A tip–gap mesh-like bilayer SERS substrate for highly sensitive detection

Abstract

Tips of noble metal nanostructures and the gaps between closely packed noble metal nanostructures are widely claimed as hot-spots for SERS sensing. A significant amount of effort and expertise has been devoted to the reformation and maximum utilization of the “tips” and “gaps”. However, most studies focus on the “tips” or the “gaps” separately. Here we report a novel SERS substrate that contains a particular mesh structure of curved-edge gold nanocubes (CENCs) and Au nanospheres (Au NSs), one of the tips of CENCs inserted into the gaps between three closely packed Au NSs. Meanwhile, a facile and time-saving novel protocol has been proposed to fabricate this mesh structure in the form of a bilayer SERS substrate. The as-fabricated substrate exhibited extraordinary SERS sensitivity for malachite green (MG) and melamine, which could be attributed to the tip–gap mesh structure. The detection limit is as low as 10⁻¹² M and 10⁻⁹ M, respectively.