Preparation And SERS Performance Of Polyaniline Porous Membrane/Noble Metal Composites

In recent years, surface-enhanced raman scattering （SERS） has been a hotresearch field of science, due to its great enhancement factor, very low detectionlimit, so the SERS on the surface trace analysis, single molecule detection andnano-materials field has a lot of applications. However, in order to get satisfactorilyenhanced signal, a certain active substrate must be get. Therefore, a kind of goodstability, good enhancement, and repetitive system is the key to get good SERSsignal. As reported, polyaniline has a certain conductivity reduction （its reductionpotential is lower than some of precious metals such as gold, silver）. To restore theprecious metal ions using polyaniline porous membrane can obtain PANI/preciousmetal composite materials. In the thesis we studied effects of dopant, acid,surfactant, reaction time, reaction temperature and other conditionsons on the morp-hologies of precious metal particles, and obtained composite materials are used asactive substrates for some probe molecules such as mercapto-benzoicacid （4-MBA）for SERS performance study.With polyaniline porous membrane to restore AgNO₃, the polyaniline/silverparticle composite materials are obtained, regulating the dopant, acid and otherconditions in order to get silver particles with different kinds of shapes. The studyfound that silver particles obtained by citric acid doped porous membrane are basi-cally spherical, and with camphor sulfonic acid doping porous membrane, most ofthe resulting silver particles are like some flower shapes. Using camphor sulfonicacid doped porous membrane, and adding phosphoric acid, succinic acid, lactic acid,p-toluene sulfonic acid to AgNO₃solution, then get micron silver particles that areself-assembled with secondary nanostructures, and whoes morphologies are similarto the cube, rose, Chinese rose, maple leaf shape. When using composite materialsadding of lactic acid as base materials for SERS study to4-MBA solution, thedetection limit can reach10^-14mol/L.Polyaniline/gold composite materials can be obtained by reduction of HAuCl₄with polyaniline porous membrane. When adding a certain amount of surfactant toHAuCl₄solution, gold particles that both own structure and overall distribution arerelatively uniform in porous membrane above can be get. Among them somegold particles are myriapod-like when CTAB or CTAC are added. And paper furtherstudied the impact of reaction temperature on the composites’ morphologies andSERS performance. Mixed solution of HAuCl₄and PVP reacts with the polyanilineporous membrane at the temperature of80degrees for15minutes,30minutes, and60minutes, separately getting gold particles of micron star, sea urchin-like, flower globular structure. Among them using gold particles of micron star structure asactive substrate for SERS study of4-MBA solution, the detection limit can beachieved to10^-9mol/L.