Focused ion beam-fabricated Au microanostructures used as a surface enhanced Raman scattering-active substrate for trace detection of molecules and influenza virus

摘要

The focused ion beam (FIB) technique was used to precisely fabricate patterned Au microanostructures (fibAu). The effects of surface enhanced Raman scattering (SERS) on the fibAu samples were investigated by adjusting the geometrical, dimensional, and spacing factors. The SERS mechanism was evaluated using low-concentration rhodamine 6G (R6G) molecules, physically adsorbed or suspended on/within the microanostructures. The results indicated that for detecting R6G molecules, hexagon-like microanostructures induced a higher electromagnetic mechanism (EM) due to the availability of multiple edges and small curvature. By decreasing the dimensions from 300 to 150nm, the laser-focused area contained an increasing number of microanostructures and therefore intensified the excitation of SERS signals. Moreover, with an optimized geometry and dimensions of the microanostructures, the relative intensity/surface area value reached a maximum as the spacing was 22nm. An exponential decrease was found as the spacing was increased, which most probably resulted from the loss of EM. The spacing between the microanostructures upon the fibAu was consequently regarded as the dominant factor for the detection of R6G molecules. By taking an optimized fibAu to detect low-concentration influenza virus, the amino acids from the outermost surface of the virus can be well distinguished through the SERS mechanism.