Session:

Two-dimensional MXenes have demonstrated promising results in catalysis, battery storage, electromagnetic shielding, and more, however, these materials tend to oxidize which has devastating impacts on overall performance. Passivation against oxidation as well as precise control over the chemical terminations and optoelectronic behavior is critical for scalable, widespread applications. Herein, we functionalized exfoliated MXene (Ti₃C₂T_x) surfaces with organosilanes to change local electron density based on the inclusion of electron-donating or electron-withdrawing groups. Ultraviolet photoelectron spectroscopy (UPS) quantified valence-band and Fermi energies for the resulting derivatized Ti₃C₂T_x thin films. UPS reveals 1 eV shifts in band-edge positioning based on interfacial dipoles resulting from covalent organosilane attachment. Moreover, a combination of transient absorption (TA) and terahertz (THz) spectroscopy characterize the interplay between surface chemistry and the resulting changes in electronic structure and carrier dynamics. These results inform current research efforts which aim to exploit chemical and optoelectronic tunability via mixed organic monolayers with orthogonal reactivities at Ti₃C₂T_x edges versus terraces. Candidate molecular organics to impart passivation against oxidatation, optoelectronic tunability, and chemical handles for tethering to polymers and other surfaces include silanes, catechols, and alkyl triphosphates as well as polyanionic salts. We discuss these results in the context of electromagnetic shielding, catalysis, chemical sensing, and energy applications

Co-Author(s): Erika Colin-Ulloa (Worcester Polytechnic Institute), Andrew Fitzgerald (Worcester Polytechnic Institute), Kateryna Kushnir (Worcester Polytechnic Institute), Rebecca Ramthun (Worcester Polytechnic Institute), Kiana Montazeri (Drexel University), Mary Hassig (Drexel University), Ken Ngo (U.S. Army Research Laboratory), Joshua Uzarski (U.S. Army Research Laboratory), Michel Barsoum (Drexel University), Lyubov Titova (Worcester Polytechnic Institute), Ronald Grimm (Worcester Polytechnic Institute)

Julia Martin

Appearances