Figure 1. Schematic of Q3D-PNAs SERS optofluidic system and hierarchical zwitterionic surface modifications.

(a) Schematic of SERS optofluidic system incorporating a Q3D-PNAs SERS substrate to provide fingerprint spectra of analytes and quantitative, real-time monitoring. (b) Schematic of hierarchical pCBAA-based zwitterionic non-fouling modification on the SERS-active surface. Top: mixed SAM containing initiators and ‘attracting' molecules, which have terminal functional groups that physically attract analytes to the surface for direct SERS detection. Bottom: mixed SAM containing initiators and ‘probing' molecules (Raman reporters), which have functional groups that chemically interact with analytes to facilitate indirect analyte detection by monitoring changes in the SERS spectra of the probes.