JP2008166697A - Optical energy transfer element and artificial photosynthetic element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical energy transfer element allowing a photosystem complex to be stably retained and permitting an increase in area with high efficiency. <P>SOLUTION: An optical energy transfer element 1 has a plurality of micropores 12 inside. To a dielectric base material 11 with a plurality of micropores 12 opened at least on the surface 11s of a base material, there are fixed a plurality of micro-metal bodies 20 comprising a filling section 21 filling the inside of the micropores 12 of the dielectric base material 11 and a projecting section 22 formed on the filling section 21 to project from the surface 11s of the base material with a diameter larger than that of the filling section 21 and having the size of inducing localized plasmon. On the surface of the projecting section 22 of a plurality of micro-metal bodies 20, there is formed a photosystem complex 30 comprising an energy donor 30D and an energy acceptor 30A. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light energy transfer device including a photochemical complex composed of an energy donor and an energy acceptor, and an artificial photosynthesis device using the light energy transfer device.

  Solar energy is regarded as a promising safe and clean new energy to replace fossil fuels such as oil, and a light energy transfer element that efficiently uses solar energy is being studied. Examples include solar cells that have been studied for a long time, and photocatalysts that can directly produce hydrogen and oxygen, which are clean fuels, from sunlight and water. The energy conversion of these light energy transfer elements Efficiency is still not enough.

  Aiming at higher efficiency, research has been conducted on a light energy transfer element (artificial photosynthetic element) including a photochemical complex in which a photosynthetic function is artificially constructed, focusing on the photosynthetic function of plants. A photochemical complex includes an energy donor and an energy acceptor. In the photochemical complex, the energy acceptor receives the energy obtained by the energy donor absorbing light. Energy transfer is possible.

  Patent Documents 1 and 2 disclose a light energy transfer element (photoelectric conversion system) having a photochemical complex composed of a mixed self-assembled monolayer on the surface of a base composed of metal or semiconductor. It is described that high efficiency can be achieved by an organized monolayer.

  The photochemical complex composed of the mixed self-assembled monolayer described in Patent Documents 1 and 2 is easy to manufacture, and the light absorbed in the complex can be converted into energy with high efficiency. Is a monomolecular film of several nm, so that the absorption efficiency of incident light is extremely low.

On the other hand, Patent Document 3 discloses a photoelectric conversion element structure in which a photochemical composite is formed on an electrode on which gold nanoparticles are deposited, and has a high specific surface area and high local plasmon effect. It describes that a photochemical complex is immobilized on an electrode with a density and photoelectric conversion of incident light is performed with high efficiency.
JP 2001-303022 A JP 2002-25635 A JP 2005-259664 A

  However, in the structure in which the gold nanoparticle is deposited, since the bond between the deposited particle and the base material is weak, the particle is easily peeled off, and it is difficult to stably hold the photochemical complex. In addition, since it is difficult to deposit fine particles uniformly on the substrate surface, it is difficult to uniformly fix the photochemical complex, and it is difficult to express a uniform function over the entire surface. Since it is difficult to deposit fine particles uniformly on the substrate surface, it is difficult to increase the area.

  The present invention has been made in view of the above circumstances, and a light energy transfer element in which a photochemical complex is stably held and has high light energy transfer efficiency (photoelectric conversion efficiency), and the same are used. An object of the present invention is to provide an artificial photosynthesis device.

  Another object of the present invention is to provide a light energy transfer element that can obtain a uniform structure and can have a large area in addition to the above characteristics, and an artificial light synthesizing element using the same. Is.

The light energy transfer element of the present invention comprises a photochemical composite comprising an energy donor that absorbs light energy and supplies energy, and an energy acceptor that receives energy from the energy donor. In
A dielectric substrate having a plurality of micropores therein and having the plurality of micropores opened at least on the substrate surface,
A filled portion filled in the micropores of the dielectric substrate, and formed on the filled portion so as to protrude from the surface of the substrate, and is larger than the diameter of the filled portion and induces localized plasmon. A plurality of fine metal bodies composed of protrusions having a diameter of a possible size are fixed,
It has an element structure in which the photochemical composite is formed on the surface of the protruding portion of the plurality of fine metal bodies,
The substrate surface is irradiated with incident light including light having a wavelength that can excite localized plasmons in the protrusion and the energy donor absorbs the light energy. It is characterized by.

  In the present specification, the shape of the “dielectric substrate” is not limited and may be a dielectric substrate or a dielectric layer. The “diameter” of the filling part and the protruding part means the maximum width of each part.

  The distribution of the plurality of micropores in the dielectric substrate is preferably substantially regular.

  In this specification, “the distribution of the plurality of micropores in the dielectric base material is substantially regular” means that the diameter and pitch of the plurality of micropores are substantially the same as a whole. Specifically, it is defined that the diameter of the plurality of fine holes is within an average diameter of ± 10% and the pitch of the plurality of fine holes is within an average pitch of ± 10%.

  The light energy transfer element of the present invention may further include a conductor on the back surface of the dielectric substrate. The light energy transfer element having such a structure is a non-through hole in which the plurality of micro holes do not reach the back surface of the base material, the filling portion of the plurality of fine metal bodies, and the base material The conductors formed on the back surface are non-conductive with each other, and the plurality of fine holes are through-holes that reach the back surface of the base material, and are formed of a plurality of fine metal bodies. There is one in which the filling portion and the conductor are electrically connected to each other. In the case where the filling portions of the plurality of fine metal bodies and the conductor are electrically connected to each other, a current can be taken out using the conductor as an electrode.

  As a preferred embodiment of the dielectric substrate, a metal oxide body obtained by anodizing at least a part of a metal body to be anodized is formed, and the plurality of micropores are oxidized in the process of the anodization. Those formed in the object are listed. In the case where a conductor is provided on the back surface of the dielectric base material, the anodic oxidation is performed only on a part of the anodized metal body, and the anodized metal body remaining without being anodized is non-anodized. The portion can be the conductor.

  In the above embodiment, the metal to be anodized is preferably composed mainly of Al. In this specification, the “main component” of the anodized metal body is defined as a component having a content of 90% or more.

  In the light energy transfer element of the present invention, the fine metal body is formed by performing metal growth by plating until a part protrudes from the surface of the base material in the fine hole of the dielectric base material. It is preferable that

  In the light energy transfer element of the present invention, it is preferable that an average separation distance between the protrusions of the fine metal bodies adjacent to each other is 10 nm or less. In this specification, the “average separation distance between protrusions” is defined as the average value of the shortest separation distances between adjacent protrusions.

  A preferred embodiment of the photochemical complex includes a mixed self-assembled monolayer of the energy acceptor and the energy donor.

In the light energy transfer element of the present invention, the photochemical complex may be formed directly on the surface of the protrusion, or the protrusion may be interposed via a transparent insulator layer. It may be formed on the surface. The “transparent insulator layer” is specifically a layer composed of an inorganic substance such as SiO ₂ or an organic substance such as a polymer, and is an insulator layer that substantially transmits light irradiated on the surface of the substrate. I just need it.

  The artificial light synthesizing element of the present invention comprises the light energy transfer element of the present invention.

  The artificial photosynthetic device of the present invention can generate oxygen and / or hydrogen by decomposing water molecules in contact with the photochemical complex.

  The light energy transfer element of the present invention comprises a dielectric base material having at least a plurality of micropores opened on the surface of the base material, a filling portion filled in the micropores, and a base material surface on the filling portion. A plurality of fine metal bodies formed with protrusions and having a diameter larger than the diameter of the filling portion and having a size capable of inducing localized plasmons are fixed, and the protrusions of the plurality of fine metal bodies are fixed. A photochemical complex composed of an energy donor that absorbs light energy and supplies energy, and an energy acceptor that receives energy from the energy donor is formed on the surface.

  In such a configuration, when the substrate surface is irradiated with incident light including light having a wavelength that can excite localized plasmons at the protrusion and the energy donor absorbs light energy, Localized plasmons are induced in the protrusions of the fine metal body on the surface of which the system complex is formed, and the incident light is generated by the light confinement effect in the protrusions by the localized plasmon effect and the electric field enhancement effect in the vicinity of the protrusions. The absorption efficiency into the photochemical complex is increased, and a highly efficient light energy transfer efficiency (photoelectric conversion efficiency) is obtained.

  Moreover, since the fine metal body has a structure in which the fine metal body is partially embedded in the fine holes of the dielectric base material, the structure of Patent Document 3 in which the fine metal body is merely deposited on the dielectric base material. Compared to the above, the bond between the fine metal body and the dielectric base material is strong, and the fine metal body is less likely to peel off from the dielectric base material, so that the photochemical composite can be stably held.

  In addition, the light energy transfer element of the present invention, for example, if a plurality of micropores are formed so as to be distributed substantially uniformly in the substrate surface, the protruding portion of the fine metal body that is uniformly formed on the substrate surface Since the photochemical complex can be immobilized on the surface, a substantially uniform function can be expressed over the entire surface.

  In the present invention, even if the device area is increased, the photochemical composite can be stably held, and a substantially uniform structure can be obtained. Therefore, the area can be increased.

  In addition, when the photochemical composite is formed on the surface of the protruding portion of the fine metal body through the transparent insulator layer, direct charge transfer from the photochemical composite to the fine metal body is prevented, Energy conversion efficiency can be further improved.

“Light Energy Transfer Element of First Embodiment”
A structure of a light energy transfer element according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view in the thickness direction. 2 and 3 are diagrams showing a manufacturing process of the light energy transfer element of the present embodiment, FIG. 2 is a perspective view, and FIG. 3 is a cross-sectional view (for a view provided with a photochemical complex, FIG. It is described only in (d), and the perspective view is omitted from illustration.)

  The light energy transfer element 1 of the present embodiment absorbs the energy of the incident light L and receives energy from the energy donor (donor) 30D that supplies energy to the energy acceptor (acceptor) 30A and the energy donor 30D. A photochemical complex 30 including the energy acceptor 30A is provided.

  The light energy transfer element 1 includes a dielectric base material 11 formed on a conductor 13 and having a large number of fine holes 12 having substantially the same shape in plan view that are opened on the base material surface 11s and arranged in a regular order. The body base material 11 is formed with a filling portion 21 filled in the micropores 12 and protruded from the base material surface 11 s on the micropores 12, larger than the diameter of the filling portion 21, and with localized plasmons. A plurality of fine metal bodies 20 including projecting portions 22 having a diameter that can be induced are fixed, and a photochemical composite 30 is formed on the surface of the projecting portions 22 of the plurality of fine metal bodies 20. is there.

  In the light energy transfer element 1, the incident light L includes light having a wavelength with which the localized plasmon can be excited in the protruding portion 22 with respect to the substrate surface 11s and the energy donor 30D absorbs light energy. Is irradiated. The incident light L is not particularly limited, and may be natural light such as sunlight, or may be single wavelength light or broad light emitted from a specific light source.

  In the light energy transfer element 1, the fine hole 12 is a non-through hole that is opened substantially straight from the front surface 11s of the dielectric substrate 11 in the thickness direction and does not reach the back surface 11r.

In this embodiment, as shown in FIGS. 2 and 3, the dielectric base material 11 includes a part of the anodized metal body 10 that is mainly composed of aluminum (Al) and may contain minute impurities. It is an alumina (Al ₂ O ₃ ) layer (metal oxide layer) obtained by anodizing. The conductor 13 is composed of a non-anodized portion of the anodized metal body 10 that remains without being anodized.

  The shape of the anodized metal body 10 is not limited, and examples thereof include a plate shape. Further, it may be used in a form with a support such as a layered metal object 10 to be anodized on a support.

  In anodization, for example, the metal body 10 to be anodized is used as an anode, carbon or aluminum is used as a cathode (counter electrode), these are immersed in an anodizing electrolyte, and a voltage is applied between the anode and the cathode. Can be implemented. The electrolytic solution is not limited, and an acidic electrolytic solution containing one or more acids such as sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, and amidosulfonic acid is preferably used.

  When the anodized metal body 10 shown in FIGS. 2 (a) and 3 (a) is anodized, as shown in FIGS. 2 (b) and 3 (b), the surface 10s (upper surface in the drawing) is exposed to the surface. As a result, the oxidation reaction proceeds in a substantially vertical direction, and the alumina layer 11 is generated.

  The alumina layer 11 produced by anodic oxidation has a structure in which fine columnar bodies 14 having a substantially regular hexagonal shape in plan view are arranged adjacent to each other. A minute hole 12 is opened in a depth direction from the surface 10 s at a substantially central portion of each minute columnar body 14. Further, the bottom surfaces of the fine holes 12 and the fine columnar bodies 14 have rounded shapes as shown in the figure. The structure of the alumina layer produced by anodization is described in Hideki Masuda, “Preparation of mesoporous alumina by anodization and its application as a functional material”, Material Technology Vol.15, No.10, 1997, p.34, etc. Are listed.

  The anodizing conditions are such that the non-anodized portion remains and the depth d of the fine hole 12 is deep enough that the fine metal body 20 is not easily peeled off from the alumina layer 11 (dielectric substrate). What is necessary is just to design suitably. When oxalic acid is used as the electrolytic solution, preferable conditions include an electrolytic solution concentration of 0.5 M, a liquid temperature of 15 ° C., and an applied voltage of 40 V. By changing the electrolysis time, the alumina layer 11 having an arbitrary layer thickness can be generated. If the thickness of the anodized metal body 10 before anodization is set to be thicker than the alumina layer 11 to be produced, the non-anodized part remains and is provided on the conductor 13 composed of the non-anodized part, An alumina layer 11 (dielectric substrate) in which a large number of micropores 12 having substantially the same shape in plan view are opened on the substrate surface 11s and are approximately regularly arranged can be obtained.

  Usually, the pitch between adjacent fine holes 12 can be controlled in the range of 10 to 500 nm, and the diameter of the fine holes can be controlled in the range of 5 to 400 nm. Japanese Patent Application Laid-Open Nos. 2001-9800 and 2001-138300 disclose methods for finely controlling the formation position and the hole diameter of fine holes. By using these methods, the micropores having an arbitrary pore diameter and depth within the above range can be arranged almost regularly.

  As shown in FIGS. 2C and 3C, the fine metal body 20 including the filling portion 21 and the protruding portion 22 is subjected to an electroplating process or the like on the fine holes 12 of the dielectric substrate 11. It is formed by.

  When electroplating is performed, the conductor 13 functions as an electrode, and the metal is preferentially deposited from the bottom of the fine hole 12 where the electric field is strong. By continuing this electroplating process, the fine holes 12 are filled with metal, and the filling portion 21 of the fine metal body 20 is formed. If the electroplating process is further continued after the filling portion 21 is formed, the filling metal overflows from the fine holes 12, but since the electric field near the fine holes 12 is strong, the metal is continuously deposited around the fine holes 12. As a result, a protruding portion 22 that protrudes from the base material surface 11 s and has a diameter larger than the diameter of the filling portion 21 is formed on the filling portion 21.

  The fine metal body 20 may have any size as long as the protruding portion 22 can induce localized plasmons. In consideration of the wavelength of the incident light L, the diameter of the protruding portion 22 is in the range of 10 nm to 300 nm. It is preferable that

  The adjacent protrusions 22 are preferably separated from each other, and the average separation distance w is more preferably in the range of several nm to 10 nm. When the average separation distance is within the above range, the electric field enhancement effect by the localized plasmon effect can be effectively obtained.

  The localized plasmon phenomenon is a phenomenon in which a free electric field in a convex portion resonates with an electric field of light and vibrates to generate a strong electric field around the convex portion. Therefore, the fine metal body 20 is an arbitrary metal having free electrons. Good. The light energy transfer element 1 has a wavelength that can excite localized plasmons at the protrusion 22 with respect to the substrate surface 11s, and incident light L including light having a wavelength that the energy donor 30D absorbs light energy. Since it is irradiated, a metal that produces localized plasmons at a wavelength substantially coincident with the absorption wavelength of the energy donor 30D is preferable, and examples thereof include Au, Ag, Cu, Pt, Ni, Ti, and the like. High Au, Ag, etc. are particularly preferred.

  In the present embodiment, the fine hole 12 is a non-through hole that is opened without reaching the substrate back surface 11r, and the filling portion 21 of the fine metal body 20 is filled in the fine hole 12, The fine metal body 20 and the conductor 13 are not electrically connected to each other.

  The photochemical composite 30 is preferably capable of absorbing light energy with high efficiency in light having a wavelength that induces localized plasmons of the fine metal body 20. Therefore, it is preferable to determine the combination of the photochemical composite 30 and the fine metal body 20 so that the energy absorption efficiency of the photochemical composite 30 is improved.

  Examples of the photochemical complex 30 include a mixed self-assembled monolayer of an energy donor 30D and an energy acceptor 30A. The mixed self-assembled monomolecular film is a monomolecular film having a high degree of orientation, in which a large number of energy donors 30D and energy acceptors 30A are naturally and regularly arranged by the interaction between organic molecules and the like. Is formed. Examples of the mixed self-assembled monolayer include self-assembled monolayers composed of PSI and PSII of cyanobacteria plants and higher plants, photochemical protein materials such as red bacteria, and the self-organization described in Patent Documents 1 and 2. And monomolecular film.

  For example, when the photochemical complex 30 is the PSI, the absorption peak wavelength is around 700 nm. Therefore, if Au or the like that causes localized plasmon resonance near 700 nm is used as the constituent material of the fine metal body 20, the energy absorption efficiency can be effectively increased.

  FIG. 3 (d) shows an enlarged view of the bonding portion so that the bonding state between the protrusion 22 and the photochemical complex 30 can be seen. In the enlarged view of FIG. 3 (d), the arrows schematically show energy transfer.

  In the present embodiment, the energy donor 30D and the energy acceptor 30A are each covalently bonded or coordinated to the surface of the protruding portion 22 of the fine metal body 20 via a bonding group.

  Examples of the linking group include a thiol group, a disulfide group, and a sulfide group. FIG. 3D illustrates the case where the bonding group is a thiol group as an example.

  A solution containing an energy donor 30D having a property of forming a self-assembled monolayer and having a binding group bonded to the fine metal body 20 introduced therein and an energy acceptor 30A is prepared, and a photochemical complex is prepared in the solution. 3C is immersed in the structure shown in FIG. 3C from the self-assembled monolayer of the energy donor 30D and the energy acceptor 30A on the structure shown in FIG. A photochemical complex 30 can be formed.

  The photochemical complex 30 may be one in which a large number of energy donors 30D and energy acceptors 30A are alternately artificially arranged. In this case, the combination of the energy donor 30D and the energy acceptor 30A is preferably one having good energy transfer efficiency. Examples of the combination of the energy donor 30D and the energy acceptor 30A include pyrene-porphyrin and fullerene-porphyrin.

  As shown in FIG. 1, when incident light L is incident on the light energy transfer element 1, the energy donor 30D of the photochemical complex 30 is excited by absorbing the light energy of the incident light L and emits electrons. . Next, the released excited electrons are received by the energy acceptor 30A of the photochemical complex 30 to transfer the electrons, and thus the light energy is transferred. As described above, in the present embodiment, the incident light L is light including a wavelength that induces localized plasmons in the fine metal body 20, so that the protrusion 22 to which the photochemical complex 30 is coupled is used. The light confinement effect in the protrusion 22 by the localized plasmon and the electric field enhancement effect in the vicinity of the protrusion 22 can be obtained. Accordingly, the incident light L can be kept near the photochemical complex 30 for a longer time, and the incident light L can be absorbed by the photochemical complex 30 more efficiently. In particular, at the localized plasmon resonance wavelength, the electric field enhancement effect is 100 times or more, so that the absorption efficiency can be remarkably improved.

As described in the section of the background art, the film thickness of the self-assembled monolayer is several nm under the condition that there is no light confinement effect in the protrusions 22 due to localized plasmons and no electric field enhancement effect in the vicinity of the protrusions 22. Because of this monomolecular film, the absorption efficiency of incident light is extremely low. However, according to the present embodiment, since the absorption efficiency of the incident light L can be effectively increased, more efficient light energy transfer in the photochemical complex 30 forming the self-assembled monolayer. Can be made possible.
As described above, the light energy transfer element 1 of the present embodiment is configured.

  The light energy transfer element 1 of the present embodiment includes a filling portion 21 filled in the micropores 12 in the dielectric base material 11 having a plurality of micropores 12 opened at least on the base material surface 11s. A plurality of fine metal bodies 20 are formed on the portion 21 so as to protrude from the substrate surface 11s, and have a protrusion 22 having a diameter larger than the diameter of the filling portion 21 and capable of inducing localized plasmons. The surface of the protrusions 22 of the plurality of fine metal bodies 20 is fixed, and includes an energy donor 30D that absorbs light energy and supplies energy, and an energy acceptor 30A that receives energy from the energy donor 30D. A photochemical complex 30 is formed.

  In such a configuration, the substrate surface 11s is irradiated with incident light L including light having a wavelength that can excite localized plasmons in the protrusion 22 and the energy donor 30D absorbs light energy. Then, localized plasmon is induced in the protrusion 22 of the fine metal body 20 on which the photochemical complex 30 is formed, and the light confinement effect and the protrusion in the protrusion 22 due to the localized plasmon effect. By the electric field enhancement effect in the vicinity of 22, the absorption efficiency of the incident light L into the photochemical complex 30 is increased, and a high-efficiency light energy transfer efficiency (photoelectric conversion efficiency) is obtained.

  Further, since the fine metal body 20 has a structure in which the fine metal body 20 is partially embedded in the fine holes 12 of the dielectric base material 11, the fine metal body 20 is simply deposited on the dielectric base material 11. Compared with the structure of Patent Document 3, the bonding between the fine metal body 20 and the dielectric base material 11 is strong, and the fine metal body 20 is not easily peeled off from the dielectric base material 11, so that the photochemical composite 30 can be stably provided. It is possible to hold

  Further, for example, if the light energy transfer element 1 is formed so that the plurality of fine holes 12 are distributed substantially uniformly in the base material surface 11s, the fine metal body 20 uniformly formed on the base material surface 11s. Since the photochemical complex 30 can be immobilized on the protrusion 22, a substantially uniform function can be expressed over the entire surface.

  In the present embodiment, even if the element area is increased, the photochemical composite 30 can be stably held, and a substantially uniform structure can be obtained. Therefore, the area can be increased.

  As described above, according to this embodiment, it is possible to provide the light energy transfer element 1 in which the photochemical complex 30 is stably held and the area can be increased with high efficiency.

  In the above embodiment, the conductor 13 is a non-anodized portion of the anodized metal body 10, but the anodized metal body 10 is entirely anodized to form a metal oxide body 11 (dielectric substrate), and the substrate You may comprise by the metal separately provided by vapor deposition etc. in the back surface 11r. In this case, the material of the conductor 13 is not limited, and may be any metal or conductive material such as ITO (indium tin oxide).

Moreover, although the case where the conductor 13 is provided on the back surface 11r of the base material has been described, as a method of filling the fine metal body 20 into the fine hole 12, the fine hole 12 needs to be electrically conductive, such as an electroplating method. When the method to do is not used, the conductor 13 may not be provided.
Alternatively, the conductor 13 may be removed after the fine metal body 20 is formed.

“Light Energy Transfer Element of Second Embodiment”
A structure of a light energy transfer element according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a diagram corresponding to FIG. 1 of the above embodiment. As shown in the drawing, in the light energy transfer element 2 of the present embodiment, in the dielectric base material 11, the plurality of micro holes 12 are through holes opened to reach the base material back surface 11 r, and the fine metal body The configuration is the same as that of the light energy transfer element 1 according to the first embodiment shown in FIG.

  The light energy transfer element 2 of this embodiment is manufactured by the same method as that of the first embodiment. When the fine metal body 20 is grown by electroplating, depending on the conditions, a thin layer between the bottom surface of the fine hole 12 and the conductor 13 formed of the non-anodized portion of the metal body 10 to be anodized is broken. The configuration of the embodiment is obtained.

  The light energy transfer element 2 of the present embodiment removes the non-anodized portion and the vicinity thereof after anodizing the entire anodized metal body 10 or anodizing a part of the anodized metal body 10. Thus, the dielectric base material 11 having the fine holes 12 made of the through holes can be obtained, and the conductor 13 can be formed separately by vapor deposition or the like.

  Also in the light energy transfer element 2 of this embodiment, the same effect as the first embodiment can be obtained.

“Light Energy Transfer Element of Third Embodiment”
A structure of a light energy transfer element according to a third embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a diagram corresponding to FIG. 1 of the above embodiment. As shown in the drawing, in the light energy transfer element 3 of the present embodiment, the photochemical composite 30 is formed on the surface of the protruding portion 22 of the fine metal body 20 via the transparent insulator layer 31. The light energy transfer element 3 has the same configuration as the light energy transfer element 1 of the first embodiment shown in FIG. 1 except that the transparent insulator layer 31 is provided.

The transparent insulator layer 31 is a SiO ₂ film having a thickness of 50 nm or less, and substantially transmits the light L irradiated on the substrate surface. The main function of the transparent insulator layer 31 is to prevent direct charge transfer from the photochemical composite 30 to the fine metal body 20. In general, the degree of energy transfer from a substance in the vicinity of a metal to the metal is inversely proportional to the third power of the distance if the metal has a semi-infinite thickness, and the fourth power of the distance if the metal is an infinitely thin plate. If the metal is a fine particle, it decreases in inverse proportion to the sixth power of the distance. In the light energy transfer element 3, the thickness of the transparent insulator layer 31 that can prevent direct charge transfer from the photochemical composite 30 to the fine metal body 20 depends on the material, size, and shape of the fine metal body 20. It depends on the order of several nm to several tens of nm. As the film thickness of the transparent insulator layer 31, it is preferable to ensure a film thickness equal to or greater than a thickness capable of preventing direct charge transfer. On the other hand, it is known that the electric field enhancement effect by the localized plasmon effect attenuates exponentially according to the distance from the metal surface. In addition, the strength of the electric field enhancement effect also depends on the shape of the metal surface. Therefore, in consideration of the diameter and shape of the protruding portion 22 of the fine metal body 20 in the present embodiment, the film thickness of the transparent insulator layer 31 is 50 nm or less so that an effective electric field enhancing effect can be obtained. preferable.

Furthermore, the material of the transparent insulator layer 31 is not limited to the SiO ₂ film. Other specific examples of preferred materials include polymers. More specifically, examples of preferred materials for the transparent insulator layer include hydrophobic polymers and inorganic oxides.

  The hydrophobic polymer preferably contains 50% by weight or more of a monomer having a water solubility of 20% by weight or less. Specific examples of monomers having a water solubility of 20% by weight or less include vinyl esters, acrylic acid esters, methacrylic acid esters, olefins, styrenes, crotonic acid esters, itaconic acid diesters, maleic acid diesters. , Fumaric acid diesters, allyl compounds, vinyl ethers, vinyl ketones and the like, and styrene, methyl methacrylate, hexafluoropropane methacrylate, vinyl acetate, acrylonitrile and the like are preferably used. The hydrophobic polymer compound may be a homopolymer composed of one type of monomer or a copolymer composed of two or more types of monomers.

  Furthermore, you may use together the high molecular compound which copolymerized the monomer whose solubility with respect to water is 20 weight% or more. Specific examples of the monomer having a solubility in water of 20% by weight or more include 2-hydroxyethyl methacrylate, methacrylic acid, acrylic acid, and allyl alcohol. As the hydrophobic polymer, polyacrylic acid ester, polymethacrylic acid ester, polyester, and polystyrene are more preferable. By doing so, film formation becomes easy and it becomes easy to expose a functional group for immobilizing a physiologically active substance on the surface. For example, a film made of polyacrylic acid ester, polymethacrylic acid ester, or polyester can easily expose the carboxyl group and hydroxyl group on the surface by hydrolyzing the surface with acid or base, and it is made of polystyrene. The film can be easily exposed to a carboxyl group by performing an oxidation treatment such as UV / ozone treatment.

  As an inorganic oxide that can be used as a material for the transparent insulator layer, silica, alumina, titania, zirconia, ferrite, and composite materials and derivatives thereof can be selected.

  The film formation method of the transparent insulator layer 31 can be performed by an ordinary method. For example, a sol-gel method, a sputtering method, a vapor deposition method, a plating method, or the like can be employed.

  Also in the light energy transfer element 3 of this embodiment, the same effect as the first embodiment can be obtained. Further, since direct charge transfer from the photochemical composite 30 to the fine metal body 20 is prevented, the energy conversion efficiency can be further improved.

  The light energy transfer elements 1, 2 and 3 of the first, second and third embodiments can be used as artificial light combining elements. An artificial photosynthetic element is an element that utilizes a function expressed by the transfer of electrons generated by absorbing light energy.

  By bringing water molecules into contact with the light energy transfer element 1 or 3 of this embodiment and irradiating the light energy, the photochemical transfer complex 30 bonded to the surface of the light energy transfer element 1 or 3 is brought into contact. The water molecules that are present can be decomposed to generate oxygen and / or hydrogen. That is, the artificial photosynthesis device using the light energy transfer device 1 or 3 of the present embodiment can be used as an oxygen generation device and / or a hydrogen generation device. The water molecules may be contained in normal liquid water or water molecules contained in the air.

  The light energy transfer element 2 of the second embodiment can take out the current generated in the photochemical complex 30 from the electrode made of the conductor 13, and can also be used as a photoelectric conversion element.

<Design changes>
In the first, second and third embodiments, only Al is cited as the main component of the anodized metal body 10 used for manufacturing the dielectric substrate 11, but any metal can be used as long as it can be anodized. Can be used. Other than Al, Ti, Ta, Hf, Zr, Si, In, Zn, etc. can be used. The anodized metal body 10 may contain two or more types of metals that can be anodized.

  Depending on the type of anodized metal to be used, the planar pattern of the fine holes 12 to be formed varies, but the dielectric substrate 11 having a structure in which the fine holes 12 having substantially the same shape in plan view are arranged adjacent to each other is formed. Will not change.

  Moreover, although the case where the micropores 12 are regularly arranged using anodization has been described, the method of forming the micropores 12 is not limited to anodic oxidation. The first, second, and third embodiments using anodization are preferable because the entire surface can be collectively processed, can cope with an increase in area, and does not require an expensive apparatus, but other than using anodization. In addition, a plurality of concave portions regularly arranged by a nanoimprint technique is formed on the surface of a substrate such as a resin. The surface of a substrate such as a metal is regularly arranged by an electron drawing technique such as a focused ion beam (FIB) or an electron beam (EB). And a fine processing technique such as drawing a plurality of recesses.

  The light energy transfer element of the present invention can be preferably used for artificial light synthesis elements such as photoelectric conversion elements, oxygen generation elements, and hydrogen generation elements.

Sectional view in thickness direction of the light energy transfer element of the first embodiment according to the present invention. The perspective view which shows the manufacturing process of the optical energy transfer element of FIG. Manufacturing process cross-sectional view corresponding to FIG. Sectional view in thickness direction of the light energy transfer element of the second embodiment according to the present invention. Sectional view in thickness direction of a light energy transfer element according to a third embodiment of the present invention.

Explanation of symbols

1, 2, 3 Light energy transfer element, artificial photosynthesis element 10 Metal object to be anodized 11 Dielectric substrate (metal oxide layer)
11s substrate surface 11r substrate back surface 12 micropore 13 conductor (non-anodized portion) (electrode)
DESCRIPTION OF SYMBOLS 20 Fine metal body 21 Filling part 22 Protrusion part 30 Photochemical system complex 30D Energy donor 30A Energy acceptor 31 Transparent insulator layer L Incident light w Separation distance of protrusion parts

Claims (16)

In a light energy transfer element comprising a photochemical complex composed of an energy donor that absorbs light energy and provides energy, and an energy acceptor that receives energy from the energy donor,
A dielectric substrate having a plurality of micropores therein and having the plurality of micropores opened at least on the surface of the substrate, a filling portion filled in the micropores of the dielectric substrate, and A plurality of fine metal bodies formed on the filling portion so as to protrude from the surface of the base material and having a diameter larger than the diameter of the filling portion and having a size large enough to induce localized plasmons are fixed. , Having an element structure in which the photochemical complex is formed on the surface of the protruding portion of the plurality of fine metal bodies,
The substrate surface is irradiated with incident light including light having a wavelength that can excite localized plasmons at the protrusion and the energy donor absorbs the light energy. A light energy transfer element characterized by the above.   The light energy transfer element according to claim 1, wherein the distribution of the plurality of micropores in the dielectric substrate is substantially regular.   The dielectric substrate is made of a metal oxide body obtained by anodizing at least a part of a metal body to be anodized, and the plurality of micropores are formed in the metal oxide body in the process of the anodization. The light energy transfer element according to claim 1, wherein the light energy transfer element is an element.   The light energy transfer element according to claim 1, further comprising a conductor on a back surface of the dielectric base material. In the dielectric base material, the plurality of micro holes are non-through holes that are opened in a range not reaching the back surface of the base material,
5. The light energy transfer element according to claim 4, wherein the filling portion of the plurality of fine metal bodies and the conductor formed on the back surface of the base material are made non-conductive with each other. In the dielectric base material, the plurality of micro holes are through holes that are opened by reaching the back surface of the base material,
5. The light energy transfer element according to claim 4, wherein the filling portion of the plurality of fine metal bodies and the conductor formed on the back surface of the base material are electrically connected to each other.   The light energy transfer element according to claim 6, wherein the conductor formed on the back surface of the base material is an electrode for taking out an electric current to the outside. The dielectric substrate is made of a metal oxide body obtained by anodizing a part of an anodized metal body, and the plurality of micropores are formed in the metal oxide body during the anodization process. Is,
The light energy transfer element according to any one of claims 4 to 7, wherein the conductor formed on the back surface of the substrate comprises a non-anodized portion of the metal to be anodized.   9. The light energy transfer element according to claim 3, wherein the metal to be anodized contains Al as a main component.   The fine metal body is formed by performing metal growth by plating until the part protrudes from the surface of the base material in the fine hole of the dielectric base material. The light energy transfer element according to claim 1.   The light energy transfer element according to claim 1, wherein an average separation distance between the protrusions of the fine metal bodies adjacent to each other is 10 nm or less.   12. The light energy transfer element according to claim 1, wherein the photochemical complex is a mixed self-assembled monolayer of the energy acceptor and the energy donor.   The light energy transfer element according to claim 1, wherein the photochemical complex is directly formed on a surface of the protrusion.   The light energy transfer element according to claim 1, wherein the photochemical composite is formed on a surface of the protruding portion via a transparent insulator layer.   An artificial photosynthesis device comprising the light energy transfer device according to claim 1.   16. The artificial photosynthetic device according to claim 15, wherein the artificial photosynthesis device is a device that generates oxygen and / or hydrogen by decomposing water molecules in contact with the photochemical complex.

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