\”Father Mxene of\” Yury Gogotsi: – the text read Mxene Raman spectroscopy

MXenes, as a large class of 2D transition metal carbide, nitride or carbonitride, causing great concern to researchers, mainly by selective etching of the corresponding phase A precursor atomic layer is patterned MAX etching, forming a layered structure. 2D, its versatility in chemical structure and have a competitive advantage with such MXenes graphene and other two-dimensional materials in high conductivity, large surface area, particularly in a variety of applications is has broad application prospects in the field of energy conversion and energy storage batteries, super capacitors and catalysis. On the basis of previous studies found that Synthesis of precursors and etching conditions will affect the composition of MXene , such as, MXene Different surface groups may change the Fermi level, and change the material strip gap; intercalation substance and sheet size can also affect the optical properties and electrical conductivity of MXene. Therefore, How to accurately characterize the MXene composition, structure and morphology of great scientific significance. But in terms of detailed characterization work MXene also rarely reported. Recently, United States Drexel (Drexel) University, has a \”father Mxene,\” said the Professor Yury Gogotsi team use [123 ] Ti3C2Tx multi-wavelength Raman spectroscopy carried out research, its main synthetic methods, the relationship between the state of the material (single, colloidal solution, stacked sheets) and the intercalated material and the Raman spectrum changes from fine spectrum MXene obtain vibration characteristics difference, thereby determining the composition, structure and morphology of Mxene. The study mainly emphasizes versatility in MXene Raman spectroscopy analysis, as well as the importance of choosing the right conditions to obtain accurate information and Raman spectroscopy avoid artifacts. The research results entitled \”Raman Spectroscopy Analysis of of Ti3C2Tx MXene the Structure and Surface Chemistry\” is published in \” Chemistry of materials \” on (see the text description link). In order to study author Ti3C, The relationship between the state of the material (single, colloidal solution, stacked sheets) and the intercalated material and the Raman spectrum 2Tx synthetic methods. Etching using different ways (1 hydrofluoric acid, a mixed solution of hydrochloric acid; 2 mixed solution of hydrofluoric acid and water; 3 mixed solution of lithium fluoride and hydrochloric acid) and various concentrations of an aqueous solution of HF (5, 10, 20 and 30%), powders of Ti3AlC2 etching, the prepared materials Ti3C2Tx different forms. In the Raman spectrum, MXene spectral characteristics has four main areas: formant region sheet; the Tx region; carbon region. It may be characterized according to the feature region MXene peak displacement, intensity and width characteristics. “Mxene 之父” Yury Gogotsi :—文读懂Mxene的拉曼光谱分析

“Mxene 之父” Yury Gogotsi :—文读懂Mxene的拉曼光谱分析 FIG 1. Ti3C2Tx schematic synthesis and distribution of Raman peaks.

Raman peaks associated form Raman spectra of different materials Morphological Ti3C2Tx found that the sample type is not

AIg ( C) peak showed different peak displacement. The multilayer Ti3C2T A1g (C) since the interlayer spacing is small and the accumulation effect, the vibration is limited, which is the minimum peak shift. A1g Ti3C2T film (C) of the peak due to the introduction of the intercalating agent to expand the spacing between layers, such AIg (C) to move the peak 720 cm-1. Deposited on Si / SiO2 substrate monolithically Ti3C2Tx peak shift to upgrade to 720 736 cm-1, and since the outer surface of the substrate side of the vibration is restricted, leading to the emergence of asymmetric peak. MXene MXene solution and the clay since the sheet is surrounded by H2O molecules, limited by the small, so the peak shifts to a higher number (726 cm-1) waves. Another aspect of the features associated with is A1g (C) / Alg (Ti, C, O) peak ratio ; Ti3C2Tx in the multilayer structure whose value is equal to 1.1, indicating that the sheet stacking parent Ti3C2Tx MAX similar. When the ratio will increase to 1.2, which means that the interaction strength between the sheet of randomly oriented sheet due to weakened. MAX compared to the parent phase, post-etch layer M and X ordering reduced; therefore, the entire sheet of Alg (Ti, C, O) of vibration will diminish. The single sheet A1g (C) / A1g (Ti, C,O) ratio of 0.9, which is mainly due to the overall strength of the sheet caused by vibration A1g (Ti, C, O) is increased. In the aqueous dispersed solution, since the flakes in a solution and randomly oriented continuous movement, causing Alg (Ti, C, O) peak has almost completely disappeared.

“Mxene 之父” Yury Gogotsi :—文读懂Mxene的拉曼光谱分析 Raman spectra of different states 2.MXene FIG. Diversity (a) Raman spectra: All samples showed the photo represents Ti3C2Tx different states. (B) a multilayer Ti3C2Tx powder prepared by clays Ti3C2Tx LiF-HCl etch, single Ti3C2Tx sheet on Si / SiO2 substrate, in water, a colloidal suspension and Ti3C2Tx Ti3C2Tx layered films made of HF-HCl etching.

The relationship between the etching method and Raman spectroscopy On the relationship between the etching method when Raman spectroscopy and found, through the HF-HCl method, and LiF-HCl etching Ti3C2Tx spectrum obtained showed a strong OH surface groups and similar Alg (C) peak position. However, in the multilayer Ti3C2Tx spectrum HF-etched O component dominates, and A1g (C) moved to the peak shift 711 cm-1, mainly because HCl was added resulting in a pH decrease of the surface plasmon. When exploring the influence of the concentration of HF etching solution, the authors found that Alg (C) summit with increasing HF concentration decreases. And, as the HF concentration, Alg (Ti, C, Tx) / ratio Alg (C) continue to decrease. Wherein, A1g (Ti, C, Tx) show peak sharpening enhancement and low defect concentration, and the mutual interaction between the rotating sheet weakened. Comparing obtained by layering at HF, HF / HCl and LiF / HCl and then etching the stack Ti3C2Tx found only in the HF-HCl etching method, formant has moved, the vibration characteristics described resonance Raman peaks associated with the material , MXene will affect the electrical characteristics of resonance spectroscopy. Ti3C2Tx thin sheets of different sizes prepared found formant sonicated platelet-shaped sheet is moved to a higher number (123 cm-1) wave, mainly because of the small increase in the number of the sheet edge, resulting in defects concentratedIncrease of

“Mxene 之父” Yury Gogotsi :—文读懂Mxene的拉曼光谱分析 Figure 3. Effect of the etching solution and the intercalant Ti3C2Tx vibration mode. When

The relationship between the excitation wavelength and the Raman spectrum Ti3C2Tx In the study of excitation significant relationship between the wavelength and the Raman spectrum Ti3C2Tx found at 785 nm under the action of a laser, a normalized count after a higher power, mainly because the wavelength of light, a large penetration depth. The study found that the objective lens, the objective lens 20 times, larger spot large, higher strength Alg (C) peak. Spectral analysis monolithic Ti3C2Tx found, with the increase of the number of sheets stacked, the overall strength increases. Further, the inner surface of the relative intensity of the peak also increased Eg.

“Mxene 之父” Yury Gogotsi :—文读懂Mxene的拉曼光谱分析 Figure 4. Effect of laser wavelength Raman spectrum.

Raman effect lasers with different spectral Ti3C2Tx film Since the material degradation will cause spectroscopy, Raman spectrum so that the recording quality becomes complex, but it also helps to understand the intrinsic properties of substances. We investigated Ti3C2Tx membrane under Raman spectrum in the nanometer range of action different lasers, found photoluminescence oxide. When using a high power laser, the film degradation observed to form and rutile, anatase and of free carbon. Furthermore, the degree of oxidative damage depends not only on the laser power, but also depends on the wavelength used. At 2.37 mW of power, with 514 and 633 nm laser ablation process found anatase. However, the greater the noise spectrum after the laser irradiation of 633 nm, and Alg (C) peak shift has moved. Shorter wavelengths result in a higher power, which helps to MXene into anatase and rutile transformation.

“Mxene 之父” Yury Gogotsi :—文读懂Mxene的拉曼光谱分析 FIG. 5. Ti3C2Tx membrane degradation in Raman spectroscopic analysis.

[summary] Analysis by systematically explored MXene synthesis, material condition (single, colloidal solution, stacked sheets) and the intercalation material of the pull the impact of Raman spectroscopy to obtain MXene composition from the nuances of the spectrum, the structure andMorphological characteristics, provides practical guidance for the preparation and characterization of future Mxene, provide a reliable basis for future applications in other areas Mxene. Also demonstrated the versatility of Raman spectroscopy in MXene analysis. Original link: https: //pubs.acs.org/doi/10.1021/acs.chemmater.0c00359