JP4727287B2 - Molecular control method - Google Patents

Description

The present invention relates to a technique for controlling molecular conformation , and more particularly, to a molecular control method using a molecular adsorption material.

Various methods for controlling molecules have been studied. As a method for controlling the position and orientation of molecules, Non-Patent Document 1 discloses a method of manipulating molecules and molecular assemblies (particles) with optical tweezers using laser light, and Non-Patent Document 2 discloses scanning. A method of moving atoms and molecules with an end needle of a scanning microprobe microscope is disclosed.
Non-Patent Document 3 describes a technique for adsorbing molecules in a self-organizing manner by utilizing the affinity of a molecule having a thiol group at the terminal and the two-dimensional clean surface of gold. Describes alignment control using liquid crystal molecules having a strong interaction with an electric field. Non-Patent Document 5 describes a method of synthesizing and arranging carbon nanotubes only at specific positions on a substrate using laser light.
A. Ashkin, JMDziedzic, JEBjorkholm and S. Chu, Optics Letters 11, 228 (1986) DMEigler and EKSchweizer, Nature 344, 524 (1990) MDPorter, TBBright, DLAllara and CED Chidseyi, J. Am. Chem. Soc. 109, 3559 (1987) Z.Zou and M.Clark, Phys.Rev.lett.75, 1799 (1995) PGCollins, MSArnold and P.Avouris, Science 292, 706 (2001)

  However, although the methods disclosed in Non-Patent Documents 1 and 2 can control the position and orientation of one molecule, it is difficult to control the conformation of the molecule. Further, in these methods, a plurality of molecules cannot be manipulated at the same time, and only one molecule can be manipulated. Thus, for example, when trying to align the orientation of a plurality of molecules, it is necessary to maintain the orientation of the molecule that has been manipulated until the manipulation of the other molecule is completed. It was difficult to control “order irregularity”. Also, as the number of molecules of interest increased, the control became more difficult.

  In addition, the techniques described in Non-Patent Documents 3 to 5 use a phenomenon called adsorption to control the arrangement state of molecules, but in any case, the target molecules are limited, and various molecule arrangements and The orientation could not be controlled.

  The present invention has been made in view of the above circumstances, a molecular control method capable of effectively controlling the conformation of various molecules and the arrangement state of a plurality of molecules, and the molecular adsorption used at that time. It is an object of the present invention to provide a material and a method for producing the molecular adsorption material.

In the molecular control method of the present invention, after a molecule is adsorbed on a molecular adsorbing material, the molecule is irradiated with ultraviolet light while irradiating the molecule with an electromagnetic wave having a frequency of 0.1 to 15 THz to control the conformation of the molecule. It is characterized by.
The molecular adsorbing material has periodically formed pores composed of mesopores having a pore diameter of 1 nm or more and 100 nm or less and micropores having a pore diameter of 0.2 nm or more and less than 1 nm formed on a wall of the mesopores. Is preferred.
The mesopore diameter is preferably 1 nm or more and 50 nm or less.
The molecular adsorbing materials are SiO ₂ , TiO ₂ , ZrO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , Al ₂ O ₃ , WO ₃ , SnO ₂ , HfO ₂ , SiAlO _3.5 , SiAlO _5.5. , Al ₂ TiO ₅ , ZrTiO ₄ , and SiTiO ₄ are preferably used.
Furthermore, the molecular adsorption _{material, SiO 2, SiAlO 3.5, SiAlO} 5.5, are formed from one selected from the group consisting of SiTiO _4, the proportion of the silanol groups in the entire surface functional group is 15 to 85% It is preferable to be controlled within the range.

  According to the present invention, the conformation of various molecules and the arrangement state of a plurality of molecules can be effectively controlled.

Hereinafter, the present invention will be described in detail.
In the molecular control method of the present invention, a molecule is adsorbed on a molecule adsorbing material, and then the molecule is irradiated with an electromagnetic wave (terahertz wave) having a frequency of 0.1 to 15 THz, and the molecular conformation or the plurality of molecules It controls the arrangement state (how to arrange and how to align).
A terahertz wave is an electromagnetic wave in a boundary region between light and radio waves, and has a property of transmitting plastic, wood, paper, etc. like radio waves while having a straight traveling property like light. Although the terahertz wave is an electromagnetic wave having such a specific property, it has been called “an undeveloped electromagnetic wave frequency region” because of difficulty in developing a light source, a spectroscope, a detector, and the like. However, recently, “Terahertz Imaging Spectroscopy” has been attracting attention as a living body measurement, and it can be applied to non-destructive detection technology such as drugs, atmospheric environment measurement technology, inspection of agricultural products and foods, It is expected to be used for wireless large-capacity communication.

By irradiating a molecule with terahertz waves, interactions such as van der Waals force, hydrophobic bond (hydrophobic force), electrostatic force, and hydrogen bond can be manipulated, resulting in the conformation of each molecule. Can be controlled arbitrarily. Furthermore, by applying such terahertz wave irradiation to molecules adsorbed and dispersed on the surface and pores of molecular adsorbent materials, various interactions are selectively imparted between molecules and molecular adsorbent materials. Or the interaction between them can be selectively removed, so that the conformation of each molecule can be controlled, and the arrangement state of a plurality of molecules can be controlled. For example, as specifically described in the examples, the conformation of azobenzene can be controlled, and the arrangement state of ethanol molecules can be controlled. Note that there is almost no risk of the molecule itself being destroyed or denatured by irradiation with terahertz waves.
There is no restriction | limiting in particular as a molecule | numerator used as object, Protein, DNA, an antibody, a general organic compound, etc. are mentioned.

  The molecular adsorbing material used here is a mesopore having a pore diameter of 1 nm or more and 100 nm or less, preferably 1 nm or more and 50 nm or less, and a pore diameter of 0.2 nm or more and less than 1 nm formed on the pore wall of the mesopore. What formed the micropore periodically is preferable. When such a material is used, the molecules can be dispersed in the pores without aggregating, and as a result, the conformation of each molecule and the arrangement state of a plurality of molecules can be controlled effectively. . Examples of the structure in which the mesopores and the micropores are periodically formed include a hexagonal crystal structure.

The molecular adsorbing material transmits terahertz waves, and includes SiO ₂ , TiO ₂ , ZrO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , Al ₂ O ₃ , WO ₃ , SnO ₂ , HfO ₂ , _{SiAlO 3.5, SiAlO 5.5, Al 2} TiO 5, ZrTiO 4, is preferably formed from one selected from the group consisting of SiTiO _4.
Further, the molecular adsorbing material is formed from one of these materials selected from the group consisting of SiO ₂ , SiAlO _3.5 , SiAlO _5.5 and SiTiO _4, and the ratio of silanol groups in the whole surface functional groups is 15 When the hydrophobicity / hydrophilicity is controlled by adjusting within a range of ˜85%, the molecules are efficiently introduced while being dispersed in the pores according to the degree of hydrophobicity or hydrophilicity. be able to.

As a method for producing such a molecule adsorbing material, a method using a template agent (template agent) is suitable.
As the template agent, a polymer that forms a periodic structure in a self-organized manner, for example, polyethylene oxide-polypropylene oxide-polyethylene oxide (hereinafter referred to as EO _n -PO _m -EO _n ), which is a nonionic surfactant, is described. And the like).

For example, using the _{EO n -PO} m -EO n as a template agent, in the production of molecular adsorption material consisting of SiO ₂ (silica) _is, EO _n -PO m -EO _n dilute hydrochloric acid solution of about 40 ° C. The Into this, tetraethylorthosilicate (TEOS) is added as a silica precursor, and a precipitate is deposited. Next, after the precipitate is kept in the solution at a predetermined temperature for a predetermined time, filtration, washing with water, and air drying are sequentially performed to obtain a dried precipitate. Thereafter, this is baked at about 450 ° C. for a predetermined time, whereby the template agent is removed and silica is obtained. The removal of the template agent may be performed by a method other than calcination, and examples thereof include solvent extraction and cleaning with a supercritical fluid.

  By using the template agent, the pore structure of the molecular adsorption material can be controlled. Specifically, by changing the molecular size of the template agent and its hydrophilicity / hydrophobicity, the mesopores can be arbitrarily controlled in the pore diameter range of 1 to 100 nm. Therefore, various molecules can be adsorbed by controlling the pore diameter of the mesopores according to the type of molecules adsorbed on the molecule adsorbing material. For example, in the case of a low molecular weight molecule such as benzene, it is important that the mesopore diameter is about 1 nm, and in the case of a high molecular weight molecule such as a protein, the mesopore diameter is about 50 to 100 nm. Is important. In addition, for pores with a pore diameter of 100 nm or less, the influence of scattering by visible light can be ignored. Therefore, by controlling the mesopores within the pore diameter range of 1 to 100 nm, the restriction on the handling of the molecular adsorption material should be reduced. Can do.

Moreover, as a method of adjusting the ratio of the silanol group in all the surface functional groups of a molecule | numerator adsorption material within the range of 15 to 85%, the method of adjusting the calcination temperature at the time of removing a template agent is mentioned, for example. When the firing temperature is 500 ° C. or lower, the ratio of silanol groups in all surface functional groups in the obtained molecular adsorbent material can be increased, and can be about 85%. On the other hand, as the firing temperature is increased, silanol groups are removed due to the dehydration effect and decrease to about 15% at about 900 ° C. In addition, the silanol group ratio can be adjusted by using a silane coupling agent. The silane coupling agent is generally represented by a chemical formula of R—Si—X ₃ (X is an alkoxy group such as methoxy group (—OCH ₃ )), which is a silanol group of the molecular adsorption material. By reacting with (Si—OH), this silanol group can be replaced with a (Si—OR) group. As a result, the ratio of silanol groups in all surface functional groups can be adjusted. Since the degree of substitution varies depending on the concentration of the silane coupling agent, the reaction time, and the reaction temperature, the silanol groups can be adjusted to a desired ratio by appropriately setting these conditions.

  As described above, terahertz wave irradiation is performed on molecules adsorbed and dispersed on the surface and pores of molecular adsorbent materials in particular, so that the molecular conformation and the arrangement state of multiple molecules can be effectively achieved. It becomes possible to control.

Hereinafter, the present invention will be specifically described with reference to examples.
[Example 1]
<Manufacture of molecular adsorption materials>
As a template agent, EO ₂₀ -PO ₇₀ -EO ₂₀ which is a nonionic surfactant made of a triblock copolymer was used, and a molecular adsorption material made of silica was produced as follows.
First, 3.95 g of EO ₂₀ -PO ₇₀ -EO ₂₀ was added to a diluted hydrochloric acid solution obtained by diluting 19.50 ml of hydrochloric acid having a concentration of 36% with 125 ml of water, and dissolved at 40 ° C. Next, while stirring the solution, 8.335 g of TEOS as a precursor of silica was added thereto. Next, the deposited precipitate and solution were kept at 80 ° C. for 1 day, and then filtered, washed with water, and air-dried (room temperature) in that order to obtain a dried product.
Subsequently, this dried product was calcined under mild conditions. Specifically, the temperature was raised to 450 ° C. over 8 hours, held at 450 ° C. for 6 hours, and cooled from 450 ° C. to 100 ° C. over 8 hours. Then, it returned to room temperature by natural cooling.
In this way, a molecular adsorption material made of porous silica was obtained.
This porous silica is a hexagonal crystal, in which uniform mesopores having a pore diameter of 5.5 nm and periodic micropores having a pore diameter of 0.7 nm formed in the wall of the mesopore are periodically formed. Met. Moreover, the ratio of the silanol group in all the surface functional groups was controlled to 80 to 85%.

<Conformational control of azobenzene molecule>
Next, a solution containing azobenzene was dropped onto the obtained molecular adsorbing material, and dried in the atmosphere (room temperature) to adsorb azobenzene molecules.
In the pores of the molecular adsorption material, azobenzene is physically adsorbed by hydrogen bonds between π electrons of the benzene ring and silanol groups present on the surface of the molecular adsorption material. Azobenzene has two isomers, a cis isomer and a trans isomer. Usually, the trans isomer is stable, but it is known that the cis isomer undergoes photoisomerization by irradiation with ultraviolet light, and the photoisomerized cis isomer returns to the trans isomer by irradiation with visible light.

  The molecular adsorbent material that adsorbed azobenzene molecules in this manner was irradiated with ultraviolet rays for a sufficient time while irradiating 2.5 THz electromagnetic waves, and photoisomerized into cis form. Thereafter, the 2.5 THz electromagnetic wave was cut off, and the ultraviolet irradiation was also cut off. Then, visible light was irradiated, and the state of photoisomerization from the cis form to the trans form was measured by visible absorption spectroscopy. As a result, almost no photoisomerization from the cis form to the trans form occurred, and it was found that the conformation was controlled by the cis form.

Such conformational control can be explained as follows.
That is, as shown in FIG. 1A, first, the azobenzene molecule 1 is adsorbed on the pores 3 of the molecular adsorbing material 2 in a stable trans form. Then, hydrogen bonds (shown by broken lines in the figure) are formed between the azobenzene molecules 1 and the molecular adsorbing material 2. Next, when 2.5 THz electromagnetic wave irradiation is performed on this, as shown in FIG. 1B, the hydrogen bond between the trans azobenzene molecule 1 and the molecule adsorbing material 2 is broken, and the trans azobenzene molecule 1 can move freely in the pores 3 as compared to before electromagnetic wave irradiation. Subsequently, as shown in FIG. 1C, the trans azobenzene molecule 1 is photoisomerized into a cis azobenzene molecule 1 ′ as shown in FIG. 1 (c). Thereafter, by blocking the electromagnetic wave during the irradiation of ultraviolet rays, as shown in FIG. 1 (d), the hydrogen bond between the cis azobenzene molecule 1 ′ and the molecular adsorbing material 2 is re-formed. Due to this hydrogen bond re-formation, even when visible light is irradiated thereafter, the cis azobenzene molecule 1 ′ is not photoisomerized to the trans isomer, and the conformation is cis as shown in FIG. Can be kept in the body.
As described above, according to the method of this example, it has been clarified that the molecular conformation can be controlled.

[Example 2 (reference example) ]
<Control of the alignment state of ethanol molecules>
Ethanol was dropped on the molecular adsorbing material obtained in Example 1 to adsorb ethanol molecules.
Subsequently, the molecular adsorbent material adsorbing ethanol in this way was irradiated with 2 THz electromagnetic waves, and the structural change of ethanol was observed by an infrared absorption spectrum. As a result, it was found that the ethanol molecules randomly arranged before the electromagnetic wave irradiation were in a highly ordered molecular arrangement after the electromagnetic wave irradiation.

Such control of the arrangement state of molecules can be explained as follows.
Ethanol molecules are known to have a very regular pseudocrystalline structure due to intermolecular hydrogen bonding in pores having a hydrophobic surface such as a porous carbon material (T. Ohkubo, T. Iiyama, K. Nishikawa, T. Suzuki and K Kaneko, J. Phys. Chem. B 103, 1859 (1999)).
However, as shown in FIG. 2A, in the pores 3 of the molecular adsorption material 2 having functional groups that form hydrogen bonds such as silanol groups on the surface, not only such intermolecular hydrogen bonds, Since the hydrogen bond between the ethanol molecule 4 and the silanol group also acts, the regular pseudo-crystal structure as described above is hardly formed, and the ethanol molecules 4 are randomly arranged. Therefore, when an electromagnetic wave of 2 THz is irradiated, only the hydrogen bond between the ethanol molecule 4 and the silanol group is selectively cut as shown in FIG. Thereby, as shown in FIG. 2 (c), only the intermolecular hydrogen bond acts on each ethanol molecule 4, and even in the pore 3 of the molecular adsorbing material 2 having a silanol group on the surface like silica, As in the case of the pores of the porous carbon material, each ethanol molecule 4 can be controlled to a highly ordered molecular arrangement state.
As described above, according to the method of this example, it has been clarified that the molecular arrangement state can be controlled.

It is explanatory drawing which illustrates Example 1 typically, Comprising: About the molecular adsorption material, the cross section perpendicular | vertical with respect to the length direction of a pore is shown. It is explanatory drawing which illustrates Example 2 typically, Comprising: About the molecular adsorption material, the cross section along the length direction of a pore is shown.

Explanation of symbols

2 Molecular adsorption material 3 Pore

Claims (5)

A molecular control method comprising: adsorbing a molecule to a molecule adsorbing material, and then irradiating the molecule with ultraviolet rays while irradiating the molecule with an electromagnetic wave having a frequency of 0.1 to 15 THz to control the conformation of the molecule. The molecular adsorbing material has periodically formed pores composed of mesopores having a pore diameter of 1 nm or more and 100 nm or less and micropores having a pore diameter of 0.2 nm or more and less than 1 nm formed on a wall of the mesopores. The molecular control method according to claim 1. The molecular control method according to claim 2, wherein the mesopore has a pore diameter of 1 nm or more and 50 nm or less . Wherein the molecular adsorption _{material, SiO 2, TiO 2, ZrO} 2, Nb 2 O 5, Ta 2 O 5, Al 2 O 3, WO 3, SnO 2, HfO 2, SiAlO 3.5, SiAlO 5.5, Al _4. The molecular control method according to claim 1, wherein the molecular control method is formed from one selected from the group consisting of ₂ TiO ₅ , ZrTiO ₄ , and SiTiO ₄ . The molecular adsorbing material is formed from one selected from the group consisting of SiO ₂ , SiAlO _3.5 , SiAlO _5.5 and SiTiO _4, and the ratio of silanol groups in the whole surface functional groups is in the range of 15 to 85%. The molecular control method according to claim 4, wherein the molecular control method is controlled as follows .

Images