Multi-hot spot configuration on urchin-like Ag nanoparticle/ZnO hollow nanosphere arrays for highly sensitive SERS

Abstract

Urchin-like Ag nanoparticle (NP)/ZnO hollow nanosphere (HNS) arrays were fabricated employing a simple, low cost and wafer scale method consisting of nanosphere lithography (NSL) and solution processes. This three-dimensional (3D) multi-hot spot decorated nanocomposite presents an as high as 10⁸ Raman enhancement using Rhodamine 6G (R6G) as the probe with the concentration down to 10⁻¹⁰ M. The high density hot spots in a unit area and strong field intensity around each individual hot spot in 3D layout are believed to be the major reasons for this high sensitivity Raman phenomenon, which is further proved by the theoretical simulation results. Given its high Raman sensitivity and good reproducibility in a large area, this urchin-like Ag NP/ZnO HNS hybrid nanoarray can be reasonably proposed to be used as a SERS substrate in practical applications, including bio-sensing, materials characterization, environmental science and so on.