| The orientation and surface bonding of the molecules adsorbed on metal electrodes has been considered as the fundamental issue in the surface electrochemistry. By using the surface enhanced optics phenomenon at nanometer scale-surface enhanced Raman spectroscopy (SERS), one can obtain the structural information of the adsorbates on metal surface at molecular level. Based on the high surface sensitivity of SERS, electrochemical technique combined with SERS and theoretical simulation has been employed to investigate the relationship between the frequencies/intensities of relevant vibrational modes and the applied potential, and thus the interfacial structure and mechanisms of surface reaction was deduced. The main results and conclusions of the dissertation are listed as follows:1.The adsorption and dissociation of 4-CNPy and 2-CNPy were investigated by SERS on several metal electrodes. By analyzing the changes in the spectral feature of the CN and pyridine ring followed with the applied potential, it is reasonable to determine the different adsorption orientation and surface dissociation of the above two molecules o different metal electrodes surface. (a). 4-CNPy adsorbed on Au electrode by the N atom of pyridine ring in a vertical orientation in a wide potential region. At extreme negative potential region, the dissociation adsorption with the CN- anion was observed, and the competitive adsorption was occurred between pyridine and CN- in this region. The dissociation processes were depended on the concentration of adsorbate and the solution pH values. (b). the similar adsorption configuration was observed on Ag electrode and no dissociation appeared in the relative negative potential region (c). On Pt and Cu electrode surfaces, 4-CNPy adsorbed with a vertical orientation by the N atom from CN group due to the determination of Stark effect of CN. At the extreme negative potential, the orientation of adsorbate was transferred from vertical to flat configuration. (d). The adsorption behaviors of 2-CNPy was more complex than that of 4-CNPy, because of the special structural of 2-CNPy in which the adjacent N atoms from pyridine and CN could be adsorbed on the surface together. The interaction between N from pyridine and Au surface was observed, while the N from CN interacted with Pt surface and it adsorbed on the surface in flat orientation in extreme negative potential region. Furthermore, the adsorption configuration of 2-CNPy was depended on the concentration on Ag surface. i.e. bridge adsorption in the very low concentration, N from CN vertical adsorption for the high concentration and both in the certain concentration range.2.The relationship between the adsorbate orientation and surface charge was studied by density function theory (DFT). The results indicated that 4-CNPy adsorbed by the N atom from CN in a vertical configuration on Au surface with two positive charges, while interacted through the N atom from pyridine ring on the relative positive charged and neutralized surface. The reorientation of 4-CNPy from vertical to flat adsorption was observed on the surface with negative charge. The theoretical simulation is in good agreement with the experimental results.3.By using the TEOS and ammonia as catalyst, the layer of SiO2 was attached onto gold nanoparticles with different thickness to produce Au@SiO2 core-shell nanoparticles. The relationship between the intensities of SERS bands and the thickness of SiO2 was determined by employing thiophenol as probe molecule. The results indicated that the electromagnetic enhancement (EM) was damped with the increase in the thickness of SiO2, and the damping effect was weaker that the dual-metal core-shell structure with the same size as the Au@SiO2. Moreover, the Au@SiO2 structure can be served as the substrate for the on-line and cycle-SERS detection.
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