Multimolecular film, method for producing multimolecular film, and laminate

Abstract

To provide a multimolecular membrane which can be chemically modified and is excellent in handleability.SOLUTION: A multimolecular membrane includes: a first monomolecular layer; and a second monomolecular layer disposed on the first monomolecular layer. The first monomolecular layer and the second monomolecular layer have a structure derived from a fullerene derivative molecule represented by the following formula (1) (where, R1s each independently represent an organic group having a hydrogen-bonding group or a hydrocarbon group, where at least one R1 is the organic group having the hydrogen-bonding group, and R2 represents a hydrogen atom, or a C1 to C10 hydrocarbon group or a metallocene group which optionally has a substituent).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a multimolecular film, a method for producing a multimolecular film, and a laminate. [Background technology]

[0002] Thin films with thicknesses on the order of micrometers to nanometers are used in various fields for the purpose of surface modification. That is, by covering the surface of a material with such a thin film, desired physical properties can be imparted to the material without affecting its size. For example, thin films play an important role in controlling material properties, such as improving wettability, as a scaffold for surface modification.

[0003] An example of such a thin film is a thin film obtained by stretching a polymer. Such thin films are widely produced industrially and used for various applications, but due to the manufacturing principle, they cannot be made to have a thickness of a single molecule or a thickness equivalent thereto, making it difficult to meet the demand for further thinning. On the other hand, Langmuir-Blodgett films (LB films) formed at the air-water interface and spherical vesicles made of lipid bilayers are known as membranes with a monomolecular thickness. However, these membranes are poorly stable and difficult to chemically modify, which greatly limits their applications. Self-assembled monolayer (SAM) films, which are formed on the interface between a solid surface and a liquid phase, are also known as monolayers that are more stable and can be chemically modified. For example, Patent Documents 1 and 2 propose producing SAM films using fullerenes and using them as photoelectric conversion materials. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5062765 [Patent Document 2] Patent No. 5062766 Summary of the Invention [Problem to be solved by the invention]

[0005] The SAM films described in Patent Documents 1 and 2 have a strong interaction with the substrate and a robust structure, which tends to increase the degree of freedom in chemical modification, etc. However, because the film shape is maintained by the interaction between the film and the substrate, after being formed on the substrate, it cannot be separated from the substrate as a monolayer. In other words, such SAM films cannot be made into independent films. As such, the technologies described in Patent Documents 1 and 2 have significant limitations in terms of handleability, and there is room for improvement in this area.

[0006] The present invention has been made in view of the problems inherent in the above-mentioned conventional techniques, and has as its object to provide a polymolecular film that can be chemically modified and is easy to handle. [Means for solving the problem]

[0007] As a result of intensive research aimed at solving the above problems, the present inventors have found that the above problems can be solved by appropriately orienting predetermined fullerene derivative molecules to form a multilayer film, and have thus completed the present invention.

[0008] That is, the present invention includes the following aspects. [1] a first monolayer; and a second monolayer disposed on the first monolayer; and A multilayer film comprising: The multimolecular film, wherein the first monomolecular layer and the second monomolecular layer have a structure derived from a fullerene derivative molecule represented by the following formula (1): [ka] (In formula (1), R 1 each independently represents an organic group having a hydrogen-bonding group or a hydrocarbon group, and at least one R 1 is an organic group having a hydrogen-bonding group, and R 2is a hydrogen atom, a C1-C 10 represents a hydrocarbon group or a metallocene group. [2] The multilayer film according to [1], wherein at least one hydrogen-bonding group on the first monolayer side is oriented toward at least one hydrogen-bonding group on the second monolayer side. [3] The multimolecular film according to [1] or [2], wherein the fullerene derivative molecule is represented by the following formula (A): [ka] [4] The multimolecular film according to claim [1] or [2], wherein the fullerene derivative molecule is represented by the following formula (B): [ka] [5] The multimolecular film according to any one of [1] to [4], wherein the thickness of the multimolecular film is 3 to 90 nm. [6] A method for producing a multimolecular film according to any one of [1] to [4], A method for producing a polymolecular film, comprising the steps of dropping a mixed solution of the fullerene derivative molecules, toluene, and n-butanol into water, and forming the polymolecular film in a mixed system of the mixed solution and water. [7] The method for producing a multilayer film according to [6], wherein the concentration of the fullerene derivative molecules in the mixed solution is 1 μM to 10 mM. [8] The method for producing a multimolecular film according to [6] or [7], wherein the volume ratio of toluene to n-butanol in the mixed solution is 1 / 100 to 10 / 1 in terms of toluene / n-butanol. [9] A substrate; The multimolecular film according to any one of [1] to [4], which is disposed on the substrate; A laminate comprising:

[10] The laminate according to [9], wherein the substrate is a member for an electron microscope. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a multi-molecular film that can be chemically modified and has excellent handleability. [Brief explanation of the drawings]

[0010] [Figure 1] 1 shows the results of atomic force microscope (AFM) observation of the multimolecular films obtained in Examples 1 to 4. [Figure 2] FIG. 1 is an explanatory diagram illustrating a structural model of a multilayer film. [Figure 3] 1 is a scanning electron microscope (SEM) image of the multilayer film (transferred onto a Cu mesh grid) of Example 1. [Figure 4] 1 is an SEM observation image of the multilayer film (transferred onto a Cu mesh grid) of Example 4. [Figure 5] 10 is a production scheme of a laminate in Example 5. [Figure 6] 1 is a photograph of a multilayer film transferred onto a silicon substrate (diameter 12.7 cm) having an oxide film with a thickness of 290 nm in Example 5. [Figure 7] 1 is a photograph of a multilayer film transferred onto a silicon substrate (diameter 10.2 cm) having an oxide film with a thickness of 160 nm in Example 5. [Figure 8] 10 is an optical microscope image of a 6 nm multilayer film transferred onto a copper grid (on a mesh having 40 μm square holes) in Example 6. [Figure 9] 10 is a chemical modification scheme of a multilayer film in Example 8. [Figure 10] 1 shows the results of measuring the contact angle of the multilayer film in Examples 8 and 14-3. [Figure 11] 1 shows the results of measuring the contact angle of the multilayer film in Examples 8 and 14-3. [Figure 12] 10 is a photograph of a sample for measuring reflectance in Example 10. [Figure 13] 10 is a graph showing the reflectance measurement results in Example 10. [Figure 14]10 is an SEM observation image obtained in Example 12. [Figure 15] 10 is an SEM observation image obtained in Example 13. [Figure 16] 1 is a high-resolution TEM image obtained in Example 13. [Figure 17] 1 is a photograph taken at the time of measuring the contact angle in Example 14-1. [Figure 18] 1 shows the contact angle measurement results of the multilayer film in Example 14-2. [Figure 19] 10 is a graph showing the results of infrared spectroscopy in Example 15. [Figure 20] 1 is an electron microscope image obtained in Example 12. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a mode for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. The following present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out in various modifications within the scope of its gist.

[0012] [Polymer membrane] The multimolecular film of this embodiment is a multimolecular film including a first monomolecular layer and a second monomolecular layer disposed on the first monomolecular layer, and the first monomolecular layer and the second monomolecular layer have a structure derived from a fullerene derivative molecule represented by the following formula (1): [ka] (In formula (1), R 1 each independently represents an organic group having a hydrogen-bonding group or a hydrocarbon group, and at least one R 1 is an organic group having a hydrogen-bonding group, and R 2 is a hydrogen atom, a C1-C 10 represents a hydrocarbon group or a metallocene group.

[0013] The multimolecular film of this embodiment is configured as described above, and therefore can be chemically modified and is easy to handle. Whether chemical modification is possible or not can be evaluated by, but not limited to, the following, typically, after producing a freestanding membrane, confirming that predetermined functional groups are introduced without damaging the membrane shape even when the membrane is exposed to a surfactant or subjected to a hydrophilization treatment such as plasma discharge. Whether or not a material has excellent handleability can be evaluated, but is not limited to, typically by confirming that a transferable multilayer can be formed on the water surface. The multilayer film of this embodiment is also referred to as a free-standing film in the technical field. A free-standing film means a film that can exist independently in air, a vacuum, or a liquid. Whether or not a film is free-standing can be evaluated by, but is not limited to, typically confirming that a film with an aspect ratio of thickness to surface dimensions of 100 or more has self-supporting properties. Whether or not a multilayer film has self-supporting properties can be evaluated by, but is not limited to, typically confirming whether or not the film shape is maintained on the substrate after transfer of the multilayer film to the substrate, and / or by, but is not limited to, confirming whether or not the film maintains its film shape by supporting only the edges of the multilayer film. The above-mentioned verification methods are merely typical examples, and are not intended to limit the verification methods for determining whether or not a film corresponds to the multimolecular film of this embodiment. That is, as long as it is confirmed that a multimolecular film includes a first monomolecular layer and a second monomolecular layer disposed on the first monomolecular layer, and that the first monomolecular layer and the second monomolecular layer have a structure derived from fullerene derivative molecules, the multimolecular film can be treated as corresponding to the multimolecular film of this embodiment.

[0014] (First Monolayer and Second Monolayer) The multilayer film of this embodiment includes a first monolayer and a second monolayer, each of which has a thickness equivalent to one fullerene derivative molecule, and the multilayer film of this embodiment can be said to have a bilayer structure as a basic unit.

[0015] In the above formula (1), R 1 each independently represents an organic group having a hydrogen-bonding group or a hydrocarbon group, and at least one R 1 is an organic group having a hydrogen-bonding group. The hydrogen-bonding group is not particularly limited, and examples thereof include -COOH, -OH, -NH, >C=O, -F, etc. That is, the organic group having a hydrogen-bonding group is, but is not limited to, a C1-C substituted with a hydrogen-bonding group such as -COOH, -OH, -NH, >C=O (excluding esters), or -F. 30 Alkyl groups, C2-C 30 Alkenyl groups, C2-C 30 Alkynyl groups, C4-C 30 Alkyldienyl group, C6-C 18 Aryl groups, C7-C 30 Alkylaryl group, C7-C 30 Aryl alkyl groups, C4-C 30 Cycloalkyl group or C4-C 30 The hydrogen-bonding group is preferably —COOH, and the organic group having a hydrogen-bonding group is preferably a C6-C alkyl group substituted with —COOH. 18 An aryl group is preferred. The organic group having a hydrocarbon group is not limited to the following, but examples thereof include the above-mentioned C1-C 30 Alkyl groups, C2-C 30 Alkenyl groups, C2-C 30 Alkynyl groups, C4-C 30 Alkyldienyl group, C6-C 18 Aryl groups, C7-C 30 Alkylaryl group, C7-C 30 Aryl alkyl groups, C4-C 30 Cycloalkyl groups and C4-C 30 Examples thereof include a cycloalkenyl group. In the above formula (1), R 2 is a hydrogen atom, a C1-C 10 R represents a hydrocarbon group or a metallocene group, and is preferably a methyl group or a metallocene group. 2The substituent in is not particularly limited, and may be, for example, the above-mentioned hydrogen-bonding group. In this embodiment, the metallocene group is a C 60 It means that one cyclopentadiene moiety and an -M(C5H5) moiety constituting the skeleton form -M(C5H5)2. In this embodiment, it is preferable that M in the metallocene group is Fe, that is, the metallocene group is a ferrocene group.

[0016] As used herein, "C x ~C y " means that the number of carbon atoms is x to y. Furthermore, in this specification, unless otherwise specified, the notation "to" includes the numerical values ​​on both ends as the upper and lower limits. In this specification, "C1 to C 30 The alkyl group is C1 to C 10 An alkyl group is preferred, and a C1 to C6 alkyl group is more preferred. Examples of the alkyl group include, but are not limited to, a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, and a dodecanyl group. In this specification, "C2 to C 30 The alkenyl group is a C2-C 10 An alkenyl group is preferred, and a C2 to C6 alkenyl group is more preferred. Examples of the alkenyl group include, but are not limited to, a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a 2-methyl-1-propenyl group, a 2-methylallyl group, and a 2-butenyl group. In this specification, "C2 to C 30 The alkynyl group is a C2-C 10 An alkynyl group is preferred, and a C2 to C6 alkynyl group is more preferred. Examples of the alkynyl group include, but are not limited to, an ethynyl group, a propynyl group, and a butynyl group. In this specification, "C4 to C 30 The alkyldienyl group is a C4-C 10An alkyldienyl group is preferred, and a C4 to C6 alkyldienyl group is more preferred. Examples of the alkyldienyl group include, but are not limited to, a 1,3-butadienyl group. In this specification, "C6 to C 18 The aryl group is a C6-C 10 An aryl group is preferred. Examples of the aryl group include, but are not limited to, a phenyl group, a 1-naphthyl group, a 2-naphthyl group, an indenyl group, a biphenylyl group, an anthryl group, and a phenanthryl group. In this specification, "C7 to C 30 The alkylaryl group is a C7-C 12 An alkylaryl group is preferred. Examples of the alkylaryl group include, but are not limited to, an o-tolyl group, a m-tolyl group, a p-tolyl group, a 2,3-xylyl group, a 2,4-xylyl group, a 2,5-xylyl group, an o-cumenyl group, a m-cumenyl group, a p-cumenyl group, and a mesityl group. In this specification, "C7 to C 30 Arylalkyl groups are C7 to C 12 An arylalkyl group is preferred. Examples of the arylalkyl group include, but are not limited to, a benzyl group, a phenethyl group, a diphenylmethyl group, a triphenylmethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 2,2-diphenylethyl group, a 3-phenylpropyl group, a 4-phenylbutyl group, and a 5-phenylpentyl group. In this specification, "C4 to C 30 Cycloalkyl groups are C4 to C 10 A cycloalkyl group is preferred. Examples of the cycloalkyl group include, but are not limited to, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. In this specification, "C4 to C 30 The cycloalkenyl group is a C4-C 10A cycloalkenyl group is preferred. Examples of the cycloalkenyl group include, but are not limited to, a cyclopropenyl group, a cyclobutenyl group, a cyclopentenyl group, and a cyclohexenyl group.

[0017] The present inventors came up with the idea of ​​using the fullerene derivative molecule represented by the above formula (1) to prepare a highly tough thin film without a cleavage plane, since the molecule exhibits the properties of an isotropic amorphous particle, and they thought that by introducing a hydrogen bonding site into the molecule, an association form in which two molecules face each other via hydrogen bonds can be induced, thereby promoting the formation of a bilayer film. More specifically, in this embodiment, the fullerene derivative molecule has five substituents R at predetermined positions. 1 In addition to the structure having the formula (I), at least one of the substituents has a hydrogen-bonding group, so that the fullerene derivative molecules do not associate one-to-one with each other, but rather one fullerene derivative molecule (a molecule constituting the first monolayer) associates with at least two fullerene derivative molecules (molecules constituting the second monolayer) in a manner that interacts (hydrogen bonds) with them, forming a uniform bilayer structure with in-plane expansion. It is believed that this structure provides stability to the extent that self-supporting properties are ensured. However, the mechanism of action of this embodiment is not intended to be limited to the above-described content.

[0018] In this embodiment, from the viewpoint of further enhancing the stability of the film structure, it is preferable that at least one hydrogen-bonding group on the first monolayer side is oriented toward at least one hydrogen-bonding group on the second monolayer side. Such a structure can be confirmed, for example, by the method described in the Examples below, and such a structure tends to be obtained by employing the preferred manufacturing method described below. From the same viewpoint as above, it is particularly preferable that the fullerene derivative molecule is represented by the following formula (A) or (B). [ka] [ka]

[0019] In this embodiment, from the viewpoint of producing a thin film with a uniform thickness, the thickness of the polymolecular film is preferably 3 to 90 nm, more preferably 3 to 15 nm, and even more preferably 3 to 9 nm. The above-mentioned film thickness can be measured, for example, based on the method described in the Examples below, and can be adjusted to fall within the above-mentioned range by employing the preferred manufacturing method described below.

[0020] The multilayer film of this embodiment can be chemically modified, and the fullerene derivative molecules constituting each monolayer are R 1 and R 2 The functional group derived from chemical modification may have a functional group derived from chemical modification at a position other than the position indicated by the arrow. Examples of the functional group derived from chemical modification include, but are not limited to, a hydroxyl group, a carboxylic acid group, an amino group, an epoxy group, an alkyl group, an aryl group, and an alkoxy group. In addition to the above, the functional group derived from chemical modification may also be a group derived from a surfactant, which will be described later.

[0021] The multilayer film of this embodiment may be one in which the fullerene derivative molecules constituting each monolayer are polymerized by subsequent polymerization. That is, the fullerene derivative molecules constituting each monolayer may be polymerized together by the R 1 and R 2 The polymolecular film may be covalently linked at any position other than the position indicated by the arrow. Such a polymolecular film tends to have improved durability when exposed to an organic solvent for a long period of time.

[0022] The multilayer film of this embodiment can be chemically modified and is easy to handle, making it suitable for use in many fields, including analytical science, sensing, and semiconductors. Furthermore, since the multilayer film of this embodiment has a structure derived from fullerene, it can be endowed with properties unique to fullerenes, such as mechanical strength and flexibility. For example, it can be preferably used as an amorphous, ultrathin support film. More specifically, as a support film for electron microscopy, atomic resolution transmission electron microscopes and scanning electron microscopes, it can be applied to cryo-electron microscopy. Among these, as a support film for cryo-electron microscopy, the ease of chemical modification of multilayer films allows the molecular orientation of proteins to be appropriately changed. By combining data obtained using various modified films (multilayer films obtained by chemical modification), single-particle analysis data with little orientation bias can be obtained. This accelerates the analysis of protein-drug complexes and is expected to be useful in the pharmaceutical field. The multilayer film of this embodiment has a surface area of ​​10 nanometers per square meter. 10 It is possible to achieve such stability that no changes in the membrane structure are observed even when irradiated with an electron beam (100,000 times the electron beam dose used in conventional cryo-electron microscopy). Furthermore, proton conductivity is another property derived from fullerenes, and since a water channel can exist between the first monolayer and the second monolayer in the multilayer membrane of this embodiment, it can be preferably used as a hydrogen ion conductor. That is, as a hydrogen ion conductive nanosheet with high hydrogen ion conductivity, it can be used particularly in fields such as oxygen-hydrogen fuel cells, electrolytes for water electrolysis, solid electrolyte sensors such as hydrogen sensors, solid electrolytes for all-solid-state nickel-hydrogen batteries, electrodialysis membranes, and electrochemical devices. Furthermore, because the fullerene moieties in the multilayer film function as an insulating film and have hydrogen ion conducting sites within the film, it can be used as a device that operates in water. Specifically, it can be used as a sensor for biomolecules and ions, an electrode, or a humidity meter that operates in high-humidity environments.

[0023] The multilayer film of this embodiment can be transferred to various substrates to form a laminate of the substrate and the multilayer film. That is, the laminate of this embodiment includes a substrate and the multilayer film of this embodiment disposed on the substrate. As described above, the multilayer film of this embodiment can be preferably used as an electron microscope component, and therefore, in the laminate of this embodiment, the substrate is preferably an electron microscope component. More preferably, the substrate is a cryo-electron microscope component, and in this case, the multilayer film of this embodiment functions as a support membrane for cryo-electron microscope observation.

[0024] As described above, the multilayer film of this embodiment can provide various effects, including, but not limited to, the following (i) to (iv): (i) It can be used as a flexible hydrogen ion conducting membrane made of organic molecules. (ii) Because fullerenes have extremely low water permeability, they can be used as liquid cells for electron microscope observations by sandwiching a water layer between membranes. (iii) Because the surface can be modified with appropriately designed molecules, by modifying the surface with ligands, it is possible to selectively capture the target protein from a mixture such as cell lysate, and data can be obtained without purification procedures that may cause structural changes in the protein. (iv) The increased mechanical strength of the amorphous ice film that embeds the object to be observed in a cryo-electron microscope significantly reduces the radiation damage caused by the electron beam compared to water or ice.

[0025] [Method of manufacturing multi-molecular film] The method for producing the polymolecular film of the present embodiment is not limited as long as the above-described structure can be obtained. A preferred production method includes the steps of dropping a mixed solution of the fullerene derivative molecules, toluene, and n-butanol into water, and forming the polymolecular film in the mixed system of the mixed solution and water.

[0026] In this embodiment, fullerene derivative molecules can be dissolved in a mixed solvent of toluene and n-butanol to prepare a mixed solution. By adding this mixed solvent dropwise to water, the multilayer film is formed in the mixed system of the mixed solution and water. It is believed that the n-butanol gradually migrates toward the aqueous phase, which makes it easier for the fullerene derivative molecules to assume the desired orientation. Therefore, the multilayer film of this embodiment tends to be obtained efficiently and uniformly. However, the mechanism of action of this embodiment is not intended to be limited to the above-described mechanism.

[0027] As described above, a multimolecular film is formed by dropping the mixed solvent into water. The production system may be left at room temperature and pressure. By doing so, toluene and n-butanol are gradually evaporated naturally, exposing the multimolecular film on the water surface. After the multimolecular film is obtained in this manner, it can be removed by various methods. For example, the multimolecular film formed on the water surface can be transferred to the surface of the substrate by contacting it with a desired substrate. The removed multimolecular film may then be dried. In this manner, a laminate of a substrate and a multimolecular film can be obtained. Furthermore, the number of multimolecular film layers in the laminate can be appropriately increased by contacting the multimolecular film side of the laminate with a separately prepared multimolecular film on the water surface and transferring it. Here, the additional monomolecular layer disposed on the surface of the first monomolecular layer and / or the second monomolecular layer is thought to be integrated due to the influence of van der Waals forces and π-π interactions between two fullerene molecules. Although van der Waals forces and π-π interactions are present between two fullerene molecules in conventional techniques, the lack of overall molecular orientation, as in the present invention, makes it unlikely that these interactions will be the dominant factor in film formation, and thus makes it impossible to form a freestanding film. In other words, in this embodiment, the fullerene derivative molecules are appropriately oriented, which makes the effects of van der Waals forces and π-π stacking more pronounced, resulting in the realization of a stable freestanding film overall, even in a structure with more than two layers. However, the mechanism of action of this embodiment is not intended to be limited to the above.

[0028] In this embodiment, from the viewpoint of uniformity of the resulting multimolecular film, the mass ratio of toluene to n-butanol in the mixed solution is preferably 1 / 100 to 10 / 1, more preferably 1 / 1 to 5 / 1, and even more preferably 2 / 1 to 4 / 1, as toluene / n-butanol.

[0029] The thickness of the multilayer film of this embodiment, i.e., the number of layers contained in the multilayer film, can be adjusted by the concentration of the fullerene derivative molecules in the mixed solution. In this embodiment, from the viewpoint of controlling the absolute value and uniformity of the film thickness, the concentration of the fullerene derivative molecules in the mixed solution is preferably 1 μM to 10 mM, more preferably 5 to 300 μM, and even more preferably 15 to 60 μM.

[0030] In this embodiment, the fullerene derivative molecule itself can be synthesized by the methods described in Japanese Patent Nos. 5,062,765 and 5,062,766, for example.

[0031] The multilayer film of this embodiment can be chemically modified, and for example, after each monolayer is formed, it can be subjected to various chemical modifications. Methods of chemical modification include, but are not limited to, hydrophilization treatment such as plasma treatment, and surface treatment with a surfactant. Various known surfactants can be used, including cationic surfactants, anionic surfactants, zwitterionic surfactants, and nonionic surfactants. These surfactants may also contain hydrophilic groups such as ether chains or hydroxyl groups. Specific examples include, but are not limited to, polyoxyethylene sorbitan monolaurate (also referred to as "Tween 20"), lauryl sulfobetaine (also referred to as "LS"), and 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (also referred to as "CHAPS"). Other surfactants include polystyrene sulfonic acid (also referred to as "PSS"), α-poly-L-lysine (also referred to as "PLL"), γ-cyclodextrin (also referred to as "γ-CD"), and 1-sodium pyrenecarboxylate (also referred to as "Py-CO2Na"). The multilayer membrane of this embodiment can also be surface-modified below the critical micelle concentration of the surfactant.

[0032] The multilayer film of this embodiment can be polymerized afterward, for example, after each monolayer is formed. Polymerization methods include, but are not limited to, photopolymerization by ultraviolet irradiation, polymerization by electron beam irradiation, radical polymerization with the addition of a radical initiator, and copolymerization with the addition of a crosslinker molecule.

[0033] The method for producing a multilayer film according to this embodiment can achieve various effects, including, but not limited to, the following (v) to (ix): (v) The thickness of the multilayer film can be easily adjusted from about 3 nanometers to about 12 micrometers by changing the concentration of the fullerene derivative molecules in the mixed solution. When used for electron microscopy, the thickness can be adjusted to an optimum value depending on the observation purpose. (vi) It is possible to prepare multilayer films with a diameter of 10 cm at the air-liquid interface, and when used for electron microscopy, it is possible to simultaneously prepare more than 100 grid samples. (vii) When using the fullerene derivative as a support film for cryo-electron microscopy, it is theoretically possible to produce 1 million support films from 1 mg of fullerene derivative molecules. (viii) When using the support membrane for cryo-electron microscopy, no special equipment or facilities are required for the preparation of the support membrane, so it is possible to prepare a new support membrane under any experimental environment. (ix) It is also possible to prepare a porous support membrane with nanometer- to micrometer-sized pores by mixing a different type of molecule (heterogeneous molecule) from fullerene derivative molecules into a mixed solution, forming a multilayer film using the same procedure as for fullerene derivative molecules alone, and then immersing it in a solvent that selectively dissolves only one of the compounds. By using such a membrane to support amorphous ice films, which are used as embedding materials for samples in cryo-electron microscopy, within the pores, it is expected that high-resolution structural analysis will be possible. [Example]

[0034] Hereinafter, the present embodiment will be described in more detail with reference to specific examples and comparative examples. However, the present embodiment is not limited to these examples and comparative examples as long as they do not depart from the gist of the present invention.

[0035] The various reagents and evaluations used in the examples were as follows unless otherwise specified.

[0036] Anhydrous ether solvents (without stabilizers) were purchased from Kanto Chemical Co., Inc. and purified before use using a solvent purification apparatus (GlassContour) equipped with an activated alumina column. The organic solvent used for the film formation step was of HPLC grade. The water used was ultrapure water obtained by further purifying distilled water with Millipore Milli-Q. The mica plates used were purchased from Nisshin EM Co., Ltd. Cu mesh grids precoated with lacey carbon film (NS-C15) and copper grids (Cu G-600HSS) were purchased from Oken Shoji Co., Ltd. Cu mesh grids precoated with holey carbon film (Quantifoil R1.2 / 1.3 Cu 300 mesh grids, Quantifoil R1.2 / 1.3 Cu 400 mesh grids, Quantifoil R2 / 2 Cu 300 mesh grids, and Quantifoil R2 / 2 Cu 400 mesh grids) were purchased from Quantifoil Micro Tools GmbH.

[0037] Various evaluations in the examples were carried out by the following methods unless otherwise specified. Scanning electron microscope (SEM) and scanning transmission electron microscope (STEM) observations were performed using an FEI Magellan 400L equipped with a retractable STEM detector with BF / DF / HAADF segments. Optical microscope observation was performed using an Olympus BX51. Transmission electron microscope (TEM) observation was performed using a JEOL JEM-ARM200F. For differential scanning calorimetry (DSC), a NETZSCH DSC 204 F1 / LM Phoenix was used. UV-visible reflectance measurements and spectral simulations by microspectroscopy were performed using a Techno-Synergy Microspectroscopy System DF-1037 and a W. Theiss Hard- and Software SCOUT. The contact angle was measured using a DM-301 manufactured by Kyowa Interface Science Co., Ltd. Infrared spectroscopy of the powder samples was performed at 25°C using a JASCO FT / IR-6100 equipped with an ATR attachment, and infrared spectroscopy of the film samples was performed at 25°C using a ThermoFisher Nicolet iS-50 FT-IR. Hydrophilization by plasma treatment was carried out using PIB-10 manufactured by Vacuum Devices Co., Ltd.

[0038] <Preparation of multilayers> [Example 1] According to the examples of Japanese Patent No. 5062765, a fullerene derivative molecule A represented by the following formula (A) was synthesized. [ka]

[0039] Next, the following procedure was carried out in a windless room set at 25°C. First, 2.0 mg of the fullerene derivative molecule A obtained above was weighed and dissolved in 25 mL of n-butanol, and 75 mL of toluene was added to prepare a 15 μM solution of fullerene derivative molecule A (the volume ratio of the solvents was 3 / 1 as toluene / n-butanol; hereinafter referred to as "solution A1"). Then, 80 mL of ultrapure water was placed in a glass Petri dish (inner diameter 10 cm) placed in a glass desiccator (inner diameter 30 cm), and solution A1 (1 mL) was gently dropped onto the water surface. The desiccator was left standing for 2 hours with the lid half-open to evaporate the organic solvent, resulting in a multilayer film on the water surface. The average film thickness was determined to be 3.0 nm by AFM measurement, which will be described later.

[0040] [Example 2] A 30 μM solution of fullerene derivative molecule A (solvent volume ratio of toluene / n-butanol: 3 / 1; hereinafter referred to as “solution A2”) was prepared in the same manner as in Example 1, except that 4.0 mg of fullerene derivative molecule A was used. A multilayer film was obtained in the same manner as in Example 1, except that solution A2 was used instead of solution A1. As a result of AFM measurement carried out in the same manner as in Example 1, the average film thickness was determined to be 6.0 nm.

[0041] [Example 3] A 45 μM solution of fullerene derivative molecule A (solvent volume ratio of toluene / n-butanol: 3 / 1; hereinafter referred to as “solution A3”) was prepared in the same manner as in Example 1, except that 6.0 mg of fullerene derivative molecule A was used. A multilayer film was obtained in the same manner as in Example 1, except that solution A3 was used instead of solution A1. As a result of AFM measurement carried out in the same manner as in Example 1, the average film thickness was found to be 8.9 nm.

[0042] [Example 4] According to the examples of Japanese Patent No. 5062766, a fullerene derivative molecule B represented by the following formula (B) was synthesized. [ka]

[0043] Next, the following procedure was carried out in a windless room set at 25°C. First, 1.44 mg of the fullerene derivative molecule B obtained above was weighed and dissolved in 10 mL of n-butanol, and 30 mL of toluene was added to prepare a 25 μM solution of fullerene derivative molecule B (the volume ratio of the solvents was 3 / 1, as toluene / n-butanol; hereinafter referred to as "solution B1"). Then, 80 mL of ultrapure water was placed in a glass Petri dish (inner diameter 10 cm) placed in a glass desiccator (inner diameter 30 cm), and solution B1 (1 mL) was gently dropped onto the water surface. The desiccator was left standing for 2 hours with the lid half-open to evaporate the organic solvent, resulting in a multilayer film on the water surface. As a result of AFM measurement carried out in the same manner as in Example 1, the average film thickness was found to be 7.1 nm.

[0044] <Film thickness measurement> Each of the multimolecular films prepared in Examples 1 to 4 was transferred onto a clean mica substrate surface prepared by peeling with Scotch tape. The multilayer film prepared in Example 1 was observed with an atomic force microscope (AFM), and the thickness measured from a crack approximately 1 μm wide was 3.0 nm. A uniformly flat structure was observed throughout the sample, and the roughness (root-mean-square height) was measured to be 0.6 nm. Figure 1 shows an AFM image. The AFM measurements were performed using a Bruker Multimode 8 equipped with a silicon nitride cantilever (SCANASYST-AIR). The molecular height (vertical height of the molecule) of fullerene derivative molecule A was determined to be 1.5 nm from the molecular model, confirming that the multilayer film had a bilayer structure. A structural model of the multilayer film is shown in Figure 2. The left side of Figure 2(A) shows that one multilayer film with a thickness of 3 μm corresponds to a bilayer film, and the center of Figure 2(A) shows that two multilayer films are stacked to form a 6 μm film. The left side of Figure 2(A) is a model diagram of the bilayer film structure, simply illustrating how the spherical fullerene moieties associate via hydrogen-bonding groups. Figure 2(B) shows a molecular model diagram of the bilayer film structure. The thicknesses of the multilayer films prepared in Examples 2 and 3 were determined to be 6.0 nm and 8.9 nm, respectively (see Figure 1). This indicates that the multilayer film is formed using bilayer films as building blocks.

[0045] <Confirming self-supporting ability> A Cu mesh grid (Quantifoil R2 / 2, Cu 300 mesh grid) precoated with a perforated carbon film was slowly placed on top of the multimolecular film obtained on the water surface in Example 1, with the carbon-coated surface facing downward, and allowed to float on the water surface. Release paper was then placed on top of the Cu mesh grid, allowing the Cu mesh grid to adhere. The Cu mesh grid was then peeled from the water and dried at 25°C under atmospheric pressure for 12 hours, transferring the multimolecular film to the Cu mesh grid. SEM observation revealed that the multimolecular film maintained its shape even on the Cu mesh grid (see Figure 3). The same procedure was carried out for Examples 2 to 4, and the multimolecular films in all cases maintained their film shape on the Cu mesh grid. An SEM photograph corresponding to Example 4 is shown in FIG. All of the multilayer films had an aspect ratio of the thickness direction size to the plane direction size of over 100, and therefore were evaluated as having self-supporting properties.

[0046] <Preparation of laminate> [Example 5] The stack was fabricated using the scheme shown in Figure 5. The bottom of a 13 cm inner diameter Buchner funnel 1 was sealed with a septum 2, and a 12.7 cm (5 inch) or 10.2 cm (4 inch) diameter silicon wafer 3 with a SiO2 oxide film was placed inside the funnel 2. A filter holder (7 cm inner diameter) for membrane filtration (apparatus 4) was attached with wire legs 2 mm high on all four sides, and the center of apparatus 4 was aligned with the center of silicon wafer 3. 400 mL of ultrapure water 5 was added to the funnel 1 until the water level reached approximately 1 cm above the silicon wafer 3. 0.50 mL of a 15 μM PCA solution (toluene / n-butanol = 3 / 1) was slowly dripped onto the inside of apparatus 4, and the entire system was covered with a plastic bag. After leaving it to stand for 8 hours, it was confirmed that a multimolecular film 6 had formed on the water surface, and a syringe needle 7 was inserted into the septum 2 from below to remove the water 5 in the direction of arrow α over 1 to 2 hours, followed by drying at 25°C under atmospheric pressure for 12 hours to transfer the multimolecular film 6 onto the silicon wafer 3. In this way, a laminate of a silicon wafer substrate and a multimolecular film was obtained. A silicon substrate (diameter 12.7 cm) with an oxide film of 290 nm thickness was used as the silicon wafer 3. A photograph of the multilayer film transferred onto the substrate is shown in FIG. 6, and a silicon substrate (diameter 10.2 cm) with an oxide film of 160 nm thickness was used. A photograph of the fullerene molecular film transferred onto the substrate is shown in FIG. 7.

[0047] [Example 6] A multilayer film was prepared on the water surface according to Example 2. A 3 mm diameter copper grid (Cu G-600HSS) was slowly placed on the multilayer film on the water surface with the carbon-coated surface facing downwards, and allowed to float on the water surface. Release paper was then placed on the copper grid to allow the copper grid to adhere. The copper grid was then peeled off from the water and dried at 25°C under atmospheric pressure for 12 hours, transferring the multilayer film to the copper grid. In this way, a laminate of a copper grid and a multilayer film was obtained. Figure 8 shows an optical microscope image of a 6-nm multilayer film transferred onto a copper grid (a mesh with 40-μm square holes). The multilayer film is supported freestanding on 90% of the holes (aspect ratio of the film surface direction to the film thickness direction: 8300), demonstrating the structural rigidity of the multilayer film.

[0048] As shown in Examples 5 and 6, it was demonstrated that the multimolecular film of this embodiment can be transferred to various substrates and can be formed into laminates with these substrates. In other words, the self-supporting properties on various substrates were confirmed.

[0049] <Chemical modification of multilayers> [Example 7] The 3.0 nm thick multilayer film prepared in Example 1 was transferred onto an electron microscope grid (Quantifoil R1.2 / 1.3, Cu 300 mesh grid) in the same manner as in Example 6 to obtain a laminate of the electron microscope grid and multilayer film. The surface of this laminate facing the multilayer film was subjected to plasma treatment by glow discharge (500 V, 10 mA, 30 seconds), thereby introducing hydroxyl groups and carboxyl groups into the surface of the fullerene moiety in the multilayer film.

[0050] [Example 8] A laminate was prepared in the same manner as in Example 7, and the multilayer film was chemically modified according to the scheme shown in Figure 9. Specifically, 5 μL of a 0.1% by mass aqueous solution of the surfactant shown in Figures 10 and 11 was placed on the multilayer surface of a laminate of an electron microscope grid and an (unmodified) multilayer film. After standing for 2 minutes at 25°C, the solution was blotted and removed using a thin piece of filter paper. The film was left to dry at 25°C under atmospheric pressure for 2 hours, and the stability of the film was evaluated by STEM observation.

[0051] [Example 9] The electron microscope grid (Quantifoil R1.2 / 1.3, Cu 300 mesh grid) with the 3.0 nm thick multilayer film prepared in Example 1 transferred thereto was attached to Teflon tape and loosely attached to the surface of a 500 mL glass jacket containing a high-pressure mercury lamp (400 W) so as not to deform the electron microscope grid. The multilayer film side was then irradiated with ultraviolet light for 2 hours. The degree of improvement in stability due to photopolymerization of the multilayer film was evaluated using the solvent durability test described below.

[0052] As shown in Examples 7 to 9, a multimolecular film comprising a first monomolecular layer and a second monomolecular layer disposed on the first monomolecular layer, wherein the first monomolecular layer and the second monomolecular layer have a structure derived from a predetermined fullerene derivative molecule, can be chemically modified on any substrate. The multimolecular film of Example 4 also has a structure similar to that of Example 1, etc., and can be chemically modified in the same manner as in Examples 7 to 9.

[0053] <Structural analysis of multilayers> [Example 10] For the silicon wafer with an SiO2 oxide film having a diameter of 10.2 cm used in Example 5, the reflectance was measured at 10 points within a 60 μm diameter area on the surface, and the thickness of the oxide film was determined to be 160.5 nm by fitting the spectrum. In the laminate of the silicon wafer and the multilayer film obtained in Example 5 (see FIG. 7), the area occupied by the multilayer film (transfer area) was 29 cm 2was obtained. Reflectance measurements were then carried out at six points on the surface on the multilayer film side (see Figure 12). In Figure 12, the positions of the numbers written correspond to measurement points 1 to 6. As shown in Figure 13, the reflection spectra of measurement points 1 to 6 were confirmed to match, suggesting the uniformity of the multilayer film. When the film thickness of one of the measurement points was set to 3.0 nm, which is the film thickness value obtained by AFM measurement described below, and the film thickness of the other measurement points was estimated by simulation, the average film thickness of the multilayer film was 3.2 nm, indicating the uniformity of the film thickness.

[0054] [Example 11] When the laminate of the silicon wafer with a 10.2 cm diameter and 160 nm thick SiO2 oxide film and the multilayer film obtained in Example 5 was observed, the multilayer film was visually recognized as a difference in color tone (see Figure 6). In Figure 6(A), the area where the multilayer film was formed is enclosed by a dashed line, which is shown in Figure 6(B). The area was measured from this optical image, and calculations were made based on the bilayer film structure using the amount of fullerene derivative molecule A used in the synthesis (15 μM, 0.5 mL). As a result, the occupied area per molecule (the area occupied in the horizontal direction of the molecule) was 1.32 nm 2 was asked.

[0055] [Example 12] The laminate of the silicon wafer with a 12.7 cm diameter and 290 nm thick SiO2 oxide film and the multilayer film obtained in Example 5 was observed from the top view of the multilayer film. Specifically, by observing the multilayer film transferred onto the silicon wafer using a scanning electron microscope, images showing a clear contrast difference between the silicon wafer substrate and the multilayer film were obtained. The acceleration voltage was 500 V and the current was 6.3 μA. Images of the multilayer film on the substrate were acquired at 1.0 mm and 1.2 mm intervals in the vertical and horizontal directions, respectively, revealing a nearly uniform distribution of the multilayer film over an area measuring 6.80 cm in length and 6.72 cm in width. SEM images of the central portion of these multilayer films are shown on the left side of Figure 14. SEM images of the peripheral portion of the multilayer film are shown on the right side of Figure 14.

[0056] [Example 13] The 3.0 nm thick multilayer film prepared in Example 1 was transferred to a Cu mesh grid precoated with a lacey carbon film (NS-C15) so as to uniformly cover it, as in Example 6, to obtain a laminate of the Cu mesh grid and multilayer film. The results of STEM observation are shown in Figure 15. In STEM observation, the Cu mesh grid was used as a support to confirm the self-supporting nature of the multilayer film. Figure 16 shows a high-resolution TEM image. The absence of a periodic pattern in the TEM image confirmed that the multilayer film was amorphous. Furthermore, at the cleft in the multilayer film indicated by the arrow in Figure 15, a spherical molecular image with a diameter of 1 nm corresponding to a single fullerene derivative molecule A was captured (see the arrow in the photograph on the right side of Figure 16). This spherical molecular image is thought to correspond to the fullerene moiety in the fullerene derivative molecule A. This multilayer film was observed using an electron beam with an accelerating voltage of 0.5-200 kV and 10 10 electron / nm 2 It showed excellent stability even under such a large amount of electron beam irradiation.

[0057] [Example 14-1] The multilayer film obtained in Example 1 was used as a target, and the contact angle of water was measured on a Cu mesh grid precoated with a lacey carbon film (NS-C15). As shown in Figure 17, the edge of the multilayer film formed on the water surface was pinched and scooped up, and the contact angles of the surfaces that would become the upper and lower surfaces when the film was formed on the water surface were measured. As a result, the contact angle of the upper surface was 113°, and the contact angle of the lower surface was 106°. These values ​​are close to the contact angle value (98±3°) reported for fullerene self-assembled films, and this result indicates that C of fullerene derivative molecule A was present on both sides of the multilayer film. 60 The figure shows that the part is presented.

[0058] [Example 14-2] The plasma-treated multilayer film obtained in Example 7 was measured in the same manner as in Example 14-1, and the water contact angle of the multilayer film surface was found to be 3.7°, indicating extremely high hydrophilicity (see Figure 18). This result indicates that the mechanical robustness of the multilayer film is derived from intermolecular hydrogen bonds within the film, and that functionalization of the fullerene moieties by glow discharge does not affect the intermolecular interactions that maintain the self-supporting properties of the fullerene film.

[0059] [Example 14-3] Measurements were performed in the same manner as in Example 14-1 for each of the surfactant-modified multilayer films prepared in Example 8. The water contact angle of the multilayer film surface decreased, indicating improved hydrophilicity (see Figures 10 and 11). These results indicate that the multilayer film surface was modified with these surfactants, presenting hydrophilic groups on the multilayer film surface. Furthermore, the mechanical robustness of the multilayer film is derived from intermolecular hydrogen bonds within the film, indicating that surfactant modification of the film surface does not affect the intermolecular interactions that maintain the self-supporting properties of the fullerene film.

[0060] [Example 15] The 8.9 nm thick multilayer film (first multilayer film) prepared in Example 3 was scooped up on a 2 cm square glass slide and dried at room temperature in air for 2 hours. Next, a 8.9 nm thick multilayer film (second multilayer film) was prepared separately on water in the same manner as above. The slide glass was manipulated so that the first multilayer film, which had been transferred earlier, was in contact with the second multilayer film on the water, and the second multilayer film was scooped up and dried at room temperature in air for 2 hours. This process was repeated until 10 multilayer films were stacked on the slide glass, resulting in a 90 nm thick multilayer film. The slide glass onto which the multilayer film had been transferred was attached to the prism of the ATR attachment, and infrared spectroscopy was performed. The results are shown in Figure 19. 2900-3500 cm -1 In the region of the OH stretching vibration originating from hydrogen-bonded water molecules was observed, indicating that water molecules and carboxylic acids form a hydrogen-bonded network structure within the multilayer film.

[0061] [Example 16] The 6.0 nm thick multilayer film prepared in Example 2 was transferred to a Cu mesh grid (Quantifoil R2 / 2, Cu 300 mesh grid) precoated with a holey carbon film. STEM observation confirmed that 99% or more of the holes in the Cu mesh grid were covered with the multilayer film. The multilayer film was immersed in 10 mL of perfluorohexane (solvent) and left at 25°C for 30 minutes. The grid was then removed from the solvent and dried at 65 Pa for 2 hours. The number of holes in each metal frame that showed no loss, peeling, or detachment of the multilayer film was determined by STEM observation. The results are shown in Table 1. The multilayer film was also immersed in the nine organic solvents listed in Table 1 in the same manner as above, and the results are also shown in Table 1. The storage rate of the multilayer film photopolymerized by UV irradiation as described in Example 9 was also determined in the same manner as above, using ethanol or methanol as the solvent. The results are shown in Table 2. UV irradiation caused the molecules constituting the multilayer film to be linked together by covalent bonds, improving physical stability.

[0062] [Table 1]

[0063] [Table 2]

[0064] [Comparative Example 1] The formation of a multilayer film was attempted in the same manner as in Example 2, except that the same volume of methanol was used instead of n-butanol. As a result, the film-like substance formed on the water surface was transferred to a mesh grid as in Example 6, and an electron microscope image was obtained. A heterogeneous structure in which fullerene derivative molecules A were aggregated was observed (see FIG. 20), and the formation of a homogeneous film was not confirmed. That is, in the film-like substance obtained in Comparative Example 1, no structure including a first monolayer and a second monolayer disposed on the first monolayer was observed, and it was evaluated as lacking self-supporting properties and difficult to chemically modify. Furthermore, when the obtained laminate was subjected to a storage rate measurement similar to that in Example 17, the storage rate was 5% or less in all of the 10 organic solvents listed in Table 1.

[0065] Comparative Example 2 Fullerene derivative molecule C represented by the following formula (C) was synthesized according to the examples of Japanese Patent No. 5062765. An attempt was made to form a multimolecular film in the same manner as in Example 2, except that the same amount of fullerene derivative molecule C was used instead of fullerene derivative molecule A. However, when the organic solvent was evaporated, fullerene derivative molecule C precipitated as a lumpy solid, and no film was confirmed to be formed on the water surface. That is, in the film-like material obtained in Comparative Example 2, no structure including a first monolayer and a second monolayer disposed on the first monolayer was observed, and it was evaluated as lacking self-supporting properties and difficult to chemically modify. [ka]

Claims

1. a first monolayer; and a second monolayer disposed on the first monolayer; and A multilayer film comprising: The multimolecular film, wherein the first monomolecular layer and the second monomolecular layer have a structure derived from a fullerene derivative molecule represented by the following formula (1): 【Chemistry 1】 (In formula (1), R 1 are each independently an organic group having a hydrogen-bonding group, and R 2 is a hydrogen atom, a C 1 ~C 10 represents a hydrocarbon group or a metallocene group.

2. 2. The multilayer film according to claim 1, wherein at least one hydrogen-bonding group on the first monolayer is oriented toward at least one hydrogen-bonding group on the second monolayer.

3. 3. The multilayer film according to claim 1, wherein the fullerene derivative molecule is represented by the following formula (A): 【Chemistry 2】

4. 3. The multilayer film according to claim 1, wherein the fullerene derivative molecule is represented by the following formula (B): 【Transformation 3】

5. The multilayer film according to any one of claims 1 to 4, wherein the thickness of the multilayer film is 3 to 90 nm.

6. A method for producing a multilayer film according to any one of claims 1 to 4, A method for producing a polymolecular film, comprising the steps of: adding dropwise a mixed solution of the fullerene derivative molecules, toluene, and n-butanol to water; and forming the polymolecular film in a mixed system of the mixed solution and water.

7. 7. The method for producing a multilayer film according to claim 6, wherein the concentration of the fullerene derivative molecules in the mixed solution is 1 μM to 10 mM.

8. 8. The method for producing a polymolecular film according to claim 6, wherein the volume ratio of toluene to n-butanol in the mixed solution is 1 / 100 to 10 / 1, in terms of toluene / n-butanol.

9. A substrate; The multilayer film according to any one of claims 1 to 4, which is disposed on the substrate; A laminate comprising:

10. The laminate according to claim 9 , wherein the substrate is a member for an electron microscope.

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