Shape-controlled synthesis of gold nanoplates and their self-assembly by repulsive electrostatic interactions

This study focuses on understanding the growth and control of the gold nanoplates by seed-mediated growth approach. These monodispersive size-controlled gold nanoplates have the average thickness of 8-10 nm and average size tunable from 70 to 150 nm, exhibiting strong surface plasmon absorption in the near infrared (NIR) region. For the gold nanoplates formation, the seeds serve as nucleation sites, ascorbic acid (AA) serves as a new reductant to reduce hydrogen tetrachloroaurate (HAuCl4), surface activity system cetyltrimethylammonium bromide (CTAB) and potassium iodide (KI) are critical factors. X-ray diffraction (XRD) and selected-area electron diffraction (SAED) analyses reveal that gold nanoplates with the (111) lattice plane as the basal plane are single crystals. CTAB are absorbed on the surface of the (111) lattice plane of the single crystals, accounting for self-assembled monolayer and head-to-head arrays. The two arrays have been shown to serve as effective surface-enhanced Raman scattering substrates using Niel blue A (NBA) sulfate as Raman report molecule.