Ultrathin transition-metal dichalcogenide nanosheet-based colorimetric sensor for sensitive and label-free detection of DNA

Two-dimensional transition-metal dichalcogenide (TMD) nanosheets have been regarded as a class of promising nanomaterials in various applications due to their outstanding optical, electronic, and catalytic properties. Here, we explored the metal ion-induced optical behavior of four typical TMD nanosheets (WS2, MoS2, WSe2, and MoSe2) prepared via a kitchen blender-assisted shear exfoliation method. Results show that upon the addition of certain amount of metal ions, layered 2H phase TMD nanosheets would aggregate rapidly, resulting in their growth in both planar size and thickness, which leads to the change of their characteristic absorption peak position. Inspired by this phenomenon, a sensitive and label-free colorimetric sensing strategy for DNA detection was develop combined with the discriminative affinity of TMD nanosheets towards single-strand DNA and double-strand DNA. Furthermore, hybridization chain reaction is introduced to achieve higher sensitivity towards DNA detection. We anticipate that this proposed colorimetric sensor would significantly expand the scope of 2D TMD nanosheets and hold great application prospects in DNA sensing strategies in various fields.