2D titanium carbide MXenes as emerging optical biosensing platforms.

Transition metal carbides/carbonitrides (MXenes), as one of the emerging two-dimensional (2D) materials, have attracted tremendous attention in recent years. Developing MXenes based biosensing platforms is fantastic for the applications of diagnostic and biological research. In this regard, it is pressing need for the synthesis, exfoliation, intercalation, and tuning the surface of MXenes. Compared with the electrochemical implements of MXenes, the optical biosensing applications are in the earlier stage. In this review, the research significance and types of MXenes are introduced followed by the recent progress of synthesis and functionalization of two kinds of titanium carbide (Ti3C2) MXenes including nanosheets (NSs) and quantum dots (QDs). In addition, the special properties and applications in optical biosensing platforms including photoluminescence, electrogenerated chemiluminescence (ECL), surface plasmon resonance (SPR), surface-enhanced Raman scattering (SERS), photoelectrochemical (PEC), colorimetric and photothermal sensors are highlighted. Finally, the possible remaining challenges and future trends of Ti3C2 MXenes in optical biosensing platforms are outlined.