Single plasmon-active optical fiber probe for instantaneous chiral detection.

Abstract

The chiral recognition of organic compounds is of vital importance in the field of pharmacology and medicine. Unfortunately, the common analytical routes used in this field are significantly restricted by time spent and equipment demands. In this work, we propose unprecedented alternative, aimed on enantiomers discrimination and estimation of their concentrations in uncomplicated and instantaneous manner. Proposed approach is based on the creation of optical fiber probe with two pronounced plasmonic bands attributed to gold and silver. The gold or silver surfaces were grafted with moieties, able to enantioselective entrap chiral amines from solution, resulting in a wavelength shift corresponding to each plasmonic metals. As a model compound of chiral amine, we chose the DOPA, also taking in mind its high medical relevancy. For the chiral detection, the optical fiber probe was simply immersed in the analytical solution of DOPA, and the selective shift of gold or silver plasmon band was observed in the reflected light depending on the DOPA chirality. The observed shifts depend on the concentration of DOPA enantiomers. In the case of racemic mixture, the shifts of both plasmonic bands emerge, making possible simultaneous determination of enantiomers concentrations and their ratio. The analytical cycle takes several minutes and requires very simple laboratory equipment.