CN114058368B - Quantum dot with alloyed core-shell structure and preparation method thereof - Google Patents
Quantum dot with alloyed core-shell structure and preparation method thereof Download PDFInfo
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Abstract
The invention provides an alloyed core-shell structure quantum dot, which structurally comprises an alloying crystal nucleus, wherein an alloying layer is arranged on the surface of the alloying crystal nucleus; further, the alloying crystal nucleus is an alloying CdSeS crystal nucleus, and an alloying ZnCdSeS layer is arranged on the surface of the alloying CdSeS crystal nucleus. The preparation method of the quantum dot with the alloyed core-shell structure comprises the following steps: 1. preparing a solution containing alloyed CdSeS crystal nucleus by adopting a hot injection method; 2. and carrying out surface modification on the alloyed CdSeS crystal nucleus by adopting an ion implantation method to form an alloyed ZnCdSeS layer. The invention solves the problems of the existing core-shell structure quantum dot that the surface defects are more, the lattice constant mismatch is easy to occur between the crystal nucleus and the intermediate alloy layer, and the lattice stress is large.
Description
Technical Field
The invention relates to an alloyed core-shell structure quantum dot and a preparation method thereof, belonging to the technical field of semiconductor functional materials.
Background
The inorganic semiconductor quantum dot has three dimensions of which the size is smaller than twice of the exciton wave radius of the corresponding semiconductor material, so that the inorganic semiconductor quantum dot shows a plurality of characteristics different from the traditional material, including quantum size effect, surface effect and the like; these characteristics make quantum dots widely used in the fields of quantum dot light emitting diodes, solar cells, lasers, biosensors, and the like.
For colloids-/>The synthesis of the group quantum dots is mainly focused on binary systems such as CdSe, cdS and ZnSe, but recently researchers find that for the ternary alloy system quantum dots, the band gap can be adjusted by controlling the size of the ternary alloy system quantum dots and controlling the stoichiometric ratio and the internal structure of the components, so that the ternary alloy system quantum dots have wider peak position tuning range; the lattice constants of CdSe and CdS are similar, so that the lattice mismatch degree is smaller, and the alloy structure is more favorable to be formed; however, the luminescence performance of the CdSeS alloy quantum dot in the blue-green luminescence range is still poor, because most of the CdSeS alloy quantum dots synthesized at present are in a CdSeS bare alloy nuclear structure, and the problems of more surface defects, low fluorescence quantum yield, poor stability and insufficient exciton confinement exist; therefore, it is important to find a simple and effective method for improving the luminescence performance of CdSeS quantum dots.
Disclosure of Invention
The invention provides an alloyed core-shell structure quantum dot and a preparation method thereof, and aims to solve the problems of multiple surface defects and low fluorescence quantum yield of the existing alloy quantum dot.
The technical solution of the invention is as follows: the structure of the quantum dot with the alloyed core-shell structure comprises an alloying crystal nucleus, wherein an alloying layer is arranged on the surface of the alloying crystal nucleus.
Further, the quantum dot with the alloyed core-shell structure further comprises an outer shell layer; the alloying crystal nucleus is an alloying CdSeS crystal nucleus, an alloying ZnCdSeS layer is arranged on the surface of the alloying CdSeS crystal nucleus, and the outer shell layer is coated on the periphery of the alloying ZnCdSeS layer; the shell layer is a ZnS shell.
The preparation method of the quantum dot with the alloyed core-shell structure comprises the following steps:
1. preparing a solution containing alloyed CdSeS crystal nucleus by adopting a hot injection method;
2. and carrying out surface modification on the alloyed CdSeS crystal nucleus by adopting an ion implantation method to form an alloyed ZnCdSeS layer.
Further, the preparation method of the quantum dot with the alloyed core-shell structure further comprises the following steps:
3. and coating an outer shell layer on the periphery of the alloyed ZnCdSeS layer.
Further, the method for preparing the solution containing the alloyed CdSeS crystal nucleus by adopting the hot injection method specifically comprises the following steps:
1-1, mixing selenium powder with liquid paraffin solution to prepare selenium powder-liquid paraffin suspension;
1-2, mixing sulfur powder with octadecene solution, and heating under the condition of anhydrous oxygen to obtain sulfur powder-octadecene precursor;
1-3, under the condition of anhydrous oxygen, mixing cadmium oleate with octadecene solution, heating to a nucleation temperature, and injecting selenium powder-liquid paraffin suspension and sulfur powder-octadecene precursor to form a mixed solution to obtain a solution containing alloyed CdSeS crystal nucleus.
Further, the nucleation temperature is 230-260 ℃; the selenium powder-liquid paraffin suspension is selenium powder-liquid paraffin suspension with the selenium concentration of 0.1 mol/L; the sulfur powder-octadecene precursor is sulfur powder-octadecene precursor with the sulfur concentration of 0.5 mol/L; the ratio of the total substances of the selenium powder and the sulfur powder to the substances of the cadmium oleate in the mixed solution is 1:1-1:1.4, and the ratio of the substances of the selenium powder and the sulfur powder in the mixed solution is 1:1-1:5; when the cadmium oleate and the octadecene solution are mixed, the mass ratio of the octadecene solution to the cadmium oleate is 50:1-55:1.
Further, the surface modification is carried out on the alloyed CdSeS crystal nucleus by adopting an ion implantation method to form an alloyed ZnCdSeS layer, which specifically comprises the following steps:
2-1, mixing an organic solvent with a zinc source to form an organic mixed solution, and heating to an organic mixing temperature under the condition of anhydrous oxygen to obtain an organic mixed solution containing a zinc precursor;
2-2, stirring and heating the solution containing the alloying CdSeS crystal nucleus prepared in the step 1 to an alloying modification temperature, adding an organic mixed solution containing a zinc precursor, and then preserving heat for a certain time to form an alloying ZnCdSeS layer on the surface of the alloying CdSeS crystal nucleus.
Further, the mass ratio of the organic solvent to the zinc source is 20.5:1-25.5:1 when the organic solvent and the zinc source are mixed to form an organic mixed solution; the organic mixing temperature is 300 ℃; the alloying modification temperature is 300-320 ℃; the organic mixed solution containing the zinc precursor in the step 2-2 is injected into the solution containing the alloyed CdSeS crystal nucleus at the speed of 20 ml/h-30 ml/h, and then the temperature is kept for 1 h-2 h; the ratio of the amount of the zinc source substances of the organic mixed solution to the total amount of the anions and cations in the CdSeS crystal nucleus is 1:1-5:1.
Further, the outer coating layer is a ZnS outer coating layer coated on the periphery of the alloyed ZnCdSeS layer, and specifically comprises the following steps:
3-1, dissolving sulfur powder in tri-n-octyl phosphorus to prepare TOP-S precursor with certain sulfur concentration;
3-2, stirring and heating the reaction temperature to a coating temperature, adding an organic mixed solution containing a zinc precursor, then dropwise adding a TOP-S precursor with a certain sulfur concentration by using a syringe pump, and carrying out ZnS shell reaction growth to finally obtain the blue fluorescent alloyed CdSeS/ZnCdSeS/ZnS core-shell structure quantum dot.
Further, the coating temperature is 300-350 ℃, and the ratio of the amount of substances added with the zinc precursor to the amount of substances of sulfur powder in the TOP-S precursor in the step 3-2 is 1:1-2:1; the TOP-S precursor with a certain sulfur concentration is prepared by the method that the sulfur concentration is 0.5 mol/L; the speed of dripping TOP-S precursor with a certain sulfur concentration by a syringe pump is 2ml/h.
The invention has the beneficial effects that:
1) The problems that the existing nuclear shell structure quantum dot has many surface defects and large lattice stress due to mismatching of lattice constants between the crystal nucleus and an intermediate alloy layer are solved;
2) The blue fluorescent CdSeS/ZnCdSeS/ZnS alloyed core-shell structure quantum dot designed and synthesized by the invention carries out Zn on the surface of the quantum dot after synthesizing the alloyed CdSeS crystal nucleus 2+ Modifying, namely forming a ZnCdSeS shell layer on the surface of the alloying CdSeS crystal nucleus, and passivating surface defects; the preparation method has the advantages that the stability is improved by finally coating the ZnS shell layer, the problems of multiple surface defect states, low quantum yield, poor stability and insufficient exciton confinement of the conventional CdSeS alloy quantum dot are solved, and the finally prepared blue fluorescent quantum dot with the alloyed core-shell structure has the fluorescent peak position of 450-nm-490 nm and has the advantages of high quantum yield, good stability and single-channel attenuation fluorescent service life.
Drawings
FIG. 1 is a schematic diagram of an experimental mechanism of an example.
FIG. 2 is a graph showing the ultraviolet absorption spectrum of the CdSeS nucleus of example 1.
FIG. 3 is a fluorescence spectrum of the quantum dot of the CdSeS/ZnCdSeS/ZnS alloyed core-shell structure of example 2.
FIG. 4 is a transmission electron micrograph of the alloyed CdSeS nuclei prepared in example 1.
FIG. 5 is a transmission electron microscope image of example 2 after an alloyed ZnCdSeS layer is formed on the surface of the alloyed CdSeS crystal nuclei.
FIG. 6 is a transmission electron microscope image of the finally prepared CdSeS/ZnCdSeS/ZnS alloyed core-shell structure quantum dot of example 2.
FIG. 7 is a graph of the transient fluorescence spectrum of the quantum dot of the CdSeS/ZnCdSeS/ZnS alloyed core-shell structure of example 2.
FIG. 8 is a graph of photochemical stability of example 2 CdSeS/ZnCdSeS/ZnS alloyed core-shell structured quantum dots.
Detailed Description
The structure of the quantum dot with the alloyed core-shell structure comprises an alloying crystal nucleus, wherein an alloying layer is arranged on the surface of the alloying crystal nucleus.
The quantum dot with the alloying core-shell structure further comprises an outer shell layer, wherein the outer shell layer is coated on the periphery of the alloying layer.
The alloying crystal nucleus is an alloying CdSeS crystal nucleus, and an alloying ZnCdSeS layer is arranged on the surface of the alloying CdSeS crystal nucleus.
The shell layer is a ZnS shell.
When preparing the blue fluorescent alloyed core-shell structure quantum dot, the alloyed CdSeS crystal nucleus is preferably an alloyed CdSeS crystal nucleus with an ultraviolet absorption spectrum peak position of 420-450 nm, and is more preferably an alloyed CdSeS crystal nucleus with an ultraviolet absorption spectrum peak position of 440 nm.
The preparation method of the quantum dot with the alloyed core-shell structure comprises the following steps:
1. preparing a solution containing alloyed CdSeS crystal nucleus by adopting a hot injection method;
2. and carrying out surface modification on the alloyed CdSeS crystal nucleus by adopting an ion implantation method to form an alloyed ZnCdSeS layer.
The preparation method of the quantum dot with the alloyed core-shell structure further comprises the following steps:
3. and coating an outer shell layer on the periphery of the alloyed ZnCdSeS layer.
The method for preparing the solution containing the alloyed CdSeS crystal nucleus by adopting the hot injection method specifically comprises the following steps:
1-1, mixing selenium powder with liquid paraffin solution to prepare selenium powder-liquid paraffin suspension; preferably preparing selenium powder-liquid paraffin suspension with the selenium concentration of 0.1 mol/L;
1-2, mixing sulfur powder with octadecene solution, and heating to 150 ℃ under the condition of anhydrous oxygen to obtain a sulfur powder-octadecene precursor; preferably, a sulfur powder-octadecene precursor with the sulfur concentration of 0.5mol/L is obtained;
1-3, mixing cadmium oleate with a solution of octadecene under the condition of anhydrous oxygen, wherein the mass ratio of the solution of octadecene to the cadmium oleate is 50:1-55:1, heating to a nucleation temperature, and injecting selenium powder-liquid paraffin suspension and sulfur powder-octadecene precursor to form a mixed solution to obtain a solution containing alloyed CdSeS crystal nucleus; the prepared alloying CdSeS crystal nucleus has ultraviolet absorption spectrum of 420 nm-450 nm.
The nucleation temperature is 230 to 260 ℃, and the nucleation temperature is more preferably 240 ℃.
The mixed solution is formed by injecting selenium powder-liquid paraffin suspension and sulfur powder-octadecene precursor, the mixed solution is formed by injecting selenium powder-liquid paraffin suspension with the selenium concentration of 0.1mol/L and sulfur powder-octadecene precursor with the sulfur concentration of 0.5mol/L, the ratio of the total substances of the selenium powder and the sulfur powder to the substances of cadmium oleate in the mixed solution is 1:1-1:1.4, and the ratio of the substances of the selenium powder and the sulfur powder in the mixed solution is 1:1-1:5.
The process for forming the mixed solution by injecting selenium powder-liquid paraffin suspension with the selenium concentration of 0.1mol/L and sulfur powder-octadecene precursor with the sulfur concentration of 0.5mol/L specifically comprises the following steps: mixing selenium powder-liquid paraffin suspension with the selenium concentration of 0.1mol/L and sulfur powder-octadecene precursor with the sulfur concentration of 0.5mol/L, and injecting the mixture into a solution formed by mixing cadmium oleate and octadecene solution at the speed of 45 ml/h-60 ml/h; preferably, the ratio of the total mass of selenium powder in the selenium powder-liquid paraffin suspension with the selenium concentration of 0.1mol/L and the mass of sulfur powder in the sulfur powder-octadecene precursor with the sulfur concentration of 0.5mol/L to the mass of cadmium oleate is 1:1; preferably, the mass ratio of selenium powder in the selenium powder-liquid paraffin suspension with the selenium concentration of 0.1mol/L to the mass ratio of sulfur powder in the sulfur powder-octadecene precursor with the sulfur concentration of 0.5mol/L is 1:1.
The method adopts an ion implantation method to carry out surface modification on the alloying CdSeS crystal nucleus to form an alloying ZnCdSeS layer, and specifically comprises the following steps:
2-1, mixing an organic solvent and a zinc source to form an organic mixed solution, wherein the mass ratio of the organic solvent to the zinc source is 20.5:1-25.5:1, and heating to the organic mixed temperature under the condition of anhydrous oxygen to obtain an organic mixed solution containing a zinc precursor; the organic mixing temperature is preferably 300 ℃;
2-2, stirring and heating the solution containing the alloying CdSeS crystal nucleus prepared in the step 1 to an alloying modification temperature, adding an organic mixed solution containing a zinc precursor, and then preserving heat for 1-2 h to form an alloying ZnCdSeS layer on the surface of the alloying CdSeS crystal nucleus; the alloying modification temperature is preferably 300-320 ℃.
The organic mixed solution containing the zinc precursor in the step 2-2 is preferably injected into the solution containing the alloyed CdSeS crystal nucleus at the speed of 20 ml/h-30 ml/h, and the ratio of the amount of the zinc source substance of the organic mixed solution to the total amount of the anions and cations in the alloyed CdSeS crystal nucleus is 1:1-5:1.
The alloying ZnCdSeS layer prepared by the invention is prepared by carrying out Zn on the surface of the alloying CdSeS crystal nucleus 2+ Surface modification to form Zn during modification of the surface of the CdSeS crystal nucleus 2+ Penetrating and diffusing from the surface of the alloyed CdSeS crystal nucleus to a certain depth inside the alloyed CdSeS crystal nucleus, and forming a Zn-doped alloy on the surface of the alloyed CdSeS crystal nucleus 2+ Part of the infiltrated Zn 2+ Forming an alloyed ZnCdSeS layer with the alloyed CdSeS crystal nucleus, and finally forming the alloyed ZnCdSeS layer on the surface of the alloyed CdSeS crystal nucleus; since the alloyed ZnCdSeS layer prepared by the invention is prepared by combining Zn 2+ The crystal nucleus is formed by penetrating and diffusing the surface of the alloying CdSeS crystal nucleus into the alloying CdSeS crystal nucleus, so that the alloying CdSeS layer and the alloying CdSeS crystal nucleus belong to an integrated structure, the lattice constants of the CdSeS crystal nucleus and the ZnCdSeS layer, which are caused by the fact that the ZnCdSeS layer is additionally grown and wrapped outside the CdSeS crystal nucleus, are not matched, and the problems that the lattice stress between the CdSeS crystal nucleus and the ZnCdSeS layer is large, defects are easy to generate, and the blue fluorescence quantum yield is low are solved; in addition, the prepared alloyed ZnCdSeS layer can passivate the surface defects of the alloyed CdSeS crystal nucleus, and the fluorescence quantum yield is improved.
The outer shell layer is coated on the periphery of the alloyed ZnCdSeS layer, preferably the ZnS outer shell is coated on the periphery of the alloyed ZnCdSeS layer, and the method specifically comprises the following steps of:
3-1, dissolving sulfur powder in tri-n-octyl phosphorus (TOP) to prepare a TOP-S precursor with certain sulfur concentration;
3-2, stirring and heating the reaction temperature to a coating temperature, firstly adding an organic mixed solution containing a zinc precursor (the organic mixed solution containing the zinc precursor is preferably the same as the organic mixed solution containing the zinc precursor in the step 2-1), then dripping TOP-S precursor with the sulfur concentration of 0.5mol/L at the speed of 2ml/h by using a syringe pump, and carrying out ZnS shell reaction growth to finally obtain the blue fluorescent alloyed CdSeS/ZnCdSeS/ZnS core-shell structure quantum dot; the ZnS outer shell layer is coated, so that the exciton effective limit area is in an alloyed CdSeS crystal core with an alloyed ZnCdSeS layer on the surface, the influence of oxygen and moisture in the external environment on the quantum dot is isolated, and the stability of the quantum dot is improved; preferably, the coating temperature is 300-350 ℃, and the ZnS shell coating temperature is further preferably 315 ℃; the ratio of the amount of the substances added with the zinc precursor to the amount of the substances of the sulfur powder in the TOP-S precursor in the step 3-2 is 1:1-2:1; the TOP-S precursor with a certain sulfur concentration is preferably prepared in the step 3-1, wherein the sulfur concentration of the TOP-S precursor is 0.5 mol/L.
The preparation method of the CdSeS/ZnCdSeS/ZnS alloyed quantum dot provided by the invention synthesizes the alloyed CdSeS crystal nucleus at low temperature and then carries out Zn at high temperature 2+ The surface modification reduces the surface defect of the CdSeS crystal nucleus and further coats the ZnS shell, because the band gap of ZnS is wider, after the ZnS shell is coated, the exciton effective limit can be arranged in the alloyed CdSeS crystal nucleus with the alloyed ZnCdSeS layer on the surface, the fluorescence quantum yield is improved, the influence of the external environment on the quantum dot can be isolated, the stability of the quantum dot is improved, and the problems of more surface defect states, low quantum yield and insufficient exciton limit of the conventional CdSeS alloy quantum dot are solved; the prepared blue fluorescent CdSeS/ZnCdSeS/ZnS alloyed core-shell structure quantum dot has the advantages of good monodispersity, uniform size distribution, high fluorescent quantum yield and good stability; the ultraviolet absorption spectrum of the alloying CdSeS crystal nucleus prepared by the invention is 420 nm-450 nm, the size is 3 nm-7 nm, and Zn is carried out 2+ After the surface of the ion is modified to form an alloyed ZnCdSeS layer, the size is still 3 nm-7 nm, the size after the ZnS outer shell layer is coated is 7-10 nm, the fluorescence emission peak position is 450-490 nm, the fluorescence quantum yield is 80-95%, and the blue fluorescence quantum dot has good characteristics; the invention has great value in both laboratory research and display lighting applications.
In order to further illustrate the present invention, the following examples are used to describe the blue fluorescent CdSeS/ZnCdSeS/ZnS alloyed core-shell structure quantum dots and the preparation method thereof in detail, the experimental mechanism is shown in fig. 1, but they should not be construed as limiting the protection scope of the present invention.
Example 1:
preparation of alloyed CdSeS nuclei:
preparation of selenium precursor (selenium powder-liquid paraffin suspension with selenium concentration of 0.1 mmol/L): weighing 0.0789g of selenium powder and 10ml of liquid paraffin in a 20ml sample bottle, and putting the sample bottle into an ultrasonic machine for ultrasonic use;
preparation of sulfur precursor (ODE-S precursor with sulfur concentration of 0.5 mmol/L): putting 0.3207g of sulfur powder and 20ml of octadecene into a 50ml three-necked bottle, blowing nitrogen for 10min at 120 ℃, and heating to 150 ℃ and keeping for 30min;
preparation of alloyed CdSeS nuclei: mixing 0.22mmol of cadmium oleate with 10ml of octadecene solution, blowing nitrogen for 10min at 120 ℃, stirring and heating to 240 ℃, taking 0.2 ml of ODE-S precursor and 1.0ml of selenium powder-liquid paraffin suspension, injecting the mixture into the mixed solution of cadmium oleate and octadecene at a speed of 45 ml/h-60 ml/h, and carrying out a reaction, wherein the ultraviolet absorption spectrum of the alloyed CdSeS crystal nucleus is shown in figure 2, the absorption spectrum of the alloyed CdSeS crystal nucleus is rapidly red-shifted along with the reaction, and the ultraviolet absorption spectrum of the alloyed CdSeS crystal nucleus is preferably at 440nm at 240 ℃.
Example 2:
zinc precursor (0.4 mmol/L Zn (OA) 2 ) Is prepared from the following steps: 0.8137g of zinc oxide, 10ml of oleic acid and 15ml of octadecene are taken in a 100ml three-necked flask, nitrogen is blown for 20min at 120 ℃, and the temperature is raised to 300 ℃ and maintained for 30min.
On the basis of example 1, the reaction temperature was raised to 310℃with stirring, and an excess of zinc oleate (Zn (OA) was added 2 ) The solution is kept at 310 ℃ for 1h, so that the reaction is completely carried out, and along with Zn 2+ Gradually diffusing into the nucleus of the alloying CdSeS crystal nucleus, forming an alloying ZnCdSeS layer on the surface of the alloying CdSeS crystal nucleus on the basis of not changing the size of the alloying CdSeS crystal nucleus, and passivating surface defects.
Further heating the reaction temperature to 315 ℃, firstly dropwise adding a zinc oleate solution into the reaction solution, wherein the total volume of the zinc oleate is 3 ml; and (3) dropwise adding a TOP-S precursor with the volume of 2ml and the sulfur concentration of 0.5mol/L into the reaction solution at the speed of 5ml/h according to the molar ratio of anions to cations of 1:1.2, so as to obtain the CdSeS/ZnCdSeS/ZnS alloyed core-shell structure quantum dot.
And (3) carrying out fluorescence detection on the CdSeS/ZnCdSeS/ZnS alloyed core-shell structure quantum dot prepared in the embodiment 2, wherein the final fluorescence emission peak position is 470nm, and the half-peak width is 23nm as shown in the attached figure 3.
For alloying CdSeS crystal nucleus and Zn 2+ As a result of transmission electron microscope observation of the CdSeS/ZnCdSeS/ZnS alloyed core-shell structure quantum dots with the surface modified and coated ZnS outer shell layers, as shown in the accompanying drawings 4-6, the diameter of the initial alloyed CdSeS crystal nucleus is 6nm, the diameter of the quantum dots is not increased to be 6nm after the surface modification, which indicates that the synthesis of the alloyed ZnCdSeS layer, and the diameter of the final CdSeS/ZnCdSeS/ZnS alloyed core-shell structure quantum dots is 9nm, and the quantum dots have good monodispersity and uniformity.
The quantum dots with the CdSeS/ZnCdSeS/ZnS alloyed core-shell structure prepared in the embodiment 2 are tested for transient fluorescence life, and as shown in the attached figure 7, the quantum dots with the CdSeS/ZnCdSeS/ZnS alloyed core-shell structure have fluorescence life with single exponential decay.
The quantum yield of the CdSeS/ZnCdSeS/ZnS alloyed core-shell structure quantum dot prepared in the embodiment 2 under different illumination time is tested, the change of the fluorescence quantum yield of the quantum dot under different time is shown in figure 8, and the fluorescence quantum yield is not obviously reduced after long-time ultraviolet irradiation, so that the prepared quantum dot is good in stability.
The above examples are only preferred embodiments of the present invention and are not intended to limit the present invention in any way; it should be noted that modifications and adaptations to the present invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be comprehended within the scope of the present invention.
Claims (5)
1. An alloyed core-shell structure quantum dot is characterized by comprising an alloyed CdSeS crystal nucleus and a ZnS shell; the surface of the alloying CdSeS crystal nucleus is provided with an alloying ZnCdSeS layer, and a ZnS shell is coated on the periphery of the alloying ZnCdSeS layer;
the preparation method of the quantum dot with the alloyed core-shell structure specifically comprises the following steps:
1) Preparing a solution containing alloyed CdSeS crystal nucleus by adopting a hot injection method;
2) Performing surface modification on the alloyed CdSeS crystal nucleus by adopting an ion implantation method to form an alloyed ZnCdSeS layer;
3) A ZnS shell is coated on the periphery of the alloying ZnCdSeS layer;
the method adopts an ion implantation method to carry out surface modification on the alloying CdSeS crystal nucleus to form an alloying ZnCdSeS layer, and specifically comprises the following steps:
2-1), mixing an organic solvent with a zinc source to form an organic mixed solution, and heating to an organic mixing temperature under the condition of anhydrous oxygen to obtain an organic mixed solution containing a zinc precursor;
2-2), stirring and heating the solution containing the alloying CdSeS crystal nucleus prepared in the step 1) to an alloying modification temperature, adding an organic mixed solution containing a zinc precursor, and then preserving heat for a certain time to form an alloying ZnCdSeS layer on the surface of the alloying CdSeS crystal nucleus;
mixing an organic solvent and a zinc source to form an organic mixed solution, wherein the mass ratio of the organic solvent to the zinc source is 20.5:1-25.5:1; the organic mixing temperature is 300 ℃; the alloying modification temperature is 300-320 ℃; the organic mixed solution containing the zinc precursor in the step 2-2) is injected into the solution containing the alloyed CdSeS crystal nucleus at the speed of 20 ml/h-30 ml/h, and then the temperature is kept for 1 h-2 h; the ratio of the amount of the zinc source substances in the organic mixed solution to the total amount of the anions and cations in the alloyed CdSeS crystal nucleus is 1:1-5:1.
2. The quantum dot with the alloyed core-shell structure according to claim 1, wherein the solution containing the alloyed CdSeS crystal nuclei is prepared by a hot injection method, and specifically comprises the following steps:
1-1), mixing selenium powder with liquid paraffin solution to prepare selenium powder-liquid paraffin suspension;
1-2), mixing sulfur powder with octadecene solution, and heating under anhydrous oxygen condition to obtain sulfur powder-octadecene precursor;
1-3) under the condition of anhydrous oxygen, mixing cadmium oleate with octadecene solution, heating to a nucleation temperature, and injecting selenium powder-liquid paraffin suspension and sulfur powder-octadecene precursor to form a mixed solution to obtain a solution containing alloyed CdSeS crystal nucleus.
3. The quantum dot with the alloyed core-shell structure according to claim 2, wherein the nucleation temperature is 230-260 ℃; the selenium powder-liquid paraffin suspension is selenium powder-liquid paraffin suspension with the selenium concentration of 0.1 mol/L; the sulfur powder-octadecene precursor is sulfur powder-octadecene precursor with the sulfur concentration of 0.5 mol/L; the ratio of the total substances of the selenium powder and the sulfur powder to the substances of the cadmium oleate in the mixed solution is 1:1-1:1.4, and the ratio of the substances of the selenium powder and the sulfur powder in the mixed solution is 1:1-1:5; when the cadmium oleate and the octadecene solution are mixed, the mass ratio of the octadecene solution to the cadmium oleate is 50:1-55:1.
4. The quantum dot with the alloyed core-shell structure according to claim 1, wherein the periphery of the alloyed ZnCdSeS layer is coated with a ZnS shell, and the quantum dot comprises the following steps:
3-1), dissolving sulfur powder in tri-n-octyl phosphorus to prepare TOP-S precursor with certain sulfur concentration;
3-2), stirring and heating the reaction temperature to a coating temperature, adding an organic mixed solution containing a zinc precursor, then dropwise adding a TOP-S precursor with a certain concentration by using a syringe pump, and carrying out ZnS shell reaction growth to finally obtain the blue fluorescent alloyed CdSeS/ZnCdSeS/ZnS core-shell structure quantum dot.
5. The quantum dot with the alloying core-shell structure according to claim 4, wherein the cladding temperature is 300-350 ℃, and the ratio of the amount of substances added with the zinc precursor to the amount of substances of sulfur powder in the TOP-S precursor in the step 3-2) is 1:1-2:1; the TOP-S precursor with a certain sulfur concentration is prepared by the method that the sulfur concentration is 0.5 mol/L; the speed of dropping TOP-S precursor with a certain concentration by a syringe pump is 2ml/h.
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