Study On Surface Enhanced Raman Scattering Of MXene/Au Nanocomposite Structure

Surface-enhanced Raman scattering(SERS)spectroscopy,as an ultra-sensitive analytical detection technique,can study the structural information of material at the molecular level.In the study of SERS substrates,metal nanostructures usually have a high SERS effect,but its properties of inactivation of biomolecules limit its scope of application;non-metallic substrates are often difficult to produce great enhancement.Therefore,in this research,a MXene nano-sheet/Au nano-antenna composite structure is proposed,which combines the electromagnetic enhancement mechanism and chemical enhancement mechanism to achieve the maximum SERS effect in theory and break through the limitation of Raman detection.The excellent biocompatibility and electrostatic attractions for organic molecules of MXene nano-sheets can effectively avoid the distrotion of probe molecules induced by Au nano-antennas and enhance the attractions of probe molecules,which ultimately enhance the Raman signal.Firstly,FDTD solutions software was used to study the surface plasmon characteristics of Au nano-spheres with different sizes.By analyzing the variation of surface plasmon resonance peak and surface electromagnetic field distribution,it provides theoretical guidance for adjusting its optical absorption band and optimizing Au nanostructure.After the simulation of the surface electromagnetic field distribution of the MXene nanosheet/Au nano-antenna composite structure,with the introduction of the MXene nanosheet,the enhanced region of the electromagnetic field extends longitudinally,and the SERS effect is enhanced.Secondly,the Au nano-antenna was prepared by rapid annealing self-assembly method,the morphology and size of which were controlled by adjusting the deposition thickness of Au.Based on the Volmer-Weber growth mode,the morphology of Au nano-antenna underwent a dramatic evolution from nano-spheres,nano-ellipses to coral-like nano-islands.In the spherical phase,the average diameter also grew from17.33 nm to 24.94 nm.The MXene nano-sheets were then etched by hydrofluoric acid and spin-coated onto the Au nano-antenna.By controlling the number of spin-coated layers,the surface coverage of the MXene nano-sheets was changed.Finally,the SERS spectra of Rhodamine 6G(R6G)molecules were obtained on MXene nano-sheet/Au nano-antenna composite structures.By changing the morphology of the Au nano-antenna,it was found that the Raman enhanced signal of the Au nano-ellipsoid was most obvious.At the same time,by changing the number of MXene layers,it is found that the Raman signal gradually increases with the increase of the surface coverage of MXene nanosheets,but the Raman signal gradually weakens after 5 layers.Finally,the maximum enhancement factor was calculated to be 2.9×10⁷and the detection limit was 10^-10M.Subsequently,the internal chemical enhancement mechanism was studied based on the photoelectric characteristics of the composite nanostructure.At the same time,the substrate also obtained Raman signals of ultra-low concentration of crystal violet molecules and methylene blue molecules,which proved the universality of the substrate.In addition,the substrate has also been tested to have good stability.This work is of great significance for the study of ultrasensitive,highly stable and universal Raman detection substrates.