WO2009116829A1

WO2009116829A1 - Method for dispersing nanostructures and method for adsorbing nanostructures on the surface of solid using the dispersed nanostructures

Info

Publication number: WO2009116829A1
Application number: PCT/KR2009/001423
Authority: WO
Inventors: Seung-Hun Hong; Kwang Heo; Min-Baek Lee
Original assignee: Seoul National University Industry Foundation
Priority date: 2008-03-20
Filing date: 2009-03-19
Publication date: 2009-09-24

Abstract

Disclosed is a method for dispersing nanostructures, the method including: adsorbing functional molecules on the surface of nanostructures; and dispersing the nanostructures on which the functional molecules are adsorbed in a solvent to form a nanostructure-containing solution. Moreover, disclosed is a method for selectively adsorbing nanostructures, the method including: adsorbing functional molecules on the surface of nanostructures; dispersing the nanostructures on which the functional molecules are adsorbed in a solvent to form a nanostructure-containing solution; patterning a molecular membrane for patterning a solid surface on which the nanostructures are to be adsorbed with a molecular membrane for patterning, which has a higher interface energy for the nanostructures than that of the solid surface, in a predetermined form; and immersing the patterned solid in the nanostructure-containing solution or dripping the nanostructure-containing solution onto the solid surface on which the nanostructures are to be adsorbed and evaporating solvent from the solution to selectively adsorb and align the nanostructures on the surface of solid on which the molecular membrane for patterning has not been formed.

Description

METHOD FOR DISPERSING NANOSTRUCTURES AND METHOD FOR ADSORBING NANOSTRUCTURES ON THE SURFACE OF SOLID USING THE DISPERSED NANOSTRUCTURES

The present invention relates to a method for dispersing nanostructures in a solvent and a method for selectively adsorbing the nanostructures dispersed by the same on the surface of solid; and, more particularly, to a method for improving dispersibility of nanostructures in a solvent by combining functional molecules on the surface of the nanostructures and a method for selectively adsorbing dispersed nanostructures to have a specific orientation at a desired location on the surface of solid.

With the current rapid progress of research on nanotechnology in a wide range of applications, various efforts have been made to develop devices using nanostructures, such as nanowires or nanotubes having significantly enhanced performances compared to conventional semiconductor devices.

According to a method for manufacturing nanostructures such as nanowires most commonly conducted, nanostructures are synthesized in solution or in the form of powder. Thus, in order to manufacture devices using nanostructures synthesized in this way, nanostructures need to be adsorbed on specific locations of a solid surface and be aligned with a desired orientation. In order to attain commercialization of device development using nanostructures actually, adsorption and alignment of nanostructures is the most important than anything else.

Following methods are known as technologies for adsorbing and aligning nanostructures.

Flow cell method (US 2003/00899) refers to a method by which nanowires are adsorbed on specific locations of the surface of solid, a fluid is subsequently run to control the direction, and the nanowires are induced to be aligned in the direction of the flow. According to the method, nanowires may be all aligned on a large area in the same direction, but it is very difficult to control the nanowires to have a desired orientation on a local area.

The method for aligning carbon nanotubes on a solid surface using linker molecules (See Nature 425, 36 (2003)) is to adsorb nanotubes on specific locations by patterning two different kinds of molecular membranes on the solid surface and using a difference in the degree of adsorption of nanotubes on the surface of each molecular membrane. In the method, because nanotubes are adsorbed on a molecular membrane, they are aligned in the direction of a molecular membrane pattern, and the direction and position of nanowires may be locally controlled as desired, unlike the flow cell method as described above. However, due to adsorption of nanowires using molecules with chemical functional groups as linker molecules, there may be problems such as contaminating nanowires or samples.

A method for positioning and aligning nanowires using an anti-adsorption molecular membrane pattern is proposed to solve these problems. The method is to use natural adsorptivities that all solid surfaces have. According to the method, all regions of the solid surface, except for locations on which nanowires are to be adsorbed, are patterned with an anti-adsorption molecular membrane which has a very low adsorptivity with nanowires, samples having a patterned surface are put into a nanowires-containing solution to adsorb the nanowires on a surface which is not covered with an anti-adsorption molecular membrane and align them in the shape of the pattern.

However, because in general nanostructures such as nanowires are not well dispersed in a solvent, it is not only difficult for nanostructures to be adsorbed on a solid surface, but also devices may not be manufactured using various kinds of nanostructures such as nanotubes, nanowires, and nanoparticles simultaneously. Furthermore, it is impossible to manufacture a complex structure, not a simple connection.

An embodiment of the present invention is directed to providing a method for dispersing nanostructures and a method for selectively adsorbing the nanostructures dispersed by the same on the surface of solid to be used in manufacture of devices by adsorbing and aligning the nanostructures with the improved dispersibility on desired locations of the surface of solid to have a specific orientation.

Other objects and advantages of the present invention can be understood by the following description, and become apparent with reference to the embodiments of the present invention. Also, it is obvious to those skilled in the art of the present invention that the objects and advantages of the present invention can be realized by the means as claimed and combinations thereof.

In accordance with an aspect of the present invention, there is provided a method for dispersing nanostructures, the method including: adsorbing functional molecules on the surface of nanostructures; and dispersing the nanostructures on which the functional molecules are adsorbed in a solvent to form a nanostructure-containing solution.

In accordance with another aspect of the present invention, there is provided a method for selectively adsorbing nanostructures, the method including: adsorbing functional molecules on the surface of nanostructures; dispersing the nanostructures on which the functional molecules are adsorbed in a solvent to form a nanostructure-containing solution; patterning a solid surface on which the nanostructures are to be adsorbed with a molecular membrane for patterning, which has a higher interface energy for the nanostructures than that of the solid surface, in a predetermined form; and immersing the patterned solid in the nanostructure-containing solution to selectively adsorb and align the nanostructures on the surface of solid on which the molecular membrane for patterning has not been formed.

In accordance with another aspect of the present invention, there is provided a method for selectively adsorbing nanostructures, comprising; adsorbing functional molecules on the surface of nanostructures; dispersing the nanostructures on which the functional molecules are adsorbed in a solvent to form a nanostructure-containing solution; patterning a solid surface on which the nanostructures are to be adsorbed with a molecular membrane for patterning, which has a higher interface energy for the nanostructures than that of the solid surface, in a predetermined form; and dripping the nanostructure-containing solution onto the solid surface on which the nanostructures are to be adsorbed and evaporating solvent from the solution to selectively adsorb and align the nanostructures on the surface of solid on which the molecular membrane for patterning has not been formed.

According to the present invention, the dispersibility of nanostructures in a solvent may be improved by adsorbing functional molecules on the nanostructures. Furthermore, nanostructures may be dispersed efficiently in various kinds of solvents by appropriately selecting hydrophobic or hydrophilic molecules as functional molecules to be adsorbed on the nanostructures according to a kind of solvent in which nanostructures are to be dispersed.

In addition, nanostructures may be selectively adsorbed and aligned to have a specific orientation on desired locations of a solid surface more efficiently by using a nanostructure-containing solution with the improved dispersibility.

According to the method of the present invention, devices may be manufactured by using various-shaped nanostructures such as nanotubes, nanowires, and nanoparticles simultaneously, and a possible complex structure manufacture, not a simple connection may lead to commercialization of devices using nanostructures.

Fig. 1 shows a schematic illustration of a method for dispersing nanostructures in accordance with Example 1.

Fig. 2 shows a schematic illustration of a method for selectively adsorbing nanostructures in accordance with Example 3.

Fig. 3 shows a schematic illustration of a method for selectively adsorbing nanostructures in accordance with Example 5.

Figs. 4 and 5 show SEM images of silicon nanowires selectively adsorbed on a silicon surface formed in accordance with Example 3 (Fig. 5 is a enlarged image of Fig. 4).

Figs. 6 and 7 show SEM images of silicon nanowires selectively adsorbed on a gold surface formed in accordance with Example 5 (Fig. 7 is an enlarged image of Fig. 6).

The advantages, features and aspects of the invention will become apparent from the following description of the embodiments with reference to the accompanying drawings, which is set forth hereinafter.

In one embodiment of the present invention, a method for dispersing nanostructures is characterized by the ability to disperse nanostructures effectively in a solvent by adsorbing appropriate functional molecules on the surface of the nanostructures according to the properties of the solvent in which the nanostructures are to be dispersed.

In the present invention, the nanostructure may be selected from nanowire, nanoparticle, nanotube, or a mixture thereof.

Nanostructures grown according to a known method may improve their adsorption efficiency when the nanostructures undergo a cleaning process and are subsequently adsorbed on a solid surface such as an oxide surface. The cleaning of nanostructures may be performed by treating a substrate on which the nanostructures are grown with a piranha cleaning (sulfuric acid: hydrogen peroxide = 3:1) or performing a plasma cleaning on the same substrate with equipment such as a plasma cleaner.

A functional molecule useful in the present invention may be selected according to a kind of solvent, and for example, a hydrophilic molecule is preferred when the solvent is a hydrophilic solvent, and a hydrophobic molecule is preferred when the solvent is a hydrophobic solvent.

A molecule with sufficient surface charges, such as a molecule having NH₃ or COOH, may be useful as a hydrophilic molecule.

A specific example of an available hydrophilic molecule may be a molecule selected from the group consisting of aminopropyltriethoxysilane (APTES), (3-mercaptopropyl)-triethoxysilane (MPTMS), 16-mercaptohexadecanoic acid (MHA), cystamine, and a mixture thereof.

Besides, among compounds represented by R-SH, RSSR' (disulfide), RSR' (sulfide), RSO₂H, R₃P, RNC, RSiCl₃, RSi(OR')₃, (RCOO)₂(neat), RCH=CH₂, RLi, RMgX, RCOOH, RCONHOH, and RPO₃H₂ (where R represents a substituent), a molecule where R contains NH₃ or COOH, or a molecule where R contains DNA or a protein may be an example of the hydrophilic molecules.

A specific example of an available hydrophobic molecule may be a molecule selected from the group consisting of octadecyltrichlorosilane (OTS), octadecyltrimethoxysilane (OTMS), octadecyltriethoxysilane (OTE), octadecanethiol (ODT), and a mixture thereof.

Besides, among compounds represented by R-SH, Ar-SH, RSSR' (disulfide), RSR' (sulfide), RSO₂H, R₃P, RNC, RSiCl₃, RSi(OR')₃, (RCOO)₂(neat), RCH=CH₂, RLi, RMgX, RCOOH, RCONHOH, RPO₃H₂ (where R and Ar represent a substituent, respectively), a molecule which shows hydrophobic character as a compound except for compounds useful as a hydrophilic molecule as described above, for example, a saturated aliphatic hydrocarbon or an aromatic molecule may be used. C₁₂H₂₅SH, C₆H₅SH, n-hexadecanethiol, n-docosanethiol, C₁₀H₂₁SH, C₈H₁₇SH, C₆H₁₃SH, (C₂₂H₄₅)₂S₂ (C₁₉H₃₉)₂S₂, [CH₃(CH₂)₁₅S]₂, C₆H₅-SO₂H, (C₆H₁₁)₃P, (C₅H₆)Fe(C₅H₅)-(CH₂)₁₂-NC, C₁₀H₂₁SiCl₃, C₁₂H₂₅SiCl₃, C₁₆H₃₃SiCl₃, C₁₂H₂₅SiCl₃, CH₂=CHCH₂SiCl₃, [CH₃(CH₂)₁₀COO]₂, [CH₃(CH₂)₁₆COO]₂, CH₃(CH₂)₁₅CH=CH₂, CH₃(CH₂)₈CH=CH₂, C₄H₉Li, C₁₈H₃₇Li, C₄H₉MgX (X = Br or Cl), C₁₂H₂₅MgX (X = Br or Cl), C₁₅H₃₁COOH, and H₂C=CH(CH₂)₁₉COOH may be useful as a specific example.

Adsorption of functional molecules on nanostructures may be performed by immersing the nanostructures in a functional molecule-containing solution or exposing the nanostructures to a functional molecule-containing gas.

The time for immersion in a functional molecule-containing solution or exposure to a functional molecule-containing gas may be appropriately selected according to a kind of functional molecule. For example, the time is preferably 1 sec to 10 days, more preferably 1 min to 24 hours, even more preferably 10 min to 10 hours, particularly preferably 20 min to 1 hour. When the time is shorter than the time range, the dispersibility in a solvent may not be improved because the functional molecules may not be adsorbed on the surface of the nanostructures to a sufficient degree. In addition, when the time is longer than the time range, the dispersion is not efficient because the improvement in adsorption of functional molecules caused by the time increase may not be expected any more, and in case of specific functional molecules, for example, molecules with silane groups, dispersion may be rather inhibited due to possible aggregation of functional molecules on the surface of the nanostructures.

A functional molecule-containing solution is a solution formed from dispersion of functional molecules in an appropriate solvent, and may be prepared by dispersing hydrophilic functional molecules in a hydrophilic solvent and hydrophobic functional molecules in a hydrophobic solvent.

A particularly preferred example of a hydrophilic solvent available in formation of the solution may be a solvent selected from the group consisting of deionized water (DI-water), ethanol, methanol, 1,2-dichlorobenzene, isopropyl alcohol (IPA) and a mixture thereof. In addition, a particularly preferred example of a hydrophobic solvent may be a solvent selected from the group consisting of hexane, benzene, and a mixture thereof.

In one embodiment of the present invention, after functional molecules are adsorbed on the surface of nanostructures by immersing the nanostructures in a functional molecule-containing solution or exposing the nanostructures to a functional molecule-containing gas, cleaning of the nanostructures may be further included selectively. The cleaning may be suitably performed by a method known to the art, and for example, residues or impurities may be removed by cleaning the nanostructures with acetone or ethanol.

A functional molecule-containing gas may be formed by putting functional molecules into a sealed container and heating it. The heating temperature may be appropriately selected according to a kind of functional molecule, and a functional molecule-containing gas may be formed by heating the container, for example, at a temperature of 50 to 200 ℃.

In one embodiment of the present invention, functional molecules may be adsorbed on the surface of nanostructures by disposing the nanostructures and the functional molecules apart in a sealed container, and then heating the container at a temperature of 50 to 200 ℃.

Thus, a nanostructure-containing solution may be formed by dispersing nanostructures on the surface of which functional molecules are adsorbed in a desired solvent.

As described above, a solvent in which nanostructures are to be dispersed may be selected according to a kind of functional molecule adsorbed on the surface of nanostructures. When the functional molecule is a hydrophilic molecule, the functionalized nanostructures may be dispersed in a hydrophilic solvent, and when the functional molecule is a hydrophobic molecule, the functionalized nanostructures may be dispersed in a hydrophobic solvent.

An example of the hydrophilic or hydrophobic solvent may be a hydrophilic or hydrophobic solvent exemplified in formation of the functional molecule-containing solution as described above, but is not limited thereto. An example of a particularly preferred hydrophilic solvent may be a solvent selected from the group consisting of deionized water (DI-water), ethanol, methanol, 1,2-dichlorobenzene, isopropyl alcohol (IPA), and a mixture thereof. An example of a particularly preferred hydrophobic solvent may be a solvent selected from the group consisting of hexane, benzene, and a mixture thereof.

For efficient dispersion of nanostructures, nanostructures are put into a solvent and the resulting solution is dispersed in an ultrasonic cleaner for a suitable time. The time for the ultrasonic cleaning may be appropriately selected for controlling concentration of a nanostructure solution and length of nanostructures, and for example, the time for ultrasonic cleaning is 1 sec to 1 hour, preferably 5 sec to 30 min, more particularly 30 sec to 10 min, particularly preferably 1 min to 2 min. When the time for ultrasonic cleaning is even shorter than the time range, the concentration of the nanostructure solution becomes too low, and when the cleaning time is longer than the time range, the nanostructures may be broken.

According to a method for dispersing nanostructures in one embodiment of the present invention, dispersibility of nanostructures may be improved by adsorbing appropriate functional molecules on the surface of nanostructures according to a kind of solvent to be dispersed, leading to efficient dispersion of the nanostructures.

In one embodiment of the present invention, a method for selectively adsorbing nanostructures is characterized by the ability to adsorb and align nanostructures to have a specific orientation at desired locations on the surface of solid using a nanostructure-containing solution dispersed by a method for dispersing nanostructures as described above.

In the embodiment, the cleaning of the surface of solid on which nanostructures are to be adsorbed may be selectively further included prior to the patterning.

In the embodiment, the surface of solid on which nanostructures are to be adsorbed may be patterned in a predetermined form with a molecular membrane for pattering, which has a higher interface energy for the nanostructures than that of the surface of solid.

An example of a solid with the surface to be patterned may be selected from the group consisting of Au, Ag, Cu, GaAs, InP, Pt, glass, Si, Soild wit h Si-H bonding, oxide, and a mixture thereof. The oxide may include various oxides such as SiO₂, Al₂O₃, ZrO₂, HfO₂, and In₂O₃/SnO₂ (ITO).

For the nanostructures to be adsorbed, the molecular membrane for patterning has a higher interface energy than the solid surface. And the membrane may be appropriately selected according to a kind of functional molecule adsorbed on the nanostructure. For example, when the functional molecule adsorbed on nanostructure is a hydrophilic molecule, the molecular membrane for patterning may be formed as a hydrophobic molecular membrane and when the functional molecule adsorbed on nanostructure is a hydrophobic molecule, the molecular membrane for patterning may be formed as a hydrophilic molecular membrane.

The hydrophilic molecular membrane may comprise a hydrophilic functional molecule in the method for dispersing nanostructures as described above. A molecule useful as a hydrophilic molecular membrane may be one selected from the group consisting of, for example, aminopropyltriethoxysilane (APTES), (3-mercaptopropyl)-triethoxysilane (MPTMS), 16-mercaptohexadecanoic acid (MHA), cystamine, and a mixture thereof, but is not limited thereto.

These hydrophilic molecular membranes may be appropriately selected according to the surface of solid on which nanostructures are to be adsorbed. Among those exemplified as a molecular form available with respect to various solid surfaces as described in following Table 1, when the substituent R has sufficient surface charges, for example, a molecule where R contains NH₃ or COOH, or a molecule where R contains DNA or a protein may be useful as a hydrophilic molecular membrane. R and Ar as a molecular form described in following Table 1 represent a substituent, respectively.

Table 1

The hydrophobic molecular membrane may comprise a hydrophobic functional molecule in the method for dispersing nanostructures as described above, for example, a molecule selected from the group consisting of octadecyltrichlorosilane (OTS), octadecyltrimethoxysilane (OTMS), octadecyltriethoxysilane (OTE), octadecanethiol (ODT), and a mixture thereof, but is not limited thereto.

These hydrophobic molecular membranes may be appropriately selected according to the surface of solid on nanostructures are to be adsorbed, and the examples are shown in following Table 2. R and Ar as a molecular form described in following Table 2 represent a substituent, respectively.

Table 2

The patterning may be carried out by a method such as microcontact printing, photoplithography, dip-pen nanolithography, e-beam lithography, ion-beam lithography, nano grafting, nano shaving or STM lithography. Considering the compatibility with conventional semiconductor processes, the photolithography method is particularly desirable.

When a surface-patterned solid is immersed in a nanostructure-containing solution according to one embodiment of the present invention, the nanostructures are selectively adsorbed and aligned on the surface of solid on which the molecular membrane for patterning is not formed.

A method for adsorbing the nanostructures is to use a interface energy difference between materials, that is, a surface energy difference between materials. Particulary, for the nanostructures to be adsorbed, if a molecular membrane having a higher interface energy than that of the bare solid surface is formed on the solid surface, the nanostructures can be more easily adsorbed on the bare solid surface. That is, the nanostructures are selectively adsorbed and aligned on the surface of solid on which the molecular membrane for patterning is not formed, that is, on a region with a relatively low interface energy.

Specifically, when hydrophilic functional molecules are adsorbed on the surface of nanostructures, the solid surface is patterned with a hydrophobic molecular membrane, and thus the nanostructure on which the hydrophilic functional molecules are adsorbed may be selectively adsorbed on an exposed surface of solid on which the hydrophobic molecular membrane is not formed to have a desired orientation. Conversely, when hydrophobic functional molecules are adsorbed on the surface of nanostructures, the surface of solid is patterned with a hydrophilic molecular membrane, and accordingly the nanostructures on which the hydrophobic functional molecules are adsorbed may be selectively adsorbed and aligned on an exposed solid surface on which the hydrophilic molecular membrane is not formed to have a desired orientation.

For example, when silicon nanowires are functionalized with aminopropyltriethoxysilane (APTES) and the surface of an oxide substrate is patterned with octadecyltrichlorosilane (OTS), the exposed oxide substrate on which OTS is not formed has weak negative charges, and thus the silicon nanowires are adsorbed on the exposed oxide substrate which has the opposite charge with respect to the adsorbed APTES.

The sliding of nanostructure from a molecular membrane for patterning formed on the solid surface may be greatly induced by increasing the temperature of a nanostructure-containing solution in which a solid with a selectively-patterned surface is immersed, applying a vibration to the solution, or applying a voltage to the solid surface. Accordingly, the adsorption efficiency of nanostructures on the surface of solid on which the molecular membrane for patterning is not formed may be improved.

In another embodiment of the present invention, the nanostructures are selectively adsorbed and aligned on the surface of solid on which the molecular membrane for patterning is not formed by dripping a nanostructure-containing solution onto the patterned surface of solid and then evaporating solvent from the solution.

According to the embodiment, nanostructure may be adsorbed more efficiently on the surface of solid by a capillary force created as a result of evaporation of the solvent from the nanostructure-containing solution.

In addition, in one embodiment of the present invention, the forming of a molecular membrane for adsorption of nanostructures on the surface of solid on which the molecular membrane for patterning is not formed, that is, on the solid surface on which nanostructures are to be adsorbed, may be further included.

The molecular membrane for adsorption of nanostructures may be appropriately selected according to a kind of functional molecule adsorbed on the nanostructure. For example, when a functional molecule adsorbed on nanostructures is a hydrophilic molecule, the molecular membrane for adsorption of nanostructures may be a hydrophilic molecular membrane, and when a functional molecule adsorbed on nanostructures is a hydrophobic molecular molecule, the molecular membrane for adsorption of nanostructures may be a hydrophobic membrane. Examples of available hydrophilic and hydrophobic molecular membranes are the same as those of molecular membranes for patterning as described above.

In addition, the adsorption efficiency of nanostructures may be improved selectively by forming a molecular membrane which can have a chemical bond with a functional molecule adsorbed on nanostructure further on the surface of solid on which the molecular membrane for patterning is not formed, or on the molecular membrane for adsorption of nanostructures formed on the surface of solid.

The chemical bond is not particularly limited and may be formed using appropriate materials according to a kind of functional molecule adsorbed on nanostructure. For example, the chemical bond may include a bond between NH₂ ⁺ and COO^-, a bond between thiol and acryl amidite, a bond between biotin and avidin, and an antibody-antigen bond, but is not limited thereto.

For example, when aminopropyltriethoxysilane is adsorbed on nanostructures as a functional molecule and the surface of solid is patterned with octadecyltrichlorosilane as a molecular membrane for patterning and with aminopropyltriethoxysilane as a molecular membrane for adsorption of nanostructures, a reaction of glutaraldehyde with aminopropyltriethoxysilane which is a molecular membrane for adsorption of nanostructures on the surface of solid may lead to selective adsorption and alignment of the aminopropylethoxysilane-functionalized nanostructures on locations of the surface of solid on which glutaraldehyde is formed.

According to a method for selectively adsorbing nanostructures of the present invention, nanostructures may be efficiently adsorbed and aligned to have a specific orientation on desired locations of the solid surface by using a nanostructure-containing solution which has an improved dispersibility.

As described above, a method for dispersing nanostructures and a method for selectively adsorbing nanostructures may be applied directly to conventional semiconductor processes, and mass production of nanostructures integrated circuits such as nanowires or nanotubes may be allowed.

Furthermore, not only manufacture of devices using various types of nanostructures simultaneously may be allowed, but also a wide range of applications such as sensors for signal amplification or protein chips may be achieved.

<Examples>

Example 1: Dispersion of silicon nanowires (1)

Fig. 1 shows a schematic illustration of a method for dispersing silicon nanowires according to the present example. First, a substrate on which silicon nanowires had been grown was processed by a piranha cleaning treatment. The substrate on which silicon wires had been grown was put into an aminopropyltriethoxysilane (APTES) solution and left for about 30 min. Subsequently, the substrate was withdrawn and cleaned with ethanol to separate silicon wires from the substrate. Thus, silicon nanowires were obtained with APTES, a hydrophilic functional molecule, adsorbed on the surface.

The silicon nanowires with APTES adsorbed on the surface were put into DI-water which is a hydrophilic solvent, and dispersed in an ultrasonic cleaner for about 2 min to prepare a solution in which the silicon nanowires were dispersed.

Example 2: Dispersion of silicon nanowires (2)

First, a substrate on which silicon nanowires had been grown was processed by a piranha cleaning treatment. After the substrate on which silicon nanowires had been grown and aminopropyltriethoxysilane (APTES) were put into a sealed container without contacting each other, the container was heated to about 60 ℃ to expose the silicon nanowires for about 1 hour to the vapor of APTES. About 1 hour later, the substrate was withdrawn and cleaned with ethanol. Subsequently, silicon nanowires were separated from the substrate to obtain silicon nanowires with APTES, a hydrophilic functional molecule, adsorbed on the surface.

Similarly to Example 1, the silicon nanowires with APTES adsorbed on the surface were put into DI-water which is a hydrophilic solvent, and dispersed in an ultrasonic cleaner for about 2 min to prepare a solution in which the silicon nanowires were dispersed.

Example 3: Selective adsorption of silicon nanowires (1)

Fig. 2 shows a schematic illustration of a method of dispersing silicon nanowires according to the present example. An AZ series photoresist was patterned on the surface of a SiO₂ substrate in a predetermined form by the photolithography method. A solution was prepared by dissolving octadecylchlorosilane (OTS) in anhydrous hexane. The patterned SiO₂ substrate was put into the prepared octadecylchlorosilane solution, and an OTS molecular membrane was adsorbed on the SiO₂ substrate on which the photoresist had not been formed. Subsequently, acetone was used to remove the photoresist, and a SiO₂ substrate patterned with a molecular membrane for patterning produced from OTS was obtained. The parts shown as neutral regions in Fig. 2 were the surfaces on which OTS had been formed, while the parts shown as negatively-charged regions were the exposed surfaces of SiO₂ on which OTS had not been formed.

The patterned SiO₂ substrate was put into a silicon nanowire-containing solution in which the silicon nanowires had been functionalized with APTES, prepared in the Example 1 or 2. Accordingly, silicon nanowires were adsorbed and aligned on the SiO₂ substrate on which a molecular membrane for patterning produced from OTS had not been formed.

On the SiO₂ substrate on which silicon nanowires were adsorbed and aligned, electrodes were formed and devices were manufactured by a known method to form a nanowire circuit.

Fig. 4 and Fig. 5 show Scanning Electron Microscope (SEM) images of silicon nanowires selectively adsorbed on the SiO₂ surface obtained in the present example. From Fig. 4 and Fig. 5, it can be confirmed that silicon nanowires were adsorbed on locations of the SiO₂ surface on which a molecular membrane produced from OTS had not been formed, and aligned at a specific orientation.

Example 4: Selective adsorption of silicon nanowires (2)

An AZ series photoresist was patterned on the surface of a SiO₂ substrate in a predetermined form by the photolithography method. A solution was prepared by dissolving octadecylchlorosilane (OTS) in anhydrous hexane. The patterned SiO₂ substrate was put into the prepared octadecylchlorosilane solution, and an OTS molecular membrane was adsorbed on the SiO₂ substrate on which the photoresist had not been formed. Subsequently, acetone was used to remove the photoresist, and a SiO₂ substrate patterned with a molecular membrane for patterning produced from OTS was obtained.

The SiO₂ substrate surface on which the molecular membrane for patterning produced from OTS had not been formed was treated with aminopropylethoxysilane (APTES), and then APTES was reacted with glutaraldehyde to pattern the SiO₂ substrate surface with OTS and glutaraldehyde.

The patterned SiO₂ substrate was put into a silicon nanowire-containing solution in which the silicon nanowires had been functionalized with APTES, prepared in the Example 1 or 2, and then APTES adsorbed on the surface of silicon nanowire was reacted with glutaraldehyde patterned on the SiO₂ substrate surface. Accordingly, on the glutaraldehyde-patterned parts of the SiO₂ substrate surface, silicon nanowires were selectively adsorbed and aligned at a specific orientation.

Example 5: Selective adsorption of silicon nanowires (3)

Fig. 3 shows a schematic illustration of a method for adsorbing silicon nanowires according to the present example. An AZ series photoresist was patterned on the surface of an Au substrate in a predetermined form by the microcontact printing method. A solution was prepared by dissolving octadecanethiol (ODT) in hexane. The patterned Au substrate was put into the octadecanethiol solution prepared above, and an ODT molecular membrane was adsorbed on the substrate on which the photoresist had not been formed. Subsequently, acetone was used to remove the photoresist, and an Au substrate patterned with a molecular membrane for patterning produced from ODT was obtained. The parts shown as neutral regions in Fig. 3 were the surfaces on which ODT had been formed, while the parts shown as negatively-charged regions were the exposed Au substrate surfaces on which OTS had not been formed.

A silicon nanowire-containing solution prepared in the Example 1 or 2 was dripped into the patterned Au substrate surface, and then solvent was slowly evaporated. As the adsorption of nanowires was achieved more efficiently by a capillary force created as a result of evaporation of the solvent, silicon nanowires were selectively adsorbed and aligned on the Au substrate surface on which a molecular membrane for patterning produced from ODT had not been formed.

On the Au substrate surface on which silicon nanowires were adsorbed and aligned, electrodes were formed and devices were manufactured by a known method to form a nanowire circuit.

Fig. 6 and Fig. 7 show SEM images of silicon nanowires selectively adsorbed on the Au surface obtained according to the present example. From Fig. 6 and Fig. 7, it can be confirmed that silicon nanowires were selectively adsorbed on locations of the Au surface on which a molecular membrane produced from ODT had not been formed, and aligned at a specific orientation.

Example 6: Selective adsorption of silicon nanowires (4)

An AZ series photoresist was patterned on the surface of an Au substrate in a predetermined form by the microcontact printing method. A solution was prepared by dissolving octadecanethiol (ODT) in hexane. The patterned Au substrate was put into the octadecanethiol solution prepared above, and an ODT molecular membrane was adsorbed on the substrate on which the photoresist had not been formed. Subsequently, acetone was used to remove the photoresist, and an Au substrate patterned with a molecular membrane for patterning produced from ODT was obtained.

The Au substrate surface on which the molecular membrane for patterning produced from ODT had not been formed was treated with aminopropylethoxysilane (APTES), and then the APTES was reacted with glutaraldehyde to pattern the Au substrate surface with ODT and glutaraldehyde.

The patterned Au substrate was put into a silicon nanowire-containing solution in which the silicon nanowires had been functionalized with APTES, prepared in the Example 1 or 2, and then APTES adsorbed on the surface of silicon nanowire was reacted with glutaraldehyde patterned on the Au substrate surface. Accordingly, on the glutaraldehyde-patterned parts of the Au substrate surface, silicon nanowires were selectively adsorbed and aligned at a specific orientation.

While the present invention has been described with respect to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.

Claims

A method for dispersing nanostructures, comprising:

adsorbing functional molecules on the surface of nanostructures; and

dispersing the nanostructures on which the functional molecules are adsorbed in a solvent to form a nanostructure-containing solution.
The method of claim 1, wherein the solvent is a hydrophilic solvent when the functional molecule is a hydrophilic molecule, and the solvent is a hydrophobic solvent when the functional molecule is a hydrophobic molecule.
The method of claim 2, wherein the hydrophilic molecule is selected from the group consisting of aminopropyltriethoxysilane (APTES), (3-mercaptopropyl)-triethoxysilane (MPTMS), 16-mercaptohexadecanoic acid (MHA), cystamine, and a mixuture thereof.
The method of claim 2, wherein the hydrophobic molecule is selected from the group consisting of octadecyltrichlorosilane (OTS), octadecyltrimethoxysilane (OTMS), octadecyltriethoxysilane (OTE), octadecanethiol (ODT), and a mixture thereof.
The method of claim 2, wherein the hydrophilic solvent is selected from the group consisting of deionized water (DI-water), ethanol, methanol, 1,2-dichlorobenzene, isopropyl alcohol (IPA), and a mixture thereof.
The method of claim 2, wherein the hydrophobic solvent is selected from the group consisting of benzene, hexane, and a mixture thereof.
The method of claim 1, wherein said adsorbing functional molecules is performed by immersing the nanostructures in a functional molecule-containing solution or exposing the nanostructures to a functional molecule-containing gas.
The method of claim 7, wherein said adsorbing functional molecules is performed for about 1 sec to about 10 days.
The method of claim 7, wherein in said exposing the nanostructures to a functional molecule-containing gas, the nanostructures and functional molecules are disposed apart in a sealed container, and heated at a temperature of about 50 to about 200 ℃.
The method of claim 1, further comprising cleaning the nanostructures on which the functional molecules are adsorbed after said adsorbing functional molecules on the surface of nanostructures.
The method of claim 1, wherein said dispersing the nanostructures comprises immersing the nanostructures on which the functional molecules are adsorbed in a solvent; and dispersing the nanostructures in an ultrasonic cleaner for about 1 sec to about 1 hour.
The method of claim 1, wherein the nanostructure is selected from the group consisting of nanowire, nanoparticle, nanotube, and a mixture thereof.
A method for selectively adsorbing nanostructures, comprising:

adsorbing functional molecules on the surface of nanostructures;

dispersing the nanostructures on which the functional molecules are adsorbed in a solvent to form a nanostructure-containing solution;

patterning a solid surface on which the nanostructures are to be adsorbed with a molecular membrane for patterning, which has a higher interface energy for the nanostructures than that of the solid surface, in a predetermined form; and

immersing the patterned solid in the nanostructure-containing solution to selectively adsorb and align the nanostructures on the surface of solid on which the molecular membrane for patterning has not been formed.
A method for selectively adsorbing nanostructures, comprising;

adsorbing functional molecules on the surface of nanostructures;

dispersing the nanostructures on which the functional molecules are adsorbed in a solvent to form a nanostructure-containing solution;

patterning a solid surface on which the nanostructures are to be adsorbed with a molecular membrane for patterning, which has a higher interface energy for the nanostructures than that of the solid surface, in a predetermined form; and

dripping the nanostructure-containing solution onto the solid surface on which the nanostructures are to be adsorbed and evaporating solvent from the solution to selectively adsorb and align the nanostructures on the surface of solid on which the molecular membrane for patterning has not been formed.
The method of claim 13 or claim 14, wherein the molecular membrane for patterning is a hydrophobic molecular membrane when the functional molecule adsorbed on the surface of nanostructures is a hydrophilic molecule, and the molecular membrane for patterning is a hydrophilic molecular membrane when the functional molecule adsorbed on the surface of nanostructures is a hydrophobic molecule.
The method of claim 15, wherein the hydrophobic molecular membrane comprises a molecule selected from the group consisting of octadecyltrichlorosilane (OTS), octadecyltrimethoxysilane (OTMS), octadecyltriethoxysilane (OTE), octadecanethiol (ODT), and a mixture thereof.
The method of claim 15, wherein the hydrophilic molecular membrane comprises a molecule selected from the group consisting of aminopropyltriethoxysilane (APTES), (3-mercaptopropyl)-triethoxysilane (MPTMS), 16-mercaptohexadecanoic acid (MHA), cystamine, and a mixture thereof.
The method of claim 13 or claim 14, further comprising forming a molecular membrane for adsorption of nanostructures on a solid surface on which a molecular membrane for patterning has not been formed after said patterning a solid surface on which the nanostructures are to be adsorbed with a molecular membrane for patterning.
The method of claim 18, further comprising, after said forming a molecular membrane for adsorption of nanostructures, forming a molecular membrane which can have a chemical bond with a functional molecule adsorbed on the nanostructure on the molecular membrane for adsorption of nanostructures.
The method of claim 18, wherein the molecular membrane for patterning is a hydrophobic molecular membrane and the molecular membrane for adsorption of nanostructures is a hydrophilic molecular membrane when the functional molecule adsorbed on the surface of nanostructures is a hydrophilic molecule, and the molecular membrane for patterning is a hydrophilic molecular membrane and the molecular membrane for adsorption of nanostructures is a hydrophobic molecular membrane when the functional molecule adsorbed on the surface of nanostructures is a hydrophobic molecule.
The method of claim 20, wherein the hydrophilic molecular membrane comprises a molecule selected from the group consisting of aminopropylethoxysilane (APTES), (3-mercaptopropyl)-triethoxysilane (MPTMS), 16-mercaptohexadecanoic acid (MHA), cystamine, and a mixture thereof.
The method of claim 20, wherein the hydrophobic molecular membrane comprises a molecule selected from the group consisting of octadecyltrichlorosilane (OTS), octadecyltrimethoxysilane (OTMS), octadecyltriethoxysilane (OTE), octadecanethiol (ODT), and a mixture thereof.
The method of claim 13 or claim 14, further comprising forming a molecular membrane which can have a chemical bond with a functional molecule adsorbed on the nanostructure on a solid surface on which the molecular membrane for patterning has not been formed after said patterning a solid surface on which the nanostructures are to be adsorbed with a molecular membrane for patterning.
The method of claim 13 or claim 14, wherein said pattering a solid surface on which the nanostructures are to be adsorbed with a molecular membrane for patterning is performed by a method selected from the group consisting of microcontact printing, photolithography, dip-pen nanolithography, e-beam lithography, ion-beam lithography, nano grafting, nano shaving, or STM lithography.
The method of claim 13 or claim 14, wherein the nanostructure is selected from the group consisting of nanowire, nanoparticle, nanotube, and a mixture thereof.
The method of claim 13 or claim 14, wherein in said pattering a solid surface on which the nanostructures are to be adsorbed with a molecular membrane for patterning, the solid, on the surface of which the molecular membrane for patterning is to be patterned, is selected from Au, Ag, Cu, GaAs, InP, Pt, glass, Si, solid with Si-H bonding, oxide, and a mixture thereof.