KR101089274B1 - Nanocomposite and preparation method thereof - Google Patents

Abstract

The present invention relates to a nano hybrid material and a method of manufacturing the same, and more particularly, a CdS quantum dot is formed between the titanium oxide by reacting a titanium oxide having a two-dimensional sheet structure having a surface negative charge with a CdS quantum dot having a positive charge. Titanium oxide of the two-dimensional sheet structure is gathered to have a three-dimensional structure in the form of a layer structure or a card house, and a pore in the range of 0.1 to 1,000 nm in the inner space of the three-dimensional structure of the layer structure or a card house form. The present invention relates to a nano hybrid material, wherein the nano hybrid material according to the present invention is chemically very stable, has a particularly large specific surface area, and has a high photoactivity, so that it can be applied to various environmental aspects such as catalysts and photocatalysts. Very useful in

Nano Hybrids, Photoactive, Titanium Oxide, CdS Quantum Dots

Description

NANOCOMPOSITE AND PREPARATION METHOD THEREOF

The present invention relates to a nano hybrid material and a method for manufacturing the same, and more particularly, a CdS quantum dot is formed between a titanium oxide having a two-dimensional sheet structure having a surface negative charge and a CdS quantum dot having a positive charge therebetween. Titanium oxide of the two-dimensional sheet structure is gathered to have a three-dimensional structure in the form of a layer structure or a card house, and a pore in the range of 0.1 to 1,000 nm in the inner space of the three-dimensional structure of the layer structure or a card house form. The present invention relates to a nano hybrid material and a method for producing the same.

In the past, various literatures have developed hybrid materials that are combinations of CdS quantum dots and layered compounds. However, synthetic methods that are harmful to the human body due to the gaseous reaction of H ₂ S, which is very toxic in the conventional development method, have been widely known. In the solution phase reaction, most of the reaction between the layered compound and the quantum dot is performed by ion exchange, which has a problem of diffusion of the quantum dot into the interlayer space and has a limitation in inserting a large amount of quantum dots between the layered layers of the layered compound. This is very disadvantageous in terms of surface area expansion. Therefore, in order to overcome these limitations, quantum dots having a specific size are controlled and synthesized, and the surface is developed at once to have a positive charge, and the surface is recombined with the exfoliated layered titanium oxide having a negative charge, which has uniform pores and has a large surface area. We want to develop a sieve.

Accordingly, the present invention is to provide a method for producing nano hybrids of layered titanium oxide-metal chalcogen quantum dot compounds that are chemically stable, have a large specific surface area, and have photoactivity to visible light as well as ultraviolet light.

In order to achieve the above technical problem, the present invention is formed by inserting a CdS quantum dot between the titanium oxide by reacting a titanium oxide having a two-dimensional sheet-like structure having a surface negative charge and a CdS quantum dot having a positive charge, the two-dimensional sheet Titanium oxide of the structure is gathered to have a three-dimensional structure in the form of a layer structure or a card house, and the nano-hybrid, characterized in that the pores in the range of 0.1 to 1,000 nm is formed in the inner space of the layer or card house three-dimensional structure Provide a sieve.

In another aspect, the present invention provides a nano-hybrid, characterized in that the ratio of Cd: S of the CdS quantum dots is prepared by adjusting the range of 1: 0.1 to 10 in molar ratio.

In addition, the present invention provides a nano-hybrid, characterized in that the CdS quantum dot is in the size of 0.2 to 10 nm range.

The invention also ⅰ) to prepare a titanium oxide of the formula _{H x / 4 Ti 2-x} / 4 □ x / 4 O 4 is expressed in a two-dimensional sheet having a surface structure and a negative charge; Ii) CdS quantum dots having positive charges react with the titanium oxide to allow CdS quantum dots to be inserted between the titanium oxides in the form of ionic bonds so that titanium oxides having a two-dimensional sheet structure are gathered to form a layered or card house type three-dimensional structure. It provides a method for producing a nano- hybrid comprising a step to have.

In another aspect, the present invention provides a method for producing a nano-hybrid, characterized in that the ratio of Cd: S of the CdS quantum dots is prepared in a molar ratio of 1: 0.1 to 10 range.

The nano hybrid of the present invention provides a nano hybrid material of a layered titanium oxide and a quantum dot metal chalcogen compound which is chemically stable, has a large specific surface area, and is excellent in light activity, and a method of preparing the same. In the present invention, the visible light responsiveness and the large specific surface area are very advantageous for catalyst or photocatalyst properties, and thus can be usefully used for various environmental catalysts.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The nano hybrid material of the present invention is formed by reacting a titanium oxide having a two-dimensional sheet-like structure having surface negative charges with a CdS quantum dot having a positive charge, thereby inserting CdS quantum dots between the titanium oxides, and having a titanium having the two-dimensional sheet-like structure. Oxides are aggregated to have a three-dimensional structure in the form of a layered or card house, characterized in that the pores in the range of 0.1 to 1,000 nm in the inner space of the three-dimensional structure of the layered or card house form.

1 is a diagram schematically illustrating a process of manufacturing a nano hybrid of the present invention. The initial starting material was synthesized with a layered titanium oxide Cs _0.67 Ti _1.83 □ _0.17 O ₄ at high temperature and stirred with a predetermined acid solvent and Cs _0.67 Ti _1.83 □ _0.17 O ₄ compound to form H _0.67 Ti _1.83 □ _0.17 O _{4 ·} H ₂ O Synthesize. Thereafter, the mixture is reacted with a solvent containing alkyl ammonium again to obtain a layered titanium oxide colloid exfoliated. In addition, the method of Example 2 below synthesizes a quantum dot having a positive charge on the surface. In this case, the specific quantum dot size may be adjusted by adjusting Cd: S. Finally, nano hybrid materials having a certain size of micro / mesopores can be developed by reacting a layered titanium oxide having a negatively charged surface and a quantum dot having a positively charged surface at a predetermined ratio.

Hereinafter, the present invention will be described in more detail with reference to examples which are preferred embodiments of the present invention.

Example 1 (Separated Laminated Titanium Oxide Synthesis with Surface Negative Charge)

Cs _0.67 Ti _1.83 □ _0.17 O ₄ was prepared using cesium carbonate (Cs ₂ CO ₃ ) and titanium dioxide (TiO ₂ ) (“□” in the formula means vacancy). Cesium carbonate and titanium dioxide were mixed well according to the chemical amount, and mixed at the same time for about 1 hour in the mortar at the same time and heat-treated for 24 hours in 750 ℃ air. For the optimized synthesis, the heat treated compound was finely divided again, and then a specimen was prepared and heat treated again in an air at 800 ° C. for 24 hours. As a result, Cs _0.67 Ti _1.83 □ _0.17 O _{4 in the} form of lepidocrocite having a solid and orthorhombic layer structure was produced. The prepared Cs _0.67 Ti _1.83 □ _0.17 O ₄ was acid-treated to prepare H _0.67 Ti _1.83 □ _0.17 O ₄ · H ₂ O ion-exchanged with protons (H ⁺ ). First, 100 ml of an aqueous 1 M hydrochloric acid solution was added per 1 g of Cs _0.67 Ti _1.83 □ _0.17 O _4, followed by strong stirring. At this time, it was repeated five times while changing a new acid aqueous solution every day for three days. Acid treated powders were collected using a centrifuge and dried in an oven at 60 ° C. to remove moisture. The dried to ensure that the X-ray diffraction analysis of the Cs _0.67 Ti _1.83 □ _0.17 O ₄ is ion-exchanged with Cs ions instead of protons (H ⁺⁾ was confirmed that the _{H 0.67 Ti 1.83 □ 0.17 O 4} · H 2 O are formed. The prepared H _0.67 Ti _1.83 □ _0.17 O ₄ · H ₂ O was subjected to cation treatment to prepare exfoliated titanium oxide having a negative charge. First, the H _0.67 Ti _1.83 O ₄ · H ₂ O sample is finely divided, and in order to exfoliate the titanium oxide, 100 ml of distilled water is added per 0.4 g of H _0.67 Ti _1.83 □ _0.17 O ₄ · H ₂ O sample, and bulky One cation, TBA.OH (Tetrabuthylammonium hydroxide), was sufficiently added so that the mole ratio of H _0.67 Ti _1.83 □ _0.17 O ₄ · H ₂ O was 3: 1. The mixed solution was then vigorously stirred for 10 days. Thereafter, to separate H _0.67 Ti _1.83 □ _0.17 O ₄ · H ₂ O samples that were not ion-exchanged with cations, they were separated by a centrifuge (10,000 rpm, 10 minutes) and the supernatants were collected separately. At this time, the supernatant was cloudy, and a titanium oxide having a negative charge in the colloidal solution state was obtained through the same process.

Example 2 (CdS quantum dot synthesis with surface positive charges of specific size)

2 is a method for synthesizing the quantum dot CdS having the positively charged surface described in Example 2. FIG. As shown in FIG. 2, the synthesis of CdS quantum dots was performed as follows. First, 200 ml of distilled water, a solvent, is added with thioacetamide as a raw material of Cd acetate dihydrate and S, and 2-mercaptoethylamine hydrochloride as a raw material for positive charge on the surface, and reacted at 40 and 60 degrees for 5 hours at reflux. After the reaction the color of the solution is light yellow. Concentrate the solution to 10 ml using an evaporator. After washing with 2-propanol and distilled water, the concentrated solution is washed several times to remove excess residue. After rinsing, the separator is finally separated by centrifugation and dried in a vacuum oven at 35 ° C for 12 hours. In this way, the powder was obtained by adjusting the molar ratio of Cd and S (Cd: S = 3: 1, 1: 1, 1: 3, 1: 5).

3 is a powder X-ray diffraction pattern of the quantum dots synthesized in Example 2. FIG. The graph on the left side of the figure is a pattern adjusted by adjusting the molar ratio of Cd: S. XRD results of (a) 3: 1, (b) 1: 1, (c) 1: 3, and (d) 1: 5 showed sharper patterns as the amount of S increased. have. This indicates that the grains of the quantum dot particles become larger. The figure on the right shows that the pattern of the synthesized quantum dots has cubic crystal structure. In addition, Figure 4 shows the UV-vis spectrum of the quantum dots synthesized in Example 2. Depending on the size, the first exiton peak between 350 and 450 nm is shifted to longer wavelength as the amount of S increases during synthesis. The size and the structure of the former are due to the change in the band structure due to the quantum confinement effect. As the size becomes smaller (a), the bule shift can be seen. In addition, the band wavelengths were theoretically calculated to predict the size, and it was confirmed that they had (a) 2.47, (b) 2.71, (c) 3.58, and (d) 3.75 nm. 5 is a quantum dot synthesized in Example 2 of Cd: S = 1: 1 by transmission electron microscopy (transmission electron microscopy), as shown in the picture confirmed a spherical quantum dot of about 2.6 ~ 7nm size can do. Therefore, the spectrum of FIG. 4 clearly shows that the results closely match the theoretically predicted quantum dot size. 6 is a photograph of a quantum dot obtained in Example 2. FIG. On the left is an image photograph obtained as a powder, which shows that the powder is well dispersed when put in water.

Example 3 (Preparation of nano hybrids through hybridization of quantum dots and exfoliated layered titanium oxide)

Nanocomposites were developed by reacting a layered titanium oxide suspension having a negatively charged surface and a quantum dot CdS having a positively charged surface, respectively, obtained in Examples 1 and 2, respectively. First, the quantum dot is vigorously stirred with the magnetic bar in distilled water. In addition, the ultrasound was applied for 5 minutes in the middle. Slowly drop a titanium oxide suspension (titanium oxide suspension 0.1g / L, pH = 9) into a quantum dot colloidal solution that is well dispersed in a stirrer through a burette.

  After this reaction is continued, stirring is continued for 3 days at room temperature. After completion of the reaction, CdS remaining without reaction was separated by a filter and a centrifuge through a pressure reducer, and then rinsed several times with 50:50 wt.% Of ethanol and water, and finally rinsed again with water. Finally, the resultant was separated by a centrifuge and dried in a vacuum oven at 35 degrees to obtain a nano hybrid.

7 is (a) Cs _0.67 Ti _1.83 □ _0.17 O ₄ compound, (b) H _0.67 Ti _1.83 □ _0.17 , which is compared with the powder X-ray diffraction pattern of the nanocomposite obtained in Example 3 O ₄ H ₂ O, and (c) exfoliated Ti _1.83 O ₄ nanosheet colloid. Cs _0.67 Ti _1.83 □ _0.17 O ₄ synthesized by the solid phase synthesis method can be confirmed to have a body-centered orthorhombic unit cell. In addition, in the case of H _0.67 Ti _1.83 □ _0.17 O ₄ · H ₂ O acid treated with 1M HCl, the (020) peak moved more forward than Cs _0.67 Ti _1.83 □ _0.17 O ₄ . This indicates that the interlayer space is expanded by the exchange of Cs ⁺ ions with H ₃ O ⁺ , and the increase in intensity of the (020) peak is strongly anisotropic in the (020) plane direction. (c) shows no pattern as XRD result of exfoliated layered titanium oxide colloid obtained by strong stirring with H _0.67 Ti _1.83 □ _0.17 O ₄ H ₂ O and bulky cation TBA.OH (Tetrabuthylammonium hydroxide) It is not visible because it is disordered due to delamination. Finally, the developed nano hybrids were recombined with electrostatic attraction to have a two-dimensional structure, and accordingly, only the (010) peak could be seen. At this time, the interlayer distance of (010) is about 1.44 nm and the distance between the layers, that is, the gallery height is about 0.74 nm, considering that the distance of the titanate layer is about ˜0.7 nm. Therefore, the size of quantum dots used at the time of synthesis is about 2.7-3.0nm, but only quantum dots of less than 1nm at the time of generation was considered to participate in interlayer insertion.

FIG. 8 is a graph showing weight loss with thermal temperature by a thermogravimetric analysis of a nano hybrid obtained in Example 3. FIG. Decomposition is carried out in three stages, which is reduced by evaporation of water on the surface up to about 130 degrees, and is reduced by oxidation of -OH groups and some lyric organic matter on the surface at 130 degrees and 400 degrees. Finally, the sharp decrease at 500 degrees is a step in which the crystal of the layered titanium oxide is transformed into another structure. In addition, Figure 9 is an image of a transmission electron microscopy (transmission electron microscopy) measuring the shape of the nano-hybrid obtained in Example 3. (a) is an image of the cross section after hybridization. Black lines represent layered titanium oxide with quantum dots between layers. It can also be seen that the layers are well aligned and recombined. The image of (b) is the image taken from above, and the wide plate is a layered titanium oxide, in which small, spherical quantum dots are distributed.

FIG. 10 is an energy dispersive x-ray spectroscopy spectrum measured to analyze qualitative and quantitative elements of the nanocomposite obtained in Example 3. FIG. As can be seen in Figure 10, in the case of the nano- hybrid obtained in Example 3 it can be seen that the presence of Ti, Cd, S well. In addition, it can be confirmed that the quantitative results of Cd and S are 1: 1.

FIG. 11 is an EDS electron mapping (energy dispersive x-ray spectroscopy-electron mapping) scan to confirm the distribution of components of the nanocomposite obtained in Example 3. FIG. The scan results show that Ti and Cd, S, and C are evenly distributed.

12 is a diffuse reflectance UV-vis spectrum showing the electron band structure of the nano hybrid obtained in Example 3. FIG. It can be seen that the acid-treated layered titanium oxide, which is a control group, has a band structure of about 3.4 eV. This is the absorption band in the ultraviolet region. In addition, it was confirmed that the CdS (manufactured with 1: 1) has an electron band structure of about ˜3.2 eV. However, the two materials were found to have an electronic band structure of about 2.7 ~ 2.8 eV after hybridization. It can be seen that the two materials are modified into a new band structure through hybridization to absorb not only ultraviolet light but also light in the visible light region.

13 is a nitrogen adsorption graph showing the specific surface area size before and after hybridization of the nanohybrids obtained in Example 3. FIG. In the case of the starting material Cs _0.67 Ti _1.83 □ _0.17 O ₄ , the specific surface area showed a small value of almost 1 m ² / g. In addition, the acid-treated layered titanium oxide H _0.67 Ti _1.83 □ _0.17 O _{4 ·} H ₂ O also showed a value of about ~ 10 m ² / g. However, after hybridization, it showed a very extended surface area of about 126.70 m ² / g. Therefore, it showed about 100 times more surface area increase than the starting material. In addition, strong nitrogen adsorption was observed at the initial relative pressure of the hysteresis loop, indicating that a large amount of micropores exist in the material. In addition, as a result of analyzing mesopores by the BJH method using the adsorption curve, it was confirmed that mesopores of about 3-4 nm were distributed. As a result, the pores that did not exist before the hybridization can be seen that the formation of a large amount of pores after the hybridization contributes to the increase of the specific surface. As a result, micropores are generated by inserting interlayers of layered titanium oxide into small layers of average size (ie 0.3 nm <1.5 nm) and micropores between various grains, and mesopores (ie 3 nm <pores <7 nm) is considered to be a case where a three-dimensional house of cards form is generated by inserting quantum dots between grain boundaries of titanium oxides.

An embodiment of the present invention described above should not be construed as limiting the technical spirit of the present invention. The scope of protection of the present invention is limited only by the matters described in the claims, and those skilled in the art can modify and change the technical idea of the present invention in various forms. Therefore, such improvements and modifications will fall within the protection scope of the present invention, as will be apparent to those skilled in the art.

1 is a diagram illustrating the manufacturing process of the nano-hybrid of the present invention

FIG. 2 is a flow chart showing a synthesis sequence for preparing CdS quantum dots with a surface prepared according to Example 2 of the present invention.

3 is a powder X-ray diffraction graph of quantum dot CdS having a positively charged surface prepared according to Example 2 of the present invention.

4 is a UV-vis spectrum of the quantum dot CdS synthesized for each concentration of Cd and S prepared according to Example 2 of the present invention.

FIG. 5 is a photograph of a transmission electron microscopy measuring the shape of the quantum dot CdS prepared according to Example 2 of the present invention and the corresponding illustration.

6 is an image photograph of a quantum dot prepared according to Example 2 of the present invention

FIG. 7 is a powder X-ray diffraction measurement graph for a nano hybrid prepared according to Example 3 of the present invention. FIG. (a) is the starting layered layered titanium oxide Cs _0.67 Ti _1.83 □ _0.17 O ₄ , (b) is the acid-treated layered titanium oxide H _0.67 Ti _1.83 □ _0.17 O _{4 ·} H ₂ O, (c) exfoliated layered Titanium oxide colloid, (d) A nanocomposite synthesized by recombination with a quantum dot having a positively charged surface and a titanium oxide colloid having a negatively charged surface.

Figure 8 is a graph showing the weight loss with thermal temperature by the thermogravimetric analysis (thermogravimetric analysis) of the prepared product of the nano hybrid prepared according to Example 2 of the present invention.

FIG. 9 is an image photograph of a transmission electron microscopy measuring the shape of a nano hybrid prepared according to Example 2 of the present invention. (a) is a cross-sectional photograph and (b) is a photograph measured from above.

FIG. 10 is an energy dispersive x-ray spectroscopy spectrum measured to analyze qualitative and quantitative elements of a nanocomposite prepared according to Example 2 of the present invention. FIG.

11 is an EDS electron mapping (energy dispersive x-ray spectroscopy-electron mapping) photograph for confirming the distribution of the components of the nanocomposite prepared according to Example 2 of the present invention.

12 is a diffuse reflectance UV-vis spectrum showing the electronic band structure before and after hybridization.

13 is a nitrogen adsorption plot showing the specific surface area size before and after hybridization

Claims (5)

CdS quantum dots are inserted between the titanium oxides by reacting titanium oxide having a two-dimensional sheet-like structure having surface negative charges with CdS quantum dots having positive charges,  The titanium oxide of the two-dimensional sheet structure is gathered to have a three-dimensional structure in the form of a layer structure or a card house, and the average pore of 0.1 to 1,000 nm is formed in the inner space of the three-dimensional structure of the layer structure or a card house form. Nano hybrids characterized by. The method of claim 1, The CdS quantum dot is a nano-hybrid, characterized in that the Cd: S ratio is prepared by adjusting the range of 1: 0.1 to 10 in molar ratio. The method of claim 1, The CdS quantum dots are nano-hybrid, characterized in that the size in the range of 0.2 to 10 nm. Iii) preparing a titanium oxide having a two-dimensional sheet structure having the surface negative charge represented by the formula H _{x / 4} Ti _{2-x / 4} □ _{x / 4} O ₄ (wherein “□” denotes vacancy and , x / 4 is 0.67 to 0.73); Ii) CdS quantum dots having positive charges react with the titanium oxide to allow CdS quantum dots to be inserted between the titanium oxides in the form of ionic bonds so that titanium oxides having a two-dimensional sheet structure are gathered to form a layered or card house type three-dimensional structure. Nanocomposite manufacturing method comprising the step of having a. 5. The method of claim 4, The CdS quantum dot is a nano-hybrid manufacturing method, characterized in that the Cd: S ratio is prepared by adjusting the range of 1: 0.1 to 10 in molar ratio.

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