Molecular sensors and molecular detection devices

Abstract

To suppress deterioration of a molecular sensor.SOLUTION: A molecular sensor includes a substrate and a sensitive membrane provided above the substrate and containing a metallic organic structure and a hydrophobic polymer having a larger contact angle with water than that with the metallic organic structure. In the sensitive membrane, the metallic organic structure exists on the substrate side and the hydrophobic polymer exists on the metallic organic structure.SELECTED DRAWING: Figure 4B

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the present invention relate to molecular sensors and molecular detection devices. [Background technology]

[0002] Sensing technology using odor (gas) sensors can quantify odors in the air. This technology is widely used for odor determination, measuring volatile organic compounds (VOCs) in the air, checking the performance of air purifiers, and detecting equipment problems. In recent years, there has been growing interest in applications such as detecting explosives, narcotics, and stimulants, which previously relied on dogs' sense of smell, as well as diagnosing certain diseases using breath samples. Therefore, there is a demand for higher performance odor (gas) sensors.

[0003] Conventional gas sensing methods include devices such as flame ionization detectors (FIDs), photoionization detectors (PIDs), and non-dispersive infrared gas analyzers (NDIRs). These devices are required to be more portable, less susceptible to the danger of using flammable gases, the lifespan and cost of the light source used for measurement, and to improve substance recognition. Furthermore, development is underway to develop compact sensors that are advantageous for incorporation into processing equipment and for measurements at work sites.

[0004] Semiconductor gas sensors, which are small sensors, measure gas concentrations by utilizing changes in electrical properties such as electrical resistance that occur when oxygen adsorbed on a metal oxide is consumed by a reducing substance. In recent years, many types of metal oxides have come into use, including tin oxide (SnO2), zinc oxide (ZnO2), indium oxide (In2O3), tungsten oxide (WO3), and vanadium oxide (V2O3). Studies have also been conducted to improve sensitivity and selectivity by doping these with palladium (Pd), platinum (Pt), gold (Au), silver (Ag), etc. However, sensitivity and selectivity are still not sufficient. Meanwhile, from the perspective of further improving the sensitivity, selectivity, simplicity, speed, reliability, stability, etc. of odor (gas) sensors, mass-detection sensors using quartz crystal microbalances (QCMs), surface acoustic waves (SAWs), microcantilevers (MCLs), etc. have also been attracting attention in recent years. For example, in the case of QCMs, sensors are known in which a sensitive film that adsorbs target molecules, such as organic polymers, is formed on the device surface.

[0005] When a target molecule is adsorbed onto the sensitive membrane, the mass of the membrane increases, causing a change in the resonant frequency of the quartz crystal oscillator. The amount of frequency change is proportional to the mass of the adsorbed sample molecule, so the concentration of the sample molecule can be measured. Metal organic frameworks, or MOF, are new porous materials that have been actively researched in recent years. These materials consist of metal ions and organic ligands that connect them, and are structures with many nanometer-sized pores. They can be used for up to 10,000m 2 It is characterized by a large specific surface area of ​​up to 1 / g and a heat resistance temperature exceeding 300°C, and is expected to be applied in a variety of fields such as gas storage, separation, purification, catalysts, batteries, and sensors. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-124700 A [Patent Document 2] Patent No. 5404534 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-313105 [Non-patent literature]

[0007] [Non-Patent Document 1] Suttipong Wannapaiboon et al, J. Mater. Chem. A, 2015,3, 23385-23394 [Non-patent document 2] Lars Heinke et al, Nature Communications volume 5, Article number: 4562 (2014) [Non-patent document 3] Erika Virmani et al, J.Am.Chem.Soc.2018,140,4812-4819 Summary of the Invention [Problem to be solved by the invention]

[0008] The problem to be solved by the present invention is to suppress the deterioration of a molecular sensor. [Means for solving the problem]

[0009] A molecular sensor according to an embodiment includes a substrate and a sensitive film provided above the substrate, the sensitive film containing a metal-organic framework and a hydrophobic polymer having a larger contact angle with water than the metal-organic framework. The sensitive film has the metal-organic framework on the substrate side and the hydrophobic polymer on the metal-organic framework. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a molecular detection device. [Figure 2A] FIG. 1 is a schematic diagram illustrating an example of a molecular sensor. [Figure 2B] FIG. 1 is a schematic diagram illustrating an example of a molecular sensor. [Figure 2C] FIG. 1 is a schematic diagram illustrating an example of a molecular sensor. [Figure 3] FIG. 1 is a schematic diagram showing an example of an MOF having a structure in which dicarboxylic acid is coordinated to a Zr6O4(OH)4 cluster. [Figure 4A] 2 is a schematic cross-sectional view for explaining an example of the structure of an example of the sensitive film 3. FIG. [Figure 4B] 4B is an enlarged schematic view of a part of the sensitive film 3 shown in FIG. 4A. FIG. [Figure 5A] FIG. 10 is a schematic diagram showing another example of a molecular sensor. [Figure 5B] FIG. 10 is a schematic diagram showing another example of a molecular sensor. [Figure 6] FIG. 1 is a diagram showing an example of a cross-sectional STEM image. [Figure 7] FIG. 1 is a diagram showing an example of an elemental mapping image of Zr. [Figure 8] FIG. 1 is a diagram showing an example of an elemental mapping image of Si. [Figure 9] 9 is an enlarged image of a portion of the elemental mapping image of Si shown in FIG. 8. [Figure 10] FIG. 10 is a diagram showing the measurement results of the ratio Si / Zr. [Figure 11] FIG. 1 is a diagram showing an example of a cross-sectional STEM image. [Figure 12] FIG. 1 is a diagram showing an example of a cross-sectional STEM image. [Figure 13] FIG. 1 is a diagram showing an example of a cross-sectional STEM image. [Figure 14] FIG. 1 is a diagram showing an example of an elemental mapping image of Zr. [Figure 15] FIG. 1 is a diagram showing an example of an elemental mapping image of Si. [Figure 16] FIG. 10 is a diagram showing an example of a composite mapping image of Zr and Si. [Figure 17] FIG. 1 is a diagram showing an example of a cross-sectional STEM image. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments will be described with reference to the drawings. In each embodiment, substantially identical components are denoted by the same reference numerals, and some of the description thereof may be omitted. The drawings are schematic, and the relationship between the thickness of each component and the planar dimensions, the thickness ratio of each component, etc. may differ from the actual ones.

[0012] Fig. 1 is a block diagram showing an example of the configuration of a molecular detection device according to an embodiment. The molecular detection device shown in Fig. 1 is a device that detects target molecules (detection targets) 11 in a fluid 1 generated from, for example, a gas source, and includes a filter device 12, a molecule distributor 13, a collector 14, a detector 15, an analyzer 16, and a controller 17.

[0013] The collection unit 14 collects a fluid 1 containing target molecules 11. The fluid 1 is in a liquid or gaseous state. The collection unit 14 has a collection port for the fluid 1 and is connected to a pump via a flow path. The collection unit 14 may also be equipped with a filter that removes impurities such as fine particles contained in the fluid 1. Note that a valve may be provided instead of a pump, and the start and stop of the introduction of the fluid 1 may be controlled by opening and closing the valve.

[0014] The fluid 1 may contain, as impurities, substances having a molecular weight or a molecular structure similar to that of the target molecule 11. Furthermore, the target molecule 11 floating in the air is often present in a state mixed with various impurities such as odor components and fine particles. For this reason, it is preferable that the fluid 1 be pre-treated in advance using a filter device 12, a molecular distributor 13, or the like before being sent to the collection unit 14.

[0015] A typical medium- to high-performance filter or the like is used for the filter device 12. Particulate matter such as fine particles contained in the fluid 1 is removed in the filter device 12. The fluid 1 from which the particulate matter has been removed by the filter device 12 is sent to the molecular distributor 13. An example of the molecular distributor 13 is a device that ionizes the fluid 1 to form an ionized substance group, applies a voltage to the ionized substance group to make it fly at a speed proportional to its mass, and separates the ionized substance of the target molecule 11 from the ionized substance group using the flight speed due to this mass difference and the flight time based thereon. Such a molecular distributor is equipped with an ionization unit, a voltage application unit, and a time-of-flight separation unit. Note that the filter device 12 and the molecular distributor 13 are not necessarily required.

[0016] The fluid 1 is collected in the collection unit 14 either directly or after pre-treatment using a filter device 12, a molecular distributor 13, or the like. The fluid 1 collected in the collection unit 14 is sent to the detection unit 15 via a flow path.

[0017] The detection unit 15 is disposed in the flow channel. The detection unit 15 has a molecular sensor for detecting the target molecule 11. The detection unit 15 outputs an electrical signal based on the detected target molecule 11 to the analysis unit 16.

[0018] The analysis unit 16 has a signal processing unit that processes the electrical signal from the detection unit 15 and identifies the target molecule 11. The analysis unit 16 identifies the target molecule 11, for example, by comparing the change in the electrical signal before and after the introduction of the fluid 1 with pre-stored data on the change in the electrical signal of the corresponding molecule.

[0019] The control unit 17 is electrically connected to each of the collection unit 14, the detection unit 15, and the analysis unit 16, and outputs a control signal to each of them. For example, the control unit 17 controls the start and stop of the introduction of the fluid 1 into the detection unit 15 using the control signal. The control unit 17 may also control the identification of the target molecule 11 by the analysis unit 16 using the control signal.

[0020] The analysis unit 16 and the control unit 17 may be configured using hardware that uses, for example, a processor, etc. Each operation may be stored as an operation program in a computer-readable recording medium such as a memory, and each operation may be executed by the hardware by appropriately reading out the operation program stored in the recording medium.

[0021] Next, an example of a molecular sensor that can be used in the detection unit 15 will be described below.

[0022] (First embodiment) 2A, 2B, and 2C are schematic diagrams showing an example of the molecular sensor of the first embodiment. FIG. 2A shows a plan view of the molecular sensor. FIG. 2B is a cross-sectional view taken along line A1-A2 in FIG. 2A. FIG. 2C is an enlarged view of enclosure C in FIG. 2A. The molecular sensor of the first embodiment has a measurement mechanism that uses a quartz crystal microbalance (QCM) as a detection unit.

[0023] The molecular sensor 10 has a QCM detection unit 2 and a sensitive film 3 provided on the surface of the QCM detection unit 2. The QCM detection unit 2 has a disk-shaped substrate 4, an upper electrode 5, and a lower electrode 6.

[0024] Examples of the substrate 4 include a quartz crystal substrate. The substrate 4 is preferably an AT-cut quartz crystal substrate. The planar shape of the substrate 4 is not limited to a disk shape as shown in FIG. 2A, but may be a polygon or the like.

[0025] The upper electrode 5 is provided on the substrate 4. As shown in FIG. 2A , for example, the upper electrode 5 includes an upper excitation portion 5a that is concentric with the substrate 4 and has a smaller diameter than the substrate 4, and an upper extraction portion 5b that extends from a part of the periphery of the upper excitation portion 5a to the periphery of the substrate 4.

[0026] The lower electrode 6 is provided below the substrate 4. The lower electrode 6 includes a lower excitation portion 6a that is concentric with the substrate 4 and has a smaller diameter than the substrate 4, and a lower extraction portion 6b that extends from a part of the periphery of the lower excitation portion 6a to the periphery of the substrate 4.

[0027] The upper electrode 5 and the lower electrode 6 are, for example, two thin plate-like electrodes arranged on either side of the substrate 4. The upper electrode 5 and the lower electrode 6 preferably contain materials such as platinum (Pt), gold (Au), silver (Ag), copper (Cu), molybdenum (Mo), nickel (Ni), titanium (Ti), tungsten (W), aluminum (Al), indium-tin oxide (ITO), and aluminum-doped zinc oxide (AZO). An example of the upper electrode 5 and the lower electrode 6 includes a laminated film having a 10-nm-thick Ti layer and a 200-nm-thick Au layer provided on the Ti layer. To ensure adhesion to the sensitive film 3, a 10-nm-thick Ti layer and a 100-nm-thick silicon dioxide (SiO2) layer may be laminated on the surface of the Au electrode as an underlayer. The upper electrode 5 and the lower electrode 6 do not have to have the shape shown in FIG. 2A as long as they are capable of exciting the substrate 4.

[0028] The sensitive film 3 is provided, for example, on the surface (upper surface) of the upper excitation part 5a opposite to the substrate 4. Without being limited to this, the sensitive film 3 may also be provided on the upper side of the surface (lower surface) of the lower excitation part 6a opposite to the substrate 4.

[0029] As shown in FIGS. 2B and 2C, the sensitive film 3 includes a metal-organic framework (MOF) 7 and a hydrophobic polymer 8.

[0030] The metal-organic framework 7 preferably contains zirconium (Zr) as the main component, because Zr-based MOFs have high heat resistance and water resistance. A main component is a component that is contained in a greater amount than other components. In particular, it is preferable to use an MOF in which organic coordination is bonded to a hexanuclear Zr6O4(OH)4 cluster. More preferably, it is preferable to use an MOF having a structure in which dicarboxylic acid is coordinated to a Zr6O4(OH)4 cluster, as shown in Figure 3. In the structure shown in Figure 3, ○ (open circle) indicates a Zr6O4(OH)4 cluster, and solid lines indicate dicarboxylic acid ligands.

[0031] Examples of MOFs having such a structure include UIO-66, UIO-67, UIO-68, and at least one of their derivatives. UIO-66, UIO-67, and UIO-68 have structures in which the dicarboxylic acid ligands are 1,4-benzenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and 4,4"-terphenyldicarboxylic acid, respectively.

[0032] Derivatives are organic compounds having a new functional group introduced into the benzene ring of the ligand contained therein. Examples of the introduced functional group include alkyl groups, amino groups, hydroxy groups, alkoxy groups, amide groups, nitro groups, sulfo groups, aldehyde groups, acyl groups, ester groups, carbonyl groups such as carboxyl groups, and halogen groups such as fluorine, chlorine, bromine, and iodine. Examples of derivatives are organic compounds in which the benzene ring of the ligand is substituted with a heteroaromatic ring such as a pyridine ring or an imidazole ring.

[0033] Examples of UIO-67 include organic compounds in which 4,4'-biphenyldicarboxylic acid is replaced with a heterocyclic compound such as 9-fluorenone-2,7-dicarboxylic acid, fluorene-2,7-dicarboxylic acid, or carbazole-2,7-dicarboxylic acid.

[0034] These MOFs not only have high heat resistance and water resistance, but are also relatively easy to synthesize and have a wide range of formation methods, from microcrystalline hair production to thin film formation, making them suitable for use in the sensitive membrane 3. In addition to these, MOFs containing Zr as the main component such as MOF-801, MOF-808, NU-1000, and CAU-24 can also be used. In addition to Zr-based MOFs, other MOFs such as MIL-53, MIL-101, MOF-74, and ZIF-8 can also be used.

[0035] MOFs have micropores, the size of which varies depending on the type of metal-organic framework and the organic ligand, but is often less than 1 nm. Molecules larger than the micropores of the metal-organic framework cannot be adsorbed, but smaller molecules can. Therefore, metal-organic frameworks with different pore sizes can be used depending on the size of the target molecule 11. When incorporating an MOF film into the sensitive film 3, for example, in the case of a QCM sensor, a sensor is known in which a dense thin film with high crystallinity and orientation is formed using a layer-by-layer (LBL) method, in which films are grown layer by layer. However, this method is only applicable to a limited number of MOF species. Furthermore, in the case of a single crystalline thin film, the only route for adsorption of target molecules is the pores present at the outermost surface. Therefore, if the pores at the outermost surface are blocked by water molecules or the like, sensitivity drops dramatically. This phenomenon is known as the surface barrier phenomenon. Therefore, the sensitive film 3 preferably contains metal-organic framework particles, with an average particle size of 5 nm to 500 nm. If the particle size is smaller than 5 nm, the three-dimensional structure loses its properties, the physical and chemical stability decreases, and deterioration and decomposition become more likely. If the particle size is larger than 500 nm, the cohesive force between particles also decreases, and the film becomes more likely to become brittle. In light of this tendency, a particle size of 10 nm or more and 100 nm or less is more preferable.

[0036] The hydrophobic polymer 8 has a larger contact angle with water than the metal-organic framework 7. The hydrophobic polymer 8 is preferably a polymer that is gas permeable and more hydrophobic than the MOF. The hydrophobic polymer 8 is preferably composed primarily of an organosilicon polymer or a fluoropolymer. The hydrophobic polymer 8 may contain both an organosilicon polymer and a fluoropolymer. The hydrophobic polymer 8 may be mixed with other organic materials, but is preferably a polymer containing 80% by mass or more of an organosilicon polymer or a fluoropolymer as a main component. The organosilicon polymer is preferably an organic polysiloxane. Examples of the organic polysiloxane include polydimethylsiloxane (PDMS), polymethylphenylsiloxane, and polytrifluoropropylmethylsiloxane. The organic polysiloxane may be crosslinked by peroxide vulcanization, addition reaction vulcanization, or condensation reaction vulcanization, and may be a so-called silicone resin. For various organic polysiloxanes, see "Silicone Handbook," edited by Ito Kunio, Nikkan Kogyo Shimbun, Tokyo (1990), pp. 88-109. In addition to organic polysiloxanes, polymers of disubstituted acetylenically unsaturated compounds substituted with a group containing an organic silyl group, such as a trimethylsilyl group, typified by 1-(trimethylsilyl)-1-propyne, may also be used. The fluoropolymer is not particularly limited, but preferred examples include perfluoroalkyl acrylate copolymers, copolymers of vinyl ether and fluoroolefin, such as Lumiflon manufactured by AGC Inc., and butenyl vinyl ether copolymers, such as Cytop manufactured by AGC Inc., that can be applied with a solvent.

[0037] It is preferable that the contact angle of the outermost surface of the sensitive film 3 with water is 60 degrees or more. If the contact angle is less than 60 degrees, water may penetrate the sensitive film 3, causing deterioration of the metal-organic framework 7.

[0038] In the sensitive membrane 3, MOF7 is present on the substrate 4 side, and hydrophobic polymer 8 is present on top of MOF7. In other words, hydrophobic polymer 8 is present directly on top of MOF7. MOF7 and hydrophobic polymer 8 are layered. In the boundary region between hydrophobic polymer 8 and MOF7, for example, when hydrophobic polymer 8 is not present on the MOF7 side, the concentration of hydrophobic polymer 8 may be 100% by mass on the hydrophobic polymer 8 side and 0% by mass on the MOF7 side. Furthermore, the boundary region between hydrophobic polymer 8 and MOF7 may have a concentration gradient, for example, including cases where hydrophobic polymer 8 penetrates the MOF7 side. This concentration gradient is preferably significant in the boundary region between hydrophobic polymer 8 and MOF7. This significant gradient means that the gradient is at its steepest. For example, the concentration of hydrophobic polymer 8 in the boundary region between hydrophobic polymer 8 and MOF7 changes more significantly than in regions of the sensitive membrane 3 other than the boundary region. FIG. 4A is a cross-sectional schematic diagram illustrating an example structure of the sensitive membrane 3. 4A has a layer of MOF 7 and a layer of hydrophobic polymer 8, with the layer of hydrophobic polymer 8 covering the layer of MOF 7. MOF 7 is, for example, an MOF containing Zr as its main component, and hydrophobic polymer 8 is, for example, an organosilicon polymer or a fluoropolymer.

[0039] The hydrophobic polymer 8 layer and the metal-organic framework 7 layer are analyzed by cross-sectional observation of the sensitive film 3 using an optical microscope, a scanning transmission electron microscope (STEM), a transmission electron microscope (TEM), or a scanning electron microscope (SEM), followed by analysis using analytical methods such as energy dispersive X-ray spectroscopy (EDX). If a metal element is detected in the EDX spectrum, it is likely that the MOF is primarily composed of that metal. Therefore, information about the crystal structure can be obtained using high-resolution HAADF (High-Angle Annular Dark-Field)-STEM images, and the type of MOF7 can be identified. Furthermore, oxygen (O) and carbon (C) are common elements in organic materials and therefore difficult to distinguish. However, if silicon (Si) or fluorine (F) is detected, it is likely that the MOF7 contains hydrophobic polymer 8, and elemental mapping analysis of the metal element, Si, and F in MOF7 is performed. In particular, when the main component of MOF 7 is Zr and hydrophobic polymer 8 is an organosilicon polymer, the metal-organic framework 7 layer and the hydrophobic polymer 8 layer can be distinguished by elemental mapping analysis of Si and Zr. More specifically, by elemental mapping analysis or line analysis, the region in the sensitive film 3 where the elemental concentration ratio of Si to Zr, Si / Zr, is 10 or greater is defined as the hydrophobic polymer 8 layer (surface coating layer). However, since the peripheral edge of the sensitive film 3 is a singular point where the organosilicon polymer component is the main component, the elemental analysis is determined by the cross-sectional profile of the region within 25% of the total area of ​​the sensitive film 3 from the center of the sensitive film 3 when the surface of the sensitive film 3 is viewed from above. In the cross-sectional profile, the concentration ratio Si / Zr of Si element to Zr element is calculated at a plurality of regions located at different positions in the thickness direction from the surface side of the sensitive film 3, and a region where the concentration ratio Si / Zr is 10 or more is defined as a region of the hydrophobic polymer 8, and a region where the concentration ratio Si / Zr is less than 10 is defined as a region of the metal-organic framework 7 or a mixed region of the metal-organic framework 7 and the hydrophobic polymer 8. This mixed region is included in the boundary region.

[0040] 4B is an enlarged schematic diagram of a portion of the sensitive membrane 3 shown in FIG. 4A. As shown in FIG. 4B, the concentration of the hydrophobic polymer 8 has a concentration gradient that decreases along the thickness direction of the sensitive membrane 3 from the outermost surface of the sensitive membrane 3 toward the substrate 5, and the concentration gradient is particularly pronounced in the boundary region between the hydrophobic polymer 8 and the MOF 7. As shown in FIG. 4B, the concentration gradient is pronounced in the boundary region between the hydrophobic polymer 8 and the MOF 7 even when the MOF is in the form of particles, and similarly, the concentration gradient is pronounced in the boundary region between the hydrophobic polymer 8 and the MOF 7 even when the MOF is formed into a plate shape.

[0041] The thickness of the sensitive film 3 can be measured, for example, using the following method. First, the portion of the molecular sensor where the sensitive film 3 is formed is removed, and the sensitive film 3 is observed at a low magnification so that the entire sensitive film 3 is visible. The sensitive film 3 is then cut in the thickness direction at a position where there are no obvious cracks, defects, protrusions, or foreign matter. Next, the sensitive film 3 is processed using a focused ion beam (FIB), and the cut cross section is observed. Here, examples of FIB devices that can be used include the Hitachi SMI3300SE and the FEI Strata 400s. Observation of the entire film and the cross section can be performed using, for example, an optical microscope, STEM, TEM, or SEM.

[0042] After obtaining a cross section in the thickness direction of the sensitive film 3 by the above FIB processing, mapping images are taken by EDX for elements (such as Zr) derived from the components of the metal-organic framework 7 and elements Si or F derived from the components of the hydrophobic polymer 8 in the entire cross section. This makes it possible to distinguish between the layer of the hydrophobic polymer 8 and the layer of the metal-organic framework 7.

[0043] During the above-described cross-sectional observation, if there is a portion where the hydrophobic polymer 8 is not present and the metal-organic framework 7 is exposed, a portion where the metal-organic framework 7 is not present and only the hydrophobic polymer 8 is present, or a membrane defect portion where neither is present, this cross-section is not adopted, and the above-described selection of cutting locations in the entire sensitive membrane 3 and observation of the cross-section of the sensitive membrane 3 are performed until an adoptable cross-section is obtained, thereby selecting a cross-section for measuring the thickness of the sensitive membrane 3. By the above-described selection of cutting locations in the entire sensitive membrane 3, observation of the cross-section of the sensitive membrane 3, and selection of a cross-section for measuring the thickness of the sensitive membrane 3, three or more different cross-sections in the sensitive membrane 3 are selected.

[0044] Once the cross section where the thickness of the sensitive film 3 is to be measured is selected, the thickness of the sensitive film 3 is measured using the STEM or the like described above. When selecting the observation site, the cross section is observed at a magnification that includes the entire area where the sensitive film 3 is formed, and the site with the thickest film thickness is selected. However, when observing the entire film, it is best to avoid selecting a site where there are clearly specific cracks, burns, defects, protrusions, foreign matter, etc. Furthermore, the magnification is increased to a range where the film thickness of the selected site is included in the field of view, and observation is performed.

[0045] The thickness of the sensitive film 3 is measured at three or more selected cross sections using the method described above. The thickness of the sensitive film 3 at each cross section thus obtained is averaged, and the measured thickness of the sensitive film 3 can be calculated.

[0046] The average particle size of the metal-organic framework 7 can be measured using optical microscopes, STEM, TEM, and SEM image observations, similar to the measurement of the thickness of the sensitive film 3. Methods include extracting particle outlines using image analysis software such as ImageJ, or manually extracting particle outlines while viewing the image. In addition to image observation using STEM, the size and shape of particles can be determined by combining EDX mapping images of elements (e.g., Zr) derived from the components of the metal-organic framework 7 captured on the same cross section during the measurement of the thickness of the sensitive film 3. Furthermore, for crystalline materials such as MOFs, the average particle size can also be estimated from the pattern obtained by XRD (X-ray diffraction) using the Debye-Scherrer method, which states that the half-width of the main diffraction peak is inversely proportional to the crystalline particle size.

[0047] Specifically, the crystal grain diameter D (Å) is expressed as D = Kλ / (β cos θ), where K is a constant, typically 0.9, depending on the shape factor. β is the half-width (rad) of the diffraction peak, λ is the wavelength of the X-ray, e.g., 1.5406 (Å) for CuKa1 radiation, and θ is the Bragg angle (rad).

[0048] The metal organic framework 7 preferably contains 50% or more Zr. This is because Zr-based MOFs have high heat resistance and water resistance. 50% or more Zr in the MOF means that the Zr concentration is 50% or more of the metal element concentrations detectable by EDX described above.

[0049] The molecular sensor of the first embodiment has a surface coating layer made of hydrophobic polymer 8, which selectively absorbs and permeates volatile organic compounds (VOCs) present in the environment. The VOCs are then adsorbed and concentrated by the metal-organic framework (MOF) present in the lower layer, which has higher adsorption performance. This enables highly sensitive detection that cannot be achieved by using a metal-organic framework or an organosilicon polymer alone. In other words, MOF7 functions as a molecular sensor by trapping target molecules in its pores. Therefore, providing a membrane on the surface of MOF7 that blocks the pores is expected to reduce sensitivity. However, in this embodiment, MOF7 captures VOCs that permeate the surface coating layer of hydrophobic polymer 8, thereby generating a concentration gradient for target molecules reaching MOF7. In particular, when high concentrations of VOCs are generated, the surface coating layer acts as a buffer layer, creating a time lag for the VOCs to reach the MOF7 surface. This prevents the pores on the MOF7 surface from suddenly becoming blocked, resulting in a decrease in sensitivity. Furthermore, metal-organic frameworks generally adsorb water vapor well, and therefore, if they come into contact with water vapor, the adsorption of the target molecules to be detected may be inhibited. Furthermore, when placed in a humid environment, the sensitive membrane 3 may deteriorate due to hydrolysis, but the presence of the surface coating layer can suppress water vapor adsorption and hydrolysis. By providing the hydrophobic polymer 8 in this way, the pores of the MOF 7 can be used efficiently, thereby improving the sensitivity as a molecular sensor.

[0050] As shown in FIG. 4 , when the thickness of the sensitive film 3 is represented by L and the thickness of the region in the sensitive film 3 where the element concentration ratio Si / Zr of Si and Zr is 10 or more is represented by d, the sensitive film 3 preferably satisfies the following conditions: 20 nm≦L≦10 μm, 5 nm≦d, and d / L≦0.7. If the thickness L is less than 10 nm, the layer of the metal-organic framework 7 (Zr-based MOF 7a) is thin, resulting in a small absolute amount of the metal-organic framework and a small amount of the target molecules 11 that can be adsorbed, resulting in reduced sensitivity. Furthermore, to maintain the sensitivity of the sensitive film 3, the area of ​​the sensitive film 3 must be increased, which necessitates a larger device size. If the thickness L exceeds 10 μm, not only does the incidence of cracks and other defects due to internal stress in the sensitive film 3 increase, but also, when combined with a measurement mechanism such as a QCM or MCL, the oscillation resistance increases, potentially preventing oscillation. Furthermore, even if oscillation is possible, the sensitivity decreases.

[0051] The thickness L of the sensitive film 3 is preferably 50 nm or more and 5 μm or less. This range allows for a larger absolute amount of MOFs and a larger amount of target molecules to be adsorbed, resulting in improved sensitivity. If the thickness d of the region of the sensitive film 3 where the element concentration ratio Si / Zr of Si and Zr is 10 or more is 5 nm or more, a uniform coating without pinholes is possible, ensuring the aforementioned effect of improving sensitivity and barrier properties against water vapor. However, if the thickness d is too large, the adsorption rate of target molecules slows and the responsiveness of the sensor decreases. Therefore, by setting the ratio d / L of the thickness d to the thickness L to be 0.7 or less, a balance between responsiveness and sensitivity can be maintained.

[0052] The dimensions of the QCM detection unit 2 are not particularly limited and may be similar to those of a general QCM element. For example, the diameter of the substrate 4 is preferably approximately 2 mm to 10 mm. The sensitive film 3 is preferably formed, for example, in a disk shape that is concentric with the upper excitation unit 5a when viewed in plan and has a diameter smaller than that of the upper excitation unit 5a. The diameter of the sensitive film 3 is not limited, but is preferably set to have an area that is 20% to 90% of the planar area of ​​the substrate 4. As described above, the thickness of the sensitive film 3 preferably satisfies the following conditions: 20 nm≦L≦10 μm, 5 nm≦d, and d / L≦0.7.

[0053] When a target molecule adheres to the sensitive film 3 of the molecular sensor 10, an energy loss equivalent to the mass of the molecule occurs, causing a change in the vibration frequency of the substrate 4. By measuring this change, an electrical signal is generated. The generated electrical signal is sent to the analysis unit 16, allowing the target molecule 11 to be detected.

[0054] The molecular sensor 10 may further include an AC power supply that applies a voltage to the upper electrode 5 and the lower electrode 6 via wiring such as lead wires, and a frequency measuring device that detects the frequency of the substrate 4. The molecular sensor 10 may also include a temperature adjusting device that heats the sensitive film 3. By heating the sensitive film 3, it is possible to remove, for example, adsorbed target molecules.

[0055] (Second embodiment) The molecular sensor of the second embodiment has a measurement mechanism that uses a microcantilever (MCL) as a detection unit.

[0056] 5A and 5B are schematic diagrams showing another example of a molecular sensor, in which Fig. 5A is a schematic plan view of the molecular sensor 20, and Fig. 5B is a schematic cross-sectional view of the molecular sensor 20 taken along line B1-B2.

[0057] The molecular sensor 20 includes an MCL detection unit 21 and a sensitive membrane 3.

[0058] The MCL detection unit 21 has a long and narrow rectangular shape in a plan view and has a fixed end 21a fixed to the support 22 and a free end 21b that is not fixed. That is, the MCL detection unit 21 has a cantilever shape. The MCL detection unit 21 has a layered structure and includes a substrate 23 provided at the bottom layer, a lower electrode 24 stacked on the substrate 23, a piezoelectric body 25 stacked on the lower electrode 24, a first upper electrode 26a and a second upper electrode 26b stacked on the piezoelectric body 25 and extending long and narrow along the two long sides, and a detection electrode 27 stacked on the piezoelectric body 25 located on the fixed end 21a side between the first upper electrode 26a and the second upper electrode 26b.

[0059] The substrate 23 is made of a material such as silicon, glass, or resin.

[0060] The sensitive film 3 is preferably fixed to a portion close to the free end 21b on the uppermost surface of the MCL detection unit 21. The sensitive film 3 is fixed, for example, on the piezoelectric body 25 between the first upper electrode 26a and the second upper electrode 26b. Between the piezoelectric body 25 and the sensitive film 3, a conductive film such as an Au thin film (not shown), an insulating film such as SiO2, a metal oxide film such as aluminum oxide (Al2O3) or titanium oxide (TiO2), a silane coupling agent, a self-assembled monolayer, or the like may be provided.

[0061] The first upper electrode 26a, the second upper electrode 26b, and the lower electrode 24 are connected to, for example, an AC power source to apply an AC voltage to the piezoelectric body 25. The detection electrode 27 detects the frequency of the piezoelectric body 25.

[0062] Each of the first upper electrode 26a, the second upper electrode 26b, the lower electrode 24, and the detection electrode 27 includes a metal material such as platinum, gold, molybdenum, tungsten, aluminum, etc. One of the first upper electrode 26a, the second upper electrode 26b, the lower electrode 24, and the detection electrode 27 may be formed using a different material.

[0063] The piezoelectric body 25 deforms when a voltage is applied, and therefore expands and contracts when an AC voltage is applied, vibrating at a predetermined resonance frequency. The piezoelectric body 25 is formed using, for example, lead zirconate titanate (PZT), lead zinc niobate-lead titanate solid solution (PZN-PT), lead manganate niobate-lead zirconate titanate solid solution (PMnN-PZT), aluminum nitride (AlN), zinc oxide (ZnO), potassium sodium niobate (KNN), lithium niobate (LiNbO), or the like.

[0064] The dimensions of the MCL detecting section 21 are not particularly limited and may be similar to those of a general MCL element. For example, the dimensions of the sensitive film 3 in plan view may be set to have an area that is 20% to 90% of the area of ​​the MCL detecting section 21. As in the first embodiment, the sensitive film 3 preferably satisfies 20 nm≦L≦10 μm, 5 nm≦d, and d / L≦0.7. For other details of the sensitive film 3, the description of the first embodiment can be used as appropriate.

[0065] The molecular sensor 20 can also use the same detection method as the molecular sensor 10 of the first embodiment. When a target molecule adheres to the sensitive film 3 of the molecular sensor 20, an energy loss equivalent to the mass of the molecule occurs, causing a change in the resonant frequency of the piezoelectric body 25. This change is measured by the detection electrode 27, and an electric signal is generated. The generated electric signal is sent to the analysis unit 16. This allows the target molecule to be detected.

[0066] Although FIGS. 5A and 5B illustrate examples using the QCM detection unit 2 and the MCL detection unit 21, the detection unit is not limited to these, and other measurement mechanisms may be used. The detection unit is preferably a mechanism capable of measuring, for example, a change in mass of the sensitive film 3. Another example of the detection unit may include a surface acoustic wave (SAW). A detection unit including SAW includes, for example, two pairs of interdigitated electrodes (IDE) arranged at a desired distance on the surface of a piezoelectric substrate. The sensitive film 3 may be disposed between, for example, two pairs of electrodes on the piezoelectric substrate. When target molecules adhere to the sensitive film 3, changes occur in the propagation velocity and amplitude of the surface acoustic waves propagating on the surface of the piezoelectric substrate. These changes are detected by the two electrodes to generate electrical signals. The generated electrical signals are sent to the analysis unit 16. This allows the target molecules to be detected.

[0067] Another example of the detection unit may include a measurement mechanism capable of measuring changes in the electrical resistance, impedance, electrical conductivity, etc. of the sensitive membrane 3. Such a detection unit may have, for example, a field effect transistor (FET) or an interdigitated electrode (IDE) type sensor. For example, when a FET is used, the sensitive membrane 3 functions as a channel layer that forms a channel between, for example, a source electrode and a drain electrode. When an IDE type sensor is used, the sensitive membrane 3 is provided, for example, between or on the electrodes of the IDE. For other descriptions of the sensitive membrane 3, the description of the first embodiment can be used as appropriate. [Example]

[0068] A QCM molecular sensor equipped with a sensitive film 3 was manufactured, and the target molecule was detected using this molecular sensor.

[0069] Example 1 [Preparation of UIO-66 precursor solution] 18.6 mg ZrOC l2 A precursor solution was formed by weighing and mixing 8H2O, 9.5 mg of benzenedicarboxylic acid, 280 mg of acetic acid, and 9.4 g of dimethylformamide.

[0070] [Application of precursor solution onto QCM] A laminated film consisting of a 10 nm thick Ti layer and a 100 nm thick SiO2 layer was formed as a base layer on one side of the QCM detection unit 2, which has a resonant frequency of 20 MHz. The QCM detection unit 2 was ultrasonically cleaned with acetone and pure water, respectively, and then dried with an N2 blower before being placed in the center of a mini Petri dish. An appropriate amount of the precursor solution was applied dropwise using a micropipette so that it spread over the entire QCM surface, with the SiO2 layer facing up. The mini Petri dish was then covered with a top lid and left to evaporate until the solvent evaporated. The QCM detection unit 2 was then removed and placed on a fluororesin block with a side length of 1 cm.

[0071] [UIO-66 film formation] A 100 ml glass container was filled with a mixed solution of 0.8 ml of acetic acid and 4.2 ml of dimethylformamide, and the fluororesin block containing the QCM detector 2 was placed horizontally at the bottom of the container. The glass container was placed in an oven and heated at 100°C for 3 hours to prevent direct contact of the solution in the glass container with the QCM detector 2. This promoted crystallization in the solvent atmosphere, resulting in a thin film of UIO-66 nanoparticles. The QCM detector 2 was then removed from the glass container and heated on a hot plate in the atmosphere at 120°C for 2 hours to remove excess solvent and moisture. This resulted in a QCM molecular sensor containing UIO-66.

[0072] [Layering of organosilicon polymer films] Shin-Etsu Silicone's KR-255 organosilicon polymer was diluted with toluene to a solids content of 0.2% by mass. An appropriate amount of diluted KR-255 was dropped onto the resulting UIO-66 film using a microsyringe, and the solvent was evaporated at room temperature. The film was then pre-heated at 110°C for 15 minutes, and then heated at 200°C for 2 hours to form an organosilicon polymer film, which was then laminated on top of the UIO-66 film. This formed the sensitive film 3.

[0073] [Cross-sectional membrane analysis] An example of a method for evaluating the physical properties of the sensitive film 3 formed by the above method is shown below. First, an optical microscope was used to observe the area where the sensitive film 3 was formed, and the thickest part was selected when the area was observed at a magnification that allowed the entire area where the sensitive film 3 was formed to be viewed. However, when observing the entire film, parts that clearly showed specific cracks, burns, defects, protrusions, foreign matter, etc. were not selected. Next, the selected part of the sensitive film 3 was processed with a focused ion beam (FIB), and the cross section was observed by STEM. The area of ​​the observation area was set to be at least the square of the film thickness defined above.

[0074] Furthermore, the magnification was increased so that the film thickness of the selected portion was within the field of view, and observations were performed. In Example 1, the thickness of the sensitive film 3 was measured from the cross-sectional STEM image of Figure 6, and the thickest part of the sensitive film 3 within the field of view was 270 nm, and the thinnest part was 225 nm. Furthermore, when the distribution of Zr and the distribution of Si were confirmed by element mapping using EDX, the Zr-based MOF layer and the organosilicon polymer layer were confirmed by contrast, as shown in Figures 7 and 8. Figure 7 is a mapping image of Zr. Figure 8 is a mapping image of Si.

[0075] As shown in Figure 6, the thickness of the organosilicon polymer film was 10 nm at its thinnest point and 140 nm at its thickest point. Furthermore, in a magnified image of Figure 6, the concentration ratio Si / Zr of Si element to Zr element was calculated for regions 31, 32, and 33, which are located at different positions in the thickness direction from the surface of the sensitive film 3. Figure 9 shows a magnified image of a portion of the Si element mapping image shown in Figure 8. Figure 10 shows the measurement results of the concentration ratio Si / Zr. As shown in Figure 10, the Si / Zr ratio at region 31 in the organosilicon polymer layer was 39.38, the Si / Zr ratio at region 32 was 1.88, and the Si / Zr ratio at region 33 was 1.87.

[0076] [Particle size analysis] In Example 1, the average particle size of the UIO-66 microparticles was estimated to be 10 nm as the average value of 10 points obtained by contour extraction from the cross-sectional STEM image of Fig. 11. Fig. 11 is a cross-sectional STEM image obtained by enlarging and observing a portion of the cross section of the sample from which the element mapping image was obtained.

[0077] (Comparative Example 1) [Formation of dispersion film] As in Example 1, a laminated film was formed on one side of a QCM detector 2 with a resonant frequency of 20 MHz. The film had a 10-nm-thick Ti layer as a base layer and a 100-nm-thick SiO2 layer on top of the Ti layer. The QCM detector 2 was ultrasonically cleaned with acetone and pure water, respectively, and then dried with an N2 blower before being placed in the center of a mini Petri dish. Shin-Etsu Silicone's KR-255 was diluted with toluene to a solids content of 0.2% by mass. An appropriate amount of the diluted KR-255 solution was dripped onto the SiO2 layer-formed surface using a micropipette. Before the solvent in the KR-255 solution completely dried, an appropriate amount of UIO-66 precursor solution, similar to that in Example 1, was dripped onto the surface. The sample was then dried at room temperature until the solvent was visually removed. The sample was then heated in an oven at 100°C for 3 hours to promote crystal growth, resulting in a thin film composed of UIO-66 nanoparticles. The QCM detection unit 2 was then removed from the glass container and heated on a hot plate in the atmosphere at 200°C for 2 hours to remove excess solvent and moisture and complete the silicone curing reaction, resulting in a QCM molecular sensor with a sensitive film 3, which is a dispersion film containing UIO-66 and an organosilicon polymer.

[0078] [Cross-sectional membrane analysis] Using a method similar to that used in Example 1, the thickness of the sensitive film 3 within the field of view of the cross-sectional STEM image shown in Figure 12 was measured. It was 1290 nm at its thickest point and 1040 nm at its thinnest point. Furthermore, observations were performed at increased magnifications so that the film thickness of selected areas was within the field of view. In Comparative Example 1, elemental mapping of the Si and Zr distributions was performed using EDX from the cross-sectional STEM image of Figure 13, as shown in Figures 14 and 15. As shown in Figure 16, the Si component derived from the silicone resin and the Zr component derived from UIO-66 were mixed. The outermost surface of the sensitive film 3 had many exposed Zr components, but there was no region where the Si / Zr concentration ratio was 10 or greater, making it impossible to determine the presence of a surface coating layer. Figure 14 shows a Zr mapping image. Figure 15 shows a Si mapping image. Figure 16 shows a mixed mapping image of Zr and Si. The average particle size of the UIO-66 microparticles was estimated to be 9 nm as the average value of 10 points obtained by extracting contours from the STEM image in Fig. 17 using the same method as in Example 1. Fig. 17 is a cross-sectional STEM image obtained by enlarging and observing a portion of the cross section of the sample from which the element mapping image was obtained.

[0079] (Comparative Example 2) A laminated film consisting of a 10 nm thick Ti layer and a 100 nm thick SiO2 layer was formed as a base layer on one side of a QCM detection part 2 having a resonant frequency of 20 MHz, and UIO-66 microparticles were formed in the same manner as in Example 1. By not forming an organosilicon polymer film, a MOF-only film was formed.

[0080] (Comparative Example 3) A laminated film consisting of a 10 nm thick Ti layer and a 100 nm thick SiO2 layer was formed as an underlayer on one side of a QCM detection part 2 having a resonant frequency of 20 MHz, and an organosilicon polymer film was formed using KR-255 in the same manner as in Example 1, without forming UIO-66 as in Example 1.

[0081] [Contact angle evaluation] The water contact angles of the films prepared in Example 1 and Comparative Examples 1, 2, and 3 were evaluated. The results are shown in Table 1. The water contact angle of the MOF film surface prepared in Example 1 was approximately 20 degrees. In contrast, the water contact angle of the sensitive film 3 after the polymer film was formed was approximately 89 degrees. These results confirmed that the MOF film in Example 1 was coated with a hydrophobic polymer film. On the other hand, the water contact angle of the hydrophobic polymer monolayer film prepared in Comparative Example 3 was approximately 89 degrees. The water contact angle of the MOF and hydrophobic polymer dispersion film prepared in Comparative Example 1 was approximately 55 degrees. The water contact angle of the MOF monolayer film prepared in Comparative Example 2 was approximately 20 degrees. Therefore, the MOF and hydrophobic polymer dispersion film of Comparative Example 1 had a contact angle between the contact angles of Comparative Examples 2 and 3, indicating that the UIO-66 component and the KR-255 component were exposed on the surface.

[0082] [First humidity dependency and sensitivity evaluation test] The QCM molecular sensor of Example 1 was connected to a personal computer (PC) using a portable QCM measuring instrument (THQ-100P-SW) manufactured by Tama Devices. The VOC used was 2-MIB (2-methylisoborneol), known to be one of the substances causing the musty odor often cited as a complaint about tap water. Gas generated from a 2-MIB reagent bottle was sent to the QCM molecular sensor at a flow rate of 300 ml / min using air as a carrier gas, and the frequency change was recorded. The frequency change in response to humidity changes was also evaluated in air with an absolute humidity of 6800 ppm to 8000 ppm at room temperature of approximately 20°C. The frequency change in response to humidity changes was also evaluated in Comparative Examples 2 and 3 using the same method. The results are shown in Table 1.

[0083] The humidity dependence of the sample having the MOF monolayer film of Comparative Example 2 was 0.081 Hz / ppm, and the frequency change per unit time for 2-MIB gas equivalent to 40 ppb was 0.68 Hz / min. In contrast, the humidity dependence of the sample having the laminated film of MOF and hydrophobic polymer of Example 1 was 0.051 Hz / ppm, and the frequency change per unit time for 2-MIB gas equivalent to 40 ppb was 2.92 Hz / min. Furthermore, the humidity dependence of the sample having the hydrophobic polymer monolayer film of Comparative Example 3 was 0.005 Hz / ppm, and the frequency change per unit time for 2-MIB gas equivalent to 40 ppb was 0.036 Hz / min.

[0084] [Second humidity dependency and sensitivity evaluation test] The QCM molecular sensor of Comparative Example 1 was connected to a PC using a portable QCM measuring instrument (THQ-100P-SW model) manufactured by Tama Devices. As in Example 1, 2-MIB (2-methylisoborneol) was used, and gas generated from a reagent bottle was sent to the QCM molecular sensor at a flow rate of 300 ml / min using air as a carrier gas, and the frequency change was recorded. The frequency change in response to humidity changes was also evaluated in air with an absolute humidity of 4600 ppm to 4800 ppm at room temperature of approximately 20°C. The frequency change in response to humidity changes was also evaluated in Example 1 and Comparative Example 3 using the same method. The results are shown in Table 1.

[0085] The humidity dependence of the sample having a laminated film of MOF and hydrophobic polymer in Example 1 was 0.167 Hz / ppm, and the frequency change per unit time for 2-MIB gas equivalent to 150 ppb was 6.55 Hz / min. On the other hand, the humidity dependence of the sample having a dispersed film of MOF and hydrophobic polymer in Comparative Example 1 was 0.024 Hz / ppm, and the frequency change per unit time for 2-MIB gas equivalent to 150 ppb was 1.13 Hz / min. Furthermore, the humidity dependence of the sample having a hydrophobic polymer only film in Comparative Example 3 was 0.009 Hz / ppm, and the frequency change per unit time for 2-MIB gas equivalent to 150 ppb was 0.144 Hz / min. From the above results, it was found that the dispersed film of MOF and hydrophobic polymer has lower water repellency than the laminated film of MOF and hydrophobic polymer. Furthermore, it was found that the dispersed film of MOF and hydrophobic polymer tends to have improved humidity dependence, but its sensitivity to 2-MIB is significantly reduced.

[0086] [Table 1]

[0087] The above evaluation results show that coating the MOF layer with a hydrophobic polymer layer reduces the effects of humidity and improves sensitivity. Furthermore, while a hydrophobic polymer film alone has a high VOC permeability, it cannot retain VOCs and therefore does not provide sensitivity. However, by layering the hydrophobic polymer on a MOF film with high adsorption performance, sensitivity far exceeds that of the MOF film alone.

[0088] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0089] 1...fluid, 2...QCM detection unit, 3...sensitive membrane, 4...substrate, 5...upper electrode, 5a...upper excitation unit, 5b...upper extraction unit, 6...lower electrode, 6a...lower excitation unit, 6b...lower extraction unit, 7...metal organic framework, 7a...Zr-based MOF, 8...hydrophobic polymer, 8a...organosilicon polymer, 10...molecular sensor, 11...target molecule, 12...filter device, 13...molecular distribution device, 14...collection unit, 15...detection unit, 16...analysis unit, 17...control unit, 20...molecular sensor, 21...MCL detection unit, 21a...fixed end, 21b...free end, 22...support, 23...substrate, 24...lower electrode, 25...piezoelectric body, 27...detection electrode, 31...part, 32...part, 33...part.

Claims

1. A molecular sensor capable of detecting a target molecule by measuring a change in a physical quantity due to adhesion of the target molecule, A substrate; a sensitive film provided above the substrate, the sensitive film containing a metal-organic framework and a hydrophobic polymer having a larger contact angle with water than the metal-organic framework; the sensitive film has the metal-organic framework on the substrate side, and the hydrophobic polymer on the metal-organic framework; When the hydrophobic polymer is an organosilicon polymer, When the thickness of the sensitive film is represented by L and the thickness of a region of the sensitive film where the element concentration ratio of silicon to zirconium, Si / Zr, is 10 or more is represented by d, 20 nm≦L≦10 μm, 5 nm≦d, and A molecular sensor that satisfies d / L≦0.

7.

2. A molecular sensor capable of detecting a target molecule by measuring a change in a physical quantity due to adhesion of the target molecule, A substrate; a sensitive film provided above the substrate, the sensitive film containing a metal-organic framework and a hydrophobic polymer having a larger contact angle with water than the metal-organic framework; the sensitive film has the metal-organic framework on the substrate side, and the hydrophobic polymer on the metal-organic framework; a molecular sensor, wherein the sensitive film has a concentration gradient of the hydrophobic polymer in a boundary region between the hydrophobic polymer and the metal-organic framework, from the surface of the sensitive film toward the substrate along a thickness direction of the sensitive film.

3. The molecular sensor according to claim 1 , wherein the sensitive film has a concentration of the hydrophobic polymer that changes significantly at a boundary region between the hydrophobic polymer and the metal-organic framework.

4. 2. The molecular sensor according to claim 1, wherein the contact angle of the surface of the sensitive film with water is 60 degrees or more.

5. The molecular sensor of claim 1 , wherein the hydrophobic polymer is an organosilicon polymer or a fluoropolymer.

6. 6. The molecular sensor according to claim 5, wherein the organosilicon polymer is an organic polysiloxane, a crosslinked product of the organic polysiloxane obtained by peroxide vulcanization, a crosslinked product of the organic polysiloxane obtained by addition reaction vulcanization, a crosslinked product of the organic polysiloxane obtained by condensation reaction vulcanization, or a silicone resin.

7. The molecular sensor of claim 1 , wherein the metal-organic framework contains zirconium.

8. The molecular sensor according to claim 1 , wherein the metal-organic framework has particles with an average particle size of 5 nm to 500 nm.

9. The metal organic framework is a hexanuclear Zr ６ O ４ (OH) ４ The molecular sensor according to claim 1 , having a structure in which a carboxylic acid is coordinated to a cluster.

10. 2. The molecular sensor of claim 1, wherein the metal-organic framework is at least one of UIO-66, UIO-67, UIO-68, or derivatives thereof.

11. The molecular sensor according to claim 1 , further comprising a temperature adjustment device for heating the sensitive film.

12. A molecular detection device comprising the molecular sensor according to any one of claims 1 to 11.

13. 13. The molecular detection device according to claim 12, wherein the molecular sensor comprises at least one measurement mechanism using a quartz crystal microbalance, a surface acoustic wave, or a microcantilever.

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