CN114736669B

CN114736669B - CMC-Na/CdS@ZnS flexible quantum dot film and preparation method thereof

Info

Publication number: CN114736669B
Application number: CN202210505175.2A
Authority: CN
Inventors: 张丹; 吕焘; 司鹏翔; 田苗; 祝博文
Original assignee: Jiangnan University
Current assignee: Jiangnan University
Priority date: 2022-05-10
Filing date: 2022-05-10
Publication date: 2023-06-13
Anticipated expiration: 2042-05-10
Also published as: CN114736669A

Abstract

The invention discloses a CMC-Na/CdS@ZnS flexible quantum dot film and a preparation method thereof, and belongs to the field of materials. The method for preparing the CMC-Na/CdS@ZnS flexible quantum dot film comprises the following steps: (1) Dissolving sodium carboxymethylcellulose in water, and regulating pH to 8-8.5; then adding a cadmium source solution into the sodium carboxymethyl cellulose solution, and reacting for 2-3 hours at 50-60 ℃ in an inert gas atmosphere; after the reaction is finished, adding a sulfur source solution, and uniformly mixing; alternately adding zinc source solution and sulfur source solution, and reacting at 50-60deg.C for 2-5min; after the reaction is finished, CMC-Na/CdS@ZnS quantum dot dispersion liquid is obtained; (2) Concentrating CMC-Na/CdS@ZnS quantum dot dispersion liquid to 1/3-1/4 of the original mass; mixing the concentrated solution with polyurethane emulsion, and drying to obtain the CMC-Na/CdS@ZnS flexible quantum dot film. The flexible quantum dot film can have certain mechanical strength on the premise of keeping the original fluorescence performance; meanwhile, the heat stability is excellent, the application range is wide, and the heat-resistant material can be used in the temperature range of room temperature to 200 ℃.

Description

CMC-Na/CdS@ZnS flexible quantum dot film and preparation method thereof

Technical Field

The invention relates to a CMC-Na/CdS@ZnS flexible quantum dot film and a preparation method thereof, belonging to the field of materials.

Background

The quantum dots have small size, can emit the wavelength covering the whole visible light region, have adjustable wavelength, assemble the quantum dots with different sizes into a light-emitting device, can randomly adjust the light-emitting wavelength of a light source, and have excellent advantages in LED manufacture. In the display field, the typical color gamut value of the LCD display device based on the common LEDs is improved from 72% to more than 100% by adding quantum dot devices, so that the color reproducibility of the display device is greatly improved, and the following-up of all large display manufacturers worldwide is caused.

Materials related to polyurethane have been incorporated into a large number of consumer products for many years and continue to play an important role in our daily lives. With the increasing wide application of polymer films, the requirements on the properties of the film materials are higher, and the commonly used polysulfone, polyolefin films and the like cannot completely meet the market demands, so that polyurethane films are generated. The polyurethane film has the advantages of optical transparency, soft hand feeling, high extensibility, durability, easy processing, water resistance and air permeability, and can be widely used as high-grade or special textile fabrics in daily life.

The most convenient and direct method for manufacturing the quantum dot composite film is to mix colloid quantum dots with polymer, and dry the mixture to form the film. However, aggregation of colloidal quantum dots during blending or solvent evaporation can significantly reduce the PL strength of the resulting quantum dot composite film. There are researchers to mix aqueous polyurethane with quantum dots as a surface coating material, and although fluorescence and mechanical properties are obtained, it can be seen from experimental results that the increase in photoluminescence intensity increases with the proportion of quantum dots added, and it is impossible to achieve simultaneous increase in mechanical strength and photoluminescence intensity. There have also been attempts to prepare quantum dot films by QDs/PU/POSS systems, but POSS was introduced only for the purpose of improving the optical and thermal stability of the quantum dot films, and there has been no study in terms of improving both PL strength and mechanical strength of composite films. And it is difficult to maintain long-term stability of the capping agent coated quantum dots due to oxidation and degradation of the polymer. In addition, the nano-carriers need to be decorated with surface charges to avoid aggregation. In order to maintain the stability of colloidal quantum dots, high loading of the nanocarriers is generally required. However, a large amount of nano-carriers are often aggregated in the solvent evaporation process, so that the nano-carriers are seriously separated from the polymer resin, and the PL strength and mechanical property of the quantum dot composite film are further reduced. Therefore, it remains a great challenge to obtain both high PL strength and mechanical properties of quantum dot composite films.

From the current quantum dot film preparation method, although various preparation methods have been developed, it is not difficult to find that many problems such as complex preparation method process, low economic benefit, practicality, environmental pollution, and limitation of external conditions exist in film use.

Disclosure of Invention

[ technical problem ]

The existing preparation method of the carbon quantum dot film has the problems of complex process, low economic benefit, practicability, environmental pollution, limited external conditions in film use, incapability of considering high PL intensity and mechanical property and the like.

Technical scheme

In order to solve at least one problem, CMC-Na/CdS@ZnS quantum dots and polyurethane are combined to prepare the CMC-Na/CdS@ZnS flexible quantum dot film.

The first object of the invention is to provide a method for preparing CMC-Na/CdS@ZnS flexible quantum dot film, comprising the following steps:

(1) Preparation of CMC-Na/CdS@ZnS quantum dot dispersion

Dissolving sodium carboxymethyl cellulose in water, and regulating the pH value to 8-8.5 to obtain sodium carboxymethyl cellulose solution; then adding a cadmium source solution into the sodium carboxymethyl cellulose solution, and reacting for 2-3 hours at 50-60 ℃ in an inert gas atmosphere; after the reaction is finished, adding a sulfur source solution, and uniformly mixing; alternately adding zinc source solution and sulfur source solution, and reacting at 50-60deg.C for 2-5min; after the reaction is finished, CMC-Na/CdS@ZnS quantum dot dispersion liquid is obtained;

(2) Preparation of CMC-Na/CdS@ZnS flexible quantum dot film

Concentrating CMC-Na/CdS@ZnS quantum dot dispersion liquid to 1/3-1/4 of the original mass to obtain concentrated liquid; mixing the concentrated solution with polyurethane emulsion, and drying to obtain the CMC-Na/CdS@ZnS flexible quantum dot film.

In one embodiment of the present invention, the ratio of sodium carboxymethyl cellulose to water in the sodium carboxymethyl cellulose solution of step (1) is 0.02 to 0.04g:50mL.

In one embodiment of the present invention, the adjusting the pH in step (1) is performed by using a sodium hydroxide solution having a concentration of 0.1 to 0.2M.

In one embodiment of the present invention, the cadmium source solution in step (1) comprises one of a cadmium chloride solution and a cadmium acetate solution; wherein the concentration of the cadmium source solution is 0.02M.

In one embodiment of the present invention, the inert gas in step (1) includes one or more of nitrogen, helium and neon.

In one embodiment of the present invention, the sulfur source solution in step (1) comprises one of a sodium sulfide solution and a thiourea solution, wherein the concentration of the sulfur source solution is 0.01-0.04M.

In one embodiment of the present invention, the zinc source solution in step (1) includes one of zinc nitrate solution and zinc sulfate; wherein the concentration of the zinc source solution is 0.01-0.04M.

In one embodiment of the present invention, the solvent of the sulfur source solution, the cadmium source solution, and the zinc source solution in the step (1) is water.

In one embodiment of the present invention, the concentration ratio of the cadmium source solution, the sulfur source solution, and the zinc source solution in the step (1) is 1:1, a step of; the adding volume ratio of the cadmium source solution to the sulfur source solution added for the first time to the zinc source solution to the sulfur source solution added for the second time is 1:1:1:1.

in one embodiment of the present invention, the volume ratio of the water to the cadmium source solution in the sodium carboxymethyl cellulose solution in the step (1) is 48-52:1.

in one embodiment of the present invention, the first adding sulfur source solution, zinc source solution, and second adding sulfur source solution in step (1) have an addition rate of 0.1-0.2mL/min.

In one embodiment of the invention, the concentration in step (2) is performed at 60-70 ℃.

In one embodiment of the present invention, the mass ratio of the concentrated solution to the polyurethane emulsion in the step (2) is 5:6-8.

In one embodiment of the present invention, the polyurethane emulsion in the step (2) is an aqueous polyurethane emulsion, and has a viscosity of 300 to 350mpa·s and a solid content of 20 to 40% (mass percent) and is commercially available.

In one embodiment of the present invention, the mixing in the step (2) is performed by ultrasonic vibration for 0.5-2min.

In one embodiment of the present invention, the drying in the step (2) may be normal temperature drying.

The second purpose of the invention is to prepare the CMC-Na/CdS@ZnS flexible quantum dot film by the method.

The third purpose of the invention is the application of the CMC-Na/CdS@ZnS flexible quantum dot film in displays and LEDs.

[ advantageous effects ]

(1) The cadmium source and the sulfur source adopted in the invention have certain harm, but the harm of the isolator can be effectively reduced to a certain extent through the core-shell structure, the ZnS shell layer can effectively protect the CdS core layer, the contact between the core layer and external oxygen is reduced, the lattice strength can be enhanced through Zn/Cd alloy, and the stability of the lattice is greatly improved. Therefore, the invention not only can prepare the water phase quantum dots which are stable, but also has the characteristic of environmental protection.

(2) The flexible quantum dot film can have certain mechanical strength on the premise of keeping the original fluorescence performance; meanwhile, the heat stability is excellent, the application range is wide, and the heat-resistant material can be used in the temperature range of room temperature to 200 ℃.

(3) The method is simple, easy to operate and high in repeatability.

Drawings

FIG. 1 is a flow chart of the preparation of CMC-Na/CdS@ZnS quantum dot dispersion.

FIG. 2 is a PL spectrum (A) and luminescence pattern (B) of CMC-Na/CdS@ZnS flexible quantum dot films prepared in examples 1-4.

FIG. 3 is a graph of spectra of different CMC-Na/CdS@ZnS quantum dot dispersions and different ratios of flexible quantum dot films.

Fig. 4 is a graph of the transmittance of different CMC-Na/cds@zns flexible quantum dot films.

Fig. 5 is an SEM morphology of different CMC-Na/cds@zns flexible quantum dot films.

Fig. 6 is a graph of tensile strength of different CMC-Na/cds@zns flexible quantum dot films.

Fig. 7 is a luminescence diagram of different CMC-Na/cds@zns flexible quantum dot films.

Fig. 8 is a graph showing the results of thermal stability testing of different CMC-Na/cds@zns flexible quantum dot films.

Detailed Description

The following description of the preferred embodiments of the present invention is provided for better illustration of the invention, and should not be construed as limiting the invention.

The testing method comprises the following steps:

PL spectrum test: using a fluorescence spectrometer (FS 5), in particular placing the dispersion in a quartz cuvette; the quantum dot solution does not need to be subjected to any pretreatment; the quantum dot film is placed in a glass vessel special for measuring solids by a fluorescence spectrometer; the rest of the operations are referred to the specific method of operation of the instrument used.

Transmittance test: an ultraviolet-visible spectrophotometer (UV-vis) is adopted, and specifically: the sample preparation specification is smaller than the size of the cuvette, and the transmittance can be measured by attaching the quantum dot film to one side of the inner wall of the cuvette; the rest of the operations are referred to the specific method of operation of the instrument used.

Tensile strength test: using an electronic universal tester, sample standard: 2cm long and 0.6cm wide, dumbbell shape, and stretching rate of 2mm/sec; the rest of the operations are referred to the specific method of operation of the instrument used.

Test of thermal stability: a thermogravimetric analyzer (TGA) is carried out under nitrogen flow at a temperature ranging from room temperature to 400 ℃ and a heating rate of 10 ℃/min; the rest of the operations are referred to the specific method of operation of the instrument used.

Example 1

A method for preparing a CMC-Na/cds@zns flexible quantum dot film, comprising the steps of:

(1) Preparation of CMC-Na/CdS@ZnS quantum dot dispersion

0.03g of sodium carboxymethyl cellulose is dissolved in 50mL of water and stirred at room temperature to be completely dissolved; adjusting the pH to 8 with dilute sodium hydroxide solution (0.1M concentration) to obtain sodium carboxymethyl cellulose solution; then adding 1mL of cadmium chloride solution (0.02M) into the sodium carboxymethyl cellulose solution, performing ultrasonic oscillation for 15min, and stirring (250 rpm) at 50 ℃ for reaction for 2h under the nitrogen atmosphere; after the reaction was completed, 1mL of sodium sulfide solution (0.02M) was added at a rate of 0.1 mL/min; after stirring for 2min, 1mL of zinc nitrate solution (0.02M) and 1mL of sodium sulfide solution (0.02M) were added alternately in sequence at a rate of 0.2mL/min, and reacted at 50℃for 5min; after the reaction is finished, CMC-Na/CdS@ZnS quantum dot dispersion liquid is obtained; as in fig. 1;

(2) Preparation of CMC-Na/CdS@ZnS flexible quantum dot film

Heating and concentrating CMC-Na/CdS@ZnS quantum dot dispersion liquid at 60 ℃ until the mass is 1/3 of that of the original dispersion liquid to obtain concentrated liquid; mixing the concentrated solution and aqueous polyurethane emulsion (viscosity 250-350 mPa.S, solid content 20-40%) at a ratio of 5:8, uniformly mixing the materials according to the mass ratio, performing ultrasonic vibration for 1min, and naturally drying the mixed solution in a culture dish to obtain the CMC-Na/CdS@ZnS flexible quantum dot film; wherein the thickness of the film is 0.14mm.

Example 2

(1) Preparation of CMC-Na/CdS@ZnS quantum dot dispersion

0.03g of sodium carboxymethyl cellulose is dissolved in 50mL of water and stirred at room temperature to be completely dissolved; adjusting the pH to 8 with dilute sodium hydroxide solution (0.1M concentration) to obtain sodium carboxymethyl cellulose solution; then adding 1mL of cadmium chloride solution (0.02M) into the sodium carboxymethyl cellulose solution, performing ultrasonic oscillation for 15min, and stirring (250 rpm) at 50 ℃ for reaction for 2h under the nitrogen atmosphere; after the reaction was completed, 1mL of sodium sulfide solution (0.01M) was added at a rate of 0.1 mL/min; after stirring for 2min, 1mL of zinc nitrate solution (0.01M) and 1mL of sodium sulfide solution (0.01M) were added alternately in sequence at a rate of 0.2mL/min, and reacted at 50℃for 5min; after the reaction is finished, CMC-Na/CdS@ZnS quantum dot dispersion liquid is obtained;

(2) Preparation of CMC-Na/CdS@ZnS flexible quantum dot film

Example 3

(1) Preparation of CMC-Na/CdS@ZnS quantum dot dispersion

0.03g of sodium carboxymethyl cellulose is dissolved in 50mL of water and stirred at room temperature to be completely dissolved; adjusting the pH to 8 with dilute sodium hydroxide solution (0.1M concentration) to obtain sodium carboxymethyl cellulose solution; then adding 1mL of cadmium chloride solution (0.02M) into the sodium carboxymethyl cellulose solution, performing ultrasonic oscillation for 15min, and stirring (250 rpm) at 50 ℃ for reaction for 2h under the nitrogen atmosphere; after the reaction was completed, 1mL of sodium sulfide solution (0.03M) was added at a rate of 0.1 mL/min; after stirring for 2min, 1mL of zinc nitrate solution (0.03M) and 1mL of sodium sulfide solution (0.03M) were added alternately in sequence at a rate of 0.2mL/min, and reacted at 50℃for 5min; after the reaction is finished, CMC-Na/CdS@ZnS quantum dot dispersion liquid is obtained;

(2) Preparation of CMC-Na/CdS@ZnS flexible quantum dot film

Example 4

(1) Preparation of CMC-Na/CdS@ZnS quantum dot dispersion

0.03g of sodium carboxymethyl cellulose is dissolved in 50mL of water and stirred at room temperature to be completely dissolved; adjusting the pH to 8 with dilute sodium hydroxide solution (0.1M concentration) to obtain sodium carboxymethyl cellulose solution; then adding 1mL of cadmium chloride solution (0.02M) into the sodium carboxymethyl cellulose solution, performing ultrasonic oscillation for 15min, and stirring (250 rpm) at 50 ℃ for reaction for 2h under the nitrogen atmosphere; after the reaction was completed, 1mL of sodium sulfide solution (0.04M) was added at a rate of 0.1 mL/min; after stirring for 2min, 1mL of zinc nitrate solution (0.04M) and 1mL of sodium sulfide solution (0.04M) were added alternately in sequence at a rate of 0.2mL/min, and reacted at 50℃for 5min; after the reaction is finished, CMC-Na/CdS@ZnS quantum dot dispersion liquid is obtained;

(2) Preparation of CMC-Na/CdS@ZnS flexible quantum dot film

The CMC-Na/CdS@ZnS flexible quantum dot dispersion obtained in examples 1-4 was tested, and the test results are shown in FIG. 2 and Table 1:

TABLE 1 Performance test of CMC-Na/CdS@ZnS Flexible Quantum dot Dispersion obtained in examples 1-4

Example(s)	Maximum emission wavelength (nm)	Luminous intensity (a.u.)
			Example 1	620	517094.041
Example 2	590	330769.606
			Example 3	690	380184.243
Example 4	730	286535.260

As can be seen from fig. 2: along with Na ₂ The maximum emission wavelength of the CMC-Na/CdS@ZnS quantum dot dispersion liquid gradually shifts to red due to the increase of the concentration of S and ZnS, and the emission color changes from yellow to red.

Example 5

The mass ratio of the concentrated solution to the aqueous polyurethane emulsion in the step (2) of the example 1 is adjusted to be 5:6, other was kept consistent with example 1 to give CMC-Na/cds@zns flexible quantum dot films.

Comparative example 1

The mass ratio of the concentrated solution to the aqueous polyurethane emulsion in the step (2) of the example 1 is adjusted to be 5:2, otherwise consistent with example 1, CMC-Na/cds@zns flexible quantum dot films were obtained.

Comparative example 2

The mass ratio of the concentrated solution to the aqueous polyurethane emulsion in the step (2) of the example 1 is adjusted to be 5:4, otherwise consistent with example 1, CMC-Na/cds@zns flexible quantum dot films were obtained.

Comparative example 3

The mass ratio of the concentrated solution to the aqueous polyurethane emulsion in the step (2) of the example 1 is adjusted to be 5:16, other was kept consistent with example 1, yielding a CMC-Na/cds@zns flexible quantum dot film.

Comparative example 4

Naturally drying the aqueous polyurethane emulsion in a culture dish to obtain a pure water polyurethane film; wherein the thickness of the film is 0.14mm.

CMC-Na/CdS@ZnS flexible quantum dot films obtained in examples 1 and 5 and comparative examples 1 to 4 (CMC-Na content by mass ratio of 0.37wt%, 0.50wt%, 1.50wt%, 0.74wt%, 0.19wt%, 0 in examples 1 and 5 and comparative examples 1, 2, 3, 4, respectively) were tested;

the duty ratio is calculated as follows:

CMC-Na(wt％)＝m _CMC-Na /(m _CMC-Na +m _PU * Solids content).

The test results were as follows:

TABLE 2 Performance testing of Quantum dot films

As can be seen from table 2 and fig. 3, 4, 6:

(1) The emission wavelength of the CMC-Na/CdS@ZnS flexible quantum dot film remained unchanged as the CMC-Na concentration was reduced, but the luminous intensity increased, and the luminous intensity was 66503.762 when the concentration was 0.37%.

(2) The transmittance of the pure polyurethane film was about 85.81%. Along with the decrease of CMC-Na concentration, the transmittance of the CMC-Na/CdS@ZnS flexible quantum dot film is increased;

(3) The elongation at break of the pure polyurethane film is 887.1 percent, and the elongation at break of the CMC-Na/CdS@ZnS flexible quantum dot film gradually increases along with the reduction of the CMC-Na concentration. The elongation at break was about 730.6% at a CMC-Na concentration of 0.37%.

(4) As CMC-Na concentration decreases, the luminescent and mechanical strength of the quantum dot film increases simultaneously.

Fig. 5 is an SEM morphology of CMC-Na/cds@zns flexible quantum dot films of different concentrations. As can be seen from fig. 5: when the CMC-Na concentration is too high, the surface of the CMC-Na/CdS@ZnS flexible quantum dot film is incomplete, a plurality of fractures are distributed, the surface fractures gradually decrease along with the decrease of the CMC-Na concentration, and when the CMC-Na concentration ratio is 0.37%, the film with complete cross section shape can be formed.

Table 3 shows the fluorescence intensities of CMC-Na/CdS@ZnS flexible quantum dot films of example 1 at different tensile elongations. As can be seen from table 3: as the tensile elongation increases, the fluorescence intensity decreases.

TABLE 3 fluorescence intensity of CMC-Na/CdS@ZnS Flexible Quantum dot films of example 1 at different tensile elongations

Tensile elongation	Fluorescence intensity
			100％	17725.593
150％	12355.946
		200％	10429.737
250％	8967.859
		300％	6855.372

Fig. 7 is a luminescence diagram of different concentrations of CMC-Na/cds@zns flexible quantum dot films. As can be seen from fig. 7: the color of the CMC-Na/CdS@ZnS flexible quantum dot film gradually becomes lighter along with the reduction of the CMC-Na concentration, and the color of the film is not yellow when the CMC-Na concentration is reduced to 0.19% from dark yellow to light yellow.

Fig. 8 shows the thermal stability test results of CMC-Na/cds@zns flexible quantum dot films with different concentrations, as can be seen from fig. 8: after the polyurethane is added, the thermal stability of the film can be greatly improved, and the thermal stability of the polyurethane with different quality is similar.

Comparative example 5

And (3) adjusting sodium carboxymethylcellulose in the step (1) of the example 1 to sodium carboxymethylcellulose (CNC-Na) and Cellulose Nanofibers (CNFs), and keeping the same with the example 1, thereby obtaining the CMC-Na/CdS@ZnS flexible quantum dot film.

Sodium carboxymethyl cellulose is replaced by sodium carboxylated cellulose and cellulose nanofiber, and during the experimental process, the following steps are found:

(1) Compared with CMC-Na, the stability of carboxylated cellulose sodium and cellulose nanofibers in dispersion liquid (dispersion liquid obtained by adding cadmium chloride after carboxylated cellulose sodium (CNC-Na) and Cellulose Nanofibers (CNFs) are dissolved in water) is poor, the carboxylated cellulose sodium and the cellulose nanofibers are difficult to play a role in balancing charges as polyelectrolyte salt, and in the process of synthesizing quantum dot dispersion liquid, the solution is easy to become turbid;

(2) When the mass ratio of the sodium carboxymethyl cellulose to water is 0.03:50, sodium carboxymethyl cellulose is well dissolved, but carboxylated cellulose sodium and cellulose nanofiber are difficult to dissolve, so that the experimental difficulty is increased;

(3) Sodium carboxymethylcellulose is much cheaper than the remaining two from an economic point of view, and is more cost effective (CMC-Na: about 0.07 yuan/g, CNC-Na: about 10 yuan/g, CNFs: about 4 yuan/g).

Therefore, sodium carboxymethyl cellulose is selected as polyelectrolyte salt to synthesize the CMC-Na/CdS@ZnS flexible quantum dot film.

Comparative example 6

The amount of sodium carboxymethylcellulose in step (1) of example 1 was adjusted to 15mg and 40mg, and the other was kept the same as example 1, to obtain a CMC-Na/CdS@ZnS flexible quantum dot film.

The result shows that: CMC-Na, as a polyelectrolyte salt, cannot function to maintain the charge balance of the solution system if the concentration is too low. In contrast, if the concentration is too high, the anions carried on the main chain of sodium carboxymethyl cellulose are mixed with anionic aqueous polyurethane, and the electrostatic interaction of the whole system is increased due to the too high ionic strength, so that a normal film cannot be formed (as can be seen from SEM (figure 5) of CMC-Na/CdS@ZnS flexible quantum dot film).

Comparative example 7

And (3) adjusting concentration to 1/5 and 1/10 of the original mass in the step (2) of the embodiment 1, and keeping the same with the embodiment 1 to obtain the CMC-Na/CdS@ZnS flexible quantum dot film.

The result shows that: when the concentration multiple is too high, the concentration of CMC-Na is also greatly increased, so that electrostatic interaction in a system is increased, a coagulation phenomenon occurs, and a normal film cannot be formed.

Comparative example 8

The concentration in the step (2) of the example 1 is omitted, CMC-Na/CdS@ZnS quantum dot dispersion liquid and polyurethane emulsion are directly adopted for mixing, and the other steps are kept the same as the example 1, so that the CMC-Na/CdS@ZnS flexible quantum dot film is obtained.

The result shows that: the fluorescence intensity of the film was insufficient, about 8X 10 ⁴ The fluorescence intensity of the quantum dot film prepared after concentration is far lower than that of the quantum dot film prepared after concentration.

While the invention has been described with reference to the preferred embodiments, it is not limited thereto, and various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. The method for preparing the CMC-Na/CdS@ZnS flexible quantum dot film is characterized by comprising the following steps of:

(1) Preparation of CMC-Na/CdS@ZnS quantum dot dispersion

Dissolving sodium carboxymethylcellulose CMC-Na in water, and regulating the pH value to 8-8.5 to obtain sodium carboxymethylcellulose CMC-Na solution; then adding a cadmium source solution into a CMC-Na solution of sodium carboxymethylcellulose, and reacting for 2-3h at 50-60 ℃ in an inert gas atmosphere; after the reaction is finished, adding a sulfur source solution, and uniformly mixing; alternately adding zinc source solution and sulfur source solution, and reacting at 50-60deg.C for 2-5min; after the reaction is finished, CMC-Na/CdS@ZnS quantum dot dispersion liquid is obtained;

(2) Preparation of CMC-Na/CdS@ZnS flexible quantum dot film

2. The method of claim 1, wherein the mass ratio of the concentrate to the polyurethane emulsion in step (2) is 5:6-8.

3. The method of claim 1, wherein the sulfur source solution of step (1) comprises one of a sodium sulfide solution and a thiourea solution, wherein the concentration of the sulfur source solution is 0.01-0.04M.

4. The method of claim 1, wherein the zinc source solution of step (1) comprises one of a zinc nitrate solution and zinc sulfate; wherein the concentration of the zinc source solution is 0.01-0.04M.

5. The method of claim 1, wherein the cadmium source solution, the first sulfur source solution, the zinc source solution, and the second sulfur source solution are added in the step (1) in a volume ratio of 1:1:1:1.

6. the method of claim 1, wherein the cadmium source solution of step (1) comprises one of a cadmium chloride solution and a cadmium acetate solution; wherein the concentration of the cadmium source solution is 0.02M.

7. The method according to claim 1, wherein the polyurethane emulsion in the step (2) is an aqueous polyurethane emulsion, the viscosity is 300-350 mpa.s, and the solid content is 20-40% (mass percent).

8. The method according to claim 1, wherein the ratio of sodium carboxymethyl cellulose CMC-Na to water in the sodium carboxymethyl cellulose CMC-Na solution of step (1) is 0.02-0.04g:50mL.

9. The CMC-Na/cds@zns flexible quantum dot film prepared by the method of any one of claims 1-8.

10. Use of the CMC-Na/cds@zns flexible quantum dot film of claim 9 in displays, LEDs.