CN112082980B - Preparation method of carbon dot-based ion imprinting fluorescence sensor - Google Patents
Preparation method of carbon dot-based ion imprinting fluorescence sensor Download PDFInfo
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- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
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Abstract
The invention belongs to the technical field of material synthesis, and provides a preparation method of an ion imprinting fluorescence sensor based on carbon dots, which specifically comprises the following steps: activating hydroxyl of the SBA-15 molecular sieve; amination of the SBA-15 molecular sieve; adding the carbon quantum dot powder into ultrapure water for dissolving and stirring uniformly, then adding the coupling agent and the carboxyl activating agent for ultrasonic treatment, and then carrying out ultrasonic treatment on the SBA-15 molecular sieve amination product SBA-15-NH2Adding into the above solution, magnetically stirring, washing with ultrapure water until the washing solution has no fluorescence response, and drying to obtain light yellow solid powder (SBA-15-CQDs); and mixing the SBA-15-CQDs serving as a substrate carrier with template ions, functional monomers, a cross-linking agent and an initiator, and magnetically stirring to obtain light yellow powder, namely the carbon-point-based ion imprinting fluorescence sensor CQDs @ Cu-IIP. The carbon dot-based ion imprinting fluorescence sensor (CQDs @ Cu-IIP) prepared by the invention is used for detecting copper ions in an aqueous solution, and has low detection limit, and is quick and accurate.
Description
Technical Field
The invention relates to the technical field of material synthesis, in particular to a preparation method of an ion-imprinted fluorescent sensor based on carbon dots.
Background
With the popularization of the current social industrialization, wastewater and solid waste leachate of various industries (such as power generation, smelting, electroplating, mining and the like) are inevitably and directly discharged into a water body, so that the content of heavy metals in the water body and soil is very high. Heavy metals are not only characterized by difficult degradation, easy accumulation, high toxicity and the like, but also can be absorbed by plants and enter a food chain, thereby harming the health of human beings and various animals. For example, copper exists in various forms in natural water bodies, is distributed in various components of aquatic ecosystems, and influences various components of the ecosystems. Wherein free Cu2+Is generally recognized as the major ionic form of copper toxic to aquatic organisms. Chlorophyll is one of important substances of plant photosynthesis, and copper is involved in electron transfer and photosynthetic phosphorylation of the photosynthesis and synthesis of various chloroplast enzymes, and has direct influence on the chlorophyll content of the plant and the photosynthesis. Uneven water ecology caused by excessive copper entering waterThe water body has peculiar smell, is dyed and reduces the transparency. Copper is a strong cell metabolism inhibitor, can poison the microorganisms in the water body, prevents the decomposition of organic matters in the water body, influences the self-cleaning capacity of the water body and has adverse effect on the ecology of the water body.
Therefore, the method has great significance for controlling and separating toxic heavy metals in sewage discharged by chemical enterprises by quickly and accurately detecting the content of metal ions in a complex solution system. In various analysis methods of trace substances, the colorimetric method and the spectrophotometric method are most widely applied, but the sensitivity of the colorimetric method and the spectrophotometric method for detecting copper ions is low, a complex sample pretreatment process is generally needed, a large amount of time and cost are needed for equipment maintenance, the detection range is narrow, and the detection process is complicated.
Disclosure of Invention
In order to solve the technical problems, the invention provides a preparation method of a carbon dot-based ion imprinting fluorescence sensor, which is used for detecting copper ions in an aqueous solution through the prepared ion imprinting fluorescence sensor (CQDs @ Cu-IIP), and has the advantages of low detection limit, rapidness and accuracy.
The invention provides a preparation method of an ion imprinting fluorescence sensor based on carbon dots, which specifically comprises the following steps:
the method comprises the following steps: preparing a hydroxyl activated product SBA-15-OH of the SBA-15 according to the SBA-15 and hydrochloric acid;
step two: preparing an amination product SBA-15-NH of the SBA-15 according to the hydroxyl activation product SBA-15-OH of the SBA-15, a surface modifier and ultrapure water2；
Step three: according to the carbon quantum dots, ultrapure water, a coupling agent, a carboxyl activating agent and the SBA-15-NH2Preparing carbon quantum dot composite material SBA-15-CQDs;
step four: and preparing the carbon dot-based ion imprinting fluorescence sensor CQDs @ Cu-IIP according to the carbon quantum dot composite material SBA-15-CQDs, ultrapure water, template ions, a functional monomer, a cross-linking agent and concentrated ammonia water.
Preferably, the step one specifically comprises:
mixing the SBA-15 molecular sieve with the hydrochloric acid according to the mass ratio of 1:100 to obtain a first mixture;
stirring the first mixture in a water bath, and condensing and refluxing to obtain a second mixture;
washing the second mixture with ultrapure water until the ultrapure water washing liquid is neutral;
and (3) placing the solid phase obtained after the second mixture is washed in an oven for drying to obtain a hydroxyl activated product SBA-15-OH of the SBA-15.
Preferably, the SBA-15 molecular sieve is prepared using a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.
Preferably, the second step specifically includes:
mixing the SBA-15-OH of the hydroxyl activated product SBA-15 with a surface modifier and ultrapure water according to a mass ratio of 1: 20: 80, and stirring and dissolving to obtain a third mixture;
washing the third mixture with ultrapure water until the ultrapure water washing liquid is neutral;
putting the solid phase obtained after washing the third mixture into an oven for drying to obtain an amination product SBA-15-NH of the SBA-152。
Preferably, the surface modifier is 3-Aminopropyltriethoxysilane (ATPES).
Preferably, the third step specifically comprises:
mixing a carbon quantum dot, ultrapure water, a coupling agent and a carboxyl activating agent according to the mass ratio of 1:100:100:100, and ultrasonically stirring and dissolving to obtain a fourth mixture;
the amination product SBA-15-NH of the SBA-152Adding into the fourth mixture, and magnetically stirring at room temperature to obtain a fifth mixture, wherein the amination product SBA-15-NH of SBA-152The mass ratio of the carbon quantum dots to the carbon quantum dots is 10: 1;
washing the fifth mixture with ultrapure water until the ultrapure water washing solution has no fluorescent response;
and (3) placing the solid phase obtained after washing the fifth mixture in an oven for drying to obtain the carbon quantum dot composite material SBA-15-CQDs.
Preferably, the coupling agent and the carboxyl activating agent are 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC) solution and N-hydroxysuccinimide (NHS), respectively.
Preferably, the concentration of the 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC) solution is 20mg/mL and the concentration of the N-hydroxysuccinimide (NHS) is 10 mg/mL.
Preferably, the step four specifically includes:
mixing and stirring the carbon quantum dot composite material SBA-15-CQDs, ultrapure water, template ions, functional monomers, a cross-linking agent and concentrated ammonia water according to the mass ratio of 50:20000:5:76:100:250 to obtain a sixth mixture;
washing the sixth mixture with hydrochloric acid until copper ions cannot be detected in the hydrochloric acid washing solution by using a flame atomic absorption spectrophotometer to obtain a seventh mixture;
washing the seventh mixture with ultrapure water until the ultrapure water washing liquid is neutral;
and (3) placing the solid phase obtained after washing the seventh mixture in an oven for drying and grinding to obtain the carbon dot-based ion imprinting fluorescence sensor CQDs @ Cu-IIP.
Preferably, the template ion, the functional monomer and the cross-linking agent are copper sulfate pentahydrate, ATPES and Tetraethoxysilane (TEOS), respectively.
In the invention, SBA-15-OH is prepared by activating hydroxyl of an SBA-15 molecular sieve; then preparing an amination product SBA-15-NH of the SBA-15 molecular sieve according to the SBA-15-OH2(ii) a Adding the carbon quantum dot powder into ultrapure water for dissolving and stirring uniformly, then adding the coupling agent and the carboxyl activating agent for ultrasonic treatment, and then carrying out amination on the SBA-15 molecular sieve to obtain an SBA-15-NH product2Adding into the above solution, and magnetically stirring at room temperature. After the reaction is finished, washing with ultrapure water until the washing liquid has no fluorescent response, and drying to obtain light yellow solid powder (SBA-15-CQDs); subjecting said SBA-15-CQ to a reactionPlacing Ds as a substrate carrier and template ions in a beaker, adding ultrapure water, stirring for dissolving, adding a functional monomer, and magnetically stirring again at room temperature. Then adding a cross-linking agent and an initiator, and magnetically stirring at room temperature. And taking out after the reaction is finished, washing with hydrochloric acid until copper ions cannot be detected in the eluent by using a flame atomic absorption spectrophotometer, and then washing with ultrapure water until the washing liquid is neutral. And (3) drying and grinding to obtain light yellow powder, namely the carbon dot-based ion imprinting fluorescence sensor CQDs @ Cu-IIP. The carbon dot-based ion imprinting fluorescence sensor (CQDs @ Cu-IIP) prepared by the invention is used for detecting copper ions in an aqueous solution, and has low detection limit, and is quick and accurate.
Drawings
1. FIG. 1 is an XRD spectrum of an ion imprinted fluorescence sensor based on carbon dots before and after SBA-15 activation provided by an embodiment of the present invention;
2. FIG. 2 is an infrared spectrum of an ion imprinted fluorescence sensor based on carbon dots before and after SBA-15 activation according to an embodiment of the present invention;
3. FIG. 3 is a TEM analysis diagram of a carbon dot-based ion imprinting fluorescence sensor provided by the embodiment of the invention;
4. FIG. 4 is a UV-Vis spectrum diagram of a carbon dot-based ion imprinting fluorescence sensor provided by the embodiment of the invention;
5. FIG. 5 is a fluorescence spectrum of a carbon dot-based ion imprinting fluorescence sensor provided by an embodiment of the invention;
6. FIG. 6(a) is a fluorescence spectrum of a CQDs @ Cu-IIP solution with a concentration of 1-10 g/L according to an embodiment of the present invention;
7. FIG. 6(b) is a graph showing fluorescence intensity spectra of CQDs @ Cu-IIP solution with a concentration of 4g/L at different times after adding a copper ion solution according to an embodiment of the present invention;
8. FIG. 7 is a graph of the fluorescence spectra of CQDs @ Cu-IIP solutions at various pH values provided by the present example;
9. fig. 8 is a schematic diagram of a linear detection range of a carbon dot-based ion imprinting fluorescence sensor provided by an embodiment of the invention.
Best mode for carrying out the invention
In order to make the preparation method of the carbon dot-based ion imprinting fluorescence sensor more clearly understood by those skilled in the art, the following detailed description will be made with reference to the accompanying drawings.
The embodiment of the invention provides a preparation method of an ion imprinting fluorescence sensor based on carbon dots, which specifically comprises the following steps:
1. activating hydroxyl of the SBA-15 molecular sieve:
the method comprises the following steps: preparing a hydroxyl activated product SBA-15-OH of the SBA-15 according to the SBA-15 and hydrochloric acid;
the specific implementation mode can be as follows: preparing an SBA-15 molecular sieve by using a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer as a raw material and adopting a template method; mixing the SBA-15 molecular sieve with the hydrochloric acid according to the mass ratio of 1:100, obtaining a first mixture by mixing, stirring and condensing the first mixture in a water bath at 75 ℃ for reflux for 24 hours, obtaining a second mixture after the reaction is finished, taking out the second mixture, washing the second mixture for multiple times by using ultrapure water until the ultrapure water washing liquid is neutral, placing a solid phase obtained after washing the second mixture in an oven for drying, wherein the temperature of the oven is 60 ℃ and the drying time is 24 hours, obtaining a hydroxyl activated product SBA-15-OH of the SBA-15, and observing the pore structure of the hydroxyl activated product SBA-15-OH by using a Transmission Electron Microscope (TEM).
2. Amination of SBA-15 molecular sieve:
preparing an amination product SBA-15-NH of the SBA-15 according to the hydroxyl activation product SBA-15-OH of the SBA-15, a surface modifier and ultrapure water2；
The specific implementation mode can be as follows: mixing the SBA-15 subjected to hydroxylation in the step one, namely SBA-15-OH with a surface modifier, adding ultrapure water for dissolving, and then stirring and reacting in a water bath kettle to obtain a third mixture, wherein the surface modifier is 3-aminopropyl triethoxy silane (ATPES), the water bath temperature is 50 ℃, the stirring and reacting time is 4h, and the mass ratio of a hydroxyl activated product SBA-15-OH of the SBA-15 to the surface modifier to the ultrapure water is 1: 20: 80.
then taking out the third mixture solution, washing the third mixture solution for multiple times by using ultrapure water until the ultrapure water washing solution is neutral, and placing the solid phase obtained after washing the third mixture in a drying oven for drying to obtain the amination product SBA-15-NH of the SBA-152. Wherein the temperature of the oven is 60 ℃, and the drying time is 24 h.
For example, 1) SBA-15-OH1.0g is weighed, 80mL of ultrapure water and 20mL of 3-aminopropyltriethoxysilane ATPES are added, and the mixture is stirred and reacted for 4 hours in a water bath at 50 ℃; 2) taking the aminated product (SBA-15-NH) in the step 1)2) FTIR (Fourier Transform infrared spectroscopy) tests show that characteristic peaks of Si-O-Si appear at wave numbers of 1079 and 801, which respectively correspond to asymmetric stretching and symmetric stretching vibration peaks of Si-O-Si, and show that the SBA-15 molecular sieve is successfully synthesized.
3. Synthesis of molecular sieve-carbon quantum dot composite materials (SBA-15-CQDs):
step three: according to the carbon quantum dots, ultrapure water, a coupling agent, a carboxyl activating agent and the SBA-15-NH2Preparing carbon quantum dot composite material SBA-15-CQDs;
the specific implementation mode can be as follows: adding carbon quantum dot powder into ultrapure water for dissolving, wherein the mass ratio of the carbon quantum dot powder to the ultrapure water is as follows: 1:100, after stirring evenly, adding a coupling agent and a carboxyl activating agent for mixing, and after ultrasonic treatment is finished for 10min, performing ultrasonic treatment on the SBA-15 amination product SBA-15-NH2Adding into the solution after the ultrasonic treatment, and magnetically stirring at room temperature for 18h to obtain a fifth mixture, wherein the carbon quantum dots, ultrapure water, coupling agent, carboxyl activating agent and the SBA-15 amination product SBA-15-NH of SBA-152The mass ratio of (A) to (B) is as follows: 1:100:100: 100: 10. after the reaction is finished, washing the fifth mixture by ultrapure water until the ultrapure water washing liquid has no fluorescent response, then placing the solid phase obtained after washing the fifth mixture in an oven for drying for 24 hours to obtain light yellow solid powder, namely the carbon quantum dot composite material SBA-15-CQDs, and carrying out XRD (X-ray diffraction) and FTIR (Fourier Transform infrared spectroscopy), wherein the temperature of the oven is 50 ℃.
Preferably, the carbon quantum dots can be prepared by using a traditional hydrothermal method and using citric acid as a carbon source to dope ethylenediamine for synthesis.
Preferably, the coupling agent and the carboxyl activating agent are 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC) solution and N-hydroxysuccinimide (NHS), respectively.
Preferably, the concentration of the 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC) solution is 20mg/mL, and the concentration of the N-hydroxysuccinimide (NHS) is 10 mg/mL.
For example, 1) 0.1002g of carbon quantum dot powder is weighed, 10mL of ultrapure water is added for dissolving, and the mixture is stirred uniformly; 2) respectively adding 10mL of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC) solution of 20mg/mL and N-hydroxysuccinimide (NHS) solution of 10mg/mL, and performing ultrasonic treatment for 10 min; 3) 1.0011g of SBA-15-NH were weighed out2Adding the mixture into the solution in the step 2), and magnetically stirring the mixture for 18 hours at room temperature; 4) washing the solution in the step 3) with ultrapure water until the washing solution has no fluorescent response; 5) the solid phase was dried in an oven at 50 ℃ for 24 hours to give a pale yellow solid powder (SBA-15-CQDs).
4. Synthesis of carbon dot-based ion imprinting fluorescence sensor (CQDs @ Cu-IIP):
step four: and preparing the carbon dot-based ion imprinting fluorescence sensor CQDs @ Cu-IIP according to the carbon quantum dot composite material SBA-15-CQDs, ultrapure water, template ions, a functional monomer, a cross-linking agent and concentrated ammonia water.
The specific implementation mode can be as follows: putting the carbon quantum dot composite material SBA-15-CQDs as a substrate carrier and template ions in a beaker, adding ultrapure water into the template ions such as blue vitriod, stirring and dissolving the template ions, adding a functional monomer, performing magnetic stirring again for 30min at room temperature, then adding a cross-linking agent and concentrated ammonia water, performing magnetic stirring for 30min at room temperature, and obtaining a sixth mixture after the reaction is finished, wherein the mass ratio of the carbon quantum dot composite material SBA-15-CQDs, the ultrapure water, the template ions, the functional monomer, the cross-linking agent and the concentrated ammonia water is 50:20000:5:76:100: 250. Taking out the sixth mixture, washing with hydrochloric acid with the concentration of 0.1mol/L until the template ions can not be detected by a flame atomic absorption spectrophotometer in the hydrochloric acid washing solution to obtain a seventh mixture, wherein if the template ions are blue vitriol, washing the sixth mixture with hydrochloric acid with the concentration of 0.1mol/L until the copper ions can not be detected by the flame atomic absorption spectrophotometer in the hydrochloric acid washing solution. And then, washing the seventh mixture with ultrapure water until the ultrapure water washing liquid is neutral, and drying and grinding the solid phase obtained after washing the seventh mixture in an oven to obtain light yellow powder, namely the carbon-point-based ion imprinting fluorescence sensor CQDs @ Cu-IIP, wherein the temperature of the oven is 40 ℃, and the drying time is 24 hours.
Preferably, the template ion, the functional monomer and the cross-linking agent are copper sulfate pentahydrate, ATPES and Tetraethoxysilane (TEOS), respectively.
In the embodiment of the invention, CQDs are used as a fluorescence source, SBA-15 is used as a substrate material, copper ions are used as template ions, ATPES is used as a functional monomer, TEOS is used as a cross-linking agent, ammonia water is used as an initiator, the carbon-dot-based ion imprinting fluorescence sensor CQDs @ Cu-IIP is prepared, high identification and sensitivity are achieved, the carbon-dot-based ion imprinting fluorescence sensor CQDs @ Cu-IIP prepared by the embodiment of the invention is used for detecting the copper ions in an aqueous solution, and the detection limit is low and the detection is rapid and accurate.
For example, the following steps are carried out:
1) weighing 0.5g of SBA-15-CQDs substrate material, placing the SBA-15-CQDs substrate material in a 50mL beaker, adding 20mL of ultrapure water and 0.0049g of copper sulfate, stirring and dissolving the SBA-15-CQDs substrate material at room temperature, adding 76 mu L of ATPES, and magnetically stirring the mixture for 30min at room temperature again;
2) then adding 100 mu L of Tetraethoxysilane (TEOS) and 250 mu L of strong ammonia water, and magnetically stirring for 4 hours at room temperature;
3) taking out after the reaction is finished, washing for 3-5 times by using 0.1mol/L hydrochloric acid until copper ions can not be detected in the eluent by using a flame atomic absorption spectrophotometer, and then washing by using ultrapure water until the washing liquid is neutral;
4) and (3) putting the solid into an oven, drying for 24 hours at 40 ℃, taking out and grinding after drying to obtain light yellow powder, namely the fluorescent sensor (CQDs @ Cu-IIP).
The resulting fluorescence sensor (CQDs @ Cu-IIP) can be characterized as follows:
1) x-ray powder diffraction (XRD) was performed to determine the crystal phase before and after activation of the starting material and the product.
2) Fourier transform infrared spectroscopy (FTIR) to determine the surface groups of the raw materials and the products.
3) And (4) a Transmission Electron Microscope (TEM) is used for visually observing the pore structure of the product.
4) Ultraviolet-visible absorption spectrum (UV-Vis) and determining transition types of raw materials and products.
5) Fluorescence emission spectrum, and determining the optimal excitation wavelength of the raw material and the product.
6) And determining the optimal concentration of the product by the fluorescence spectrum of the CQDs @ Cu-IIP solution with the concentration of 1-10 g/L.
7) And determining the optimal adsorption time by the fluorescence spectrum of the CQDs @ Cu-IIP solution with different adsorption times.
8) CQDs @ Cu-IIP solution fluorescence spectra at different pH values determined the optimal pH of the solution.
9) And the linear detection range of the ion imprinting fluorescence sensor is used for calculating the concentration of copper ions.
As shown in fig. 1, XRD patterns of carbon dot-based fluorescence sensors (CQDs @ Cu-IIP) provided before and after SBA-15 activation and in the examples of the present invention, it can be seen that, for CQDs (a), a distinct broad peak appears at an angle of 18-22 ° 2 θ, which correlates with a high degree of disorder of carbon atoms, indicating that carbon quantum dots have been successfully prepared.
This characteristic peak was observed in SBA-15-CQDs (b) as well as CQDs @ Cu-IIP (c), indicating that carbon quantum dots have been successfully grafted onto the surface of SBA-15 and eventually encapsulated in the ion imprinted polymer. The absence of diffraction peaks in the other ranges indicates that the product remains amorphous material and no crystalline impurities are present.
FIG. 2 is an infrared spectrum of a carbon dot-based fluorescence sensor (CQDs @ Cu-IIP) provided before and after activation of SBA-15 and in accordance with an embodiment of the present invention, as shown in FIG. 2(a), where the absorption peak at 3125 cm-1 for CQDs represents the tensile vibration of the O-H bond. 1707cm-1The peak at (a) is due to the stretching vibration of C ═ O. Also respectively at 1400cm-1And 3006cm-1Characteristic absorption bands for C-N and N-H are observed. It can be concluded that the synthesized CQDs have a large number of hydrophilic groups, such as hydroxyl groups and carboxyl groups. These groups help to enhance the water solubility of CQDs for further modification. In the spectrum of the synthesized SBA-15 as shown in FIG. 2(b), Si-O-Si was 1079cm in length-1And 799cm-1Asymmetric stretching, symmetric stretching at 965cm-1Bending vibration at Si-OH and symmetrical Si-O-Si at 799cm-1Tensile vibration of (1). FIG. 2(c) shows that the peak value in SBA-15-CQDs is 1079cm-1、799cm-1And 965cm-1(Si-O-Si asymmetric stretching, symmetric stretching and bending vibration) indicates the presence of TEOS in the synthesized SBA-15. FIG. 2(d) FT-IR spectrum at CQDs @ Cu-IIP, 1384cm-1(C-N stretching vibration), 3125cm-1The peak of (N-H bending vibration) indicates the presence of ATPES. All these bonds further confirmed that the surface of SBA-15 has been successfully modified by APTES and that imprinted polymers were successfully synthesized.
FIG. 3 is a TEM analysis diagram of a carbon dot-based fluorescence sensor (CQDs @ Cu-IIP) provided by the embodiment of the invention, and FIG. 3(a) is a transmission electron microscope photograph of an SBA-15 molecular sieve, which can obviously observe the long-range ordered structure of the mesoporous substrate, wherein the diameter of the pore channel is about 9 nm. FIG. 3(b) is a transmission electron micrograph of SBA-15-CQDs, and the channel structure of SBA-15 is difficult to observe, which shows that the channel is covered or occupied after the quantum dot material is modified, thus proving that the quantum dot is successfully modified on the surface. FIG. 3(c) is a transmission electron micrograph of CQDs @ Cu-IIP in different directions. As can be seen, the inner and outer layers of the SBA-15 molecular sieve are SBA-15-CQDs substrate for the darker colored regions, while the lighter colored regions at the edges are imprinting layers with a thickness of about 50 nm. The ion imprinted polymer layer is successfully wrapped on the surface of the fluorescent substrate, and CQDs @ Cu-IIP is successfully prepared.
Fig. 4 is a graph of the UV-Vis absorption spectra of CQDs (a) and CQDs @ Cu-iip (b), for which the absorption peak at 238nm is assigned to the pi-pi transition of C ═ C bonds in the aromatic ring and the peak at 343nm is assigned to the n-pi transition of C ═ O bonds. CQDs @ Cu-IIP have a lower absorbance at 343nm due to the reduction of carboxyl groups on the surface of CQDs during polymerization, as compared to pure CQDs.
FIG. 5 is a fluorescence spectrum of CQDs, in which the emission wavelength position is substantially unchanged and always maintained at about 445nm as the excitation wavelength is changed. And when the excitation wavelength is 346nm, the fluorescence intensity emitted by CQD can reach the strongest, and can reach 200a.u. under the test condition. Under the irradiation of 346nm ultraviolet light, the quantum dot solution can emit bright blue light which is visible to the naked eye, which shows that the optical property is good, and the metal ion detection can be carried out. In subsequent fluorescence detection, the excitation wavelength is set to be 346.0nm, and the emission wavelength detection range is 370.0-550.0 nm.
FIG. 6(a) is a fluorescence spectrum of a CQDs @ Cu-IIP solution with a concentration of 1-10 g/L, and it is obvious that the fluorescence intensity rapidly increases with the increase of the concentration of CQDs @ Cu-IIP when the concentration is less than 4 g/L. At concentrations greater than 4g/L and less than 8g/L, the fluorescence intensity slowly increased with increasing concentrations of CQDs @ Cu-IIP. At concentrations greater than 8g/L, the fluorescence intensity decreased with increasing concentrations of CQDs @ Cu-IIP. When the concentration is more than 4g/L, the effect of the concentration on the fluorescence intensity is not significant, and therefore, the concentrations of CQDs @ Cu-IIP are all 4g/L in the following experiments.
FIG. 6(b) is a graph showing the fluorescence intensity of CQDs @ Cu-IIP (4g/L) solution after adding a copper ion solution (10 ppm) for various periods of time. Fluorescence spectrum of the solution. The fluorescence intensity of the mixed solution gradually decreased with the increase of the detection time, and the fluorescence intensity continued to decrease within 15min, after which the fluorescence changed slowly and remained stable. The fluorescent material has certain application prospect in the aspect of rapidly detecting copper ions. Thus, CQDs @ Cu-IIP were compared to Cu in subsequent fluorescence assays2+The reaction time of the ions was controlled to 15 min.
It should be noted that the specific embodiments may be: preparing copper ion solutions with the concentrations of 0.25 ppm, 0.5 ppm, 0.75 ppm, 1 ppm, 2ppm, 4 ppm, 6 ppm, 8 ppm and 10ppm by using a copper ion standard solution, weighing 0.05g of CQDs @ Cu-IIP, putting the CQDs @ Cu-IIP into a 50mL volumetric flask, respectively adding the solutions to a constant volume, shaking up the solution after the constant volume is finished, shaking for 15min after ultrasonic dispersion, and measuring the fluorescence intensity of the solution. And a linear fit is performed.
Fluorescence detection: 1) weighing 0.05g of CQDs @ Cu-IIP, putting the CQDs @ Cu-IIP into a 50mL volumetric flask, adding a copper ion solution with unknown concentration, fixing the volume to a scale, and shaking up after the fixing of the volume is finished; 2) Injecting the solution into a conical flask, and placing the conical flask in a water bath at 25 ℃ for oscillation for 15 min; 3) Taking out the solution in the conical flask, measuring the fluorescence intensity of the solution by using a fluorescence spectrophotometer, and calculating the concentration of copper ions according to the working curve.
FIG. 7 is a fluorescence spectrum of CQDs @ Cu-IIP solution at different pH values of 1-12 to determine the optimal pH value during detection. As can be seen, the fluorescence intensity of CQDs @ Cu-IIP under basic conditions is higher than that under acidic conditions. In addition, when the pH of the solution is less than 3 or more than 10, the fluorescence is low, and when the pH is 10, the fluorescence intensity of the solution can reach a maximum. Therefore, the pH of the solution was adjusted to 10 in the subsequent fluorescence detection to obtain the optimal fluorescence intensity.
FIG. 8 shows the linear detection range of the ion imprinting fluorescence sensor, which can be fitted in two segments. When the concentration of copper ions is 0-2 ppm (a), the equation F can be used0/F＝0.05307C(Cu2+) +1.01602, linear regression coefficient R20.9982; when the concentration of copper ions is 2 to 10ppm (b), equation F can be used0/F＝0.01705C(Cu2+) +1.12073, linear regression coefficient R20.9883. Through calculation, the detection Limit (LOD) of CQDs @ Cu-IIP is about 0.182ppm, the linear regression coefficients of the two sections reach over 0.98, and the method has certain guiding significance for the detection of actual samples.
In summary, according to the technical scheme provided by the invention, CQDs are used as a fluorescence source, SBA-15 is used as a substrate material, copper ions are used as template ions, ATPES is used as a functional monomer, TEOS is used as a cross-linking agent, and ammonia water is used as an initiator to prepare the carbon dot-based ion imprinting fluorescence composite material (CQDs @ Cu-IIP), the obtained ion imprinting fluorescence sensor has high identification and sensitivity, and the carbon dot-based ion imprinting fluorescence sensor (CQDs @ Cu-IIP) prepared by the embodiment of the invention is used for detecting the copper ions in an aqueous solution, so that the detection limit is low, and the detection is rapid and accurate.
The above embodiments of the present invention are described in detail, and the principle and the implementation of the present invention are explained by applying specific embodiments, and the description of the above embodiments is only used to help understand the core idea of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (10)
1. A preparation method of an ion imprinting fluorescence sensor based on carbon dots is characterized by comprising the following steps:
the method comprises the following steps: preparing a hydroxyl activation product SBA-15-OH of the SBA-15 according to SBA-15 and hydrochloric acid, wherein the mass ratio of the SBA-15 molecular sieve to the hydrochloric acid is 1:100, respectively;
step two: preparing an amination product SBA-15-NH2 of the SBA-15 according to the hydroxyl activation product SBA-15-OH of the SBA-15, a surface modifier and ultrapure water, wherein the mass ratio of the hydroxyl activation product SBA-15-OH of the SBA-15 to the surface modifier to the ultrapure water is 1: 20: 80;
step three: preparing carbon quantum dot composite material SBA-15-CQDs according to carbon quantum dots, ultrapure water, a coupling agent, a carboxyl activating agent and the SBA-15-NH2, wherein the mass ratio of the carbon quantum dots, the ultrapure water, the coupling agent and the carboxyl activating agent is 1:100:100:100, and the mass ratio of the SBA-15-NH2 to the carbon quantum dots is 10: 1;
step four: the ion imprinting fluorescence sensor CQDs @ Cu-IIP based on the carbon dots is prepared according to the carbon quantum dot composite material SBA-15-CQDs, ultrapure water, template ions, a functional monomer, a cross-linking agent and concentrated ammonia water, wherein the mass ratio of the carbon quantum dot composite material SBA-15-CQDs, the ultrapure water, the template ions, the functional monomer, the cross-linking agent and the concentrated ammonia water is 50:20000:5:76:100: 250.
2. The method for preparing the carbon dot-based ion imprinting fluorescence sensor according to claim 1, wherein the first step specifically comprises:
mixing the SBA-15 molecular sieve with the hydrochloric acid according to the mass ratio of 1:100 to obtain a first mixture;
stirring the first mixture in a water bath, and condensing and refluxing to obtain a second mixture;
washing the second mixture with ultrapure water until the ultrapure water washing liquid is neutral;
and (3) placing the solid phase obtained after the second mixture is washed in an oven for drying to obtain a hydroxyl activated product SBA-15-OH of the SBA-15.
3. The method for preparing the carbon dot-based ion imprinting fluorescence sensor according to claim 2, wherein the SBA-15 molecular sieve is prepared by using a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.
4. The method for preparing the carbon dot-based ion imprinting fluorescence sensor according to claim 3, wherein the second step specifically comprises:
mixing the hydroxyl activated product SBA-15-OH of the SBA-15 with a surface modifier and ultrapure water according to the mass ratio of 1: 20: 80, and stirring and dissolving to obtain a third mixture;
washing the third mixture with ultrapure water until the ultrapure water washing liquid is neutral;
and (3) drying the solid phase obtained after washing the third mixture in an oven to obtain an amination product SBA-15-NH2 of the SBA-15.
5. The method for preparing a carbon dot-based ion imprinting fluorescence sensor according to claim 4, wherein the surface modifier is 3-Aminopropyl Triethoxysilane (ATPES).
6. The method for preparing the carbon dot-based ion imprinting fluorescence sensor according to claim 5, wherein the third step specifically comprises:
mixing a carbon quantum dot, ultrapure water, a coupling agent and a carboxyl activating agent according to the mass ratio of 1:100:100:100, and ultrasonically stirring and dissolving to obtain a fourth mixture;
adding the SBA-15 amination product SBA-15-NH2 into the fourth mixture, and performing magnetic stirring at room temperature to obtain a fifth mixture, wherein the mass ratio of the SBA-15 amination product SBA-15-NH2 to the carbon quantum dots is 10: 1;
washing the fifth mixture with ultrapure water until the ultrapure water washing solution has no fluorescent response;
and (3) placing the solid phase obtained after washing the fifth mixture in an oven for drying to obtain the carbon quantum dot composite material SBA-15-CQDs.
7. The method for preparing a carbon dot-based ion imprinting fluorescence sensor according to claim 6, wherein the coupling agent and the carboxyl activating agent are 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC) solution and N-hydroxysuccinimide (NHS), respectively.
8. The method for preparing a carbon dot-based ion imprinting fluorescence sensor according to claim 7, wherein the concentration of the 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC) solution is 20mg/mL, and the concentration of the N-hydroxysuccinimide (NHS) is 10 mg/mL.
9. The method for preparing the carbon dot-based ion imprinting fluorescence sensor according to claim 8, wherein the fourth step specifically comprises:
mixing and stirring the carbon quantum dot composite material SBA-15-CQDs, ultrapure water, template ions, functional monomers, a cross-linking agent and concentrated ammonia water according to the mass ratio of 50:20000:5:76:100:250 to obtain a sixth mixture;
washing the sixth mixture with hydrochloric acid until the template ions are not detected in the hydrochloric acid washing solution by using a flame atomic absorption spectrophotometer to obtain a seventh mixture;
washing the seventh mixture with ultrapure water until the ultrapure water washing liquid is neutral;
and (3) placing the solid phase obtained after washing the seventh mixture in an oven for drying and grinding to obtain the carbon dot-based ion imprinting fluorescence sensor CQDs @ Cu-IIP.
10. The method for preparing a carbon dot-based ion imprinting fluorescence sensor according to claim 9, wherein the template ions, the functional monomer and the cross-linking agent are copper sulfate pentahydrate, ATPES and tetraethyl orthosilicate (TEOS), respectively.
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