Flexible free-standing composite films having 3D continuous structures of hollow graphene ellipsoids

Toward a New Understanding of Graphene Oxide Photolysis: The Role of Photoreduction in Degradation Pathway

Graphene oxide (GO) is developed in various applications owing to its fascinating physicochemical properties. However, the weak photostability always leads to inevitable photolysis of GO during the use, storage, and application. Indirect photolysis has a significant impact on the structure of GO via causing fragmentation and degradation, while the pathway can be divided into two stages. In the early stage, photoreduction is the dominant reaction to generate porous reduction GO (PrGO). Then H2O2 breaks PrGO into fragments, and eventually, the fragmented GO is converted into CO2 by OH radicals. The generation of porous structures in early photoreduction is a crucial premise for the subsequent photodegradation, while GO flakes without porous structure cannot be broken by H2O2 and OH. In this work, a deep insight into the indirect photolysis pathway and the committed step is provided, which may bring some advanced ideas for enhancing GO stability in practical application.

Transient chemical and structural changes in graphene oxide during ripening

Graphene oxide (GO)-the oxidized form of graphene-is actively studied in various fields, such as energy, electronic devices, separation of water, materials engineering, and medical technologies, owing to its fascinating physicochemical properties. One major drawback of GO is its instability, which leads to the difficulties in product management. A physicochemical understanding of the ever-changing nature of GO can remove the barrier for its growing applications. Here, we evidencde the presence of intrinsic, metastable and transient GO states upon ripening. The three GO states are identified using a [Formula: see text] transition peak of ultraviolet-visible absorption spectra and exhibit inherent magnetic and electrical properties. The presence of three states of GO is supported by the compositional changes of oxygen functional groups detected via X-ray photoelectron spectroscopy and structural information from X-ray diffraction analysis and transmission electron microscopy. Although intrinsic GO having a [Formula: see text] transition at 230.5 ± 0.5 nm is stable only for 5 days at 298 K, the intrinsic state can be stabilized by either storing GO dispersions below 255 K or by adding ammonium peroxydisulfate.

Ultrafast Interfacial Self-Assembly of 2D Transition Metal Dichalcogenides Monolayer Films and Their Vertical and In-Plane Heterostructures

Cost effective scalable method for uniform film formation is highly demanded for the emerging applications of 2D transition metal dichalcogenides (TMDs). We demonstrate a reliable and fast interfacial self-assembly of TMD thin films and their heterostructures. Large-area 2D TMD monolayer films are assembled at air-water interface in a few minutes by simple addition of ethyl acetate (EA) onto dilute aqueous dispersions of TMDs. Assembled TMD films can be directly transferred onto arbitrary nonplanar and flexible substrates. Precise thickness controllability of TMD thin films, which is essential for thickness-dependent applications, can be readily obtained by the number of film stacking. Most importantly, complex structures such as laterally assembled 2D heterostructures of TMDs can be assembled from mixture solution dispersions of two or more different TMDs. This unusually fast interfacial self-assembly could open up a novel applications of 2D TMD materials with precise tunability of layer number and film structures.