Gold mesoparticles with precisely controlled surface topographies for single-particle surface-enhanced Raman spectroscopy

Abstract

Understanding of the influence of nanotextured surface topographies on surface-enhanced Raman scattering (SERS) is still rather limited, even after intensive research in recent years; this is mainly due to the absence of a synthesis system to control the surface morphologies on metal meso-/nanoparticles. Here, a facile particle-mediated aggregation protocol was reported to synthesize a series of uniform gold mesoparticles with a nanotextured rough surface. The surface topographies can be precisely controlled by varying the temperatures and concentrations of dopa and Au ions. For example, the tips can be well changed from half-sphere to spike, and then to blade, and the size of the tips also can be tuned, such that the thickness of the blade-like tips can be artificially controlled from 9 to 14 nm. Single-particle SERS analysis reveals that the uniform Au mesoparticles with highly nanotextured topography have enhancement factors greater than 1.0 × 10⁸ with narrow distribution. The effect of the precisely controlled mesoparticle topographies on SERS properties was deeply studied using Raman analysis and finite-difference time-domain (FDTD) simulation. The result indicated that a strong electric field will be induced at the tips and slits on the flower-like mesoparticle surface by the confined light in the cavities between the petals. As such, the current protocol opens up avenues for the fabrication of structurally reproducible mesosuperstructure-based SERS sensors.