Fabrication and Properties of Au Nanoflowers for SERS Substrates

摘要

Nanoscale metal structures are applied widely due to their size effective properties. The nanotechnology boom has resulted in discovery of a host of forms of nanoparticles/ nanoaggregated. One of the current challenges in the chemistry of materials is the elaboration of complex nanoscale structures. Flower-like nanostructures that exhibit unique physical and chemical properties are among the most interesting anisotropic nanomaterials (1-3). Such synthesis of branched and flower-shaped nanomaterials is a fairly recent development. Template-based synthesis (4-5), phenomenon of oriented attachment of primary nanoparticles when surfaces with similar atomic arrangements approach each other (6), and use of specific capping agents to induce anisotropic growth (7-8) are the three principal strategies for generating Au complex structures. Thus far, these methods are able to produce Au multipods with a limited number of tips (less than 10); the control of the size of these particles remains as a challenge. Herein we present a modified galvanic displacement to produce metallic (Au) nanocrystals with flower-like structures. The size of the nanoflowers could be tuned by controlling the reaction conditions at room temperature. These nanoflowers have wide applications such as optoelectronic devices or sensors. Since the first observation of single-molecule level Surface Enhanced Raman Scattering (SERS) from randomly aggregated noble metal nanoparticles, much effort has been made to understand the electromagnetic and chemical mechanisms behind the observed enhancement, and to fabricate structures that exhibiting strong and reproducible SERS activities (9-10).