Sensors for Detection of Metal Cations

Monomeric porphyrins are thought to metalate and demetalate according to the overall chemical equilibrium 

The rate of polymerization and morphology of the film formed strongly depends on the inclusion of the central metal within the porphyrin. Free-base TMHPP polymerizes 

With fully water-soluble porphyrins, the metal-incorporation rate has been found to be first order in free base, metal, and anion. However, it has been suggested that during incorporation of metals in poorly soluble porphyrins, which would correspond to the situation of polymeric porphyrins, intermediate ( sitting-atop complexes) can be formed. Incorporation kinetics were suggested to be second order in metal and first order in porphyrin. The number of monolayers of polymeric porphyrins occupied by Ni(II) increases with its initial concentration. At trace concentration levels, film thickness is not important because only the first few layers are occupied, and the analyte signal does not depend on film thickness. The concentration levels (10 -10 M) and preconcentration times (40-100 seconds) are not sufficient to exceed the film capacity of monolayer film to incorporate Ni(II). However, for high Ni(II) concentra- 

Sensor fabrication Supporting material GCB or carbon fiber 

A three-step procedure is used in sensor fabrication. First, the carbon fiber is sharpened using a microbumer. In 

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