Synthesis of Janus Nanorods for Assemblies of Thermoresponsive Rod Pairs

Janus particles offer unique functionality; for example micron-scale Janus spheres are used for electronic paper. At the nanoscale, reproducible, scalable fabrication of Janus particles is one of the key enabling technologies for “bottom-up” assembly processes. For example, selfassembly of Au nanorod pairs created from Au Janus rods would provide a bottom-up, self-limiting assembly pathway alternative to current e-beam lithography methods. Commonly, Janus particles are synthesized using one of two masking concepts, either self masking resulting from directional vapor deposition or substrate masking to block non-directional modification chemistry. Using surface masks and non-directional chemistry, the ligand size was found to provide a limited range of tunability of the extent of asymmetric functionalization. This was found to agree well with geometrical-based theoretical predictions. The extent of asymmetry in the nanoparticle coverage was found to affect the protoassemblies of rods, where the greater the attractive coverage the larger the protoassemblies formed. This approach can potentially enable affordable fabrication of tangible quantities of thermoresponsive nanorods pairs for fundamental and application studies of gold nanorods pair spacing parameters and the effect on optical properties such as surface plasmon resonances.