چكيده به لاتين
In this research, the Tip-Enhanced Raman Spectroscopy (TERS) method has been introduced as a precise method for analysis of biological samples. Using Finite-Difference Time-Domain (FDTD) simulation method by Lumerical software, it has been tried to design the required structures for biological samples. At first, by comparing different TERS structures and considering the material, dimensions and other parameters in the simulation, the most ideal structure is introduced due to the electric field enhancement. Most biomolecular experiments using TERS require strong field enhancement, and metal tips and substrates are usually used to provide this enhancement. However, metal surfaces are usually not biocompatible. The hydrophobicity of metal surfaces leads to difficulty in deposition and can also have a destructive effect on the structure of native proteins or nucleic acids. To overcome this problem, a thin layer of biocompatible materials is used as a substrate coating. In this study, in order to prevent sample damage, five biocompatible materials have been used as thin layers on metal substrates and their effects on enhancement in different states are compared. The results of the simulations show that gold, copper, and silver provide the highest electric field enhancement, respectively, and the presence of gold next to copper and the presence of gold and copper next to silver lead to an increase in the electric field enhancement in these materials. The results also show that the material and thickness of the underlying coating layer in the substrate and tip have a great effect on the electric field enhancement. Finally, it was observed that when using the five biocompatible materials used in the simulations, muscovite mica, polystyrene, polyvinyl pyrrolidone (PVP), polyethylene (PE) and PNIPAM respectively create the greatest electric field enhancement, although the amount of enhancement in these five materials has a small difference from each other. It was also observed that using a 1 nm layer of biocompatible coating creates a much more favorable effect on enhancement than higher thicknesses.
