Precisely controlled shape and size of gold nanostructures by seed-mediated reduction reaction method

Abstract

Here we present synthesis of different shapes and sizes of Au nanostructures using seed-mediated growth method. The effect of concentration of seed solution (SS), reducing reagent, and capping molecule are investigated. Further, the growth mechanism involved of nanoshapes is discussed. A systematic red shift in the surface plasmon resonance peak observed with the decreasing SS in NP suspension demonstrates the growth of different sizes of NPs. Two surface resonance peaks (TSPR and LSPR) exhibited in the optical spectra of NRs suspension confirms the growth of NRs. The aspect ratio of NR was found increased from 1.8 to 3.2 with increasing the contents of AgNO3. For lower pH, the fixed position of TSPR peak confirms the growth of uniform diameter of NBPs. The increased transverse and longitudinal length of Au NBPs is proposed due to the absorption of more Au(0) ions on the facets of Au seed particles. A broad absorbance pattern revealed in visible to near-infrared region for NSR suspensions was due to the complex response from the branches and plamon response of nanostar core. The Ag + ions combine with the halide significantly influence the shape and growth of NSRs. XRD data revealed that the NRs and NBPs were preferential orientation (111) crystalline rich, whereas NSRs were not abundant in (111) and (200) facets. TEM images confirm the change in shape and size of nanostructures by changing the SS, AgNO3, HCl, and AA in the respective solutions of NPs, NRs, NBPs, and NSRs. A clear lattice fringe in HRTEM images with inter-planner distance ~ 2.27 A corresponds to (111) Bragg reflection and dotted bright circular rings evident the good crystallinity of Au nanostructures with FCC crystal structure. The ability to produce the controlled shape and size of Au nanostructures could be beneficial for solar cell applications to enhance the absorption of electromagnetic radiation in the visible region.