Experimental and theoretical investigation for a hierarchical SERS activated platform with 3D dense hot spots

Hot spots generated from the ultra-small nanogaps will tremendously contribute to the strong electromagnetic field. Therefore, the establishment and design of nanogaps are extremely significant. Here, a hierarchical structure, AgNPs/bilayer graphene/Au nanonet, was proposed to form the dense three-dimensional (3D) hot spots and demonstrated in experiment and theory. Numerous nanometer gaps in the complex Au nanonet structure (∼8.67 nm) and in AgNPs/Au nanonet isolated by bilayer graphene (0.64 nm) were achieved, which is much beneficial for the obtainment of the hot spots. Based on this SERS substrate, an excellent SERS activity (EF ∼ 9.1 × 109), high sensitivity (10−13 and 10−12 M respective for Rhodamine 6G (R6G) and crystal violet (CV)), and SERS signals homogeneity, outstanding reproducibility (maximum intensity deviation from substrate to substrate ∼10.43%) were obtained, which can be attributed to the abundant lateral and vertical hot spots introduced by the hierarchical structure. Moreover, the proposed SERS substrate was used to sensitively detect the harmful Malachite green (MG), which exhibits a great prospect as a potential SERS sensor in food safety field and biochemical molecules.