Gold nanoshurikens with uniform sharp tips for chemical sensing by the localized surface plasmon resonance

Creation of uniform sharp tips in noble metal nanostructures is highly desirable for chemical sensing applications that rely on their localized surface plasmon resonance (LSPR), while it remains a great challenge as typically it is not energetically favorable. Herein, we report a robust synthesis route to a novel family of unique shuriken-shaped Au nanostructures with four in-plane sharp tips in high yield and uniformity. The success of the synthesis relies on the anisotropic crystal growth of quasi-planar Au seeds by taking advantage of the capping effect of a ligand on the specific facets, as well as the predominant deposition of Au over its surface diffusion that accounts for the formation of the sharp tips. The resulting Au nanoshurikens show remarkable LSPR in the near-infrared range of the spectrum, which proves to be sensitive to a minor change in the sharp tips, thus enabling superior chemical sensing activity, as demonstrated by detection of mercury of ultralow concentrations. This novel nanostructure promises not only great potential in monitoring mercury in aquatic ecosystems, but also wide applicability to many other sensing scenarios, such as analyzing various chemicals and biologically active species, with excellent sensitivity.