Reaction-Modulated\nSurface-Enhanced Raman Scattering\nStrategy for Stereoselective Differentiation and Identification of\nAmino Acids

Surface-enhanced Raman scattering (SERS) sensing of racemates\nis\na remarkably fascinating yet very sophisticated objective because\nof similar physicochemical features of enantiomers. Inspired by the\nenantiomeric selectivity of nucleophilic addition reaction (NAR) toward\namino acids, we herein propose highly effective, robust SERS discrimination\nof d- and l-valine by synergizing asymmetric gold\nnanorods-embedded ZIF-8 nanoparticles (AGNZ) with NAR to engender\nstereoselective molecular fingerprint. Experimental and chemometric\nanalyses disclose that enantioselectivity lies in dual aspects: (i)\nabundant interfacial cavities and 3D hot-spots in AGNZ offer necessary\nconfined asymmetrical surroundings to trigger enantiospecific molecular\nadsorption and interaction affinity, and (ii) the specified NAR drags\nthe racemates adjacent to the interfacial area of AGNZ for maximum\nanalytes–substrate interaction. This strategy is universal\nand can be utilized for the recognition of different amino acid enantiomers.\nImportantly, multiple quantifications of the racemic ratio can be\nrealized with superior prognostic performances. This synergizing strategy\ntherefore provides a significant paradigm shift from traditional methods\nto realize highly effective SERS discrimination of racemates.