Self-assembly and tunable plasmonic property of gold nanoparticles on mercapto-silica microspheres

We report the self-assembly behavior and tunable plasmonic property of gold nanoparticles on the surface of mercapto-silica colloidal spheres. The mercapto-silica spheres provide a quasi two-dimensional surface for nanoparticle immobilization through the strong gold-thiol interactions, making it convenient to control the interparticle separation by varying both the length of the capping ligands and the molar ratio of gold nanoparticles to the supporting mercapto-silica microspheres. With the ability to fine tune the interparticle separation and consequently the strength of the electromagnetic coupling, we demonstrate a high degree of control over the plasmon resonance property of the resulting composite microspheres. The colloidal form of the assembled nanostructures promises broad applications in which tailored plasmonic property and solution dispersibility are required.