Highly sensitive and uniform surface-enhanced Raman spectroscopy from grating-integrated plasmonic nanograss

Surface-enhanced Raman scattering (SERS) spectroscopy has found a wide range of applications in biomedicine, food safety and environmental monitoring. However, to date, it is difficult for most SERS substrates to provide an extremely sensitive and highly uniform Raman response simultaneously. Here, we developed a sensitive and uniform SERS sensing strategy based on grating-integrated gold nanograsses (GIGNs), which can amplify the SERS signal up to 10-fold compared to the nanograss without grating (namely on the flat substrate) experimentally. Numerical simulation results show that such an improvement of SERS sensitivity arises from the enhanced hotspots relying on the strong coupling between the localized surface plasmon resonances of individual stripe-regulated gold nanorod assemblies and Wood's anomalies in air and dielectric grating. Importantly, these hotspots on the substrate can be flexibly tailored by adjusting the height and periodicity of the loaded grating. The SERS performances of the GIGNs have further been successfully demonstrated with the label-free detection of adenine and cytosine (DNA bases) molecules at the nanomolar level. Moreover, the GIGNs also presented the uniform spot-to-spot and sample-to-sample SERS signals of the analyte molecules (relative standard deviations down to ∼11% and 13%, respectively). These advantages suggest that our GIGN substrates are of great potential for SERS-related sensing.