Preparation And Sers Properties Of Silver Nanostructures Fabricated On Polyaniline Films

Since scholars doped iodine into polyacetylene at room temperature andpolyacetylene transform from an insulator into a conductor in1977, researchersgradually set off the boom of conductive polymer materials. With the polymers werefound one by one, the doped methods of insulating polymer into the conductor orsemiconductor are gradually increasing, and its fields of application have also beengradually extended. Polyaniline（PANI） soon became one of the most research and themost advanced conductive polymer materials, due to its cheap raw material, simplesynthetic process, good enviromental stability, electromagnetic performance as wellas special doping phenomenon. It has been successfully applied to the eletrodematerial, anti-corrosion coatings, electrochromic photochromic materials, microwavematerials and other related fields.Surface-enhanced Raman spectroscopy （SERS） technique is a mean ofcharacterization of a molecular structure, which can be used for trace detection andsingle molecucle detection, because of its enhanced signal is several orders ofmagnitude of the conventional Raman signal. The advantage of free from waterovercome the shortcomings of the liquid substance which can not be dectcted byinfrared absorption spectroscopy. However, SERS technology further used in traceanalysis, quantitative analysis and the detection of single-molecule level as acommon means of analysis and testing needs an in-depth study of preparation of theSERS substrate.In this thesis, preparation of PANI-Ag composite which can be used as SERSsubstrate is based on the chemical reducing of the polyaniline film by reduction ofAg⁺ions into Ag. Studying the method of preparation of the film, the concetration ofsilver nitrate and the typy of doping acids influence on the silver nanostructures. Thesize, morphology, lattice type and SERS performance of the as-prepared silvernanostructures were characterized by SEM, XRD, EDAX and SERS. The succinicacid pre-doped PANI film was immersed in a mixture of different directing acids andAgNO₃solution. It was found that the silver particles with different size andmorphology were covered on the PANI film surface, and the degree of coverage ofthe film was varied. With camphor sulfonic acid present in the AgNO₃solution, onecan get homogeneous silver particles with standard nanosheets fully covered on thefilm surface. The XRD patterns shown that as-prepared silver nanostructures areface-centered cubic （fcc） crystals. A well-resolved SERS of MBA can be detected ata concentation of10^-9mol/L. PANI chains of the film treated by hot stretching will be more ordered, leading to increasing the electrical conductivity properties ofpolyaniline film, where the silver particles grew along the stretching derection andshown the matrix strucrure. A hydrazine doped film accelerate the growth rate ofsilver particles by the change of oxidation state of the PANI. The composite withhigh reproducibility and stability can attain the fast preparation of SERS substrate.