KR20160085570A - Preparing method of self-assembling 2-D nanostructure - Google Patents

Abstract

The present invention relates to a method of preparing a self-assembling 2-D nanostructure, and more specifically, to a method of preparing a self-assembling 2-D nanostructure by using an etching agent that selectively etches the terminal of a capped nanorod. Through the method of the present invention, a terminal-terminal connection network of the nanorods can be facilitated and the nanorods can be distributed evenly over large areas on a substrate. Also, the present method allows the density of the nanorod network to be controlled. The self-assembling 2-D nanostructure prepared by the present method shows a high electrical conductivity while retaining the characteristics of the nanorod, and therefore can be advantageously used in electric devices as a transport layer and the like.

Description

{Preparing method of self-assembling 2-D nanostructure}

The present invention relates to a method of fabricating a self-assembled 2-D structure, and more particularly, to a method of fabricating a self-assembled 2-D structure using an etchant that selectively etches the ends of the capped nanorods.

Assemblies of colloidal nanomaterials can have ensembles properties suitable for a variety of applications. Such ensemble characteristics are difficult to achieve in individual colloids. In particular, aggregated nanorods often exhibit unique polarity optics or high conductivity and are very useful for applications in photonics, electronics or energy collection devices. The nanorods may form a side-to-side or end-to-end arrangement, and the ensemble produced exhibits different properties depending on the ratio of the two arrangements. Side-to-side coupling in such assemblies can be observed by solvent evaporation with nanorods forming a parallel or vertical arrangement in the substrate and assisted occasionally by template or external forces. In terms of thermodynamic advantages of this arrangement, the positional and orientational arrangement of the nanorods is similar to liquid crystal molecules. Such nanorod assemblies are capable of linearly polarized emission or enhanced optical absorption. On the other hand, the end-to-end network of nanorods opens up new and exciting opportunities. For example, in a terminal-to-end conglomerate, nanorods have the unique properties of individual nanorods, such as quantum confinement, and serve as channels for carrier transport. Despite intensive demand and potential, end-to-end connections of colloidal nano-rods are relatively under investigation, because strong van der Waals or dipole attraction keeps the nanorods side-to-side array.

1. Korean Patent No. 10-1287350 2. Korean Patent Publication No. 10-2013-0102072

The present invention provides a method for manufacturing a 2D nanostructure that enables a terminal-end connecting network of nanorods more easily using an etchant that selectively etches the ends of the capped nanorods.

The present invention provides a method for manufacturing a self-assembled 2D nanostructure that adjusts the density of a nanorod network by controlling the concentration of a nano-rod, the concentration of an etchant, the pull-up rate of a substrate, or the evaporation rate of a solvent.

The present invention provides a self-assembled 2D nanostructure that can exhibit high electrical conductivity while preserving the properties of individual nanorods and can be used as an effective transport layer or the like in an electric device or the like.

In one aspect,

Mixing the nanorods surrounded by the capping material and the etchant in a solvent; And exposing the nanorods to an air / solvent interface to self-assemble the nanorods.

In another aspect,

A nanorod structure manufactured according to the method for manufacturing a self-assembled 2-D nanostructure, wherein the structure is formed of a mono layer structure in which nanorods and nano- Nanostructures.

In yet another aspect,

Relates to an element comprising the self-assembled 2-D nanostructure.

The end-to-end connection network of the nano rod can be made more easily by using the self-assembled 2D nanostructure manufacturing method of the present invention.

By using the self-assembled 2D nanostructure manufacturing method of the present invention, the NARO rod can be uniformly distributed over a wide area on the substrate.

The density of the nanorod network can be controlled by using the self-assembled 2D nanostructure manufacturing method of the present invention.

The self-assembled 2D nanostructure produced by the method of manufacturing the self-assembled 2D nanostructure of the present invention can exhibit high electrical conductivity while preserving the characteristics of the nanorod, and can be used as an effective transport layer or the like in an electric device.

FIG. 1 (a) is a schematic view showing a self-assembled 2D nanostructure of the present invention and a method of producing a control. FIGS. 2 (b) to 2 ) Image.
2 (a) to 2 (c) are optical images of CdSe nanorods at the air / liquid (toluene) interface of the mixed liquid of the present embodiment over time, TEM image of the case.
3 (a) and 3 (b) are images of a self-assembled 2D nanostructure and a control group according to the present embodiment, and FIGS. 3 (c) and 3 (d) are schematic views showing the behavior of the nanorods respectively.
Figure 4 is a TEM image of self-assembled 2D nanostructures of this example uniformly distributed over a large area of the substrate.
5 (a) to 5 (d) are TEM images of the self-assembled 2D nanostructure of this embodiment according to the drawing speed, FIG. 5 (e) And the number of nanorods per unit area of the CdSe nano-rods.
6 is a graph showing the number of end-to-end bonding of CdSe nano-rods in the self-assembled 2D nanostructure of the present embodiment according to the drawing speed.
7 (a) and 7 (b) are high-resolution TEM images of a self-assembled 2D nanostructure according to the present embodiment, and FIG. 7 (c) is a schematic diagram showing end-to-end contact between the nanorods. (d) to (e) are high-resolution TEM images of the control group, and (f) are schematic diagrams showing side-to-side bonding between nanorods in this regard.
8 is a high-resolution TEM image of the self-assembled 2D nanostructure according to the present embodiment in accordance with the number of terminal bonds of CdSe nanorods.
FIGS. 9A and 9B are TEM images of the end-to-end bonding network of the self-assembled 2D nanostructure according to the present embodiment, wherein FIGS. 9C and 9D are CdSe nanorods, X-ray photoelectron spectroscopy (XPS) spectra of the treated CdSe nanorods.
10 is a TEM image of CdSe nanorod aggregates after washing the mixed solution according to the present embodiment.
11 is an X-ray photoelectron spectroscopy (XPS) spectrum of CdSe nanorods at the Cl 2p level and CdSe nanorods treated with chloride and DDAB.
12 is an X-ray diffraction (XRD) pattern of CdSe nanorods and CdSe nanorods treated with chloride and DDAB.
13 (a) to 13 (d) are TEM images according to the hydrochloric acid concentration of a self-assembled 2D nanostructure treated with hydrochloric acid instead of hydrochloric acid in this embodiment, wherein (e) and (f) It is a later image.
14 is a TEM image of the self-assembled 2D nanostructure of this example according to the concentration of silver chloride relative to the DDAB concentration.
15 (a) to 15 (d) are TEM images of the self-assembled 2D nanostructure of this example according to the concentration of DDAB versus silver chloride, (e) The average of the number of terminal bonds of the nanorods and the relative absorbance of the mixed solution according to this embodiment.
16 is a TEM image of the self-assembled 2D nanostructure of this example according to the concentration of DDAB versus silver chloride.
17 is a graph showing the number of end-to-end bonds of the CdSe nano-rods in the self-assembled 2D nanostructure of the present example according to the concentration of DDAB versus silver chloride.

The present inventors have fabricated self assembled 2D nanostructures using wettability of particles, shape of particles and capillary attraction. Hereinafter, the present invention will be described in detail.

The self assembled 2D nanostructure manufacturing method of the present invention includes a mixing step and a self-assembling step.

In the mixing step, the nanorods surrounded by the capping material and the etchant are mixed in a solvent.

The capping material enables the nanorod to be dispersed in a solvent. For example, a surfactant may be used. The hydrophilic portion of the surfactant is in contact with the surface of the nanorod, and the lipophilic portion facilitates dispersion in the solvent. Specific examples of the capping material may include, but not limited to, TDPA, TOPO, TOP, DOPA, OPA, OA, HPA, ODPA and HDA.

The solvent can disperse the capped nanorods and use non-polar solvents that have poor wettability to the exposed surfaces of the nanorods after etching. For example, the solvent may be, but is not limited to, toluene, tetrahydrofuran, chlorobenzene, hexane or cyclohexane. The nano-rod may be made of a semiconductor material. For example, the semiconductor material may be at least one selected from the group consisting of CdSe, CdS, CdTe, ZnSe, ZnS, ZnTe, ZnO, HgS, HgSe, InAs, InP, InN, InSb, InAsP, InGaAs, GaN, GaAs, GaP, GaSb, AlP, But are not limited to, AlAs, AlSb, PbSe, PbTe, PbS, CdZnSe, CdSeTe, ZnCdSe, PbSnTe, Si, or Ge.

The mixing step includes an etching step in which the etchant selectively etches the capping material at the nano rod end. The selective etching is because the capping material has a low density because the capped nanorod has rounded ends, so that the etching agent can easily access the end surface of the nanorod. Through this selective etching, the nanorods have low wettability in the solvent and thus are spontaneously exposed to the air / solvent interface region.

The etchant may include a chloride ion, an oxide ion, or an aqueous sulfide ion solution. For example, the chloride anion can access the semiconductor molecule at the end of the nanorod having a relatively small number of the capping molecules due to the side surface of the nanorod having the capping molecules densely. The cation anion of the semiconductor molecule having relatively less electrons than the chloride anion You can attack and detach parts. As a result, the chloride anion can selectively remove molecules capped at the end of the nanorod.

The etchant may include a metal salt. When the etchant is a metal salt, the etching step may include a step of selectively removing the capping material at the end of the nano rod, and then reducing the metal ion of the metal salt at the end of the nano rod to be attached to the metal. Even without a reducing agent, the metal ion can be reduced to metal by oxidizing a portion of the anion portion of the semiconductor molecule on the surface of the nanorod. The metal ions may be reduced to metal at the ends of the nano-rods and grow to metal layers at the ends of the nano-rods. The metal layer prevents etching of the ends of the nanorods to shorten the length of the nanorods.

The metal salt may be a metal salt including a chloride ion, an oxide ion and a sulfide ion. For example, the metal salt may be chloride, silver chloride, copper chloride, platinum chloride, cobalt chloride, or iron chloride.

The self-assembling step is a step of self-assembling the nanorod by exposing the nanorod to an air / solvent interface.

The self-assembling step may form a network by bonding the ends of the nano-rods at the air / solvent interface with a capillary attraction force. The ends of the etched nanorod deform the air / solvent interface and generate a capillary attraction.

Referring to FIG. 7C, the tip of the etched nanorod is accompanied by a solvent / air interface deformation. In order to reduce the high surface free energy due to the interface deformation, a capillary attraction is generated, So that the etched nanorods are moved and attached to each other in a direction decreasing the surface area of the interface.

More specifically, the isotropic spherical microparticles immobilized on the free interface do not deform the interface and do not cause capillary interaction, but the anisotropic microparticles such as the ellipsoid or the cylinder used in the present invention deform the interface and minimize interface strain The capillary attraction is induced. Therefore, in the present invention, a capillary attraction occurs in order to lower the surface free energy existing in the interfacial deformation between the anisotropic nano-rods which are the colloidal particles. In addition, even if the capillary attraction induced in this anisotropic shape is weak, the surface characteristics of the anisotropic nano-rod can be modified by selectively etching the capping of the anisotropic nano-rods to increase interfacial deformation and capillary attraction. When the ends of the anisotropic nano-rods come into contact with each other through the capillary attraction, the ends and the ends are fused to form a strong network to reduce the interfacial energy.

The self-assembling step may include immersing the substrate in the solvent. 1, a nanoload 110 surrounded by a capping material and an etchant 120 capable of etching the capped material are placed in a solvent 130 and mixed to prepare a mixed solution 100 . When the base material 200 is dipped in the mixed solution and the solvent 130 is evaporated, the 2D nanorod structure 300 is formed on the base material. Further, the self-assembling step may further include dipping the substrate in the solvent and then drawing the substrate at a predetermined speed. When the substrate is pulled up instead of evaporating or evaporating the solvent 130, the solvent is evaporated in a meniscus formed on the substrate, and the 2D nanorod structure 300 of the present invention is finally formed on the substrate .

The method of fabricating the 2D nanorod structure may control the density of the nanorod network formed on the substrate by controlling the pulling rate of the substrate. In particular, decreasing the pulling rate of the substrate can increase the density of the nanorod network formed on the substrate. Also, increasing the pulling rate of the substrate can reduce the network density of the nano-rods formed on the substrate.

The network density of the nanorods refers to the number of nanorods in the self-assembled 2D nanostructure and the number of end-to-end bonds of each nanorod. As the pulling rate of the substrate is reduced, the number of total nanorods in the self-assembled 2D nanostructure increases and the number of end-to-end bonds of each nanorod increases. The increase in the number of end-terminal bonds of a nanorod can be, for example, increasing the number of ends of other nanorods that bind to the end of one nanorodor from 1 to 6.

The method of fabricating the 2D nanorod structure may be to control the density of the nanorod network at the air / solvent interface by controlling the concentration of the etchant. Specifically, increasing the concentration of the etchant can increase the density of the nanorod network. Also, decreasing the concentration of the etchant can reduce the network density of the nanorods. The concentration of the etchant may be controlled by controlling the concentration ratio of the etchant and the relative concentration of the reverse micellar substance that controls the activity of the etchant. The density of the nanorod network can be increased by reducing the concentration of the reverse micelles relative to the concentration of the etchant.

The 2D nanorod structure may be prepared by controlling the concentration of the nanorod or the evaporation rate of the solvent to control the density of the nanorod network at the air / solvent interface. In particular, increasing the concentration of the nanorod can increase the density of the nanorod network, and decreasing the rate of evaporation of the solvent can increase the density of the nanorod network. If the evaporation rate of the solvent is decreased, the time at which the network can be formed due to the end-to-end bonding of the nanorods at the air / solvent interface is increased.

According to another aspect of the present invention, there is provided a nano-rod structure manufactured by a method of manufacturing a self-assembled 2D nanorod structure of the above-described aspect, wherein the structure is a self-assembled 2D nanorod formed of a single layer structure in which nanorods and nano- Structure.

The nano rod structure manufactured according to the above manufacturing method is characterized in that the ends and the ends of the nano rods are fused so that there is no separation space between the ends and the ends of the nano rods and each of the nano rods and nano rods is completely bonded Thereby forming the nanorod structure. The bond is not a contact but a bond that is not separated unless an external force of a certain level or more is applied. Therefore, the nanorod structure can function as a new structure including nanorods, rather than a simple arrangement of nanorods.

The side walls of the nanorods in the self-assembled 2D nanostructure are coated with a capping material. The nanostructures in the self-assembled 2D nanostructure may have a metal attached to the ends to which the nanorods are bonded. The attached metal can prevent the length of the nano-rods from being shortened by continuing the etching of the end of the nano-rods.

In another aspect, the present invention is an element comprising a self-assembled 2D nanorod structure as described above, wherein the element is a transistor, a transmitter, a laser, a Q-switch, a switch switch, an optical switch, an optical fiber, a gain device, an amplifier, a display, a detector, a communication system, a light emitting diode (LED) diode, a light conversion layer, a solar cell, or a sensor.

The detailed description of the self-assembled 2D nanostructure and the device including the structure is omitted. However, the method of manufacturing the self-assembled 2D nanostructure described above can be similarly applied.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

Example  1: Fabrication of self-assembled 2D nanostructures

(1) Synthesis of CdSe nanorods

1.6 mmol of CdO and 3.2 mmol of TDPA (Tetradecylphosphonic acid) (3.1 g) of trioctylphosphine oxide (TOPO) were loaded into a three-necked flask, and the mixture was degassed at 120 ° C. for 1 hour. The mixture was heated to 300 < 0 > C until colorless and cooled to ambient temperature under an argon atmospheric stream to give a Cd-complex solution. The Cd-complex solution was allowed to stand for 24 hours, and then the Cd-complex solution was reheated to 320 DEG C, and a Se stock solution (0.08 mmol Se, 0.19 g TBP (tributylphosphine) prepared in a glove box, 1.447 g TOP (trioctylphosphine) and 0.3 g of anhydrous toluene] were mixed. The nanorods were grown at 250 DEG C for 30 minutes and then cooled at room temperature. The nanorods were washed by addition of chloroform and methanol in succession, and centrifuged twice to obtain CdSe nanorods (size: 37 x 7 nm).

(2) Manufacture of self-assembled 2D nanostructure

First, the CdSe nanorod was dissolved in toluene. (AuCl ₃ ) and DDAB (didecyldimethylammonium bromide) were dissolved in toluene for contact between the ends of the CdSe nanorods, and ultrasonic treatment was performed to prepare a solution (etchant) containing an etching agent. 7 ml of the colloidal solution containing the CdSe nano-rod was mixed with 2 ml of the etchant to prepare a mixed solution. The mixture contains a DDAB of 3.18 × 10 ^-9 M of the CdSe nano-rod, 1.41 × 10 ^-5 M yeomhwageum and 8.53 × 10 ^-5 M of. In order to control the network density in the self - assembled 2D nanostructure, the concentration of CdSe nanorod was made constant and the concentration of chloride and DDAB varied.

A transmission electron microscope grid consisting of carbon coated copper was immersed in the mixed solution at a 45 degree angle from vertical. The 2D nanorod structure deposited on the TEM grid was measured and examined as the solvent evaporated completely and a meniscus was formed on the grid. For control of network density in a self-assembled 2D nanostructure, the grid was drawn and varied in pull rate.

Comparative Example

In Example 1, a self-assembled 2D nanostructure was prepared using only a colloidal solution containing a nano-rod except for the etching solution. The remainder is the same as in Embodiment 1.

Experimental Example  : Optical microscope ( OM ), Transmission electron microscope ( TEM ), X-ray photoelectron spectrum (XPS) analysis, and X-ray diffraction XRD ) analysis

The self-assembled 2D nanostructures prepared in the examples and the comparative examples were analyzed with an optical microscope (Nikon Optiphot microscope with a Roper Scientific CoolSnap Photometrics camera), a transmission electron microscope (Tecnai F20), and a field emission transmission electron microscope (Tecnai F20, ). Further, X-ray photoelectron spectrum analysis (Sigma Probe) and X-ray diffraction analysis (RIGAKU Ultima IV) were performed.

result

The anisotropic surface properties of CdSe nanorods can be increased by the use of chloride, which selectively etches their ends. Although chloride is used as a precursor to the growth of gold particles on the ends of the nanorods, it can also etch the ends of the nanorods without a reducing agent. Once TDPA, a steric stabilizer at the surface of the nanorods, is selectively removed from the ends, the nanorods are no longer wetted by toluene and are spontaneously adsorbed at the air / toluene interface. The nanorod solution containing chloride and DDAB forms a film at the interface (FIG. 2). 2 (a) to 2 (c) are optical images showing nanorods at the air / toluene interface over time. And d and e in Fig. 2 are TEM images in Fig. 2C. Once the solution is deposited on the TEM grid, the agglomerated nanorods are connected end-to-end (Figure 3a). Without additives, the nanorods are laterally-side packed (Figure 3b). And c and d in Fig. 3 are schematic views showing the concept of a and b in Fig. 3, respectively.

To illustrate this unique assembly operation and strategy for developing a uniform network structure over a large area, the present invention employs a vertical immersion-coating technique. Figure 1 a shows an immersion-coating schematic. During the vertical coding, toluene evaporates in the meniscus and causes convection flow. This convective flow helps to feed the nanorod to the interface and facilitates interfacial assembly, which almost happens near the contact line. At the same time, the continuous drying of the toluene moves down the contact line and moves the nanorod network to near contact on the substrate. The simultaneous assembly and transfer process promotes the development of a large single-layer, uniform layer thickness fractal network (FIG. 1 b and FIG. 4). Aggregates or voids are rarely observed throughout the 3 x 3 mm carbon coated copper grid used as the substrate. The nanorods adsorbed at the interface are only transportable sideways, and the convective flow can not collect nanorods below the meniscus, inhibit nanorod dummy formation, and produce a uniform film as shown in Figure 1 (b). . The network also consists of pure end-to-end connections of nanorods with negligible side-to-side contact, where most of the nanorod chains participate in forming a single network (FIG. Such networks have tremendous potential to create effective penetration into applications including bulk heterojunction solar junction solar cells and transistor-based quantum rods.

When toluene does not contain chloride and DDAB, the nanorod suspension is very stable for flocculation or precipitation and the immersion-coated precipitate forms a completely different shape. Figure 1 (d) shows a low-resolution TEM image of the CdSe nanorods forming the coffee ring. The coffee ring shape results from contact line fixation due to impurities or defects on the substrate. If the contact lines are fixed, the nanorods will gather in the line and form bands by convection flow and accumulation. As the toluene is evaporated, the clamping force can no longer avoid gravity, and the contact line slips and forms the next band of nano-rods that are fixed and accumulated at low levels. The enlarged TEM image of FIG. 1e shows that each coffee ring consists of a stack of packed nanorods. The stick-slip deposition causes non-uniform distribution of the nanorods. In the presence of chloride and DDAB, nanorod assembly effectively inhibits the formation of coffee rings and can create a single-layer fractal film over a large area through interfacial adsorption of the nanorods. The formation of a continuous network across the solid substrate and air / toluene interface causes smooth movement of the contact line instead of stick-slim motion.

During the dip-coating process, the rate of nanorod feed to the air-toluene interface is determined by the drawing speed of the substrate and the evaporation rate of toluene. To demonstrate the quantitative effect of pulling rate, the concentrations of nanorods, chloride, and DDAB were kept constant and the speed varied to 0, 0.189, 0.567, and 0.944 μm / min. Figures 5a-d show a tremendous change in the density of nanorods in the resulting network structure. a lift-up speed from zero to increase to 0.189 μm / min is reduced the number of coating the nanorods of NRs, ρAN on the network to a ^{1.33 × 10-3NRs / nm 2 to 9.04} × 10-4 NRs / nm 2. The network is prepared at 0.189 μm / min and still maintains full continuity. Increasing the speed to 0.567 μm / min reduces the speed of the nanorod supply and loses overall continuity, resulting in only local connections due to insufficient ρAN values (5.35 × 10 -4 NRs / nm ² ). Predictably, a faster speed of 0.944 μm / min lowers the value of ρAN to 1.99 × 10 -4 NRs / nm ² , resulting in a pair of individual nanorods (NRs) or nanorods. Figure 5 e shows the average number of NRs forming a single connection, with N _NRs having a similar trend to ρAN (Figure 6). 6 is a graph showing the density of the nanorod network according to the pulling rate. In a dense network prepared without impression, N _NRs is as high as 2.6 (a in FIG. 5) and 2.2 in a loose network with an impression rate of 0.189 μm / min (FIG. 5b). At a faster pull rate, N _NRs is lower than 2 (c, d in FIG. 5), indicating unconnected dead ends and no overall continuity. To ensure continuity, the average distance between trapped NRs centers is ca. Should be shorter than 33 nm, and this value was approximated from ρAN-1/2 at a pulling rate of 0.189 μm / min (FIG. 5B).

7a and 7b show a high-resolution TEM image of the nanorod network formed in the presence of chloride. The nanorod terminals were perfectly fused and formed a strong connection without any noticeable separation (FIG. 8). No TDPA remains at the ends. There is no nearly parallel arrangement, which shows a narrow gap between the nanorods (Figure 7b). This confirms the presence of TDPA on the sidewall. This selective local etching is due to the low density of the capping molecules at the rounded ends. Chloride ions, including chloride, are accessible to the CdSe surface at the ends, which are away from the sidewalls by dense camping molecules. Chloride anions can attack and separate Cd atoms that lack electrons, stripping plane [001] of NR and making it unstable. A similar mechanism has been applied to grow CdSe nanowires from spherical nanoparticles in the [001] direction. Through selective etching, the nanorods were made to have low wettability in toluene, which allowed them to spontaneously fix at the air / toluene interface. The etched ends are susceptible to deforming the interface, forming multiple poles, which increases the end-to-end attraction (FIG. 7c). Once the ends are in contact, the unstable ends are fused to reduce the interfacial energy. The formation of strong end-to-end connections enables stable migration of the nanorod network on the substrate without structural deterioration. In contrast, nanorods decorated with TDPA without chloride form side-to-side packing. The high-magnification images of d and e in Fig. 7 show that the layer of TDPA is separated by about 2 nm from the surface. The nanorods can attract the surrounding nano-rods by van der Waals and dipole-dipole bonding while the steric layer prevents aggregation or interfacial adsorption of the nanorods (Figure 7f). Considering that van der Waals and dipole-dipole forces are the major forces for interaction, the energy drawn between the side-side packed neighboring nanorods is several orders of magnitude higher than the energy between the end-aligned nanorods . Therefore, parallel alignment is dominant in the bulk solution (FIG. 1e).

Figures 9a, b and 10 show a TEM image of a CdSe nanorod network before and after the network is exposed to an incident electron beam. 10 (a) is a low-resolution TEM image at the condition shown in the image at a nano-rod concentration of 3.18 × 10 ^-9 M, and (b) and (c) are images after exposure to the incident electron beam.

 Interestingly, gold nanoparticles grow in the bonds of the network within a few minutes under e-beam irradiation. Au species can cover the ends of CdSe nanorods during selective etching by cleaning the nanorods prior to TEM analysis. X-ray photoelectron spectroscopy (XPS) analysis confirms the presence of amorphous Au species on the surface of CdSe nanorods (c and d in FIG. 9). FIG. 9C shows the XPS spectrum of the CdSe nanorods, and FIG. 9D shows the XPS spectrum of the nanorods treated with silver chloride and DDAB. While the CdSe nanorods show characteristic peaks around Cd 3d and Se 3d, the nanorods show peaks of oxidized Cd, oxidized Se and Au species after chlorine treatment. In addition, in the XPS spectrum of the gold-coated CdSe nanorods, there is no peak of Cl (FIG. 11). The absence of the Cl signal suggests that covering the surface of the nanorod is gold rather than chloride. Even without a reducing agent, the gold ion can be reduced to AuO by oxidizing a portion of the selenium ion on the surface of the nanorod. There is no gold crystal peak detected in the XRD pattern of the chlorinated CdSe nanorods (Fig. 12), which means that gold is present as an amorphous gold shell covering the etched ends of the nanorods. This encapsulation is observed on the surface of CdSe nanoparticles at low ligand density and incomplete gold reduction, which is similar to the experimental environment of the present invention.

The present invention uses hydrochloric acid as a terminal-etchant instead of chloride to separate the effect of etching from gold deposition. Similarly, end-to-end alignment was observed despite the coexistence of the side-to-side packing (Fig. 13a and b). In order to further etch the ends and increase the end-to-end connecting portion, the present invention used a darker concentration of hydrochloric acid. However, concentrated hydrochloric acid shortened the length of the nanorod in the end-to-end connection (c and d in FIG. 13), which contributed to non-uniform etching by hydrochloric acid. Nonetheless, it has been concluded that end-etching results in spontaneous system area adsorption and end-to-end necking. In particular, darker concentrations of chloride did not produce shorter nanorods but significantly impacted the density of the network (Figure 14). The obvious difference between chloride and hydrochloric acid is that the amorphous gold layer deposited during surface etching protects against further etching and maintains the length of the nanorods.

The etchant, chlorine, is insoluble in toluene and forms reversed micelles with DDAB. Therefore, the relative amount of chloride relative to DDAB has a tremendous impact on etch activity: the high range of chloride for DDAB causes low activity due to stable encapsulation. , As it can affect the rate and the assembly of the etching rate of the total area of suction, relative concentrations of yeomhwageum (C _AuCl3) for relative DDAB (C _DDAB) provides a means to control the density of the nanorods on the derived Network . C _{AuCl 3} increases from 0.65 × 10 ^-5 M to 2.82 × 10 ^-5 M, while the density of nanorods in the derived network also increases when C _DDAB is maintained at 8.53 × 10 ^-5 M (FIG. 14). In a similar manner, 1.41 × 10 ^-5 C the _DDAB at constant C M _AuCl3 of from ^{4.27 × 10 -5 M 17.1 × 10} - when increasing to ⁵ M, the network, as in Figure 16 as a to c in FIG. 8 It has become extremely loose. At 4.27 × 10 ^-5 M ([DDAB] / [AuCl ₃ ] = 3.03) of C _DDAB , chloride etched the sidewalls as well as the terminal portions and formed a dense network. There is also a small portion of the side-to-side packing (Fig. 15a). Interestingly, the sidewalls contacted without a gap. In bulk suspensions, the nanorods become unstable at such relative concentrations because of low steric repulsion and form random segregates without an immersion-coating process. Once a separation occurs, the nanorod forms a precipitate for 9 hours and leaves a pale solution as shown in Figure 15 (e) (Figure 17). In contrast, at 8.53 × 10 ^-5 M and 17.1 × 10 ^-5 M ([DDAB] / [AuCl ₃ ] = 6.05 and 12.1, respectively) of C _DDAB , the chloride selectively etches the ends and the terminal- . As shown in FIG. 15 e, the relative absorbance is maintained almost constant after 9 hours, which means that the nanorod suspension is relatively stable at this concentration. When the C _DDAB is as high as 25.6 × 10 ^-5 M ([DDAB] / [AuCl 3] = 18.2), side-side packing of the nanorods predominates because the chloride tightly surrounded by DDAB has low activity in etching do. The sidewalls are packed closely, similar to the nanorod assembly without additive, but are separated to about 2 nm (Figure 15, d). The number of other nanorod ends (the average number of nano rod arms) bound to one nanorod end decreases as the relative concentration of DDAB relative to chloride increases, as shown by the filled circles of Figure 15, e. The number is higher by 5 in the dense network of Figure 15, and lower than 2 in the loose network due to the increased portion of dead ends in Figure 15c. High density and control of the network connectivity castle opens a new way of the optical transmittance and electrical conductivity studies of the penetration network (Fig. 15 a to d are, ^{respectively, 4.27 × 10 -5 M, 8.53} × 10 -5 M, 17.1 × 10 - ⁵ M, and 25.6 x 10 ^-5 M, respectively).

In summary, the present invention provides a highly controllable method of introducing 2-D end-terminal self-assembly of nanorods by capturing nanorods at defined air / liquid interfaces using immersion-coating techniques. This penetration network spreads over the entire substrate with a single layer thickness while maintaining uniformity. This remarkable assembly was created by interfacial adsorption and directional capillary attraction. The nanorod ends are selectively etched by chloride and form reversed micelles with DDAB in toluene. As a result, the nanorod ends are not wetted by toluene. Changes in surface properties cause spontaneous fixation of the nanorods at the air / liquid interface and are subsequently deformed. As a result, the capillary attraction attracts neighboring nanorods defined in the two-dimensional geometry along the terminal-end direction and forms a network structure. Dip-coating enables a limited supply of nanorods to the network via convective flow at the air / liquid interface, and 2-D, a single-layer-thick nanorods of fractal clusters, . Another approach is that the density of the network can be precisely controlled as a result of adjusting the substrate drawing speed or the relative concentration of chloride relative to DDAB. Interfacial assembly of these nanorods offers a unique means of creating end-to-end networks with controlled density and thickness over a large area, avoiding costly multi-step processes such as high temperature annealing or lithography patterning . The end-to-end network can provide high electrical conductivity while preserving the unique properties of the nanorods. In a wide 2-D network, many charge paths are expected to serve as the most effective electron transport layer in film devices. In addition, a simple approach to assembling anisotropic nano rods at fluid-fluid interfaces opens up new possibilities for designing macroscopic materials with various nanostructures from nano-colloidal building blocks.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

100: capped nanorod, etchant, and solvent mixture
110: capped nanorod
120: Etching agent
130: Solvent
200: substrate
300: 2D nano-rod structure

Claims (18)

Mixing the nanorods surrounded by the capping material and the etchant in a solvent; And
And exposing the nanorods to an air / solvent interface to self-assemble the 2-D nanostructure. 2. The method of claim 1, wherein the mixing step comprises an etching step in which the etchant selectively etches the capping material at the end of the nano-rod. 2. The method of claim 1, wherein the etchant comprises a chloride ion, an oxide ion, or an aqueous sulfide ion solution. 2. The method of claim 1, wherein the etchant comprises a metal salt. 5. The method of claim 4, wherein the metal salt is chloride, silver chloride, copper chloride, platinum chloride, cobalt chloride, or ferric chloride. 5. The method of claim 4, wherein the etching step comprises selectively removing the capping material at the end of the nanorods, and then reducing metal ions of the metal salt to the ends of the nanorods and attaching the metal to the ends of the nanorods. -D A method for producing a nanostructure. 2. The method of claim 1, wherein the capping material is a surfactant. [2] The method of claim 1, wherein the self-assembling step forms a network by bonding capillary attraction between the nano rod ends at an air / solvent interface. 2. The method of claim 1, wherein the self-assembling comprises immersing the substrate in the solvent. [2] The method of claim 1, wherein the self-assembling comprises immersing the substrate in the solvent and then raising the substrate at a predetermined rate. 11. The method of claim 10, wherein the method controls the pulling rate of the substrate to control the density of the nanorod network formed on the substrate. The method of claim 1, wherein the density of the nanorod network is controlled at the air / solvent interface by controlling at least one of the concentration of the etchant, the concentration of the nanorods, and the evaporation rate of the solvent A method for manufacturing a self-assembled 2-D nanostructure. 2. The method of claim 1, wherein the nanorod is a semiconductor material. 2. The method of claim 1, wherein the solvent is a non-polar solvent. The nano-rod structure according to any one of claims 1 to 14, wherein the structure is formed of a mono-layer structure in which nano-rods and nano-rods are bonded only to each other at their terminals. D nano structure. 16. The self-assembled 2-D nanostructure of claim 15, wherein the nanorod sidewalls are coated with a capping material. 16. The self-assembled 2-D nanostructure according to claim 15, wherein a metal is attached to the end where the nanorods are bonded.  15. A device comprising the self-assembled 2D nanorod structure of claim 15, wherein the device comprises a transistor, a transmitter, a laser, a Q-switch, a switch, an optical switch an optical switch, an optical fiber, a gain device, an amplifier, a display, a detector, a communication system, a light emitting diode, a light conversion layer, a solar cell, or a sensor.

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