NANOSTRUCTURE SUBSTRATE

Abstract

A nanostructure substrate includes groups of composite particles in which a reduced and deposited coating layer shows cohesive polarization action and/or electromagnetic polarization action. Also, to provide a nanostructure substrate, such active sites are dramatically increased to allow a medium to react homogenously over the entire nanostructure substrate. On a transparent semi-curable polyester resin film, groups of gold fine particles (average particle diameter: 20 nm) are reduced and deposited from an aqueous solution and self-aggregated. A half of the lower part of the groups of gold fine particles is submerged in the polyester resin film, and embedded in the front surface side of the transparent resin base body. Then, this transparent substrate is immersed in an electroless gold-plating solution repeatedly to deposit gold crystal grains on the fixed groups of gold fine particles.

Claims

1. A nanostructure substrate having a front surface and a back surface, comprising a metal structure body including groups of composite particles, and a substrate including a resin base body and a support body, wherein a geometric surface area of a front surface side of the groups of composite particles is larger than a geometric surface area of a back surface side, and each of the composite particles includes fine particles of metal or the like and a coating layer having an upper part being reduced and deposited and including metal or a co-deposit, a lower part of the fine particles of metal or the like is embedded in the resin base body, and the embedded fine particles of metal or the like is present apart from another fine particles of metal or the like.

2. The nanostructure substrate according to claim 1, wherein the coating layer is reduced and deposited from an aqueous solution, and comprises metal, an alloy, or a co-deposit.

3. The nanostructure substrate according to claim 1, wherein the coating layer is linked.

4. The nanostructure substrate according to claim 1, wherein an average diameter of the fine particles of metal or the like is 10 nm to 90 nm.

5. The nanostructure substrate according to claim 1, wherein the fine particles of metal or the like are self-aggregated.

6. The nanostructure substrate according to claim 1, wherein the coating layer and the fine particles of metal or the like are same kind of metal.

7. The nanostructure substrate according to claim 1, wherein the coating layer is a noble metal.

8. The nanostructure substrate according to claim 1, wherein the groups of composite particles show plasmon characteristics.

9. The nanostructure substrate according to claim 1, wherein the fine particles of metal or the like are a light receiving surface of an electromagnetic wave or an electric field.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0076] FIG. 1 is a conceptual diagram for describing the principle of the present invention.

[0077] FIG. 2 is a view showing a group of fine particles of metal or the like of Comparative Example.

[0078] FIG. 3 is a view showing an Example of the present invention.

[0079] FIG. 4 is a view showing an Example of the present invention.

[0080] FIG. 5 is a view showing an Example of the present invention.

[0081] FIG. 6 is a view showing an absorbance curve in accordance with the present invention and Comparative Example.

DESCRIPTION OF EMBODIMENTS

[0082] Hereinafter, Examples and the like of the present invention will be described in more detail appropriately with reference to the drawings.

<Aggregate of Group of Gold Fine Particles>

[0083] In FIG. 2, a group of gold fine particles having an average particle diameter of 20 nm reduced on a thermosetting transparent resin base body is fixed on the front surface side of a transparent resin support body. As shown in FIG. 1, adjacent gold fine particles are separated from each other and arranged two-dimensionally. Therefore, the cross sections of all the groups of gold fine particles shown in FIG. 2, which may be the three gold fine particles continuous in the x-axis direction and the three gold fine particles continuous in the y-axis direction seen in FIG. 2, are in the same plane.

[0084] The resin base body in accordance with this embodiment can be used alone. The resin base body in accordance with this embodiment can be used in combination with another support body. The support body is preferably a transparent body. Furthermore, as the shape of the substrate, for example, a plate shape, a sheet shape, a thin film shape, a mesh shape, a geometric pattern shape, an uneven shape, a fibrous shape, a bellows shape, a multilayer shape, a spherical shape, or the like, can be applied. When the substrate does not have light transmitting property, it can be used as a sensitivity sensor for detecting external changes.

[0085] The resin base body can also work as a base layer. As the base layer, glass, ceramics, silicon wafers, semiconductors, paper, metals, alloys, metal oxides, synthetic resins, organic/inorganic composite materials, and the like, can be used. Furthermore, base layers, having surfaces subjected to, for example, silane coupling agent treatment, chemical etching treatment, plasma treatment, alkali treatment, acid treatment, ozone treatment, ultraviolet ray treatment, electrical polishing treatment, polishing treatment with an abrasive, and the like, may be used.

[0086] When the group of fine particles of metal or the like in accordance with this embodiment and a coating layer with the upper side reduced and deposited are combined, it is necessary to set the optimal conditions. In order to find the optimal conditions, for example, a step of being immersed in a dilute wet plating solution for a certain period of time can be repeated for several cycles. Furthermore, it is possible to specify a predetermined plating time in which the strongest plasmon is expressed. By repeating the wet plating at this specified time, stable plasmons can be repeatedly generated. Furthermore, by performing wet plating in this way, the nanostructure substrate of the present invention can be mass-produced.

[0087] The metal structure according to this embodiment of the present invention is not limited to the above embodiment, and the metal structure of the present invention can be implemented with various modification within the scope of the technical idea of the present invention. Specific examples of this embodiment will be described in detail in the following examples and the like. However, the present invention is not limited to these Examples.

Comparative Example

<Arrangement of Group of Gold Fine Particles>

[0088] Groups of gold fine particles (average particle diameter: 20 nm) reduced and deposited from an aqueous solution were self-aggregated on a transparent semi-curable polyester resin film (glass transition temperature (measured value): 140° C.) and subjected to a predetermined heat treatment. The lower part of the groups of gold fine particles was half submerged in the polyester resin film and embedded in the front surface side of the transparent resin base body. This back surface side is the light receiving surface of the electromagnetic wave or electric field. This is a Comparative Example.

[0089] As shown in FIG. 2, groups of gold fine particles are arranged at intervals on a transparent polyester resin film. In other words, the embedded gold fine particles are present apart from one another. This structure is Comparative Example. The geometric surface area on the front surface side is the same as the geometric surface area on the back surface side in the group of composite particles of the Comparative Example. The gap between adjacent gold fine particles in the horizontal direction in the group of gold fine particles is about 20 nm.

[0090] The transparent substrate on which the groups of gold fine particles were fixed had a light pink color.

[0091] Next, for this Comparative Example, the absorbance was measured in the wavelength in the range of 400 nm to 900 nm, and the absorption spectrum distribution of gold was observed. A fiber multi-channel spectroscope (Flame manufactured by Ocean Optics) was used for measurement of the absorbance. The absorption spectrum curve of the Comparative Example is the bottom curve of FIG. 6. In this curve, it is shown that a plasmon peculiar to the groups of gold fine particles having an absorbance of 0.15 appears in the vicinity of 550 nm.

Example 1

<Deposition of Gold Coating Layer>

[0092] Next, this transparent substrate was immersed in an electroless gold plating solution at 65° C. (an improved bath of Precious Fab ACG3000WX manufactured by Nippon Electroplating Engineers Co., Ltd.) for 10 seconds, and this step was defined as one cycle. This step was repeated for three cycles to obtain a gold coating layer. In other words, gold crystal grains were deposited on the fixed gold fine particles. This is shown in FIG. 3.

[0093] As can be seen from FIG. 3, in the gold coating layer, the diameters of most of the groups of gold fine particles increase in a form of a mushroom, and the gold coating layer grows in a hemispherical shape seen from above. As shown in FIG. 1, in the groups of composite particles, the geometric surface area on the front surface side is larger than the geometric surface area on the back surface side. When the average particle diameter of the gold-coating layer was measured from the image of the scanning electron microscope, the average particle diameter of the gold- coating layer was in the range of 40 nm to 50 nm.

[0094] When the gold coating layer of FIG. 3 was formed, the color of the transparent resin substrate changed from light pink before electroless gold plating to light purple after electroless gold plating. The absorption spectrum distribution of gold was observed in the same manner as in the comparative example. The second curve from the bottom is the plasmon curve of Example 1.

[0095] This curve shows that the groups of gold composite particles are shifted from the peak value around 550 nm to the long wavelength side. This shows that the apparent aspect ratio is shifted due to the increase in weight of the gold coating layer. In other words, since the heights of the groups of gold composite particles vary, the plasmons of the individual gold coating layers show different peak values. However, when viewed from the whole groups of gold composite particles, there is an imbalance by the weight of the groups of gold fine particles and the weight increase of the gold coating layer. This imbalance appears as a plasmon shift in FIG. 6. The plasmon shift as shown in FIG. 6 are similar to the plasmon shift by a nanorod having a high aspect ratio.

[0096] Furthermore, the absorbance of plasmon in the transverse mode of the gold coating layer is 0.22. In other words, the absorbance is increased by 0.07 points from 0.15 of the gold fine particle. This increase occurs because an area in the horizontal direction of the gold coating layer (the area of the umbrella part of the mushroom) increases.

Example 2

<Sea-Island Structure of L-Shaped Block>

[0097] When the electroless gold plating step was repeated for another three cycles, the color of the nanostructure substrate changed from blue-violet to dark purple. A photograph of the nanostructure substrate after heat treatment observed from the front surface side is shown in FIG. 4. In FIG. 4, a place corresponding to the start of the sea-island structure of Example 2 is still seen.

[0098] Furthermore, in FIG. 4, many places where the gold coating layers are linked and grow into an L-shaped block are observed. Traces of a plurality of gold coating layers can still be seen in this L-shaped block. This shows that the heights of the gold coating layers of the L-shaped blocks are different from each other. Furthermore, in the group of composite particles, the geometric surface area on the front surface side is larger than the geometric surface area on the back surface side.

[0099] The absorption spectrum distribution of gold was observed in the same manner as in Example 1. This absorption spectrum curve is shown in the second curve from the top of FIG. 6. The curve of Example 2 shows that the peak value of plasmon in the transverse mode of the gold coating layer shifts from about 550 nm to about 580 nm of the groups of gold fine particles. In other words, this shift indicates that the apparent aspect ratio of the gold coating layer has increased. Furthermore, the peak value of plasmon in the transverse mode of the gold coating layer is significantly increased from 0.15 to 0.3. This increase occurs because an area in the horizontal direction (total volume) of the gold coating layer increases.

[0100] Furthermore, a plasmon in the longitudinal mode can be seen in the vicinity of 750 nm in the right direction of this curve. This plasmon is expressed in a position similar to that of the plasmon in the longitudinal mode observed in a gold nanorod. This also shows that the apparent aspect ratio of the gold coating layer becomes large.

Example 3

[0101] The electroless gold plating step was repeated for another three cycles to granulate the gold coating layer. As shown in FIG. 5, a part of the sea that looks black started to disappear. It can be said that this is the final stage of the sea-island structure. Since the groups of composite particles still remain spherical, the geometric surface area on the front surface side is larger than the geometric surface area on the back surface side in the groups of composite particles. The color of the nanostructure substrate changed from blue-violet to gold. The uppermost curve in FIG. 6 is the plasmon curve of Example 3.

[0102] As is apparent from the results of the Examples and the conventional examples mentioned above, it is shown that when the nanostructure substrate composed of the coating layer according to the present invention is used, the absorbance becomes higher than that of Comparative Example. In other words, it is shown that when an electromagnetic wave is incident on the nanostructure substrate of the present invention from the back surface side, the electromagnetic wave radiated from the front surface side becomes gentle. Furthermore, comparison of the graphs of Examples 1 to 3 shows that the influence of the wavelength of visible light on the absorbance decreases as the amount of precipitation increases. Further comparison of the graphs of Example 1 and Example 2 shows that in Example 2, a new plasmon resonance in the longitudinal mode having a wavelength of 700 to 800 nm was also expressed.

INDUSTRIAL APPLICABILITY

[0103] The nanostructure substrate of the present invention can be used for a surface-enhanced Raman spectrum substrate having sensitivity for single molecule detection. It can also be used for a substrate for detecting environmentally harmful substances and detecting viruses and the like. Furthermore, the nanostructure substrate of the present invention can be used as a substrate for improving the luminous efficiency of light emitting elements utilizing the localized plasmon resonance phenomenon and improving the conversion efficiency of the photoelectric conversion element or the thermophotovoltaic element. In addition, the nanostructure substrate of the present invention utilizes the action of localized plasmon resonance, and is applicable in chemical and biometric industries such as chemical sensors and biosensors.