Self-assembled 2D Plasmonic Nanorice Film And Its SERS Detecion

With the rapid development of nanofabrication technology in recent decades,the optical properties of metal nanostructures have attracted more attention from researchers.This is mainly because the free electrons in metal nanostructures can be excited by light to cause collective oscillation,which is called Surface plasmon（SPP）.This collective oscillation will resonate at the appropriate incident light frequency.At this time,the time is greatly confined to the nanometer-scale area on the metal surface,and surface plasmon resonance（SPR）appears.The excellent optical properties of metals are also used in various fields,and surface enhanced Raman spectroscopy（SERS）is one of the most common and important applications.Since the role of surface plasmons depends to a large extent on the size,shape and material of the metal,metal nanostructures have a great influence on the enhancement of SERS signals,and it is also important to conduct research on SERS substrates composed of metal nanostructures.It is one of the core tasks of SERS application.In addition to common metal nanoparticles,in recent years,self-assembled two-dimensional nanoparticle films have shown broad application prospects in SERS substrates due to their convenient manufacturing process,uniform signal,high sensitivity,and low cost.Because the SERS performance of a two-dimensional plasmon film is determined by the excitation and coupling of the surface plasmons of the nanoparticles that make up the film,and the excitation and coupling of the surface plasmons are strongly affected by the shape and size of the nanoparticles.Therefore,the study of two-dimensional plasmonic films using novel nanoparticles as SERS substrates may be an interesting topic in related fields.This paper mainly does the following research around the two-dimensional SERS substrate:（1）Ag nanorices were synthesized by reduction of polyol,and the synthesized silver nanometers are used as the assembly unit.The liquid-liquid interface self-assembly technology is used to assemble them into the 2D Ag nanorice film.Then use Methylene Blue（MB）,Rhodamine 6G（Rhodamine 6G:R6G）,and PATP as probe molecules,and use Raman spectroscopy and Mapping to verify the feasibility of 2D Ag nano-films as SERS substrates.The results show that The substrate has a significant enhancement effect on each signal molecule,the detection limit of MB can reach 10^-9,and the enhancement factor EF=1.40*10⁵.（2）The surface plasmon performance of the 2D Ag nano-film as the SERS substrate was studied.First,the COMSOL software is used to calculate the charge distribution of a single silver nanometer.The results show that a single silver nanometer has anisotropy.However,after arranging it into a 2D silver nanometer film,the reflection spectrum of the 2D silver nanometer film is measured.The anisotropy has been destroyed,and experiments have also proved that the substrate has no polarization dependence.（3）Through COMSOL simulation,simplify the 2D silver nano-film structure into silver nano-dimer models of different configurations,and then calculate the electric field distribution of the silver nano-dimer under different laser wavelengths,and analyze the2D theoretically The Raman enhancement of the silver nanomembrane to the molecules adsorbed on its surface mainly comes from the gap.It is concluded that the 2D silver nanomembrane substrate is wavelength-dependent,and the 785 nm excitation light source has better SERS performance.（4）A tentative study was carried out.The 2D silver nano-film was placed in a formaldehyde vapor environment to verify the feasibility of using its SERS substrate to detect trace harmful gases using Raman technology,providing a new method for detecting trace amounts of gas.method.（5）Using the 2D silver nano-film as the SERS substrate,the Raman spectroscopy technology is applied to food safety detection to determine whether the wolfberry has been dyed with carmine.A simple and fast detection method for bad food additives is provided,which further expands the application range of Raman spectroscopy.