Bipotentiostat, described

Three-electrode control systems are widely available in the market and there are also four-electrode systems for double working electrodes. The construction is either integral or modular. It is perfectly possible to construct the necessary electronics in-house and, in this case, modular construction is suggested as being more flexible. Operational amplifiers and other components of high quality should be used, particularly for kinetic applications. The elements of a bipotentiostat (independent control of two working electrodes) and a galvanostat are described in ref. 139. 

The model 900 SECM (CH Instruments) is the first commercial instrument specifically designed for SECM. Although STM instruments equipped with electrochemical accessories can be adapted for some SECM experiments, they cannot replace a general purpose SECM instrument. This section will describe the features of the model 900. The model 900 includes the cell and probe positioner illustrated in Figure 5 as well as a computer, motor controller, and bipotentiostat (35). 

SECM instruments suitable for imaging require a PC equipped with an interface board to synchronize acquisition of the electrochemical data with the movement of the tip. Building an SECM for kinetic experiments at fixed tip position or approach curve measurements is relatively easy, but fairly sophisticated software and some electronic work is necessary to construct a computer-controlled apparatus for imaging applications. Details on the construction of SECM instruments can be found elsewhere [6, 13-18, 53, 55]. An SECM is now available commercially from CH Instruments, Inc. (Austin, TX, USA). The instrument employs piezoelectric actuators, a three-axis stage, and a bipotentiostat controlled by an external PC under a 32-bit Windows environment. Various standard electrochemical techniques are incorporated along with SECM imaging, approach curves, and the modes described in Sect. 3.3.I.I. 

An electrochemical inclusion junction has also been described [118, 119]. It consists of two HMDEs, both of which support a SAM of the ruthenium pentamine pyridine-terminated thiol, HS(CH2)ioCONHCH2pyRu(NH3)s, and are brought into contact in an aqueous solution. The potentials of the two electrodes are controlled independently with respect to a common reference electrode immersed in the solution, by using a bipotentiostat. Under certain... 

The review by Siegenthaler describes a detailed comparison between various types of electric circuits to control the electrode potentials of the tunneling tip and the substrate independently using the so-called bipotentiostat [5]. Figure 2(a) illustrates the apparatus of in situ STM with the... 

In situ conductimetry is a convenient tool for studying the influence of different conditions on the preparation of conductive polymers. Conductivity is perhaps the best single parameter that describes the quality of a CP. In addition, the dopingundoping processes can be studied by monitoring conductance as potential is being scanned. Unfortunately, no commercial instrument directly applicable for in situ conductimetry is yet available, although it is possible to construct one from a commercial bipotentiostat and appropriate microelectrodes. The double-band platinum electrode can be constructed relatively easily without any special tools [7] (Fig. 12).. 

The potentiostat described earlier is used to control the potential of the working electrode and to measure the corresponding current for an RDE. A bipotentiostat is... 

Using a split RDE, one may analyze two products simultaneously, i.e., the dissolution of Cu+ and Cu " or of Fe and Fe. These measurements require a tripotentiostat, which allows setting the electrode potentials for the disc and the two rings independently whereas an RRD electrode requires a bipotentiostat only. For these measurements, the electronic circuits require a common RE and a grounded CE. Differential amplifiers at the entrance of the three (or two) potentiostats uncouple the WEs (rings and disc) so that the whole circuit is grounded at one point. The related equipment and the procedure to produce electrodes for corrosion studies is described in the literature [45-47]. 

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