Reaction-Modulated Surface-Enhanced Raman Scattering Strategy for Stereoselective Differentiation and Identification of Amino Acids

Surface-enhanced Raman scattering (SERS) sensing of racemates is a remarkably fascinating yet very sophisticated objective because of similar physicochemical features of enantiomers. Inspired by the enantiomeric selectivity of nucleophilic addition reaction (NAR) toward amino acids, we herein propose highly effective, robust SERS discrimination of d- and l-valine by synergizing asymmetric gold nanorods-embedded ZIF-8 nanoparticles (AGNZ) with NAR to engender stereoselective molecular fingerprint. Experimental and chemometric analyses disclose that enantioselectivity lies in dual aspects: (i) abundant interfacial cavities and 3D hot-spots in AGNZ offer necessary confined asymmetrical surroundings to trigger enantiospecific molecular adsorption and interaction affinity, and (ii) the specified NAR drags the racemates adjacent to the interfacial area of AGNZ for maximum analytes-substrate interaction. This strategy is universal and can be utilized for the recognition of different amino acid enantiomers. Importantly, multiple quantifications of the racemic ratio can be realized with superior prognostic performances. This synergizing strategy therefore provides a significant paradigm shift from traditional methods to realize highly effective SERS discrimination of racemates.