A mixed solvent-induced highly fluorescent silver nanoclusters, its preparation method, and its application in LEDs

Abstract

This invention relates to a mixed solvent-induced highly fluorescent silver nanoclusters, its preparation method, and its application in LEDs. These highly fluorescent silver nanoclusters are formed by the self-assembly of Ag6 in a mixed solvent of water and NMP through non-covalent interactions such as hydrogen bonding and π-π / π* interactions. Due to the restriction of ligand rotation and vibration, the silver nanoclusters exhibit significant fluorescence properties, with fluorescence intensity reaching 10⁻⁶. 7 The fluorescence lifetime is 11.77 μs and the quantum yield is 17.57%. The method for preparing high-fluorescence silver nanoclusters of the present invention is simple and inexpensive; when mixed with commercial phosphors, it can modulate white LEDs and can be used as a light conversion material for environmentally friendly WLEDs.

Description

Technical Field

[0001] This invention relates to a mixed solvent-induced highly fluorescent silver nanoclusters, its preparation method, and its application in LEDs, belonging to the fields of new materials and LED lighting technology. Background Technology

[0002] Light-emitting diodes (LEDs), as semiconductor components, were initially used primarily as indicator lights and display LED boards. With the advent of white LEDs (WLEDs), their application in lighting gradually expanded. LEDs are not only long-lasting but also small in size, making them widely used in various indication, display, decoration, and general lighting applications. The light conversion materials used in LED manufacturing typically include rare-earth phosphors, organic phosphors, and luminescent quantum dots. However, these materials have drawbacks such as resource scarcity, environmental friendliness, and poor resistance to photobleaching; some even pose health risks. Therefore, the demand for environmentally friendly LEDs is steadily increasing.

[0003] Metal nanoclusters typically consist of several to hundreds of atoms, with sizes approximately equivalent to the Fermi wavelength of electrons (<2 nm). They exhibit low toxicity, low cost, and good biocompatibility. Strong fluorescence emission can be achieved by realizing charge transfer from the peripheral ligands of metal nanoclusters to the metal or through metal-metal interactions. Among numerous metal nanoclusters, silver nanoclusters have been widely studied and reported due to their excellent properties and readily available raw materials. Silver nanoclusters are a class of clusters with precise atomic structures, ranging in size from 1 to 3 nm. Their cores are generally composed of three or more silver atoms interacting through argyrophilic bonds, and are protected by organic ligands. The peripheral ligands of silver nanoclusters provide abundant interaction sites for various non-covalent interactions, allowing them to self-assemble into aggregates and exhibit aggregation-induced emission. Therefore, as a novel luminescent nanomaterial, silver nanoclusters hold great promise for the fabrication of environmentally friendly LEDs.

[0004] Due to the excellent optical properties of silver nanoclusters, numerous studies have reported on luminescent silver nanoclusters. For example, Chinese patent document CN112175608A (application number: 202011138639.8) discloses a method for preparing blue fluorescent silver nanoclusters. The blue fluorescent silver nanocluster solution is prepared using histidine as a reducing agent and a protecting agent, and silver nitrate solution as a matrix, via microwave synthesis. Its fluorescence intensity is stable at 10. 5The fluorescence quantum yield is on the order of magnitude higher (up to 5.2%), and the fluorescence intensity remains essentially unchanged after one hour. Chinese patent document CN112916863A (application number: 202110069410.1) discloses a method for preparing water-soluble luminescent silver nanoclusters. The method uses 3,4-dihydroxy-L-phenylalanine as a reducing agent and ligand protecting agent to prepare the water-soluble luminescent silver nanoclusters. The fluorescence emission peak is around 460 nm, exhibiting strong blue fluorescence under ultraviolet light (against a black background). The fluorescence quantum yield reaches 3.50%, and the stability at room temperature can reach more than 6 months. Chinese patent document CN111748340A (application number: 202010610300.7) discloses a method for synthesizing fluorescent silver nanoclusters. This method involves mixing the silver acetylide precursor AgC≡CR, silver salt, and trace amounts of chlorine atoms, and then reacting the mixture under the action of a reducing agent to obtain a fluorescent silver nanocluster compound that emits bright red light at room temperature. Chinese patent document CN109111912A (application number: 201811214768.3) discloses a method for preparing nanocluster core-shell phosphors for high-power white LEDs. The method prepares core-shell phosphor conversion materials modified with silver nanoclusters by hydrothermal method, prepares Bi / Mn ion-doped fluoride micron particles by microwave method, and controls the phosphor to achieve dual absorption in the ultraviolet and blue light regions, while generating high-intensity emission in the blue, green, yellow and red light regions.

[0005] Chinese patent document CN115780818A discloses an aggregation-induced gold-silver alloy nanoclusters, its preparation method, and its application. Using L-cysteine ​​as a protective agent and reducing agent, and silver nitrate and chloroauric acid as the matrix, an aqueous solution of yellow-green fluorescent gold-silver alloy nanoclusters is prepared by an ultrasound-assisted method. This method requires the assistance of ultrasound.

[0006] Chinese patent document CN110591702A discloses a method for preparing and applying aggregation-induced luminescent silver nanoclusters. The preparation of aggregation-induced luminescent silver nanoclusters involves mixing 5-17.5 parts by volume of a 20 mmol / L N-acetyl-L-cysteine ​​aqueous solution and 20 parts by volume of a 2.5 mmol / L silver nitrate solution. The mixture is stirred evenly and refluxed at 60-80℃ for 12-48 hours. After cooling, the mixture is taken out and freeze-dried to obtain aggregation-induced luminescent silver nanoclusters with a fluorescence quantum yield as high as 0.44. This method requires heating to induce aggregation.

[0007] In summary, current methods for preparing fluorescent nanoclusters, whether microwave synthesis, hydrothermal synthesis, or stirring-heating-reflux, all require high energy levels, are cumbersome, and increase production costs. Furthermore, most fluorescent nanoclusters exhibit low quantum yields, with luminescence intensities below 10⁻⁶. 5 Below, very few exceed 10 5Order of magnitude; most fluorescent silver nanoclusters require the addition of reducing agents such as sodium borohydride or even halogens during synthesis, which harms the environment.

[0008] There are few reports on obtaining luminescent silver nanoclusters of phosphor using simple and environmentally friendly methods, and studying their self-assembly behavior, optical properties, and applications in LEDs. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides a mixed solvent-induced highly fluorescent silver nanoclusters, its preparation method, and its application in LEDs.

[0010] Terminology Explanation:

[0011] Ag6 is a hexanuclear silver nanocluster. Due to π-π interactions between ligands, charge transfer from ligands to metals, charge transfer from ligands to metals, and metal-metal interactions, Ag6 exhibits certain luminescent properties after assembly.

[0012] The technical solution of the present invention is as follows:

[0013] A mixed solvent-induced high-fluorescence silver nanoclusters, wherein the silver nanoclusters are supramolecular self-assemblies of Ag6 induced by mixed solvents. The microstructure of the self-assemblies is a bow-shaped structure that is narrow in the middle and wide at both sides, and is composed of twisted and crossed nanosheets formed by fiber aggregation.

[0014] According to a preferred embodiment of the present invention, the length of the self-assembled high-fluorescence silver nanoclusters is 8-12 μm and the width is 2-4 μm.

[0015] According to a preferred embodiment of the present invention, the fluorescence spectrum of the highly fluorescent silver nanoclusters shows a maximum fluorescence intensity of 2.4 × 10⁻⁶. 7 The excitation wavelength is 310-460 nm, and the emission wavelength is stable at 565±3 nm.

[0016] According to a preferred embodiment of the present invention, the fluorescence lifetime of the high-fluorescence silver nanoclusters is 11.77 μs and the quantum yield is 17.57%.

[0017] The high-fluorescence silver nanoclusters of the present invention are obtained through non-covalent interactions such as intermolecular hydrogen bonds and π-π interactions.

[0018] This invention provides a method for preparing the above-mentioned mixed solvent-induced highly fluorescent silver nanoclusters.

[0019] According to the present invention, a method for preparing highly fluorescent silver nanoclusters induced by mixed solvents includes the following steps:

[0020] Ag6 was dissolved in ultrapure water to obtain an aqueous solution of Ag6. N-methylpyrrolidone (NMP) was added to the aqueous solution of Ag6, and vortexing was performed to produce a precipitate. The precipitate was allowed to stand at room temperature for 2-6 days, centrifuged, and freeze-dried to obtain pale yellow high-fluorescence silver nanoclusters.

[0021] According to a preferred embodiment of the present invention, the concentration of the Ag6 aqueous solution is 40-60 mmol·L⁻¹. -1 .

[0022] More preferably, the concentration of the Ag6 aqueous solution is 50 mmol·L⁻¹. -1 .

[0023] According to a preferred embodiment of the present invention, the mixing volume ratio of Ag6 aqueous solution to NMP is (1-3):(7-9).

[0024] More preferably, the volume ratio of Ag6 aqueous solution to NMP is (1-2):(8-9).

[0025] According to a preferred embodiment of the present invention, the vortex time is 20-30 s and the settling time is 3 days.

[0026] According to the present invention, the NMP is a commercially available product.

[0027] According to a preferred embodiment of the present invention, the centrifugation speed is 7000-9000 r / min and the centrifugation time is 8-12 minutes.

[0028] According to a preferred embodiment of the present invention, the freeze-drying temperature is -50 to -70°C, and the freeze-drying time is 1 to 3 days.

[0029] According to the present invention, highly fluorescent silver nanoclusters induced by mixed solvents are obtained by freeze drying.

[0030] In this invention, Ag6 is placed in a mixed solvent of water and NMP. The mixed solvent causes the ligands on the periphery of Ag6 to interact with NMP in a π-π* manner. At the same time, through hydrogen bonding, the rotation and vibration of the ligands are restricted. Accompanied by electron transfer between the ligands and the metal, highly fluorescent silver nanoclusters are obtained by the mixed solvent.

[0031] According to a preferred embodiment of the present invention, Ag6 is prepared by the following method:

[0032] Silver nitrate (AgNO3) and 2-mercaptonicotinic acid (H2mba) were dissolved in water sequentially to obtain a mixed solution. The mixed solution was ultrasonically treated at room temperature to produce a precipitate. Ammonia was added dropwise to the precipitate until a transparent yellow solution was formed. The solution was freeze-dried to obtain yellow crystals Ag6.

[0033] According to the present invention, preferably, the concentration of silver nitrate in the mixed solution is 0.05-0.3 mol·L⁻¹.-1 The concentration of 2-mercaptonicotinic acid in the mixed solution was 0.05-0.3 mol·L⁻¹. -1 .

[0034] According to the present invention, preferably, the molar ratio of AgNO3 to H2mna is 1:1;

[0035] According to the present invention, preferably, the ultrasonic frequency of the ultrasonic treatment is 30-50kHz, the ultrasonic power is 150-170W, and the ultrasonic time is 10-30 minutes.

[0036] According to the present invention, preferably, the mass concentration of ammonia water is 25%; the amount of ammonia water added is until the precipitate is completely dissolved. The resulting solution is a yellow transparent solution.

[0037] According to the present invention, the above-mentioned highly fluorescent silver nanoclusters are obtained by Ag6 self-assembly induced by a mixed solvent.

[0038] This invention provides the application of the above-mentioned mixed solvent-induced highly fluorescent silver nanoclusters in LEDs, which are used as light conversion materials for LEDs.

[0039] The principle of this invention:

[0040] The Ag6 aqueous solution prepared in this invention is non-fluorescent at room temperature, but exhibits amphiphilicity in solvents of appropriate polarity, with its surrounding mna 2- The carboxylate ion in it is a solvent-loving element, as are the silver nucleus in the middle and the mna. 2- The portion of mna, except for the carboxylate group, is a solvent-phobic. 2- There are π-π interactions between them, therefore, the amphiphilicity of Ag6 molecules and the π-π interactions allow Ag6 to aggregate and form self-assembled structures.

[0041] By adding the polar solvent NMP to an aqueous solution of Ag6, π-π* interactions are induced between the Ag6 ligands and NMP. Simultaneously, hydrogen bonding restricts the rotation and vibration of the ligands, accompanied by electron transfer between the ligands and the metal. The non-covalent interactions induced by the mixed solvent lead to aggregation-induced emission (AIE) of Ag6, thus the silver nanoclusters exhibit significant fluorescence properties. WLED lamps can be fabricated by mixing highly fluorescent silver nanocluster phosphors with commercially available phosphors in a specific ratio.

[0042] The key features and beneficial effects of this invention are:

[0043] 1. Ag6 is a noble metal cluster compound with a size of less than 2 nm. It belongs to a new type of inorganic material with a novel structure and unique properties. This invention utilizes a supramolecular self-assembly method induced by good / poor solvents to construct an ordered nanostructure, thereby achieving fluorescence emission and improving the fluorescence properties in the solid state.

[0044] 2. The NMP used in this invention is miscible with water, has low toxicity and good stability, and induces Ag6 to self-assemble into self-assembled organisms, thus ensuring the stability of the highly fluorescent silver nanoclusters.

[0045] 3. The emission wavelength of the high-fluorescence silver nanoclusters of the present invention is stable at around 565 nm and does not shift with changes in the excitation wavelength.

[0046] 4. The high-fluorescence silver nanoclusters of this invention exhibit strong fluorescence properties; the fluorescence intensity can reach 10 when the slit size is 3 nm. 7 The fluorescence lifetime was on the order of magnitude higher than that of Ag6 crystal (0.56 μs), reaching 11.77 μs, a 21-fold increase compared to Ag6 crystal (0.56 μs); the quantum yield was 17.57%, a 7.8-fold increase compared to Ag6 crystal (2.26%). A WLED prototype was demonstrated using the Ag6 assembly as a color conversion layer on a 365 nm LED chip.

[0047] 5. The high-fluorescence silver nanoclusters of the present invention can successfully replace traditional light conversion materials, and can produce environmentally friendly LEDs.

[0048] 6. The method for preparing high-fluorescence silver nanoclusters of the present invention is simple and low in cost; the LEDs prepared as light conversion materials for LEDs have excellent luminous intensity and meet environmental protection requirements. Attached Figure Description

[0049] Figure 1 This is a molecular structure model diagram of Ag6, the substance synthesized in Example 1 of the present invention.

[0050] Figure 2 These are micrographs of the highly fluorescent silver nanoclusters prepared in Example 1 of the present invention, wherein (a) is a TEM image, (b) is a SEM image, and (c) is a CLSM image.

[0051] Figure 3 Optical photographs of the highly fluorescent silver nanoclusters prepared in Example 1 of the present invention, wherein (a) is an optical photograph (left) and a fluorescent photograph (right) in solution, and (b) is an optical photograph (left) and a fluorescent photograph (right) of the powder.

[0052] Figure 4The fluorescence spectrum of the highly fluorescent silver nanoclusters prepared in Example 1 of this invention is shown in (a), where (a) is the emission spectrum at excitation wavelengths of 320-460 nm, and (b) is the spectrum of fluorescence intensity at different excitation wavelengths and the spectrum of the optimal emission wavelength.

[0053] Figure 5 The infrared spectrum of the highly fluorescent silver nanoclusters prepared in Example 1 of this invention is shown.

[0054] Figure 6 The TGA spectrum of the highly fluorescent silver nanoclusters prepared in Example 1 of this invention.

[0055] Figure 7 This is a fluorescence decay diagram of the highly fluorescent silver nanoclusters prepared in Example 1 of the present invention.

[0056] Figure 8 These are digital photographs of LEDs of different colors prepared in Experimental Examples 1, 2 and 3 of the present invention under 365 nm excitation, wherein (a) is Experimental Example 1, (b) is Experimental Example 2 and (c) is Experimental Example 3.

[0057] Figure 9 The fluorescence spectra of LEDs of different colors prepared in Experimental Examples 1, 2 and 3 of this invention are shown. Among them, (a) is Experimental Example 1, (b) is Experimental Example 2 and (c) is Experimental Example 3.

[0058] Figure 10 The images show the CIE color coordinate diagrams of the samples prepared in Experimental Examples 1, 2, and 3 of this invention. Among them, (a) is Experimental Example 1, (b) is Experimental Example 2, and (c) is Experimental Example 3. Detailed Implementation

[0059] The present invention will be further described below with reference to specific embodiments and accompanying drawings, but is not limited thereto.

[0060] All raw materials used in the examples are conventional raw materials and commercially available products. Among them, AgNO3 and H2mna are available from Sigma-Aldrich (Shanghai) Trading Co., Ltd., NMP is available from Aladdin Reagent (Shanghai) Co., Ltd., and blue fluorescent powder is available from Jinan Cyber ​​Chemical Reagent Co., Ltd. No further purification was performed before use.

[0061] KQ5200DE instrument, a commercially available product.

[0062] High-refractive-index LED patches and silicone A and B adhesives, commercially available products, are manufactured according to existing technology in this field.

[0063] The material characteristics described in this invention were tested using the following methods:

[0064] 1. Transmission electron microscopy (TEM). The morphology of silver nanoclusters was observed using TEM.

[0065] 2. Scanning electron microscopy (SEM). The morphology of silver nanoclusters was observed using SEM.

[0066] 3. Fluorescence spectroscopy. The fluorescence intensity of the silver nanoclusters was measured using a fluorescence spectrophotometer.

[0067] 4. Laser confocal microscopy (CLSM). The morphology and luminescence properties of silver nanoclusters were observed using CLSM.

[0068] 5. Fourier transform infrared spectroscopy (FT-IR). The interactions during the self-assembly of silver nanoclusters were characterized using FT-IR spectra.

[0069] 6. Thermogravimetric analysis (TGA). Changes in the thermal stability of Ag6 are characterized using TGA spectra.

[0070] Example 1

[0071] A method for preparing highly fluorescent silver nanoclusters induced by mixed solvents, comprising the following steps:

[0072] (1) Synthesis of Ag6 molecules

[0073] Accurately weigh 1 mmol (167 mg) of AgNO3 solid and 1 mmol (155 mg) of H2mna solid into a round-bottom flask, add 6 mL of water-dispersed solids, and sonicate using a KQ5200DE instrument for 20 minutes at a frequency of 40 kHz and a power of 160 W to obtain a precipitate. Add 8 drops (25 wt%) of ammonia water to the precipitate dropwise to obtain a clear yellow solution. Freeze-dry the solution to obtain yellow crystalline Ag6; the molecular structure diagram of Ag6 is shown below. Figure 1 As shown. By Figure 1 It can be seen that Ag6 is a hexanuclear silver nanocluster with Ag as the core and H2mna as the ligand.

[0074] (2) Preparation of Ag6 aqueous solution

[0075] Weigh 418.5 mg of Ag6 and dissolve it in 5 mL of ultrapure water. Vortex for 20 s to dissolve the solution, yielding a molar concentration of 50 mmol·L⁻¹. -1 Aqueous solution of Ag6.

[0076] (3) Preparation of highly fluorescent silver nanoclusters induced by mixed solvents

[0077] Take 100 μL of Ag6 aqueous solution and add 900 μL of NMP to it. The ratio of aqueous solution to NMP is 1:9. After mixing, the concentration of Ag6 is 5 mmol·L⁻¹. -1 Vortex for 30 seconds, and a precipitate will appear in the solution. After standing for 3 days, the precipitate will be centrifuged and freeze-dried for 2 days to obtain the final product.

[0078] TEM, SEM, and CLSM images of the highly fluorescent silver nanoclusters obtained in this embodiment are shown below. Figure 2 As shown. By Figure 2 It is known that the silver nanoclusters are bow-shaped assemblies that are slightly narrower in the middle and wider on both sides. The assemblies are composed of twisted and crossed nanosheets formed by fiber aggregation, with a length of about 8-12 μm and a width of about 2-4 μm, and have good fluorescence properties.

[0079] Optical images of the highly fluorescent silver nanoclusters obtained in this embodiment are as follows: Figure 3 As shown. Figure 3 (a) shows the state of highly fluorescent silver nanoclusters in a mixed solvent. The left side is a photograph taken under sunlight, and the right side is a photograph taken under a UV lamp (observed against a black background). Figure 3 (b) shows the high-fluorescence silver nanoclusters in solid powder form. The left image is a photograph taken under sunlight, and the right image is a photograph taken under ultraviolet light (observed against a black background). Whether in a mixed solvent or in solid powder form, the silver nanoclusters emit strong yellow fluorescence under ultraviolet light.

[0080] The fluorescence spectrum of the highly fluorescent silver nanoclusters obtained in this embodiment is as follows: Figure 4 As shown. By Figure 4 (a) It can be seen that silver nanoclusters have a wide excitation range, with optimal excitation at 400 nm and optimal emission at 565 nm, exhibiting a large Stokes shift (~165 nm). From Figure 4 (b) It can be seen that the emission wavelength of silver nanoclusters does not change with the excitation wavelength, while the fluorescence intensity first increases and then decreases with the increase of the excitation wavelength.

[0081] The infrared spectrum of the highly fluorescent silver nanoclusters obtained in this embodiment is as follows: Figure 5 As shown. By Figure 5 It can be seen that the self-assembly of silver nanoclusters is driven by hydrogen bonding interactions.

[0082] The TGA spectrum of the highly fluorescent silver nanoclusters obtained in this embodiment is as follows: Figure 6 As shown. By Figure 6 It can be seen that silver nanoclusters have better thermal stability after self-assembly.

[0083] The fluorescence decay diagram of the high-fluorescence silver nanoclusters obtained in this embodiment is shown below. Figure 7As shown, the fluorescence lifetime of the silver nanoclusters is 11.77 μs, which is 21 times longer than that of Ag6 crystals (0.56 μs), indicating that they are phosphorescent emitters.

[0084] Example 2

[0085] The preparation method is the same as that described in Example 1, except that:

[0086] Take 100 μL of the Ag6 aqueous solution stock solution, add 100 μL of ultrapure water and 800 μL of NMP to it, with a solvent ratio of aqueous solution:NMP = 2:8. After mixing, the Ag6 concentration is 5 mmol·L⁻¹. -1 The solution was vortexed for 30 seconds, and a precipitate appeared. After standing for 3 days, the precipitate was centrifuged and freeze-dried for 2 days to obtain the silver nanoclusters. The fluorescence intensity of the silver nanoclusters obtained in this example was approximately 1.6 × 10⁻⁶. 7 The fluorescence lifetime is 10.61 μs.

[0087] Example 3

[0088] The preparation method is the same as that described in Example 1, except that:

[0089] Take 100 μL of the Ag6 aqueous solution stock solution, add 200 μL of ultrapure water and 700 μL of NMP to it, with a solvent ratio of aqueous solution:NMP = 3:7. After mixing, the Ag6 concentration is 5 mmol·L⁻¹. -1 After vortexing for 30 s, a small amount of precipitate appeared in the solution. Since the amount of precipitate obtained in this embodiment was insufficient to meet the requirements for solid-state fluorescence intensity and lifetime testing, the silver nanoclusters obtained in this embodiment were characterized as a suspension. The fluorescence intensity of the silver nanoclusters obtained in this embodiment was approximately 7.3 × 10⁻⁶. 6 The fluorescence lifetime is 10.95 μs.

[0090] Experimental Example 1

[0091] A method for preparing a yellow-emitting LED, comprising the following steps:

[0092] Accurately weigh 5 mg of the high-fluorescence silver nanocluster powder prepared in Example 1, grind it thoroughly in a mortar, and then accurately weigh 5 mg and 20 mg of the high-refractive LED chip silicone A and B adhesives respectively. Mix them evenly at a mass ratio of 1:4. Mix the high-fluorescence silver nanocluster sample powder with the silicone evenly, take a mixture of about the size of a bean, deposit it on a commercially available LED chip, and cure it in an oven at 60 °C for 3 hours to manufacture the LED.

[0093] The LED image obtained in this experiment, emitting yellow light, is shown below. Figure 8As shown in (a), spectral analysis shows that the chromaticity coordinates of the fluorescence emission spectrum of the yellow LED prepared in this experimental example at an excitation wavelength of 400 nm are (0.44, 0.51).

[0094] Experimental Example 2

[0095] A method for preparing a blue-emitting LED includes the following steps:

[0096] Accurately weigh 5 mg of commercial blue phosphor and grind it thoroughly in a mortar. Then, accurately weigh 5 mg and 20 mg of high-refractive LED chip silicone A and B respectively, mix them evenly at a mass ratio of 1:4, and mix the commercial blue phosphor with the silicone evenly. Take a mixture of viscous liquid about the size of a bean and deposit it on a commercially available LED chip. Then, cure it in an oven at 60°C for 3 hours to manufacture the LED.

[0097] The blue-emitting LED image obtained in this experiment is shown below. Figure 8 As shown in (b), spectral analysis shows that the chromaticity coordinates of the fluorescence emission spectrum of the blue LED prepared in this experimental example at an excitation wavelength of 350 nm are (0.15, 0.15).

[0098] Experimental Example 3

[0099] A method for fabricating a white-light-emitting LED includes the following steps:

[0100] Accurately weigh 20 mg and 50 mg of the high-fluorescence silver nanocluster powder and commercial blue phosphor prepared in Example 1, respectively. Mix the two phosphors (high-fluorescence silver nanocluster powder and commercial blue phosphor) at a mass ratio of 2:5, grind them thoroughly in a mortar and pestle, and mix them evenly. Then accurately weigh 5 mg of the mixed powder. Next, accurately weigh 5 mg and 20 mg of high-refractive LED chip silicone A and B adhesives, respectively, and mix them evenly at a mass ratio of 1:4. Mix the sample powder with the silicone evenly, take a mixture of approximately pea-sized amounts, deposit them onto a commercially available LED chip, and cure them in an oven at 60 °C for 3 hours to manufacture the LED.

[0101] The white-light LED image obtained in this experiment is shown below. Figure 8 As shown in (c), spectral analysis shows that the color coordinates of the fluorescence emission spectrum of the white LED prepared in this experimental example at an excitation wavelength of 365 nm are (0.31, 0.33).

[0102] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Based on the technical solutions of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

Claims

1. A method for preparing high-fluorescent silver nanoclusters induced by mixed solvents, the silver nanoclusters being self-assembly bodies of Ag6 after self-assembly under the induction of mixed solvents, the micro-morphology of the self-assembly bodies being a bow tie shape with narrow middle and wide both sides, the nanosheet formed by fiber aggregation being twisted and crossed, comprising the following steps: dissolving Ag6 in ultrapure water to obtain an Ag6 aqueous solution, adding N-methyl pyrrolidone (NMP) to the Ag6 aqueous solution, vortexing to produce a precipitate, standing at room temperature for 2-6 days, centrifuging the precipitate, and freeze-drying to obtain the high-fluorescent silver nanoclusters in light yellow. The length of the high-fluorescent silver nanocluster self-assembly body is 8-12 μm, and the width is 2-4 μm.

2. The production method according to claim 1, characterized by, The volume ratio of the Ag6 aqueous solution to NMP is (1-2):(8-9).

3. The production method according to claim 1, characterized by, The fluorescence spectrum of the high-fluorescent silver nanoclusters showed that the maximum fluorescence intensity was 2.4 x 10 7 , the excitation wavelength was 310-460 nm, the emission wavelength was stable at 565 ± 3 nm, the fluorescence lifetime of the high-fluorescent silver nanoclusters was 11.77 μs, and the quantum yield was 17.57 %.

4. The method of claim 1, wherein, The concentration of Ag6 aqueous solution is 40-60 mmol·L -1 The volume ratio of Ag6 aqueous solution to NMP is (1-3):(7-9).

5. The preparation method according to claim 1, characterized in that, The vortexing time is 20-30 s, the standing time is 3 days, the centrifugation speed is 7000-9000 r / min, the centrifugation time is 8-12 min, the freeze-drying temperature is -50 to -70℃, and the freeze-drying time is 1-3 days.

6. The method of claim 1, wherein, Ag6 is prepared as follows:

7. The preparation method according to claim 1, characterized in that, Silver nitrate (AgNO3) and 2-mercapto-nicotinic acid (H2mba) are sequentially dissolved in water to obtain a mixed solution, the mixed solution is ultrasonically treated at room temperature to produce a precipitate, ammonia is added dropwise to the precipitate until a transparent yellow solution is formed, and the solution is freeze-dried to obtain yellow crystals of Ag6. 9.Use of the high-fluorescent silver nanoclusters prepared in claim 1 in LEDs as light conversion materials for LEDs.

8. The method of claim 1, wherein, The concentration of silver nitrate in the mixed solution is 0.05-0.3 mol·L -1 The concentration of 2-mercaptonicotinic acid in the mixed solution is 0.05-0.3 mol·L -1 The ultrasonic frequency of the ultrasonic treatment is 30-50 kHz, the ultrasonic power is 150-170 W, and the ultrasonic time is 10-30 minutes; the mass concentration of the ammonia water is 25 %; the addition amount of the ammonia water is until the precipitation is completely dissolved, and the obtained solution is a yellow transparent solution. ​

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