Silver Nanoplates with Special Shapes: Controlled Synthesis and Their Surface Plasmon Resonance and Surface-Enhanced Raman Scattering Properties

Shape-controlled synthesis of metal nanostructures has opened many new possibilities to design ideal building blocks for future nanodevices. In this work, new types of monodisperse silver nanoplates with complex shapes, namely, a disklike shape and flowerlike shapes, were controllably synthesized in high yield by reducing [Ag(NH3)2]+ with ascorbic acid in the presence of silver seed at room temperature. Unlike previous methods for synthesizing the silver nanoplates in the presence of cetyltrimethylammonium bromide (CTAB) micelles, the use of the precursor [Ag(NH3)2]+, other than Ag+, provides a flexible strategy to control the procession of the reduction reaction in a mild way. These silver nanoplates with shapes of disk and flower were shown to possess surface plasmon resonance (SPR) that directly relates to their geometric shapes. As a result of their high anisotropy in shape, the flowerlike silver nanoplates exhibit excellent surface-enhanced Raman scattering (SERS) enhancement ability relative to spherical silver nanoparticles and the disklike silver nanoplates. We believe that with the efficient synthesis and excellent SERS enhancement ability, these novel flowerlike silver nanoplates may find potential applications for biological sensing and labeling systems

Oriented Attachment-Based Assembly of Dendritic Silver Nanostructures at Room Temperature

How particles aggregate into an interesting dendritic structure has been the object of research for many years because of its importance in understanding physical processes involved and in designing novel materials. In this work, we for the first time describe an oriented attachment-based assembly mechanism for formation of different types of dendritic silver nanostructures at room temperature. It is found that the concentration of both AgNO3 and p-aminoazobenzene (PA) molecules has a significant effect on the formation and growth of these novel nanostructures. Characterization by transmission electron microscopy (TEM) clearly shows that the dendritic silver nanostructures can be obtained through the preferential oriented growth along a crystallographically special direction. Interestingly, we observe that the oriented attachment at room temperature can also take place between relatively large single-crystalline silver particles with a diameter range from 20 to 60 nm, which may provide a new possibility for the design of novel metal nanostructures by using large metal nanoparticles as building blocks at room temperature. Moreover, a surface-enhanced Raman scattering (SERS) technique is used to investigate the role of PA molecules during the growth of the dendritic silver nanostructures