One-Step Hydrothermal Preparation of Chiral Carbon Quantum Dots and Enantioselective Sensing of Glutamine Enantiomeric Isomers

A novel method for chiral identification of glutamine enantiomers based on chiral carbon quantum dots (cCQDs) fluorescence probe. cCQDs were prepared by a one-step hydrothermal method using L-tryptophan as the carbon source and chiral source, which were spherical nanoparticles exhibiting blue color luminescence. The fluorescence intensity(F) of cCQDs is enhanced or quenched when the addition of chiral enantiomeric glutamine (L/D-Gln), and thus cCQDs, as a fluorescence probe, can be used for enantioselective sensing of the L/D-Gln. The fluorescence enhancement value (∆FE) exhibited good linearity with L-Gln concentration in the range of 0.23-10.0 mM and the limit of detection was 0.14mM. The fluorescence quenching value (∆FQ) showed a good linear relationship with D-Gln concentration in the range of 0.29-10.0mM, and the detection limit was 0.18mM. The mechanism of fluorescence enhancement/quenching was explored by molecular modelling and the type of quenching. The method was applied to the determination of L-Gln content in real samples and the recovery rate was satisfactory. This study provided a novel approach for the synthesis of chiral carbon quantum dots and the recognition of amino acid enantiomers.