Fabrication of single crystal ultramicroelectrodes of noble metals

Techniques for the fabrication of gold and platinum single crystal ultramicroelectrodes (scumes) are outlined. The ultramicroelectrodes were characterized by the various techniques such as cyclic voltammetry, atomic force microscopy and scanning electron microscopy.; Gold crystals of micron dimensions were grown in a sodium silicate gel. These single crystals were utilized in the fabrication of the gold (111) and gold (100) scumes.; The single crystallinity of these ultramicroelectrodes was confirmed by cyclic voltammetry. The gold oxide formation region on the current-voltage curve for Au (111) scume shows the same number and intensity of the current peaks as an electrode of normal size prepared by the conventional technique.; Cyclic voltammograms for gold (100) scumes obtained in perchloric acid show similar features to gold (100) single crystal electrodes of more conventional sizes, but with the differences that are a result of different surface preparation methods used. The gold crystals used to prepare Au (100) scumes were grown at room temperature so that the current-voltage curve reflects the unique properties of a room temperature ordered surface.; A technique for fabrication of annealable platinum (111) scumes of disk shape with diameters from 25 μm–50 μm is also outlined. The fabricated scumes encapsulated in soft sodium glass can be annealed in a furnace at temperatures up to 700°C. The current-voltage curve of the Pt scume in 0.5 M sulfuric acid shows adsorption/desorption states of hydrogen typical for platinum (111) surfaces for the given region of potentials in a carefully purified system. This indicates that the surface of the fabricated single crystal ultramicroelectrode is clean and well oriented. The method chosen for growing the platinum single crystals utilizes annealing of platinum microspheres in a methane flame for several hours. The crystals produced this way developed all eight (111) and six (100) facets. Development of large (100) facets has been observed on all beads, which were annealed for more than 30 minutes. Depending on the time of annealing this method can also produce crystals with the shape of a truncated octahedron.; Silver single crystals of high quality were grown by reverse pulse electrolysis (RPE). Use of the short anodic pulse during the course of the silver deposition results in a decreased number of the silver nuclei formed on the cathode. The effect of the deposition current density on morphology and crystallinity of silver particles was also studied.