Surface Functionalization of 2D Transition Metal Oxides and Dichalcogenides via Covalent and Non-covalent Bonding for Sustainable Energy and Biomedical Applications

Abstract

The interest in two-dimensional (2D) nanomaterials has been increased rapidly after the discovery of graphene. The 2D graphene analogs (2DGAs) with ultrathin-layered feature exhibit a unique property which their bulk counterparts cannot possess. Among various 2D nanomaterials, the transition metal dichalcogenides (TMDs) and transition metal oxides (TMOs) have attracted considerable attention from scientific communities. The availability of various transition metals and their binding states in 2D TMDs and TMOs enable them to show a wide spectrum of properties such as metals to wide band gap semiconductors. Although properties of 2D TMDs and TMOs are excellent, further enhancement of their properties is still required for cutting-edge applications. The surface functionalization of 2DGAs is a potential route for enhancing their properties. The surfaces of 2D TMDs and TMOs could be functionalized with various types of organic or inorganic nanomaterials via covalent or non-covalent interactions. The functionalization may alter the Fermi level of 2D nanomaterials, also having this potential to add extra functionalities to the basis of the fabricated devices using them. In this review, we first introduce and specify the characteristics of 2D TMDs and TMOs as two important 2DGAs. Then, we discuss their limitations and how surface functionalization may enhance their performance. The covalent and non-covalent modes of surface functionalization with organic and inorganic nanomaterials on both 2D TMDs and TMOs are then considered. The current state and challenge of the functionalized 2D TMDs and TMOs are also discussed by their application point of view in energy storage and conversion, sensing, biomedical, catalytic combustion, and (opto)­electronic devices.

Theoretical Study of Interfacial and Electronic Properties of Transition Metal Dichalcogenides and Organic Molecules Based van der Waals Heterostructures

“…Making heterostructure or functionalized by various inorganic materials or organic molecules could overcome this issue by isolating from exterior environment. [ 21 ] Very recently, the tailored electronic/optical properties of TMDs by making TMD/organic heterostructures have been realized for optoelectronics such as photodetectors, light‐emitting devices, and neuromorphic application. [ 10,11,13,18,22–24 ] In addition, perylene tetracarboxylic dianhydride (PTCDA) and pentacene molecules are popular organic small molecules used in the organic based light‐emitting and light‐harvesting devices due to their excellent electrical properties.…”

Recent Trends in Photoacoustic Imaging Techniques for 2D Nanomaterial-Based Phototherapy

“…Their wide bandgap results in excellent photochemical and electric properties [ 86 , 87 ]. They can also directly interact with drugs, genes, or other biomolecules by surface modification and thus can be utilized in biomedical applications including drug delivery, cancer therapy, tissue engineering, bio-imaging, and biosensing [ 88 , 89 , 90 ]. Mxenes are the most recently discovered 2D materials and have been applied in various biomedical applications because of their extreme thinness, large surface area, high surface–volume ratio, and mechanical strength [ 91 , 92 , 93 , 94 , 95 ].…”

Optical Signatures of Defect Centers in Transition Metal Dichalcogenide Monolayers

“…[ 9 ] Chalcogen vacancies can also be used as grafting sites for functional groups, to create bio and chemical sensors. [ 10,11 ] Alkane and other functional groups can be incorporated directly into the matrix (as opposed to thiol links, for instance, which necessitate Au). Carbon atoms have also been used as acceptor dopants for bulk semiconductors.…”