Large-area, uniform and low-cost dual-mode plasmonic naked-eye colorimetry and SERS sensor with handheld Raman spectrometer

Abstract

We demonstrated a highly-sensitive, wafer-scale, highly-uniform plasmonic nano-mushroom substrate based on plastic for naked-eye plasmonic colorimetry and surface-enhanced Raman spectroscopy (SERS). We gave it the name FlexBrite. The dual-mode functionality of FlexBrite allows for label-free qualitative analysis by SERS with an enhancement factor (EF) of 10⁸ and label-free quantitative analysis by naked-eye colorimetry with a sensitivity of 611 nm RIU⁻¹. The SERS EF of FlexBrite in the wet state was found to be 4.81 × 10⁸, 7 times stronger than in the dry state, making FlexBrite suitable for aqueous environments such as microfluid systems. The label-free detection of biotin–streptavidin interaction by both SERS and colorimetry was demonstrated with FlexBrite. The detection of trace amounts of the narcotic drug methamphetamine in drinking water by SERS was implemented with a handheld Raman spectrometer and FlexBrite. This plastic-based dual-mode nano-mushroom substrate has the potential to be used as a sensing platform for easy and fast analysis in chemical and biological assays.