CN110699066A - Multi-component gradient energy level core-shell structure quantum dot and preparation method thereof - Google Patents

Multi-component gradient energy level core-shell structure quantum dot and preparation method thereof Download PDF

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CN110699066A
CN110699066A CN201910976232.3A CN201910976232A CN110699066A CN 110699066 A CN110699066 A CN 110699066A CN 201910976232 A CN201910976232 A CN 201910976232A CN 110699066 A CN110699066 A CN 110699066A
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彭俊彪
兰林锋
宁洪龙
王磊
徐苗
姚日晖
王丹
张曙光
李海洋
李丹阳
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South China University of Technology SCUT
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Abstract

The invention belongs to the field of photoelectric materials, and discloses a multi-component gradient energy level core-shell structure quantum dot and a preparation method thereof. The multi-component gradient level core-shell structure quantum dot is CdS/CdxZn1‑ xS/ZnS、CdSySe1‑y/CdS/CdxZn1‑xS/ZnS or CdSe/CdSySe1‑y/CdS/CdxZn1‑xS/ZnS, x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 1. The photoluminescence spectra of the three quantum dots are respectively between 400-480 nm, 480-560 nm and 560-660 nm, and the maximum crystal of each quantum dotThe bulk particle size does not exceed 20 nm. The preparation method of the multi-component gradient energy level core-shell structure quantum dot is simple and low in cost, and is an effective method for preparing the core-shell structure quantum dot with strong photoluminescence intensity.

Description

Multi-component gradient energy level core-shell structure quantum dot and preparation method thereof
Technical Field
The invention belongs to the field of photoelectric materials, and particularly relates to a multi-component gradient energy level core-shell structure quantum dot and a preparation method thereof.
Background
Due to the obvious quantum confinement effect, the nanocrystalline (quantum dot) can show adjustable absorption spectrum and photoluminescence spectrum through a series of measures of adjusting size, components and structure and the like, and has absorption spectrum and luminescence
Narrow spectrum, strong luminous intensity, long fluorescence lifetime and the like, and has great advantages in applications such as photoelectric devices, biomarkers and the like.
For example, displays using quantum dots as light emitting layers are widely accepted in the market. Home appliances such as samsung electronics and TCL have been in a strong competitive relationship with OLED displays, similar liquid crystal televisions having blue light as a backlight and red and green quantum dots as light emitting layers. Meanwhile, quantum dots are also gradually transiting from laboratories to human lives as biological cell markers and rapid diagnosis. However, the lifetime and stability of quantum dot-based optoelectronic devices, as well as the stability of rapid diagnostic reagents, have always been the biggest hurdles that restrict quantum dot products from moving to market paths. As one of the nanomaterials, instability due to large specific surface area has been a problem to be solved by the current synthetic chemistry.
Disclosure of Invention
Aiming at the defects and shortcomings of the prior art, the invention mainly aims to provide the multi-component gradient energy level core-shell structure quantum dot.
The invention also aims to provide a preparation method of the multi-component gradient energy level core-shell structure quantum dot.
The purpose of the invention is realized by the following technical scheme:
the quantum dot with the multi-component gradient energy level core-shell structure is CdS/CdxZn1-xS/ZnS、CdSySe1-y/CdS/CdxZn1-xS/ZnS or CdSe/CdSySe1-y/CdS/CdxZn1-xS/ZnS, wherein x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 1.
Further, the CdS/CdxZn1-xThe photoluminescence range of S/ZnS is 400-480 nm; CdSySe1-y/CdS/CdxZn1-xThe photoluminescence range of S/ZnS is 480-560 nm; CdSe/CdSySe1-y/CdS/CdxZn1-xThe photoluminescence range of the S/ZnS is 560-660 nm.
Further, the average particle size of the multi-component gradient energy level core-shell structure quantum dot is 2-20 nm. Can be adjusted according to the size of the nanometer seed crystal and the thickness of the shell layer.
Further, the CdS/CdxZn1-xIn the S/ZnS quantum dot, the CdS crystal grain size of the seed crystal is not more than 4nm, and the Cd of the shell layerxZn1-xThe thickness of S is not more than 15nm, and the thickness of ZnS is not more than 4 nm; in CdSySe1-y/CdS/CdxZn1-xSeed crystal CdS in S/ZnS quantum dotsySe1-yCrystal grain size is not more than 5nm, shell CdS thickness is not more than 2nm, CdxZn1-xThe thickness of S is not more than 20nm, and the thickness of ZnS is not more than 4 nm; in CdSe/CdSySe1-y/CdS/CdxZn1-xIn the S/ZnS quantum dot, a seed crystal CdSe crystalParticle size not more than 5nm, shell CdSySe1-yHas a thickness of 2nm or less, CdS has a thickness of 1.5nm or less, and CdxZn1- xThe thickness of S is not more than 20nm, and the thickness of ZnS is not more than 4 nm.
Further, the CdS/CdxZn1-xIn the S/ZnS quantum dots, the photoluminescence range of the seed crystal CdS is 375-435 nm; in CdSySe1-y/CdS/CdxZn1-xSeed crystal CdS in S/ZnS quantum dotsySe1-yThe photoluminescence range of (a) is 430-500 nm; in CdSe/CdSySe1-y/CdS/CdxZn1-xIn the S/ZnS quantum dot, the photoluminescence range of the seed crystal CdSe is 520-580 nm.
The preparation method of the multi-component gradient energy level core-shell structure quantum dot comprises the following preparation steps:
(1) the multi-component gradient level core-shell structure quantum dot is CdS/CdxZn1-xThe preparation method of the S/ZnS comprises the following steps:
a) synthesizing CdS seed crystals: mixing a Cd source and an organic solvent, introducing inert gas to remove air, heating, injecting an S source to form a nanocrystal nucleus, keeping the temperature at 180-300 ℃, and promoting the nucleus to grow to a required size to obtain CdS seed nanocrystals;
b) putting CdS seed nanocrystals into a reaction device, adding an organic solvent, introducing inert gas to remove air and water vapor, heating, adding a Cd source and a Zn source, and dropwise adding an S source for reaction to obtain CdxZn1-xS, a shell layer;
c) adding a Zn source into the reaction system in the step b), and then dropwise adding an S source for reaction to obtain the multi-component gradient level core-shell structure quantum dot CdS/CdxZn1-xS/ZnS；
(2) The multi-component gradient energy level core-shell structure quantum dot is CdSySe1-y/CdS/CdxZn1-xThe preparation method of the S/ZnS comprises the following steps:
a) synthesis of CdSySe1-ySeed crystal: mixing Cd source and organic solvent, introducing inert gas to remove air, addingInjecting S source and Se source after heating to form nanocrystalline crystal nucleus, keeping the temperature at 180-300 ℃, promoting the crystal nucleus to grow to the required size, and obtaining CdSySe1-ySeed nanocrystals;
b) CdS (cadmium sulfide)ySe1-yAdding the seed nanocrystal and an organic solvent into a reaction device, introducing inert gas to remove air and water vapor, heating, adding a Cd source, and then dropwise adding an S source to react to obtain a CdS shell;
c) after the reaction in the step b) is finished, heating, adding a Cd source and a Zn source again, and then dropwise adding an S source for reaction to obtain CdxZn1-xS, a shell layer;
d) adding a Zn source into the reaction system in the step c), and then dropwise adding an S source for reaction to obtain the quantum dot CdS with the multi-component gradient energy level core-shell structureySe1-y/CdS/CdxZn1-xS/ZnS；
(3) The multi-component gradient level core-shell structure quantum dot is CdSe/CdSySe1-y/CdS/CdxZn1-xThe preparation method of the S/ZnS comprises the following steps:
a) synthesizing CdSe seed crystal: mixing Cd precursor fatty acid cadmium and an organic solvent, introducing inert gas to remove air, heating, adding a Se source to form a nanocrystal nucleus, keeping the temperature at 180-300 ℃, and promoting the nucleus to grow to a required size to obtain CdSe seed nanocrystals;
b) adding CdSe seed nanocrystals and organic solvent into a reaction device, introducing inert gas to remove air and water vapor, heating, adding Cd source, dropwise adding S source and Se source, and reacting to obtain CdSySe1-yA shell layer;
c) after the reaction in the step b) is finished, heating, adding a Cd source, and then dropwise adding an S source for reaction to obtain a CdS shell;
d) after the reaction in the step c) is finished, heating, adding a Cd source and a Zn source again, and then dropwise adding an S source for reaction to obtain CdxZn1-xS, a shell layer;
e) adding a Zn source into the reaction system of the step d), and then dropwise adding an S source for reaction to obtain the multi-component gradient level core-shell structure quantum dot CdSe/CdSySe1-y/CdS/CdxZn1-xS/ZnS。
Further, the Cd source in (1) to (3) is cadmium fatty acid, preferably cadmium acetate, cadmium octanoate, cadmium decanoate, cadmium dodecanoate, cadmium tetradecanoate, cadmium hexadecanoate, cadmium oleate or cadmium stearate; the S source is sulfur dissolved in an organic solvent or organophosphorus TOP, TBP and DDP, or organic mercaptan; the Zn source is fatty acid zinc, preferably zinc acetate, zinc caprylate, zinc caprate, zinc laurate, zinc myristate, zinc palmitate, zinc oleate or zinc stearate; the Se source is selenium dissolved in organic solvent or organophosphorus TOP, TBP and DDP.
Further, the organic solvent in (1) to (3) is octadecene, hexadecene, tetradecene, tetradecane, dodecane, decaalkane or octane.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) in the multi-component gradient energy level core-shell structure quantum dot, the core composition is different from the shell composition surrounding the core. If the band offset of the core-shell structure is type 1 and the shell semiconductor has a larger band gap than the core material, the photon-generated electrons and holes within the nanocrystal are confined primarily within the core. Type 1 band offset as used herein refers to a core-shell electronic structure in which the conduction and valence bands of the shell semiconductor are both higher or lower than the conduction and valence bands of the core semiconductor. Thus, the core-shell nanocrystals can exhibit high photoluminescence and electroluminescence efficiencies, and can be more stable against photooxidation than "simple core" semiconductor nanocrystals comprising a single material, as long as the band gap of the core semiconductor is less than that of the shell semiconductor.
(2) In the multi-component gradient energy level core-shell structure quantum dot, along with the formation of a shell layer, the surface defects of the seed nanocrystal are gradually reduced until the size is smaller to the minimum. The photoluminescence efficiency of the multi-component gradient energy level core-shell structure quantum dots is gradually increased (the photoluminescence spectral intensity is continuously increased on the premise of the same concentration) until the fluorescence efficiency is close to 100%.
(3) The photoluminescence fluorescence quantum efficiency (PLQY) of the multi-component gradient energy level core-shell structure quantum dot in organic solvents such as octadecene, hexadecene, tetradecane, dodecane, decaalkane, octane, normal hexane, trichloromethane, dichloromethane, carbon tetrachloride, toluene and the like is more than 90%, and the multi-component gradient energy level core-shell structure quantum dot can keep long-time stability in an air environment.
Drawings
FIG. 1 is a photoluminescence spectrum of CdS seed nanocrystals obtained in example 1.
FIG. 2 shows the multi-component gradient core-shell structure quantum dot CdS/Cd obtained in example 1xZn1-xEnergy band diagram of S/ZnS.
FIG. 3 shows the multi-component gradient core-shell structure quantum dot CdS/Cd obtained in example 1xZn1-xAnd the shape and size of the S/ZnS under a high power electron microscope.
FIG. 4 is CdS obtained in example 2ySe1-yPhotoluminescence spectrum of the seed nanocrystals.
FIG. 5 shows CdS as multi-component gradient core-shell structure quantum dots obtained in example 2ySe1-y/CdS/CdxZn1-xEnergy band diagram of S/ZnS.
FIG. 6 shows CdS as multi-component gradient core-shell structure quantum dots obtained in example 2ySe1-y/CdS/CdxZn1-xAnd the shape and size of the S/ZnS under a high power electron microscope.
FIG. 7 shows CdS as multi-component gradient core-shell structure quantum dots obtained in example 3ySe1-y/CdS/CdxZn1-xEnergy band diagram of S/ZnS.
FIG. 8 shows CdS as multi-component gradient core-shell structure quantum dots obtained in example 3ySe1-y/CdS/CdxZn1-xAbsorption and fluorescence spectrum of S/ZnS.
FIG. 9 shows CdSe/CdS of multi-component gradient core-shell quantum dots obtained in example 3ySe1-y/CdS/CdxZn1- xAnd the shape and size of the S/ZnS under a high power electron microscope.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
Example 1
The method for synthesizing the quantum dot CdS/Cd with the multi-component gradient energy level core-shell structurexZn1-xA method of S/ZnS comprising:
1) and synthesizing CdS seed crystals. Mixing 1mmol of Cd precursor cadmium oleate with 10ml of solvent octadecylene, discharging air, filling nitrogen, heating to 180-300 ℃, quickly injecting a sulfur source, dissolving 1mmol of elemental sulfur in 10ml of octadecylene), forming nanocrystal crystal nuclei, and keeping the temperature within the temperature range of 180-300 ℃ to promote the growth of the crystal nuclei. During the heat preservation for 30 seconds to 20 minutes, the absorption spectrum is sampled and tested for judging the size of the nanocrystalline. And when the crystal nucleus grows to be within the range of 1.5 nanometers to 5 nanometers, removing the heating device, cooling to room temperature, and purifying to obtain the CdS seed nanocrystal. The photoluminescence spectrum of the obtained CdS seed nanocrystal is shown in FIG. 1.
2) 0.1g of the purified CdS seed nanocrystal and 5ml of octadecene serving as a solvent are added into a reaction device, air and water vapor are removed, and inert gas is filled. Heating CdS seed nanocrystals and a solvent under an inert gas environment to 200-320 ℃, adding 0.5mmol of cadmium oleate and 1.5mmol of zinc oleate, and dropwise adding 2mmol of dodecyl mercaptan into a reaction device at a dropping speed of 1ml per minute for reaction. Repeatedly adding cadmium oleate and zinc oleate and dripping mercaptan for 4 times, wherein the reaction time is within 2 hours each time, and forming multilayer gradient CdS/CdxZn1-xAnd (4) S quantum dots. Wherein CdxZn1-xS is a stepwise gradient layer structure, CdxZn1-xIn the S-layer structure, as the Zn element is diffused at different rates along with the change of reaction time and temperature, the proportion of Cd and Zn elements in each layer is continuously changed, and the value range of x in each layer structure is more than or equal to 0 and less than or equal to 1.
3) Adding 4mol of zinc oleate into the reaction system, dropwise adding a sulfur source (4mmol of elemental sulfur dissolved in 2ml of organophosphorus TOP) into the reaction device at a dropping speed of 1ml per minute, and reacting to obtain core-shell nanocrystal CdS/CdxZn1-xS/ZnS. Removing heating meansCooling to room temperature, and purifying.
The multi-component gradient-level core-shell structure quantum dot CdS/Cd obtained in the embodimentxZn1-xThe band diagram of S/ZnS is shown in FIG. 2.
The multi-component gradient-level core-shell structure quantum dot CdS/Cd obtained in the embodimentxZn1-xThe morphology and size diagram of S/ZnS under a high power electron microscope is shown in FIG. 3.
Example 2
The synthetic multi-component gradient core-shell structure quantum dot CdS of the embodimentySe1-y/CdS/CdxZn1-xA method of S/ZnS comprising:
1) synthesis of CdSySe1-yAnd (4) seed crystals. Mixing 1mmol of Cd precursor cadmium acetate with 10ml of solvent octane, discharging air, filling nitrogen, heating to 180-300 ℃, quickly injecting 0.5mmol of sulfur source into 5ml of octadecene) and 0.5mmol of selenium source into 5ml of octadecene to form nanocrystal nuclei. Wherein the element ratio of S to Se is 1: 1. Keeping the temperature for 30 seconds to 20 minutes at the temperature of between 180 and 300 ℃ for the growth of crystal nuclei. And sampling, testing and absorbing according to different reaction time and temperature, and judging the size of the nano seed crystal. When the growth of the nanocrystalline seeds in the reaction system reaches 3nm, removing the heating device, cooling to room temperature, and purifying to obtain CdSySe1-ySeed nanocrystals of CdS thereinySe1-yThe seed nanocrystalline has the proportion that the seed nanocrystalline is not changed continuously due to different temperatures, the reaction rate of anions and the like in the reaction process to form CdSySe1-yThe layer structure is gradually graded, and the value range of y in each layer structure is more than or equal to 0 and less than or equal to 1. The obtained CdSySe1-yThe photoluminescence spectrum of the seed nanocrystals is shown in fig. 4.
2) 0.1g CdSySe1-yThe seed nanocrystals and 10ml of hexadecene, an organic solvent, were added to the reaction apparatus, air and water vapor were removed, and then inert gas was filled. Heating the whole reaction device to 200-310 ℃, adding 0.5mol of Cd precursor cadmium oleate, and then adding 0.5mmol ten of Cd precursor cadmium oleate at the dropping speed of 1ml per minuteAnd adding dithiol dropwise into the reaction system. And after the dropwise adding is finished, preserving the temperature of the reaction system for 30 minutes to 2 hours to obtain the CdS shell.
3) After the reaction is finished, the temperature is further increased to be within the range of 300-320 ℃, 1mmol of cadmium oleate and 4mmol of zinc oleate are added, and 2.5mmol of dodecyl mercaptan is dripped into the reaction device at the dripping speed of 1ml per minute. Repeating the process of adding cadmium oleate and zinc oleate and dripping mercaptan for 3 times, wherein each time is within 2 hours, and obtaining the core-shell nanocrystal CdSySe1-y/CdS/CdxZn1-xS, wherein, CdxZn1-xS is a stepwise gradient layer structure, CdxZn1-xIn the S-layer structure, as the Zn element is diffused at different rates along with the change of reaction time and temperature, the proportion of Cd and Zn elements in each layer is continuously changed, and the value range of x in each layer structure is more than or equal to 0 and less than or equal to 1.
4) Adding 4mmol Zn source zinc oleate into the reaction system, dripping a sulfur source (4mmol elemental sulfur dissolved in 2ml organophosphorus TOP) into the reaction device at a dripping speed of 1ml per minute, and obtaining the core-shell nanocrystal CdSySe1-y/CdS/CdxZn1-xS/ZnS. Removing the heating device, cooling to room temperature, and purifying. Removing the heating device, cooling to room temperature, and purifying.
The quantum dot CdS with the multi-component gradient energy level core-shell structure obtained in the embodimentySe1-y/CdS/CdxZn1-xThe band diagram of S/ZnS is shown in FIG. 5.
The quantum dot CdS with the multi-component gradient energy level core-shell structure obtained in the embodimentySe1-y/CdS/CdxZn1-xThe morphology and size graph of S/ZnS under a high power electron microscope is shown in FIG. 6.
Example 3
The method for synthesizing the quantum dot CdSe/CdS with the multi-component gradient energy level core-shell structureySe1-y/CdS/CdxZn1-xA method of S/ZnS comprising:
1) synthesizing CdSe seed crystal. Mixing 1mmol of Cd precursor cadmium caprylate with 10ml of organic solvent dodecane, discharging air, filling nitrogen, heating to 180-300 ℃, injecting 1mmol of selenium source (1mol of selenium is dissolved in 1ml of organic phosphorus TOP), and keeping the temperature for 30 seconds to 20 minutes at the temperature of 180-300 ℃. Then removing the heating device, cooling to room temperature, and purifying to obtain the CdSe seed nanocrystal.
2) 0.1g of CdSe seed nanocrystals and 10ml of dodecane, an organic solvent, were charged into the reaction apparatus, air and water vapor were removed, and an inert gas was filled. 1mmol of Cd precursor cadmium laurate and 2ml of organic solvent dodecane are discharged, air is filled with inert gas, the mixture of an S source (0.5mmol of elemental sulfur dissolved in 1ml of organophosphorus TOP) and a Se source (0.5mol of selenium dissolved in 1ml of organophosphorus TOP) is dripped at the dripping speed of 1ml per minute after heating to 180-250 ℃, the dripping is completed within 2 hours, and then the temperature is preserved for 20 minutes to promote the growth, so that CdSe/CdS is formedySe1-yCore-shell structure wherein CdSySe1-yThe ratio of the seed-free nanocrystal is continuously changed due to different temperatures, anion reaction rate and other reasons in the reaction process of the layer, so that CdS is formedySe1-yThe layer structure is gradually graded, and the value range of y in each layer structure is more than or equal to 0 and less than or equal to 1.
3) Heating the whole reaction device to 200-310 ℃, adding 2mmol of Cd precursor cadmium oleate, and then dropwise adding 2mmol of dodecyl mercaptan into the reaction system at a dropwise adding speed of 1ml per minute. After the dropwise adding is finished, the reaction system is kept for 2 hours to form CdSe/CdSySe1-ya/CdS core-shell structure.
4) After the reaction is finished, the temperature is further increased to be within the range of 300-320 ℃, 2mmol of cadmium oleate and 2mmol of zinc oleate are added, and 4mmol of dodecyl mercaptan is dripped into the reaction device at the dripping speed of 1ml per minute. Repeating the process of adding cadmium oleate and zinc oleate and dripping mercaptan for 3 times, wherein each time is within 2 hours, and obtaining the core-shell nanocrystal CdSe/CdSySe1-y/CdS/CdxZn1-xS, wherein, CdxZn1-xS is a stepwise gradient layer structure, CdxZn1-xThe S layer structure is subjected to diffusion at different rates due to the change of Zn element along with the reaction time and temperature, so that each layer of Cd and each layer of Cd are mixedThe proportion of Zn element is changed constantly, and the value range of x in each layer structure is more than or equal to 0 and less than or equal to 1.
5) Adding 4mmol Zn source zinc oleate into the reaction system, dropwise adding a sulfur source (4mol elemental sulfur is dissolved in organophosphorus TOP) at a dropping speed of 1ml per minute into the reaction device for reaction, and obtaining the core-shell nanocrystal CdSe/CdSySe1-y/CdS/CdxZn1-xS/ZnS. Removing the heating device, cooling to room temperature, and purifying.
The multi-component gradient level core-shell structure quantum dot CdSe/CdS obtained in the embodimentySe1-y/CdS/CdxZn1-xThe band diagram of S/ZnS is shown in FIG. 7. The absorption and fluorescence spectra are shown in FIG. 8. The appearance and size of the film under a high power electron microscope are shown in FIG. 9.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims (8)

1. A multi-component gradient energy level core-shell structure quantum dot is characterized in that: the multi-component gradient level core-shell structure quantum dot is CdS/CdxZn1-xS/ZnS、CdSySe1-y/CdS/CdxZn1-xS/ZnS or CdSe/CdSySe1-y/CdS/CdxZn1-xS/ZnS, wherein x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 1.
2. The quantum dot with the multi-component gradient energy level core-shell structure according to claim 1, wherein: the CdS/CdxZn1-xThe photoluminescence range of S/ZnS is 400-480 nm; CdSySe1-y/CdS/CdxZn1-xThe photoluminescence range of S/ZnS is 480-560 nm; CdSe/CdSySe1-y/CdS/CdxZn1-xThe photoluminescence range of the S/ZnS is 560-660 nm.
3. The quantum dot with the multi-component gradient energy level core-shell structure according to claim 1, wherein: the average particle size of the multi-component gradient energy level core-shell structure quantum dot is 2-20 nm.
4. The quantum dot with the multi-component gradient energy level core-shell structure according to claim 1, wherein: the CdS/CdxZn1-xIn the S/ZnS quantum dot, the CdS crystal grain size of the seed crystal is not more than 4nm, and the Cd of the shell layerxZn1-xThe thickness of S is not more than 15nm, and the thickness of ZnS is not more than 4 nm; in CdSySe1-y/CdS/CdxZn1-xSeed crystal CdS in S/ZnS quantum dotsySe1-yCrystal grain size is not more than 5nm, shell CdS thickness is not more than 2nm, CdxZn1-xThe thickness of S is not more than 20nm, and the thickness of ZnS is not more than 4 nm; in CdSe/CdSySe1-y/CdS/CdxZn1-xIn the S/ZnS quantum dot, the CdSe crystal grain size of the seed crystal is not more than 5nm, and CdS is in the shell layerySe1-yHas a thickness of 2nm or less, CdS has a thickness of 1.5nm or less, and CdxZn1-xThe thickness of S is not more than 20nm, and the thickness of ZnS is not more than 4 nm.
5. The quantum dot with the multi-component gradient energy level core-shell structure according to claim 1, wherein: the CdS/CdxZn1-xIn the S/ZnS quantum dots, the photoluminescence range of the seed crystal CdS is 375-435 nm; in CdSySe1-y/CdS/CdxZn1-xSeed crystal CdS in S/ZnS quantum dotsySe1-yThe photoluminescence range of (a) is 430-500 nm; in CdSe/CdSySe1-y/CdS/CdxZn1-xIn the S/ZnS quantum dot, the photoluminescence range of the seed crystal CdSe is 520-580 nm.
6. The preparation method of the multi-component gradient energy level core-shell structure quantum dot in claim 1 is characterized by comprising the following preparation steps:
(1) the multi-component gradient level core-shell structure quantum dot is CdS/CdxZn1-xThe preparation method of the S/ZnS comprises the following steps:
a) synthesizing CdS seed crystals: mixing a Cd source and an organic solvent, introducing inert gas to remove air, heating, injecting an S source to form a nanocrystal nucleus, keeping the temperature at 180-300 ℃, and promoting the nucleus to grow to a required size to obtain CdS seed nanocrystals;
b) putting CdS seed nanocrystals into a reaction device, adding an organic solvent, introducing inert gas to remove air and water vapor, heating, adding a Cd source and a Zn source, and dropwise adding an S source for reaction to obtain CdxZn1-xS, a shell layer;
c) adding a Zn source into the reaction system in the step b), and then dropwise adding an S source for reaction to obtain the multi-component gradient level core-shell structure quantum dot CdS/CdxZn1-xS/ZnS；
(2) The multi-component gradient energy level core-shell structure quantum dot is CdSySe1-y/CdS/CdxZn1-xThe preparation method of the S/ZnS comprises the following steps:
a) synthesis of CdSySe1-ySeed crystal: mixing a Cd source and an organic solvent, introducing inert gas to remove air, heating, injecting an S source and a Se source to form a nanocrystal nucleus, keeping the temperature at 180-300 ℃, and promoting the nucleus to grow to a required size to obtain CdSySe1-ySeed nanocrystals;
b) CdS (cadmium sulfide)ySe1-yAdding the seed nanocrystal and an organic solvent into a reaction device, introducing inert gas to remove air and water vapor, heating, adding a Cd source, and then dropwise adding an S source to react to obtain a CdS shell;
c) after the reaction in the step b) is finished, heating, adding a Cd source and a Zn source again, and then dropwise adding an S source for reaction to obtain CdxZn1-xS, a shell layer;
d) adding a Zn source into the reaction system in the step c), and then dropwise adding an S source for reaction to obtain the quantum dot CdS with the multi-component gradient energy level core-shell structureySe1-y/CdS/CdxZn1-xS/ZnS；
(3) The multi-component gradient level core-shell structure quantum dot is CdSe/CdSySe1-y/CdS/CdxZn1-xThe preparation method of the S/ZnS comprises the following steps:
a) synthesizing CdSe seed crystal: mixing Cd precursor fatty acid cadmium and an organic solvent, introducing inert gas to remove air, heating, adding a Se source to form a nanocrystal nucleus, keeping the temperature at 180-300 ℃, and promoting the nucleus to grow to a required size to obtain CdSe seed nanocrystals;
b) adding CdSe seed nanocrystals and organic solvent into a reaction device, introducing inert gas to remove air and water vapor, heating, adding Cd source, dropwise adding S source and Se source, and reacting to obtain CdSySe1-yA shell layer;
c) after the reaction in the step b) is finished, heating, adding a Cd source, and then dropwise adding an S source for reaction to obtain a CdS shell;
d) after the reaction in the step c) is finished, heating, adding a Cd source and a Zn source again, and then dropwise adding an S source for reaction to obtain CdxZn1-xS, a shell layer;
e) adding a Zn source into the reaction system of the step d), and then dropwise adding an S source for reaction to obtain the multi-component gradient level core-shell structure quantum dot CdSe/CdSySe1-y/CdS/CdxZn1-xS/ZnS。
7. The preparation method of the multi-component gradient energy level core-shell structure quantum dot according to claim 6, characterized in that: (1) the Cd source in the (3) to (3) is cadmium acetate, cadmium octanoate, cadmium decate, cadmium laurate, cadmium tetradecanoate, cadmium hexadecanoate, cadmium oleate or cadmium stearate; the S source is sulfur dissolved in an organic solvent or organophosphorus TOP, TBP and DDP, or organic mercaptan; the Zn source is zinc acetate, zinc caprylate, zinc caprate, zinc laurate, zinc myristate, zinc palmitate, zinc oleate or zinc stearate; the Se source is selenium dissolved in organic solvent or organophosphorus TOP, TBP and DDP.
8. The preparation method of the multi-component gradient energy level core-shell structure quantum dot according to claim 6, characterized in that: (1) the organic solvent in (1) to (3) is octadecene, hexadecene, tetradecene, tetradecane, dodecane, decaalkane or octane.
CN201910976232.3A 2019-10-15 2019-10-15 Multi-component gradient energy level core-shell structure quantum dot and preparation method thereof Pending CN110699066A (en)

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