Narrow half-peak width quantum dot as well as preparation method and application thereof

Abstract

The invention provides a narrow-half-peak-width quantum dot and a preparation method and application thereof.The narrow-half-peak-width quantum dot is of a multi-shell core-shell structure, a quantum dot core comprises ZnCdSe, and a ZnSe shell layer, a CdS shell layer and a ZnS shell layer are sequentially formed on the surface of the quantum dot core in an epitaxial growth mode. According to the quantum dot provided by the invention, through specific quantum dot core and shell layer components and structural design, the quantum dot has a specific emission wavelength of about 600nm, corresponds to an orange red spectral region, is small in wavelength shift, narrow in half-peak width, high in fluorescence yield and high in stability, and can still keep relatively high fluorescence yield under long-time air exposure.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, and relates to a quantum dot, particularly a narrow half-peak quantum dot and its preparation method and application. Background Technology

[0002] Quantum dots, as an emerging semiconductor nanomaterial, exhibit broad application prospects in optics and electronics due to their unique size-dependent quantum confinement effect. By precisely controlling the size of quantum dots, their fluorescence emission wavelength can be continuously tunable across a wide spectral range, while also possessing characteristics such as high quantum yield, good monochromaticity, and excellent photostability. In display technology, quantum dots with a wavelength of 600nm correspond to the orange-red emission region and are one of the key materials for achieving wide color gamut displays. The accuracy of their emission wavelength and their full width at half maximum (FWHM) directly determine the precision and purity of color reproduction. In particular, the FWHM, as a core indicator of monochromaticity, represents higher color purity with a smaller value, significantly reducing color crosstalk and enhancing the color realism and visual experience of the displayed image.

[0003] Currently, the synthesis of 600nm quantum dots mainly relies on high-temperature hot-injection synthesis and aqueous synthesis routes. Among them, high-temperature hot-injection synthesis is widely used because it can produce quantum dots with high crystallinity, but some technical bottlenecks still exist. First, this process is extremely sensitive to reaction conditions. Even slight variations in temperature and precursor injection rate can lead to uneven nucleation and growth, resulting in broadened quantum dot size distribution. Consequently, the fluorescence half-width typically exceeds 30 nm, making it difficult to meet the stringent requirements of high color gamut displays for narrow emission bandwidth. Second, 600 nm is a critical wavelength point for display color coordinates, and its positioning accuracy needs to be controlled within ±2 nm. However, existing methods have significant shortcomings in fine-tuning particle size: the growth of CdSe nuclei is extremely sensitive to changes in temperature and time parameters, and local reaction inhomogeneities during the shell coating process further cause abrupt changes in particle size, ultimately leading to wavelength shifts exceeding 5 nm, severely restricting the color standard matching of display devices. Third, quantum dots prepared by traditional processes have numerous dangling bonds and vacancy defects on their surface. This not only exacerbates the nonradiative recombination process, resulting in a quantum yield generally below 70%, but also reduces material stability. Fluorescence quenching easily occurs in air or humid environments, with fluorescence intensity retention typically below 80% within 30 days, limiting its long-term reliable application in display backlight modules, bio-imaging, and other fields.

[0004] Therefore, there is an urgent need to develop quantum dots with precisely controllable emission wavelengths and narrow half-width at half-maximum. Summary of the Invention

[0005] The purpose of this invention is to provide a quantum dot with a specific emission wavelength, narrow half-peak width, and high stability.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a narrow half-peak width quantum dot, wherein the narrow half-peak width quantum dot has a multi-shell core-shell structure, wherein the quantum dot core includes ZnCdSe, and a ZnSe shell, a CdS shell, and a ZnS shell are epitaxially grown sequentially on the surface of the quantum dot core.

[0008] The quantum dots provided by this invention have a three-shell core-shell structure with specific quantum dot core and shell composition and structural design: ZnCdSe serves as the luminescent core, whose core function is to fix the emission wavelength at 600nm through quantum confinement effect; the ZnSe shell acts as a buffer transition layer, achieving lattice adaptation and energy level connection with the outer shell, while initially passivating core surface defects and appropriately improving quantum dot yield, laying a stable foundation for subsequent shell growth; the CdS shell, without disrupting lattice matching, further redshifts the fluorescence wavelength and strengthens the confinement of electron-hole pairs within the core, reducing the escape of excited-state carriers, and interacting with the core and ZnSe. The shell layer forms an "energy level synergy," further enhancing the stability of quantum dots. The ZnS shell is chemically inert with low surface energy, making it resistant to reactions with oxygen, water, and organic solvents. This effectively blocks oxidants (such as oxygen and water vapor), reducing agents, or impurity ions from the external environment from invading the core, preventing luminescence quenching caused by core oxidation. For example, when ZnCdSe is oxidized to CdO or ZnO, the band gap changes, the wavelength shifts, and the efficiency drops sharply. Simultaneously, its good light resistance reduces "photobleaching" (light damage to the quantum dot structure) under strong light, significantly extending the quantum dot's lifespan and forming a "stability synergy" with the inner shell. The quantum dot structure maintains a narrow half-width, controllable wavelength, and high fluorescence yield through a triple effect of energy level gradient, lattice gradient, and outer layer protection. Quantum dots have a specific emission wavelength around 600 nm, corresponding to the orange-red spectral region, with small wavelength shift, narrow half-width, high fluorescence yield, and high stability, maintaining a high fluorescence yield even after prolonged exposure to air.

[0009] Preferably, the emission wavelength of the narrow half-peak quantum dot is 580-610nm, for example, it can be 580nm, 585nm, 590nm, 595nm, 600nm, 605nm or 610nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0010] Preferably, the emission half-width of the narrow half-width quantum dot is <25nm, for example, it can be 15nm, 18nm, 19nm, 20nm, 21nm, 22nm or 24nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0011] Preferably, the average particle size of the narrow half-peak quantum dots is 9-14 nm, for example, it can be 9 nm, 10 nm, 11 nm, 12 nm, 13 nm or 14 nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0012] Preferably, the diameter of the quantum dot core is 6-7 nm, for example, it can be 6 nm, 6.2 nm, 6.5 nm, 6.8 nm or 7 nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0013] Preferably, the thickness of the ZnSe shell is 0.5-2nm, for example, it can be 0.5nm, 1nm, 1.5nm, 1.8nm or 2nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0014] Preferably, the thickness of the CdS shell is 0.5-3nm, for example, it can be 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, 2.8nm or 3nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Preferably, the thickness of the ZnS shell is 1-3 nm, for example, it can be 1 nm, 1.5 nm, 2 nm, 2.5 nm, 2.8 nm or 3 nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] In a second aspect, the present invention provides a method for preparing narrow full width at half maximum (FWHM) quantum dots as described in the first aspect, the method comprising the following steps:

[0017] (1) Cadmium oxide, zinc oxide, organic acid ligand and non-coordination solvent are mixed, vacuumed and heated, and then selenium precursor is injected into it to react and obtain ZnCdSe quantum dot nucleus solution.

[0018] (2) A selenium precursor solution is injected into the ZnCdSe quantum dot nucleus stock solution to carry out the reaction, and a ZnSe shell is grown outside the quantum dot nucleus to obtain a ZnCdSe / ZnSe quantum dot stock solution;

[0019] (3) Add cadmium oxide to the ZnCdSe / ZnSe quantum dot stock solution to dissolve it, evacuate and heat it, and then inject sulfur precursor solution to react and grow CdS shell outside ZnSe shell to obtain ZnCdSe / ZnSe / CdS quantum dot stock solution.

[0020] (4) Add zinc oxide to the ZnCdSe / ZnSe / CdS quantum dot stock solution to dissolve it, evacuate and heat it, and then inject sulfur precursor solution to react and grow a ZnS shell outside the CdS shell to obtain ZnCdSe / ZnSe / CdS / ZnS quantum dot stock solution.

[0021] (5) The ZnCdSe / ZnSe / CdS / ZnS quantum dot stock solution is purified to obtain the narrow half-peak quantum dots.

[0022] Preferably, the molar ratio of zinc in the zinc oxide to selenium in the selenium precursor in step (1) is 15.5:(1.2-2), for example, it can be 15.5:1.2, 15.5:1.3, 15.5:1.4, 15.5:1.5, 15.5:1.6, 15.5:1.7, 15.5:1.8, 15.5:1.9 or 15.5:2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] Preferably, the organic acid ligand in step (1) includes oleic acid.

[0024] Preferably, the molar ratio of the organic acid ligand to cadmium in the cadmium oxide in step (1) is (55-65):1, for example, it can be 55:1, 58:1, 60:1, 62:1 or 65:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the noncoordination solvent in step (1) comprises 1-octadecene.

[0026] Preferably, the molar ratio of the noncoordinating solvent to cadmium in the cadmium oxide in step (1) is (55-65):1, for example, it can be 55:1, 58:1, 60:1, 62:1 or 65:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the mixing temperature in step (1) is 80-100℃, for example, it can be 80℃, 85℃, 90℃, 95℃ or 100℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] Preferably, the vacuuming temperature in step (1) is 140-170°C, for example, it can be 140°C, 145°C, 150°C, 155°C, 160°C, 165°C or 170°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the selenium precursor in step (1) comprises an organophosphorus solution of elemental selenium.

[0030] Preferably, the organophosphine comprises tributylphosphine.

[0031] Preferably, in the selenium precursor of step (1), the concentration of selenium is 3-5 mol / L, for example, it can be 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L or 5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the molar ratio of cadmium in the cadmium oxide to selenium in the selenium precursor in step (1) is 1.7:(1.2-2), for example, it can be 1.7:1.2, 1.7:1.3, 1.7:1.4, 1.7:1.5, 1.7:1.6, 1.7:1.7, 1.7:1.8, 1.7:1.9 or 1.7:2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] In this invention, step (1) prepares ZnCdSe quantum dot cores with a zinc, cadmium and selenium molar ratio of 15.5:1.7:(1.2-2).

[0034] Preferably, the reaction temperature in step (1) is 300-320℃, for example, it can be 300℃, 305℃, 310℃, 315℃ or 320℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the reaction time in step (1) is 25-35 min, for example, it can be 25 min, 28 min, 30 min, 32 min or 35 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, in the selenium precursor solution in step (2), the mass concentration of the selenium precursor is 15-25%, for example, it can be 15%, 18%, 20%, 22% or 25%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, in the selenium precursor solution of step (2), the solvent includes 1-octadecene.

[0038] Preferably, the injection rate of the selenium precursor solution in step (2) is 0.8-1.2 mL / min, for example, it can be 0.8 mL / min, 0.9 mL / min, 1.0 mL / min, 1.1 mL / min or 1.2 mL / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, the reaction temperature in step (2) is 290-310℃, for example, it can be 290℃, 295℃, 300℃, 305℃ or 310℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the reaction time in step (2) is 10-20 min, for example, it can be 10 min, 12 min, 14 min, 16 min, 18 min or 20 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] Preferably, the dissolution temperature in step (3) is 80-100℃, for example, it can be 80℃, 85℃, 90℃, 95℃ or 100℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] Preferably, the vacuuming temperature in step (3) is 140-170℃, for example, it can be 140℃, 145℃, 150℃, 155℃, 160℃, 165℃ or 170℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] Preferably, in the sulfur precursor solution of step (3), the sulfur precursor includes an organophosphorus solution of elemental sulfur.

[0044] Preferably, the sulfur concentration in the sulfur precursor is 5-7 mol / L, for example, it can be 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L or 7 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0045] Preferably, the organophosphine comprises tributylphosphine.

[0046] Preferably, in the sulfur precursor solution of step (3), the solvent includes 1-octadecene.

[0047] Preferably, in the sulfur precursor solution of step (3), the mass concentration of sulfur precursor is 12-18%, for example, it can be 12%, 13%, 14%, 15%, 16%, 17% or 18%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0048] Preferably, the injection rate of the sulfur precursor solution in step (3) is 0.4-0.6 mL / min, for example, it can be 0.4 mL / min, 0.45 mL / min, 0.5 mL / min, 0.55 mL / min or 0.6 mL / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0049] Preferably, the reaction temperature in step (3) is 290-310℃, for example, it can be 290℃, 295℃, 300℃, 302℃, 305℃, 308℃ or 310℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] Preferably, the dissolution temperature in step (4) is 80-100℃, for example, it can be 80℃, 85℃, 90℃, 95℃ or 100℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0051] Preferably, the vacuuming temperature in step (4) is 140-170°C, for example, it can be 140°C, 145°C, 150°C, 155°C, 160°C, 165°C or 170°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0052] Preferably, in the sulfur precursor solution of step (4), the sulfur precursor includes an organophosphorus solution of elemental sulfur.

[0053] Preferably, the sulfur concentration in the sulfur precursor is 5-7 mol / L, for example, it can be 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L or 7 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0054] Preferably, the organophosphine comprises tributylphosphine.

[0055] Preferably, in the sulfur precursor solution of step (4), the solvent includes 1-octadecene.

[0056] Preferably, in the sulfur precursor solution of step (4), the mass concentration of sulfur precursor is 12-18%, for example, it can be 12%, 13%, 14%, 15%, 16%, 17% or 18%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0057] Preferably, the injection rate of the sulfur precursor solution in step (4) is 0.4-0.6 mL / min, for example, it can be 0.4 mL / min, 0.45 mL / min, 0.5 mL / min, 0.55 mL / min or 0.6 mL / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0058] Preferably, the reaction temperature in step (4) is 270-290°C, for example, it can be 270°C, 275°C, 280°C, 285°C or 290°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0059] Preferably, the purification in step (5) adopts a three-stage purification method, including the following steps:

[0060] (a) The ZnCdSe / ZnSe / CdS / ZnS quantum dot stock solution is mixed with a dispersant to obtain a dispersion solution. The dispersion solution is then mixed with a precipitant, centrifuged, and the precipitate is collected.

[0061] (b) Mix the precipitate obtained in step (a) with the dispersant, centrifuge, and take the supernatant;

[0062] (c) Mix the supernatant obtained in step (b) with the precipitant, centrifuge and collect the precipitate, and then dry it.

[0063] Preferably, the dispersant in step (a) comprises n-hexane.

[0064] Preferably, the volume ratio of the ZnCdSe / ZnSe / CdS / ZnS quantum dot stock solution to the dispersant in step (a) is 1:(0.7-0.9), for example, it can be 1:0.7, 1:0.75, 1:0.8, 1:0.85 or 1:0.9, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0065] Preferably, the precipitant in step (a) comprises methanol and / or ethanol.

[0066] Preferably, the volume ratio of the dispersion solution to the precipitant in step (a) is 1:(0.6-0.8), for example, it can be 1:0.6, 1:0.65, 1:0.7, 1:0.75 or 1:0.8, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0067] Preferably, the centrifugation speed in step (a) is 3000-4000 rpm, for example, it can be 3000 rpm, 3200 rpm, 3500 rpm, 3800 rpm or 4000 rpm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0068] Preferably, the volume ratio of the precipitate to the dispersant in step (b) is 1:(1-2), for example, it can be 1:1, 1:1.2, 1:1.5, 1:1.8 or 1:2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0069] Preferably, the centrifugation speed in step (b) is 3000-4000 rpm, for example, it can be 3000 rpm, 3200 rpm, 3500 rpm, 3800 rpm or 4000 rpm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0070] Preferably, the precipitant in step (c) includes ethanol.

[0071] Preferably, the volume ratio of the supernatant to the precipitant in step (c) is 1:(0.5-1.5), for example, it can be 1:0.5, 1:0.8, 1:1, 1:1.2 or 1:1.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0072] Preferably, the centrifugation speed in step (c) is 3000-4000 rpm, for example, it can be 3000 rpm, 3200 rpm, 3500 rpm, 3800 rpm or 4000 rpm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0073] Thirdly, the present invention provides an application of the narrow half-width quantum dot as described in the first aspect, wherein the narrow half-width quantum dot is applied to display devices and / or biofluorescence imaging.

[0074] Compared with the prior art, the present invention has the following beneficial effects:

[0075] The quantum dots provided by this invention have a specific emission wavelength of around 600 nm through the design of specific quantum dot core and shell composition and structure. Corresponding to the orange-red spectral region, the quantum dots have small wavelength shift, narrow half-width, high fluorescence yield, and high stability. They can still maintain a high fluorescence yield even after long-term exposure to air. Attached Figure Description

[0076] Figure 1 This is a scanning electron microscope image of the ZnCdSe / ZnSe / CdS / ZnS quantum dots prepared in Example 1;

[0077] Figure 2 This is the fluorescence spectrum of the ZnCdSe / ZnSe / CdS / ZnS quantum dots prepared in Example 1. Detailed Implementation

[0078] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0079] Example 1

[0080] This embodiment provides a method for preparing narrow full width at half maximum (FWHM) quantum dots, the method comprising the following steps:

[0081] (1) Tributylphosphine and Se powder were mixed and dissolved, and then vacuumed for 5 min to obtain a solution with a Se concentration of 4 mol / L under anaerobic conditions, which is a selenium precursor and is denoted as TBP-Se; 1.7 mmol cadmium oxide, 15.5 mmol zinc oxide, 99.1 mmol OA (oleic acid) and 99 mmol ODE (1-octadecene) were mixed and dissolved at 90 °C until clear and transparent, heated to 160 °C and vacuumed for 15 min, heated to 310 °C and held for 10 min, and 0.4 mL TBP-Se was rapidly injected into it. The reaction was carried out for 30 min to grow an alloyed ZnCdSe quantum dot core to obtain the quantum dot core stock solution;

[0082] (2) TBP-Se was diluted with ODE to obtain a TBP-Se solution with a mass concentration of 20%. The TBP-Se solution was injected into the quantum dot nucleus stock solution at a rate of 1 mL / min. The reaction was carried out at 300℃ for 15 min to grow a ZnSe shell outside the ZnCdSe nucleus. The temperature was then lowered to obtain the ZnCdSe / ZnSe quantum dot stock solution.

[0083] (3) After mixing and dissolving tributylphosphine and S powder, vacuum for 5 min to obtain a solution with an S concentration of 6 mol / L under anaerobic conditions, which is a sulfur precursor, denoted as TBP-S; add 4.5 mmol of cadmium oxide to the ZnCdSe / ZnSe quantum dot stock solution, dissolve at 90℃ for 5 min, heat to 160℃ and vacuum for 15 min, then heat to 310℃, dilute TBP-S with ODE to obtain a TBP-S solution with a mass concentration of 15%, inject 1.5 mL of TBP-S solution into it at a rate of 0.5 mL / min, react at 310℃ for 20 min to grow a CdS shell, cool down to obtain the ZnCdSe / ZnSe / CdS quantum dot stock solution;

[0084] (4) Add 5.8 mmol of zinc oxide to the ZnCdSe / ZnSe / CdS quantum dot stock solution, dissolve at 90℃ for 5 min, heat to 160℃ and vacuum for 15 min, then heat to 280℃ and inject 1.5 mL of TBP-S solution (the same solution concentration as in the previous step) at a rate of 0.5 mL / min to grow the ZnS shell and obtain the ZnCdSe / ZnSe / CdS / ZnS quantum dot stock solution;

[0085] (5) Heat the quantum dot stock solution obtained in step (4) to 85°C, add hexane at a volume ratio of 1:0.8 to dissolve for 5 min to obtain a dispersion solution, add precipitant to the dispersion solution at a volume ratio of 1:0.7 to obtain a mixed solution, the precipitant is a mixture of methanol and ethanol, then centrifuge the mixed solution at 3500 rpm for 5 min and take the precipitate;

[0086] (6) Dissolve the precipitate obtained in step (5) in hexane at a volume ratio of 2:3 between the precipitate and hexane, centrifuge at 3500 rpm for 5 min, and take the supernatant.

[0087] (7) The supernatant obtained in step (6) is mixed with ethanol at a volume ratio of 1:1, centrifuged at 3500 rpm for 5 min, the precipitate is collected and dried at 60°C to obtain the narrow half-peak quantum dots.

[0088] In this embodiment, the obtained narrow half-peak width quantum dot has a multi-shell core-shell structure, wherein the quantum dot core is ZnCdSe, and a ZnSe shell, a CdS shell, and a ZnS shell are formed sequentially on the surface of the quantum dot core, denoted as ZnCdSe / ZnSe / CdS / ZnS quantum dot.

[0089] The ZnCdSe / ZnSe / CdS / ZnS quantum dots have a particle size of 14 nm, a quantum dot core size of 6 nm, a ZnSe shell thickness of 2 nm, a CdS shell thickness of 3 nm, and a ZnS shell thickness of 3 nm. Scanning electron microscope images of the ZnCdSe / ZnSe / CdS / ZnS quantum dots are shown below. Figure 1 As shown, the quantum dots exhibit a uniform particle size distribution.

[0090] The fluorescence spectrum of the ZnCdSe / ZnSe / CdS / ZnS quantum dots is as follows: Figure 2 As shown, the quantum dot emits at a wavelength of 601 nm and has a full width at half maximum (FWHM) of 19.5 nm.

[0091] Example 2

[0092] This embodiment provides a method for preparing narrow full width at half maximum (FWHM) quantum dots, the method comprising the following steps:

[0093] (1) Tributylphosphine and Se powder were mixed and dissolved, and then vacuumed for 5 min to obtain a solution with a Se concentration of 3 mol / L under anaerobic conditions, which is a selenium precursor and is denoted as TBP-Se; 1.7 mmol cadmium oxide, 15.5 mmol zinc oxide, 99.1 mmol OA (oleic acid) and 99 mmol ODE (1-octadecene) were mixed and dissolved at 80 °C until clear and transparent, heated to 150 °C and vacuumed for 15 min, heated to 300 °C and held for 10 min, and 0.4 mL TBP-Se was rapidly injected into it. The reaction was carried out for 35 min to grow an alloyed ZnCdSe quantum dot core to obtain the quantum dot core stock solution;

[0094] (2) TBP-Se was diluted with ODE to obtain a TBP-Se solution with a mass concentration of 15%. The TBP-Se solution was injected into the quantum dot nucleus stock solution at a rate of 1.2 mL / min. The reaction was carried out at 290℃ for 15 min to grow a ZnSe shell outside the ZnCdSe nucleus. The temperature was then lowered to obtain the ZnCdSe / ZnSe quantum dot stock solution.

[0095] (3) After mixing and dissolving tributylphosphine and S powder, vacuum for 5 min to obtain a solution with an S concentration of 7 mol / L under anaerobic conditions, which is a sulfur precursor, denoted as TBP-S; add 4.5 mmol of cadmium oxide to the ZnCdSe / ZnSe quantum dot stock solution, dissolve at 80℃ for 5 min, heat to 150℃ and vacuum for 15 min, then heat to 290℃, dilute TBP-S with ODE to obtain a TBP-S solution with a mass concentration of 18%, inject 1.5 mL of TBP-S solution into it at a rate of 0.4 mL / min, react at 290℃ for 20 min to grow a CdS shell, cool down to obtain the ZnCdSe / ZnSe / CdS quantum dot stock solution;

[0096] (4) Add 5.8 mmol of zinc oxide to the ZnCdSe / ZnSe / CdS quantum dot stock solution, dissolve at 80℃ for 5 min, heat to 150℃ and vacuum for 15 min, then heat to 270℃ and inject 1.5 mL of TBP-S solution (the same solution concentration as in the previous step) at a rate of 0.6 mL / min to grow the ZnS shell and obtain the ZnCdSe / ZnSe / CdS / ZnS quantum dot stock solution;

[0097] (5) Heat the quantum dot stock solution obtained in step (4) to 85°C, add hexane at a volume ratio of 1:0.7 to dissolve for 5 min to obtain a dispersion solution, add precipitant to the dispersion solution at a volume ratio of 1:0.8 to obtain a mixed solution, the precipitant is a mixture of methanol and ethanol, then centrifuge the mixed solution at 3000 rpm for 5 min and take the precipitate;

[0098] (6) Dissolve the precipitate obtained in step (5) in hexane at a volume ratio of 1:1 between the precipitate and hexane, centrifuge at 3000 rpm for 5 min, and take the supernatant.

[0099] (7) The supernatant obtained in step (6) is mixed with ethanol at a volume ratio of 1:0.5, centrifuged at 3000 rpm for 5 min, the precipitate is collected and dried at 60℃ to obtain the narrow half-peak quantum dots.

[0100] In this embodiment, the obtained narrow half-peak width quantum dot has a multi-shell core-shell structure, wherein the quantum dot core is ZnCdSe, and a ZnSe shell, a CdS shell, and a ZnS shell are formed sequentially on the surface of the quantum dot core, denoted as ZnCdSe / ZnSe / CdS / ZnS quantum dot.

[0101] The ZnCdSe / ZnSe / CdS / ZnS quantum dots have a particle size of 10.5 nm, a quantum dot core particle size of 7 nm, a ZnSe shell thickness of 1 nm, a CdS shell thickness of 1 nm, and a ZnS shell thickness of 1.5 nm.

[0102] Example 3

[0103] This embodiment provides a method for preparing narrow full width at half maximum (FWHM) quantum dots, the method comprising the following steps:

[0104] (1) Tributylphosphine and Se powder were mixed and dissolved, and then vacuumed for 5 min to obtain a solution with a Se concentration of 5 mol / L under anaerobic conditions, which is a selenium precursor and is denoted as TBP-Se; 1.7 mmol cadmium oxide, 15.5 mmol zinc oxide, 99.1 mmol OA (oleic acid) and 99 mmol ODE (1-octadecene) were mixed and dissolved at 100 °C until clear and transparent, heated to 170 °C and vacuumed for 15 min, heated to 320 °C and held for 10 min, and 0.4 mL TBP-Se was rapidly injected into it. The reaction was carried out for 25 min to grow an alloyed ZnCdSe quantum dot core to obtain the quantum dot core stock solution;

[0105] (2) TBP-Se was diluted with ODE to obtain a TBP-Se solution with a mass concentration of 25%. The TBP-Se solution was injected into the quantum dot nucleus stock solution at a rate of 0.8 mL / min. The reaction was carried out at 310℃ for 12 min to grow a ZnSe shell outside the ZnCdSe nucleus. The temperature was then lowered to obtain the ZnCdSe / ZnSe quantum dot stock solution.

[0106] (3) After mixing and dissolving tributylphosphine and S powder, vacuum for 5 min to obtain a solution with S concentration of 5 mol / L under anaerobic conditions, which is a sulfur precursor, denoted as TBP-S; add 4.5 mmol of cadmium oxide to the ZnCdSe / ZnSe quantum dot stock solution, dissolve at 100℃ for 5 min, heat to 170℃ and vacuum for 15 min, then heat to 305℃, dilute TBP-S with ODE to obtain a TBP-S solution with a mass concentration of 12%, inject 1.5 mL of TBP-S solution into it at a rate of 0.6 mL / min to grow a CdS shell, cool down, and obtain the ZnCdSe / ZnSe / CdS quantum dot stock solution;

[0107] (4) Add 5.8 mmol of zinc oxide to the ZnCdSe / ZnSe / CdS quantum dot stock solution, dissolve at 100℃ for 5 min, heat to 170℃ and vacuum for 15 min, then heat to 290℃ and inject 1.5 mL of TBP-S solution (the same concentration as in the previous step) at a rate of 0.4 mL / min to grow the ZnS shell and obtain the ZnCdSe / ZnSe / CdS / ZnS quantum dot stock solution;

[0108] (5) Heat the quantum dot stock solution obtained in step (4) to 85°C, add hexane at a volume ratio of 1:0.9 to dissolve for 5 min to obtain a dispersion solution, add precipitant to the dispersion solution at a volume ratio of 1:0.6 to obtain a mixed solution, the precipitant is a mixture of methanol and ethanol, then centrifuge the mixed solution at 4000 rpm for 5 min and take the precipitate;

[0109] (6) Dissolve the precipitate obtained in step (5) in hexane at a volume ratio of 1:2 between the precipitate and hexane, centrifuge at 4000 rpm for 5 min, and take the supernatant.

[0110] (7) The supernatant obtained in step (6) is mixed with ethanol at a volume ratio of 1:1.5, centrifuged at 4000 rpm for 5 min, the precipitate is collected and dried at 60℃ to obtain the narrow half-peak quantum dots.

[0111] In this embodiment, the obtained narrow half-peak width quantum dot has a multi-shell core-shell structure, wherein the quantum dot core is ZnCdSe, and a ZnSe shell, a CdS shell, and a ZnS shell are formed sequentially on the surface of the quantum dot core, denoted as ZnCdSe / ZnSe / CdS / ZnS quantum dot.

[0112] The ZnCdSe / ZnSe / CdS / ZnS quantum dots have a particle size of 9.5 nm, a quantum dot core particle size of 7 nm, a ZnSe shell thickness of 0.5 nm, a CdS shell thickness of 0.8 nm, and a ZnS shell thickness of 1.2 nm.

[0113] Comparative Example 1

[0114] This comparative example provides a quantum dot having a core-shell structure, wherein the quantum dot core is CdSe, and a ZnSe shell, a CdS shell, and a ZnS shell are sequentially formed on the surface of the quantum dot core, denoted as CdSe / ZnSe / CdS / ZnS quantum dot.

[0115] That is, the difference from Example 1 is that the quantum dot core is replaced by CdSe instead of ZnCdSe.

[0116] To obtain the quantum dots described above, the preparation method of the quantum dots is the same as in Example 1, except that zinc oxide is replaced with cadmium oxide in equimolar amounts.

[0117] Comparative Example 2

[0118] This comparative example provides a quantum dot having a core-shell structure, wherein the quantum dot core is ZnCdSe, and a CdS shell and a ZnS shell are sequentially formed on the surface of the quantum dot core, denoted as ZnCdSe / CdS / ZnS quantum dot.

[0119] That is, the difference from Example 1 is that no ZnSe shell is grown.

[0120] To obtain the quantum dots described above, the preparation method of the quantum dots is the same as in Example 1, except that step (2) is omitted.

[0121] Comparative Example 3

[0122] This comparative example provides a quantum dot having a core-shell structure, wherein the quantum dot core is ZnCdSe, and a ZnSe shell and a ZnS shell are sequentially formed on the surface of the quantum dot core, denoted as ZnCdSe / ZnSe / ZnS quantum dot.

[0123] That is, the difference from Example 1 is that no CdS shell is grown.

[0124] To obtain the quantum dots mentioned above, the preparation method of the quantum dots is the same as in Example 1 except for step (3).

[0125] Comparative Example 4

[0126] This comparative example provides a quantum dot having a core-shell structure, wherein the quantum dot core is ZnCdSe, and a ZnSe shell and a CdS shell are sequentially formed on the surface of the quantum dot core, denoted as ZnCdSe / ZnSe / CdS quantum dot.

[0127] That is, the difference from Example 1 is that no ZnS shell is grown.

[0128] To obtain the quantum dots mentioned above, the preparation method of the quantum dots is the same as in Example 1 except for step (4).

[0129] Performance testing

[0130] The quantum dots provided in the examples and comparative examples were subjected to fluorescence luminescence performance tests and stability tests, and the results are shown in Table 1.

[0131] The stability test method is as follows: place the quantum dots at 25°C in air for 15 to 30 days and test their fluorescence yield.

[0132] Table 1

[0133]

[0134] As shown in Table 1, the quantum dots prepared in this invention, with their emission wavelength fixed by the ZnCdSe luminescent core and lattice adaptation and energy level connection of the outer shell, exhibit extremely narrow emission half-width, high fluorescence yield, and long-term stability, maintaining a high fluorescence yield even under prolonged exposure to air. Furthermore, in comparison with the results of Example 1, in Comparative Examples 1-4, changes in the quantum dot structure significantly deteriorated their emission half-width, fluorescence yield, and stability.

[0135] In summary, the quantum dots provided by this invention, through specific quantum dot core and shell composition and structural design, have a specific emission wavelength of around 600 nm, corresponding to the orange-red spectral region, with small wavelength shift, narrow half-width, high fluorescence yield, and high stability, and can still maintain a high fluorescence yield under long-term air exposure.

[0136] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A narrow full width at half maximum (FWHM) quantum dot, characterized in that, The narrow half-peak width quantum dot has a multi-shell core-shell structure, wherein the quantum dot core includes ZnCdSe, and ZnSe shell, CdS shell, and ZnS shell are epitaxially grown sequentially on the surface of the quantum dot core.

2. The narrow full width at half maximum (FWHM) quantum dot according to claim 1, characterized in that, The emission wavelength of the narrow half-peak quantum dot is 580-610 nm; Preferably, the emission half-width of the narrow half-width quantum dot is <25nm; Preferably, the particle size of the narrow half-peak quantum dots is 9-14 nm; Preferably, the particle size of the quantum dot core is 6-7 nm; Preferably, the thickness of the ZnSe shell is 0.5-2 nm; Preferably, the thickness of the CdS shell is 0.5-3 nm; Preferably, the thickness of the ZnS shell is 1-3 nm.

3. A method for preparing narrow half-peak quantum dots as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) Cadmium oxide, zinc oxide, organic acid ligand and non-coordination solvent are mixed, vacuumed and heated, and then selenium precursor is injected into it to react and obtain ZnCdSe quantum dot nucleus solution. (2) A selenium precursor solution is injected into the ZnCdSe quantum dot nucleus stock solution to carry out the reaction, and a ZnSe shell is grown outside the quantum dot nucleus to obtain a ZnCdSe / ZnSe quantum dot stock solution; (3) Add cadmium oxide to the ZnCdSe / ZnSe quantum dot stock solution to dissolve it, evacuate and heat it, and then inject sulfur precursor solution to react and grow CdS shell outside ZnSe shell to obtain ZnCdSe / ZnSe / CdS quantum dot stock solution. (4) Add zinc oxide to the ZnCdSe / ZnSe / CdS quantum dot stock solution to dissolve it, evacuate and heat it, and then inject sulfur precursor solution to react and grow a ZnS shell outside the CdS shell to obtain ZnCdSe / ZnSe / CdS / ZnS quantum dot stock solution. (5) The ZnCdSe / ZnSe / CdS / ZnS quantum dot stock solution is purified to obtain the narrow half-peak quantum dots.

4. The preparation method according to claim 3, characterized in that, In step (1), the molar ratio of zinc in the zinc oxide to selenium in the selenium precursor is 15.5:(1.2-2); Preferably, the organic acid ligand in step (1) includes oleic acid; Preferably, the molar ratio of the organic acid ligand to cadmium in the cadmium oxide in step (1) is (55-65):1; Preferably, the noncoordination solvent in step (1) comprises 1-octadecene; Preferably, the molar ratio of the noncoordinating solvent to cadmium in the cadmium oxide in step (1) is (55-65):1; Preferably, the mixing temperature in step (1) is 80-100℃; Preferably, the vacuuming temperature in step (1) is 140-170℃; Preferably, the selenium precursor in step (1) comprises an organophosphorus solution of elemental selenium; Preferably, the organophosphine comprises tributylphosphine; Preferably, in the selenium precursor described in step (1), the concentration of selenium is 3-5 mol / L; Preferably, the molar ratio of cadmium in the cadmium oxide to selenium in the selenium precursor in step (1) is 1.7:(1.2-2); Preferably, the reaction temperature in step (1) is 300-320℃; Preferably, the reaction time in step (1) is 25-35 min.

5. The preparation method according to claim 3 or 4, characterized in that, In step (2), the mass concentration of the selenium precursor in the selenium precursor solution is 15-25%. Preferably, in the selenium precursor solution of step (2), the solvent includes 1-octadecene; Preferably, the injection rate of the selenium precursor solution in step (2) is 0.8-1.2 mL / min; Preferably, the reaction temperature in step (2) is 290-310℃; Preferably, the reaction time in step (2) is 10-20 min.

6. The preparation method according to any one of claims 3-5, characterized in that, The dissolution temperature in step (3) is 80-100℃; Preferably, the vacuuming temperature in step (3) is 140-170℃; Preferably, in the sulfur precursor solution in step (3), the sulfur precursor includes an organophosphorus solution of elemental sulfur; Preferably, the sulfur concentration in the sulfur precursor is 5-7 mol / L; Preferably, the organophosphine comprises tributylphosphine; Preferably, in the sulfur precursor solution of step (3), the solvent includes 1-octadecene; Preferably, in the sulfur precursor solution of step (3), the mass concentration of the sulfur precursor is 12-18%; Preferably, the injection rate of the sulfur precursor solution in step (3) is 0.4-0.6 mL / min; Preferably, the reaction temperature in step (3) is 290-310℃.

7. The preparation method according to any one of claims 3-6, characterized in that, The dissolution temperature in step (4) is 80-100℃; Preferably, the vacuuming temperature in step (4) is 140-170℃; Preferably, in the sulfur precursor solution in step (4), the sulfur precursor includes an organophosphorus solution of elemental sulfur; Preferably, the sulfur concentration in the sulfur precursor is 5-7 mol / L; Preferably, the organophosphine comprises tributylphosphine; Preferably, in the sulfur precursor solution of step (4), the solvent includes 1-octadecene; Preferably, in the sulfur precursor solution of step (4), the mass concentration of the sulfur precursor is 12-18%; Preferably, the injection rate of the sulfur precursor solution in step (4) is 0.4-0.6 mL / min; Preferably, the temperature of the reaction in step (4) is 270-290℃.

8. The preparation method according to any one of claims 3-7, characterized in that, The purification process described in step (5) employs a three-stage purification method, comprising the following steps: (a) The ZnCdSe / ZnSe / CdS / ZnS quantum dot stock solution is mixed with a dispersant to obtain a dispersion solution. The dispersion solution is then mixed with a precipitant, centrifuged, and the precipitate is collected. (b) Mix the precipitate obtained in step (a) with the dispersant, centrifuge, and take the supernatant; (c) Mix the supernatant obtained in step (b) with the precipitant, centrifuge and collect the precipitate, and then dry it.

9. The preparation method according to claim 8, characterized in that, The dispersant in step (a) includes n-hexane; Preferably, the volume ratio of the ZnCdSe / ZnSe / CdS / ZnS quantum dot stock solution to the dispersant in step (a) is 1:(0.7-0.9); Preferably, the precipitant in step (a) comprises methanol and / or ethanol; Preferably, the volume ratio of the dispersion solution to the precipitant in step (a) is 1:(0.6-0.8); Preferably, the centrifugation speed in step (a) is 3000-4000 rpm; Preferably, the volume ratio of the precipitate to the dispersant in step (b) is 1:(1-2); Preferably, the centrifugation speed in step (b) is 3000-4000 rpm; Preferably, the precipitant in step (c) includes ethanol; Preferably, the volume ratio of the supernatant to the precipitant in step (c) is 1:(0.5-1.5); Preferably, the centrifugation speed in step (c) is 3000-4000 rpm.

10. An application of the narrow half-peak width quantum dot as described in claim 1 or 2, characterized in that, The narrow half-peak width quantum dots are used in display devices and / or biofluorescence imaging.

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