Si/ZnO nanocomb arrays decorated with Ag nanoparticles for highly efficient surface-enhanced Raman scattering

High-density ZnO nanocombs were first grown on a nanoporous silicon pillar array, and pre-prepared 3D Si/ZnO/Ag nanocomb arrays were employed as substrates for surface-enhanced Raman scattering (SERS). The finite-difference time-domain simulation result shows that two kinds of inter-Ag-NP nanogaps in the geometry create a large number of SERS "hot spots," which contributes to the detection limits for rhodamine-6G as low as 10⁻¹² M and the Raman enhancement factor as large as 10⁹. The linear dependence between the Raman peak intensities and the concentrations of thiram provides a new calibration method for rapid and quantitative detection of trace organic molecules.