Aluminum-doped indium phosphide core-shell quantum dots with tunable emission spectra and preparation method thereof
The one-pot method for preparing aluminum-doped indium phosphide core-shell quantum dots solves the problems of complex operation and charge mismatch in existing technologies, and achieves efficient and stable spectral tuning and large-scale production, which is suitable for applications such as multicolor displays.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHAN UNIV
- Filing Date
- 2023-10-08
- Publication Date
- 2026-06-05
AI Technical Summary
Existing methods for preparing indium phosphide core-shell quantum dots suffer from complex operations, poor reproducibility, high costs, and charge mismatch issues, making it difficult to achieve large-scale production and color adjustment.
Indium phosphide cores were prepared in a single-pot reaction vessel and coated with aluminum-doped zinc sulfide shells. Aluminum phosphate doping was generated by reacting aluminum isopropoxide with a sulfur source, which reduced the charge mismatch and improved the shell stability.
The efficient fabrication of aluminum-doped indium phosphide core-shell quantum dots with tunable emission spectra has been achieved, improving luminous efficiency and stability, and making them suitable for applications such as multicolor displays.
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Figure CN117487538B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of luminescent materials technology, specifically relating to an aluminum-doped indium phosphide core-shell quantum dot with tunable emission spectrum and its preparation method. Background Technology
[0002] Colloidal quantum dots, as fluorescent nanomaterials with quantum confinement effects, play an important role in human life. Although traditional cadmium selenide (CdSe) quantum dots and novel perovskite (CsPbX3, X = Cl, Br, I) quantum dots have achieved excellent optical properties, the use of heavy metal elements in them limits their applications. Indium phosphide (InP) quantum dots, with their large Bohr exciton radius (9.6 nm), narrow band gap (1.34 eV), wide range of emission wavelength tuning, environmental friendliness, and non-biotoxicity, are considered the most promising alternative materials and are expected to be applied in fields such as green lighting, display technology, and biomedicine.
[0003] The hot-injection method is the most commonly used method for preparing indium phosphide cores, and the selection of reactants and control of experimental conditions are crucial. In early studies, highly reactive tris(trimethylsilyl)phosphine was used as a phosphorus precursor. Although it yielded quantum dots with good luminescence properties, silylphosphine is expensive and produces highly toxic phosphine gas upon contact with air. Until 2015, Tessier et al. at Ghent University in Belgium developed a synthesis scheme using tris(dimethylamino)phosphine and indium halide as precursors. Compared to silylphosphine, aminophosphine has advantages such as low toxicity, high stability, and economy, making it more suitable for industrial production and thus sparking a research boom. Aminophosphine is usually used in combination with indium halide and zinc halide. By changing the type of halogen, reaction temperature, and time, the size of the indium phosphide core can be controlled, thereby achieving fine adjustment of the band gap width.
[0004] Because indium phosphide cores have weak exciton confinement capabilities, a common strategy is to use a shell material to suppress nonradiative recombination of electron-hole pairs and improve photoluminescence quantum yield (PLQY) by constructing a type I band structure at the interface. The mainstream shell materials are group II-VI compounds, such as zinc sulfide (ZnS), zinc selenide (ZnSe), and zinc sulfide-selenide alloy (ZnSe). X S 1-XAmong various quantum dot materials, zinc sulfide shells exhibit the widest band gap and the strongest exciton confinement capability. Furthermore, the shell coating effectively isolates the indium phosphide core from the external environment, enhancing the stability and extending the lifespan of the quantum dot. However, current research on shells primarily focuses on reducing the lattice mismatch between the material and the indium phosphide core, rarely considering the inherent charge mismatch between shells composed of group II-VI elements and indium phosphide cores composed of group III-V elements. Charge mismatch can also lead to stress accumulation, localized delamination, and defect formation at the core-shell interface, affecting the final quantum dot performance. Introducing a suitable intermediate transition layer and doping the shell material with group IIIA elements such as gallium and aluminum can help regulate the electronic structure and charge distribution between the shell and the core, representing a possible approach to solving the interfacial charge imbalance problem.
[0005] To date, indium phosphide core-shell quantum dots based on aminophosphine have made significant progress, with their luminescence performance approaching that of cadmium-based quantum dots. However, they are mostly synthesized using a two-pot method. The two-pot method is characterized by the complete separation of the indium phosphide core preparation and shell coating processes. Specifically, the desired size indium phosphide core is first synthesized in one reaction vessel, purified, and then placed in another reaction vessel for epitaxial growth of the shell. While the two-pot method allows for better control of the core and shell growth processes, the indium phosphide core faces the risk of oxidation during purification, leading to surface defects. It also suffers from complex experimental procedures, long preparation cycles, and poor reproducibility. In contrast, the one-pot method, which completes the preparation of the indium phosphide core and shell coating in a single reaction vessel, is more convenient, efficient, economical, and environmentally friendly, demonstrating unique advantages in large-scale production. To obtain indium phosphide core-shell quantum dots with tunable color and excellent luminescence performance, the one-pot method also places higher demands on the selection of reactants, the proportion of reactants, and the control of reaction conditions. However, related research is very limited.
[0006] Based on this, a one-pot method for preparing indium phosphide core-shell quantum dots with different light colors has been developed by combining shell doping strategies. This method is of great significance for promoting the large-scale production and commercialization of indium phosphide-based quantum dots and is also a technical problem that urgently needs to be solved. Summary of the Invention
[0007] One of the objectives of this invention is to provide a one-pot method for preparing indium phosphide core-shell quantum dots with different light colors. This method is simple to process, convenient to synthesize, easy to scale up for production, and yields quantum dots with high luminous efficiency.
[0008] The second objective of this invention is to provide an aluminum-doped indium phosphide core-shell quantum dot with high luminous efficiency and tunable emission spectrum.
[0009] One of the technical solutions adopted by this invention to achieve its objective is to provide a method for preparing aluminum-doped indium phosphide core-shell quantum dots with tunable emission spectra.
[0010] In the same reaction vessel, an indium phosphide core is first prepared, and then coated with a zinc sulfide shell. During the coating process, a certain proportion of aluminum isopropoxide is added to react with the sulfur source solvent tri-n-octylphosphine, thereby doping aluminum into the zinc sulfide shell in the form of aluminum phosphate.
[0011] The general idea of the method for preparing aluminum-doped indium phosphide core-shell quantum dots with tunable emission spectra provided by this invention is as follows: To simplify the preparation process of core-shell quantum dots, this invention adopts a one-pot method, that is, the preparation of indium phosphide cores and shell coating are completed sequentially in the same reaction vessel. During the zinc sulfide shell coating process, aluminum isopropoxide is used as the aluminum source to dope the shell. The reducing aluminum isopropoxide reacts with the sulfur source solvent tri-n-octylphosphine under trace amounts of water and oxygen. This reaction occurs throughout the entire shell coating process, so that aluminum is uniformly doped into the zinc sulfide shell in the form of aluminum phosphate. The introduction of trivalent aluminum can reduce the 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, thereby obtaining core-shell quantum dots with excellent luminescence performance. The above preparation method has wide applicability. By shell-doping and coating indium phosphide cores of different sizes, indium phosphide core-shell quantum dots of different colors with tunable light color and high luminescence efficiency can be obtained.
[0012] Furthermore, the preparation method includes the following steps:
[0013] S1. Mix indium source, phosphorus source and zinc halide in a certain proportion and react at a certain temperature for a certain time to obtain indium phosphide core;
[0014] S2. Dissolve the sulfur source in tri-n-octylphosphine, and then add it together with aluminum isopropoxide into the indium phosphide core. Heat the mixture to perform the first shell coating to obtain an aluminum-doped zinc sulfide thin shell.
[0015] S3. Sulfur source, aluminum isopropoxide and zinc source dissolved in tri-n-octylphosphine are added to continue the reaction for the second shell coating, resulting in a thickened aluminum-doped zinc sulfide shell.
[0016] S4. The product from step S3 is purified to obtain aluminum-doped indium phosphide core-shell quantum dots with tunable emission spectra.
[0017] In the above preparation method, indium phosphide cores are first prepared, then a sulfur source and aluminum isopropoxide are added and the temperature is raised. While the sulfur source reacts with the original zinc halide in the reaction system, the reducing aluminum isopropoxide reacts with the sulfur source solvent tri-n-octylphosphine to generate aluminum phosphate, thereby achieving the coating of an aluminum-doped zinc sulfide thin shell on the surface of the indium phosphide core. By continuing to add sulfur source, aluminum isopropoxide and zinc source, and adjusting the reaction temperature and time, the aluminum-doped zinc sulfide shell is further thickened, improving the optical performance and stability of the quantum dots. Finally, the heat source is removed, the reaction system is cooled to room temperature, and the purification operation is completed, thus obtaining aluminum-doped core-shell indium phosphide quantum dots.
[0018] Preferably, in step S1, the product after the reaction is subjected to multiple vacuuming and argon purging operations to remove the remaining phosphorus source and low-boiling-point byproducts from the system. This invention employs a suitable method to remove the remaining phosphorus source during the indium phosphide preparation stage, which can prevent the residual phosphorus source from causing Oswald ripening of the indium phosphide core, providing a more favorable environment and conditions for shell epitaxial growth, further improving the luminescence efficiency of the finally obtained quantum dots, and reducing the full width at half maximum (FWHM).
[0019] Further, in step S1, the indium source is selected from one or more combinations of indium chloride, indium bromide, and indium iodide; the phosphorus source is selected from tris(dimethylamino)phosphine and / or tris(diethylamino)phosphine; and the zinc halide is selected from one or more combinations of zinc chloride, zinc bromide, and zinc iodide.
[0020] Further, in step S1, the molar ratio of indium source to phosphorus source is 1:(3-5). Preferably, the molar ratio of indium source to phosphorus source is 1:4. Under this ratio, the conversion rate of nucleation raw materials can be improved and the residual phosphorus source in the system after nucleation can be reduced.
[0021] Furthermore, in step S1, the molar ratio of zinc halide to indium source is (4-6):1, preferably 5:1. The addition of zinc halide can act as a catalyst in step S1 to promote the nucleation reaction, and can also serve as a reaction raw material for the first shell zinc sulfide in step S2.
[0022] Furthermore, in step S1, the reaction temperature is 140–220°C, and the reaction time is 5–30 min.
[0023] In step S1 of the present invention, an inexpensive and air-stable aminophosphine is selected as the phosphorus source. By controlling the type of halogen in the indium halide and zinc halide used during nucleation, the reaction temperature and time are controlled to adjust the size of the indium phosphide nucleus and the emission wavelength of the final core-shell quantum dot.
[0024] In some preferred embodiments, indium iodide is used in combination with zinc iodide to synthesize blue indium phosphide quantum dots; indium iodide is used in combination with zinc bromide to synthesize green indium phosphide quantum dots; indium bromide is used in combination with zinc chloride to synthesize yellow indium phosphide quantum dots; and indium chloride is used in combination with zinc chloride to synthesize orange and red quantum dots.
[0025] Further, in step S2, the sulfur source is selected from one or more combinations of sulfur powder, octyl mercaptan, and 1-dodecyl mercaptan. Preferably, the molar ratio of the sulfur source to the indium source in step S1 is 1:2 to 10:1; and the molar ratio of aluminum isopropoxide to the sulfur source is 1:10 to 3:1.
[0026] In step S2 of this invention, when the indium phosphide core is initially coated with a shell, only a sulfur source and aluminum isopropoxide are added. This avoids the oxidation of the core caused by the thermal decomposition of zinc sources, such as zinc carboxylate.
[0027] Further, in step S3, the sulfur source is selected from one or more combinations of sulfur powder, octyl mercaptan, and 1-dodecyl mercaptan; the zinc source is selected from one or more combinations of zinc oleate, zinc stearate, zinc laurate, anhydrous zinc acetate, and zinc acetate dihydrate.
[0028] Preferably, the ratio of the amount of sulfur source and zinc source added to the amount of indium source in step 1 is 1:2 to 10:1, and the ratio of the amount of aluminum isopropoxide added to the amount of sulfur source is 1:10 to 3:1.
[0029] Further, in step S2, the temperature of the first shell coating is 240–320°C and the time is 30–60 min; in step S3, the temperature of the second shell coating is 180–320°C and the time is 30–150 min.
[0030] Further, in step S4, the purification process includes: first, using a poor solvent to precipitate the product from step S3, separating the solid and liquid and collecting the precipitate; then, adding a good solvent to dissolve the precipitate, separating the solid and liquid and collecting the supernatant.
[0031] Preferably, the undesirable solvent is selected from one or more combinations of anhydrous ethanol, methanol, and acetone; the good solvent is selected from one or more combinations of n-hexane, n-octane, toluene, and dichloromethane.
[0032] The second objective of this invention is to provide an aluminum-doped indium phosphide core-shell quantum dot with tunable emission spectrum, prepared by the preparation method described in the first objective of this invention.
[0033] In the aluminum-doped indium phosphide core-shell quantum dots, aluminum is uniformly distributed in the zinc sulfide shell in the form of aluminum phosphate. Aluminum phosphate has low electrical conductivity and dielectric constant and is regarded as an insulator. Under the effect of physical isolation, it can reduce and inhibit the oxidation and other damage to the indium phosphide core and shell caused by substances such as water and oxygen in the external environment, thereby improving the stability of the quantum dots.
[0034] Furthermore, the emission wavelength of the aluminum-doped indium phosphide core-shell quantum dots is tuned within the range of 480–630 nm. The emission color of the quantum dots includes one of red, orange, yellow, green, and blue light.
[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0036] (1) The present invention provides a method for preparing aluminum-doped indium phosphide core-shell quantum dots with tunable emission spectrum. Based on the one-pot preparation method, aluminum isopropoxide is added during the zinc sulfide shell coating process. The introduced aluminum ions are uniformly distributed in the zinc sulfide shell in the form of aluminum phosphate, which reduces the charge mismatch between the zinc sulfide shell and the indium phosphide core, passivates the oxidation defects of the indium phosphide core and improves the stability of the shell. Specifically, this is manifested in the improvement of luminescence efficiency and the narrowing of the half-width of the emission spectrum.
[0037] (2) The present invention provides a method for preparing aluminum-doped indium phosphide core-shell quantum dots with adjustable emission spectrum. The reaction raw materials are green, environmentally friendly, inexpensive and readily available, with high conversion rate. The synthesis process is simple, reproducible and reliable. The overall reaction time can be controlled within four hours, showing great potential for industrial production.
[0038] (3) The aluminum-doped indium phosphide core-shell quantum dots with tunable emission spectra prepared by this invention have emission wavelengths that can be tuned in the range of 480–630 nm. Among them, the photoluminescence quantum yield of the orange quantum dots exceeds 95%, and the photoluminescence quantum yields of the green, yellow, and red quantum dots are all higher than 60%. The excellent optical properties further indicate that the core-shell indium phosphide quantum dots prepared by this method have broad application prospects in fields such as multicolor displays. Attached Figure Description
[0039] Figure 1 The images show a high-angle annular dark field image (STEM-HAADF) of the aluminum-doped red quantum dots prepared in Example 1, as well as distribution images of five elements, Zn, S, P, In, and Al, in the quantum dots.
[0040] Figure 2 The infrared spectrum of the aluminum-doped red quantum dots prepared in Example 1;
[0041] Figure 3The X-ray diffraction pattern of aluminum-doped red quantum dots prepared in Example 1, and the XRD standard cards of InP, ZnS, and AlPO4;
[0042] Figure 4 This is a transmission electron microscope image of the aluminum-doped red quantum dots prepared in Example 1;
[0043] Figure 5 The EDS energy spectrum of the aluminum-doped red quantum dots prepared in Example 1 is shown below.
[0044] Figure 6 The ultraviolet absorption and fluorescence spectra of the aluminum-doped red quantum dots prepared in Example 1 are shown below.
[0045] Figure 7 The ultraviolet absorption and fluorescence spectra of the aluminum-doped red quantum dots prepared in Example 2 are shown below.
[0046] Figure 8 The ultraviolet absorption and fluorescence spectra of the aluminum-doped red quantum dots prepared in Example 3 are shown below.
[0047] Figure 9 This is a transmission electron microscope image of the aluminum-doped orange quantum dots prepared in Example 4;
[0048] Figure 10 The image shows the EDS energy spectrum of the aluminum-doped orange quantum dots prepared in Example 4.
[0049] Figure 11 The UV absorption and fluorescence spectra of the aluminum-doped orange quantum dots prepared in Example 4 are shown below.
[0050] Figure 12 This is a transmission electron microscope (TEM) image of the aluminum-doped yellow quantum dots prepared in Example 5;
[0051] Figure 13 The image shows the EDS energy spectrum of the aluminum-doped yellow quantum dots prepared in Example 5.
[0052] Figure 14 The ultraviolet absorption and fluorescence spectra of the aluminum-doped yellow quantum dots prepared in Example 5 are shown below.
[0053] Figure 15 This is a transmission electron microscope image of the aluminum-doped green quantum dots prepared in Example 6;
[0054] Figure 16 The image shows the EDS energy spectrum of the aluminum-doped green quantum dots prepared in Example 6.
[0055] Figure 17 The UV absorption and fluorescence spectra of the aluminum-doped green quantum dots prepared in Example 6 are shown below.
[0056] Figure 18 This is a transmission electron microscope image of the aluminum-doped blue quantum dots prepared in Example 7;
[0057] Figure 19 The EDS energy spectrum of the aluminum-doped blue quantum dots prepared in Example 7;
[0058] Figure 20 The UV absorption and fluorescence spectra of the aluminum-doped blue quantum dots prepared in Example 7 are shown below.
[0059] Figure 21 Transmission electron microscope image of undoped red quantum dots prepared for comparison;
[0060] Figure 22 EDS energy spectrum of undoped red quantum dots prepared for comparison;
[0061] Figure 23 The ultraviolet absorption and fluorescence spectra of undoped red quantum dots prepared for comparison;
[0062] Figure 24 The emission spectra of five different colored quantum dots obtained in Examples 1 and 4-7 of this invention are shown.
[0063] Figure 25 These are optical photographs of the quantum dot n-octane solutions prepared in Examples 1 and 4-7 of this invention under natural light and under 365nm ultraviolet light irradiation. Detailed Implementation
[0064] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0065] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.
[0066] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.
[0067] Example 1: One-pot preparation of aluminum-doped red core-shell indium phosphide quantum dots
[0068] Step 1: Accurately weigh 200 mg of indium trichloride and 615 mg of zinc chloride, dissolve them in a three-necked flask containing 15 mL of oleylamine, repeat the vacuuming and argon purging process three times to create an inert atmosphere, then heat to 200 °C, inject a mixed solution of 0.66 mL of tris(dimethylamino)phosphine and 1.34 mL of tri-n-octylphosphine, react at 200 °C for 30 min, then vacuum and argon purging again to remove residual tris(dimethylamino)phosphine and low-boiling-point byproducts from the reaction vessel, obtaining indium phosphide core.
[0069] Step 2: Simultaneously and rapidly inject the pre-prepared sulfur precursor (120 mg of sulfur powder dissolved in 1.8 mL of tri-n-octylphosphine) and aluminum precursor (250 mg of aluminum isopropoxide dissolved in 1.2 mL of oleylamine) into the reaction vessel. The molar ratio of aluminum isopropoxide to sulfur powder is 1:3. Then, heat the mixture to 300 °C and maintain the temperature for 40 min.
[0070] Step 3: Simultaneously inject the pre-prepared zinc precursor (2.30 g of zinc stearate dissolved in 9 mL of 1-octadecene), sulfur precursor (120 mg of sulfur powder dissolved in 1.8 mL of tri-n-octylphosphine), and aluminum precursor (250 mg of aluminum isopropoxide dissolved in 1.2 mL of oleylamine), wherein the molar ratio of aluminum isopropoxide to sulfur powder is 1:3, and react at 300℃ for 60 min; then rapidly lower the temperature of the reaction system to 230℃, inject 2 mL of octyl mercaptan and react at a constant temperature for 60 min; continue to lower the temperature of the reaction system to 190℃, inject a mixed solution containing 460 mg of zinc acetate dihydrate and 2 mL of oleic acid and react at a constant temperature for 30 min to complete the shell coating.
[0071] Step 4: Remove the heat source and cool the reaction system to room temperature using an ice-water bath; mix the mixture in the reaction vessel with anhydrous ethanol at a volume ratio of 1:3, and centrifuge at high speed (10000 r / min, 5 min) to obtain a precipitate containing quantum dots; add 10 mL of n-octane, shake to fully dissolve the quantum dots, centrifuge at high speed (10000 r / min, 5 min) and take out the supernatant; mix the supernatant with anhydrous ethanol at a volume ratio of 1:3, and centrifuge at high speed (10000 r / min, 5 min) to obtain clean core-shell indium phosphide quantum dots.
[0072] Figure 1 The images show a high-angle annular dark-field image (STEM-HAADF) of the aluminum-doped red quantum dots prepared in Example 1, as well as distribution images of the five elements Zn, S, P, In, and Al in the quantum dots; [The text abruptly ends here, likely due to an incomplete translation or source material.] Figure 1 It can be seen that Al is uniformly distributed in the zinc sulfide shell and not at the core-shell interface.
[0073] Figure 2The infrared spectrum of the aluminum-doped red quantum dots prepared in Example 1; by Figure 2 It can be seen that the infrared spectrum of the red quantum dots obtained in Example 1 is in the range of 1270-930 cm⁻¹. -1 The characteristic absorption peak of phosphate (attributable to the stretching vibration of the P=O bond) was observed in the wavenumber range, consistent with the characteristic absorption peak of phosphate in the infrared spectrum of aluminum phosphate purchased from Aladdin.
[0074] Figure 3 The X-ray diffraction pattern of aluminum-doped red quantum dots prepared in Example 1, and the XRD standard cards of InP, ZnS, and AlPO4; Figure 2 infrared spectrum and Figure 3 The X-ray diffraction spectra of all samples showed characteristic signals of AlPO4. This indicates that the aluminum doped in this invention exists in the form of aluminum phosphate within the zinc sulfide shell.
[0075] Example 2: Preparation of Red Core-Shell Indium Phosphide Quantum Dots by One-Pot Method with Adjusted Doping Amount of Aluminum Precursor
[0076] Based on Example 1, steps 2 and 3 were adjusted, and the amount of aluminum isopropoxide added was adjusted to 75 mg (the molar ratio of aluminum isopropoxide to sulfur powder was 1:10), while other steps and conditions remained unchanged.
[0077] Example 3: Preparation of Red Core-Shell Indium Phosphide Quantum Dots by One-Pot Method with Adjusted Doping Amount of Aluminum Precursor
[0078] Based on Example 1, steps 2 and 3 were adjusted, and the amount of aluminum isopropoxide added was adjusted to 2.25g (the molar ratio of aluminum isopropoxide to sulfur powder was 3:1), while other steps and conditions remained unchanged.
[0079] Example 4: One-pot preparation of aluminum-doped orange core-shell indium phosphide quantum dots
[0080] The nucleation temperature used in Example 1 was changed to 175°C, and the other steps were the same as in Example 1.
[0081] Example 5: One-pot preparation of aluminum-doped yellow core-shell indium phosphide quantum dots
[0082] The 200 mg indium trichloride used in Example 1 was replaced with 320 mg indium tribromide, and the nucleation temperature and time were changed to 170 °C and 20 min, respectively. The other steps were the same as in Example 1.
[0083] Example 6: One-pot preparation of aluminum-doped green core-shell indium phosphide quantum dots
[0084] The 200 mg indium trichloride and 615 mg zinc chloride used in Example 1 were replaced with 445 mg indium iodide and 1.01 g zinc bromide, respectively. The nucleation temperature and time were changed to 180 °C and 10 min, respectively. The other steps were the same as in Example 1.
[0085] Example 7: One-pot preparation of aluminum-doped blue core-shell indium phosphide quantum dots
[0086] The 200 mg indium trichloride and 615 mg zinc chloride used in Example 1 were replaced with 445 mg indium iodide and 1.43 g zinc iodide, respectively. The nucleation temperature and time were changed to 160 °C and 10 min, respectively. The other steps were the same as in Example 1.
[0087] Comparative one-pot preparation of undoped red core-shell indium phosphide quantum dots
[0088] Based on Example 1, steps 2 and 3 were adjusted to remove the addition of aluminum isopropoxide, while other steps and conditions remained unchanged.
[0089] Characterization and performance
[0090] Transmission electron microscopy (TEM) images, transmission electron microscopy (TEM) X-ray (EDS) spectra, and ultraviolet absorption and fluorescence spectra of the core-shell indium phosphide quantum dots prepared in Examples 1-7 and Comparative Examples are shown below. Figure 4-23 As shown.
[0091] The energy dispersive spectroscopy (EDS) data summarized in Table 1 confirms the successful aluminum doping in the core-shell quantum dots obtained in the examples. For the quantum dots in Examples 1 and 4-7, the ratio of zinc to indium atoms was 4.3, 5.6, 5.4, 7.8, and 16.4, respectively, generally showing an increasing trend with the blue shift of light color. The increase in the ratio of zinc to indium atoms indicates that the proportion of the outer doped shell relative to the indium phosphide core is increasing, and the crystal structure of the quantum dots is gradually approaching that of zinc sulfide with a zincblende structure. The high-resolution transmission electron microscopy (TEM) images are consistent with the above inferences. The interplanar spacing of the red quantum dots (111) obtained in Example 1 is 0.34 nm, while the corresponding interplanar spacing of the blue quantum dots obtained in Example 7 is only 0.31 nm, which is more consistent with the structure of zinc sulfide. In addition, by analyzing the TEM images and EDS data of Examples 1 and the comparative examples, it can be seen that aluminum doping promotes the epitaxial growth of the shell, making the shell thickness and particle size of the quantum dots in Example 1 significantly larger than those in the comparative examples.
[0092] Table 1: EDS energy dispersive spectral data of quantum dots
[0093]
[0094] Table 2: Optical Properties of Quantum Dots
[0095]
[0096]
[0097] The photophysical properties of the quantum dots prepared in Examples 1-7 and the comparative examples in a dilute n-octane solution (0.5 mg / mL) are summarized in Table 2. Compared with the quantum dots obtained in the comparative examples, the introduction of aluminum caused the emission spectrum of the quantum dots in Example 1 to redshift to 627 nm, the photoluminescence quantum yield to increase to 85%, and the full width at half maximum (FWHM) to narrow by 5 nm. When the zinc sulfide shell was coated in the comparative examples, the high temperature environment promoted the etching of the indium phosphide core by zinc ions, forming an indium zinc phosphide (InZnP) alloy, which led to a reduction in the core size and a shift of the emission spectrum to a shorter wavelength. Due to the high lattice mismatch between zinc sulfide and indium phosphide (7.7%), the strong lattice stress limited the growth of the shell in the comparative examples, resulting in a thinner shell. In contrast, the trivalent aluminum ions introduced in Example 1 easily interact with the anions on the core surface due to electrostatic attraction, which not only passivates surface defects but also alleviates the charge mismatch at the core-shell interface, inhibits the etching of the core by zinc ions, and thus yields quantum dots with improved optical properties. Examples 2 and 3, by adjusting the amount of aluminum isopropoxide added, still yielded quantum dots with higher luminous efficiency and narrower full width at half maximum (FWHM) compared to the comparative examples. Furthermore, the quantum dots prepared in Examples 4-7 using a combination of doping strategies and the one-pot method all exhibited excellent optical properties. The emission wavelengths of the orange, yellow, green, and blue quantum dots were located at 600 nm, 560 nm, 514 nm, and 480 nm, respectively, with photoluminescence quantum yields reaching 96%, 86%, 62%, and 34%, respectively.
[0098] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.
Claims
1. A method for preparing aluminum-doped indium phosphide core-shell quantum dots with tunable emission spectra, characterized in that, In the same reaction vessel, an indium phosphide core is first prepared and then coated with a zinc sulfide shell. During the process of coating the zinc sulfide shell, a certain proportion of aluminum isopropoxide is added to react with the sulfur source solvent tri-n-octylphosphine, so that aluminum is doped into the zinc sulfide shell in the form of aluminum phosphate. The preparation method includes the following steps: S1. Mix indium source, phosphorus source and zinc halide in a certain proportion and react at a certain temperature for a certain time to obtain indium phosphide core; S2. Dissolve the sulfur source in tri-n-octylphosphine, and then add it together with aluminum isopropoxide into the indium phosphide core. Heat the mixture to perform the first shell coating to obtain an aluminum-doped zinc sulfide thin shell. S3. Sulfur source, aluminum isopropoxide and zinc source dissolved in tri-n-octylphosphine are added to continue the reaction for the second shell coating, resulting in a thickened aluminum-doped zinc sulfide shell. S4. The product from step S3 is purified to obtain aluminum-doped indium phosphide core-shell quantum dots with tunable emission spectra. In steps S2 and S3, the molar ratio of aluminum isopropoxide to sulfur source is 1:10 to 3:
1.
2. The preparation method according to claim 1, characterized in that, In step S1, the indium source is selected from one or more combinations of indium chloride, indium bromide, and indium iodide; the phosphorus source is selected from tris(dimethylamino)phosphine and / or tris(diethylamino)phosphine; and the zinc halide is selected from one or more combinations of zinc chloride, zinc bromide, and zinc iodide.
3. The preparation method according to claim 1, characterized in that, In step S1, the molar ratio of indium source to phosphorus source is 1:(3~5), and the molar ratio of zinc halide to indium source is (4~6):
1.
4. The preparation method according to claim 1, characterized in that, In step S1, the reaction temperature is 140~220℃ and the reaction time is 5~30min.
5. The preparation method according to claim 1, characterized in that, In step S2, the sulfur source is selected from one or more combinations of sulfur powder, octyl mercaptan, and 1-dodecyl mercaptan; the ratio of the amount of sulfur source added to the amount of indium source in step S1 is 1:2 to 10:
1.
6. The preparation method according to claim 1, characterized in that, In step S3, the sulfur source is selected from one or more combinations of sulfur powder, octyl mercaptan, and 1-dodecyl mercaptan; the zinc source is selected from one or more combinations of zinc oleate, zinc stearate, zinc laurate, anhydrous zinc acetate, and zinc acetate dihydrate; the ratio of the amount of sulfur source and zinc source added to the amount of indium source in step S1 is 1:2 to 10:
1.
7. The preparation method according to claim 1, characterized in that, In step S2, the temperature of the first shell coating is 240~320 ℃ and the time is 30~60 min; in step S3, the temperature of the second shell coating is 180~320 ℃ and the time is 30~150 min.
8. The preparation method according to claim 1, characterized in that, In step S4, the purification process includes: first, using a poor solvent to precipitate the product from step S3, separating the solid and liquid and collecting the precipitate; then, adding a good solvent to dissolve the precipitate, separating the solid and liquid and collecting the supernatant.
9. An aluminum-doped indium phosphide core-shell quantum dot with tunable emission spectrum prepared by the method according to any one of claims 1-8, characterized in that, Aluminum is uniformly distributed in the form of aluminum phosphate within the zinc sulfide shell; the emission wavelength of the aluminum-doped indium phosphide core-shell quantum dots is tuned within the range of 480~630nm.