Spatially Resolved Covalent Functionalization Patterns on Graphene

2D Atomic-Molecular Heterojunctions toward Brainoid Applications

Brainoid computing using 2D atomic crystals and their heterostructures, by emulating the human brain's remarkable efficiency and minimal energy consumption in information processing, poses a formidable solution to the energy-efficiency and processing speed constraints inherent in the von Neumann architecture. However, conventional 2D material based heterostructures employed in brainoid devices are beset with limitations, performance uniformity, fabrication intricacies, and weak interfacial adhesion, which restrain their broader application. The introduction of novel 2D atomic-molecular heterojunctions (2DAMH), achieved through covalent functionalization of 2D materials with functional molecules, ushers in a new era for brain-like devices by providing both stability and tunability of functionalities. This review chiefly delves into the electronic attributes of 2DAMH derived from the synergy of polymer materials with 2D materials, emphasizing the most recent advancements in their utilization within memristive devices, particularly their potential in replicating the functionality of biological synapses. Despite ongoing challenges pertaining to precision in modification, scalability in production, and the refinement of underlying theories, the proliferation of innovative research is actively pursuing solutions. These endeavors illuminate the vast potential for incorporating 2DAMH within brain-inspired intelligent systems, highlighting the prospect of achieving a more efficient and energy-conserving computing paradigm.

Synergistic Combination of Reductive Covalent Functionalization and Atomic Layer Deposition-Towards Spatially Defined Graphene-Organic-Inorganic Heterostructures

Three-dimensionally (3D) well-ordered and highly integrated graphene hybrid architectures are considered to be next-generation multifunctional graphene materials but still remain elusive. Here, we report the first realization of unprecedented 3D-patterned graphene nano-ensembles composed of a graphene monolayer, a tailor-made structured organophenyl layer, and three metal oxide films, providing the first example of such a hybrid nano-architecture. These spatially resolved and hierarchically structured quinary hybrids are generated via a two-dimensional (2D)-functionalization-mediated atomic layer deposition growth process, involving an initial lateral molecular programming of the graphene lattice via lithography-assisted 2D functionalization and a subsequent stepwise molecular assembly in these regions in the z-direction. Our breakthrough lays the foundation for the construction of emerging 3D-patterned graphene heterostructures.

The Covalent Functionalization of Surface-Supported Graphene: An Update

In the last decade, the use of graphene supported on solid surfaces has broadened its scope and applications, and graphene has acquire a promising role as a major component of high-performance electronic devices. In this context, the chemical modification of graphene has become essential. In particular, covalent modification offers key benefits, including controllability, stability, and the facility to be integrated into manufacturing operations. In this Review, we critically comment on the latest advances in the covalent modification of supported graphene on substrates. We analyze the different chemical modifications with special attention to radical reactions. In this context, we review the latest achievements in reactivity control, tailoring electronic properties, and introducing active functionalities. Finally, we extended our analysis to other emerging 2D materials supported on surfaces, such as transition metal dichalcogenides, transition metal oxides, and elemental analogs of graphene.

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.

Molecular Stacking on Graphene

The sequential vertical polyfunctionalization of 2D addend-patterned graphene is still elusive. Here, we report a practical realization of this goal via a "molecular building blocks" approach, which is based on a combination of a lithography-assisted reductive functionalization approach and a post-functionalization step to sequentially and controllably link the molecular building blocks ethylpyridine, cis-dichlorobis(2,2'-bipyridyl)ruthenium, and triphenylphosphine (4-methylbenzenethiol, respectively) on selected lattice regions of a graphene matrix. The assembled 2D hetero-architectures are unambiguously characterized by various spectroscopic and microscopic measurements, revealing the stepwise stacking of the molecular building blocks on the graphene surface. Our method overcomes the current limitation of a one-layer-only binding to the graphene surface and opens the door for a vertical growth in the z-direction.

Evolution of Graphene Patterning: From Dimension Regulation to Molecular Engineering

The realization that nanostructured graphene featuring nanoscale width can confine electrons to open its bandgap has aroused scientists' attention to the regulation of graphene structures, where the concept of graphene patterns emerged. Exploring various effective methods for creating graphene patterns has led to the birth of a new field termed graphene patterning, which has evolved into the most vigorous and intriguing branch of graphene research during the past decade. The efforts in this field have resulted in the development of numerous strategies to structure graphene, affording a variety of graphene patterns with tailored shapes and sizes. The established patterning approaches combined with graphene chemistry yields a novel chemical patterning route via molecular engineering, which opens up a new era in graphene research. In this review, the currently developed graphene patterning strategies is systematically outlined, with emphasis on the chemical patterning. In addition to introducing the basic concepts and the important progress of traditional methods, which are generally categorized into top-down, bottom-up technologies, an exhaustive review of established protocols for emerging chemical patterning is presented. At the end, an outlook for future development and challenges is proposed.

Iodide mediated reductive decomposition of diazonium salts: towards mild and efficient covalent functionalization of surface-supported graphene

Covalent functionalization of graphene is highly sought after, not only in view of the potential applications of the chemically modified material, but also because it brings fundamental insight into the chemistry of graphene. Thus, strategies that yield chemically modified graphene with densely grafted films of aryl groups via simple experimental protocols have been the focus of intense research. Here we report a mild, straightforward and efficient approach to graphene/graphite functionalization using iodide mediated reductive dediazoniation of aryldiazonium salts. The experimental protocol employs aqueous solutions of the reagents. The reaction proceeds rapidly at room temperature without the need of any environmental or electrochemical control. The covalently modified surfaces were characterized at the nanometer scale using a combination of complementary surface analytical techniques. The degree of covalent functionalization, and the morphology, as well as the thickness of the grafted films were studied at the molecular level using Raman spectroscopy and scanning probe microscopy, respectively. Furthermore, solution phase UV-Vis spectroscopy was employed to understand the mechanistic aspects. This work demonstrates a facile and scalable covalent modification method compatible for both bulk and monolayer functionalization of graphene.

Synthesis of an amphibious superamphiphilic carbon-based materials with unique properties

The synthesis of carbon cloth and polyurethane foam possessing amphibious superamphiphilicity (i.e., superamphiphilicity simultaneously in air and in pre-wetted state).

Synthesis and characterization of tannic acid–PEG hydrogel via Mitsunobu polymerization

Tannic acid (TA) based materials have received significant interest owing to their broad spectrum of chemical and biological properties. Herein, a novel tannic acid based hydrogel, TA–PEG hydrogel, was synthesized via Mitsunobu polymerization/polycondensation, in which TA and polyethylene glycol (PEG) were simply crosslinked together by ether linkages. This method was performed in one pot, straightforward, metal free and robust, ignoring the strong ionic/hydrophobic interactions between tannic acid and PEG. Bearing catechol and pyrogallol units from TA, TA–PEG hydrogel did not only reduce the silver and gold precursor, but also served as a capping agent and stabilizer for the in situ formed Au and Ag nanoparticles (NPs). Furthermore, the antioxidant activity of the hydrogel was excellent (94%) in the case of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging. TA–PEG hydrogel also showed antibacterial activity against Staphylococcus aureus and Escherichia coli. This work suggested a new method leading to polyphenol based soft materials rather than a complex coacervated microstructure. The resulting TA–PEG hydrogel has potential application in biomedical materials.

Mitsunobu polymerization was involved to construct bulk hydrogel via direct PEGylation of tannic-acid under mild condition.

Synergistic additive-mediated CVD growth and chemical modification of 2D materials

This review summarizes significant advances in the use of typical synergistic additives in growth of 2D materials with chemical vapor deposition, and the corresponding performance improvement of field effect transistors and photodetectors.