Homochiral metal-organic frameworks functionalized SERS substrate for atto-molar enantio-selective detection

Abstract

In this work, the plasmon-active gold grating functionalized by homochiral metal-organic frameworks (HMOF) L- or D-MOF-6 was proposed as unprecedent tool for enantio-selective SERS-based discrimination. The gold grating surface possesses the homogeneous distribution of plasmon intensity along the active sample area, responsible for excitation of consistent SERS signal. L- and D- lactic acids enantiomers were used for the preparation of enantio-selective surface grafted MOF layer with opposite chiral-entrapping selectivity. The HMOFs films, grafted onto gold gratings provide the selective enantiomers entrapping from solution and contribute to the chemical enhancement of SERS. Obtained SERS substrates were able to selectively entrap the (R)-(+)- and (S)-(−)-methylphenylsulfoxide (model analyte) from solution and recognize them with atto-molecular concentration limits and perfect reproducubility. Moreover, the possibility of enantiomers detection and recognition in their mixtures was also demonstrated with similar recognition limits. The unprecedented detection and enantioselective recognition were further demonstrated on the biorelevant analytes, including complex sample.