Combination of a rhodamine derived chemosensor and up-conversion excitation nanocrystals for cysteine detection

This paper developed a rhodamine-based chemosensor for cysteine optical sensing. Aiming at improved photostability, up-conversion excitation nanocrystals were constructed, serving as excitation source. After being modified by α-cyclodextrin, these excitation nanocrystals became water dispersible. It was found that their up-conversion emission overlapped well with absorption of our chemosensor, resulting in an efficiency energy transfer between them which was confirmed by emission decay lifetime analysis. Further analysis suggested that the sensing mechanism between our chemosensor and cysteine was a simple complexation one with binding stoichiometry of 1:1. Sensing performance of Nanocrystal:Chemosensor system showed emission "turn-on" effect towards cysteine with good photostability and high selectivity over competing amino acids and thiols.