Dimerizing DNA-AgNCs via a C–Ag+–C structure for fluorescence sensing with dual-output signals†

The unique insertion capability of Ag⁺ into cytosine–cytosine (C–Ag⁺–C) mismatch-base pairs enables precise fabrication of DNA-trapped silver nanoclusters (DNA-AgNCs) through varying the DNA sequences, thereby offering precise assembly of DNA-AgNCs and demonstrating great fluorescence applications. However, most of the DNA-AgNC-based fluorescence sensors have a single output signal. Herein, we developed a dimerized DNA-AgNC system through C–Ag⁺–C connection at the 3′-end of a designed DNA. The formation and crack-up of C–Ag⁺–C endows DNA-AgNCs with the ability to identify Ag⁺ and cysteine (Cys) with dual-output signals, changed fluorescence intensity (FI) and wavelength-shift in NIR emission around 815 nm via photoinduced electron transfer (PET), respectively. Superior linearity of FI for Cys and Ag⁺ concentrations was demonstrated. Meanwhile, the practical utility of this platform was also successfully verified in milk and lake water.