Nanostars Shine Bright for You: Colloidal Synthesis, Properties and Applications of Branched Metallic Nanoparticles*

Research on metal nanoparticles has been boosted by a wide variety of applications that often require a precise definition of the morphological features at the nanometer scale. Although the preparation (often based on colloid chemistry) of metal nanoparticles with many different shapes and sizes has been developed and optimized for spheres, rods, cubes, platelets and other shapes, the last few years have seen a rising interest in branched morphologies. This review article describes the main synthetic processes for the fabrication of such branched nanoparticles, often termed as nanostars, as well as some of the principal applications that have been found. A special emphasis is given to optical properties related to localized surface plasmon resonances and surface enhanced spectroscopies, for which nanostars have been predicted and demonstrated to shine brighter than any other shapes, thus opening new avenues for highly sensitive detection or biolabelling, among other applications.