Interfacial Asymmetric Post-Functionalization of Graphene: Amphiphilic Graphene Derivatives Self-Assembled to 3D Superstructures

Spatially Resolved Janus Patterning of Graphene by Direct Laser Writing

Covalently patterned Janus-functionalized graphene featuring a spatially defined asymmetric bifacial addend binding motif remains a challenging synthetic target. Here, a facile and universal laser writing approach for a one-step covalent Janus patterning of graphene is reported, leading to the formation of up to now elusive graphene architectures, solely consisting of antaratopically functionalized superlattices. The structurally defined covalent functionalization procedure is based on laser-triggered concurrent photolysis of two different photosensitizers situated on both sides of the graphene plane, generating radicals and subsequent addend binding in the laser-irradiated areas only. Careful structure analysis was performed by Raman spectroscopy and Kelvin probe force microscopy. In terms of the advantages of our newly established concept, including a simple/easy-to-operate patterning procedure, arbitrary pattern availability, and a high degree of addend binding, an easy access to tailor-designed Janus-functionalized graphene devices with spatially resolved functional entities can be envisaged.

Inorganic material-based Janus nanosheets: asymmetrically functionalized 2D-inorganic nanomaterials

During the past decade, various inorganic material-based Janus nanosheets have been prepared and their applications have been proposed. Inorganic material-based Janus nanosheets have various advantages over polymer-based Janus nanosheets, including the maintenance of their characteristic two-dimensional shape, and are expected to be applied as unique functional materials. Methods for regioselective functionalization of the two sides of the individual nanosheets are extremely important for the development of inorganic material-based Janus nanosheets. In this review, the preparation methods and applications of inorganic material-based Janus nanosheets are summarized from the point of view of inorganic nanosheet functionalization.

Janus 2D materials via asymmetric molecular functionalization

Janus two-dimensional materials (2DMs) are a novel class of 2DMs in which the two faces of the material are either asymmetrically functionalized or are exposed to a different local environment. The diversity of the properties imparted to the two opposing sides enables the design of new multifunctional materials for applications in a broad variety of fields including opto-electronics, energy storage, and catalysis. In this perspective, we summarize the most enlightening experimental methods for the asymmetric chemical functionalization of 2DMs with tailored made (macro)molecules by means of a supratopic binding (one side) or antaratopic binding (two sides) process. We describe the emergence of unique electrical and optical characteristics resulting from the asymmetric dressing of the two surfaces. Representative examples of Janus 2DMs towards bandgap engineering, enhanced photoresponse and photoluminescence are provided. In addition, examples of Janus 2DMs for real applications such as energy storage (batteries and supercapacitors) and generation (photovoltaics), opto-electronics (field-effect transistors and photodetectors), catalysis, drug delivery, self-healing materials, chemical sensors and selective capture and separation of small molecules are also described. Finally, we discuss the future directions, challenges, and opportunities to expand the frontiers of Janus 2DMs towards technologies with potential impact in environmental science and biomedical applications.

Functional Catechol-Metal Polymers via Interfacial Polymerization for Applications in Water Purification

Phenols and polyphenols have been used as a scaffold for generating multidimensional molecular architectures via complexation with metal ions. Here, we report the synthesis and characterization of metallopolymer films from three catechol derivatives having different alkyl/aryl substituents via complexation with iron and copper ions at the organic-water interface. Such interfacial polymerization is instantaneous, one step to generate functional materials, and gives good control over the organization of repeating units along the film. The films were transferred to different substrates such as filter paper, cotton, or polyester fabrics. The films are superhydrophobic with a contact angle >160° which can be tuned by regulating the orientation of nonpolar groups at the interface during polymerization. In addition, the fabricated cloth membrane showed excellent oil/water separation efficiency of more than 99% even after 50 cycles. The polymers also showed good dye extraction capacity from aqueous solutions with fast kinetics data. Such metallopolymer networks can serve as a versatile material for applications in catalysis, protective coatings, drug delivery, water filtration membranes, and liquid separations.

One-Step Synthesis of Janus Fluorographene Derivatives

Fluorographene, a two-dimensional derivative of graphene, is an excellent starting material for the synthesis of graphene derivatives. In this work, a one-step, substrate-free method for the asymmetric functionalization of fluorographene layers with hydroxyl groups by a facile nucleophilic substitution reaction is reported. Such a chemical modification occurs in a biphasic aqueous-organic system under mild conditions, leading to Janus graphene nanosheets functionalized by hydroxyl groups on one side and retaining fluorine atoms on the other. The reported experimental route paves the way for two-dimensional bifacial graphene templates, thus broadening the application potential of graphene materials.