TWI421208B - Method to prepare nano-structure - Google Patents

Description

Preparation method of nano structure

The invention relates to a method for preparing a nanostructure, in particular to a method for preparing a nanostructure by using a supercritical fluid.

The application of nanostructures can include the fabrication of micro-semiconductor components or micro-optical components. In the future, forward-looking display components can be optimally obtained by introducing various nanostructures and utilizing the characteristics of the structure.

The currently known nanomaterials are the carbon nanotubes discovered by Dr. Iijima in 1991, while other nanowire materials can be roughly classified into two categories: metal and metal oxide. Metal-type nanomaterials such as gold (Au), silver (Ag), platinum (Pt), etc.; and in metal oxide nanomaterials, several materials having a wide band gap Such as indium oxide (In ₂ O ₃ ), zinc oxide (ZnO), titanium oxide (TiO ₂ ), magnesium oxide (MgO), tin oxide (SnO ₂ ), etc., which are most representative, and are currently commonly used to prepare nanostructures. The method includes the following: 1. using Vapor-Liquid-Solid process (hereinafter referred to as VLS growth method), 2. preparing by hydrothermal synthesis, 3. using anodized alumina template For the base of the stent, after filling the metal oxide material, the metal oxide nanostructure is formed by heat treatment, and 4. The chemical vapor deposition (hereinafter referred to as MOCVD) is used, and the organic metal source is used as a starting material. Chemical substitution and substitution are carried out in a carrier gas atmosphere to produce a nanostructure.

However, the formation of linear nanostructures by VLS growth method or hydrothermal method requires higher temperature (300-400 ° C) or longer time (12-24 hours), while the nanostructure is prepared by MOCVD. The composition is not easy to control and is still in the experimental stage, and there is still a short distance from commercialization; therefore, how to develop a simpler and more precise control of the growth of the nanostructure and its size in the process to improve the nanowire The commercial availability and the development of component materials for the next generation of nanoelectronics have been one of the important directions for researchers in this field.

Accordingly, it is an object of the present invention to provide a method of preparing a nanostructure.

Thus, the preparation method of the nanostructure of the present invention comprises the following two steps.

First, a substrate having a reaction zone is prepared, and the constituent material of the reaction zone is selected from the group consisting of an amphoteric metal, an amphoteric metal oxide, a transition metal, a transition metal oxide, and a combination thereof.

Next, the substrate is placed in a high pressure chamber, and a supercritical fluid composition containing water and carbon dioxide supercritical fluid is fed into the high pressure chamber under a reaction temperature of not less than 35 ° C and a pressure of not less than 1072 psi. The reaction is initiated in contact with the reaction zone to obtain the nanostructure.

The invention has the advantages that the nanostructure is prepared by the carbon dioxide supercritical fluid method, can be carried out at low temperature, the method is simple, and the process time can be effectively reduced and the size of the nanostructure can be controlled.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention.

Referring to Fig. 1, a preferred embodiment of the method for preparing a nanostructure of the present invention comprises the following two steps, and the nanostructure can be prepared simply and rapidly at a low temperature.

First, in step 11, a substrate having a reaction zone in direct contact with the outside is prepared, and the constituent material of the reaction zone is selected from the group consisting of an amphoteric metal, an amphoteric metal oxide, a transition metal, a transition metal oxide, and the like. Combined, and selected from the group consisting of an amphoteric metal, an amphoteric metal oxide, a transition metal, or a transition metal oxide which reacts with water under acidic conditions and under acidic conditions and is soluble in water; preferably, The amphoteric metal is selected from the group consisting of zinc, tin, and aluminum, and the amphoteric metal oxide is selected from the group consisting of zinc oxide, tin oxide, and aluminum oxide; the transition metal is selected from the group consisting of chromium, titanium, cobalt, nickel, and rhenium, and the transition metal The oxide is selected from the group consisting of chromium oxide, titanium oxide, cobalt oxide, and nickel oxide.

More preferably, the constituent material of the reaction zone is selected from the group consisting of zinc, tin, aluminum, zinc oxide, tin oxide, or aluminum oxide.

Next, in step 12, the substrate is placed in a high pressure chamber, and a supercritical fluid composition containing water and carbon dioxide supercritical fluid is fed into the reaction under a temperature of not less than 35 ° C and a pressure of not less than 1072 psi. The high pressure chamber is directly in contact with the reaction zone, and the supercritical fluid composition reacts with the reaction zone under the reaction conditions, and the reaction time is not more than 1 hour to obtain a nanostructure.

More specifically, the temperature and pressure of the high pressure chamber are in the temperature and pressure conditions for maintaining the supercritical phase of the carbon dioxide supercritical fluid, and the phase diagram of carbon dioxide shows that the supercritical phase of carbon dioxide is at a temperature greater than 31 ° C. And the pressure is formed under conditions of more than 1072 psi, and therefore, preferably, the step 12 is carried out under the conditions of a temperature of not less than 35 ° C and a pressure of not less than 1080 psi.

It should be noted that when the volume percentage of water is more than 20 vol%, the nucleation rate of water in the supercritical fluid of carbon dioxide is too fast, and it is easy to form excessive droplets on the surface of the reaction zone, and the expected naphthalene cannot be obtained. The rice structure, therefore, preferably, the volume percentage of water is not more than 10 vol%, and more preferably, the volume percentage of water is not more than 5 vol%, based on 100% of the total volume of the supercritical fluid composition.

It is worth mentioning that the supercritical fluid composition may further comprise an organic solvent for changing the surface tension of the water in the supercritical fluid composition, thereby changing the droplets formed on the surface of the reaction zone. The size is such that a different nanostructure is obtained. Preferably, the volume percentage of the organic solvent is not more than 20 vol%, and more preferably, the volume percentage of the organic solvent is not more than 10 vol%, and is the same as the volume percentage of water. The organic solvent may be selected from polar organic solvents. Preferably, the organic solvent is selected from the group consisting of alcohols, acids, or ketones; more preferably, the organic solvent is selected from the group consisting of methanol, ethanol, propanol, or acetone.

The present invention allows water to form droplets on the surface of the reaction zone under the reaction conditions of high pressure and supercritical fluid composition composed of carbon dioxide and water, so that the reaction zone and the droplet contact interface react; Since the droplet reacts with the carbon dioxide supercritical fluid to form carbonic acid, and the acidity of the droplet increases as it approaches the contact interface with the carbon dioxide supercritical fluid, the product formed by the reaction zone and the droplet reaction is The solubility between the droplet and the carbon dioxide supercritical fluid interface is poor, and the interface between the droplet and the carbon dioxide supercritical fluid is precipitated and deposited to obtain the nanostructure of the present invention, and at the same time can be changed by the addition of the organic solvent. The surface tension of the water is used to change the size of the formed droplets, and the diameter of the prepared linear nanostructure can be further controlled.

The above and other technical contents, features and effects of the present invention will be apparent from the following detailed description of the three specific examples, but it should be understood that the specific examples are only illustrative and should not be It is to be construed as limiting the implementation of the invention.

<Specific example 1>

A specific example 1 of the method for producing a nanostructure of the present invention is briefly described below.

First, a substrate having a carrier made of glass and a film reaction zone formed on the surface of the carrier and made of zinc and having a thickness of about 80 nm is prepared.

Next, the substrate is placed horizontally in the high pressure chamber, the temperature in the chamber is maintained at 60 ° C, and the pressure is maintained at 3000 psi, a 99.7 vol% carbon dioxide supercritical fluid and 0.3 vol% A supercritical fluid composition composed of water is injected into the high-pressure chamber, and a polycrystalline nanotube structure composed of zinc oxide can be obtained after a reaction time of 1 hour.

By forming a droplet of water on the surface of a reaction zone composed of zinc under high pressure and a reaction condition of a supercritical fluid composition composed of carbon dioxide and water, and contact of zinc and droplets under such high pressure conditions The interface reacts to form zinc hydroxide (Zn(OH) ₂ ); at the same time, the droplets react with the carbon dioxide supercritical fluid to form carbonic acid and the acidity increases with the contact interface with the carbon dioxide supercritical fluid, while zinc and water The zinc hydroxide formed after the reaction will react to form zinc oxide (ZnO) under the acidic condition, and the formed zinc oxide has different solubility under different acidic conditions, so the zinc oxide is in the droplet and in the droplet A difference in solubility is formed between the interface with the supercritical fluid of carbon dioxide, and a linear nanostructure of the present invention is obtained by depositing and depositing along the interface of the droplet and the supercritical fluid of carbon dioxide. 2 to FIG. 7, FIG. 2 is a scanning electron microscope (hereinafter referred to as SEM) photograph of the reaction zone of the specific example 1 before the reaction, and FIG. 3 and FIG. 4 show the substrate in the high pressure chamber and the supercritical fluid. SEM photograph of different magnifications of the reaction zone after the composition was reacted for 1 hour, and FIG. 5 is a transmission electron microscope (hereinafter referred to as TEM) photograph of the reaction zone after the substrate was reacted with the supercritical fluid composition in the high pressure chamber for 1 hour. Fig. 6 is an electron beam diffraction pattern of the nanostructure, and Fig. 7 is an analysis result of energy dispersive spectroscopy (hereinafter referred to as EDX) of the nanostructure by using a carbon-coated copper mesh as a supporting carrier.

As can be seen from FIG. 3 and FIG. 4, a large amount of tubular nanostructures can be obtained after the reaction zone is reacted with the supercritical fluid composition for 1 hour in the high pressure chamber, and the outer diameter of the nanostructure is about 35 as shown in FIG. ~50nm, the length is about 1.5μm, and the electron beam diffraction pattern of Fig. 6 and the EDX measurement result of Fig. 7 show that the nanostructure is composed of polycrystalline zinc oxide (ZnO).

<Specific example 2>

A specific example 2 of the preparation method of the nanostructure of the present invention is substantially the same as the specific example 1, except that the supercritical fluid composition of the specific example 2 is 99.4 vol% of carbon dioxide supercritical fluid, 0.3. Between vol% water and 0.3 vol% ethanol (CH ₃ CH ₂ OH).

Referring to FIGS. 8-13, FIG. 8, 9, and 10 are SEM photographs of different magnifications of the reaction zone after the substrate is reacted with the supercritical fluid composition in the high pressure chamber for 1 hour, and FIG. 11 is the substrate at a high pressure. TEM photograph of the reaction zone in the chamber after reacting with the supercritical fluid composition for 1 hour, FIG. 12 is an electron beam diffraction pattern of the nanostructure formed in the reaction zone, and FIG. 13 is a carbon-coated copper mesh as a support carrier pair. The nanostructure was analyzed by energy dispersive spectroscopy (hereinafter referred to as EDX).

The linear nanostructure prepared by the preparation method of the specific example 2 described above is substantially similar to the specific example 1, and therefore will not be further described, and more particularly, the supercritical fluid composition of the specific example 2 An organic solvent composed of ethanol is included to reduce the surface tension of water to reduce the particle size of the droplet formed on the surface of the reaction zone, and therefore, when the formed zinc oxide is supercritical along the droplet and carbon dioxide due to poor solubility When the fluid interface is deposited and deposited, the nanostructure with a small diameter is obtained because the droplet size is reduced.

8 and FIG. 9, when the reaction zone is reacted with the supercritical fluid composition in the high pressure chamber for 1 hour, a tubular nanostructure can be obtained, and the SEM and TEM results of FIGS. 10 and 11 show that The outer diameter of the nanostructure is about 15 nm and the length is about 2 μm. From the electron beam diffraction pattern of FIG. 12 and the EDX measurement result of FIG. 13, the nanostructure is composed of polycrystalline zinc oxide (ZnO). ) constitutes.

<Specific example 3>

A specific example 3 of the method for producing a nanostructure of the present invention is produced in substantially the same manner as in the specific example 1, except that the reaction zone of the specific example 3 is composed of zinc oxide having a thickness of about 100 nm.

In this embodiment, the reaction zone is composed of zinc oxide, which is soluble in the droplets under such high pressure conditions, and the zinc oxide dissolved in the droplets has different solubility under different pHs, so the oxidation is performed. Zinc forms a poor solubility between the droplets and the interface between the droplets and the supercritical fluid of carbon dioxide, and precipitates and deposits along the interface of the droplets and the supercritical fluid of carbon dioxide to obtain the nanostructure of the present invention.

14 to 18 and FIG. 14 are SEM photographs of the reaction zone of the specific example 3 before the reaction, and FIGS. 15 to 16 are reaction zones of the substrate after reacting with the supercritical fluid composition in the high-pressure chamber for 1 hour. The SEM and TEM photographs, FIG. 17 is an electron beam diffraction pattern of the nanostructure, and FIG. 18 is an EDX analysis result of the nanostructure by using a carbon-coated copper mesh as a supporting carrier.

15 and FIG. 16, when the reaction zone is reacted with the supercritical fluid composition in the high pressure chamber for 1 hour, a nanotube having an outer diameter of about 150 nm and a length of about 5 μm can be obtained, and the electron of FIG. 17 is obtained. The beam diffraction pattern and the EDX measurement result of Fig. 18 show that the nanostructure is composed of single crystal zinc oxide (ZnO).

In summary, the nanostructure of the present invention grown in a supercritical manner can be carried out not only at a low temperature (above 35 ° C) but also in a very short time (1 hour) to obtain a length of several micrometers to several tens of micrometers. The linear nanostructure, and the surface tension of the water in the supercritical fluid composition can be changed by the addition of the organic solvent, and the droplet size formed on the surface of the reaction zone can be further changed, and different diameters can be controlled. The linear nanostructure, and when the constituent material of the reaction zone is zinc oxide, the zinc oxide (ZnO) nanowire of single crystal structure can be obtained by the supercritical method of the present invention, and the process is simple and easy to control, and can be greatly reduced. The process time is indeed achieved by the purpose of the present invention.

The above is only the preferred embodiment and the specific examples of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent change according to the scope of the invention and the description of the invention. And modifications are still within the scope of the invention patent.

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12. . . step

1 is a flow chart showing a preferred embodiment of a method for preparing a nanostructure of the present invention;

Figure 2 is an SEM image showing the SEM photograph of the reaction zone of a specific example 1 of the method for preparing a nanostructure of the present invention before the reaction;

Figure 3 is an SEM image showing an SEM photograph of the reaction zone of the specific example 1 of the present invention after reacting with the supercritical fluid composition for 1 hour;

Figure 4 is an SEM image showing an SEM photograph of the reaction zone of the specific example 1 of the present invention after reacting with the supercritical fluid composition for 1 hour;

Figure 5 is a TEM image showing a TEM photograph of the reaction zone of the specific example 1 of the present invention after reacting with the supercritical fluid composition for 1 hour:

Figure 6 is an electron beam diffraction diagram illustrating the electron beam diffraction pattern of the nanostructure of the specific example 1 of the present invention;

Figure 7 is an energy dispersive spectrum diagram illustrating the energy dispersion spectrum of the nanostructure of the specific example 1 of the present invention;

Figure 8 is an SEM image showing an SEM photograph of the reaction zone of the specific example 2 of the present invention after reacting with the supercritical fluid composition for 1 hour;

Figure 9 is an SEM image showing an SEM photograph of the reaction zone of the specific example 2 of the present invention after reacting with the supercritical fluid composition for 1 hour;

Figure 10 is an SEM image showing an SEM photograph of the reaction zone of the specific example 2 of the present invention after reacting with the supercritical fluid composition for 1 hour;

Figure 11 is a TEM image showing a TEM photograph of the reaction zone of the specific example 2 of the present invention after reacting with the supercritical fluid composition for 1 hour;

Figure 12 is an electron beam diffraction diagram illustrating an electron beam diffraction pattern of the nanostructure of the specific example 2 of the present invention;

Figure 13 is an energy dispersive spectrum diagram illustrating the energy dispersion spectrum of the nanostructure of the specific example 3 of the present invention;

Figure 14 is an SEM image showing the SEM photograph of the reaction zone of a specific example 3 of the method for preparing a nanostructure of the present invention before the reaction;

Figure 15 is an SEM image showing an SEM photograph of the reaction zone of the specific example 3 of the present invention after reacting with the supercritical fluid composition for 1 hour;

Figure 16 is a TEM image showing a TEM photograph of the reaction zone of the specific example 3 of the present invention after reacting with the supercritical fluid composition for 1 hour;

Figure 17 is an electron beam diffraction diagram illustrating an electron beam diffraction pattern of the nanostructure of the specific example 3 of the present invention;

Fig. 18 is an energy dispersive spectrum chart showing the energy dispersion spectrum of the nanostructure of the specific example 3 of the present invention.

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Claims (7)

A method for preparing a nanostructure, comprising: (a) preparing a substrate having a reaction zone, wherein the constituent material of the reaction zone is selected from the group consisting of an amphoteric metal, an amphoteric metal oxide, a transition metal, a transition metal oxide, and the like (b) placing the substrate in a high pressure chamber and supercritically containing a supercritical fluid comprising water and carbon dioxide at a temperature of not less than 35 ° C and a pressure of not less than 1072 psi. The nanostructure is obtained by feeding the fluid composition into the high pressure chamber and contacting the reaction zone, wherein the volume percentage of the water is not more than 20 vol% based on the total volume of the supercritical fluid composition being 100 vol%. . The method for producing a nanostructure according to the first aspect of the invention, wherein the amphoteric metal is selected from the group consisting of zinc, tin, or aluminum, and the amphoteric metal oxide is selected from the group consisting of zinc oxide, tin oxide, or aluminum oxide. The method for preparing a nanostructure according to claim 1, wherein the transition metal is selected from the group consisting of chromium, titanium, cobalt, or nickel, and the transition metal oxide is selected from the group consisting of chromium oxide, titanium oxide, and cobalt oxide. Or nickel oxide. The method for preparing a nanostructure according to claim 1, wherein the supercritical fluid composition of the step (b) further comprises an organic solvent, and the total volume of the supercritical fluid composition is 100%. The volume percentage of the organic solvent is not more than 20 vol%. The method for producing a nanostructure according to the fourth aspect of the invention, wherein the organic solvent is selected from the group consisting of polar solvents. a method for preparing a nanostructure according to item 5 of the patent application scope, The organic solvent is selected from the group consisting of alcohols, acids, or ketones. The method for producing a nanostructure according to the sixth aspect of the invention, wherein the organic solvent is selected from the group consisting of methanol, ethanol, or propanol.