KR20100081098A - Single-walled carbon nanotube hydrogen gas sensor and its fabrication method - Google Patents

Abstract

PURPOSE: A single-walled carbon nanotube hydrogen sensor and a method of manufacture thereof are provided to reduce the reaction time. CONSTITUTION: One or more single-walled carbon nanotubes(10) are prepared. A dendrimer(13) is formed on the carbon nanotube surface. The metal nanoparticle is functioned in the formed dendrimer as the reaction catalyzer with the hydrogen. Dendrimer is composed of the polyamidoamine dendrimer(14). The metal nanoparticle comprises one selected from palladium(Pd), platinum(Pt), rhodium(Rd), nickel(Ni), aluminum(Al), manganese(Mn), molybdenum(Mo), magnesium(Mg), and vanadium(V).

Description

SINGLE-WALLED CARBON NANOTUBE HYDROGEN GAS SENSOR AND ITS FABRICATION METHOD}

The present invention relates to a hydrogen sensor using a single-walled carbon nanotubes, and more particularly, by synthesizing a dendrimer (dendrimer) on a single-walled carbon nanotubes by functionalizing the metal nanoparticles excellent in the adsorption and reaction properties for hydrogen. One single-walled carbon nanotube hydrogen sensor and a method of manufacturing the same.

Recently, with the continuous use of fossil fuels, problems of environmental pollution such as global warming and energy supply and demand due to the depletion of fossil fuels are emerging, and as an alternative to overcome this, interest in hydrogen, which is a clean energy resource and shows potential for future development. This is concentrated and the development of hydrogen energy is proceeding at a rapid pace.

At present, various technologies for generalizing such hydrogen energy have reached the practical stage, but since hydrogen is exposed to more than 4% of concentration in air before being used as clean energy, it is flammable and easily exploded, so In order to be easy to use, a technique for quickly and accurately detecting trace amounts of hydrogen is essential.

Recently, technologies using thin film materials and semiconductors such as MISFETs have been reported as hydrogen detection technologies for sensors (F.Dimeo et al., 2003 Annual Merit Review). However, despite their respective advantages, their performance is still insignificant in terms of detectable initial hydrogen concentration, reaction time, sensing temperature, and driving power consumption. .

As an alternative, a hydrogen sensor using single-walled carbon nanotubes (hereinafter referred to as SWCNT) has been announced. SWCNTs have high reactivity, low density, and high surface-to-volume ratios for various gases. Therefore, the SWCNT has been studied as a hydrogen sensor for this purpose.

However, pure SWCNT hardly reacts with hydrogen. In order to solve this problem, numerous studies have used various methods such as sputtering palladium (Pd) nanoparticles as a catalyst, chemical vapor deposition (CVD), e-beam evaporation, and electroplating. Functionalization through maximizing reactivity with hydrogen (Kong J, Chapline G and Dai H, Adv. Mater. 13, (2001)). 1 is a transmission electron microscope (TEM) tissue photograph of an example in which Pd nanoparticles are directly functionalized in SWCNTs according to the prior art.

In the manufacturing process, the SWCNT is made of a mixture of metallic and semiconductor characteristics. In the case of dominant semiconductor characteristics, it has high sensitivity, but the reaction time is rapidly decreased at low concentrations, and stability and discrimination against continuous hydrogen concentration change have not been verified. In addition, it exhibits much lower sensitivity when the metallic properties prevail. When these two properties are mixed, there is a problem that the sensitivity and response time are low.

As such, the conventional SWCNT-type hydrogen sensors supplement the problems of the existing hydrogen sensor to some extent, but are not an alternative to the conventional sensors in the problems of sensing ability, sensitivity, stability, and fast reaction time at low concentration.

Hydrogen sensor is a necessary technology for all machinery that uses hydrogen energy such as hydrogen car to be developed in the near future, and it is urgent to develop the technology as a source technology that can guarantee safety measures and effectiveness for future fuel. to be.

Therefore, the present inventors have pursued a better detection capability and stability than a hydrogen sensor manufactured in the form of a conventional SWCNT, and at the same time, a method of realizing a hydrogen sensor having excellent sensitivity and a fast reaction time even at a low concentration is examined. It was. As a result, it was found that a hydrogen sensor having excellent performance can be obtained by synthesizing a dendrimer in SWCNT and functionalizing metal nanoparticles having excellent adsorption and reaction properties for hydrogen as a catalyst for reaction with hydrogen. Furthermore, it was found that hydrogen sensor having better performance can be obtained by decomposing the dendrimer through a predetermined heat treatment in the hydrogen sensor thus obtained. The present invention is therefore presented.

Therefore, an object of the present invention is to provide a method for producing a hydrogen sensor having excellent hydrogen detection ability by synthesizing a dendrimer in SWCNT prepared by a conventional method and functionalizing specific metal nanoparticles as a catalyst.

In addition, the present invention synthesizes a dendrimer in the SWCNT prepared by a conventional method, and functionalize the specific metal nanoparticles and then decompose the dendrimer through a predetermined heat treatment to narrow the gap between the SWCNTs and the metal nanoparticles, the reaction time is fast at low concentration Another object is to provide a method of manufacturing a hydrogen sensor having excellent sensitivity.

In addition, the present invention has another object to provide a hydrogen sensor manufactured through the above manufacturing method.

The present invention for achieving the above object,

Preparing at least one single-walled carbon nanotube (SWCNT);

Forming a dendrimer on the surface of the SWCNT; And

Functionalizing the metal nanoparticles with the reaction catalyst with hydrogen in the formed dendrimer; It relates to a method of manufacturing a single-wall carbon nanotube hydrogen sensor comprising a.

According to another aspect of the present invention,

Preparing at least one single-walled carbon nanotube (SWCNT);

Forming a dendrimer on the surface of the SWCNT;

Functionalizing the metal nanoparticles as the reaction catalyst with hydrogen in the formed dendrimer; And

Decomposing the dendrimer as heat through heat treatment; It relates to a method of manufacturing a single-wall carbon nanotube hydrogen sensor comprising a.

At this time, the present invention preferably comprises the step of maintaining the heat treatment step for 10 to 13 hours at 200 ℃, and may further include a step of reducing the temperature to 25 ℃ after the temperature maintenance process.

In the present invention, the dendrimer is preferably a polyamidoamine [poly (amidoamine) (PAMAM)] dendrimer.

In the present invention, the metal as the catalyst is palladium (Pd), platinum (Pt), rhodium (Rb), nickel (Ni), aluminum (Al), manganese (Mn), molybdenum (Mo), magnesium (Mg), vanadium It is preferable that it is any selected from (V).

In the present invention, the step of forming a dendrimer on the SWCNT surface,

Forming a carboxyl group on the surface of the SWCNT by sonicating the SWCNT in a mixed solution of nitric acid (H ₂ NO ₃ ) and sulfuric acid (H ₂ SO ₄ ) for 2 to 4 hours; The SWCNTs were mixed in ethylenediamine and HATU (N-[(dimethylamino) -1H-1,2,3-triazolo (4,5,6) pyridine-1-ylmethylmethanaminium hexafluorophosphate N-oxide]) Sonicating for 3-5 hours to form amine groups at the ends of the oxidized SWCNTs; And synthesizing the dendrimer by first immersing the SWCNT in methyl acrylate and then, secondly, in ethylene diamine solution. It is preferable to include.

Here, the temperature of the mixed solution of nitric acid and sulfuric acid is preferably 35 ~ 45 ℃, the SWCNT (mg): nitric acid solution (ml): sulfuric acid solution (ml) is preferably 2: 1: 3. In addition, the ratio of SWCNT (mg): ethylenediamine (mg): HATU (mg) is preferably 20: 10: 1.

In the present invention, the step of synthesizing the dendrimer,

Synthesizing an initial dendrimer having an ester group formed at the terminal through the Michael addition reaction; And forming a final dendrimer by forming an amine group in the ester group formed at the initial dendrimer end; It is preferable to include.

In the present invention, the amine group forming step and the dendrimer synthesis step may be repeatedly performed additionally two to five times.

In the present invention, the metal nanoparticles can be functionalized using any one method selected from sputtering, chemical layer (CVD), electron beam deposition or electroplating.

In the present invention, the metal nanoparticles are made of Pd and can be functionalized by reduction of 0.1M PdCl42- and 1.0M NaBH4 on the SWCNT in which the dendrimer is formed in an aqueous solution or an acid solution of pH2.

The present invention also relates to a single-walled carbon nanotube hydrogen sensor manufactured by the above-described manufacturing methods.

In addition, the present invention,

At least one single-walled carbon nanotube (SWCNT);

A dendrimer formed on the surface of the SWCNT; And

Metal nanoparticles functionalized as reaction catalysts with hydrogen in the dendrimer; It relates to a single-wall carbon nanotube hydrogen sensor comprising a.

Furthermore, the present invention,

At least one single-walled carbon nanotube (SWCNT);

A dendrimer debris layer after the dendrimer formed on the surface of the SWCNT is decomposed by heat; And

Metal nanoparticles functionalized as a reaction catalyst with hydrogen on the SWCNT surface and the residue layer of the dendrimer; It relates to a single-wall carbon nanotube hydrogen sensor comprising a.

In the present invention, the SWCNT in the hydrogen sensor is preferably 1.0 ~ 1.2nm in diameter, 20㎛ in length, purity is 60 ~ 70wt%.

In the present invention, the dendrimer is preferably a polyamidoamine [poly (amidoamine) (PAMAM)] dendrimer.

 In the present invention, the metal as the catalyst is palladium (Pd), platinum (Pt), rhodium (Rb), nickel (Ni), aluminum (Al), manganese (Mn), molybdenum (Mo), magnesium (Mg), vanadium It is preferable that it is any selected from (V).

In the present invention, the hydrogen sensor,

A power supply unit supplying power to the SWCNT; And a signal analyzer for analyzing the electrical signal according to the resistance change of the SWCNT. It is preferred to further include.

According to the present invention, by applying a dendrimer to the SWCNT, the reaction time is greatly reduced by a mechanism different from the conventional one, and by inducing thermal decomposition of the dendrimer through heat treatment, hydrogen detection time is dramatically reduced while maintaining the existing sensitivity. Can be reduced.

In addition, according to the present invention, a faster and more accurate detection is possible for a lower hydrogen concentration than the conventional one, and reversible in response to continuous hydrogen, and it is possible to clarify the differentiation for each detected concentration.

Furthermore, according to the present invention, there is an advantage in that low concentration of hydrogen due to initial exposure of hydrogen can be detected more quickly and accurately.

Hereinafter, with reference to the accompanying drawings showing a preferred embodiment of the present invention will be described in more detail the present invention.

Figure 2 is a schematic diagram showing the manufacturing process of a single-wall carbon nanotube (SWCNT) hydrogen sensor according to the present invention.

As shown in FIG. 2 (a), first, at least one single-walled carbon nanotubes (SWCNTs) 10 are provided in the present invention. Preferably, a bundle of SWCNTs consisting of a plurality of SWCNTs is provided. Such SWCNT (s) may be prepared by a conventional known technique (Korean Patent No. 0432056, International Publication No. WO06 / 055679, WO02 / 038496 et al.). In the present invention, it is also possible to purchase and arrange known SWCNT products manufactured by Hyperion Catalysis, Carbon Nanotechnologies, NEC, MITSUBISHI, iljin nanotech, and the like. This SWCNT has a tube structure with a diameter of several nm.

Subsequently, in the present invention, as shown in FIG. 2 (b), the SWCNT 10 is immersed in a mixed solution of sulfuric acid and nitric acid and then sonicated for 2 to 4 hours to form carboxyl groups on the surface of the SWCNT. do. Preferably, the carboxyl group (-COOH) 11 is bonded to SWCNT. At this time, the temperature of the mixed solution is preferably 35 ~ 45 ℃. It is more preferable that it is especially 40 degreeC. In addition, the nitric acid solution (HNO ₃ ) (ml) and the sulfuric acid solution (H ₂ SO ₄ ) (ml) are preferably mixed in a 1: 3 ratio. More preferably, the surface of SWCNT is oxidized in a 2: 1: 3 ratio of SWCNT (mg), nitric acid solution (ml) and sulfuric acid solution (ml).

Subsequently, in the present invention, as shown in FIG. 2 (c), SWCNTs oxidized in the above-mentioned form may be substituted with ethylenediamine and HATU (N-[(dimethylamino) -1H-1,2,3-triazolo (4,5,6). immersed in a mixed solution of pyridine-1-ylmethylmethanaminium hexafluorophosphate N-oxide]) and then sonicated for 3 to 5 hours to form an amine group 12 at the end of the oxidized SWCNT. At this time, the ratio of SWCNT (mg): ethylenediamine (mg): HATU (mg) is preferably 20: 10: 1.

Subsequently, in the present invention, as shown in FIG. 2 (d), the initial dendrimer 13 is formed through the Michael addition reaction to the SWCNT in which the amine group is formed. For example, SWCNTs in which amine groups are formed are immersed in methyl acrylate so that ethylenediamine provides ester end groups in methanol to primarily synthesize the initial dendrimer 13.

Then, in the present invention, as shown in Figure 2 (e), by immersing the SWCNT in which the initial dendrimer 13 is formed in an ethylenediamine solution, the initial dendrimer in the terminal ester has an ethylenediamine contained in excess methanol The final dendrimer 14 is synthesized secondary by creating groups at its ends. Preferably it forms a polyamidoamine (PAMAM) dendrimer. Such dendrimer is preferably formed to a thickness of 0.5 ~ 3nm.

At this time, in another embodiment of the present invention, if necessary, the first and second processes may be repeated two to four times as shown in FIGS. 2 (d) and 2 (e). This is to form more dendrimers in the SWCNT as shown in FIG. 2 (f). However, the present invention is not limited thereto, and the first and second processes may be repeated once or five times or more.

In the present invention, as shown in Figure 2 (g), after forming the dendrimer 14, the predetermined metal nanoparticles (15) having excellent adsorption and reaction properties for hydrogen as a catalyst for the reaction with hydrogen to the SWCNT (10) Functionalized. The functionalization of the metal nanoparticles 15 may be implemented through various methods such as sputtering, chemical vapor deposition (CVD), e-beam evaporation, and electroplating. Thus, by functionalizing the metal nanoparticles excellent in the reactivity with hydrogen SWCNT can be maximized the reactivity with hydrogen. At this time, in the embodiment of the present invention, the metal nanoparticle 15 is preferably a metal material having excellent adsorption and reactivity with hydrogen as a catalyst for the reaction with hydrogen. For example, the metal nanoparticles 15 may include palladium (Pd), platinum (Pt), rhodium (Rd), nickel (Ni), aluminum (Al), manganese (Mn), molybdenum (Mo), magnesium (Mg), It is preferable to include any one selected from vanadium (V).

The SWCNT (s) hydrogen sensor of the present invention manufactured by the above-described process is a single-walled carbon nanotube (SWCNT (s)) 10, a dendrimer 14 formed on the surface of the SWCNT (s) 10, such a dendrimer It can be configured to include the metal nanoparticles (15) functionalized in the (14). In this case, the metal nanoparticles 15 may be Pd, Pt, Rd, Ni, Al, Mn, Mo, Mg, V, or the like. The SWCNT (s) hydrogen sensor thus manufactured is much more metal due to the formation of three-dimensional branches of the dendrimer than in the case where the metal nanoparticles 15 are functionalized in the SWCNT (s) 10 without a dendrimer. Since the nanoparticles 15 are functionalized in the SWCNT (s) 10, the reaction time for hydrogen may be increased and the sensitivity may be improved. In addition, the high density Pd nanoparticles 15 may not only lower initial hydrogen concentration, but also quickly and accurately detect low concentration hydrogen gas.

Meanwhile, in the present invention, the SWCNT device 10 selectively implemented through FIG. 2 (af), that is, the SWCNT device 10 in which the metal nanoparticles 15 are functionalized after forming the dendrimer 14 as described above. May be heat treated. At this time, the heat treatment is performed for 10 to 13 hours at 200 ℃. It may also optionally be further reduced to 25 ° C thereafter. This heat treatment step is for decomposing the dendrimer 14 as heat while maintaining the number of the metal nanoparticles 15 as it is. As a result, the dendrimer 2 can be thermally decomposed (decomposed debris may remain), further narrowing the distance between the metal nanoparticles 15 and the SWCNT 10, thereby providing a catalyst for the reaction of the metal with hydrogen. As a result, the reaction time and sensitivity of the SWCNT 10 to hydrogen can be improved. This heat treatment process can be selectively adopted and shows much better reaction time and sensitivity than without heat treatment.

As such, the SWCNT hydrogen sensor implemented through the heat treatment process may include SWCNT (s) 10 and metal nanoparticles 15 functionalized on the surface of the SWCNT (s). In the SWCNT (s) hydrogen sensor manufactured as described above, much more metal nanoparticles 15 are added to the SWCNT (s) (10) than when the metal nanoparticles (15) are functionalized directly in the SWCNT (s) without a conventional dendrimer. Functionalization can result in faster reaction time for hydrogen and improved sensitivity. In addition, the high density metal nanoparticles 15 may not only lower initial hydrogen concentration, but also quickly and accurately detect low concentration hydrogen gas.

Figure 3 is a schematic diagram showing a device implemented as a single-walled carbon nanotube hydrogen sensor according to an embodiment of the present invention.

As shown in FIG. 3, the single-walled carbon nanotube hydrogen sensor 200 according to an exemplary embodiment of the present invention includes a single-walled carbon nanotube (SWCNT) 210 and a dendrimer 220 formed on the surface of the SWCNT 210. And a Pd nanoparticle 230 functionalized to the dendrimer 220, a power supply unit 240 for supplying power to the SWCNT 210, and a signal analysis unit 250 for analyzing an electrical signal of the SWCNT 210. have. The SWCNT hydrogen sensor 200 may be preferably implemented on a Si / SiO ₂ substrate. In this case, the SWCNT is preferably implemented as a bundle of SWCNTs.

When the SWCNT hydrogen sensor 200 according to the present invention is exposed to the atmosphere of hydrogen gas, hydrogen molecules are adsorbed to the metal in the form of atoms. Adsorbed hydrogen atoms supply their electrons to the metal and serve to lower the work function of the metal. The excess electrons move from the metal to the SWCNT, bringing about a carrier reduction effect of the SWCNT in which the hole acts as a carrier, thereby increasing the resistance of the SWCNT.

On the other hand, although not shown in the drawings, in another embodiment of the present invention may provide a hydrogen sensor decomposed as heat by heat treatment of the dendrimer 220 in the SWCNT hydrogen sensor of FIG. This may shorten the distance between the SWCNT 210 and the metal nanoparticles 230 by decomposing the dendrimer, thereby speeding up the reaction time for hydrogen. Accordingly, the hydrogen sensor includes at least one single-walled carbon nanotube (SWCNT), a dendrimer debris layer after thermal decomposition of a dendrimer formed on the surface of the SWCNT, and metal nanoparticles functionalized on the SWCNT surface and the dendrimer debris layer. You may.

The SWCNT hydrogen sensor 200 of the present invention is to change the resistance of the SWCNT in accordance with the concentration of hydrogen and thereby to detect the change in the electrical signal according to the signal analyzer 250 can effectively measure the hydrogen concentration.

4 and 5 are transmission electron microscope (TEM) tissue photographs of SWCNTs functionalized with Pd nanoparticles as a reaction catalyst with hydrogen according to one embodiment of the present invention.

Figure 4 (a) is a TEM tissue photograph when the Pd nanoparticles are functionalized directly on the SWCNTs without forming a dendrimer in the prior art, Figure 4 (b) is a Pd nanoparticle after forming the dendrimer once in accordance with the present invention Is a TEM tissue photograph when the functionalized to SWCNTs, Figure 4 (c) is a TEM tissue photograph when the Pd nanoparticles functionalized in the SWCNTs after forming the dendrimer three times in accordance with the present invention.

As shown in the TEM tissue picture of Figure 4, it can be seen that the number of functionalized Pd nanoparticles in the SWCNTs in order of (c)-(b)-(a) of FIG. In other words, more Pd nanoparticles could be functionalized when dendrimers were formed than without dendrimers in the SWCNTs bundle, and more Pd nanoparticles would be functionalized when formed three times than when dendrimers were formed once. It can be seen that. This is because the formation of three-dimensional branches of the dendrimer has increased the sites where the Pd nanoparticles can be functionalized.

The formation of dendrimers allows more Pd nanoparticles to be functionalized, resulting in very good performance in response time and sensitivity to hydrogen, and faster hydrogen detection even at low concentrations.

5 is another TEM tissue picture of SWCNTs according to the present invention.

Figure 5 (a) is a TEM tissue photograph when the functionalized Pd nanoparticles directly to SWCNTs without a dendrimer in the prior art, Figure 5 (b) is functionalized Pd nanoparticles to SWCNTs after forming the dendrimer according to the present invention Figure 5 is a TEM tissue picture, Figure 5 (c) is a TEM tissue picture of the SWCNTs after the heat treatment of Figure 5 (b) in accordance with the present invention.

As can be seen from the TEM tissue photograph of FIG. 5, the size of SWCNTs is increased in FIG. 5 (b) in which a dendrimer is formed than in FIG. 5 (a) in which no dendrimer is formed. In other words, it can be seen that the formation of the dendrimer is fine but increases the overall diameter of the SWCNTs. Due to the increase in size, the surface area capable of detecting hydrogen is considerably increased compared to the conventional one, and thus, it is possible not only to provide excellent hydrogen sensing ability, but also to realize the best reaction time and sensitivity for hydrogen. have.

In addition, as can be seen in Figure 5 (c), after the heat treatment can be seen that the number of Pd nanoparticles is maintained as compared to before the heat treatment. Therefore, the dendrimer decomposes due to the heat treatment, so that the distance between the SWCNTs and the Pd nanoparticles is close, while the amount of the Pd nanoparticles is maintained.

4 and 5 show an example in which Pd nanoparticles are used as a reaction catalyst with hydrogen, but other metal materials excellent in adsorption and reaction properties to hydrogen may be used as described above.

Hereinafter, the present invention will be described in detail through experimental examples.

Experimental Example

In this experimental example, a bundle of SWCNTs (20 mg) having a diameter of 1.0 to 1.2 nm, a length of 20 μm, and a purity of 60 to 70 wt% was purchased from iljin nanotech Co., Ltd. This bundle of SWCNTs was immersed in a mixed oxide mixture containing 10:10 HNO ₃ and H ₂ SO ₄ : 30mL and sonicated for 3 hours to form carboxyl groups on the surface of the SWCNTs. It was. At this time, the temperature of the oxide mixture solution was 40 degreeC.

Subsequently, the oxidized SWCNTs (20 mg) were immersed in a mixed solution containing 10 ml of ethylene diamine and HATU: 1 mg and sonicated for 4 hours to form an amine group at the terminal of the carboxy group. It was.

Subsequently, the steps of immersing the SWCNTs in which the amine groups are formed in the methyl acrylate solution and immersing them again in the ethylenediamine solution are repeated three times to synthesize the branched poly (amidoamine) (PAMAM) dendrimer. The dendrimer was formed on the surface.

Thereafter, the Pd nanoparticles were functionalized on the dendrimer-formed SWCNTs using a conventional electroplating method. Functionalization of Pd nanoparticles by electroplating was accomplished by reduction of 0.1M PdCl42- and 1.0M NaBH4 on dendrimer-formed SWCNTs in aqueous or pH2 acid solutions. Through this process, a dendrimer-SWCNTs device in which Pd nanoparticles were functionalized was manufactured. It is preferable that the size of such Pd nanoparticles is 1-5 nm. It is more preferable that it is 2-5 nm especially. If it is 2 nm or less or 5 nm or more, the functionalization is not good and the bonding strength between each other tends to be inferior. An example of measuring Pd nanoparticles by TEM in the hydrogen sensor of this embodiment is shown in FIG. Figure 7 (b) shows the frequency according to the size of the Pd nanoparticles in the present embodiment. In this embodiment, it can be seen that the most 3nm, the average size was 3.3nm.

On the other hand, in another experimental example of the present invention, the Pd nanoparticles were functionalized dendrimer-SWCNTs device was maintained for 12 hours at 200 ℃ and then subjected to a heat treatment process to lower the temperature to 25 ℃. Through the heat treatment process, the dendrimer could be decomposed as heat. As a result, the distance between the Pd nanoparticles and the SWCNTs was narrowed while maintaining the number of Pd nanoparticles. Through this process, a SWCNTs device in which Pd nanoparticles were functionalized was manufactured.

In order to manufacture the hydrogen sensor using the SWCNTs device manufactured in the above-described experimental example, in the experimental example of the present invention, the agglomerate of the SWCNTs device was removed through ultrasonic sonication (ultra-sonication) in IPA. Then Si oxidized by heat The micro-pipette was sprayed onto the Au electrode prepared by sputtering on the substrate, thereby saving SWCNT and Pd by selectively applying SWCNTs only to necessary portions. An application example of implementing the manufactured hydrogen sensor is illustrated in FIG. 6. Reference numeral 61 denotes a Si substrate, 62 an Au electrode, 63 a micropipette, and 64 a hydrogen sensor.

This dispersion led to the formation of a network of SWCNTs. The dispersed substrate was measured for a change in voltage at a constant current through a four-terminal wiring. The supply of current and the measurement of voltage were used as sourcemeter: keithley236 and voltmeter: keithley2182, respectively. At this time, the flow of hydrogen gas was controlled and flowed, and the voltage was measured in real time according to the change of resistance by the reaction with hydrogen. All data was run with LabView software program via GPIB interface card.

The device shown in FIG. 3 was configured to evaluate the characteristics of the SWCNTs hydrogen sensor according to the above experimental example, and the measured evaluation values are shown together with the conventional SWCNTs in FIG. 7 to compare the measured densities with the conventional dendrimer-free SWCNTs. At this time, in the experimental example above, the gas was introduced at room temperature. First, it waited until it stabilized in the environment of pure air, and then it flowed by adjusting the desired hydrogen concentration (10-20,000ppm) in the air base, and waited until the reaction was saturated. Finally, the process was repeated again to create an air environment in the chamber and to wait until it returned to normal state.

8 is a graph showing an example of the reaction according to the hydrogen concentration of the SWCNTs device according to the prior art and the present invention. In detail, FIG. 8 (a) shows the reaction according to the hydrogen concentration in the SWCNTs device in which the Pd nanoparticles are directly functionalized without the dendrimer according to the prior art, and FIGS. 8 (b) and 8 (c) respectively show the present invention. According to the concentration of hydrogen before and after heat treatment in the SWCNTs device functionalized Pd nanoparticles after forming in the dendrimer according to the present invention.

In the case of FIG. 8 (a), the basic resistance was 600 kΩ or more, which indicates that the resistance is greatly increased by the direct contact of Pd, compared to the number of kW (normally, about 7 kΩ) of pure SWCNTs. Can be. However, in the case of FIG. 8 (b), it can be seen that the resistance of about 13 kW is formed by the formation of the dendrimer. In addition, in the case of FIG. 8 (c) in which the dendrimer is decomposed into heat by performing a heat treatment process, the initial resistance may be restored. These results are according to one experimental example and may show different results in other experimental examples. But overall initial resistance and recovery results are similar.

In the case of the present experiment, the analysis by Raman spectrum shows that the present invention has a higher content of semiconductor SWCNT (s). In general, the metallic and semiconductor features are mixed in the SWCNT (s). In the present invention, it can be seen that the electrical flow of the metallic features to the SWCNT (s) proceeds and the metallic characteristics as a whole. This can be confirmed by measuring the resistance value against temperature change in each example of FIG. 8 (a-c). If the semiconductor characteristic of Fig. 8 (a) is strong, it has a resistance value of several kV to kV and its sensitivity is very high. However, it can be seen that the metal characteristic of FIG. 8 (b-c) has a wider driving range although the sensitivity is slightly lower. In addition, the present invention is stable and recovers the existing resistance as soon as possible after the gas reaction, it can be seen that there is an advantage that can be clearly distinguished for each concentration and sensitively even in the low concentration range.

As such, the change in resistance of SWCNTs due to the presence of a dendrimer is related to the reaction with hydrogen as follows.

First, as shown in FIG. 8 (a), when the dendrimer is not formed and the Pd nanoparticles are functionalized directly in the SWCNTs, the reaction time for hydrogen appears to be very slow and the recovery time is much slower. On the other hand, the sensitivity is up to 25%.

As shown in FIG. 8 (b), when dendrimers were formed on SWCNTs and Pd nanoparticles were functionalized, a large number of Pd nanoparticles resulted in very fast hydrogen concentrations of 10,000 ppm to 3 s (time to e ⁻¹ of the overall reaction). It can be seen that the reaction time. Thus, such a SWCNTs device can realize a fast reaction time for hydrogen concentration. However, as shown in FIG. 8 (b), the sensitivity is 8.6% which is very low compared to FIG. 8 (a) without the dendrimer. In this case, it is caused by a dendrimer, a kind of polymer composed of a single bond between carbons. In other words, because the dendrimer has the nature of an insulator, the movement of electrons is not free. However, evenly distributed oxygen and nitrogen (in the presence of unshared pairs of electrons) are highly dependent on distance and the size of the Pd nanoparticles, forming inductive charges that allow the formation of dipole moments. Unlike the conventional case where the Pd nanoparticles are in direct contact with the SWCNTs by the force of the dipole moment, the formation of the dipole captures the holes that are carriers of the SWCNTs and increases the resistance. The reaction with hydrogen proceeds rapidly but with low sensitivity due to the distance between Pd nanoparticles and SWCNTs by dendrimers.

As shown in FIG. 8 (c), when the dendrimer was formed on the SWCNTs, the Pd nanoparticles were functionalized, and the dendrimer was thermally decomposed through the heat treatment process, the reaction time and the high sensitivity were shown. The dendrimers between SWCNTs and Pd nanoparticles are thermally decomposed (dendrimers can decompose and leave debris), so that the mutual distance between SWCNTs and Pd nanoparticles is closer and the reaction to hydrogen is reduced by the direct contact with polarization It can be seen that the increase. As a result, when comparing the characteristics of the reaction to hydrogen at 10,000ppm, the sensitivity is restored to the initial level and the reaction time can bring about 46 times as shortening time as 7s compared to 324s of FIG. 8 (a). Able to know.

In order to evaluate the characteristics of each hydrogen sensor of Figure 8 (a-c) compared to the prior art and the hydrogen sensor of the present invention look at the characteristics are as shown in Table 1.

Table 1

division The prior art of Fig. 8 (a)
(Functionalizes Pd nanoparticles directly to SWCNT) Invention 1 of FIG. 8 (b)
(Pd nanoparticle functionalization after dendrimer formation in SWCNT-before heat treatment) 8 (c) of the present invention
(After the heat treatment of the dendrimer in Figure 8 (b)) responsiveness ~ 25% ~ 8.6% ~ 25% Reaction time 324s 3s 7s Recovery time 30 minutes or more 7s 15 s Recovery
(stability) Incomplete recovery Instability stability mechanism Electromigration by Direct Contact Indirect dipole moment formation Indirect dipole moment formation

As shown in Table 1, the present invention 1 and 2 before and after the heat treatment shows much better results in sensitivity, reaction time, recovery time, stability, and the like, compared to the hydrogen sensor according to the prior art, and thus sufficient as a hydrogen sensor. You can see that you can play a role.

9 is a view showing a continuous reaction example for a low hydrogen concentration in the SWCNTs hydrogen sensor according to the present invention, Figure 10 is a view showing a reaction example at a hydrogen concentration of 10ppm of the SWCNTs hydrogen sensor according to the present invention.

9, in the case of the SWCNT (s) hydrogen sensor according to the present invention, a reversible reaction in which the basic resistance hardly changes even after continuous inflow of hydrogen and repetition of the air environment, and the degree of differential reaction for each hydrogen concentration Is showing. In addition, in the SWCNT (s) hydrogen sensor according to the present invention, a change in resistance occurs even at a low hydrogen concentration of 1000 ppm or less, and it can be seen that the hydrogen quickly recovers to the same basic resistance after the hydrogen detection. As such, low concentration of hydrogen gas can be detected, and it can be seen that fast and accurate detection is possible even with a change in gas amount.

As described above, in SWCNT (s) according to the present invention, the metallic characteristic of increasing resistance as temperature increases is predominant, and the bone functionalized Pd nanoparticles by synthesizing a dendrimer to SWCNT (s) having such metallic characteristic. The hydrogen sensor of the present invention solves the problems in the prior art and has excellent results in terms of stability and hydrogen detection, and can be expected to play a role as a hydrogen sensor developed in the future through reducing the uncertainty of hydrogen detection and accurate detection.

Referring to FIG. 10, it can be seen that the SWCNTs hydrogen sensor of the present invention can be detected quickly and clearly even at 10 ppm, which is a minimum detection concentration of hydrogen, which has been disclosed in the existing literature. As such, it can be seen that the present invention accurately detects even at low concentrations.

Meanwhile, the above-described embodiments of the present invention are merely preferred embodiments, and are not limited to the description of these embodiments of the present invention. That is, various improvements and modifications are possible within the scope of the technical idea of the present application described above, and it is obvious that any of them fall within the technical scope of the present invention as long as they belong to the appended claims.

As the need for technology for environmentally friendly clean energy increases, hydrogen energy is in the spotlight as the fuel of the future. Due to the nature of flammable and explosive hydrogen, technology for detecting trace hydrogen quickly and accurately must be supported for easy and safe use of such hydrogen.

In view of this aspect, the hydrogen sensor using single-walled carbon nanotubes (SWCNTs) according to the present invention can secure excellent detection capability and stability compared to the prior art, and further has excellent sensitivity and fast reaction time at low concentrations. Therefore, it can be very useful in the field of hydrogen sensing technology.

1 is a transmission electron microscope (TEM) tissue photograph of an example in which Pd nanoparticles are directly functionalized in SWCNTs according to the prior art.

Figure 2 is a schematic diagram showing the manufacturing process of a single-wall carbon nanotube (SWCNT) hydrogen sensor according to the present invention.

Figure 3 is a schematic diagram showing a device implemented with a single-walled carbon nanotube (SWCNT) hydrogen sensor according to an embodiment of the present invention.

Figure 4 is a transmission electron microscope (TEM) tissue photograph of the SWCNTs according to the present invention.

5 is another TEM tissue picture of SWCNTs according to the present invention.

6 is a view showing an application example implementing the SWCNT hydrogen sensor according to an embodiment of the present invention.

7 is a view showing the frequency distribution according to the size of the TEM tissue picture and Pd nanoparticles measured Pd nanoparticles in the SWCNT hydrogen sensor according to an embodiment of the present invention.

8 is a graph showing the reaction according to the hydrogen concentration of the SWCNTs device according to the prior art and the present invention.

9 is a view showing a continuous reaction example for a low hydrogen concentration in the SWCNTs hydrogen sensor according to the present invention.

10 is a view showing a reaction example at a hydrogen concentration of 10ppm in the SWCNTs hydrogen sensor according to the present invention.

Claims (40)

Preparing at least one single-walled carbon nanotube (SWCNT); Forming a dendrimer on the surface of the SWCNT; And Functionalizing the metal nanoparticles as the reaction catalyst with hydrogen in the formed dendrimer; Method for producing a single-wall carbon nanotube hydrogen sensor comprising a. The method of claim 1, The dendrimer is a method for producing a single-walled carbon nanotube hydrogen sensor, characterized in that the poly (amidoamine (PAMAM)) dendrimer. The method of claim 1, The metal nanoparticles include palladium (Pd), platinum (Pt), rhodium (Rd), nickel (Ni), aluminum (Al), manganese (Mn), molybdenum (Mo), magnesium (Mg) and vanadium (V). Method for producing a single-wall carbon nanotube hydrogen sensor, characterized in that any one selected. The method of claim 1, wherein the step of forming a dendrimer on the surface of the SWCNT, Forming a carboxyl group on the surface of the SWCNT by sonicating the SWCNT in a mixed solution of nitric acid (H ₂ NO ₃ ) and sulfuric acid (H ₂ SO ₄ ) for 2 to 4 hours; The SWCNT is mixed in ethylenediamine and HATU (N-[(dimethylamino) -1H-1,2,3-triazolo (4,5,6) pyridine-1-ylmethylmethanaminium hexafluorophosphate N-oxide]) Sonicating for 3-5 hours to form amine groups at the ends of the oxidized SWCNTs; And Synthesizing the dendrimer by immersing the SWCNT first in methyl acrylate and secondly in ethylenediamine solution; Method for producing a single-walled carbon nanotube hydrogen sensor, characterized in that it comprises a. The method of claim 4, wherein Method for producing a single-wall carbon nanotube hydrogen sensor, characterized in that the temperature of the mixed solution of nitric acid and sulfuric acid is 35 ~ 45 ℃. The method of claim 4, wherein The SWCNT (mg): nitric acid solution (ml): sulfuric acid solution (ml) ratio of 2: 1: 3 method for producing a single-wall carbon nanotube hydrogen sensor. The method of claim 4, wherein The SWCNT (mg): ethylenediamine (mg): HATU (mg) ratio is 20: 10: 1, the method of manufacturing a single-wall carbon nanotube minority sensor. The method of claim 4, wherein The step of synthesizing the dendrimer, Synthesizing an initial dendrimer having an ester group formed at the terminal through the Michael addition reaction; And Forming a final dendrimer by forming an amine group in the ester group formed at the initial dendrimer end; Method for producing a single-walled carbon nanotube hydrogen sensor comprising a. The method of claim 4, wherein The amine group forming step and the dendrimer synthesis step is a method of manufacturing a single-walled carbon nanotube hydrogen sensor, characterized in that it is carried out sequentially repeated 2 to 5 times. The method of claim 1, The metal nanoparticle is a method of manufacturing a single-walled carbon nanotube hydrogen sensor, characterized in that the functionalized by one of the method selected from sputtering, chemical layer (CVD), electron beam deposition or electroplating method. The method of claim 1, The metal nanoparticles are made of Pd, and the method of producing a single-walled carbon nanotube hydrogen sensor, characterized in that functionalized by reduction of 0.1M PdCl42- and 1.0M NaBH4 on the SWCNT in which the dendrimer is formed in an aqueous solution or an acid solution of pH 2 . The method of claim 1, The metal nanoparticles is a method of manufacturing a single-walled carbon nanotube hydrogen sensor, characterized in that 2 ~ 5nm. Preparing at least one single-walled carbon nanotube (SWCNT); Forming a dendrimer on the surface of the SWCNT; Functionalizing the metal nanoparticles as the reaction catalyst with hydrogen in the formed dendrimer; And Decomposing the dendrimer as heat through heat treatment; Method for producing a single-wall carbon nanotube hydrogen sensor comprising a. The method of claim 13, The heat treatment process is a method of manufacturing a single-walled carbon nanotube hydrogen sensor, characterized in that it comprises a step of maintaining for 10 to 13 hours at 200 ℃. The method of claim 14, After the temperature holding step, Method for producing a single-wall carbon nanotube hydrogen sensor, characterized in that it further comprises a step of reducing the temperature to 25 ℃. The method of claim 13, The dendrimer is a method for producing a single-walled carbon nanotube hydrogen sensor, characterized in that the poly (amidoamine (PAMAM)) dendrimer. The method of claim 13, The metal nanoparticles include palladium (Pd), platinum (Pt), rhodium (Rb), nickel (Ni), aluminum (Al), manganese (Mn), molybdenum (Mo), magnesium (Mg) and vanadium (V). Method for producing a single-wall carbon nanotube hydrogen sensor, characterized in that any one selected. The method of claim 13, Forming a dendrimer on the surface of the SWCNT, Forming a carboxyl group on the surface of the SWCNT by sonicating the SWCNT in a mixed solution of nitric acid (H ₂ NO ₃ ) and sulfuric acid (H ₂ SO ₄ ) for 2 to 4 hours; The SWCNT is mixed in ethylenediamine and HATU (N-[(dimethylamino) -1H-1,2,3-triazolo (4,5,6) pyridine-1-ylmethylmethanaminium hexafluorophosphate N-oxide]) Sonicating for 3-5 hours to form amine groups at the ends of the oxidized SWCNTs; And Synthesizing the dendrimer by immersing the SWCNT first in methyl acrylate and secondly in ethylenediamine solution; Method for producing a single-walled carbon nanotube hydrogen sensor, characterized in that it comprises a. The method of claim 18, The SWCNT (mg): nitric acid solution (ml): sulfuric acid solution (ml) is a method of manufacturing a single-wall carbon nanotube hydrogen sensor, characterized in that 2: 1: 3. The method of claim 18, Method for producing a single-wall carbon nanotube hydrogen sensor, characterized in that the temperature of the mixed solution of nitric acid and sulfuric acid is 35 ~ 45 ℃. The method of claim 18, The SWCNT (mg): ethylenediamine (mg): HATU (mg) ratio is 20: 10: 1, the method of manufacturing a single-wall carbon nanotube minority sensor. The method of claim 18, The step of synthesizing the dendrimer, Synthesizing an initial dendrimer having an ester group formed at the terminal through the Michael addition reaction; And Forming a final dendrimer by forming an amine group in the ester group formed at the initial dendrimer end; Method for producing a single-walled carbon nanotube hydrogen sensor comprising a. The method of claim 18, The amine group forming step and the dendrimer synthesis step is a method of manufacturing a single-walled carbon nanotube hydrogen sensor, characterized in that it is carried out sequentially repeated 2 to 5 times. The method of claim 13, The metal nanoparticle is a method of manufacturing a single-walled carbon nanotube hydrogen sensor, characterized in that the functionalized by one of the method selected from sputtering, chemical layer (CVD), electron beam deposition or electroplating method. The method of claim 13, The metal nanoparticles are made of Pd, and the method of producing a single-walled carbon nanotube hydrogen sensor, characterized in that functionalized by reduction of 0.1M PdCl42- and 1.0M NaBH4 on the SWCNT in which the dendrimer is formed in an aqueous solution or an acid solution of pH 2 . The method of claim 13, The metal nanoparticles is a method of manufacturing a single-walled carbon nanotube hydrogen sensor, characterized in that 2 ~ 5nm. The single-walled carbon nanotube hydrogen sensor manufactured by the manufacturing method of any one of Claims 1-12. A single-walled carbon nanotube hydrogen sensor manufactured by the manufacturing method according to any one of claims 13 to 26. At least one single-walled carbon nanotube (SWCNT); A dendrimer formed on the surface of the SWCNT; And Metal nanoparticles functionalized as reaction catalysts with hydrogen in the dendrimer; Single-walled carbon nanotube hydrogen sensor comprising a. 30. The method of claim 29, The SWCNT is a single-walled carbon nanotube hydrogen sensor, characterized in that the diameter is 1.0 ~ 1.2nm, the length is 20㎛, purity is 60 ~ 70wt%. 30. The method of claim 29, The metal nanoparticle is a single-walled carbon nanotube hydrogen sensor, characterized in that 2 ~ 5nm. 30. The method of claim 29, The metal nanoparticles include palladium (Pd), platinum (Pt), rhodium (Rb), nickel (Ni), aluminum (Al), manganese (Mn), molybdenum (Mo), magnesium (Mg) and vanadium (V). Single-walled carbon nanotube hydrogen sensor, characterized in that any one selected. 30. The method of claim 29, The dendrimer is a poly-amidoamine [poly (amidoamine) (PAMAM)] single-walled carbon nanotube hydrogen sensor, characterized in that the dendrimer. 30. The method of claim 29, A power supply unit supplying power to the SWCNT; And A signal analyzer for analyzing the electrical signal according to the resistance change of the SWCNT; Single-walled carbon nanotube hydrogen sensor, characterized in that it further comprises. At least one single-walled carbon nanotube (SWCNT); A dendrimer debris layer after the dendrimer formed on the surface of the SWCNT is decomposed by heat; And Metal nanoparticles functionalized as a catalyst for reaction with hydrogen on the SWCNT surface and the residue layer of the dendrimer; Single-walled carbon nanotube hydrogen sensor comprising a. 36. The method of claim 35 wherein The SWCNT is a single-walled carbon nanotube hydrogen sensor, characterized in that the diameter is 1.0 ~ 1.2nm, the length is 20㎛, purity is 60 ~ 70wt%. 36. The method of claim 35 wherein The metal nanoparticle is a single-walled carbon nanotube hydrogen sensor, characterized in that 2 ~ 5nm. 36. The method of claim 35 wherein The metal nanoparticles include palladium (Pd), platinum (Pt), rhodium (Rb), nickel (Ni), aluminum (Al), manganese (Mn), molybdenum (Mo), magnesium (Mg) and vanadium (V). Single-walled carbon nanotube hydrogen sensor, characterized in that any one selected. 36. The method of claim 35 wherein The dendrimer is a poly-amidoamine [poly (amidoamine) (PAMAM)] single-walled carbon nanotube hydrogen sensor, characterized in that the dendrimer. 36. The method of claim 35 wherein A power supply unit supplying power to the SWCNT; And A signal analyzer for analyzing the electrical signal according to the resistance change of the SWCNT; Single-walled carbon nanotube hydrogen sensor, characterized in that it further comprises.

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