KR20090033947A - Fabrication method of quantum dot nanoparticle/polymer core/shell nanoparticles by interfacial polymerization - Google Patents

Abstract

A fabrication method for quantum dot/polymer core-shell nano complex through interfacial polymerization is provided to secure thermal stability for a long period while maintaining a light-emitting property of the quantum dot. A fabrication method for quantum dot/polymer core-shell nano complex comprises the following steps of: dissolving a solution containing quantum dot in the presence of a reaction solvent; absorbing the solution on a surface of the quantum dot by adding metal initiator; re-dispersing initiator-treated quantum dot in a non-polar solvent wherein no initiator comes out; and adding monomers to the solvent so that the monomers are polymerized on the surface of the quantum dot. The quantum dot represents cadmium telluride, cdSe or zinc selenide.

Description

Fabrication method of quantum dot / polymer core-cell nanocomposite using interfacial polymerization {Fabrication method of quantum dot nanoparticle / polymer core / shell nanoparticles by interfacial polymerization}

The present invention relates to a method of coating a monomer on the surface by using an interfacial polymerization (interfacial polymerization) on the surface of the quantum dots, and provides a method of coating a polymer thin film having a uniform thickness on the surface of the quantum dots.

Quantum dots have unique chemical, optical, and physical properties that differ from conventional bulk materials, which are greatly influenced by the size of nanoparticles. This is called quantum dot effect. Especially, Group 2-6 semiconductor nanomaterials have high luminous efficiency and easy control of particle size in nanometer unit, so biological application, application to LED material, single electron transistor, solar cell , And photocatalyst materials. Quantum dots have been studied a lot of methods using a surfactant to maintain uniformity in size. However, since the surfactant has a strong bond with the quantum dots, there are many limitations in the application of the quantum dots. Also, if the surfactant is removed for the direct application of the quantum dots, agglomeration and entanglement of the quantum dots may occur, and thermal and optical stability may decrease due to oxygen, water, etc. in the air, and the intrinsic properties thereof may be lost. There is a problem with stability. Therefore, many methods have been studied to coat quantum dots with polymers and other stabilizers.

The core-cell nanocomposite structure not only improves the stability and dispersibility of the core material therein, but also provides additional functions to the functions possessed by a single core material by using a cell material having unique properties. Therefore, efforts have been made to implement core-cell nanocomposite structures using emulsion polymerization, atomic transfer radical polymerization, graft polymerization, and layer-by-layer polymerization. . However, disadvantages of the above methods include complicated processes and the use of expensive reactants. In addition, when manufacturing the core-cell, there is a problem that the stability of the quantum dot is reduced and entanglement and agglomeration occur during the removal of the surfactant to maintain the original properties of the core material.

Therefore, in consideration of the direct application of quantum dots, a new manufacturing method capable of mass production by a simple and inexpensive process in which a polymer can be coated on the surface of the quantum dots while maintaining the stability of the quantum dots can be maintained It is strongly demanded.

An object of the present invention is to solve the problems of the prior art by coating a semiconductor nanoparticle with a polymer using a novel selective interfacial polymerization method to obtain a semiconductor nanoparticle / polymer core / cell nanocomposite coated with a polymer of uniform thickness It is to provide a method of manufacturing.

After numerous experiments and in-depth studies, the inventors adsorbed a positively charged initiator onto the surface of a negatively charged quantum dot, a method completely different from the known method, and then introduced a monomer, whereby the monomer was selected only on the surface of the quantum dot. It is confirmed that the surface can be coated with a polymer having a uniform thickness by using an interfacial polymerization that causes the polymerization to occur, and even after the surfactant is removed from the prepared core-cell nanocomposite, its phase separation and stability are Significant improvements have been found and led to the present invention.

The present invention utilizes interfacial polymerization of quantum dot core particles of several tens of nanometers in size to polymethylmethacrylate, polyacrylonitrile, polydivinylbenzene, poly (3,4 ethylenedioxythiophene), polypyrrole, The coating is performed with polyaniline.

Method for producing a quantum dot coated with a polymer according to the present invention,

(A) diluting a solution comprising quantum dots prepared under a surfactant and reaction solvent having an average particle diameter of several nanometers to several tens of nanometers;

(B) adding a cationic series metal initiator to the quantum dot surface;

(C) redispersing the quantum dots treated with the initiator in a non-polar solvent or the like in which the initiator does not melt;

(D) adding a monomer to the solvent to polymerize at the surface of the quantum dots.

A method of coating a polymer by interfacial polymerization between an adsorbed initiator and a monomer by treating the semiconductor nanoparticles according to the present invention by treating a cation-based initiator with only an initiator present on the surface thereof is a completely new method. Quantum dots can be easily prepared core-cell nanocomposites with constant size and cell thickness regardless of the type of polymer by treating cationic initiators through simple dilution without completely removing the surfactant used when manufactured. Do. In addition, it is possible to prepare a core-cell nanocomposite in which entanglement between quantum dots is suppressed by polymer coating. In particular, when a core-cell material is manufactured using a quantum dot having a luminescent property as a core and a light transparent polymer as a cell component, the luminescent property of the quantum dot is maintained as it is, and a core-cell which ensures thermal and optical stability for a long time. The preparation of nanocomposites is possible.

In the case of the quantum dots used in step (A), it is possible to use quantum dots of several tens of nanometers produced using the pyrolysis method. The composition of the quantum dot is not particularly limited, and all of cadmium sulfide (CdS), cadmium telluride (CdTe), cadmium selenide (CdSe), zinc selenide (ZnSe), and the like can be used. The size and shape are not limited to specific shapes, but spherical particles are preferred for evenly treating the surface with a cationic initiator.

In the manufacturing process of the semiconductor nanoparticles, the material that can be used as a surfactant and a solvent used to prevent entanglement is not particularly limited, and all oleylamine, oleylacid, etc. may be used. In the production of quantum dots using pyrolysis, the reaction is preferably performed for about 12 to 24 hours at 160 to 200 degrees Celsius, but is not particularly limited to these ranges. The concentration of the quantum dot precursor relative to the total solvent is preferably an amount from one hundredth to one thousandth, but is not particularly limited thereto.

Although there is no particular limitation on the solvent for dilution, in the present invention, ethanol which can effectively remove the compound used as the surfactant and the unreacted reactant is preferable. When using ethanol, most of the surfactant is removed, but since the surfactant strongly adsorbed on the surface of the nanoparticles remains, entanglement can be suppressed. The amount of dilution solvent added is preferably 10 to 100 times, but is not particularly limited thereto.

The cationic initiator in step (B) is not particularly limited as long as it is a metal ion capable of polymerizing a polymer due to oxidation potential, and in the present invention, both redox polymerization and radical polymerization have strong oxidation potential. Preference is given to cerium ammonium nitrate which can be initiated. Also applicable are iron chloride (FeCl ₃ ) and copper chloride (CuCl ₂ ) which can initiate redox reactions such as conductive polymers. Generally, an excess of cationic metal initiator relative to the quantum dots is added, and residual material not attached to the surface of the quantum dots is removed by dilution.

As a non-polar solvent that can be used in step (C), the monomer can be dissolved, but any polymers and non-polar solvents capable of forming an interface between the quantum dots and the solvent can not be dissolved because the initiator adsorbed on the surface of the quantum dots can be used. It is possible. In this study, nucleic acid is preferred. It is preferable to add a solvent 20 to 300 times the weight of the quantum dot treated with the initiator, but is not particularly limited thereto.

Monomers that can be used in step (D) can be used if all can be polymerized with the above-described initiator, in the present invention, methyl methacrylate, acrylonitrile, divinylbenzene, 3,4 ethylenedioxythiophene, pyrrole And aniline are preferable.

The amount of the monomer to be introduced is not particularly limited, but a mass ratio of 2 to 10 times is preferable with respect to the quantum dots surface-treated with the initiator.

The temperature suitable for the polymerization is not limited, but in the case of the radical initiation form, it is preferred between 65 ° C and 80 ° C, and in the case of the initiation form through the oxidation-reduction reaction, it can be reacted between 0 ° C and 100 ° C. The polymerization time of the polymer required for the polymerization is preferably 1 hour to 24 hours, but is not limited thereto, and may be shorter or longer than the above range depending on the type of monomer.

The present invention also relates to a quantum dot / polymer core / cell nanocomposite having a core-cell structure prepared by the above method. The quantum dot / polymer core / cell nanocomposite prepared by the method of the present invention is uniformly coated with a thickness of several nanometers without the entanglement even after removing the surfactant. In the prepared core-cell nanocomposite, the polymer improves the thermal and optical stability of the core particles and provides a function of maintaining the core's inherent properties for a long time. When a quantum dot having excellent luminous efficiency is used and coated with an optically transparent polymer, a stable crystal structure appears for a long time while maintaining luminescent properties. It is also expected that other applications of the quantum dot / polymer core / cell nanocomposites may be used in photocatalysts, nanocomposites, high efficiency lasers, biological nanolabels, and other biological applications, but the quantum dot-polymer nano of the core-cell structure according to the present invention. The composite is not limited to these exemplary uses but can be applied and applied to various anticipated uses in the future, and their use is not outside the scope of the present invention.

      EXAMPLE

Although specific examples of the present invention will be described with reference to the following Examples, the scope of the present invention is not limited thereto.

      Example 1

Dissolve 1 × 10 ⁻³ mol of cadmium chloride in 10 ml of oleylamine solvent and raise the temperature of the solvent to 160 ° C. and dissolve the same molar sulfur precursor in 5 ml of oleylamine and slowly inject into the solution. When reacted for 20 hours with vigorous stirring, cadmium sulfide quantum dots having a uniform size of about 5.4 nm can be obtained as shown in FIG. 1. After the solvent is cooled to room temperature, 10 times of ethanol is added and diluted using a centrifuge, and most of oleylamine and unreacted precursors can be removed except for oleylamine remaining on the surface.

0.2 g of cerium ammonium nitrate is added to 10 ml of the solution, and the surface of the cadmium sulfide quantum dot is treated with a cerium-based initiator. Cerium initiators of the cationic nature have an anionic nature of the cadmium sulfide surface and thus can be easily treated on the quantum dot surface by attraction between opposite charges. 0.1 g of cadmium sulfide quantum dots treated with a cerium-based initiator are placed in 30 ml of nucleic acid, heated to 65 ° C, and 0.1 ml of methylmethacrylate monomer is injected to carry out polymerization for 12 hours on the cadmium sulfide surface. When the prepared cadmium sulfide quantum dot / polymethyl methacrylate core / cell nanocomposite was observed with a transmission electron microscope, as shown in Figure 2 excellent dispersibility and uniform cadmium sulfide quantum dot / polymethyl methacrylate of 19.4 nm size Core / cell nanocomposites could be prepared. As a result of analysis by Fourier infrared spectroscopy, as shown in b) of FIG. 3, it was confirmed that the polymethylmethacrylate was successfully polymerized.

      Example 2

As a result of measuring the cadmium sulfide quantum dot / polymethyl methacrylate core / cell nanocomposite prepared in Example 1 by using a photoluminescence, as shown in FIG. It was confirmed that the efficiency does not decrease much. Therefore, when using an optically transparent polymer such as polymethyl methacrylate, it was confirmed that the intrinsic luminescence properties of the core is maintained unchanged.

      Example 3

After the cadmium sulfide quantum dot / polymethylmethacrylate core / cell nanocomposite prepared in Example 1 was left in air for a long time and measured by X-ray diffraction spectroscopy, as shown in FIG. Cadmium sulfide and the crystal lattice structure were found to be the same. On the other hand, when the polymer-coated cadmium sulfide was exposed to air for a long time, there was a significant change in the crystal lattice structure. Therefore, it was confirmed that the polymer coated on the surface of the cadmium sulfide quantum dot greatly contributes to the stability of the core material.

Example 4

Using the same method as in Example 1, 0.5 mL of methylmethacrylate monomer was added to polymerize the polymethylmethacrylate. The prepared cadmium sulfide / polymethyl methacrylate nanocomposite was confirmed by the transmission electron microscope to confirm the spherical particles of 25 nanometers.

Example 5

Using the same method as in Example 1, polymethylmethacrylate was polymerized by dispersing cadmium sulfide quantum dots treated with cerium in other nonpolar solvents such as heptane, octane, and isooctane. As a result of confirming the prepared nanocomposite through a transmission electron microscope, it was confirmed that the same spherical particles of 19.4 nm as in Example 1.

Example 6

Using the same method as in Example 1, polymethyl methacrylate was polymerized using quantum dot cadmium telluride as a core particle. It was confirmed that the prepared core / cell nanocomposite has a uniform size of about 19 nm and excellent dispersibility, and the intrinsic luminescence properties of the core material did not change, and thermal and optical stability were also maintained.

Example 7

0.1 ml of acrylonitrile monomer was injected using the same method as Example 1 to prepare a cadmium sulfide / polyacrylonitrile core / cell nanocomposite. As a result of confirming the prepared core / cell nanocomposite through a transmission electron microscope, a core / cell nanocomposite having a dispersibility of 20 nm was confirmed.

Example 8

Using the same method as in Example 1, 0.1 ml of pyrrole monomer was injected to polymerize polypyrrole, polyaniline, and poly (3,4 ethylenedioxythiophene), which are conductive polymers, on the cadmium sulfide quantum dot surface. As a result of confirming the prepared cadmium sulfide / conductive polymer nanocomposite through a transmission electron microscope, spherical particles having a size of 15 nm could be identified.

Example 9

Using the same method as in Example 1, in the process of treating the initiator on the surface of the cadmium sulfide quantum dots, 0.2 g of iron chloride (FeCl ₃ ) was added to recover using a centrifuge, and then 0.1 g of iron ions. The treated cadmium sulfide quantum dots were dispersed in 30 ml of hexane and 0.1 ml of pyrrole monomer was injected to prepare a cadmium sulfide / polypyrrole nanocomposite. As a result of confirming the prepared nanocomposite with a transmission electron microscope, spherical particles having a size of 12 nm could be identified.

      Example 10

Using the same method as in Example 1, in the process of treating the initiator on the surface of the cadmium sulfide quantum dots, 0.2 g of copper chloride (CuCl ₂ ) was added to recover using a centrifuge, 0.1 g of copper ions Cadmium sulfide quantum dots treated with were dispersed in 30 ml of hexane and 0.1 ml of pyrrole monomer was injected to prepare a cadmium sulfide / polypyrrole nanocomposite. As a result of confirming the prepared nanocomposite with a transmission electron microscope, spherical particles having a size of 10 nm could be identified.

1 is a transmission electron micrograph of cadmium sulfide used in Example 1 of the present invention;

2 is a transmission electron micrograph of the cadmium sulfide / polymethylmethacrylate core / cell nanocomposite prepared in Example 1 of the present invention;

3 is a Fourier infrared spectroscopy graph of cadmium sulfide and cadmium sulfide / polymethylmethacrylate core / cell nanocomposite prepared in Example 1 of the present invention;

4 is a light emission graph of cadmium sulfide and cadmium sulfide / polymethylmethacrylate core / cell nanocomposite prepared in Example 1 of the present invention.

FIG. 5 is an X-ray diffraction spectrogram of cadmium sulfide and cadmium sulfide / polymethylmethacrylate nanocomposites exposed for one month in the air and cadmium sulfide at the beginning of the present invention shown in Example 3 of the present invention.

Claims (6)

Diluting a solution comprising quantum dots prepared under a surfactant and reaction solvent having an average particle diameter of several nanometers to several tens of nanometers; Adding a cation-based metal initiator to adsorb the quantum dot surface; Redispersing the quantum dots treated with the initiator in a nonpolar solvent in which the initiator is not dissolved: Method of producing a quantum dot / polymer core-cell nanocomposite comprising the step of adding a monomer to the solvent to polymerize on the surface of the quantum dot. The method according to claim 1, wherein the quantum dots are cadmium telluride, cadmium selenide, zinc selenide, and the like. The method of claim 1, wherein the added cationic initiator is cerium ammonium nitrate, iron chloride, or copper chloride. The method according to claim 1, wherein the non-polar solvent to be redispersed is a nucleic acid, heptane, octane, isooctane. The method of claim 1, wherein the monomer to be polymerized is methylmethacrylate, acrylonitrile, divinylbenzene, pyrrole, aniline, 3,4 ethylenedioxythiophene. The method according to claim 1, wherein the polymerization time is 24 hours per hour.

Images