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Ti₃C₂T_x MXene is an emerging family of two-dimensional materials, and because of its large specific surface area, it has potential for many applications. Herein, a new application using Cu-doped MILD (minimally intensive layer delamination) synthesized Ti₃C₂T_x MXene for urea removal is demonstrated. The doping of Cu on MXene results in an increase in its affinity for urea adsorption as compared to the pristine MILD synthesized MXene due to the formation of the Cu–urea complex. Previous computational studies have shown that the adsorption energies of urea on the MXene surface can be improved in the presence of Cu. The valence statemore » of Cu in the doped MILD synthesized MXene, which binds on to the surface via Ti–O–Cu linkage, is between 0 and +1 as verified by XAS and XPS. As the optimal urea adsorption occurs on Cu as a single atom site, an increase in Cu doping on MXene does not increase urea removal due to Cu agglomeration. Furthermore, looking at the adsorption behaviour, it seems that Cu-doped MXene follows the monolayer adsorption on homogenous surface model.« less

Strong spin–orbit coupling, resulting in the formation of spin–momentum–locked surface states, endows topological insulators with superior spin–to–charge conversion characteristics, though the dynamics that govern it have remained elusive. Here, an all–optical method is presented, which enables unprecedented tracking of the ultrafast dynamics of spin–to–charge conversion in a prototypical topological insulator Bi₂Se₃/ferromagnetic Co heterostructure, down to the sub–picosecond timescale. Compared to pure Bi₂Se₃ or Co, a giant terahertz emission is observed in the heterostructure that originates from spin–to–charge conversion, in which the topological surface states play a crucial role. A 0.12 ps timescale is identified that sets a technological speed limitmore » of spin–to–charge conversion processes in topological insulators. Additionally, it is shown that the spin–to–charge conversion efficiency is temperature independent in Bi₂Se₃ as expected from the nature of the surface states, paving the way for designing next–generation high–speed optospintronic devices based on topological insulators at room temperature.« less