Gold Nanorod Based NOHMs that Exhibit Tunable Optical and Viscoelastic Properties
Nanoscale Organic Hybrid Materials (NOHMs) are a new class of polymer nanocomposites that are composed of a nanoparticle core and organic corona. This construction leads to a wide range of novel material properties (optical, rheological, thermal, etc.) that can be achieved by controlling the chemical and geometric characteristics of the components. In particular, gold nanorod based NOHMs have been previously shown to exhibit interesting spectral shifts upon shearing, however, this phenomenon is not fully understood and additional investigation is required. Monodisperse gold nanorods (GNRs) of controllable aspect ratio are synthesized using seed mediated growth in the presence of surfactants. By exploiting noble metal chemistry, we show that a thiol terminated oligomer can be grafted on to GNRs to create a self suspending system. The resulting system demonstrates a solid-like behavior with a shear thinning response of the viscosity typical of soft gels and the presence of a responsive and partially reversible optical interaction of the gold particles with new peaks arising in the visible light range upon shearing.