Synthesis Of Anisotropic Gold Nanoparticles And Their Surface-Eenhanced Raman Scattering Properties

In recent years, metal nanoparticles have already attracted the widely attention in biology, medicine, optica, catalysis and eletronics due to the special size and shape of nanostructures. The anisotropic nanoparticles, including of flower-like, branched, and polyhedral, which exhibiting efficient surface-enhanced Raman scattering(SERS) and potential applications due to their unique morphological characteristics. However, a convenient and controllable synthesis of anisotropic nanoparticles is still a big challenge with respect to the mature synthesis technology of flower-like, branched, and polyhedral nanostructure. This research mainly explores the preparation techniques of anisotropic nanoparticles(including of mesoflower-shaped and hexoctahedron nanoparticles) in the aspects of controllable morphology and tunable optical characteristics, as well as the growth process and growth mechanism of the nanoparticles. This paper focuses on the following three aspects:Firstly, this paper provides a facile, one-pot,seedless synthesis method of hydrangea flower-like hierarchical gold nanostructures(Au HFs) with tunable surface topographies and optical properties using ascorbic acid(AA) as a reducing agent of gold salt(HAuCl4) with cetyltrimethylammonium chloride(CTAC) as surfactant. The Au HFs have many advantages, including of the hydrangea flower-like nanostructure, high yield, monodispersity and stability, the tunable particle morphology and optical absorption from the visible to NIR. Due to the highly textured surface with rich hot spots, the Au HFs exhibit a remarkable performance in single-particle SERS.Secondly, the different flower-like Au nanoparticles(Au NFs) can be prepared by putting the silver nitrate(AgNO3) into the above solutions. The morphology and optical properties of particles could be tuned by changing the amount of silver nitrate. A smaller amount of AgNO3 is more conducive to the anisotropic growth of AuNFs, revealing a small amount of irregular flakes grow outward from the previous protrusions, which can greatly increase the SERS enhancement.Thirdly, hexoctahedral gold nanocrystals(HOH AuNCs) are prepared by a seed-mediated method. The tunable particle morphology and optical properties from the NIR to visible can be also mediated by changing the growth temperature and the feeding amount of the reagents. HOH AuNCs can serve as highly sensitive and reproducible SERS substrates.