A method for reducing the full width at half maximum (FWHM) of fluorescence in core-shell indium phosphide quantum dots by aluminum doping and its product

Abstract

This invention discloses a method for reducing the fluorescence half-width at half-maximum (HWHM) of core-shell indium phosphide quantum dots (IPDs) and its product, belonging to the field of luminescent materials technology. In this invention, aluminum isopropoxide is added to the nucleation step of the IPDs to passivate surface defects, suppress the formation of defect states, and inhibit Ostwald ripening during nucleation, resulting in a more uniform nucleus size distribution. The method of this invention has the advantages of simple process, convenient synthesis, and ease of large-scale production; the prepared IPDs exhibit narrower HWHM, higher quantum yield, and environmental friendliness, making them suitable for widespread application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of luminescent materials, and particularly relates to a method for reducing the half-peak width of core-shell indium phosphide quantum dots doped with aluminum and a product thereof. BACKGROUND

[0002] Colloidal quantum dots have excellent optical properties, their energy levels, light absorption and fluorescence wavelengths are adjustable with size, and they have a wide excitation spectrum range and good fluorescence monochromaticity, so they are widely used in fields such as fluorescent probes, cell imaging, quantum dot light-emitting diodes (LEDs) and quantum dot sensitized solar cells. Colloidal quantum dots have high fluorescence intensity, and the emission wavelength can be easily adjusted according to the size and composition, and they have excellent light absorption characteristics in a wide spectral range and long-term optical stability, so they are widely studied as luminescent materials, and are expected to be widely used in light-emitting diodes, displays and lasers. At present, the efficiency and working stability of quantum dot light-emitting diodes (QLEDs) using the most advanced cadmium chalcogenide quantum dots have basically met the requirements of commercial displays. However, regulations related to cadmium toxicity have severely limited the application of these cadmium-based quantum dots in commercial displays. Among various types of semiconductor quantum dot (QD) materials, indium phosphide-based quantum dots constitute one of the most promising materials for display applications because (i) their optical band gap can cover the entire visible wavelength by controlling the size, and (ii) compared with cadmium and lead-containing quantum dot materials, indium phosphide quantum dots have no toxicity problems.

[0003] Although great progress and breakthroughs have been made in synthesis, the quantum yield and emission width of indium phosphide quantum dots are still not as competitive as cadmium-based quantum dots. There are still some problems to be solved in indium phosphide quantum dots, such as many surface defects, low fluorescence quantum yield, and too wide half-peak width to meet the application requirements of display, etc. The quantum yield of indium phosphide quantum dots alone is very low, but it can be significantly improved by epitaxial growth of zinc chalcogenides with a wide band gap. In the inventor's prior application, for example, Chinese invention patent No. CN115710505A discloses a method for reducing the fluorescence half-peak width of core-shell indium phosphide quantum dots. By introducing a certain amount of ligand zinc halide during the temperature rising step after purification of the indium phosphide core and before coating of the shell layer (ZnSeS / ZnS), the addition of ligand zinc halide can alleviate the situation of continuous shedding of ligands on the surface of indium phosphide quantum dots during the temperature rising process. On the other hand, the ligand zinc halide combines with the unbound indium and phosphorus on the surface, inhibiting Ostwald ripening during heating, making the particle size distribution more uniform, and the fluorescence peak half-peak width (full width at half maxima, FWHM) smaller. In Chinese invention patent No. CN117487538A, the inventor provides a kind of aluminum-doped indium phosphide core-shell quantum dots with adjustable emission spectrum and a preparation method thereof. During the process of coating the zinc sulfide shell, aluminum isopropoxide is used as the aluminum source to dope the shell layer. The reducing aluminum isopropoxide reacts with the solvent of sulfur source, tri-n-octylphosphine, under the condition of trace water and oxygen, and this reaction exists throughout the process of coating the shell layer, so that aluminum is finally doped uniformly in the form of aluminum phosphate in the zinc sulfide shell layer. The introduction of trivalent aluminum can reduce the degree of charge mismatch between the zinc sulfide shell and the indium phosphide core, passivate the oxidation defects of the indium phosphide core, and improve the stability of the shell layer, thereby obtaining a core-shell quantum dot with excellent luminescent performance. For example, Chinese invention patent No. CN118289720A provides a two-step method for synthesizing aluminum-doped indium phosphide quantum dots and the product thereof. The inventor passivates the surface defects of the indium phosphide quantum dots, making the particle size distribution more uniform, the fluorescence peak half-peak width smaller, and the quantum yield higher. The use of aluminum isopropoxide forms an oxide film on the outer layer of the quantum dots to inhibit the oxidation of the quantum dot core-shell interface, improve the photo-thermal stability of the quantum dots, and alleviate Ostwald ripening.

[0004] In display applications, there are usually strict requirements for the half-peak width of quantum dots. Specifically, in order to achieve high color purity and good display effect, it is desirable to have as narrow a half-peak width of quantum dots as possible. A narrower half-peak width means that the colors are more vivid and pure, and various colors can be accurately presented, thereby improving the display quality and color performance. This can make the displayed images clearer and more vivid, and reduce the mixing and blurring of colors. Common methods for reducing the half-peak width of quantum dots include optimizing the synthesis process, post-processing techniques, and surface modification, etc. Doping can reduce the defects on the surface of the material and improve the surface roughness, thereby further improving the half-peak width. Based on the research results of the inventors, the half-peak width of indium phosphide quantum dots is currently controlled at about 40 nm, and in actual preparation, the lowest level can reach 38 nm. It is particularly difficult to further reduce the fluorescence half-peak width on this basis. Through metal ion doping or surface coating, it is expected to improve the absorption and fluorescence properties of indium phosphide quantum dots, and even improve the performance of indium phosphide quantum dot QLEDs. Therefore, the study of the doping synthesis and optical properties of indium phosphide quantum dots is of great significance.

[0005] In summary, developing a new method for reducing the fluorescence half-peak width of core-shell type indium phosphide quantum dots by aluminum doping can further reduce the half-peak width of quantum dots, which has a positive significance for promoting the large-scale production and commercialization of indium phosphide quantum dots. SUMMARY

[0006] In view of the above-mentioned defects of the prior art, in the first aspect of the present application, a method for reducing the fluorescence half-peak width of core-shell type indium phosphide quantum dots by aluminum doping is provided, which is simple in process, convenient in synthesis, and easy to scale up, comprising the following steps:

[0007] (1) Isopropyl aluminum, indium source and phosphorus source are reacted in a solution environment in the presence of zinc halide, aluminum is introduced in the preparation of the core layer to form an aluminum-doped indium phosphide core;

[0008] (2) The aluminum-doped indium phosphide core is passivated by treating it with zinc chloride in a solution environment, and then the shell layer raw materials of zinc source, selenium source and sulfur source are used to react in batches to coat the aluminum-doped indium phosphide core layer by layer to form a gradient type zinc sulfoselenide shell;

[0009] (3) The surface layer of the gradient type zinc sulfoselenide shell is reacted with a sulfur source to form a zinc sulfide shell; then the surface of the zinc sulfide shell is treated with zinc acetate in a solution environment to obtain core-shell type indium phosphide quantum dots.

[0010] Preferably, in the step (1), the indium source includes at least one of indium chloride, indium bromide, indium iodide, and indium acetate; the phosphorus source includes at least one of tris(trimethylsilyl)phosphine, tris(dimethylamino)phosphine, and tris(diethylamino)phosphine; and the zinc halide includes at least one of zinc chloride, zinc bromide, and zinc iodide.

[0011] Preferably, in the step (1), the molar ratio of the indium source to the phosphorus source is 1:3-5; the molar ratio of the indium source to the zinc halide is 1:2-5; and the molar ratio of the indium source to the aluminum isopropoxide is 1:1-4.

[0012] Preferably, in the step (1), the reaction temperature is 120-220 ℃, and the reaction time is 1-60 min.

[0013] In the present application, the recovery and purification of the aluminum-doped indium phosphide core can be achieved in various ways. Those skilled in the art can select appropriate methods according to actual conditions to collect the target product after the reaction is completed. For example, as presented in one or more embodiments of the present application, a desolvent is added to the crude reaction solution obtained in the reaction to precipitate the product, and then the lower layer of the precipitate is collected by centrifugation, thereby achieving the above-mentioned purpose simply and conveniently. Based on the physical and chemical properties of the product, ethanol, acetone, methanol, and the like are suitable types of desolvents.

[0014] Preferably, in the step (2), the treatment temperature for passivation is 100-150 ℃, and the treatment time is 1-2 h.

[0015] Preferably, in the step (2), the zinc source includes at least one of zinc stearate and zinc(II) acetate; the selenium source includes at least one of selenium and selenium oxide; and the sulfur source includes at least one of sulfur, 1-dodecanethiol, and octanethiol.

[0016] Preferably, in the step (2), the molar ratio of the zinc chloride to the indium source is 1:2-5; the molar ratio of the zinc source to the indium source, based on the proportion of the raw material to the indium source in the step (1), is 1-5:1; the molar ratio of the sulfur source to the indium source is 0.5-10:1; and the molar ratio of the selenium source to the indium source is 0.5-5:1.

[0017] Preferably, in the step (2), the reaction temperature is 240-320 ℃, and the reaction time is 1-3 h.

[0018] Further preferably, the shell layer raw materials are reacted in a solution environment in 4 batches to coat the passivated indium phosphide core layer by layer; the first batch is reacted at 250 ℃ for 2 h; the second batch is reacted at 260 ℃ for 2 h; the third batch is reacted at 270 ℃ for 2 h; and the fourth batch is reacted at 280 ℃ for 3 h.

[0019] In the inventors' prior research, it was confirmed that introducing aluminum doping during shell preparation is beneficial for reducing the fluorescence half-width at half-maximum (HWHM) of core-shell indium phosphide quantum dots. After completing the preparation of the aluminum-doped indium phosphide core, this invention can also add aluminum isopropoxide during shell preparation to further optimize the fluorescence HWHM of the product.

[0020] Furthermore, when the shell material is reacted in solution in 4 batches, aluminum isopropoxide is added during the reaction process to dope each layer of the gradient zinc sulfide shell; the molar ratio of aluminum isopropoxide to sulfur source in step (2) is 0.2-3:1.

[0021] Preferably, in step (3), the sulfur source includes at least one of sulfur, 1-dodecyl mercaptan, and octyl mercaptan.

[0022] Preferably, in step (3), the molar ratio of the sulfur source to the indium source in step (1) is 0.5-10:1; and the molar ratio of zinc acetate to the sulfur source in step (3) is 0.25-1:1.

[0023] Preferably, in step (3), when using sulfur source to carry out surface reaction of gradient zinc sulfide shell, aluminum isopropoxide is added during the reaction process to dope the zinc sulfide shell; the molar ratio of aluminum isopropoxide to sulfur source in step (3) is 1:2-15.

[0024] Preferably, in step (3), the reaction temperature is 190-220 ℃ and the reaction time is 0.5-2 h; the treatment temperature is 190-220 ℃ and the treatment time is 0.5-2 h.

[0025] In this invention, the solution environment involved in each step is created by a suitable type of solvent. Those skilled in the art know that solvents play a role in promoting the dispersion of substances and creating a suitable environment for the reaction, and are chemically inert relative to the substrate or product. Therefore, the type or amount of solvent involved in the above reactions can be determined based on the physicochemical properties of the substrate and actual conditions. As presented in one or more embodiments of this invention, indium sources are soluble in oleylamine, phosphorus sources are soluble in tri-n-octylphosphine, and zinc halides or zinc acetate are soluble in oleylamine, octadecene, etc. Other suitable solvent types can also achieve the objectives of this invention.

[0026] In a second aspect of the present invention, a core-shell indium phosphide quantum dot with narrow fluorescence half-peak width and no heavy metal elements in its composition is provided, which is prepared by the method of the first aspect of the present invention.

[0027] Based on the above technical solutions, the design concept and principle of this invention lies in introducing a certain amount of aluminum isopropoxide during the nucleation step of indium phosphide. The addition of aluminum isopropoxide introduces aluminum into the core, making the core particle size more uniform during formation and accompanied by a reduction in core size. On one hand, it may bind to the quantum dot surface in the form of Z-type ligands, thereby passivating the surface defects of the indium phosphide quantum dots, resulting in a more uniform particle size distribution and a smaller full width at half maximum (FWHM) of the ultraviolet absorption peak, thus improving the quantum yield after shell formation. On the other hand, aluminum isopropoxide can effectively inhibit Ostwald ripening during synthesis, making the particle size distribution of the indium phosphide core more uniform. Furthermore, the indium phosphide core can be activated by aluminum isopropoxide, making the growth of the zinc sulfoselenide shell more favorable. Combined with the characterization results, the final quantum dot size is larger than that without aluminum doping, indicating that aluminum doping in the core before shell formation results in a thicker shell, further demonstrating that the activation of the core after aluminum doping is beneficial to shell growth. In the inventors' prior research, aluminum isopropoxide was introduced into the outer shell layer to passivate surface defects and improve the quantum yield of quantum dots. In contrast, the process described in this invention is more direct and effective than shell-based treatment. Similarly, the core-shell indium phosphide quantum dots prepared by this invention have advantages such as being free of heavy metals and being environmentally friendly, making them suitable for widespread application.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] This invention provides a method for reducing the full width at half maximum (FWHM) of fluorescence in core-shell indium phosphide quantum dots by aluminum doping, which has the advantages of simple process, convenient synthesis and easy large-scale production.

[0030] This invention provides a core-shell indium phosphide quantum dot with narrow fluorescence half-peak width. Its components do not contain heavy metal elements, making it environmentally friendly and suitable for promotion and application. Attached Figure Description

[0031] Figure 1 The UV-vis spectrum of the aluminum-doped indium phosphide core in Comparative Example 1 is shown.

[0032] Figure 2 The image shows a transmission electron microscope (TEM) image of the aluminum-doped indium phosphide core in Comparative Example 1.

[0033] Figure 3 The fine spectrum of aluminum in Comparative Example 1 is obtained by X-ray photoelectron spectroscopy (XPS).

[0034] Figure 4 The UV absorption and fluorescence spectra of the core-shell indium phosphide quantum dots in Example 1 are shown.

[0035] Figure 5 This is a transmission electron microscope image of the core-shell indium phosphide quantum dots from Example 1;

[0036] Figure 6 The UV absorption spectrum of the undoped indium phosphide core in Comparative Example 2 is shown.

[0037] Figure 7 The image shows a transmission electron microscope (TEM) image of the undoped indium phosphide core in Comparative Example 2.

[0038] Figure 8 The UV absorption and fluorescence spectra of undoped core-shell indium phosphide quantum dots in Comparative Example 3 are shown.

[0039] Figure 9 This is a transmission electron microscope (TEM) image of undoped core-shell indium phosphide quantum dots, as shown in Comparative Example 3. Detailed Implementation

[0040] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0041] Example 1

[0042] The method for reducing the full width at half maximum (FWHM) of fluorescence in core-shell indium phosphide quantum dots by aluminum doping is as follows:

[0043] (1) Take 0.8920 g of indium iodide, 0.5998 g of zinc chloride and 0.153 g of aluminum isopropoxide, dissolve them in a 50 mL three-necked flask containing 12 mL of oleylamine, first evacuate for 1 h, add 2 mL of tri-n-octylphosphine (TOP) solution containing 0.7 mL of tri(dimethylamino)phosphine under argon conditions, heat to 180 °C and react for 5 min; during this period, the solution color changes from colorless to orange and then to brown; after 5 min, immediately cool the solution to room temperature, then mix the obtained crude indium phosphide core with excess anhydrous ethanol, centrifuge at high speed (10000 rpm, 5 min) to collect the precipitate, obtain aluminum-doped indium phosphide core, then completely dissolve it with n-hexane for later use;

[0044] (2) Mix 6 mL of oleylamine, 6 mL of octadecene and 0.5998 g of zinc chloride in a 100 mL four-necked flask. First, evacuate the flask at room temperature, and then heat it to 130 °C for 1 h in an argon atmosphere (to keep the whole apparatus in an anhydrous and oxygen-free environment) to completely dissolve the zinc chloride. At this time, add the aluminum-doped indium phosphide core solution dissolved in n-hexane into the reaction system and collect the n-hexane vapor through a reflux condenser to complete the passivation.

[0045] A zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), a selenium source, and a sulfur source (0.8 mmol selenium powder and 0.9 mmol sulfur powder dissolved in 1.25 mL tri-n-octylphosphine) were rapidly injected into a reaction flask and heated to 200 °C, mixing continuously for 30 min. Next, the mixture was heated to 250 °C and reacted for 2 h. A second injection of the zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), selenium source, and sulfur source (0.6 mmol selenium powder and 1.8 mmol sulfur powder dissolved in 1.5 mL tri-n-octylphosphine) was injected, and the reaction was carried out at 260 °C for 2 h. A third injection of the zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), selenium source, and sulfur source (0.4 mmol selenium powder and 2.7 mmol sulfur powder dissolved in 1.75 mL tri-n-octylphosphine) was injected, and the reaction was carried out at 270 °C for 2 h. A fourth injection of the zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), selenium source, and sulfur source (0.4 mmol selenium powder and 2.7 mmol sulfur powder dissolved in 1.75 mL tri-n-octylphosphine) was injected. g of zinc stearate dissolved in 4 mL of octadecene) and selenium source and sulfur source (0.2 mmol selenium powder and 3.6 mmol sulfur powder dissolved in 2 mL of tri-n-octylphosphine), reacted at 280 °C for 3 h to form a gradient aluminum-doped zinc sulfoselenide shell;

[0046] (3) The temperature was rapidly cooled to 210 °C, 1.5 mL of octyl mercaptan was added, and the reaction was carried out at 210 °C for 30 min. The temperature was then lowered to 190 °C, and zinc acetate solution (2 mmol of zinc acetate dihydrate dissolved in 2 mL of oleylamine and 10 mL of octadecene) was added. The reaction was carried out at 190 °C for 1 h and then cooled to room temperature to obtain crude quantum dots. The crude quantum dots were mixed with anhydrous ethanol at a volume ratio of 1:7, centrifuged and purified, and the obtained core-shell indium phosphide quantum dots were redispersed in n-hexane.

[0047] Example 2

[0048] A method for reducing the full width at half maximum (FWHM) of fluorescence in core-shell indium phosphide quantum dots by aluminum doping is described in this embodiment. Aluminum isopropoxide is added during the preparation of the gradient-doped zinc sulfide selenide shell, and the steps are as follows:

[0049] (1) Take 0.8920 g of indium iodide, 0.5998 g of zinc chloride and 0.153 g of aluminum isopropoxide, dissolve them in a 50 mL three-necked flask containing 12 mL of oleylamine, first evacuate for 1 h, add 2 mL of tri-n-octylphosphine (TOP) solution containing 0.7 mL of tri(dimethylamino)phosphine under argon conditions, heat to 180 °C and react for 5 min; during this period, the solution color changes from colorless to orange and then to brown; after 5 min, immediately cool the solution to room temperature, then mix the obtained crude indium phosphide core with excess anhydrous ethanol, centrifuge at high speed (10000 rpm, 5 min) to collect the precipitate, obtain aluminum-doped indium phosphide core, then completely dissolve it with n-hexane for later use;

[0050] (2) Mix 6 mL of oleylamine, 6 mL of octadecene and 0.5998 g of zinc chloride in a 100 mL four-necked flask. First, evacuate the flask at room temperature, and then heat it to 130 °C for 1 h in an argon atmosphere (to keep the whole apparatus in an anhydrous and oxygen-free environment) to completely dissolve the zinc chloride. At this time, add the aluminum-doped indium phosphide core solution dissolved in n-hexane into the reaction system and collect the n-hexane vapor through a reflux condenser to complete the passivation.

[0051] Aluminum isopropoxide solution (0.5 mmol aluminum isopropoxide dissolved in 0.5 mL oleylamine), along with a zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), a selenium source, and a sulfur source (0.8 mmol selenium powder and 0.9 mmol sulfur powder dissolved in 1.25 mL tri-n-octylphosphine), was rapidly injected into a reaction flask and heated to 200 °C, mixing continuously for 30 min. The mixture was then heated to 250 °C and reacted for 2 h. A second injection of aluminum isopropoxide solution (0.5 mmol aluminum isopropoxide dissolved in 0.5 mL oleylamine), along with a zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), a selenium source, and a sulfur source (0.6 mmol selenium powder and 1.8 mmol sulfur powder dissolved in 1.5 mL tri-n-octylphosphine), was injected, and the reaction was carried out at 260 °C for 2 h. A third injection of aluminum isopropoxide solution (0.5 mmol aluminum isopropoxide dissolved in 0.5 mL oleylamine), along with a zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), was injected, and the reaction was carried out at 260 °C for 2 h. 1.0 g of zinc stearate dissolved in 4 mL of octadecene) and selenium and sulfur sources (0.4 mmol of selenium powder and 2.7 mmol of sulfur powder dissolved in 1.75 mL of tri-n-octylphosphine) were added and reacted at 270 °C for 2 h. A fourth injection of aluminum isopropoxide solution (0.5 mmol of aluminum isopropoxide dissolved in 0.5 mL of oleylamine) and zinc source (1.0 g of zinc stearate dissolved in 4 mL of octadecene) and selenium and sulfur sources (0.2 mmol of selenium powder and 3.6 mmol of sulfur powder dissolved in 2 mL of tri-n-octylphosphine) was added and reacted at 280 °C for 3 h to form a gradient aluminum-doped zinc sulfoselenide shell.

[0052] (3) The temperature was rapidly cooled to 210 °C, 1.5 mL of octyl mercaptan was added, and the reaction was carried out at 210 °C for 30 min. The temperature was then lowered to 190 °C, and zinc acetate solution (2 mmol of zinc acetate dihydrate dissolved in 2 mL of oleylamine and 10 mL of octadecene) was added. The reaction was carried out at 190 °C for 1 h and then cooled to room temperature to obtain crude quantum dots. The crude quantum dots were mixed with anhydrous ethanol at a volume ratio of 1:7, centrifuged and purified, and the obtained core-shell indium phosphide quantum dots were redispersed in n-hexane.

[0053] Example 3

[0054] A method for reducing the full width at half maximum (FWHM) of fluorescence in core-shell indium phosphide quantum dots by aluminum doping is described in this embodiment, where aluminum isopropoxide is added during the preparation of the zinc sulfide shell, as follows:

[0055] (1) Take 0.8920 g of indium iodide, 0.5998 g of zinc chloride and 0.153 g of aluminum isopropoxide, dissolve them in a 50 mL three-necked flask containing 12 mL of oleylamine, first evacuate for 1 h, add 2 mL of tri-n-octylphosphine (TOP) solution containing 0.7 mL of tri(dimethylamino)phosphine under argon conditions, heat to 180 °C and react for 5 min; during this period, the solution color changes from colorless to orange and then to brown; after 5 min, immediately cool the solution to room temperature, then mix the obtained crude indium phosphide core with excess anhydrous ethanol, centrifuge at high speed (10000 rpm, 5 min) to collect the precipitate, obtain aluminum-doped indium phosphide core, then completely dissolve it with n-hexane for later use;

[0056] (2) Mix 6 mL of oleylamine, 6 mL of octadecene and 0.5998 g of zinc chloride in a 100 mL four-necked flask. First, evacuate the flask at room temperature, and then heat it to 130 °C for 1 h in an argon atmosphere (to keep the whole apparatus in an anhydrous and oxygen-free environment) to completely dissolve the zinc chloride. At this time, add the aluminum-doped indium phosphide core solution dissolved in n-hexane into the reaction system and collect the n-hexane vapor through a reflux condenser to complete the passivation.

[0057] A zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), a selenium source, and a sulfur source (0.8 mmol selenium powder and 0.9 mmol sulfur powder dissolved in 1.25 mL tri-n-octylphosphine) were rapidly injected into a reaction flask and heated to 200 °C, mixing continuously for 30 min. Next, the mixture was heated to 250 °C and reacted for 2 h. A second injection of the zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), selenium source, and sulfur source (0.6 mmol selenium powder and 1.8 mmol sulfur powder dissolved in 1.5 mL tri-n-octylphosphine) was injected, and the reaction was carried out at 260 °C for 2 h. A third injection of the zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), selenium source, and sulfur source (0.4 mmol selenium powder and 2.7 mmol sulfur powder dissolved in 1.75 mL tri-n-octylphosphine) was injected, and the reaction was carried out at 270 °C for 2 h. A fourth injection of the zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), selenium source, and sulfur source (0.4 mmol selenium powder and 2.7 mmol sulfur powder dissolved in 1.75 mL tri-n-octylphosphine) was injected. g of zinc stearate dissolved in 4 mL of octadecene) and selenium source and sulfur source (0.2 mmol selenium powder and 3.6 mmol sulfur powder dissolved in 2 mL of tri-n-octylphosphine), reacted at 280 °C for 3 h to form a gradient aluminum-doped zinc sulfoselenide shell;

[0058] (3) The temperature was rapidly cooled to 210 °C, and a solution of 0.75 mmol aluminum isopropoxide dissolved in 1.5 mL of octyl mercaptan was added. The reaction was carried out at 210 °C for 30 min. The temperature was then lowered to 190 °C, and a zinc acetate solution (2 mmol of zinc acetate dihydrate dissolved in 2 mL of oleylamine and 10 mL of octadecene) was added. The reaction was carried out at 190 °C for 1 h and then cooled to room temperature to obtain crude quantum dots. The crude quantum dots were mixed with anhydrous ethanol at a volume ratio of 1:7. After centrifugation and precipitation purification, the obtained core-shell indium phosphide quantum dots were redispersed in n-hexane.

[0059] Example 4

[0060] A method for reducing the full width at half maximum (FWHM) of fluorescence in core-shell indium phosphide quantum dots by aluminum doping is described in this embodiment. Aluminum isopropoxide is added during the preparation of the gradient-doped zinc sulfide selenide shell and the zinc sulfide shell. The steps are as follows:

[0061] (1) Take 0.8920 g of indium iodide, 0.5998 g of zinc chloride and 0.153 g of aluminum isopropoxide, dissolve them in a 50 mL three-necked flask containing 12 mL of oleylamine, first evacuate for 1 h, add 2 mL of tri-n-octylphosphine (TOP) solution containing 0.7 mL of tri(dimethylamino)phosphine under argon conditions, heat to 180 °C and react for 5 min; during this period, the solution color changes from colorless to orange and then to brown; after 5 min, immediately cool the solution to room temperature, then mix the obtained crude indium phosphide core with excess anhydrous ethanol, centrifuge at high speed (10000 rpm, 5 min) to collect the precipitate, obtain aluminum-doped indium phosphide core, then completely dissolve it with n-hexane for later use;

[0062] (2) Mix 6 mL of oleylamine, 6 mL of octadecene and 0.5998 g of zinc chloride in a 100 mL four-necked flask. First, evacuate the flask at room temperature, and then heat it to 130 °C for 1 h in an argon atmosphere (to keep the whole apparatus in an anhydrous and oxygen-free environment) to completely dissolve the zinc chloride. At this time, add the aluminum-doped indium phosphide core solution dissolved in n-hexane into the reaction system and collect the n-hexane vapor through a reflux condenser to complete the passivation.

[0063] Aluminum isopropoxide solution (0.5 mmol aluminum isopropoxide dissolved in 0.5 mL oleylamine), along with a zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), a selenium source, and a sulfur source (0.8 mmol selenium powder and 0.9 mmol sulfur powder dissolved in 1.25 mL tri-n-octylphosphine), was rapidly injected into a reaction flask and heated to 200 °C, mixing continuously for 30 min. The mixture was then heated to 250 °C and reacted for 2 h. A second injection of aluminum isopropoxide solution (0.5 mmol aluminum isopropoxide dissolved in 0.5 mL oleylamine), along with a zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), a selenium source, and a sulfur source (0.6 mmol selenium powder and 1.8 mmol sulfur powder dissolved in 1.5 mL tri-n-octylphosphine), was injected, and the reaction was carried out at 260 °C for 2 h. A third injection of aluminum isopropoxide solution (0.5 mmol aluminum isopropoxide dissolved in 0.5 mL oleylamine), along with a zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), was injected, and the reaction was carried out at 260 °C for 2 h. 1.0 g of zinc stearate dissolved in 4 mL of octadecene) and selenium and sulfur sources (0.4 mmol of selenium powder and 2.7 mmol of sulfur powder dissolved in 1.75 mL of tri-n-octylphosphine) were added and reacted at 270 °C for 2 h. A fourth injection of aluminum isopropoxide solution (0.5 mmol of aluminum isopropoxide dissolved in 0.5 mL of oleylamine) and zinc source (1.0 g of zinc stearate dissolved in 4 mL of octadecene) and selenium and sulfur sources (0.2 mmol of selenium powder and 3.6 mmol of sulfur powder dissolved in 2 mL of tri-n-octylphosphine) was added and reacted at 280 °C for 3 h to form a gradient aluminum-doped zinc sulfoselenide shell.

[0064] (3) The temperature was rapidly cooled to 210 °C, and a solution of 0.75 mmol aluminum isopropoxide dissolved in 1.5 mL of octyl mercaptan was added. The reaction was carried out at 210 °C for 30 min. The temperature was then lowered to 190 °C, and a zinc acetate solution (2 mmol of zinc acetate dihydrate dissolved in 2 mL of oleylamine and 10 mL of octadecene) was added. The reaction was carried out at 190 °C for 1 h and then cooled to room temperature to obtain crude quantum dots. The crude quantum dots were mixed with anhydrous ethanol at a volume ratio of 1:7. After centrifugation and precipitation purification, the obtained core-shell indium phosphide quantum dots were redispersed in n-hexane.

[0065] Comparative Example 1

[0066] The aluminum-doped indium phosphide cores in this comparative example were prepared using the following method:

[0067] Take 0.8920 g of indium iodide, 0.5998 g of zinc chloride, and 0.153 g of aluminum isopropoxide, and dissolve them in a 50 mL three-necked flask containing 12 mL of oleylamine. First, evacuate the flask for 1 h, then add 2 mL of a tri-n-octylphosphine solution containing 0.7 mL of tris(dimethylamino)phosphine under argon atmosphere. Heat the flask to 180 °C and react for 5 min. During this time, the solution color changes from colorless to orange and then to brown. After 5 min, immediately cool the solution to room temperature, then mix the obtained crude indium phosphide core with excess anhydrous ethanol, centrifuge at high speed (10000 rpm, 5 min) to collect the precipitate, and obtain aluminum-doped indium phosphide core, which is then completely dissolved in n-hexane.

[0068] Comparative Example 2

[0069] The undoped indium phosphide core in this comparative example was prepared using the following method:

[0070] Take 0.8920 g of indium iodide and 0.5998 g of zinc chloride, dissolve them in a 50 mL three-necked flask containing 12 mL of oleylamine, evacuate for 1 h, add 2 mL of tri-n-octylphosphine solution containing 0.7 mL of tri(dimethylamino)phosphine under argon atmosphere, heat to 180 °C and react for 5 min; during this period, the solution color changes from colorless to orange and then to brown; immediately after 5 min, cool the solution to room temperature, then mix the obtained indium phosphide core with excess anhydrous ethanol, centrifuge at high speed (10000 rpm, 5 min) to collect the precipitate, and then completely dissolve the indium phosphide core with n-hexane.

[0071] Comparative Example 3

[0072] The undoped core-shell indium phosphide quantum dots in this comparative example were prepared using the following method:

[0073] (1) Take 0.8920 g of indium iodide and 0.5998 g of zinc chloride, dissolve them in a 50 mL three-necked flask containing 12 mL of oleylamine, first evacuate for 1 h, add 2 mL of tri-n-octylphosphine solution containing 0.7 mL of tri(dimethylamino)phosphine under argon conditions, heat to 180 °C and react for 1 min; during this period, the solution color changes from colorless to orange and then to brown; after 1 min, immediately cool the solution to room temperature, then mix the obtained indium phosphide core with excess anhydrous ethanol, centrifuge at high speed (10000 rpm, 5 min) to collect the precipitate, and then completely dissolve the indium phosphide core with n-hexane;

[0074] (2) Mix 6 mL of oleylamine, 6 mL of octadecene and 0.5998 g of zinc chloride in a 100 mL four-necked flask. First, evacuate the flask at room temperature, and then heat it to 130 °C for 1 h in an argon atmosphere (to keep the whole apparatus in an anhydrous and oxygen-free environment) to completely dissolve the zinc chloride. At this time, add the indium phosphide core solution dissolved in n-hexane into the reaction system and collect the n-hexane vapor through a reflux condenser to complete the passivation.

[0075] A zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), a selenium source, and a sulfur source (0.8 mmol selenium powder and 0.9 mmol sulfur powder dissolved in 1.25 mL tri-n-octylphosphine) were rapidly injected into a reaction flask and heated to 200 °C, mixing continuously for 30 min. Next, the mixture was heated to 250 °C and reacted for 2 h. A second injection of the zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), selenium source, and sulfur source (0.6 mmol selenium powder and 1.8 mmol sulfur powder dissolved in 1.5 mL tri-n-octylphosphine) was injected, and the reaction was carried out at 260 °C for 2 h. A third injection of the zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), selenium source, and sulfur source (0.4 mmol selenium powder and 2.7 mmol sulfur powder dissolved in 1.75 mL tri-n-octylphosphine) was injected, and the reaction was carried out at 270 °C for 2 h. A fourth injection of the zinc source (1.0 g zinc stearate dissolved in 4 mL octadecene), selenium source, and sulfur source (0.4 mmol selenium powder and 2.7 mmol sulfur powder dissolved in 1.75 mL tri-n-octylphosphine) was injected. g of zinc stearate dissolved in 4 mL of octadecene) and selenium source and sulfur source (0.2 mmol selenium powder and 3.6 mmol sulfur powder dissolved in 2 mL of tri-n-octylphosphine), reacted at 280℃ for 3 h to form a gradient zinc sulfoselenide shell;

[0076] (3) The temperature was rapidly cooled to 210 °C, 1.5 mL of octyl mercaptan was added, and the reaction was carried out at 210 °C for 30 min. The temperature was then lowered to 190 °C, and zinc acetate solution (2 mmol of zinc acetate dihydrate dissolved in 2 mL of oleylamine and 10 mL of octadecene) was added. The reaction was carried out at 190 °C for 1 h and then cooled to room temperature to obtain undoped crude quantum dots. The crude quantum dots were mixed with anhydrous ethanol at a volume ratio of 1:7. After centrifugation and precipitation purification, the obtained undoped core-shell indium phosphide quantum dots were redispersed in n-hexane.

[0077] Test Example 1

[0078] Examples 1-4 were used as typical embodiments of the present invention, and the quantum dots prepared therein and those prepared in Comparative Examples 1-3 were characterized. The properties of the various quantum dots were tested using ultraviolet absorption and fluorescence spectra, transmission electron microscopy, and X-ray photoelectron spectroscopy, and the corresponding results are as follows: Figures 1-9 As shown in the figure, the indium phosphide core prepared in Comparative Example 1 exhibits better size uniformity than the undoped quantum dots prepared in Comparative Example 2, as can be seen from the comparison of transmission electron microscopy images.

[0079] The UV absorption peak, fluorescence emission peak, full width at half maximum (FWHM), and quantum yield of the quantum dots prepared in the above examples and comparative examples were statistically analyzed and calculated. The FWHM was measured using a CaryEclipse fluorescence spectrophotometer (Agilent Technologies) at a solution concentration of 0.5 mg / mL. The characterization results of the optical properties of the quantum dots are shown in Table 1.

[0080] Table 1: Characterization results of optical properties of quantum dots

[0081]

[0082] In the table, " / " indicates that there is no data available for testing.

[0083] As shown in the table above, the successful aluminum doping of the quantum dots in Comparative Example 1 is evident from the XPS spectra shown in Figure 3. Furthermore, compared to Comparative Example 2, from... Figure 1 , Figure 6 The UV absorption spectrum shows an increased peak-to-valley ratio, indicating that the addition of aluminum during nucleation effectively suppressed Ostwald ripening; from Figure 2 , Figure 7 The TEM images show that adding aluminum during nucleation makes the particle size distribution of the resulting indium phosphide nuclei more uniform. The fluorescence emission peak of the indium phosphide quantum dots prepared after aluminum doping in Examples 1-4 of this invention remains around 530 nm, exhibiting green light emission. Compared to Comparative Example 3, the addition of a certain proportion of aluminum isopropoxide in Examples 1-4 significantly narrowed the full width at half maximum (FWHM) of the quantum dots, decreasing from 44 nm to 35-37 nm. This indicates that the method provided by this invention can significantly improve the size uniformity of core-shell indium phosphide quantum dots, which is more intuitively apparent from the corresponding TEM images. Furthermore, compared to the comparative example, the addition of a certain proportion of aluminum isopropoxide in Examples 1-4 significantly improved the quantum yield, increasing it from 67% to 76%-86%. This demonstrates that the method provided by this invention can alleviate Ostwald ripening during the synthesis process, reduce the FWHM of the quantum dots, and improve the luminescence efficiency and performance of the quantum dots.

[0084] Based on the above test results, the primary function of adding aluminum to the core is to make the core particle size more uniform during formation. This is evident in the narrower peak shape in the UV absorption spectrum, indicating a more uniform core size. The introduction of the outer shell is mainly to passivate surface defects and improve the quantum yield of the quantum dots. Therefore, processing the core is more direct and effective than processing the shell. The full width at half maximum (FWHM) can be reduced to a much lower level, reaching as low as 35 nm. While adding aluminum to the core results in a narrower core size, the final quantum dot size is still larger than that without aluminum doping. This indicates that adding aluminum to the core before forming the shell results in a thicker shell, further demonstrating that aluminum doping of the core is beneficial for shell growth, and that the core is activated during this process.

[0085] Further reducing the fluorescence half-width at half-maximum (WHM) based on the inventors' previous research presents a significant technical challenge. This difficulty in further optimization stems from inherent defects in the system itself. The fundamental problem is that the selection of phosphorus sources is limited during the synthesis of indium phosphide quantum dots, and these sources are extremely reactive. When the phosphorus source is injected into the indium source at high temperature, it instantly binds with the indium, rapidly reaching a critical concentration of monomers. Therefore, nucleation occurs rapidly upon injection, but due to the excessive reactivity of the phosphorus source, there is insufficient phosphorus monomer for subsequent growth. The nucleated particles then ripen at high temperatures, leading to uneven particle size distribution and consequently, a broadened peak width. In this invention, aluminum is introduced into the nucleus preparation process to suppress Ostwald ripening during the nucleation process, thus overcoming the technological shortcomings of existing techniques.

[0086] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for reducing the full width at half maximum of a core-shell InP quantum dot fluorescence by aluminum doping, characterized in that, Comprising the following steps: (1) reacting aluminum isopropoxide, an indium source and a phosphorus source in a solution environment with zinc halide to form an aluminum-doped indium phosphide core in the preparation of the core layer; In this step, the indium source includes at least one of indium chloride, indium bromide, indium iodide and indium acetate; the phosphorus source includes at least one of tris(trimethylsilyl) phosphine, tris(dimethylamino) phosphine and tris(diethylamino) phosphine; the zinc halide includes at least one of zinc chloride, zinc bromide and zinc iodide; the molar ratio of the indium source to the phosphorus source is 1:3-5; the molar ratio of the indium source to the zinc halide is 1:2-5; the molar ratio of the indium source to the aluminum isopropoxide is 1:1-4; the reaction temperature is 120-220 ℃, and the reaction time is 1-60 min; (2) treating the aluminum-doped indium phosphide core with zinc chloride in a solution environment to passivate the core, and then using a zinc source, a selenium source and a sulfur source as shell materials to react in batches to form a gradient zinc sulfoselenide shell layer by layer on the aluminum-doped indium phosphide core; In this step, the reaction temperature is 240-320 ℃, and the reaction time is 1-3 h; the passivation treatment temperature is 100-150 ℃, and the treatment time is 1-2 h; the shell materials are reacted in batches in a solution environment to coat the passivated indium phosphide core layer by layer; the first batch is reacted at 250 ℃ for 2 h; the second batch is reacted at 260 ℃ for 2 h; the third batch is reacted at 270 ℃ for 2 h; and the fourth batch is reacted at 280 ℃ for 3 h; when the shell materials are reacted in batches in a solution environment, aluminum isopropoxide is added during the reaction process to dope each layer of the gradient zinc sulfoselenide shell layer; the molar ratio of the aluminum isopropoxide to the sulfur source in this step is 0.2-3:1; (3) using a sulfur source to perform surface layer reaction on the gradient zinc sulfoselenide shell layer to form a zinc sulfide shell layer; and then treating the surface of the zinc sulfide shell layer with zinc acetate in a solution environment to obtain core-shell type indium phosphide quantum dots; In this step, when the sulfur source is used to perform surface layer reaction on the gradient zinc sulfoselenide shell layer, aluminum isopropoxide is added during the reaction process to dope the zinc sulfide shell layer; the molar ratio of the aluminum isopropoxide to the sulfur source in this step is 1:2-15. 2.The method for reducing the full width at half maximum of core-shell indium phosphide quantum dot fluorescence according to claim 1, characterized in that: In the step (2), the zinc source includes at least one of zinc stearate and zinc(II) acetate; the selenium source includes at least one of selenium and selenium oxide; the sulfur source includes at least one of sulfur, 1-dodecanethiol and octanethiol; the molar ratio of the zinc chloride to the indium source is 1:2-5; the molar ratio of the zinc source to the indium source, based on the proportion of the raw materials to the indium source in the step (1), is 1-5:1; the molar ratio of the sulfur source to the indium source is 0.5-10:1; and the molar ratio of the selenium source to the indium source is 0.5-5:

1.

3. The method for reducing the fluorescence full width at half maximum of aluminum-doped reduced core-shell indium phosphide quantum dots according to claim 1, characterized in that: In the step (3), the sulfur source includes at least one of sulfur, 1-dodecanethiol and octanethiol; the molar ratio of the sulfur source to the indium source in the step (1) is 0.5-10:1; the molar ratio of the zinc acetate to the sulfur source in the step (3) is 0.25-1:1; the reaction temperature is 190-220 ℃, and the reaction time is 0.5-2 h; the treatment temperature is 190-220 ℃, and the treatment time is 0.5-2 h.

4. A core-shell indium phosphide quantum dot, characterized by: The method is made by using the method as claimed in any one of claims 1-3.

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