Controllable Electrodeposition Of Metallic Nano-particles And Their Applications

Noble metal nanoparticles have been studied extensively because of their unique physicochemical characteristics. Since the properties of metal nanoparticles can be adjusted by controlling their size, shape, composition, and crystalloid, there is a wide range of potential applications for metal nanoparticles in areas such as optics, electronics, catalysis, magnetic storage, biosensor, and chemical sensor etc.In this paper, we developed a synthetic method to controllable prepare metallic nano-particles by electrolyzing hydrogen tetrachloroaurate (HAuCl4). Gold nanospheres for average diameter in the range of 25-150nm were directly deposited onto the indium tin oxide (ITO) glass surface by controlling deposition potential, concentration of HAuCl4, and deposition circles by cyclic voltammetric method. The GNPs on ITO substrate were characterized by means of scanning electron microscopy (SEM), UV-vis spectroscopy, synchronous fluorescence spectroscopy and X-ray diffraction (XRD). The three different sizes of gold nanospheres for average diameter of 35, 90, 130nm were used to investigate the changes of localized surface plasmon resonance (LSPR) properties due to small changes in the refractive index (RI) of the surrounding medium close to the particle surface. Results demonstrated that the sensitivity of refractive index sensor increased as gold nano-particles became larger. The sensitivity of the 130nm gold nanosphere can reach 187 nm/RIU.On the other hand, we electrochemical deposited different size of gold nanoclusters onto ITO surface by regulating temperature, deposition circles, and the concentration of addition KCl. The GNPs on ITO substrate were characterized by means of scanning electron microscopy (SEM), UV-vis spectroscopy and X-ray diffraction (XRD). Then the gold nanoclusters were used to investigate the response of different organic solvents and showed a sensitivity of 245nm/RIU, that is higher than nanospheres. The activity of these nanoparticles as SERS substrates was checked by using thiophenol as an adsorbate probe. It was found that the SERS signal intensity is dependent upon the diameter of these nanospheres. Compared with gold nanospheres, the activity of gold nanoclusters is much higher, whose SERS signal intensity is 6.7 times stronger than monodisperse gold nanospheres with the same diameter.Third, we developed an effective approach to deposit Au/Ag alloy nano-particles directly on ITO surface through electrochemical method. The alloy nano-particles on ITO substrate were characterized by means of scanning electron microscopy (SEM), UV-vis spectroscopy, synchronous fluorescence spectroscopy, electrochemistry method and X-ray diffraction (XRD). The electrochemical reduction toward oxygen (O2) on the Au/Ag (Au/Pt) alloy nano-particles modified electrodes has been performed in alkaline and neutral mediums. By systematic comparing the catalytic activities with single metallic nano-particles in alkaline and neutral solution, we discovered that alloy nano-particles have unique properties.