Plasmon spectroscopy for the determination of Ti3C2Tx MXene few layer stacks architecture

International audienceAbstract Like many 2D materials, numerous properties of MXene multilayers, and especially the most popular one Ti 3 C 2 T x , have been shown to significantly depend on their architecture, i.e. the number of layers and interlayer distance. These structural parameters are thus key elements to be characterized for the analysis of MXene properties. Focusing on valence electron energy-loss spectroscopy (VEELS) as performed in a transmission electron microscope (TEM), and using density functional theory (DFT) simulations, we here analyze the layer dependent large changes in the VEEL spectra of Ti 3 C 2 T x multilayers as a probe of their total thickness, and emphasize the bulk plasmon energy sensitivity to interlayer distance. Together these findings allow to directly quantify the absolute number of layers in a Ti 3 C 2 T x stack up to ∼10 nm thickness and give access to interlayer distance modifications with sub-angström sensitivity, evidencing VEELS as a powerful method for the characterization of MXene multilayers on the nanometer scale. We expect these results to be relevant for the study of structure/properties correlations in this class of materials, especially with the development of in situ or environmental TEM experiments

Electronic Structure Sensitivity to Surface Disorder and Nanometer-Scale Impurity of 2D Titanium Carbide MXene Sheets as Revealed by Electron Energy-Loss Spectroscopy

International audienceTwo-dimensional (2D) carbides and/or nitrides (so-called MXenes) are among the latest and largest family of 2D materials. Due to their 2D nature and their unique properties of hydrophilicity, good metallic conductivity, and structural diversity, these materials are intensively studied for sensing applications or as supports for nanomaterials toward, e.g., plasmonics, catalytic, or energy storage applications. For these potential usages, the extent to which the electronic properties of MXene sheets are modified upon functionalization or intercalation is critical, and an optimized nondestructive probing of the interaction between MXene layers and functionalization is important to be determined. Here, these issues are addressed using a combination of first-principles simulations and electron energy loss spectroscopy (EELS) experiments performed at the nanoscale on Ti3C2Tx and Ti2CTx MXene multilayers, where T denotes the surface functionalization groups. Based on a detailed analysis of the carbon and surface group K edge fine structure, we show that the C-K edge is an ideal marker for surface-induced electronic structure modifications in the Tin+1Cn conducting core. These results highlight how a nanometer-scale impurity can very locally interact with a Ti3C2Tx multilayer and modify its electronic structure. This approach allows discrimination between the surface and core alteration of the Ti3C2Tx layers. Finally, the higher sensitivity to surface states of the Tin+1Cn conducting core in Ti2CTx as compared to Ti3C2Tx is discussed. We expect these results to offer an approach for understanding MXenes’ behavior and especially characterize their interactions with other nanomaterials when used in composite