Two emission turn-on optical chemosensors for cysteine detection using up-conversion nanocrystals as excitation host: Synthesis, characterization and performance

Abstract In this paper, two rhodamine derived chemosensors were synthesized for cysteine optical recognition. Up-conversion NaYF 4 :Yb 3+ /Er 3+ nanocrystals were modified as hydrophilic ones by α-cyclodextrin (α-CD) and used as excitation host, hoping to improve photostability of our chemosensors. Spectral analysis and emission decay lifetime comparison suggested that there was an efficient energy transfer between our excitation host and chemosensors. Job’s plot analysis indicated a simple recognition mechanism with binding stoichiometry of 1:1. Chemosensor emission was increased with increasing cysteine concentration, showing good selectivity and linear sensing response. The correlation between sensing performance and chemosensor molecular structure was discussed. Sulfur substituent effect improved selectivity of chemosensors.