High-refractive-index tin sulfide core–shell spheres for photonic applications

We describe the fabrication of core–shell colloidal spheres composed of a shell of tin sulfide and a core of polystyrene. The tin sulfide shell is deposited on micrometer-sized latex spheres using a sonochemical technique. By angle-dependent light scattering and electron microscopy, we find that the refractive index of the shell is 3.0 at a wave length of 1064 nm, and the shell’s thickness is controllable in the range of 30–60 nm. The resulting spheres have a narrow distribution of sizes, are stable in aqueous suspension, and are very strong scatterers in the near infrared with potential application in photonic band gap materials or other photonic devices.