DEVELOPMENT OF AN OPTICAL AND SPECTROELECTROCHEMICAL SENSORS FOR COPPER AND CADMIUM
The spectroelectrochemical sensor with three modes of selectivity has been developed in our research group recently. This sensor consists of a planar optical electrode coated with a selective film. The analyte must partition into the selective film, be electroactive at an applied potential, and change the optical properties at reduced and oxidized states. Enhancing the sensitivity of the spectroelectrochemical sensor for a metal complex by ligand exchange within the sensing film during spectroelectrochemical modulation has been demonstrated in the first part of this research with a sensor for Cu(en)22+, where en = ethylenediamine, in aqueous solution. The ligand exchange reaction increases the difference in the molar absoptivities of the two species involved in spectroelectrochemical modulation, giving a larger optical response. The sensor consist of cation-selective Nafion-SiO2 composite film spin-coated on indium tin oxide (ITO) glass optically transparent electrode (OTE). The film was loaded with 2, 9-dimethyl-1, 10-phenanthroline (neocuproine) for the ligand exchange reaction. The electrodeposition and subsequent stripping of copper and cadmium on the ITO OTE were monitored by attenuated total internal reflectance in the second part of this research. Light passing through the ITO OTE is attenuated proportionally to the concentration of metal ion and deposition time. The wavelength dependence of the optical responses of deposited copper and cadmium were determined and compared with calculations. The morphology of the resulting metallic films on ITO surface was examined by scanning electron microscopy. Calibration curves for copper and cadmium were obtained over the range of 1 x 10-7 M 1 x 10-4 M and 1 x 10-9 1 x 10-5 M for Cu and Cd, respectively. The simultaneous determination of copper and cadmium was also demonstrated.
School:University of Cincinnati
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:spectroelectrochemistry copper cadmium sensing
Date of Publication:01/01/2003