Fabrication Of Ultrathin Nanoporous Gold Films And Investigation Of Their Surface Plasmon Resonance Enhancement

Surface plasmon resonance (SPR) is a sensitive, rapid, label-free analytical technique that can monitor reactions at solid-liquid interface. As a branch of SPR technique, electrochemical SPR (EC-SPR) has successfully applied to many fields. In conventional EC-SPR experiments, the SPR angular shifts caused by an externally applied electrode potential could disturb the observation of the slight SPR angular shifts caused by conformational change of organic or biological molecules, In recent years, SPR sensor chips based on nanomaterials have gotten much attention because of it’s high sensitivity. In this thesis, electrochemical method was employed to fabricate size-controllable nanomaterials, using the nanomaterials as SPR sensor chips, the SPR signal were effectively enhanced. The mian results include:(1) Ultrathin nanoporous gold films (NPGFs) with a thickness of approximately50nm were fabricated via simple and convenient electrochemical alloy-dealloy method. The relevant parameters including scan rate, range and cycles which affect the roughness and stability of NPGFs are investigated. The optimal condition for producing stable and rough NPGFs were investigated. The optimal condition for producing stable and rough NPGFs were obtained (scan rate:50mV/s scan potential above-0.1V,and scan cycles20). Electrochemical and SEM results displayd the exact roughness and corresponding surface morphologies of NPGFs.(2) Localized surface plasmon resonance (LSPR) and PSPR (Propagating SPR) of NPGFs were investigated. LSPR is a typical physical phenomenon Of nanomaterials. The LSPR effect of NPGFs were investigated with UV-Vis refractance spectrum. With optimal roughness factor of9, NPGF displayed a linear relationship between the ethanediol concentration and the absorbance intensity at λ=450nm. The PSPR effect of NPGFs was investigated with flow injection SPR in alcohol solution. The results show NPGF with a roughness factor of10has the most enhanced SPR signal,3.2times larger than smooth gold film. To explain the enhanced PSPR signal, Fresnel theory used to simulate SPR shifts of NPGF in alcohol solution. The distinct deviation of the simulation results from the experiment curves implied that the plane film model is not suitable for NPGFs. The appropriate model for NPGFs will provided in our future research.(3) A typical application of NPGFs was shown in the detection of redox-induced conformation change of cytochrome c. The SPR signal of oxided cytochrome c on NPGF (with a roughness factor of10) is2.4times as high as that on smooth gold film. It prove NPGF can really enlarge SPR signal.