Applications of X‐Ray‐Based Characterization in MXene Research

Abstract

X‐rays are a penetrating form of high‐energy electromagnetic radiation with wavelengths ranging from 10 pm to 10 nm. Similar to visible light, X‐rays provide a powerful tool to study the atoms and elemental information of objects. Different characterization methods based on X‐rays are established, such as X‐ray diffraction, small‐ and wide‐angle X‐ray scattering, and X‐ray‐based spectroscopies, to explore the structural and elemental information of varied materials including low‐dimensional nanomaterials. This review summarizes the recent progress of using X‐ray related characterization methods in MXenes, a new family of 2D nanomaterials. These methods provide key information on the nanomaterials, covering synthesis, elemental composition, and the assembly of MXene sheets and their composites. Additionally, new characterization methods are proposed as future research directions in the outlook section to enhance understanding of MXene surface and chemical properties. This review is expected to provide a guideline for characterization method selection and aid in precise interpretation of the experimental data in MXene research.

Switchable Charge Storage Mechanism via in Situ Activation of MXene Enables High Capacitance and Stability in Aqueous Electrolytes

“…It is well-known that the hydroxyl groups can act as active sites for electrochemical reactions, ultimately leading to an improvement in energy storage. 63 A peak at ∼1550 cm –1 , arising from the vibrational N–H stretching bonds, is present in both the KOH and MgSO 4 electrodes, while being absent in the H 2 SO 4 sample. A plausible explanation for the absence of this peak in the H 2 SO 4 sample could be the presence of excess protons in the electrolyte allowing for the reduction of the N–H bond.…”

“…For all pristine and activated samples, the FTIR analysis revealed the presence of characteristic peaks at ∼3300 and ∼1400 cm –1 , which are assigned to the stretching and bending vibrations of the −OH group, arising from the strong adsorption and coordination of water molecules on the electrode surface. It is well-known that the hydroxyl groups can act as active sites for electrochemical reactions, ultimately leading to an improvement in energy storage . A peak at ∼1550 cm –1 , arising from the vibrational N–H stretching bonds, is present in both the KOH and MgSO 4 electrodes, while being absent in the H 2 SO 4 sample.…”

Reversible Fusion–Fission MXene Fiber-Based Microelectrodes for Target-Specific Gram-Positive and Gram-Negative Bacterium Discrimination

“…The X-ray diffraction (XRD) pattern showed the Al layer had been etched completely owing to the disappearance of the (104) peak that belongs to MAX powders. The (002) peak shifted to a lower angle also ascribed to the removal of Al (Figure c) . The terminal groups (oxygen and fluorine) in MXene were further indicated via energy-dispersive X-ray spectroscopy (EDX) (Figure S3a–e) and X-ray photoelectron spectroscopy (XPS).…”

“…The (002) peak shifted to a lower angle also ascribed to the removal of Al (Figure 1c). 20 The terminal groups (oxygen and fluorine) in MXene were further indicated via energy-dispersive X-ray spectroscopy (EDX) (Figure S3a−e) and X-ray photoelectron spectroscopy (XPS). The deconvoluted C 1s, O 1s, and Ti 2p peaks indicated that terminal groups existed on the surface like C−Ti−F x , C−Ti− (OH) x , and C−Ti−O x (Figures S4a−d and S5).…”

Review—Fundamentals to Applications of MXenes for Biosensing

“…XPS is less prevalent than other X-ray based techniques due to requirement of synchrotron radiation to achieve the required X-ray brightness. 76 Energy-dispersive X-ray (EDX or EDS) analysis.-This technique is unique from other X-ray based tools as it involves the production of X-rays instead of using it directly. In EDX, the high energy electron beam strikes inner orbit of an atom emitting a charged electron from its shell and creating a positive charged space.…”