CN113845098A

CN113845098A - InP quantum dot and preparation method thereof

Info

Publication number: CN113845098A
Application number: CN202111311547.XA
Authority: CN
Inventors: 孙笑; 程陆玲
Original assignee: Hefei Funa Technology Co ltd
Current assignee: Hefei Funa Technology Co ltd
Priority date: 2021-11-08
Filing date: 2021-11-08
Publication date: 2021-12-28
Anticipated expiration: 2041-11-08
Also published as: CN113845098B

Abstract

The invention relates to the technical field of quantum dot preparation, in particular to InP quantum dots and a preparation method thereof. The preparation method of the InP quantum dot comprises the following steps: and preparing the InP quantum dots by using indium acetylacetonate as an indium source. The indium acetylacetonate is used as an indium source to prepare the InP quantum dots, so that the generation of acid gas is avoided, the generation of various phosphorus-containing compounds is avoided, and the acetylacetone generated by the reaction is beneficial to reducing InP self-nucleation and the growth of the quantum dots, so that the size uniformity of the quantum dots is finally improved.

Description

InP quantum dot and preparation method thereof

Technical Field

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

Background

Quantum Dots (QDs), also known as fluorescent semiconductor nanocrystals, have significant quantum size effects, exhibit unique electronic and optical properties, such as broad excitation spectra, narrow emission spectra, tunable emission wavelengths with size components, good light stability, and the like, and thus have potential application values in the fields of illumination, display, solar energy, biomarkers, and the like.

At present, the most applied quantum dots are binary quantum dots, the quantum dots are mainly composed of II-VI and IV-VI semiconductor elements, such as CdSe, CdTe, PbS and the like, the quantum dots contain heavy metal elements such as Cd, Pb and the like, the potential toxicity greatly limits the practical application of the quantum dots, and meanwhile, the quantum dots are bonded by ionic bonds, so that the optical structure is unstable, and the application of the quantum dots is also limited.

The InP quantum dots do not contain heavy metal elements, have the advantages of low toxicity and environmental protection, are bonded by covalent bonds, have a better optical structure compared with the traditional II-VI family element quantum dots bonded by ionic bonds, are direct band gap semiconductors, and have higher dielectric constant and larger exciton radius. Therefore, the InP quantum dots are widely used in the fields of optical communication, detection, light emitting diodes, bio-imaging, and the like.

For the synthesis of InP quantum dots, the synthetic chemistry has been far behind that of II-VI quantum dots. Currently, indium salts such as indium acetate, indium chloride and indium iodide are mainly used as indium sources for preparing InP quantum dots, and the preparation of indium precursors by using the indium salts generates a large amount of acid gas, and the acid gas and a phosphorus source P (SiMe)₃)₃Reacting to form a plurality of complexes, e.g. H₃P、H₂P(SiMe₃₎、HP(SiMe₃)₂Therefore, the development of a synthesis method with good controllability and repeatability has important significance for the use and development of the InP quantum dots.

In view of this, the invention is particularly proposed.

Disclosure of Invention

The invention aims to provide InP quantum dots and a preparation method thereof. The preparation method of InP quantum dots provided by the embodiment of the invention solves the problems of large size dispersion, poor repeatability and the like in the preparation method of InP quantum dots in the prior art.

The invention is realized by the following steps:

in a first aspect, the present invention provides a method for preparing InP quantum dots, comprising: and preparing the InP quantum dots by using indium acetylacetonate as an indium source.

In an alternative embodiment, the method comprises the following steps: indium acetylacetonate is used for forming an indium precursor, the indium precursor is used for forming a cluster intermediate, and then the cluster intermediate is used for forming InP quantum dots.

In an alternative embodiment, the step of forming the indium precursor comprises: mixing the acetylacetone indium with a first ligand in an inert gas atmosphere, keeping the mixture at 120-260 ℃ for 30-90 min, changing the inert gas atmosphere to a vacuum state, reducing the temperature to 80-150 ℃, and keeping the temperature for 30-90 min;

preferably, the temperature under the inert gas atmosphere is 180-220 ℃, and the temperature under the vacuum state is 120-140 ℃.

In alternative embodiments, the molar ratio of the indium acetylacetonate to the first ligand is 1:0.5 to 8, more preferably 1: 3;

preferably, the first ligand is saturated or unsaturated fatty acid with carbon atom more than or equal to 6;

preferably, the first ligand is at least one of palmitic acid, oleic acid, myristic acid, palmitic acid, lauric acid and stearic acid.

In an alternative embodiment, the step of forming the clustered intermediate comprises: and adding a phosphorus source and a second ligand into the indium precursor to react under the inert gas atmosphere.

In an alternative embodiment, the temperature for adding the phosphorus source and the second ligand and the reaction temperature are both 30-250 ℃, preferably 130-170 ℃.

In an alternative embodiment, the molar ratio of the phosphorus source to the indium acetylacetonate is 1:1 to 5, preferably 1: 2;

preferably, the molar ratio of the indium acetylacetonate to the second ligand is 1: 0.8-8, more preferably 1: 2; preferably, the second ligand is selected from at least one of oleylamine, trioctylamine, trioctylphosphine, tributylphosphine, triphenylphosphine, dioctylamine, octylamine, dodecylamine and hexadecylamine;

preferably, the phosphorus source is tris (trimethylsilyl) phosphine.

In an alternative embodiment, the step of forming InP quantum dots using the clustered intermediate comprises: and removing water and oxygen in the solvent to form an exhaust solvent, then raising the temperature of the exhaust solvent to a nucleation temperature, adding the cluster intermediate to rapidly nucleate, then adjusting the temperature to a growth temperature until the mononuclear InP quantum dots grow to a required wavelength, cooling to 80-150 ℃, adding a passivating agent to passivate for 5-20 min, cooling again, and separating to obtain the InP quantum dots.

In an optional embodiment, the nucleation temperature is 260-290 ℃, the growth temperature is always 10-30 ℃ lower than the nucleation temperature, and the molar ratio of the indium acetylacetonate to the passivating agent is 1:0.2 to 3; the passivating agent is tri-n-octyl phosphine;

preferably, the solvent is selected from one or more of octadecene, diphenyl ether, iso-tridecane and paraffin oil;

preferably, the temperature for removing water and oxygen in the solvent is 100-130 ℃, and the time is 30-60 min;

preferably, the molar ratio of the indium acetylacetonate to the solvent is 1:10 to 60, preferably 1: 30.

In a second aspect, the present invention provides an InP quantum dot prepared by the method for preparing an InP quantum dot according to any one of the preceding embodiments.

The invention has the following beneficial effects: according to the embodiment of the invention, the indium acetylacetonate is used as the indium source to prepare the InP quantum dots, so that the generation of acid gas is avoided, the generation of various phosphorus-containing compounds is avoided, and the size uniformity of the quantum dots is improved. Meanwhile, acetylacetone generated by the reaction is beneficial to reducing InP self-nucleation and further beneficial to the growth of quantum dots, thereby further improving the size uniformity.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

Fig. 1 is a diagram of the uv-vis absorption of InP quantum dots provided in example 1 of the present invention;

fig. 2 is a uv-vis absorption diagram of InP quantum dots provided in example 2 of the present invention;

fig. 3 is a uv-vis absorption diagram of InP quantum dots provided in example 3 of the present invention;

fig. 4 is a uv-vis absorption diagram of InP quantum dots prepared in example 4;

fig. 5 is a uv-visible absorption diagram of the InP quantum dots prepared in comparative example 1;

fig. 6 is a uv-visible absorption diagram of the InP quantum dots prepared in comparative example 2;

fig. 7 is a uv-visible absorption diagram of the InP quantum dots prepared in comparative example 3.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The embodiment of the invention provides a preparation method of InP quantum dots, which comprises the following steps:

s1, preparation of an indium precursor:

and adding the indium acetylacetonate and the first ligand into the reaction container under an inert gas (such as argon) atmosphere, wherein the inert gas atmosphere in the reaction container is in a dynamic equilibrium state of exhaust and gas inlet, namely, gas in the reaction container is discharged, and meanwhile, continuously introducing the inert gas into the reaction container. The reaction vessel is maintained under an inert gas atmosphere, and the inert gas prevents the oxidation of the reactants and the formation of indium precursors and intermediates during the reaction. And the temperature is kept at 120-260 ℃ in the process, preferably 180-220 ℃, and the keeping time is 30-90 min. And keeping the time for fully reacting the acetylacetone indium with the first ligand, then reducing the temperature to 80-150 ℃, preferably 120-140 ℃, and keeping the temperature for 30-90 min to finally obtain the indium precursor.

Further, the first ligand is saturated or unsaturated fatty acid with carbon atom more than or equal to 6; preferably, the first ligand is at least one of palmitic acid, oleic acid, myristic acid, palmitic acid, lauric acid, and stearic acid, but the first ligand is not limited to the above-mentioned fatty acids. The first ligand has a great influence on the quality of the InP quantum dots, and the preferred fatty acid not only allows the subsequent seed formation to react at an optimal rate, but also makes the size of the seed uniform.

The acetylacetone indium is adopted as the indium source, so that acid gas can be prevented from being generated, and acetylacetone generated by the reaction of the acetylacetone indium and the first ligand is beneficial to the growth of quantum dots, so that the size uniformity of the quantum dots is improved.

Further, the molar ratio of the indium source to the first ligand directly affects the size dispersibility of the quantum dots and finally affects the performance of the quantum dots, and the indium source and the first ligand can make the size of the InP quantum dots very uniform and have monodispersity at a proper feed ratio, so that the molar ratio of the indium acetylacetonate to the first ligand in the embodiment of the invention is 1: 0.5-8, and more preferably 1: 3.

S2, preparation of a clustering intermediate:

and adding a phosphorus source and a second ligand into the indium precursor to react under the atmosphere of inert gas (such as argon), so as to obtain a cluster intermediate containing both cations and anions. The indium precursor prepared in the S1 is kept in an inert gas atmosphere, a certain amount of phosphorus source and second ligand are rapidly injected at a certain temperature to be mixed and reacted with the indium precursor, and after a certain time of reaction, a cluster intermediate containing both cations and anions is obtained. Among the phosphorus sources in the examples of the present invention are tris (trimethylsilyl) phosphine.

The proportion of the phosphorus source and the acetylacetone indium, the injection temperature of the phosphorus source and the reaction temperature can influence the performance of the quantum dots, so that in the embodiment of the invention, the temperature for adding the phosphorus source and the reaction temperature are both 30-250 ℃, and preferably 130-170 ℃. The molar ratio of the phosphorus source to the indium acetylacetonate is 1: 1-5, preferably 1: 2; the performance of the InP quantum dots can be improved by adopting the proportion and the temperature.

Further, the second ligand is at least one selected from oleylamine, trioctylamine, trioctylphosphine, tributylphosphine, triphenylphosphine, dioctylamine, octylamine, dodecylamine and hexadecylamine.

Further, the amount of the second ligand is the reaction speed and the product quality of the indium source and the phosphorus source, too little amount of the second ligand causes the reaction speed to be very fast, which is not beneficial to the control of the reaction, too much amount of the second ligand causes the quantum dot quality to be poor, and even quantum dots cannot be obtained, based on the above reasons, the molar ratio of the acetylacetone indium to the second ligand in the embodiment of the invention is 1: 0.8-8, and more preferably 1: 2.

S3, preparing InP quantum dots;

forming a degassing solvent: measuring a certain amount of solvent, placing in another three-neck flask, heating with a heating jacket in a vacuum environment to remove water and oxygen existing in the solvent, then changing the vacuum system into an exhaust system (i.e. removing gas in the flask-introducing inert gas), and keeping the solution in an argon atmosphere all the time to obtain the exhaust solvent.

Wherein the solvent is one or more selected from octadecene, diphenyl ether, iso-tridecane and paraffin oil;

meanwhile, water and oxygen existing in the solvent are harmful to the fluorescence performance of the quantum dots, so that the water and the oxygen existing in the solvent need to be removed firstly, and the water and the oxygen can be sufficiently removed at proper temperature and time to ensure the smooth preparation of the quantum dots. Based on this, in the embodiment of the invention, the temperature for removing water and oxygen is 100-130 ℃ and the time is 30-60 min.

Furthermore, the solvent provides an environment for nucleation and growth of the InP quantum dots, and too much solvent is not favorable for subsequent extraction of the InP quantum dots, which also causes unnecessary waste, and too little solvent is not favorable for good nucleation and growth of the InP quantum dots. Therefore, in the embodiment of the present invention, the molar ratio of the indium acetylacetonate to the solvent is 1:10 to 60, and more preferably 1: 30.

Nucleation and growth of InP quantum dots: raising the temperature of the exhaust solvent to a nucleation temperature, adding a cluster intermediate formed by rapid S2 to rapidly nucleate InP quantum dots at a high temperature, adjusting the temperature to a growth temperature to allow the mononuclear InP quantum dots to grow at a low temperature until the mononuclear InP quantum dots grow to a required wavelength, cooling to 80-150 ℃ (for example, blowing a three-neck flask with a nitrogen gun to rapidly cool the mononuclear InP quantum dots), adding a passivator to passivate the quantum dots for 5-20 min, cooling (for example, cooling to 90 ℃ with a nitrogen gun and naturally cooling to room temperature), taking out magnetons, and blowing an inert gas (such as argon) to protect the quantum dots to prevent InP from being oxidized to obtain the mononuclear InP quantum dots, and then cleaning with ethanol for three times to finally obtain the clean and high-quality mononuclear InP quantum dots.

From the cluster intermediate to the InP quantum dots, different temperatures are needed for nucleation and growth of the quantum dots, higher temperature is needed for high-quality rapid nucleation for nucleation, and lower temperature is needed for growth to make the sizes of the quantum dots more uniform, so that in the embodiment of the invention, the nucleation temperature is 290-260 ℃, and the growth temperature is always 10-30 ℃ lower than the nucleation temperature.

Further, many defects and dangling bonds exist on the surface of the mononuclear InP quantum dot generated by the reaction, which is not favorable for the performance and stability of the mononuclear InP quantum dot. Thus, in the present examples, tri-n-octylphosphine was used as a passivating agent to passivate mononuclear InP quantum dots. Meanwhile, due to the proper using amount, the passivation effect can be good, and the luminescent property of a quantum dot is improved, so that the feeding ratio of the acetylacetone indium to the tri-n-octylphosphine is 1: 0.2-3 in the embodiment of the invention.

Furthermore, some impurities and reactants can remain in the stock solution of the mononuclear InP quantum dot, and in the method, the InP quantum dot is cleaned by using ethanol for three times, so that the mononuclear InP quantum dot with high cleanness and high quality is obtained.

The preparation method of the InP quantum dots provided by the embodiment of the invention increases the size uniformity of the quantum dots, improves the preparation process of the InP quantum dots at present and improves the repeatability of experiments.

The embodiment of the invention also provides the InP quantum dot which is prepared by the preparation method of the InP quantum dot.

The features and properties of the present invention are described in further detail below with reference to examples.

Example 1

Indium acetylacetonate (C) for use in this example₁₅H₂₁lnO₆) The InP quantum dots are prepared by taking indium source, Palmitic Acid (PA) as a first ligand and tri-n-octylphosphine (TOP) as a second ligand, and the specific process is as follows:

1) weigh 3.6mmol C₁₅H₂₁lnO₆And 10.8mmol of PA are put in a 50ml three-neck flask, the three-neck flask is kept under Ar atmosphere, a heating sleeve is used for heating to 240 ℃ and keeping for 45min, then the temperature is reduced to 180 ℃, an exhaust system is changed into a vacuum system and kept for 30min, and an indium source precursor is obtained;

2) keeping the reaction system prepared above in inert gas, cooling to 170 deg.C, and rapidly injecting 0.80mmol TMS₃P and 2ml of tri-n-octyl phosphine TOP react for 5min to finally obtain a cluster intermediate;

3) placing 40mL of ODE in a 100mL three-neck flask, heating to 120 ℃, vacuumizing for 30min, heating to 270 ℃, quickly injecting the obtained cluster intermediate into the ODE, quickly cooling to 250 ℃, keeping for 8min, then cooling to 150 ℃, and adding 2mL of tri-n-octylphosphine for passivation to finally obtain the InP quantum dots.

Example 2

The embodiment provides a preparation method of an InP quantum dot, which comprises the following steps:

1) weigh 3.6mmol C₁₅H₂₁lnO₆And 9mmol oleic acid is put in a 50ml three-neck flask, kept under Ar atmosphere, heated to 260 ℃ by a heating jacket, kept for 30min, then cooled to 150 ℃, an exhaust system is changed into a vacuum system, kept for 60min, and an indium source precursor is obtained;

2) cooling the reaction system to 140 deg.C, and rapidly injecting 1.6mmol TMS₃P and 4ml of tri-n-octyl phosphine TOP react for 10min to finally obtain a cluster intermediate;

3) and (3) placing 30mL of ODE in a 100mL three-neck flask, heating to 100 ℃, vacuumizing for 50min, heating to 280 ℃, quickly injecting the obtained cluster intermediate into the ODE, cooling to 260 ℃, and keeping for 10min to finally obtain the InP quantum dots.

Example 3

1) weigh 3.6mmol C₁₅H₂₁lnO₆And 10.8mmol dodecanoic acid is put in a 50ml three-neck flask, kept under Ar atmosphere, heated to 250 ℃ by a heating jacket, kept for 30min, then cooled to 130 ℃, an exhaust system is changed into a vacuum system, kept for 90min, and an indium source precursor is obtained;

2) heating the reaction system to 170 deg.C, and rapidly injecting 1.6mmol TMS₃P and 2ml of tributyl phosphine TOP react for 2min to finally obtain a cluster intermediate;

3) and (3) placing 40mL of ODE in a 100mL three-neck flask, heating to 120 ℃, vacuumizing for 30min, heating to 290 ℃, quickly injecting the obtained cluster intermediate into the ODE, cooling to 260 ℃, and keeping for 4min to finally obtain the InP quantum dots.

Example 4

1) weigh 3,6mmol C₁₅H₂₁lnO₆And 10.8mmol palmitic acid are put in a 50ml three-neck flask, the three-neck flask is kept under Ar atmosphere, heated to 180 ℃ by a heating jacket and kept for 60min, then cooled to 120 ℃, an exhaust system is changed into a vacuum system, and the vacuum system is kept for 90min, so that an indium source precursor is obtained;

2) cooling the reaction system to 100 deg.C, and rapidly injecting 1,2mmol TMS₃P and 2ml of tri-n-octyl phosphine TOP react for 15min to finally obtain a cluster intermediate;

3) and (3) placing 60mL of ODE in a 100mL three-neck flask, heating to 130 ℃, vacuumizing for 30min, heating to 260 ℃, quickly injecting the obtained cluster intermediate into the ODE, cooling to 230 ℃, and keeping for 15min to finally obtain the InP quantum dots.

Comparative example 1: the InP quantum dots are prepared by referring to the preparation method of the InP quantum dots provided in example 1, except that the indium source is changed to indium acetate.

Comparative example 2: the InP quantum dot was prepared with reference to the preparation method of the InP quantum dot provided in example 1, except that the molar ratio of the indium source and the first ligand was changed to 1: 9.

Comparative example 3: the InP quantum dots were prepared by referring to the preparation method of InP quantum dots provided in example 1, except that the nucleation temperature was 240 ℃ and the growth temperature was 100 ℃ in an inert gas state.

And (3) detection:

the results of ultraviolet detection of the InP quantum dots prepared in examples 1 to 4 and comparative examples 1 to 3 are shown in fig. 1 to 3, where fig. 1 is a graph of ultraviolet-visible absorption of the InP quantum dots prepared in example 1, fig. 2 is a graph of ultraviolet-visible absorption of the InP quantum dots prepared in example 2, fig. 3 is a graph of ultraviolet-visible absorption of the InP quantum dots prepared in example 3, fig. 4 is a graph of ultraviolet-visible absorption of the InP quantum dots prepared in example 4, fig. 5 is a graph of ultraviolet-visible absorption of the InP quantum dots prepared in comparative example 1, fig. 6 is a graph of ultraviolet-visible absorption of the InP quantum dots prepared in comparative example 2, and fig. 7 is a graph of ultraviolet-visible absorption of the InP quantum dots prepared in comparative example 3.

According to the fig. 1-4, the first exciton peak of the prepared quantum dot is obvious, and the valley-peak ratio is kept good, which shows that the size uniformity of the quantum dot is good; while the first exciton peak of the quantum dots in fig. 5-7 is weak, even without the first exciton absorption peak, such as fig. 6, which illustrates the poor size uniformity of the quantum dots.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of InP quantum dots is characterized by comprising the following steps: and preparing the InP quantum dots by using indium acetylacetonate as an indium source.

2. The method for preparing InP quantum dots according to claim 1, comprising: indium acetylacetonate is used for forming an indium precursor, the indium precursor is used for forming a cluster intermediate, and then the cluster intermediate is used for forming InP quantum dots.

3. The method of claim 2, wherein the step of forming the indium precursor comprises: mixing the acetylacetone indium with a first ligand in an inert gas atmosphere, keeping the mixture at 120-260 ℃ for 30-90 min, changing the inert gas atmosphere to a vacuum state, reducing the temperature to 80-150 ℃, and keeping the temperature for 30-90 min;

4. The method for preparing InP quantum dots according to claim 3, wherein the molar ratio of the indium acetylacetonate to the first ligand is 1: 0.5-8, and more preferably 1: 3;

5. The method of claim 2, wherein the step of forming the cluster intermediate comprises: and adding a phosphorus source and a second ligand into the indium precursor to react under the inert gas atmosphere.

6. The method for preparing InP quantum dots according to claim 5, wherein the temperature and the reaction temperature for adding the phosphorus source and the second ligand are both 30-250 ℃, preferably 130-170 ℃.

7. The preparation method of InP quantum dots according to claim 5, wherein the molar ratio of the phosphorus source to the indium acetylacetonate is 1: 1-5, preferably 1: 2;

preferably, the molar ratio of the indium acetylacetonate to the second ligand is 1: 0.8-8, more preferably 1: 2;

preferably, the second ligand is selected from at least one of oleylamine, trioctylamine, trioctylphosphine, tributylphosphine, triphenylphosphine, dioctylamine, octylamine, dodecylamine and hexadecylamine;

preferably, the phosphorus source is tris (trimethylsilyl) phosphine.

8. The method of claim 2, wherein the step of forming the InP quantum dots using the cluster intermediate comprises: and removing water and oxygen in the solvent to form an exhaust solvent, then raising the temperature of the exhaust solvent to a nucleation temperature, adding the cluster intermediate to rapidly nucleate, then adjusting the temperature to a growth temperature until the mononuclear InP quantum dots grow to a required wavelength, cooling to 80-150 ℃, adding a passivating agent to passivate for 5-20 min, cooling again, and separating to obtain the InP quantum dots.

9. The preparation method of the InP quantum dots according to claim 8, wherein the nucleation temperature is 260-290 ℃, the growth temperature is 10-30 ℃ lower than the nucleation temperature, and the molar ratio of the indium acetylacetonate to the passivating agent is 1:0.2 to 3; the passivating agent is tri-n-octyl phosphine;

10. An InP quantum dot produced by the method for producing an InP quantum dot according to any one of claims 1 to 9.