Synthesis and characterization of flexible, composite, nanorod nunchucks†

Nanowires have seen a host of new applications in recent years from self-propulsion and transportation of colloidal cargo, to energy generation, biosensing, and the fabrication of advanced optical and acoustic devices. One factor that has undoubtedly contributed to the rise of nanowire technology has been the ability to grow these nanowires and modify their surfaces via a variety of methods. Recently, Ozin and coworkers reported the first synthesis of nanorod structures with well-defined flexible regions. Wang and coworkers followed by publishing a second, simpler synthetic procedure for making flexible nanorods in a communication that focused on the applications of the rods rather than a detailed characterization. This paper explores the makeup of these as-yet ill-defined flexible nanorods and describes a related method to prepare a new type of more robust, reinforced flexible nanorods. Flexible nanorods were prepared by a method similar to that reported by Wang and coworkers (see Methods). Briefly, when three-segmented gold-silver-gold, {Au-Ag-Au}, nanorods that had been synthesized via the template method were placed in solutions of dilute H2O2 ( 1% v/v) and imaged under a microscope, their central sections became transparent over the course of a fewminutes. (Fig. 1, Supporting Video 1). Although the central sections of these partially dissolved {Au/Au} nanorods could not be observed directly via optical microscopy, the central region was obviously still present in some form, since the two gold ends of the rods remained translationally paired in dilute peroxide even after enduring the randomization associated with Brownian motion in dilute hydrogen peroxide for 24 h (Supporting Video 2). In addition, these nanorods with their flexible, transparent centres remained intact even when subjected to the chaotic fluid motions associated with gentle pipette transfers.