A sensitive colorimetric chiral recognition for thiol-containing amino acids based on NIR plasmonic MoO3-x nanoparticles

Colorimetric chiral recognition has attracted much attention due to its advantages of facile operation and quick response compared with conventional methods. However, its applicability and sensitivity are remaining challenges. Herein, we develop a universal, high-throughput and sensitive colorimetric chiral recognition and sensing method for discriminating chiral thiol-containing amino acids via sonication of a mixed solution of MoO3 nanoparticles and enantiomers. The enantiomeric type could be rapidly recognized using the color discrepancy of the MoO3-x colloid nanoparticles, due to the different concentrations of oxygen vacancies caused by the different degrees of coordination interaction between the MoO3-x nanoparticles and the carboxyl groups from the enantiomer, which could be certified by investigation using quasi in situ spectroscopy. The mechanism of different coordination interactions between the MoO3-x nanoparticles and the enantiomer might be caused by different competitve outcomes between coordination interactions and intermolecular hydrogen bonds on reaction with carboxyl groups due to the different intensities of the intermolecular hydrogen bonds of the chiral enantiomers. Moreover, the colorimetric sensing system based on modified MoO3-x nanoparticles exhibited a detection limit for l-cysteine of 43 nM, which is one order of magnitude lower than current colorimetric probes. This work provides a new inorganic nanoparticle system for universal and high-throughput colorimetric chiral recognition and sensing, and gives insight into the formation mechanism of plasmonic MoO3-x nanoparticles.