Deep ultraviolet fluorescence emission tunable colloidal aluminum nitride quantum dots and preparation method and application thereof

Abstract

The present invention discloses a deep ultraviolet fluorescence emission tunable colloidal aluminum nitride quantum dot, a preparation method and an application thereof. The present invention uses aluminum halide or a mixture of aluminum halide and gallium halide as a reaction precursor of the colloidal aluminum nitride quantum dot, and a quaternary amine type cationic surfactant as a surfactant, and prepares, by means of ammonia reduction, a colloidal aluminum nitride quantum dot with uniform dispersion, uniform particles, deep ultraviolet fluorescence emission and tunable fluorescence emission. The present invention successfully prepares a colloidal aluminum nitride quantum dot with an average particle size of about 3.7 nm, which exhibits high quantum yield fluorescence emission in the deep ultraviolet band; at the same time, the excellent performance of tunable fluorescence emission is realized by changing the band gap of the quantum dot through co-doping. The synthetic method of the colloidal aluminum nitride quantum dot realized by the present invention is different from all the synthetic methods of aluminum nitride crystals reported so far. It is expected to reduce the preparation cost and difficulty of aluminum nitride crystals while improving the application of the colloidal aluminum nitride quantum dot in multiple fields.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor nanomaterials, and particularly relates to a deep ultraviolet fluorescence emission tunable colloidal aluminum nitride quantum dot, a preparation method thereof, and an application thereof. Background Art

[0002] Efficient light sources that can operate in the range of 200 nm or shorter wavelengths have been widely studied and applied in sterilization, medical treatment, surface cleaning, and industrial manufacturing. Currently, the mainstream methods (mercury lamps and excimer lamps) all have problems such as low efficiency, short lifespan, poor stability, and the emission of toxic gases. So far, it is still challenging to obtain a highly efficient surface emission light source based on semiconductors through electrical injection in such a wavelength range. Compared with traditional UV lamps, UV-LEDs not only do not contain mercury, but also have (1) higher energy efficiency, (2) longer service life, (3) more constant light intensity, and (4) are easy to control their temperature and heat. For all these reasons, it is expected that UV-LEDs will be more widely applied in the future. Among various wide-bandgap semiconductor materials, the direct bandgap energy of aluminum nitride is approximately 6.2 eV (wavelength approximately 200 nm). In principle, the epitaxy of high-crystallinity AlN requires high temperatures because the surface mobility of Al adsorbed atoms is too low at temperatures below 1200 °C. However, it is very difficult for the mainstream equipment of AlN technologies such as metalorganic chemical vapor deposition (MOCVD) and MBE used for growth to exceed 1400 °C. Therefore, the research on how to reduce the difficulty of preparing high-quality AlN crystals is of great significance.

[0003] In recent years, quantum dots (QDs) have gradually become a research hotspot. Due to their reduced dimensionality, they can provide a narrower fluorescence emission bandwidth, high quantum yield (QY), and the advantage of tunable fluorescence emission through surface chemistry or particle size control; at the same time, the feasible route based on solution preparation means lower processing costs and compatibility with various chemical media. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the invention object of the present invention is a deep ultraviolet fluorescence emission tunable colloidal aluminum nitride quantum dot, a preparation method thereof, and an application thereof.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] A preparation method of a deep ultraviolet fluorescence emission and fluorescence emission tunable colloidal aluminum nitride quantum dot: using aluminum halide or a mixture of aluminum halide and gallium halide as a reaction precursor of the colloidal aluminum nitride quantum dot, a quaternary ammonium cationic surfactant as a surfactant, and ammonia reduction to prepare a uniformly dispersed and particle-uniform deep ultraviolet fluorescence emission and fluorescence emission tunable colloidal aluminum nitride quantum dot, including the following steps:

[0007] 1) Weigh a quaternary amine type cationic surfactant into a dried container, add xylene as a solvent, and disperse by ultrasonication until a transparent and clear reverse micelle solution is obtained;

[0008] 2) taking aluminum halide or a mixture of aluminum halide and gallium halide as a reaction precursor, weighing and placing it in the reverse micelle solution obtained in step 1), and ultrasonically dispersing it until the reverse micelle system becomes transparent and clear;

[0009] 3) extracting the internal air from the above solution to ensure that the reaction solution is in an environment without water and oxygen, and then heating the reaction mixture;

[0010] 4) slowly adding ammonia reducing agent to the mixed solution obtained in step 3), and stirring the mixture under high temperature magnetic stirring for a period of time under the protection of an inert gas atmosphere;

[0011] 5) Cooling the mixed solution obtained in step 4), adding a polar solvent to destroy the reverse micelle system, centrifuging and removing anhydrous xylene by rotary evaporation, and then redispersing in ethanol for storage, thereby obtaining colloidal aluminum nitride quantum dots with deep ultraviolet fluorescence emission and adjustable fluorescence emission.

[0012] The aluminum halide described in step 2) includes aluminum chloride 、 Aluminum bromide, gallium halides include gallium chloride and gallium bromide.

[0013] In step 4), ammonia ethanol solution is used to carry out a slow reduction process.

[0014] The polar solvent used in step 5) is methanol or ethanol.

[0015] Preferably, the preparation method comprises the following steps:

[0016] 1) Weigh 355 mg of tetraoctylammonium bromide into a dry three-necked flask, add 100 ml of anhydrous xylene as the reaction solvent, and then perform ultrasonic treatment until a clear and transparent reverse micelle solution is obtained;

[0017] 2) Weigh 133 mg of anhydrous aluminum chloride as a reaction precursor, add it to the reverse micelle solution in step 1) above, and continue ultrasonic treatment. The solution changes from the initial light yellow to a clear transparent solution, indicating that the reaction solution is ready;

[0018] 3) Transfer the solution in step 2) to a Schlenk line, use argon to purge the air inside the reaction system, and keep the argon flowing to ensure that the reaction system is carried out in an environment without water and oxygen;

[0019] 4) Slowly heat the solution in step 3) to 120 °C, and add 0.5 ml of 2.4 M ammonia ethanol solution at a rate of 1 ml / h through a microfluidic injection pump, and continue to keep warm for 5 hours;

[0020] 5) After the solution in step 4) is cooled to room temperature, add 3 ml of methanol to break the reverse micelle system, centrifuge to obtain the supernatant, and rotary evaporate to remove anhydrous xylene. The obtained oily sample is redispersed in ethanol for storage, and the colloidal aluminum nitride quantum dots with deep ultraviolet fluorescence emission are obtained.

[0021] Preferably, for another said preparation method, the steps are as follows:

[0022] 1) Weigh 355 mg of tetraoctylammonium bromide into a dry three-necked flask, add 100 ml of anhydrous xylene to the reaction solvent, and ultrasonically treat until a clear and transparent reverse micelle solution is obtained; 5 portions of the same reverse micelle solution are prepared simultaneously for subsequent mixing of different reaction precursors at different concentrations;

[0023] 2) Weigh 176 mg of anhydrous gallium chloride and add it to the reverse micelle solution in step 1) to prepare a gallium chloride reaction precursor, and then

[0024] Weigh 133 mg of anhydrous aluminum chloride and add it to the reverse micelle solution in step 1) to prepare an aluminum chloride reaction precursor; in the following experiments, a total of four experimental groups are set: The first group: a reaction precursor solution with 0% gallium doping, that is, all aluminum chloride precursor solution; The second group: a reaction precursor solution with 10% gallium doping, that is, 10 ml of gallium chloride precursor solution is added to 90 ml of aluminum chloride precursor solution; The third group: a reaction precursor solution with 20% gallium doping, that is, 20 ml of gallium chloride precursor solution is added to 80 ml of aluminum chloride precursor solution; The second group: a reaction precursor solution with 30% gallium doping, that is, 30 ml of gallium chloride precursor solution is added to 70 ml of aluminum chloride precursor solution;

[0025] 3) Transfer the four groups of solutions in step 2) to a double-tube (Schlenk line), use argon to purge the air inside the reaction system, and keep argon flowing to ensure that the reaction system proceeds in an anhydrous and oxygen-free environment;

[0026] 4) Slowly heat the solution in step 3) to 120 °C, and add 0.5 ml of 2.4 M ammonia ethanol solution at a rate of 1 ml / h through a microfluidic injection pump, and continue to keep warm for 5 hours;

[0027] 5) After the solution in step 4) is cooled to room temperature, 3 ml of methanol is added to disrupt the reverse micelle system. The supernatant is obtained by centrifugation and the anhydrous xylene is removed by rotary evaporation. After obtaining the oily sample, it is respectively redispersed in ethanol for storage, and thus the colloidal aluminum nitride quantum dots with continuously tunable fluorescence emission from the UV-B to UV-A band are obtained.

[0028] A kind of colloidal aluminum nitride quantum dots obtained according to the described preparation method, which are uniformly dispersed and have a uniform particle size, and can realize continuously tunable fluorescence emission from the UV-B to UV-A band.

[0029] The application of the deep ultraviolet fluorescence emission colloidal aluminum nitride quantum dots described above is used to manufacture high-efficiency UV-LED devices to achieve deep ultraviolet fluorescence emission with a wavelength as low as 210 nm; and / or

[0030] Narrowband 310 nm UV-B phototherapy is used to treat cancer and skin diseases; and / or

[0031] The narrowband 310 nm UV-B light source can be used to enrich the phytochemicals in fruits and vegetables.

[0032] Another application of the deep ultraviolet fluorescence emission colloidal aluminum nitride quantum dots described above is used for high-efficiency optoelectronic devices, high-power high-frequency electronic devices, ultra-high-voltage power electronic devices, deep ultraviolet warning and guidance, and deep ultraviolet LED disinfection.

[0033] The beneficial effects of the present invention are as follows:

[0034] 1) The deep ultraviolet fluorescence emission and fluorescence emission tunable colloidal aluminum nitride quantum dots prepared by the present invention have good dispersibility and significant photoluminescence, and the precise internal structure can be understood, so as to realize further understanding of its microstructure.

[0035] 2) The deep ultraviolet fluorescence emission and fluorescence emission tunable colloidal aluminum nitride quantum dots prepared by the present invention can be used for the preparation and application of the third-generation colloidal quantum dot LEDs, and it is convenient and easy to prepare ultraviolet LEDs, etc.

[0036] 3) The deep ultraviolet fluorescence emission tunable colloidal aluminum nitride quantum dots prepared by the present invention are expected to have significant advantages in optoelectronic devices.

[0037] 4) The synthesis route involved in the present invention has the advantages of simple and easily available raw materials, simple and easy reaction conditions, simple operation, and high product quality. It is the first time to prepare colloidal aluminum nitride quantum dots by the solution method.

[0038] 5) Colloidal aluminum nitride quantum dots with an average particle size of about 3.7 nm and high quantum yield fluorescence emission in the deep ultraviolet band were successfully prepared; at the same time, the excellent performance of adjustable fluorescence emission was achieved by changing the band gap of the quantum dots through co-doping. The colloidal aluminum nitride quantum dots realized in the present invention are different from all the synthesis methods of aluminum nitride crystals reported so far, and are expected to greatly reduce the preparation cost and difficulty of aluminum nitride crystals while significantly improving the application of colloidal aluminum nitride quantum dots in optoelectronic devices. Description of the Drawings

[0039] Figure 1 Transmission electron microscope image (TEM) of small-sized 3.7 ± 0.65 nm colloidal aluminum nitride quantum dots prepared in Example 1.

[0040] Figure 2 Aberration-corrected electron microscope image (ACTEM) of small-sized 3.7 ± 0.65 nm colloidal aluminum nitride quantum dots prepared in Example 1.

[0041] Figure 3 Particle size distribution of small-sized 3.7 ± 0.65 nm colloidal aluminum nitride quantum dots prepared in Example 1.

[0042] Figure 4 Absorption spectrum of colloidal aluminum nitride quantum dots with adjustable fluorescence emission prepared in Example 1.

[0043] Figure 5 Photoluminescence spectrum of colloidal aluminum nitride quantum dots with adjustable fluorescence emission prepared in Example 2.

[0044] Figure 6 Quantum yield of colloidal aluminum nitride quantum dots with adjustable fluorescence emission prepared in Example 2. Detailed Description of the Invention

[0045] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described below in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0046] Example 1: Synthesis of Deep Ultraviolet Fluorescent Emission Colloidal Aluminum Nitride Quantum Dots

[0047] A simple and efficient synthesis method for controlling small-sized 3.7 ± 0.65 nm deep ultraviolet fluorescent emission colloidal aluminum nitride quantum dots, specifically including the following steps:

[0048] 1) In the experimental preparation stage, put glass containers such as three-necked flasks into an oven and bake at 140 ° for 12 hours to ensure that the used glass containers are dry enough. Pour 100 ml of anhydrous xylene into the flask, and then weigh 1 mmol of tetraoctylammonium bromide (TOAB) and put it into xylene for ultrasonic dispersion until a clear, transparent and colorless solution is obtained; then weigh 1 mmol of aluminum chloride (AlCl3) and add it to the reverse micelle solution prepared above and ultrasonicate until AlCl3 is evenly dispersed in the solution. Then flush with argon for 20 min, and the flow rate of argon is 1 ml / h.

[0049] 2) Then slowly heat the solution to 140 °C, with a heating rate of 20 °C / min.

[0050] 3) Slowly add 0.5 ml of 2.4 M ammonia ethanol solution to the solution. Stir magnetically at high temperature for 4 hours, and the whole experiment is carried out under the protection of an argon atmosphere. The rotation speed is 800 rpm / min.

[0051] 3) Add methanol to the solution after reacting for 4 hours in step 3) to destroy the reverse micelle system. Naturally cool the reaction solution to room temperature and then centrifuge the reaction solution, and take the supernatant for liquid-liquid extraction.

[0052] 4) Take the upper layer solution of the extract in step 3) and heat it under rotary evaporation to remove the organic solvents xylene and ethanol in the solution. Add ethanol to the flask after rotary evaporation and ultrasonically disperse it to dissolve the product after rotary evaporation; finally, purify it by dialysis to obtain the final product.

[0053] By observing the microstructure and surface morphology of the synthesized deep ultraviolet fluorescence-emitting colloidal aluminum nitride quantum dots through TEM and ACTEM, Figure 1 it is shown that the prepared deep ultraviolet fluorescence-emitting colloidal aluminum nitride quantum dots are usually spherical and evenly dispersed, with an average particle size of 3.7 ± 0.65 nm. Figure 2 The spherical aberration electron microscope image shows the surface morphology of the synthesized deep ultraviolet fluorescence-emitting colloidal aluminum nitride quantum dots.

[0054] Example 2: Synthesis of colloidal aluminum nitride quantum dots with tunable fluorescence emission

[0055] We successfully synthesized colloidal aluminum nitride quantum dots with tunable fluorescence emission by controlling the molar ratio of AlCl3 and GaCl3. In different synthesis schemes, when the molar ratios of AlCl3 and GaCl3 are 1:9, 2:8, and 3:7 respectively, and the reaction temperature is kept at 140 °C, we synthesized colloidal aluminum nitride quantum dots with sizes of 3.40 ± 0.74 nm, 3.75 ± 0.88 nm, and 3.84 ± 0.73 nm, and simultaneously observed a red shift in photoluminescence.

[0056] 1) In the experimental preparation stage, glass containers such as three-necked flasks were placed in an oven at 140 °C for 12 hours to ensure that the glass containers used were sufficiently dry. 100 ml of anhydrous xylene was poured into the flask respectively, and then 1 mmol of tetraoctylammonium bromide (TOAB) was weighed and put into xylene and ultrasonically dispersed until a clear, transparent and colorless solution was obtained; subsequently, four groups of aluminum chloride (AlCl3) and gallium chloride (GaCl3) with different concentration ratios (ensuring that their molar ratios were 1, 1:9, 2:8, 3:7 respectively) were weighed and added to the reverse micelle solution prepared above and ultrasonically treated until the solutes were evenly dispersed in the solution. Subsequently, it was flushed with argon for 20 min, and the flow rate of argon was 1 L / min.

[0057] 2) Subsequently, the solution was slowly heated to 140 °C, and the heating rate was 20 °C / min.

[0058] 3) 0.5 ml of 2.4 M ammonia ethanol solution was slowly added to each bottle of solution. It was magnetically stirred at a high temperature for 4 hours, and the whole experiment was carried out under the protection of an argon atmosphere. The rotation speed was 800 rpm / min.

[0059] 3) Methanol was added to the solution after reacting for four hours in step 3) to destroy the reverse micelle system. After the reaction solution was naturally cooled to room temperature, the reaction solution was centrifuged, and the supernatant was separated and extracted.

[0060] 4) The upper layer solution of the extract in step 3) was heated and rotary evaporated to remove the organic solvents xylene and ethanol in the solution. Ethanol was added to the flask after rotary evaporation and ultrasonically dispersed to dissolve the product after rotary evaporation; finally, it was purified by dialysis to obtain the final product.

[0061] By studying the absorption and photoluminescence of the synthesized deep ultraviolet fluorescence-emitting and fluorescence-emission-tunable colloidal aluminum nitride quantum dots (as shown in Figure 4 、 5 ), it was found that as the Ga content increased, its emission gradually redshifted from 298 nm to 347 nm. At the same time, the quantum yields of different samples were tested, and it was found that the 20% Ga-doped aluminum nitride quantum dots showed the highest quantum yield (as shown in Figure 6 ).

[0062] Applications of Deep Ultraviolet Fluorescence-Emitting Colloidal Aluminum Nitride Quantum Dots

[0063] Aluminum nitride (AlN) crystals have a relatively wide direct bandgap (6.2 eV) and can be used to manufacture high-efficiency UV-LED devices to achieve deep ultraviolet light with a wavelength as low as 210 nm. Narrow-band (310 nm) UV-B phototherapy can be used to treat cancer and skin diseases while minimizing adverse side effects on nearby unaffected tissues; in the agricultural field, it has recently been found that 310-nm narrow-band UV-B light sources can be used to enrich phytochemicals in fruits and vegetables. Aluminum nitride (AlN) crystals have great application prospects in high-efficiency optoelectronic devices, high-power high-frequency electronic devices, extra-high voltage power electronic devices, deep ultraviolet early warning and guidance, deep ultraviolet LED disinfection, etc. Therefore, the successful preparation of colloidal aluminum nitride quantum dots is expected to develop aluminum nitride (AlN) crystals into key materials supporting fields such as information, energy, transportation, and national defense.

[0064] The embodiments described above can be further combined or replaced, and the embodiments are only descriptions of the preferred embodiments of the present invention, not limitations on the concept and scope of the present invention. Without departing from the design concept of the present invention, various changes and improvements made by those of ordinary skill in the art to the technical solutions of the present invention all belong to the protection scope of the present invention. The protection scope of the present invention is given by the appended claims and any equivalent technical solutions thereof.

Claims

1. A preparation method of deep ultraviolet fluorescence-emitting and fluorescence-emission tunable colloidal aluminum nitride quantum dots, characterized in that, A mixture of aluminum halide and gallium halide is used as the reaction precursor of colloidal aluminum nitride quantum dots, and a quaternary ammonium cationic surfactant is used as the surfactant. Ammonia reduction is used to prepare colloidal aluminum nitride quantum dots with uniform dispersion, uniform particles, deep ultraviolet fluorescence emission and adjustable fluorescence emission, including the following steps: 1) Weigh the quaternary ammonium cationic surfactant into a dried container, add xylene as the solvent, and ultrasonically disperse until a transparent and clear reverse micelle solution is obtained; 2) Using the mixture of aluminum halide and gallium halide as the reaction precursor, weigh it and place it in the reverse micelle solution obtained in step 1), and ultrasonically disperse until the reverse micelle system presents a transparent and clear state; 3) Extract the internal air of the solution obtained in step 2) to ensure that the reaction solution is in an anhydrous and oxygen-free environment, and then heat the reaction mixture; 4) Slowly add an ammonia reducing agent to the mixed solution obtained in step 3), and magnetically stir at a high temperature for a period of time under the protection of an inert gas atmosphere; 5) Cool the mixed solution obtained in step 4), add a polar solvent to destroy the reverse micelle system, centrifuge to take the supernatant, rotary evaporate to remove anhydrous xylene, and then redisperse in ethanol for storage, that is, colloidal aluminum nitride quantum dots with deep ultraviolet fluorescence emission and adjustable fluorescence emission are obtained; The aluminum halide described in step 2) includes aluminum chloride 、 aluminum bromide, and the gallium halides include gallium chloride and gallium bromide; In step 4), a slow reduction process is carried out using an ethanol solution of ammonia; The polar solvent used in step 5) is methanol or ethanol.

2. The preparation method according to claim 1, characterized in that, The steps are as follows: 1) Weigh 355 mg of tetraoctylammonium bromide into a dry three-necked flask, add 100 ml of anhydrous xylene as the reaction solvent, and ultrasonically treat until a clear and transparent reverse micelle solution is obtained; 5 portions of the same reverse micelle solution are prepared simultaneously for subsequent realization of different concentration mixtures of different reaction precursors; 2) Weigh 176 mg of anhydrous gallium chloride and add it to the reverse micelle solution in step 1) to prepare a gallium chloride reaction precursor, and then Weigh 133 mg of anhydrous aluminum chloride and add it to the reverse micelle solution in step 1) to prepare an aluminum chloride reaction precursor; A total of four experimental groups were set up in the following experiment: The first group: a reaction precursor solution with 0% gallium doping, that is, all aluminum chloride precursor solution; The second group: a reaction precursor solution with 10% gallium doping, that is, 10 ml of gallium chloride precursor solution is added to 90 ml of aluminum chloride precursor solution; The third group: a reaction precursor solution with 20% gallium doping, that is, 20 ml of gallium chloride precursor solution is added to 80 ml of aluminum chloride precursor solution; The second group: a reaction precursor solution with 30% gallium doping, that is, 30 ml of gallium chloride precursor solution is added to 70 ml of aluminum chloride precursor solution; 3) Transfer the four groups of solutions in step 2) to a double-row tube (Schlenk line), use argon to flush to remove the internal air of the reaction system, and keep argon flowing in to ensure that the reaction system is carried out in an anhydrous and oxygen-free environment; 4) Slowly heat the solution in step 3) to 120 °C, and add 0.5 ml of 2.4 M ammonia ethanol solution at a speed of 1 ml / h through a microfluidic injection pump, and continue to keep warm for 5 hours; 5) After the solution in step 4) is cooled to room temperature, 3 ml of methanol is added to disrupt the reverse micelle system. The supernatant is obtained by centrifugation and the anhydrous xylene is removed by rotary evaporation. After obtaining the oily sample, it is redispersed in ethanol and stored respectively, thus obtaining colloidal aluminum nitride quantum dots with continuously tunable fluorescence emission from the UV-B to UV-A band.

3. A colloidal aluminum nitride quantum dot obtained by the preparation method according to claim 1, characterized in that, They are uniformly dispersed with uniform particle sizes, and can achieve continuously tunable fluorescence emission from the UV-B to UV-A band.

4. The application of the deep ultraviolet fluorescence-emitting colloidal aluminum nitride quantum dots according to claim 3, wherein it is used to manufacture high-efficiency UV-LED devices to achieve deep ultraviolet fluorescence emission with a wavelength as low as 210 nm; and / or narrow-band 310 nm UV-B phototherapy is used to treat cancer and skin diseases; and / or narrow-band 310 nm UV-B light sources can be used to enrich the phytochemicals in fruits and vegetables.

5. The application of the deep ultraviolet fluorescence-emitting colloidal aluminum nitride quantum dots according to claim 3, wherein, It is used for high-efficiency optoelectronic devices, high-power high-frequency electronic devices, ultra-high-voltage power electronic devices, deep ultraviolet early warning and guidance, and deep ultraviolet LED disinfection.

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