Highly Pure Gold Nanotriangles with almost 100% Yield for Surface-Enhanced Raman Scattering

Gold nanotriangle (Au NT), a unique anisotropic-shaped plasmonic nanostructure with distinctive optical, electrical, and catalytic characteristics, has been utilized in a variety of high-technological applications. However, the basic and practical applications of Au NTs are often hindered by size and yield (less than 60%) and engineering a facile and manageable approach to acquire Au NTs with high yields is still challenging. Herein, a simple and rapid seed-mediated method to prepare high-purity Au NTs (up to 97.4%) is proposed by precisely controlling the reaction kinetics. Importantly, there are two key factors to achieve high-yield Au NTs (70%) during the two-growth synthesis: (1) the high concentration of hexadecyltrimethylammonium chloride (CTAC) that can provide a greater binding force on the ⟨111⟩ facet of Au seed and (2) the selective adsorption of potassium iodide (KI) on the ⟨111⟩ facet. Additionally, Au NTs with a wide range of sizes from 58 to 137 nm with a high uniformity can be tailored by a small window parameter regulation. Additionally, it is found that the addition of optimized salts can induce the rapid precipitation of Au NTs to form self-assembled microfibers and the efficient purification of Au NTs with a yield of about 97.4%. Furthermore, the finite difference time domain (FDTD) simulation shows that anisotropic electromagnetic field enhancements and hot spot excitation modes can be generated in different assembling models of Au NTs. Finally, we construct macroscopic two-dimensional (2D) ordered monolayer films of Au NTs through volatilizing self-assembly. As a proof of concept, the ordered Au NT arrays exhibit both high surface-enhanced Raman spectroscopy (SERS) sensitivity and detecting stability compared to random assembling structures and Au NPs. Therefore, we believe that our proposed rapid synthesis and high-yield purification approach of Au NTs would pave a way to prepare designed nanomaterials for a variety of basic and high-technological practical applications.