Two rhodamine derived chemosensors excited by up-conversion lattice for cysteine detection: Synthesis, characterization and sensing behavior

• Two rhodamine-derived chemosensors were reported for cysteine optical sensing.
• NaYF4 lattice was applied as excitation host to minimize photobleaching effect.
• The recognition mechanism was a simple one with binding stoichiometry of 1:1.
• Emission “off–on” effect towards cysteine was observed with good photostablity.
• S substituent was found positive to improve selectivity.

In this paper, two chemosensors derived from rhodamine were reported for cysteine optical recognition. An up-conversion NaYF4 lattice was applied as excitation host to minimize chemosensor photobleaching. This NaYF4 lattice was firstly modified with α-cyclodextrin, making it water dispersible. It was found that chemosensor absorption matched well with host emission. The energy transfer between this excitation host and our chemosensors was analyzed and confirmed by their spectral analysis and emission decay lifetime comparison. Detailed analysis suggested that the recognition mechanism between our chemosensors and cysteine was a simple one with binding stoichiometry of 1:1. Our chemosensors showed emission “off–on” effect towards cysteine with good photostability. Maximum sensitivity was obtained as 7.90 for our chemosensors with a linear working curve. S substituent was found positive to improve selectivity.

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