Three-component spectroelectrochemical sensor module for the detection of pertechnetate (TcO4-)

Abstract

This review looks at the advancements in the development of a sensor for technetium (Tc) that is applicable to characterizing and monitoring the vadose zone and associated subsurface water. Subsurface contamination by Tc is of particular concern for two reasons: the long lifetime of its most common isotope 99 Tc (half-life = 2 × 10 5 years) and the fast migration in soils of pertechnetate (TcO 4 -), which is considered to be the dominant 99 Tc species in ground water. TcO 4 -does not have a characteristic spectral signature which prevents its rapid, sensitive, and economic in situ detection. To address this problem, a novel spectroelectrochemical sensor has been designed, that combines three modes of selectivity (electrochemistry, spectroscopy, and selective partitioning) into a single sensor to substantially improve specificity, which is critical in the specific detection of an analyte in the presence of potential interfering species. The sensor consists of a basic spectroelectrochemical configuration: a waveguide with an optically transparent electrode (OTE) that is coated with a thin chemically-selective film that preconcentrates the analyte. The key to adapting this generic sensor to detect TcO 4 -and Tc complexes lies in the development of chemically-selective films that preconcentrate the analyte and, when necessary, chemically convert it into a complex with electrochemical and spectroscopic properties appropriate for sensing. The chemically selective films can be combined with ligands which are capable of reacting with TcO 4 -to form coordination complexes, the spectral properties of which can be used to enhance the sensitivity of detection. The first half of this review describes the general concept of the sensor and the rationale for the selection of its specific components, and the development and characterization of the sensor for the different detection modules. The second half summarizes the synthesis and characterization of complexes relevant for the detection of technetium, and the progress in the utilization of the sensor module for the effective detection of these complexes.

A Highly Efficient Coordination Polymer for Selective Trapping and Sensing of Perrhenate/Pertechnetate

“…Thus, it can be concluded that the ligand-to-ReO 4electron transfer will also be responsible for the observed fluorescence quenching. 30,32,55…”

Optically Transparent Thin-Film Electrode Chip for Spectroelectrochemical Sensing

“…Some commercially available electrodes designed for spectroelectrochemistry are useful for absorption, 23 but these products are not available for fluorescence, due to the strong background interference from plastic substrates. 24 Our group has demonstrated the use of optically transparent electrodes (OTEs) consisting of ITO deposited on a glass substrate for a variety of applications, 25 including the spectroelectrochemical sensing of polycyclic aromatic hydrocarbons by fluorescence, 26,27 rhenium 28 and technetium detection by absorption 29 and fluorescence, 10,30,31 ruthenium in natural and drinking water, 32 and ferrocyanide detection in the presence of interfering species in Hanford tank nuclear waste samples. 33−35 ITO has also recently been shown to be useful for nonspectroscopic techniques, such as cathodic stripping voltammetry to detect manganese where the positive potential limit and low background current are advantageous.…”

Influence of Ionic Liquids on the Selectivity of Ion Exchange-Based Polymer Membrane Sensing Layers

“…For example spectroelectrochemical sensors utilize polymeric polyelectrolyte films as the first mode of selectivity that facilitate the selective extraction and pre-concentration of analyte from the sample. This is then followed by ion transport to the optically transparent electrode where the electrochemical and optical signals are measured [ 3 , 4 , 5 ]. “Electronic tongues” are sensors that utilize a number of low selective membranes in conjunction with advanced mathematical procedures for signal processing and analyte detection [ 6 ].…”