Simultaneous and Reversible Triggering of the Phase Transfer and Luminescence Change of Amidine-Modified Carbon Dots by CO 2 .

The ability to reversibly manipulate the surface nature of luminescent nanoparticles upon external stimulation enables the development of advanced optical probes for biological sensing and data encoding. Herein, we report the synthesis of a new class of smart carbon dots (CDs) via surface modification of amine-enriched CDs with CO-responsive groups of amidine. We present that alternative CO and N bubbling can not only lead to a reversible phase transfer of the CDs between an organic phase and an aqueous phase but also give rise to a corresponding reversible luminescence change between blue and cyan-green. We attribute these observations to changes in both the surface chemistry and the emission states of the CDs triggered by the alternative CO/N introduction. We also find a similar luminescence change of the CDs upon alternative exposure to a humid vapor of CO and a mixture of NH and N at room temperature, allowing them to be used as a new class of optical materials for optical encoding.