Molecularly-mediated assembly of gold nanoparticles

The understanding of the interparticle interactions and reactivities is essential to the exploitation of the unique optical, electronic, and chemical or biological properties of gold nanoparticles in many areas of nanotechnology. This paper describes findings of a comparison of optical properties of molecularly-mediated assemblies of gold nanoparticles where the interparticle interactions and spatial properties are defined by molecular mediators and templates. The changes of the surface plasmon resonance band of the assemblies of gold nanoparticles mediated by several different types of molecular mediators, including multidendate methylthiosilane thioether, homocysteine, 1-(4-methyl)-piperazinyl fullerene, and indolenine cyanine dye, are compared. In the assembly process, the size of individual Au nanoparticles and the volume fraction of gold nanoparticles in the solution should remain largely constant, whereas the interparticle distance changes, which leads to changes in the interparticle dielectric medium constant or refractive index. The changes in the SP band in relation to the change in effective refractive index are discussed, along with their implications to assembly sizes, interparticle interactions, and potential applications in designing electrical and optical sensors.