CN110373177B

CN110373177B - Quantum dot and preparation method thereof

Info

Publication number: CN110373177B
Application number: CN201910535771.3A
Authority: CN
Inventors: 刘雅俊; 刘玉婧; 韩璐; 林佳丽
Original assignee: Shenzhen Zowee Technology Co Ltd
Current assignee: Shenzhen Zowee Technology Co Ltd
Priority date: 2019-06-19
Filing date: 2019-06-19
Publication date: 2023-03-03
Anticipated expiration: 2039-06-19
Also published as: CN110373177A

Abstract

The invention relates to a quantum dot and a preparation method thereof. The quantum dot comprises a core layer and a shell layer, wherein the core layer is made of materials comprising phosphorus, indium, zinc and sulfur, the radius of the core layer is 2-6 nm, the thickness of the shell layer is 8-16 nm, the shell layer comprises an inner shell layer coated on the core layer and an outer shell layer coated on the inner shell layer, the inner shell layer is made of one of ZnSeS and ZnSe, and the outer shell layer is made of ZnS. The half-peak width of the quantum dot is about 40nm, and the quantum yield is as high as 78%.

Description

Quantum dot and preparation method thereof

Technical Field

The invention relates to the field of quantum dot preparation, in particular to a quantum dot and a preparation method thereof.

Background

The quantum dots are also called semiconductor nanocrystals, are approximately spherical, have three-dimensional radiuses within the range of 2nm to 20nm, and have obvious quantum effects. The quantum dots are generally made of semiconductor materials of II-VI group elements (such as CdS, cdSe, cdTe, znSe, znS and the like) or III-V group elements (such as InP, inAs and the like), and the core/shell structure quantum dots (such as common CdSe/ZnS core/shell structure quantum dots and the like) can also be made of two or more semiconductor materials. The quantum dots have the advantages of wide absorption spectrum, narrow and symmetrical emission spectrum, good light stability, high quantum yield, adjustable emission wavelength and the like, and are widely applied to five fields of display, medicine, biology, solar cells and energy sources, wherein the development of the display field is the fastest one for human life.

The CdSe quantum dots are developed and compared perfectly at present, and have the advantages of small half-peak width and high luminous efficiency, but Cd is heavy metal and harmful to the environment and human bodies, and the use of heavy metal Cd is forbidden in countries such as European Union, so that the CdSe quantum dots are not beneficial to the development of commerce.

In addition, the III-V group compound quantum dots are formed by covalent bond bonding, have more perfect structures compared with the traditional II-VI group compound quantum dots formed by ionic bond bonding, and become the focus of attention of scientific researchers.

However, since the development of InP quantum dots is still immature, there are problems of a wide half-peak width and low light emission efficiency.

Disclosure of Invention

Accordingly, there is a need for quantum dots with narrow half-peak width and high luminous efficiency.

In addition, a preparation method of the quantum dot is also provided.

The quantum dot comprises a core layer and a shell layer, wherein the constituent elements of the material of the core layer comprise phosphorus, indium, zinc and sulfur, the radius of the core layer is 2-6 nm, the thickness of the shell layer is 8-16 nm, the shell layer comprises an inner shell layer coated on the core layer and an outer shell layer coated on the inner shell layer, the material of the inner shell layer is selected from one of ZnSeS and ZnSe, and the material of the outer shell layer is ZnS.

In one embodiment, the mol ratio of the zinc element to the indium element in the core layer is 1.1: 5.0-5.0: 1.1; and/or the like, and/or,

the mol ratio of the phosphorus element to the indium element is 0.1: 1.0-3.0: 1.0; and/or the presence of a catalyst in the reaction mixture,

the molar ratio of the sulfur element to the indium element is 0.1: 1.0-2.0: 1.0.

In one embodiment, the ratio of the thickness of the shell layer to the radius of the core layer is 1:1 to 6:1.

In one embodiment, the number of the inner shell layers is 10-20, and the number of the outer shell layers is 1-10.

A preparation method of quantum dots comprises the following steps:

adding a first zinc source and an indium source into the first mixed solution, and heating to 100-200 ℃ for reaction to obtain a first reaction solution, wherein the first mixed solution contains a ligand and a non-complexing solvent;

adding a phosphorus source and a first sulfur source into the first reaction liquid, and then heating to 200-300 ℃ for reaction to obtain a second reaction liquid;

mixing at least one of a selenium source and a second sulfur source with the second reaction solution and the second mixed solution, and heating to 250-300 ℃ for reaction to obtain a third reaction solution, wherein the second mixed solution contains a second zinc source; and

and adding a third zinc source and a third sulfur source into the third reaction solution, and heating to 300-350 ℃ for reaction to obtain the quantum dots.

In one embodiment, the step of adding the first zinc source and the indium source to the first mixed solution comprises: respectively preparing the first zinc source and the indium source into solutions, and simultaneously injecting the solutions into the first mixed solution at a rate of 10-20 mL/min; and/or the presence of a catalyst in the reaction mixture,

the step of adding a phosphorus source and a first sulfur source to the first reaction liquid comprises: and preparing the phosphorus source and the first sulfur source into a solution, and injecting the solution into the first reaction solution at the speed of 20-40 mL/min.

In one embodiment, the step of mixing at least one of a selenium source and a second sulfur source with the second reaction solution and the second mixed solution includes: the second reaction solution is injected into the second mixed solution at a rate of 10-20 mL/min, and then at least one of the selenium source and the second sulfur source is injected into the second mixed solution at a rate of 0.1-2.0 mL/min.

In one embodiment, the step of adding a third zinc source and a third sulfur source to the third reaction solution comprises: and preparing a solution from the third zinc source and the third sulfur source, and injecting the solution into the third reaction solution at the speed of 0.1-2.0 mL/min.

In one embodiment, in the step of adding the first zinc source and the indium source into the first mixed solution and then heating to 100-200 ℃ for reaction, the temperature is 130-150 ℃ and the reaction time is 1-60 min.

In one embodiment, the phosphorus source and the first sulfur source are added into the first reaction solution, and then the temperature is increased to 200-300 ℃ for reaction, wherein the temperature is 250-280 ℃ and the reaction time is 10-100 min.

The quantum dots have the advantages that the phosphor, the indium, the sulfur and the zinc are selected as the constituent elements of the core layer material, the specific inner shell layer and the specific outer shell layer are wrapped outside the core layer, and the radius of the core layer and the thickness of the shell layer are adjusted, so that the obtained quantum dots are narrow in half-peak width and high in luminous efficiency. Experiments prove that the half-peak width of the quantum dots is about 40nm, and the luminous efficiency is as high as 78%.

Drawings

Fig. 1 is a process flow diagram of a method of preparing quantum dots according to an embodiment;

FIG. 2 is a UV spectrum of a ZnInPS quantum dot core of example 1;

FIG. 3 is a fluorescence spectrum of ZnInPS/ZnSeS/ZnS quantum dots in example 1;

FIG. 4 is a TEM image of ZnInPS/ZnSeS/ZnS quantum dots in example 1.

Detailed Description

In order that the invention may be more fully understood, reference will now be made to the following description taken in conjunction with the accompanying drawings. The detailed description sets forth the preferred embodiments of the invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

In this specification, the thickness of the shell layer, the particle size of the quantum dot, and the radius of the outer shell layer are the same concept, and both represent the total radius size of the core layer and the shell layer.

The quantum dot comprises a core layer and a shell layer, wherein the core layer is made of materials comprising phosphorus, indium, zinc and sulfur, the core layer has a radius of 2-6 nm, the shell layer has a thickness of 8-16 nm, the shell layer comprises an inner shell layer coated on the core layer and an outer shell layer coated on the inner shell layer, the inner shell layer is made of one of ZnSeS and ZnSe, and the outer shell layer is made of ZnS.

Specifically, the mol ratio of zinc element to indium element in the core layer is 1.1: 5.0-5.0: 1.1. Furthermore, the mol ratio of the zinc element to the indium element is 1.1: 3.0-3.0: 1.1. The effect of setting the molar ratio of the zinc element to the indium element to the above value is: when the zinc element and the indium element in the molar ratio react with the subsequent phosphorus element and the sulfur element, the formed lattice structure is symmetrical and complete, the stability is high, and in addition, the ratio is adjusted to obtain the target wavelength and particle size, so that the effect of adjusting the wavelength and the particle size can be achieved.

In the nuclear layer, the mol ratio of the phosphorus element to the indium element is 0.1: 1.0-3.0: 1.0. Furthermore, the mol ratio of the phosphorus element to the indium element is 0.5: 1.0-2.0: 1.0. Setting the molar ratio of the phosphorus element to the indium element to the above value functions to: the reactivity between the phosphorus element and the indium element at the molar ratio reaches an optimal state, and the phosphorus element and the indium element, the zinc element and the sulfur element at the reactivity are combined at an optimal rate when reacting, so that the uniformity of the result is facilitated, and the function of adjusting the wavelength and the particle size is also realized.

The mol ratio of the sulfur element to the indium element is 0.1: 1.0-2.0: 1.0. Furthermore, the mol ratio of the sulfur element to the indium element is 0.2: 1.0-0.5: 1.0. The effect of setting the molar ratio of the sulfur element to the indium element to the above value is: when the sulfur element and the indium element react with the phosphorus element and the zinc element at the molar ratio, the formed lattice structure is symmetrical and complete, the stability is high, and in addition, the ratio is adjusted to obtain the target wavelength and the target particle size, so that the effect of adjusting the wavelength and the particle size can be achieved.

The zinc element and the sulfur element are introduced into the InP quantum dot core, so that the radius of the quantum dot core layer is larger, and the quantum yield of the InP quantum dot core layer is improved.

Specifically, the number of layers of the inner shell layer is 10 to 20. The number of layers of the outer shell layer is 1-10. The inner shell layer is used for controlling wavelength, and the outer shell layer is used for better reducing lattice defects, thereby improving luminous efficiency.

Specifically, the ratio of the thickness of the shell layer to the radius of the core layer is 1: 1-6: 1. Setting the ratio of the thickness of the shell layer to the radius of the core layer to the above values has the effect of: the wavelength of the quantum dots can be regulated, the lattice defects can be effectively reduced, and the luminous efficiency is improved.

The ZnS shell layer is coated outside the nuclear layer, so that the non-radiative recombination of InP can be reduced, but the lattice adaptation degree of ZnS and InP is high, defects are easily generated at an interface, and the ZnS is difficult to effectively grow on the surface of InP in the coating process, so that the quantum yield is reduced, and the stability is poor. And the lattice constant difference between ZnSe or ZnSeS and InP is small, and the ZnSe or ZnSeS and InP are easy to coat on the surface of the core layer. Therefore, the ZnSe or ZnSeS is coated outside the core layer, and then the ZnS layer is coated, so that the lattice adaptation degree of the core layer and the shell layer is smaller, and the quantum yield of the quantum dot is improved.

The thickness of the middle shell layer of the quantum dot is thicker, so that the quantum yield of the obtained quantum dot is higher, and the half-peak width is narrower.

The quantum dots have at least the following advantages:

(1) The quantum yield of the quantum dots reaches 78%, the half-peak width is about 40nm, and the narrower the half-peak width is, the better the uniformity of the particles is, and the purer the color emitted by the quantum dots is.

(2) The quantum dots do not contain cadmium which is harmful to the environment, and have the advantage of environmental protection.

Referring to fig. 1, a method for preparing a quantum dot according to an embodiment includes the following steps:

step S110: mixing the first ligand and the first non-complex solvent, and then heating to 50-150 ℃ to form a first mixed solution.

Further, the first ligand and the first non-complexing solvent are mixed, and the temperature is raised to 50-150 ℃, preferably 70-110 ℃.

Wherein the first ligand plays a role in coordination stability, and the first non-complexing solvent plays a role in dissolving and dispersing the reactant.

Step S120: adding a first zinc source and an indium source into the first mixed solution, and heating to 100-200 ℃ for reaction to form a first reaction solution.

Specifically, the step of adding the first zinc source and the indium source to the first mixed solution includes: the first zinc source and the indium source are respectively prepared into solution and then are simultaneously injected into the first mixed solution at the speed of 10mL/min to 20 mL/min.

In the step of preparing the first zinc source and the indium source into solutions respectively, the first zinc source and the indium source are dissolved by adopting a second non-complex solvent and a third non-complex solvent respectively to prepare the solutions. It is to be understood that the second non-complexing solvent and the third non-complexing solvent are for dissolving or dispersing the first zinc source and the indium source, and that the second non-complexing solvent or the third non-complexing solvent may be omitted when the first zinc source or the indium source is a solution.

With the above injection rates, the resulting lattice structure is most stable and, as a result, the reaction is most vigorous if the rate is higher than this, the solution will run into the condenser tube, causing loss or contamination of the solution, which is detrimental to the reaction result.

Further, in the step of adding the first zinc source and the indium source into the first mixed solution and then heating to 100 ℃ to 200 ℃ for reaction, the temperature is preferably 130 ℃ to 150 ℃. The reaction time is 1 min-60 min.

Further, before the step of adding the first zinc source and the indium source to the first mixed solution, a step of degassing the first mixed solution is further included. The degassing time is 10 min-90 min. Further, the degassing time is 10 min-60 min. The purpose of the degassing is to allow the subsequent reaction to proceed under an inert gas blanket. The inert gas may be nitrogen, argon, or the like.

Step S130: and adding a phosphorus source and a first sulfur source into the first reaction liquid, and heating to 200-300 ℃ for reaction to obtain a second reaction liquid.

The step of adding a phosphorus source and a first sulfur source to the first reaction liquid comprises: the phosphorus source and the first sulfur source are prepared into a solution, and then the solution is injected into the first reaction solution at the speed of 20-40 mL/min. The quantum dots can be uniformly nucleated using the above injection rates.

In the step of preparing the phosphorus source and the first sulfur source into a solution, a fourth non-complexing solvent is adopted to prepare the phosphorus source and the first sulfur source into a solution. It will be appreciated that when the phosphorus source is in solution with the first sulfur source, the fourth non-complexing solvent may be omitted.

Further, in the step of adding a phosphorus source and a first sulfur source into the first reaction solution and heating to 200-300 ℃ for reaction, the temperature is preferably 250-280 ℃. The reaction time is 10 min-100 min.

In the nucleation process, the nucleation temperature is low, which is beneficial to the stability of the lattice structure, and the temperature is too high, which can form metal precipitation and is not beneficial to nucleation. In the process of crystal nucleus growth, the temperature is higher, which is beneficial to the growth of the crystal nucleus. Therefore, in the process of preparing the quantum dot core layer structure, a mode of gradually increasing the temperature is adopted, so that a stable and uniform quantum dot core is obtained.

Furthermore, the position of a first exciton absorption peak of the ZnInPS quantum dot core under an ultraviolet visible spectrum is adjustable within the range of 400 nm-500 nm, and quantum dots with different particle sizes are obtained by adjusting the proportion of Zn, S, P and In, so that the wavelength of the quantum dot core is adjusted.

Step S140: and mixing the second zinc source, the second ligand and the fifth non-complexing solvent, and then heating to 100-150 ℃ to form a second mixed solution.

Further, in step S140, the temperature is preferably 110 to 130 ℃.

Further, the second ligand is different from the first ligand, and a ligand exchange process is further included in the step of mixing the second zinc source, the second ligand and the fifth non-complex solvent. Through ligand exchange treatment, the activity of the zinc source after ligand exchange is improved, and the combination with an indium source, a phosphorus source and a sulfur source is facilitated.

Step S150: at least one of the selenium source and the second sulfur source is mixed with the second reaction liquid and the second mixed liquid, and then the temperature is raised to 250 ℃ to 300 ℃ for reaction to form a third reaction liquid.

Further, in the step of mixing at least one of the selenium source and the second sulfur source with the second reaction solution and the second mixed solution and then heating to 250 ℃ to 300 ℃ for reaction, the temperature is preferably 270 ℃ to 290 ℃.

Specifically, the step of mixing at least one of the selenium source and the second sulfur source with the second reaction solution and the second mixed solution includes: the second reaction solution is injected into the second mixed solution at a rate of 10mL/m to 20mL/min, and at least one of the selenium source and the second sulfur source is injected into the second mixed solution at a rate of 0.1mL/min to 2.0 mL/min. The injection rate is used to form quantum dots having a uniform particle size.

Further, the step of mixing at least one of a selenium source and a second sulfur source with the second reaction solution and the second mixed solution further includes a step of mixing with a third ligand. And injecting a third ligand into the second mixed solution.

In the present embodiment, the addition of the third ligand serves to increase the activity of the second reaction solution, and it is understood that the third ligand may be omitted when the activity of the second reaction solution is high.

Further, the method may further include a step of degassing before the step of mixing the second reaction liquid and the second mixed liquid with at least one of the selenium source and the second sulfur source. Specifically, the step of degassing comprises: degassing at 100-150 deg.c for 10-90 min. Further, in the degassing step, the temperature is 100-130 ℃, and the degassing time is 10-60 min.

Step S160: and adding a third zinc source and a third sulfur source into the third reaction solution, and then heating to 300-350 ℃ to form a fourth reaction solution.

Further, in the step of adding a third zinc source and a third sulfur source to the third reaction solution and raising the temperature to 300 to 350 ℃, the temperature is preferably 310 to 330 ℃.

Specifically, the step of adding the third zinc source and the third sulfur source to the third reaction solution includes: and preparing a solution from a third zinc source and a third sulfur source, and injecting the solution into the third reaction solution at the speed of 0.1-2.0 mL/min. The injection rate is used to form quantum dots having a uniform particle size.

And in the step of preparing the third zinc source and the third sulfur source into a solution, preparing the third zinc source and the third sulfur source into a solution by adopting a sixth non-complex solvent. It is to be understood that the sixth non-complexing solvent is intended to dissolve or disperse the third zinc source and the third sulfur source, and that the sixth non-complexing solvent may be omitted when the third zinc source and the third sulfur source are in solution.

Step S170: and purifying the fourth reaction solution to obtain the quantum dots.

Step S170 specifically includes: cooling the fourth reaction liquid to room temperature, and precipitating the fourth reaction liquid by adopting a mixed solvent of methanol and n-butyl alcohol with the volume ratio of 1: 1-1: 5 to obtain a precipitate. And dissolving the precipitate in toluene to obtain the quantum dot.

The ZnS shell layer is coated outside the nuclear layer, so that the non-radiative recombination of InP can be reduced, but the lattice adaptation degree of ZnS and InP is high, defects are easily generated at an interface, and the ZnS is difficult to effectively grow on the surface of InP in the coating process, so that the quantum yield is reduced, and the stability is poor. And the lattice constant difference between ZnSe or ZnSeS and InP is small, and the ZnSe or ZnSeS and InP are easy to coat on the surface of the core layer. Therefore, the core layer is coated with a layer of ZnSe or ZnSeS and then coated with a ZnS layer.

Specifically, the first zinc source, the second zinc source, and the third zinc source used in the preparation step of the quantum dot are each independently at least one selected from zinc adipate, zinc caprylate, zinc laurate, zinc myristate, zinc palmitate, zinc dithiocarbamate, diethyl zinc, dimethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide, zinc nitrate, zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate, zinc stearate, zinc laurate, zinc undecylenate, and zinc diethyldithiocarbamate.

The indium source is at least one selected from tributylphosphine indium, indium octadecene solution, indium oleylamine solution, indium oleate solution, indium myristate solution, indium carbonate, indium nitrate, indium acetate, indium stearate, indium iodide, indium bromide, trimethyl indium and indium chloride.

The phosphorus source is at least one selected from the group consisting of tris (dimethylamino) phosphine, tris (diethylamino) phosphine, tris (trimethylsilyl) phosphine, trioctylphosphine and tributylphosphine.

The first sulfur source, the second sulfur source, and the third sulfur source are each independently selected from at least one of elemental sulfur, hydrogen sulfide, bis (trimethylsilyl) sulfide, hexa-aminosulfide, and dodecanethiol.

The selenium source is at least one selected from diisobutylphosphine selenide, trioctylphosphine selenide, tri (n-butyl) phosphine selenide, tri (sec-butyl) phosphine selenide, tri (tert-butyl) phosphine selenide, trimethyl phosphine selenide, triphenyl phosphine selenide, tricyclohexylphosphine selenide, 1-octane selenol, 1-dodecane selenol, phenylselenol, elemental selenium, hydrogen selenide, bis (trimethylsilyl) selenide, and selenourea.

The first non-complexing solvent, the second non-complexing solvent, the third non-complexing solvent, the fourth non-complexing solvent, the fifth non-complexing solvent and the sixth non-complexing solvent are respectively and independently selected from at least one of olefin, alkane, ether and aromatic compound. Further, the first non-complexing solvent, the second non-complexing solvent, the third non-complexing solvent, the fourth non-complexing solvent, the fifth non-complexing solvent and the sixth non-complexing solvent are respectively and independently selected from at least one of biphenyl, octadecene, nonadecene, eicosene, tetracosane, docosane, eicosane, octadecane, liquid paraffin and isotridecane. The selection of the first non-complexing solvent, the second non-complexing solvent, the third non-complexing solvent, the fourth non-complexing solvent, the fifth non-complexing solvent and the sixth non-complexing solvent mainly considers the better solubility of the raw materials and the change of the experiment temperature.

The first ligand and the second ligand are both acidic ligands. Specifically, the first ligand and the second ligand are respectively and independently selected from at least one of the group consisting of decaacid, undecylenic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, oleic acid and stearic acid. The first ligand and the second ligand are selected mainly in consideration of the reactivity of the raw materials.

The third ligand is selected from at least one of long-chain aliphatic amines, arylamines and thiols. Further, the third ligand is at least one selected from the group consisting of dodecyl mercaptan, n-octyl mercaptan, oleyl amine, dipropyl amine, n-hexyl amine, n-octyl amine, trioctyl amine, octa amine, dodecyl amine, hexadecyl amine and octadecyl amine.

The quantum dot obtained by the preparation method of the quantum dot has a core-shell structure. The core layer comprises phosphorus, indium, zinc and sulfur, the radius of the core layer is 2-6 nm, the shell layer comprises an inner shell layer coated on the core layer and an outer shell layer coated on the inner shell layer, the inner shell layer is selected from one of ZnSeS and ZnSe, the outer shell layer is ZnS, the thickness of the shell layer is 8-16 nm, and the ratio of the thickness of the shell layer to the radius of the core layer is 1: 1-6: 1. Experiments prove that the quantum yield of the quantum dots obtained by the preparation method of the quantum dots is up to 78%, and the half-peak width is about 40 nm.

The preparation method of the quantum dot at least has the following advantages:

(1) The preparation method of the quantum dots has the advantages of simple operation, stable result and good repeatability.

(2) The preparation method of the quantum dot can enable the half-peak width of the obtained quantum dot to be about 40nm, the luminous efficiency to be as high as 78%, and the preparation method of the quantum dot can still achieve the same result when the mass production is expanded.

(3) The preparation method of the quantum dot can also adjust the wavelength and the energy band structure of the quantum dot by changing the reaction temperature, the injection rate, the element proportion, the reaction time and the like.

The following are specific examples:

example 1

The preparation process of the quantum dot of this example is as follows:

(1) 35mmol of oleic acid and 255.8mmol of octadecene were mixed and heated to 90 ℃ to obtain a first mixed solution. Degassing was carried out for 30min, and the reactions were all carried out under argon. At this temperature, 8.24mmol of a trimethylindium solution (dissolved in 20mL of octadecene) and 20.54mmol of a diethylzinc solution (dispersed in 20mmol of octadecene) were uniformly injected into the first mixed solution at a rate of 10mL/min, and the temperature was raised to 100 ℃ and maintained for 30min to obtain a first reaction solution. 11.86mmol of tris (trimethylsilyl) phosphine and 1.84mmol of bis (trimethylsilyl) sulfide are dispersed in 4mL of octadecene, and then injected into the first reaction solution at the rate of 30mL/min, the temperature is raised to 280 ℃, and the reaction is carried out for 45min, so as to obtain a second reaction solution containing ZnInPS quantum dot cores.

(2) 22.2mmol of zinc acetate, 23.35mmol of myristic acid and 30mL of isotridecane were mixed and heated to 130 ℃ to form a second mixture, and degassed for 30min, after which the reaction was carried out under argon. And heating to 250 ℃, injecting 21.3mmol of dodecylamine and 10mmol of second reaction solution into the second mixed solution at the speed of 10mL/min, and injecting a mixed solution of 21.3mmol of diisobutylphosphine selenide and 2.2mmol of bis (trimethylsilyl) sulfide into the second mixed solution at the speed of 0.1mL/min to form a ZnSeS shell layer coated on a ZnInPS core, thereby obtaining a third reaction solution. And raising the temperature to 300 ℃, injecting 42mL of zinc oleate and 12.5mmol of bis (trimethylsilyl) sulfide dispersed in 39mL of octadecene into the third reaction solution at the rate of 0.1mL/min at the same time, and keeping the temperature for 10min to form a ZnS shell coated on the ZnSeS shell, thereby obtaining a fourth reaction solution.

(3) Cooling the fourth reaction solution to room temperature, adding a mixed solvent of methanol and n-butyl alcohol with the volume ratio of 1: 3 into the fourth reaction solution to precipitate the quantum dots, and centrifuging to obtain a precipitate. And dissolving the precipitate in toluene to obtain the purified ZnInPS/ZnSeS/ZnS quantum dots. Wherein ZnInPS is a core layer of the quantum dot, znSeS is an inner shell layer of the quantum dot, znS is an outer shell layer of the quantum dot, and "/" represents a layer.

Example 2

The preparation process of the quantum dot in this embodiment is a preparation process of the quantum dot in mass production expansion, and specifically includes the following steps:

(1) 140mol of oleic acid and lmol octadecene are mixed and heated to 90 ℃ to obtain a first mixed solution. Degassing was carried out for 30min, and the reactions were all carried out under argon. At this temperature, 33mmol of a trimethylindium solution (dissolved in 80mL of octadecene) and 82.16mmol of a diethylzinc solution (dispersed in 80mL of octadecene) were uniformly injected into the first mixed solution at an injection rate of 10mL/min, and then the temperature was raised to 100 ℃ and maintained for 30min to obtain a first reaction solution. 47.44mmol of tris (trimethylsilyl) phosphine and 7.36mmol of bis (trimethylsilyl) sulfide are dispersed in 16mL of octadecene, and then injected into the first reaction solution at a rate of 30mL/min, the temperature is raised to 280 ℃, and the reaction is carried out for 45min, so as to obtain a second reaction solution containing ZnInPS quantum dot cores.

(2) 666mmol zinc acetate, 700mmol myristic acid and 900ml isotridecane are mixed and heated to 130 ℃ to form a second mixed solution, degassing is carried out for 30min, and the subsequent reactions are carried out under the protection of argon. And heating to 250 ℃, injecting 640mmol of dodecylamine and 300mmol of second reaction solution into the second mixed solution at the speed of 10mL/min, and then injecting a mixed solution of 640mmol of diisobutylphosphine selenide and 66mmol of bis (trimethylsilyl) sulfide into the second mixed solution at the speed of 0.1mL/min to form a ZnSeS shell layer coated on the ZnInPS core, thereby obtaining third reaction solution. The temperature is raised to 300 ℃, 1.26L of zinc oleate and 375mmol of bis (trimethylsilyl) sulfide dispersed in 1.17L of octadecene are injected into the third reaction liquid at the rate of 0.1mL/min at the same time, and finally the temperature is kept for 10min to form a ZnS shell layer coated on the ZnSeS shell layer, so as to obtain a fourth reaction liquid.

(3) Cooling the fourth reaction solution to room temperature, adding a mixed solvent of methanol and n-butyl alcohol with the volume ratio of 1: 3 into the fourth reaction solution to precipitate the quantum dots, and centrifuging to obtain a precipitate. And dissolving the precipitate in toluene to obtain the purified ZnInPS/ZnSeS/ZnS quantum dots.

Example 3

The preparation process of the quantum dot of this example is as follows:

(1) 35mmol of myristic acid was mixed with 255.81mmol of octadecene and heated to 50 deg.C to obtain a first mixed solution. Degassing was carried out for 60min, and the reactions were all carried out under argon. At this temperature, 8.24mmol of a trimethylindium solution (dissolved in 17mL of diphenyl sulfide) and 6.54mmol of a diethylzinc solution (dispersed in 17mL of diphenyl sulfide) were uniformly injected into the first mixed solution at a rate of 20mL/min, and the temperature was raised to 150 ℃ and maintained for 30min to obtain a first reaction solution. Dispersing 16.48mmol of trioctyl phosphine selenide and 4.12mmol of bis (trimethylsilyl) sulfide in 4mL of octadecene, quickly injecting into the first reaction liquid at the speed of 40mL/min and the temperature of 150 ℃, raising the temperature to 200 ℃, and reacting for 45min to obtain a second reaction liquid containing ZnInPS quantum dot cores.

(2) 22.2mmol of zinc stearate, 23.3mmol of myristic acid and 30mL of isotridecane are mixed and heated to 100 ℃ to form a second mixed solution, degassing is carried out for 60min, and then the reactions are carried out under the protection of argon. And heating to 300 ℃, injecting 10mmol of second reaction liquid into the second mixed liquid at the speed of 10mL/min, and injecting 21.3mmol of trioctylphosphine selenide into the second mixed liquid at the speed of 2mL/min to form a ZnSe shell layer coated on the ZnInPS core, thereby obtaining a third reaction liquid. And raising the temperature to 350 ℃, injecting 42mL of zinc oleate and 12.5mmol of bis (trimethylsilyl) sulfide dispersed in 39mL of octadecene into the third reaction solution at the same time, reacting for 40min, and finally preserving the temperature for 10min to form a ZnS shell layer coated on the ZnSe shell layer to obtain a fourth reaction solution.

(3) And cooling the fourth reaction solution to room temperature, adding a mixed solvent of methanol and n-butyl alcohol in a volume ratio of 1: 3 into the fourth reaction solution to precipitate the quantum dots, and centrifuging to obtain a precipitate. And dissolving the precipitate in toluene to obtain the purified ZnInPS/ZnSe/ZnS quantum dot.

Example 4

The preparation process of the quantum dot of the embodiment is as follows:

(1) 35mmol of octadecanoic acid and 255.81mmol of octadecene were mixed and heated to 150 ℃ to obtain a first mixed solution. Degassing was carried out for 10min, and the reactions were all carried out under argon. At this temperature, 8.24mmol of trimethylindium solution (dissolved in 17mL of biphenyl) and 1.81mmol of zinc oleate solution were uniformly injected into the first mixed solution at an injection rate of 15mL/min, and the temperature was raised to 200 ℃ and maintained for 45min to obtain a first reaction solution. Dispersing 4.12mmol of tris (trimethylsilyl) phosphine and 2.47mmol of bis (trimethylsilyl) sulfide in 4mL of octadecene, rapidly injecting into the first reaction solution at the temperature of 200 ℃ at the speed of 30mL/min, raising the temperature to 300 ℃, and reacting for 30min to obtain a second reaction solution containing ZnInPS quantum dot cores.

(2) 22.2mmol of zinc stearate, 23.3mmol of myristic acid and 30mL of isotridecane are mixed and heated to 150 ℃ to form a second mixed solution, degassing is carried out for 60min, and then all reactions are carried out under the protection of argon. And heating to 270 ℃, injecting 10mmol of second reaction liquid into the second mixed solution at the rate of 20mL/min, and then injecting a mixed solution of 21.3mmol of trioctylphosphine selenide and 2.2mmol of bis (trimethylsilyl) sulfide into the second mixed solution at the rate of 1mL/min to form a ZnSeS shell layer coated on the ZnInPS core, thereby obtaining third reaction liquid. And raising the temperature to 340 ℃, injecting 42mL of zinc oleate and 12.5mmol of bis (trimethylsilyl) sulfide dispersed in 39mL of octadecene into the third reaction solution at the same time, reacting for 50min, and finally preserving the temperature for 10min to form a ZnS shell layer coated on the ZnSeS shell layer to obtain a fourth reaction solution.

(3) And cooling the fourth reaction solution to room temperature, adding a mixed solvent of methanol and n-butyl alcohol in a volume ratio of 1: 3 into the fourth reaction solution to precipitate the quantum dots, and centrifuging to obtain a precipitate. And dissolving the precipitate in toluene to obtain the purified ZnInPS/ZnSeS/ZnS quantum dots.

Example 5

The preparation process of the quantum dot of the embodiment is as follows:

(1) 35mmol of oleic acid and 255.81mmol of octadecene were mixed and heated to 90 ℃ to obtain a first mixed solution. Degassing was carried out for 60min, and the reactions were all carried out under argon. The temperature was maintained at 90 ℃ while injecting uniformly 8.24mmol of indium chloride solution (dissolved in 17mL of octadecene) and 24.72mmol of diethyl zinc solution (dispersed in 17mL of octadecene) at an injection rate of 10mL/min into the first mixed solution, and the temperature was raised to 140 ℃ and maintained for 30min to obtain a first reaction solution. Dispersing 16.48mmol of tris (dimethylamino) phosphine and 8.24mmol of bis (trimethylsilyl) sulfide in 4mL of octadecene, rapidly injecting into the first reaction solution at the temperature of 140 ℃ at the speed of 20mL/min, raising the temperature to 270 ℃, and reacting for 45min to obtain a second reaction solution containing ZnInPS quantum dot cores.

(2) 22.2mmol of zinc stearate, 23.35mmol of myristic acid and 30mL of isotridecane are mixed and heated to 120 ℃ to form a second mixed solution, degassing is carried out for 30min, and then the reactions are carried out under the protection of argon. And heating to 285 ℃, injecting 10mmol of second reaction liquid into the second mixed liquid at the speed of 15mL/min, and injecting a mixed solution of 21.3mmol of trioctyl phosphine selenide and 2.2mmol of bis (trimethylsilyl) sulfide into the second mixed liquid at the speed of 0.1mL/min to form a ZnSeS shell layer coated on the ZnInPS core, thereby obtaining a third reaction liquid. And raising the temperature to 320 ℃, simultaneously injecting 42mL of zinc oleate and 12.5mmol of bis (trimethylsilyl) sulfide dispersed in 39mL of octadecene into the third reaction solution again, injecting for 60min, and keeping the temperature for 10min to form a ZnS shell coated on the ZnSeS shell, thereby obtaining a fourth reaction solution.

(3) Cooling the fourth reaction solution to room temperature, adding a mixed solvent of methanol and n-butanol with the volume ratio of 1: 3 into the fourth reaction solution to precipitate the quantum dots, and centrifuging to obtain a precipitate. And dissolving the precipitate in toluene to obtain the purified ZnInPS/ZnSeS/ZnS quantum dot.

Comparative example 1

The preparation process of the quantum dot in comparative example 1 is different from that of the quantum dot in example 1 in that: the step (1) is as follows: mixing 35mmol of oleic acid and 245.8mmol of octadecene, heating to 90 ℃ to obtain a first mixed solution, degassing for 30min, and carrying out the subsequent reactions under the protection of argon. The temperature was maintained at 90 ℃ and 8.24mmol of trimethylindium solution (dissolved in 20mL of octadecene) was injected uniformly at an injection rate of 10mL/min, and then the temperature was raised to 100 ℃ and maintained for 30min to obtain a first reaction solution. 17.8mmol of tris (trimethylsilyl) phosphine was dispersed in 4mL of octadecene, and then rapidly injected into the first reaction solution at 100 ℃ at a rate of 30mL/min, and the temperature was raised to 280 ℃ to react for 45min, thereby obtaining a second reaction solution containing InP quantum dot nuclei.

The steps (2) and (3) are respectively the same as the steps (2) and (3) in the embodiment 1, and InP/ZnSeS/ZnS quantum dots are obtained.

Comparative example 2

The preparation process of the quantum dot in comparative example 2 is different from that of the quantum dot in example 1 in that: in comparative example 2, T1 was 90 ℃, T2 was 90 ℃, T3 was 230 ℃, T4 was 130 ℃, T5 was 200 ℃ and T6 was 250 ℃. Wherein T1 is the temperature of the first mixed solution, T2 is the temperature of the first reaction solution, T3 is the temperature of the second reaction solution, T4 is the temperature of the second mixed solution, T5 is the temperature of the third reaction solution, and T6 is the temperature of the fourth reaction solution.

Comparative example 3

The preparation process of the quantum dot in comparative example 3 is different from that of the quantum dot in example 1 in that: in comparative example 3, v1 was 30mL/min, v2 was 10mL/min, v3 was 5mL/min, v4 was 2.5mL/min, and v5 was 2.5mL/min. Where v1 denotes an injection rate of the first zinc source and the indium source into the first mixed liquid, v2 denotes an injection rate of the phosphorus source and the first sulfur source into the first mixed liquid, v3 denotes an injection rate of the third ligand and the second mixed liquid into the second mixed liquid, v4 denotes an injection rate of the selenium source and the second sulfur source into the second mixed liquid, and v5 denotes an injection rate of the third zinc source and the third sulfur source into the third mixed liquid.

Comparative example 4

The quantum dot in comparative example 4 was prepared as follows:

(1) 35mmol of oleic acid and 255.8mmol of octadecene were mixed and heated to 300 ℃ to obtain a first mixed solution. And degassing the first mixed solution for 30min, and then carrying out the reaction under the protection of argon. Simultaneously, 8.24mmol of trimethylindium solution (dissolved in 17mL of octadecene) and 10.54mmol of diethylzinc solution (dispersed in 17mL of octadecene) were added to the first mixed solution to obtain a first reaction solution. And dispersing 7.8mmol of tris (trimethylsilyl) phosphine and 1.84mmol of bis (trimethylsilyl) sulfide in 4mL of octadecene, quickly injecting into the first reaction liquid, and reacting for 60min to obtain a second reaction liquid containing ZnInPS quantum dot cores.

(2) Reducing the reaction temperature to 150 ℃, adding 22.2mmol of zinc acetate, exhausting for 30min, heating to 260 ℃, adding 21.3mmol of diisobutylphosphine selenide, reacting for 20min to form a ZnSe shell layer coated on the ZnInPS core, adding 12.5mmol of bis (trimethylsilyl) sulfide dispersed in 39mL of octadecene, and reacting for 20min to form a ZnS shell layer coated on the ZnSe shell layer to obtain a fourth reaction solution.

(3) Cooling the fourth reaction solution to room temperature, adding a mixed solvent of methanol and n-butanol with the volume ratio of 1: 3 into the fourth reaction solution to precipitate the quantum dots, and centrifuging to obtain a precipitate. And dissolving the precipitate in toluene to obtain the purified ZnInPS/ZnSe/ZnS quantum dots.

Comparative example 5

The quantum dot in comparative example 5 was prepared as follows:

(1) Mixing 120mol of oleic acid and 1mol of octadecene, and heating to 300 ℃ to obtain a first mixed solution. And degassing the first mixed solution for 30min, and then carrying out the reaction under the protection of argon. At the same time, 33mmol of trimethylindium solution (dissolved in 70mL of octadecene) and 42.16mmol of diethylzinc solution (dispersed in 70mL of octadecene) were uniformly injected into the first mixed solution to obtain a first reaction solution. 31.2mmol of tris (trimethylsilyl) phosphine and 7.36mmol of bis (trimethylsilyl) sulfide are dispersed in 16mL of octadecene, and the mixture is rapidly injected into the first reaction solution to react for 60min, so that second reaction solution containing ZnInPS quantum dot cores is obtained.

(2) Reducing the reaction temperature to 150 ℃, adding 666mmol of zinc acetate, exhausting gas for 30min, heating to 260 ℃, adding 640mmol of diisobutylphosphine selenide, reacting for 20min to form a ZnSe shell layer coated on the ZnInPS core, adding 375mmol of bis (trimethylsilyl) sulfide dispersed in 1.17L of octadecene, and reacting for 20min to form a ZnS shell layer coated on the ZnSe shell layer to obtain a fourth reaction solution.

The radius of the core layer, the thickness of the shell layer, the number of inner shell layers, the number of outer shell layers, the emission peak, the half-peak width, and the quantum yield of the quantum dots obtained in examples 1 to 5 and comparative examples 1 to 5 were respectively tested, and the test results are shown in table 1. The radius of a core layer and the thickness of a shell layer of the quantum dot are tested by adopting a JEM-2100TEM transmission electron microscope, and the number of layers of an inner shell layer and the number of layers of an outer shell layer are calculated according to the following formula: the number of layers of the inner shell layer = (inner shell layer radius-core layer radius)/thickness of each layer, and the number of layers of the outer shell layer = (outer shell layer radius-inner shell layer radius)/thickness of each layer, in this context, the outer shell layer radius is the thickness of the shell layer, and each layer thickness is 0.23nm. And (3) testing the emission peak of the quantum dot by adopting a Cary Eclipse fluorescence spectrophotometer instrument, and testing the half-peak width of the quantum dot by adopting the Cary Eclipse fluorescence spectrophotometer instrument. And testing the quantum yield of the quantum dots by adopting a Labsphere QEMS-2000-PL integrating sphere fluorescence quantum testing system.

TABLE 1 Experimental data for Quantum dots in examples and comparative examples

As can be seen from table 1 above, the quantum dots prepared in examples 1 to 5 have thicker shell layers than the quantum dots in comparative examples 1 to 5, and have a larger number of layers, so that the quantum dots have narrower half-peak widths and quantum yields of 70% or more, wherein the quantum yield of the quantum dots in example 5 is as high as 78%. And as can be seen from table 1 above, the emission peak wavelength of the quantum dot prepared in the example can be adjusted from 525nm to 630nm, so that quantum dots with different luminescent colors can be obtained.

It can be seen from the experimental data of the quantum dots prepared in example 2 that the preparation method in example 2 can be used to increase the mass production of the quantum dots, and the quantum dots obtained by mass production have narrow half-peak widths and high quantum yields without significant reduction. As can be seen from comparative example 5, the quantum yield was significantly reduced after mass production using the method of comparative example 4, indicating that the preparation method using the quantum dot of the conventional comparative example 4 was not applicable to mass production.

The ultraviolet spectrum of the zninp core of the quantum dots in example 1 is shown in fig. 2. The fluorescence spectrum of the ZnInPS/ZnSeS/ZnS quantum dots in example 1 is shown in FIG. 3. A TEM image of the zninp/ZnSeS/ZnS quantum dots in example 1 is shown in fig. 4. Wherein, the ultraviolet spectrum test is carried out by adopting an ultraviolet visible spectrophotometer with the model number of Cary 4000. The fluorescence spectroscopy was performed using a Cary Eclipse fluorescence spectrophotometer. The instrument adopted for TEM test is a Labsphere QEMS-2000-PL integrating sphere fluorescence quantum test system.

As can be seen from FIG. 2, the absorption peak of the ZnInPS/ZnSeS/ZnS quantum dot in example 1 is 425nm. As can be seen from FIG. 3, the emission peak of the ZnInPS/ZnSeS/ZnS quantum dot is 525nm. As can be seen from fig. 4, the particle size of the quantum dot obtained in example 1 was about 6nm.

The above experimental results all show that the preparation method of the quantum dot in the embodiment can make the half-peak width of the obtained quantum dot narrower, and the quantum yield higher.

All possible combinations of the technical features of the above embodiments may not be described for the sake of brevity, but should be considered as within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent should be subject to the appended claims.

Claims

1. The quantum dot is characterized by comprising a core layer and a shell layer, wherein the core layer is made of materials comprising phosphorus, indium, zinc and sulfur, the radius of the core layer is 2-6 nm, the thickness of the shell layer is 8-16 nm, the shell layer comprises an inner shell layer coated on the core layer and an outer shell layer coated on the inner shell layer, the inner shell layer is made of ZnSeS, and the outer shell layer is made of ZnS; the number of layers of the inner shell layer is 10-20, and the number of layers of the outer shell layer is 1-10.

2. The quantum dot according to claim 1, wherein in the core layer, a molar ratio of the zinc element to the indium element is 1.1; and/or the presence of a catalyst in the reaction mixture,

the molar ratio of the phosphorus element to the indium element is 0.1 to 3.0; and/or the presence of a catalyst in the reaction mixture,

the molar ratio of the sulfur element to the indium element is 0.1 to 2.0.

3. The quantum dot of claim 1, wherein the ratio of the thickness of the shell layer to the radius of the core layer is 1.

4. The quantum dot of claim 1, wherein the number of inner shell layers is 10 to 15, and the number of outer shell layers is 7 to 10.

5. A method for preparing the quantum dot as claimed in any one of claims 1 to 4, comprising the steps of:

6. The method of claim 5, wherein the step of adding a first zinc source and an indium source to the first mixed solution comprises: respectively preparing the first zinc source and the indium source into solutions, and simultaneously injecting the solutions into the first mixed solution at a rate of 10-20 mL/min; and/or the presence of a catalyst in the reaction mixture,

7. The method for preparing a quantum dot according to claim 5, wherein the step of mixing at least one of a selenium source and a second sulfur source with the second reaction solution and the second mixed solution comprises: the second reaction solution is injected into the second mixed solution at a rate of 10-20 mL/min, and then at least one of the selenium source and the second sulfur source is injected into the second mixed solution at a rate of 0.1-2.0 mL/min.

8. The method of claim 5, wherein the step of adding a third zinc source and a third sulfur source to the third reaction solution comprises: and preparing a solution from the third zinc source and the third sulfur source, and injecting the solution into the third reaction solution at the speed of 0.1-2.0 mL/min.

9. The method for preparing quantum dots according to claim 5, wherein the step of adding the first zinc source and the indium source into the first mixed solution and then heating to 100 ℃ to 200 ℃ for reaction is carried out at 130 ℃ to 150 ℃ for 1min to 60min.

10. The method for preparing the quantum dot according to claim 5, wherein the step of adding the phosphorus source and the first sulfur source into the first reaction solution and then heating to 200-300 ℃ for reaction is carried out at 250-280 ℃ for 10-100 min.