Fabrication of an insect-like compound-eye SERS substrate with 3D Ag nano-bowls and its application in optical sensor

To enhance the intensity of Raman signal from a novel perspective in bio-inspiration, a SERS substrate similar to the insects' compound eyes was designed. The interface assembly and interface transfer of PS spheres were used to fabricate continuous Ag nano-bowls on the Si micro-cones, which avoids the limitation that the traditional method cannot realize the assembly of Ag nano-bowls on the substrate with obviously undulated structure. This bio-inspired structure is an excellent absorber of light, which greatly enhances the SERS signal intensity. The enhancement factor of 3D Ag nano-bowls is 5.5 times than that of 2D Ag nano-bowls on the flat substrate. At the same time, this bio-inspired SERS substrate was applied to the quantitative and qualitative detection of Hg²⁺, and its detection limit for Hg²⁺ can reach to 10⁻¹¹ M. Adding the bio-inspired concept to the design of the SERS substrate will provide a new insight to realize the highly sensitive Raman detection.