Phase-Dependent Fluorescence Quenching Efficiency of MoS2 Nanosheets and Their Applications in Multiplex Target Biosensing

Two-dimensional layered transition-metal dichalcogenide nanosheets have shown great potential in biosensors owing to their unique properties. Here, we exfoliated ultrathin metallic and semiconductive MoS 2 nanosheets based on a chemical exfoliation method. We compared the difference of fluorescence quenching efficiency between metallic and semiconductive MoS 2 nanosheets. We found that the fluorescence quenching efficiency of MoS 2 nanosheets is phase-dependent. The ultrathin metallic MoS 2 nanosheets with larger contents of a 1T-phase structure show higher fluorescence quenching efficiency than semiconductive MoS 2 nanosheets, which can be ascribed to the higher conductivity of metallic MoS 2 nanosheets. On the basis of the excellent fluorescence quenching efficiency of metallic MoS 2 nanosheets and their discriminative adsorption toward single-strand DNA and double-strand DNA, a fluorescent biosensor for multiplex detection of DNA was developed. This fluorescent biosensing platform allows simultaneous fluorescence quenching of two single-strand DNA probes labeled with different fluorophores, resulting in multiplex detection of different DNA sequences in one homogeneous solution with high sensitivity.