JP2015187299A - Photoresponsive solution, method for preparing the same and method for manufacturing metal nano particle - Google Patents
Photoresponsive solution, method for preparing the same and method for manufacturing metal nano particle Download PDFInfo
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Landscapes
- Manufacture Of Metal Powder And Suspensions Thereof (AREA)
Abstract
Description
本発明は、光を照射すると分散し、光を遮断すると沈殿する性質を持つ光応答性溶液、その調製方法、及び金属ナノ粒子の製造方法に関する。 The present invention relates to a photoresponsive solution having a property of dispersing when irradiated with light and precipitating when blocked by light, a method for preparing the solution, and a method for producing metal nanoparticles.
ナノスケールの金属微粒子（金属ナノ粒子という。）は、バルクにはないユニークな物理的性質を発現することが知られており、ナノテクノロジー分野を含む様々な分野で大きな関心を集めている。そうした物理的性質は、金属ナノ粒子のサイズや形状に大きく依存することから、サイズや形状を自在に制御することができる金属ナノ粒子の合成法の研究開発が盛んに行われている。 Nanoscale metal microparticles (referred to as metal nanoparticles) are known to express unique physical properties that do not exist in the bulk, and are attracting great interest in various fields including the nanotechnology field. Since such physical properties greatly depend on the size and shape of the metal nanoparticles, research and development of methods for synthesizing metal nanoparticles that can freely control the size and shape have been actively conducted.
金属ナノ粒子の代表的な合成法として、有機溶媒を使用する逆ミセル法が挙げられる。逆ミセル法は、溶液中で形成する金属ナノ粒子のサイズ、形状、分散量等を高度に制御する方法として広く利用されているが、有機溶媒を使用していることから、溶媒の水への転換が求められるようになってきている。 A typical method for synthesizing metal nanoparticles includes a reverse micelle method using an organic solvent. The reverse micelle method is widely used as a method for highly controlling the size, shape, amount of dispersion, etc. of metal nanoparticles formed in a solution, but since an organic solvent is used, the solvent is dissolved in water. There is a need for conversion.
水系での金属ナノ粒子の合成法としては、一般に、界面活性剤や水溶性ポリマー中に金属塩を溶解し、還元剤（水素化ホウ素ナトリウムやヒドラジン等）によって金属イオンを還元して金属ナノ粒子を合成する湿式化学還元法が行われている。このときの金属イオンの還元は、加熱、光照射、超音波照射、マイクロ波照射等のような外部エネルギーを印加して行う場合が多い。これらの方法も、水溶液中に形成される金属ナノ粒子のサイズ、形状、分散量を高度に制御する方法として知られている。 In general, metal nanoparticles in water are synthesized by dissolving metal salts in a surfactant or water-soluble polymer and reducing metal ions with a reducing agent (such as sodium borohydride or hydrazine). A wet chemical reduction method for synthesizing is carried out. The reduction of metal ions at this time is often performed by applying external energy such as heating, light irradiation, ultrasonic irradiation, microwave irradiation and the like. These methods are also known as methods for highly controlling the size, shape, and amount of dispersion of metal nanoparticles formed in an aqueous solution.
上記方法で合成された金属ナノ粒子は、一般にアルカンチオール等の配位子、界面活性剤等の両親媒性分子、ポリマー等の保護剤によって覆われている。金属ナノ粒子を覆う配位子、両親媒性分子、ポリマー等は、金属ナノ粒子の機能や性能を低下させる。例えば、金属ナノ粒子を集積した電子デバイス等では、配位子や両親媒性分子等の存在により、電気伝導性が低下する。そのため、金属ナノ粒子を覆う配位子や両親媒性分子等を除去しなければならない。 The metal nanoparticles synthesized by the above method are generally covered with a protective agent such as a ligand such as alkanethiol, an amphiphilic molecule such as a surfactant, or a polymer. Ligands, amphiphilic molecules, polymers, etc. covering the metal nanoparticles reduce the function and performance of the metal nanoparticles. For example, in an electronic device or the like in which metal nanoparticles are integrated, the electrical conductivity decreases due to the presence of a ligand, an amphiphilic molecule, or the like. Therefore, ligands and amphiphilic molecules that cover the metal nanoparticles must be removed.
しかし、配位子や両親媒性分子等を除去する一般的な方法である焼成処理を行うと、電子デバイスの基板であるプラスチック基板が破損してしまため、焼成処理によって除去することができない。また、環境浄化用触媒や燃料電池用触媒等の触媒として利用される金属ナノ粒子も焼成処理によって配位子や両親媒性分子等を除去することが行われているが、その焼成処理を行うと、金属ナノ粒子が融合（シンタリング）してしまい、触媒機能が低下するという問題が生じる。そのため、金属ナノ粒子のサイズ、形状、分散量を高度に制御することができるとともに、配位子や両親媒性分子等を使用しない金属ナノ粒子の合成法が要請されている。 However, if a baking process, which is a general method for removing ligands, amphiphilic molecules, and the like, is performed, the plastic substrate, which is the substrate of the electronic device, is damaged and cannot be removed by the baking process. In addition, metal nanoparticles used as catalysts for environmental purification catalysts, fuel cell catalysts, etc. are also subjected to removal of ligands, amphiphilic molecules, etc. by firing treatment. Then, the metal nanoparticles are fused (sintered), resulting in a problem that the catalytic function is lowered. Therefore, there is a demand for a method for synthesizing metal nanoparticles that can highly control the size, shape, and amount of dispersion of metal nanoparticles and that does not use ligands or amphiphilic molecules.
こうした要請に対し、本発明者は、特許文献１において、界面活性剤や両親媒性高分子を用いることなく形状を制御できる金属微粒子の製造方法を提供した。この製造方法は、金属塩溶液中の金属塩を還元して所定の形状の金属微粒子とする金属微粒子の製造方法であって、前記金属塩濃度、前記金属塩溶液中への超音波照射周波数、前記金属塩溶液中への光照射、前記金属塩溶液のｐＨ、前記金属塩溶液中の温度のうち少なくとも１条件と還元後の金属微粒子の所定の形状の予め求めた相関関係に基づき、所望の形状の金属微粒子に製造することを特徴としている。 In response to such a request, the present inventor in Patent Document 1 provided a method for producing metal fine particles capable of controlling the shape without using a surfactant or an amphiphilic polymer. This production method is a method for producing metal fine particles by reducing a metal salt in a metal salt solution to form metal fine particles of a predetermined shape, the metal salt concentration, the ultrasonic irradiation frequency into the metal salt solution, Based on a predetermined correlation between at least one of the light irradiation into the metal salt solution, the pH of the metal salt solution, and the temperature in the metal salt solution and a predetermined shape of the metal fine particles after reduction, a desired It is characterized in that it is manufactured into shaped metal fine particles.
本発明者は、配位子や両親媒性分子等を使用せずに金属ナノ粒子を合成できる新しい合成法の研究を継続して行っている過程で、合成した金属ナノ粒子を含む溶液が、光を照射すると分散し、光を遮断すると沈殿する性質を持つことを見出し、その性質を安定して生じさせることができる溶液の調製方法についてさらに研究した。 In the process of continuing research on a new synthesis method capable of synthesizing metal nanoparticles without using a ligand, an amphiphilic molecule, etc., the inventor has a solution containing the synthesized metal nanoparticles, We found that it has the property of dispersing when irradiated with light and precipitating when blocked by light, and further studied a method for preparing a solution capable of stably producing the property.
本発明は、そうした研究の結果得られたものであって、その目的は、光を照射すると分散し、光を遮断すると沈殿する性質を持つ光応答性溶液、その光応答性溶液の調製方法、及び金属ナノ粒子の製造方法を提供することにある。 The present invention has been obtained as a result of such research, and the object thereof is a photoresponsive solution having the property of dispersing when irradiated with light and precipitating when blocked by light, a method for preparing the photoresponsive solution, And it is providing the manufacturing method of a metal nanoparticle.
（１）本発明に係る光応答性溶液は、水素ラジカルで還元された平均粒径２ｎｍ以上１００ｎｍ以下の金属ナノ粒子と溶媒とを含み、前記金属ナノ粒子は、光の照射によって前記溶媒中に分散し、光を遮蔽することによって前記溶媒中で沈殿することを特徴とする。 (1) The photoresponsive solution according to the present invention includes metal nanoparticles having an average particle diameter of 2 nm to 100 nm reduced by hydrogen radicals and a solvent, and the metal nanoparticles are irradiated into the solvent by light irradiation. Precipitating in the solvent by dispersing and shielding light.
この発明は、金属塩を還元剤で還元せず、界面活性剤も含まない方法で合成された金属ナノ粒子を含む光応答性溶液であり、水素ラジカルで還元された平均粒径２ｎｍ以上１００ｎｍ以下の範囲内の金属ナノ粒子と溶媒とを含むことにより、光スイッチング機能を示す。その光スイッチング機能は、光の照射によって溶媒中に金属ナノ粒子が分散し、光を遮蔽することによって溶媒中で金属ナノ粒子が沈殿し、さらに光を照射すると再び溶媒中に金属ナノ粒子が分散するという特異な性質を奏する。 The present invention is a photoresponsive solution containing metal nanoparticles synthesized by a method that does not reduce a metal salt with a reducing agent and does not contain a surfactant, and has an average particle size of 2 nm to 100 nm reduced by hydrogen radicals. The optical switching function is exhibited by including metal nanoparticles and a solvent within the range of. Its light switching function is that the metal nanoparticles are dispersed in the solvent by light irradiation, the metal nanoparticles are precipitated in the solvent by shielding light, and the metal nanoparticles are dispersed in the solvent again when irradiated with light. Has the unique property of being
本発明に係る光応答性溶液において、前記金属ナノ粒子が、球状粒子又は略球状粒子であることが好ましい。この発明によれば、より分散が良好になる。 In the photoresponsive solution according to the present invention, the metal nanoparticles are preferably spherical particles or substantially spherical particles. According to this invention, the dispersion becomes better.
（２）本発明に係る光応答性溶液の調製方法は、金属塩と水とを含む溶液に超音波を照射して水素ラジカルを生じさせ、生じた水素ラジカルを還元種として金属塩を還元し、平均粒径２ｎｍ以上１００ｎｍ以下の範囲内の金属ナノ粒子を前記溶液中で合成することを特徴とする。 (2) In the method for preparing a photoresponsive solution according to the present invention, a solution containing a metal salt and water is irradiated with ultrasonic waves to generate hydrogen radicals, and the generated hydrogen radicals are used as reducing species to reduce the metal salt. The metal nanoparticles having an average particle diameter in the range of 2 nm to 100 nm are synthesized in the solution.
この発明によれば、従来のように金属塩と還元剤と保護剤と溶媒とを用いる湿式化学還元法とは異なり、金属塩と水とを含む溶液に超音波を照射して金属ナノ粒子を得ることができるので、必要最小限の原料から必要な金属ナノ粒子を極めて簡単な方法で得ることができる。また、水中で合成された金属ナノ粒子は、分散剤や界面活性剤等の有機化学種を含まなくても光の照射により分散し、遮光により沈殿するという特異な現象を生じることができる。 According to this invention, unlike the conventional wet chemical reduction method using a metal salt, a reducing agent, a protective agent, and a solvent, a metal nanoparticle is formed by irradiating a solution containing the metal salt and water with ultrasonic waves. Since it can be obtained, the necessary metal nanoparticles can be obtained by a very simple method from the minimum necessary raw materials. In addition, the metal nanoparticles synthesized in water can cause a unique phenomenon that they are dispersed by irradiation with light and precipitated by shading without containing organic chemical species such as a dispersant and a surfactant.
本発明に係る光応答性溶液の調製方法において、前記金属ナノ粒子が、球状粒子又は略球状粒子であることが好ましい。この発明によれば、より分散が良好な光応答性溶液を製造できる。 In the method for preparing a photoresponsive solution according to the present invention, the metal nanoparticles are preferably spherical particles or substantially spherical particles. According to the present invention, a photoresponsive solution with better dispersion can be produced.
（３）本発明に係る金属ナノ粒子の製造方法は、金属塩と水とを含む溶液に超音波を照射して水素ラジカルを生じさせ、生じた水素ラジカルを還元種として金属塩を還元し、平均粒径２ｎｍ以上１００ｎｍ以下の範囲内の金属ナノ粒子を前記溶液中で合成し、前記金属ナノ粒子を含む溶液を遮光して前記金属ナノ粒子を沈殿させて得ることを特徴とする。 (3) In the method for producing metal nanoparticles according to the present invention, a solution containing a metal salt and water is irradiated with ultrasonic waves to generate hydrogen radicals, and the generated hydrogen radicals are used as reducing species to reduce the metal salt, Metal nanoparticles having an average particle size of 2 nm or more and 100 nm or less are synthesized in the solution, and the solution containing the metal nanoparticles is shielded from light to precipitate the metal nanoparticles.
この発明によれば、従来のように金属塩と還元剤と保護剤と溶媒とを用いる湿式化学還元法とは異なり、金属塩と水とを含む溶液に超音波を照射して金属ナノ粒子を合成し、合成した金属ナノ粒子含有溶液を遮光して溶液中に分散する金属ナノ粒子を沈殿させて得ることができる。 According to this invention, unlike the conventional wet chemical reduction method using a metal salt, a reducing agent, a protective agent, and a solvent, a metal nanoparticle is formed by irradiating a solution containing the metal salt and water with ultrasonic waves. It can synthesize | combine and it can obtain by precipitating the metal nanoparticle disperse | distributed in a solution, shielding the synthesized metal nanoparticle containing solution.
本発明によれば、光を照射すると分散し、光を遮断すると沈殿する性質を持つ光応答性溶液、その光応答性溶液の調製方法、及び金属ナノ粒子の製造方法を提供することができる。特に、従来のように金属塩と還元剤と保護剤と溶媒とを用いる湿式化学還元法で得たものとは異なり、金属塩と水とを含む溶液に超音波を照射して金属ナノ粒子を得ることができるので、必要最小限の原料から必要な金属ナノ粒子を極めて簡単な方法で得ることができる。また、水中で合成された金属ナノ粒子は、分散剤や界面活性剤等の有機化学種を含まなくても光の照射により分散し、遮光により沈殿するという特異な現象を生じることができる。 ADVANTAGE OF THE INVENTION According to this invention, the photoresponsive solution which has the property to disperse | distribute when irradiated with light and to precipitate when light is interrupted, the preparation method of the photoresponsive solution, and the manufacturing method of a metal nanoparticle can be provided. In particular, unlike conventional methods obtained by a wet chemical reduction method using a metal salt, a reducing agent, a protective agent, and a solvent, a metal nanoparticle is formed by irradiating a solution containing the metal salt and water with ultrasonic waves. Since it can be obtained, the necessary metal nanoparticles can be obtained by a very simple method from the minimum necessary raw materials. In addition, the metal nanoparticles synthesized in water can cause a unique phenomenon that they are dispersed by irradiation with light and precipitated by shading without containing organic chemical species such as a dispersant and a surfactant.
本発明に係る光応答性溶液、その光応答性溶液の調製方法及び金属ナノ粒子の製造方法について詳しく説明する。本発明は、その要旨に範囲内であれば、以下の実施形態に限定されない。 The photoresponsive solution according to the present invention, a method for preparing the photoresponsive solution, and a method for producing metal nanoparticles will be described in detail. The present invention is not limited to the following embodiment as long as it falls within the scope of the gist thereof.
本発明に係る光応答性溶液は、水素ラジカルで還元された平均粒径２ｎｍ以上１００ｎｍ以下の金属ナノ粒子と溶媒とを含み、その金属ナノ粒子は、光の照射によって前記溶媒中に分散し、光を遮蔽することによって前記溶媒中で沈殿することを特徴とする。この光応答性溶液の調製方法は、生じた水素ラジカルを還元種として金属塩を還元し、平均粒径２ｎｍ以上１００ｎｍ以下の範囲内の金属ナノ粒子を前記溶液中で合成することに特徴がある。 The photoresponsive solution according to the present invention includes a metal nanoparticle having an average particle size of 2 nm or more and 100 nm or less reduced with hydrogen radicals, and the metal nanoparticle is dispersed in the solvent by light irradiation, It precipitates in the said solvent by shielding light. This method for preparing a photoresponsive solution is characterized in that the metal salt is reduced using the generated hydrogen radical as a reducing species, and metal nanoparticles having an average particle diameter in the range of 2 nm to 100 nm are synthesized in the solution. .
得られた光応答性溶液は、金属塩を還元剤で還元せず、界面活性剤も含まない方法で合成された金属ナノ粒子を含む光応答性溶液であり、水素ラジカルで還元された上記平均粒径範囲の金属ナノ粒子と溶媒とを含むことにより、光スイッチング機能を示す。その光スイッチング機能は、光の照射によって溶媒中に金属ナノ粒子が分散し、光を遮蔽することによって溶媒中で金属ナノ粒子が沈殿するという特異な性質を奏する。そして、さらに光を照射すると再び溶媒中に金属ナノ粒子が分散する。 The obtained photoresponsive solution is a photoresponsive solution containing metal nanoparticles synthesized by a method that does not reduce a metal salt with a reducing agent and does not contain a surfactant. An optical switching function is exhibited by including metal nanoparticles having a particle size range and a solvent. The light switching function has a unique property that metal nanoparticles are dispersed in a solvent by light irradiation, and metal nanoparticles are precipitated in the solvent by shielding light. When further irradiated with light, the metal nanoparticles are dispersed again in the solvent.
こうした特異な性質は、配位子や両親媒性分子等の有機化学種を使用せずに金属ナノ粒子を合成できる新しい合成法の研究を継続して行っている過程で見出したものであり、本発明は、そうした特異な性質を安定して生じさせることができる溶液の調製方法について研究して成し得たものである。 These unique properties were discovered in the course of continuing research on new synthetic methods that can synthesize metal nanoparticles without using organic species such as ligands and amphiphilic molecules, The present invention has been made by researching a method for preparing a solution capable of stably producing such unique properties.
以下、本発明に係る光応答性溶液及びその調製方法の構成要素について詳しく説明する。 Hereinafter, components of the photoresponsive solution and the preparation method thereof according to the present invention will be described in detail.
（金属ナノ粒子）
金属ナノ粒子は、平均粒径２ｎｍ以上、１００ｎｍ以下の範囲内の粒子である。この範囲内の粒子は、分散剤や両親媒性分子等の有機化学種を含まない水溶液中での光存在時の分散や遮光時の沈殿が良好である。平均粒径が１００ｎｍを超えると、光存在下であっても分散性が低下して沈殿気味になることがある。なお、平均粒径の下限値を２ｎｍにしたのは、２ｎｍ未満の粒子は十分に得ることができないために便宜的に設定したものであり、特性上の限界値ではない。
(Metal nanoparticles)
The metal nanoparticles are particles having an average particle diameter of 2 nm or more and 100 nm or less. Particles within this range have good dispersion in the presence of light in an aqueous solution that does not contain organic chemical species such as dispersants and amphiphilic molecules, and precipitation during light shielding. When the average particle diameter exceeds 100 nm, the dispersibility may be lowered even in the presence of light, resulting in a slight precipitation. The reason why the lower limit of the average particle diameter is set to 2 nm is that it is set for convenience because particles less than 2 nm cannot be obtained sufficiently, and is not a limit value in terms of characteristics.
図１（Ａ）〜（Ｄ）に示すように、Ａｕナノ粒子の平均粒径が２ｎｍ以上１００ｎｍ以下の範囲内の場合は、光存在下の水溶液中での良好な分散を確認でき、遮光時の良好な沈殿を確認できる。一方、図１（Ｅ）と（Ｆ）に示すように、Ａｕナノ粒子の平均粒径が凝集したり連結したりして１００ｎｍを超える場合は、光存在下であっても水溶液中で沈殿気味になる。 As shown in FIGS. 1 (A) to (D), when the average particle diameter of Au nanoparticles is in the range of 2 nm to 100 nm, good dispersion in an aqueous solution in the presence of light can be confirmed. Good precipitation can be confirmed. On the other hand, as shown in FIGS. 1E and 1F, when the average particle size of Au nanoparticles exceeds 100 nm due to aggregation or connection, it appears to precipitate in an aqueous solution even in the presence of light. become.
金属ナノ粒子の形状は特に限定されないが、球状、略球状、棒状、略棒状、三角板状、略三角板状、六角板状、略六角板状のうちいずれか１又は２以上の形状であればよい。これらのうち、球状に近い形状、例えば球状、略球状、多角形状（六角板状、略六角板状等）の金属ナノ粒子は、光存在下での良好な分散性と、遮光下での良好な沈殿性を示す点で好ましい。 The shape of the metal nanoparticles is not particularly limited, but may be any one or more of a spherical shape, a substantially spherical shape, a rod shape, a substantially rod shape, a triangular plate shape, a substantially triangular plate shape, a hexagonal plate shape, and a substantially hexagonal plate shape. . Among these, metal nanoparticles having a shape close to a sphere, for example, a sphere, a substantially sphere, or a polygon (such as a hexagonal plate or a substantially hexagonal plate) have good dispersibility in the presence of light and good under light shielding. It is preferable at the point which shows a favorable precipitation.
（金属ナノ粒子の合成）
金属ナノ粒子は、原料である金属塩が水素ラジカルで還元されて合成される。詳しくは、上記の平均粒径の範囲内の金属ナノ粒子は、原料である金属塩が水素ラジカルを還元種として還元され、水溶液中で合成される。
(Synthesis of metal nanoparticles)
Metal nanoparticles are synthesized by reducing a metal salt as a raw material with hydrogen radicals. Specifically, the metal nanoparticles in the above average particle size range are synthesized in an aqueous solution by reducing the metal salt as a raw material using a hydrogen radical as a reducing species.
水素ラジカルは、還元種として機能し、溶媒である水に超音波を照射することにより、Ｈ２Ｏ→Ｈ・＋ＯＨ・として生成できる。この水素ラジカル（Ｈ・）が、例えば塩化金であるＡｌＣｌ4 -を還元するように作用し、ＡｌＣｌ4 -＋３Ｈ・→Ａｕ0＋４Ｃｌ-＋３Ｈ+となって、金ナノ粒子を合成できる。超音波は、任意の周波数に調整して照射することができるが、２００ｋＨｚ以上、１０００ｋＨｚ以下の範囲内であると好適である。なお、後述する実施例では、２００ｋＨｚや９５０ｋＨｚを適用しているが、これに限定されない。超音波を照射する超音波照査装置としては、各種のものを用いることができる。 The hydrogen radical functions as a reducing species and can be generated as H 2 O → H · + OH · by irradiating water as a solvent with ultrasonic waves. This hydrogen radical (H.) acts to reduce, for example, AlCl 4 − , which is gold chloride, and becomes AlCl 4 − + 3H · → Au 0 + 4Cl − + 3H + , thereby synthesizing gold nanoparticles. Ultrasound can be irradiated with an arbitrary frequency adjusted, but is preferably in the range of 200 kHz or more and 1000 kHz or less. In addition, in the Example mentioned later, although 200 kHz and 950 kHz are applied, it is not limited to this. Various devices can be used as the ultrasonic inspection device for irradiating ultrasonic waves.
溶媒は、水である。水は、水素ラジカを発生させることができる。水の詳しい種類は特に限定されず、化学合成に一般に用いられる蒸留水、純水、超純水、イオン交換水等であればよい。 The solvent is water. Water can generate hydrogen radios. The detailed type of water is not particularly limited, and may be distilled water, pure water, ultrapure water, ion exchange water or the like generally used for chemical synthesis.
金属塩は、水素ラジカルで還元されて金属ナノ粒子を合成できるものであれば特に限定されず、各種のものを適用できる。例えば、金、銀、白金、パラジウム等の貴金属の金属塩、銅、鉄、コバルト、ニッケル、亜鉛、クロミウム、マンガン、マグネシウム、カドミウム、アルミニウム、錫、タングステン等の金属塩を挙げることができる。 The metal salt is not particularly limited as long as it can be synthesized with metal radicals by being reduced with hydrogen radicals, and various kinds of metal salts can be applied. Examples thereof include metal salts of noble metals such as gold, silver, platinum and palladium, and metal salts such as copper, iron, cobalt, nickel, zinc, chromium, manganese, magnesium, cadmium, aluminum, tin and tungsten.
具体的には、Ａｇ+，Ａｇ（ＣＮ）2 -，ＡｌＣｌ4 -，Ａｕ3+，ＡｕＣｌ4 -，ＡｕＢｒ4 -，ＰｔＣｌ6 2-，Ｍｇ2+，Ｍｎ2+，Ｃｏ2+，Ｎｉ2+，Ｃｕ2+，Ｚｎ2+，Ｃｄ2+，Ｆｅ3+，Ａｌ3+，Ｐｄ2+，ＰｄＣｌ4 2-，Ｓｎ2+，ＳｎＯ3 2-，Ｇａ3+，ＷＯ4 2-）等のように、溶液中でイオンになることができる金属塩、ＡｇＡｓＦ6，ＡｇＢＦ4，ＡｇＢｒ，ＡｇＣｌ，ＡｇＣｌＯ3，ＡｇＣｌＯ4，ＡｇＦ，ＡｇＦ2，ＡｇＦ6Ｐ，ＡｇＦ6Ｓｂ，ＡｇＩ，ＡｇＩＯ3，ＡｇＭｎＯ4，ＡｇＮＯ2，ＡｇＮＯ3，ＡｇＯ3Ｖ，ＡｇＯ4Ｒｅ，Ａｇ2ＣｒＯ4，Ａｇ2Ｏ，Ａｇ2Ｏ3Ｓ，Ａｇ2Ｏ4Ｓ，Ａｇ2Ｓ，Ａｇ2Ｓｅ，Ａｇ2Ｔｅ，Ａｇ3ＡｓＯ4，Ａｇ3ＡｓＯ4，Ａｇ3ＡｓＯ4，Ａｇ3Ｏ4Ｐ，Ａｇ8Ｏ16Ｗ4，ＫＡｇ（ＣＮ）2，ＣＨ3ＣＯ2Ａｇ，ＡｇＣＮ，ＡｇＣＮＯ，ＡｇＣＮＳ，Ａｇ2ＣＯ3、ＡｌＣｌ3Ｏ12，ＡｌＣｌ4Ｃｓ，ＡｌＣｌ4Ｋ，ＡｌＣｌ4Ｌｉ，ＡｌＣｌ4Ｎａ，ＡｌＣｌ2Ｔｉ3，ＡｌＣｓＯ4Ｓｉ，ＡｌＣｓＯ6Ｓｉ2，ＡｌＣｓＯ8Ｓ2，ＡｌＦ4Ｋ，ＡｌＦ6Ｎａ3，ＡｌＫＯ8Ｓ2，ＡｌＬｉＯ2，ＡｌＮ3Ｏ9，ＡｌＯ4Ｐ，ＡｌＯ9Ｐ3，Ａｌ2ＢａＯ4，Ａｌ2ＭｇＯ4，Ａｌ2Ｏ5Ｔｉ，Ａｌ3Ｏ12Ｓ3，Ａｌ6Ｂｉ2Ｏ12，Ａｌ6Ｏ13Ｓｉ2，Ｈ4ＡｌＬｉ，Ｈ4ＡｌＮＯ8Ｓ2，ＡｕＢｒ3，ＫＡｕＢｒ4，ＮａＡｕＢｒ4，ＡｕＣｌ3，ＫＡｕＣｌ4，ＮａＡｕＣｌ4，ＨＡｕＣｌ4，ＡｕＩ3，Ａｕ2Ｓ3，ＨＡｕＣｌ4Ｎ，ＡｕＣＮ、ＣｏＦ2，ＣｏＦ3，ＣｏＩ2，ＣｏＬｉＯ2，ＣｏＮ2Ｏ6，ＣｏＮ6Ｎａ3Ｏ12，ＣｏＯ，ＣｏＯ4Ｓ，ＣｏＳｅ，Ｃｏ3Ｏ4，Ｃｏ3Ｏ8Ｐ2，Ｃｏ5Ｓｍ，Ｃｏ7Ｓｍ2，Ｈ8ＣｏＮ2Ｏ8Ｓ2，Ｈ12ＣｏＮ9Ｏ9，Ｈ15Ｃｌ3ＣｏＮ5，ＣｏＣＯ3、ＣｄＣｌ2，ＣｄＣｌ2Ｏ8，ＣｄＦ2，ＣｄＩ2，ＣｄＭｏＯ4，ＣｄＮ2Ｏ6，ＣｄＯ3Ｚｒ，ＣｄＯ4Ｓ，ＣｄＯ4Ｗ，ＣｕＦ2，ＣｕＩ，ＣｕＭｏＯ4，ＣｕＮ2Ｏ6，ＣｕＮｂ2Ｏ6，ＣｕＯ，ＣｕＯ3Ｓｅ，ＣｕＯ4Ｓ，ＣｕＯ4Ｗ，ＣｕＳ，ＣｕＳｅ，ＣｕＴｅ，Ｃｕ2ＨｇＩ4，Ｃｕ2Ｏ，Ｃｕ2Ｏ7Ｐ2，Ｃｕ2Ｓ，Ｃｕ2Ｓｅ，Ｃｕ2Ｔｅ，Ｈ8Ｃｌ4ＣｕＮ2，Ｈ12ＣｕＮ4Ｏ4Ｓ，ＣｕＣＮ，ＣｕＣＮＳ、ＭｇＭｎ2Ｏ8，ＭｇＭｏＯ4，ＭｇＮ2Ｏ6，ＭｇＯ3Ｓ2，ＭｇＯ3Ｔｉ，ＭｇＯ3Ｚｒ，ＭｇＯ4Ｓ，ＭｇＯ4Ｗ，Ｍｇ2Ｏ7Ｐ2，Ｍｇ3Ｏ8Ｐ2，Ｈ4ＭｇＮＯ4Ｐ，ＭｎＭｏＯ4，ＭｎＮ2Ｏ6，ＭｎＮｏＯ４，ＭｎＯ4Ｓ，Ｈ4ＭｎＯ4Ｐ2，ＮｉＯ，ＮｉＯ3Ｔｉ，ＮｉＯ4Ｓ，Ｈ4Ｎ2ＮｉＯ6Ｓ2，Ｈ2ＰｔＣｌ6，Ｈ6Ｃｌ2Ｎ2Ｐｔ，Ｈ6Ｃｌ4Ｎ2Ｐｔ，Ｈ6Ｎ4Ｏ4Ｐｔ，Ｈ6Ｎａ2Ｏ6Ｐｔ，Ｈ8Ｂｒ6Ｎ2Ｐｔ，Ｈ8Ｃｌ4Ｎ2Ｐｔ，Ｈ8Ｃｌ6Ｎ2Ｐｔ，Ｈ8Ｏ6Ｐｔ，Ｈ12Ｃｌ2Ｎ4Ｐｔ，Ｈ12Ｃｌ4Ｎ4Ｐｔ2，Ｈ12Ｎ6Ｏ6Ｐｔ，Ｈ14Ｎ4Ｏ2Ｐｔ，Ｃ2Ｎ2Ｐｔ，Ｈ6Ｂｒ2Ｎ2Ｐｄ，Ｈ6Ｃｌ2Ｎ2Ｐｄ，Ｈ6Ｉ2Ｎ2Ｐｄ，Ｈ6Ｎ4Ｏ4Ｐｄ，Ｈ8Ｃｌ4Ｎ2Ｐｄ，Ｈ8Ｃｌ6Ｎ2Ｐｄ，Ｈ12Ｂｒ2Ｎ4Ｐｄ，Ｈ12Ｃｌ2Ｎ4Ｐｄ，Ｈ12Ｃｌ4Ｎ4Ｐｄ2，Ｈ12Ｎ6Ｏ6Ｐｄ，Ｃ2Ｎ2Ｐｄ，Ｐｄ（ＯＡｃ）2，Ｐｄ（ＮＯ3）2，Ｈ4ＦｅＮＯ8Ｓ2，Ｈ8ＦｅＮ2Ｏ8Ｓ2，ＦｅＣｌ3，Ｃ2Ｎ2Ｚｎ，Ｈ2ＳｎＯ3，Ｎａ2ＳｎＯ3，ＳｎＣｌ２・２Ｈ2Ｏ，ＳｎＯ，ＳｎＳＯ4，ＳｎＯ2，ＧａＢｒ3，ＧａＣｌ3，ＧａＩ3，Ｇａ（ＮＯ3）3・Ｈ2Ｏ，Ｇａ（ＳＯ4）3・Ｈ2Ｏ，Ｇａ2（ＳＯ4）3，ＧａＡｓ，ＧａＮ，ＧａＰ，ＧａＳ，Ｇａ2Ｓ3，ＧａＳｅ，ＧａＳｅ，Ｇａ2Ｓｅ3，ＧａＴｅ，Ｇａ2Ｔｅ3，ＧａＯ2Ｈ，Ｈ2ＷＯ4等を挙げることができる。これらのうち好ましくは、ＡｇＮＯ3，ＫＡｕＣｌ4，ＮａＡｕＣｌ4，ＨＡｕＣｌ4，Ｈ2ＰｔＣｌ6，Ｐｄ（ＯＡｃ）2，Ｐｄ（ＮＯ3）2，Ｇａ（ＮＯ3）3・Ｈ2Ｏ等を挙げることができる。 Specifically, Ag + , Ag (CN) 2 − , AlCl 4 − , Au 3+ , AuCl 4 − , AuBr 4 − , PtCl 6 2− , Mg 2+ , Mn 2+ , Co 2+ , Ni 2 + , Cu 2+ , Zn 2+ , Cd 2+ , Fe 3+ , Al 3+ , Pd 2+ , PdCl 4 2− , Sn 2+ , SnO 3 2− , Ga 3+ , WO 4 2− ), etc. Metal salts that can become ions in solution, such as AgAsF 6 , AgBF 4 , AgBr, AgCl, AgClO 3 , AgClO 4 , AgF, AgF 2 , AgF 6 P, AgF 6 Sb, AgI, AgIO 3 , AgMnO 4 , AgNO 2 , AgNO 3 , AgO 3 V, AgO 4 Re, Ag 2 CrO 4 , Ag 2 O, Ag 2 O 3 S, Ag 2 O 4 S, Ag 2 S, Ag 2 Se, Ag 2 Te, Ag 3 AsO 4 , Ag 3 AsO 4 , Ag 3 AsO 4 , Ag 3 O 4 P, Ag 8 O 16 W 4 , KAg (CN) 2 , CH 3 CO 2 Ag, AgCN, AgCNO, AgCNS, Ag 2 CO 3 , AlCl 3 O 12 , AlCl 4 Cs, AlCl 4 K, AlCl 4 Li, AlCl 4 Na, AlCl 2 Ti 3 , AlCsO 4 Si, AlCsO 6 Si 2 , AlCsO 8 S 2 , AlF 4 K, AlF 6 Na 3 , AlKO 8 S 2 , AlLiO 2 , AlN 3 O 9 , AlO 4 P, AlO 9 P 3 , Al 2 BaO 4 , Al 2 MgO 4 , Al 2 O 5 Ti, Al 3 O 12 S 3 , Al 6 Bi 2 O 12 , Al 6 O 13 Si 2 , H 4 AlLi, H 4 AlNO 8 S 2 , AuBr 3 , KAuBr 4 , NaAuBr 4 , AuCl 3 , KAuCl 4 , NaAuCl 4 , HAuCl 4 , AuI 3 , Au 2 S 3 , HAuCl 4 N, AuCN, CoF 2 , CoF 3 , CoI 2 , CoLiO 2 , CoN 2 O 6 , CoN 6 Na 3 O 12 , CoO, CoO 4 S, CoSe, Co 3 O 4 , Co 3 O 8 P 2 , Co 5 Sm, Co 7 Sm 2 , H 8 CoN 2 O 8 S 2 , H 12 CoN 9 O 9 , H 15 Cl 3 CoN 5 , CoCO 3 , CdCl 2 , CdCl 2 O 8 , CdF 2 , CdI 2 , CdMoO 4 , CdN 2 O 6 , CdO 3 Zr, CdO 4 S, CdO 4 W, CuF 2 , CuI, CuMoO 4, CuN 2 O 6, CuNb 2 O 6, CuO, CuO 3 Se, CuO 4 S, CuO 4 W, CuS, CuSe, CuTe, Cu 2 HgI 4, Cu 2 O, Cu 2 O 7 P 2 , Cu 2 S, Cu 2 Se, Cu 2 Te, H 8 Cl 4 CuN 2 , H 12 CuN 4 O 4 S, CuCN, CuCNS, MgMn 2 O 8 , MgMoO 4 , MgN 2 O 6 , MgO 3 S 2 , MgO 3 Ti, MgO 3 Zr, MgO 4 S, MgO 4 W, Mg 2 O 7 P 2 , Mg 3 O 8 P 2 , H 4 MgNO 4 P, MnMoO 4 , MnN 2 O 6 , MnNoO 4 , MnO 4 S, H 4 MnO 4 P 2 , NiO, NiO 3 Ti, NiO 4 S, H 4 N 2 NiO 6 S 2, H 2 PtCl 6, H 6 Cl 2 N 2 Pt, H 6 Cl 4 N 2 Pt, H 6 N 4 O 4 Pt, H 6 Na 2 O 6 Pt, H 8 Br 6 N 2 Pt, H 8 Cl 4 N 2 Pt, H 8 Cl 6 N 2 Pt, H 8 O 6 Pt, H 12 Cl 2 N 4 Pt, H 12 Cl 4 N 4 Pt 2 , H 12 N 6 O 6 Pt, H 14 N 4 O 2 Pt, C 2 N 2 Pt, H 6 Br 2 N 2 Pd, H 6 Cl 2 N 2 Pd, H 6 I 2 N 2 Pd, H 6 N 4 O 4 Pd, H 8 Cl 4 N 2 Pd, H 8 Cl 6 N 2 Pd, H 12 Br 2 N 4 Pd, H 12 Cl 2 N 4 Pd, H 12 Cl 4 N 4 Pd 2 , H 12 N 6 O 6 Pd, C 2 N 2 Pd, Pd (OAc) 2 , Pd (NO 3 ) 2 , H 4 FeNO 8 S 2 , H 8 FeN 2 O 8 S 2 , FeCl 3 , C 2 N 2 Zn, H 2 SnO 3 , Na 2 SnO 3 , SnCl 2 2H 2 O, SnO, SnSO 4 , SnO 2 , GaBr 3 , GaCl 3 , GaI 3 , Ga (NO 3 ) 3 .H 2 O, Ga (SO 4 ) 3 .H 2 O, Ga 2 (SO 4 ) 3, can be GaAs, GaN, GaP, GaS, Ga 2 S 3, GaSe, GaSe, Ga 2 Se 3, GaTe, Ga 2 Te 3, GaO 2 H, be mentioned H 2 WO 4 and the like. Of these, AgNO 3 , KAuCl 4 , NaAuCl 4 , HAuCl 4 , H 2 PtCl 6 , Pd (OAc) 2 , Pd (NO 3 ) 2 , Ga (NO 3 ) 3 .H 2 O and the like are preferable. Can do.
金属塩の濃度は、特に限定されないが、溶媒である水中における金属塩の濃度が１０ｍＭ以下であることが好ましい。 The concentration of the metal salt is not particularly limited, but the concentration of the metal salt in water as a solvent is preferably 10 mM or less.
本発明では、金属ナノ粒子の合成の際に、分散剤、両親媒性分子、界面活性剤等の有機化学種を添加しない点にも特徴がある。その結果、金属ナノ粒子を合成した後に、分散剤、両親媒性分子、界面活性剤等の有機化学種を除去する必要がなく、また、副生成物も生じないので、その後の廃棄処理等が不要になるという利点がある。 The present invention is also characterized in that no organic chemical species such as a dispersant, an amphiphilic molecule, and a surfactant are added during the synthesis of metal nanoparticles. As a result, it is not necessary to remove organic chemical species such as dispersants, amphiphilic molecules, and surfactants after synthesizing the metal nanoparticles, and no by-products are produced. There is an advantage that it becomes unnecessary.
（光応答性溶液）
光応答性溶液は、上記したように、水素ラジカルで還元された平均粒径２ｎｍ以上１００ｎｍ以下の金属ナノ粒子と溶媒とを含み、その金属ナノ粒子は、光の照射によって前記溶媒中に分散し、光を遮蔽することによって前記溶媒中で沈殿する。この光応答性溶液の調製方法は、上記したように、生じた水素ラジカルを還元種として金属塩を還元し、平均粒径２ｎｍ以上１００ｎｍ以下の範囲内の金属ナノ粒子を前記溶液中で合成し、合成された金属ナノ粒子を溶液中にそのまま含む状態で光応答性溶液とすることができる。
(Photoresponsive solution)
As described above, the photoresponsive solution includes metal nanoparticles with an average particle diameter of 2 nm to 100 nm reduced by hydrogen radicals and a solvent, and the metal nanoparticles are dispersed in the solvent by light irradiation. Precipitate in the solvent by shielding the light. As described above, the photoresponsive solution is prepared by reducing the metal salt using the generated hydrogen radical as a reducing species, and synthesizing metal nanoparticles having an average particle size in the range of 2 nm to 100 nm in the solution. A photoresponsive solution can be obtained in a state in which the synthesized metal nanoparticles are directly contained in the solution.
この光応答性溶液は、光スイッチング機能を示す点に特徴があり。光スイッチング機能は、光の照射によって溶媒中に金属ナノ粒子が分散し、光を遮蔽することによって溶媒中で金属ナノ粒子が沈殿するという特異な性質を奏する。そして、さらに光を照射すると再び溶媒中に金属ナノ粒子が分散する。 This photoresponsive solution is characterized in that it exhibits an optical switching function. The light switching function has a unique property that metal nanoparticles are dispersed in a solvent by light irradiation, and metal nanoparticles are precipitated in the solvent by shielding light. When further irradiated with light, the metal nanoparticles are dispersed again in the solvent.
（金属ナノ粒子の製造）
上記した知見から、金属ナノ粒子の製造方法を提案できる。すなわち、金属塩と水とを含む溶液に超音波を照射して水素ラジカルを生じさせ、生じた水素ラジカルを還元種として金属塩を還元し、平均粒径２ｎｍ以上１００ｎｍ以下の範囲内の金属ナノ粒子を前記溶液中で合成し、前記金属ナノ粒子を含む溶液を遮光して前記金属ナノ粒子を沈殿させて得ることによって、金属ナノ粒子を製造することができる。この方法では、金属ナノ粒子を含む溶液を遮光するだけで、容器の底に沈殿させることができるので、沈殿した状態で溶媒である水を捨てれば、平均粒径２ｎｍ以上１００ｎｍ以下の範囲内の極めて微細な金属ナノ粒子を容易に回収することができる。この方法は、金属ナノ粒子の製造方法であるが、金属ナノ粒子の沈殿方法と言い換えることもできる。
(Manufacture of metal nanoparticles)
From the above knowledge, a method for producing metal nanoparticles can be proposed. That is, a hydrogen radical is generated by irradiating a solution containing a metal salt and water with ultrasonic waves, the metal salt is reduced using the generated hydrogen radical as a reducing species, and a metal nanoparticle having an average particle diameter of 2 nm to 100 nm. Metal nanoparticles can be produced by synthesizing particles in the solution and obtaining the metal nanoparticles by precipitation by shielding the solution containing the metal nanoparticles from light. In this method, since the solution containing the metal nanoparticles can be precipitated at the bottom of the container only by shading, if the solvent water is discarded in the precipitated state, the average particle diameter is in the range of 2 nm to 100 nm. Extremely fine metal nanoparticles can be easily recovered. This method is a method for producing metal nanoparticles, but can also be referred to as a method for precipitation of metal nanoparticles.
以下、実施例により本発明をさらに詳しく説明する。 Hereinafter, the present invention will be described in more detail with reference to examples.
［平均粒径と光分散性についての実験例１］
先ず、Ａｕナノ粒子の平均粒径と光応答性の関係について検討した。塩化金酸四水和物（ＨＡｕＣｌ４・４Ｈ２Ｏ）を金属塩として用い、超純水を溶媒として用いた。０．１ｍＭに調整したＨＡｕＣｌ4水溶液（５０ｍＬ）をアルゴンバブリングした後、その水溶液の温度を５℃、１０℃、２０℃、４０℃、５０℃、６０℃の各温度にして、それぞれの水溶液に超音波（９５０ｋＨｚ、３００Ｗ）を８分間照射し、水素ラジカルを発生させるとともに、その水素ラジカルで還元反応を進行させ、金ナノ粒子を水中で合成した。得られたＡｕナノ粒子を含む水溶液を採取し、顕微鏡で観察した。その結果を図１に示す。図１中、（Ａ）は５℃、（Ｂ）は１０℃、（Ｃ）は２０℃、（Ｄ）は４０℃、（Ｅ）は５０℃、（Ｆ）は６０℃の結果である。
[Experimental Example 1 on Average Particle Size and Light Dispersibility]
First, the relationship between the average particle diameter of Au nanoparticles and the photoresponsiveness was examined. Chloroauric acid tetrahydrate (HAuCl 4 .4H 2 O) was used as a metal salt, and ultrapure water was used as a solvent. After HAbCl 4 aqueous solution (50 mL) adjusted to 0.1 mM was bubbled with argon, the temperature of the aqueous solution was adjusted to 5 ° C., 10 ° C., 20 ° C., 40 ° C., 50 ° C., 60 ° C. Ultrasonic waves (950 kHz, 300 W) were irradiated for 8 minutes to generate hydrogen radicals, and the reduction reaction proceeded with the hydrogen radicals, thereby synthesizing gold nanoparticles in water. The obtained aqueous solution containing Au nanoparticles was collected and observed with a microscope. The result is shown in FIG. In FIG. 1, (A) is 5 ° C., (B) is 10 ° C., (C) is 20 ° C., (D) is 40 ° C., (E) is 50 ° C., and (F) is the result of 60 ° C.
図１（Ａ）〜（Ｄ）は、Ａｕナノ粒子の平均粒径がいずれも２ｎｍ以上１００ｎｍ以下の範囲内であり、光存在下の水溶液中での良好な分散を確認でき、遮光時の良好な沈殿を確認できた。一方、図１（Ｅ）と（Ｆ）は、Ａｕナノ粒子の平均粒径が凝集したり連結したりして１００ｎｍを超えており、光存在下であっても水溶液中で沈殿気味になっていた。なお、平均粒径は、図１に示すように観察された顕微鏡画像から５００個の金属ナノ粒子を無作為に測定し、その平均値で表したものである。 FIGS. 1A to 1D show that the average particle diameter of Au nanoparticles is in the range of 2 nm to 100 nm, and good dispersion in an aqueous solution in the presence of light can be confirmed. Was confirmed. On the other hand, FIGS. 1E and 1F show that the average particle diameter of Au nanoparticles exceeds 100 nm due to agglomeration and connection, and they appear to precipitate in an aqueous solution even in the presence of light. It was. In addition, an average particle diameter measures 500 metal nanoparticles randomly from the microscope image observed as shown in FIG. 1, and represents it with the average value.
［実施例１］
塩化金酸四水和物（ＨＡｕＣｌ４・４Ｈ２Ｏ）を金属塩として用い、超純水を溶媒として用いた。０．１ｍＭに調整したＨＡｕＣｌ4水溶液（５０ｍＬ、２０℃）をアルゴンバブリングした後、超音波（９５０ｋＨｚ、３００Ｗ）を８分間照射し、水素ラジカルを発生させるとともに、その水素ラジカルで還元反応を進行させ、金ナノ粒子を水中で合成し、実施例１に係る金ナノ粒子を含む光応答性溶液を得た。得られた光応答性溶液は、Ａｕナノ粒子の表面プラズモン共鳴（ＳＰＲ）に起因する赤色からピンク色であった。
[Example 1]
Chloroauric acid tetrahydrate (HAuCl 4 .4H 2 O) was used as a metal salt, and ultrapure water was used as a solvent. HAbCl 4 aqueous solution (50 mL, 20 ° C.) adjusted to 0.1 mM is subjected to argon bubbling and then irradiated with ultrasonic waves (950 kHz, 300 W) for 8 minutes to generate hydrogen radicals, and the reduction reaction proceeds with the hydrogen radicals. The gold nanoparticles were synthesized in water to obtain a photoresponsive solution containing the gold nanoparticles according to Example 1. The resulting photoresponsive solution was red to pink due to surface plasmon resonance (SPR) of Au nanoparticles.
光応答性溶液を複数準備し、波長４００ｎｍ〜７００ｎｍの光を発する蛍光灯を照射し、１日ごとの光応答性溶液を観察した。その結果を、図２（Ａ）に示す。また、光応答性溶液に光が当たらないように遮光し、１日ごとの光応答性溶液を観察した。その結果も図２（Ｂ）に示す。この結果より、明所に置いたときの光応答性溶液は、図２（Ａ）に示すように１０日経過しても沈殿が生じなかったが、暗所に置いたときの光応答性溶液は、図２（Ｂ）に示すように徐々に透明度が増して沈殿しているのが確認できた。 A plurality of photoresponsive solutions were prepared, irradiated with a fluorescent lamp emitting light having a wavelength of 400 nm to 700 nm, and the photoresponsive solutions were observed every day. The result is shown in FIG. Further, the photoresponsive solution was shielded from light so as not to be exposed to light, and the photoresponsive solution was observed every day. The result is also shown in FIG. From this result, the photoresponsive solution when placed in a light place did not precipitate even after 10 days as shown in FIG. 2 (A), but the photoresponsive solution when placed in a dark place. As shown in FIG. 2B, it was confirmed that the transparency gradually increased and precipitated.
図３は、図２に示した０日間〜１０日間の各試料のＵＶ−ｖｉｓスペクトル結果であり、（Ａ）は明所に置いた試料のＵＶ−ｖｉｓスペクトルであり、（Ｂ）は暗所に置いた試料のＵＶ−ｖｉｓスペクトルである。図３（Ａ）に示すように、明所に置いた試料のＵＶ−ｖｉｓスペクトルは、波長５４０ｎｍに吸収ピークを持った全て同様のスペクトルであり、分散が維持していることが確認できた。一方、図３（Ｂ）に示すように、暗所に置いた試料のＵＶ−ｖｉｓスペクトルは、波長５４０ｎｍの吸収ピークが日数の経過とともに低下したことから、徐々に沈殿していくのが確認された。図４は、図３（Ａ）（Ｂ）に示すＵＶ−ｖｉｓスペクトルの吸収ピーク（波長５４０ｎｍ）の経時変化を示すグラフである。図４に示すように、明所に置いた試料の１０日後の吸収ピークは、０日目の吸収ピークと同じで変化しなかったが、暗所に置いた試料の１０日後の吸収ピークは、０日目の吸収ピークの５０％になっていた。 FIG. 3 is a UV-vis spectrum result of each sample from 0 to 10 days shown in FIG. 2, (A) is a UV-vis spectrum of a sample placed in a light place, and (B) is a dark place. Is a UV-vis spectrum of a sample placed in As shown in FIG. 3 (A), the UV-vis spectrum of the sample placed in a bright place is all the same spectrum having an absorption peak at a wavelength of 540 nm, and it was confirmed that dispersion was maintained. On the other hand, as shown in FIG. 3B, the UV-vis spectrum of the sample placed in the dark was confirmed to gradually precipitate because the absorption peak at a wavelength of 540 nm decreased with the passage of days. It was. FIG. 4 is a graph showing the change with time of the absorption peak (wavelength 540 nm) of the UV-vis spectrum shown in FIGS. 3 (A) and 3 (B). As shown in FIG. 4, the absorption peak after 10 days of the sample placed in the light place was the same as the absorption peak at day 0, but the absorption peak after 10 days of the sample placed in the dark place was It was 50% of the absorption peak on the 0th day.
図５は、暗所に置いたときのゼータ電位の測定結果である。暗所に置いたときのゼータ電位は、−３８ｍＶから−１９ｍＶまで低下した（図５）が、明所に置いたときのゼータ電位は一定であった（図示しない）。この結果は、超音波還元法により調製された金ナノ粒子の表面電位が暗所で低下し、表面電荷が減っていることを意味している。表面電荷の低下は、ナノ粒子の静電反発力が低下して分散性が低下し、沈殿が進んでいるものと考えられる。暗所で表面電荷の低下がなぜ起こるかについては、明所下では、Ａｕナノ粒子の表面プラズモン共鳴（ＳＰＲ）により光を吸収して、Ａｕナノ粒子の表面電荷が誘発されるが、暗所下では、吸収する光が存在しないため、Ａｕナノ粒子の表面電荷が誘発されないためであるということが考察できる。なお、ゼータ電位の測定は、ゼータ電位・粒径測定システム（大塚電子株式会社製、製品名：ELSZ-1000ZS）を用い、電気泳動光散乱法により測定した。 FIG. 5 shows the measurement results of the zeta potential when placed in a dark place. The zeta potential when placed in the dark decreased from −38 mV to −19 mV (FIG. 5), but the zeta potential when placed in the light was constant (not shown). This result means that the surface potential of the gold nanoparticles prepared by the ultrasonic reduction method is lowered in the dark and the surface charge is reduced. The decrease in the surface charge is considered to be due to a decrease in electrostatic repulsion force of the nanoparticles, a decrease in dispersibility, and precipitation. The reason why the surface charge decreases in the dark is as follows. Under the light, the surface plasmon resonance (SPR) of the Au nanoparticles absorbs light and induces the surface charge of the Au nanoparticles. Below, it can be considered that the surface charge of Au nanoparticles is not induced because there is no light to absorb. The zeta potential was measured by electrophoretic light scattering using a zeta potential / particle size measurement system (manufactured by Otsuka Electronics Co., Ltd., product name: ELSZ-1000ZS).
［比較例１］
塩化金酸四水和物（ＨＡｕＣｌ４・４Ｈ２Ｏ）を金属塩として用い、クエン酸を含む超純水を溶媒として用いた。１重量％のＨＡｕＣｌ4水溶液（０．５ｍＬ）と、１重量％のクエン酸ナトリウム4水溶液（２．５ｍＬ）と、超純水４７ｍＬとを８０℃で撹拌し、アルゴンバブリングした後、クエン酸還元法によって金ナノ粒子を合成し、比較例１に係る金ナノ粒子を含む溶液を得た。得られた溶液は、Ａｕナノ粒子の表面プラズモン共鳴（ＳＰＲ）に起因する赤色からピンク色であった。
[Comparative Example 1]
Chloroauric acid tetrahydrate (HAuCl 4 .4H 2 O) was used as a metal salt, and ultrapure water containing citric acid was used as a solvent. 1 wt% HAuCl 4 aqueous solution (0.5 mL), 1 wt% sodium citrate 4 aqueous solution (2.5 mL) and ultrapure water 47 mL were stirred at 80 ° C., and after argon bubbling, citrate reduction Gold nanoparticles were synthesized by the method to obtain a solution containing gold nanoparticles according to Comparative Example 1. The resulting solution was red to pink due to surface plasmon resonance (SPR) of Au nanoparticles.
溶液を複数準備し、波長４００ｎｍ〜７００ｎｍの光を発する蛍光灯を照射し、１日ごとの光応答性溶液を観察した。その結果を、図６（Ａ）に示す。また、その溶液に光が当たらないように遮光し、１日ごとの溶液を観察した。その結果も図６（Ｂ）に示す。この結果より、明所に置いたときも暗所に置いたときも、いずれも沈殿が生じなかった。 A plurality of solutions were prepared and irradiated with a fluorescent lamp emitting light having a wavelength of 400 nm to 700 nm, and the photoresponsive solution was observed every day. The result is shown in FIG. Further, the solution was shielded from light so as not to be exposed to light, and the solution was observed every day. The result is also shown in FIG. From this result, no precipitation occurred in either the light place or the dark place.
図７は、図６に示した０日間〜７日間の各試料のＵＶ−ｖｉｓスペクトル結果であり、（Ａ）は明所に置いた試料のＵＶ−ｖｉｓスペクトルであり、（Ｂ）は暗所に置いた試料のＵＶ−ｖｉｓスペクトルである。図７（Ａ）に示すように、明所に置いた試料のＵＶ−ｖｉｓスペクトルは、波長５４０ｎｍに吸収ピークを持った全て同様のスペクトルであり、分散が維持していることが確認できた。また、図７（Ｂ）に示すように、暗所に置いた試料のＵＶ−ｖｉｓスペクトルも波長５４０ｎｍに吸収ピークを持った全て同様のスペクトルであり、分散が維持していることが確認できた。図８は、図７（Ａ）（Ｂ）に示すＵＶ−ｖｉｓスペクトルの吸収ピーク（波長５４０ｎｍ）の経時変化を示すグラフである。図８に示すように、明所に置いた試料及び暗所に置いた試料のいずれも、７日後の吸収ピークは０日目の吸収ピークと同じで変化しなかった。 FIG. 7 is a UV-vis spectrum result of each sample from 0 to 7 days shown in FIG. 6, (A) is a UV-vis spectrum of a sample placed in a light place, and (B) is a dark place. Is a UV-vis spectrum of a sample placed in As shown in FIG. 7 (A), the UV-vis spectrum of the sample placed in a bright place is all the same spectrum having an absorption peak at a wavelength of 540 nm, and it was confirmed that dispersion was maintained. Further, as shown in FIG. 7B, the UV-vis spectrum of the sample placed in the dark place is also the same spectrum having an absorption peak at a wavelength of 540 nm, and it was confirmed that dispersion was maintained. . FIG. 8 is a graph showing the change with time of the absorption peak (wavelength 540 nm) of the UV-vis spectrum shown in FIGS. 7 (A) and 7 (B). As shown in FIG. 8, the absorption peak after 7 days was the same as the absorption peak at day 0 in both the sample placed in the light place and the sample placed in the dark place, and did not change.
図９は、暗所に置いたときのゼータ電位の測定結果である。暗所に置いたときのゼータ電位は、−５５ｍＶ付近で一定していた。この結果は、クエン酸還元法により調製された金ナノ粒子の表面電位が暗所でも変化せず、表面電荷に変動がないことを意味している。表面電荷が変化しないため、ナノ粒子の静電反発力が変化せず分散性が維持され、沈殿しないものと考えられる。クエン酸還元法により調製された金ナノ粒子の表面電荷が暗所で低下しないのは、Ａｕナノ粒子の表面にクエン酸が吸着しているため、常に（光の有無にかかわらず）、Ａｕナノ粒子の表面は負の電荷を帯びているためであるということが考察できる。 FIG. 9 shows the measurement results of the zeta potential when placed in a dark place. The zeta potential when placed in the dark was constant around -55 mV. This result means that the surface potential of the gold nanoparticles prepared by the citrate reduction method does not change even in the dark, and the surface charge does not vary. Since the surface charge does not change, the electrostatic repulsive force of the nanoparticles does not change, the dispersibility is maintained, and it is considered that precipitation does not occur. The reason why the surface charge of the gold nanoparticles prepared by the citrate reduction method does not decrease in the dark is that, since citric acid is adsorbed on the surface of the Au nanoparticles, the Au nanoparticles are always (regardless of the presence or absence of light). It can be considered that the surface of the particles is negatively charged.
［実施例２］
実施例１で沈殿した光応答性溶液を再び明所に置いた。図１０は、０時間〜４８時間まで６時間ごとに観察したときの写真である。時間の経過とともに色が濃くなって、沈殿していたＡｕナノ粒子が、徐々に分散する様子が観察できた。
[Example 2]
The photoresponsive solution precipitated in Example 1 was again placed in the light. FIG. 10 is a photograph when observed every 6 hours from 0 to 48 hours. The color became darker as time passed, and it was observed that the precipitated Au nanoparticles were gradually dispersed.
図１１は、図１０に示した０時間〜４８時間の各試料のＵＶ−ｖｉｓスペクトル結果であり、図１１（Ａ）は再び明所に置いた試料のＵＶ−ｖｉｓスペクトルであり、波長５４０ｎｍの吸収ピークが時間の経過とともに上昇したことから、徐々に分散していくのが確認された。また、図１１（Ｂ）は、図１１（Ａ）に示すＵＶ−ｖｉｓスペクトルの吸収ピーク（波長５４０ｎｍ）の経時変化を示すグラフである。図１１（Ｂ）に示すように、４８時間後の吸収ピークは、０時間の吸収ピークの約２倍になっていた。 FIG. 11 is a UV-vis spectrum result of each sample from 0 to 48 hours shown in FIG. 10, and FIG. 11 (A) is a UV-vis spectrum of a sample placed in a bright place again, and has a wavelength of 540 nm. Since the absorption peak increased with time, it was confirmed that the absorption peak was gradually dispersed. FIG. 11B is a graph showing a change with time of the absorption peak (wavelength 540 nm) of the UV-vis spectrum shown in FIG. As shown in FIG. 11 (B), the absorption peak after 48 hours was about twice the absorption peak at 0 hour.
［各種の測定手段］
超音波照射は、超音波照射器（三井電気精機株式会社製、製品名：ＳＤ−３２ＣＰ−９５０Ｋ）を用いて行った。
[Various measurement methods]
Ultrasonic irradiation was performed using an ultrasonic irradiator (Mitsui Electric Seiki Co., Ltd., product name: SD-32CP-950K).
光の照射は、紫外光、蛍光灯、赤外光を照射し、それぞれの波長は、４００ｎｍ以下、４００ｎｍ〜７００ｎｍ、７００ｎｍ以上であった。また、太陽光も照射した場合、その波長は、３００ｎｍ〜２５００ｎｍであった。遮光は、光が入らない暗所に入れて行った。 The light was irradiated with ultraviolet light, fluorescent light, or infrared light, and the respective wavelengths were 400 nm or less, 400 nm to 700 nm, or 700 nm or more. Moreover, when sunlight was also irradiated, the wavelength was 300 nm-2500 nm. Shading was performed in a dark place where no light could enter.
紫外・可視吸光分光（ＵＶ−ｖｉｓ）測定は、紫外・可視吸光分光器（日立ハイテクノロジーズ株式会社製、製品名：Ｕ−１９００）を用いた。また、透過型電子顕微鏡（ＴＥＭ）観察は、日本電子株式会社製のＪＥＭ−２０１０（製品名）を用いて行った。 For ultraviolet / visible absorption spectroscopy (UV-vis) measurement, an ultraviolet / visible absorption spectrometer (manufactured by Hitachi High-Technologies Corporation, product name: U-1900) was used. Further, transmission electron microscope (TEM) observation was performed using JEM-2010 (product name) manufactured by JEOL Ltd.
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