Metal fine particles, composition containing the same, and production method for producing metal fine particles

Abstract

The present invention provides metal fine particles which have selective wavelength absorption characteristics in a wavelength region from visible light to near infrared light, and have sharp absorption characteristics, and influences little the surrounding wavelength, and therefore, they yield tones having high chroma. The present invention provides metal fine particles wherein an aspect ratio is in a range from 1.1 to 8.0, a maximum absorption wavelength in plasmon absorption is in a range from 400 nm to 1,200 nm, and an absorption coefficient at a peak position of the maximum absorption wavelength is in a range from 6,000 to 20,000 L/mol·cm (measurement concentration: 1.6×10 −4 mol/L, and solvent:water).

1 . Metal fine particles wherein an aspect ratio is in a range from 1.1 to 8.0, a maximum absorption wavelength in plasmon absorption is in a range from 400 nm to 1,200 nm, and an absorption coefficient at a peak position of the maximum absorption wavelength is in a range from 6,000 to 20,000 L/mol·cm (measurement concentration: 1.6×10 −4  mol/L, and solvent:water).  
     
     
         2 . Metal fine particles wherein an aspect ratio is in a range from 1.1 to 8.0, a maximum absorption wavelength in plasmon absorption is in a range from 550 nm to 1,200 nm, and a half band width of an absorption spectrum at the maximum absorption wavelength is 200 nm or less.  
     
     
         3 . Metal fine particles according to  claim 1 , wherein the metal fine particles are gold nano-rods and a maximum absorption wavelength in plasmon absorption is in a range from 550 nm to 1,200 nm.  
     
     
         4 . Metal fine particles according to  claim 3 , wherein the gold nano-rods are produced by chemically reducing chloroauric acid in a solution and then light reducing, an absorption coefficient at a peak position of the maximum absorption wavelength is in a range from 6,000 to 20,000 L/mol·cm (measurement concentration: 1.6×10 −4  mol/L, and solvent:water), and a half band width of an absorption spectrum at the maximum absorption wavelength is 200 nm or less.  
     
     
         5 . A composition containing the metal fine particles according to  claim 1 .  
     
     
         6 . A composition according to  claim 5 , wherein the composition further contains a dispersing agent containing at least one of a nitrogen atom and a sulfur atom, and a binder.  
     
     
         7 . A production method for producing metal fine particles comprising the steps of: 
 reducing metal ions in an aqueous solution containing a surfactant; and    controlling an aspect ratio of the metal fine particles by obtaining the metal fine particles under conditions in which an acid or alkali is added.    
     
     
         8 . A production method for producing metal fine particles according to  claim 7 , wherein the acid is selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, and hydrobromic acid, and the alkali is selected from the group consisting of sodium hydroxide, potassium hydroxide, and aqueous ammonia.  
     
     
         9 . A production method for producing metal fine particles comprising the steps of: 
 reducing metal ions in an aqueous solution containing a surfactant; and    controlling an aspect ratio of the metal fine particles by performing the reduction reaction while adjusting a solution temperature.    
     
     
         10 . A production method for producing metal fine particles according to  claim 7 , wherein the metal ions are reduced in an aqueous solution containing a surfactant by a method selected from the group consisting of a chemical reduction method, an electrochemical reduction method, a photoreduction method, and a combination of a chemical reduction method and a photoreduction method, and the obtained metal fine particles are metal nano-rods.  
     
     
         11 . A production method for producing metal fine particles according to  claim 7 , wherein the metal ions are reduced in an aqueous solution containing a surfactant by an electrochemical reduction method using an aqueous solution containing at least one selected from the group consisting of surfactants denoted by the following chemical formulas A, B, and C as an electrolyte, and the aspect ratio of the metal fine particles is made small by adding the acid or the aspect ratio of the metal fine particles is made large by adding the alkali.  
         CH 3 (CH 2 ) n N + (CH 3 ) 3 Br −  (n is an integer from 1 to 15)   A  [CH 3 (CH 2 ) n ] 4 N + Br −  (n is an integer from 1 to 15)   B  [CH 3 (CH 2 ) n ] 2 N + (CH 3 ) 2 Br −  (n is an integer from 7 to 17)   C  
     
     
         12 . A production method for producing metal fine particles according to  claim 7 , wherein the metal ions are reduced by a combination of a chemical reduction method using a reducing agent and a photoreduction method, and the aspect ratio of the metal fine particles is made large by adding the acid or the aspect ratio of the metal fine particles is made small by adding the alkali.  
     
     
         13 . A production method for producing metal fine particles according to  claim 12 , wherein the reducing agent in a metal ion aqueous solution is selected from the group consisting of ascorbic acid, citric acid and salts thereof; hydroxylamine hydrochloride, a hydrazine compound, succinic acid, and salts thereof; and an amine, the acid is selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, and hydrobromic acid, and the alkali is selected from the group consisting of sodium hydroxide, potassium hydroxide, and aqueous ammonia.  
     
     
         14 . A production method for producing metal fine particles according to  claim 9 , wherein the aspect ratio of the metal fine particles is made small by increasing the solution temperature of the aqueous solution containing metal ions, or the aspect ratio of the metal fine particles is made large by decreasing the solution temperature of the aqueous solution containing metal ions.  
     
     
         15 . A composition containing metal fine particles produced by the production method for producing metal fine particles according to  claim 7 .  
     
     
         16 . A coating composition, coating, transparent sheet, or film made of the composition according to  claim 5 .  
     
     
         17 . An optical filter material, wiring material, electrode material, catalyst, pigment, cosmetic, near infrared light absorbing material, anticounterfeit ink, electromagnetic interference shielding material, surface reinforcing fluorescence sensor, biomarker, nano-waveguide, recording material, recording element, polarization material, drug supporter for drug delivery system (DDS), biosensor, DNA chip, or test drug, which contains the metal fine particles according to  claim 1 .  
     
     
         18 . An optical filter material, wiring material, electrode material, catalyst, pigment, cosmetic, near infrared light absorbing material, anticounterfeit ink, electromagnetic interference shielding materials, surface reinforcing fluorescence sensor, biomarker, nano-waveguide, recording material, recording element, polarization material, drug supporter for drug delivery system (DDS), biosensor, DNA chip, or test drug, which contains the metal fine particles obtained by the production method for producing metal fine particles according to  claim 7 .  
     
     
         19 . Metal fine particles according to  claim 2 , wherein the metal fine particles are gold nano-rods and a maximum absorption wavelength in plasmon absorption is in a range from 550 nm to 1,200 nm.  
     
     
         20 . Metal fine particles according to  claim 19 , wherein the gold nano-rods are produced by chemically reducing chloroauric acid in a solution and then light reducing, an absorption coefficient at a peak position of the maximum absorption wavelength is in a range from 6,000 to 20,000 L/mol·cm (measurement concentration: 1.6×10 −4  mol/L, and solvent:water), and a half band width of an absorption spectrum at the maximum absorption wavelength is 200 nm or less.  
     
     
         21 . A composition containing the metal fine particles according to  claim 2 .  
     
     
         22 . A composition according to  claim 21 , wherein the composition further contains a dispersing agent containing at least one of a nitrogen atom and a sulfur atom, and a binder.  
     
     
         23 . A composition containing metal fine particles produced by the production method for producing metal fine particles according to  claim 9 .  
     
     
         24 . A coating composition, coating, transparent sheet, or film made of the composition according to  claim 15 .  
     
     
         25 . A coating composition, coating, transparent sheet, or film made of the composition according to  claim 23 .  
     
     
         26 . An optical filter material, wiring material, electrode material, catalyst, pigment, cosmetic, near infrared light absorbing material, anticounterfeit ink, electromagnetic interference shielding material, surface reinforcing fluorescence sensor, biomarker, nano-waveguide, recording material, recording element, polarization material, drug supporter for drug delivery system (DDS), biosensor, DNA chip, or test drug, which contains the metal fine particles according to  claim 2 .  
     
     
         27 . An optical filter material, wiring material, electrode material, catalyst, pigment, cosmetic, near infrared light absorbing material, anticounterfeit ink, electromagnetic interference shielding materials, surface reinforcing fluorescence sensor, biomarker, nano-waveguide, recording material, recording element, polarization material, drug supporter for drug delivery system (DDS), biosensor, DNA chip, or test drug, which contains the metal fine particles obtained by the production method for producing metal fine particles according to  claim 9 .  
     
     
         28 . A coating composition, coating, transparent sheet, or film made of the composition according to  claim 21 .  
     
     
         29 . A production method for producing metal fine particles according to  claim 7 , wherein the reducing and controlling are conducted at least partly simultaneously.  
     
     
         30 . A production method for producing metal fine particles according to  claim 9 , wherein the reducing and controlling are conducted at least partly simultaneously.