WO2019024523A1

WO2019024523A1 - Preparation method for thin film capable of improving up-conversion luminescence

Info

Publication number: WO2019024523A1
Application number: PCT/CN2018/081333
Authority: WO
Inventors: 倪亚茹; 朱成; 方姣姣; 张炜鑫; 陆春华; 许仲梓
Original assignee: 南京工业大学
Priority date: 2017-07-31
Filing date: 2018-03-30
Publication date: 2019-02-07
Also published as: CN107418580A; GB2578540A; GB2578540B; CN107418580B; GB201919427D0

Abstract

The present invention relates to a preparation method for a thin film capable of improving up-conversion luminescence, comprising the following specific steps: first preparing a suspension of monodisperse SiO2 microspheres having a mass percentage of 6-10%; then adding an adhesive and an up-conversion fluorescent material into the suspension, and stirring until a self-assembly solution is obtained; and finally, vertically inserting two substrates into a container containing the self-assembly solution, and performing self-assembly using a microfluidic pump to obtain a fluorescent photonic crystal thin film by means of self-assembly. According to the present invention, fluorescent photonic crystal thin films of different thicknesses can be obtained, and the thickness can be adjusted from 3.0 µm to 9.0 µm. The thicker the fluorescent photonic crystal thin film is, the more obvious the forbidden band effect is, and the better the up-conversion enhancement effect is. The present invention has the advantages that required materials are simple, the cost is low, and the process is simple and convenient, such that large-scale production can be easily achieved.

Description

Method for preparing improved upconversion luminescent film

Technical field

The invention belongs to the field of optical functional materials and relates to a simple method for improving the preparation of upconversion luminescent films.

Background technique

Solar energy is a clean, green renewable energy source. Visible light in the solar spectrum is widely used in our daily lives. However, 43% of the infrared light in the solar spectrum has not been fully exploited. Up-conversion technology can greatly improve the utilization of sunlight. Up-conversion luminescence is an anti-Stokes phenomenon that converts low-energy long-wave light into high-energy short-wave light. At present, the development of relatively mature up-conversion materials such as fluorine sodium has become a common material in the fields of LED, medical and scientific research, etc. in lighting equipment, display screens, various displays, X-ray intensifying screens, and biological Imaging and other directions have broad application prospects. However, there are still some problems in the application of upconversion materials. One of the major problems is that the luminescence spectrum is difficult to control. In response to this problem, researchers have proposed the use of photonic crystals to control the luminescence spectrum. Photonic crystal refers to a dielectric material formed by periodic arrangement. When the structure changes periodically, the refractive index changes periodically. Therefore, light of certain wavelengths in the photonic crystal cannot propagate to generate a band gap. Obvious reflection peaks can be observed in the reflection spectrum, which we call the forbidden effect of photonic crystals. Therefore, by controlling the position of the photonic crystal band gap, the luminescence performance at this band can be adjusted. At present, the methods for preparing photonic crystals in the laboratory have been relatively mature, including mechanical drilling, layer-by-layer superposition, photolithography, self-assembly, etc., but their production has not yet been industrialized. In addition, it is relatively easy to prepare photonic crystals separately. Researchers have also made a series of studies on the mechanism of fluorescent substances, the improvement of photonic crystals, the regulation of phosphorescence, and other mechanisms that regulate the emission of fluorescent substances. However, when the photonic crystal is combined with the fluorescent material, the structural unit arrangement in the photonic crystal is often disordered, and the periodic structure is destroyed, which causes the performance of the luminescence spectrum to be lost. This problem has not been a good solution.

Summary of the invention

The invention aims to solve the problem that the photonic crystal and the fluorescent substance are combined to cause disorder of the arrangement of the photonic crystal structural unit and the upconversion luminescence is difficult to control, and a simple method for preparing the ordered and regular fluorescent photonic crystal film and enhancing the up-conversion luminescence is proposed. A method for improving the preparation of an up-conversion luminescent film.

The invention aims at the problem that the photonic crystal and the up-converting fluorescent substance are difficult to be compounded, and proposes to use KH570 and acrylic acid as a binder to make the up-conversion material and the silica effectively and uniformly compound by chemical bonding, thereby preparing an ordered and regular fluorescent photonic crystal. film. By preparing different thickness, different period of photonic crystal film can change its forbidden band effect and position, and achieve the performance of regulating the luminescence spectrum.

The technical scheme of the present invention is: a simple method for improving the up-conversion luminescent film, characterized in that the rare earth up-conversion material is uniformly and sequentially compounded in the photonic crystal structure through a binder, and the forbidden band position and the luminescent substance are prepared. The photonic crystal film with the same emission band can regulate the luminescence spectrum of the luminescent substance, thereby realizing the spectral enhancement and regulation of the up-conversion luminescence.

A specific technical solution of the present invention is: a method for improving the preparation of an up-conversion luminescent film, the specific steps of which are as follows:

(1) Preparing a suspension of monodisperse SiO ₂ microspheres: synthesizing monodisperse silica microspheres having a particle size dispersion index of 0.2%-1.0% and an average microsphere size of 350-450 nm, and then SiO ₂ The microspheres are formulated into a suspension having a mass fraction of between 6 and 10%;

(2) Recombination of SiO ₂ microspheres and upconversion fluorescent material: taking the SiO ₂ suspension prepared in the step (1), taking a binder of 0.05-0.10% of the suspension mass, and dropping it into the suspension of SiO ₂ , Then, an up-converting fluorescent material containing 0.01-0.03% of the mass of the suspension is added; stirring is performed to form a uniform dispersion of the up-converting fluorescent material and the SiO ₂ microspheres as a self-assembly liquid;

(3) Self-assembly of fluorescent photonic crystal film: Two substrates are vertically inserted into a container equipped with a self-assembling liquid, self-assembled using a microfluidic pump, and a liquid absorbing speed of 5-50 ul/min is set for vertical self-assembly. A fluorescent photonic crystal film is obtained.

The synthesis of the monodisperse SiO ₂ microspheres in the step (1) can be carried out by a conventional method. Preferably, the modified stober method is used, wherein the specific step is: taking a volume ratio of deionized water, ethanol and ammonia water to 1: (2-3): 1 as a component-solution, and taking a volume ratio of ethanol to tetraethyl orthosilicate (8-9): 1 is the component two solution, and the components one and two are stirred at a speed of 600-800 rpm for 30-40 min respectively; then the process of stirring the component one at 600-800 rpm using an electric stirrer Add component 2, adjust the stirrer rotation speed to 300-500 rpm after 1-2 min, stir for 2-3 h; after the stirring is stopped, centrifuge water washing and alcohol washing to obtain monodisperse SiO ₂ microspheres.

The SiO ₂ microsphere suspension is prepared in the step (1). Preferably, the monodisperse SiO ₂ microspheres are added to an ethanol solvent to prepare a SiO ₂ microsphere suspension having a mass fraction of 6-10%.

Preferably, the up-converting fluorescent material described in the step (2) is an antimony-doped ytterbium-doped fluorofluorene sodium phosphor, wherein the doping mass of the cerium ion is 10-15% of the mass of the fluoroquinone sodium phosphor, and the doping of the cerium ion The mass is 0.5-1.0% of the mass of the sodium fluorocarbon phosphor. The preparation method is preferably a solvothermal method.

Preferably, the above binder is a mixture of KH570 and acrylic acid; the mass ratio of KH570 to acrylic acid is 1: (1-2).

Preferably, the stirring speed described in the step (2) is 300-500 rpm, and the stirring time is 12-24 h.

Preferably, the substrate described above is a glass sheet or an aluminum sheet.

Preferably, the fluorescent photonic crystal film prepared in the self-assembly step has a thickness of between 3.0 um and 9.0 um.

Beneficial effects:

The composite structure of photonic crystal and upconversion fluorescent material described in this patent is a systematic experiment of the optimal dosage of the drug by using KH570 and acrylic acid as a binder, and an ordered and regular fluorescent photonic crystal film is prepared.

The regulation and enhancement of the luminescence of the up-converting fluorescent material described in the patent is achieved by preparing a photonic crystal film having a band gap and a luminescent band of the fluorescent substance, suppressing the emission of the long-wavelength band and enhancing the emission of short-wave light. At the same time, the strength of the forbidden band effect can be changed by preparing photonic crystal films of different thicknesses. By adjusting the size of the silica microspheres of the photonic crystal film to form a forbidden band of light of a specific wavelength band, suppressing long-wave light emission and enhancing short-wave light emission, the short-wave fluorescence intensity is enhanced by 1.05 times, and the up-conversion efficiency is enhanced by 18%.

DRAWINGS

1 is a scanning electron micrograph of a fluorescent photonic crystal film prepared in Example 1.

2 is a graph showing the particle size distribution of SiO ₂ in the fluorescent photonic crystal film prepared in Example 1.

3 is a reflection spectrum diagram of a fluorescent photonic crystal film prepared in Example 1.

4 is a scanning electron micrograph of a fluorescent photonic crystal film prepared in Example 2-4; wherein a and b are Example 2, c and d are Example 3, and e and f are Example 4.

Figure 5 is a cross-sectional top view of a fluorescent photonic crystal film prepared in Example 2-4; wherein a is Example 2, b is Example 3, and c is Example 4.

Fig. 6 is a reflection spectrum diagram of a fluorescent photonic crystal film prepared in Example 4.

Fig. 7 is a fluorescence spectrum diagram of a fluorescent photonic crystal film prepared in Example 4.

Detailed ways

Example 1

The volume ratio of deionized water, ethanol and ammonia water is 1:2:1 as the component-solution, and the volume ratio of ethanol to tetraethyl orthosilicate is 8:1 as the component two solution, respectively, at a speed of 600 rpm. Stir in portions 1 and 2 for 30 min. Component 2 was then added during the agitation of component one at 600 rpm using a power agitator. After 1 min, the stirrer speed was adjusted to 500 rpm and stirred for 3 h. After the stirring was stopped, the mixture was washed once with water, twice with alcohol, and the obtained SiO ₂ microspheres were added to an ethanol solvent to prepare a 6 wt% suspension of SiO ₂ microspheres to be used. The erbium-doped ytterbium-doped fluoroquinone sodium phosphor was prepared by a solvothermal method, wherein the cerium ion content was 10% by weight and the cerium ion content was 0.5% by weight.

A 6 wt% suspension of SiO ₂ ethanol was about 10 mL in a beaker, and 0.05 wt% of KH570 and 0.05 wt% of acrylic acid were taken into the suspension by two syringes respectively, and then 0.03 wt% of erbium-doped strontium fluoride was added. Phosphor. After stirring for 24 h and stirring at 300 rpm, the erbium-doped cerium-doped fluorohalic sodium phosphor was uniformly dispersed in the SiO ₂ microsphere suspension, and the suspension system was used as a self-assembly liquid. The cleaned two pieces of aluminum are vertically inserted into the self-assembling liquid. The self-assembly liquid was extracted using a microfluidic pump, and the liquid absorption speed was set to 20 μL/min for vertical self-assembly. Figure 1 is a surface topography of the sample. It can be seen from the figure that the microspheres in the sample are tightly and orderly arranged with fewer defects. The prepared sample had a thickness of 6.60 um. 2 is a particle size distribution diagram of the sample SiO ₂ microspheres. The statistical analysis results show that the particle size of the SiO ₂ microspheres is concentrated between 420 nm and 450 nm, the average value is 435 nm, and the particle size dispersion index is 0.5%. Figure 3 is a reflection spectrum of the sample, the sample has a distinct reflection peak at the 980 nm position, and the forbidden band effect of the sample is remarkable.

Example 2

The volume ratio of deionized water, ethanol and ammonia water was 1:3:1 as the component-solution, and the volume ratio of ethanol to tetraethyl orthosilicate was 9:1 as the component two solution, respectively, at a speed of 800 rpm. Stir in portions 1 and 2 for 40 min. Component 2 was then added during the agitation of component one at 800 rpm using a power agitator. After 2 min, the stirrer speed was adjusted to 300 rpm and stirred for 2 h. After the stirring was stopped, the mixture was washed once with water, twice with alcohol, and the obtained SiO ₂ microspheres were added to an ethanol solvent to prepare a 10 wt% suspension of SiO ₂ microspheres to be used. The erbium-doped ytterbium-doped fluoroquinone sodium phosphor was prepared by a solvothermal method in which the amount of cerium ions was 15% and the amount of cerium ions was 1.0%.

Take 10% by weight of SiO ₂ ethanol suspension about 20mL in a beaker, respectively, add 0.02wt% KH570 and 0.04wt% acrylic acid into the above beaker with two syringes, add 0.01wt% erbium-doped ytterbium-doped fluorofluorene sodium phosphor. Beaker. After stirring for 12 h and stirring at 500 rpm, the erbium-doped cerium-doped fluoroquinone sodium was uniformly dispersed in the SiO ₂ microsphere suspension, and the suspension system was used as a self-assembly liquid. The cleaned two pieces of glass are inserted vertically into the self-assembling solution. The microfluidic pump was used to extract the self-assembly liquid, and the microfluidic pump was set to have a liquid absorption speed of 50 μL/min for vertical self-assembly. The surface morphology of the photonic crystal film obtained at this liquid absorbing speed is shown in Fig. 4a-b, and the sectional shape is shown in Fig. 5a. It can be seen from the surface topography that the SiO ₂ microspheres are regularly arranged in order, and the thickness of the film layer is 3.30 μm. The SiO ₂ microspheres had an average particle diameter of 380 nm and a particle size dispersion index of 1.0%.

Example 3

The volume ratio of deionized water, ethanol and ammonia was 1:2:1 as the component-solution, and the volume ratio of ethanol to tetraethyl orthosilicate was 8:1 as the component two solution, respectively, at a speed of 700 rpm. Stir one and two for 35 min. Component 2 was then added during the agitation of component one at 700 rpm using a power agitator. After 1 min, the stirrer speed was adjusted to 300 rpm and stirred for 2 h. After the stirring was stopped, the mixture was washed once with water, twice with alcohol, and the obtained SiO ₂ microspheres were added to an ethanol solvent to prepare an 8 wt% suspension of SiO ₂ microspheres to be used. The erbium-doped ytterbium-doped fluoroquinone sodium phosphor was prepared by a solvothermal method, in which the amount of cerium ions was 12% and the amount of cerium ions was 0.6%.

Take 8 wt% of SiO ₂ ethanol suspension about 25 mL in a beaker, and then add 0.02 wt% KH570 and 0.03 wt% acrylic acid to the above beaker with two syringes, and add 0.02 wt% of erbium-doped erbium-doped fluorescein sodium phosphor. Beaker. After stirring for 20 h and stirring at 400 rpm, the erbium-doped ytterbium-doped fluorofluorene phosphor was uniformly dispersed in the SiO ₂ microsphere suspension, and the suspension system was used as a self-assembly liquid. The cleaned two pieces of glass are inserted vertically into the self-assembling solution. The microfluidic pump was used to extract the self-assembly liquid, and the microfluidic pump was set to have a liquid absorption speed of 30 μL/min for vertical self-assembly. The surface morphology of the photonic crystal film obtained at this liquid absorbing speed is shown in Fig. 4c-d, and the sectional shape is shown in Fig. 5b. It can be seen from the surface topography that the SiO ₂ microspheres are regularly and orderly arranged, and the thickness of the film layer is 5.12 μm by the section topography. The SiO ₂ microspheres have an average particle diameter of 360 nm and a particle size dispersion index of 0.2%.

Example 4

Take 8 wt% of SiO ₂ ethanol suspension about 15 mL in a beaker, and add 0.03 wt% KH570 and 0.06 wt% acrylic acid to the above beaker with two syringes respectively, and add 0.01 wt% of erbium-doped erbium-doped fluorescein sodium phosphor. Beaker. After stirring for 15 h and stirring at a speed of 500 rpm, the erbium-doped cerium-doped fluorofluorene phosphor was uniformly dispersed in the SiO ₂ microsphere suspension, and the suspension system was used as a self-assembly liquid. The cleaned two pieces of glass are inserted vertically into the self-assembling solution. The microfluidic pump was used to extract the self-assembly liquid, and the microfluidic pump was set to have a liquid absorption speed of 10 μL/min for vertical self-assembly. The surface morphology of the photonic crystal film obtained at this liquid absorbing speed is shown in Fig. 4e-f, and the sectional shape is shown in Fig. 5c. It can be seen from the surface topography that the SiO ₂ microspheres are regularly arranged in an orderly manner, the average size of the microspheres is 360 nm, and the particle size dispersion index is 0.2%. The thickness of the film layer was 8.76 μm by the section topography. Figure 6 is a reflection spectrum of the sample. It can be seen from the figure that the forbidden band position has appeared in the near-infrared luminescence 800 nm band of erbium-doped ytterbium-doped yttrium fluoride. Figure 7 is a fluorescence spectrum of the corresponding sample. Due to the forbidden band effect of the photonic crystal in the long-wave region, the erbium-doped ytterbium-doped fluorofluorene phosphor is suppressed in this band, resulting in weakening of the long-wavelength luminescence, so short-wave The relative luminous intensity of the zone is enhanced by 1.05 times.

Claims

A preparation method for improving an up-conversion luminescent film, the specific steps of which are as follows:

(1) Preparing a suspension of monodisperse SiO 2 microspheres: synthesizing monodisperse silica microspheres having a particle size dispersion index of 0.2%-1.0% and an average microsphere size of 350-450 nm, and then SiO 2 The microspheres are formulated into a suspension having a mass fraction of between 6 and 10%;

(2) Recombination of SiO 2 microspheres and upconversion fluorescent material: taking the SiO 2 suspension prepared in the step (1), taking a binder of 0.05-0.10% of the suspension mass, and dropping it into the suspension of SiO 2 , Then, an up-converting fluorescent material containing 0.01-0.03% of the mass of the suspension is added; stirring is performed to form a uniform dispersion of the up-converting fluorescent material and the SiO 2 microspheres as a self-assembly liquid;

(3) Self-assembly of fluorescent photonic crystal film: Two substrates are vertically inserted into a container equipped with a self-assembling liquid, self-assembled using a microfluidic pump, and a liquid absorbing speed of 5-50 ul/min is set for vertical self-assembly. A fluorescent photonic crystal film is obtained.
The preparation method according to claim 1, characterized in that the synthetic monodisperse SiO 2 microspheres are modified by the stober method, and the specific steps are as follows: taking a volume ratio of deionized water, ethanol and ammonia water to 1: (2-3) :1 As a component-solution, the volume ratio of ethanol to ethyl orthosilicate is (8-9): 1 is the component two solution, and components 1 and 2 are stirred at a speed of 600-800 rpm for 30-40 min respectively. Then, the component 2 is added during the process of stirring the component one at 600-800 rpm using an electric stirrer, and after adjusting the stirrer rotation speed to 300-500 rpm for 1-2 hours, stirring for 2-3 hours; after the stirring is stopped, after centrifugation washing , monodisperse SiO 2 microspheres were obtained.
The preparation method according to claim 1, wherein the SiO 2 microsphere suspension is prepared in the step (1) by adding monodisperse SiO 2 microspheres to an ethanol solvent to prepare a SiO 2 microsphere having a mass fraction of 6-10%. suspension.
The preparation method according to claim 1, wherein the up-converting fluorescent material in the step (2) is an antimony-doped ytterbium-doped fluorofluorium-fluoride phosphor, wherein the doping quality of the cerium ion is a sodium fluorofluoride phosphor 10-15% of the mass, the doping quality of the cerium ion is 0.5-1.0% of the mass of the fluoroquinone sodium phosphor.
The preparation method according to claim 1, wherein the binder is a mixture of KH570 and acrylic acid; and the mass ratio of KH570 to acrylic acid is 1: (1-2).
The preparation method according to claim 1, wherein the stirring speed in the step (2) is 300 to 500 rpm, and the stirring time is 12 to 24 hours.
The method according to claim 1, wherein the substrate is a glass sheet or an aluminum sheet.
The preparation method according to claim 1, wherein the fluorescent photonic crystal film prepared in the self-assembly step has a thickness of between 3.0 μm and 9.0 μm.