CN113388393B

CN113388393B - Method for preparing InP@ZnS core-shell quantum dots through supergravity reactor and obtained InP@ZnS core-shell quantum dots

Info

Publication number: CN113388393B
Application number: CN202110642064.1A
Authority: CN
Inventors: 蒲源; 冯子墨; 王丹; 周玉波; 刘欣然; 王洁欣; 陈建峰
Original assignee: Beijing University of Chemical Technology; Ningbo Solartron Technology Co Ltd
Current assignee: Beijing University of Chemical Technology; Ningbo Solartron Technology Co Ltd
Priority date: 2021-06-09
Filing date: 2021-06-09
Publication date: 2023-05-09
Anticipated expiration: 2041-06-09
Also published as: CN113388393A

Abstract

The invention discloses a method for preparing InP@ZnS core-shell quantum dots through a hypergravity reactor and the obtained InP@ZnS core-shell quantum dots. According to the method, sulfur source, zinc source and InP core quantum dots are used as reaction precursor materials, long-chain carboxylic acid is used as a stabilizer, liquid paraffin is used as a solvent, and shell coating is carried out in a hypergravity reactor to obtain the InP@ZnS core-shell quantum dots. The method has the advantages of simple synthesis process, reduced reaction temperature and reaction time, saved cost, and environment friendliness due to the adoption of the green organic solvent liquid paraffin as the solvent in the shell coating process. The application of the hypergravity reactor not only greatly reduces the reaction time, but also plays a key role in the uniformity and the repeatability of the product, and the production process is quick, thereby being beneficial to large-scale industrial production.

Description

Method for preparing InP@ZnS core-shell quantum dots through supergravity reactor and obtained InP@ZnS core-shell quantum dots

Technical Field

The invention belongs to the field of material synthesis. More particularly, the invention relates to a method for preparing InP@ZnS core-shell quantum dots by a hypergravity reactor and the obtained InP@ZnS core-shell quantum dots.

Background

Quantum dots are nanocrystals which are interposed between bulk material and molecules, composed of a small number of atoms, and have a particle size of about 1-10nm. The InP quantum dot can well replace quantum dots containing cadmium and lead due to low toxicity and good luminescence characteristic based on the quantum dot, and the band gap adjustable performance covers the whole visible light range, so that the InP quantum dot has extremely high application prospect in the field of commercial electronic display. However, the pure InP quantum dot has a larger specific surface area, and the existence of surface defects quenches the luminescence property of the pure InP quantum dot, so that an inorganic semiconductor shell layer with a large cladding forbidden band width is generally adopted in the research field to enhance the optical properties of the pure InP quantum dot, wherein the lattice mismatch rate of ZnS and InP is smaller and is 7.8%, so that ZnS is adopted as a shell layer cladding material of the InP quantum dot, and the luminescence property of the core-shell quantum dot is improved. At present, methods for coating ZnS shell layers on InP quantum dots mainly comprise a thermal injection method and a solvothermal method, but the methods have defects. The long-time reaction temperature and reaction time and the use of toxic organic solvents limit the application of the method from the aspect of reaction conditions, and the method has low batch-to-batch repeatability, low yield and high cost from the aspect of engineering, and is unfavorable for the commercial production of enterprises. Therefore, the preparation of the InP@ZnS core-shell quantum dot by shell cladding through the selection of economical raw materials and the simple, convenient and quick cost-reducing synthesis process has extremely high research value.

The super gravity means that the material is accelerated by gravity (9.8 m/s ² ) In a much larger environment, the substance is subjected to forces (including attractive or repulsive forces). Under the supergravity environment, the molecular diffusion and interphase mass transfer processes among molecules with different sizes are much faster than those under the conventional gravity field, the two phases generate flow contact in a porous medium or a pore canal under the supergravity environment, the liquid is torn into a liquid film, a liquid wire and liquid drops with micron to nanometer level by huge shearing force, a huge fast updated phase interface is generated, the interphase mass transfer rate is improved by 1-3 orders of magnitude compared with that in the conventional stirring kettle, and the micromixing and mass transfer processes are greatly enhanced. According to the invention, the InP@ZnS core-shell quantum dots can be produced by the super-gravity method, so that the particle uniformity can be effectively optimized, and the production scale can be enlarged.

Disclosure of Invention

Based on the background technology, the invention provides a method for preparing InP@ZnS core-shell quantum dots by a hypergravity reactor and the obtained InP@ZnS core-shell quantum dots. The application of the hypergravity reactor not only greatly reduces the reaction time, but also plays a key role in the uniformity and the repeatability of the product, and the production process is quick, thereby being beneficial to large-scale industrial production.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

the invention provides a method for preparing InP@ZnS core-shell quantum dots by a supergravity reactor, which uses a sulfur source, a zinc source and the InP core-shell quantum dots as reaction precursor materials, long-chain carboxylic acid as a stabilizer and liquid paraffin as an organic solvent, and carries out shell coating in the supergravity rotating packed bed reactor to obtain the InP@ZnS core-shell quantum dots.

In the InP@ZnS core-shell quantum dot, the core is an InP core quantum dot, and the shell is ZnS.

Preferably, the method according to the invention comprises the following steps:

dispersing InP core quantum dots in liquid paraffin to obtain an InP core quantum dot solution; preferably, the concentration of the InP core quantum dot solution is 0.5mol/L;

adding a zinc source into liquid paraffin, and adding oleic acid and the InP core quantum dot solution to obtain a zinc precursor oil phase solution; preferably, this step is carried out in a protective atmosphere, such as a nitrogen atmosphere; or directly using nitrogen to purge;

adding a sulfur source and an emulsifier into ultrapure water to obtain a sulfur precursor aqueous phase solution;

adding the zinc precursor oil phase solution and the sulfur precursor aqueous phase solution into a hypergravity reactor to carry out shell coating;

and adding a poor solvent into the mixture after the shell coating is completed for centrifugal separation, wherein the obtained precipitate is the InP@ZnS core-shell quantum dot, and preferably, the poor solvent is ethanol or acetone.

Preferably, the long-chain carboxylic acid is selected from one or a combination of two or more of stearic acid, myristic acid and oleic acid, based on the method of the invention.

Preferably, the zinc source is selected from one or a combination of two or more of zinc stearate, zinc oleate and anhydrous zinc acetate.

Preferably, the sulfur source is selected from one or a combination of two or more of sodium sulfide nonahydrate, sodium sulfide pentahydrate and sodium sulfide anhydrous.

Preferably, the emulsifier is selected from one or a combination of more than two of Tween-20, tween-80, span-20 and Span-80, based on the method of the present invention.

Preferably, the zinc source concentration in the zinc precursor oil phase solution is 20mmol/L-100mmol/L; the volume ratio of the liquid paraffin to the stabilizer in the zinc precursor oil phase solution is (5-10): 1.

preferably, the concentration of the sulfur source in the aqueous solution of the sulfur precursor is 20mmol/L to 100mmol/L; the volume ratio of the emulsifier to the ultrapure water is 1 (100-200).

Preferably, the method according to the present invention further comprises: and dispersing the InP@ZnS core-shell quantum dots in an organic solvent to obtain an InP@ZnS core-shell quantum dot dispersion.

Preferably, the organic solvent is selected from one or a combination of more than two of n-hexane, cyclohexane, toluene, liquid paraffin, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, dichloromethane and chloroform.

Preferably, the high gravity reactor is a high gravity rotating packed bed reactor based on the method of the invention; in the shell coating process, the rotating speed of the super-gravity rotating packed bed reactor is 500rpm-2000rpm, and the shell coating time is 1s-60min.

Preferably, the zinc precursor oil phase solution and the sulfur precursor aqueous phase solution are added into the hypergravity reactor through peristaltic pumps; more preferably, the feeding flow rate of peristaltic pumps corresponding to the zinc precursor oil phase solution and the sulfur precursor water phase solution is 1: (0.5-2); the specific feeding is carried out simultaneously.

Based on the method of the present invention, preferably, the InP core quantum dot is prepared by:

adding tris (dimethylamino) phosphine, indium chloride, zinc chloride, oleylamine and toluene into a polytetrafluoroethylene-lined hydrothermal kettle liner, then placing the kettle into a hydrothermal kettle, and reacting for 6-48h at the temperature of 150-180 ℃ in an oven;

adding a poor solvent into the mixture after the reaction is finished for centrifugal separation, and obtaining a precipitate, namely the InP nuclear quantum dot; the poor solvent is preferably absolute ethanol or acetone, and the poor solvent is added to precipitate the product.

Preferably, according to the method of the present invention, the molar ratio of tris (dimethylamino) phosphine to indium chloride is (0.5-2) In terms of the element P: in: 1, for example (1-2): 1, preferably 2:1. The zinc chloride is prepared from the following components in parts by weight: the molar ratio of In element is (0.5-2): 1, for example (0.5-1): 1, preferably 1:1. preferably, the volume ratio of the oleylamine to toluene is 3:8.

In addition, the specification of the hydrothermal kettle used is 50-200mL, and at this time, the addition amount of toluene is 24-80mL.

Compared with the thermal injection method and the solvothermal method used by the commercial InP@ZnS core-shell quantum dots at present, the invention adopts an ultra-gravity method, and has obvious improvement in the aspects of quantum dot reaction conditions, controllable size, green products and mass preparation. In the method, liquid paraffin is adopted as an organic solvent in the shell coating process, and compared with the organic solvents such as normal hexane, toluene, chloroform and the like, the method has the advantages of stable property, no toxicity, no harm and low cost, and ensures laboratory preparation and large-scale industrial production.

The invention provides a preferred scheme, namely a method for preparing InP@ZnS core-shell quantum dots by using a supergravity rotating packed bed reactor, wherein tris (dimethylamino) phosphine, indium chloride and zinc chloride are used as reactants, oleylamine is used as a stabilizer, toluene is used as a solvent, and the InP core-shell quantum dots are prepared in a hydrothermal kettle; and then sodium sulfide nonahydrate, zinc stearate and InP core quantum dots are used as reaction precursor materials, long-chain carboxylic acid is used as a stabilizer, liquid paraffin is used as an organic solvent, and the precursor solution is introduced into a super-gravity rotating packed bed reactor for shell coating. The preparation method specifically comprises the following steps:

1) And (3) taking tri (dimethylamino) phosphine, indium chloride and zinc chloride, adding the tri (dimethylamino) phosphine, indium chloride and zinc chloride into a liner of a hydrothermal kettle with a polytetrafluoroethylene liner, adding oleylamine and toluene, then placing the mixture into the hydrothermal kettle, and reacting for 24 hours at 180 ℃ in an oven.

2) Adding a large amount of absolute ethyl alcohol into the mixture to separate in a centrifuge, and dispersing the separated product in liquid paraffin through ultrasonic treatment to obtain InP nuclear quantum dot solution.

3) Zinc stearate is taken as a zinc source, added into liquid paraffin, and after nitrogen treatment, quantitative oleic acid and InP nuclear quantum dots are added, and the mixture is stirred at a certain temperature to obtain a zinc precursor oil phase solution.

4) Sodium sulfide nonahydrate is taken as a sulfur source, an emulsifier is added into ultrapure water, and stirring is carried out at room temperature to obtain a sulfur precursor aqueous phase solution.

5) And (3) simultaneously introducing the zinc precursor oil phase solution prepared in the step (3) and the sulfur precursor aqueous phase solution prepared in the step (4) into a supergravity rotating packed bed reactor through a peristaltic pump, and coating the shell under the supergravity environment.

6) After the shell coating process is finished, separating the mixture of the zinc precursor oil phase solution and the sulfur precursor aqueous phase solution in a centrifuge by adding a large amount of absolute ethyl alcohol, and dispersing the separated product in an organic reagent by ultrasonic treatment to obtain the final product InP@ZnS core-shell quantum dot dispersion.

The invention also provides the InP@ZnS core-shell quantum dot prepared by the method.

According to the InP@ZnS core-shell quantum dot disclosed by the invention, the emission spectrum of the InP@ZnS core-shell quantum dot is preferably 540-700 nm.

The InP@ZnS core-shell quantum dots according to the invention preferably have a particle size distribution centered at 3-7nm.

The method adopts a supergravity rotating packed bed reactor to prepare InP@ZnS core-shell quantum dots, and the characterization results of a Transmission Electron Microscope (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction analysis (XRD) show that: compared with the traditional quantum dot preparation method, the method provided by the invention has the advantages that the mass transfer is enhanced by using the supergravity rotating packed bed reactor, the InP core is coated with the ZnS shell layer in a short time at low temperature, and the InP@ZnS core-shell quantum dot which is uniform and stable, long in fluorescence quantum life and good in dispersion effect in an organic solvent is prepared. Wherein, liquid paraffin is used as an organic solvent in a reaction medium, so that the reaction process is environment-friendly, and the particle size distribution is concentrated at 3-7nm.

Drawings

Fig. 1 is an emission spectrum of inp@zns core-shell quantum dots prepared in example 1.

Fig. 2 is an X-ray diffraction (XRD) pattern of inp@zns core-shell quantum dots prepared in example 1.

Fig. 3 is an X-ray photoelectron spectroscopy (XPS) spectrum of inp@zns core-shell quantum dots prepared in example 1.

Fig. 4 is a Transmission Electron Microscope (TEM) image of inp@zns core-shell quantum dots prepared in example 1.

Fig. 5 is a High Resolution Transmission Electron Microscope (HRTEM) image of inp@zns core-shell quantum dots prepared in example 1.

FIG. 6 is a photograph of a dispersion of InP@ZnS core-shell quantum dots prepared in example 1 under sunlight and 365nm excitation light.

Fig. 7 is a graph of particle size distribution analysis of inp@zns core-shell quantum dots prepared in example 1.

Fig. 8 is a graph comparing fluorescence quantum yields of inp@zns core-shell quantum dots prepared in example 2.

Fig. 9 is a graph comparing fluorescence quantum yields of inp@zns core-shell quantum dots prepared in example 3.

Fig. 10 is a graph comparing fluorescence quantum yields of inp@zns core-shell quantum dots prepared in example 4.

Fig. 11 is an emission spectrum of inp@zns core-shell quantum dots prepared in example 5.

Fig. 12 is an emission spectrum of inp@zns core-shell quantum dots prepared in comparative example 1.

Fig. 13 is a Transmission Electron Microscope (TEM) image of inp@zns core-shell quantum dots prepared in comparative example 1.

Fig. 14 is an emission spectrum of inp@zns core-shell quantum dots prepared in comparative example 2.

Fig. 15 is a Transmission Electron Microscope (TEM) image of inp@zns core-shell quantum dots prepared in comparative example 2.

Detailed Description

In order to more clearly illustrate the present invention, the present invention will be further described with reference to preferred embodiments. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and that this invention is not limited to the details given herein.

All numerical designations of the invention (e.g., temperature, time, concentration, weight, etc., including ranges for each) can generally be approximations that vary (+) or (-) as appropriate in 0.1 or 1.0 increments. All numerical designations are to be understood as preceded by the term "about".

Example 1

The embodiment prepares InP@ZnS core-shell quantum dots by a supergravity rotating packed bed reactor, and specifically comprises the following steps:

0.8g (3.6 mmol) of indium chloride and 0.48g (3.6 mmol) of zinc chloride are weighed into a 100mL polytetrafluoroethylene liner, 12mL of oleylamine, 32mL of toluene and 1mL (7.2 mmol) of tris (dimethylamino) phosphine are added, the mixture is put into a hydrothermal kettle after being sealed, the mixture is heated for 24 hours at 180 ℃ in an oven, and ethanol is added to purify the mixture, so as to obtain InP nuclear quantum dots.

Into a 250mL three-necked flask, 0.632g (1 mmol) of zinc stearate was added, and the obtained InP core quantum dots were dispersed in 50mL of liquid paraffin under nitrogen atmosphere, and then injected into the three-necked flask, and after 5mL of oleic acid was injected, the mixture was heated to 80℃for 20 minutes under stirring with a magnet, and the obtained zinc precursor oil phase solution was designated as solution A.

Into a 100mL beaker, 0.5g (2.1 mmol) of sodium sulfide nonahydrate and 75mL of ultrapure water were added, 1.5mL of Tween-20 was added, and the resulting sulfur precursor aqueous solution after shaking and dissolution was designated as solution B.

The rotating speed of the super-gravity rotating packed bed reactor is set to be 1000rpm, the feeding flow rate of the solution A and the solution B in a peristaltic pump is set to be 2:3, the solution A, B is introduced into the super-gravity rotating packed bed reactor through the peristaltic pump, and the discharged solution is immediately collected. Adding absolute ethyl alcohol, centrifugally separating and purifying for 3 times, obtaining precipitate, and dispersing the precipitate in n-hexane by ultrasonic to obtain the final product InP@ZnS core-shell quantum dot dispersion.

FIG. 1 is an emission spectrum of the obtained InP@ZnS core-shell quantum dot, wherein the emission peak is 640nm and is orange. Fig. 2 is an X-ray diffraction (XRD) pattern of the obtained inp@zns core-shell quantum dots, and the obtained product has InP matching peaks and a good crystal form. Fig. 3 is an X-ray photoelectron spectrum (XPS) of the obtained inp@zns core-shell quantum dot, wherein In, P, zn, S elements are present, and in addition, the InP core and ZnS quantum dot are not luminescent, whereas the product prepared in this example emits light, which proves that the InP core quantum dot successfully coats the ZnS shell layer, and the obtained product is an inp@zns core-shell quantum dot. Fig. 4 is a Transmission Electron Microscope (TEM) image of the obtained inp@zns core-shell quantum dots, which have good dispersibility. FIG. 5 is a High Resolution Transmission Electron Microscope (HRTEM) image of the resulting InP@ZnS core-shell quantum dots from which it can be estimated that the average particle size of the quantum dots is 5.1nm; fig. 6 is a photograph of a dispersion of the obtained inp@zns core-shell quantum dots under sunlight and 365nm excitation light, and it is understood that the prepared core-shell quantum dots have fluorescence and strong fluorescence effect. FIG. 7 is a graph showing the particle size distribution analysis of the InP@ZnS core-shell quantum dots, wherein the particle size distribution is concentrated at 3-7nm.

Example 2

The oleic acid injection amount in example 1 was changed to 7.5mL and 10mL, and the rest of the reaction process and conditions were unchanged.

Fig. 8 is a graph showing the comparison of fluorescence quantum yields of inp@zns core-shell quantum dot dispersions prepared at oleic acid injection levels of 5mL, 7.5mL and 10mL, and as can be seen from fig. 8, the fluorescence quantum yield of inp@zns core-shell quantum dot dispersions prepared at oleic acid injection levels of 7.5mL is the greatest.

Example 3

The injection amount of oleic acid in example 1 was changed to 7.5mL, immediately collecting the discharged solution was changed to circulation for 15 minutes, then collecting the discharged solution and circulation for 30 minutes, then collecting the discharged solution, and the rest of the reaction process and conditions were unchanged.

Fig. 9 is a graph showing the comparison of the fluorescence quantum yields of inp@zns core-shell quantum dot dispersions prepared at a cycle reaction time of 0 minutes, 15 minutes and 30 minutes, and as can be seen from fig. 9, the fluorescence quantum yield of inp@zns core-shell quantum dot dispersions prepared at a cycle reaction time of 30 minutes is the greatest.

Example 4

The injection amount of oleic acid in example 1 was changed to 7.5mL, immediately collecting the discharged solution was changed to circulation for 30 minutes, then collecting the discharged solution, the rotation speed of the super gravity rotary packed bed reactor was changed to 1500rpm and 2000rpm, and the rest of the reaction process and conditions were unchanged.

FIG. 10 is a graph showing the comparison of the fluorescence quantum yields of InP@ZnS core-shell quantum dot dispersions prepared at the supergravity level of 1000rpm, 1500rpm and 2000rpm, and shows that the fluorescence quantum yield of InP@ZnS core-shell quantum dot dispersions prepared at the supergravity level of 2000rpm is the greatest.

Example 5

Into a 250mL three-necked flask, 0.632g (1 mmol) of zinc stearate was added, and the obtained InP core quantum dots were dispersed in 50mL of liquid paraffin under nitrogen atmosphere, and then the three-necked flask was filled with 7.5mL of oleic acid, and then the mixture was heated to 120℃for 20 minutes under stirring with a magnet, and the obtained zinc precursor oil phase solution was designated as solution A.

The rotating speed of the super-gravity rotating packed bed reactor is set to be 1000rpm, the feeding flow rate of the solution A and the solution B in a peristaltic pump is set to be 2:3, the solution A, B is introduced into the super-gravity rotating packed bed reactor through the peristaltic pump to circulate for 30 minutes, and then discharged solution is collected. Adding absolute ethyl alcohol, separating and purifying for 3 times, and dispersing the obtained precipitate in n-hexane by ultrasonic to obtain the final product InP@ZnS core-shell quantum dot dispersion.

FIG. 11 is an emission spectrum of the obtained InP@ZnS core-shell quantum dot, wherein the emission peak is 700nm and is red.

Comparative example 1

The embodiment prepares InP@ZnS core-shell quantum dots by a hydrothermal kettle, and specifically comprises the following steps:

0.2g (1.5 mmol) of zinc chloride was weighed into a 100mL polytetrafluoro-liner, 0.72mL of dodecanethiol, 5mL of toluene, 1mL of oleylamine and 3mL of InP core quantum dot solution were added, and after sealing, the solution was put into a hydrothermal kettle and heated in an oven at 180℃for 6 hours. And adding absolute ethyl alcohol into the mixture, separating and purifying for 3 times, and dispersing the obtained precipitate in n-hexane by ultrasonic to obtain the final product InP@ZnS core-shell quantum dot dispersion.

Fig. 12 is an emission spectrum of the obtained inp@zns core-shell quantum dot, with an emission peak of 606nm, in orange light.

Fig. 13 is a Transmission Electron Microscope (TEM) image of the obtained inp@zns core-shell quantum dots, which have good dispersibility.

Comparative example 2

The embodiment prepares InP@ZnS core-shell quantum dots by a beaker, and specifically comprises the following steps:

Injecting the solution B into a three-neck flask containing the solution A through a 50mL injector, reacting for 15 minutes, pouring the product in the three-neck flask into a 250mL beaker, adding absolute ethyl alcohol, centrifugally separating and purifying for 3 times, and obtaining a precipitate, and dispersing the precipitate in n-hexane by ultrasonic waves to obtain the final product InP@ZnS core-shell quantum dot dispersion.

Fig. 14 is an emission spectrum of the obtained inp@zns core-shell quantum dot, with an emission peak of 620nm, in orange light.

Fig. 15 is a Transmission Electron Microscope (TEM) image of the obtained inp@zns core-shell quantum dots, which show agglomeration phenomenon and poor dispersibility.

It should be understood that the foregoing examples of the present invention are provided merely for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention, and that various other changes and modifications may be made therein by one skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A method for preparing InP@ZnS core-shell quantum dots by a hypergravity reactor is characterized in that,

weighing 0.8g of indium chloride and 0.48g of zinc chloride into 100mL of polytetrafluoroethylene liner, adding 12mL of oleylamine, 32mL of toluene and 1mL of tris (dimethylamino) phosphine, sealing, putting into a hydrothermal kettle, heating at 180 ℃ for 24 hours in an oven, adding ethanol into the mixture, and purifying to obtain InP nuclear quantum dots;

adding 0.632g of zinc stearate into a 250mL three-neck flask, dispersing the obtained InP nuclear quantum dots in 50mL liquid paraffin under nitrogen atmosphere, injecting the liquid paraffin into the three-neck flask, injecting 7.5mL oleic acid, heating to 80 ℃ for 20 minutes under stirring of a magnet, and recording the obtained zinc precursor oil phase solution as a solution A;

adding 0.5g of sodium sulfide nonahydrate and 75mL of ultrapure water into a 100mL beaker, adding 1.5mL of Tween-20, and recording the obtained sulfur precursor aqueous phase solution after shaking and dissolving as solution B;

setting the rotating speed of the super-gravity rotating packed bed reactor to 2000rpm, setting the feeding flow rate of the solution A and the solution B in a peristaltic pump to be 2:3, introducing the solution A, B into the super-gravity rotating packed bed reactor through the peristaltic pump, and collecting the discharged solution after 30 minutes of circulation; adding absolute ethyl alcohol, centrifugally separating and purifying for 3 times, obtaining precipitate, and dispersing the precipitate in n-hexane by ultrasonic to obtain the final product InP@ZnS core-shell quantum dot dispersion.