Universal Ligands for Dispersion of Two-Dimensional MXene in Organic Solvents

Abstract

Ligands can control the surface chemistry, physicochemical properties, processing, and applications of nanomaterials. MXenes are the fastest growing family of two-dimensional (2D) nanomaterials, showing promise for energy, electronic, and environmental applications. However, complex oxidation states, surface terminal groups, and interaction with the environment have hindered the development of organic ligands suitable for MXenes. Here, we demonstrate a simple, fast, scalable, and universally applicable ligand chemistry for MXenes using alkylated 3,4-dihydroxy-l-phenylalanine (ADOPA). Due to the strong hydrogen-bonding and π-electron interactions between the catechol head and surface terminal groups of MXenes and the presence of a hydrophobic fluorinated alkyl tail compatible with organic solvents, the ADOPA ligands functionalize MXene surfaces under mild reaction conditions without sacrificing their properties. Stable colloidal solutions and highly concentrated liquid crystals of various MXenes, including Ti2CT x , Nb2CT x , V2CT x , Mo2CT x , Ti3C2T x , Ti3CNT x , Mo2TiC2T x , Mo2Ti2C3T x , and Ti4N3T x , have been produced in various organic solvents. Such products offer excellent electrical conductivity, improved oxidation stability, and excellent processability, enabling applications in flexible electrodes and electromagnetic interference shielding.

Snake Scale-Inspired Poly(vinylidene fluoride)/Ti3CNTx@Polypyrrole Coatings for Ultrawide-Bandwidth Microwave and Visible Light Absorption

“…The average thickness of single-/few-layer Ti 3 CNT x is 2.8 nm as characterized by atomic force microscopy (AFM) (Figure a). This result is in general agreement with the thickness range of monolayered Ti 3 CNT x MXene reported previously . In addition, the PPyNFs prepared by the oxidative template method (OTA) have a distinct “paperclip-like” folded chain structure with diameters ranging 30–70 nm and an aspect ratio of more than 1000:1 (Figure b).…”

“…This result is in general agreement with the thickness range of monolayered Ti 3 CNT x MXene reported previously. 30 In addition, the PPyNFs prepared by the oxidative template method (OTA) 31 have a distinct "paperclip-like" folded chain structure with diameters ranging 30−70 nm and an aspect ratio of more than 1000:1 (Figure 2b). After the electrostatic selfassembly, the nanostructure clearly shows the dependence of the mass ratio of the two components (Figure S8a1−g1).…”

Organic Solvent Dispersible MXene Integrated Colloidal Quantum Dot Photovoltaics

“…[ 31 ] The attachment of PCA onto the MXene surfaces proceeds through the hydrogen bonds and strong titanium‐catechol coordination bonds. [ 38 ] Transmission electron microscopy (TEM) and atomic force microscopy (AFM) images in Figure 2b,c demonstrate that PCA‐MXene maintains an identical morphology to that of the pristine MXene, indicating that the functionalization with PCA has a negligible effect on the morphology of MXene nanosheets. On the other hand, in contrast to the smooth and clear surface observed in pristine MXene, PCA‐MXene exhibited an even distribution of ultra‐small particles of PCA on its surface and edges (as shown in Figure 2b) demonstrating successful anchoring of PCAs onto the MXene surfaces.…”

Bubble Printing of Ti3C2TX MXene for Patterning Conductive and Plasmonic Nanostructures

“…In previous studies, Armon et al used diethylene glycol butyl ether to print silver nanoparticles, while Edri et al used N -methyl-2-pyrrolidon for BP of polyaniline emeraldine base lines . Ti 3 C 2 T X MXene is dispersible in a wide range of solvents; however, beyond 6 h, it is only stable in relatively polar organic solvents such as dimethylformamide or dimethyl sulfoxide, whereas in ethanol it starts to precipitate after a short time, and in water, it is stable for a few days …”

“…26 Ti 3 C 2 T X MXene is dispersible in a wide range of solvents; however, beyond 6 h, it is only stable in relatively polar organic solvents such as dimethylformamide or dimethyl sulfoxide, whereas in ethanol it starts to precipitate after a short time, and in water, it is stable for a few days. 44 An aqueous MXene dispersion without any added cosolvent led to increased adhesion of the MXene-laden bubble to the substrate, which resulted in "smearing" of the MXene that was bound to the bubble interface over the substrate as the bubble drags along the surface (Figure 3a, Video S3). With the addition of ethanol (EtOH) to 25% (v/v), such smearinginduced structures are no longer observed, and at 25% and 50% EtOH, the printing process is well-controlled with minimal interruption due to bubble collapse or dragging (Figure 3b,c, Video S4).…”