KR102292184B1 - Multifunctional porous inorganic nanotube aerogel, gas sensor member and gas sensor using the same, and method for manufacturing the same - Google Patents

Abstract

According to various embodiments, the present invention relates to multifunctional porous inorganic nanotube aerogel, a gas sensor member using the same, a gas sensor and a method for manufacturing the same. The multifunctional porous inorganic nanotube aerogel includes tin oxide (SnO_2) nanoparticles and platinum (Pt) nanoparticles, and is obtained by binding the tin oxide nanoparticles and platinum nanoparticles with OH-functionalized single-walled carbon nanotube hydrogel platform as a matrix. In addition, the gas sensor member and the gas sensor may be provided and configured to detect nitrogen dioxide (NO_2) by using the multifunctional porous inorganic nanotube aerosol.

Description

Multifunctional porous inorganic nanotube airgel, member for gas sensor using same, gas sensor and manufacturing method thereof

Various embodiments relate to a multifunctional porous inorganic nanotube airgel, a member for a gas sensor using the same, a gas sensor, and a method for manufacturing the same.

The multifunctional porous inorganic material airgel has a high surface area, low density, and is easy to control electrical, optical, magnetic, thermal, catalytic and mechanical properties in the fields of sensors, heterocatalysis, adsorption, ion exchange, medical therapy, energy absorption, and energy storage. It is in the spotlight in a wide range of applications such as However, a manufacturing method for assembling a multifunctional inorganic material into a three-dimensional porous structure is very limited. Airgels of these materials can be divided into dry and wet methods using an atomic layer deposition method (depositing inorganic atoms on a porous template prepared by photolithography) and a sol-gel or hydrothermal synthesis method. Since these methods are generally performed at high temperature and/or high pressure, the process is very complicated, requires expensive equipment, and the use of temperature-sensitive inorganic materials is limited. Moreover, the inconsistency of the coefficients of thermal expansion of different inorganic materials imposes significant limitations on combining inorganic materials with multifunctional properties.

Various embodiments provide an inorganic material airgel to which different inorganic materials are readily combined and a method of making the same.

Various embodiments provide an inorganic material airgel that can be easily prepared and a method for preparing the same.

The method for producing a multifunctional porous inorganic nanotube airgel according to various embodiments comprises the steps of forming a functionalized single-walled carbon nanotube (OH-functionalized Single-Walled Carbon Nano Tube; fSWNT) hydrogel platform, the By binding multifunctional inorganic nanoparticles to the fSWNT hydrogel platform to form a tin oxide-platinum nanotube hydrogel, and drying the tin oxide-platinum nanotube hydrogel, the multifunctional porous inorganic nanotube airgel It may include the step of forming

The multifunctional porous inorganic nanotube airgel according to various embodiments includes tin oxide (SnO ₂ ) nanoparticles, and platinum (Pt) nanoparticles, and a functionalized single-walled carbon nanotube (OH-functionalized Single-Walled) Based on a Carbon Nano Tube (fSWNT) hydrogel platform, it can be manufactured by combining the tin oxide nanoparticles and the platinum nanoparticles.

The gas sensor according to various embodiments may be configured to detect _{nitrogen dioxide (NO 2 ) using a multifunctional porous inorganic nanotube airgel.}

According to various embodiments, a multifunctional porous inorganic nanotube airgel can be easily prepared. At this time, based on the fSWNT hydrogel platform, by combining multifunctional inorganic nanoparticles at room temperature and pressure, a multifunctional porous inorganic nanotube airgel can be prepared.

1 is a view showing a method of manufacturing a multifunctional porous inorganic nanotube airgel according to various embodiments.
2, 3 and 4 are views for explaining the characteristics of the multifunctional porous inorganic nanotube airgel.
5, 6, 7, 8, 9, 10 and 11 are multifunctional porous inorganic nanotube airgels according to various embodiments, that is, Pt-SnO _{2 It} is a view for explaining the structural characteristics of the airgel. .
12 and 13 are diagrams for explaining the dynamic NO ₂ sensing characteristics of the multifunctional porous inorganic nanotube airgel, that is, the Pt-SnO _{2 airgel according to various embodiments.}
14 shows various embodiments; It is a drawing showing a sensing mechanism using a multifunctional porous inorganic nanotube airgel.

Hereinafter, various embodiments of the present document will be described with reference to the accompanying drawings.

In recent years, carbon-based nanomaterials (carbon nanotube, graphene), metal oxides (MnO ₂ , TiO ₂ , Co ₂ Fe ₃ , RuO ₂ ), metals (Cu, Ag), semiconductors (SiO ₂ , MoS ₂ ), and insulators have been A new method (shape anisotropy methodology; Shape An-Isotropy methodology) for manufacturing highly porous airgel using various nanomaterials such as (h-BN) was developed. When anisotropic nanoparticles (eg, 1D nanotubes/nanowires or 2D nanosheets) are dispersed in a solvent, when the concentration of the dispersion solution is increased, the nanotubes/nanosheets are physically physically affected by van der Waals force. They contact each other and connect to form a three-dimensional gel network. In order to maintain the pore structure of such a three-dimensional porous gel, supercritical drying (replacing the solvent in the gel with air above the supercritical point) or freeze-drying (replacing the solvent in the gel with air by cooling the solvent and sublimating the crystals) is used. Airgel was prepared. The airgel thus prepared has high porosity, low density, and high surface area. In addition, it can be applied to various fields (water filter/membrane, wicking materials, supercapacitor, Li-air battery) by optimizing the shape, chemical, and physical properties of the airgel by controlling the aspect ratio and gel-forming concentration of the anisotropic nanomaterial.

In various embodiments, using a functionalized single-walled carbon nanotube (OH-functionalized SWNT) hydrogel (when the solvent of the gel is water, it is called a hydrogel) as a platform, multifunctional inorganic nanoparticles are transferred to the fSWNT hydrogel platform. Combined and supercritically dried to prepare a multifunctional inorganic nanotube airgel. The multifunctional inorganic nanotube airgel ( _{fSWNT aerogel combined with Pt-SnO 2} ) made in this way has the characteristics of ultra-high porosity, high surface area, and low density, so it can be applied as a gas sensor.

Here, the fSWNT hydrogel has high porosity, ultra-high surface area, low density, robustness, high conductivity and thermal stability. In addition, the fSWNT hydrogel platform was used as a 3D platform for multifunctional inorganic nanomaterial binding because it was easy to selectively control the surface functionalization of fSWNTs by non-covalent adsorption or covalent incorporation. Here, SnO ₂ and Pt nanoparticles were bound (coated) to the fSWNT hydrogel platform, and the particle size and distribution were controlled by controlling the surface reaction conditions. In _{the case of SnO 2} nanoparticles, the functional groups (OH) of fSWNTs serve as a core growth site (nucleation site) where _{SnO 2} ^{can be generated, so Sn 2+} ions are _{oxidized to SnO 2} particles on the surface of the functionalized nanotube. . In the conventional case, _{in order to bind the SnO 2} nanoparticles to the nanotubes, a hydrothermal synthesis method or a chemical vapor deposition method at a high temperature was used. However, in various embodiments, by immersing the fSWNT hydrogel in the SnCl _{4 precursor solution and stirring it at room temperature and under normal pressure, SnO 2} having a size of several nanometers (1.5-3.5 nm) can be very uniformly bound to the fSWNT hydrogel. there was. And, in the case of Pt coating, Pt ions are reduced on the surface of the _{SnO 2 coated fSWNT hydrogel in the Pt precursor solution at room temperature and pressure.} At this time, the size of the Pt nanoparticles was controlled to 2-2.5 nm.

According to various embodiments, the carbon nanotubes are uniformly dispersed without bundles with a dispersant, and when the concentration of the carbon nanotube dispersion is increased, the carbon nanotubes are crosslinked to each other to form a gel. In this case, since carbon nanotubes having a subdiameter are interlinked, they may have an ultra-high surface area. In various embodiments, the carbon nanotube hydrogel (the solvent in the gel is water) is replaced with air using a critical point drying method or a freeze-drying method to prepare a porous airgel. The porous airgel made in this way maintains the pore structure and has a very high surface area. In various embodiments, the OH group on the surface of the carbon nanotube (CNT) hydrogel (using OH-SWNT from the beginning) serves as a key growth site so that inorganic nanoparticles can be formed, and SnCl ₄ (SnCl ₂ ) as a precursor, and has the advantage of being naturally oxidized at room temperature without a reaction accelerator or oxidizing agent. In addition, the room temperature reaction can easily control the inorganic particle size by subnanometer than the high temperature reaction. Since Pt also acts as a catalyst, it can be reacted in alcohol at room temperature (without the use of additional reducing agents) in order to bind at least to a low concentration distribution with a small particle size.

The fSWNT airgel with porosity, high active surface area (393 m ² g ⁻¹ ), and ultrafine Pt-SnO ₂ bound to it showed _{excellent NO 2 sensing properties at room temperature.} In particular, compared to the state-of-the-art SMO-based NO _{2 sensor at room temperature, Pt-SnO 2} aerogels are sensitive (S = 14.77% at 5 ppm), insensitive to toluene, hydrogen, ethanol, ammonia, and acetone, whereas very _{sensitive to NO 2} Selectively high sensitivity and very fast and stable detection behavior. Multifunctional inorganic nanotube airgels designed to have ultra-high surface area and high porosity are potential material platforms for high-performance gas sensors and can be broadly extended to a wide range of applications including catalysts, bio-engineered scaffolds, and energy storage devices.

In the following description, the inorganic nanotube hydrogel/airgel may refer to a hydrogel/airgel to which inorganic nanoparticles are bound.

1 is a view showing a method of manufacturing a multifunctional porous inorganic nanotube airgel according to various embodiments. 2, 3 and 4 are views for explaining the characteristics of the multifunctional porous inorganic nanotube airgel.

Referring to FIG. 1 , in step 110 , a functionalized single-walled carbon nanotube (OH-functionalized single-walled carbon nanotube; fSWNT) hydrogel may be formed. At this time, the fSWNT hydrogel is formed into a porous 3D structure through the SAI strategy.

For the formation of the 3D fSWNT hydrogel platform (via the SAI method), the hydroxyl group (-OH) functionalized fSWNT and the dispersant (sodium dodecylbenzene sulfate (SDBS)) were mixed in a 1:5 mass ratio in deionized water. and uniformly dispersed using tip-sonication. The fSWNT suspension was formed by evaporation of the solvent (water) at 313 K to form the fSWNT hydrogel. At this time, the fSWNT hydrogel concentration is 0.4wt%, the carbon nanotubes are not agglomerated like bundles with each other, and the ultrafine fSWNTs are physically bonded to each other by van der Waals force to form a three-dimensional porous network structure. This can result in fSWNT airgels with a very high surface area compared to the network. The shape of the hydrogel platform could be designed into a desired shape using a mold to obtain a desired type of aerogel. For example, the hydrogel was molded using a thin rectangular frame, and the molded hydrogel was washed several times with hot distilled water to completely remove SDBS. Importantly, the morphology of the fSWNT hydrogel platform can be controlled by adjusting the hydrogel concentration so that the porosity, density, and mechanical properties of the hydrogel platform can be designed for specific applications.

In steps 120 and 130, the multifunctional inorganic nanoparticles of the precursor solution can be bound to the 3D fSWNT hydrogel platform. Here, the inorganic nanoparticles may include tin oxide (SnO ₂ ) nanoparticles and platinum (Pt) nanoparticles. In step 120, SnO ₂ nanoparticles may be coated on the 3D fSWNT hydrogel to form a _{3D SnO 2 hydrogel.} Then, in step 130, the Pt nanoparticles is coated on the 3D SnO ₂ hydrogel, it may be a 3D Pt-SnO ₂ hydrogel forming.

For SnO ₂ coating, SnCl ₄ precursor was dissolved in distilled water, and then the fSWNT hydrogel was immersed in the precursor solution by shaking at 100 rpm at ambient conditions for 2 hours. OH-fSWNT and SnO _{2 SnCl 4} precursor adsorbed on the surface of the nanoparticles was chemically bonded to the fSWNT hydrogel at room temperature by a reaction as shown in [Scheme 1] below. Here, OH-fSWNTs may act as a core growth site (nucleation site) in which _{SnO 2 is uniformly formed.} Then, in ethanol with _{H 2} PtCl ₆ precursor, Pt cations (Pt ⁴⁺ _{) on the surface of negatively charged SnO 2} -fSWNT hydrogel can be partially reduced to Pt nanoparticles, which is a relatively high electron affinity of Pt compared to Sn. also because

[Scheme 1]

In step 140, 3D fSWNT airgel may be formed by supercritical point drying. 3D Pt-SnO ₂ hydrogel can be converted into 3D fSWNT airgel, ie, 3D Pt-SnO _{2 airgel.} 3D fSWNT airgel is a multifunctional porous inorganic nanotube airgel, which has the characteristics of ultra-high porosity, high surface area, and low density.

The Pt-SnO ₂ hydrogel was converted to a highly porous Pt-SnO _{2 aerogel by critical point drying.} Electron emission-based electron microscopy (FE-SEM) images of Pt-SnO ₂ airgel show a 3D interlocking Pt-SnO ₂ nanotube network with ^{high porosity and a density of 16 mgcm -3 .} The porous network shows an open pore structure and pore size in the range of several nanometers to several hundreds of nanometers as shown in FIG. 2 ( _{confirmed by N 2} adsorption/desorption analysis). Surprisingly, the surface area of the Pt-SnO ₂ airgel was 8.3 and 25 times higher than those of Pt-SnO ₂ -SWNT powder and SnO ₂ ^{nanotubes previously reported as 393 m 2} g ^{−1 , respectively, as shown in FIG. 3 .} Through these results, it was confirmed that the porosity, low density, and very high surface area of the fSWNT hydrogel platform affected the morphology of the _{Pt-SnO 2 airgel. Here, the presence and well-dispersed distribution of Pt and SnO 2} nanoparticles in the porous fSWNT hydrogel platform was clearly confirmed by an energy dispersive spectrum analysis (EDS) element mapping image as shown in FIG. 4 .

Structural characteristics of the multifunctional porous inorganic nanotube airgel prepared as described above will be described below.

5, 6, 7, 8, 9, 10 and 11 are multifunctional porous inorganic nanotube airgels according to various embodiments, that is, Pt-SnO _{2 It} is a view for explaining the structural characteristics of the airgel. .

SnCl ₄ and H ₂ PtCl ₆ Pt-SnO ₂ airgel was produced _{by combining SnO 2} and Pt nanoparticles on a 3D fSWNT hydrogel platform of various concentrations of precursors. In the fSWNT hydrogel, as shown in FIG. 5, ultrafine nanotubes with a diameter of 2 to 10 nm form a three-dimensional hydrogel network structure, so the porous fSWNT airgel as shown in FIG. (4mgcm ^-3 ) and ultra-high surface area (1133 m ² g ^-1 , close to the theoretical value). Also, as shown in the EDS spectrum of FIG. 9(b), the oxygen content of fSWNTs is 9.4 wt%. SnCl was ₄ concentration is increased to 5, 10, 20, 30wt% gradually increased, SnO ₂ is bonded fSWNT airgel (hereinafter SnO ₂ aerogels), respectively the mass ratio of Sn to C 1.3, 1.8, 3.1, 4.3, as in (The mass ratio of _{Sn to C} is indicated by WR Sn/C). The FE-SEM image of FIG. 6 shows the _{porous SnO 2} airgel network with the residual pore structure of the fSWNT hydrogel platform.

SnCl ₄ ・5H ₂ O
Concentration (wt%) Weight % Weight ratio of Sn to C
(WR _Sn/C ) C O Sn 5 34.8 19.3 45.9 1.3 10 28.3 21.3 50.4 1.8 20 19.1 21.5 59.4 3.1 30 15.12 19.74 65.14 4.3

In addition, the distribution _{of SnO 2} nanoparticles incorporated into fSWNTs was investigated by high-resolution transmission electron microscopy (HR-TEM) characterization as shown in FIG. 7 . As shown in the upper part (f) of FIG. 7 _{, SnO 2} nanoparticles at a low Sn content of _{1.3 WR Sn/C} were coated on the surface of fSWNTs with a helical structure and an average diameter of 1.52 nm. As shown in the lower (g) of FIG. 7, _{when Sn increased up to a maximum of 4.3 WR Sn/C , SnO 2} nanoparticles having a diameter of 2 to 3.5 nm were combined on the surface of the fSWNT platform network. Next, Pt nanoparticles (2-2.5 nm) were bound to the _{3.1 WR Sn/C} SnO _{2 airgel.} As shown in the EDS analysis of FIG. 10 , the Pt content of the _{Pt-SnO 2} airgel was increased from 0.1 to 0.5 wt% by increasing the _{H 2} PtCl _{6 concentration from 0.01 to 0.1 wt%.} As mentioned earlier, the Pt-SnO ₂ airgel exhibited a highly porous network in which _{individually aligned Pt-SnO 2} nanotubes were interconnected, as shown in FIG. 6 . _{Also, the distribution of Pt and SnO 2} nanoparticles in individual fSWNTs and fSWNT networks was confirmed by HR-TEM images and EDS mapping images as shown in FIG. 8, revealing well-distributed functionalization.

The crystal structure of Pt-SnO ₂ airgel (0.1 wt% Pt, 3.1 WR _Sn/C ) was analyzed by HR-TEM and selective-area electron diffraction (SAED), respectively, as shown in some figures (i, j) of FIG. 8 , respectively. characterized by a pattern. The lattice planes of Pt(111) and SnO ₂ (101) were observed in the HR-TEM image. In the SAED image _{, the lattice plane of SnO 2} (110), (101), and (211) showed a rutile structure, and the diffraction ring pattern of Pt (111) was also observed in the SAED image.

Furthermore, the chemical composition and binding state of the Pt-SnO ₂ airgel bound to the fSWNT platform were investigated by X-ray photoelectron spectroscopy (XPS) as shown in FIG. 11 . The high-resolution characteristic peaks of Sn 3d and Pt 4f are shown in (a) and (b) of FIG. 11 , respectively. According to (a) of FIG. 11, two distinct peaks are _{located at 486.5 and 494.9 eV corresponding to Sn 3d 5/2} and Sn 3d _3/2 , and the spin-orbit coupling energy is 8.4 eV, respectively. The peak has a binomial characteristic that can be assigned to ^{Sn 4+} in the lattice _{of SnO 2 .} According to (b) of FIG. 11 , the main peaks of 71.2 and 74.5 eV correspond to _{spin coupling energies of 3.3 eV, Pt 4f 7/2} and Pt 4f _{5/2 .} Additional small peaks at 72.6 and 75.5 eV indicate PtO 4f _7/2 and PtO 4f _5/2 , indicating that the Pt nanoparticles were partially oxidized to PtO on the surface of the fSWNT hydrogel. Partially oxidized Pt nanoparticles may play an essential role in enhancing the gas reaction by the formation of a pn junction with _{SnO 2 .} 11 (c) and (d) show spectra of C 1s and O 1s, respectively. The deconvolution C 1s spectrum of Pt-SnO ₂ airgel shows four types of carbon bonds. According to (c) of FIG. 11, the peaks located at 284.0, 285.0, 286.2, and 287.7 eV correspond to C=C, CC, CO, and C=O, respectively. The spectrum of O 1s shows _{peaks corresponding to SnO 2} (530.4 eV), chemically adsorbed O ⁻ (531.5 eV), _{and O 2} ⁻ ions in the _{O 2} ⁻ state (532.4 eV). The chemically adsorbed peak is explained by the oxygen coordination of Sn-O-Pt as well as Sn-OC linked to the fSWNT surface.

_{The dynamic NO 2} sensing characteristics of the multifunctional porous inorganic nanotube airgel prepared as described above will be described below.

As described above, _{it was demonstrated that ultrafine SnO 2} and Pt nanoparticles were successfully bound to the surface of fSWNTs. These well-immobilized nano-sized SnO ₂ and Pt nanoparticles can play an important role in obtaining synergistic effects and interfacial stability in a wide range of applications such as catalysis, sensing, bio-scaffold, and energy storage. . _{In particular, SnO 2} , a semiconductor metal oxide (SMO), offers surprising advantages such as high sensitivity and low power consumption as a chemical gas sensor. Moreover, novel metal (Pt, Pd, Au) nanoparticles serve as sensitizers or catalysts to improve the sensitivity and selectivity of SMO gas sensors. Moreover, the airgel according to various embodiments provides a very high surface area and high porosity, and plays an important role in increasing the sensitivity by providing a rich reaction site for surface reactions. Considering these advantages, a multifunctional porous inorganic airgel was selected as an active sensing material for chemical sensor applications.

12 and 13 are diagrams for explaining the dynamic NO ₂ sensing characteristics of the multifunctional porous inorganic nanotube airgel, that is, the Pt-SnO _{2 airgel according to various embodiments.}

First, to investigate the sensing properties of fSWNT airgel and SnO ₂ airgel, the airgel was prepared in half the size of an alumina substrate, and then, silver foil was used to contact the gold electrode on the alumina substrate. _{H 2, C 2 H 5 OH} , NH 3, CH 3 COCH 3, C 7 H 8 NO ₂ and three kinds fSWNT airgel with different Sn contents and detection characteristics of the sensor of the SnO ₂ airgel (1-5 ppm) at room temperature evaluated. 12 shows the dynamic NO ₂ sensing properties of _{fSWNT airgel and three different SnO 2} sensors in the range of 1-5 ppm at room temperature. The fSWNT airgel sensor showed almost negligible detection characteristics in the range of 1-5 ppm _{of NO 2 .} However, as shown in Fig. 12(a), the SnO ₂ airgel sensor was _{sensitive to NO 2} , and in particular, the 3.1 WR _Sn/C SnO _{2 airgel sensor was NO 2} sensitivity compared to the fSWNT airgel sensor (S = 1.70%). (S = 9.28%) was improved by 5.5 times. In order to confirm the effect of the new metal catalyst on the sensing properties, Pt catalysts with different contents of 0.1, 0.3, and 0.5 wt% Pt were uniformly combined with _{3.1 WR Sn/C} SnO _{2 airgel.} As a result, as shown in FIG. 12(b), the Pt-SnO ₂ airgel (0.1 wt% Pt) sensor showed the highest sensitivity (S = 14.77%), _{1.60 times compared to the SnO 2} airgel, fSWNT airgel sensor, 8.69 times improved. In _{the case of reaction kinetics for NO 2} , the fSWNT airgel sensor showed very slow response and recovery rates with drift of basal resistance in air. On the other hand, SnO ₂ and Pt-SnO ₂ airgel sensor showed much faster response and recovery rate compared to fSWNT airgel sensor. Here, in _{order to quantitatively investigate the improved response and recovery rate of airgel sensors such as fSWNT, SnO 2} , and Pt-SnO ₂ , the sensitivity curve is fitted to the following [Equation 1] and [Equation 2], and the NO ₂ adsorption constant (k _ads ) and the desorption constant (k _des ) were calculated. Here, _{the sensitivity when NO 2} is desorbed, S _{max ,} is the maximum sensitivity, and C _a is the target gas concentration.

The calculated adsorption and desorption rate constants are summarized in Figure 13 of the supporting information and in Tables 2 and 3 below. As a result, the reaction and recovery rate constants of _{SnO 2} airgel (3.1 WR _Sn/C ^{) were 0.23 ppm -1} s ^-1 and 0.23s ^{-1, which} were higher than the fSWNT airgel sensor values (0.11 ppm ^-1 s ^-1 , 0.09s ^-1 ). They were found to be 2.09 times and 2.56 times higher, respectively. As shown in (c), (d) and (e) of FIG. 12 , in the case of the 0.1 wt% Pt catalyst-integrated SnO ₂ airgel (3.1 WR _Sn/C ) sensor, the reaction rate and recovery rate constant were higher than that of the fSWNT airgel sensor. They were further strengthened to ^{0.50 ppm -1} and 0.27s ^{-1 respectively.} Stability and selectivity are also important factors for high-performance and reliable gas sensors. According to Fig. 12(f), for the Pt-SnO ₂ airgel (3.1 WR _Sn/C , 0.1 wt% Pt) sensor _{, the response to 1 ppm of NO 2} was very reliable for repeated exposures of 11 driving hours. . More importantly, this sensor showed negligible sensing behavior for several interfering gases such as hydrogen, ethanol, ammonia, acetone, toluene gas, etc., as shown in Fig. 12(g), while sensing for _{NO 2 .} The action clearly showed rapid response and recovery.

Composite k _ads
[ppm ^-1 s ^-1 ] k _des
[s ^-1 ] K (k _ads /k _des ) fSWNT aerogel 0.11 0.09 1.22 SnO ₂ aerogel (1.3 WR _Sn/C ) 0.12 0.11 1.09 SnO ₂ aerogel (1.8 WR _Sn/C ) 0.20 0.17 1.18 SnO ₂ aerogel (3.1 WR _Sn/C ) 0.23 0.23 1.00 SnO ₂ aerogel (4.3 WR _Sn/C ) 0.25 0.17 1.47

Composite k _ads
[ppm ^-1 s ^-1 ] k _des
[s ^-1 ] K(k _ads /k _des ) SnO ₂ aerogel (3.1 WR _Sn/C ) 0.23 0.23 1.00 Pt-SnO ₂ aerogel (0.1 wt% Pt) 0.50 0.27 1.85 Pt-SnO ₂ aerogel (0.3 wt% Pt) 0.86 0.29 2.96 Pt-SnO ₂ aerogel (0.5 wt% Pt) 0.36 0.23 1.56

A sensing mechanism using the multifunctional porous inorganic nanotube airgel prepared as described above will be described below.

14 shows various embodiments; It is a drawing showing a sensing mechanism using a multifunctional porous inorganic nanotube airgel.

In terms of the sensing mechanism, the improved sensing properties are attributed to i) _{the formation of a pn junction between the p-type fSWNT and the n-type SnO 2} and ii) the efflux effect of Pt nanoparticles. In general, the base resistance of fSWNTs can be changed by adsorption by showing the p-type sensing properties of gas molecules. More specifically, when fSWNTs are exposed to air, hole accumulation occurs on the surface of fSWNTs due to adsorption of oxygen molecules. NO ₂ is a very electrical molecule and captures electrons during a reaction with adsorbed oxygen species as shown in [Reaction Equation 2] below. Therefore _{, when exposed to NO 2} , the thickness of hole accumulation increases. Therefore, the conversion of hole accumulation leads to a change in resistance in fSWNTs, thus _{lowering the resistance of the surrounding NO 2} and increasing the resistance of the surrounding air.

[Scheme 2]

In the case of the SnO ₂ bound fSWNT airgel, as shown in FIG. 14(c), pn between _{SnO 2 and fSWNT due to the work function difference between SnO 2} (ф=4.44 eV) and fSWNT (ф=4.77 eV) A connection is formed. Therefore, the electrons are passed from the SnO ₂ in the fSWNT higher resistance than the fSWNT as shown in Figure 14, the carrier density decreases in both SnO ₂ and fSWNT and, thereby (a). Adsorbed oxygen molecules on the _{SnO 2} surface that can extract electrons from the SnO ₂ complex improve the surface reactivity with _{NO 2 .} When SnO ₂ was exposed to NO ₂ , as shown in FIG. 14(b) , SnO ₂ nanoparticles partially covered the surface of the fSWNT, and SnO ₂ exhibited p-type sensing properties. During the reaction, electrons are _{transferred from the SnO 2} molecule to the NO ₂ molecule, which reduces the resistance. The pn junction between SnO ₂ and fSWNTs enables a large resistance change between the _{ambient air and NO 2 .} Moreover, the Pt catalyst-integrated SnO ₂ airgel further increases the resistance by the efflux effect of Pt nanoparticles and the formation of a small barrier between _{SnO 2} and Pt nanoparticles due to the difference in work function, as shown in FIG. 14(d). increase Pt can easily dissociate oxygen molecules and diffuse oxygen molecules into _{SnO 2} providing more reactive sites with _{electrically NO 2 molecules.}

In addition, partially oxidized Pt _{can form a pn junction with SnO 2} , resulting in a large resistance change during the reaction. Moreover, the high porosity and large surface area of the airgel structure ensure that NO ₂ molecules can easily penetrate the sensing layer and react quickly. As a result, the Pt-SnO _{2 airgel sensor showed remarkable room temperature NO 2} sensing characteristics, such as particularly high and fast sensitivity and ultra-high selectivity. Considering that many NO ₂ sensing materials showed significant base resistance drift, low sensitivity, and slow operation at room temperature, the Pt-SnO ₂ airgel sensor has a very stable sensing action and negligible base resistance drift and response and even at room temperature. It has remarkable detection performance in terms of detection speed.

According to various embodiments, the multifunctional porous inorganic nanotube airgel was first achieved by the surface reaction between the inorganic precursor solution and the OH-fSWNT hydrogel platform. _{Pt and SnO 2} nanoparticles with a particle size of 1.5-3.5 nm were uniformly bound to the fSWNT hydrogel by adjusting the surface reaction conditions. As a result, the Pt-SnO ₂ airgel showed high porosity, low density, high surface area (393 m ² g ^-1 ), and robustness according to the shape and characteristics of the fSWNT hydrogel platform. For potential applications, the chemical sensing properties of _{Pt-SnO 2 airgels were evaluated.} Compared with other RT NO ₂ sensors, Pt-SnO ₂ aerogels are (i) very stable and sensitive sensing (reaction/recovery) NO ₂ (14.77% to 5 ppm at S = 25 °C) and (ii) H ₂ , C ₂ H ₅ OH, NH ₃ , CH ₃ COCH ₃ and C ₇ H _{8 NO 2} has two advantages of ultra-high selectivity for interfering gases. Multifunctional porous inorganic nanotube airgels could be produced by this simple, robust and low-cost process for a variety of applications such as catalysts, adsorbents, biotissue scaffolds, energy storage, and especially future sensors.

The method for producing a multifunctional porous inorganic nanotube airgel according to various embodiments includes forming a functionalized single-walled carbon nanotube (OH-functionalized Single-Walled Carbon Nano Tube; fSWNT) hydrogel platform, fSWNT Forming a tin oxide-platinum nanotube hydrogel by binding the multifunctional inorganic nanoparticles to the hydrogel platform, and drying the tin oxide-platinum nanotube hydrogel to form a multifunctional porous inorganic nanotube airgel may include the step of

According to various embodiments, the nanoparticles include tin oxide (SnO ₂ ) nanoparticles and platinum (Pt) nanoparticles, and the step of forming the tin oxide-platinum nanotube hydrogel is performed on the fSWNT hydrogel platform. binding the tin oxide nanoparticles to form a tin oxide nanotube hydrogel, and binding the platinum nanoparticles to the tin oxide nanotube hydrogel to form a tin oxide-platinum nanotube hydrogel. have.

According to various embodiments, the fSWNT hydrogel platform may be formed in a porous 3D structure.

According to various embodiments, the forming of the multifunctional porous inorganic nanotube airgel comprises at least one of a supercritical drying method or a freeze drying method, converting the tin oxide-platinum nanotube hydrogel into a multifunctional porous inorganic nanotube airgel. conversion may be included.

According to various embodiments, the forming of the tin oxide nanotube hydrogel comprises immersing the fSWNT hydrogel platform in _{a precursor solution of tin chloride (SnCl 4} ) and stirring at room temperature and pressure, thereby forming the tin oxide on the fSWNT hydrogel platform. It may include binding nanoparticles.

According to various embodiments, the step of forming the tin oxide-platinum nanotube hydrogel comprises immersing the additive tin oxide nanotube hydrogel in a platinum (Pt) precursor solution at room temperature and pressure, so that platinum ions are converted into tin oxide nanotubes. It can be reduced on the surface of the tube hydrogel, thus forming a tin oxide-platinum nanotube hydrogel.

The multifunctional porous inorganic nanotube airgel according to various embodiments includes tin oxide (SnO ₂ ) nanoparticles, and platinum (Pt) nanoparticles, and a functionalized single-walled carbon nanotube (OH-functionalized Single-Walled) Based on the Carbon Nano Tube (fSWNT) hydrogel platform, it can be manufactured by combining tin oxide nanoparticles and platinum nanoparticles.

According to various embodiments, the multifunctional porous inorganic nanotube airgel combines tin oxide nanoparticles on an fSWNT hydrogel platform to form a tin oxide nanotube hydrogel, and adds platinum nanoparticles to the tin oxide nanotube hydrogel. binding to form a tin oxide-platinum nanotube hydrogel, and drying the tin oxide-platinum nanotube hydrogel.

According to various embodiments, the multifunctional porous inorganic nanotube airgel may be converted from a tin oxide-platinum nanotube hydrogel through at least one of a supercritical drying method or a freeze drying method.

According to various embodiments, the multifunctional porous inorganic nanotube airgel may be used as a member for a gas sensor or a gas sensor.

The gas sensor according to various embodiments may be configured to detect _{nitrogen dioxide (NO 2 ) using a multifunctional porous inorganic nanotube airgel.}

According to various embodiments, a multifunctional porous inorganic nanotube airgel can be easily prepared. At this time, based on the fSWNT hydrogel platform, by combining multifunctional inorganic nanoparticles at room temperature and pressure, a multifunctional porous inorganic nanotube airgel can be prepared.

It should be understood that the various embodiments of this document and the terms used therein are not intended to limit the technology described in this document to a specific embodiment, and include various modifications, equivalents, and/or substitutions of the embodiments. In connection with the description of the drawings, like reference numerals may be used for like components. The singular expression may include the plural expression unless the context clearly dictates otherwise. In this document, expressions such as “A or B”, “at least one of A and/or B”, “A, B or C” or “at least one of A, B and/or C” refer to all of the items listed together. Possible combinations may be included. Expressions such as "first", "second", "first" or "second" can modify the corresponding elements regardless of order or importance, and are used only to distinguish one element from another element. The components are not limited. When an (eg, first) component is referred to as being “connected (functionally or communicatively)” or “connected” to another (eg, second) component, that component is It may be directly connected to the component or may be connected through another component (eg, a third component).

According to various embodiments, each component (eg, a module or a program) of the described components may include a singular or a plurality of entities. According to various embodiments, one or more components or operations among the above-described corresponding components may be omitted, or one or more other components or operations may be added. Alternatively or additionally, a plurality of components (eg, a module or a program) may be integrated into one component. In this case, the integrated component may perform one or more functions of each component of the plurality of components identically or similarly to those performed by the corresponding component among the plurality of components prior to integration. According to various embodiments, operations performed by a module, program, or other component are executed sequentially, in parallel, repeatedly, or heuristically, or one or more of the operations are executed in a different order, omitted, or , or one or more other operations may be added.

Claims (10)

In the method for producing a multifunctional porous inorganic nanotube airgel,
Forming a functionalized single-walled carbon nanotube (OH-functionalized Single-Walled Carbon Nano Tube; fSWNT) hydrogel (hydrogel) platform;
binding multifunctional inorganic nanoparticles to the fSWNT hydrogel platform to form a tin oxide-platinum nanotube hydrogel; and
Through drying the tin oxide-platinum nanotube hydrogel, comprising the step of forming a multifunctional porous inorganic nanotube airgel,
The nanoparticles are
It contains tin oxide (SnO ₂ ) nanoparticles and platinum (Pt) nanoparticles,
The step of forming the tin oxide-platinum nanotube hydrogel,
binding the tin oxide nanoparticles to the fSWNT hydrogel platform to form a tin oxide nanotube hydrogel; and
binding the platinum nanoparticles to the tin oxide nanotube hydrogel to form the tin oxide-platinum nanotube hydrogel.
delete According to claim 1, wherein the fSWNT hydrogel platform,
A method of being formed into a porous 3D structure.
According to claim 1, wherein the step of forming the multifunctional porous inorganic nanotube airgel,
A method comprising converting the tin oxide-platinum nanotube hydrogel into the multifunctional porous inorganic nanotube airgel through at least one of a supercritical drying method or a freeze drying method.
The method of claim 1, wherein the forming of the tin oxide nanotube hydrogel comprises:
A method comprising binding the tin oxide nanoparticles to the fSWNT hydrogel platform by immersing the fSWNT hydrogel platform in a precursor solution of _{tin chloride (SnCl 4} ) and stirring under normal temperature and pressure.
According to claim 1, wherein the step of forming the tin oxide-platinum nanotube hydrogel,
By immersing the additive tin oxide nanotube hydrogel in a platinum (Pt) precursor solution under normal temperature and pressure, platinum ions are reduced on the surface of the tin oxide nanotube hydrogel, and thus the tin oxide-platinum nanotube hydrogel is How to form.
In the multifunctional porous inorganic nanotube airgel,
tin oxide (SnO ₂ ) nanoparticles; and
Contains platinum (Pt) nanoparticles,
Based on a functionalized single-walled carbon nanotube (OH-functionalized single-walled carbon nanotube; fSWNT) hydrogel platform, a multifunctional porous inorganic material manufactured by combining the tin oxide nanoparticles and the platinum nanoparticles nanotube airgel.
The method of claim 7, wherein the multifunctional porous inorganic nanotube airgel,
By binding the tin oxide nanoparticles to the fSWNT hydrogel platform to form a tin oxide nanotube hydrogel,
By binding the platinum nanoparticles to the tin oxide nanotube hydrogel, to form a tin oxide-platinum nanotube hydrogel,
A multifunctional porous inorganic nanotube airgel produced by drying the tin oxide-platinum nanotube hydrogel.
9. The method of claim 8,
A multifunctional porous inorganic nanotube airgel converted from the tin oxide-platinum nanotube hydrogel through at least one of a supercritical drying method or a freeze drying method.
Using the multifunctional porous inorganic nanotube airgel according to any one of claims 7 to 9, a gas sensor configured to detect _{nitrogen dioxide (NO 2 ).}

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