Authors: R.I. MacCuspie, K. Park, R. Naik, R.A. Vaia
Affilation: Air Force Research Lab, United States
Pages: 762 - 765
Keywords: janus, gold nanorod, rod pairs, nanoparticle assemblies
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, self-assembly of Au nanorod pairs created from Au Janus rods would provide an alterative resonance structure for near IR negative index of refraction (NIM) structures currently created by e-beam lithography. 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. Using a thermoresponsive pair-linker material, such as P-NIPAAM, was also examined to determine if thermoresponsive properties of a linker is retained when bound by more than one nanoparticle. Finally, demonstration that the synthesis of self-assembling nanorods pairs is scalable enables affordable synthesis of enough rod pairs to characterize bulk material properties such as negative index of refraction in wedges of materials. This approach can potentially enable affordable fabrication of tangible quantities of thermoresponsive nanorods pairs for fundamental and application studies of novel near IR NIM materials.