Sensitive and selective chem/bio sensing based on surface-enhanced Raman spectroscopy (SERS)

This paper summarizes our recent progress toward developing anthrax and glucose sensors based on surface-enhanced Raman spectroscopy (SERS). Ag film over nanosphere (AgFON) substrates was used as the SERS sensor platform in both cases. The AgFON substrates have been optimized for near-infrared (NIR) laser excitations by tuning the extinction maximum of their localized surface plasmon resonance (LSPR). Bacillus subtilis spores, harmless simulants for Bacillus anthracis, were studied using SERS. Calcium dipicolinate, a biomarker for bacillus spores, was efficiently extracted from spores and rapidly detected by SERS. A limit of detection (LOD) of ∼2.6 × 103 spores, below the anthrax infectious dose of 104 spores, has been achieved within 11 min. For glucose detection, a mixed decanethiol (DT)/mercaptohexanol (MH) partition layer is used to bring glucose closer to the AgFON surface. Quantitative detection of glucose in bovine plasma, as well as complete and rapid partitioning and departitioning, was demonstrated. The root mean square error of prediction (RMSEP) is 83.16 mg/dL (4.62 mM) with 85% of the validation points falling within the A and B range of the Clarke error grid.