JP2013254940A - Photothermal conversion element and method of manufacturing the same, photothermal power generation device, and method of detecting material to be detected - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photothermal conversion element having high photothermal conversion efficiency and a method of manufacturing the same, a photothermal power generation device, and a method of detecting a material to be detected.SOLUTION: A photothermal conversion element 1 includes metal nanoparticle stacked structures 10 and substrates 2 and 3. The metal nanoparticle stacked structures 10 are fixed to a surface of the substrate 2. The metal nanoparticle stacked structures 10 are fixed to the substrate 2 by coating the substrate 2 with a dispersion liquid in which the metal nanoparticle stacked structures 10 are dispersed and then drying the substrate 2. The photothermal conversion element 1 is formed by putting the substrate 3 on teh substrate 2. Light transmitted through at least one of the substrates 2 and 3 causes localized surface plasmon resonance of the metal nanoparticle stack structures 10, which generate heat. A photothermal power generation device comprises the photothermal conversion element 1 and a photothermal conversion part. A material to be detected can be detected by solidifying or melting a thermally solidifying material or thermally melting material in the dispersion liquid as the material to be detected with the heat generated through the light irradiation.

Description

  The present invention relates to a photothermal conversion element, a manufacturing method thereof, a photothermal power generation apparatus, and a detection method of a substance to be detected. In particular, the present invention relates to a photothermal conversion element including a metal nanoparticle integrated structure, a method for manufacturing the photothermal conversion element, a photothermal power generation apparatus including the photothermal conversion element, and a method for detecting a target substance using the method for manufacturing the photothermal conversion element.

  In recent years, thermoelectric power generation that converts sunlight into heat and uses the heat has attracted attention. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2003-332607) discloses a thermophotovoltaic power generation system (TPV power generation system), a wavelength-selective solar absorption material used in the power generation system, and manufacture of the solar absorption material. A method is disclosed.

  The wavelength-selective solar light absorbing material described in Patent Document 1 is made of a heat-resistant substrate (for example, a tungsten substrate). The incident surface of the heat resistant substrate has a number of cavities that are two-dimensionally arranged to form a periodic surface fine unevenness pattern. The cavity is formed to have an opening diameter and a predetermined depth substantially the same as the specific wavelength of sunlight, and has a predetermined spectral diffuse reflectance, spectral absorptance, and spectral emissivity.

The wavelength selective solar light absorbing material described in Patent Document 1 is prepared through the following steps. First, a metal aluminum sheet is anodized. Then, the anodized sheet is processed using a predetermined etching method. As a result, a mask made of an alumina film having a large number of regularly arranged holes is obtained. Next, the alumina film mask is placed on a heat resistant substrate (for example, a tungsten substrate). By a fast atomic beam (FAB) etching method using SF ₆ gas, a periodic surface fine uneven pattern arranged two-dimensionally is transferred and formed on the surface of the heat resistant substrate. Subsequently, the alumina film mask is removed from the substrate. As a result, a structure is obtained in which cavities having an opening diameter substantially the same as the wavelength of sunlight are periodically two-dimensionally arranged on the surface of the substrate.

JP 2003-332607 A

  The manufacturing method described in Patent Document 1 includes complicated processing. From the viewpoint of cost, it is desired that the photothermal conversion element can be manufactured by a simpler manufacturing method.

  Furthermore, in order to increase the usefulness of the photothermal conversion element, a photothermal conversion element that can achieve higher photothermal conversion efficiency is desired.

  An object of the present invention is to provide a photothermal conversion element having high photothermal conversion efficiency, a method for manufacturing the photothermal conversion element, a photothermal power generation apparatus using the photothermal conversion element, and a method for detecting a substance to be detected using the method for manufacturing the photothermal conversion element. That is.

  A photothermal conversion element according to an aspect of the present invention includes a plurality of metal nanoparticle assembly structures each formed by integrating a plurality of metal nanoparticles, and a plurality of metal nanoparticle assembly structures fixed. A first substrate having a fixed surface.

  Preferably, each of the plurality of metal nanoparticle integrated structures used for the photothermal conversion element includes base particles (beads) having a surface on which the plurality of metal nanoparticles are fixed. Preferably, the metal nanoparticle assembly structure is a structure in which a plurality of metal nanoparticles are fixed to the surface of the bead via an interaction site, and a gap is provided between each metal nanoparticle, and the metal nanoparticles are arranged at intervals equal to or smaller than the diameter of the metal nanoparticles. It is. The interaction site is, for example, a site that generates a chemical bond, van der Waals force, electrostatic interaction, hydrophobic interaction, and adsorption force. For example, when the metal nanoparticle is a gold nanoparticle, examples of the site (group) that can interact with gold include, but are not limited to, a thiol group.

  Hereinafter, a metal nanoparticle integrated structure using base particles (beads) in particular is referred to as metal nanoparticle-immobilized beads. Preferably, the base particle (bead) is an acrylic resin.

  Preferably, the metal nanoparticles forming each of the plurality of metal nanoparticle assembly structures are gold nanoparticles or silver nanoparticles. Hereinafter, in particular, metal nanoparticle-immobilized beads using gold nanoparticles are referred to as gold nanoparticle-immobilized beads, and metal nanoparticle-immobilized beads using silver nanoparticles are referred to as silver nanoparticle-immobilized beads.

  Preferably, the fixing surface of the first substrate forms a dense region where at least two of the plurality of metal nanoparticle assembly structures are present at a distance closer than the diameter of the beads.

Preferably, the fixing surface of the first substrate has hydrophobicity.
Preferably, the first substrate is a resin film having a transparent electrode formed on a fixed surface.

  Preferably, the photothermal conversion element further includes a second substrate disposed so as to sandwich the plurality of metal nanoparticle integrated structures together with the first substrate. At least one of the first and second substrates is light transmissive to light that causes localized surface plasmon resonance on the surfaces of the plurality of metal nanoparticles.

  Preferably, in the photothermal conversion element, a plurality of layers of a plurality of metal nanoparticle integrated structures are formed between the first substrate and the second substrate.

  A method for producing a photothermal conversion element according to another aspect of the present invention includes a step of preparing a dispersion liquid in which a plurality of metal nanoparticle assembly structures each formed by integrating a plurality of metal nanoparticles are dispersed; Preparing a first substrate, applying a dispersion liquid to the fixed surface of the first substrate, and fixing the metal nanoparticle integrated structure to the fixed surface of the first substrate.

  Preferably, the fixing surface of the first substrate has hydrophobicity. In the step of applying the dispersion, the dispersion is dropped onto the fixed surface of the first substrate.

  Preferably, in the step of fixing the metal nanoparticle integrated structure, the dispersion is naturally evaporated. Alternatively, the dispersion may be dried while being warmed with a hot plate or a heater.

  Preferably, in the step of preparing the first substrate, a resin film having a transparent electrode formed on one surface thereof is prepared as the first substrate. The fixed surface of the first substrate is the surface of the resin film on which the transparent electrode is formed.

  Preferably, in the step of fixing the metal nanoparticle assembly structure, the metal nanoparticle assembly structure is integrated by irradiating the dispersion with laser light.

  Preferably, the dispersion contains a thermosettable material. In the step of fixing the metal nanoparticle assembly structure, the dispersion liquid is irradiated with a laser beam to solidify the thermosetting material.

  Preferably, the dispersion is a liquid in which a heat-soluble material is thermally dissolved. In the step of fixing the metal nanoparticle assembly structure, the dispersion liquid is irradiated with laser light to accumulate the metal nanoparticle assembly structure, and the thermally soluble material is cooled or solidified.

  Preferably, the method for manufacturing a photothermal conversion element further includes a step of irradiating the heat solidifiable material including the metal nanoparticle integrated structure with laser light to process the shape of the heat solidifiable material.

  Preferably, the method for manufacturing a photothermal conversion element further includes a step of irradiating the heat-soluble material including the metal nanoparticle-immobilized beads with laser light to process the shape of the heat-soluble material.

  Preferably, the manufacturing method of the photothermal conversion element further includes a step of superimposing the second substrate on the first substrate so that the plurality of metal nanoparticle integrated structures are sandwiched between the first substrate and the second substrate. . At least one of the first and second substrates is light transmissive to light that causes localized surface plasmon resonance on the surfaces of the plurality of metal nanoparticles.

  Preferably, the manufacturing method of the photothermal conversion element further includes a step of fixing the metal nanoparticle integrated structure to the fixing surface of the second substrate prior to the step of superimposing the second substrate on the first substrate. In the step of superimposing the second substrate on the first substrate, the fixed surfaces of the first substrate and the second substrate are opposed to each other.

  A photothermal power generation device according to still another aspect of the present invention includes a photothermal conversion element and a thermoelectric conversion unit thermally connected to the photothermal conversion element. The photothermal conversion element includes a plurality of metal nanoparticle integrated structures each formed by integrating a plurality of metal nanoparticles, and a first surface having a fixed surface to which the plurality of metal nanoparticle integrated structures are fixed. And a second substrate disposed so as to sandwich the plurality of metal nanoparticle integrated structures together with the first substrate. One of the first and second substrates is light transmissive to light that causes localized surface plasmon resonance on the surfaces of the plurality of metal nanoparticles, and is arranged to receive light. The The other of the first and second substrates is thermally connected to the thermoelectric converter.

  Preferably, one substrate is a second substrate. The other substrate is the first substrate. Each of the first and second substrates is a resin film having a transparent electrode formed on one surface thereof. The fixed surface of the first substrate is the surface of the resin film on which the transparent electrode is formed. The surface of the first substrate opposite to the fixed surface is thermally connected to the thermoelectric converter. The second substrate is arranged so that the surface on which the transparent electrode is formed faces the fixed surface of the first substrate, and the surface opposite to the surface on which the transparent electrode is formed receives light.

  Preferably, one substrate is the first substrate. The other substrate is a second substrate. Each of the first and second substrates is a resin film having a transparent electrode formed on one surface thereof. The fixed surface of the first substrate is the surface of the resin film on which the transparent electrode is formed. The surface of the first substrate opposite to the fixed surface receives light. The second surface is formed such that the surface on which the transparent electrode is formed is thermally and electrically connected to the thermoelectric conversion unit, and the surface opposite to the surface on which the transparent electrode is formed faces the fixed surface of the first substrate. Substrate is arranged.

  Preferably, a plurality of layers of a plurality of metal nanoparticle integrated structures are formed between the first substrate and the second substrate.

  Preferably, the photothermal conversion element includes a dye-sensitized photoelectric conversion element. Each of the first and second substrates is a resin film having a transparent electrode formed on one surface thereof. The first and second substrates function as a dye-sensitized photoelectric conversion element.

  Preferably, each of the plurality of metal nanoparticle integrated structures used for the photothermal conversion element includes base particles (beads) having a surface on which the plurality of metal nanoparticles are fixed. Preferably, the substrate particles (beads) are titanium oxide particles.

  A method for detecting a substance to be detected according to still another aspect of the present invention is a method for detecting a substance to be detected using the above-described method for producing a photothermal conversion element. The dispersion includes a thermocoagulable material or a heat-soluble material as a substance to be detected. In the detection method of the substance to be detected, the substance to be detected is detected by irradiating the dispersion liquid with laser light to solidify or dissolve the dispersion liquid.

ADVANTAGE OF THE INVENTION According to this invention, the photothermal conversion element which has high photothermal conversion efficiency can be provided.
According to the present invention, a photothermal conversion element can be manufactured by a simple process.

  According to the present invention, the efficiency of the photothermal power generation device can be increased.

It is the figure which showed the schematic structure of the photothermal conversion element which concerns on embodiment of this invention. It is the figure which showed the typical structure of the metal nanoparticle integrated structure used for embodiment of this invention. It is a scanning electron microscope (SEM) photograph of an example of a metal nanoparticle integrated structure. It is a flowchart which illustrates roughly the manufacturing method of the photothermal conversion element which concerns on embodiment of this invention. It is the figure which showed typically the manufacturing method of the photothermal conversion element which concerns on embodiment of this invention. It is the figure which showed the surface of the 1st board | substrate by which the edge part was masked with the tape. It is the figure which showed that the ITO-PEN film is a hydrophobic substrate. It is a SEM photograph (magnification: 8000 times) of the surface of the photothermal conversion element containing the silver nanoparticle fixed bead formed according to the manufacturing method concerning an embodiment of the invention. It is a SEM photograph (magnification: 6000 times) of the surface of the photothermal conversion element containing the gold nanoparticle fixed bead formed according to the manufacturing method concerning an embodiment of the invention. It is a graph for demonstrating the light heating effect by the photothermal conversion element containing the silver nanoparticle fixed bead which concerns on embodiment of this invention. It is a graph for demonstrating the light-heating effect by the photothermal conversion element containing the gold nanoparticle fixed bead which concerns on embodiment of this invention. It is the figure which showed the result of having measured the temperature rise of the photothermal conversion element which concerns on embodiment of this invention using the measurement system comprised so that the heat dissipation to a measurement stand might be suppressed. It is the figure which showed the spectrum of sunlight. It is the figure which showed the transmission spectrum of the ITO-PEN film. It is the figure which showed the theoretical value of the absorption spectrum about each of the gold nanoparticle fixed bead and the silver nanoparticle fixed bead. It is the figure which showed the theoretical value of the calorie | heat amount per unit time about each of a gold nanoparticle fixed bead and a silver nanoparticle fixed bead. It is the graph which showed the numerical calculation result of the time dependence of the temperature change expected in the ideal case assumed that the amount of heat radiation is completely zero. It is a typical lineblock diagram of a photothermal power generator concerning an embodiment of the invention. It is the figure which showed the structure of the photothermal electric power generation apparatus 101 which concerns on the 1st Embodiment of this invention. It is the figure which showed the result of having experimented with the time change of the output by the photothermal electric power generation apparatus 101 shown in FIG. It is the figure which showed the structure of the photothermal power generation apparatus 102 which concerns on the 2nd Embodiment of this invention. It is the figure which showed typically the structure of the photothermal electric power generation apparatus 103 which concerns on the 3rd Embodiment of this invention. It is the figure which showed the structure of 1 C of solar cells / photothermal conversion elements shown by FIG. It is a figure for demonstrating the three-dimensional model of a silver nanoparticle fixed bead. It is the figure which showed the calculation model of the silver nanoparticle fixed bead shown in FIG. It is the figure which showed the calculation result of the extinction spectrum of a silver nanoparticle fixed bead. It is the figure which showed electric field strength distribution according to the number N of clusters. It is the figure which showed the other structure of the photothermal conversion element which concerns on embodiment of this invention. It is the figure which showed further another structure of the photothermal conversion element which concerns on embodiment of this invention. 30 is a flowchart schematically illustrating a method for manufacturing the photothermal conversion element 1D illustrated in FIG. 29. It is a figure which illustrates typically the effect by photothermal conversion element 1D shown in FIG. It is the figure which showed an example of the transmission spectrum of the PEN film applicable as a transparent substrate of the photothermal conversion element which concerns on embodiment of this invention. It is the figure which showed the experimental result of the light heating effect by the photothermal conversion element which concerns on embodiment of this invention. It is a figure which shows the characteristic of the solar cell site | part (photoelectric conversion element) in the structure shown by FIG. 22 and FIG. 23 collectively in a table | surface form. It is a conceptual diagram of integration | stacking of the metal nanoparticle fixed bead by an optical trap. It is the figure which showed the mode from the laser beam irradiation start to the 57th time at the time of making into the object the sample which disperse | distributed the silver nanoparticle fixed bead in water. It is the enlarged view of the 1st photograph which showed the silver nanoparticle fixed bead disperse | distributed in water before integrating | stacking by an optical trap (24 seconds after a laser beam irradiation start). It is an enlarged view of the 2nd photograph which showed the silver nanoparticle fixed bead integrated by the optical trap (39 seconds after a laser beam irradiation start). It is a microscope picture for demonstrating the difference in the integration degree of the metal nanoparticle fixed bead by an optical trap at the time of changing the power of a laser beam. It is a figure for demonstrating the effect by integrating | stacking a silver nanoparticle fixed bead using an optical tweezers. (a) is a photograph showing a sample dried while irradiating a solution in which silver nanoparticle fixed beads are dispersed with 0.6 W laser light, and (b) is a position shown in (a). It is the figure which showed the average value of the Raman scattering spectrum in a and the Raman scattering spectrum in the position b, and the rectangular area | region shown as the area | region which takes an average. (A) is the photograph which showed the sample which air-dried the solution which disperse | distributed the silver nanoparticle fixed bead, (b) shows the Raman scattering spectrum in the frame shown in (a). It is a figure. It is a figure explaining the heat_generation | fever effect by the metal nanoparticle fixed bead which concerns on embodiment of this invention. It is the figure which showed the example of a process by the laser beam of the thermocoagulable material containing the metal nanoparticle fixed bead which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  In the present invention and its embodiments, the “metal nanoparticle assembly structure” is a structure formed by integrating a plurality of metal nanoparticles. “Metal nanoparticles” are metal particles having a size on the order of nanometers. “Nanometer order” includes the range of 1 to several hundred nanometers, typically in the range of 1 to 100 nm, and preferably in the range of 1 to 50 nm.

  In the present invention and its embodiments, the term “having light transparency” means the property that the intensity of light passing through a substance is greater than zero. When light passes through a material, the remaining light energy may be absorbed, scattered or reflected by the material. In addition, the wavelength region of the light is one of an ultraviolet region, a visible region, and a near infrared region, a region that spans two of these three regions, and a region that spans all three regions. Either of these may be used.

  The light transmittance can be defined by the range of transmittance, for example. In this case, the lower limit of the transmittance range is not particularly limited as long as it is larger than 0. Similarly, the upper limit of the transmittance range is 100 (%) at the maximum. However, the upper limit of the transmittance range may be smaller than 100 (%).

  In the present invention and its embodiments, the term “hydrophobic” means a property of low affinity with water. “Hydrophobic” includes, for example, the property that the surface of the material is water or an aqueous solution, or an aqueous dispersion becomes droplets (water repellency). In the present invention and its embodiments, “water repellency” means that the water contact angle is greater than 0 °. More preferably, in the present invention and its embodiment, the contact angle with water is 40 ° or more.

[Photothermal conversion element]
FIG. 1 is a diagram showing a schematic structure of a photothermal conversion element according to an embodiment of the present invention. Referring to FIG. 1, the photothermal conversion element 1 includes a metal nanoparticle integrated structure 10 and substrates 2 and 3.

  The metal nanoparticle integrated structure 10 is a structure formed by integrating a large number of metal nanoparticles 12. In this embodiment, the plurality of metal nanoparticle assembly structures 10 are fixed to the surface of the substrate 2. The substrate 3 is disposed so as to sandwich the plurality of metal nanoparticle assembly structures 10 together with the substrate 2. That is, the metal nanoparticle assembly structure 10 is disposed between the substrates 2 and 3.

  The substrates 2 and 3 are substrates having optical transparency. In this embodiment, both the substrates 2 and 3 are light transmissive. Therefore, even if light is irradiated from either side of the substrates 2 and 3, the light can be introduced into the metal nanoparticle integrated structure 10.

  However, only one of the substrates 2 and 3 may have optical transparency. In this case, the metal nanoparticle integrated structure 10 is irradiated with light through the one substrate. The other substrate may reflect or absorb light that has passed through the one substrate. For example, if the board | substrate 3 has a light transmittance, the board | substrate 2 does not need to have a light transmittance.

  Free electrons on the surface of the metal nanoparticles 12 are vibrated by light transmitted through at least one of the substrates 2 and 3. This causes polarization. As a result, localized surface plasmon resonance occurs in the metal nanoparticle integrated structure 10. The metal nanoparticle assembly structure 10 generates heat by the localized surface plasmon resonance. Due to localized surface plasmon resonance, the energy of light is confined in a very narrow region. Furthermore, since many metal nanoparticle integrated structures 10 are arrange | positioned between the board | substrates 2 and 3, the photothermal conversion element 1 which concerns on embodiment of this invention can confine more optical energy. Thereby, the photothermal conversion element 1 which concerns on embodiment of this invention can generate more heat.

  In FIG. 1, a plurality of metal nanoparticle assembly structures 10 are shown to be regularly arranged on the surface of the substrate 2. However, it is not essential for the present invention that the plurality of metal nanoparticle assembly structures 10 are regularly arranged. As will be described in detail later, in this embodiment, a region where a large number of metal nanoparticle assembly structures 10 are densely formed is formed on the surface of the substrate 2. In this embodiment, the “region where the metal nanoparticle assembly structure 10 is dense” is defined as a region where at least two of the plurality of metal nanoparticle assembly structures exist at a distance closer than the diameter of the beads. can do. When many metal nanoparticle integrated structures 10 are densely packed, the density of light energy confined by these metal nanoparticle integrated structures 10 can be increased. As a result, the photothermal conversion efficiency can be increased.

  The fixing surface of the substrate 2, that is, the surface on which the metal nanoparticle assembly structure 10 is fixed has hydrophobicity. By the manufacturing method described in detail later, the metal nanoparticle assembly structure 10 can be densely packed on the hydrophobic surface.

  In this embodiment, the substrates 2 and 3 are resin films having transparent electrodes formed on the surfaces thereof. By using the transparent electrode, electrical connection between the photothermal conversion element 1 and another device can be easily realized. Thereby, the usefulness of the photothermal conversion element 1 which concerns on embodiment of this invention is improved. Furthermore, since the surface on which the transparent electrode is formed has hydrophobicity, it can be used as a fixing surface for fixing the metal nanoparticle assembly structure 10.

  Moreover, the board | substrates 2 and 3 have a softness | flexibility by using a resin film for the board | substrates 2 and 3. FIG. Therefore, the freedom degree of the installation place of the photothermal conversion element 1 can be raised. For example, the photothermal conversion element 1 can be installed not only on a flat surface but also on a curved surface. Furthermore, the photothermal conversion element 1 can be easily fixed by sticking a resin film as a substrate on the installation surface.

  In one embodiment, an ITO-PEN (polyethylene naphthalate) film is used as the substrates 2 and 3. The ITO-PEN film has PEN film and ITO (indium tin oxide) formed as a transparent electrode on the surface of the PEN film. ITO-PEN can be easily obtained because it is used for a wide range of applications such as flat panel displays, electronic devices, solar cells, touch panels, and optical elements. Therefore, the manufacturing cost of the photothermal conversion element 1 can be reduced.

  In addition, the kind of board | substrates 2 and 3 is not limited to an ITO-PEN film. Any resin film having a transparent electrode formed on its surface can be used for the substrates 2 and 3. As the substrates 2 and 3, for example, an ITO-PET (polyethylene terephthalate) film can be used.

  Conductivity is not an essential property for the substrates 2 and 3. If it is not necessary to electrically connect the photothermal conversion element 1 to another device, the substrates 2 and 3 may not have conductivity. In this case, a resin film that is hydrophobic and light transmissive but not conductive can be used for the substrates 2 and 3. For example, a PET film can be used for the substrates 2 and 3.

  FIG. 2 is a diagram showing a schematic structure of a metal nanoparticle integrated structure used in the embodiment of the present invention. FIG. 3 is a scanning electron microscope (SEM) photograph of an example of a metal nanoparticle integrated structure. In this example, beads having a particle diameter of 400 nm on which silver nanoparticles having a particle diameter of 7.4 nm were fixed were observed.

  2 and 3, the metal nanoparticle assembly structure 10 includes beads 11 and metal nanoparticles 12. The metal nanoparticles 12 cover the surface of the bead 11 and are immobilized on the surface of the bead 11. Thereby, an integrated structure of the metal nanoparticles 12 is formed. More specifically, in the metal nanoparticle assembly structure 10, a plurality of metal nanoparticles 12 are fixed to the surface of the beads 11 through the interaction sites, and a gap is provided between the metal nanoparticles 12 and the diameter of the metal nanoparticles 12 or less. Structures arranged at intervals. The interaction site is, for example, a site that generates a chemical bond, van der Waals force, electrostatic interaction, hydrophobic interaction, and adsorption force.

  The average particle diameter of the beads is on the order of several tens of nanometers to micrometer, for example, 0.03 to 100 μm, and more preferably 0.1 to 10 μm.

  The beads 11 are, for example, resin particles. If the particle | grains which have a desired particle size can be formed, the material of the bead 11 will not be specifically limited. The material used for the beads 11 is, for example, a resin such as acrylic, polyolefin, polyethylene, polypropylene, polystyrene, but is not limited thereto. Moreover, the shape of the bead 11 is substantially spherical. However, the beads 11 may be non-spherical as long as the metal nanoparticles 12 can be integrated with high density.

  The metal nanoparticles 12 are metal nanoparticles that can cause localized surface plasmon resonance by light in the ultraviolet to near infrared region. In this embodiment, gold nanoparticles or silver nanoparticles can be employed as such metal nanoparticles. It is known that gold nanoparticles or silver nanoparticles cause localized surface plasmon resonance by light from the visible region to the near infrared region. Therefore, gold nanoparticles or silver nanoparticles can be used for the metal nanoparticles 12.

  The average particle diameter of the metal nanoparticles is sub-nano order to nano order (about 2 nm to 1000 nm), and may be, for example, 2 to 500 nm, preferably 2 to 100 nm, and more preferably 5 to 50 nm.

[Production Method of Photothermal Conversion Element]
FIG. 4 is a flowchart schematically illustrating a method for manufacturing a photothermal conversion element according to an embodiment of the present invention. FIG. 5 is a diagram schematically showing a method for manufacturing a photothermal conversion element according to an embodiment of the present invention. Referring to FIGS. 4 and 5, in step S1, the first substrate (substrate 2) is cleaned. In step S2, the edge of the surface of the substrate 2 is masked with masking tapes 4 and 5. In step S3, the metal nanoparticle fixed bead dispersion is diluted to adjust the concentration of the dispersion. Steps S2 and S3 are not essential.

  In step S <b> 4, a diluted dispersion 6 of metal nanoparticle fixed beads is applied to the surface of the substrate 2. In step S5, the substrate 2 is left to dry. Thereby, the metal nanoparticle fixed bead is fixed to the surface of the substrate 2. A region 6a shown in FIG. 5 schematically shows a region where the metal nanoparticle-immobilized beads are fixed. In step S6, the second substrate (substrate 3) is bonded to the first substrate (substrate 2). Thereby, the photothermal conversion element 1 which concerns on embodiment of this invention is completed.

Next, specific examples of the above manufacturing method will be described.
First, an ITO-PEN film having a size of 4 cm × 4 cm was prepared as the substrates 2 and 3. The ITO-PEN film used as the substrate 2 was washed with alcohol, and then the alcohol was removed with nitrogen (step S1).

  FIG. 6 is a view showing the surface of the first substrate whose end is masked by the tape. With reference to FIG. 6, the coating surface 7 was formed by affixing the masking tapes 4 and 5 to the edge part of two places of the board | substrate 2 (step S2). Double-sided tape was used for the masking tapes 4 and 5. A portion of the surface of the substrate 2 that is not masked by the masking tapes 4 and 5 is the coating surface 7. The application surface 7 corresponds to a fixed surface to which the plurality of metal nanoparticle assembly structures 10 are fixed.

  A photothermal conversion element containing gold nanoparticle-immobilized beads and a photothermal conversion element containing silver nanoparticle-immobilized beads were prepared as evaluation samples. For example, a dispersion of gold nanoparticle-immobilized beads and a dispersion of silver nanoparticle-immobilized beads produced by a known method disclosed in Japanese Patent Application Laid-Open No. 2003-213442 and Japanese Patent Application Laid-Open No. 2008-101260 are used. Got ready. Details of these dispersions will be described below.

  In both the gold nanoparticle-immobilized beads and silver nanoparticle-immobilized beads, the material of the beads (base particles) was an acrylic resin (specific gravity 1.19), and the bead particle size was 0.40 μm.

In the case of gold nanoparticle-immobilized beads, the particle size of the gold nano before immobilization on the beads was 32 nm. The ratio of the metal component estimated from the reagent usage amount was 79.9 wt%. The content of gold nanoparticle-immobilized beads in the dispersion was estimated to be 49.76 mg / mL (2.49 × 10 ¹¹ particles / mL). The number of gold nanoparticles per bead was estimated to be 586.

In the case of silver nanoparticle-immobilized beads, the average diameter of silver nanoparticles was 2.5 nm. The particle diameter of silver nano before immobilizing on beads was 2 to 20 nm. The ratio of the metal component estimated from the amount of reagent used was 30.7 wt%. The content of the silver nanoparticle-immobilized beads in the dispersion was estimated to be 14.4 mg / mL (2.49 × 10 ¹¹ particles / mL). The number of silver nanoparticles per bead was estimated to be 207,478.

  Various known methods can be used as a method for producing gold nanoparticle-immobilized beads or silver nanoparticle-immobilized beads. For example, the methods disclosed in Japanese Patent Application Laid-Open Nos. 2003-213442 and 2008-101260 can be applied.

  For example, when gold nanoparticles are immobilized on the surface of the beads, the beads may be mixed with a gold nanoparticle dispersion, and the gold nanoparticle dispersion may be stirred or allowed to stand. The gold nanoparticle dispersion may optionally contain an organic binder. The fixed reaction temperature can be any temperature as long as the dispersion does not completely freeze or evaporate during the reaction period. Preferably, the fixed reaction temperature is around room temperature (for example, 10 to 35 ° C.).

  As the gold nanoparticle dispersion liquid, a commercially available product may be used, or it may be produced by an in-solution reduction reaction using a gold ion (gold complex ion) -containing solution and a reducing agent. For example, citric acid may be added to the chloroauric acid solution.

  Gold nanoparticles are immobilized on beads by the following method, for example. First, a gold nanoparticle dispersion liquid and beads are put into a binder liquid. The binder liquid is, for example, an alkylthiol water or ethanol solution. The solution is stirred at room temperature. The color of the solution is initially red, but changes to clear (colorless) as it is stirred. Stirring is continued for a predetermined time after the solution becomes clear. Thereby, gold nanoparticle fixed beads are generated. In the gold nanoparticle-immobilized beads prepared by this method, an interaction site (group) that can interact with gold is a thiol group. The interaction site may be formed in advance on the surface of the bead, or may be formed in advance on the surface of the gold colloid.

  Preparation of a sample of a photothermal conversion element including gold nanoparticle-immobilized beads will be described. Water was added to the gold nanoparticle fixed bead dispersion described above to prepare a dispersion diluted 10 times (step S3).

  2 mL of the dispersion 6 diluted by the above procedure was dropped onto the substrate 2 and the diluted dispersion 6 was applied to the substrate 2 (step S4).

  Subsequently, the substrate 2 was allowed to stand in a draft chamber and dried at a temperature of 25 ° C. for 24 hours (step S5). The dispersion may be dried while being warmed by a hot plate or a heater.

  Then, the board | substrate 2 and the board | substrate 3 were bonded together with the double-sided tape used as the masking tapes 4 and 5 (step S6).

  According to the same procedure, in step S3, a dispersion diluted 100 times and a dispersion diluted 400 times were prepared, and samples having different concentrations of gold nanoparticle-immobilized beads were prepared by the processing in steps S4 to S6. . In both cases of the 100-fold diluted dispersion and the 400-fold diluted dispersion, the dropping amount of the dispersion onto the substrate was 2 mL.

  The procedure for preparing the sample of the photothermal conversion element containing the silver nanoparticle-immobilized beads is the same as the above procedure. The dispersion of silver nanoparticle-immobilized beads was diluted 10 times (step S3). 2 mL of the diluted dispersion was dropped onto the substrate 2 and the diluted dispersion 6 was applied to the substrate 2 (step S4). A sample was prepared by the processes of steps S5 and S6. According to the same procedure, in step S3, a dispersion diluted 100 times and a dispersion diluted 400 times were prepared, and samples having different concentrations of silver nanoparticle-immobilized beads were prepared by the processing in steps S4 to S6. . In both cases of the 100-fold diluted dispersion and the 400-fold diluted dispersion, the dropping amount of the dispersion onto the substrate was 2 mL.

  FIG. 7 is a diagram showing that the ITO-PEN film is a hydrophobic substrate. As shown in FIG. 7, the water droplet 6b is raised on the surface of the ITO-PEN film (substrate 2). Therefore, it can be seen that the ITO-PEN film has water repellency.

  FIG. 8 is an SEM photograph (magnification: 8000 times) of the surface of the photothermal conversion element including silver nanoparticle-immobilized beads formed according to the manufacturing method according to the embodiment of the present invention. FIG. 9 is an SEM photograph (magnification: 6000 times) of the surface of the photothermal conversion element including gold nanoparticle-immobilized beads formed according to the manufacturing method according to the embodiment of the present invention. Both the photothermal conversion elements shown in FIGS. 8 and 9 were formed by applying 2 mL of a 10-fold diluted dispersion to a substrate. The dispersion applied on the hydrophobic substrate becomes water droplets (see FIG. 7). As a result, as shown in FIGS. 8 and 9, it is possible to easily achieve the high density integration of the metal nanoparticle-immobilized beads on the substrate surface. 8 and 9 are enlarged views of a part of the region 6a shown in FIG.

[Characteristics of photothermal conversion element]
In order to evaluate the light heat generation effect of the photothermal conversion element according to the embodiment of the present invention, the photothermal conversion element was irradiated with light from a solar simulator, and the temperature of the photothermal conversion element was measured.

  FIG. 10 is a graph for explaining the light heating effect by the photothermal conversion element including the silver nanoparticle fixed beads according to the embodiment of the present invention. Referring to FIG. 10, the horizontal axis of the graph indicates the elapsed time from the start of irradiation of the solar simulator, that is, the irradiation time of light of the solar simulator. The vertical axis of the graph represents the temperature of the photothermal conversion element.

The description “2.49 × 10 ¹⁰ pieces / mL” in the graph of FIG. 10 indicates a first sample prepared by applying 2 mL of a 10-fold diluted dispersion to a substrate. The description “2.49 × 10 ⁹ pieces / mL” indicates a second sample prepared by applying 2 mL of a 100-fold diluted dispersion to a substrate. The description “0.62 × 10 ⁹ pieces / mL” indicates a third sample prepared by applying 2 mL of a 400-fold diluted dispersion to a substrate. These three types of samples were prepared by the above manufacturing method. The description “without metal nanoparticles” refers to a comparative sample in which the diluted dispersion is not applied to the substrate.

  When the solar simulator light was irradiated for 100 seconds, the temperature of the first sample reached 40 ° C. or higher. At this time, the temperature difference between the first sample and the comparative sample was about 9.0 ° C.

  FIG. 11 is a graph for explaining the light heating effect by the photothermal conversion element including the gold nanoparticle-immobilized beads according to the embodiment of the present invention. Referring to FIG. 11, the horizontal axis of the graph indicates the elapsed time from the start of irradiation of the solar simulator, and the vertical axis of the graph indicates the temperature of the photothermal conversion element.

Similarly to the graph shown in FIG. 10, the description “2.49 × 10 ¹⁰ pieces / mL” in the graph of FIG. 11 is the first one prepared by applying 2 mL of 10-fold diluted dispersion to the substrate. Samples are shown. The description “2.49 × 10 ⁹ pieces / mL” indicates a second sample prepared by applying 2 mL of a 100-fold diluted dispersion to a substrate. The description “0.62 × 10 ⁹ pieces / mL” indicates a third sample prepared by applying 2 mL of a 400-fold diluted dispersion to a substrate. These three types of samples were prepared by the above manufacturing method. The description “without metal nanoparticles” indicates a comparative sample in which the diluted dispersion is not applied to the substrate.

  When the solar simulator light was irradiated for 100 seconds, the temperature of the first sample reached 50 ° C. or higher. The temperature difference between the first sample and the comparative sample at this time was about 18.5 ° C.

  10 and 11 that the temperature of the photothermal conversion element can be changed under the same irradiation conditions by changing the concentration of the metal nanoparticle integrated structure 10 in the photothermal conversion element. This indicates the possibility of temperature control by controlling the concentration of the metal nanoparticle-immobilized beads.

  10 and 11 show the measurement results of the temperature rise of the light-to-heat conversion element when the light-to-heat conversion element according to the embodiment of the present invention is placed directly on the measurement table. FIG. 12 is a diagram showing a result of measuring a temperature rise of the photothermal conversion element according to the embodiment of the present invention using a measurement system configured to suppress heat dissipation to the measurement table. Specifically, a transparent frame formed of an ITO-PEN film was placed on a measurement table, and the photothermal conversion element according to the embodiment of the present invention was placed on the transparent frame to constitute a measurement system. The distance between the measurement table and the photothermal conversion element was about 1.3 cm.

  Referring to FIG. 12, in the case of gold nanoparticle-immobilized beads (Au NP fixed beads), the temperature of the photothermal conversion element reached about 59 ° C. by irradiation with light from a solar simulator for 100 seconds.

  The broken line in the graph of FIG. 12 shows room temperature. In the case of the photothermal conversion element using the gold nanoparticle-immobilized beads, the temperature increase value with respect to room temperature is about 31.4 ° C., and the relative temperature increase value for the sample without “metal nanoparticles” is 19.9 ° C. there were. Similarly, in the case of a photothermal conversion element using silver nanoparticle-immobilized beads (Ag NP fixed bead), the temperature rise value with respect to room temperature is about 23.1 ° C., which is a relative temperature with respect to the sample “without metal nanoparticles”. The increase value was 10.6 ° C. In these cases, the solar simulator was irradiated with light for 100 seconds.

  Next, the result of theoretical verification of the light heating effect by the light-to-heat conversion element according to the embodiment of the present invention will be shown. FIG. 13 is a diagram showing a spectrum of sunlight. FIG. 14 is a diagram showing a transmission spectrum of the ITO-PEN film. FIG. 15 is a diagram showing theoretical values of absorption spectra for each of gold nanoparticle-immobilized beads and silver nanoparticle-immobilized beads. Curves A1 and A2 shown in FIG. 15 indicate the theoretical value of the absorption spectrum of one gold (Au) nanoparticle-immobilized bead and the theory of the absorption spectrum of one silver (Ag) nanoparticle-immobilized bead, respectively. Indicates the value.

  FIG. 16 is a theoretical value of FIG. 15 calculated by solving the Maxwell equation by a discrete integration method (cluster DDA (discrete dipole approximation) method) for each of gold nanoparticle-immobilized beads and silver nanoparticle-immobilized beads. It is the figure which showed the theoretical value of the calorie | heat amount per unit time calculated | required by the overlap integral of FIG. 13 and FIG. Referring to FIG. 16, the vertical axis of the graph represents the product of the amount of heat per unit time of the metal nanoparticle-immobilized beads and the number of metal nanoparticle-immobilized beads immobilized on the substrate.

For both the photothermal conversion element including the silver nanoparticle-immobilized beads and the photothermal conversion element including the gold nanoparticle-immobilized beads, the number of metal nanoparticle-immobilized beads of the first sample was estimated. The number of metal nanoparticle-immobilized beads in the first sample is 2.49 × 10 ¹⁰ (pieces / mL) × 2 (mL) = 4.98 × 10 ¹⁰ (pieces). Therefore, the amount of heat per unit time was calculated by setting the number of metal nanoparticle-immobilized beads fixed to the substrate to 5.0 × 10 ¹⁰ .

  Curve B1 represents the theoretical value of heat per unit time of the gold nanoparticle-immobilized beads calculated from the curve A1 of FIG. 15, the sunlight spectrum of FIG. 13, and the transmission spectrum of the ITO-PEN film of FIG. Show. Curve B2 is the theoretical value of the heat per unit time of the silver nanoparticle-immobilized beads calculated from the curve A2 in FIG. 15, the sunlight spectrum in FIG. 13, and the transmission spectrum of the ITO-PEN film in FIG. Indicates.

  On the other hand, as shown in FIGS. 10 and 11, the actual temperature increase width of the gold nanoparticle-immobilized beads is 18.9 ° C., and the actual temperature increase width of the silver nanoparticle-immobilized beads is 9. 0 ° C. The reason why the actual temperature rise width is lower than the theoretical temperature rise width is considered to be that the heat generated by the photothermal conversion element 1 is released around the photothermal conversion element 1. Therefore, by suppressing the heat radiation of the photothermal conversion element 1, it is possible to further increase the temperature rise width of the photothermal conversion element 1.

  Furthermore, the ratio between the temperature increase width of the gold nanoparticle-immobilized beads and the temperature increase width of the silver nanoparticle-immobilized beads was evaluated. The ratio of the temperature rise width according to the theoretical value is 50.9 ° C./25.8° C. = 1.97. The ratio of the temperature rise width according to the experimental value is 18.5 ° C./9.0° C. = about 2.06. The ratio of the theoretical value of the temperature rise width agrees well with the ratio of the experimental value of the temperature rise width. This shows the validity of the theoretical considerations.

  FIG. 17 is a graph showing the numerical calculation result of the time dependence of the temperature change, which is expected in an ideal case assuming that the heat radiation amount is completely zero. Referring to FIG. 17, the horizontal axis of the graph indicates the irradiation time of light, and the vertical axis of the graph indicates the value of temperature change. In both the photothermal conversion element using gold nanoparticle-immobilized beads and the photothermal conversion element using silver nanoparticle-immobilized beads, the temperature change value increases in proportion to the light irradiation time.

By integrating the theoretical value of the amount of heat per unit time represented by the curve B1, the temperature rise width of the gold nanoparticle-immobilized beads (number: 5 × 10 ¹⁰ ) by irradiation with sunlight for 100 seconds was calculated. . The temperature increase width of the gold nanoparticle-immobilized beads was calculated to be 50.9 ° C. Similarly, by integrating the theoretical value of the amount of heat per unit time represented by curve B2, the temperature rise width of the silver nanoparticle-immobilized beads (number: 5 × 10 ¹⁰ ) due to sunlight irradiation for 100 seconds can be obtained. Calculated. The temperature increase width of the silver nanoparticle-immobilized beads was calculated to be 25.8 ° C.

[Photothermal power generator]
FIG. 18 is a schematic configuration diagram of the photothermal power generation device according to the embodiment of the present invention. Referring to FIG. 18, the photothermal power generation device 100 includes a photothermal conversion element 1 and a thermoelectric conversion unit 20. The thermoelectric conversion unit 20 includes a high temperature part 21, low temperature parts 22 and 23, a P-type thermoelectric semiconductor 24, and an N-type thermoelectric semiconductor 25.

  The high temperature part 21 and the photothermal conversion element 1 are thermally connected. The P-type thermoelectric semiconductor 24 is thermally connected to the high temperature part 21 and the low temperature part 22. The N-type thermoelectric semiconductor 25 is thermally connected to the high temperature part 21 and the low temperature part 23.

  The light source 40 is, for example, the sun. The photothermal conversion element 1 receives light 41 (sunlight) from the light source and generates heat. Therefore, the temperature of the high temperature part 21 rises. On the other hand, the low temperature parts 22 and 23 are cooled by, for example, a heat sink (not shown). As a result, a temperature difference is generated between both ends of the P-type thermoelectric semiconductor 24 and the N-type thermoelectric semiconductor 25. In this embodiment, the light source 40 is the sun. However, the light source 40 is not limited to the sun.

  Inside the P-type thermoelectric semiconductor 24, the holes 24h are diffused and gathered on the low temperature portion 22 side. For this reason, in the P-type thermoelectric semiconductor 24, the potential on the low temperature portion 22 side is increased. On the other hand, inside the N-type thermoelectric semiconductor 25, the electrons 25e diffuse to the low temperature portion 23 side. Therefore, in the N-type thermoelectric semiconductor 25, the potential on the low temperature portion 23 side is lowered. Therefore, a potential difference is generated between the low temperature portions 22 and 23. By connecting the load 50 to the low temperature sections 22 and 23, current flows from the low temperature section 22 to the load 50. That is, electric energy is supplied from the photothermal power generation device 100 to the load 50.

  Thus, the photothermal power generation device 100 converts light energy into heat energy, and further converts the heat energy into electrical energy. Next, a specific form of the photothermal power generation apparatus 100 according to the embodiment of the present invention will be described.

(Embodiment 1)
FIG. 19 is a diagram showing a configuration of the photothermal power generation device 101 according to the first embodiment of the present invention. Referring to FIG. 19, the photothermal power generation device 101 includes a photothermal conversion element 1 and a thermoelectric conversion unit 20.

  The photothermal conversion element 1 includes a metal nanoparticle integrated structure 10 and substrates 2 and 3. The substrates 2 and 3 are, for example, ITO-PEN films. The substrate 2 includes a PEN film 2a and an ITO film 2b. The substrate 3 includes a PEN film 3a and an ITO film 3b. The metal nanoparticle integrated structure 10 is fixed to the surface of the ITO film 2b. That is, the surface of the substrate 2 on which the ITO film 2 b is formed becomes a fixing surface for fixing the metal nanoparticle assembly structure 10. The substrate 3 is arranged so that the ITO film 3b faces the ITO film 2b.

  The thermoelectric conversion unit 20 includes high-temperature parts 21a and 21b, low-temperature parts 22a, 22b, and 22c, P-type thermoelectric semiconductors 24a and 24b, N-type thermoelectric semiconductors 25a and 25b, and a heat sink 27.

  The high temperature part 21a is composed of an electrode 31a and a conductive paste 32a. The high temperature part 21b is composed of an electrode 31b and a conductive paste 32b.

  P-type thermoelectric semiconductor 24a and N-type thermoelectric semiconductor 25a are thermally and electrically connected to electrode 31a via conductive paste 32a. The P-type thermoelectric semiconductor 24b and the N-type thermoelectric semiconductor 25b are thermally and electrically connected to the electrode 31b via the conductive paste 32b.

  The low temperature part 22a is composed of a conductive paste 33a, an electrode 34a, and a conductive paste 35a. The P-type thermoelectric semiconductor 24a is thermally and electrically connected to the electrode 34a through the conductive paste 33a. The low temperature part 22a is thermally connected to the heat sink 27 via the conductive paste 35a. The heat sink 27 is made of an alumina substrate, for example. Therefore, the low temperature part 22 a is electrically insulated from the heat sink 27.

  The low temperature part 22b is composed of a conductive paste 33b, an electrode 34b, and a conductive paste 35b. The N-type thermoelectric semiconductor 25b is thermally and electrically connected to the electrode 34b through the conductive paste 33b. Although the low temperature part 22b is thermally connected to the heat sink 27 via the conductive paste 35b, it is electrically insulated from the heat sink 27.

  The low temperature part 22c is composed of a conductive paste 33c, an electrode 34c, and a conductive paste 35c. N-type thermoelectric semiconductor 25a and P-type thermoelectric semiconductor 24b are thermally and electrically connected to electrode 34c through conductive paste 33c. Although the low temperature part 22b is thermally connected to the heat sink 27 via the conductive paste 35b, it is electrically insulated from the heat sink 27.

  According to the configuration shown in FIG. 19, the light 41 is incident on the surface of the substrate 3 opposite to the surface on which the ITO film 3b is formed. The surface of the substrate 2 opposite to the surface (fixed surface) on which the ITO film 2b is formed is thermally connected to the electrodes 31a and 31b. Therefore, the high temperature portions 21 a and 21 b are thermally connected to the photothermal conversion element 1 and are electrically insulated from the photothermal conversion element 1. The light that has passed through the substrate 3 is irradiated to the plurality of metal nanoparticle integrated structures 10. As a result, localized surface plasmon resonance occurs in the plurality of metal nanoparticle integrated structures 10 to enhance heat generation. Furthermore, the heat generated by the photothermal conversion element 1 is directly transmitted to the electrodes 31a and 31b. Therefore, a large amount of heat energy can be transmitted from the photothermal conversion element 1 to the thermoelectric conversion unit 20.

  Further, in the configuration shown in FIG. 19, a thermoelectric conversion unit composed of a P-type thermoelectric semiconductor 24a and an N-type thermoelectric semiconductor 25a and a thermoelectric conversion unit composed of a P-type thermoelectric semiconductor 24b and an N-type thermoelectric semiconductor 25b are electrically connected in series. Connected. Thereby, the output voltage of the thermoelectric conversion part 20 can be made high.

  FIG. 19 shows a case where the number of pairs of P-type thermoelectric semiconductors and N-type thermoelectric semiconductors is two. However, the number of pairs of P-type thermoelectric semiconductors and N-type thermoelectric semiconductors is not limited to two.

  FIG. 20 is a diagram illustrating a result of an experiment on a temporal change in output by the photothermal power generation device 101 illustrated in FIG. Referring to FIG. 20, the horizontal axis of the graph indicates the irradiation time of light, and the vertical axis of the graph indicates the power output from the thermoelectric conversion module. In this experiment, the thermoelectric conversion module is a ceramic substrate, a reference substrate (shown as “REF” in the figure), a photothermal conversion element using gold nanoparticle-immobilized beads, and photothermal conversion using silver nanoparticle-immobilized beads. Each of the elements was mounted. Furthermore, in FIG. 20, the output of the thermoelectric conversion module when there is no photothermal conversion element is also shown for reference. As shown in FIG. 20, by using the photothermal conversion element according to the embodiment of the present invention, the output of the thermoelectric conversion module becomes higher than when a ceramic substrate or a reference substrate is used. This indicates the feasibility of photothermal power generation using the heat generation effect of the photothermal conversion element according to the embodiment of the present invention.

Furthermore, it is preferable to use an element having higher conversion efficiency for the thermoelectric conversion section 20 shown in FIG. For example, Bi _0.4 Sb _1.6 Te ₃ can be used as the material of the P-type thermoelectric semiconductor 24 in the thermoelectric converter 20. A material in which Bi ₂ Te ₃ is doped with Sb exhibits high thermoelectric properties in a temperature range from around room temperature to around 100 ° C. Therefore, by combining the thermoelectric conversion unit 20 including such a P-type thermoelectric semiconductor 24 and the photothermal conversion element according to the present embodiment, the photothermal power generation apparatus 101 shown in FIG. The output can be increased.

(Embodiment 2)
FIG. 21 is a diagram showing a configuration of the photothermal power generation device 102 according to the second embodiment of the present invention. Referring to FIG. 21, photothermal conversion elements 1A and 1B are formed, for example, by dividing photothermal conversion element 1 in accordance with the size of the thermoelectric conversion portion.

  Each of the photothermal conversion elements 1A and 1B is arranged so that the light 41 is incident on the surface of the substrate 2 opposite to the surface on which the ITO film 2b is formed. Further, each of the photothermal conversion elements 1A and 1B is formed so that the ITO film 3b of the substrate 3 faces outward.

  In the configuration of the photothermal power generation device 102 according to the second embodiment, the electrodes 31a and 31b are omitted from the configuration of the photothermal power generation device 101 according to the first embodiment. In the photothermal conversion element 1A, the ITO film 3b of the substrate 3 is electrically and thermally connected to the P-type thermoelectric semiconductor 24a and the N-type thermoelectric semiconductor 25a via the conductive paste 32a. In the photothermal conversion element 1B, the ITO film 3b of the substrate 3 is electrically and thermally connected to the P-type thermoelectric semiconductor 24b and the N-type thermoelectric semiconductor 25b via the conductive paste 32b.

  The sizes of the photothermal conversion elements 1A and 1B are determined so that the N-type thermoelectric semiconductor 25a and the P-type thermoelectric semiconductor 24b are not electrically short-circuited by the ITO film 3b of the substrate 3. In this embodiment, the high temperature portion is realized by the ITO film 3b of the substrate 3 and the conductive pastes 32a and 32b. Since the structure of the other part of the photothermal power generation apparatus 102 is the same as the structure of the corresponding part of the photothermal power generation apparatus 101 shown in FIG. 19, the following description will not be repeated.

  According to the second embodiment, the effect obtained by the first embodiment can be obtained. Furthermore, according to the second embodiment, the electrode in the high temperature part can be omitted. Therefore, the configuration of the photothermal power generation device can be further simplified.

(Embodiment 3)
FIG. 22 is a diagram schematically showing the configuration of the photothermal power generation device 103 according to the third embodiment of the present invention. Referring to FIG. 22, the photothermal power generation device 103 includes a solar cell / photothermal conversion element 1 </ b> C and a thermoelectric conversion unit 20.

  Solar cell / photothermal conversion element 1 </ b> C is an element having both a solar battery and the photothermal conversion element according to the embodiment of the present invention. In this embodiment, a dye-sensitized solar cell (a dye-sensitized photoelectric conversion element) is employed. FIG. 23 is a diagram showing the structure of the solar cell / photothermal conversion element 1C shown in FIG.

Referring to FIG. 23, solar cell / photothermal conversion element 1C includes substrates 2 and 3, metal nanoparticle integrated structure 10 fixed on the surface of substrate 2, and titanium oxide (TiO 2) to which sensitizing dye 62 is attached. ₂ ) 61 and an electrolyte solution 63 containing iodine. In many cases, a film of titanium oxide 61 is formed on the surface of the ITO film 2 b of the substrate 2, and the sensitizing dye 62 is attached to the titanium oxide 61. Note that, in order to avoid complication of the figure, in FIG. 23, the titanium oxide 61 is shown apart from the ITO film 2b.

  In the substrate 3, a catalyst layer made of platinum or the like is formed on the surface of the ITO film 3b. An electrolyte solution 63 exists between the substrates 2 and 3. The electrolyte solution 63 is typically an iodine-based electrolyte.

The dye-sensitized solar cell generates power based on the following principle. The sensitizing dye 62 is excited by absorbing light 41 from the light source 40 (for example, the sun) and emits electrons. The electrons reach the ITO film 2b (transparent electrode) via the titanium oxide 61 and flow to the outside. The electrons reach the ITO film 3b (transparent electrode) via an external circuit. The triiodide ions (I ₃ ⁻ ) in the electrolyte solution 63 change to iodide ions (I ⁻ ) by receiving electrons from the ITO film 3b. The iodide ion is changed to triiodide ion by passing electrons to the sensitizing dye 62. On the other hand, the sensitizing dye 62 that has received the electrons returns to the original state. While the sensitizing dye 62 is irradiated with light, the above series of operations is repeated.

  From the configuration shown in FIG. 23, in Embodiment 3, it can be said that the photothermal conversion element includes a dye-sensitized solar cell. The substrates 2 and 3 function as electrodes of the dye-sensitized solar cell.

  It is preferable to apply titanium oxide particles to the base particles of the metal nanoparticle assembly structure 10. Thereby, not only the heat generation effect can be enhanced, but also light scattering can be enhanced inside and on the surface of the metal nanoparticle integrated structure 10. By enhancing the light scattering, the light absorption efficiency of the sensitizing dye 62 can be improved, so that the power generation efficiency of the dye-sensitized solar cell can be increased. The effect of enhancing light scattering by the metal nanoparticle integrated structure 10 will be described below.

FIG. 24 is a diagram for explaining a three-dimensional model of beads immobilized with silver nanoparticles. Referring to FIG. 24, D _b is the diameter of the silver nanoparticle assembly structure. D _c is the diameter of the cluster 12A. _ap is the diameter of the silver nanoparticles (metal nanoparticles 12) constituting the cluster 12A. d _p is the interval of the cluster 12A.

  FIG. 25 is a diagram showing a calculation model of the silver nanoparticle-immobilized beads shown in FIG. Referring to FIG. 25, in the calculation model, an aggregate of silver nanoparticles is handled as a cluster (cluster DDA (discrete dipole approximation) method).

In the model shown in (A), the number N of clusters is 546, and d _p = 10 nm. In the model shown in (B), the number N of clusters is 793, and d _p = 5 nm. In the model shown in (C), the number N of clusters is 1024, and d _p = 2 nm. In the models shown in FIGS. 25A to 25C, D _b = 400 nm, a _p = D _c = 20 nm, and one cluster includes one silver nanoparticle.

  FIG. 26 is a diagram showing the calculation result of the extinction spectrum of the silver nanoparticle-immobilized beads. Referring to FIG. 26, the number of clusters N = 546 (corresponding to FIG. 25A), N = 793 (corresponding to FIG. 25B), and N = 1024 (FIG. 25C 3) extinction spectra corresponding to) are shown. Further, FIG. 26 also shows the result of multiplying the spectrum when N = 1 by 50.

  When N = 1, the peak wavelength of the extinction spectrum is approximately 400 nm. As the number N of clusters increases, the peak wavelength of the extinction spectrum shifts to the longer wavelength side and the spectrum becomes broader.

  FIG. 27 is a diagram showing an electric field intensity distribution according to the number N of clusters. Referring to FIG. 27, there is shown an electric field intensity distribution in a region having a size of 2 μm × 2 μm when polarized light having a wavelength λ = 600 nm traveling perpendicularly to a plane with the center of the bead as the origin is incident. The spot diameter is 1 μm. FIGS. 27A to 27D show electric field intensity distributions when the number of clusters N = 0, N = 546, N = 793, and N = 1024, respectively.

  In each of FIGS. 27A, 27B, 27C, and 27D, a circle is indicated by a dotted line. The inside of this circle corresponds to the inside of the core. The case of N = 0 corresponds to the case of only the incident electric field. The integrated intensity of the electric field inside the core when N = 0 is set to 1. In the case of N = 546, the integrated intensity of the electric field inside the core is 3.59 times that in the case of N = 0. In the case of N = 793, the integrated intensity of the electric field inside the core is 14.6 times that in the case of N = 0. When N = 1024, the integrated intensity of the electric field inside the core is 75.9 times that when N = 0.

  In the above description, the configuration relating to the dye-sensitized solar cell using the electric field enhancement effect inside and outside the metal nanoparticle-immobilized beads is disclosed, but the present invention is not limited to this. If the light receiving portion has a hydrophobic surface, it can be used for various solar cells such as silicon-based, compound-based, organic-based, and quantum dot types.

  From FIG. 26 and FIG. 27, it is possible to cover all of the ultraviolet region, visible region, and infrared region by appropriately selecting the type of metal nanoparticles from plasmonic super-radiation in a small area. Indicated.

  Furthermore, in the metal nanoparticle assembly structure 10, the average interparticle distance of the metal nanoparticles 12 is preferably shorter than those in FIGS. That is, in the metal nanoparticle assembly structure 10, it is preferable that the metal nanoparticles 12 are accumulated at a higher density. Thereby, the power generation efficiency of the solar cell part (photoelectric conversion element) in the configuration shown in FIGS. 22 and 23 can be increased.

FIG. 34 is a diagram collectively showing the characteristics of the solar cell part (photoelectric conversion element) in the configuration shown in FIGS. 22 and 23 in a table format. Silver nanoparticles (diameter 4.2 nm) were used as the sensitizing dye 62, and beads used for the metal nanoparticle integrated structure 10 and titanium oxide (TiO ₂ ) particles (diameter 50 nm) were used as the sensitizing dye 62. Referring to FIG. 34, in the sample having a density of silver nanoparticles of 2 × 10 ¹⁴ particles / mL (average interparticle distance: 4.87 nm), the open circuit voltage is 0.755 (V) and the short circuit current density is 16 0.0 (μA / cm ² ). The area of a region coated with TiO ₂ particles of this sample was 11.84cm ^2.

In the sample having a silver nanoparticle density of 2 × 10 ¹³ particles / mL (average interparticle distance of 15.4 nm), the open circuit voltage is 0.698 (V) and the short circuit current density is 12.4 (μA / cm ^2. )Met. The area of a region coated with TiO ₂ particles of this sample was 11.84cm ^2.

For comparison with these samples, the open-circuit voltage and short-circuit current density of the sample using TiO ₂ particles to which an organic dye (sensitizing dye) was attached were measured. The open circuit voltage was 0.720 V, and the short circuit current density was 5.7 (μA / cm ² ). The area of a region coated with TiO ₂ particles of this sample was 15.70cm ^2.

According to this embodiment, the photoelectric conversion element using TiO ₂ particles to which silver nanoparticles are fixed can realize higher-efficiency photovoltaic power generation than the photoelectric conversion element using TiO ₂ particles to which a sensitizing dye is attached. . Further, the TiO ₂ particles with a fixed silver nanoparticles, a higher density of the silver nanoparticles (to shorten the average interparticle distance) by, it is possible to increase the efficiency of the photovoltaic. Specifically, the open circuit voltage can be increased in the same area, and the short circuit current density can be increased. In the above embodiment, the current density was increased by about 127% and the open circuit voltage was increased by 108% by increasing the average interparticle distance of the silver nanoparticles from 15.4 nm to 4.87 nm. In addition, when the silver nanoparticles are high density, both the short-circuit current and the open-circuit voltage are larger than the result of the comparative experiment using the TiO ₂ particles to which the organic dye (sensitizing dye) is attached. confirmed.

[Other configuration of photothermal conversion element]
The structure of the photothermal conversion element according to the embodiment of the present invention is not limited as shown in FIG. FIG. 28 is a diagram showing another structure of the photothermal conversion element according to the embodiment of the present invention. The photothermal conversion element shown in FIG. 28 is different from the structure shown in FIG. 1 in that the substrate 3 is not provided. In this configuration, the metal nanoparticle integrated structure 10 can be irradiated with light from the opposite side to the substrate 2. Therefore, it is not essential that the substrate 2 has light transmittance.

  For example, the metal nanoparticle integrated structure 10 can be integrated on the surface of the substrate 2 with high density using PDMS (polydimethylsiloxane). As a method for fixing the metal nanoparticle assembly structure 10 using PDMS, for example, the following method can be used. First, the metal nanoparticle integrated structure is dispersed in a low-viscosity solution (for example, SILPOT 184 manufactured by Toray Dow Corning Co., Ltd.), and the dispersion is applied to the substrate 2. Next, a liquid for solidifying the dispersion (for example, CATALYST SILPOT 184 manufactured by Toray Dow Corning Co., Ltd.) is added to the dispersion on the substrate, and the substrate is heated. This solidifies PDMS. In addition, the method for solidifying PDMS can also use another well-known method.

  FIG. 29 is a diagram showing still another structure of the photothermal conversion element according to the embodiment of the present invention. The photothermal conversion element 1D shown in FIG. 29 is different from the configuration shown in FIG. 1 in that the metal nanoparticle integrated structure 10 is arranged in two layers between the substrate 2 and the substrate 3. The photothermal conversion element 1D shown in FIG. 29 can be applied to the photothermal power generation device shown in FIG. 19 (Embodiment 1) or FIG. 21 (Embodiment 2), for example.

  FIG. 30 is a flowchart schematically illustrating a manufacturing method of the photothermal conversion element 1D shown in FIG. 4 and 30, the manufacturing method of the photothermal conversion element 1D is basically the same as the manufacturing method of the photothermal conversion element 1, but the metal nanoparticle-immobilized beads are provided on both of the two substrates. Is different from the manufacturing method of the photothermal conversion element 1 in that

  Specifically, in step S1A, both the first substrate (substrate 2) and the second substrate (substrate 3) are cleaned. In step S2A, the edge portions of the surfaces of the substrates 2 and 3 are masked by the masking tapes 4 and 5. In step S3A, the metal nanoparticle-immobilized bead dispersion is diluted to adjust the concentration of the dispersion. Steps S2A and S3A are not essential.

  In step S4A, the diluted dispersion 6 of metal nanoparticle-immobilized beads is applied to both surfaces of the substrates 2 and 3. In step S5A, the substrates 2 and 3 are left to dry. As a result, the metal nanoparticle-immobilized beads are fixed to the respective surfaces of the substrates 2 and 3. In step S6A, the second substrate (substrate 3) is bonded to the first substrate (substrate 2). At this time, the substrate 2 and the substrate 3 are bonded together so that the surfaces coated with the diluted dispersion 6 of metal nanoparticle-immobilized beads are opposed to each other. Thereby, the photothermal conversion element 1D shown in FIG. 29 can be produced.

  FIG. 31 is a diagram schematically illustrating the effect of the photothermal conversion element 1D shown in FIG. Referring to FIG. 31, light 41 (for example, sunlight) from a light source is converted into more heat by arranging metal nanoparticle assembly structure 10 in two layers between substrate 2 and substrate 3. be able to. That is, heat generation can be further enhanced.

  Furthermore, in order to enhance the heat generation in the photothermal conversion element 1D, the substrates 2 and 3 are preferably substrates having high transmittance for visible light.

  FIG. 32 is a diagram showing an example of a transmission spectrum of a PEN film applicable as a transparent substrate of the photothermal conversion element according to the embodiment of the present invention. Referring to FIG. 32, the transmittance exceeds 80% in the wavelength region of 400 nm to 800 nm. By applying such a transparent resin film to a photothermal conversion element as a substrate, the light heat generation effect of the photothermal conversion element can be enhanced.

  FIG. 33 is a diagram showing experimental results of the light heat generation effect by the light-to-heat conversion element according to the embodiment of the present invention. In addition, as the metal nanoparticle integrated structure 10, gold nanoparticle fixed beads were used. A solar simulator was used as the light source.

  Referring to FIG. 33, when the substrates 2 and 3 are ITO-PEN films and the substrates 2 and 3 are high transmittance films having the transmission spectrum shown in FIG. It can be seen that the light heating effect is enhanced by arranging the structures 10 in two layers. Further, in the case where the metal nanoparticle assembly structure 10 is arranged in a single layer or in the case where the metal nanoparticle assembly structure 10 is arranged in two layers, by using a high transmittance film for the substrates 2 and 3, It can be seen that the photothermal effect is enhanced as compared with the case of using an ITO-PEN film for No. 3.

  Therefore, the configuration in which the high transmittance films are used for the substrates 2 and 3 and the metal nanoparticle integrated structure 10 is arranged in two layers (shown as “2layer (high transmittance film)” in FIG. 33) is shown in FIG. The temperature increase range can be made larger than any of the other configurations shown in FIG. In the results shown in FIG. 33, the temperature rose about 45 ° C. after 100 seconds from the light irradiation start time (0 seconds).

  Here, as shown in FIG. 17, the theoretical temperature rise when the metal nanoparticle integrated structure 10 is irradiated with sunlight for 100 seconds is about 50 ° C. In contrast, in the above experiment, the temperature rise was about 45 ° C. That is, with the configuration of “2 layer (high transmittance film)”, the temperature increase range could be brought closer to the theoretical limit.

  29 to 33 disclose a case in which the metal nanoparticle-immobilized beads are formed in two layers between the substrate 2 and the substrate 3. However, it is only necessary that the metal nanoparticle-immobilized beads are formed in a plurality of layers between the substrate 2 and the substrate 3, and the number of layers of the metal nanoparticle-immobilized beads is not limited to two.

  Regarding the method for manufacturing the light-emitting element, in step S5 of FIG. 4 and step S5A of FIG. 30, in order to increase the integration density of the metal nanoparticle-immobilized beads, the metal nanoparticles as shown in FIG. 5 and FIG. The dispersion liquid of the integrated structure was dropped on a hydrophobic substrate and dried. In place of such an integration method or in addition to the above integration method, in order to further increase the integration density of the metal nanoparticle-immobilized beads, the dispersion of metal nanoparticle-immobilized beads is irradiated with laser light, A method of collecting metal nanoparticle-immobilized beads using an optical trap can be adopted. The laser power described below is the power at the light source, and is about 10% when passing through the objective lens. The spot diameter is about 1 μm.

  FIG. 35 is a conceptual diagram of integration of metal nanoparticle-immobilized beads using an optical trap. FIG. 36 is a diagram systematically showing a state from the start of irradiation with laser light having a power of 1.0 W to a sample in which silver nanoparticle-immobilized beads are dispersed in water. FIG. 37 is a first enlarged photograph showing the silver nanoparticle fixed beads dispersed in water before being integrated by the optical trap (after 24 seconds from the start of laser light irradiation). FIG. 38 is an enlarged view of the second photograph showing the silver nanoparticle-immobilized beads integrated by the optical trap (39 seconds after the start of laser light irradiation).

  FIG. 37 shows the state 24 seconds after the dispersion of the metal nanoparticle integrated structure is irradiated with laser light having a power of 1.0 W, and the thermal convection generated in the initial stage of laser light irradiation is stable. As a result, it was confirmed that the silver nanoparticle-immobilized beads were gathered near the focal point of the laser beam. When the laser beam irradiation is further continued, as shown in FIG. 36, micro bubbles having a size of about several tens of μm are generated in the dispersion liquid after about 27 seconds, and as shown in FIG. It was confirmed that the beads immobilized with silver nanoparticles gathered on the surface.

  FIG. 39 is a photograph for explaining the difference in the degree of integration of the silver nanoparticle fixed beads by the optical trap when the power of the laser beam is changed. Referring to FIG. 39, when the power of the laser beam was 0.2 W and 0.6 W, respectively, the dispersion of silver nanoparticle fixed beads was irradiated with the laser beam for 1 minute. It can be seen that the effect of collecting the silver nanoparticle fixed beads by the optical trap is higher when the power of the laser light is 0.6 W than when the power of the laser light is 0.2 W.

  FIG. 40 is a diagram for explaining the effect of integrating the silver nanoparticle-immobilized beads using optical tweezers. FIG. 40A is a diagram showing a state where metal nanoparticle-immobilized beads are integrated. FIG. 40B shows a Raman scattering spectrum at the positions a and b of the sample shown in FIG. 40A and an average value in a rectangular region (“averaged region” in the figure). It is. The position a is a position irradiated with trapping light. The position b is a position where the metal nanoparticle fixed beads are integrated. When the laser light power is 0.6 W, as shown in FIG. 40B, Raman scattering having the same spectral shape as that of the silver nanoparticle-immobilized beads integrated by natural drying in FIG. I was able to observe. From this, it was confirmed that the metal nanoparticle-immobilized beads can be collected at high density without denaturing the sample.

  In particular, the peak value of the Raman scattering spectrum at the position b of the sample corresponding to the bubble surface is 30,000 or more, and the average value is 10000 or more. The value at the position b is 4 times or more than the peak value (about 7000) of the Raman scattering spectrum in the sample obtained by natural drying of the solution in which the metal nanoparticle fixed beads are dispersed as shown in FIG. It became the value of. The reason why the peak value is small at the position a is considered to be that the density was reduced by the silver nanoparticle-immobilized beads being pushed away by a very strong heat generation effect near the laser light spot or light pressure. FIG. 40 shows that the efficiency of photothermal conversion can be increased by integrating the metal nanoparticle-immobilized beads using an optical trap.

  Moreover, in said embodiment, the structure regarding the photothermal power generation and photoelectric conversion was shown as a manufacturing method of a photothermal conversion element, and the example of application. However, the application field of the heat generation effect by the photothermal conversion element is not limited to the field of photothermal power generation or photoelectric conversion. For example, the metal nanoparticle-immobilized beads according to the embodiment of the present invention may be contained in a thermocoagulable material or a heat-soluble material. A solution obtained by adding a thermocoagulable material to a dispersion of metal nanoparticle-immobilized beads may be applied to the surface of the substrate, and the thermocoagulable material may be solidified by irradiating the thermocoagulable material with laser light. The metal nanoparticle-immobilized beads may be dispersed while the heat-soluble material is heated, and then cooled and solidified again.

  Here, a configuration using a heat-solidifying material will be described representatively. The thermocoagulable material is not particularly limited as long as it is a material that changes from a liquid to a solid by applying heat. The thermocoagulable material is, for example, a liquid containing protein. However, the thermosetting material is not limited to protein, and may be, for example, a thermosetting resin.

  FIG. 42 is a diagram illustrating the heat generation effect of the metal nanoparticle-immobilized beads according to the embodiment of the present invention. Referring to FIG. 42, the silver nanoparticle fixed bead solution diluted with egg white was irradiated with an infrared laser beam having a wavelength of 1064 nm. The intensity of the laser beam was 1.0W. When the laser beam is irradiated onto the silver nanoparticle-immobilized bead solution, the silver nanoparticle-immobilized beads are accumulated by the optical trap. It was confirmed that the egg white was solidified by the heat generation effect of the silver nanoparticle-immobilized beads. Since the freezing point of egg white is 75 ° C. to 78 ° C., it has been confirmed that the temperature has been reached by laser light irradiation.

  Moreover, in order to confirm the influence by the presence or absence of silver nanoparticle fixed beads, 1064 nm infrared laser light (the intensity of the laser light was 1.0 W) was applied to egg white not containing silver nanoparticle fixed beads. In this case, the egg white did not coagulate. From these experimental results, it can be concluded that the experimental results shown in FIG. 42 are obtained by the photothermal effect of the silver nanoparticle-immobilized beads. Therefore, the present invention can be applied to a heat-denatured protein sensor that performs allergen detection and the like by utilizing protein coagulation by irradiating a laser beam to a metal nanoparticle-immobilized bead solution diluted with protein such as egg white. Can do.

  The heat-settable material after solidification can be processed by various methods. FIG. 43 is a diagram showing an example of processing with a laser beam of a thermocoagulable material including metal nanoparticle-immobilized beads according to an embodiment of the present invention. Here, silver nanoparticle-immobilized beads were used as the metal nanoparticle-immobilized beads, and egg white was used as the thermocoagulable material. Referring to FIG. 43, for example, laser light can be used not only for solidification of the thermosetting material, but also for cutting the solidified thermosetting material. Therefore, the development to the micro processing technology can be achieved. If a heat-soluble material is used instead of a heat-solidifying material, the metal nanoparticle-immobilized beads are dispersed and cooled or solidified in a thermally dissolved state, and then locally dissolved by laser light irradiation. Similar micromachining can be performed. Although it does not specifically limit as a heat-soluble material, The material which melt | dissolves at 75 degrees C or less is preferable, for example, gelatin and a plastic can be used.

  As described above, according to the embodiment of the present invention, the photothermal conversion element can be produced simply by applying the metal nanoparticle-immobilized beads to the substrate. Specifically, a dispersion of metal nanoparticle-immobilized beads is applied to a substrate, and the dispersion is naturally evaporated. With such a manufacturing method, a photothermal conversion element can be manufactured at low cost.

  In the embodiment of the present invention, a commercially available metal nanoparticle fixed bead dispersion is used. That is, the metal nanoparticle fixed bead can also be easily produced. According to the embodiment of the present invention, it is possible to manufacture a photothermal conversion element at low cost also from this point.

  Furthermore, according to the embodiment of the present invention, in the case of a photothermal conversion element including gold nanoparticle-immobilized beads, the temperature of the photothermal conversion element reaches 50 ° C. or more by irradiation with sunlight for about 100 seconds. confirmed. Theoretically, the temperature rise of the photothermal conversion element reaches 50.9 ° C. under the same conditions. Therefore, the temperature of the photothermal conversion element can be raised to 80 ° C. or higher without placing the photothermal conversion element in a vacuum environment. However, this does not exclude the case where the photothermal conversion element is placed in a vacuum environment. By placing the photothermal conversion element in a vacuum environment, it is possible to prevent the heat generated by the photothermal conversion element from escaping around the photothermal conversion element.

  Furthermore, according to the embodiment of the present invention, an ITO-PEN film can be used as the substrate of the photothermal conversion element. Therefore, the freedom degree of installation of a photothermal conversion element can be raised.

  Furthermore, according to the embodiment of the present invention, not only the infrared region but also the light in the ultraviolet region and the visible region can be used effectively.

  Furthermore, according to the embodiment of the present invention, the temperature can be controlled by the concentration of the metal nanoparticle-immobilized beads.

  Furthermore, according to the embodiment of the present invention, the photothermal conversion efficiency can be further improved by forming the metal nanoparticle-immobilized beads in two layers.

  Furthermore, according to the embodiment of the present invention, the metal nanoparticle-immobilized beads can be integrated at a high density by irradiating the dispersion containing the metal nanoparticle-immobilized beads with laser light. Further, by adding a thermocoagulable material to the dispersion, the thermocoagulable material can be coagulated by irradiating the dispersion on the substrate with laser light. Furthermore, the heat solidified material after heat solidification can be processed by the laser beam. In addition to this, after thermally dissolving the heat-soluble material, the metal nanoparticle-immobilized beads are dispersed and cooled or solidified, and then the heat-soluble material is locally irradiated by laser irradiation. It can also be dissolved.

  The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be used for photothermal power generation in which sunlight is converted into heat. For example, the present invention relates to an outlet-free power source for portable information terminals (cell phones, tablets, etc.), an auxiliary power source for in-vehicle devices (auxiliaries or batteries for car navigation systems, etc.), solar power generators for satellites, roofs of houses, It can be used as a solar power generation device that can be installed on windows.

  The present invention can also be used as a heat source or a temperature control device. When used as a heat source, for example, it can be used for medical applications such as thermotherapy such as affixing to an affected area and locally heating. In addition, it can be used for a catalyst whose catalytic activity is enhanced by an increase in temperature to increase the chemical reaction efficiency.

  In addition, the present invention can be used for coagulation of thermocoagulable substances and dissolution of thermosoluble materials. This can be used for bio- and medical-related technologies such as micro-control and detection of heat-denatured proteins using the photo-induced heat generation effect. Furthermore, the solidified thermosetting substance can be cut with a laser beam. Therefore, the present invention can be used for fine processing.

  1, 1A, 1B, 1D photothermal conversion element, 1C solar cell / photothermal conversion element, 2, 3 substrate, 2a, 3a PEN film, 2b, 3b ITO film, 4, 5 masking tape, 6 diluted dispersion, 6a region, 6b Water droplet, 7 coating surface, 10 metal nanoparticle integrated structure, 11 beads, 12 metal nanoparticles, 12A cluster, 20 thermoelectric conversion part, 21, 21a, 21b high temperature part, 22, 23, 22a-22c low temperature part, 24 , 24a, 24b P-type thermoelectric semiconductor, 24h hole, 25, 25a, 25b N-type thermoelectric semiconductor, 25e electron, 27 heat sink, 31a, 31b, 34a-34c electrode, 32a, 32b, 33a-33c, 35a-35c Paste, 40 light source, 41 light, 50 load, 61 titanium oxide, 62 sensitizing dye, 63 electrolyte solution 100 to 103 light-to-heat power generation apparatus.

Claims (26)

A plurality of metal nanoparticle assembly structures each formed by the integration of a plurality of metal nanoparticles;
A photothermal conversion element comprising: a first substrate having a fixed surface to which the plurality of metal nanoparticle integrated structures are fixed.   2. The photothermal conversion element according to claim 1, wherein each of the plurality of metal nanoparticle integrated structures includes base particles having a surface on which the plurality of metal nanoparticles are fixed.   The photothermal conversion element according to claim 2, wherein the metal nanoparticles forming each of the plurality of metal nanoparticle integrated structures are gold nanoparticles or silver nanoparticles.   2. The photothermal conversion element according to claim 1, wherein the fixed surface of the first substrate forms a region where the plurality of metal nanoparticle assembly structures are densely packed.   The photothermal conversion element according to claim 4, wherein the fixing surface of the first substrate has hydrophobicity.   The photothermal conversion element according to claim 4, wherein the first substrate is a resin film having a transparent electrode formed on the fixed surface. A second substrate disposed so as to sandwich the plurality of metal nanoparticle assembly structures together with the first substrate;
At least one of the first and second substrates has optical transparency to light that causes localized surface plasmon resonance on the surfaces of the plurality of metal nanoparticles. The photothermal conversion element according to Item.   The photothermal conversion element according to claim 7, wherein a plurality of layers of the plurality of metal nanoparticle integrated structures are formed between the first substrate and the second substrate. Preparing a dispersion liquid in which a plurality of metal nanoparticle assembly structures each formed by integrating a plurality of metal nanoparticles are dispersed;
Providing a first substrate;
Applying the dispersion to the fixed surface of the first substrate;
And a step of fixing the metal nanoparticle integrated structure to the fixing surface of the first substrate. The fixing surface of the first substrate has hydrophobicity;
The method for manufacturing a photothermal conversion element according to claim 9, wherein in the step of applying the dispersion, the dispersion is dropped onto the fixed surface of the first substrate.   The manufacturing method of the photothermal conversion element of Claim 10 which naturally evaporates the said dispersion liquid in the step which fixes the said metal nanoparticle integrated structure. In the step of preparing the first substrate, a resin film having a transparent electrode formed on one surface thereof is prepared as a first substrate,
The method for manufacturing a photothermal conversion element according to claim 9, wherein the fixed surface of the first substrate is a surface of the resin film on which the transparent electrode is formed.   The method for producing a photothermal conversion element according to claim 9, wherein in the step of fixing the metal nanoparticle integrated structure, the metal nanoparticle integrated structure is integrated by irradiating the dispersion with a laser beam. The dispersion includes a thermocoagulable material,
The method for producing a photothermal conversion element according to claim 9, wherein in the step of fixing the metal nanoparticle integrated structure, the thermosetting material is solidified by irradiating the dispersion with a laser beam. The dispersion is a liquid in which a heat-soluble material is thermally dissolved,
10. In the step of fixing the metal nanoparticle assembly structure, the dispersion liquid is irradiated with laser light to accumulate the metal nanoparticle assembly structure, thereby cooling or solidifying the thermally soluble material. The manufacturing method of the photothermal conversion element of description.   The method for manufacturing a photothermal conversion element according to claim 14, further comprising a step of irradiating the thermocoagulable material including the metal nanoparticle integrated structure with a laser beam to process a shape of the thermocoagulable material.   The method for producing a photothermal conversion element according to claim 15, further comprising a step of irradiating the heat-soluble material including the metal nanoparticle-immobilized beads with a laser beam to process the shape of the heat-soluble material. Further comprising the step of overlaying the second substrate on the first substrate such that the plurality of metal nanoparticle assembly structures are sandwiched between the first substrate and the second substrate;
10. The photothermal conversion element according to claim 9, wherein at least one of the first and second substrates is light-transmissive to light that causes localized surface plasmon resonance on the surfaces of the plurality of metal nanoparticles. Manufacturing method. Prior to the step of superimposing the second substrate on the first substrate, further comprising the step of fixing the metal nanoparticle assembly structure to the fixing surface of the second substrate;
The method for manufacturing a photothermal conversion element according to claim 14, wherein in the step of superimposing the second substrate on the first substrate, the fixed surfaces are opposed to each other between the first substrate and the second substrate. A photothermal conversion element;
A thermoelectric conversion unit thermally connected to the photothermal conversion element,
The photothermal conversion element is
A plurality of metal nanoparticle assembly structures each formed by the integration of a plurality of metal nanoparticles;
A first substrate having a fixed surface to which the plurality of metal nanoparticle assembly structures are fixed;
And a second substrate disposed so as to sandwich the plurality of metal nanoparticle assembly structures together with the first substrate,
One of the first and second substrates is light transmissive to light that causes localized surface plasmon resonance on the surfaces of the plurality of metal nanoparticles, and receives the light. Placed in
The other board | substrate of the said 1st and 2nd board | substrate is a photothermal power generation apparatus thermally connected to the said thermoelectric conversion part. The one substrate is the second substrate;
The other substrate is the first substrate;
Each of the first and second substrates is a resin film having a transparent electrode formed on one surface thereof,
The fixed surface of the first substrate is a surface of the resin film on which the transparent electrode is formed,
The surface of the first substrate opposite to the fixed surface is thermally connected to the thermoelectric converter,
The second substrate is disposed so that the surface on which the transparent electrode is formed faces the fixed surface of the first substrate, and the surface opposite to the surface on which the transparent electrode is formed receives the light. The photothermal power generation device according to claim 20. The one substrate is the first substrate;
The other substrate is the second substrate;
Each of the first and second substrates is a resin film having a transparent electrode formed on one surface thereof,
The fixed surface of the first substrate is a surface of the resin film on which the transparent electrode is formed,
A surface of the first substrate opposite to the fixed surface receives the light;
The surface on which the transparent electrode is formed is thermally and electrically connected to the thermoelectric converter, and the surface opposite to the surface on which the transparent electrode is formed faces the fixed surface of the first substrate. The photothermal power generation device according to claim 20, wherein the second substrate is arranged.   The photothermal power generation according to any one of claims 20 to 22, wherein a plurality of layers of the plurality of metal nanoparticle integrated structures are formed between the first substrate and the second substrate. apparatus. The photothermal conversion element includes a dye-sensitized photoelectric conversion element,
Each of the first and second substrates is a resin film having a transparent electrode formed on one surface thereof,
The photothermal power generation device according to claim 20, wherein the first and second substrates function as the dye-sensitized photoelectric conversion element. Each of the plurality of metal nanoparticle assembly structures includes base particles having a surface on which the plurality of metal nanoparticles are fixed;
The photothermal power generation device according to claim 20, wherein the base particle is a titanium oxide particle. A method for detecting a substance to be detected using the method for producing a photothermal conversion element according to claim 9,
The dispersion includes a thermocoagulable material or a heat-soluble material as the substance to be detected,
A method for detecting a substance to be detected, wherein the substance to be detected is detected by irradiating the dispersion with a laser beam to solidify or dissolve the dispersion.