Gas detection method using surface-enhanced raman spectroscopy

Abstract

A gas detection method using surface-enhanced Raman spectroscopy (SERS) according to the present invention may comprise the steps of: (a) vertically forming a plurality of nanowires on a base substrate; (b) depositing metal nanoparticles on the nanowires to manufacture a SERS substrate having a three-dimensional structure; (c) cooling the manufactured SERS substrate to condense an analyte gas on the SERS substrate; (d) irradiating the condensed analyte gas particles with excitation light and detecting light scattered from the analyte gas particles; and (e) analyzing the detected light to detect the analyte gas.

Description

Gas detection method using surface-enhanced Raman spectroscopy

[0001] The present invention relates to a gas detection method using surface-enhanced Raman spectroscopy, wherein a SERS substrate is manufactured by repeatedly depositing metal nanoparticles to optimize the size of the metal nanoparticles, and the analyzed gas is condensed by cooling the manufactured substrate to improve gas detection sensitivity.

[0002]

[0003] Raman spectroscopy can analyze the composition of various substances by measuring inelastic scattering that occurs within a sample due to excitation light irradiated onto the sample. When light is incident on a sample to be measured, inelastically scattered light of a wavelength different from the incident light is detected and measured.

[0004] The wavelength shift between incident and scattered light is called the Raman shift, and this shift represents the vibrational or rotational energy states of molecules. Since the intensity of Raman scattered light is known to correspond directly to the concentration of the target molecule, molecular analysis using Raman spectroscopy is highly useful.

[0005] In particular, the discovery of surface-enhanced Raman scattering, a phenomenon in which the Raman signal of molecules adsorbed on a roughly surface-treated metal substrate is significantly increased, has improved the disadvantage of conventional Raman spectroscopy, which has low detection sensitivity due to the very small signal intensity of Raman scattered light. Much research is being conducted to elucidate the principles of surface-enhanced Raman scattering.

[0006] For example, when a laser is irradiated onto a metal, it is predicted that surface plasmons are intensively excited in specific regions depending on the metal's surface structure, leading to surface-enhanced Raman scattering. Additionally, electromagnetic interactions between molecules adsorbed on the metal and the metal itself are also predicted to contribute to surface-enhanced Raman scattering.

[0007] In daily life, we face hidden dangers such as toxic vapors and gases emitted from various sources, including industrial plants and vehicles. Detecting and managing these substances is essential for public health and environmental protection. While Surface Enhanced Raman Spectroscopy (SERS) is promising for identifying chemicals, significant research is required for the accurate detection of gas and vapor samples, including the ability to identify specific gases and detectable concentrations.

[0008] Therefore, research is needed on a gas detection method using surface-enhanced Raman spectroscopy that can improve sensitivity for detecting trace amounts of vapor to solve the aforementioned problem.

[0009]

[0010] [Prior Art Literature]

[0011] [Patent Literature]

[0012] (Patent Document 0001) 1. Korean Registered Patent No. 10-2650657

[0013] (Patent Document 0002) 2. Korean Registered Patent No. 10-2542469

[0014]

[0015] The objective of the present invention is to provide a gas detection method using surface-enhanced Raman spectroscopy capable of analyzing various types of gases while simultaneously detecting low concentrations of gases with excellent sensitivity.

[0016]

[0017] A gas detection method using surface-enhanced Raman spectroscopy according to one embodiment of the present invention may include the following steps: (a) forming a plurality of nanowires vertically on a base substrate; (b) manufacturing a SERS substrate with a three-dimensional structure by depositing metal nanoparticles on the nanowires; (c) cooling the manufactured SERS substrate to condense a gas to be analyzed on the SERS substrate; (d) irradiating the condensed gas particles to be analyzed with excitation light and detecting light scattered from the gas particles to be analyzed; and (e) analyzing the detected light to detect the gas to be analyzed.

[0018] In addition, the step of (e) detecting the gas to be analyzed according to one embodiment of the present invention may include the step of analyzing the detected light to identify the type of the gas to be analyzed by the position of the Raman peak point of the surface-enhanced Raman scattering spectrum, and the step of calculating the concentration of the gas to be analyzed based on the relationship between the intensity of the Raman peak point and the concentration of the gas to be analyzed that is stored in advance.

[0019] In addition, the step of detecting the gas to be analyzed (e) according to one embodiment of the present invention may further include the step of correcting the concentration of the gas to be analyzed according to the temperature of the SERS substrate.

[0020] In addition, step (b) according to one embodiment of the present invention may form a three-dimensional SERS substrate by repeatedly depositing at least one metal nanoparticle among Au, Ag, Cu, and Al 5 to 10 times using liquid phase deposition (LPD).

[0021] In addition, the average diameter of the metal nanoparticles according to one embodiment of the present invention may be 40 to 60 nm.

[0022] In addition, step (c) according to one embodiment of the present invention may cool the SERS substrate to room temperature or lower.

[0023] In addition, the gas to be analyzed according to one embodiment of the present invention may include at least one of ethanol, methanol, toluene, and ethylbenzene.

[0024] In addition, the lowest detection limit of the ethanol according to one embodiment of the present invention is 0.124 × 10 6 It may be less than ppm.

[0025] In addition, the lowest detection limit of methanol according to one embodiment of the present invention is 0.215 × 10 6 It may be less than ppm.

[0026] In addition, the lowest detection limit of the toluene according to one embodiment of the present invention is 0.075 × 10⁻⁶ 6 It may be less than ppm.

[0027] In addition, the lowest detection limit of the ethylbenzene according to one embodiment of the present invention is 0.066 × 10⁻⁶. 6 It may be less than ppm.

[0028] A gas detection device using surface-enhanced Raman spectroscopy according to one embodiment of the present invention may include a SERS substrate comprising a plurality of nanowires formed vertically on a base substrate and metal nanoparticles with a three-dimensional structure deposited on the nanowires, a cooling unit that cools the SERS substrate to a set temperature to condense a gas to be analyzed onto the SERS substrate, a light source that irradiates excitation light onto the condensed gas particles to be analyzed, a light detection unit that detects light scattered from the gas particles to be analyzed, and a data analysis unit that analyzes the detected light to detect the gas to be analyzed.

[0029] In addition, the data analysis unit according to one embodiment of the present invention analyzes the detected light to identify the type of gas to be analyzed using the Raman peak of the surface-enhanced Raman scattering spectrum, and can calculate the concentration of the gas to be analyzed based on the relationship between the intensity of the Raman peak point stored in advance and the concentration of the gas to be analyzed.

[0030] In addition, the data analysis unit according to one embodiment of the present invention can correct the concentration of the gas to be analyzed based on the relationship between the temperature of the SERS substrate and the concentration of the gas to be analyzed.

[0031] In addition, the metal nanoparticle according to one embodiment of the present invention may be at least one nanoparticle among Au, Ag, Cu and Al having an average diameter of 40 to 60 nm.

[0032]

[0033] The gas detection method using surface-enhanced Raman spectroscopy according to the present invention can improve gas detection sensitivity by manufacturing a SERS substrate by optimizing the size of metal nanoparticles through repeated deposition of metal nanoparticles and cooling the manufactured substrate to condense the analysis gas.

[0034] Accordingly, the gas detection method using surface-enhanced Raman spectroscopy according to the present invention can analyze various types of gases while simultaneously detecting gases at low concentrations with excellent sensitivity.

[0035]

[0036] Figure 1 is a schematic diagram illustrating a Raman analysis method using surface enhanced Raman spectroscopy (SERS) containing metal nanoparticles.

[0037] Figure 2 is a schematic diagram illustrating the SERS principle.

[0038] Figure 3 is a conceptual diagram showing Rayleigh scattering and Raman scattering.

[0039] FIG. 4 is a schematic diagram showing a method for manufacturing a SERS substrate including Au nanoparticles according to one embodiment of the present invention.

[0040] Figure 5 is an SEM image of a manufactured SERS substrate according to one embodiment of the present invention.

[0041] Figure 6 is the result of surface analysis using SEM-EDS (scanning electron microscopy-energy dispersive spectroscopy) of a SERS substrate manufactured according to one embodiment of the present invention.

[0042] FIG. 7 is a schematic diagram of a gas detection device using SERS according to one embodiment of the present invention.

[0043] Figure 8 is a graph showing the SERS intensity according to the concentration of gases (ethanol, methanol, toluene, ethylbenzene) measured according to a gas detection method using SERS according to one embodiment of the present invention.

[0044] Figure 9 is a graph showing the SERS intensity by peak according to the concentration of gas (ethanol, methanol, toluene, ethylbenzene) measured according to a gas detection method using SERS according to one embodiment of the present invention.

[0045] Figure 10 is a graph of the relationship between the representative SERS intensity for each peak and the gas (ethanol, methanol, toluene, ethylbenzene) concentration measured according to the gas detection method using SERS according to one embodiment of the present invention.

[0046]

[0047] Specific embodiments of the present invention will be described in detail below with reference to the drawings. However, the concept of the present invention is not limited to the presented embodiments. Those skilled in the art who understand the concept of the present invention may easily propose other inventions that are inferior or other embodiments included within the scope of the concept of the present invention by adding, changing, or deleting other components within the same scope of the concept, and such are also to be considered to be included within the scope of the concept of the present invention.

[0048] Additionally, components with the same function within the scope of the same concept appearing in the drawings of each embodiment are described using the same reference numeral.

[0049]

[0050] Figure 1 is a schematic diagram illustrating a Raman analysis method using surface enhanced Raman spectroscopy (SERS) containing metal nanoparticles. Raman analysis utilizes the phenomenon in which energy states shift when light of a single wavelength is scattered through interaction with the molecular vibrations of a material.

[0051] The irradiated excitation light is scattered by the molecular structure and, in the form of wavelength-converted inelastic scattering, contains various spectra with different degrees of wavelength conversion depending on the molecular state. The detected Raman signal includes a wavelength shift relative to the wavelength of the incident light; this energy shift may contain information related to the molecular vibrations of the material, such as information regarding molecular structure or bonding types, as well as information regarding functional groups.

[0052] Figure 2 is a schematic diagram illustrating the principle of surface-enhanced Raman scattering. Surface-enhanced Raman scattering is used to amplify weak Raman signals. It is based on the phenomenon in which molecular vibrations occur due to the interaction between a light source and a molecule, resulting in localized surface plasmon resonance (LSPR) excitation and photon dispersion.

[0053] Raman signals are inherently weak because the number of scattered photons available for detection is statistically low. Typically, nanostructures of gold or silver or rough metal surfaces are used. Laser excitation of these metal structures induces surface charges to generate a localized plasmon field, which is an enhanced electric field.

[0054] It can be observed that as molecules approach the surface and the electric field is consequently strengthened, the Raman signal is significantly enhanced, resulting in the generation of a Raman signal tens of times larger than that of normal Raman scattering. This enables the detection of low concentrations without the need for additional processes.

[0055] Figure 3 is a conceptual diagram illustrating Rayleigh scattering and Raman scattering. When light passes through a medium, some of it is scattered and travels in a different direction from its original direction of propagation. At this time, the scattered light may retain its original energy, but it may also have less or more energy than the original light. The process of elastic scattering in which the scattered light maintains its original energy is called Rayleigh scattering, while the process of inelastic scattering in which it loses or gains energy is called Raman scattering. Raman scattering is divided into Stokes scattering and anti-Stokes scattering. Stokes scattering refers to the scattering of long-wavelength light that loses energy compared to the incident light source, while anti-Stokes scattering refers to the scattering of short-wavelength light that gains energy.

[0056] A gas detection method using surface enhanced Raman spectroscopy (SERS) according to the present invention comprises: (a) a nanowire formation step; (b) a nanoparticle deposition step; (c) a SERS substrate cooling step; (d) an excitation light irradiation and scattered light detection step; and (e) a gas detection step.

[0057] FIG. 4 is a schematic diagram illustrating a method for manufacturing a surface-enhanced Raman spectroscopy (SERS) substrate containing Au nanoparticles according to an embodiment of the present invention. The nanowire formation step (a) is a step of forming a plurality of nanowires vertically on a base substrate. The base substrate may be a semiconductor substrate, a metal substrate, a polymer substrate, etc., and in particular, may be a semiconductor wafer made of Si, Ge, GaAs, GaP, SiO2, etc.

[0058] A plurality of nanowires are formed vertically on the base substrate. The nanowires may be made of a material that does not affect Raman scattering, even if they are not removed in a subsequent process.

[0059] In one embodiment, the nanowire may be made of materials such as Si, InP, GaN, and ZnO, and the nanowire may be formed by coating a seed layer on the base substrate, placing it in a solution containing a precursor, and then heat treating it.

[0060] In particular, when forming nanowires with ZnO, a ZnO seed layer can be formed by spraying a ZnO seed solution onto a substrate and then heat-treating it at a temperature of 350°C on a hot plate.

[0061] After that, ZnO nanowires can be formed by immersing them in a ZnO nanowire precursor solution and heating them at a temperature of 95°C for two and a half hours. To increase the thickness of the metal nanoparticle layer, it is necessary to grow the ZnO nanowires longer, and the above process can be repeated.

[0062] The above (b) nanoparticle deposition step is a step of manufacturing a three-dimensional SERS substrate by depositing metal nanoparticles on the nanowire. Metal nanoparticles can be deposited on the surface of the nanowire to form a three-dimensional structure.

[0063] In one embodiment, the metal nanoparticles may be deposited as at least one metal nanoparticle selected from Au, Ag, Cu, and Al, and a plurality of metal nanoparticle clusters may be formed by repeating the deposition process. Deposition can be performed using a liquid phase deposition method in which a base substrate having a plurality of nanowires formed thereon is immersed in a metal nanoparticle precursor solution and heated. The metal nanoparticle precursor solution may be heated at a temperature of 90°C for 1 hour in a convection oven.

[0064] This liquid phase deposition process can be repeated multiple times until a number of conductive metal nanoparticles are densely packed to form a metal nanoparticle cluster. In particular, a three-dimensional SERS substrate can be formed by repeatedly depositing at least one metal nanoparticle selected from Au, Ag, Cu, and Al 5 to 10 times using liquid phase deposition (LPD). Additionally, the average diameter of the formed metal nanoparticles may be 40 to 60 nm.

[0065] Step (b) above can remove the nanowires formed after depositing metal nanoparticles. For materials that do not affect Raman scattering, Au nanoparticles can be repeatedly deposited without removing the nanowires. In this case, a three-dimensional structure can be formed more clearly.

[0066] The above (c) SERS substrate cooling step is a step of cooling the manufactured SERS substrate to condense the gas to be analyzed onto the SERS substrate. The SERS substrate may be cooled to a temperature below room temperature. The gas to be analyzed may be condensed within a temperature range below room temperature, or it may be cooled to a sub-zero temperature range. The lower the temperature of the SERS substrate, the lower the concentration of gas can be detected.

[0067] The above (d) step of excitation light irradiation and scattered light detection is a step of irradiating the condensed gas particles to be analyzed with excitation light and detecting the light scattered from the gas particles to be analyzed.

[0068] The above (e) step of detecting the gas to be analyzed is a step of detecting the gas to be analyzed by analyzing the detected light. It may include a step of identifying the type of the gas to be analyzed by the position of the Raman peak point of the surface-enhanced Raman scattering spectrum by analyzing the detected light, and a step of calculating the concentration of the gas to be analyzed based on the relationship between the intensity of the Raman peak point and the concentration of the gas to be analyzed that is stored in advance.

[0069] The position of the Raman peak corresponds to the change in energy possessed by the molecule; since it represents the energy exchanged with photons during the transition process between the molecule's intrinsic energy levels, it can possess molecular characteristics. Accordingly, the type of gas being analyzed can be identified.

[0070] By utilizing the relationship between the intensity of a pre-stored Raman peak and the concentration of the target gas, the type of gas can be effectively and accurately identified, and the gas concentration can be quantitatively detected.

[0071] The above-mentioned gas to be analyzed may include at least one of ethanol, methanol, toluene, and ethylbenzene.

[0072] The concentration of the above ethanol and the SERS intensity satisfy the following relationship 1.

[0073] [Relationship 1]

[0074]

[0075] (In the above relationship 1, I SERS Is Representative Raman peak point of ethanol (878 cm⁻¹) -1 ) is the strength, and C is the ethanol concentration.)

[0076] The above methanol concentration and SERS intensity satisfy the following relationship Equation 2.

[0077] [Relationship 2]

[0078]

[0079] (In the above relationship 2, I SERS Is Representative Raman peak of methanol (1027 cm⁻¹) -1 ) is the intensity, and C is the methanol concentration.)

[0080] The above concentration of toluene and SERS intensity satisfy the following relationship Equation 3.

[0081] [Relationship 3]

[0082]

[0083] (In the above relationship 3, I SERS Is Toluene's representative Raman peak (785 cm) -1 ) is the intensity, and C is the toluene concentration.)

[0084] The concentration of ethylbenzene and SERS intensity above satisfy the relationship 4 below.

[0085] [Relationship 4]

[0086]

[0087] (In the above relationship 4, I SERS Is Representative Raman peak point of ethylbenzene (767 cm⁻¹) -1 ) is the intensity, and C is the ethylbenzene concentration.)

[0088] In addition, the step of detecting the gas to be analyzed (e) may further include a step of correcting the concentration of the gas to be analyzed according to the temperature of the SERS substrate.

[0089] As the temperature of the SERS substrate decreases, a larger amount of the target gas can be condensed, which may result in a lower detectable gas concentration. Consequently, as the temperature of the substrate decreases, the intensity of the Raman peak increases. Accordingly, the concentration of the target gas can be corrected based on the temperature of the SERS substrate.

[0090] By utilizing Raman peak point data across various temperature ranges obtained by controlling the cooling temperature, it is possible to accurately identify various types of vapors and perform precise analysis of gas concentrations.

[0091] In particular, the lowest detection limit of the above ethanol is 0.124 × 10⁻⁶ 6 It is ppm or less, and the lowest detection limit of the methanol is 0.215 × 10⁻⁶ 6 It may be ppm or less. In addition, the lowest detection limit of the above toluene is 0.075 × 10⁻⁶ 6 It is less than ppm, and the lowest detection limit of the above ethylbenzene is 0.066 × 10⁻⁶ 6 It may be less than ppm.

[0092] FIG. 7 is a schematic diagram of a gas detection device using SERS according to an embodiment of the present invention. The gas detection device using surface enhanced Raman spectroscopy (SERS) according to the present invention includes a SERS substrate, a cooling unit, a light source, a photodetector, and a data analysis unit.

[0093] The SERS substrate may include a plurality of nanowires formed vertically on a base substrate and metal nanoparticles with a three-dimensional structure deposited on the nanowires. The metal nanoparticles may be Au nanoparticles with an average diameter of 40 to 60 nm.

[0094] The cooling unit can cool the SERS substrate to condense the gas to be analyzed onto the SERS substrate. By condensing the gas to be analyzed onto the SERS substrate, molecular contact of the gas to be analyzed on the SERS substrate can be enhanced. The gas to be analyzed may include at least one of ethanol, methanol, toluene, and ethylbenzene.

[0095] The above cooling unit may be positioned excluding the portion where the gas is condensed on the SERS substrate to condense the gas to be analyzed on the SERS substrate, and may be positioned in contact with the lower surface of the SERS substrate to ensure a uniform temperature distribution over the entire SERS substrate.

[0096] The light source irradiates excitation light onto the condensed gas particles to be analyzed, and the light detector detects light scattered from the gas particles to be analyzed. The data analysis unit can detect the gas to be analyzed by analyzing the detected light.

[0097] In particular, the data analysis unit analyzes the detected light to identify the type of gas to be analyzed using the Raman peak of the surface-enhanced Raman scattering spectrum, and can calculate the concentration of the gas to be analyzed based on the relationship between the intensity of the Raman peak point stored in advance and the concentration of the gas to be analyzed.

[0098] In addition, the data analysis unit can correct the concentration of the gas to be analyzed based on the relationship between the temperature of the SERS substrate and the concentration of the gas to be analyzed.

[0099] The lowest detection limit of the above ethanol is 0.124 × 10⁻⁶ 6 It is ppm or less, and the lowest detection limit of the methanol is 0.215 × 10⁻⁶ 6 It may be ppm or less. In addition, the lowest detection limit of the above toluene is 0.075 × 10⁻⁶ 6 It is less than ppm, and the lowest detection limit of the above ethylbenzene is 0.066 × 10⁻⁶6 It may be less than ppm.

[0100] The gas detection method using surface-enhanced Raman spectroscopy according to the present invention can improve gas detection sensitivity by manufacturing a SERS substrate by optimizing the size of metal nanoparticles through repeated deposition of metal nanoparticles and cooling the manufactured substrate to condense the analysis gas.

[0101] Accordingly, the gas detection method using surface-enhanced Raman spectroscopy according to the present invention can analyze various types of gases while simultaneously detecting gases at low concentrations with excellent sensitivity.

[0102]

[0103] The following describes examples of manufacturing and experimental methods of the present invention. However, it is specified that these examples of manufacturing and experimental methods are intended to explain the composition and effects of the present invention more specifically, and that the scope of the present invention is not limited thereto.

[0104]

[0105] <SERS 기판 제조>

[0106] A three-dimensional SERS substrate was fabricated by forming ZnO nanowires vertically on a 4-inch Si wafer and growing Au nanoparticles on the ZnO nanowires using repetitive liquid phase deposition (LPD).

[0107] After coating a Si wafer with a ZnO seed solution containing 5 mM zinc acetate dihydrate dissolved in ethanol, the Si wafer and the ZnO seed solution were heat-treated on a hot plate at 350°C for 20 minutes to ensure the seed layer adhered securely to the Si wafer. Then, the Si wafer was immersed in a ZnO precursor solution and heated in a convection oven at 95°C for about 2.5 hours.

[0108] The ZnO precursor solution is a solution containing zinc nitrate hexahydrate at a concentration of 25 mM, hexamethylenetetramine (HMTA) at a concentration of 25 mM, and poly ether imide (PEI) at a concentration of 5 mM in ultrapure water (DI water).

[0109] ZnO nanowires were formed by repeating the above process twice to increase the thickness of the Au nanoparticle layer. Subsequently, a SERS substrate was fabricated by repeatedly depositing Au nanoparticles eight times using LPD. A Si wafer with multiple nanowires formed thereon was immersed in an Au nanoparticle precursor solution, and the Au nanoparticle precursor solution was heated in a convection oven at a temperature of 90°C for one hour. This liquid-phase deposition process was repeated eight times until multiple Au nanoparticles were densely packed to form metal nanoparticle clusters. During the deposition of Au, the ZnO melts and is automatically removed; most of the ZnO is removed after five or more repeated depositions, and the density of Au nanoparticles increases.

[0110]

[0111] <SERS 기판 특성 분석>

[0112] Figure 5 is an SEM image of a SERS substrate manufactured according to one embodiment of the present invention, and Figure 6 is the result of surface analysis using SEM-EDS (scanning electron microscopy-energy dispersive spectroscopy) of a SERS substrate manufactured according to one embodiment of the present invention. The composition of the SERS substrate was confirmed using SEM-EDS.

[0113] Through SEM images, the 3D stack structure of Au nanoparticle clusters deposited at high density can be confirmed, and the average diameter of the Au nanoparticles was measured to be 50 nm.

[0114] The composition of the fabricated SERS substrate was confirmed through SEM-EDS data. 7.50 at.% Si was identified as the base substrate, and 4.47 at.% Zn and 25.85 at.% O were identified as the ZnO nanowires. The Au nanoparticles deposited in a three-dimensional structure on the ZnO nanowires were identified as 62.18 at.% Au.

[0115] It was confirmed that the atomic ratio of Au to Zn was 62:4, and most of the ZnO nanowires were removed during the Au nanoparticle synthesis process, leaving only Au nanoparticle clusters.

[0116]

[0117] <SERS를 이용한 가스 측정을 위한 환경 조성>

[0118] The Au nanoparticle SERS substrate fabricated above was placed in a vapor chamber and supplied with vapors of various concentrations. Experiments were conducted using ethanol, methanol, toluene, and ethylbenzene vapors. A cooling device was placed in contact with the bottom surface of the SERS substrate and cooled to 20°C. The cooled SERS substrate came into contact with the vapor and liquefied.

[0119] In particular, as shown in Fig. 7, the upper part of the vapor chamber is configured with a crystalline quartz window to minimize interference with the Raman signal in the window, allowing the light source to irradiate the excitation light and the photodetector to detect the scattered light.

[0120]

[0121] <SERS을 이용한 가스 감지 결과>

[0122] Figure 8 is a graph showing the SERS intensity according to the concentration of gases (ethanol, methanol, toluene, ethylbenzene) measured according to a gas detection method using SERS according to one embodiment of the present invention.

[0123] As shown in FIG. 8, the lowest detection limit of the ethanol on a SERS substrate cooled to 20°C is 0.124 × 10⁻⁶6 It is ppm or less, and the lowest detection limit of the methanol is 0.215 × 10⁻⁶ 6 It was confirmed to be below ppm, and the lowest detection limit of the above toluene is 0.075 × 10⁻⁶ 6 It is less than ppm, and the lowest detection limit of the above ethylbenzene is 0.066 × 10⁻⁶ 6 It was confirmed to be below ppm.

[0124] Through Raman spectroscopic analysis, fingerprint peaks of ethanol, methanol, toluene, and ethylbenzene vapors were identified, and it was confirmed that the peak intensity increased as the vapor concentration increased.

[0125] Figure 9 is a graph showing peak-specific SERS intensity according to the concentration of gases (ethanol, methanol, toluene, ethylbenzene) measured according to a gas detection method using SERS according to one embodiment of the present invention. In addition, Table 1 shows the peak-specific SERS intensity results according to the concentration (ppm) of ethanol, Table 2 shows the concentration of methanol, Table 3 shows the concentration of toluene, and Table 4 shows the concentration of ethylbenzene.

[0126] Ethanol 0.124 × 10⁻⁶ 6 0.206 × 10 6 0.313 × 10 6 0.498 × 10 6 878 cm -1 61338.221069.542279.33

[0127]

[0128] Methanol 0.215 × 10⁻⁶ 6 0.268 × 10 6 0.555 × 10 6 0.822 × 10 6 1027 cm -1 105.54299.97838.281322.69

[0129]

[0130] Toluene 0.075 × 10⁻⁶ 6 0.176 × 10 6 0.367 × 10 6 0.719 × 106 785 cm -1 455.75649.644015.7213685.771000 cm -1 4691708.099039.7223425.171027 cm -1 123.95424.052374.426074.271207 cm -1 94.84298.901597.424126.971603 cm -1 59.20156.31622.721723.17

[0131]

[0132] Ethylbenzene 0.066 × 10⁻⁶ 6 0.153 × 10 6 0.321 × 10 6 0.613 × 10 6 767 cm -1 138.51570.991870.444122.801001 cm -1 401.192323.607674.7316100.361028 cm -1 192.24528.981846.214118.42

[0133] FIG. 10 is a graph of the relationship between the representative SERS intensity for each peak and the gas (ethanol, methanol, toluene, ethylbenzene) concentration measured according to the gas detection method using SERS according to one embodiment of the present invention. The relationship between Raman intensity and concentration is exponential.

[0134] The result was corrected to minimize the square of the deviation of the logarithmic function by considering the deviations of low and high concentrations, and the relationship between the concentrations of ethanol, methanol, toluene, and ethylbenzene gases and the intensity of representative Raman peak points can be obtained as follows.

[0135] The concentration of the above ethanol and the SERS intensity satisfy the following relationship 1.

[0136] [Relationship 1]

[0137]

[0138] (In the above relationship 1, I SERS Is Representative Raman peak point of ethanol (878 cm⁻¹) -1 ) is the strength, and C is the ethanol concentration.)

[0139] The above methanol concentration and SERS intensity satisfy the following relationship Equation 2.

[0140] [Relationship 2]

[0141]

[0142] (In the above relationship 2, I SERS Is Representative Raman peak of methanol (1027 cm⁻¹) -1 ) is the intensity, and C is the methanol concentration.)

[0143] The above concentration of toluene and SERS intensity satisfy the following relationship Equation 3.

[0144] [Relationship 3]

[0145]

[0146] (In the above relationship 3, I SERS Is Toluene's representative Raman peak (785 cm) -1 ) is the intensity, and C is the toluene concentration.)

[0147] The concentration of ethylbenzene and SERS intensity above satisfy the relationship 4 below.

[0148] [Relationship 4]

[0149]

[0150] (In the above relationship 4, I SERS Is Representative Raman peak point of ethylbenzene (767 cm⁻¹) -1 ) is the intensity, and C is the ethylbenzene concentration.)

[0151] As described above, through Raman spectroscopic analysis, it was confirmed that the relationship between Raman intensity and the vapor concentrations of ethanol, methanol, toluene, and ethylbenzene is exponential. Subsequently, the above process can be repeated over various temperature ranges and the data can be saved.

[0152] The gas detection device using surface-enhanced Raman spectroscopy according to the present invention can effectively and accurately identify the type of gas based on variations in Raman peak points across different gas types, temperature ranges, and concentration ranges, and can quantitatively detect the gas concentration.

[0153] Furthermore, gas detection sensitivity can be improved by cooling the substrate to condense the analysis gas onto it. In particular, even when controlling the cooling temperature, it is possible to accurately identify various vapors and precisely analyze gas concentrations by utilizing Raman peak point data across various temperature ranges.

[0154] The gas detection method using surface-enhanced Raman spectroscopy according to the present invention manufactures a SERS substrate by repeatedly depositing metal nanoparticles to optimize the size of the metal nanoparticles, and improves gas detection sensitivity by cooling the manufactured substrate to condense the analysis gas, thereby enabling effective detection and identification of various organic solvent vapors.

Claims

In a gas detection method using surface enhanced Raman spectroscopy (SERS), (a) A step of forming a plurality of nanowires vertically on a base substrate; (b) a step of manufacturing a three-dimensional SERS substrate by depositing metal nanoparticles on the nanowires; (c) a step of cooling the manufactured SERS substrate to condense the gas to be analyzed onto the SERS substrate; (d) a step of irradiating the condensed gas particles to be analyzed with excitation light and detecting light scattered from the gas particles to be analyzed; and (e) A gas detection method using surface-enhanced Raman spectroscopy characterized by including the step of analyzing the detected light to detect the gas to be analyzed. In paragraph 1, The step of detecting the gas to be analyzed (e) above is, A step of analyzing the detected light to determine the type of gas to be analyzed by the position of the Raman peak point of the surface-enhanced Raman scattering spectrum; and A gas detection method using surface-enhanced Raman spectroscopy characterized by including a step of calculating the concentration of the gas to be analyzed based on the relationship between the intensity of a previously stored Raman peak point and the concentration of the gas to be analyzed. In paragraph 2, The step of detecting the gas to be analyzed (e) above is, A gas detection method using surface-enhanced Raman spectroscopy, characterized by further including a step of correcting the concentration of the gas to be analyzed according to the temperature of the SERS substrate. In paragraph 1, A gas sensing method using surface-enhanced Raman spectroscopy, characterized in that step (b) above involves forming a three-dimensional SERS substrate by repeatedly depositing at least one metal nanoparticle selected from Au, Ag, Cu, and Al 5 to 10 times using liquid phase deposition (LPD). In paragraph 4, A gas detection method using surface-enhanced Raman spectroscopy characterized by the average diameter of the metal nanoparticles being 40 to 60 nm. In paragraph 1, The above step (c) is a gas detection method using surface-enhanced Raman spectroscopy characterized by cooling the SERS substrate to a temperature below room temperature. In paragraph 1, A gas detection method using surface-enhanced Raman spectroscopy, characterized in that the gas to be analyzed comprises at least one of ethanol, methanol, toluene, and ethylbenzene. In Paragraph 7, The lowest detection limit of the above ethanol is 0.124 × 10⁻⁶ 6 A gas detection method using surface-enhanced Raman spectroscopy characterized by being less than ppm. In Paragraph 7, The lowest detection limit of the above methanol is 0.215 × 10⁻⁶ 6 A gas detection method using surface-enhanced Raman spectroscopy characterized by being less than ppm. In Paragraph 7, The lowest detection limit of the above toluene is 0.075 × 10⁻⁶ 6 A gas detection method using surface-enhanced Raman spectroscopy characterized by being less than ppm. In Paragraph 7, The lowest detection limit of the above ethylbenzene is 0.066 × 10⁻⁶ 6 A gas detection method using surface-enhanced Raman spectroscopy characterized by being less than ppm. In a gas detection device using surface enhanced Raman spectroscopy (SERS), A SERS substrate comprising a plurality of nanowires formed vertically on a base substrate and metal nanoparticles with a three-dimensional structure deposited on the nanowires; A cooling unit that cools the above SERS substrate to a set temperature to condense the gas to be analyzed onto the above SERS substrate; A light source that irradiates excitation light onto the condensed gas particles to be analyzed; A photodetector for detecting light scattered from the above-mentioned gas particles to be analyzed; and A gas detection device using surface-enhanced Raman spectroscopy, characterized by including a data analysis unit that analyzes the detected light to detect the gas to be analyzed. In Paragraph 12, The above data analysis unit analyzes the detected light to identify the type of gas to be analyzed using the Raman peak of the surface-enhanced Raman scattering spectrum, and A gas detection device using surface-enhanced Raman spectroscopy characterized by calculating the concentration of the gas to be analyzed based on the relationship between the intensity of a pre-stored Raman peak point and the concentration of the gas to be analyzed. In Paragraph 13, A gas detection device using surface-enhanced Raman spectroscopy, characterized in that the data analysis unit corrects the concentration of the gas to be analyzed based on the relationship between the temperature of the SERS substrate and the concentration of the gas to be analyzed. In Paragraph 12, A gas detection device using surface-enhanced Raman spectroscopy, characterized in that the metal nanoparticles are at least one nanoparticle selected from Au, Ag, Cu, and Al, with an average diameter of 40 to 60 nm.

Images