A reversible fluorescence nanoswitch based on carbon quantum dots nanoassembly for detection of pyrophosphate ion

A convenient and reversible nanoswitch with the assistance of cerium ions based on aggregation and disaggregation of carbon quantum dots was developed to achieve highly sensitive detection of pyrophosphate ions. Two states including aggregation state and disaggregation state corresponding to fluorescence on and off signaling can be readily switched in a reversible way. The aggregation state is resulted from large nanoassembly formed by carbon quantum dots and cerium ions due to their strong complexation affinity. The disaggregation state comes from competitive combination between cerium ion and pyrophosphate ion. The PPi ion severs as the external chemical stimulus to CQDs/Ce(III) nanoassembly, and its quantity is responsive to fluorescence intensity of the sensing system. Quantitative evaluation of PPi in a broad range from 0.3 to 29.7   μM with the detection limit of 0.1   μM can be realized in this way. The PPi detection in human HeLa cells was also assessed, and fluorescence switching between ON and OFF can be readily observed in response to presence and absence of PPi.