Photodeposition of Molecular Layers on Nanoparticle Substrates

Abstract

We report the photodeposition of polymeric layers of nanometer scale thickness onto silica nanoparticle substrates. This was accomplished by ultraviolet irradiation of a solution of functionalized diacetylene monomers in which the silica nanoparticles were suspended. Following photodeposition, the coated nanoparticles were analyzed using transmission electron microscopy and UV−visible spectroscopy. Highly regular polydiacetylene films with thicknesses from 2.5 to 25 nm were produced. The thickness measurements were facilitated by the attachment of small gold nanoparticles onto the surface of the silica nanoparticle substrates prior to photodeposition, to provide contrast in the final TEM image. UV−visible spectroscopy of the deposited films indicates that approximately 40% less conjugation is present relative to that of macroscopic polydiacetylene thin films grown with the same approach. This process yields a unique “nanolaminate” coating which may be useful in the modification of the physical, chemical, or optical properties of nanoparticles.