CN113604219A - Ligand-modified CsPbBr3Quantum dot, preparation method thereof and application of ionic liquid - Google Patents

Abstract

The invention relates to ligand modified CsPbBr₃A quantum dot material, a preparation method thereof and application of an ionic liquid compound belong to the technical field of quantum dot materials. Ligand modified CsPbBr of the invention₃The preparation method of the quantum dot material comprises the following steps: carrying out solvothermal reaction on the reaction liquid; the reaction liquid comprises a Cs source, a Pb source, a ligand and a solvent; the ligand has a structure shown in a formula I. The preparation method uses the functionalized ionic liquid as a surface ligand and a bromine source at the same time to obtain the perovskite quantum which can be stably dispersed in the aqueous solutionAnd (4) point. And the adopted ionic liquid bromine salt can be used as a bromine source at the same time to separate a Br source from a Pb source, so that the defect that the traditional heat injection method adopts PbBr₂Simultaneously generating synthetic CsPbBr for Br source and Pb source₃The toxic Pb source is not reacted completely in the process, so that the toxic Pb source is lost and wasted.

Description

Ligand-modified CsPbBr3Quantum dot, preparation method thereof and application of ionic liquid

Technical Field

The invention relates to ligand modified CsPbBr₃A quantum dot material, a preparation method thereof and application of an ionic liquid compound belong to the technical field of quantum dot materials.

Background

In recent years, all-inorganic perovskite quantum dots have excellent optical properties such as large absorption cross section, small exciton confinement energy, high fluorescence quantum yield, narrow emission spectrum, unique carrier bipolar diffusion, tunable fluorescence emission wavelength and the like, and have great application prospects in the fields of solar cells, light-emitting diodes, photoelectric sensing, photocatalysis, fluorescence detection and the like.

The existing perovskite quantum dot preparation method mainly adopts a high-temperature hot injection method, but the preparation method has the following defects: (1) the reaction process is complicated: preparing a reaction solution containing a Cs source, injecting the reaction solution into the prepared reaction solution containing a Pb source and a Br source, stopping the reaction by using an ice water bath after the reaction, and then centrifuging at a high speed and washing; (2) the reaction conditions are severe: the preparation of the solution containing the Cs source and the Pb and Br source needs to be carried out by firstly vacuumizing to remove air in the three-neck bottle, then introducing nitrogen for protection and keeping the high temperature of 150-180 ℃; (3) the reaction reagents are complex: require Cs₂CO₃Is cesium source, PbBr₂Lead source and bromine source, oleic acid/oleylamine as assistant, octadecene as reaction solvent (although PbBr is used)₂A Pb source and a Br source at the same time but causes excessive and waste of a Pb source with high toxicity); (4) the use of oleic acid/oleylamine dual ligands causes quantum dots to be unstable: because the chemical combination of oleylamine/oleic acid and the surface of the quantum dot is relatively weak, when protonated oleylamine leaves the surface of the quantum dot, oleic acid or halogen is often taken away to ensure charge balance, so that a ligand is easy to fall off in the purification or use process, and the protection effect on perovskite is lost; (5) the prepared quantum dots can not be dispersed in polar solvents such as water and are unstable to the polar solvents: the prior oleic acid/oleylamine ligand is also limited by the non-polar long carbon chainThe synthesized perovskite nanocrystal has dispersibility in polar solvents such as water and ethanol. The defects greatly limit the application of the perovskite quantum dots, particularly the application in the fields of photocatalysis, biological marking and the like.

Disclosure of Invention

The invention aims to provide ligand modified CsPbB₃The preparation method of the quantum dot material is simple and convenient, and can improve CsPbB₃The quantum dots are stable in dispersion in polar solvents.

The invention also provides ligand modified CsPbB₃Quantum dot material and an ionic liquid compound.

To achieve the above object, the ligand-modified CsPbBr of the present invention₃The preparation method of the quantum dot material adopts the technical scheme that:

ligand modified CsPbBr₃The preparation method of the quantum dot material comprises the following steps: carrying out solvothermal reaction on the reaction liquid; the reaction liquid comprises a Cs source, a Pb source, a ligand and a solvent; the ligand has a structure shown in formula I:

in the formula I, R₁Is C1-C6 alkylene, R₂Is a carboxyl group or a sulfonic acid group, X^-Is Cl^-、Br^-Or I^-。

Ligand modified CsPbBr of the invention₃The preparation method of the quantum dot material prepares the perovskite quantum dot by a solvothermal synthesis method with simple reaction equipment and easily controlled reaction conditions, and overcomes the defects of complicated preparation process, harsh reaction conditions and complex reaction reagents in the traditional high-temperature hot-injection method; and creatively applies the functionalized ionic liquid as a surface ligand and a halogen source to the synthesis of the perovskite quantum dot, and finally prepares the perovskite quantum dot which can be stably dispersed in the aqueous solution. In addition, the adopted ionic liquid halogen salt can be used as a halogen source at the same time, so that the halogen source and the Pb source are separated, and the defect of the traditional hot injection method is overcomeBy using PbX₂Simultaneously generates synthesized CsPbBr for halogen source and Pb source₃The toxic Pb source is not reacted completely in the process, so that the toxic Pb source is lost and wasted.

The solvothermal method has been developed on the basis of the hydrothermal method by dissolving one or more precursors in a non-aqueous solvent to form the desired product in liquid phase or supercritical conditions. It will be appreciated that the solvent employed in the present invention is a good non-aqueous solvent for both the Cs source, the Pb source and the ligand. The solvent is preferably N-methylpyrrolidone. The solvothermal reaction is carried out in a closed high-temperature high-pressure reaction kettle. Method for preparing ligand modified CsPbBr by solvothermal method₃The quantum dot material has the advantages of simple required equipment, easily controlled reaction conditions, controllable morphology and particle size of the prepared material, and capability of avoiding the influence of air and environment on the reaction in a closed system.

Preferably, the ligand is 1-carboxybutyl-3-methylimidazolium bromide and/or 1-butylsulfonic acid-3-methylimidazolium bromide. 1-Carboxybutyl-3-methylimidazolium bromide (molecular weight 251.18) is an ionic liquid (also known as [ HOOCC ]₃mim]Br ionic liquid) due to carboxyl functional groups in the ionic liquid with CsPbB₃Pb in Quantum dots²⁺The strong coordination energy of the ions can prevent CsPbB₃Surface Pb of quantum dot²⁺Dissolution and exfoliation of ions, and Br in ionic liquids^-The presence of ions increases Br in aqueous solution^-Can also prevent CsPbB₃Surface Br of quantum dot^-The falling of ions can greatly improve CsPbB₃Stability of quantum dots. Furthermore, due to [ HOOCC₃mim]Good water solubility of Br ionic liquid, resulting in CsPbB modified by ionic liquid ligand₃The quantum dots can also have good dispersibility in polar solvents such as water.

The source of Cs may be selected from salts containing Cs. Preferably, the source of Cs is selected from Cs₂CO₃、Cs(OOCCH₃) One or any combination thereof. The Pb source may be selected from Pb-containing salts. Preferably, the Pb source is selected from Pb (OOCCH)₃)₂、Pb(acac)₂(diacetyl acetone lead) or any combination thereof.

Preferably, the molar ratio of Cs, Pb and ligand in the reaction solution is 1 (0.8-1.0) to 3.0-3.5.

Preferably, the molar concentration of Cs in the reaction liquid is 0.04-0.06 mol/L.

Preferably, the temperature of the solvothermal reaction is 150-180 ℃. The solvothermal reaction time is 10-20min, preferably 10-15 min.

Preferably, the rate of heating to the solvothermal reaction temperature is 15-20 deg.C/min.

Preferably, the ligand-modified CsPbBr is as described above₃The preparation method of the quantum dot material is characterized by comprising the following steps: further comprising the steps of: carrying out solid-liquid separation on a system obtained by the hydrothermal reaction, and washing the obtained solid; the washing liquid adopted by the washing is a mixed liquid of ethyl acetate and ethanol. And before solid-liquid separation, naturally cooling the hydrothermal reaction system to room temperature. The solid-liquid separation is preferably performed by centrifugation. The rotating speed of the centrifugal treatment is 8000r/min, and the time is 15 minutes.

Preferably, the volume ratio of the ethyl acetate to the ethanol in the washing liquid is 1: 2-4.

Ligand modified CsPbB of the invention₃The technical scheme adopted by the quantum dot material is as follows:

ligand modified CsPbB₃Quantum dot materials, including CsPbBr₃Quantum dots and adsorption on CsPbBr₃A ligand modifier on the surface of the quantum dot, wherein the ligand modifier has a structure shown in a formula I:

in the formula I, R₁Is C1-C6 alkylene, R₂Is a carboxyl group or a sulfonic acid group, X^-Is Cl^-、Br^-Or I^-。

Ligand modified CsPbB of the invention₃The quantum dot material is modified in CsPbB by taking an ionic liquid compound shown as a formula I as a surface ligand₃The surface of the quantum dot can improve CsPbB₃Stability of quantum dotsAlso, CsPbB can be used₃The quantum dots have good aqueous solution dispersibility, so that the defects that the quantum dots are unstable and the prepared quantum dots cannot be dispersed in a polar solvent due to the use of the traditional oleic acid/oleylamine double ligand are overcome.

Preferably, the ligand is 1-carboxybutyl-3-methylimidazolium bromide.

The technical scheme adopted by the application of the ionic liquid compound is as follows:

an ionic liquid compound shown as formula I is used as CsPbBr₃Application of quantum dot modified ligand:

in the formula I, R₁Is C1-C6 alkylene, R₂Is a carboxyl group or a sulfonic acid group, X^-Is Cl^-、Br^-Or I^-。

The ionic liquid compound of formula I is used as CsPbBr₃The quantum dot modified ligand can not only improve CsPbB₃The stability of quantum dots can also ensure that CsPbB₃The quantum dots have good aqueous solution dispersibility, so that the defects that the quantum dots are unstable and the prepared quantum dots cannot be dispersed in a polar solvent due to the use of the traditional oleic acid/oleylamine double ligand are overcome.

Drawings

FIG. 1 shows ligand-modified CsPbBr prepared in example 1₃A picture of the quantum dot material under natural light;

FIG. 2 shows ligand-modified CsPbBr prepared in example 1₃A fluorescent photograph of the quantum dot material under 365nm ultraviolet irradiation;

FIG. 3 shows ligand-modified CsPbBr prepared in example 1₃Fluorescence spectrum of the quantum dot material under 365nm ultraviolet light excitation;

FIG. 4 shows ligand-modified CsPbBr prepared in example 1₃Ultraviolet-visible absorption spectra of quantum dot materials;

FIG. 5 shows ligand-modified CsPbBr prepared in example 1₃A Transmission Electron Microscope (TEM) characterization picture of the quantum dot material;

FIG. 6 shows ligand-modified CsPbBr prepared in example 1₃High Resolution Transmission Electron Microscopy (HRTEM) characterization photographs of quantum dot materials;

FIG. 7 shows ligand-modified CsPbBr prepared in example 1₃An X-ray diffraction (XRD) characterization curve of the quantum dot material;

FIG. 8 shows ligand-modified CsPbBr prepared in example 1₃Fluorescence spectrum of quantum dot material after 1 month of storage.

Detailed Description

The technical solution of the present invention will be further described with reference to the following embodiments.

The kettle body and the kettle cover of the reaction kettle adopted in the embodiment are made of stainless steel and are designed by screw threads, so that the kettle body and the kettle cover are directly connected to achieve a better sealing effect. The lining material is polytetrafluoroethylene, an external heating mode is adopted, the pressure in the kettle is generated by a heating medium, and the filling degree can be controlled within a certain range.

Example 1

Ligand-modified CsPbB of this example₃The preparation method of the quantum dot material comprises the following steps:

1) 0.1536g Cs (OOCCH)₃)、0.2081g Pb(OOCCH₃)₂、0.6028g[HOOCC₃mim]Adding Br ionic liquid into 20mL of N-methylpyrrolidone, stirring at room temperature until the Br ionic liquid is dissolved, and enabling the molar concentration of the Cs salt in the mixed solution to be 0.04mol/L to obtain a reaction solution; cs in the reaction solution: pb: [ HOOCC₃mim]The molar ratio of Br is 1:0.8: 3;

2) transferring the reaction solution prepared in the step 1) to a reaction kettle, placing the reaction solution in an oven, controlling the heating rate to be 20 ℃/min to 150 ℃, keeping the temperature for 10min, taking out the reaction kettle, and naturally cooling to room temperature;

3) purification and washing: opening the reaction kettle, centrifuging the reaction solution cooled in the step 2) for 15min at 8000r/min, removing supernatant, washing the precipitate twice by using a mixed solution of ethyl acetate and ethanol with the volume ratio of 1:3, and finally drying the product in vacuum to obtain a powder sample.

Ligand-modified CsPbB prepared in this example₃The quantum dot material is light brown yellow solid under natural light (shown in figure 1), and can emit bright green fluorescence under 365nm ultraviolet light irradiation (shown in figure 2).

The ligand prepared in the example is modified CsPbB respectively₃The quantum dot material is tested by ultraviolet visible absorption spectrum, fluorescence spectrum (water dispersion), transmission electron microscope, high-resolution transmission electron microscope and X-ray diffraction spectrum, and the results are respectively shown in figures 3-7. Ligand modification of CsPbB from FIG. 3₃The ultraviolet visible absorption spectrum of the quantum dot water dispersion liquid can show that the band edge absorption of the sample is 510 nm; as can be seen from the fluorescence spectrum of the sample aqueous dispersion in FIG. 4, the emission spectrum of the sample is narrow, and the corresponding emission peak is located at 520 nm; as can be seen from the TEM image of the sample in FIG. 5, the particle size is about 15 nm; from the transmission electron micrograph of this sample, it can be seen in FIG. 6 that CsPbBr was measured₃The spacing between crystal faces of the nano-crystals is 0.29nm, which is just matched with the (100) crystal face of the cubic phase perovskite nano-crystals; PDF-75# -0412 in FIG. 7 is CsPbBr₃The X-ray diffraction spectrum of the sample in fig. 7 and a standard card control, the CsPbBr₃The nanocrystalline sample had a cubic phase.

Ligand-modified CsPbBr prepared in example 1₃After the perovskite nanocrystalline water dispersion liquid is left for one month, the fluorescence spectrum of the perovskite nanocrystalline water dispersion liquid is observed and measured under 365nm ultraviolet light irradiation, and the result is shown in fig. 8. As can be seen from FIG. 8, the sample still emitted bright green fluorescence with no change in light intensity after being dispersed in the aqueous solution for one month, and the emission peak thereof was still located at 520nm and the peak shape was narrow, indicating that the prepared CsPbBr was₃The nanocrystalline sample has good stability.

Example 2

Ligand-modified CsPbB of this example₃The preparation method of the quantum dot material comprises the following steps:

1) 0.1303g of Cs₂CO₃、0.2602g Pb(OOCCH₃)₂、0.6028g[HOOCC₃mim]Adding Br ionic liquid into 20mL of N-methylpyrrolidone, stirring at room temperature until the Br ionic liquid is dissolved, and enabling the molar concentration of the Cs salt in the mixed solution to be 0.04mol/L to obtain a reaction solution; cs in the reaction solution: pb: [ HOOCC₃mim]The molar ratio of Br is 1:1: 3;

2) transferring the reaction solution prepared in the step 1) to a reaction kettle, placing the reaction solution in an oven, controlling the heating rate to be 20 ℃/min to 160 ℃, keeping the temperature for 10min, taking out the reaction kettle, and naturally cooling to room temperature;

3) purification and washing: opening the reaction kettle, centrifuging the reaction solution cooled in the step 2) for 15 minutes at 8000r/min, removing supernatant, washing the precipitate twice by using a mixed solution of ethyl acetate and ethanol with the volume ratio of 1:3, and finally drying the product in vacuum to obtain a powder sample.

Example 3

Ligand-modified CsPbB of this example₃The preparation method of the quantum dot material comprises the following steps:

1) 0.2303g Cs (OOCCH)₃)、0.4865g Pb(acac)₂、1.055g[HOOCC₃mim]Adding Br ionic liquid into 20mL of N-methylpyrrolidone, stirring at room temperature until the Br ionic liquid is dissolved, and enabling the molar concentration of the Cs salt in the mixed solution to be 0.06mol/L to obtain a reaction solution; cs in the reaction solution: pb: [ HOOCC₃mim]The molar ratio of Br is 1:1: 3.5;

2) transferring the reaction solution prepared in the step 1) to a reaction kettle, placing the reaction solution in an oven, controlling the heating rate to be 20 ℃/min to 180 ℃, keeping the temperature for 15min, taking out the reaction kettle, and naturally cooling to room temperature;

3) opening the reaction kettle, centrifuging the reaction solution cooled in the step 2) for 15 minutes at 8000r/min, removing supernatant, washing the precipitate twice by using a mixed solution of ethyl acetate and ethanol with the volume ratio of 1:3, and finally drying the product in vacuum to obtain a powder sample.

Example 4

Ligand-modified CsPbB of this example₃The preparation method of the quantum dot material comprises the following steps:

1) 0.2304g Cs (OOCCH)₃)、0.3902g Pb(OOCCH₃)₂0.98181-Butylsulfonic acid-3-methylimidazolium bromide salt [ HO ]₃SC₄mim]Adding Br ionic liquid into 20mL of N-methylpyrrolidone, stirring at room temperature until the Br ionic liquid is dissolved, and enabling the molar concentration of the Cs salt in the mixed solution to be 0.04mol/L to obtain a reaction solution; cs in the reaction solution: pb: [ HO ]₃SC₄mim]The molar ratio of Br is 1:1: 3;

2) transferring the reaction solution prepared in the step 1) to a reaction kettle, placing the reaction solution in an oven, controlling the heating rate to be 15 ℃/min to 150 ℃, keeping the temperature for 12min, taking out the reaction kettle, and naturally cooling to room temperature;

3) purification and washing: opening the reaction kettle, centrifuging the reaction solution cooled in the step 2) for 15min at 8000r/min, removing supernatant, washing the precipitate twice by using a mixed solution of ethyl acetate and ethanol with the volume ratio of 1:3, and finally drying the product in vacuum to obtain a powder sample.

Example 5

Ligand-modified CsPbB of this example₃Quantum dot materials, including CsPbBr₃Quantum dots and adsorption on CsPbBr₃The ligand modifier on the surface of the quantum dot is 1-carboxybutyl-3-methylimidazolium bromide. Ligand-modified CsPbB of this example₃The quantum dot material can be prepared by any method of the above-mentioned examples 1 to 3.

Example 6

Ligand-modified CsPbB of this example₃Quantum dot materials, including CsPbBr₃Quantum dots and adsorption on CsPbBr₃The ligand modifier on the surface of the quantum dot is 1-butyl sulfonic acid-3-methylimidazolium bromide. Ligand-modified CsPbB of this example₃The quantum dot material can be prepared by the method in the above example 4.

Claims (10)

1. Ligand modified CsPbBr₃The preparation method of the quantum dot material is characterized by comprising the following steps: the method comprises the following steps: carrying out solvothermal reaction on the reaction liquid; the reaction liquid comprises a Cs source, a Pb source, a ligand and a solvent; the ligand has a structure shown in formula IThe structure is as follows:

in the formula I, R₁Is C1-C6 alkylene, R₂Is a carboxyl group or a sulfonic acid group, X^-Is Cl^-、Br^-Or I^-。

2. The ligand-modified CsPbBr of claim 1₃The preparation method of the quantum dot material is characterized by comprising the following steps: the ligand is 1-carboxybutyl-3-methylimidazole bromine salt and/or 1-butylsulfonic acid-3-methylimidazole bromine salt.

3. The ligand-modified CsPbBr according to claim 1 or 2₃The preparation method of the quantum dot material is characterized by comprising the following steps: the source of Cs is selected from Cs₂CO₃、Cs(OOCCH₃) One or any combination thereof; the Pb source is selected from Pb (OOCCH)₃)₂、Pb(acac)₂One or any combination thereof.

4. The ligand-modified CsPbBr according to claim 1 or 2₃The preparation method of the quantum dot material is characterized by comprising the following steps: the molar ratio of Cs, Pb and ligand in the reaction liquid is 1 (0.8-1.0) to 3.0-3.5.

5. The ligand-modified CsPbBr according to claim 1 or 2₃The preparation method of the quantum dot material is characterized by comprising the following steps: the molar concentration of Cs in the reaction liquid is 0.04-0.06 mol/L.

6. The ligand-modified CsPbBr according to claim 1 or 2₃The preparation method of the quantum dot material is characterized by comprising the following steps: the temperature of the solvothermal reaction is 150-180 ℃; the solvothermal reaction time is 10-20 min.

7. The ligand-modified CsPb of claim 1 or 2Br₃The preparation method of the quantum dot material is characterized by comprising the following steps: the rate of heating to the solvothermal reaction temperature is 15-20 ℃/min.

8. The ligand-modified CsPbBr according to claim 1 or 2₃The preparation method of the quantum dot material is characterized by comprising the following steps: further comprising the steps of: carrying out solid-liquid separation on a system obtained by the hydrothermal reaction, and washing the obtained solid; the washing liquid adopted by the washing is a mixed liquid of ethyl acetate and ethanol; in the washing liquid, the volume ratio of ethyl acetate to ethanol is 1 (2-4).

9. Ligand modified CsPbB₃A quantum dot material, characterized by: comprising CsPbBr₃Quantum dots and adsorption on CsPbBr₃A ligand modifier on the surface of the quantum dot, wherein the ligand modifier has a structure shown in a formula I:

in the formula I, R₁Is C1-C6 alkylene, R₂Is a carboxyl group or a sulfonic acid group, X^-Is Cl^-、Br^-Or I^-。

10. An ionic liquid compound shown as formula I is used as CsPbBr₃Application of quantum dot modified ligand:

in the formula I, R₁Is C1-C6 alkylene, R₂Is a carboxyl group or a sulfonic acid group, X^-Is Cl^-、Br^-Or I^-。

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