Evaluation of electrodes coated with metal hexacyanoferrate as amperometric sensors for nonelectroactive cations in flow systems

Two electrodes modified with either nickel or cupric hexacyanoferrate films were evaluated and compared as sensors for nonelectroactive cations in a flow-injection system. Both gave responses for group 1A and ammonium ions, but only the electrode modified with cupric hexacyanoferrate was sufficiently stable for use in flowing solutions. This electrode responded to K⁺, NH, Rb⁺, and Cs⁺ ions rather selectively. Within this group, the selectivity could be controlled from general to almost specific toward Cs⁺ by the potential at which the electrode was poised. The electrode was compatible with a mobile phase of dilute nitric acid commonly used in ion chromatography, and chromatographic detection limits of 2 × 10⁻⁷ M and linear responses over two decades were obtained. The electrode was applied to the ion chromatographic analysis of K⁺ and NH in urine and K⁺ in blood serum samples.     

Computer simulations of the role of group V molecular reactions at steps during molecular beam epitaxial growth of III-V semiconductors

The Configuration Dependent Reactive Incorporation (CDRI) model is used to study the growth of III-V semiconductors by MBE. In particular, the role of the dissociative reaction of the group V molecular species from the physisorbed precursor state is studied. The model allows for the reaction to occur at pairs of vacant group V sites which are intra- or interplanar nearest neighbors on the group V sublattice. Within this model, it is shown that a relatively small number of depositions at steps can play an important role in determining the smoothness of the growth front and the effective migration length of the group III species. Conditions under which these depositions are likely to be less influential are also discussed.