KR20160124399A - a method for manufacturing of 2D polyaniline nanosheet with high conductivity at ice surface - Google Patents

Abstract

Provided is a new method to develop two-dimensional polyaniline (PANI) nanosheets using ice as a hard template. Distinctly high current flows of 5.5 mA at 1 V and a high electrical conductivity of 35 S cm were obtained for the PANI nanosheets, which are prepared by the method and are marked a significant improvement from previously values on other PANIs reported over the past decades. These improved electrical properties of ice-templated PANI nanosheets were attributed to the long-range ordered edge-on -stacking of the quinoid ring, ascribed to the ice surface-assisted vertical growth of PANI. The unprecedented advantages of the ice-templated PANI nanosheets are two-fold. First, the prepared PANI nanosheet can be easily transferred onto various types of substrates via float-off from the ice surfaces. Second, prepared PANI can be patterned into any shape using predetermined masks, and this is expected to facilitate the eventual convenient and inexpensive application of conducting polymers in versatile electronic device forms.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a high-conductivity two-dimensional polyaniline nanosheet and a method for manufacturing the same,

The present invention relates to a polyaniline nanosheet and a method of manufacturing the same, and more particularly, to a method for producing a highly conductive two-dimensional polyaniline nanosheet on an ice surface.

Since the discovery of conductive polymers in the middle of the 19th century, much research and efforts have been made on this material, and in recent decades it has been applied to various applications in electronic devices such as thin film transistors, light emitting diodes, solar cells, batteries, super capacitors, Active research is underway. Among them, many researchers are working on new synthetic methods to improve the electrical conductivity and process of these conductive polymers. Conductive polymers generally known to be synthesized at present include polyaniline (PANI), polypyrrole (PPy), polyparaphenylene vinylene (PPV), and polythiophene (PT) derivatives.

Of these various conductive polymers, PANI has long been regarded as a next-generation material for use in microelectronic devices and electrodes for batteries due to its high electrical conductivity, easy and cheap wet chemical synthesis, easy doping process, and high stability. In the case of PANI in the form of emeraldine salt, which is a doping type of PANI, high conductivity (10 ^-3 to 10 ² S / cm), depending on the conjugation bond length and doping degree of the substance and the type of dopant . In addition, several decades of studies have shown that the electrical conductivity of PANI plays a major role in the dimensional change of PANI nanostructures.

Template synthesis has been widely used as an efficient method for synthesizing various PANI nanostructures, and it can be classified as follows. First, there is a method of directly inducing the growth of aniline using structured hard templates and a second method of oxidizing and polymerizing aniline using soft templates. Through these two types of template synthesis, various PANI structures such as nanoparticles, nanotubes, nanofibers, nanowires, nanosheets, and networks have been produced. Through these studies, studies on the relationship between structure and properties of PANI As a result of these studies, it has been emphasized that the development of a two-dimensional structure is very important in order to improve the electrical performance, in particular, to realize the application of highly electric devices and electronic devices.

In order to successfully synthesize two-dimensional PANI nanostructures, many studies have used graphene oxide (GO) as a light-weight plate, which is attributed to the 2D structure of the GO itself, which has an atomic thickness and a high surface area . In particular, the oxygen functional group present in the GO provides an active site capable of hydrogen bonding with aniline, thereby enabling aniline to grow in two dimensions in the direction of the base surface of the GO through a π-π superposition interaction. The resulting "PANI / GO composite nanosheets" show high electrical conductivity and mechanical strength, but in the case of GO, non-uniform distribution of PANI and irreversible masses are induced, Difficulties arise. In addition, the PANI / GO complex has many disadvantages in that it is very difficult to remove the high cost, complex synthetic process, and GO template.

A problem to be solved by the present invention is to provide a novel method for synthesizing a PANI nanostructure having a large and uniform two-dimensional PANI in order to use PANI in a next generation electronic apparatus.

Another problem to be solved by the present invention is to provide a method of controlling properties of a surface and an interface at which synthesis occurs so that a pure and homogeneous two-dimensional PANI nanostructure can be synthesized in a large area.

In order to solve the above problems,

The present invention provides a method for producing an aniline nanosheet, characterized in that the aniline is polymerized on the ice surface.

In the present invention, the aniline may be provided in a liquid state by dropping, casting, or coating on the ice surface.

In the present invention, the polymerization may be a chemical oxidation polymerization.

In the present invention, the reaction temperature is preferably 0 ° C or lower.

In the present invention, the polymerization may be carried out for 30 minutes or less, preferably 20 minutes or less, and most preferably 10 minutes or less.

In the present invention, the aniline nanosheet may further include separating the polymerized nanosheet by melting ice.

In the present invention, it is preferable that the ice is a flat ice plate.

In the present invention, the nanosheet may be a nanosheet having a thickness of 100 nm or less, preferably 50 nm or less, more preferably 10 to 40 nm, and most preferably a nanosheet having a thickness of 30 nm.

In one aspect, the present invention provides a method for producing an aniline nanosheet according to a specific pattern by polymerizing an aniline on an ice surface having a specific pattern formed.

In one aspect, the present invention provides an aniline nanosheet according to the present invention, wherein the quinide rings are arranged substantially vertically and the conjugated rings are orthorhombic with an edge-on? -Π arrangement ) Crystalline nanocrystalline nanocrystalline nano-sheet.

In the present invention, the highly conductive aniline nanosheet comprises an emerandine salt.

In the present invention, the highly conductive aniline nanosheet has a conductivity of 10 S / cm or more, preferably 20 S / cm or more, more preferably 30 S / cm or more, and has a conductivity of, for example, 35 S / Aniline nanosheet.

According to another aspect of the present invention, there is provided a composite body comprising an ice substrate and a conductive aniline nanosheet formed on the ice substrate. Conductive aniline nanosheets can be patterned nanosheets.

The key to this successful result is the use of ice, a new hard template, which provides a special surface for water molecules with lower potential energy than ordinary water. In addition, ice can be easily removed using a simple fusing process, which enables the formation of thin PANIs of the order of tens of nanometers with the substrate removed.

Figure 1 (a) Real-time image of PANI synthesis on ice surface. The photographs were taken during the reaction and are shown in the figure. (b) Voltage-current characteristic curves of PANI-ICE, PANI-ED, and Graphene-CVD. The optical image of PANI-ICE placed on gold electrodes is illustrated.
Figure 2 shows the structural characteristics of PANI-ICE by combining (a) X-ray powder diffraction and (b) selected area electron diffraction. This means that the highly crystalline PANI-ICE has an orthorhombic structure as shown in (a) and (b). The established orthorhombic structure in which the conjugated ring in PANI-ICE forms an edge-on π-π array is depicted in (c).
Fig. 3 (a) Photographs of PANI-ICE transferred onto another substrate. (B) PANI-ICE optics showing lines bent periodically and periodically with parallel lines using a metal mask, as shown in Fig. pictures.
Figure 4: Confinement Raman spectrum of graphene using CVD technique; The D-band, G-band, and 2D band of graphene correspond to 1350, 1580, and 2700 cm ^-1 , respectively, and are shown in the figure.
(B) Fourier transform infrared spectroscopy (FT-IR) spectrum of PANI-ICE and PANI-ED, PANI-ICE and PANI-ED have similar doping levels It is present in the form of an emeraldine salt.
6 Current-voltage characteristic curve of PANI nanosheet synthesized on glass substrate. Illustration: Optical microscope photograph of PANI synthesized on glass substrate.
Fig. 7 Optical microscope photograph of PANI nanosheet synthesized on a glass substrate at 0 ° C in real time.
Figure 8 Schematic illustration of a synthetic process for 2D PANI nanosheets (PANI-ICE) on ice surface. The TEM photographs assured the synthesis of 2D nanosheets with some defects.

Figure 8 shows the process of synthesizing 2D PANI nanosheets on an ice surface (hereinafter referred to as PANI-ICE). First, drop the aniline solution of 1M HCl onto frozen ice on the padridish. Invert ice to provide a flat surface of ice. The quantized anilinium can easily attach to the hydroxide group on the ice surface through hydrogen bonding and electrostatic interaction. To chemically oxidize aniline monomers, 1 M HCl solution of ammonium persulfate is added slowly to the ice immediately, keeping the reaction temperature at 0 ° C. Through the 3-minute oxidation polymerization, the generation of PANI-ICE of several millimeters in size can be observed visually. PANI-ICE has a thickness of about 30 nanometers, which is measured with a scanning probe microscope after transferring the sample onto a Si / SiO ₂ substrate. The 2D nanosheets were confirmed by transmission electron microscopy (TEM) to show that they were produced with some defects as illustrated. Considering the facts of most papers on chemical oxidation polymerization of PANI, 0 D or 1 D PANI structures are due to surface induced clustering, and the easy synthesis of 2D PANI with ice templates is noteworthy.

In order to study the mechanism of synthesis of PANI-ICE, PANI on the ice surface was observed in real time using an optical microscope equipped with a cryogenic sample stage. Photographs of PANI-ICE were obtained immediately during each reaction and can be seen in Figure 1A. An interesting formation of a few millimeters of uniform aniline membrane can be seen in the early hours of the reaction (<30 seconds), which can be attributed to the ease of adsorption of oligomers or coagulants through hydrogen bonding interactions. Potential energy at relatively low PANI and ice surface as compared to bulk water also plays a key role in developing a large area wet aniline membrane by lowering the nucleation barriers. During the oxidation process, changes in the size of nanosheets were not observed. However, the preferential vertical growth of PANI can be recognized by the increase of dark blue. As a result, a uniform and large area PANI can be obtained within 3 minutes of the reaction. We first tried to verify the electrical properties of PANI-ICE at constant temperature and humidity (25 ° C and 20%) through the current-voltage behavior in the -1.0 ~ 1.0V voltage range. 1B shows the current-voltage curve of PANI-ICE. (10 mm wide and 10 mm apart) on a Si / SiO ₂ substrate compared to a conventional PANI thin film (PANI-ED) prepared by constant current electrochemical deposition Showing PANI-ICE located). Surprisingly, PANI-ICE shows a high current flow of 5.5 mA at 1 V with a linear current-voltage curve, while a low flow current of 0.12 mA for PANI-ED. The uniformity of the global PANI-ICE was further confirmed by spatially resolved photocurrent imaging using a focused laser beam with a wavelength of 532 nm and a diameter of 500 nm in a 0.1 V bias environment. Representative results obtained on a 30 x 30 mm area are illustrated

The electrical conductivity of PANI-ICE and PANI-ED was calculated by adding the thickness and size of each sample to the following equation.

L is the distance between the gold electrodes (10 mm), I is the current, V is the applied voltage, and A is the cross-sectional area of the sample. In particular, the electrical conductivity of PANI-ICE is calculated to be 35 S / cm, which is two orders of magnitude larger than PANI-ED (0.8 S / cm). According to our knowledge, we report the highest electrical conductivity compared to the values of any other PANI reported in the paper (generally 1 S / cm similar to our PANI-ED) (the most common dopant is HCl In case you focus). This obviously means that our results have affected the structure of conductive polymers based on PANI. The current-voltage curve of graphene-CVD (graphene-CVD, approximately 360 ohm / sq of sheet resistance, Raman spectrum is synthesized in Figure 4) synthesized by chemical vapor deposition as a reference material is also noted in Figure 1b, Means that ICE can be provided as a new electrical soft material with good electrical properties. It is also worth mentioning the additional advantage that the large-area synthesis can be made at a low price quickly.

Conjugation length and doping level are well known as factors affecting the electrical properties of conductive polymer, and the molecular characteristics of PANI-ICE are compared with those of PANI-ED. As can be seen from FIG. 5, it can be seen from the results of UV-Vis and IR absorption spectra that PANI-ICE and PANI-ED have basically the same conjugation length and doping level. Thus, we infer that the enhanced electrical conductivity of PANI-ICE does not result from its chemical properties.

The fundamental mechanism of the improved electrical properties can be said to be due to the high crystallinity and interesting molecular arrangement of PANI-ICE. Structural features of PANI-ICE were analyzed by X-ray powder diffraction (XRD) and selected area electron diffraction (SAED) of TEM. The XRD profile shows that the aniline molecules in the PANI-ICE form a long-range order, and the orthorhombic, P222 space group (unit cell parameters, a = 17.356 Å, b = 7.012 c = 8.579 Å and a '= ∧a = ~ a = 90.00 °), which can be confirmed in FIG. 2A. Thus, it can be inferred that the PANI molecules form a π-π array in the c-axis direction with a spacing of about 3.51 Å and that the main chains of the PANI are perpendicular to the b-axis direction at 4.29 Å. From the SAED, it was confirmed that the quinoid rings of PANI-ICE were arranged in the vertical direction in all the regions tested. Representative results are shown in FIG. 2B, and the brightest (020) reflection of PANI-ICE is the edge-on pi-pi arrangement of the conjugated ring as shown in FIG. 2c.

This implies that the ice surface affects the arrangement properties of aniline molecules during growth of long-range aligned 2D nanosheets. Directly corresponding to the improved electrical conductivity. To further support our hypothesis, we synthesized 2D PANI nanosheets on substrates with different -OH (Si-wafer and glass) in the same experimental environment. Interestingly, the synthesized PANI nanosheets were very porous and defective, which showed a few orders of magnitude less current flow (voltage-current curves and optical images of PANI synthesized on glass substrates are shown in FIG. 6). This was due to uneven lumps and nucleation under low temperature conditions consistent with the papers, but not in PANI-ICE. Note the real-time observation of PANI synthesis on glass (FIG. 7), and the nucleation of PANI averages several micrometers in size at the initial stage of the reaction can be readily detected. Over time, they are combined into a larger PANI chunk with a common karyotypic and growth mechanism. This clearly indicates the importance of the ice surface consisting of membranes of quasi-ordered water molecules in the formation of uniform and large 2D PANI nanosheets.

We attempt to conclude the present invention by mentioning unprecedented advantages when compared to other conductive polymers reported in the paper. First, due to the easy removal of ice molds, PANI-ICE can be transferred onto various substrates, such as metal, ITO, Si-wafer, glass, and even polymer substrates, which have not been reported in the paper. In FIG. 3A, there are photographs of the PANI-ICE on another substrate. In addition, micropatterned PANI can be readily prepared using a micropatterned mask. As a representative example, an optical image of PANI-ICE consisting of horizontal lines and lines periodically bent at 90 degrees can be seen in FIG. In principle, any pattern can be patterned with a prepared mask, which presents a new path to future organic electronics technology.

In summary, this study presents an easy synthesis of highly conductive 2D PANI nanosheets through chemical oxidation polymerization. The PANI nanosheets using ice plates achieved several orders of magnitude higher electrical conductivities than the previously reported HCl doped PANIs. This can be explained by the unique advantages of the ice surface providing low potential energy and quasi-ordered hydroxyl groups. As we know, this study was the first to show examples of pure 2D conductive polymers with patternable, transferable, and high electrical properties.

Experimental content

PANI-ICE was prepared by chemical oxidation polymerization at 0 ° C on an ice surface using aniline (> 99.5%, Sigma-Aldrich) and ammonium peroxydisulfate (APS) (> 98.0%, Alfa Aesar) Were synthesized. First, freeze the petri dish at -20 ° C, then turn the ice over to make a smooth surface. Then 0.25 M aniline dissolved in 1 M hydrochloric acid solution and 0.25 M APS dissolved in 1 M hydrochloric acid solution are placed on ice to make an aniline and APS molar ratio of 8: 3. Three minutes after the reaction, a 2D nanosheet having a diameter of several millimeters is visually observed. The PANI-ICE is then "float off" from the ice surface, transferred to a silicon wafer, washed repeatedly with distilled water, and dried in a vacuum oven for a week.

The morphological properties and molecular arrangement of PANI-ICE were analyzed using limited area electron diffraction (SAED) of the transmission electron microscope (TEM, JEOL-JEM-2100F). The crystal structure of PANI was analyzed by powder X-ray scattering (XRD). The diffraction data on the crystal structure were measured using a 2D beamline of a Pohang radiation accelerator. The real-time observation of the PANI-ICE synthesis was performed using an optical microscope under cryogenic conditions. (RMC Ultramicrotome)

The current-voltage characteristic curves of PANI-ICE and PANI-ED were obtained using a semiconductor analyzer at room temperature and humidity of 20%. The data were measured in a linear sweep mode at a voltage ranging from -1.0 to 1.0 V. For the spatially-resolved photocurrent measurement, a focusing laser with a diameter of 500 nm and a wavelength of 532 nm was used under a bias of 0.1 V.

PANI -ICE and PANI Synthesis of -ED.

PANI-ICE was prepared by chemical oxidation polymerization at 0 ° C on an ice surface using aniline (> 99.5%, Sigma-Aldrich) and ammonium peroxydisulfate (APS) (> 98.0%, Alfa Aesar) Were synthesized. First, freeze the petri dish at -20 ° C, then turn the ice over to make a smooth surface. Then 0.25 M aniline dissolved in 1 M hydrochloric acid solution and 0.25 M APS dissolved in 1 M hydrochloric acid solution are placed on ice to adjust the molar ratio of aniline to APS to 8: 3. Three minutes after the reaction, a 2D nanosheet having a diameter of several millimeters is visually observed. The PANI-ICE is then "float off" from the ice surface, transferred to a silicon wafer, washed repeatedly with distilled water, and dried in a vacuum oven for a week. Synthesis of PANI-ED with a thickness of 30 nm for the control experiment uses an electrochemical deposition method using a three-electrode under a constant voltage of 1.5 V as a conventional method. A silver / silver chloride (potassium chloride saturated solution) electrode is used as a reference electrode and a strongly doped silicon wafer is used as a working electrode and a counter electrode. (&Lt; 0.005 ohm). For the electrolyte solution, use 0.25 M aniline solution dissolved in 1 M hydrochloric acid. The PANI-ED produced after the reaction is also washed repeatedly with distilled water and dried in a vacuum oven for about a week.

Characterization of molecular and nanosheet structures

The PANI-ICE and PANI-ED molecules were characterized using an ultraviolet-visible light spectrophotometer (Agilent 8453) and a Fourier transform infrared spectrophotometer (PerkinElmer). The morphological properties and molecular arrangement of PANI-ICE were analyzed using limited area electron diffraction (SAED) of the transmission electron microscope (TEM, JEOL-JEM-2100F). The crystal structure of PANI was analyzed by powder X-ray scattering (XRD). The diffraction data on the crystal structure were measured using a 2D beamline of Pohang radiation accelerator and the unit lattice structure of PANI was obtained through crystalmaker simulation. The real-time observation of the PANI-ICE synthesis was performed using an optical microscope under cryogenic conditions.

Electrical analysis

The current-voltage characteristic curves of PANI-ICE and PANI-ED were obtained using a semiconductor analyzer at room temperature and humidity of 20%. The data were measured in a linear sweep mode at a voltage ranging from -1.0 to 1.0 V. For the spatially-resolved photocurrent measurement, a focusing laser with a diameter of 500 nm and a wavelength of 532 nm was used under a bias of 0.1 V.

Micro Patterned PANI Production of -ICE

Micro patterning of PANI was made using a metal mask made in advance in size and shape. After the mask is placed on the ice surface, chemical oxidation polymerization is used at 0 ° C in the same manner as PANI-ICE is synthesized. Micro-patterned PANI-ICEs were observed using an optical microscope (ZEISS Axio scope A1).

The confocal Raman spectra of graphene synthesized by chemical vapor deposition were measured using a WITEC Alpha 300R Raman spectroscope (WITec, Ulm, Germany) using a HeNe laser. The spatial resolution of the spectrometer is 250 nm. Three kinds of the pick on the picture (1350, 1580, and 2700 cm -l) are respectively yes and that the D-band, G-band, and 2D-band of the pin which has a synthesized graphene with low defects / disorde is . The drawing is a photograph of a graphene-CVD film placed on a gold electrode, and the current-voltage characteristic data of the graphene film is shown in FIG.

PANI-ICE and PANI-ED were measured for UV-visible absorption spectra and Fourier transform infrared spectroscopy at room temperature. As shown in FIG. 5 (a), absorption spectra of both types were obtained in a similar manner. Analysis of the infrared absorption spectrum associated with the quinoid to benzenoid transition in Fig. S2 (b) showed a similar intensity ratios of 0.98 ± 0.02 for PANI- Indicating that both ICE and PANI-ED exist in the form of an emeraldine salt with similar doping levels.

We analyzed the electrical characteristics of the PANI nanosheets synthesized on substrates containing different -OH functional groups by measuring the current-voltage characteristics through a linear sweep at room temperature, voltage-1.0 V to 1.0 V range. 6 shows current-voltage characteristic curves of PANI nanosheets synthesized on a 0 ° C glass substrate. Interestingly, the PANI nanosheets thus synthesized show defective and porous structure (as seen in the optical micrographs of the drawings), which leads to current flow that is several hundred times lower. The calculated electrical conductivity value is very low, 0.07 S / cm.

PANI synthesis was observed on glass substrates at 0 ℃ in real time. Referring to FIG. 7, it can be seen that crystal nuclei of PANI having a size of several micrometers are generated at the initial stage of the reaction, and they follow a general crystal growth process that forms a large PANI structure as time goes by. This clearly demonstrates the importance of the quasi-ordered water molecule layer present on the ice surface in the formation of uniformly large-area, two-dimensional PANI nanosheets.

Claims (12)

A method for producing an aniline nanosheet, comprising polymerizing aniline on an ice surface. The method of claim 1, wherein the aniline is provided in a liquid state by dropping, casting, or coating on an ice surface. The method of claim 1, wherein the polymerization is a chemical oxidation polymerization. 2. The method of claim 1, wherein the polymerization is performed at 0 DEG C or lower. The method of claim 1, further comprising melting the ice to separate the polymerized nanosheets. The method of claim 1, wherein the ice is an ice substrate. The method of claim 1, wherein the nanosheet is a nanosheet having a thickness of 10 to 40 nm. Wherein an aniline nanosheet is produced by forming a specific pattern on an ice surface and polymerizing the aniline on the ice surface to produce an aniline nanosheet according to a specific pattern. A highly conductive crystalline aniline nanosheet in which the quinoid rings are arranged in a substantially vertical direction and the conjugated rings have an orthorhombic structure in which they form an edge-on pi-pi arrangement. 10. The highly conductive aniline nanosheet of claim 9, wherein the aniline nanosheet is doped with an emerandine salt. 10. The highly conductive aniline nanosheet of claim 9, wherein the highly conductive aniline nanosheet has a conductivity of at least 10 S / cm. An ice substrate, and a highly conductive aniline nanosheet f attached to the surface of the ice substrate.

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