JP2009221563A - Gold nanorod, method for producing the same, electromagnetic wave absorber using the nanorod, color material, optical recording material, and two photon reaction material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method which can efficiently obtain a gold nanorod having a desired aspect ratio and a grain size and can suppress the scattering of light other than absorption wavelengths, and to provide functional optical materials using the rod. <P>SOLUTION: Gold ions coexistent with silver ions in a micell solution composed of a water phase comprising a quaternary ammonium salt (e.g., CTAB) and an oil phase (e.g., addition of cyclohexanone and diisobutyl) are subjected to reduction using a reducing agent (e.g., an ascorbic acid solution) in such a manner that the reducing agent in a prescribed amount is dropt till the color of the gold ions is lost, and thereafter, while performing reduction using no reducing agents (e.g., photoreduction), the reducing agent is additionally charged, so as to grow a gold nanorod. A functional optical material such as a three-dimensional recording medium is composed using the obtained gold nanorod. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing gold nanorods and a functional material using the gold nanorods, and more specifically, a production method for obtaining gold nanorods having a desired aspect ratio and a desired rod diameter or length in a high concentration in a short time, and The present invention relates to functional optical materials using gold nanorods (for example, light and electromagnetic wave absorbers, coloring materials, optical recording materials, and two-photon reaction materials).

  Spherical gold nanoparticles have long been used as a coloring material showing red color dispersed in glass. In recent years, by controlling the shape of the gold nanoparticles to a rod shape, the absorption characteristics can be controlled by controlling the aspect ratio of the rod-shaped gold nanoparticles. It has been found possible. As a method for producing the rod-shaped gold nanoparticles, an electrolytic method, a photoreduction method, or the like is known.

As an electrolysis method, for example, a method of obtaining metal nanorods by performing constant current electrolysis using a gold electrode as an anode in a cationic surfactant solution such as a quaternary ammonium salt containing silver ions is known. (For example, refer to Patent Document 1).
In the above-described method, the raw material gold ions are supplied by dissolving the gold electrode. Further, the silver ions to be coexisted in the solution are sequentially supplied as a solution, or supplied from a silver plate immersed in the electrolytic solution as other than the electric field electrode. Although it is stated that the aspect ratio of nanorods can be controlled by the electric field conditions and the ratio of gold ions to silver ions, it is easy to produce spherical particles, and since the raw materials are sequentially supplied, stable operating conditions Difficult to get.
In order to improve this, there has been proposed a method for obtaining metal nanorods having a high proportion of rod-like metal fine particles by electrochemical reaction in a solution containing dialkyldimethylammonium bromide as a surfactant (for example, didodecyldimethylammonium bromide). (For example, refer to Patent Document 2), but it is not sufficient.

In the photoreduction method, an aqueous quaternary ammonium salt solution containing silver ions is used as the growth solution, as in the above electrolytic method. In this case, the gold raw material is present in the growth solution as chloroauric acid from the beginning. It is known that the aspect ratio of growing gold nanorods can be controlled by the ratio of gold ions to silver ions.
For example, according to Non-Patent Document 1, it is known that the production of nanorods by photoreduction requires 10 hours or more even when acetone, which is a reaction aid, is used. For example, it is described that it can be shortened to several tens of minutes by performing one step of the reaction by chemical reduction.

Gold nanorods produced by photoreduction are characterized in that it is easy to obtain sharply-absorbed particles having a uniform aspect ratio, and relatively few spherical particles are produced. However, with photoreduction alone, the formation of nanorods is an inefficient method that requires 10 hours or more, and even when chemical reduction is used in combination with part of the reaction, the color of the trivalent gold ion is reduced by the reducing agent. The reaction does not proceed easily in the state of being simply decolored, and acetone is still used as a reaction aid. In other words, the presence of acetone as a reaction aid in the solution is a necessary condition for shortening the reaction time.
However, when the reaction proceeds under the condition where acetone, which is a reaction aid, is present, the resulting particles have almost the same aspect ratio, but due to the excess and deficiency of the reducing agent at the start of the reaction, A size distribution occurs in the gold nanorods themselves.

  On the other hand, various functional materials (for example, new coloring materials, functional optical materials, etc.) utilizing the unique properties of the gold nanorods have attracted attention. For example, gold nanorods are used as means for generating a surface plasmon enhancement field. Technology research is ongoing. By using a two-photon absorption material containing gold nanorods with a plasmon enhancement field or a material containing a reaction aid, it is possible to reduce the reaction threshold of the two-photon absorption reaction or to cause a reaction at the focal point. Therefore, for example, application as an optical recording material (three-dimensional recording medium), an optical modeling material, and a two-photon absorption fluorescent material has attracted attention.

  For example, looking at the fields in which applications of three-dimensional optical recording media (three-dimensional multilayer optical memory) including gold nanorods and two-photon absorption materials are expected, recently, networks such as the Internet and high-definition TVs have rapidly spread. Yes. In addition, HDTV (High Definition Television) will soon be broadcast, and there is an increasing demand for large-capacity recording media for inexpensively and easily recording image information of 50 GB or more, preferably 100 GB or more for consumer use. Furthermore, in business use such as computer backup use and broadcast backup use, an optical recording medium capable of recording large-capacity information of about 1 TB or more at high speed and at low cost is required. Under such circumstances, the conventional two-dimensional optical recording medium such as DVD ± R is about 25 GB at most even if the recording / reproducing wavelength is shortened due to the physical principle, and is sufficiently large enough to meet future demands. It cannot be said that capacity can be expected.

  Under the circumstances as described above, a three-dimensional optical recording medium has attracted attention as an ultimate high-density, high-capacity recording medium. Three-dimensional optical recording media can be used for recording dozens or hundreds of layers in the three-dimensional (film thickness) direction, or the recording layer can be used as a thick film to record and reproduce multiple layers in the light incident direction. Can be done. That is, by using a three-dimensional recording medium, it is possible to achieve tens or hundreds of times the ultra-high density and ultra-high capacity recording of the conventional two-dimensional recording medium.

In order to provide a three-dimensional optical recording medium, it is necessary to be able to access and write at an arbitrary place in the three-dimensional (film thickness) direction. As a means for this, a method using a two-photon absorption material or holography (interference) ).
In a three-dimensional optical recording medium using a two-photon absorption material, tens or hundreds of times of recording, so-called bit recording, can be performed based on the physical principle described above, and higher density recording is possible. From this, it can be said that the three-dimensional optical recording medium is an ultimate high-density, high-capacity optical recording medium.

  For example, as a three-dimensional original optical recording medium using a two-photon absorption material, a method of reading with fluorescence using a fluorescent substance for recording and reproduction (for example, see Patent Documents 4 and 5), absorption or fluorescence using a photochromic compound (For example, refer to Patent Document 6) and the like.

However, neither of the above-mentioned Patent Documents 4 and 5 describes a specific two-photon absorption material, and even an example of an abstractly presented two-photon absorption compound is a two-photon absorption compound with extremely small two-photon absorption efficiency. Is used.
Further, since the photochromic compounds used in Patent Documents 6 and 7 are reversible materials, there are problems in nondestructive reading, long-term storage stability, S / N ratio of reproduction, and the like, which are practical as optical recording media. It cannot be said that it is a certain method. In particular, in terms of non-destructive readout, long-term storage stability of recording, etc., it is preferable to reproduce by changing the reflectance (refractive index or absorptivity) or emission intensity using an irreversible material, but a two-photon having such a function. There is no example that specifically describes the absorbent material.

  In addition, a recording apparatus, a reproducing apparatus, a reading method, and the like that perform three-dimensional recording by refractive index modulation have been proposed, but there is no description of a method using a two-photon absorption three-dimensional optical recording material (for example, a patent) References 8 and 9).

JP 2003-315531 A JP 2005-68447 A JP-A-2005-97718 JP-T-2001-524245 Special table 2000-512061 gazette Special table 2001-522119 gazette Special table 2001-508221 gazette JP-A-6-28672 JP-A-6-118306 (J.AM.CHEM.SOC, 2002,124, pp14316-14317, F.Kim, J.H.Song, and P.Yang)

  The present invention has been made in view of the above-described prior art, and has a desired aspect ratio and a desired rod diameter or length from the viewpoint of stabilization of characteristics as a functional material, and light other than the absorption wavelength. An object of the present invention is to provide a method for producing gold nanorods composed of particles with a small rod diameter capable of suppressing scattering and to provide a production method for obtaining gold nanorods with a higher concentration in a short time from the viewpoint of economy. Furthermore, it aims at providing the functional optical material (For example, light and electromagnetic wave absorber, a coloring material, an optical recording material, a two-photon reaction material etc.) using gold nanorods.

  As a result of intensive studies, the present inventors have found that the above problems can be solved by the inventions described in the following [1] to [14], and have reached the present invention. Hereinafter, the present invention will be specifically described.

[1]: The above problem is that gold ions coexisting with silver ions in a micellar solution composed of an aqueous phase containing a quaternary ammonium salt and an oil phase are reduced using a reducing agent and reduced without using a reducing agent. In the gold nanorod manufacturing method of growing gold nanorods in combination,
A method for producing gold nanorods, wherein a predetermined amount of a reducing agent is dropped into a micelle solution until the color of the gold ions is lost, and then the reducing agent is further added while performing reduction without using the reducing agent. It is solved by.

  [2]: The method for producing gold nanorods according to [1] above, wherein the reduction without using the reducing agent is photoreduction performed by light irradiation or electrolytic reduction performed by energization.

  [3]: The method for producing gold nanorods according to [1] or [2] above, wherein the oil phase does not contain acetone.

  [4]: In the gold nanorod manufacturing method according to any one of [1] to [3], the reducing agent is continuously added while controlling the amount of addition during the reduction step without using the reducing agent. It is characterized by being put into a micelle solution.

  [5]: The method for producing gold nanorods according to any one of [1] to [4] above, wherein the concentration of the quaternary ammonium salt is 0.1 mol / l or more.

  [6]: The gold nanorod manufacturing method according to any one of [1] to [5], wherein the length of the gold nanorod in the minor axis direction is controlled by adjusting the concentration of the gold ion.

  [7]: The method for producing gold nanorods according to any one of [1] to [6], wherein a component for suppressing reduction precipitation of gold ions in an aqueous phase is added to the micelle solution. To do.

  [8]: The method for producing gold nanorods according to [7] above, wherein the component that suppresses reduction and precipitation of gold ions in the aqueous phase has solubility in both the aqueous phase and the oil phase. To do.

  [9]: In the method for producing gold nanorods according to [7] or [8] above, the component that suppresses reduction and precipitation of gold ions in the aqueous phase is selected from at least one of diisobutyl ketone and methyl isobutyl ketone. It is characterized by being.

  [10] The above problem is solved by a gold nanorod produced by the method according to any one of [1] to [9].

  [11] The above problem is solved by a light and electromagnetic wave absorber comprising the gold nanorod described in [10].

  [12] The above problem is solved by a color material comprising the gold nanorod described in [10].

  [13]: The above problem is solved by an optical recording material comprising the gold nanorod described in [10].

  [14]: The above problem is solved by a two-photon reaction material comprising at least the gold nanorod according to [10] and a two-photon absorption material.

According to the gold nanorod manufacturing method of the present invention, when a gold nanorod is grown by a combination of reduction using a reducing agent and reduction without using a reducing agent, a predetermined amount of reducing agent is lost until the color of the gold ion is lost. After dropping into the micelle solution, the reducing agent is additionally added while performing reduction without using a reducing agent (main reduction), so that the reduction precipitation reaction is shortened and gold nanorods are rapidly generated. Further, since the supersaturation degree of gold can be controlled by adding a reducing agent, gold nanorods having a desired aspect ratio and particle size can be obtained in a short time. For this reason, highly functional gold nanorods with uniform characteristics can be obtained at a high concentration.
According to the gold nanorod of the present invention, a particle having a desired aspect ratio, a desired rod diameter or length and a small rod diameter (for example, a size capable of suppressing light scattering other than the absorption wavelength) by the above production method. Therefore, it can be suitably applied to highly functional optical materials such as light and electromagnetic wave absorbers, color materials, optical recording materials, and two-photon reaction materials.
The light and electromagnetic wave absorber comprising the gold nanorod of the present invention can be used as a highly functional material having sharp absorption characteristics, small scattering loss outside the absorption band, and excellent light and electromagnetic wave absorption ability.
If it is a color material comprising the gold nanorods of the present invention, it can be used as a highly functional material having excellent weather resistance and high color purity.
If the two-photon reaction material comprising the gold nanorods of the present invention is used, it can be used as a highly functional material with high sensitivity (for example, a material for optical modeling).
The optical recording material comprising the gold nanorod of the present invention can be used as a highly functional material (for example, a three-dimensional optical recording medium) with high sensitivity and high recording density.

As described above, the method for producing gold nanorods in the present invention reduces gold ions that coexist with silver ions in a micellar solution composed of an aqueous phase and an oil phase containing a quaternary ammonium salt, a reducing agent, and a reducing agent. In a gold nanorod manufacturing method in which gold nanorods are grown in combination with reduction that is not used,
A predetermined amount of a reducing agent is dropped into the micelle solution until the color of the gold ions is lost, and then the reducing agent is further added while performing reduction without using the reducing agent ( The present invention [1]). Here, the quaternary ammonium salt plays a role as a surfactant.
Hereinafter, “reduction without using a reducing agent” may be expressed as “main reduction” or “main reduction step”.

In general, in order to obtain fine particles of uniform size, it is desirable that the nucleation and particle growth processes are separated in time. For this reason, a reaction design in which a large degree of supersaturation occurs in the early stage of growth, a remarkably large number of nuclei are generated, and then the raw materials are consumed as the particles grow.
However, considering the growth conditions of the gold nanorods, the reduction of the starting material continued slowly until the material was depleted during the reduction process without using a reducing agent (that is, during the main reduction process). This is different from the production process of spherical fine particles.
“Reduction without using a reducing agent” refers to, for example, photoreduction performed by light irradiation or electrolytic reduction performed by energization.
That is, the present inventors control the degree of supersaturation due to reduction of raw metal ions to the extent that anisotropy crystals grow after nucleation, from the growth conditions of gold nanorods different from the general reaction design ( It was found that it was necessary to be controlled), and as a method for that, it was found that the purpose can be achieved by additionally introducing a reducing agent during the main reduction step.

  That is, when the introduction of the reducing agent is stopped when the color of the gold ions disappears, the promotion of the production of gold nanorods by the main reduction process is limited, and the reduction precipitation reaction takes several hours. However, in addition to the predetermined dripping amount in which the color of the gold ions disappears, when a reducing agent is additionally added, it is possible that the gold nanorods are generated promptly after the start of the main reduction process. From the absorption characteristics.

  According to the present invention [1], since the supersaturation degree of gold during the reaction can be controlled by adding a reducing agent, gold nanorods having a desired aspect ratio and particle size can be obtained over a wide range of gold raw material concentrations. be able to. As a result, highly functional gold nanorods with uniform characteristics can be obtained at a high concentration.

Here, in the present invention [1], the reduction without using the reducing agent is preferably photoreduction performed by light irradiation or electrolytic reduction performed by energization (the present invention [2]).
As in the present invention [2], the reduction of the gold nanorods can be effectively performed while controlling the supersaturation degree of gold during the reaction by using the reduction including the additional addition using a reducing agent and the photoreduction or electrolytic reduction in combination. Production can be promoted, and highly functional gold nanorods having a desired aspect ratio and particle size can be efficiently obtained at a high concentration. In particular, photoreduction can be preferably used because it is easy to obtain particles having a uniform aspect ratio and size.

Moreover, in this invention [1], it is preferable that the said oil phase does not contain acetone (this invention [3]).
In order to accelerate the reduction precipitation reaction with acetone, which has been reported as a reaction aid, a large amount of acetone is added so that the reaction reaches the end point. As a reduction without using a reducing agent, for example, when photoreduction is performed, if it is an oil-based solvent system to which acetone is added as will be described later, it is difficult to control the particle size of the gold nanorods, etc., because gold is rapidly reduced and precipitated. There is a problem to become. Furthermore, it has been found that spherical particles can be obtained when photoreduction is performed by adding a large amount of a strong reducing agent such as ascorbic acid.
In other words, the absence of acetone as in the present invention [3] avoids the influence on the yield of gold nanorods due to excess or deficiency of the reducing agent at the start of the reaction and the distribution of gold nanorods in size. can do.

On the other hand, when the reducing agent was additionally added in the present invention, the amount of gold nanorods generated was controlled by the amount thereof, and it became clear that the reduction precipitation rate was drastically decreased due to depletion of the reducing agent. In other words, it has been found that the supersaturation degree control for controlling the nucleation and the growth region control of the anisotropic growth of the particles can be indirectly controlled by the introducing sequence and the amount of the reducing agent.
That is, in the present invention, it is preferable to continuously add the reducing agent into the micelle solution while controlling the amount of addition during the reduction (main reduction) step without using the reducing agent (the present invention [4]. ).

As described above, by continuously adding into the micelle solution while controlling the amount of addition (controlling the reducing agent introduction sequence and amount), control of nucleation, growth region of anisotropic growth of particles The control of the degree of supersaturation for performing the control can be indirectly controlled.
In order to stably carry out anisotropic growth after nucleation, a gold nanorod with uniform characteristics can be obtained by continuously introducing a reducing agent and keeping the supersaturation level substantially constant. By continuously feeding, in addition to the increase in absorbance due to the generation of new particles, a shift of the absorption peak to the longer wavelength side due to the continuous increase in aspect ratio is observed.
The concept of keeping the supersaturation approximately constant, as described here, not only means that the supersaturation is completely constant throughout the reduction process, but also for the purpose of controlling the cycle of nucleation and growth, It also includes pulsating the degree of supersaturation by intermittent charging.
According to the present invention [4], in addition to the merit of the invention of the present invention [1], it becomes possible to control the growth conditions more finely, and at the same time, the reaction conditions at the start and end of the growth can be made closer. Can be grown until the raw materials are completely consumed. As a result, a highly functional gold nanorod with more uniform characteristics can be obtained at a higher concentration.
That is, it is a growth method in which a gold nanorod having a uniform aspect ratio and size can be obtained at a high concentration by introducing a reducing agent during the main reduction step and controlling the reduction state in the solution.

In the present invention, the concentration of the quaternary ammonium salt is preferably 0.1 mol / l or more (the present invention [5]).
Gold nanorods having a small size can be easily obtained by performing growth by reduction precipitation of gold ions in the reaction system defined in the present invention [5] having a concentration higher than that of the conventionally reported quaternary ammonium salt. As a result, a gold nanorod in which the influence of light scattering is suppressed is obtained.

In the present invention, it is preferable to control the length (thickness) of the gold nanorods in the minor axis direction by adjusting the gold ion concentration (the present invention [6]).
As described above, the shape of the gold nanorod is determined by the growth process after nucleation. It is thought that the surface of the gold nanorods is specifically coated with a quaternary ammonium salt, which is a surfactant, so that anisotropy of growth occurs. However, as the growth time increases, it grows in a uniaxial direction. As a method of avoiding this, it is possible to reduce the growth time by reducing the concentration of chloroauric acid in the starting material solution and to suppress the growth of the gold nanorods in the minor axis direction. I found it.
According to the present invention [6], the growth of the gold nanorods in the short axis direction is controlled. For example, a gold nanorod having a small size can be obtained more easily and with good controllability by the combined effect with the present invention [5]. . That is, smaller nanorods can be produced with good reproducibility.

Moreover, in this invention, it is preferable to add the component which suppresses the reduction | restoration precipitation of the gold ion in an aqueous phase to the said micelle solution (this invention [7]).
The growth of gold nanorods has not yet been reported in a mixed system of water and only an organic solvent arbitrarily mixed with water without a surfactant. From this, the present inventors considered that the stability to the transport and reduction of the raw material at the interface between the aqueous phase and the oil phase was involved in the growth of the gold nanorods.
As a result of studying from such a viewpoint, when a component having high stability of chloroauric acid in an aqueous solution, that is, an oily solvent, is added to the growth solution, the formation of spherical particles is suppressed and the growth in the short axis direction is also suppressed. I found out.
From the result of adding an oily solvent to a chloroauric acid aqueous solution (no surfactant) and examining the reduction characteristics of chloroauric acid in the aqueous phase, for example, from the oily solvent system containing acetone conventionally used In this case, a solvent having a slow reduction of gold is defined as a highly stable oily solvent.

  According to the present invention [7], by adding a component that suppresses the reduction and precipitation of gold ions in the aqueous phase, the formation of spherical particles is suppressed, and the size of the short-axis direction is suppressed. Small gold nanorods are obtained. As a result, the obtained particles can provide highly functional gold nanorods with small light scattering at wavelengths other than the absorption wavelength.

In the present invention, it is preferable that the component that suppresses the reduction and precipitation of gold ions in the aqueous phase has solubility in both the aqueous phase and the oil phase (the present invention [8]).
According to the present invention [8], the above-mentioned effect of the present invention [7] can be more effectively obtained by adding a component having solubility in both the aqueous phase and the oil phase.

In the present invention, the component that suppresses the reduction and precipitation of gold ions in the aqueous phase is preferably selected from at least one of diisobutyl ketone and methyl isobutyl ketone (the present invention [9]).
When one kind selected from diisobutylketone or methylisobutylketone according to the present invention [9] is added, most of it is absorbed in the oil phase, but some remains in the water phase, and gold ions are selectively extracted into the oil phase. Show the effect of Due to this effect, spherical particles due to reduction of gold ions in the aqueous phase are suppressed. That is, the effect in the present invention [7], [8] can be obtained more effectively.
By said [7]-[9], the production | generation of the spherical particle in a reduction | restoration process is suppressed, and a smaller nanorod can be obtained with sufficient reproducibility.

The gold nanorod of the present invention is obtained by any one of the production methods described above (the present invention [10]).
The gold nanorod of the present invention [10] has a high configuration due to the preferred configuration of reduction precipitation of gold ions, the preferred configuration of environmental conditions for reduction deposition, and the preferred configuration of suppression conditions for spherical particles. Concentration is produced effectively in a short time. That is, it is a gold nanorod having a stable characteristic having a desired aspect ratio, a desired rod diameter or length, and composed of particles having a small rod diameter capable of suppressing scattering of light other than the absorption wavelength.

Moreover, in this invention, it can be set as the light and electromagnetic wave absorber characterized by including the gold | metal nanorod as described in this invention [10] (this invention [11]).
Since the light and electromagnetic wave absorber in the present invention contains gold nanorods, a light and electromagnetic wave absorber having sharp absorption characteristics can be obtained. Furthermore, if a smaller gold nanorod is used, a light and electromagnetic wave absorber having a small light scattering loss outside the absorption band can be obtained.
That is, a light and electromagnetic wave absorber having a sharp absorption characteristic and a small scattering loss outside the absorption band is provided.
The light and electromagnetic wave absorber of the present invention [11] may be formed by, for example, directly applying and forming a dispersion solution containing the gold nanorods of the present invention on the target object surface. It may be formed by coating and drying. The coating film containing gold nanorods formed in this way has a resonance absorption band unique to gold nanorods.For example, a light absorber (film) that transmits visible light but has absorption only in the near infrared region is formed. It becomes possible. The absorption band can be arbitrarily set by adjusting the aspect ratio according to manufacturing conditions.

Moreover, in this invention, it can be set as the coloring material characterized by including the gold nanorod as described in this invention [10] (this invention [12]).
The color material in the present invention is a feature of the color material using gold nanorods. In addition to the weather resistance, sharper absorption characteristics can be obtained by using the gold nanorods of the present invention, and more obtained by the present invention. By using a small gold nanorod, it is possible to obtain a color material with a small scattering loss of light outside the absorption band, so that a color material with higher color purity is obtained.
The color material of the present invention [12] may be used, for example, by directly applying a dispersion solution containing the gold nanorods of the present invention, or as a color material using a material in which gold nanorods are dispersed in a binder or the like. Good. The complementary color of plasmon absorption of gold nanorods is the coloring mechanism of this coloring material. Therefore, a color material having high color purity can be obtained by using particles having a uniform aspect ratio and sharp absorption.

Moreover, in this invention, it can be set as the optical recording material characterized by including the gold | metal | money nanorod as described in this invention [10] (this invention [13]).
The optical recording material in the present invention is a gold nanorod alone or a gold nanorod dispersed in a binder, or a recording material containing any one of the functional dyes simultaneously. Even if the recording material itself uses the change in the absorption characteristics of the gold nanorods due to light irradiation, the recording principle is based on the fluorescence of the dye contained at the same time, or the change in the refractive index generated by the enhanced field generated by plasmon resonance. Also good.
In the optical recording material of the present invention [13], sharp absorption characteristics can be obtained by the gold nanorod of the present invention. For this reason, a uniform plasmon enhancement effect is obtained, and the characteristics of the recording material can be enhanced by this plasmon enhancement field. In addition, uniform deformation characteristics can also be obtained when changes in absorption characteristics due to deformation of gold nanorods are used. Therefore, even if any characteristic is used, a uniform and highly sensitive recording / reproducing characteristic can be obtained. Furthermore, if a gold nanorod having a small rod diameter is used, a highly sensitive recording material that can be deformed with lower energy can be obtained.

Moreover, in this invention, it can be set as the two-photon reaction material characterized by including the gold | metal nanorod and two-photon absorption material as described in this invention [10] (this invention [14]).
The two-photon reaction material of the present invention contains at least a gold nanorod and a two-photon absorption material, and may contain a functional material such as a chemical sensitizer, a photo-curing resin, or a fluorescent material as necessary. Needless to say, the form can be selected according to the application such as solution, gel, solid and the like. It can be dispersed in a binder resin for the purpose of adjusting the viscosity.
In the present invention [14], the plasmon enhancement field obtained by the sharp absorption characteristic by the gold nanorod of the present invention is optimal for excitation of a two-photon absorption material. Furthermore, by using gold nanorods with a small rod diameter, the influence of scattering of excitation light is suppressed, and the resolution is improved when used as a surface modification technique, and high sensitivity when deployed in three dimensions. Bulky two-photon reaction is obtained. Needless to say, high-sensitivity bulk two-photon reaction materials are essential next-generation materials for 3D optical memory, 3D modeling, and the like.

  By providing a material including a gold nanorod having a plasmon enhancement field as described above as a stable dispersion solution and a mixture that can be applied or cast, various unprecedented applications are possible. Examples of application will be described below.

[Application of two-photon reaction materials including gold nanorods and two-photon absorption materials to three-dimensional recording media]
As described in the background art, the reaction occurs using the excitation energy obtained by non-resonant two-photon absorption, and as a result, the emission intensity when the laser focus (recording) and non-focus (non-recording) parts are irradiated. If it can be modulated by a method that cannot be rewritten, it can cause emission intensity modulation with extremely high spatial resolution anywhere in 3D space, and it can be applied to 3D optical recording media, which is considered to be the ultimate high-density recording medium. Is possible. Furthermore, since non-destructive readout is possible and the material is an irreversible material, it can be expected to have good storage stability and is practical.

  However, the currently available two-photon absorption compounds have a low two-photon absorption capability, so that a very high-power laser is required as a light source and a long recording time is required. In particular, for use in three-dimensional optical recording media, construction of a two-photon absorption three-dimensional optical recording material that can perform high-sensitivity, high-luminance recording by two-photon absorption to achieve a fast transfer rate. Is essential. For that purpose, two-photon absorption light (two-photon absorption compound) that can absorb two-photons with high efficiency and generate an excited state, and two-photon absorption light by some method using the excited state of the two-photon absorption compound. A material containing a recording component capable of efficiently forming a difference in light emitting ability of a recording material is promising, but such a material has hardly been disclosed so far, and the construction of such a material has been desired.

That is, if a two-photon reaction material comprising at least the gold nanorod and the two-photon absorption material of the present invention is used, for example, after recording using the two-photon absorption of the two-photon reaction material, light is used as the recording material. It is possible to reproduce by detecting the difference in emission intensity by irradiating or detecting the change in reflectance due to the change in refractive index. That is, by using a highly sensitive two-photon reaction material comprising the gold nanorod of the present invention and a two-photon absorption material, a two-photon absorption optical recording / reproducing method, and two-photon absorption optical recording capable of such recording / reproduction Material can be provided.
Furthermore, a two-photon absorption three-dimensional optical recording material using them, and a two-photon absorption three-dimensional optical recording method and a reproducing method can be provided.

The two-photon absorbing photomaterial containing the two-photon reaction material comprising at least the gold nanorod and the two-photon absorbing material of the present invention may be applied directly on the substrate by using a spin coater, a roll coater or a bar coater. Alternatively, it can be cast as a film and then laminated on a substrate by a usual method, and a two-photon absorption optical recording material can be obtained by these molding methods.
As used herein, “substrate” means any natural or synthetic support, preferably one that can exist in the form of a flexible or rigid film, sheet or plate.
The substrate is preferably polyethylene terephthalate, resin-undercoated polyethylene terephthalate, polyethylene terephthalate treated with flame or electrostatic discharge, cellulose acetate, polycarbonate, polymethyl methacrylate, polyester, polyvinyl alcohol, glass or the like. Further, the substrate may be provided with tracking guide grooves and address information in advance.
The solvent used for coating in the molding method can be removed by evaporation at the time of drying. Heating or reduced pressure may be used for evaporation removal.

Furthermore, a protective layer (intermediate layer) for blocking oxygen and preventing interlayer crosstalk may be formed on the two-photon absorption optical recording material. The protective layer (intermediate layer) is made of a plastic film or plate, such as polyolefin such as polypropylene or polyethylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyethylene terephthalate or cellophane film, and is electrostatically adhered or extruded. They may be bonded together by lamination or the like, or the polymer solution may be applied. Further, a glass plate may be bonded. Further, an adhesive or a liquid substance may be present between the protective layer and the photosensitive film and / or between the base material and the photosensitive film in order to improve airtightness. Further, the protective layer (intermediate layer) between the photosensitive films may be provided with tracking guide grooves and address information in advance.
By configuring the two-photon absorption optical recording material as described above as a multilayer, a three-dimensional recording medium (three-dimensional multilayer optical recording medium) is provided.
By focusing on an arbitrary layer of the above-described two-photon absorption optical recording material and performing recording and reproduction, it functions as a three-dimensional recording medium. Further, even if the layers are not separated by a protective layer (intermediate layer), three-dimensional recording in the depth direction is possible from the two-photon absorption dye characteristics.

Specific examples of preferred embodiments of the three-dimensional multilayer optical recording medium (three-dimensional multilayer optical memory) are shown below, but the present invention is not limited to these embodiments, and three-dimensional recording (recording in the plane and film thickness direction) is performed. Any other structure may be used as long as the structure is possible.
A schematic diagram of a recording / reproducing system of a three-dimensional multilayer optical memory is shown in FIG. 1A, and a schematic sectional view of a recording medium is shown in FIG.

The outline of the recording method will be described with reference to the system schematic diagram of FIG. The recording light from the recording laser light source 1 (for example, a high power pulse laser light source) is focused into the three-dimensional recording medium 6 by the objective lens 5. At the focus point, recording is performed by two-photon absorption. However, at positions other than the focus point, as described above, the light irradiation power is low, and recording is not performed due to the square effect.
That is, selective recording is possible. Next, as a reproduction method, the light from the reproduction laser 2 (not as high power as the recording light but also a semiconductor laser can be used) is focused in a three-dimensional medium. Signal light is generated from each layer. By detecting the signal light with a point detector composed of a pinhole 3 and a detector 4, signals from a specific layer can be selectively selected using the principle of a confocal microscope. To detect. With the above configuration, the three-dimensional recording / reproducing functions.

  In the recording medium of FIG. 1B, a two-photon absorption photomaterial (containing a two-photon reaction material comprising the gold nanorod of the present invention and a two-photon absorption material) is used on a flat support (substrate 1). The recording layer and the intermediate layer (protective layer) for preventing crosstalk were alternately laminated by 50 layers, and each layer was formed by spin coating. The thickness of the recording layer is preferably 0.01 to 0.5 μm, and the thickness of the intermediate layer is preferably 0.1 μm to 5 μm. With this structure, the disk size is the same as the currently popular CD / DVD, and the terabyte class Can be realized. Further, a substrate (protective layer) B similar to the substrate A or a reflective layer made of a highly reflective material is formed by a data reproduction method (transmission / or reflection type).

A single beam is used at the time of recording in the three-dimensional multilayer optical memory, and in this case, ultrashort pulse light on the order of femtoseconds can be used. At the time of reproduction, it is also possible to use a light having a wavelength different from that of the beam used for data recording or the same wavelength of low output. Recording and playback can be performed in either bit units or page units, and parallel recording / playback using a surface light source, a two-dimensional detector, or the like is effective in increasing the transfer rate.
Note that a three-dimensional multilayer optical memory similarly formed according to the present invention may have a card shape, a plate shape, a tape shape, a drum shape, or the like.

[Application to stereolithography materials]
The optical modeling using the material for optical modeling will be described with reference to the apparatus (optical modeling system) for the two-photon optical modeling method shown in the schematic diagram of FIG.
In the apparatus shown in FIG. 2, the light from the light source 1 of the near-infrared pulsed laser beam having transparency with respect to the photocurable resin liquid 9 passes through the mirror scanner 5 and is then used for the photocurable property using a lens. The resin liquid 9 is condensed, scanned with a laser spot, and two-photon absorption is induced to cure the resin only in the vicinity of the focal point, thereby forming an arbitrary three-dimensional structure. That is, the optical modeling is performed by the two-photon optical modeling method (two-photon micro optical modeling method).
In addition, the photocurable resin liquid 9 is a material for optical modeling (photocurable resin for two-photon optical modeling) including the gold nanorod of the present invention.

Specifically, the pulsed laser beam is condensed with a lens, and a region with high photon density is formed in the vicinity of the focal point. At this time, since the total number of photons passing through each cross section of the beam is constant, when the beam is scanned two-dimensionally within the focal plane, the total light intensity in each cross section is constant. However, since the probability of occurrence of two-photon absorption is proportional to the square of the light intensity, a region where the generation of two-photon absorption is high is formed only near the condensing point where the light intensity is high.
Thus, by condensing the pulsed laser light with the lens and inducing two-photon absorption, it is possible to limit the light absorption near the condensing point and to cure the resin in a pinpoint manner. The focusing point can be freely moved in the photocurable resin liquid by the Z stage 6 and the galvanometer mirror, so that the desired three-dimensional workpiece (optical modeling object 10) can be freely formed in the photocurable resin liquid. can do.
In FIG. 2, reference numeral 3 denotes a shutter for temporally controlling the excessive light amount, reference numeral 4 denotes an ND filter, reference numeral 7 denotes a lens as a condensing means, and reference numeral 8 denotes a computer.

The features of the two-photon stereolithography include the following items.
(1) Processing resolution exceeding the diffraction limit: Processing resolution exceeding the diffraction limit of light can be realized by the non-linearity of the two-photon absorption with respect to the light intensity.
(2) Ultra-high speed modeling: When two-photon absorption is used, the photo-curing resin does not cure in principle in a region other than the focal point. For this reason, the light intensity to be irradiated can be increased, and the beam scanning speed can be increased. For this reason, modeling speed can be improved about 10 times.
(3) Three-dimensional processing: The photocurable resin is transparent to near-infrared light that induces two-photon absorption. Therefore, even when the focused light is condensed deeply into the resin, internal curing is possible. In the conventional method (SIH), when the beam is condensed deeply, the light intensity at the condensing point is reduced by light absorption, and the internal hardening becomes difficult. In the present invention, these problems are surely solved. be able to.
(4) High yield: In the conventional method, there is a problem that the molded object is damaged or deformed due to the viscosity or surface tension of the resin. However, in this method, the problem is solved because the modeling is performed inside the resin.
(5) Application to mass production: By using ultra-high-speed modeling, it is possible to manufacture a large number of parts or movable mechanisms continuously in a short time.

Here, the photocurable resin for two-photon stereolithography is a resin having a characteristic of causing a two-photon polymerization reaction when irradiated with light and changing from a liquid to a solid. The main components are a resin component consisting of an oligomer and a reactive diluent and a photopolymerization initiator (including a photosensitizing material as required). An oligomer is a polymer having a degree of polymerization of about 2 to 20, and has a large number of reactive groups at its ends. Further, a reactive diluent is added to adjust the viscosity, curability and the like.
When irradiated with light, the polymerization initiator or photosensitizer, which is a two-photon absorption material, is effectively excited by two-photon absorption of the irradiation light due to the plasmon-enhanced field effect of the gold nanorods. Reactive species are generated through the light-sensitive material and react with the reactive groups of the oligomer and reactive diluent to initiate polymerization. Thereafter, a chain polymerization reaction takes place between them to form a three-dimensional cross-link, and in a short time, a solid resin having a three-dimensional network structure is formed.

Photocurable resins are used in fields such as photocurable inks, photoadhesives, and layered three-dimensional modeling, and resins having various characteristics have been developed. In particular, in the layered three-dimensional modeling, (1) good reactivity, (2) small deposition shrinkage during curing, (3) excellent mechanical properties after curing, etc. are important. .
These characteristics are equally important in this method. Therefore, resins developed for layered three-dimensional modeling that have two-photon absorption characteristics are also used as photocurable resins for two-photon photomolding in this method. Can be used. As specific examples, acrylate-based and epoxy-based photocurable resins are often used, and urethane acrylate-based photocurable resins are particularly preferable.

As a technique related to the optical modeling in the present invention, for example, a technique of performing interference exposure of pulsed laser light on a surface of a photosensitive polymer film including gold nanorods without using a mask can be applied. It is important that the pulse laser beam in this case is a pulsed laser beam in a wavelength region that exhibits a photosensitive function through the plasmon enhancement field effect of the gold nanorods in the photosensitive polymer film and the excitation action thereby. It is.
Therefore, the wavelength region of the pulsed laser light can be appropriately selected according to the type of the photosensitive polymer or the type of group or part that exhibits the photosensitive function in the photosensitive polymer. In particular, even when the wavelength of the pulsed laser light emitted from the light source is not in a wavelength region that causes the photosensitive polymer film to exhibit a photosensitive function, by using a multiphoton absorption process upon irradiation with the pulsed laser light, The photosensitive polymer film can exhibit a photosensitive function.
An example of a technique for performing interference exposure on the surface of the photosensitive polymer film without using a mask with a pulsed laser beam is an example described in JP-A-2005-134873.

Specifically, when the pulsed laser light emitted from the light source is condensed and irradiated with the condensed pulsed laser light, multiphoton absorption (for example, two-photon absorption, three-photon absorption, four-photon absorption) Even if the wavelength of the pulsed laser light emitted from the light source is not in the wavelength region that causes the photosensitive polymer film to perform the photosensitive function, the photosensitive polymer film Thus, the pulsed laser beam in the wavelength region that substantially exerts the photosensitive function on the photosensitive polymer film is irradiated through the plasmon enhancement field effect of the gold nanorods in the polymer film and the excitation action thereby.
As described above, the pulse laser beam for interference exposure may be any pulse laser beam in a wavelength region that causes the photosensitive polymer film to exhibit the photosensitive function, and the wavelength is appropriately selected depending on the irradiation conditions. be able to. For example, a two-photon reaction material (a high-efficiency, high-efficiency two-photon absorption material) comprising at least the gold nanorod of the present invention and a two-photon absorption material is used as a photosensitizer and dispersed in an ultraviolet curable resin or the like, and a photosensitive solid Then, it is possible to obtain an ultra-precise three-dimensional structure using the characteristic that only the focal spot is cured by utilizing the two-photon absorption ability of the photosensitive material solid.

  The two-photon reaction material of the present invention can be used as a two-photon absorption polymerization initiator or a two-photon absorption photosensitizer. Compared with conventional two-photon absorption materials (two-photon absorption polymerization initiators or two-photon absorption photosensitizers), the two-photon absorption sensitivity is high, so high-speed modeling is possible, and the laser light source is small and inexpensive as an excitation light source. Can be used for practical applications that can be mass-produced.

[Two-photon absorption fluorescent material using two-photon reaction material, application to two-photon excitation laser scanning microscope]
A two-photon excitation laser scanning microscope (two-photon fluorescence microscope) is an image obtained by condensing and scanning a near-infrared pulse laser on a specimen surface and detecting fluorescence generated by excitation by two-photon absorption there. It is a microscope to obtain
A schematic diagram of a basic configuration of a two-photon excitation laser scanning microscope (two-photon fluorescence microscope) is shown in FIG.
The two-photon fluorescence microscope of FIG. 3 includes a laser light source 1 that emits a sub-picosecond monochromatic coherent light pulse in the near-infrared region, a light beam conversion optical system 2 that changes a light beam from the laser light source to a desired size, and a light beam conversion optics. A scanning optical system 3 for condensing and scanning the light beam converted by the system on the image plane of the objective lens, an objective lens system 4 for projecting the collected converted light beam on the sample surface 5, and a photodetector 7. I have.

  The pulsed laser light passes through the dichroic mirror 6, is condensed by the light beam conversion optical system and the objective lens system, and is focused on the specimen surface, so that the gold nanorod and the two-photon are formed on the two-photon absorption fluorescent material in the specimen. Fluorescence induced by two-photon absorption through a two-photon reactive material comprising the absorbing material is generated. The sample surface is scanned with a laser beam, the fluorescence intensity at each location is detected by a photodetection device such as the photodetector 7, and a three-dimensional fluorescence image is plotted by a computer based on the obtained positional information. Is obtained. As the scanning mechanism, for example, a laser beam may be scanned using a movable mirror such as a galvanometer mirror, or a sample including a two-photon absorption material placed on a stage may be moved.

  With such a configuration, it is possible to obtain high resolution in the optical axis direction by utilizing the nonlinear effect of two-photon absorption itself. In addition, if a confocal pinhole plate is used, higher resolution (both in-plane and in the optical axis direction) can be obtained.

  Fluorescent dyes for two-photon fluorescence microscopes are used by staining specimens with the fluorescent dyes or by dispersing the fluorescent dyes in specimens, as well as industrial applications, as well as three-dimensional image micro-imaging of biological cells. Therefore, a compound having a high two-photon absorption cross section is desired.

As a photon fluorescence microscope, the example described in Unexamined-Japanese-Patent No. 9-230246 is mentioned, for example.
The scanning fluorescence microscope in this case includes a laser irradiation optical system that emits collimated light expanded to a desired size, and a substrate on which a plurality of condensing elements are formed. A beam splitter that transmits the long wavelength and reflects the short wavelength is disposed between the objective lens system and the substrate on which the light condensing element is formed, and is arranged so as to coincide with the image position of the objective lens system. The fluorescent light is generated by multiphoton absorption on the specimen surface. With such a configuration, it is possible to obtain high resolution in the optical axis direction by utilizing the nonlinear effect of multiphoton absorption itself. In addition, if a confocal pinhole plate is used, higher resolution (both in-plane and in the optical axis direction) can be obtained.
As such a multi-photon optical element, a solid material dispersed in a material having a high two-photon absorption ability, a thin film, or a photocurable resin of the present invention is used as the optical element in exactly the same manner as the above-described light control element. It is possible.

  The two-photon reaction material of the present invention can be used as a two-photon absorption fluorescent material for a two-photon excitation laser scanning microscope. Compared to conventional two-photon absorption fluorescent materials, it has a large two-photon absorption cross-sectional area, so that it exhibits high two-photon absorption characteristics at a low concentration. Therefore, according to the present invention, not only a highly sensitive two-photon reaction material can be obtained, but there is no need to increase the intensity of light applied to the material, and deterioration and destruction of the material can be suppressed. The adverse effect on the properties of other components can also be reduced.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by these examples unless it exceeds the gist.

Example 1
First, a micelle solution consisting of an aqueous phase and an oil phase in which silver ions and gold ions coexist was prepared as follows.
50 ml of 0.15 mol / l of CTAB (cetyltrimethylammonium bromide) aqueous solution was prepared, and 0.3 ml of cyclohexanone and 0.15 ml of diisobutylketone were added as an oily solvent while stirring with a stirrer. As raw materials for gold nanorods, 4 ml of 0.024 mol / l chloroauric acid aqueous solution and 1.5 ml of silver nitrate aqueous solution 0.01 mol / l were added.
To the prepared micelle solution, 0.055 ml of ascorbic acid aqueous solution as a reducing agent was added in increments of 0.05 ml and added until the color of the gold ion disappeared. In this example, the amount of the ascorbic acid aqueous solution added was 0.65 ml.
After dropping the reducing agent into the micelle solution until the color of the gold ions disappears, the reaction solution is transferred to a petri dish and stirred with a stirrer, and UV light is sampled from the high-pressure mercury lamp (made by Ushio Electric, UIS25102) using an optical fiber (reaction solution). ) Introduced directly above and irradiated. Sampling and ascorbic acid as a reducing agent were added dropwise (0.05 ml each) every 5 minutes after the start of irradiation with ultraviolet rays, and additional charging was performed sequentially. Here, the sampled sample was accommodated in a quartz cell having an optical path length of 1 mm, and the absorbance was measured. The measurement results of absorbance are shown in FIG.

  As shown in FIG. 4, after 5 minutes, weak absorption at a wavelength of 720 nm and weaker absorption at a wavelength of 520 nm are observed, indicating that a small number of particles having a relatively small aspect ratio are obtained. . Furthermore, by performing photoreduction with ultraviolet rays while sequentially introducing ascorbic acid, the concentration of gold nanorods increases and the absorption spectrum becomes longer, so the generation of nuclei and the increase in aspect are progressing simultaneously. It can be seen that the concept of nucleation and growth described in the best mode of the invention is realized. Furthermore, almost the same spectrum was obtained at 40 minutes and 45 minutes, and after the reduction reaction was completed due to the depletion of the gold raw material, there was no influence of the deformation of the gold nanorods even when irradiated with ultraviolet rays. The range was found to be limited. In addition, it cannot be overemphasized that the density | concentration of each component which comprises a reaction solution is an example, and can be changed in the range which does not deviate from the thought of this invention.

(Example 2)
First, a micelle solution consisting of an aqueous phase and an oil phase in which silver ions and gold ions coexist was prepared as follows.
50 ml of 0.15 mol / l of CTAB (cetyltrimethylammonium bromide) aqueous solution is prepared, and 0.3 ml of cyclohexanone and 0.09 ml of methyl isobutyl ketone are added as an oily solvent while stirring with a stirrer. As raw materials for gold nanorods, 4 ml of 0.024 mol / l chloroauric acid aqueous solution and 1.5 ml of 0.01 mol / l silver nitrate aqueous solution were further added.
To the prepared micelle solution, 0.055 ml of ascorbic acid aqueous solution as a reducing agent was added in increments of 0.05 ml and added until the color of the gold ion disappeared. In this example, the amount of the ascorbic acid aqueous solution added was 0.65 ml.
After dropping the reducing agent into the micelle solution until the color of the gold ions disappears, transfer the reaction solution to a petri dish, stirring the sample with a stirrer, and UV light from the high-pressure mercury lamp (UIS25102, manufactured by USHIO) using the sample (reaction solution). ) Introduced directly above and irradiated. Sampling and ascorbic acid as a reducing agent were added dropwise every 5 minutes after the start of irradiation (0.04 ml added dropwise), and additional charging was performed sequentially.
The change in absorbance was measured in the same manner as in Example 1, and the completion of the reaction was confirmed by the absence of the spectrum change.

(Comparative Example 1)
First, the growth solution of gold nanorods was prepared as follows.
50 ml of 0.15 mol / l of CTAB (cetyltrimethylammonium bromide) aqueous solution was prepared, and 0.3 ml of cyclohexanone and 1 ml of acetone were added as an oily solvent while stirring with a stirrer. As raw materials for gold nanorods, 2.5 ml of 0.024 mol / l chloroauric acid aqueous solution and 1 ml of 0.01 mol / l silver nitrate aqueous solution were further added.
To the prepared micelle solution, 0.055 ml of ascorbic acid aqueous solution as a reducing agent was added in increments of 0.05 ml and added until the color of the gold ion disappeared. In this example, the amount added was 0.3 ml.
After dropping the reducing agent into the micelle solution until the color of the gold ions disappears, transfer the reaction solution to a petri dish, stirring the sample with a stirrer, and UV light from the high-pressure mercury lamp (UIS25102, manufactured by USHIO) using the sample (reaction solution). ) Introduced directly above and irradiated. The spectrum of the solution was measured every 5 minutes from 15 minutes after the start of irradiation, and the change in absorbance was measured in the same manner as in Example 1 to confirm the end of the reaction by the absence of the spectrum change.

  FIG. 5 shows the spectra after completion of each reaction for Example 1, Example 2, and Comparative Example 1. Compared to the case of Comparative Example 1 using acetone, both Examples 1 and 2 show the absorption caused by the gold nanorod long axis direction on the long wavelength side compared to the absorption caused by the gold nanorod short axis direction of wavelength 530 nm. A large spectrum was obtained. That is, in Example 1 and Example 2, the generation of gold nanorods is controlled as desired, the growth in the minor axis direction is suppressed, and the generation of spherical particles is suppressed.

(Example 3)
First, a micelle solution consisting of an aqueous phase and an oil phase in which silver ions and gold ions coexist was prepared as follows.
50 ml of 0.15 mol / l CTAB (cetyltrimethylammonium bromide) aqueous solution was prepared, and while stirring with a stirrer, 0.3 ml of cyclohexanone, 0.15 ml of diisobutylketone and methylisobutylketone (the following addition conditions were added) 1-3) were added respectively.
<Addition conditions of methyl isobutyl ketone>
Condition 1: 0.03 ml, Condition 2: 0.06 ml, Condition 3: 0.09 ml
Next, 4 ml of 0.024 mol / l chloroauric acid aqueous solution and 1.5 ml of 0.01 mol / l silver nitrate aqueous solution were further added as raw materials for the gold nanorods.
To the prepared micelle solution, 0.055 ml of ascorbic acid aqueous solution as a reducing agent was added in increments of 0.05 ml and added until the color of the gold ion disappeared. In this example, the amount of the ascorbic acid aqueous solution added was 0.65 ml.
After dropping the reducing agent into the micelle solution until the color of the gold ion disappears, transfer the reaction solution to a petri dish, and stir it with a stirrer, and sample UV light from the high-pressure mercury lamp (Ushio Electric, UIS25102) using an optical fiber (reaction solution). ) Introduced directly above and irradiated. Sampling and dropping of ascorbic acid as a reducing agent (0.04 ml each) were carried out every 5 minutes after the start of irradiation, and additional charging was carried out sequentially.
The change in absorbance was measured in the same manner as in Example 1, and the completion of the reaction was confirmed by the absence of the spectrum change.

The spectrum after completion of the reaction is shown in FIG. 6, and the spectrum of Example 1 in which only diisobutyl ketone was added (methyl isobutyl ketone was not added) is also shown.
By simultaneously adding methyl isobutyl ketone, the absorption wavelength of the gold nanorod is further increased, and the absorption wavelength (520 nm) due to the short axis of the gold nanorod and the absorption wavelength (800 nm) due to the long axis of the gold nanorod. ) Ratio was increased, and gold nanorods with a higher aspect ratio were grown, in which the growth of the short axis of gold nanorods was suppressed.
Example 3 is an example of an embodiment of the present invention, and various configurations can be taken within the scope of the idea of the present invention, and the configuration is not limited.

Example 4
First, a micelle solution consisting of an aqueous phase and an oil phase in which silver ions and gold ions coexist was prepared as follows.
50 ml of an aqueous solution of CTAB (cetyltrimethylammonium bromide) 0.10 mol / l was prepared, and 0.3 ml of cyclohexanone and 0.15 ml of diisobutylketone were added as an oily solvent while stirring with a stirrer. As raw materials for gold nanorods, 4 ml of 0.024 mol / l chloroauric acid aqueous solution and 1.5 ml of 0.01 mol / l silver nitrate aqueous solution were further added.
To the prepared micelle solution, 0.055 ml of ascorbic acid aqueous solution as a reducing agent was added in increments of 0.05 ml and added until the color of the gold ion disappeared. In this example, the amount of the ascorbic acid aqueous solution added was 0.65 ml.
After dropping the reducing agent into the micelle solution until the color of the gold ion disappears, transfer the reaction solution to a petri dish, and stir it with a stirrer, and sample UV light from the high-pressure mercury lamp (Ushio Electric, UIS25102) using an optical fiber (reaction solution). ) Introduced directly above and irradiated. Sampling was performed every 5 minutes after the start of irradiation, and ascorbic acid as a reducing agent was dropped (0.04 ml each), and additional charging was sequentially performed.
The change in absorbance was measured in the same manner as in Example 1, and the completion of the reaction was confirmed by the absence of the spectrum change.

(Comparative Example 2)
First, the growth solution of gold nanorods was prepared as follows.
50 ml each of an aqueous solution of CTAB (cetyltrimethylammonium bromide) 0.08 mol / l (for Comparative Example 2-1) and 0.06 mol / l (for Comparative Example 2-2) were prepared.
While stirring each of the CTAB aqueous solutions individually with a stirrer, 0.3 ml of cyclohexanone and 0.15 ml of diisobutyl ketone were added as an oily solvent.
As raw materials for gold nanorods, 4 ml of 0.024 mol / l chloroauric acid aqueous solution and 1.5 ml of 0.01 mol / l silver nitrate aqueous solution were further added.
To the prepared micelle solution, 0.055 ml of ascorbic acid aqueous solution as a reducing agent was added in increments of 0.05 ml and added until the color of the gold ion disappeared. In this comparative example, the addition amount of the ascorbic acid aqueous solution was 0.65 ml in any case.
After dropping the reducing agent into the micelle solution until the color of the gold ion disappears, transfer the reaction solution to a petri dish, and stir it with a stirrer, and sample UV light from the high-pressure mercury lamp (Ushio Electric, UIS25102) using an optical fiber (reaction solution). ) Introduced directly above and irradiated. Sampling was performed every 5 minutes after the start of irradiation, and ascorbic acid as a reducing agent was dropped (0.04 ml each), and additional charging was sequentially performed.
The change in absorbance was measured in the same manner as in Example 1, and the completion of the reaction was confirmed by the absence of the spectrum change.

FIG. 7 shows the relationship between the absorption wavelength and the spectral intensity with the CTAB concentration of the growth solution in Example 4 and Comparative Example 2 as parameters.
When the concentration of the CTAB solution is 0.06 mol / l (Comparative Example 2-2), the spectrum is broad, the aspect ratio of the rod is not sufficient, and there are many spherical particles due to strong absorption at a wavelength of 570 nm. It is concluded. On the other hand, when the concentration of the CTAB solution is 0.08 mol / l (Comparative Example 2-1), since the absorption on the long wavelength side due to the long axis of the gold nanorod is separated, the aspect ratio of the rod is taken. However, it is concluded that the particle diameter is large because the absorption at the wavelength of 520 nm due to the short axis of the gold nanorod is large and the scattering loss by the particles near the wavelength of 400 nm is also large.
In contrast, when the CTAB solution concentration of Example 4 is 0.10 mol / l, the absorption on the long wavelength side due to the long axis of the gold nanorod is large, but the absorption at the wavelength of 520 nm due to the short axis of the gold nanorod is In addition, since the scattering loss due to particles having a wavelength of around 400 nm is suppressed, it was found that fine gold nanorods having the same aspect ratio as the object of the present invention were obtained.

(Example 5)
First, a micelle solution consisting of an aqueous phase and an oil phase in which silver ions and gold ions coexist was prepared as follows.
50 ml of an aqueous solution of CTAB (cetyltrimethylammonium bromide) 0.10 mol / l was prepared, and 0.3 ml of cyclohexanone and 0.15 ml of diisobutylketone were added as an oily solvent while stirring with a stirrer. As raw materials for the gold nanorods, 2.7 ml of 0.024 mol / l chloroauric acid aqueous solution and 1 ml of 0.01 mol / l silver nitrate aqueous solution were further added.
To the prepared micelle solution, 0.055 ml of ascorbic acid aqueous solution as a reducing agent was added in increments of 0.05 ml and added until the color of the gold ion disappeared. In this example, the amount of the ascorbic acid aqueous solution added was 0.45 ml.
After dropping the reducing agent into the micelle solution until the color of the gold ions disappears, transfer the reaction solution to a petri dish, stirring the sample with a stirrer, and UV light from the high-pressure mercury lamp (UIS25102, manufactured by USHIO) using the sample (reaction solution). ) Introduced directly above and irradiated. Sampling was performed every 5 minutes after the start of irradiation, and ascorbic acid as a reducing agent was dropped (0.04 ml each), and additional charging was sequentially performed.
The change in absorbance was measured in the same manner as in Example 1, and the completion of the reaction was confirmed by the absence of the spectrum change.

FIG. 9 is a graph obtained by normalizing the absorption spectrum of the gold nanorod solution grown by changing the chloroauric acid concentration in Example 4 and Example 5 with the maximum value of absorption on the long wavelength side corresponding to the long axis of the gold nanorod. Show.
Example 4 and Example 5 are the differences in the amount of chloroauric acid introduced into the growth solution, and Example 5 has a concentration 2/3 that of Example 4. The absorption at a wavelength of 520 nm corresponding to the short axis of the gold nanorods in the spectrum of Example 5 and the scattering loss by the particles with a wavelength of 400 nm are both smaller than in Example 4, and the growth of the short axis of the gold nanorods was suppressed. It was confirmed that small gold nanorods were obtained. In other words, it was shown that the size of the gold nanorods in the minor axis direction can be controlled by changing the gold ion concentration with the input amount of chloroauric acid.

  As can be seen from the above results, according to the method for producing gold nanorods of the present invention, gold nanorods composed of fine particles capable of suppressing light scattering other than the absorption wavelength with a desired aspect ratio and particle size can be obtained in a short time. Obtained in concentration. Since such gold nanorods have stable functional properties, they can be applied as various high-performance optical materials.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system schematic diagram (a) and a schematic cross-sectional view (b) of a recording medium for explaining application of a two-photon reaction material containing a gold nanorod and a two-photon absorption material of the present invention to a three-dimensional recording medium. It is the schematic which shows the apparatus of the two-photon optical modeling method for demonstrating the application to the material for optical modeling of the two-photon reaction material containing the gold nanorod and two-photon absorption material of this invention. It is the schematic for demonstrating the application to the two-photon absorption fluorescent material and two-photon excitation laser scanning microscope of the two-photon reaction material containing the gold | metal | money nanorod and two-photon absorption material of this invention. It is a figure which shows the relationship between the reaction time obtained by sampling a sample, adding a reducing agent sequentially in Example 1, and the absorption spectrum of a gold nanorod. In Example 1, Example 2, and Comparative Example 1, it is a figure which compares and shows the relationship between the absorption wavelength of the gold nanorod after completion | finish of each reaction, and absorption spectrum intensity | strength. In Example 3, it is a figure which compares and shows the absorption spectrum intensity | strength of each gold | metal | money nanorod produced | generated using diisobutyl ketone and methyl isobutyl ketone (addition conditions 3 types). It is a figure which shows the relationship between the absorption wavelength of each gold | metal | money nanorod which made the CTAB density | concentration of the growth solution in Example 4 and Comparative Example 2 a parameter, and absorption spectrum intensity | strength. It is a figure which shows the relationship between the absorption wavelength and the light absorbency (after normalization) of the gold | metal | money nanorod which grew by changing the chloroauric acid density | concentration in Example 4 and Example 5. FIG.

Explanation of symbols

(Reference in FIG. 1)
DESCRIPTION OF SYMBOLS 1 Recording laser light source 2 Reproduction laser 3 Pinhole 4 Detector 5 Objective lens 6 Three-dimensional recording medium 7 Substrate A
8 Substrate B (Protective layer)
(Reference in FIG. 2)
1. Light source of near-infrared pulsed laser light having transparency with respect to one photo-curing resin 3. Shutter for temporally controlling excessive light amount 4. ND filter 5. Mirror scanner 6. Z stage 7. Lens as light collecting means 8. Computer 9. Photo-curing resin Liquid 10 Stereolithography (reference numeral in FIG. 3)
1 laser light source 2 light flux conversion optical system 3 scanning optical system 4 objective lens system 5 specimen surface 6 dichroic mirror 7 photodetector

Claims (14)

Gold that grows gold nanorods by combining gold ions that coexist with silver ions in a micellar solution consisting of an aqueous phase and an oil phase containing a quaternary ammonium salt, with reduction using a reducing agent and reduction without using a reducing agent. In the nanorod manufacturing method,
A method for producing gold nanorods, wherein a predetermined amount of a reducing agent is dropped into a micelle solution until the color of the gold ions is lost, and then the reducing agent is further added while performing reduction without using the reducing agent. .   The method for producing gold nanorods according to claim 1, wherein the reduction without using the reducing agent is photoreduction performed by light irradiation or electrolytic reduction performed by energization.   The gold nanorod manufacturing method according to claim 1 or 2, wherein the oil phase does not contain acetone.   4. The gold nanorod according to claim 1, wherein the reducing agent is continuously introduced into the micelle solution while controlling the amount of addition during the reduction step without using the reducing agent. 5. Production method.   5. The method for producing gold nanorods according to claim 1, wherein the concentration of the quaternary ammonium salt is 0.1 mol / l or more.   6. The method for producing gold nanorods according to claim 1, wherein the length of the gold nanorods in the minor axis direction is controlled by adjusting the gold ion concentration.   The method for producing gold nanorods according to any one of claims 1 to 6, wherein a component for suppressing reduction precipitation of gold ions in an aqueous phase is added to the micelle solution.   The method for producing gold nanorods according to claim 7, wherein the component that suppresses the reduction and precipitation of gold ions in the aqueous phase has solubility in both the aqueous phase and the oil phase.   The method for producing gold nanorods according to claim 7 or 8, wherein the component that suppresses the reduction and precipitation of gold ions in the aqueous phase is selected from at least one of diisobutyl ketone and methyl isobutyl ketone.   A gold nanorod produced by the method according to claim 1.   A light and electromagnetic wave absorber comprising the gold nanorod according to claim 10.   A colorant comprising the gold nanorod according to claim 10.   An optical recording material comprising the gold nanorod according to claim 10.   A two-photon reaction material comprising at least the gold nanorod according to claim 10 and a two-photon absorption material.