CN113861971B - Rare earth element doped carbon quantum dot ratiometric fluorescent probe, and preparation method and application thereof - Google Patents
Rare earth element doped carbon quantum dot ratiometric fluorescent probe, and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a rare earth element doped carbon quantum dot ratiometric fluorescent probe, and a preparation method and application thereof, and belongs to the technical field of fluorescent nano materials and environmental detection. The rare earth element doped carbon quantum dot ratiometric fluorescent probe takes citric acid as a carbon source and melamine as a nitrogen source, and is added with formaldehyde serving as a passivating agent and a rare earth compound Eu (NO)3)3·6H2And O, uniformly mixing in ultrapure water, performing high-temperature reaction, dialyzing to remove small molecules, and drying to obtain the product. The rare earth element doped carbon quantum dot ratiometric fluorescent probe is prepared by a one-step hydrothermal method, europium ions are doped into the carbon quantum dots in a hydrothermal reaction, so that the fluorescence of the carbon quantum dots can be kept, and the carbon quantum dots can be specifically combined with tetracycline molecules.
Description
Technical Field
The invention belongs to the technical field of fluorescent nano materials and environmental detection, and particularly relates to a rare earth element doped carbon quantum dot ratiometric fluorescent probe, and a preparation method and application thereof.
Background
Tetracycline (TC) is an important common antibiotic, and is widely applied to animal husbandry, aquaculture and individual treatment due to low cost, high antibacterial activity, good oral absorption and low toxicity. Unfortunately, there have been some serious adverse effects on food safety, environmental protection and human health due to the excessive use of TC products. At present, there are a large number of testsAnalytical strategies for detecting tetracycline, such as liquid chromatography-mass spectrometry (LC-MS), High Performance Liquid Chromatography (HPLC), Capillary Electrophoresis (CE), chemiluminescence, and electrochemical analysis, can accurately detect tetracycline. However, the method has the defects of strict instrument requirements, time consumption, complicated step operation, requirement of professional skills and the like. In recent years, fluorescence sensors or fluorescence analysis techniques have been successfully used for measuring TC because of their advantages of simple operation, fast response speed, low detection limit, small sample amount, good selectivity, low analysis cost, and the like. Notably, europium-based fluorescence sensing platforms exhibit highly enhanced fluorescence when combined with TCs, and have attracted considerable attention in recent years. This can be attributed to the fact that TC can react with europium ions (Eu)3+) Combine to form a europium-tetracycline complex (Eu)3+-TC) and transfers the energy absorbed by the tetracycline to Eu3+Make Eu to be3+The characteristic fluorescence of (a) is greatly enhanced, which is referred to as "antenna effect". Further, Eu3+Has unique spectral characteristics including large Stokes shift, long fluorescence lifetime and sharp linear emission region. However, since Eu3+Quenching effect due to vibration mode of coordinated water molecules, Eu3+The fluorescence intensity of the-TC complex is weak. Furthermore, these europium-based sensor platforms have limited practical applications due to poor stability in humid environments and ultraviolet light.
The detection of metal ions has attracted considerable attention due to the toxic effects caused by the excessive accumulation of metal ions in the human and animal body. Of all metals, aluminum is one of the most widely used metals in modern day life and in many industries. Acid rain and human activities can significantly increase the content of free aluminum ions in soil, and cause environmental pollution to crop production. Aluminum containers, packaging materials, electrical and electronic equipment can cause Al in drinking water and food3+And (4) pollution. Further, Al3+Can enter into organism through respiratory tract, digestive tract and skin, and cause damage to nervous system, and various diseases, such as microcytic hypopigmentation anemia, gastrointestinal tract diseases, liver and kidney damage, memory loss, etc., and human body average Al3+The intake is 3-10 mg per day and the maximum aluminum intake is 7 mg/weekKg body weight. Atomic absorption spectrometry atomic and emission spectrometry, high performance liquid chromatography, electrochemical methods, and inductively coupled plasma mass spectrometry are the most widely used conventional Al3+And (3) a detection method. These methods typically require complex sample preparation and expensive precision instruments, which make them unusable for rapid in situ detection of aluminum ions. Thus, Al is highly efficient, rapid and simple3+Visual presence detection remains a significant challenge.
Disclosure of Invention
One of the purposes of the invention is to provide a preparation method of a rare earth element doped carbon quantum dot ratiometric fluorescent probe, which specifically comprises the following steps:
the raw materials are citric acid as carbon source and melamine as nitrogen source, and rare earth compound Eu (NO) is added3)3·6H2O, uniformly mixing the three components in ultrapure water, carrying out high-temperature reaction, cooling to room temperature after the reaction is finished, and dialyzing the obtained solution with ultrapure water to remove small molecules; and evaporating and drying the residual solution to obtain the rare earth element doped carbon quantum dot ratiometric fluorescent probe powder.
Preferably, the high-temperature reaction is carried out at 180-220 ℃ for 5-10 h;
preferably, the dosage of the citric acid is 8-12 mmol; the dosage of the melamine is 0.2-0.3 mmol; the rare earth compound Eu (NO)3)3·6H2The dosage of O is 300-800 mg.
In some specific embodiments, the raw materials of the preparation method of the rare earth element doped carbon quantum dot ratiometric fluorescent probe further contain formaldehyde, the addition amount of the formaldehyde solution is 0-1000 mu L, and the concentration of the formaldehyde solution is 8 mmol/L.
In a specific embodiment, the rare earth compound Eu (NO)3)3·6H2When the dosage of O is 500mg, the fluorescence intensity is strongest.
In a specific embodiment, the amount of citric acid is 10 mmol; the dosage of the melamine is 0.25 mmol; the rare earth compound Eu (NO)3)3·6H2Use of OThe amount is 500 mg; the quantum yield is highest when the dosage of the formaldehyde is 560 mu L.
The above expression of the amount of the raw materials is only the amount used in the laboratory operation, and is not an absolute limitation of the amount thereof, and it will be understood by those skilled in the art that in the actual production, the amount may be adjusted in the above-mentioned ratio according to the production scale.
In a specific embodiment, the dialysis is performed by filtering with a 0.22 μm filter membrane, dialyzing the filtrate in ultrapure water for 24h with a dialysis bag with a cut-off molecular weight of 1000Da, and refreshing the water every 6 hours to remove small molecules.
The second purpose of the invention is to provide the rare earth element doped carbon quantum dot ratiometric fluorescent probe prepared by the method, and the rare earth element doped carbon quantum dot ratiometric fluorescent probe can be used for detecting tetracycline and/or aluminum ions and preparing tetracycline and/or aluminum ion detection products.
The preparation of the rare earth element doped carbon quantum dot and the principle of detecting tetracycline and identifying aluminum ions in a cascading manner are as follows: and doping europium ions into a lattice structure of the carbon quantum dots to serve as a specific identification unit of the TC. Without tetracycline addition, europium-doped carbon quantum dots fluoresce blue (λ em ═ 420 nm). After binding to tetracycline, based on Internal Filtration Effect (IFE) and Eu3+-antenna effect of TC, gradual quenching of blue fluorescence of carbon quantum dots, gradual enhancement of characteristic red fluorescence of europium-doped elements (λ em ═ 620nm), resulting in a ratiometric fluorescence signal change based on tetracycline content. Accordingly, the detection system gradually changed in color from blue to tan to light purple to light rose red to light pink to final red under the uv lamp. The invention is further applied to Al3+Due to the fact that Tetracycline Compounds (TCs) can react with the polyvalent cation Al3+Forming a chelate. Further adding Al after europium-doped carbon quantum dots react with TC3+The fluorescence of the europium-doped carbon quantum dots at about 468nm is gradually recovered, and Eu is3+The red fluorescence of the-TC complex at 620nm gradually disappears, and Al is realized3+With simultaneous color change from red to pink to blueAnd significantly changed.
The technical scheme of the invention has the advantages that:
the rare earth element doped carbon quantum dot ratiometric fluorescent probe is prepared by a one-step hydrothermal method, and europium ions are doped into the carbon quantum dots, so that the blue fluorescence of the carbon quantum dots can be maintained, and the red fluorescence of the europium ions can be enhanced by the specific combination of the europium ions and tetracycline molecules. The composite system may further be combined with Al3+Action on tetracycline and Al3+All produced a ratiometric fluorescence signal and a significant gradation of color. The novel fluorescent probe has excellent physical and chemical stability, does not need complex carbon quantum dot modification, can realize ratio fluorescence detection of a plurality of target molecules through a single carbon quantum dot, and can clearly observe the obvious color change of a system along with the concentration change of an object to be detected by naked eyes under an ultraviolet lamp.
In addition, a portable paper-based sensor without instrument and a POCT platform assisted by a smart phone are developed for tetracycline and Al3+The field visual detection. The developed paper-based sensor has the characteristics of easy carrying, low cost, high selectivity and high sensitivity, and can directly and easily read out a detection signal by naked eyes. The smart phone has the characteristics of portability and easiness in operation as a simple answer analyzer. When TC and Al3+When the concentration of (a) exceeds a certain level, the user is warned by a direct visual color change, and further, tetracycline and Al can be provided by mobile phone-assisted image processing3+Quantitative analysis of concentration. Is tetracycline and Al in the field and resource-poor areas3+The qualitative identification and semi-quantitative analysis of (a) provide a powerful method. Shows great potential application in food safety monitoring. Not only tetracycline and Al3+The ratiometric fluorescence and visual sensing of (a) provides a new strategy and new insights into the development of efficient ratiometric fluorescence and visual sensing platforms that hold great promise for many other in-situ assays in the future.
Drawings
FIG. 1 is a transmission electron microscopy analysis image and an HRTEM image of a rare earth element doped carbon quantum dot ratiometric fluorescent probe;
FIG. 2 is an X-ray photoelectron spectroscopy (XPS) chart of Eu-CDs;
FIG. 3 the effect of europium doping concentration on the fluorescence spectrum of the Eu-CDs-TC complex;
FIG. 4 is a fluorescence spectrum of the effect of different concentrations of TC on the fluorescence intensity of Eu-CDs;
FIG. 5 is a linear equation for detecting tetracycline by using a rare earth element doped carbon quantum dot ratiometric fluorescent probe;
FIG. 6 the specificity of a rare earth element doped carbon quantum dot ratiometric fluorescent probe for tetracycline;
FIG. 7 different concentrations of Al3+A fluorescence spectrum diagram influencing the Eu-CDs-TC fluorescence intensity;
FIG. 8 detection of Al by rare earth element doped carbon quantum dot ratiometric fluorescent probe3+A linear equation of (c);
FIG. 9Eu-CDs-TC Complex vs. Al3+Selectivity of cascade identification;
FIG. 10 is a linear equation for detecting tetracycline based on europium-doped carbon quantum dot ratiometric fluorescent probes in combination with smart phones and paper-based sensors;
FIG. 11 detection of Al based on europium-doped carbon quantum dot ratiometric fluorescent probe in combination with smartphone and paper-based sensor3+Is used as a linear equation of (a).
Detailed Description
Terms used in the present invention have generally meanings as commonly understood by one of ordinary skill in the art, unless otherwise specified.
The present invention will be described in further detail with reference to the following data in conjunction with specific examples. The following examples are intended to illustrate the invention and are not intended to limit the scope of the invention in any way.
Example 1
A preparation method of a rare earth element doped carbon quantum dot ratiometric fluorescent probe comprises the following steps:
1920mg (10.0mmol) of citric acid and 31.5mg (0.25mmol) of melamine were weighed out and dissolved in 10mL of ultrapure water, and 560. mu.L of a formaldehyde solution (formaldehyde concentration of 8.0mmol/L) and 500mg of Eu (NO) were added3)3·6H2O (99.99%). The solution was mixed well and transferred to 25mLThe reaction was carried out in a stainless autoclave lined with polytetrafluoroethylene at a temperature of 220 ℃ for 10 hours, and after cooling to room temperature, the resulting dark yellow solution was filtered through a 0.22 μm filter membrane and further dialyzed with a dialysis bag (molecular weight cut off 1000Da) in ultrapure water for 24 hours, and the water was refreshed every 6 hours to remove small molecules. Subsequently, the solution in the dialysis bag was evaporated and dried at 80 ℃ to obtain a powder of the rare earth element-doped carbon quantum dot ratiometric fluorescent probe with a quantum yield of 10.81%.
FIG. 1 is a Transmission Electron Microscope (TEM) image and a high-resolution transmission electron microscope (HRTEM) image of the rare earth element doped carbon quantum dot ratiometric fluorescent probe (Eu-CDs) prepared by the above method. As can be seen from a in FIG. 1, Eu-CDs are uniformly distributed approximately spherical nanoparticles, and the particle size distribution histogram of Eu-CDs shows that the particle size distribution is 1.0-3.0nm, and the average particle size is 2.0 nm. HRTEM images (b in FIG. 1) show that Eu-CDs have sharp lattice fringes with a lattice spacing of about 0.20nm, which is consistent with the (100) plane of graphitic carbon.
In order to further confirm the elemental composition and chemical bonds of Eu-CDs, X-ray photoelectron spectroscopy (XPS) measurements were performed. FIG. 2 is an XPS plot of Eu-CDs, wherein a is an XPS survey scan spectrum of Eu-CDs, b is an XPS spectrum of C1s, C is an XPS spectrum of N1s, d is an XPS spectrum of O1s, and e is an XPS spectrum of Eu3 d;
as can be seen from fig. 2, the XPS full scan spectrum shows four distinct peaks at 281.08,398.08,537.08 and 1131.08eV, due to C1s, N1s, O1s and Eu3d, with element contents of 60.11%, 2.99%, 33.03% and 3.87%, respectively. The high Eu content confirms successful doping of Eu in CDs (a in fig. 2). In high resolution spectra (fig. 2b-e), the C1s band can be deconvoluted at 284.7,285.7 and 288.4eV into three peaks, corresponding to C-C/C ═ C, C-N/C-O and C ═ O groups, respectively; in the N1s spectrum, the peaks at 399.9 and 401.5eV correspond to the N-C and N-H groups; the O1s band is 531.2, 532.0 and 532.9eV, and can be deconvoluted into three peaks, which are respectively assigned to C ═ O and C — OH groups. Eu3d is attributed to 3d at 1134.0 and 1164.0eV, respectively5/2And 3d3/2Photoemission of the structure. The spectrum of the high-resolution Eu3d consists of four peaks, Eu respectively3+(1165.0 and 1135.4eV) and Eu2+(1155.0 and 1125.5 eV).
Example 2
A preparation method of a rare earth element doped carbon quantum dot ratiometric fluorescent probe comprises the following steps:
1536mg (8.0mmol) of citric acid and 25.2mg (0.2mmol) of melamine are weighed out and dissolved in 10mL of ultrapure water, and 300mg of Eu (NO) is added3)3·6H2O (99.99%). The solution was mixed well, transferred to a 25mL stainless steel autoclave lined with polytetrafluoroethylene, reacted at a temperature of 220 ℃ for 10 hours, cooled to room temperature, and after the resulting dark yellow solution was filtered through a 0.22 μm filter membrane and further dialyzed with a dialysis bag (molecular weight cut off 1000Da) in ultrapure water for 24 hours, and the water was refreshed every 6 hours to remove small molecules. Subsequently, the solution in the dialysis bag was evaporated and dried at 80 ℃ to obtain a powder of the rare earth element-doped carbon quantum dot ratiometric fluorescent probe with a quantum yield of 7.50%.
Example 3
A preparation method of a rare earth element doped carbon quantum dot ratiometric fluorescent probe comprises the following steps:
2304mg (12.0mmol) of citric acid and 37.8mg (0.3mmol) of melamine were weighed out and dissolved in 10mL of ultrapure water, and 1000. mu.L of a formaldehyde solution (formaldehyde concentration of 8.0mmol/L) and 800mg of Eu (NO) (NO concentration)3)3·6H2O (99.99%). The solution was mixed well, transferred to a 25mL stainless steel autoclave lined with polytetrafluoroethylene, reacted at a temperature of 220 ℃ for 10 hours, cooled to room temperature, and after the resulting dark yellow solution was filtered through a 0.22 μm filter membrane and further dialyzed with a dialysis bag (molecular weight cut off 1000Da) in ultrapure water for 24 hours, and the water was refreshed every 6 hours to remove small molecules. Subsequently, the solution in the dialysis bag was evaporated and dried at 80 ℃ to obtain a powder of the rare earth element-doped carbon quantum dot ratiometric fluorescent probe with a quantum yield of 9.02%.
Example 4
Influence of europium doping concentration on fluorescence spectrum of Eu-CDs-TC complex
Based on the method of example 1, Eu (NO) is set3)3·6H2The doping concentrations of O are respectively 300mg and 500mg and 800mg, respectively, to prepare different Eu (NO)3)3·6H2Eu-CDs with O doping concentration; and detecting the fluorescence spectrum after adding TC, wherein the result is shown in figure 3, and the fluorescence spectrum shows strong doping concentration dependence as can be seen from the fluorescence intensity curve and the fluorescence intensity photograph, and the fluorescence intensity enhancement amplitude of Eu-CDs-TC becomes larger as the Eu doping concentration is increased from 300mg to 500 mg; after the Eu doping concentration exceeds 500mg, the fluorescence intensity can be reduced due to newly generated defects and reduced surface passivation, and the fluorescence intensity enhancement amplitude of the Eu doping concentration of 800mg is lower than that of the Eu doping sample of 500mg instead; thus, 500mg of doped Eu-CDs produced the highest fluorescence intensity enhancement after interaction with TC compared to other doping concentrations. Therefore, the Eu doping concentration of 500mg is the optimum concentration.
Example 5
A method for detecting tetracycline comprises the following steps:
(1) the rare earth element doped carbon quantum dot ratiometric fluorescent probe prepared in example 1 was prepared to have a concentration of 60. mu.g.mL-1The aqueous solution of (1) is Eu-CDs solution;
(2) taking the Eu-CDs solution prepared in the step (1), adding different amounts of tetracycline into the Eu-CDs solution, and preparing the Eu-CDs solution into standard solutions with tetracycline of different concentration gradients, wherein the concentration of the tetracycline is 0-100 mu M; mixing, and culturing at room temperature for 5 min;
(3) recording emission spectra of standard solutions with different concentration gradients of tetracycline under 380nm excitation by adopting a fluorescence spectrometry; the results are shown in FIG. 4; from FIG. 4, it can be seen that the fluorescence intensity of the Eu-CDs system at 468nm decreases significantly with increasing tetracycline concentration, while the fluorescence intensity at 620nm increases gradually. When the concentration of tetracycline is higher than 80. mu.M, F468In a quenched state, but F620No longer increasing and begins to decrease.
(4) The experimental data obtained are arranged and plotted as I620/I468The intensity ratio of (a) is taken as the ordinate, the TC concentration is taken as the abscissa, and a linear equation is obtained as shown in fig. 5, wherein the linear relation is that Y is 0.0630 x-0.242; linear correlation coefficient R2＝0.999。
(5) Mixing the solution of the sample to be tested with the Eu-CDs solution prepared in the step (1) according to the ratio of 1:1, and culturing for 5min at room temperature; fluorescence intensities at 468nm and 620nm of the solution to be measured are obtained by fluorescence spectrometry under the excitation of 380nm, and I is calculated620/I468And (4) comparing the intensity ratio with the linear equation obtained in the step (4), and calculating to obtain the content of the tetracycline in the sample solution to be detected.
The method for detecting tetracycline has good stability and high repeatability, and the detection limit is 6.9 nM.
The specificity of the rare earth element doped carbon quantum dot ratiometric fluorescent probe to tetracycline is as follows:
respectively mixing Tetracycline (Tetracycline) and analogues thereof (Oxytetracycline, Chlortetracycline, Erythromycin) solutions with the same concentration (100 mu M) with the Eu-CDs solution prepared in the step (1) in the same volume, culturing for 5min at room temperature, and recording the emission spectrum of the mixture under the excitation of 380nm by adopting a fluorescence spectrometry. As shown in FIG. 6, only tetracycline can cause fluorescence quenching of Eu-CDs at 420nm and generate a strong new fluorescence emission peak at 620 nm.
Example 6
A method for detecting aluminum ions comprises the following steps:
(1) the rare earth element doped carbon quantum dot ratiometric fluorescent probe prepared in example 1 was prepared to have a concentration of 60. mu.g.mL-1Then tetracycline is added to the aqueous solution of (4) to prepare a tetracycline solution having a tetracycline concentration of 100. mu. M, Eu-CDs concentration of 60. mu.g.mL-1Mixed solution of (1) (Eu-CDs-TC complex);
(2) taking the mixed solution prepared in the step (1), adding Al with different amounts into the mixed solution3+Prepared into Al3+Standard solutions with different concentration gradients (Al (ClO) was used in the preparation of the standard solutions4)3·9H2O) of Al3+The concentration of (A) is 0-50 μ M; mixing, and culturing at room temperature for 5 min;
(3) recording Al under 380nm excitation by fluorescence spectrometry3+Eu-CDs-TC-Al with different concentration gradients3+Emission spectrum of the solution; the results are shown in FIG. 7Shown in the specification; as can be seen from fig. 7: with Al3+Increase in concentration, Eu-CDs-TC-Al3+Fluorescence emission at 468nm is enhanced, at 620nm the fluorescence emission follows Al3+The amount increases and decreases.
(4) The experimental data obtained are arranged and plotted as I468/I620Intensity ratio of (1) as ordinate, Al3+Taking the concentration as an abscissa, obtaining a linear equation as shown in fig. 8, wherein the linear relation is that Y is 0.160 x-0.379; linear correlation coefficient R2＝0.996。
(5) Mixing the solution of the sample to be tested with the Eu-CDs-TC compound solution prepared in the step (1) according to the proportion of 1:1, and culturing for 5min at room temperature; fluorescence intensities at 468nm and 620nm of the solution to be measured are obtained by fluorescence spectrometry under the excitation of 380nm, and I is calculated468/I620Comparing the intensity ratio with the standard curve obtained in the step (4), and calculating to obtain Al in the solution of the sample to be detected3+The content of (a).
Detection of Al3+The method has good stability and high repeatability; the detection limit was 28.6 nM; al (Al)3+LOD of (A) is calculated as: LOD is 3Sb/S, where Sb represents the standard error of 10 consecutive scans of the blank sample and S represents the slope of the calibration curve.
Detection of Eu-CDs-TC Complex vs Al3+Selectivity of cascade recognition and other metal ions (Ca)2+、Ni2+、Co2 +、Mg2+、Cd2+、Hg2+、Zn2+、Cu2+) For Al3+Interference of (2):
the metal ion solutions each having a concentration of 50 μ M were added to the Eu-CDs-TC complex solutions prepared in the above step (1), respectively, and the Eu-CDs-TC complex solution to which the metal ion solution was not added was used as a Blank (Blank). After 5min incubation, the emission spectrum of the mixture was recorded under 380nm excitation using fluorescence spectroscopy to study Eu-CDs-TC for Al3+Selectivity of (2). As a result, only Al was observed as shown in FIG. 93+Can cause the fluorescence recovery of the Eu-CDs-TC complex at 468 nm.
Example 7
A method for detecting tetracycline based on a europium-doped carbon quantum dot ratio fluorescent probe combined with a smart phone and a paper-based sensor comprises the following steps:
(1) the rare earth element doped carbon quantum dot ratiometric fluorescent probe prepared in example 1 was prepared to have a concentration of 60. mu.g.mL-1An aqueous solution of (a);
(2) the filter paper was cut into a circular shape having a diameter of about 6mm, and then immersed in Eu-CDs (60. mu.g. mL) prepared in step (1)-1) In solution; incubating for 10min at room temperature, and drying in air at room temperature; obtaining a paper-based sensor for detecting tetracycline;
(3) adding TC aqueous solutions with different concentrations (0-150 mu M) to the surface of the circular paper-based sensor prepared in the step (2); the addition amount is 200 mu L/piece of paper-based sensor;
(4) the fluorescent color change of the circular paper-based sensor was observed with the naked eye under an ultraviolet lamp. Digitalizing and outputting the fluorescence color of the paper-based sensor by downloading an obtained color scanning application program (APP) through an application store to obtain an RGB value; the obtained experimental data (R/B) are arranged and plotted to obtain a linear equation (figure 10), and the linear relation is Y-0.049 x-0.219; linear correlation coefficient R2＝0.998。
(5) Adding a sample solution to be detected to the surface of the paper-based sensor prepared in the step (2); the addition amount is 200 mu L/piece of paper-based sensor; recording the fluorescence color of the paper-based sensor under an ultraviolet lamp by using a color scanning application program on the smart phone, and digitizing and outputting the fluorescence color of the paper-based sensor to obtain RGB values; calculating R/B; and (5) substituting the numerical value of the R/B into the linear equation obtained in the step (4), and calculating to obtain the content of the tetracycline in the sample solution to be detected.
The tetracycline detected by the method has good stability and high repeatability, and the detection limit is 13.2 nM.
Example 8
Al detection based on europium-doped carbon quantum dot ratio fluorescent probe combined smart phone and paper-based sensor3+The method comprises the following steps:
(1) the rare earth element doped carbon quantum dot ratiometric fluorescent probe prepared in example 1 was prepared to a concentration60. mu.g/mL-1An aqueous solution of (a); then adding tetracycline to prepare tetracycline with concentration of 100 mu M, Eu-CDs with concentration of 60 mu g/mL-1Mixed solution of (1) (Eu-CDs-TC complex);
(2) cutting filter paper into a circle with the diameter of about 6mm, and then immersing the filter paper into the Eu-CDs-TC compound solution prepared in the step (1); incubating for 10min at room temperature, and drying in air at room temperature; obtaining for detecting Al3+The paper-based sensor of (1);
(3) mixing Al with different concentrations (0-80 μ M)3+Adding the aqueous solution to the surface of the circular paper-based sensor prepared in the step (2); the addition amount is 200 mu L/piece of paper-based sensor;
(4) the fluorescent color change of the circular paper-based sensor was observed with the naked eye under an ultraviolet lamp. Digitalizing and outputting the fluorescence color of the paper-based sensor by downloading an obtained color scanning application program (APP) through an application store to obtain an RGB value; the obtained experimental data (B/R) are arranged and plotted to obtain a linear equation (figure 11), and the linear relation is Y-0.1445 x-0.1445; linear correlation coefficient R2＝0.998。
(5) Adding a sample solution to be detected to the surface of the paper-based sensor prepared in the step (2); the addition amount is 200 mu L/piece of paper-based sensor; recording the fluorescence color of the paper-based sensor under an ultraviolet lamp by using a color scanning application program on the smart phone, and digitizing and outputting the fluorescence color of the paper-based sensor to obtain RGB values; B/R is calculated; substituting the numerical value of B/R into the linear equation obtained in the step (4), and calculating to obtain Al in the sample solution to be detected3+The content of (a).
Al detection by the above method3+The stability of (A) is good, the repeatability is high, and the detection limit is 160 nM.
The foregoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.
Claims (8)
1. A preparation method of a rare earth element doped carbon quantum dot ratiometric fluorescent probe is characterized by comprising the following steps:
the raw materials are citric acid as carbon source and melamine as nitrogen source, and rare earth compound Eu (NO) is added3)3·6H2O, uniformly mixing the three components in ultrapure water, carrying out high-temperature reaction, cooling to room temperature after the reaction is finished, and dialyzing the obtained solution with ultrapure water to remove small molecules; evaporating and drying the residual solution to obtain rare earth element doped carbon quantum dot ratiometric fluorescent probe powder;
the high-temperature reaction is carried out at 180-220 ℃ for 5-10 h;
the dosage of the citric acid is 8-12 mmol; the dosage of the melamine is 0.2-0.3 mmol; the rare earth compound Eu (NO)3)3·6H2The dosage of O is 300-800 mg.
2. The method for preparing the rare earth element doped carbon quantum dot ratiometric fluorescent probe according to claim 1, wherein a formaldehyde solution is further contained in the raw material, the addition amount of the formaldehyde solution is 0-1000 μ L, and the concentration of the formaldehyde solution is 8 mmol/L.
3. The method for preparing a rare earth element doped carbon quantum dot ratiometric fluorescent probe according to claim 2, wherein the amount of citric acid is 10 mmol; the dosage of the melamine is 0.25 mmol; the rare earth compound Eu (NO)3)3·6H2The dosage of O is 500 mg; the amount of the formaldehyde solution is 560. mu.L.
4. The method for preparing a rare earth element doped carbon quantum dot ratiometric fluorescent probe according to any one of claims 1 to 3, wherein the dialysis is performed by filtering with a 0.22 μm filter membrane, dialyzing the filtrate in ultrapure water for 24 hours with a dialysis bag with a cut-off molecular weight of 1000Da, and refreshing the water every 6 hours to remove small molecules.
5. The rare earth element doped carbon quantum dot ratiometric fluorescent probe prepared by the method of claim 4.
6. The use of the rare earth element doped carbon quantum dot ratiometric fluorescent probe of claim 5 in tetracycline detection.
7. The use of the rare earth element doped carbon quantum dot ratiometric fluorescent probe of claim 5 in aluminum ion detection.
8. The use of the rare earth element doped carbon quantum dot ratiometric fluorescent probe of claim 5 in the preparation of products for detecting tetracycline and/or aluminum ions.
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