Current Trends in the Optical Characterization of Two-Dimensional Carbon Nanomaterials

Abstract

Graphene and graphene-related materials have received great attention because of their outstanding properties like Young's modulus, chemical inertness, high electrical and thermal conductivity, or large mobility. To utilize two-dimensional (2D) materials in any practical application, an excellent characterization of the nanomaterials is needed as such dimensions, even small variations in size, or composition, are accompanied by drastic changes in the material properties. Simultaneously, it is sophisticated to perform characterizations at such small dimensions. This review highlights the wide range of different characterization methods for the 2D materials, mainly attributing carbon-based materials as they are by far the ones most often used today. The strengths as well as the limitations of the individual methods, ranging from light microscopy, scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy, scanning tunneling microscopy (conductive), atomic force microscopy, scanning electrochemical microscopy, Raman spectroscopy, UV-vis, X-ray photoelectron spectroscopy, X-ray fluorescence spectroscopy, energy-dispersive X-ray spectroscopy, Auger electron spectroscopy, electron energy loss spectroscopy, X-ray diffraction, inductively coupled plasma atomic emission spectroscopy to dynamic light scattering, are discussed. By using these methods, the flake size and shape, the number of layers, the conductivity, the morphology, the number and type of defects, the chemical composition, and the colloidal properties of the 2D materials can be investigated.

Glass‐Assisted Chemical Vapor Deposition‐Grown Monolayer MoS2: Effective Control of Size Distribution via Surface Patterning

“…[26,27] However, other concerns still need to be resolved such as domain size control and rotational domain boundaries of CVD-grown almost polycrystalline structures, which prevent the full potential of 2D materials. [28][29][30] Atoms at the edges and center of a flake may differ, which affects the physical and chemical properties of the flake [31] and thus, understanding the relationship between flake size and optical and electronic properties is of decisive importance, as size-dependent changes affect device performance. For instance, large 2D flakes exhibit higher carrier mobility and thus enhance performance of electronic devices, while small flakes are suitable for sensors [32] and medical applications.…”

Advancements in defect engineering of two-dimensional nanomaterial-based membranes for enhanced gas separation

“…67 For example, the number of layers of a two-dimensional material and to confirm the presence of defects on the surface. 68 However, there is a height difference of the probe during the scanning process, which affects the cantilever bending and ultimately leads to inaccurate estimation of the thickness. Furthermore, the ability to visualize the structure and morphology of 2D materials using AFM is hampered by its limited resolution.…”

Recent trends in covalent functionalization of 2D materials

“…High energy spectroscopy, 536 such as X-ray photoelectron spectroscopy (XPS), 189,232,393,537 electron energy loss This journal is © the Owner Societies 2022 spectroscopy (EELS), 286,538 energy-dispersive X-ray spectroscopy (EDS or EDX), 286 and Auger electron spectroscopy (AES), 192 are direct methods to analyze element composition of 2D materials using high energy beam radiation (e.g., photon, electron, or ion).…”