Experimentally Observed Electronic Coupling between Natively Functionalized 2-D layers of Ti3C2Tx MXenes*

MXenes are a new class of 2-D layered compounds that show promise as a highly tunable material for next generation composites. The electronic properties of MXenes depend on their chemical composition as well as the native surface functional groups that arise during synthesis and processing. Here we present spectroscopic observations of the electronic coupling in few layered MXenes with the topography being verified by atomic force microscopy (AFM). Energy resonances below 2 eV were observed and found to change with laminate thickness. We attribute these to plasmonic resonances that result from the electronic coupling between the different transverse and longitudinal plasmonic modes of individual MXene flakes that have been stacked into larger structures. These resonances were also observed to enhance the Raman spectroscopy response, which proved invaluable for routinely studying the lattice structures of ultrathin MXene flakes. Future applications for MXenes in energy storage and nanoscale optical devices are discussed.