Visible to infrared tunable plasmonic nanoantennae via directed assembly

Radio- and microwave antennae are fundamental building blocks in modern technologies. As the miniaturization of devices continues down to nanometer length scales, the need to sense and signal using nanoantennae has become vital to enabling disruptive nanotechnologies. Yet, to-date, the widespread use of nanoantennae has been limited due in part to the inability to create these structures in large, uniform quantities with nanoscale precision. Here, we present a generalized approach to solve this longstanding issue by ‘gluing’ small aspect ratio gold nanorods together end to end with molecular linkers forming linear chains and ‘welding’ the chains together upon exposure to femtosecond laser pulses, producing trillions of infrared plasmonic nanoantennae per minute. We report experimental tuning ranges of over 2,000 nm from visible to infrared wavelengths. We also experimentally show that the nanoantenna absorption peak depends linearly on the chain length, in agreement with simulations, providing a straightforward means to understand and predict the infrared response of these materials.