MCF: Janus MXene nanosheets for macroporous assembly

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Janus materials with different chemical properties or polarities on opposite surfaces have attracted extensive research interest in many fields, such as oil recovery, optical probes, and nanomotors. Generally speaking, Janus materials can be divided into three categories, including zero-dimensional (0D) Janus spheres, one-dimensional (1D) Janus rods/wires, and two-dimensional (2D) Janus sheets. Compared with 0D and 1D Janus nanomaterials, which have been widely studied, 2D Janus nanosheets have received increasing attention due to their highly anisotropic structure (i.e., high aspect ratio) and inherent chemical/physical properties. . As a solid-state surfactant, Janus nanosheets are able to stabilize emulsions due to the interfacial area they occupy compared to spherical polymers. To date, many Janus nanosheets based on polymer nanosheets or 2D nanomaterials such as graphene oxide have been reported. However, these usually require multi-step synthetic procedures, which are not conducive to large-scale production and application. Therefore, it is particularly important to design a simple synthetic way for the desired function to prepare Janus nanosheets.

In recent years, a new class of 2D materials, MXenes, has been extensively studied due to their hydrophilicity, electrical conductivity, outstanding adsorption capacity, and catalytic activity. The diverse functional groups on the surface of MXenes provide diverse sites for surface modification. This opens up the possibility of anchoring the hydrophobic chain on one side of the MXene, which will expand the diversity of Janus nanosheet materials and expand their applications.


The rich surface chemistry of MXene provides more possibilities for the surface modification of MXene nanosheets. Recently, the team of Professor Zhang Haobin, Professor Shi Shaowei and Professor Yu Zhongzhen of Beijing University of Chemical Technology published a research paper titled: Janus MXene Nanosheets for Macroscopic Assemblies in the international high-level academic journal Materials Chemistry Frontiers. By selectively reducing polystyrene grafting To one side of MXene nanosheets, a novel dual-surfactant nanomaterial was designed and synthesized, called Janus MXene nanosheets (JMNs) or MXene nanosheet surfactants (MNSs).

Figure 1. Schematic diagram of the synthesis method of JMN.



Figure 2. SEM images of MXene/PS composites at different magnifications.


Figure 3. AFM images of pure MXene, Janus MXene with hydrophilic surface, and Janus MXene with hydrophobic surface and the corresponding thicknesses.



Figure 4. Investigation of the behavior of the water-dichloromethane interface and the toluene-water interface before and after the addition of JMN.


Figure 5. AFM and TEM images of Janus MXene films.


This paper presents a facile method for in situ transfer of polymeric ligands to one side of MXene nanosheets in one step. The as-prepared JMNs greatly expand the diversity of Janus nanomaterials. JMNs are interfacially active and can be assembled at the water/oil interface due to their bifaciality, making JMNs promising as solid-state surfactants to stabilize emulsions. 2D JMN nanofilms and emulsions can be fabricated through oil-water interface assembly. Furthermore, by using emulsion droplets as templates, MXene aerogels with controllable packing density can be prepared. This approach opens up a new avenue for the assembly of MXene materials from 2D and 3D structures.

Literature link:

DOI: 10.1039/C9QM00681H