Ultralarge Flakes of Ti₃C₂T_x MXene via Soft Delamination

Abstract

Two-dimensional (2D) titanium carbide MXene (Ti3C2T x ) has attracted significant attention due to its combination of properties and great promise for various applications. The size of the 2D sheets is a critical parameter affecting multiple properties of assembled films, fibers and 3D structures. The increased lateral size of MXene flakes can benefit not only their assemblies by improving the interflake contacts and alignment but also fundamental studies at the individual flake level, allowing for facile patterning and investigation of intrinsic physical properties of MXenes. Increasing the average size of the parent MAX phase is one of the strategies previously used to increase the flake size of the resultant MXene. Here, we show that the protocol used for the next step of the synthesis procedure, delamination of multilayer MXene into individual nanosheets, significantly affects the lateral size of the resultant flakes. We developed a soft delamination approach, which prevents fracture of flakes and preserves their size. Combining this approach with the large-grain Ti3AlC2 MAX phase precursor, we achieved individual flakes of up to 40 μm in lateral size. These flakes can be used for patterning multiple contacts and fabrication of field-effect transistors for multiprobe electrical characterization and other measurements. These findings indicate the importance of controlling the delamination process in order to achieve large MXene flakes and improve properties of MXene-based materials and devices.

High-yield fabrication of electromechanical devices based on suspended Ti3C2Tx MXene monolayers

“…Following the recent report by Shekhirev, et al, we delaminated the etching product into MXene sheets by very mild shaking, which was shown to increase the average flake size compared to the sonicationassisted exfoliation. 37 Fig. 1 summarizes the results of the materials characterization of Ti 3 C 2 T x MXene.…”

“…20 Later research resulted in the MILD method, in which the etched product was not sonicated, and the resulting MXene flakes were considerably larger, in the several μm range. 27 A recent study further advanced the synthesis of ultralarge MXene flakes, 37 demonstrating that by further minimizing the shaking of the etching product, it is possible to produce Ti 3 C 2 T x monolayers of up to 40 µm in lateral size. In this work, we used the conclusions of this approach as a guidance to produce large flakes of Ti 3 C 2 T x , avoiding any unnecessary agitation of a MXene solution as well as high-speed centrifugation.…”

“…Then, the washed sample was delaminated into flakes using a very gentle swirling. 37 The delaminated Ti 3 C 2 T x MXene sample was kept under nitrogen at 4 °C for further experiments.…”

“…In this study, we used Ti 3 C 2 T x , the most popular MXene material, 17 and demonstrate a high-yield fabrication of electromechanical devices based on suspended monolayer flakes. With recent advances in increasing the average flake size of MXenes 37 and important optimizations of the PDMS-based flake transfer procedure that we report in this paper, it is possible to produce hundreds of electromechanical devices based on suspended MXene monolayers on a single substrate. In order to demonstrate the generality of this approach for devices with different geometries, we did not repeat the previously reported circular nanodrums, 22,24,32 and instead fabricated Ti 3 C 2 T x flakes suspended over trenches with different gaps ranging from 200 nm to 2 μm.…”

Chalcogen (S, Se, and Te) decorated few-layered Ti3C2Tx MXene hybrids: modulation of properties through covalent bonding

“…[13][14][15][16] Four molecular structures of M 2 X, M 3 X 2 , M 4 X 3 , and M 5 C 4 MXene nanosheets (M and X stand for transition metal elements, and C or N elements, respectively) have been made accessible so far with single-, few-and multi-layer structures, 17 and the sizes of a few micrometers to the recently achieved ultra-large flakes. 18 Surface termination species (T x ) or intercalated compounds (ICs) are replaced with the "A" atoms as a result of the A-layer selective etching from the initial MAX phase. The resulting MXenes have a chemical formula of M n+1 X n T x or M n+1 X n T x -IC after the substitution of the end groups by the intercalation.…”