Efficient approach to in-situ preparation of anisotropic and assemblable gold nanoparticles mediated by stimuli-responsive PDMAEMA

Nowadays, stimuli-responsive materials have attracted much attention because of their potential applications in various fields, specifically when a plasmonic nanoparticle is chemically bonded to a polymeric chain. On the other hand, preparation of assemblable anisotropic gold nanoparticles is an interesting challenge and also, synthetic methods and tunability of the plasmonic properties are usually multi-step and complicated. Here, poly (N,N-dimethylaminoethyl methacrylate) (PDMAEMA) was used as a stimuli-responsive polymer substrate for in-situ reduction of chloroauric acid (HAuCl4) and synthesis of smart Au-PDMAEMA nanocomposites with anisotropic shapes. pH- and temperature-sensitive PDMAEMA played its role as a reducing, stabilizing and shape controlling agent to produce triangular gold nanoparticles with tunable UV-Vis absorption domain. Effect of some structural parameters like molar ratio of reducing group to Au ions, addition type and seed-mediated growth methods were studied comprehensively. Responsivity of Au-PDMAEMA nanocomposites to some stimuli like temperature and pH and also their reversibility were examined. Optical investigations revealed reversible and reproducible shifts between UV-Vis (550 nm) and near-IR (700 nm) absorptions by triggering with pH and temperature. The introduced strategy may facilitate synthesis of smart plasmonic nanoparticles with multi-responsivity. Assembly and disassembly of triangular plate-like nanoparticles with several stimulants may open up new fields due to their orientation/packing toward self-assembly.