Dual Sensing Arrays for Surface Plasmon Resonance (SPR) and Surface-Enhanced Raman Scattering (SERS) Based on Nanowire/Nanorod Hybrid Nanostructures

A multifunctional sensing array with gold nanowire-nanorod hybrid nanostructures for dual detection of surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS) is presented. The cost-effective and arrayed nanostructures are made simply onto plastic films using hot-embossing nanoimprint lithography. Five different hybrid nanostructures are studied and compared by measuring SERS enhancement factor and SPR thickness sensitivity. The combination of nanowire and nanorod structures in specific arrangement and quantities of nanorods can not only enhance the SERS effect but also further increase the SPR thickness sensitivity. The area percentage of nanorods of 16.51% can achieve the highest SPR thickness sensitivity and 10(6) SERS enhancement. On comparison of the nanowire structure, the SERS signal and SPR thickness sensitivity of nanowire/nanorod hybrid nanostructure are increased up to 6 times and 2 times simultaneously. The estimated SERS enhancement factor and SPR thickness sensitivity are 2.82 x 10(6) and 0.74 (nm/nm), respectively. The enhanced sensitivity is attributed to the increased nanorods contributing to dense hot spots and the reduced SPR evanescent length caused by the localized surface plasmons. These results are verified by finite-difference time-domain (FDTD) calculations. Such low-cost SPR-SERS chips for multifunctional chemical analysis can increase the reliability of biological detection and broaden sensing applications.