KR100821699B1 - Carbon nano tube chemical sensor and method for manufacturing the same - Google Patents

Abstract

Carbon nanotube chemical sensors are provided.

Carbon nanotube chemical sensor according to the present invention comprises an insulating layer laminated on a glass, silicon or ceramic substrate; At least a pair of electrodes stacked on the insulating layer so as to face each other; And a sensing unit in which a plurality of carbon nanotubes are dispersed in a portion where the pair of electrodes are spaced apart from each other, wherein the plurality of carbon nanotubes and the pair of electrode sensing units and the carbon nanotube ends of the sensing unit are It is characterized by being electrically energized. The carbon nanotube chemical sensor according to the present invention can detect fine pH changes and very small amount of substances with excellent sensitivity even with a simple structure, and can improve mass productivity by reducing manufacturing costs.

Description

Carbon nano tube chemical sensor and method for manufacturing the same

1 is a cross-sectional view of a carbon nanotube chemical sensor according to the present invention.

Figure 2 is a schematic cross-sectional view of a spray process for forming a sensing unit of the carbon nanotube chemical sensor manufacturing method according to the present invention.

3 is a SEM photograph showing a carbon nanotube detector according to an embodiment of the present invention.

Figure 4 is a graph showing the response characteristics according to the OH ^- concentration of the sensor manufactured according to Example 1, the figure inserted in the upper right is a view showing the conductivity change according to pH.

<Description of the symbols for the main parts of the drawings>

1 substrate 2 insulation layer

3: electrode 4: shadow mask

5: carbon nanotube dispersion 6: spray

7: detection unit 8: hot plate

The present invention relates to a carbon nanotube chemical sensor, and more particularly, to a carbon nanotube chemical sensor and a method of manufacturing the same having excellent characteristics without expensive equipment and complicated processes.

In general, carbon nanotubes are hollow tubular carbon conjugates ranging in diameter from several nm to several tens of nanometers in length, and from several micrometers to several tens of micrometers, and are singlewalled depending on the number of walls that form the carbon nanotubes. ), Multiwall, and rope carbon nanotubes. These carbon nanotubes have the properties of conductors or semiconductors, depending on their shape, and have very strong and stable physical and chemical properties. Currently, carbon nanotubes are being applied to various fields. When carbon nanotubes are used as the sensing unit of the sensor, they have high precision and fast response speed due to very large surface-to-volume ratio and nano-sized sensing unit. Not only does it have the advantage of low power consumption. In particular, the diameter of the carbon nanotubes is about 2nm similar to the size of the biomolecule, and since all carbon atoms constituting the carbon nanotubes are present on the surface, the surface area that can react with the biomolecules can be used as a very sensitive sensor. It can be usefully used for biosensor because it can detect the adsorbed material precisely by monitoring the electrical property and pH change by the adsorbed material.

      Koen et al. Fabricated a carbon nanotube field effect transistor that has a large surface area and excellent electrical conductivity, so that molecules such as glucose oxidase are adsorbed on carbon nanotubes to increase immobilization and real-time detection sensitivity. It has been reported to study electrical reactions (Koen Bestenman, et al., "Enzyme-Coated Carbon nano tubes as Single-Molecule Bio sensors", Nano Letters, Vol. 3, No. 6, pp. 727-730, 2003 .), Alexander et al. Fabricated carbon nanotube field effect transistors, and coated a polymer (polyethylene imine / ethylene glycol) on a carbon nanotube channel used as a sensing unit, and biotin molecules were connected to bind to biotin. It has been reported that it can be used to detect changes in electrical properties of cultured streptavidin with or without binding (Alexander Star, et al., "Electronic Detection of Specifi c Protein Binding Using Nanotube FET Devices ", Nano Letters, Vol. 3, No. 4, pp. 459-463, 2003).

In addition, the Republic of Korea Patent Publication No. 0451084 discloses a gas sensor using carbon nanotubes, but in the prior art, the manufacturing method is subjected to a process of growing directly at high temperature when forming a sensing unit or a sensing film using carbon nanotubes. It was difficult to commercialize because it had to go through a lot of tricky processes.

Meanwhile, US Patent Publication No. 2006 / 0010996A1 arranges a conductor including a plurality of carbon nanotubes between two electrodes, wherein the plurality of carbon nanotubes are configured to be substantially arranged along an axis connecting the electrodes. Although disclosed, in order to arrange the carbon nanotubes in the axial direction, first depositing a carbon nanotube affinity material in the space between the electrodes and then aligning the carbon nanotubes by applying an electric field, and then the carbon nanotube affinity material There was a problem in that the manufacturing process is complicated because the sensing unit is formed by washing the remaining carbon nanotubes that are not bonded to each other.

Therefore, the first technical problem to be achieved by the present invention is to provide a carbon nanotube chemical sensor that is easy to manufacture and excellent in sensitivity because it has a simple structure.

The second technical problem to be achieved by the present invention is to provide a method for manufacturing a carbon nanotube chemical sensor that can be manufactured simply and efficiently the sensing unit of a sensor comprising a carbon nanotube.

The present invention to achieve the first technical problem,

An insulating layer laminated on the glass, silicon or ceramic substrate;

At least a pair of electrodes stacked on the insulating layer so as to face each other;

A plurality of carbon nanotubes formed in a network structure in the area where the pair of electrodes are spaced apart and consists of a sensing unit,

The plurality of carbon nanotubes and the pair of electrodes and the carbon nanotube end of the sensing unit is provided with a carbon nanotube chemical sensor, characterized in that the electrical current.

According to one embodiment of the present invention, the carbon nanotubes may be single-walled, multi-walled or bundled carbon nanotubes.

According to another embodiment of the present invention, the substrate may be a glass, silicon or ceramic substrate.

According to another embodiment of the present invention, the electrode may be Cr, Au or Pt.

According to another embodiment of the present invention, the chemical sensor is preferably a pH sensor.

The present invention to achieve the second technical problem,

(a) forming an electrode on the substrate;

(b) preparing a carbon nanotube dispersion comprising carbon nanotubes and ethanol;

(c) spraying the carbon nanotube dispersion between the electrodes using a shadow mask and a spray to form a sensing unit; And

(d) providing a method for manufacturing a carbon nanotube chemical sensor comprising removing the ethanol by heating the sensing unit and simultaneously connecting the electrodes with the carbon nanotubes.

According to one embodiment of the present invention, the preparing of the carbon nanotube dispersion may be performed by mixing the carbon nanotubes and ethanol, followed by an ultrasonic dispersion process.

According to a preferred embodiment of the present invention, the step of heating the sensing unit may be to use a hot plate.

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

The carbon nanotube chemical sensor according to the present invention includes carbon nanotubes in a sensing unit, and the carbon nanotubes are not grown directly on the sensing unit, using a separately manufactured carbon nanotube using a shadow mask and a high precision spray. By uniformly dispersing on the sensing unit, manufacturing cost can be reduced through a simple process, and fine pH change and extremely small amount of material detection can be detected by detecting that the charge amount and the electrical conductivity change as the fine material is adsorbed onto the carbon nanotube. Since it is possible, it can be usefully used as a chemical sensor or a biosensor.

1 is a cross-sectional view of a carbon nanotube chemical sensor according to an embodiment of the present invention.

The substrate 1 used in the present invention may be used without particular limitation as long as it is commonly used in the art, and may be, for example, a ceramic substrate such as glass, silicon, or alumina.

On the other hand, the insulating layer (2, insulator) used in the present invention can also be used without particular limitation as long as it is commonly used in the art, for example, Soda lime glass Etc. can be used.

In addition, the electrode 3 is not particularly limited as long as it is a material having excellent electrical conductivity and corrosion resistance, and for example, a metal material such as Cr, Au, or Pt may be used.

Finally, in the carbon nanotube chemical sensor according to the present invention, the sensing unit 7 which detects a change in charge amount or electrical conductivity by adsorbing chemicals has a plurality of carbon nanotubes forming a network structure. The carbon nanotubes of each other and the pair of electrodes and the carbon nanotube end of the sensing unit are electrically energized.

Carbon nanotube chemical sensor manufacturing method according to the present invention, unlike the prior art, does not require expensive vacuum equipment, it is characterized in that the carbon nanotube chemical sensor with excellent sensitivity can be manufactured through a simple process.

Figure 2 shows a schematic cross-sectional view of the spray process for forming the sensing unit 7 of the carbon nanotube chemical sensor manufacturing method according to the present invention.

First, the carbon nanotube dispersion (5) used in the carbon nanotube chemical sensor according to the present invention is mixed with carbon nanotube powder in volatile ethanol (C ₂ H ₅ OH) and then ultrasonically cleaned using an ultrasonic cleaning device. By dispersing, the carbon nanotubes are uniformly dispersed in the ethanol solution.

Next, the insulating layer 2 is deposited on a glass substrate, a silicon substrate, or a ceramic substrate 1 such as alumina (Al ₂ O ₃ ), and then a pair of electrodes are made of a metal material such as Cr, Au, or Pt. After the formation, the carbon nanotube dispersion 5 prepared above is uniformly dispersed between the pair of electrodes using a shadow mask 4 and a precision spray 6. Finally, the sensing unit 7 is heated by removing the ethanol from the dispersed carbon nanotubes and heating the lower part of the chemical sensor through a hot plate 8 to connect the electrode and the carbon nanotubes. To form.

Hereinafter, the present invention will be described in more detail with reference to preferred examples, but the present invention is not limited thereto.

Example 1

After heating a heating furnace (ULTECH: HLF series) on a silicon substrate having a width of 1 cm and a length of 1 cm, a SiO ₂ insulating layer was formed to have a thickness of 3000 Å through thermal oxidation, and the Pt electrode was formed by an electron beam evaporator ( ULVAC Technologies Inc: EBX-1000) was formed to 3000㎛ thickness, the distance between both electrodes was adjusted to 4㎛. Next, 40 mg of single-walled carbon nanotubes (ASP-100F (average diameter: 1-1.2 nm , length: 5-20 µm, purity:-90%)) having an average length of 5 to 6 µm was used. After incorporation into 100 ml of ethanol, a sonicator (manufactured by Daehan Co., Ltd.) was dispersed for 30 minutes with ultrasonic waves of 50 W and 45 kHz intensity. Subsequently, the dispersion was injected into a precision spray (manufactured by Empoem Co., Ltd.), and then the dispersion was sprayed between the electrodes using a shadow mask (stainless steel) manufactured directly to a width of 6 μm and a length of 10 μm. Then, the hot plate at the bottom of the substrate was heated to 100 ℃ to connect the carbon nanotubes and the electrode to prepare a carbon nanotube chemical sensor.

Test Example 1

SEM  Measurement of photograph

The sensing layer formation structure was confirmed through a SEM photograph of the sensing unit of the carbon nanotube chemical sensor manufactured in Example 1, and the results are shown in FIG. 3. As can be seen in Figure 3, it can be seen that the carbon nanotubes have a random network structure.

Test Example 2

Performance test

The carbon nanotube chemical sensor manufactured by Example 1 was driven at an operating voltage of 0.3 V, and the response characteristics according to the concentration of OH ⁻ in contact with the sensing unit were evaluated and the results are shown in FIG. 4. The figure inserted in the upper right is a graph measuring the change in conductivity according to pH. The chemical sensor according to the present invention showed a response characteristic within 1 second according to each OH ^- concentration change, and it can be seen that the conductivity of carbon nanotubes increases with increasing pH.

As described above, the carbon nanotube chemical sensor according to the present invention can be used as a gas sensor or a biosensor because it can detect a minute pH change and a very small amount of substance even though it has a simple structure. The manufacturing method of the tube chemical sensor does not need high vacuum and can manufacture the carbon nanotube chemical sensor with excellent sensitivity through a simple process, thereby reducing the manufacturing cost and excellent in mass production.

Claims (8)

An insulating layer laminated on the glass, silicon or ceramic substrate; At least a pair of electrodes stacked on the insulating layer so as to face each other; A plurality of carbon nanotubes formed in a network structure in the area where the pair of electrodes are spaced apart and consists of a sensing unit, Carbon nanotube chemical sensor, characterized in that the plurality of carbon nanotubes and the pair of electrodes and the carbon nanotube end of the sensing unit is electrically energized. The carbon nanotube chemical sensor of claim 1, wherein the carbon nanotubes are single-walled, multi-walled, or bundle carbon nanotubes. The carbon nanotube chemical sensor of claim 1, wherein the substrate is a glass, silicon, or ceramic substrate. The carbon nanotube chemical sensor of claim 1, wherein the electrode is Cr, Au, or Pt. The carbon nanotube chemical sensor of claim 1, wherein the chemical sensor is a pH sensor. (a) forming an electrode on the substrate; (b) preparing a carbon nanotube dispersion comprising carbon nanotubes and ethanol; (c) spraying the carbon nanotube dispersion between the electrodes using a shadow mask and a spray to form a sensing unit; And (d) removing the ethanol by heating the sensing unit and simultaneously connecting the electrodes and the carbon nanotubes. The method of claim 6, wherein the preparing of the carbon nanotube dispersion is performed by mixing the carbon nanotube and ethanol, and then performing an ultrasonic dispersion process. The method of claim 6, wherein the heating of the sensing unit comprises using a hot plate.

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