High-brightness, high-stability water-soluble indium phosphide-based quantum dots, preparation method and application thereof

Abstract

This invention discloses a high-brightness, high-stability water-soluble indium phosphide-based quantum dot, its preparation method, and its applications. The preparation method includes: purifying indium phosphide-based quantum dots obtained by a hot-injection method and dispersing them in an organic solvent; the organic solvent is at least one selected from hexane, toluene, and chloroform; adding a thiol compound to the indium phosphide-based quantum dot dispersion, shaking, sonicating, centrifuging to remove the supernatant, and drying; the thiol compound is at least one selected from mercaptopropionic acid, mercaptoundecanoic acid, L-cysteine, and D-penicillamine; the molar ratio of the thiol compound to the quantum dots is 1000-50000:1; dispersing the dried indium phosphide-based quantum dots in water, and adding a strong alkali to promote dissolution, thus obtaining the quantum dots. The preparation method of this invention has a short reaction time, high fluorescence quantum yield, and produces water-soluble indium phosphide-based quantum dots with high brightness and strong stability, which can be applied to biolabeling, cell imaging, etc.

Description

Technical Field

[0001] This invention relates to the field of materials preparation and application technology, and in particular to a high-brightness, high-stability water-soluble indium phosphide-based quantum dot, its preparation method, and its application. Background Technology

[0002] Quantum dots are a class of semiconductor materials that exhibit quantum confinement effects across three dimensions. They possess advantages such as tunable band gap, excellent absorption and fluorescence properties, and easy surface modification.

[0003] Due to their excellent optical properties and stability, quantum dots have been widely used in life and health fields such as biomarking, cell imaging, and disease diagnosis and treatment. Currently, the most common quantum dot system is cadmium-based quantum dots, but their toxicity makes them difficult to use in living organisms. In contrast, emerging indium phosphide (IP) quantum dots are environmentally friendly and are rapidly developing in the field of quantum dots for life and health, playing a significant role.

[0004] Currently, quantum dot synthesis is mainly carried out in a high-temperature oil phase environment, resulting in hydrophobic quantum dot surfaces. Therefore, it is crucial to transfer oil-soluble quantum dots to an aqueous phase environment while maintaining high fluorescence yield and stability.

[0005] Currently, the most common method for quantum dot phase transition is surface ligand exchange. For example, Chinese patent CN106590662A discloses a water-soluble quantum dot and its preparation method, including the following steps: adding a nucleic acid stock solution dropwise to an oil-soluble quantum dot solution, stirring at room temperature for 20–40 min after the addition is complete; then adding deionized water to the solution and stirring for 5–20 min; when the solution shows phase separation, centrifuging the product to obtain water-soluble quantum dots. The nucleic acid used in the nucleic acid stock solution is a nucleotide or the corresponding nucleoside. For example, Chinese patent document CN113512416A discloses a method for preparing Ga-doped water-soluble InP quantum dots. The method involves reacting an indium source with a phosphorus source to form an indium phosphide core, using zinc halide as a catalyst. A gallium source is then incorporated to passivate defects within the indium phosphide core. A ZnS shell is then coated onto the surface to improve the stability and luminescence efficiency of the quantum dots. Finally, a strong binding force between a thiol-based organic acid and the quantum dots enables them to bond together, thus preparing Ga-doped water-soluble InP quantum dots. The thiol-based organic acid can be either mercaptoacetic acid or mercaptopropionic acid. The reaction temperature is 50℃-80℃, and the reaction time is 2h-8h.

[0006] Currently, the ligand exchange reaction time of indium phosphide-based quantum dots is relatively long, resulting in a significant loss of fluorescence quantum yield. Consequently, the obtained water-soluble indium phosphide-based quantum dots exhibit low fluorescence quantum yield and poor stability. Summary of the Invention

[0007] This invention provides a high-brightness, high-stability water-soluble indium phosphide-based quantum dot and its preparation method. The preparation method has a short reaction time, high fluorescence quantum yield, and the prepared water-soluble indium phosphide-based quantum dots have high brightness and strong stability.

[0008] The technical solution of the present invention is as follows:

[0009] A method for preparing high-brightness, high-stability water-soluble indium phosphide-based quantum dots includes:

[0010] (1) The indium phosphide quantum dots obtained by the hot injection method are purified and dispersed in an organic solvent;

[0011] The organic solvent is at least one of hexane, toluene, and chloroform;

[0012] (2) Add a mercapto compound to the indium phosphide quantum dot dispersion obtained in step (1), shake and sonicate, centrifuge to remove the supernatant and dry;

[0013] The thiol compound is at least one of mercaptopropionic acid, mercaptoundecanoic acid, L-cysteine, and D-penicillamine.

[0014] The molar ratio of thiol compounds to quantum dots is 1000-50000:1;

[0015] (3) Disperse the dried indium phosphide quantum dots obtained in step (2) into water, add a strong alkali to promote dissolution, and obtain the high-brightness, high-stability water-soluble indium phosphide quantum dots.

[0016] Preferably, the indium phosphide-based quantum dots are InP / ZnSe / ZnS. The preparation method of indium phosphide-based quantum dots can be found in the following reference: Li Y, Hou X, Dai X, et al. Stoichiometry-controlled InP-based quantumdots: synthesis, photoluminescence, and electroluminescence[J]. Journal of the American Chemical Society, 2019, 141(16):6448-6452.

[0017] Preferably, in step (2), the oscillation is performed for 1-20 minutes, followed by ultrasonic treatment for 1-20 minutes.

[0018] Preferably, the thiol compound is mercaptopropionic acid and / or mercaptoundecanoic acid.

[0019] Most preferably, the thiol compound is mercaptopropionic acid and mercaptoundecanoic acid.

[0020] More preferably, the molar ratio of mercaptopropionic acid to mercaptoundecanoic acid is 0.1-10:1.

[0021] The preparation method of this invention employs a surface ligand reconstruction strategy, using two ligands, mercaptopropionic acid and mercaptoundecanoic acid, to perform ligand exchange on oil-soluble indium phosphide quantum dots. The long carbon chain of mercaptoundecanoic acid provides excellent dispersibility for the prepared water-soluble indium phosphide-based quantum dots, avoiding the precipitation caused by the aggregation of water-soluble quantum dots after ligand exchange. Meanwhile, the small steric hindrance of mercaptopropionic acid makes it easier to reach the surface of the quantum dots, passivating the surface defects of the quantum dots to a greater extent. At the same time, the ligand barrier formed by the two ligands isolates the external environment from the quantum dots, protecting them from etching and improving their stability.

[0022] Preferably, in step (3), the strong base is tetramethylammonium hydroxide and / or sodium hydroxide.

[0023] In step (3), the dried indium phosphide quantum dots obtained in step (2) are dispersed in water, and strong alkali is added dropwise until the indium phosphide quantum dot dispersion is dissolved, thereby obtaining the high-brightness, high-stability water-soluble indium phosphide quantum dots.

[0024] This invention also provides a high-brightness, high-stability water-soluble indium phosphide-based quantum dot prepared using the above-described method. The high-brightness, high-stability water-soluble indium phosphide-based quantum dots prepared using the method of this invention retain the high brightness of oil-soluble quantum dots prepared by the high-temperature hot-injection method. Through a simple and rapid ligand exchange method, the introduction of surface defect states of the quantum dots during ligand exchange is largely avoided. The water-soluble indium phosphide quantum dots prepared by this invention have a quantum yield of over 90% and exhibit high stability.

[0025] This invention also provides the application of the high-brightness, high-stability water-soluble indium phosphide quantum dots in biolabeling and cell imaging.

[0026] When used for cell imaging, the imaging cells can be fibroblasts or mouse breast cancer cells. The process includes: incubating the imaging cells for 24 hours, aspirating the original culture medium, adding fresh culture medium containing water-soluble indium phosphide quantum dots, continuing incubation for 12-36 hours, washing with phosphate-buffered saline (PBFS), fixing with paraformaldehyde, washing again with PBFS, staining with 4',6-diamidinyl-2-phenylindole, washing with PBFS, and observing with a fluorescence inverted microscope.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) The preparation method of the present invention controls the type and molar ratio of ligands of quantum dots and the reaction system, so that the prepared water-soluble indium phosphide-based quantum dots have excellent optical properties, extremely high brightness and stability.

[0029] (2) The preparation method of the present invention greatly reduces the reaction time of quantum dot ligand exchange and improves the reaction efficiency.

[0030] (3) The high-brightness, high-stability water-soluble indium phosphide quantum dots prepared by the present invention are applied to bioimaging for the first time. Furthermore, observations have shown that the water-soluble indium phosphide quantum dots of the present invention have excellent coloring properties, which is beneficial for the further application of quantum dots in bioimaging. Attached Figure Description

[0031] Figure 1 The images show the UV absorption spectra of quantum dot ligands before and after exchange in Examples 1-3 of this invention.

[0032] Figure 2 The fluorescence spectra of quantum dots before and after ligand exchange in Example 1 of the present invention are shown.

[0033] Figure 3 The fluorescence spectra of quantum dots before and after ligand exchange in Example 2 of the present invention are shown.

[0034] Figure 4 The fluorescence spectra of quantum dots before and after ligand exchange in Example 3 of the present invention are shown.

[0035] Figure 5 (a), (b), and (c) are TEM images of the water-soluble quantum dots prepared in Examples 1-3 of this invention, respectively.

[0036] Figure 6 This is a test image of the photobleaching resistance of the water-soluble quantum dots prepared in Example 3 of the present invention;

[0037] Figure 7 (a), (b), and (c) are single-particle PL diagrams of the water-soluble quantum dots prepared in Examples 1-3 of this invention, respectively.

[0038] Figure 8 This is a stability monitoring graph of the water-soluble quantum dots prepared in Example 3 of the present invention;

[0039] Figure 9 These are schematic diagrams of the fluorescence quantum yield in Examples 3, 6, and 7 of the present invention;

[0040] Figure 10 This is a cell imaging diagram illustrating an application example of the present invention. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0042] The preparation method of oil-soluble indium phosphide quantum dots (InP / ZnSe / ZnS) synthesized by the hot injection method used in Examples 1-7 can be found in the following reference: Li Y, Hou X, Dai X, et al. Stoichiometry-controlled InP-based quantum dots: synthesis, photoluminescence, and electroluminescence[J]. Journal of the American Chemical Society, 2019, 141(16):6448-6452.

[0043] Example 1

[0044] A method for preparing high-brightness, high-stability water-soluble indium phosphide-based quantum dots:

[0045] (1) Weigh 1 mL of indium phosphide quantum dots synthesized by hot injection into a glass bottle, add 2 mL of ethanol to precipitate, centrifuge at 8500 r / min to precipitate, discard the supernatant, add 1 mL of octane to dissolve, add 2 mL of ethanol to precipitate, centrifuge at 8500 r / min to precipitate, and repeat once more.

[0046] (2) Dissolve the quantum dot precipitate obtained in step (1) in 0.2 mL toluene, weigh 10 μL of mercaptopropionic acid and add it to the quantum dot solution, shake the glass bottle vigorously for 5 min, sonicate for 5 min, centrifuge to precipitate, wash twice with hexane and dry with N2.

[0047] (3) Add 200 μL of deionized water to the quantum dot precipitate obtained in step (2), and add 20 μL of 2 mmol / L sodium hydroxide aqueous solution to obtain water-soluble indium phosphide quantum dots 1.

[0048] Example 2

[0049] A method for preparing high-brightness, high-stability water-soluble indium phosphide-based quantum dots:

[0050] (1) Weigh 1 mL of indium phosphide quantum dots synthesized by hot injection into a glass bottle, add 2 mL of ethanol to precipitate, centrifuge at 8500 r / min to precipitate, discard the supernatant, add 1 mL of octane to dissolve, add 2 mL of ethanol to precipitate, centrifuge at 8500 r / min to precipitate, and repeat once more.

[0051] (2) Dissolve the quantum dot precipitate obtained in step (1) in 0.2 mL toluene, weigh 0.0251 g mercaptoundecanoic acid and add it to the quantum dot solution, shake the glass bottle vigorously for 10 min, sonicate for 10 min, centrifuge to precipitate, wash twice with hexane and dry with N2.

[0052] (3) Add 200 μL of deionized water to the quantum dot precipitate obtained in step (2), and add 40 μL of 2 mmol / L sodium hydroxide aqueous solution to obtain water-soluble indium phosphide quantum dots 2.

[0053] Example 3

[0054] A method for preparing high-brightness, high-stability water-soluble indium phosphide-based quantum dots:

[0055] (1) Weigh 1 mL of indium phosphide quantum dots synthesized by hot injection into a glass bottle, add 2 mL of ethanol to precipitate, centrifuge at 8500 r / min to precipitate, discard the supernatant, add 1 mL of octane to dissolve, add 2 mL of ethanol to precipitate, centrifuge at 8500 r / min to precipitate, and repeat once more.

[0056] (2) Dissolve the quantum dot precipitate obtained in step (1) in 0.2 mL toluene, weigh 5 μL mercaptopropionic acid and 0.0128 g mercaptoundecanoic acid and add them to the quantum dot solution. Shake the glass bottle vigorously for 10 min, sonicate for 10 min, centrifuge to precipitate, wash twice with hexane and dry with N2.

[0057] The molar ratio of organic acid to quantum dots is 10000:1.

[0058] (3) Add 200 μL of deionized water to the quantum dot precipitate obtained in step (2), and add 10 μL of 2 mmol / L sodium hydroxide aqueous solution to obtain water-soluble indium phosphide quantum dots 3.

[0059] Example 4

[0060] A method for preparing high-brightness, high-stability water-soluble indium phosphide-based quantum dots:

[0061] (1) Weigh 1 mL of indium phosphide quantum dots synthesized by hot injection into a glass bottle, add 2 mL of ethanol to precipitate, centrifuge at 8500 r / min to precipitate, discard the supernatant, add 1 mL of octane to dissolve, add 2 mL of ethanol to precipitate, centrifuge at 8500 r / min to precipitate, and repeat once more.

[0062] (2) Dissolve the quantum dot precipitate obtained in step (1) in 0.2 mL toluene, weigh 8 μL of mercaptopropionic acid and 0.005 g of mercaptoundecanoic acid and add them to the quantum dot solution. Shake the glass bottle vigorously for 10 min, sonicate for 10 min, centrifuge to precipitate, wash twice with hexane and dry with N2.

[0063] The molar ratio of organic acid to quantum dots is 10000:1.

[0064] (3) Add 200 μL of deionized water to the quantum dot precipitate obtained in step (2), and add 15 μL of 25% wt tetramethylammonium hydroxide solution to obtain water-soluble indium phosphide quantum dots 4.

[0065] Example 5

[0066] A method for preparing high-brightness, high-stability water-soluble indium phosphide-based quantum dots:

[0067] (1) Weigh 1 mL of indium phosphide quantum dots synthesized by hot injection into a glass bottle, add 2 mL of ethanol to precipitate, centrifuge at 8500 r / min to precipitate, discard the supernatant, add 1 mL of octane to dissolve, add 2 mL of ethanol to precipitate, centrifuge at 8500 r / min to precipitate, and repeat once more.

[0068] (2) Dissolve the quantum dot precipitate obtained in step (1) in 0.2 mL toluene, weigh 2 μL mercaptopropionic acid and 0.02 g mercaptoundecanoic acid and add them to the quantum dot solution. Shake the glass bottle vigorously for 10 min, sonicate for 10 min, centrifuge to precipitate, wash twice with hexane and dry with N2.

[0069] The molar ratio of organic acid to quantum dots is 10000:1.

[0070] (3) Add 200 μL of deionized water to the quantum dot precipitate obtained in step (2), and add 10 μL of 25% wt tetramethylammonium hydroxide solution to obtain water-soluble indium phosphide quantum dots 5.

[0071] Example 6

[0072] A method for preparing high-brightness, high-stability water-soluble indium phosphide-based quantum dots:

[0073] (1) Weigh 1 mL of indium phosphide quantum dots synthesized by hot injection into a glass bottle, add 2 mL of ethanol to precipitate, centrifuge at 8500 r / min to precipitate, discard the supernatant, add 1 mL of octane to dissolve, add 2 mL of ethanol to precipitate, centrifuge at 8500 r / min to precipitate, and repeat once more.

[0074] (2) Dissolve the quantum dot precipitate obtained in step (1) in 0.15 mL of chloroform, weigh 2.5 μL of mercaptopropionic acid and 0.0064 g of mercaptoundecanoic acid and add them to the quantum dot solution. Shake the glass bottle vigorously for 10 min, sonicate for 10 min, centrifuge to precipitate, wash twice with hexane and dry with N2.

[0075] The molar ratio of organic acid to quantum dots is 5000:1.

[0076] (3) Add 200 μL of deionized water to the quantum dot precipitate obtained in step (2), and add 15 μL of 25% wt tetramethylammonium hydroxide solution to obtain water-soluble indium phosphide quantum dots 6.

[0077] Example 7

[0078] A method for preparing high-brightness, high-stability water-soluble indium phosphide-based quantum dots:

[0079] (1) Weigh 1 mL of indium phosphide quantum dots synthesized by hot injection into a glass bottle, add 2 mL of ethanol to precipitate, centrifuge at 8500 r / min to precipitate, discard the supernatant, add 1 mL of octane to dissolve, add 2 mL of ethanol to precipitate, centrifuge at 8500 r / min to precipitate, and repeat once more.

[0080] (2) Dissolve the quantum dot precipitate obtained in step (1) in 0.15 mL of chloroform, weigh 20 μL of mercaptopropionic acid and 0.05 g of mercaptoundecanoic acid and add them to the quantum dot solution. Shake the glass bottle vigorously for 10 min, sonicate for 10 min, centrifuge to precipitate, wash twice with hexane and dry with N2.

[0081] The molar ratio of organic acid to quantum dots is 40,000:1.

[0082] (3) Add 200 μL of deionized water to the quantum dot precipitate obtained in step (2), and add 15 μL of 25% wt tetramethylammonium hydroxide solution to obtain water-soluble indium phosphide quantum dots 7.

[0083] from Figure 1 The absorption spectrum (UV) images show that the UV absorption of the quantum dots remained essentially unchanged before and after ligand exchange.

[0084] Further from Figure 2-4 The fluorescence spectrum (PL) shows that the fluorescence quantum yield of water-soluble indium phosphide-based quantum dots prepared by ligand exchange using mixed ligands is not significantly reduced.

[0085] from Figure 5 As can be seen from the electron microscopy (TEM) image (a), the water-soluble indium phosphide quantum dots prepared by ligand exchange using mercaptopropionic acid have poor dispersibility and are prone to aggregation. However, as can be seen from images (b) and (c), the water-soluble indium phosphide quantum dots prepared using mixed ligands and mercaptoundecanoic acid have better dispersibility and more uniform morphology.

[0086] from Figure 6As can be seen from the solution photobleaching test image, the water-soluble indium phosphide-based quantum dots prepared by ligand exchange using mixed ligands did not exhibit significant photobleaching after being continuously irradiated with a high-intensity ultraviolet lamp for 4 hours, demonstrating excellent photostability.

[0087] from Figure 7 The single-particle fluorescence spectrum curves show that when irradiated with a high-intensity laser, the water-soluble indium phosphide quantum dots prepared by ligand exchange using mixed ligands did not exhibit fluorescence flickering for a long time. However, the water-soluble indium phosphide quantum dots prepared by ligand exchange using a single ligand exhibited severe fluorescence flickering and bleaching under prolonged illumination. This demonstrates that the water-soluble indium phosphide quantum dots prepared using the method of this invention have excellent optical properties and resistance to photobleaching.

[0088] from Figure 8 As can be seen from the stability monitoring graph, the water-soluble indium phosphide-based quantum dots prepared by ligand exchange using mixed ligands have excellent stability.

[0089] from Figure 9 It can be seen that the water-soluble indium phosphide-based quantum dots prepared in Examples 6 and 7 have similar performance to the water-soluble indium phosphide-based quantum dots prepared in Example 3.

[0090] In summary, changing the reaction system for quantum dot ligand exchange, the type of ligand, the ratio of ligand to quantum dot, and the type of strong base all have a significant impact on the prepared aqueous indium phosphide-based quantum dots. Through effective regulation, high-brightness, high-stability water-soluble indium phosphide-based quantum dots can be obtained, enabling clear imaging of biological cells.

[0091] Application example (testing the imaging effect of quantum dots):

[0092] The cell imaging device used was a fluorescence inverted microscope. First, fibroblasts were seeded into 24-well plates and cultured for 24 hours. After incubation, the original culture medium was aspirated, and fresh culture medium containing water-soluble indium phosphide quantum dots was added. After incubation for another 24 hours, the cells were rinsed twice with phosphate buffered saline solution. Paraformaldehyde was added to each well for fixation for 10 minutes, followed by rinsing twice with phosphate buffered saline solution. 4',6-diamidinyl-2-phenylindole was added for staining, and the cells were rinsed twice with phosphate buffered saline solution. The cells were then observed using a fluorescence inverted microscope.

[0093] Observation under a microscope Figure 10 The results show that the water-soluble indium phosphide quantum dots prepared by ligand exchange using mixed ligands have good cell imaging effects and the quantum dot staining signal can be clearly observed. This indicates that the water-soluble indium phosphide quantum dots prepared in this invention exhibit excellent cell imaging effects and improve the efficiency of quantum dot bioimaging.

[0094] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing high-brightness and high-stability water-soluble indium phosphide-based quantum dots, characterized in that, include: (1) The indium phosphide-based quantum dots obtained by the hot injection method are purified and dispersed in an organic solvent; The organic solvent is at least one of hexane, toluene, and chloroform; (2) Add a thiol compound to the indium phosphide quantum dot dispersion obtained in step (1), shake for 1-20 min, sonicate for 1-20 min, centrifuge to remove the supernatant and dry; the thiol compound is mercaptopropionic acid and mercaptoundecanoic acid; the molar ratio of mercaptopropionic acid and mercaptoundecanoic acid is 0.1-10:1; The molar ratio of thiol compounds to quantum dots is 1000-50000:1; (3) Disperse the dried indium phosphide quantum dots obtained in step (2) into water, add a strong alkali to promote dissolution, and obtain the high-brightness, high-stability water-soluble indium phosphide quantum dots.

2. The method for preparing high-brightness, high-stability water-soluble indium phosphide-based quantum dots according to claim 1, characterized in that, The indium phosphide-based quantum dots are InP / ZnSe / ZnS.

3. The method for preparing high-brightness, high-stability water-soluble indium phosphide-based quantum dots according to claim 1, characterized in that, In step (3), the base is tetramethylammonium hydroxide and / or sodium hydroxide.

4. A high-brightness, high-stability water-soluble indium phosphide-based quantum dot, characterized in that, It is prepared by the preparation method described in any one of claims 1-3.

5. An application of the high-brightness, high-stability water-soluble indium phosphide quantum dots as described in claim 4 in biolabeling and cell imaging; wherein the application is not for the diagnosis or treatment of diseases.

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