| 66-CS1200 | | | 66-EI400 | | | 66-OMNI101 | | | 66-OMNI90 |
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Daniel Mandler's research utilizes the EI-400 Bipotentiostat for Electrochemical Microscopy |
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A substantial part of our research utilizes the scanning electrochemical microscope (SECM) says Daniel Mandler of The Hebrew University of Jerusalem. We have used SECM to study charge transfer across interfaces [1 -8]. The faradaic current measured at the ultramicroelectrode (UME) depends on its distance from the interface as well as the electrochemical process that takes place there. With the UME, charge transfer is limited to a localized area at the interface directly beneath the UME. So reactions with high lateral resolution, so-called microelectrochemistry can be driven and studied [3]. For example, substrates of silicon and other semiconductors were successfully etched as a result of electrochemically-generating a strong oxidant (such as bromine) at the UME a short distance above the surface [1]. The etching mechanism could be determined by changing parameters that had an effect on the etching rate. We have used the SECM for the local deposition of gold crystallites by the continuous anodic dissolution of a gold microelectrode [2]. The gold deposits were used to further anchor organic and biological substances, such as fluorescent dyes and enzymes [8]. Moreover, the SECM was used to verify the enzymatic activity. The development of a writing-reading-erasing system based on the local reduction of tungsten oxide has been reported [6]. This is a particularly interesting system since the local change of the oxidation state of tungsten oxide is accompanied by a color change as well as a change in conductivity. We have shown that it is possible to localize charge on the surface as long as the electric field does not cause the charge carriers to diffuse into the bulk of the substrate. Finally, we have also been interested in charge transfer across immiscible liquids [4, 7]. A model, which accounts for the local charge transfer across such interface, has been developed [7]. In SECM experiments the potential of the UME needs to be controlled vs. a reference electrode located in the solution. In many instances, the substrate needs to be biased as well, which requires a bipotentiostat. We have used the Cypress 66-EI400 bipotentiostat in our SECM experiments for this mission. It allows us to control the potentials of both the UME and the substrate independently vs. a reference electrode. Moreover, it is very stable and capable of measuring very small currents in the order sub-nanoamps and possibly even picoamps. The 66-EI400 is equipped with a wave generator that allows us to do cyclic voltammetry with the UME at different locations above the surface.
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