CN113150776B - Red fluorescent carbon quantum dot, preparation method thereof and fluorescent probe - Google Patents
Red fluorescent carbon quantum dot, preparation method thereof and fluorescent probe Download PDFInfo
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Abstract
The invention discloses a red fluorescent carbon quantum dot, a preparation method thereof and a fluorescent probe, wherein the preparation method comprises the following steps: obtaining o-phenylenediamine and ammonium acetate according to a molar ratio of 10: 1-1: 10, and adding 1-12M sulfuric acid solution to obtain a precursor solution; placing the precursor solution in a microwave environment for reaction to obtain a solid crude product; dissolving the solid crude product in an organic solvent, and removing insoluble substances to obtain a liquid product; adding an alkali solution into the liquid product for reaction; adding dichloromethane into the liquid product, and collecting the precipitated solid product; and washing and drying the solid product to obtain the red fluorescent carbon quantum dots. The preparation method of the red fluorescent carbon quantum dot, the red fluorescent carbon quantum dot and the fluorescent probe provided by the invention are simple, and are beneficial to large-scale preparation.
Description
Technical Field
The invention belongs to the technical field of nano luminescent materials, and particularly relates to a red fluorescent carbon quantum dot, a preparation method thereof and a fluorescent probe.
Background
The carbon quantum dots are novel nano carbon materials which are composed of dispersed spheroidal carbon particles, have extremely small sizes and have fluorescence properties. The carbon quantum dots have the advantages of fluorescence, low toxicity, easy functionalization and industrialization, simple preparation, low cost and the like, and are expected to replace the traditional quantum dots to be widely applied as high-performance fluorescent materials in the fields of luminescent materials, photoelectric devices, environmental protection, biomedicine, cell imaging, environmental detection (including qualitative and quantitative detection of chemical components of substances) and the like.
At present, carbon quantum dots which are widely researched, widely prepared, developed and applied are mostly concentrated on blue fluorescent carbon quantum dots and green fluorescent carbon quantum dots, the preparation method of red fluorescent carbon quantum dots is less, the luminous efficiency is not as good as that of traditional semiconductor quantum dots or blue and green fluorescent carbon quantum dots, and most of red fluorescent carbon quantum dots reported at present have excitation wavelength dependence, the fluorescence emission peak is red-shifted along with the increase of the excitation wavelength, the fluorescence intensity is rapidly reduced and even disappears, and strictly speaking, the red fluorescent carbon quantum dots are not real red fluorescent carbon quantum dots. More importantly, the current preparation method of the red fluorescent carbon quantum dots mostly adopts a solvothermal method, so that the problems of long reaction time consumption and high energy consumption exist, and the purification method mostly adopts a dialysis method and a chromatographic separation method, so that the operation steps are complicated and low-efficiency, so that the red fluorescent carbon quantum dots are only suitable for small-dose preparation, and large-scale preparation and application are difficult to realize. Therefore, it is of great significance to develop a method for efficiently preparing red fluorescent carbon quantum dots with independent excitation wavelengths.
On the other hand, in the application aspect of fluorescent materials, fluorescent sensors are widely used for detecting heavy metal silver ions, and currently developed fluorescent probes mainly comprise organic dye molecules, metal nanoparticles and semiconductor quantum dots, and have the problems of toxicity, low selectivity, poor water solubility and poor stability.
Accordingly, the prior art is in need of improvement and development.
Disclosure of Invention
The invention provides a red fluorescent carbon quantum dot, a preparation method thereof and a fluorescent probe, wherein the preparation method is simple, the subsequent purification method adopts an extraction method, the method is simple and efficient, and large-scale preparation is facilitated.
In order to solve the technical problem, on one hand, the preparation method of the red fluorescent carbon quantum dot provided by the invention comprises the following steps:
1) obtaining o-phenylenediamine and ammonium acetate according to a molar ratio of 10: 1-1: 10, and adding 1-12M sulfuric acid solution to obtain a precursor solution;
2) placing the precursor solution in a microwave environment for reaction to obtain a solid crude product;
3) dissolving the solid crude product in an organic solvent, and removing insoluble substances to obtain a liquid product;
4) adding an alkali solution into the liquid product for reaction;
5) adding dichloromethane into the liquid product, and collecting a precipitated solid product;
6) and washing and drying the solid product to obtain the red fluorescent carbon quantum dots.
Further, the microwave environment is formed through a microwave oven, and the microwave power of the microwave oven is 10% -100%.
Further, in the step 2), the reaction time in the microwave environment is 1-10 min.
Further, in step 5), the reaction is carried out according to a dichloromethane: liquid product = volume ratio 1:3, dichloromethane being added to the liquid product.
Further, in step 1), the o-phenylenediamine and ammonium acetate are dissolved in a sulfuric acid solution by sonication.
Further, in the step 3), the solid crude product is dissolved in an organic solvent, and is filtered through a filter membrane with the pore size of 0.22 μm to remove insoluble substances, so as to obtain a liquid product.
Further, the organic solvent is a DMF solvent.
Further, the alkali solution is a NaOH solution.
In another aspect, the present invention provides a red fluorescent carbon quantum dot prepared by any one of the methods described above.
In still another aspect, the present invention provides a fluorescent probe, which comprises the red fluorescent carbon quantum dots as described above.
According to the red fluorescent carbon quantum dot, the preparation method and the fluorescent probe, o-phenylenediamine with amino and ammonium acetate are used as carbon sources, sulfuric acid is used as a catalyst and a dehydrating agent to react, so that a larger conjugated system is favorably realized, the size of the carbon quantum dot is increased, the luminescence red shift is promoted, the red luminescence of the carbon dot is finally realized, and the yield of the fluorescent quantum dot is favorably improved; the preparation method is simple, has low requirement on equipment, adopts an extraction method for subsequent purification, is simple and efficient, has high fluorescence quantum yield, and is beneficial to large-scale preparation. The red fluorescent carbon quantum dot prepared by the method has stable luminescence and the characteristic of independence of excitation wavelength. The fluorescent probe comprising the red fluorescent carbon quantum dot has good specificity, wide detection range on silver ions and quick response.
Drawings
FIGS. 1a and 1b are diagrams of the luminescence effect of the red fluorescent carbon quantum dot aqueous solution under natural light and 365 nm excitation, respectively.
Fig. 2 is a diagram of the excitation-emission spectrum of the red fluorescent carbon quantum dot of the present invention.
Fig. 3 is a fluorescence spectrum of the red fluorescent carbon quantum dot of the present invention at different excitation wavelengths.
Fig. 4 is a graph showing the response result of the red fluorescent carbon quantum dot of the present invention to different common metal ions.
Fig. 5 is a graph showing the relationship between the fluorescence intensity of the red fluorescent carbon quantum dots of the present invention and silver ion solutions of different concentrations.
Fig. 6 is a linear analysis chart of the response result of the red fluorescent carbon quantum dots to silver ion solutions with different concentrations.
Fig. 7 is an emission spectrum of red fluorescent carbon quantum dots according to embodiments one to four of the present invention.
Detailed Description
The following describes embodiments of the present invention in detail.
The invention relates to a preparation method of red fluorescent carbon quantum dots, which comprises the following steps:
1) the method comprises the steps of obtaining o-phenylenediamine and ammonium acetate according to a molar ratio of 10: 1-1: 10, and adding 1-12M sulfuric acid solution to obtain a precursor solution.
Specifically, according to the solute: adding 1-12M sulfuric acid solution into the solvent = (1: 3-1: 10) in mass ratio.
Specifically, the solutes o-phenylenediamine and ammonium acetate are solids, and can be weighed by an analytical balance, and a test tube or a beaker can be selected as a reaction vessel according to a specific reaction amount.
In some preferred embodiments, in this step, the o-phenylenediamine and ammonium acetate are dissolved in a sulfuric acid solution by sonication to obtain the precursor solution. By adopting the technical scheme, reactants can be completely dissolved, complete reaction is promoted, and the yield is improved.
2) And placing the precursor solution in a microwave environment for reaction to obtain a solid crude product.
Specifically, after the precursor solution is reacted, standing is carried out, and after the solution is naturally cooled to room temperature, a black solid crude product can be collected through filtration.
In this step, preferably, the microwave environment is formed by a microwave oven, and the microwave power of the microwave oven is 10% to 100%. In particular, the microwave oven may be a household microwave oven, typically a household microwave oven with a 100% microwave power of 800 w.
In some preferred embodiments, the reaction time in the microwave environment in this step is 1-10 min.
3) And dissolving the solid crude product in an organic solvent, and removing insoluble substances to obtain a liquid product.
Specifically, the organic solvent is an organic solvent which has good solubility in the prior art, can dissolve the target product in the solid crude product, but cannot dissolve other impurities, and therefore, the other impurities can be separated in an insoluble form. Through this step, it is possible to remove large granular carbon substances that are excessively carbonized, and to control the product quality.
In some preferred embodiments, the organic solvent is DMF. Specifically, the organic solvent may also be formamide or NMP solvent.
In this step, preferably, filtration is performed through a filter membrane with a pore size of 0.22 μm to remove insoluble substances to obtain a liquid product.
In some embodiments, the organic solvent with the solid crude product dissolved therein may be further subjected to a centrifugation treatment before being subjected to the membrane filtration, so as to sufficiently separate insoluble materials from the target product.
4) Adding an alkali solution into the liquid product for reaction.
The main purpose of this step is to neutralize the sulfuric acid in the initial reactants. Specifically, the alkali solution may be NaOH solution.
5) Methylene chloride was added to the liquid product, and the precipitated solid product was collected.
Specifically, the precipitated solid product can be collected by filtration, after the solid product is substantially precipitated, the solid product can be further separated from the liquid by centrifugation, then filtration is performed, and dichloromethane is used as a cleaning liquid, so that loss is avoided.
Specifically, according to the volume ratio, dichloromethane: liquid product = (1: 1 to 1: 10). In some preferred embodiments, the ratio of dichloromethane: liquid product = volume ratio 1:3, dichloromethane being added to the liquid product.
6) And washing and drying the solid product to obtain the red fluorescent carbon quantum dots.
Specifically, the solid product can be washed by absolute ethyl alcohol, and dried by an air-blast drying oven, wherein the drying temperature is adjusted to 40-80 ℃, and the drying time is 6-48 h. Preferably, the drying temperature is 60 ℃ and the drying time is 24 h.
In another aspect, the present invention provides a red fluorescent carbon quantum dot prepared by any one of the methods described above.
In still another aspect, the invention provides a fluorescent probe, which comprises the red fluorescent carbon quantum dots.
According to the red fluorescent carbon quantum dot, the preparation method and the fluorescent probe, o-phenylenediamine with amino and ammonium acetate are used as carbon sources, sulfuric acid is used as a catalyst and a dehydrating agent to react, so that a larger conjugated system is facilitated to be realized, the size of the carbon quantum dot is increased, the light-emitting red shift is further promoted, the red light-emitting of the carbon dot is finally realized, and the yield of the fluorescent quantum is facilitated to be improved; the preparation method is simple, has low requirements on equipment, adopts an extraction method for subsequent purification, is simple and efficient, has high fluorescence quantum yield, and is beneficial to large-scale preparation. The red fluorescent carbon quantum dot prepared by the method has stable luminescence and the characteristic of independence of excitation wavelength. The fluorescent probe comprising the red fluorescent carbon quantum dots has good specificity, wide detection range on Ag + and quick response.
As shown in fig. 1a and 1b, the red fluorescent carbon quantum dot aqueous solution of the present invention is a graph showing the light emission effect under natural light and under 365 nm excitation, respectively, and it can be clearly shown that the red fluorescent carbon quantum dot of the present invention has good water solubility and can emit bright red fluorescence under 365 nm excitation.
As shown in fig. 2, which is a graph of excitation-emission spectra of the red fluorescent carbon quantum dots of the present invention, the red fluorescent carbon quantum dots can be characterized, wherein Ex represents the excitation spectra, and Em represents the emission spectra. As can be seen from FIG. 2, the fluorescence intensity of the red fluorescent carbon quantum dots is increased with the increase of the emission wavelength, the optimal excitation wavelength is at 540nm, and the optimal emission peak is at 615 nm.
As shown in fig. 3, which is a fluorescence spectrum diagram of the red fluorescent carbon quantum dot of the present invention at different excitation wavelengths, a plurality of curves in the diagram gradually increase the excitation wavelength from bottom to top with reference to the optimal emission peak. As can be seen from FIG. 3, the emission peak position of the red fluorescent carbon dot remains unchanged and stabilizes at 615nm with the change of the excitation wavelength, and the change trend is consistent with the excitation spectrum of FIG. 2, and the fluorescence intensity of the red fluorescent carbon quantum dot is increased with the increase of the emission wavelength, which indicates that the red fluorescent carbon dot of the present invention has the excitation wavelength independence.
As shown in fig. 4, it is a graph of the response result of the red fluorescent carbon quantum dots of the present invention to different common metal ions, wherein the concentration of the metal ions is 100 μ M. Specifically, for any one metal ion, F 0 The fluorescence intensity of the red fluorescent carbon quantum dots when metal ions are not added is shown, F is the fluorescence intensity of the red fluorescent carbon quantum dots when metal ions with certain concentration are added, and the ratio F/F 0 The quenching degree of any metal ion to the fluorescence of the red fluorescent carbon quantum dot can be shown, and in fig. 4, the smaller the ratio, the higher the quenching degree is, and the better the responsiveness of the red fluorescent carbon quantum dot is. As can be seen from fig. 4, silver ions have significant quenching on the red fluorescent carbon quantum dots of the present invention.
As shown in fig. 5, which is a graph of the relationship between the fluorescence intensities of the silver ion solutions with different concentrations and the red fluorescent carbon quantum dots of the present invention, the multiple curves in the graph, with reference to the optimal emission peak, increase gradually from top to bottom, specifically, the lower the emission peak, indicate that the smaller the fluorescence intensity, the higher the fluorescence quenching degree.
As shown in FIG. 6, which is a linear analysis diagram of the response result of the red fluorescent carbon quantum dots to silver ion solutions with different concentrations, it can be seen from FIG. 6 that when the silver ion concentration is 0.1-70 μ M, the response result has a good linear relationship, the fitting linear equation is y = 0.973 + 0.026x, and the fitting coefficient R2 = 0.995, wherein x is the concentration of silver ions, and y is the ratio F 0 In FIG. 6, the ratio F 0 The larger the F, the higher the quenching degree, and the better the responsiveness of the red fluorescent carbon quantum dot.
As can be seen by combining the figures 4, 5 and 6, the red fluorescent carbon quantum dots and the fluorescent probe have the specific recognition function on silver ions, the detection range is wide, and the detection limit is low.
The following examples further illustrate the preparation of the red fluorescent carbon quantum dots of the present invention. As shown in fig. 7, the emission spectra of the red fluorescent carbon quantum dots prepared by the following examples one-four are shown, and the detection conditions of the emission spectra are as follows: the concentration of the red fluorescent carbon quantum dot solution is 0.1mg/mL, the excitation wavelength is 520 nm, and curves c1, c2, c3 and c4 in the figure respectively correspond to one to four embodiments. As can be seen from FIG. 7, the emission peak of the red fluorescent carbon quantum dots prepared in the first to fourth examples is approximately 615 nm.
Example one
1) Weighing 0.54 g of o-phenylenediamine and 0.385g of ammonium acetate, placing the o-phenylenediamine and the ammonium acetate into a 10 mL small beaker, adding 3 mL of 3M sulfuric acid solution, and fully dissolving the mixture by ultrasound to obtain a precursor solution;
2) placing the small beaker containing the precursor solution in a household microwave oven, reacting for 2 min at 100% microwave power, naturally cooling the solution after reaction to room temperature, and filtering to collect a black solid crude product;
3) dissolving the solid crude product in 5 mL of DMF solvent, and filtering with a filter membrane with the pore size of 0.22 mu m to obtain a liquid product;
4) adding 2 mL of 1M NaOH solution into the liquid product, and reacting for 1 min;
5) adding dichloromethane into the liquid reactant reacted in the step 4) according to the volume ratio of 1:3, and filtering and collecting a precipitated red solid product after the solid product is basically precipitated;
mixing, and separating out red carbon dots; collecting precipitated solid and using ethanol;
6) and (3) washing the solid product with absolute ethyl alcohol for 3 times, placing the solid product in a forced air drying oven, and drying the solid product for 24 hours at the temperature of 60 ℃ to obtain red fluorescent carbon quantum dots which are red powder.
The prepared red fluorescent carbon quantum dots are weighed and characterized, the fluorescence quantum yield is 30% (with rhodamine B as a standard), and a specific emission spectrum is shown as c1 in FIG. 7.
Example two
1) Weighing 0.108 g of o-phenylenediamine and 0.385g of ammonium acetate, placing the o-phenylenediamine and the ammonium acetate into a 10 mL small beaker, adding 3 mL of 3M sulfuric acid solution, and fully dissolving the o-phenylenediamine and the ammonium acetate by ultrasonic to obtain a precursor solution;
2) placing the small beaker containing the precursor solution in a household microwave oven, reacting for 2 min at 100% microwave power, naturally cooling the solution after reaction to room temperature, and filtering to collect a black solid crude product;
3) dissolving the solid crude product in 5 mL of DMF solvent, and filtering with a filter membrane with the pore size of 0.22 mu m to obtain a liquid product;
4) adding 2 mL of 1M NaOH solution into the liquid product, and reacting for 1 min;
5) adding dichloromethane into the liquid reactant reacted in the step 4) according to the volume ratio of 1:3, and filtering and collecting a precipitated red solid product after the solid product is basically precipitated;
mixing and separating out red carbon dots; collecting precipitated solid and using ethanol;
6) and (3) washing the solid product with absolute ethyl alcohol for 3 times, placing the washed solid product in a forced air drying oven, and drying the solid product at the temperature of 60 ℃ for 24 hours to obtain the red fluorescent carbon quantum dots which are red powder.
The prepared red fluorescent carbon quantum dots are weighed and characterized, the fluorescence quantum yield is 10% (with rhodamine B as a standard), and a specific emission spectrum is shown as c2 in FIG. 7.
EXAMPLE III
1) Weighing 0.54 g of o-phenylenediamine and 0.385g of ammonium acetate, placing the o-phenylenediamine and the ammonium acetate into a 10 mL small beaker, adding 3 mL of 5M sulfuric acid solution, and fully dissolving the o-phenylenediamine and the ammonium acetate by ultrasonic to obtain a precursor solution;
2) placing the small beaker containing the precursor solution in a household microwave oven, reacting for 2 min at 100% microwave power, naturally cooling the solution after reaction to room temperature, and filtering to collect a black solid crude product;
3) dissolving the solid crude product in 5 mL of DMF solvent, and filtering with a filter membrane with the pore size of 0.22 mu m to obtain a liquid product;
4) adding 2 mL of 1M NaOH solution into the liquid product, and reacting for 1 min;
5) adding dichloromethane into the liquid reactant reacted in the step 4) according to the volume ratio of 1:3, and filtering and collecting a precipitated red solid product after the solid product is basically precipitated;
mixing, and separating out red carbon dots; collecting precipitated solid and using ethanol;
6) and (3) washing the solid product with absolute ethyl alcohol for 3 times, placing the washed solid product in a forced air drying oven, and drying the solid product at the temperature of 60 ℃ for 24 hours to obtain the red fluorescent carbon quantum dots which are red powder.
The prepared red fluorescent carbon quantum dots are weighed and characterized, the fluorescence quantum yield is 22% (with rhodamine B as a standard), and a specific emission spectrum is shown as c3 in FIG. 7.
Example four
1) Weighing 0.54 g of o-phenylenediamine and 0.385g of ammonium acetate, placing the o-phenylenediamine and the ammonium acetate into a 10 mL small beaker, adding 3 mL of 3M sulfuric acid solution, and fully dissolving the o-phenylenediamine and the ammonium acetate by ultrasonic to obtain a precursor solution;
2) placing the small beaker filled with the precursor solution in a household microwave oven, reacting for 3min under 100% microwave power, naturally cooling the reacted solution to room temperature, filtering and collecting a black solid crude product;
3) dissolving the solid crude product in 5 mL of DMF solvent, and filtering with a filter membrane with the pore size of 0.22 mu m to obtain a liquid product;
4) adding 2 mL of 1M NaOH solution into the liquid product, and reacting for 1 min;
5) adding dichloromethane into the liquid reactant reacted in the step 4) according to the volume ratio of 1:3, and filtering and collecting a precipitated red solid product after the solid product is basically precipitated;
mixing, and separating out red carbon dots; collecting precipitated solid and using ethanol;
6) and (3) washing the solid product with absolute ethyl alcohol for 3 times, placing the washed solid product in a forced air drying oven, and drying the solid product at the temperature of 60 ℃ for 24 hours to obtain the red fluorescent carbon quantum dots which are red powder.
The prepared red fluorescent carbon quantum dots are weighed and characterized, the fluorescence quantum yield is 18% (with rhodamine B as a standard), and a specific emission spectrum is shown as c4 in FIG. 7.
In the description herein, references to the description of the terms "one embodiment," "certain embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
What has been described above are merely some embodiments of the present invention. It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the inventive concept thereof, and these changes and modifications can be made without departing from the spirit and scope of the invention.
Claims (7)
1. A preparation method of red fluorescent carbon quantum dots is characterized by comprising the following steps:
1) obtaining o-phenylenediamine and ammonium acetate according to a molar ratio of 10: 1-1: 10, and adding 1-12M sulfuric acid solution to obtain a precursor solution;
2) placing the precursor solution in a microwave environment to react for 1-10 min to obtain a solid crude product; the microwave environment is formed by a microwave oven, and the microwave power of the microwave oven is 800W;
3) dissolving the solid crude product in an organic solvent, and removing insoluble substances to obtain a liquid product; the organic solvent is a DMF solvent;
4) adding an alkali solution into the liquid product for reaction;
5) adding dichloromethane into the liquid product, and collecting a precipitated solid product;
6) and washing and drying the solid product to obtain the red fluorescent carbon quantum dots.
2. The method for preparing red fluorescent carbon quantum dots according to claim 1, wherein in the step 5), the ratio of dichloromethane: liquid product = volume ratio 1:3, dichloromethane being added to the liquid product.
3. The method for preparing red fluorescent carbon quantum dots according to claim 1, wherein in step 1), the o-phenylenediamine and ammonium acetate are dissolved in the sulfuric acid solution by ultrasound.
4. The method for preparing red fluorescent carbon quantum dots according to claim 1, wherein in the step 3), the solid crude product is dissolved in an organic solvent, and is filtered through a filter membrane with the pore size of 0.22 μm to remove insoluble substances to obtain a liquid product.
5. The method of claim 1, wherein the alkali solution is NaOH solution.
6. A red fluorescent carbon quantum dot prepared by the method of any one of claims 1 to 5.
7. A fluorescent probe for detecting silver ions, comprising the red fluorescent carbon quantum dot according to claim 6.
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