the fluorescence intensity of the carbon quantum dot is.
Example 6:
fluorescence response of low concentration fluorescent probe solution to ethanol in ethanol-water solution: preparing ethanol-water mixed solution (0%, 10%, 20%, 30%, 40%, 50%, 52%, 53%, 60%, 65.8%, 70%, 80%, 90%, 100%) with different volume concentration, respectively, and adding 990 μ L of ethanol with different concentration into the cuvetteThe fluorescence emission spectrum of the solution was measured after mixing the solution with 10. mu.L of red-light carbon quantum dot fluorescence probe solution (the red-light carbon quantum dot fluorescence probe solution prepared in example 1 was diluted 100 times with water) and thoroughly. The relationship graph (figure 7) of the fluorescence intensity of the carbon quantum dot fluorescence emission peak and the ethanol concentration of the system is drawn to obviously show that: when the Ethanol concentration is within the range of 20-90%, the carbon quantum dot fluorescence emission peak fluorescence intensity (F) and the Ethanol concentration (Ethanol) present a better linear response relationship (R) 2 0.99107) whose linear response equation is: 6.22507 Ethanol]-8.29971。
Example 7:
detecting the alcoholic strength of the white spirit by using a fluorescent probe solution: mu.L of red light carbon quantum dot fluorescent probe solution (the red light carbon quantum dot fluorescent probe solution prepared in example 1 was diluted 100 times with water) was mixed with 990. mu.L of white spirit of different concentrations (42%, 53%, 56%, 65.8%), sodium hydroxide solution (final concentration range 2-20 mM, final concentrations 2mM, 4mM, 6mM, 8mM, 10mM, 12mM, 14mM, 16mM, 18mM, 20mM) was added dropwise to the above solution, and the fluorescence emission spectrum of the above solution was detected. FIG. 8 shows that the fluorescence intensity of the fluorescence emission peak of the carbon quantum dot in the white spirit increases with the increase of the concentration of the sodium hydroxide. By drawing a relation graph (figure 9) of the fluorescence intensity of the fluorescence emission peak of the carbon quantum dot in the white spirit and the concentration of the sodium hydroxide, it can be obviously seen that when the concentration of the sodium hydroxide is more than 10mM, the fluorescence intensity of the fluorescence emission peak of the carbon quantum dot is basically kept unchanged along with the increase of the concentration of the sodium hydroxide, so that the final concentration of the sodium hydroxide in a proper fluorescent probe solution is 10-20 mM.
Finally, 10. mu.L of red light carbon quantum dot fluorescent probe solution (the red light carbon quantum dot fluorescent probe solution prepared in example 1 was diluted 100 times with water), 990. mu.L of white spirit and sodium hydroxide (final concentration 10.0mM) were added to the cuvette, respectively, and the fluorescence emission intensity of the above solution was measured. The result shows that the recovery rate is 95.8-101.0%, which indicates that the carbon quantum dot can be used for detecting the alcoholic strength of the white spirit (Table 2). To further prove the accuracy of the method, the alcohol content detected by the carbon quantum dot is compared with the traditional method (liquid chromatography). The result shows that the consistency is 96.1-98.8% (table 3), and further shows that the method can quickly and accurately detect the alcoholic strength of the white spirit.
Table 2: detecting alcohol content of Chinese liquor with fluorescent probe solution (Chinese liquor sample from supermarket)
| Sample (I) | Raw material nominal alcohol content (%) | The method of the invention detects the alcoholic strength (%) | Recovery (%) |
| 1 # | 42 | 42.4 | 101.0 |
| 2 # | 53 | 52.0 | 98.2 |
| 3 # | 56 | 53.7 | 95.8 |
| 4 # | 65.8 | 64.1 | 97.4 |
Table 3: comparing the result of detecting the alcohol content of unknown liquor by adopting a fluorescent probe solution with the result of the traditional method (the liquor sample comes from a brewery)
| Sample (I) | Carbon quantum dot detection alcohol content (%) | Alcohol content (%) -measured by conventional method | Match (%) |
| 1 # | 32.4 | 32.8 | 98.8 |
| 2 # | 44.2 | 46.0 | 96.1 |
| 3 # | 57.3 | 59.0 | 97.1 |
| 4 # | 64.1 | 65.8 | 97.4 |
Further, it should be noted that: the specific examples set forth in this specification are intended to be illustrative of the invention and do not limit the scope of the invention in any way; modifications and variations are possible in light of the above teachings, but all such modifications and variations are within the scope of the invention as defined in the appended claims.
Reference documents:
[1]Y.Jiang,Z.Dai Sensors Actuators B Chem 234(2016)15–20.
[2]R.Guo,H.Hou Energy Stor.Mater.37(2021)8–39.
[3]Y.Jin,L.Dai Adv.Funct.Mater.28(2018)1804630.
[4]L.Cai,F.Cui J Fluoresc 30(2020)11–20.
[5]S.Bian,X.Dong Sensors Actuators B Chem 242(2017)231–2.
[6]P.Shen,J.Yao ChemistrySelect 1(2016)1314–1317.
[7] wuyuqing, a fluorescent probe based on red light carbon quantum dots and its application in detection of ethanol concentration in ethanol-water system [ P ]. Chinese patent: 202210244301.3.
Claims (4)
1. a method for detecting the concentration of white spirit ethanol by using a high-water-solubility red light carbon quantum dot fluorescent probe comprises the following steps:
(1) weighing 0.01-0.03 g of p-phenylenediamine, dissolving the p-phenylenediamine in 10mL of water, adding 8-15 mL of 1mM citric acid aqueous solution after fully dissolving, and stirring at room temperature for 8-15 min; transferring the reaction solution into a high-pressure reaction kettle with a polytetrafluoroethylene inner container, and reacting for 8-15 h at 170-190 ℃ to obtain a red light carbon quantum dot solution;
(2) diluting the red light carbon quantum dot solution obtained in the step (1) by 50-150 times with water, and mixing with an ethanol-water solution with the ethanol concentration of 0% -100%; then measuring the fluorescence emission spectrum of the mixed solution, and establishing a relation curve of fluorescence emission peak fluorescence intensity-ethanol concentration;
(3) diluting the red light carbon quantum dot solution obtained in the step (1) by 50-150 times with water, and mixing with white spirit with unknown ethanol concentration; and (3) adding sodium hydroxide with the final concentration of 10-20 mM into the mixed solution, measuring the fluorescence emission spectrum of the solution, substituting the emission peak fluorescence intensity value into the relation curve of the fluorescence emission peak fluorescence intensity-ethanol concentration established in the step (2), and calculating to obtain the concentration of the white spirit, thereby realizing the detection of the concentration of the white spirit ethanol.
2. The method for detecting the ethanol concentration of the white spirit by using the high-water-solubility red light carbon quantum dot fluorescent probe as claimed in claim 1, wherein the method comprises the following steps: the total volume of the mixed solution in the step (2) is 1000 mu L, wherein the volume of the diluted red light carbon quantum dot solution is 5-20 mu L, and the balance is ethanol-water solution.
3. The method for detecting the ethanol concentration of the white spirit by using the high-water-solubility red light carbon quantum dot fluorescent probe as claimed in claim 1, wherein the method comprises the following steps: and (4) the total volume of the mixed solution in the step (3) is 1000 mu L, wherein the volume of the diluted red light carbon quantum dot solution is 5-20 mu L, and the balance is white spirit.
4. The method for detecting the ethanol concentration of the white spirit by using the high-water-solubility red light carbon quantum dot fluorescent probe as claimed in claim 1, wherein the method comprises the following steps: the volume and the dosage of the red light carbon quantum dot solution in the step (2) and the diluted red light carbon quantum dot solution in the step (3) are the same.
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