JP7197883B2 - Method for liquefying metal nanoparticles - Google Patents

Description

The present invention relates to a method of liquefying metal nanoparticles.

In recent years, electronic devices such as mobile devices have made remarkable progress. Electronic devices are required to be smaller, thinner, lighter, more flexible, and moreover, to improve productivity. Demands on electronic parts such as semiconductor devices have become stricter, and various devices and improvements are further required for the wiring of those devices.
Under such circumstances, if there is a material that allows wiring to be formed at a temperature close to room temperature, not only heat-resistant materials but also various organic materials that are not heat-resistant can be used as the wiring substrate. Due to the development of inkjet and dispenser printing technologies, nano-sized metal fine particles are currently being studied as one of such materials (see, for example, Non-Patent Document 1). However, conventional fine metal particles are metal-formed by utilizing a sintering reaction, so they must be treated at a temperature of at least about 150° C., and their range of application is limited. Under such circumstances, there is a demand for a material that allows wiring to be formed at even lower temperatures.
Further, Patent Document 1 discloses that silver oxalate and oleylamine are reacted to form a complex compound, which is thermally decomposed to obtain silver ultrafine particles. However, when forming a conductive film or the like using this silver ultrafine particle, a sintering reaction is used, so the treatment temperature is a high temperature of 500 ° C or less, and the range of use is limited to a narrow range. A possible method is sought.
Furthermore, in Patent Document 2, a metal nanoparticle paste containing coated metal nanoparticles and a dispersion solvent is reacted with a polar solvent or a polar solvent solution containing a dissolution aid to sinter the metal nanoparticles, A method of forming wiring on a substrate is disclosed. However, since this method also uses metal sintering, there is a problem that the electrical resistivity of the formed wiring is high and there is a large variation. There are also problems.

JP 2008-214695 A JP 2008-072052 A

Mitsuru Kawazome et al., "Nanoparticle Micro Wiring Technology for Printed Electronics", Kotsu, No.50 (2006/2007), pp.27-31

The present invention has been made in view of the above, and provides a method for easily liquefying metal nanoparticles without the need to sinter metal nanoparticles at high temperatures, and a method for easily forming metals on various substrates. The purpose is to provide a method to

As a result of intensive research to achieve the above object, the present inventors have found that by utilizing the dynamic chemical equilibrium of surface-protected metal nanoparticles, which are metal nanoparticles whose surfaces are protected by protective molecules, metal nanoparticles We have found a way to easily liquefy In other words, in a system containing metal nanoparticles, protective molecules, and surface-protected metal nanoparticles, there is a dynamic chemical equilibrium in which the protective molecules adsorb and desorb to the metal nanoparticles depending on the environment, and during storage of the surface-protected metal nanoparticles, The inventors have found that the above object can be achieved by controlling the equilibrium point in the direction of adsorption of the protective molecule and moving the equilibrium point in the direction of desorption of the protective molecule during metal formation, and have completed the present invention.

〔式中、（Ｓｉｔｅ－ＰＭ）は保護分子が吸着している金属原子の吸着サイトを示し、（Ｓｉｔｅ）は保護分子が吸着していない金属原子の吸着サイトを示し、（ＰＭ）は遊離の保護分子を示す。〕
前記化学平衡の平衡点を保護分子の脱着の方向に移動させる工程を含み、
（３）前記化学平衡の平衡点を保護分子の脱着の方向に移動させる工程が、下記（ａ）及び／又は（ｂ）の工程
（ａ）前記分散液に含まれる分散媒を構成する種類及び／又はその構成割合を変える、及び／又は、前記分散液の温度を変えることにより、下記式（ＩＩ）：
Ｋｄ＝｛［Ｓｉｔｅ］ｅｑ［ＰＭ］ｅｑ｝／［Ｓｉｔｅ－ＰＭ］ｅｑ （ＩＩ）
〔式中、［Ｓｉｔｅ］ｅｑは平衡状態における保護分子が吸着していない金属原子の吸着サイト濃度（mol/L）を示し、［ＰＭ］ｅｑは平衡状態における遊離の保護分子の濃度（mol/L）を示し、［Ｓｉｔｅ－ＰＭ］ｅｑは平衡状態における保護分子が吸着している金属原子の吸着サイト濃度（mol/L）を示す。〕
で表される保護分子の脱着平衡定数（Ｋｄ）を増大させる工程、
（ｂ）前記分散液に溶媒及び／又は表面保護金属ナノ粒子を添加し、前記式（ＩＩ）における３つの濃度のうちの少なくとも１つを変化させて、前記式（Ｉ）の化学平衡が成り立たない非平衡状態とする工程、
を含む、金属ナノ粒子を液状化する方法。
２．平均粒径が１～４．６ｎｍである金属ナノ粒子を液状化する方法であって、
（１）前記金属ナノ粒子は、遷移金属ナノ粒子の表面に保護分子が被覆した表面保護金属ナノ粒子の状態で分散液中に分散されており、
（２）前記分散液を基材に塗布し、前記分散液が塗布された基材を溶媒に接触させる工程を含み、
（３）前記分散液が塗布された基材を溶媒に接触させた際に、前記表面保護金属ナノ粒子、金属ナノ粒子及び保護分子の間に、下記式（Ｉ）で表される化学平衡が成り立ち、

〔式中、（Ｓｉｔｅ－ＰＭ）は保護分子が吸着している金属原子の吸着サイトを示し、（Ｓｉｔｅ）は保護分子が吸着していない金属原子の吸着サイトを示し、（ＰＭ）は遊離の保護分子を示す。〕
前記化学平衡の平衡点を保護分子の脱着の方向に移動させる工程を含み、
（４）前記化学平衡の平衡点を保護分子の脱着の方向に移動させる工程が、下記（ａ’）及び／又は（ｂ’）の工程
（ａ’）前記溶媒の種類及び／又はその構成割合を変える、及び／又は、前記溶媒及び／又は基材の温度を変えることにより、下記式（ＩＩ）：
Ｋｄ＝｛［Ｓｉｔｅ］ｅｑ［ＰＭ］ｅｑ｝／［Ｓｉｔｅ－ＰＭ］ｅｑ （ＩＩ）
〔式中、［Ｓｉｔｅ］ｅｑは平衡状態における保護分子が吸着していない金属原子の吸着サイト濃度（mol/L）を示し、［ＰＭ］ｅｑは平衡状態における遊離の保護分子の濃度（mol/L）を示し、［Ｓｉｔｅ－ＰＭ］ｅｑは平衡状態における保護分子が吸着している金属原子の吸着サイト濃度（mol/L）を示す。〕
で表される保護分子の脱着平衡定数（Ｋｄ）を増大させる工程、
（ｂ’）前記溶媒に、溶媒及び／又は表面保護金属ナノ粒子を添加して、前記式（ＩＩ）における３つの濃度のうちの少なくとも１つを変化させて、前記式（Ｉ）の化学平衡が成り立たない非平衡状態とする工程、
を含む、金属ナノ粒子を液状化する方法。
３．前記遷移金属ナノ粒子を構成する遷移金属は、周期表第１０族～第１１族で且つ第４周期～第６周期に属する元素の少なくとも一種である、上記項１又は２に記載の方法。
４．前記遷移金属ナノ粒子を構成する遷移金属は、金、銀、銅、白金及びパラジウムからなる群から選択される少なくとも一種である、上記項１～３のいずれか一項に記載の方法。
５．前記保護分子は、アミノ基及びカルボキシル基の少なくとも一種を含有する、上記項１～４のいずれか一項に記載の方法。
６．基材に金属を形成する方法であって、
（１）平均粒径が１～４．６ｎｍである金属ナノ粒子を含有する分散液に、基材を接触させる工程を含み、
（２）前記金属ナノ粒子は、遷移金属ナノ粒子の表面に保護分子が被覆した表面保護金属ナノ粒子の状態で前記分散液中に分散されており、
（３）前記表面保護金属ナノ粒子、金属ナノ粒子及び保護分子の間に、下記式（Ｉ）で表される化学平衡が成り立ち、

〔式中、（Ｓｉｔｅ－ＰＭ）は保護分子が吸着している金属原子の吸着サイトを示し、（Ｓｉｔｅ）は保護分子が吸着していない金属原子の吸着サイトを示し、（ＰＭ）は遊離の保護分子を示す。〕
前記化学平衡の平衡点を保護分子の脱着の方向に移動させる工程を含み、
（４）前記化学平衡の平衡点を保護分子の脱着の方向に移動させる工程が、下記（ａ）及び／又は（ｂ）の工程
（ａ）前記分散液に含まれる分散媒を構成する種類及び／又はその構成割合を変える、及び／又は、前記分散液の温度を変えることにより、下記式（ＩＩ）：
Ｋｄ＝｛［Ｓｉｔｅ］ｅｑ［ＰＭ］ｅｑ｝／［Ｓｉｔｅ－ＰＭ］ｅｑ （ＩＩ）
〔式中、［Ｓｉｔｅ］ｅｑは平衡状態における保護分子が吸着していない金属原子の吸着サイト濃度（mol/L）を示し、［ＰＭ］ｅｑは平衡状態における遊離の保護分子の濃度（mol/L）を示し、［Ｓｉｔｅ－ＰＭ］ｅｑは平衡状態における保護分子が吸着している金属原子の吸着サイト濃度（mol/L）を示す。〕
で表される保護分子の脱着平衡定数（Ｋｄ）を増大させる工程、
（ｂ）前記分散液に溶媒及び／又は表面保護金属ナノ粒子を添加し、前記式（ＩＩ）における３つの濃度のうちの少なくとも１つを変化させて、前記式（Ｉ）の化学平衡が成り立たない非平衡状態とする工程、
を含む、基材に金属を形成する方法。
７．基材に金属を形成する方法であって、
（１）平均粒径が１～４．６ｎｍである金属ナノ粒子を含有する分散液を基材に塗布し、前記分散液が塗布された基材を溶媒に接触させる工程を含み、
（２）前記金属ナノ粒子は、遷移金属ナノ粒子の表面に保護分子が被覆した表面保護金属ナノ粒子の状態で前記分散液中に分散されており、
（３）前記分散液が塗布された基材を溶媒に接触させた際に、前記表面保護金属ナノ粒子、金属ナノ粒子及び保護分子の間に、下記式（Ｉ）で表される化学平衡が成り立ち、

〔式中、（Ｓｉｔｅ－ＰＭ）は保護分子が吸着している金属原子の吸着サイトを示し、（Ｓｉｔｅ）は保護分子が吸着していない金属原子の吸着サイトを示し、（ＰＭ）は遊離の保護分子を示す。〕
前記化学平衡の平衡点を保護分子の脱着の方向に移動させる工程を含み、
（４）前記化学平衡の平衡点を保護分子の脱着の方向に移動させる工程が、下記（ａ’）及び／又は（ｂ’）の工程
（ａ’）前記溶媒の種類及び／又はその構成割合を変える、及び／又は、前記溶媒及び／又は基材の温度を変えることにより、下記式（ＩＩ）：
Ｋｄ＝｛［Ｓｉｔｅ］ｅｑ［ＰＭ］ｅｑ｝／［Ｓｉｔｅ－ＰＭ］ｅｑ （ＩＩ）
〔式中、［Ｓｉｔｅ］ｅｑは平衡状態における保護分子が吸着していない金属原子の吸着サイト濃度（mol/L）を示し、［ＰＭ］ｅｑは平衡状態における遊離の保護分子の濃度（mol/L）を示し、［Ｓｉｔｅ－ＰＭ］ｅｑは平衡状態における保護分子が吸着している金属原子の吸着サイト濃度（mol/L）を示す。〕
で表される保護分子の脱着平衡定数（Ｋｄ）を増大させる工程、
（ｂ’）前記溶媒に、溶媒及び／又は表面保護金属ナノ粒子を添加して、前記式（ＩＩ）における３つの濃度のうちの少なくとも１つを変化させて、前記式（Ｉ）の化学平衡が成り立たない非平衡状態とする工程、
を含む、基材に金属を形成する方法。
８．金、銀、銅、白金及びパラジウムからなる群から選択される少なくとも一種から構成され、平均粒径が１～４．６ｎｍである金属ナノ粒子の表面に、
アミノ基及びカルボキシル基の少なくとも一種を含有する保護分子が被覆した表面保護金属ナノ粒子が、
無極性溶媒を含む分散媒に分散されている分散液。 That is, the present invention relates to a method for liquefying metal nanoparticles, a method for forming a metal on a substrate, and a dispersion, as described below.
1. A method for liquefying metal nanoparticles having an average particle size of 1 to 4.6 nm,
(1) the metal nanoparticles are dispersed in a dispersion liquid in the form of surface-protected metal nanoparticles in which the surfaces of the transition metal nanoparticles are coated with protective molecules;
(2) A chemical equilibrium represented by the following formula (I) is established between the surface-protecting metal nanoparticles, the metal nanoparticles, and the protective molecule,

[In the formula, (Site-PM) represents the adsorption site of the metal atom to which the protective molecule is adsorbed, (Site) represents the adsorption site of the metal atom to which the protective molecule is not adsorbed, and (PM) represents the free Indicates a protected molecule. ]
shifting the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule;
(3) The step of moving the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule is the following (a) and / or (b) step (a) the type and the type constituting the dispersion medium contained in the dispersion liquid / Or by changing the composition ratio and / or changing the temperature of the dispersion, the following formula (II):
Kd = {[Site] eq [PM] eq}/[Site-PM] eq (II)
[Wherein, [Site] eq represents the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is not adsorbed in the equilibrium state, and [PM] eq represents the concentration of the free protective molecule in the equilibrium state (mol/ L), and [Site-PM] eq indicates the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is adsorbed in the equilibrium state. ]
increasing the desorption equilibrium constant (Kd) of the protected molecule represented by
(b) adding a solvent and/or surface-protected metal nanoparticles to the dispersion and varying at least one of the three concentrations in the formula (II) to establish the chemical equilibrium of the formula (I); non-equilibrium state,
A method of liquefying metal nanoparticles, comprising:
2. A method for liquefying metal nanoparticles having an average particle size of 1 to 4.6 nm,
(1) the metal nanoparticles are dispersed in a dispersion liquid in the form of surface-protected metal nanoparticles in which the surfaces of the transition metal nanoparticles are coated with protective molecules;
(2) applying the dispersion to a substrate, and contacting the substrate coated with the dispersion with a solvent;
(3) When the substrate coated with the dispersion is brought into contact with a solvent, a chemical equilibrium represented by the following formula (I) occurs between the surface-protecting metal nanoparticles, the metal nanoparticles, and the protective molecule. Origin,

[In the formula, (Site-PM) represents the adsorption site of the metal atom to which the protective molecule is adsorbed, (Site) represents the adsorption site of the metal atom to which the protective molecule is not adsorbed, and (PM) represents the free Indicates a protected molecule. ]
shifting the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule;
(4) The step of moving the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule is the following (a') and/or (b') in step (a') the type and/or composition ratio of the solvent and/or by changing the temperature of the solvent and/or substrate, the following formula (II):
Kd = {[Site] eq [PM] eq}/[Site-PM] eq (II)
[Wherein, [Site] eq represents the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is not adsorbed in the equilibrium state, and [PM] eq represents the concentration of the free protective molecule in the equilibrium state (mol/ L), and [Site-PM] eq indicates the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is adsorbed in the equilibrium state. ]
increasing the desorption equilibrium constant (Kd) of the protected molecule represented by
(b′) adding a solvent and/or surface-protected metal nanoparticles to the solvent to change at least one of the three concentrations in the formula (II) to obtain the chemical equilibrium of the formula (I); A step of creating a non-equilibrium state in which
A method of liquefying metal nanoparticles, comprising:
3 . 3. The method according to item 1 or 2 , wherein the transition metal constituting the transition metal nanoparticles is at least one element belonging to Groups 10 to 11 of the periodic table and belonging to Periods 4 to 6.
4 . 4. The method according to any one of items 1 to 3 , wherein the transition metal constituting the transition metal nanoparticles is at least one selected from the group consisting of gold, silver, copper, platinum and palladium.
5 . 5. The method according to any one of items 1 to 4 , wherein the protective molecule contains at least one of an amino group and a carboxyl group.
6 . A method of forming a metal on a substrate, comprising:
(1) A step of contacting a substrate with a dispersion containing metal nanoparticles having an average particle size of 1 to 4.6 nm,
(2) the metal nanoparticles are dispersed in the dispersion in the form of surface-protected metal nanoparticles in which the surfaces of the transition metal nanoparticles are coated with protective molecules;
(3) A chemical equilibrium represented by the following formula (I) is established between the surface-protecting metal nanoparticles, the metal nanoparticles, and the protective molecule,

[In the formula, (Site-PM) represents the adsorption site of the metal atom to which the protective molecule is adsorbed, (Site) represents the adsorption site of the metal atom to which the protective molecule is not adsorbed, and (PM) represents the free Indicates a protected molecule. ]
shifting the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule;
(4) The step of moving the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule is the following (a) and / or (b) step (a) the type and the type constituting the dispersion medium contained in the dispersion liquid / Or by changing the composition ratio and / or changing the temperature of the dispersion, the following formula (II):
Kd = {[Site] eq [PM] eq}/[Site-PM] eq (II)
[Wherein, [Site] eq represents the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is not adsorbed in the equilibrium state, and [PM] eq represents the concentration of the free protective molecule in the equilibrium state (mol/ L), and [Site-PM] eq indicates the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is adsorbed in the equilibrium state. ]
increasing the desorption equilibrium constant (Kd) of the protected molecule represented by
(b) adding a solvent and/or surface-protected metal nanoparticles to the dispersion and varying at least one of the three concentrations in the formula (II) to establish the chemical equilibrium of the formula (I); non-equilibrium state,
A method of forming a metal on a substrate, comprising:
7 . A method of forming a metal on a substrate, comprising:
(1) applying a dispersion containing metal nanoparticles having an average particle size of 1 to 4.6 nm to a substrate, and contacting the substrate coated with the dispersion with a solvent;
(2) the metal nanoparticles are dispersed in the dispersion in the form of surface-protected metal nanoparticles in which the surfaces of the transition metal nanoparticles are coated with protective molecules;
(3) When the substrate coated with the dispersion is brought into contact with a solvent, a chemical equilibrium represented by the following formula (I) occurs between the surface-protecting metal nanoparticles, the metal nanoparticles, and the protective molecule. Origin,

[In the formula, (Site-PM) represents the adsorption site of the metal atom to which the protective molecule is adsorbed, (Site) represents the adsorption site of the metal atom to which the protective molecule is not adsorbed, and (PM) represents the free Indicates a protected molecule. ]
shifting the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule;
(4) The step of moving the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule is the following (a') and/or (b') in step (a') the type and/or composition ratio of the solvent and/or by changing the temperature of the solvent and/or substrate, the following formula (II):
Kd = {[Site] eq [PM] eq}/[Site-PM] eq (II)
[Wherein, [Site] eq represents the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is not adsorbed in the equilibrium state, and [PM] eq represents the concentration of the free protective molecule in the equilibrium state (mol/ L), and [Site-PM] eq indicates the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is adsorbed in the equilibrium state. ]
increasing the desorption equilibrium constant (Kd) of the protected molecule represented by
(b′) adding a solvent and/or surface-protected metal nanoparticles to the solvent to change at least one of the three concentrations in the formula (II) to obtain the chemical equilibrium of the formula (I); A step of creating a non-equilibrium state in which
A method of forming a metal on a substrate, comprising:
8 . On the surface of metal nanoparticles composed of at least one selected from the group consisting of gold, silver, copper, platinum and palladium and having an average particle size of 1 to 4.6 nm,
surface-protected metal nanoparticles coated with protective molecules containing at least one of an amino group and a carboxyl group,
A dispersion liquid dispersed in a dispersion medium containing a non-polar solvent.

In the method for liquefying metal nanoparticles of the present invention, the principle of dynamic chemical equilibrium is applied to a system of metal nanoparticles and protective molecules, which are adsorbed molecules, and various conditions are changed to protect the metal nanoparticles from the surface-protected metal nanoparticles. Molecules can be desorbed to easily liquefy metal nanoparticles. In addition, the method of forming a metal on a substrate according to the present invention is an excellent method with a very simple and easy manufacturing process.
The liquefaction method and metal formation method of the present invention do not use a method of sintering metal nanoparticles, so there is no need to heat the base material to which the metal nanoparticles are applied to a high temperature, and the heat-resistant polymer / It can be applied to various substrates including fiber substrates and the like. In addition, since the metal nanoparticles used in the present invention are extremely small, they have a strong effect of penetrating into the interior of the object that is the substrate, and the liquefied metal can be injected into various substrates. Metal can be formed not only inside but also inside. Furthermore, using the method of the present invention, the metal nanoparticles can be easily liquefied, so that metals can be formed on substrates of various shapes. Therefore, by the liquefaction method and the metal forming method of the present invention, it is possible to form a metal in a wide range of polymer/fiber materials to make them conductive, and to form metals into various shapes on the nanoscale.

1 is a TEM image showing that the gold nanoparticles of Example 1 are liquefied (fluidized). FIG. 4 is a diagram showing the liquefaction of silver nanoparticles in the dispersion liquid of Example 2. FIG. FIG. 10 is a diagram showing an electron micrograph and X-ray diffraction results of the metal thin film of Example 3; FIG. 10 is a diagram showing changes in polyurethane before and after immersion in the dispersion liquid of Example 6; FIG. 10 is a diagram showing changes in rayon before and after immersion in the dispersion liquid of Example 7;

Hereinafter, the method for liquefying metal nanoparticles of the present invention will be described in detail.

〔式中、（Ｓｉｔｅ－ＰＭ）は保護分子が吸着している金属原子の吸着サイトを示し、（Ｓｉｔｅ）は保護分子が吸着していない金属原子の吸着サイトを示し、（ＰＭ）は遊離の保護分子を示す。〕
前記化学平衡の平衡点を保護分子の脱着の方向に移動させる工程を含み、
（３）前記化学平衡の平衡点を保護分子の脱着の方向に移動させる工程が、下記（ａ）及び／又は（ｂ）の工程
（ａ）前記分散液に含まれる分散媒を構成する種類及び／又はその構成割合を変える、及び／又は、前記分散液の温度を変えることにより、下記式（ＩＩ）：
Ｋｄ＝｛［Ｓｉｔｅ］ｅｑ［ＰＭ］ｅｑ｝／［Ｓｉｔｅ－ＰＭ］ｅｑ （ＩＩ）
〔式中、［Ｓｉｔｅ］ｅｑは平衡状態における保護分子が吸着していない金属原子の吸着サイト濃度（mol/L）を示し、［ＰＭ］ｅｑは平衡状態における遊離の保護分子の濃度（mol/L）を示し、［Ｓｉｔｅ－ＰＭ］ｅｑは平衡状態における保護分子が吸着している金属原子の吸着サイト濃度（mol/L）を示す。〕
で表される保護分子の脱着平衡定数（Ｋｄ）を増大させる工程、
（ｂ）前記分散液に溶媒及び／又は表面保護金属ナノ粒子を添加し、前記式（ＩＩ）における３つの濃度のうちの少なくとも１つを変化させて、前記式（Ｉ）の化学平衡が成り立たない非平衡状態とする工程、
を含むことを特徴とするものである。 The method for liquefying metal nanoparticles of the present invention comprises:
(1) the metal nanoparticles are dispersed in the dispersion in the form of surface-protected metal nanoparticles in which the surfaces of the transition metal nanoparticles are coated with protective molecules;
(2) A chemical equilibrium represented by the following formula (I) is established between the surface-protecting metal nanoparticles, the metal nanoparticles, and the protective molecule,

[In the formula, (Site-PM) represents the adsorption site of the metal atom to which the protective molecule is adsorbed, (Site) represents the adsorption site of the metal atom to which the protective molecule is not adsorbed, and (PM) represents the free Indicates a protected molecule. ]
shifting the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule;
(3) The step of moving the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule is the following (a) and / or (b) step (a) the type and the type constituting the dispersion medium contained in the dispersion liquid / Or by changing the composition ratio and / or changing the temperature of the dispersion, the following formula (II):
Kd = {[Site] eq [PM] eq}/[Site-PM] eq (II)
[Wherein, [Site] eq represents the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is not adsorbed in the equilibrium state, and [PM] eq represents the concentration of the free protective molecule in the equilibrium state (mol/ L), and [Site-PM] eq indicates the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is adsorbed in the equilibrium state. ]
increasing the desorption equilibrium constant (Kd) of the protected molecule represented by
(b) adding a solvent and/or surface-protected metal nanoparticles to the dispersion and varying at least one of the three concentrations in the formula (II) to establish the chemical equilibrium of the formula (I); non-equilibrium state,
It is characterized by including

In the method of liquefying the metal nanoparticles (first liquefaction method), the protective molecules can be desorbed from the surface-protected metal nanoparticles in the dispersion liquid to liquefy the metal nanoparticles.

As used herein, the term “metal nanoparticles liquefy” means that the protective molecules adsorbed on the surface-protected metal nanoparticles are desorbed, and when the number of protective molecules adsorbed on the surface of the metal nanoparticles decreases, the metal It means that the metal atoms constituting the nanoparticles change from a fixed “solid” state to a kind of fluid “liquid” state, that is, “flow”. In other words, "liquefaction" means that metal atoms change into a liquid-like state and flow.
As the size of the metal nanoparticles decreases, the pressure inside the metal nanoparticles increases. Atoms are thought to move and flow like liquids.

In addition, when metal nanoparticles and protective molecules are dispersed in a dispersion liquid, the protective molecules are adsorbed on the surface of the metal nanoparticles even if the number of molecules is small, resulting in surface-protected metal nanoparticles. In the surface-protected metal nanoparticles, the maximum number of protective molecules that can be adsorbed on the surface of the metal nanoparticles can vary depending on the type of metal and the type of protective molecules. Then, when the number of protective molecules adsorbed on the metal nanoparticle surface falls below a certain value (this value can also vary depending on the type of metal and the type of protective molecule), the metal atoms composing the metal nanoparticles liquefies.

In the present invention, the metal nanoparticles are composed of transition metals. Also, one metal nanoparticle is a collection of several tens to several hundred metal atoms.
Examples of transition metals include, but are not limited to, elements belonging to Groups 3 to 12 of the periodic table. From the viewpoint of the desorption equilibrium constant, it is preferably at least one element belonging to Groups 10 to 11 of the periodic table and belonging to Periods 4 to 6, and is selected from the group consisting of gold, silver, copper, platinum and palladium. At least one selected is more preferable.
Here, the viewpoint of the desorption equilibrium constant means that the desorption equilibrium constant is made small when the dispersion is stored (before liquefaction), and when the dispersion is liquefied, the desorption equilibrium constant is increased to liquefy. (the viewpoint that the necessary amount of protective molecules can be adsorbed on the metal nanoparticle surfaces and that the protective molecules can be easily desorbed from the metal nanoparticle surfaces by changing the conditions).

From the viewpoint of adsorption/desorption of the protective molecule to/from the metal nanoparticles, the average particle size of the metal nanoparticles is preferably 1 to 30 nm (nanometers), and the melting point of the metal nanoparticles decreases as the size of the metal nanoparticles decreases. From the viewpoint of increasing the size, in order to lower the liquefaction temperature of the metal nanoparticles, it is more preferably 2 to 20 nm, even more preferably 2 to 10 nm, and particularly preferably 2 to 6 nm.
By reducing the average particle size of the metal nanoparticles, it becomes possible to adsorb even protective molecules that cannot be adsorbed by metal flat plates (the particle size can be regarded as infinite). It can be set large, and the protective molecules can be easily desorbed from the surface of the metal nanoparticles by changing the conditions.
The average particle size of metal nanoparticles can be measured by image analysis using, for example, a transmission electron microscope or a scanning electron microscope. Specifically, it can be measured by the method described in the section of Examples.

The protective molecule that coats the surface of the metal nanoparticles is not particularly limited as long as it can coat the surface of the metal nanoparticles, but from the viewpoint of the desorption equilibrium constant, it is a compound containing at least one of an amino group and a carboxyl group. is preferred.
The compound containing an amino group is not particularly limited, but examples thereof include alkylamines having 1 to 30 carbon atoms, alkenylamines having 2 to 30 carbon atoms, alkynylamines having 2 to 30 carbon atoms, arylamines, aralkylamines, and the like. mentioned. From the viewpoint of desorption equilibrium constant, alkylamines having 1 to 30 carbon atoms and alkenylamines having 2 to 30 carbon atoms are preferred; alkylamines having 10 to 30 carbon atoms and alkenylamines having 10 to 30 carbon atoms are more preferred; Alkylamines having 10 to 20 carbon atoms and alkenylamines having 10 to 20 carbon atoms are more preferable; dodecylamine, oleylamine and the like are particularly preferable.

The compound containing a carboxyl group is not particularly limited, but examples include alkylcarboxylic acids having 1 to 30 carbon atoms, alkenylcarboxylic acids having 2 to 30 carbon atoms, alkynylcarboxylic acids having 2 to 30 carbon atoms, arylcarboxylic acids, aralkylcarboxylic acids and the like. From the viewpoint of desorption equilibrium constant, alkylcarboxylic acids having 1 to 30 carbon atoms and alkenylcarboxylic acids having 2 to 30 carbon atoms are preferable; Preferred; alkylcarboxylic acids having 10 to 20 carbon atoms and alkenylcarboxylic acids having 10 to 20 carbon atoms are more preferred; decanoic acid, dodecylcarboxylic acid, oleylcarboxylic acid and the like are particularly preferred.

The metal nanoparticles are dispersed in the dispersion in the form of surface-protected metal nanoparticles in which the surfaces of the transition metal nanoparticles are coated with protective molecules.
The surface-protecting metal nanoparticles are not particularly limited as long as the surfaces of the metal nanoparticles are coated with the protective molecules.
Here, "coating" means that the protective molecule is adsorbed to the metal atoms on the surface of the metal nanoparticles, and if a part or all of the surface of the metal nanoparticles is coated with the protective molecule good.

The dispersion liquid contains a dispersion medium.
The dispersion medium is not particularly limited as long as it can disperse the surface-protected metal nanoparticles, and examples thereof include a nonpolar solvent, a mixed solvent of a nonpolar solvent and a polar solvent, and the like.
In this specification, the term "solvent" is used as a medium, regardless of whether or not it has the property of dissolving the medium.

Examples of nonpolar solvents include, but are not limited to, alkanes such as pentane, hexane, heptane, octane, and nonane; cycloalkanes such as cyclohexane, cyclopentane, cycloheptane, and cyclooctane; methylene chloride, chloroform, carbon tetrachloride, and the like. Ethers such as diethyl ether and diisopropyl ether; Alcohols having 6 or more carbon atoms such as hexanol, heptanol and octanol; Aromatic hydrocarbons such as benzene, toluene and xylene; Cyclic compounds and the like can be mentioned. From the viewpoint of desorption equilibrium constant, alkanes, halogen-substituted alkanes, and aromatic hydrocarbons are preferred, and hexane, methylene chloride, and toluene are more preferred.

The polar solvent is not particularly limited as long as it can be used in combination with the above nonpolar solvent. Examples include alcohols having 1 to 5 carbon atoms such as methanol, ethanol, 1-propanol, 2-propanol, butanol and pentanol. amides such as formamide and acetamide; and ionic liquids such as 1-ethyl-3-methylimidazolium tetrafluoroborate. From the viewpoint of desorption equilibrium constant, alcohols having 1 to 3 carbon atoms are preferred, and methanol and ethanol are more preferred.

As described above, the protective molecule is preferably a compound containing a polar group (at least one of an amino group and a carboxyl group). It is considered that they face outward (dispersion medium side).
Therefore, a nonpolar solvent is preferable as a dispersion medium for stably dispersing the surface-protecting metal nanoparticles in the dispersion during storage.
In addition, from the above structure of the surface-protected metal nanoparticles, the polar solvent has the effect of desorbing the protective molecules from the surface-protected metal nanoparticles. Therefore, it is not suitable to use a polar solvent alone as a dispersion medium, but a mixed solvent of a non-polar solvent and a polar solvent can be used as a dispersion medium, and liquefaction can be adjusted by the mixing ratio. .
When using a mixed solvent of a non-polar solvent and a polar solvent, the mixing ratio is not particularly limited, but from the viewpoint of dispersing and storing the surface-protected metal nanoparticles, it depends on the selection of the non-polar solvent and the polar solvent. When the volume of the nonpolar solvent is 100%, the volume of the polar solvent is, for example, 20% or less, preferably 10% or less, more preferably 5% or less. more than half of the total).

The method for producing the metal nanoparticles is not particularly limited, but examples thereof include chemical production by reducing a metal salt or metal complex in a solution.
In addition, the method for producing surface-protected metal nanoparticles in which the surfaces of metal nanoparticles are coated with protective molecules is not particularly limited. etc.
Furthermore, the method for producing the dispersion in which the surface-protecting metal nanoparticles are dispersed is not particularly limited, but examples thereof include the following methods. Metal salts and metal complexes are reduced in a liquid in which protective molecules are dissolved, and metal nanoparticles are nucleated to synthesize seed crystals. From there, the metal salt or metal complex is reduced around the seed crystal to grow the seed crystal large (nuclear growth). By controlling the reaction by stepwise growing the nuclei a plurality of times, it is possible to produce a dispersion liquid in which surface-protecting metal nanoparticles are dispersed and whose average particle size is adjusted to 1 to 30 nm.

〔式中、（Ｓｉｔｅ－ＰＭ）は保護分子が吸着している金属原子の吸着サイトを示し、（Ｓｉｔｅ）は保護分子が吸着していない金属原子の吸着サイトを示し、（ＰＭ）は遊離の保護分子を示す。〕 In the dispersion liquid, a chemical equilibrium represented by the following formula (I) is established between the surface-protecting metal nanoparticles, the metal nanoparticles, and the protective molecules.

[In the formula, (Site-PM) represents the adsorption site of the metal atom to which the protective molecule is adsorbed, (Site) represents the adsorption site of the metal atom to which the protective molecule is not adsorbed, and (PM) represents the free Indicates a protected molecule. ]

More specifically, (Site-PM) indicates the adsorption site of the metal atom to which the protective molecule is adsorbed in the surface-protected metal nanoparticles.
(Site) indicates the adsorption site of the metal atom to which the protective molecule is not adsorbed. This indicates both adsorption sites for metal atoms on the metal nanoparticles themselves and adsorption sites for metal atoms on the surface-protected metal nanoparticles to which protective molecules are not adsorbed.
(PM) indicates free protective molecules not adsorbed to metal nanoparticles.

The metal atom adsorption site means the following.
When the surface of the metal nanoparticles is divided into a grid pattern, and it is assumed that one protective molecule can be adsorbed per square, one square is defined as a metal atom adsorption site. When one protective molecule is adsorbed to a metal nanoparticle, the area occupied by one protective molecule (that is, the size of one square) depends on the type of protective molecule and the adsorption posture of the protective molecule. It changes depending on the state.

The method of liquefying metal nanoparticles of the present invention includes a step of shifting the equilibrium point of the chemical equilibrium of formula (I) above in the direction of desorption of the protective molecule.
The direction of desorption of the protective molecule is the direction in which the equilibrium point moves to the right in the above formula (I).

The step of shifting the chemical equilibrium point in the direction of desorption of the protective molecule includes the following steps (a) and/or (b).
(a) By changing the type and/or composition ratio of the dispersion medium contained in the dispersion and/or changing the temperature of the dispersion, the following formula (II):
Kd = {[Site] eq [PM] eq}/[Site-PM] eq (II)
[Wherein, [Site] eq represents the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is not adsorbed in the equilibrium state, and [PM] eq represents the concentration of the free protective molecule in the equilibrium state (mol/ L), and [Site-PM] eq indicates the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is adsorbed in the equilibrium state. ]
increasing the desorption equilibrium constant (Kd) of the protected molecule represented by
(b) adding a solvent and/or surface-protected metal nanoparticles to the dispersion and varying at least one of the three concentrations in the formula (II) to establish the chemical equilibrium of the formula (I); The step of creating a non-equilibrium state.

Step (a) is a step of increasing the desorption equilibrium constant (Kd) of the protective molecule represented by formula (II) above. and/or changing its constituent proportions and/or changing the temperature of said dispersion.

The desorption equilibrium constant (Kd) of the protective molecule is the equilibrium constant when the chemical equilibrium represented by the above formula (I) is established, and is represented by the above formula (II).
[Site] eq indicates the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is not adsorbed in the equilibrium state, and [PM] eq indicates the concentration (mol/L) of the free protective molecule in the equilibrium state. , [Site-PM]eq indicates the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is adsorbed in the equilibrium state.
Each concentration above indicates each concentration (mol/L) in the dispersion, that is, the number of moles (mol) of each component in the volume (L) of the dispersion.

The desorption equilibrium constant (Kd) is a function of temperature, and the temperature determines the value of Kd. Moreover, even at the same temperature, Kd shows different values depending on the type of solvent. Also, the type, concentration, and temperature of the solvent may be changed so as to increase the desorption equilibrium constant (Kd) and liquefy.
In the liquefaction method of the present invention, the desorption equilibrium constant (Kd) is controlled by the type, concentration, and temperature of the solvent. is possible.
Although the range of the desorption equilibrium constant (Kd) is not particularly limited, it is preferably 1×10 ⁻⁴ mol/L or more when Kd is increased to form a metal by liquefaction. This is because when liquefying, the number of molecules adsorbed on the particle surface should be less than a certain number, and the larger the value of Kd, the easier it is for the molecules to desorb.
In addition, before liquefying (when the particle surface is protected by molecules), the number of molecules adsorbed on the particle surface only needs to exceed a certain number, and from the viewpoint of keeping the desorption equilibrium constant (Kd) low, It is preferably 1×10 ⁻² mol/L or less. The desorption equilibrium constant (Kd) is set within the above range, and the liquefaction can be controlled by changing the solvent type, concentration, temperature, and the like.

In the step (a), the type and/or composition ratio of the dispersion medium contained in the dispersion is changed and/or the temperature of the dispersion is changed so as to increase the desorption equilibrium constant (Kd). change.

The method for changing the type and/or composition ratio of the dispersion medium contained in the dispersion is not particularly limited, but for example, the dispersion medium used in the initial dispersion (hereinafter also referred to as the initial dispersion) (hereinafter also referred to as the initial dispersion medium), adding a solvent to change the composition ratio of the solvent used as the initial dispersion medium, the solvent used as the initial dispersion medium and the like. This makes it possible to change the types and proportions of the dispersion medium, whether the initial dispersion medium is a single solvent or a mixed solvent of two or more solvents. From the viewpoint of shifting the equilibrium point in the direction of desorption, it is preferable to add a solvent different from the initial dispersion medium.
Further, when the initial dispersion medium is a mixed solvent of two or more kinds, it is possible to add only one of the solvents used as the initial dispersion medium, or to add all the solvents used in the initial dispersion medium, The constituent ratio of the solvent constituting the dispersion medium can be changed by adding it in a ratio different from that of the initial dispersion medium.

Although the solvent to be added is not particularly limited, it is preferable to use a polar solvent in order to facilitate the desorption of the protective molecule.
Polar solvents include, but are not limited to, alcohols having 1 to 5 carbon atoms such as methanol, ethanol, 1-propanol, 2-propanol, butanol and pentanol; amides such as formamide and acetamide; - ionic liquids such as methylimidazolium tetrafluoroborate. From the viewpoint of ease of desorption, alcohols having 1 to 3 carbon atoms are preferred, and methanol and ethanol are more preferred.
Moreover, when evaporating the solvent, it can be carried out by leaving it in an open state.

A method for changing the temperature of the dispersion is not particularly limited, but an example thereof includes warming the dispersion using a heater such as a heater.
The dispersion during storage before being liquefied is stored, for example, by frozen storage, refrigerated storage, normal temperature storage, or the like. Therefore, the temperature of the dispersion during storage is not particularly limited, but is generally -30°C to 35°C.
In the method of changing the temperature of the dispersion, the heating temperature of the dispersion during liquefaction for metal formation is not particularly limited, but is preferably 120° C. or less, more preferably 100° C. or less, and further preferably 80° C. or less. preferable. Also, the lower limit temperature can be set to be equal to or higher than the storage temperature. The present invention is characterized in that the metal can be formed at a lower temperature than the sintering method. Moreover, when metal is formed on the base material as described later, the temperature can be set in a wide range in consideration of the heat resistance of the base material.
Since Kd usually takes a larger value as the temperature of the dispersion increases, it is preferable to change the temperature of the dispersion by warming the dispersion.

Step (b) includes adding a solvent and/or surface-protected metal nanoparticles to the dispersion and varying at least one of the three concentrations in formula (II) to produce the chemical of formula (I) This is a step of creating a non-equilibrium state in which equilibrium is not established.

When a solvent is added to the dispersion, the added solvent may be of the same type as the initial dispersion medium or of a different type. Further, when the initial dispersion medium is a mixed solvent, the solvent may be added in the same mixing ratio as the initial dispersion medium or in a different mixing ratio.
By adding a solvent to the dispersion liquid, the chemical equilibrium of the formula (I), which had been established up to that point, is disturbed and a non-equilibrium state is established. However, within the dispersion system, the equilibrium point shifts in the direction of desorption of the protective molecule so as to reestablish the chemical equilibrium of formula (I).
Although the solvent to be added is not particularly limited, it is preferable to use a polar solvent in order to facilitate the desorption of the protective molecule. Examples of the polar solvent include those described above.

When surface-protected metal nanoparticles are added to the dispersion, the added surface-protected metal nanoparticles may be of the same type as or different from the surface-protected metal nanoparticles present in the initial dispersion. However, from the viewpoint that there is a possibility that a mixture of flowing particles and particles that maintain a solid state may occur due to a distribution in adsorption energy, it is preferable that the particles are of the same type because they can be easily controlled.
By adding the surface-protecting metal nanoparticles to the dispersion liquid, the chemical equilibrium of the formula (I), which had been established until then, is disturbed, resulting in a non-equilibrium state. However, within the dispersion system, the equilibrium point shifts in the direction of desorption of the protective molecule so as to reestablish the chemical equilibrium of formula (I).

〔式中、（Ｓｉｔｅ－ＰＭ）は保護分子が吸着している金属原子の吸着サイトを示し、（Ｓｉｔｅ）は保護分子が吸着していない金属原子の吸着サイトを示し、（ＰＭ）は遊離の保護分子を示す。〕
前記化学平衡の平衡点を保護分子の脱着の方向に移動させる工程を含み、
（４）前記化学平衡の平衡点を保護分子の脱着の方向に移動させる工程が、下記（ａ’）及び／又は（ｂ’）の工程
（ａ’）前記溶媒の種類及び／又はその構成割合を変える、及び／又は、前記溶媒及び／又は基材の温度を変えることにより、下記式（ＩＩ）：
Ｋｄ＝｛［Ｓｉｔｅ］ｅｑ［ＰＭ］ｅｑ｝／［Ｓｉｔｅ－ＰＭ］ｅｑ （ＩＩ）
〔式中、［Ｓｉｔｅ］ｅｑは平衡状態における保護分子が吸着していない金属原子の吸着サイト濃度（mol/L）を示し、［ＰＭ］ｅｑは平衡状態における遊離の保護分子の濃度（mol/L）を示し、［Ｓｉｔｅ－ＰＭ］ｅｑは平衡状態における保護分子が吸着している金属原子の吸着サイト濃度（mol/L）を示す。〕
で表される保護分子の脱着平衡定数（Ｋｄ）を増大させる工程、
（ｂ’）前記溶媒に、溶媒及び／又は表面保護金属ナノ粒子を添加して、前記式（ＩＩ）における３つの濃度のうちの少なくとも１つを変化させて、前記式（Ｉ）の化学平衡が成り立たない非平衡状態とする工程、
を含むことを特徴とするものである。 A method of liquefying metal nanoparticles as another method in the present invention is
(1) the metal nanoparticles are dispersed in a dispersion liquid in the form of surface-protected metal nanoparticles in which the surfaces of the transition metal nanoparticles are coated with protective molecules;
(2) applying the dispersion to a substrate, and contacting the substrate coated with the dispersion with a solvent;
(3) When the substrate coated with the dispersion is brought into contact with a solvent, a chemical equilibrium represented by the following formula (I) occurs between the surface-protecting metal nanoparticles, the metal nanoparticles, and the protective molecule. Origin,

[In the formula, (Site-PM) represents the adsorption site of the metal atom to which the protective molecule is adsorbed, (Site) represents the adsorption site of the metal atom to which the protective molecule is not adsorbed, and (PM) represents the free Indicates a protected molecule. ]
shifting the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule;
(4) The step of moving the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule is the following (a') and/or (b') in step (a') the type and/or composition ratio of the solvent and/or by changing the temperature of the solvent and/or substrate, the following formula (II):
Kd = {[Site] eq [PM] eq}/[Site-PM] eq (II)
[Wherein, [Site] eq represents the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is not adsorbed in the equilibrium state, and [PM] eq represents the concentration of the free protective molecule in the equilibrium state (mol/ L), and [Site-PM] eq indicates the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is adsorbed in the equilibrium state. ]
increasing the desorption equilibrium constant (Kd) of the protected molecule represented by
(b′) adding a solvent and/or surface-protected metal nanoparticles to the solvent to change at least one of the three concentrations in the formula (II) to obtain the chemical equilibrium of the formula (I); A step of creating a non-equilibrium state in which
It is characterized by including

The method of liquefying the metal nanoparticles (second liquefaction method) is the first liquefaction method, in which a dispersion containing the surface-protecting metal nanoparticles is applied to the substrate, and the dispersion is applied. It further includes the step of contacting the substrate with a solvent. Specifically, the method further includes a step of applying a dispersion containing surface-protecting metal nanoparticles to a substrate, and bringing at least a portion of the substrate coated with the dispersion into contact with a solvent.
By including this step, in the method, the metal nanoparticles can be liquefied on the surface of the substrate (any location thereof) and further inside the substrate (any location thereof).

Examples of the base material include, but are not particularly limited to, thermoplastic resins, thermosetting resins, rubbers, natural fibers, synthetic fibers, glass, paper, and ceramics.

Examples of thermoplastic resins include, but are not limited to, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polycarbonate, polyacetal, polyphenylene oxide, polyamide, polysulfone, fluororesin, polyvinyl chloride, polyvinyl alcohol, and polyvinyl acetate. , poly(meth)acrylic acid, polymethyl methacrylate, cellulose acetate and the like.
Examples of thermosetting resins include, but are not limited to, phenol resins, urea resins, xylene resins, urea resins, melamine resins, epoxy resins, silicon resins, diallyl phthalate resins, furan resins, aniline resins, acetone-formaldehyde resins, Examples include alkyd resins.

Examples of rubber include, but are not limited to, natural rubber; polydimethylsiloxane, polyurethane, elastic fiber, and synthetic rubber such as SBR.
Examples of natural fibers include, but are not limited to, cotton, silk, and wool.
Examples of synthetic fibers include, but are not limited to, polyester, rayon, and nylon.

The method of applying a dispersion containing metal nanoparticles to a substrate (not limited to coating, but also including various methods such as immersion and spraying) is not particularly limited. For example, the substrate is immersed in the dispersion. spray coating method, drop casting method, spin coating method, dispensing method, and the like.

When the substrate is immersed in the dispersion, after the immersion, the substrate coated with the dispersion may be taken out, dried, and then brought into contact with the solvent, or the substrate coated with the dispersion may be dried. The solvent may be contacted without drying, but drying is preferred.
The method for drying the substrate is not particularly limited, but includes, for example, a method of standing still at room temperature, a method of blowing off the liquid with an inert gas such as nitrogen, etc., and a method of standing still at room temperature is preferred.
When the dispersion is spray-coated onto the substrate, there is almost no dispersion medium present on the substrate to which the dispersion has been applied. In this case, the substrate coated with the dispersion does not need to be dried, and can be brought into contact with the solvent as it is.

The method of bringing the substrate coated with the dispersion liquid into contact with the solvent is not particularly limited, and examples thereof include a method of immersing the substrate coated with the dispersion liquid in the solvent.
The solvent in the step of bringing the substrate coated with the dispersion liquid into contact with the solvent is not particularly limited as long as it is a solvent capable of desorbing the protective molecule from the surface-protected metal nanoparticles. Examples include polar solvents, polar solvents, and a non-polar solvent.

Polar solvents include, but are not limited to, alcohols having 1 to 5 carbon atoms such as methanol, ethanol, 1-propanol, 2-propanol, butanol and pentanol; amides such as formamide and acetamide; - ionic liquids such as methylimidazolium tetrafluoroborate. From the viewpoint of desorption equilibrium constant, alcohols having 1 to 3 carbon atoms are preferred, and methanol and ethanol are more preferred.

The nonpolar solvent is not particularly limited as long as it can be used by mixing with the above polar solvent. Examples include alkanes such as heptane, hexane, pentane, octane, and nonane; cycloalkanes; halogen-substituted alkanes such as methylene chloride, chloroform and carbon tetrachloride; ethers such as diethyl ether and diisopropyl ether; alcohols having 6 or more carbon atoms such as hexanol, heptanol and octanol; aromatic hydrocarbons; heterocyclic compounds such as tetrahydrofuran and tetrahydropyran; From the viewpoint of desorption equilibrium constant, alkanes, halogen-substituted alkanes, and aromatic hydrocarbons are preferred, and hexane, methylene chloride, and toluene are more preferred.

A non-polar solvent has the effect of dispersing the surface-protected metal nanoparticles. Therefore, it is not preferable to use a nonpolar solvent alone as a solvent in this step, but a mixed solvent of a polar solvent and a nonpolar solvent can be used as a solvent in this step.
When using a mixed solvent of a polar solvent and a non-polar solvent, the mixing ratio is not particularly limited. The volume of the polar solvent is, for example, 40% or less, preferably 30% or less, more preferably 20% or less.

In this method, the chemical equilibrium of the above formula (I) is established in a system in which a substrate coated with a dispersion containing surface-protecting metal nanoparticles is brought into contact with a solvent. The step of shifting the equilibrium point of chemical equilibrium in the direction of desorption of the protective molecule includes the above steps (a') and/or (b').
For steps (a′) and (b′), in steps (a) and (b) in the first liquefaction method, the substrate is brought into contact with a solvent instead of being liquefied in the dispersion liquid. It can be carried out in the same manner except that it is liquefied. In this second liquefaction method, the base material can be liquefied at any position.
In addition, the temperature of the solvent and the temperature of the substrate when changing the temperature of the solvent and/or the substrate are not particularly limited, but are each in the same temperature range as the temperature for heating the dispersion in the first liquefaction method. can be used.

The concentration of each component in the desorption equilibrium constant (Kd) of the protective molecule represented by the above formula (II) is the concentration (mol/ L), that is, the number of moles (mol) of each component in the volume (L) of solvent with which the substrate coated with the dispersion is contacted.

Other liquefaction methods can also be used in the present invention. As another liquefaction method, in (2) of the second liquefaction method, instead of "the step of applying the dispersion to a substrate and bringing the substrate coated with the dispersion into contact with a solvent" 2. is a method including "a step of adding the dispersion liquid to a solvent".
In this method, the surfaces of the metal nanoparticles in the dispersion are liquefied by adding (for example, dropping) the dispersion into the solvent, and the metal nanoparticles gather together.
Examples of the solvent to be used include those exemplified in the second liquefaction method.

〔式中、（Ｓｉｔｅ－ＰＭ）は保護分子が吸着している金属原子の吸着サイトを示し、（Ｓｉｔｅ）は保護分子が吸着していない金属原子の吸着サイトを示し、（ＰＭ）は遊離の保護分子を示す。〕
前記化学平衡の平衡点を保護分子の脱着の方向に移動させる工程を含み、
（４）前記化学平衡の平衡点を保護分子の脱着の方向に移動させる工程が、下記（ａ）及び／又は（ｂ）の工程
（ａ）前記分散液に含まれる分散媒を構成する種類及び／又はその構成割合を変える、及び／又は、前記分散液の温度を変えることにより、下記式（ＩＩ）：
Ｋｄ＝｛［Ｓｉｔｅ］ｅｑ［ＰＭ］ｅｑ｝／［Ｓｉｔｅ－ＰＭ］ｅｑ （ＩＩ）
〔式中、［Ｓｉｔｅ］ｅｑは平衡状態における保護分子が吸着していない金属原子の吸着サイト濃度（mol/L）を示し、［ＰＭ］ｅｑは平衡状態における遊離の保護分子の濃度（mol/L）を示し、［Ｓｉｔｅ－ＰＭ］ｅｑは平衡状態における保護分子が吸着している金属原子の吸着サイト濃度（mol/L）を示す。〕
で表される保護分子の脱着平衡定数（Ｋｄ）を増大させる工程、
（ｂ）前記分散液に溶媒及び／又は表面保護金属ナノ粒子を添加し、前記式（ＩＩ）における３つの濃度のうちの少なくとも１つを変化させて、前記式（Ｉ）の化学平衡が成り立たない非平衡状態とする工程、
を含むことを特徴とするものである。 Next, the method of forming a metal on a substrate in the present invention includes:
(1) including a step of contacting a substrate with a dispersion containing metal nanoparticles;
(2) the metal nanoparticles are dispersed in the dispersion in the form of surface-protected metal nanoparticles in which the surfaces of the transition metal nanoparticles are coated with protective molecules;
(3) A chemical equilibrium represented by the following formula (I) is established between the surface-protecting metal nanoparticles, the metal nanoparticles, and the protective molecule,

[In the formula, (Site-PM) represents the adsorption site of the metal atom to which the protective molecule is adsorbed, (Site) represents the adsorption site of the metal atom to which the protective molecule is not adsorbed, and (PM) represents the free Indicates a protected molecule. ]
shifting the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule;
(4) The step of moving the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule is the following (a) and / or (b) step (a) the type and the type constituting the dispersion medium contained in the dispersion liquid / Or by changing the composition ratio and / or changing the temperature of the dispersion, the following formula (II):
Kd = {[Site] eq [PM] eq}/[Site-PM] eq (II)
[Wherein, [Site] eq represents the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is not adsorbed in the equilibrium state, and [PM] eq represents the concentration of the free protective molecule in the equilibrium state (mol/ L), and [Site-PM] eq indicates the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is adsorbed in the equilibrium state. ]
increasing the desorption equilibrium constant (Kd) of the protected molecule represented by
(b) adding a solvent and/or surface-protected metal nanoparticles to the dispersion and varying at least one of the three concentrations in the formula (II) to establish the chemical equilibrium of the formula (I); non-equilibrium state,
It is characterized by including

In the method of forming a metal on the base material (first metal forming method), the metal can be formed on the surface or inside of the base material in the dispersion.

The step of bringing the substrate into contact with the dispersion containing the metal nanoparticles is not particularly limited, and examples thereof include a method of immersing the substrate in the dispersion.

When the substrate is immersed in the dispersion, the step of moving the equilibrium point of the chemical equilibrium represented by formula (I) in the direction of desorption of the protective molecule enables In the dispersion, metal can form on the surface of the substrate, or on and within it.

Various components in the dispersion are as described above. Moreover, the same thing as the above-mentioned is mentioned also about the base material to be used. Furthermore, the chemical equilibrium represented by the above formula (I) is established in the system in which the substrate is brought into contact with the dispersion liquid containing the metal nanoparticles.
Steps (a) and (b) as steps for shifting the equilibrium point of chemical equilibrium in the direction of desorption of the protective molecule are as described above.

〔式中、（Ｓｉｔｅ－ＰＭ）は保護分子が吸着している金属原子の吸着サイトを示し、（Ｓｉｔｅ）は保護分子が吸着していない金属原子の吸着サイトを示し、（ＰＭ）は遊離の保護分子を示す。〕
前記化学平衡の平衡点を保護分子の脱着の方向に移動させる工程を含み、
（４）前記化学平衡の平衡点を保護分子の脱着の方向に移動させる工程が、下記（ａ’）及び／又は（ｂ’）の工程
（ａ’）前記溶媒の種類及び／又はその構成割合を変える、及び／又は、前記溶媒及び／又は基材の温度を変えることにより、下記式（ＩＩ）：
Ｋｄ＝｛［Ｓｉｔｅ］ｅｑ［ＰＭ］ｅｑ｝／［Ｓｉｔｅ－ＰＭ］ｅｑ （ＩＩ）
〔式中、［Ｓｉｔｅ］ｅｑは平衡状態における保護分子が吸着していない金属原子の吸着サイト濃度（mol/L）を示し、［ＰＭ］ｅｑは平衡状態における遊離の保護分子の濃度（mol/L）を示し、［Ｓｉｔｅ－ＰＭ］ｅｑは平衡状態における保護分子が吸着している金属原子の吸着サイト濃度（mol/L）を示す。〕
で表される保護分子の脱着平衡定数（Ｋｄ）を増大させる工程、
（ｂ’）前記溶媒に、溶媒及び／又は表面保護金属ナノ粒子を添加して、前記式（ＩＩ）における３つの濃度のうちの少なくとも１つを変化させて、前記式（Ｉ）の化学平衡が成り立たない非平衡状態とする工程、
を含むことを特徴とするものである。 As another method of forming a metal on a base material in the present invention,
(1) applying a dispersion containing metal nanoparticles to a substrate, and contacting the substrate coated with the dispersion with a solvent;
(2) the metal nanoparticles are dispersed in the dispersion in the form of surface-protected metal nanoparticles in which the surfaces of the transition metal nanoparticles are coated with protective molecules;
(3) When the substrate coated with the dispersion is brought into contact with a solvent, a chemical equilibrium represented by the following formula (I) occurs between the surface-protecting metal nanoparticles, the metal nanoparticles, and the protective molecule. Origin,

[In the formula, (Site-PM) represents the adsorption site of the metal atom to which the protective molecule is adsorbed, (Site) represents the adsorption site of the metal atom to which the protective molecule is not adsorbed, and (PM) represents the free Indicates a protected molecule. ]
shifting the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule;
(4) The step of moving the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule is the following (a') and/or (b') in step (a') the type and/or composition ratio of the solvent and/or by changing the temperature of the solvent and/or substrate, the following formula (II):
Kd = {[Site] eq [PM] eq}/[Site-PM] eq (II)
[Wherein, [Site] eq represents the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is not adsorbed in the equilibrium state, and [PM] eq represents the concentration of the free protective molecule in the equilibrium state (mol/ L), and [Site-PM] eq indicates the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is adsorbed in the equilibrium state. ]
increasing the desorption equilibrium constant (Kd) of the protected molecule represented by
(b′) adding a solvent and/or surface-protected metal nanoparticles to the solvent to change at least one of the three concentrations in the formula (II) to obtain the chemical equilibrium of the formula (I); A step of creating a non-equilibrium state in which
It is characterized by including

In the method of forming a metal on the base material (second metal forming method), the metal can be formed on the surface or inside of the base material in the solvent in which the base material is brought into contact.

In the step of applying a dispersion containing metal nanoparticles to a substrate and bringing the substrate coated with the dispersion into contact with a solvent, the method of applying the dispersion containing metal nanoparticles to the substrate includes: It is not particularly limited, and examples thereof include a method of immersing the substrate in the dispersion, a method of spray coating the substrate with the dispersion, a drop casting method, a spin coating method, a dispensing method, and the like.

When the substrate is immersed in the dispersion, after the immersion, the substrate coated with the dispersion may be taken out, dried, and then brought into contact with the solvent, or the substrate coated with the dispersion may be dried. The solvent may be contacted without drying.
When the dispersion is spray-coated onto the substrate, there is almost no dispersion medium present on the substrate to which the dispersion has been applied. In this case, the substrate coated with the dispersion does not need to be dried, and can be brought into contact with the solvent as it is.

In this second metal forming method, the chemical equilibrium of the above formula (I) is established in the system in which the substrate coated with the dispersion is brought into contact with the solvent. The step of shifting the equilibrium point of chemical equilibrium in the direction of desorption of the protective molecule includes the above steps (a') and/or (b').
For steps (a') and (b'), in steps (a) and (b) in the first metal forming method, instead of forming a metal on the substrate in the dispersion, the substrate is It can be done in a similar way, except that it is contacted with a solvent to form the metal.

Next, the dispersion of the present invention is composed of at least one selected from the group consisting of gold, silver, copper, platinum and palladium, and has an average particle size of 1 to 30 nm.
surface-protected metal nanoparticles coated with protective molecules containing at least one of an amino group and a carboxyl group,
It is characterized by being dispersed in a dispersion medium containing a non-polar solvent.

As described above, the average particle size of the metal nanoparticles is preferably 1 to 30 nm, more preferably 2 to 20 nm, even more preferably 2 to 10 nm, and particularly preferably 2 to 6 nm.

where the desorption equilibrium constant (Kd) of the protected molecule is given by formula (II):
Kd = {[Site] eq [PM] eq}/[Site-PM] eq (II)
[Wherein, [Site] eq represents the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is not adsorbed in the equilibrium state, and [PM] eq represents the concentration of the free protective molecule in the equilibrium state (mol/ L), and [Site-PM] eq indicates the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is adsorbed in the equilibrium state. ]
is represented by
In the dispersion liquid, when the metal nanoparticles are dispersed in the dispersion medium, the desorption equilibrium constant is a small value from the viewpoint of adsorbing the protective molecule on the surface of the metal nanoparticles (positioning the equilibrium point in the direction of adsorption). preferably 1×10 ⁻³ (mol/L) or less, more preferably 1×10 ⁻⁴ (mol/L) or less.
On the other hand, when the metal nanoparticles are liquefied, the desorption equilibrium constant is increased, and from the viewpoint of desorbing the protective molecules from the surface of the metal nanoparticles (positioning the equilibrium point in the direction of desorption), the desorption equilibrium constant is 1 × It is preferably 10 ⁻⁴ (mol/L) or more, and more preferably 1×10 ⁻³ or more considering the ease of desorption of molecules.

In addition, the dispersion can be used in the method for liquefying metal nanoparticles and the method for forming metal on the substrate.
Various components in the dispersion are as described above.

According to the liquefaction method and the metal forming method of the present invention, metal can be easily formed on the surface of various types of substrates, or on the surface and inside thereof.
Moreover, the following advantages can be obtained by using the method of the present invention.
(1) Metal nanoparticles can penetrate into the interior of the substrate. As a result, the adhesion strength between the formed metal and the substrate is high, the durability against repeated stretching is high, and high electrical conductivity can be obtained with a small amount of metal nanoparticles. That is, it is possible to obtain a polymer having both flexibility and conductivity.
(2) Metal can penetrate into nanoscale irregularities on the substrate surface. As a result, high adhesiveness is obtained due to the anchor effect between the base material and the metal, and the base material is coated with a thin and uniform metal film, which does not break even when bent.
(3) Metal nanoparticles can diffuse into nanoscale pores. As a result, by pouring a liquid metal into a mold, it is possible to easily form a metal such as a nano-implant.
(4) The metal can be supported on the base material, and when the metal nanoparticles are fluidized and supported in an isolated state, the ratio of atoms occupying the corners and edges on the metal surface increases, so the catalytic activity can be enhanced with a small amount. can.

In each of the above methods of the present invention, a dispersion liquid in which surface-protecting metal nanoparticles are dispersed in a dispersion medium is used. The surface-protecting metal nanoparticles are well dispersed in the dispersion medium, and since the metal concentration is low, the viscosity of the dispersion liquid is almost the same as that of the pure solvent.
Therefore, the dispersion can be applied to the substrate using a spray coating method, a dispenser method, or the like. Therefore, a conductive metal thin film can be formed not only on a smooth substrate but also on a base material having an arbitrary shape (for example, circle, triangle, square, unevenness, etc.). This has been difficult to achieve with conventional conductive pastes, which contain various substances in addition to metal nanoparticles and are made into pastes by increasing their viscosity.
The metal concentration in the dispersion is not particularly limited, but is preferably 0.1 to 100 mg/ml from the viewpoint of lowering the viscosity to facilitate processing and increasing the amount of metal nanoparticles to be processed at one time. , more preferably 1 to 80 mg/ml, more preferably 5 to 70 mg/ml.
Further, when the metal concentration in the dispersion is converted to the metal content in the dispersion, it may vary depending on the type of metal used and the type of solvent, but is preferably 0.01 to 10% by mass, more preferably 0 .1 to 8% by mass, more preferably 0.5 to 7% by mass.

Patterning can be easily performed by using a stencil (a type of pattern paper used in printing, etc., in which a letter or pattern is cut out so that a liquid can pass through it) or the like.

As a dispersion of surface-protecting metal nanoparticles, an alloy can be obtained by mixing dispersions of different types of transition metals constituting the metal nanoparticles and applying the liquefaction method of the present invention. The composition of the alloy can be arbitrarily adjusted simply by changing the mixing ratio of the dispersion.
In other words, unlike the general sputtering method and vacuum deposition method (a method of heating a solid metal in a vacuum to convert it into gaseous atoms and depositing it on a substrate to form a film), the metal forming method of the present invention can be used. , the alloy can be deposited very easily while adjusting the composition of the alloy.
In addition, although silver is often used in wiring substrates, it has the problem of short-circuiting the electrodes due to migration. , can prevent migration.

By using each of the above-described methods of the present invention, metal formation can be performed in a low-temperature environment, so that the method can be applied to polymer substrates having no heat resistance (for example, low-density polyethylene, etc.).

Also, when the solubility parameter of the polymer and the solubility parameter of the solvent are close, the polymer easily takes in the solvent and swells.
Here, Table 1 shows the solubility parameter values of various rubbers and solvents. Polydimethylsiloxane (PDMS), natural rubber, and polyurethane are representative rubber substrates (polymers). In fact, PDMS swells in hexane, natural rubber swells in cyclohexane, and polyurethane swells in methylene chloride.
Therefore, if the non-polar solvent is used as the dispersion medium for the dispersion of the surface-protecting metal nanoparticles, the metal nanoparticles will penetrate into the rubber substrate when the rubber substrate swells with the solvent, and the inside of the rubber substrate will can liquefy and form a metal.

Various metal substrates obtained by the liquefaction method and the metal formation method of the present invention can be applied not only for wiring of electronic parts, but also in various fields, such as stretchable electronics, wearable electronics, Flexible electronics, energy storage substrates, catalysts, mesoporous metals, etc. can be mentioned as examples of applications.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the embodiments of these examples.

Abbreviations used in the examples below are explained below.
DA: dodecylamine AuDA: gold nanoparticles with dodecylamine as a protective molecule adsorbed on the surface AgDA: silver nanoparticles with dodecylamine as a protective molecule adsorbed on the surface PdDA: palladium with dodecylamine as a protective molecule adsorbed on the surface Nanoparticle PDMS: Polydimethylsiloxane

Moreover, in the following examples, each numerical value was measured as follows.
(1) The average particle size of metal nanoparticles is obtained by image analysis of about 500 metal nanoparticles using a scanning transmission electron microscope (HD-2700, Hitachi), and the number average is calculated and averaged. particle size.
(2) The electron microscope (TEM) used for electron microscope observation is JEM-2100 manufactured by JEOL Ltd. The electron microscope (SEM) is JSM-7600F manufactured by JEOL Ltd.
(3) The amount of molecular adsorption is measured using a tubular furnace (ARF-50KC, manufactured by Heattech) and a micro electronic balance (BM-20, manufactured by A&D), and the amount of change in weight before and after vaporizing the protective molecules. and measured.
(4) Electrical conductivity was measured by a four-probe method using a source meter (2450 manufactured by Keithley).
(5) X-ray diffraction was measured using a wide-angle X-ray diffractometer (RINT2500 manufactured by Rigaku) under conditions of a voltage of 40 kV and a current of 200 mA. The wavelength of the characteristic X-ray used was 1.5418 Å (CuKa rays).

(Example 1)
A dispersion was prepared by dispersing AuDA in hexane. FIG. 1(A) shows a TEM image when this dispersion was applied to a Cu grid for TEM observation with a carbon support film. It can be seen that the surface-protected gold nanoparticles with the protective molecule dodecylamine adsorbed on the surface are dispersed. Figures 1(B), (C), and (D) show how the gold nanoparticles are liquefied when the Cu grid for TEM observation with a carbon support film coated with this dispersion is immersed in methanol at 30°C. shown in From FIG. 1(B), DA, which is a protective molecule, is desorbed from the surface of the gold nanoparticles, the gold nanoparticles are liquefied, and a plurality of gold nanoparticles are aggregated by flow to grow into large gold particles. I understand. FIGS. 1(C) and 1(D) are partially enlarged views of FIG. 1(B). From FIGS. 1(C) and (D), it can be seen that part of the gold nanoparticles liquefy (flow) and coalesce as part of the grown large gold particles. This state is a feature of liquefaction, unlike the phenomenon caused by sintering.

(Example 2)
A dispersion was prepared by dispersing AgDA in methylene chloride. FIG. 2A shows the state after standing at 0° C. for 24 hours. There was no change in the appearance of the dispersion immediately after preparation and after standing at 0° C. for 24 hours. The molecular adsorption amount θ (the amount of DA adsorbed to the Ag nanoparticles) measured after standing at 0° C. for 24 hours showed a high value of 21.3%, indicating that DA sufficiently covered the surface of the Ag nanoparticles. It is understood that The electrical conductivity of AgDA formed from the AgDA dispersion was as low as 4.1×10 ⁻⁵ S/cm, indicating that the Ag nanoparticles were coated with insulating protective molecules. At this time, it was also confirmed by electron microscopic observation and X-ray diffraction that the particle size of the Ag nanoparticles did not change at all from that immediately after the preparation of the dispersion liquid (Fig. 2(A)).
Next, when the AgDA dispersion after standing at 0° C. for 24 hours was taken out from 0° C. and allowed to stand at room temperature (about 20° C.), silver was deposited on the inner wall of the glass test tube in about 1 hour ( Fig. 2(B) is the one after standing still for 2 hours). At this time, the molecular adsorption amount θ showed a very low value of 0.91%, indicating that DA was desorbed from the Ag nanoparticles. When observed with an electron microscope, it was observed that the silver nanoparticles flowed and grew into large crystals (Fig. 2(B)). X-ray diffraction also confirmed the coarsening of the silver nanoparticles (FIG. 2(B)), and the silver deposits exhibited a very high electrical conductivity of 3.9×10 ⁴ S/cm.
A similar phenomenon also occurred when a mixed solvent was used as the dispersion medium. AgDA was uniformly dispersed in a mixed solvent of hexane and ethanol. Even if it was left at room temperature of 20°C for a long time, no change occurred, but when the temperature of the dispersion was raised to 50°C, silver precipitated on the inner wall of the test tube. In this way, even with a mixed solvent of a non-polar solvent and a polar solvent, the metal could be deposited on the substrate surface.

(Example 3)
An AuDA-containing dispersion (dispersion medium: hexane), an AgDA-containing dispersion (dispersion medium: hexane), and a PdDA-containing dispersion (dispersion medium: hexane) were each applied to a glass substrate by a spray coating method. The substrates coated with AuDA and AgDA were immersed in methanol at 30° C., and the substrates coated with PdDA were immersed in 2-propanol at 40° C. for 1 hour (approximately 3 mg of metal nanoparticles were immersed in 20 ml of solvent) to apply the dispersion. After the substrate was immersed, the amount of protective molecules adsorbed to the metal nanoparticles (molecular adsorption amount θ) decreased (DA desorbed from the surface of the metal nanoparticles), and the electrical conductivity increased significantly. The results are shown in Table 2.
In addition, when the state of the metal thin film formed on the glass substrate at this time was observed with an electron microscope, it was observed that the metal nanoparticles flowed and became coarse (FIGS. 3A, 3B, and 3C). ).
Furthermore, the width of the diffraction peak (full width at half maximum) was also reduced from the X-ray diffraction pattern, and it was clearly observed that the crystal had grown large (in each of FIGS. 3 (A) and (B), the lower The diffraction pattern of is the sample before soaking in alcohol, and the diffraction pattern above is the sample after soaking in alcohol).

(Example 4)
An experiment was conducted in the same manner as in Example 3, except that the substrate coated with the dispersion was immersed in another alcohol. Water was also used as a control. Table 3 shows the results. No significant increase in electrical conductivity was observed in water (the equilibrium point is located in the direction of adsorption), but alcohol showed a large increase in electrical conductivity (the equilibrium point is located in the direction of desorption).

(Example 5)
AgDA was dispersed in a mixed solution of ethanol and hexane. PDMS was immersed in the dispersion (30° C.). PDMS immediately swelled, and AgDA also penetrated inside PDMS (due to the small size of the metal nanoparticles, AgDA penetrated between the swollen polymer chains). The PDMS was allowed to stand still for 1 hour to further permeate the AgDA into the inside of the PDMS. After that, when the temperature of the dispersion is raised to 50 ° C., the equilibrium point moves in the direction of desorption, DA is desorbed from the silver nanoparticle surface, the silver nanoparticles are liquefied, and silver is precipitated inside the PDMS. did.
When the same operation was repeated three times using a new AgDA dispersion solution, PDMS with a sheet resistance of about 1 ohm/sq was produced.

(Example 6)
Silver was precipitated inside the polyurethane in the same manner as in Example 5, except that the polyurethane was immersed in a dispersion of AgDA in methylene chloride (FIG. 4). The left side of FIG. 4 is a photograph of polyurethane before being immersed in the dispersion, and the right side of FIG. 4 is a photograph of polyurethane after being immersed in the dispersion. After that, the polyurethane with silver deposited inside was stretched, and when an electric current was passed through it, it was energized. The electric conductivity showed 1.1×10 ⁴ S/cm.

(Example 7)
FIG. 5 shows a SEM photograph of a rayon fiber immersed in a dispersion of AgDA in methylene chloride and taken out. The left side of FIG. 5 is a SEM photograph of the fiber cross section (top) and the fiber plane (bottom) when stored at 0° C. The right side of FIG. It is a SEM photograph of the plane (bottom). From FIG. 5, it can be seen that silver in a liquid state flows into the irregularities on the surface of the rayon fiber and coats the fiber. A silver film with a thin and uniform thickness was formed on the fiber surface due to the interlocking of the unevenness of the fiber surface with the silver (anchor effect). The electrical conductivity of the silver-coated rayon fiber was 10 ⁴ S/cm, showing excellent electrical properties. In addition, it was confirmed that it has high adhesion and durability against repeated bending, and also has high durability against repeated wetting and drying (volume change).

Claims (7)

A method for liquefying metal nanoparticles having an average particle size of 1 to 4.6 nm,
(1) the metal nanoparticles are dispersed in a dispersion liquid in the form of surface-protected metal nanoparticles in which the surfaces of the transition metal nanoparticles are coated with protective molecules;
The dispersion liquid of the surface-protecting metal nanoparticles is produced by reducing a metal salt or metal complex in a liquid in which the protective molecules are dissolved to synthesize seed crystals of metal nanoparticles, and further growing the seed crystals. is,
(2) A chemical equilibrium represented by the following formula (I) is established between the surface-protecting metal nanoparticles, the metal nanoparticles, and the protective molecule,

[In the formula, (Site-PM) represents the adsorption site of the metal atom to which the protective molecule is adsorbed, (Site) represents the adsorption site of the metal atom to which the protective molecule is not adsorbed, and (PM) represents the free Indicates a protected molecule. ]
shifting the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule;
(3) the step of shifting the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule ,
By changing the type and/or composition ratio of the dispersion medium contained in the dispersion and/or changing the temperature of the dispersion, the following formula (II):
Kd = {[Site] eq [PM] eq}/[Site-PM] eq (II)
[Wherein, [Site] eq represents the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is not adsorbed in the equilibrium state, and [PM] eq represents the concentration of the free protective molecule in the equilibrium state (mol/ L), and [Site-PM] eq indicates the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is adsorbed in the equilibrium state. ]
A step of increasing the desorption equilibrium constant (Kd) of the protective molecule represented by and being 1×10 ⁻⁴ mol/L or more and 1×10 ⁻² mol/L or less ;
A method of liquefying metal nanoparticles , comprising: A method for liquefying metal nanoparticles having an average particle size of 1 to 4.6 nm,
(1) the metal nanoparticles are dispersed in a dispersion liquid in the form of surface-protected metal nanoparticles in which the surfaces of the transition metal nanoparticles are coated with protective molecules;
The dispersion liquid of the surface-protecting metal nanoparticles is produced by reducing a metal salt or metal complex in a liquid in which the protective molecules are dissolved to synthesize seed crystals of metal nanoparticles, and further growing the seed crystals. is,
(2) applying the dispersion to a substrate, and contacting the substrate coated with the dispersion with a solvent;
(3) When the substrate coated with the dispersion is brought into contact with a solvent, a chemical equilibrium represented by the following formula (I) occurs between the surface-protecting metal nanoparticles, the metal nanoparticles, and the protective molecule. Origin,

[In the formula, (Site-PM) represents the adsorption site of the metal atom to which the protective molecule is adsorbed, (Site) represents the adsorption site of the metal atom to which the protective molecule is not adsorbed, and (PM) represents the free Indicates a protected molecule. ]
shifting the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule;
(4) the step of shifting the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule ,
By changing the type and/or composition ratio of the solvent and/or changing the temperature of the solvent and/or the substrate, the following formula (II):
Kd = {[Site] eq [PM] eq}/[Site-PM] eq (II)
[Wherein, [Site] eq represents the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is not adsorbed in the equilibrium state, and [PM] eq represents the concentration of the free protective molecule in the equilibrium state (mol/ L), and [Site-PM] eq indicates the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is adsorbed in the equilibrium state. ]
A step of increasing the desorption equilibrium constant (Kd) of the protective molecule represented by and being 1×10 ⁻⁴ mol/L or more and 1×10 ⁻² mol/L or less ;
A method of liquefying metal nanoparticles , comprising: 3. The method according to claim 1, wherein the transition metal constituting the transition metal nanoparticles is at least one element belonging to groups 10 to 11 of the periodic table and belonging to periods 4 to 6. The method according to any one of claims 1 to 3, wherein the transition metal constituting the transition metal nanoparticles is at least one selected from the group consisting of gold, silver, copper, platinum and palladium. The method according to any one of claims 1 to 4, wherein said protective molecule contains at least one of an amino group and a carboxyl group. A method of forming a metal on a substrate, comprising:
(1) A step of contacting a substrate with a dispersion containing metal nanoparticles having an average particle size of 1 to 4.6 nm,
(2) the metal nanoparticles are dispersed in the dispersion in the form of surface-protected metal nanoparticles in which the surfaces of the transition metal nanoparticles are coated with protective molecules;
The dispersion liquid of the surface-protecting metal nanoparticles is produced by reducing a metal salt or metal complex in a liquid in which the protective molecules are dissolved to synthesize seed crystals of metal nanoparticles, and further growing the seed crystals. is,
(3) A chemical equilibrium represented by the following formula (I) is established between the surface-protecting metal nanoparticles, the metal nanoparticles, and the protective molecule,

[In the formula, (Site-PM) represents the adsorption site of the metal atom to which the protective molecule is adsorbed, (Site) represents the adsorption site of the metal atom to which the protective molecule is not adsorbed, and (PM) represents the free Indicates a protected molecule. ]
shifting the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule;
(4) the step of shifting the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule ,
By changing the type and/or composition ratio of the dispersion medium contained in the dispersion and/or changing the temperature of the dispersion, the following formula (II):
Kd = {[Site] eq [PM] eq}/[Site-PM] eq (II)
[Wherein, [Site] eq represents the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is not adsorbed in the equilibrium state, and [PM] eq represents the concentration of the free protective molecule in the equilibrium state (mol/ L), and [Site-PM] eq indicates the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is adsorbed in the equilibrium state. ]
A step of increasing the desorption equilibrium constant (Kd) of the protective molecule represented by and being 1×10 ⁻⁴ mol/L or more and 1×10 ⁻² mol/L or less ;
A method of forming a metal on a substrate , comprising: A method of forming a metal on a substrate, comprising:
(1) applying a dispersion containing metal nanoparticles having an average particle size of 1 to 4.6 nm to a substrate, and contacting the substrate coated with the dispersion with a solvent;
(2) the metal nanoparticles are dispersed in the dispersion in the form of surface-protected metal nanoparticles in which the surfaces of the transition metal nanoparticles are coated with protective molecules;
The dispersion liquid of the surface-protecting metal nanoparticles is produced by reducing a metal salt or metal complex in a liquid in which the protective molecules are dissolved to synthesize seed crystals of metal nanoparticles, and further growing the seed crystals. is,
(3) When the substrate coated with the dispersion is brought into contact with a solvent, a chemical equilibrium represented by the following formula (I) occurs between the surface-protecting metal nanoparticles, the metal nanoparticles, and the protective molecule. Origin,

[In the formula, (Site-PM) represents the adsorption site of the metal atom to which the protective molecule is adsorbed, (Site) represents the adsorption site of the metal atom to which the protective molecule is not adsorbed, and (PM) represents the free Indicates a protected molecule. ]
shifting the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule;
(4) the step of shifting the equilibrium point of the chemical equilibrium in the direction of desorption of the protective molecule ,
By changing the type and/or composition ratio of the solvent and/or changing the temperature of the solvent and/or the substrate, the following formula (II):
Kd = {[Site] eq [PM] eq}/[Site-PM] eq (II)
[Wherein, [Site] eq represents the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is not adsorbed in the equilibrium state, and [PM] eq represents the concentration of the free protective molecule in the equilibrium state (mol/ L), and [Site-PM] eq indicates the adsorption site concentration (mol/L) of the metal atom to which the protective molecule is adsorbed in the equilibrium state. ]
A step of increasing the desorption equilibrium constant (Kd) of the protective molecule represented by and being 1×10 ⁻⁴ mol/L or more and 1×10 ⁻² mol/L or less ;
A method of forming a metal on a substrate , comprising:

Images