During the past years inorganic film modified electrodes have received increased attention due to their potentials in technical applications. Various inorganic materials, such as clays 1 , zeolites 2 , metal oxides 3 , metal phthalocyanines 4 , metal porphyrins 5 , transition metal 6 , polyoxometallates 7 and polynuclear transition metal cyanides [8][9][10] , have been used to fabricate inorganic film modified electrodes. Of these, the use of polynuclear transition metal cyanides as modifiers appears to be especially attractive because a large number of these compounds can be easily prepared. In addition, the well-defined zeolite-like structure makes the description and understanding of the charge-transfer process easier compared with that of organic polymer films.
11Since the pioneering work of Neff and Itaya 8 on Prussian Blue modified electrodes, the field of polynuclear transition metal cyanides modified electrodes has undergone considerable progress over the past years. However, considering the limited diversity of these chemically synthesized compounds, there is still muchwork to be done.In this paper, we report on a method for preparing thin films of CoHNF on glassy carbon electrode surface. The modified electrode exhibits excellent stability in aqueous media. The parameters which affect the voltammetric behavior were examined. Possible analytical applications were attempted.
Experimental
Materials and apparatusAll chemicals were of certified analytical grade (Merck) and used as received. Solutions were prepared with distilled deionized water from a Millipore system (Millipore, Milford, MA, USA). A 3-mm diameter glassy carbon electrode was polished and cleaned according to a procedure published elsewhere.
10Cyclic voltammetric and electrochemical impedance spectroscopic (EIS) experiments of the modified electrode were carried out as described previously.10 All electrochemical measurements were conducted using a conventional three-electrode system with a triangle arrangement. The modified electrode was used as the working electrode, with a platinum foil counter electrode and a saturated calomel reference electrode (SCE). All potentials reported in this work are referred to the the SCE.
ProceduresThe glassy carbon electrode was scanned from -0.6 to -1.15 V in an oxygen-free 1×10 -2 M CoCl 2 -0.1 M KNO 3 solution with a potential scan rate of 20 mV/s and kept at a potential of -1.15 V for a certain period of time. After being removed from the solution and thoroughly rinsed with water, the electrode was dipped in a 0.1 M K 2 [Fe(CN) The electrochemical behavior of a cobalt(II)-heptacyanonitrosylferrate (CoHNF) film on a glassy carbon electrode has been investigated. Cyclic voltammetry shows a single electron-transfer reaction taking place at 0.51 V for the modified electrode. The ion effect of the supporting electrolyte indicates that the ion permeability in the CoHNF film is mainly determined by the hydrated radius of cation. The modified electrode catalyzes redox reactions of the Fe 2+ /Fe 3+ couple. It a...