Preparation Of Composite Substrate Based On Silver Nanoparticles And Its SERS Characteristics

The surface-enhanced Raman（SERS）effect has been in existence for decades,and it has shown increasing potential in the rapid detection of trace chemicals and in the analysis of substances.It is widely used in chemistry,materials,and Biomedical and other aspects.In recent years,a variety of SERS substrates have been prepared and widely used in the trace detection of pesticides,pigments,environmental organic pollutants and the like.The materials and structures of the SERS substrate have an important influence on the properties of the SERS substrate.The composite substrate can combine the advantages of each material,but it may also offset some of the advantages.There are many ways to prepare composite SERS substrates,such as sandwich structure assemblies,noble metal core-shell structures,dimers,etc.There are many methods,such as hydrothermal,liquid phase reduction,template,etc.,but most of the composite substrate fabrication processes are complex,and often requires a large number of reaction materials,complicated preparation steps,specific experimental instruments and experimental conditions.So how to prepare a SERS substrate with high sensitivity,high reproducibility and high stability by a simple means.It is of great significance to the field of SERS.This paper is based on the SERS effect of silver nanoparticles,and studies the construction of the composite SERS substrate and its enhancement mechanism.The following are the main research contents and results:1.A Nickel foam/Graphene oxide/Ag NPs composite SERS substrate was prepared.Graphene oxide prepared by Hummers method.The SERS composite substrate was prepared by the graphene oxide prepared by the Hummers method combined with the three-dimensional nickel foam and Ag NPs.The substrate is a high SERS active substrate that combines the advantages of nickel foam,graphene oxide and Ag NPs.Among them,the morphology,size,spacing of the Ag NPs and the properties of the GO layer are the main factors affecting the SERS properties of the Nickel foam/Graphene oxide/Ag NPs composite SERS substrate.By designing orthogonal experiments,control variables,SEM characterization,Raman spectroscopy and other means,we can obtain the optimal preparation conditions.The size of the Ag NPs prepared according to the experiment is about 500 nm,and the surface has a slightly protruding flower shape.The optimal value of GO concentration is about 3.2 mg/mL,and the bath time is 1 h.The prepared SERS substrate R6G has a minimum detection limit（LOD）of 10^-8 mol/L,and the sample has a relative standard deviation（RSD）of only 8.2%high SERS active composite substrate.Finally,we also quantitatively analyze the Raman spectrum of R6G through the algorithm developed by principal component analysis,and propose a quantitative analysis model of probe molecular concentration and Raman spectral intensity.The curve has good curve fitting goodness（R²）reaches 0.9793,which shows that the algorithm has high credibility and is worthy of promotion.2.A Titanium foil/Titanium oxide/Ag NPs composite SERS substrate was prepared.A three-dimensional titanium oxide material is formed on the surface of the two-dimensional titanium foil by a hydrothermal method to make the substrate have a nano-scale rough surface,and then silver nitrate（AgNO₃）is reduced by an ultraviolet lamp to modify the Ag NPs on the surface of the substrate.Based on the self-designed orthogonal experimental table,the effects of titanium oxide and Ag NPs on the SERS properties of the substrate were studied,and the experimental conditions for optimal substrate preparation were obtained.Among them,the optimal conditions for the hydrothermal reaction of titanium foil are:the concentration of sodium hydroxide（NaOH）is 1 mol/L,and the hydrothermal reaction time is 6 h;the optimum condition for modifying Ag NPs is:the concentration of silver nitrate（AgNO₃）is 0.5 mol/L and the UV lamp illumination time is 6 h.The sensitivity,stability,uniformity and superiority of the substrate were evaluated using the probe molecule 4-ATP.Experiments show that the bottom detection limit of the substrate can reach 10^-7 mol/L,which has good sensitivity.After one month in the air,the SERS intensity only drops by 40%,indicating that the substrate has good stability;The relative standard deviation（RSD）is as low as 6.9%with good uniformity.This indicates that the substrate is a surface-enhanced Raman substrate worth promoting.Finally,the industrial contaminant methylene blue（MB）was detected using the substrate,and a distinct Raman peak was observed.