Maxine-lignin complex and battery-less chemical sensor containing the same as an active layer

Abstract

To provide a MXene-lignin composite according to a preferred embodiment of the present invention and a power-free chemical sensor including the same as an active layer.SOLUTION: A MXene-lignin composite comprises a MXene sheet represented by Mn+1XnTx (n=1, 2, or 3) and lignin chemically bonded to the MXene sheet, in which M is Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, or two or more of these transition metals, X is C, N, or a combination thereof, and Tx is F, OH, or O. The MXene-lignin composite is hybridized by a chemical bond (M-OH) between a transition metal (M) of the MXene sheet and a hydroxyl group (-OH) functional group contained in the lignin, and includes a crystalline region formed by the MXene sheet and an amorphous region formed by the lignin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to maxin-lignin complexes and battery-less chemical sensors containing them as active layers. [Background technology]

[0002] Recent urbanization has been remarkable, and as a result, concerns about air pollution have grown, necessitating an increased need for effective management and monitoring of harmful gases. Such environmental monitoring devices offer high accuracy, sensitivity, and customizability for specific applications. Solid-state gas sensors, such as chemiresistive sensors, have already been used in air monitoring and medical diagnostics, demonstrating high sensitivity to even low concentrations of analytes through changes in resistance or current when exposed to the analyte gas. However, chemiresistive gas sensors still suffer from poor sensitivity to ultra-low analyte concentrations, such as those of environmental gases such as CO2 and NO2.

[0003] Furthermore, based on fourth-generation smart sensor technology that combines Internet of Things (IoT) technology and sensor technology, smart sensors for use in the fields of energy, industrial safety, healthcare, and biomedical sciences, namely, technology for multifunctional, ultra-sensitive chemical sensor materials, are attracting attention.

[0004] The chemical sensitivity of sensors can be improved by thinning the active layer, and there is growing interest in two-dimensional (2D) materials that can provide an electron confinement effect even at thin thicknesses, generating a large electrical response even at low concentrations of analytes, thereby enhancing chemical sensitivity.

[0005] Among two-dimensional materials, maxine can be used as the active layer of chemical sensors. It has a high specific surface area and can accept various terminal functional groups, but it has the problem of poor receptivity to chemical stimuli. Therefore, various research efforts, such as increasing the complexity and hybridization, are being actively conducted to optimize the performance of chemical sensors.

[0006] Lignin is a biomass-derived bioenergy raw material with excellent properties, such as superhydrophobicity, non-toxicity, biodegradability, ease of production, mechanical stability, chemical durability, and environmental friendliness. It can be complexed with various functional materials and used in a variety of applications. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been devised to solve the above-mentioned problems, and its object is to provide a maxin-lignin complex according to a preferred embodiment of the present invention and a battery-less chemical sensor containing the same as an active layer.

[0008] The technical problems of the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0009] In order to achieve the above technical objectives, the maxine-lignin complex according to one embodiment of the present invention comprises M n+1 X n T( The present invention comprises a maxin sheet represented by the formula (n = 1, 2 or 3) and lignin chemically bonded to the maxin sheet, wherein M is Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W or two or more transition metals thereof, and X is C, N or a combination thereof; T is , F, OH or O.

[0010] The chemical bond may include a chemical bond between a transition metal (M) of the maxine sheet and a functional group contained in the lignin.

[0011] Specifically, the chemical bond may be a bond between a transition metal (M) in the maxine sheet and a hydroxyl group (-OH) contained in the lignin, and may include a chemical bond represented by M-OH.

[0012] More specifically, the chemical bond may be a bond between Ti as the transition metal (M) of the maxine sheet and a hydroxyl group (-OH) contained in the lignin, and may include a chemical bond represented by Ti-OH.

[0013] In order to achieve the above technical objectives, another embodiment of the present invention provides a battery-free chemical sensor including a maxin-lignin complex, comprising a substrate and a maxin-lignin complex disposed on the substrate, n+1 X n T( The present invention comprises a maxin-lignin complex film containing a maxin sheet represented by n=1, 2 or 3) and lignin chemically bonded to the maxin sheet, and at least one metal electrode formed on at least a portion of the maxin-lignin complex film. [Effects of the Invention]

[0014] According to the present invention as described above, the maxin-lignin complex and the battery-less chemical sensor containing the same as an active layer according to a preferred embodiment of the present invention are n+1 X n T( By including a maxin sheet (where n = 1, 2, or 3) and lignin chemically bonded to the maxin sheet as the active layer, it is possible to easily realize a chemical sensor with high chemical sensitivity that can detect changes in current at the nanoampere (nA) level without a power source and exhibits fast reaction and repair rates.

[0015] The effects of the present invention are not limited to those described above, and other effects not mentioned will be clearly understood by those skilled in the art from the following description. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram showing a method for producing a maxine-lignin complex according to one embodiment of the present invention. [Figure 2] FIG. 1 is a schematic diagram showing the structure of a battery-less chemical sensor including a maxin-lignin complex according to one embodiment of the present invention. [Figure 3] FIG. 1 is a schematic diagram showing the structure of a battery-free chemical sensor including a maxin-lignin complex to which a flexible substrate according to one embodiment of the present invention is applied. [Figure 4] FIG. 1 is a schematic diagram illustrating a method for producing a battery-less chemical sensor containing a maxin-lignin complex according to one embodiment of the present invention. [Figure 5] 1 shows a field emission scanning electron microscopy (FE-SEM) image and an energy disperse X-ray spectroscopy (EDS) result for a Maxine sheet according to Production Example 2 of the present invention. [Figure 6] 1 shows a field emission scanning electron microscope (FE-SEM) image and energy dispersive X-ray spectroscopy (EDS) results for the maxin-lignin complex according to Production Example 1 of the present invention. [Figure 7] The following shows the results of a. Field emission transmission electron microscopy (FE-SEM), b. Selected area electron diffraction (SAED), and c. High resolution transmission electron microscopy (HR-TEM) for the Maxine sheet according to Production Example 2 of the present invention. [Figure 8]1 shows the results of a. field emission transmission electron microscopy (FE-TEM), b. selected area electron diffraction (SAED), and c. high resolution transmission electron microscopy (HR-TEM) for the maxin-lignin complex of Production Example 1 of the present invention. [Figure 9] Figure 1 shows X-ray photoelectron spectroscopy (XPS) results for the maxin-lignin complex and maxin according to Production Examples 1 and 2 of the present invention, including: a. overall irradiation spectrum, b. Ti 2p peak of maxin sheet, c. O 1s peak of maxin sheet, d. S 2p peak of maxin-lignin complex, e. Ti 2p peak of maxin-lignin complex, and f. O 1s peak of maxin-lignin complex. [Figure 10] 1 is a current-voltage (IV) graph for a battery-less chemical sensor containing maxin and maxin-lignin complexes according to Example 1 and Comparative Example 1 of the present invention. [Figure 11] This is a graph showing the current response (ΔI / I0), response time, and recovery time when a non-powered chemical sensor containing a maxin-lignin complex and maxin according to Example 1 and Comparative Example 1 of the present invention is exposed to a gas to be detected. [Figure 12] These are results showing the current response (ΔI / I0), c. response (%), and d. sensitivity (ppm-1) when a. and b. the gas to be detected are exposed in pulses to the maxin-lignin complex and maxin-containing battery-free chemical sensors of Example 1 and Comparative Example 1 of the present invention. [Figure 13] 1 shows optical photographs and bending test results of a battery-less chemical sensor including a maxin-lignin complex realized on a flexible substrate according to Example 2 of the present invention. [Figure 14] 1 is a graph showing the current-voltage (IV) curve according to the number of bending times for a battery-less chemical sensor including a maxin-lignin complex realized on a flexible substrate according to Example 2 of the present invention. [Figure 15]These results show the current response (ΔI / I0), response (%), and sensitivity (ppm-1) depending on the number of bendings when a non-powered chemical sensor containing a maxin-lignin complex realized on a flexible substrate according to Example 2 of the present invention is exposed to pulses of the gas to be detected. [Figure 16] These results show the current response (ΔI / I0), response (%), and sensitivity (ppm-1) depending on the number of bendings when a non-powered chemical sensor containing a maxin-lignin complex realized on a flexible substrate according to Example 2 of the present invention is exposed to pulses of the gas to be detected. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The advantages and features of the present invention, as well as methods for achieving them, will become more apparent with reference to the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the technical concept of the present invention is not limited to the embodiments disclosed below, and can be embodied in various different forms. The following embodiments are provided merely to fully convey the technical concept of the present invention and to fully convey the scope of the present invention to those skilled in the art. The technical concept of the present invention is only defined by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

[0018] Furthermore, unless otherwise specified herein or clearly contradictory to the context, all terms used in this specification, including technical and scientific terms, can be used in the sense commonly understood by those skilled in the art to which this invention belongs. In addition, commonly used terms and dictionary-defined terms should not be construed as ideal or overly formal unless expressly defined in this application. The terms used in this specification are merely used to describe the embodiments and are not intended to limit the present invention. In this specification, singular expressions include plural terms unless the context clearly dictates otherwise.

[0019] The terms "comprises," "has," "includes," and "comprises," as used herein, unless otherwise specified, are to be construed as open-ended terms (i.e., meaning "including, but not limited to") and merely indicate the presence of the components in question; a referenced component, step, operation, and / or element is not to be understood as excluding the presence or addition of one or more other components, steps, operations, and / or elements.

[0020] Maxine-lignin complex and its manufacturing method FIG. 1 is a schematic diagram showing a method for producing a maxin-lignin complex according to one embodiment of the present invention.

[0021] Referring to FIG. 1, a method for producing a maxine-lignin complex according to an embodiment of the present invention includes first etching a MAX phase compound to obtain M n+1 X n T(and hybridizing the maxin nanosheets with lignin to produce a maxin-lignin complex, where M is a transition metal such as Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, or any combination thereof; A is Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, Sb, or any combination thereof; and X is C, N, or any combination thereof.

[0022] Mxene is a conductive two-dimensional material that may be in the form of a sheet formed from a transition metal oxide or transition metal nitride. Such Mxene sheets may be in the form of multiple Mxene flakes or Mxene nanosheets, for example, Mxene nanosheets.

[0023] The maxine nanosheet is M n+1 X n T( The transition metal carbide or transition metal nitride may be represented by n=1, 2, or 3. In this case, M is a transition metal, and may include, for example, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, or two or more of these, and X may be C, N, or a combination thereof. T is , a number of different negatively charged end groups, which may be F, OH or O.

[0024] In particular, the maxine nanosheets contain a large number of various negatively charged terminal groups ( T) By including the above, the complexation or hybridization reaction with lignin described below can be easily carried out.

[0025] Said M n+1 X n T(The transition metal (n=1, 2, or 3) may have a structure in which, among two to four transition metal (M) atomic layers, an atomic layer of carbon, nitrogen, or a combination thereof (X, specifically, a carbon or nitrogen atomic layer) is sandwiched between adjacent transition metal (M) atomic layers and covalently bonded to the transition metal. The transition metal atomic layer may contain one transition metal, or may contain two or more different transition metals. Alternatively, the stacked transition metal atomic layers may be the same transition metal atomic layer, or may be different transition metal atomic layers. Furthermore, the stacked carbon or nitrogen layers (X) may all be carbon layers, or all may be nitrogen layers, or alternatively, some layers may be carbon layers and the remaining some layers may be nitrogen layers.

[0026] The surface of the maxine nanosheet contains negatively charged functional groups ( T) Specifically, F, OH and / or O, for example, F or O may be located.

[0027] Said M n+1 X n T( n=1) is Ti2C T、 V2C T、 Nb2C T、 Mo2C T、 Ti2N T、 V2N T , Mo2N T、 (Ti 0.5 Nb 0.5 )2C T、 (Ti 0.5 V 0.5 )2C T-mata (Mo 2 / 3 Y 1 / 3 )2C At T The above-mentioned M n+1 X n T( n=2) is Ti3C2 T、 Ti3CN T、 Zr3C2 T、 Hf3C2 T、 (Ti 0.5 V 0.5 )3C2 T、 (Cr 0.5 V 0.5)3C2 T、 (Cr 2 / 3 Ti 1 / 3 )3C2 T、 (Mo 2 / 3 Sc 1 / 3 )3C2 T、 Mo2TiC2 T-mata is Cr2TiC2 At T The above-mentioned M n+1 X n T( n=3) is Ti4N3 T、 V4C3 T、 Nb4C3 T、 Ta4C3 T、 (Nb 0.8 Ti 0.2 )4C3 T、 (Nb 0.8 Zr 0.2 )4C3 T、 (Mo 0.5 Ti 0.5 )4C3 T-mata is Mo2Ti2C3 At T For example, the maxine unit layer may be Ti3C2 At T It's okay to have one.

[0028] Such maxine nanosheets are materials having a MAX phase, i.e., M n+1 X n The material has a structure in which an A layer, specifically an A atomic layer, is sandwiched between unit layers, and is obtained by a process of selectively etching the A layer. The A may be Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, Sb, or a combination thereof, e.g., Al. In this case, the etching process may mean, for example, using a hydrofluoric acid (HF) solution to selectively remove the A atomic layer, thereby peeling off multiple layers of the MAX phase into individual maxine (MX) unit layers.

[0029] The etching process may be carried out at about 40 to 80°C, specifically 50 to 70°C, for 6 to 48 hours, specifically 12 to 24 hours, but is not limited thereto.

[0030] The concentration of the hydrofluoric acid (HF) solution may be in the range of 30 to 80% by weight, specifically 40 to 50% by weight, but is not limited thereto.

[0031] The prepared maxin nanosheets can then be dried and prepared as powder, which can then be mixed with lignin to prepare a maxin-lignin complex. In particular, the maxin nanosheets contain various negatively charged terminal groups ( T) Since it contains a large number of hydroxy groups, it can easily form chemical bonds with lignin, which will be described later, to undergo complexation or hybridization reaction.

[0032] Lignin may be an essential component of the secondary cell walls of plants and some algae. Lignin may generally be derived from plant sources, such as wood. Various well-known methods are available for isolating lignin from plant sources. These methods include decomposing and removing other plant components to leave lignin as an insoluble residue, such as treating wood fragments with saturated concentrated hydrochloric acid at 0°C and isolating the lignin from the remaining residue, and soluble lignin elution, such as dissolving lignin with sodium hydroxide and sodium sulfite. Among these, lignin can be easily obtained using commercial chemical pulping processes, but is not limited thereto.

[0033] The lignin may be a three-dimensional aromatic polymer, specifically a type of phenolic polymer, which is fat-soluble and amorphous. The lignin may roughly contain three phenyl propane units, including p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol, which are linked by COC bonds (β-O-4, α-O-4, 4-O-5), CC bonds (β-5, 5-5), etc.

[0034] The chemical structure of the lignin may contain functional groups such as hydroxyl groups, carboxyl groups, or C1-C3 alkoxide groups in at least a portion of the aromatic ring. In particular, in the complexation step of the maxin-lignin complex described below, at least one selected from the functional groups, such as a hydroxyl group, may be chemically bonded to maxin to form a maxin-lignin complex in which a chemical transition has occurred.

[0035] In addition, the lignin derivative may include a lignin derivative formed by substituting some of the functional groups contained in the chemical structure of the lignin with other functional groups, for example, a thiol (—SH) functional group.

[0036] The lignin can be represented by the following general formula 1:

[0037] [ka] ……1

[0038] The lignin may also be a sulfur (S)-containing lignin or lignin derivative obtained by a commercial chemical pulping process, and more specifically may be kraft lignin, but is not limited thereto.

[0039] The maxine-lignin complex may contain the maxine sheet described above and lignin chemically bonded to the maxine sheet.

[0040] Specifically, the chemical bond may include a chemical bond between the transition metal (M) of the maxin sheet and a functional group contained in the lignin. More specifically, the chemical bond may include a chemical bond between the transition metal (M) of the maxin sheet and a hydroxyl group (-OH) contained in the lignin, which is represented by M-OH. Even more specifically, the chemical bond may include a chemical bond between Ti as the transition metal (M) of the maxin sheet and a hydroxyl group (-OH) contained in the lignin, which is represented by Ti-OH.

[0041] Battery-less chemical sensor containing maxin-lignin complex as an active layer and method for producing the same Figure 2 is a schematic diagram showing the structure of a battery-free chemical sensor containing a maxin-lignin complex according to one embodiment of the present invention, and Figure 3 is a schematic diagram showing the structure of a battery-free chemical sensor containing a maxin-lignin complex to which a flexible substrate according to one embodiment of the present invention is applied.

[0042] Referring to FIGS. 2 and 3, the battery-less chemical sensors 100, 200 including the maxin-lignin complex of the present invention are provided on substrates 110, 210, and M n+1 X n T( The film may also include a maxin-lignin complex film 120, 220 containing a maxin sheet represented by n=1, 2, or 3) and lignin chemically bonded to the maxin sheet, and a metal electrode 130, 230 formed on at least a portion of the maxin-lignin complex film 120, 220.

[0043] The substrates 110 and 210 may be any substrate used to manufacture elements for realizing conventional chemical sensors, and may be, for example, any one selected from a semiconductor substrate, a glass substrate, a plastic substrate, and a flexible conductive substrate.

[0044] In one embodiment of the present invention (see FIG. 3), when the substrate 110 is a semiconductor substrate, a silicon (Si) 110a substrate can be used. In this case, an insulating layer 110b can be further formed on the silicon substrate 110a. The insulating layer 110b can be formed of a material with low electrical conductivity, such as an oxide such as silicon oxide, hafnium oxide, aluminum oxide, tungsten oxide, titanium oxide, or ruthenium oxide, or an insulating polymer. Specifically, the insulating layer can be silicon oxide (SiO2). In one aspect, the substrate 110 can be a Si substrate on which a SiO2 dielectric layer having a thickness of several to several hundred nanometers is formed, but is not limited thereto.

[0045] In another embodiment of the present invention (see FIG. 4 ), when the substrate 210 is a flexible conductive substrate, it can be a substrate in which an electrically conductive filler is impregnated in a flexible, chemically resistant polymer resin. The polymer resin can be, but is not limited to, an epoxy resin, a polyamide resin, a silicone resin, or a polyester resin. The conductive filler can be, for example, a carbon filler such as carbon fiber, carbon nanotube, carbon nanofiber, graphene, or graphite; a metal filler such as Au, Ni, Ag, Cu, Al, Pt, W, Pd, Si, Ti, or Rh; a conductive polymer material such as polythiophene, polyacetylene, polyaniline, polypyrrole, poly(p-phenylene), or poly(p-phenylene vinylene); or an ionic liquid. These can be used alone or in combination. In one embodiment, the substrate 210 can be an epoxy complex substrate containing carbon fiber, but is not limited thereto.

[0046] The maxine-lignin complex film 120, 220 can be used as the active layer in battery-less chemical sensors, specifically, n+1 X n T(It may contain a maxine sheet represented by n=1, 2 or 3) and lignin chemically bonded to the maxine sheet.

[0047] The maxine sheet and the lignin can be used in the same manner as described above in the section on maxine-lignin complexes, and a detailed description thereof will be omitted for the sake of brevity.

[0048] The metal electrodes 130, 230 may comprise at least one electrode, for example, two metal electrodes, formed on at least a portion of the maxin-lignin complex film 120, 220. The two metal electrodes 130, 230 may be formed as a thin film on the surface of the active layer of the sensor and may include an interdigitated electrode pair structure in which the electrodes are adjacent to each other but do not contact each other, and are arranged alternately like interfinger fingers, to increase the contact area with the active layer.

[0049] The metal electrodes 130, 230 may be made of any conductive material suitable for fabricating elements for implementing chemical sensors, including, but not limited to, Au, Ni, Ag, Cu, Al, Pt, W, Pd, Si, Ti, Rh, and combinations thereof. When two or more metal electrodes 130, 230 are used, the same or different metal materials may be used, and the types of the metal electrodes 130, 230 may differ depending on the type of substrate 110, 210 used. In one embodiment, the metal electrodes 130, 230 may be made of Au or Ni, but are not limited thereto.

[0050] FIG. 4 is a schematic diagram illustrating a method for producing a battery-less chemical sensor containing a maxin-lignin complex according to one embodiment of the present invention.

[0051] 4, a semiconductor substrate may be first prepared and cleaned, which may include cleaning the semiconductor substrate with acetone, isopropyl alcohol, ethanol, and deionized water in this order, followed by ultrasonic treatment for 10 minutes and drying to remove organic residues and impurities from the substrate.

[0052] Next, a step of coating the cleaned semiconductor substrate with a maxin-lignin complex colloidal suspension to produce a maxin-lignin complex film may be performed. The maxin-lignin complex colloidal suspension can be prepared by mixing the maxin sheet, the lignin, and an organic solvent. The maxin sheet and the lignin may be mixed in a weight ratio of 1:1 to 5:1. When mixed in this range, the functional groups on the maxin sheet surface are uniformly hybridized with the lignin without surface defects, thereby improving the sensitivity of the chemical sensor. Specifically, the maxin sheet and the lignin may be mixed in a weight ratio of 1:1 to 4:1, more specifically 1:1 to 3:1. In one embodiment, the weight ratio may be 2:1, but is not limited thereto.

[0053] The organic solvent may be any organic solvent that allows the Maxine sheet and the lignin to be easily dispersed and prevents chemical side reactions, and may be, for example, any one selected from the group consisting of dimethylsulfoxide, dimethylformamide, gamma butyrolactone, N-methylpyrrolidone, and mixtures thereof. In one embodiment, the organic solvent may include, but is not limited to, dimethylsulfoxide.

[0054] The maxin-lignin complex film may have a thickness on the scale of several tens to several hundreds of micrometers, for example, a thickness of 10 μm to 100 μm.

[0055] Next, a step of drying the substrate on which the maxin-lignin complex film has been formed may be performed in an oven. The drying step may be performed at a temperature of 100 to 200°C, and in one embodiment, 150°C.

[0056] Next, a step of depositing a metal electrode on the substrate on which the dried maxin-lignin complex film has been formed may be performed. The metal electrode may be made of, for example, at least one selected from Au, Ni, Pt, W, Pd, Si, Ti, Rh, and combinations thereof. In one embodiment, the metal electrode may be Au or Ni, but is not limited thereto.

[0057] The step of depositing the electrode can be performed using, but is not limited to, a metal thin film deposition method that applies energy at a level that does not induce defects in the active layer, such as an electron beam evaporator, a thermal evaporator, or sputtering.

[0058] The present invention will be described in more detail below with reference to examples and comparative examples. However, the following examples and comparative examples are for illustrative purposes only and do not limit the scope of the present invention.

[0059] Preparation Example 1: Preparation of colloidal solution containing maxine-lignin complex First, 1 g of the MAX phase precursor Ti3AlC2 (purity ≥ 90 wt%) was added to 20 mL of HF solution (49%, v / v) and magnetically stirred at room temperature for 24 hours to etch the Al atomic layers. The precursor powder was added gradually to prevent excessive foaming due to the exothermic nature of the etching reaction. The etched solution was then washed with deionized water, centrifuged at 3,500 rpm for 5 minutes, and the supernatant was removed and redispersed. This process was repeated several times until the pH of the solution reached 6 or higher. The Ti3AlC2 obtained using this process was T-Ma The colloidal solution containing the Maxin sheets was centrifuged at 3,500 rpm for 30 minutes to obtain a supernatant containing the exfoliated Maxin colloidal solution, which was then dried in an oven at 150°C for 24 hours.

[0060] Next, the dried Maxin sheet was crushed and mixed with lignin in a 2:1 weight ratio, and 1 mL of dimethylsulfoxide (DMSO, ≥99.9 wt%, v / v) was used as a solvent to prepare a Maxin-lignin mixed solution. The mixed solution was sonicated for 2 hours and then magnetically stirred at room temperature for 24 hours to produce a colloidal suspension containing a Maxin-lignin complex in which Maxin and lignin were homogeneously complexed.

[0061] Production Example 2: Production of colloidal solution containing Maxine Sheet A colloidal solution containing Maxine sheets was prepared in the same manner as in Preparation Example 1, except that the step of mixing lignin was not carried out.

[0062] Example 1: Fabrication of a battery-free chemical sensor containing maxine-lignin complexes A 300 nm thick SiO2 / Si wafer substrate was cut into 1 x 1 cm pieces, washed in acetone, isopropyl alcohol, ethanol, and deionized water, then ultrasonicated for 10 minutes, and dried to remove organic residues and impurities from the substrate. Next, 20 mg of the colloidal solution containing the maxin-lignin complex of Preparation Example 1 was dropped onto the cut wafer substrate using a 100 μm micropipette (drop casting method), and dried in an oven at 150 °C for 30 minutes to remove the solvent and residues, forming a maxin-lignin complex thin film. Next, a 1 x 10 cm thin film was formed by electron beam evaporation. -6 A 100-nm-thick gold electrode was deposited at a vacuum pressure of Torr. The gold electrode was an interdigitated electrode (customized interdigitated comb-shaped electrode).

[0063] Comparative Example 1: Fabrication of a battery-free chemical sensor containing Maxine sheet A battery-less chemical sensor containing maxin sheet was manufactured in the same manner as in Example 1, except that instead of using the colloidal solution containing maxin-lignin complex in Preparation Example 1, the colloidal solution containing maxin sheet in Preparation Example 2 was used.

[0064] Example 2: Fabrication of a battery-free chemical sensor containing maxine-lignin complexes realized on a flexible substrate A battery-less chemical sensor containing a maxin-lignin complex realized on a flexible substrate was fabricated in the same manner as in Example 1, except that an epoxy complex flexible substrate containing carbon fiber was used instead of a wafer substrate and a Ni electrode was used instead of an Au electrode.

[0065] <Experimental Example 1> Material properties of maxine-lignin complex Figure 5 shows a field emission scanning electron microscopy (FE-SEM) image and energy disperse X-ray spectroscopy (EDS) results for the Maxine sheet from Production Example 2 of the present invention, and Figure 6 shows a field emission scanning electron microscopy (FE-SEM) image and energy disperse X-ray spectroscopy (EDS) results for the Maxine-lignin complex from Production Example 1 of the present invention.

[0066] 5 and 6, the Ti3C2 phase after etching the MAX phase precursor T-Ma The microstructure of the Maxin sheet shows a layered structure consisting of several to several dozen Maxin sheets loosely stacked together, but the Maxin-lignin complex shows a different microstructure from the layered Maxin sheet before complexation, in that the layered sheets are not separated but rather form an aggregate. Furthermore, the detection of sulfur (S) element derived from the chemical structure of lignin confirms that lignin has been hybridized to the surface of the complex.

[0067] Figure 7 shows the results of a. field emission transmission electron microscopy (FE-SEM), b. selected area electron diffraction (SAED), and c. high resolution transmission electron microscopy (HR-TEM) for the Maxine sheet of Production Example 2 of the present invention, and Figure 8 shows the results of a. field emission transmission electron microscopy (FE-TEM), b. selected area electron diffraction (SAED), and c. high resolution transmission electron microscopy (HR-TEM) for the Maxine-lignin complex of Production Example 1 of the present invention.

[0068] Referring to Figures 7 and 8, Ti3C2 T-Ma The TiC sheet exhibits a typical lattice structure and is T(The lattice spacing of maxine, which corresponds to the (111) plane, is confirmed to be 0.25 nm (shown by the orange solid rectangle). On the other hand, the maxine-lignin complex is confirmed to contain amorphous regions due to some lignin components (shown by the yellow dotted rectangle), and the other part contains crystalline regions due to maxine, which is Ti3C2 T( 111) plane equivalent lattice spacing of 0.25 nm and Ti3C2 T( A lattice spacing of 0.3 nm corresponding to the (110) plane was measured (represented by the orange solid square), and it was confirmed that each of these lattice spacings matches the SEAD pattern of the maxine-lignin complex measured in Figure 8b.

[0069] Figure 9 shows the results of X-ray photoelectron spectroscopy (XPS) for the maxin-lignin complex and maxin according to Production Examples 1 and 2 of the present invention, including a. the overall irradiation spectrum, b. the Ti 2p peak of the maxin sheet, c. the O 1s peak of the maxin sheet, d. the S 2p peak of the maxin-lignin complex, e. the Ti 2p peak of the maxin-lignin complex, and f. the O 1s peak of the maxin-lignin complex.

[0070] Referring to FIG. 9, the Ti 2p spectrum for the maxine-lignin complex (FIG. 9e) shows a peak at 464.2 eV (Ti 2p 1 / 2 ), 459.0 eV (Ti 2p 3 / 2 ) and 455.6 eV (Ti 2p 3 / 2) peak, which is measured almost identically when compared to the peak of pure maxin. This may indicate that the Ti 2p binding energy is almost the same as that of pure maxin, and therefore no chemical bond is formed between maxin and lignin. On the other hand, the O 1s spectrum for the maxin-lignin complex (Figure 9f) shows a significant difference in peak intensity compared to the spectrum of pure maxin, which may indicate that a chemical transition occurs between lignin and maxin during the complexation process. Specifically, the maxin-lignin complex contains a strong peak at 531.9 eV due to Ti-OH groups and a weak peak at 529.98 eV due to Ti-O, confirming that the hydroxyl (-OH) functional groups in lignin induce the formation of Ti-OH chemical bonds during the complexation process.

[0071] <Experimental Example 2> Measurement of the electrical properties of a battery-free chemical sensor containing maxine-lignin complex To measure the electrical properties of the battery-free chemical sensors of the present invention, I-V measurements were performed under vacuum using a Keithley 4200SCS semiconductor parameter analyzer (Keithley Instruments, Cleveland, Ohio, USA). The output characteristics of the battery-free chemical sensors based on maxin sheets and maxin-lignin complexes were measured by measuring the source-drain current (I) while varying the voltage drain from -10 V to +10 V. ds ) was measured and obtained.

[0072] <Experimental Example 3> Measurement of gas sensing performance of battery-free chemical sensor containing maxine-lignin complex To measure the gas sensing performance of the battery-less chemical sensor of the present invention, various concentrations of target gases, such as CO2 and NO2, may be introduced into the sensor at room temperature under vacuum conditions. The sensor may be placed in a sealed Teflon chamber equipped with gas inlets and outlets.

[0073] The reaction result for the gas to be detected can be derived from the following equation 1.

[0074]

number

[0075] A battery-less chemical sensor according to one embodiment of the present invention may be prepared in a chamber into which N2 gas has been introduced before injecting the gas to be analyzed, such as CO2, NO2, etc., and the value measured at this time may be used as a reference value to normalize the data.

[0076] The gas sensing performance of the sensor can be determined by measuring the current in real time when a target gas, such as CO or NO, is injected into the chamber for several seconds, e.g., 2 seconds. Then, before reinjecting the target gas, a further process of purging with N gas for at least 20 seconds can be performed to remove previously adsorbed target gas molecules. The target gas can be controlled using a mass flow controller (MFC), and the measured gas measurement sensitivity can be calculated according to the International Union of Pure and Applied Chemistry (IUPAC) definition.

[0077] FIG. 10 is a current-voltage (IV) graph for a battery-less chemical sensor containing maxin and maxin-lignin complexes according to Example 1 and Comparative Example 1 of the present invention.

[0078] Referring to Figures 10a and 10b, it can be seen that the battery-less chemical sensor using the maxin-lignin complex as the active layer has lower conductivity than the active layer containing only maxin, and the ohmic contact characteristics change to Schottky contact characteristics.

[0079] Figure 11 is a graph showing the current response (ΔI / I0), response time, and recovery time when a gas to be detected is exposed to a battery-free chemical sensor containing a maxin-lignin complex and maxin according to Example 1 and Comparative Example 1 of the present invention.

[0080] Response time τ response is calculated as the time it takes to reach 90% of the value being responded to, and the repair time τ recovery was calculated as the time it took for the signal to return to within 10%.

[0081] 11, when exposed to NO2 and CO2 at a gas concentration of 15 ppm, the chemical sensor containing the maxin-lignin complex as the active layer (FIGS. 11c and 11d) exhibits higher reactivity than the sensor containing pure maxin (FIGS. 11a and 11b). Furthermore, when NO2 is used as the gas to be detected, the chemical sensor containing the maxin-lignin complex as the active layer (FIG. 11d) can detect current changes at the nanoampere (nA) level, demonstrating faster reaction and repair rates than the sensor containing pure maxin (FIG. 11b).

[0082] FIG. 12 shows the current response (ΔI / I0), c response (%), and d sensitivity (ppm) of the maxin-lignin complex and maxin-containing battery-less chemical sensors according to Example 1 and Comparative Example 1 of the present invention when a. and b. the gas to be detected are exposed in a pulsed manner. -1 ) are the results shown.

[0083] To determine the change in signal measured per unit of analyte concentration, the sensitivity (S) of the chemical sensor can be calculated by Equation 2 below:

[0084]

number

[0085] Here, ΔR is the sensor response, and ΔC is the change in concentration of the gas being detected.

[0086] Referring to Figure 12, it can be seen that the chemical sensor containing the maxin-lignin complex according to the present invention as an active layer exhibits high chemical sensitivity to both CO2 and NO2 at a concentration of 15 ppm as the detection target gases, while also exhibiting repeated and sustained pulse responses. Rapid attachment and detachment of the detection target molecules facilitates sensor repair and allows the sensor to return to its initial state. In particular, at a concentration of 15 ppm, the reactivity (%) for CO2 gas improved from 15.64% in Comparative Example 1, in which pure maxin was applied, to 62.22% in Example 1, in which the maxin-lignin complex was applied. It can also be seen that the reactivity (%) for NO2 gas improved significantly from 34.70% in Comparative Example 1, in which pure maxin was applied, to 89.32% in Example 1, in which the maxin-lignin complex was applied. Furthermore, at a concentration of 15 ppm, the sensitivity (ppm) of the chemical sensor -1 ) were 157.38% and 297.95% for CO2 and NO2 gases, respectively, and it can be confirmed that they increased significantly.

[0087] FIG. 13 shows an optical photograph and bending test results of a battery-less chemical sensor including a maxin-lignin complex implemented on a flexible substrate according to Example 2 of the present invention. FIG. 14 shows a current-voltage (IV) graph according to the number of bending times for the battery-less chemical sensor including a maxin-lignin complex implemented on a flexible substrate according to Example 2 of the present invention. FIGS. 15 and 16 show the current response (ΔI / I0), response (%), and sensitivity (ppm) according to the number of bending times when the battery-less chemical sensor including a maxin-lignin complex implemented on a flexible substrate according to Example 2 of the present invention is exposed to pulsed gas to be detected. -1 ) are the results shown.

[0088] 13 to 16, the battery-less chemical sensor containing the maxin-lignin complex fabricated on the flexible substrate was measured at a bending angle of 38°, ensuring flexibility, and exhibiting Schottky barrier characteristics similar to those of the non-flexible sensor fabricated on a silicon substrate. The gas exposure test and pulse conditions were the same as those for the non-flexible sensor described above. It was also confirmed that even after 50 bending tests, the sensor exhibited high chemical sensitivity to both CO2 and NO2 at 15 ppm concentrations as the target gases, while also demonstrating repetitive and sustained pulse responses. Specifically, the battery-less chemical sensor containing the maxin-lignin complex fabricated on the flexible substrate exhibited response (%) and sensitivity (ppm) to CO2 and NO2 gases at 15 ppm concentrations. -1 ) only decreased by about 10% and 15%, respectively, at the 50th bending cycle, confirming that the specimen still exhibited good response and sensitivity.

[0089] Although the embodiments of the present invention have been described above with reference to the accompanying drawings, it should be understood by those skilled in the art that the present invention can be embodied in other specific forms without changing the technical concept or essential features of the present invention. Therefore, it should be understood that the above-described embodiments are merely illustrative in all respects and are not limiting. [Explanation of symbols]

[0090] 100, 200 Battery-free chemical sensors 110, 210 board 120, 220 Maxine-lignin complex film 130, 230 metal electrode

Claims

1. In the maxine-lignin complex, M ｎ＋１ X ｎ A maxine sheet represented by T (n=1, 2 or 3); Lignin chemically bonded to the Maxine sheet; Including, wherein M is Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W or two or more transition metals selected from these; X is C; and T is F, OH or O; The maxin-lignin complex is characterized in that it contains a crystalline region due to the maxin sheet and an amorphous region due to the lignin, due to a covalent bond (M-OH) between the transition metal (M) of the maxin sheet and a hydroxyl group (-OH) functional group contained in the lignin.

2. The maxine-lignin complex according to claim 1, wherein the chemical bond is a bond between Ti as the transition metal (M) of the maxine sheet and a hydroxyl group (-OH) contained in the lignin, and includes a chemical bond represented by Ti-OH.

3. A substrate; disposed on the substrate, ｎ＋１ X ｎ a maxin-lignin complex film comprising a maxin sheet represented by T (n=1, 2 or 3) and lignin chemically bonded to the maxin sheet; At least one metal electrode formed on at least a portion of the maxine-lignin complex film; Equipped with wherein M is Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W or two or more transition metals selected from these; X is C; and T is F, OH, or O; The maxin-lignin complex film is characterized by comprising a crystalline region due to the maxin sheet and an amorphous region due to the lignin, which are formed by a covalent bond (M-OH) between the transition metal (M) of the maxin sheet and a hydroxyl group (-OH) functional group contained in the lignin. This is a battery-less chemical sensor comprising a maxin-lignin complex.

4. A battery-less chemical sensor comprising the maxin-lignin complex described in claim 3, wherein the chemical bond is a bond between Ti as the transition metal (M) of the maxin sheet and a hydroxyl group (-OH) contained in the lignin, and includes a chemical bond represented by Ti-OH.

5. The battery-less chemical sensor comprising a maxine-lignin complex according to claim 3, wherein the substrate is any one selected from the group consisting of a semiconductor substrate, a glass substrate, a plastic substrate, and a flexible conductive substrate.

6. 6. The battery-less chemical sensor comprising a maxine-lignin complex according to claim 5, wherein the flexible conductive substrate comprises an epoxy complex containing carbon fiber.

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