Research The Hotspot Effect By Nanofiber Structure And Its Raman Enhancement Effect

Surface-Enhanced Raman Scattering?SERS?can overcome the shortcomings of traditional Raman spectroscopy,such as weak scattered light intensity,small cross-sections of the molecules to be measured,and weak Raman signals,thereby,achieve detection of lower concentration of detection molecules,even to achieve the purpose of single-molecule detection.SERS can use the surface plasmon resonance effect of metal particles to achieve local electromagnetic field enhancement under specific conditions,and objectively reflect the molecular microstructure features by providing unique“fingerprint”information in the molecular spectrum.Nowadays,SERS technology is widely applied in many fields,but usually the detection sensitivity is limited.At the same time,Raman enhanced substrate material still faced with a series of problems that need to be solved,such as high biological toxicity,complicated preparation process,low detection limit,unstable physicochemical properties,and so on.Au nanoparticles have a strong absorption of photons and can generate surface plasmon resonance effect,which have natural advantages in the application of Raman enhancement.Silk fibroin nanofibers are linear proteins,which can be adjusted to obtain uniform and stable one-dimensional linear state structures.At the same time,they have adjustable mechanical properties,biocompatibility and degradability,and are easy be functionalized.So far,there have been fewer researches on the preparation of Raman enhancement material using silk fibroin nanofibers and Au nanoparticles,and no one has accurately proposed that the reasonable microscopic loading methods of Au nanoparticles aggregate in the composite system while it can produce efficient localized surface plasmon resonance effect,and then gives substrate material Raman enhancement performance.Therefore,this experiment used silk fibroin nanofibers as a template to regulate the microscopic aggregate structure of Au nanoparticles,and used the composite material for Surface-Enhanced Raman Scattering,which is of great significance for the application of silk fibroin in the field of biology and nanomaterials.The contents of this paper are as follows:?1?Au nanoparticles with a particle size of about 20-25 nm were prepared in the experiment.The surface was positively charged and could be adsorbed on both sides of the negatively charged silk fibroin nanofibers by electrostatic interaction.The three-dimensional dimensions of silk fibroin nanofibers are 1-2?m long,20-30 nm wide,and approximately 2 nm thick.Since Au nanoparticles play a decisive role in the Raman enhancement of the substrate,the relative mass ratio of Au nanoparticles and silk fibroin nanofibers was regulated in this experiment,and the trend of the Zeta potential of the composites was observed.It was concluded that the relative ratio of Au nanoparticles to silk fibroin was 1:1 when saturated.?2?In the experiment,the micromorphology of silk fibroin nanofiber-Au nanoparticles composites at different ratios was obtained by AFM,SEM,and TEM characterization tests.When the number of Au nanoparticles was found to increase,the Au nanoparticles on both sides of the silk fibroin nanofibers gradually exhibited a regular interlaced carrying structure and formed a large number of“hot spot”gaps.From a macroscopic point of view,this carrying model resembles a“sandwich”structure.At the same time,the UV-vis test confirmed that the gold particles adsorbed on the surface of silk fibroin nanofibers could generate surface plasmon resonance under laser irradiation,which was used as the basis for Raman enhancement.?3?In the Raman test of the SERS substrates,the enhancement effect of different ratios of silk fibroin nanofiber-Au nanoparticles composite substrates was explored.It was found by experiments that the effective Raman signal of the probe molecule cannot be detected when only a single Au nanoparticles is working.A large number of sandwich structures,which brings the“hotspot”effect to increase the Raman enhancement performance of the composite material,are formed by adding silk fibroin nanofibers to the system.In the scope of this experiment,the best ratio of Au nanoparticles to silk fibroin is 1:1.This is consistent with the proportion of gold particles adsorbed to saturation.After that,the three probe molecules were detected by Raman enhanced substrate.The detection limit of the 4-ATP probe molecule was10^-13M,and the detection limit of the R6G and NPT probe molecules was 10^-9M.Therefore,the substrate material prepared in this experiment not only has high sensitivity but also has wide applicability.?4?Finally,the saturation proportion of the composite material carries the 4-ATP probe molecule into the cell system.After the cells phagocytose the material carrying the probe,Raman imaging of the cells can be achieved by Raman mapping.The CCK-8 experiment proves that the composite material has excellent biocompatibility,and can carry cytotoxicity probe molecules while ensuring cell viability.The"sandwich"structured silk fibroin nanofiber-Au nanoparticles composite substrate material prepared in this study serves as the basis for the subsequent preparation of a more efficient and sensitive Raman enhanced substrate,and also lay the foundation tumor hyperthermia,real-time monitoring of cell status,and integrated diagnostic and therapeutic applications.