A metal nanoparticle colloid-quantum dot printing ink doping preparation method

Abstract

The application discloses a metal nanoparticle colloid-quantum dot printing ink doping preparation method and belongs to the technical field of photoelectricity. The method is characterized in that: firstly, silver ions are reduced into nanoparticles, and then, silica is wrapped outside the silver nanoparticles to prepare a silica-wrapped silver nanoparticle colloid solution; then, CdSe quantum dot ink is prepared; the silica-wrapped silver nanoparticle colloid solution and the CdSe quantum dot ink are mixed at a proportion of 1-5:100 in volume ratio to prepare metal nanoparticle colloid-quantum dot ink. The metal nanoparticle colloid-quantum dot ink prepared by the method successfully improves the light efficiency conversion performance of semiconductor quantum dot ink, can generate more visible light output under the same input electric energy condition, and simultaneously reduces energy loss. The technical progress brings obvious performance improvement for QLED lighting and display application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photoelectricity, and particularly relates to a metal nanoparticle colloid-quantum dot printing ink doping preparation method. BACKGROUND

[0002] In recent years, novel physical phenomena of semiconductor quantum dots (QDs) appear constantly, and excellent performance of the semiconductor quantum dots has excellent application prospects in different fields. Due to quantum confinement effect and quantum size effect, the semiconductor quantum dots have the characteristics of wide excitation spectrum, narrow half-peak width, adjustable wavelength, and the like, and application researches thereof are increasingly concerned. In recent years, photoluminescence devices have been applied to QLED lighting and display fields, especially in the display field, the line width of cadmium selenide and other quantum dots is extremely narrow, color saturation is high, and the color restoration ability for objects is relatively strong, which can reach more than 120% of ntsc color gamut, and has broad development prospects in the display field.

[0003] Based on LED display screen (LED, LCD display screen) technology, QLED after introducing quantum dots refers to converting traditional white light LED into blue light LED backlight, and adding quantum dot reinforced film LED between the backlight module and the polarizing mirror. Whenever the quantum dot reinforced film receives light or electric stimulation, the quantum dots will emit colored light, which can change the color of light emitted by the light source, display colors through the light of the dispersed LED light-emitting diode, and has the function of a filter. This can greatly reduce the loss of backlight brightness and RBG color filter. Among them, inkjet printing is a widely used and relatively direct technology, which can realize effective utilization of materials, form individual pixel points and flexible design of printing devices. At present, a full-color QLED display screen has been realized by using a commercial piezoelectric printhead, and the display screen has 120ppi and maximum brightness of 400cdm -2 However, the quantum dot ink used in the inkjet printing currently still has the problems of low light efficiency conversion, and it is difficult to obtain single extremely small and stable printing droplets.

[0004] Similar to the research of quantum dots, metal nanomaterials have also been a hot spot of researchers' attention because of many special effects, of which the most remarkable is the localized field enhancement effect based on localized surface plasmon resonance, that is, metal nanomaterials are excited to produce localized surface plasmon resonance and produce localized field enhancement effect when placed in a certain fixed waveband of light field; the surface plasmon resonance mode of the metal nanomaterials changes when the material, shape or external medium of the metal nanomaterials changes, and the localized field enhancement effect also changes accordingly. The combination of noble metal nanomaterials and quantum dot materials will produce enhanced fluorescence emission effect under the joint action of the surface plasmon localized field enhancement effect and the ultrafast charge transfer effect between them. It is found that when the distance between semiconductor quantum dots and metal nanoparticles is very small, there is a fluorescence quenching phenomenon; when the distance exceeds a certain value, the quenching phenomenon disappears, and fluorescence enhancement phenomenon replaces it. In 2007, Julie S. Biteen et al. prepared a silver nanodisk array and respectively studied the influence of the diameter of the nanodisk in the array and the distance between the silver nanoparticles and silicon quantum dots on the field enhancement effect, and the results are that the larger the diameter of the silver nanodisk, the stronger the corresponding field enhancement effect produced by excitation, and at the same time, the field enhancement effect of the silver nanoparticles on the silicon quantum dots starts to weaken as the distance between them increases. Therefore, the accurate control of the doping ratio of metal nanoparticles and quantum dot ink and the further regulation of the distance between quantum dots and metal nanoparticles are the key to exerting the optimal luminescence performance. SUMMARY

[0005] The application provides a metal nanoparticle colloid-quantum dot ink doping preparation method, which is a comprehensive silica-coated silver nanoparticle colloid solution and semiconductor quantum dot ink solution, and explores a composite nanostructure technology composed of metal nanoparticles and quantum dots. The application realizes the improvement of the light efficiency conversion performance of semiconductor quantum dot ink by more than 20%, which provides important technical support for the application of QLED lighting and display fields.

[0006] The technical scheme specifically adopted by the application is as follows:

[0007] A metal nanoparticle colloid-quantum dot ink doping preparation method, characterized in that it comprises the following steps:

[0008] Step 1. Preparation of a silica-coated silver nanoparticle colloid solution;

[0009] Step 1-1. Reduction of silver ions into nanoparticles;

[0010] Dissolve silver nitrate or silver acetate and other compounds containing silver ions in water to obtain Ag + The concentration is 1*10 -3 ~ 10*10 -3mol / L of the first solution; adding 1% of trisodium citrate solution by volume fraction to the first solution, the volume ratio of the first solution to the trisodium citrate solution being 1-10:1, mixing uniformly, drying, and obtaining silver nanoparticles.

[0011] Step 1-2. Wrapping silica on the outer layer of silver nanoparticles;

[0012] adding silver nanoparticles to anhydrous ethanol and stirring for 5-10 minutes, the mass ratio of the silver nanoparticles to the anhydrous ethanol being 1-10:10; adding 25% ammonia water by volume fraction at a volume ratio of 45-55:1, and continuing to stir for 5-10 minutes; adding tetraethoxysilane at a volume ratio of 15-20:1, and reacting for 22-24 hours; then washing and drying to obtain silica-coated silver nanoparticles; and finally dissolving the silica-coated silver nanoparticles in pure water at a mass ratio of 1-10:10 to obtain a colloidal solution of silica-coated silver nanoparticles.

[0013] Step 2. Preparing CdSe quantum dot ink;

[0014] Step 2-1. Mixing selenium powder and hexadecylamine at a molar ratio of 1-5:70, and heating to 260-270°C to form a selenium source with a concentration of 0.1-0.15 mol / L.

[0015] Step 2-2. Mixing cadmium acetate and oleic acid at a molar ratio of 1-2:1, and heating to 100-110°C to form a cadmium source with a concentration of 0.03-0.04 mol / L.

[0016] Step 2-3. Injecting the cadmium source obtained in step 2-1 into the selenium source obtained in step 2-2, the volume ratio of the cadmium source to the selenium source being 1-2:1; cooling the mixture to 55-60°C and stirring for 20-30 minutes, and then cooling to room temperature to obtain a cadmium selenide quantum dot solution.

[0017] Step 2-4. Mixing the cadmium selenide quantum dot solution obtained in step 2-3 with a solvent at a volume ratio of 1-2:1 to obtain CdSe quantum dot ink.

[0018] Step 3. Doping preparation of metal nanoparticle colloid-quantum dot ink;

[0019] Mixing the colloidal solution of silica-coated silver nanoparticles obtained in step 1 with the CdSe quantum dot ink obtained in step 2 at a volume ratio of 1-5:100, and ultrasonically treating for 25-35 minutes, and standing for 3-5 minutes to obtain metal nanoparticle colloid-quantum dot ink.

[0020] The main process of fluorescence emission is that the electron originally in the lowest energy level in S1 falls back to the ground state, and the energy released in this process is the fluorescence emitted. By simulating the electric field, magnetic field distribution, quantum conversion efficiency, and radiation decay rate of the metal nanoparticle-quantum dot composite structure, the effects of noble metal nanoparticle material, morphology, size, and the distance between quantum dots and silver nanoparticles on the fluorescence lifetime, quantum efficiency, and radiation decay rate of quantum dots are obtained. Further, the optimal doping concentration theoretical value of the photoluminescence conversion efficiency of the metal nanoparticle-quantum dot device is obtained. Based on the simulation design data of the metal nanoparticle colloid-quantum dot ink, the silver nanoparticle solution wrapped with silicon dioxide and the semiconductor quantum dot ink are mixed at an optimal ratio, and ultrasonic and other processes are used. Based on the local surface plasmon resonance field enhancement effect of the noble metal nanoparticle array and the fluorescence enhancement effect of the conductor quantum dot ink in contact with the metal nanoparticles, the maximum enhancement of the quantum dot fluorescence is realized, the light efficiency conversion performance of the quantum dot printing ink is improved, and the metal nanoparticle colloid-quantum dot ink suitable for inkjet printing, high efficiency, and good stability is formed.

[0021] Through the improved method and technology proposed in the present application, the light efficiency conversion performance of the semiconductor quantum dot ink is successfully improved. This means that under the same input electrical energy, more visible light output can be generated, while energy loss is reduced, bringing significant performance improvement for QLED lighting and display applications. By improving the light efficiency conversion performance, brighter, more saturated colors and higher brightness levels can be achieved under the same energy consumption, providing users with a better visual experience. Secondly, due to the reduction of energy loss, this innovation also helps to reduce the energy consumption of the device, improve energy utilization efficiency, and meet the requirements of sustainable development. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The flowchart of the present application;

[0023] Figure 2 The field strength distribution simulation results of silver nanoparticles and CdSe quantum dots wrapped with different thickness of silicon dioxide shells in the optical field are shown in the figure (a), where the silicon dioxide shell is 0 nm thick in figure (a), the silicon dioxide shell is 2 nm thick in figure (b), the silicon dioxide shell is 5 nm thick in figure (c), and the silicon dioxide shell is 10 nm thick in figure (d).

[0024] Figure 3 The optical photograph of the printed mixed sample 1 is shown in the figure;

[0025] Figure 4 The photoluminescence spectrum curve results of the spin-coated film are shown in the figure, where figure (a) is the luminescence intensity curve of mixed sample 1, mixed sample 2, and mixed sample 3; figure (b) is the luminescence intensity curve of mixed sample 1 and the control group. DETAILED DESCRIPTION

[0026] The specific embodiments and working principles of the present invention will be further described in detail below with reference to the accompanying drawings.

[0027] The flowchart of the preparation method of metal nanocolloid-quantum dot ink doping is as follows: Figure 1 As shown.

[0028] First, a simulation design for controlling photoluminescence performance was conducted using the finite-difference time-domain method, primarily investigating the changes in field enhancement around the silver nanoparticles as the distance between the quantum dots and the nanoparticles changes. Metal nanoparticles influence the luminescence of fluorescent materials mainly by affecting their radiation process, and this influence is limited to a certain distance range. For example... Figure 2 (ad) is a simulation of the field enhancement effect between Ag@SiO2 NPs and CdSe quantum dots at different spacing distances, using the finite-difference time-domain method. Figure 2 As shown in (ad), the large spheres are silver nanoparticles with an 80nm diameter, encased in a silica shell. The silica shell thicknesses are 0nm, 2nm, 5nm, and 10nm. The small spheres are quantum dot cores with a 10nm diameter. The light source is a 355nm ultraviolet laser used in the test. The field intensity distribution around the quantum dots is observed. The simulation simulates a field enhancement effect under the influence of an external light field.

[0029] The method for preparing metal nanocolloid-quantum dot ink doping in this embodiment specifically includes the following steps:

[0030] Step 1. Prepare a colloidal solution of silica-coated silver nanoparticles;

[0031] Step 1-1. Reduce silver ions into nanoparticles;

[0032] Dissolve 9 mg of AgNO3 in 50 ml of water to obtain Ag + The concentration is 1.06*10 -3 A first solution of mol / L was prepared; 1 ml of 1% trisodium citrate solution was added to the first solution, mixed evenly, and dried to obtain silver nanoparticles.

[0033] Steps 1-2: Coat the outer layer of silver nanoparticles with silica;

[0034] 30 g of silver nanoparticles were weighed into 100 ml of anhydrous ethanol and stirred for 5-10 minutes; 2 ml of ammonia water with a concentration of 25% was then added, and stirring was continued for 5-10 minutes; 5 ml of tetraethoxysilane with a concentration of 10 mmol / L was then added, and the reaction was allowed to proceed for 24 hours. After the reaction was completed, 5 ml of ethanol was added to the solution, and centrifugation was performed at a speed of 10,000 rpm for 10 minutes. The supernatant was then discarded, and the precipitate was washed with water and then centrifuged again. This washing process was repeated three times. The precipitate was then dissolved in water to prepare a colloidal solution of silica-coated silver nanoparticles with a concentration of 0.1 mg / mL.

[0035] Step 2. Preparation of CdSe quantum dot ink

[0036] Step 2-1. 15 mmol of selenium powder was mixed with 100 ml of hexadecylamine and heated to 270°C to form a selenium source with a concentration of 0.15 mol / L.

[0037] Step 2-2. 1.0 mmol of cadmium acetate was mixed with 30 ml of oleic acid and heated to 100°C to form a cadmium source with a concentration of 0.033 mol / L.

[0038] Step 2-3. The cadmium source obtained in step 2-1 was injected into the selenium source obtained in step 2-2. The mixture was cooled to 60°C and stirred for 30 minutes, at which temperature the quantum dots began to grow. The temperature was then cooled to room temperature to obtain a solution of cadmium selenide quantum dots. It was measured that the solution contained 1.2 g of quantum dots.

[0039] Step 2-4. The solution of cadmium selenide quantum dots obtained in step 2-3 was mixed with chloroform to obtain a cadmium selenide quantum dot ink with a total volume of 1 L and a concentration of 1.2 g / L.

[0040] Step 3. Preparation of metal nanoparticle colloids-doped quantum dot ink

[0041] The silica-coated silver nanoparticle colloidal solution obtained in step 1 was mixed with the CdSe quantum dot ink obtained in step 2 in different proportions, and ultrasonic treatment was performed for 25-35 minutes. The mixture was then allowed to stand for 3-5 minutes to prepare a metal nanoparticle colloids-quantum dot ink. Specifically, 1 ml of CdSe quantum dot ink without the addition of silica-coated silver nanoparticle colloidal solution was taken as a control group. For the mixed sample 1, 10 μl of silica-coated silver nanoparticle colloidal solution was mixed with 1 ml of CdSe quantum dot ink. For the mixed sample 2, 30 μl of silica-coated silver nanoparticle colloidal solution was mixed with 1 ml of CdSe quantum dot ink. For the mixed sample 3, 50 μl of silica-coated silver nanoparticle colloidal solution was mixed with 1 ml of CdSe quantum dot ink.

[0042] Step 4. Spin-coat the control group and mixed samples 1-3 onto glass slides respectively for photoluminescence intensity testing;

[0043] Control group, mixed sample 1, mixed sample 2, and mixed sample 3 were spin-coated onto ordinary glass slides measuring 4cm x 4cm and 0.8mm thick, respectively, until the film thickness reached 10μm. Printable samples were then printed using an OmniJet 300 printer. The photoluminescence intensity of the four spin-coated films was measured using a PR670 spectroradiometer, and the films were then observed using an optical microscope.

[0044] like Figure 2 The figure shows the simulation results of the field intensity distribution in an optical field for silver nanoparticles and CdSe quantum dots encased in silica shells of different thicknesses. It can be seen that by changing the thickness of the silica film to control the distance between the quantum dots and silver nanoparticles, the field enhancement effect tends to weaken as the distance increases.

[0045] like Figure 3 The image shown is an optical photograph of Sample 1 (10 μl of silica-coated silver nanoparticle colloidal solution mixed with 1 ml of CdSe quantum dot printing ink) after printing. The image shows that the printed film is relatively uniform, and the ink flow is smooth without clogging during the printing process, indicating that it can be used as a qualified ink.

[0046] like Figure 4 Figure (a) shows the photoluminescence spectrum results. As can be seen from Figure (a), sample emission light was observed at a wavelength of 534 nm, and the emission peak enhancement of mixed sample 1 was better than that of mixed sample 3, while that of mixed sample 2 was the worst. After ultrasonication, mixed samples 2 and 3 showed precipitate formation on the bottle wall, making printing impossible. This is likely due to the addition of excessive silver NPs, which reacted with the QDCC printing ink to form components insoluble in the QDCC printing ink. Figure (b) shows that the emission peak of mixed sample 1 was stronger than that of the control group (CdSe quantum dot ink without silica-encapsulated silver nanoparticles), with a fluorescence enhancement effect of approximately 20%. This invention successfully improved the photoluminescence conversion efficiency of semiconductor quantum dot ink by more than 20%.

[0047] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification, unless specifically stated otherwise, may be replaced by other equivalent or similar alternative features. All disclosed features, or steps in all methods or processes, except for mutually exclusive features and / or steps, may be combined in any way. Any non-essential additions or substitutions made by those skilled in the art based on the technical features of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a metal nanoparticle colloid-quantum dot ink doped, characterized in that, The method comprises the following steps: Step 1. Preparing a colloidal solution of silica-coated silver nanoparticles; Step 1-1. Reducing silver ions into nanoparticles; Step 1-2. Coating silica on the outer layer of silver nanoparticles; The silver nanoparticles are added to anhydrous ethanol and stirred for 5-10 minutes, and the mass ratio of the silver nanoparticles to the anhydrous ethanol is 1-10:10; ammonia water with a volume fraction of 25% is added at a volume ratio of 45-55:1, and the stirring is continued for 5-10 minutes; tetraethoxysilane is added at a volume ratio of 15-20:1, and the reaction is carried out for 22-24 hours; then the silica-coated silver nanoparticles are washed and dried to obtain the silica-coated silver nanoparticles; finally, the silica-coated silver nanoparticles are dissolved in pure water at a mass ratio of 1-10:10 to obtain the colloidal solution of silica-coated silver nanoparticles; Step 2. Preparing CdSe quantum dot ink; Step 3. Preparation of metal nanoparticle colloid-quantum dot ink by doping; The colloidal solution of silica-coated silver nanoparticles obtained in step 1 is mixed with the CdSe quantum dot ink obtained in step 2 at a volume ratio of 1:100, ultrasonicated for 25-35 minutes, and left to stand for 3-5 minutes to obtain the metal nanoparticle colloid-quantum dot ink.

2. The method of claim 1, wherein the metal nanoparticle colloid-quantum dot ink doping preparation method is characterized by, In step 1-1, the step of reducing silver ions into nanoparticles is: dissolving silver nitrate or silver acetate in water to obtain Ag + The concentration of the first solution is 1*10 -3 ~10*10 -3 mol / L; a 1% trisodium citrate solution is added to the first solution, the volume ratio of the first solution to the trisodium citrate solution is 1~10:1, the mixture is uniformly mixed, dried, and silver nanoparticles are prepared.

3. The method for preparing colloidal quantum dot ink from metal nanoparticles as described in claim 1 or 2, characterized in that, In step 2, the method for preparing the CdSe quantum dot ink comprises the following steps: Step 2-1. Mixing selenium powder and hexadecylamine at a molar ratio of 1-5:70, and heating to 260-270°C to form a selenium source with a concentration of 0.1-0.15 mol / L; Step 2-2. Mixing cadmium acetate and oleic acid at a molar ratio of 1-2:1, and heating to 100-110°C to form a cadmium source with a concentration of 0.03-0.04 mol / L; Step 2-3. Injecting the cadmium source obtained in step 2-1 into the selenium source obtained in step 2-2, and the volume ratio of the cadmium source to the selenium source is 1-2:1; cooling the mixture to 55-60°C and stirring for 20-30 minutes, and then cooling to room temperature to obtain a cadmium selenide quantum dot solution; Step 2-4. Mixing the cadmium selenide quantum dot solution obtained in step 2-3 with a solvent at a volume ratio of 1-2:1 to obtain the CdSe quantum dot ink.

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