Research On The Ultrafast Dynamics Of Two-dimensional Nanomaterial Ti₃C₂T_x Mxene

In recent years,two-dimensional nanomaterials have been widely used in the fields such as physics,biology,chemistry and medicine because of their special properties and good stability.As a new type of two-dimensional nanomaterial,Ti3C2Tx MXene not only has the advantages of traditional two-dimensional nanomaterials,but also has good electrical conductivity and hydrophilicity,so it has received extensive attention from researchers.Ultrafast time-resolved spectroscopy has been widely used as an important method to detect the dynamic processes inside and between molecules.In this paper,we build a femtosecond laser transient absorption system,and the molecular mechanisms process of two-dimensional nanomaterial Ti₃C₂T_x MXene in isopropanol solvent is detected using pump-probe technology.The sample Ti₃C₂T_x MXene used in the experiment was obtained by chemical etching of the ternary ceramic MAX phase with hydrofluoric acid?HF?.Its two-dimensional layered structure is"Organ".In the transient absorption experiment,we measured the transient absorption spectrum of two-dimensional material Ti₃C₂T_x MXene in isopropanol solvent,and compared the transient absorption spectrum of the Ti₃C₂T_x material with different pump light energy and different polarization direction of the pump light under 400 nm pump light and 800nm pump light respectively.While we stimulate the Ti₃C₂T_x materials by the pump light at 400 nm and 800 nm respectively.We observe that the tendency of the absorption signal changing through time is a slow decrease after the rapid decrease,and finally tends to be gentle.But when the pump light energy is high enough,the absorption signal of the material will gradually rise after 400 ps.This is due to the carrier absorbing high-energy photons and producing multiexcitons.We believe that this is due to the temperature increase caused by the coupling of carriers and phonons;the peak of the absorption peak of the sample is500 nm.Along with the increase of the pump light energy,the absorption signal of the material increases linearly,the carriers in excited state increases and excited state absorption is enhanced.We used origin software to fit the transient absorption spectrum at the wavelength of 500nm when 800 nm 8.5muj pumped light was perpendicular to the polarization direction of detected light.The fitting range was 1.82⁵24.81 ps,and we obtained two life spans,51.96±11.52 ps and182.42±16.79 ps respectively.The wavelength of pump light is 800 nm,the time period is 1 ps.The spectrum produces a strong absorption signal while the wavelength is from 640 to 680 nm.We collected the signal from the isopropanol solvent and proved that the absorption peak was generated by the isopropanol solvent.We also compared the absorption spectrum when the polarization directions of the pump light and the detection light are vertical and parallel.We found that vertical polarization absorption signal enhancement trend is higher than the parallel polarization after 400 ps.This is caused by the light absorption anisotropy of Ti₃C₂T_x material.In the anisotropic decay curve,the curve first increases to the point at 400 ps,and rapidly decreases after reach the point at 400 ps.Then it rises slowly after decay.