Fluorescent particle, with semiconductor nanoparticles dispersed therein, fabricated by the sol-gel process

Abstract

An object of the present invention is to prepare a fine particle with high durability and high brightness, in which semiconductor nanoparticles are assembled. The present invention provides fluorescent fine particles comprising Cd- and Se-containing semiconductor nanoparticles dispersed in silicon-containing fine particles, wherein the average particle size of the silicon-containing fine particles is 20 to 100 nm, and the number of semiconductor nanoparticles dispersed in the silicon-containing fine particles is 10 or more.

1 . Fluorescent fine particles comprising Cd- and Se-containing semiconductor nanoparticles dispersed in silicon-containing fine particles,
 wherein the average particle size of the silicon-containing fine particles is 20 to 100 nm, and the number of semiconductor nanoparticles dispersed in each silicon-containing fine particle is 10 or more.   
     
     
         2 . The fluorescent fine particles according to  claim 1 , wherein the average particle size of the silicon-containing fine particles is 40 to 100 nm, and the number of semiconductor nanoparticles dispersed in each silicon-containing fine particle is 20 or more. 
     
     
         3 . The fluorescent fine particles according to  claim 1 , wherein the semiconductor nanoparticles dispersed in each silicon-containing fine particle are regularly arranged. 
     
     
         4 . The fluorescent fine particles according to  claim 1 , wherein the PL efficiency is 20% or higher. 
     
     
         5 . The fluorescent fine particles according to  claim 1 , wherein the PL efficiency is 20% or higher when the semiconductor nanoparticles are dispersed at a concentration of 10 nmol/L in a pH 7.4 solution of HEPES (2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid) serving as a Good's buffer. 
     
     
         6 . The fluorescent fine particles according to  claim 1 , wherein after the semiconductor nanoparticles are dispersed in a pH 7.4 solution (HEPES concentration of 10 mmol/L) of HEPES (2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid) serving as a Good's buffer, at a concentration of X nmol/L, and maintained at room temperature for 15 hours, Y nanograms that indicate the dissolved amount of Cd in the HEPES solution (the weight of dissolved Cd in a solution of 1 mL) satisfies 10×Y/X<1. 
     
     
         7 . The fluorescent fine particles according to  claim 1 , wherein the semiconductor nanoparticles are CdSe and/or CdSe/ZnS in which CdSe is coated with ZnS. 
     
     
         8 . The fluorescent fine particles according to  claim 1 , having a silicon-containing layer which has a thickness of 2 nm or more. 
     
     
         9 . The fluorescent fine particles according to  claim 1 , comprising on the surface at least one selected from the group consisting of COOH, NH 2 , SH, salts thereof, and groups originated from polyethyleneglycol. 
     
     
         10 . The fluorescent fine particles according to  claim 1  for fluorescent probes. 
     
     
         11 . The fluorescent fine particles according to  claim 1  for electronic materials. 
     
     
         12 . The fluorescent fine particles according to  claim 1 , wherein the fluorescent fine particles exhibit electroluminescence and/or cathodeluminescence. 
     
     
         13 . A method of preparing the fluorescent fine particles according to  claim 1 , comprising the steps of:
 (A) adding a metal alkoxide (1) to an organic solvent in which Cd- and Se-containing lipophilic semiconductor nanoparticles are dispersed, and stirring the mixture, thereby obtaining organic solution A;   (B) mixing aqueous solution B containing a metal alkoxide (2) whose hydrolysis rate is lower than that of the metal alkoxide (1) with the organic solution A and stirring the mixture, thereby obtaining an semiconductor nanoparticle assembly; and   (C) adding a solution containing a metal alkoxide (3) to an alkaline aqueous solution containing the semiconductor nanoparticle assembly, thereby forming a coating layer on the surface of the semiconductor nanoparticle assembly.   
     
     
         14 . The method of preparing fluorescent fine particles according to  claim 13 , wherein the metal alkoxide (2) is a compound represented by Formula (II):
   X n —Si(OR 2 ) 4-n   (II)
   wherein X represents a group represented by CH 2 ═CH—, a group containing oxirane, a group represented by H 2 NC m H 2m —, a group represented by CH 2 ═C(CH 3 )COOC p H 2p —, a group represented by HSC q H 2q —, or a phenyl group; R 2  represents a lower alkyl group; n is an integer of 1, 2, or 3; m is an integer of 1 to 6; p is an integer of 1 to 5; and q is an integer of 1 to 10.   
     
     
         15 . The method of preparing fluorescent fine particles according to  claim 13 , wherein heating is performed during Step (C). 
     
     
         16 . A method of preparing the fluorescent fine particles according to  claim 1 , comprising the steps of:
 (A1) adding a metal alkoxide (1) and a metal alkoxide (2) whose hydrolysis rate is lower than that of the metal alkoxide (1) to an organic solvent in which Cd- and Se-containing lipophilic semiconductor nanoparticles are dispersed, and stirring the mixture, thereby obtaining organic solution A; and   (B1) adding a metal alkoxide (3) and an alkaline aqueous solution to the organic solution A, thereby forming a semiconductor nanoparticle assembly.   
     
     
         17 . A method of preparing the fluorescent fine particles according to  claim 1 , comprising the steps of:
 (A2) adding two types of metal alkoxides to a non-polar solvent in which Cd- and Se-containing lipophilic semiconductor nanoparticles are dispersed, and stirring the mixture, thereby obtaining organic solution X; and   (B2) bringing the organic solution X into contact with solution Y containing a metal alkoxide and water so as to transfer the semiconductor nanoparticles in the organic solution X to the solution Y.