A humidity interference resistant MOF photonic crystal trace gas sensing chip, a preparation method thereof, a detection device and a detection method

Abstract

The present application relates to a kind of anti-humidity interference MOFs photonic crystal trace gas sensing chip and preparation method, detection device and detection method, MOFs photonic crystal trace gas sensing chip includes bottom substrate layer, photonic crystal structure layer and anti-humidity interference function layer, photonic crystal structure layer is coated on the upper surface of bottom substrate layer, anti-humidity interference function layer is constructed on the top surface of photonic crystal structure layer or doped in the inside of photonic crystal structure layer.The trace gas sensing chip of the present application combines the optical properties of photonic crystal with the high-efficiency adsorption performance of MOFs material, can realize the stable, sensitive optical signal output of target gas in humidity environment, significantly improve the sensitivity in humidity environment, effectively reduce the influence of water molecule adsorption on the effective refractive index of photonic crystal, enhance the structural stability of MOFs material in humidity environment, maintain the rapid response characteristic.MOFs photonic crystal trace gas sensing chip preparation method process is simple and easy to integrate.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of optical sensing technology and nanomaterials science, specifically relating to a humidity-resistant MOFs photonic crystal trace gas sensing chip, its preparation method, detection device, and detection method. Background Technology

[0002] Trace gas detection has important application value in industrial process control, coal mine safety early warning, power equipment fault diagnosis and early non-invasive screening of diseases. However, the trace gas detection environment often has high requirements for the sensitivity, selectivity and stability of the sensor due to the uncertain changes in atmospheric humidity.

[0003] Existing trace gas detection devices mainly include gas chromatography-mass spectrometry (GC-MS), electrical sensors, and optical sensors. While GC-MS offers high sensitivity and accuracy, it is expensive, bulky, and complex to operate, making it difficult to meet the needs of on-site online monitoring. Although electrical sensors can be miniaturized, they require high-temperature operation and their baselines are susceptible to electrical, magnetic, and humidity interference. Therefore, developing novel room-temperature operating, high-sensitivity, and humidity-resistant trace gas sensing technologies has become a research hotspot. Photonic crystal sensors, due to their unique optical modulation capabilities and signal amplification effects, exhibit significant advantages in the field of trace gas monitoring. Photonic crystals possess photonic bandgap characteristics; when gas molecules enter the interior of a photonic crystal, they cause a local refractive index change, leading to a shift in the Bragg reflection peak or transmission peak, thereby enabling quantitative detection of gas concentration.

[0004] Metal-organic frameworks (MOFs) are a class of crystalline porous materials formed by coordination bonds between metal nodes and organic ligands. They possess unique advantages such as high specific surface area, permanent porosity, tunable pore size, and modifiable ligands. When MOFs selectively adsorb target gas molecules, their dielectric constant changes, potentially accompanied by lattice expansion or contraction, thereby amplifying the optical response signal of the photonic crystal. However, in practical applications of trace gas detection, humidity interference with sensor signals is a key bottleneck limiting the performance of MOF photonic crystal sensors, primarily due to the competitive adsorption of water molecules. Water molecules, as polar small molecules, have a smaller kinetic diameter than most gas molecules and strong diffusion capabilities. The porous structure of MOFs exhibits a natural affinity for water molecules, especially in environments with relative humidity above 30%, where water molecules preferentially occupy active adsorption sites within the MOF pores, strongly competing with trace target gases for adsorption. When the target gas concentration is in the ppb-ppm range, its molecular number is much lower than that of water molecules, resulting in severe compression of the adsorption amount of the target gas. The sensor response signal is overwhelmed by background humidity, leading to a significant decrease in detection sensitivity. Furthermore, water molecule adsorption also causes optical signal interference. When water molecules adsorb onto the channels of MOFs, they significantly alter the effective refractive index of the composite material, causing a redshift in the Bragg reflection peak of the photonic crystal. This change in optical signal caused by humidity fluctuations is difficult to distinguish effectively when superimposed with the characteristic signal generated by the adsorption of the target gas, resulting in severe cross-sensitivity.

[0005] To address the aforementioned issue of humidity interference with sensor signals, researchers both domestically and internationally have explored various approaches: Regarding gas-sensitive materials, researchers have attempted to introduce hydrophobic groups through post-synthesis modification or by doping MOFs with hydrophobic components during synthesis to reduce the affinity of water molecules; structurally, researchers have designed core-shell structures or hydrophobic film coating structures to construct physical barriers on the MOF surface, delaying water molecule diffusion; at the system level, some works have constructed sensor arrays and combined them with machine learning algorithms to correct and compensate for humidity interference. However, these explorations still suffer from the following technical limitations: introducing hydrophobic groups may alter the internal pore size, affecting the adsorption of target gases; hydrophobic coating structures may affect light signal propagation, reducing response time; arrays composed of multiple sensing units increase system complexity and cost, and correction accuracy depends on the completeness of the modeling data. Therefore, there is an urgent need to improve existing MOF photonic crystal sensors. Summary of the Invention

[0006] To address the technical challenges of reduced sensitivity and selectivity in trace gas detection caused by competitive adsorption of water molecules, optical signal interference, and decreased structural stability of MOFs in humid environments, existing MOFs photonic crystal sensors require a novel MOFs photonic crystal sensor chip that can operate stably in humid environments, possesses high sensitivity and selectivity for trace target gases, and exhibits a fast response speed. Therefore, this invention proposes a humidity-resistant MOFs photonic crystal trace gas sensor chip. The resulting MOFs photonic crystal trace gas sensor chip technology, developed through collaborative innovation in material selection, structural design, and interface control, enables reliable and accurate detection of trace gases in humid environments and is also of significant importance to the development of optical gas sensing technology.

[0007] The present invention provides a humidity-resistant MOFs photonic crystal trace gas sensing chip, comprising a bottom substrate layer, a photonic crystal structure layer and a humidity-resistant functional layer. The photonic crystal structure layer is coated on the upper surface of the bottom substrate layer, and the humidity-resistant functional layer is constructed on the top surface of the photonic crystal structure layer or doped inside the photonic crystal structure layer.

[0008] The photonic crystal structure layer is a micro / nano structure array layer. The micro / nano structure array layer refers to a functional thin layer composed of micron to nano-scale structural units arranged periodically or quasi-periodically on or inside the material surface. This type of structure can achieve the regulation of physical behaviors such as light, electricity, heat, fluid, and mechanics by precisely controlling the geometry, size, arrangement and material composition. It is widely used in optics, energy, biomedicine, microelectronics and other fields.

[0009] The humidity-resistant interference functional layer (top cover layer) is used to suppress the interference of water molecules on the detection of target gas.

[0010] Furthermore, the photonic crystal structure layer is composed of any one or any combination of one-dimensional photonic crystals, two-dimensional photonic crystals, and three-dimensional photonic crystals.

[0011] Furthermore, the one-dimensional photonic crystal is formed by alternating stacking of high-refractive-index and low-refractive-index dielectric layers.

[0012] Furthermore, both the two-dimensional photonic crystal and the three-dimensional photonic crystal are ordered macroporous materials composed of MOF gas-sensitive materials through layer-by-layer stacking self-assembly, gravity deposition self-assembly, and convection self-assembly, and the humidity interference resistance functional layer is constructed on the top surface of the MOF sensitive layer or doped inside the MOF framework to form a surface-type humidity interference resistance functional layer and a doped humidity interference resistance functional layer, respectively.

[0013] The MOFs gas-sensitive materials are porous materials with large specific surface areas and specific adsorption of trace target gases, including the UiO-series, ZIF-series and MIL-series.

[0014] Furthermore, the surface-type humidity-resistant functional layer is composed of any one or any combination of the following: an in-situ grown hydrophobic material or grown on the surface of the photonic crystal structure layer using spin coating and LB method; the hydrophobic layer material is MOFs or porous polymers including hydrogen-bonded organic frameworks; the hydrophobic layer is a hydrophobic polymer film layer or a humidity-responsive hydrogel layer; the hydrophobic polymer is any one or any combination of polytetrafluoroethylene, polydimethylsiloxane, and polyvinylidene fluoride, with a thickness of 1-150 nm; the hydrogel undergoes reversible volume swelling or contraction when humidity changes, which is used to regulate the open state of the MOFs pores and realize the gating effect of water molecule diffusion.

[0015] Furthermore, the doped humidity-resistant functional layer is constructed using any one or a combination of the following: (1) Hydrophobic functional group modification: The hydrophobic functional group includes alkyl chain, fluoroalkyl or phenyl, which are covalently bonded to the organic ligand and metal ion node of the MOF gas-sensitive material; (2) MOF core and shell: The MOFs are any one or any combination of UiO-66, UiO-66-NH2, MIL-101, MOF-801, ZIF-8 and ZIF-67, with a pore size of 0.1-4 nm and a specific surface area of ​​500-1500 m². 2 / g, which is coated onto the core surface of hydrophilic MOFs and forms a core-shell structure through in-situ growth or epitaxial growth.

[0016] Furthermore, the stacking period number of the one-dimensional photonic crystal is 1-5, the high refractive index dielectric layer adopts any one or any combination of TiO2, ZnO, SiO2, SnO2 and their modified derivatives, with a refractive index of 0.5-10; the low refractive index dielectric layer adopts any one or any combination of MOFs, SiO2, and polymers, with a refractive index of 0.05-5.

[0017] Furthermore, the two-dimensional photonic crystal is prepared using MOFs materials via the LB method, and the three-dimensional photonic crystal is a three-dimensional photonic crystal superstructure prepared by a template-free method of solvent evaporation self-assembly and / or convection self-assembly, or a three-dimensional opal and anti-opal structure photonic crystal assembled using a template method. The template is any one or any combination of SiO2, PMMA, and ZrO2.

[0018] The LB method (Langmuir-Blodgett method) is a technique for precisely controlling the assembly of organically ordered ultrathin films at the molecular level, and it is widely used in fields such as biomedicine, materials science, electronic devices, and sensing.

[0019] Furthermore, the bottom substrate layer is made of silicon substrate or quartz glass.

[0020] To address the aforementioned problems in the prior art, the present invention also provides a method for fabricating a humidity-resistant MOFs photonic crystal trace gas sensing chip. The method, used to fabricate any of the preferred humidity-resistant MOFs photonic crystal trace gas sensing chips, includes the following steps: S1: A photonic crystal structure layer is formed by assembling MOF nanoparticles on the bottom substrate layer. The MOF nanoparticles are assembled by any one or any combination of solvent evaporation self-assembly, gravity deposition self-assembly, and convection self-assembly. S2: A humidity-resistant functional layer was constructed on the surface of the MOFs photonic crystal structure layer using chemical vapor deposition, epitaxial growth, in-situ growth, and LB method. S3: Vacuum drying or activation treatment is performed on the composite structure to remove residual solvent molecules in the channels, thereby obtaining the sensor chip.

[0021] Further, S2 includes the following steps: applying the prepared hydrophobic material precursor solution to the bottom substrate layer on which the MOFs photonic crystal structure layer has been constructed by any one or any combination of dipping, spraying or sequential deposition; forming a monolayer hydrophobic coating on the surface of the photonic crystal chip with the MOFs photonic crystal structure layer by chemical vapor deposition, epitaxial growth process, in-situ growth method and LB method; wherein the hydrophobic precursor solution includes a hydrophobic hydrogen-bonded organic framework and octadecyltrichlorosilane.

[0022] Hydrophobic hydrogen-bonded organic frameworks (HOFs) are a class of porous crystalline materials formed by the self-assembly of hydrophobic organic molecules through hydrogen bonding interactions. They are characterized by low polarity on the surface of the framework or pores, thus exhibiting structural stability and selective adsorption capacity in aqueous or polar environments.

[0023] To enable the detection of the humidity-resistant MOFs photonic crystal trace gas sensing chip, this invention provides a detection device for the humidity-resistant MOFs photonic crystal trace gas sensing chip. The device is used to detect the humidity-resistant MOFs photonic crystal trace gas sensing chip as described in any of the preferred embodiments above. It includes a gas pump, a gas solvent heating stage, a gas solvent vapor flow meter, a water heating stage, a water vapor flow meter, a gas chamber, a humidity sensor, a light source, a spectrometer, and a detector. The gas chamber is a sealed chamber with a detection stage on its bottom surface. The detection stage is used to place the MOFs photonic crystal to be tested. The left and right sides of the gas chamber are... The system has dual air inlets and a single air outlet. A humidity sensor is installed on the inner wall of the left side of the air chamber. A detector is installed directly above the air chamber on the detection platform. The detector is connected to the light source and the spectrometer, respectively. The dual air inlets include a gaseous solvent vapor inlet and a water vapor inlet. The air pump is connected to the gaseous solvent heating platform and the water heating platform, respectively. The gaseous solvent heating platform is connected to the gaseous solvent vapor inlet, and the water heating platform is connected to the water vapor inlet. A gaseous solvent vapor flow meter is installed at the outlet of the gaseous solvent heating platform, and a water vapor flow meter is installed at the outlet of the water heating platform.

[0024] Furthermore, the spectrometer is a fiber optic spectrometer.

[0025] To enable the detection of the humidity-resistant MOFs photonic crystal trace gas sensing chip, this invention also provides a method for detecting the humidity-resistant MOFs photonic crystal trace gas sensing chip. This method is implemented using the preferred humidity-resistant MOFs photonic crystal trace gas sensing chip detection device described above, and includes the following steps: S11: The MOFs photonic crystal trace gas sensing chip is placed in a gas chamber containing the target gas. The gas to be measured is obtained by heating the corresponding liquid. The target gas of the required concentration is controlled by a flow meter to be input into the gas chamber for detection. S12: The detection principle uses Bragg's law of reflection. ; in, m It is an integer. λ It's the wavelength. d It is the interplanar spacing. θ It is the angle of incidence. n eff It is the effective refractive index. n eff It is calculated using the following formula: ; in, f This represents the volume fraction of nanoparticles. np The refractive index of the nanoparticles. n m The refractive index of the medium particles; therefore, the more gas molecules a photonic crystal absorbs, the better. n eff The greater the increase, the greater the redshift of the reflected wavelength; S13: A detector sends a detection signal, and a fiber optic spectrometer collects and monitors the displacement of the Bragg reflection peak of the photonic crystal in real time. The concentration of the target gas in the environment to be tested is calculated based on the pre-established quantitative relationship between the target gas concentration and the optical signal displacement.

[0026] Furthermore, the sensitivity S of the MOFs photonic crystal trace gas sensing chip is calculated based on the ratio of Bragg reflection peak shift to gas concentration.

[0027] The purpose of this invention, a humidity-resistant MOFs photonic crystal trace gas sensor chip detection device and method, is to detect toxic and harmful gases in the atmosphere. For example, in southern my country where humidity is high, this detection device and method can be used to detect toxic and harmful gases in humid atmospheric environments. The sensor chip's testing indicators include selectivity, sensitivity, response time, recovery time, stability, and reusability. Generally, several common atmospheric interfering substances are selected together to test and verify the sensor chip's selectivity. Stability is verified by observing whether the frame collapses, the structure is damaged, and the response baseline drifts significantly after high temperature and humidity. Reusability is generally verified by repeated exposure greater than 50 times. Detection results generally include ppm and ppb; the lower the detected concentration, the better. Detection using this device enables early detection and prevention. The detection results are output as data via a fiber optic spectrometer, which can be connected to a computer for real-time monitoring.

[0028] The MOFs photonic crystal trace gas sensing chip of this invention combines the optical properties of photonic crystals with the high-efficiency adsorption performance of MOFs materials. Through a rational structural design, it achieves stable and sensitive optical signal output for target gases under humid conditions. It is mainly used for the rapid detection of trace gases in complex systems, particularly in environmental monitoring, medical diagnostics, and industrial production. Compared with existing technologies, the advantages of this invention include: (1) Significantly improves sensitivity under humid conditions: This invention introduces an anti-humidity interference layer into the MOFs photonic crystal sensing chip, which effectively suppresses the competitive adsorption of water molecules on trace target gases. The anti-humidity interference layer can selectively block or delay the entry of water molecules into the MOFs channels, while allowing target gas molecules to pass freely, ensuring that the adsorption and enrichment capacity of the MOFs sensing layer for the target gas is not weakened.

[0029] (2) Effectively reduce the influence of water molecule adsorption on the effective refractive index of photonic crystals: This invention reduces the affinity of MOFs materials for water molecules by modifying them with hydrophobic functional groups or coating them with hydrophobic polymers, thereby reducing the impact of water molecule adsorption on the effective refractive index of photonic crystals.

[0030] (3) Enhance the structural stability of MOFs materials under humid conditions: The humidity-resistant layer in this MOFs photonic crystal trace gas sensor chip simultaneously acts as a protective barrier, reducing direct contact between water molecules and the MOFs framework and inhibiting framework collapse of the MOFs material in water / air environments. In production practice, humidity stability verification over 25-35 days revealed that the optical response signal (Brak reflection peak shift) of this MOFs photonic crystal trace gas sensor chip is within 2 nm, significantly superior to the unmodified chip, thus significantly extending the lifespan of the trace gas sensor.

[0031] (4) Maintain fast response characteristics: This invention optimizes the thickness and structure of the anti-humidity interference functional layer, such as by using monolayer modification or ultrathin polymer coating. This allows for the preservation of the porous characteristics and gas diffusion channels of MOFs materials to the maximum extent while achieving anti-humidity interference. As a result, the MOFs photonic crystal trace gas sensing chip can achieve a response time of less than 5 seconds for trace gases, meeting the requirements for real-time online detection.

[0032] (5) The preparation process is simple and easy to integrate: The fabrication process of this MOFs photonic crystal trace gas sensing chip is compatible with standard micro-nano fabrication processes. It can be mass-produced through methods such as spin coating, impregnation, and vapor deposition. The chip structure design is flexible, and matching MOFs materials, photonic crystal structures, and humidity interference-resistant layers can be selected according to different target gas detection requirements, thus exhibiting good versatility and scalability.

[0033] (6) Applicable to various trace gas detection scenarios: This MOFs photonic crystal trace gas sensing chip can operate at room temperature, without the need for high-temperature operation and with low power consumption. Its applications include online gas detection, ambient air quality monitoring, industrial process control, coal mine safety early warning, and human exhaled gas diagnosis. Attached Figure Description

[0034] Figure 1 This is an exploded view of the overall structure of a preferred embodiment of the humidity-resistant MOFs photonic crystal trace gas sensing chip of the present invention. Figure 2This is a schematic diagram of the overall structure of a preferred embodiment of the humidity-resistant MOFs photonic crystal trace gas sensing chip detection device of the present invention. Detailed Implementation

[0035] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

[0036] To address the aforementioned problems in the prior art, this invention provides a humidity-resistant MOFs photonic crystal trace gas sensing chip, such as... Figure 1 As shown, it includes a bottom substrate layer, a photonic crystal structure layer, and a humidity-resistant functional layer. The photonic crystal structure layer is coated on the upper surface of the bottom substrate layer, and the humidity-resistant functional layer is constructed on the top surface of the photonic crystal structure layer or doped inside the photonic crystal structure layer.

[0037] Optionally, the photonic crystal structure layer is composed of any one or any combination of one-dimensional photonic crystals, two-dimensional photonic crystals, and three-dimensional photonic crystals.

[0038] Optionally, the one-dimensional photonic crystal is formed by alternating stacking of high-refractive-index and low-refractive-index dielectric layers.

[0039] Optionally, both the two-dimensional photonic crystal and the three-dimensional photonic crystal are ordered macroporous materials composed of MOF gas-sensitive materials through layer-by-layer stacking self-assembly, gravity deposition self-assembly, and convection self-assembly. The humidity interference resistance functional layer is constructed on the top surface of the MOF sensitive layer or doped inside the MOF framework to form a surface-type humidity interference resistance functional layer and a doped humidity interference resistance functional layer, respectively.

[0040] Optionally, the surface-type humidity-resistant functional layer is composed of any one or any combination of the following: an in-situ grown hydrophobic material or grown on the surface of the photonic crystal structure layer using spin coating and LB method; the hydrophobic layer material is MOFs or porous polymers including hydrogen-bonded organic frameworks; the hydrophobic layer is a hydrophobic polymer film layer or a humidity-responsive hydrogel layer; the hydrophobic polymer is any one or any combination of polytetrafluoroethylene, polydimethylsiloxane, and polyvinylidene fluoride, with a thickness of 1-150 nm; the hydrogel undergoes reversible volume swelling or contraction when humidity changes, which is used to regulate the open state of the MOFs pores and realize the gating effect of water molecule diffusion.

[0041] Optionally, the doped humidity-resistant functional layer may be constructed using any one or a combination of the following: (1) Hydrophobic functional group modification: The hydrophobic functional group includes alkyl chain, fluoroalkyl or phenyl, which are covalently bonded to the organic ligand and metal ion node of the MOF gas-sensitive material; (2) MOF core and shell: The MOFs are any one or any combination of UiO-66, UiO-66-NH2, MIL-101, MOF-801, ZIF-8 and ZIF-67, with a pore size of 0.1-4 nm and a specific surface area of ​​500-1500 m². 2 / g, which is coated onto the core surface of hydrophilic MOFs and forms a core-shell structure through in-situ growth or epitaxial growth.

[0042] Optionally, the number of stacking periods of the one-dimensional photonic crystal is 1-5, the high refractive index dielectric layer is any one or any combination of TiO2, ZnO, SiO2, SnO2 and their modified derivatives, with a refractive index of 0.5-10; the low refractive index dielectric layer is any one or any combination of MOFs, SiO2, and polymers, with a refractive index of 0.05-5.

[0043] Optionally, the two-dimensional photonic crystal is prepared by MOFs material using the LB method, and the three-dimensional photonic crystal is a three-dimensional photonic crystal superstructure prepared by a template-free method of solvent evaporation self-assembly and / or convection self-assembly, or a three-dimensional opal and anti-opal structure photonic crystal assembled by a template method. The template is any one or any combination of SiO2, PMMA, and ZrO2.

[0044] Optionally, the bottom substrate layer is made of silicon substrate or quartz glass.

[0045] To address the aforementioned problems in the prior art, the present invention also provides a method for fabricating a humidity-resistant MOFs photonic crystal trace gas sensing chip. The method, used to fabricate any of the preferred humidity-resistant MOFs photonic crystal trace gas sensing chips, includes the following steps: S1: A photonic crystal structure layer is formed by assembling MOF nanoparticles on the bottom substrate layer. The MOF nanoparticles are assembled by any one or any combination of solvent evaporation self-assembly, gravity deposition self-assembly, and convection self-assembly. S2: A humidity-resistant functional layer was constructed on the surface of the MOFs photonic crystal structure layer using chemical vapor deposition, epitaxial growth, in-situ growth, and LB method. S3: Vacuum drying or activation treatment is performed on the composite structure to remove residual solvent molecules in the channels, thereby obtaining the sensor chip.

[0046] Optionally, S2 includes the following steps: applying the prepared hydrophobic material precursor solution to the bottom substrate layer on which the MOFs photonic crystal structure layer has been constructed by any one or any combination of immersion, spraying or sequential deposition; forming a monolayer hydrophobic coating on the surface of the photonic crystal chip with the MOFs photonic crystal structure layer by chemical vapor deposition, epitaxial growth process, in-situ growth method and LB method; wherein the hydrophobic precursor solution includes hydrophobic hydrogen-bonded organic framework (hydrophobic HOF) and octadecyltrichlorosilane.

[0047] To enable the detection of the humidity-resistant MOFs photonic crystal trace gas sensing chip, this invention provides a humidity-resistant MOFs photonic crystal trace gas sensing chip detection device, such as... Figure 2 As shown, the device is used to detect the trace gas sensing chip of the anti-humidity interference MOFs photonic crystal described in any of the above-mentioned preferred embodiments. It includes a gas pump, a gas solvent heating stage, a gas solvent vapor flow meter, a water heating stage, a water vapor flow meter, a gas chamber, a humidity sensor, a light source, a spectrometer, and a detector. The gas chamber is a sealed chamber with a detection stage on its bottom surface. The detection stage is used to place the MOFs photonic crystal to be tested. The gas chamber has dual air inlets and a single air outlet on its left and right sides, respectively. The humidity sensor is installed on the inner wall of the left side of the gas chamber. The detector is installed directly above the gas chamber on the detection stage. The detector is connected to the light source and the spectrometer, respectively. The dual air inlets include a gas solvent vapor inlet and a water vapor inlet. The gas pump is connected to the gas solvent heating stage and the water heating stage, respectively. The gas solvent heating stage is connected to the gas solvent vapor inlet, and the water heating stage is connected to the water vapor inlet. The gas solvent vapor flow meter is installed at the outlet of the gas solvent heating stage, and the water vapor flow meter is installed at the outlet of the water heating stage.

[0048] Optionally, the spectrometer is a fiber optic spectrometer.

[0049] To enable the detection of the humidity-resistant MOFs photonic crystal trace gas sensing chip, this invention also provides a method for detecting the humidity-resistant MOFs photonic crystal trace gas sensing chip. This method is implemented using the preferred humidity-resistant MOFs photonic crystal trace gas sensing chip detection device described above, and includes the following steps: S11: The MOFs photonic crystal trace gas sensing chip is placed in a gas chamber containing the target gas. The gas to be measured is obtained by heating the corresponding liquid. The target gas of the required concentration is controlled by a flow meter to be input into the gas chamber for detection. S12: The detection principle uses Bragg's law of reflection. ; in,m It is an integer. λ It's the wavelength. d It is the interplanar spacing. θ It is the angle of incidence. n eff It is the effective refractive index. n eff It is calculated using the following formula: ; in, f This represents the volume fraction of nanoparticles. n p The refractive index of the nanoparticles. n m The refractive index of the medium particles; therefore, the more gas molecules a photonic crystal absorbs, the better. n eff The greater the increase, the greater the redshift of the reflected wavelength; S13: A detector sends a detection signal, and a fiber optic spectrometer collects and monitors the displacement of the Bragg reflection peak of the photonic crystal in real time. The concentration of the target gas in the environment to be tested is calculated based on the pre-established quantitative relationship between the target gas concentration and the optical signal displacement.

[0050] Optionally, the sensitivity S of the MOFs photonic crystal trace gas sensing chip is calculated based on the ratio of Bragg reflection peak shift to gas concentration.

[0051] The purpose of this invention, a humidity-resistant MOFs photonic crystal trace gas sensor chip detection device and method, is to detect toxic and harmful gases in the atmosphere. For example, in southern my country where humidity is high, this detection device and method can be used to detect toxic and harmful gases in humid atmospheric environments. The sensor chip's testing indicators include selectivity, sensitivity, response time, recovery time, stability, and reusability. Generally, several common atmospheric interfering substances are selected together to test and verify the sensor chip's selectivity. Stability is verified by observing whether the frame collapses, the structure is damaged, and the response baseline drifts significantly after high temperature and humidity. Reusability is generally verified by repeated exposure greater than 50 times. Detection results generally include ppm and ppb; the lower the detected concentration, the better. Detection using this device enables early detection and prevention. The detection results are output as data via a fiber optic spectrometer, which can be connected to a computer for real-time monitoring.

[0052] This invention is applicable to various trace gas detection scenarios. This MOFs photonic crystal trace gas sensing chip combines the optical properties of photonic crystals with the high-efficiency adsorption performance of MOFs materials, enabling stable and sensitive optical signal output for target gases under humid conditions. It significantly improves sensitivity under humid conditions, effectively reduces the impact of water molecule adsorption on the effective refractive index of the photonic crystal, enhances the structural stability of MOFs materials under humid conditions, and maintains rapid response characteristics. The humidity-resistant MOFs photonic crystal trace gas sensing chip of this invention has a simple fabrication process and is easy to integrate.

Claims

1. A humidity-resistant MOFs photonic crystal trace gas sensing chip, characterized in that, It includes a bottom substrate layer, a photonic crystal structure layer, and a humidity-resistant functional layer. The photonic crystal structure layer is coated on the upper surface of the bottom substrate layer, and the humidity-resistant functional layer is constructed on the top surface of the photonic crystal structure layer or doped inside the photonic crystal structure layer.

2. The humidity-resistant MOFs photonic crystal trace gas sensing chip according to claim 1, characterized in that, The photonic crystal structure layer is composed of any one or any combination of one-dimensional photonic crystals, two-dimensional photonic crystals, and three-dimensional photonic crystals.

3. The humidity-resistant MOFs photonic crystal trace gas sensing chip according to claim 2, characterized in that, The one-dimensional photonic crystal is formed by alternating stacking of high-refractive-index and low-refractive-index dielectric layers.

4. The humidity-resistant MOFs photonic crystal trace gas sensing chip according to claim 2, characterized in that, Both the two-dimensional and three-dimensional photonic crystals are ordered macroporous materials composed of MOF gas-sensitive materials through layer-by-layer stacking self-assembly, gravity deposition self-assembly, and convection self-assembly. The humidity interference resistance functional layer is constructed on the top surface of the MOF sensitive layer or doped inside the MOF framework to form a surface-type humidity interference resistance functional layer and a doped-type humidity interference resistance functional layer, respectively.

5. The humidity-resistant MOFs photonic crystal trace gas sensing chip according to claim 4, characterized in that, The surface-type humidity-resistant functional layer is composed of any one or any combination of the following: an in-situ grown hydrophobic material or grown on the surface of the photonic crystal structure layer using spin coating and LB method; the hydrophobic layer material is MOFs or porous polymers including hydrogen-bonded organic frameworks; the hydrophobic layer is a hydrophobic polymer film layer or a humidity-responsive hydrogel layer; the hydrophobic polymer is any one or any combination of polytetrafluoroethylene, polydimethylsiloxane and polyvinylidene fluoride, with a thickness of 1-150 nm; the hydrogel undergoes reversible volume swelling or contraction when humidity changes, which is used to regulate the open state of the MOFs pores and realize the gating effect of water molecule diffusion.

6. The humidity-resistant MOFs photonic crystal trace gas sensing chip according to claim 4, characterized in that, The doped humidity-resistant functional layer is composed of any one or a combination of the following: (1) Hydrophobic functional group modification: The hydrophobic functional group includes alkyl chain, fluoroalkyl or phenyl, which are covalently bonded to the organic ligand and metal ion node of the MOF gas-sensitive material; (2) MOF core and shell: The MOFs are any one or any combination of UiO-66, UiO-66-NH2, MIL-101, MOF-801, ZIF-8 and ZIF-67, with a pore size of 0.1-4 nm and a specific surface area of ​​500-1500 m². 2 / g, which is coated onto the core surface of hydrophilic MOFs and forms a core-shell structure through in-situ growth or epitaxial growth.

7. The humidity-resistant MOFs photonic crystal trace gas sensing chip according to claim 3, characterized in that, The number of stacking periods of the one-dimensional photonic crystal is 1-5. The high refractive index dielectric layer is any one or any combination of TiO2, ZnO, SiO2, SnO2 and their modified derivatives, with a refractive index of 0.5-10. The low refractive index dielectric layer is any one or any combination of MOFs, SiO2 and polymers, with a refractive index of 0.05-5.

8. The humidity-resistant MOFs photonic crystal trace gas sensing chip according to claim 4, characterized in that, The two-dimensional photonic crystal is prepared using MOFs materials via the LB method. The three-dimensional photonic crystal is a three-dimensional photonic crystal superstructure prepared by a template-free method of solvent evaporation self-assembly and / or convection self-assembly, or a three-dimensional opal and anti-opal structure photonic crystal assembled by a template method. The template is any one or any combination of SiO2, PMMA, and ZrO2.

9. The humidity-resistant MOFs photonic crystal trace gas sensing chip according to claim 1, characterized in that, The bottom substrate layer is made of silicon substrate or quartz glass.

10. A method for fabricating a humidity-resistant MOFs photonic crystal trace gas sensing chip, the method being used to fabricate the humidity-resistant MOFs photonic crystal trace gas sensing chip according to claims 1-9, characterized in that, Includes the following steps: S1: A photonic crystal structure layer is formed by assembling MOF nanoparticles on the bottom substrate layer. The MOF nanoparticles are assembled by any one or any combination of solvent evaporation self-assembly, gravity deposition self-assembly, and convection self-assembly. S2: A humidity-resistant functional layer was constructed on the surface of the MOFs photonic crystal structure layer using chemical vapor deposition, epitaxial growth, in-situ growth, and LB method. S3: Vacuum drying or activation treatment is performed on the composite structure to remove residual solvent molecules in the channels, thereby obtaining the sensor chip.

11. The method for fabricating a humidity-resistant MOFs photonic crystal trace gas sensing chip according to claim 10, characterized in that, S2 includes the following steps: applying the prepared hydrophobic material precursor solution to the bottom substrate layer on which the MOFs photonic crystal structure layer has been constructed by any one or any combination of immersion, spraying or sequential deposition; forming a monolayer hydrophobic coating on the surface of the photonic crystal chip with the MOFs photonic crystal structure layer by chemical vapor deposition, epitaxial growth process, in-situ growth method and LB method; wherein the hydrophobic precursor solution includes a hydrophobic hydrogen bonded organic framework and octadecyltrichlorosilane.

12. A detection device for a humidity-resistant MOFs photonic crystal trace gas sensing chip, the device being used to detect the humidity-resistant MOFs photonic crystal trace gas sensing chip according to any one of claims 1-9, characterized in that, The device includes an air pump, a gas solvent heating stage, a gas solvent vapor flow meter, a water heating stage, a water vapor flow meter, a gas chamber, a humidity sensor, a light source, a spectrometer, and a detector. The gas chamber is a sealed chamber with a detection stage on its bottom surface. The detection stage is used to place the MOF photonic crystal to be tested. The gas chamber has a double air inlet and a single air outlet on its left and right sides, respectively. The humidity sensor is installed on the inner wall of the left side of the gas chamber. The detector is installed directly above the gas chamber on the detection stage. The detector is connected to the light source and the spectrometer, respectively. The double air inlets include a gas solvent vapor inlet and a water vapor inlet. The air pump is connected to the gas solvent heating stage and the water heating stage, respectively. The gas solvent heating stage is connected to the gas solvent vapor inlet, and the water heating stage is connected to the water vapor inlet. The gas solvent vapor flow meter is installed at the outlet of the gas solvent heating stage, and the water vapor flow meter is installed at the outlet of the water heating stage.

13. A method for detecting trace gases using a humidity-resistant MOFs photonic crystal sensor chip, characterized in that, The detection method is implemented using the humidity-resistant MOFs photonic crystal trace gas sensing chip detection device as described in claim 12, characterized by comprising the following steps: S11: The MOFs photonic crystal trace gas sensing chip is placed in a gas chamber containing the target gas. The gas to be measured is obtained by heating the corresponding liquid. The target gas of the required concentration is controlled by a flow meter to be input into the gas chamber for detection. S12: The detection principle uses Bragg's law of reflection. ; in, m It is an integer. λ It's the wavelength. d It is the interplanar spacing. θ It is the angle of incidence. n eff It is the effective refractive index. n eff It is calculated using the following formula: ; in, f This represents the volume fraction of nanoparticles. n p The refractive index of the nanoparticles. n m The refractive index of the medium particles; therefore, the more gas molecules a photonic crystal absorbs, the better. n eff The greater the increase, the greater the redshift of the reflected wavelength; S13: A detector sends a detection signal, and a fiber optic spectrometer collects and monitors the displacement of the Bragg reflection peak of the photonic crystal in real time. The concentration of the target gas in the environment to be tested is calculated based on the pre-established quantitative relationship between the target gas concentration and the optical signal displacement.

14. The method for detecting trace gas using a humidity-resistant MOFs photonic crystal sensor chip according to claim 13, characterized in that, The sensitivity S of the MOFs photonic crystal trace gas sensing chip is calculated based on the ratio of Bragg reflection peak shift to gas concentration.

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