Distinct Chemical and Physical Properties of Janus Nanosheets

Abstract

Janus particles have recently garnered significant attention for their distinct properties compared to particles that are homogeneously functionalized. Moreover, high aspect ratio Janus particles that are rod-like or planar (i.e., nanosheets) are especially intriguing considering their interfacial properties as well as their ability to assemble into higher order and hybrid structures. To date, major challenges facing the exploration and utilization of 2D Janus particles are scalability of synthesis, characterization of tailored chemical functionalization, and ability to introduce a diverse set of functionalities. Herein, a facile method to access Janus 2D graphene oxide (GO) nanosheets by combining a Pickering-type emulsion and grafting-from polymerization via ATRP is reported. Janus GO nanosheets bearing PMMA on one face as well as the symmetrically functionalized analogue are prepared, and the chemical, thermal, structural, surface, and interfacial properties of these materials are characterized. Time-of-flight secondary ion mass spectrometry coupled with Langmuir-Blodgett films is shown to be an ideal route to conclusively establish asymmetric functionalization of 2D materials. This work not only provides a facile route for the preparation of Janus nanosheets but also demonstrates the direct visualization of polymer grown from the surface of GO.

Janus Nanosheets Derived from K4Nb6O17·3H2O via Regioselective Interlayer Surface Modification

“…Janus cylinders can be prepared by masking one side of a cylinder and conducting subsequent modification of the other side [14].Janus nanosheets exhibit the highest anisotropy among Janus compounds due to their unique morphology. They are also useful as emulsifiers, because Janus nanosheets cannot rotate at the interfaces of micelles [15]. Most Janus nanosheets reported so far have consisted of polymers.…”

One-pot Synthesis of Janus Nanosheets on Strengthening and Toughening Nanocomposite Double Network Hydrogels

“…The first one is to synthesize hollow spheres and then grind them [5]. The other is selective modification on isotropic nanosheets [6]. These methods are cumbersome and have a long preparation period.…”

The pH dependent reactions of graphene oxide with small molecule thiols

“…[1][2][3][4][5][6] The applications of GO are dependent on its chemical nature, i.e., extent of oxidation, nanosheet diameter, and functionalization. [7][8][9][10] Most commonly, GO is prepared by the chemical oxidation of graphite using the strong oxidizing agent potassium permanganate (KMnO 4 ) in a strongly acidic solution (H 2 SO 4 ). 11,12 The generally accepted chemical model of GO has oxygen functionalities such as epoxides and alcohols on the basal plane and carboxylic acids on the edges of the nanosheets, as proposed in the Lerf-Klinowski model.…”

“…Moreover, the complex nature of GO means that it can be reduced using metal hydrides and borohydrides, distinct from small molecules bearing alcohol, epoxide, and alkene functionalities. 26,[28][29][30] Whereas fundamental reactions such as ring opening of epoxides and esterication of alcohols and carboxylic acids can be used to modify GO, 10,19,27,[31][32][33] functionalization is typically accompanied by reduction of the GO nanosheets, and the two reaction pathways cannot be disentangled and predictable reactivity can be obscured. An inherent reactivity of GO nanosheets also exists, with net disproportionation reactions occurring when the material is stored in water that leads to smaller diameter nanosheets, as established by Tour et al 34 Thus, understanding how reaction conditions impact the functionalization and reduction of GO is necessary to perform reactions in a controlled and repeatable fashion.…”