CM: Raman helps MXene structure and surface chemical analysis

【Research Background】

       Many different kinds of two-dimensional (2D) materials have been widely studied through Raman spectroscopy. This fast, non-destructive and sensitive method can even characterize many monolithic layers of 2D materials. The best example is graphene. Its Raman characteristic peaks are about 1355 (D peak) and 1600 cm ^-1 (G peak). When using a green laser, a higher wavenumber 2D peak can be observed. In addition, a low-frequency carbon vibration mode due to interlayer coupling can be observed at 42 cm ^-1 .

      Researchers have predicted the dynamic properties of Ti 3 C 2 T x single-layer lattices, including phonon dispersion, partial phonon state density, and infrared and Raman vibrations. According to previous reports, we know the lattice vibration by a surface functional group T X effects and how to match the change in Raman peaks and = O, -OH, and -O (OH) functional group such as in an electrochemical cycle. Based on the experimental data, the calculation model of MXene structure needs to consider the coexistence of O and OH functional groups. We need to know that the plasma characteristics affect the Raman spectrum of Ti 3 C 2 T x . When the laser wavelength and plasma resonance are coupled, the resonance peak of Ti 3 C 2 T x appears around 120 cm ^-1 .

【Achievement Introduction】

Recently, Professor Yury Gogotsi of Drexel University in the United States published a research paper titled:  Raman Spectroscopy Analysis of the Structure and Surface Chemistry of Ti 3 C 2 T x  MXene in the internationally renowned academic journal Chemistry of Materials . The thesis used multi-wavelength Raman spectroscopy to study  Ti 3 C 2 T x and determined the influence of synthesis method, material state (monolayer, dispersion, stacked lamella) and intercalated molecules on Raman spectrum.

【Graphic introduction】

Figure 1.  Ti 3 C 2 T x synthesis and Raman peak matching.

Figure 2.  Raman peak of MXene in different states.

Figure 3.  The vibration mode of Ti 3 C 2 T x is affected by the etching solution and intercalator.

Figure 4. The effect of   laser wavelength on Raman spectrum.

Figure 5.  Raman spectroscopy detects the dissolution of Ti 3 C 2 T x film

【Summary of this article】

 Raman spectroscopy can provide a lot of information on surface chemistry, stacking and the quality of Ti 3 C 2 T x . Ti 3 C 2 T x vibration mainly includes E g (in-plane) and A 1g (out-of-plane) peaks, the latter peaks are sharper and stronger. Because of the plasmon resonance at ~ 785 nm, Raman will be stronger at this wavelength. Therefore, the Raman spectrum using this laser will be clearer. At this time, the resonance peak of Ti 3 C 2 T x is around 120. The entire spectrum of Ti 3 C 2 T x in the 100-800 cm ^-1 wavelength range can be divided into four parts: resonance peak, A 1g out-of- plane vibration of Ti, C, and O , the vibration area of surface functional groups, and the carbon vibration area . These Raman characteristics will vary depending on the synthesis method and the environment of the MXene nanosheets. The most obvious change occurs in the out-of-plane peak, which is affected by surface functional groups and nanosheet stacking.

Literature link:

https://dx.doi.org/10.1021/acs.chemmater.0c00359

Source: MXene Frontier