Self-assembly of nanoparticles into macroscopic high-density, monolayer films

Abstract

A monolayer film of nanoparticles can formed from a fluid mixture by combining nanoparticles dispersed in water with a water-miscible organic solvent and a molecular ligand comprising a head group with affinity for the nanoparticle, and introducing the fluid mixture to a substrate in the presence of an air/fluid interface, thereby causing a monolayer film of nanoparticles to form on the substrate. Such monolayers films can include metallic nanoparticles such as gold, and possess substantially uniform spacing over at least a one centimeter length scale.

What is claimed is: 
     
         1 . A monolayer film comprising metallic nanoparticles having substantially uniform spacing over at least a one centimeter length scale. 
     
     
         2 . The monolayer film of  claim 1 , having consistent edge-to-edge particle spacing of less than one particle diameter. 
     
     
         3 . The monolayer film of  claim 1 , wherein the metallic nanoparticles are crosslinked together. 
     
     
         4 . The monolayer film of  claim 1 , wherein the film exhibits a positive, refractive index of near zero at a visible wavelength. 
     
     
         5 . A surface-enhanced Raman scattering (SERS) substrate comprising a monolayer film of  claim 1 . 
     
     
         6 . The monolayer film of  claim 1 , wherein said nanoparticles are metallic. 
     
     
         7 . The monolayer film of  claim 1 , wherein said nanoparticles are gold. 
     
     
         8 . The monolayer film of  claim 1 , said nanoparticles have spherical or rod-shaped geometry. 
     
     
         9 . The monolayer film of  claim 1 , in a condition of having been made by:
 forming a fluid mixture by combining a plurality of nanoparticles dispersed in water, a water-miscible organic solvent, and a plurality of molecular ligands comprising head groups having affinity for the nanoparticles; and   introducing the fluid mixture to a substrate in the presence of an air/fluid interface, thereby causing a monolayer film of nanoparticles to form on the substrate,   wherein the steps of forming the fluid mixture and introducing said fluid mixture to a substrate in the presence of the air/fluid interface are sufficient to cause formation of the monolayer film of nanoparticles.