Tailoring Perfluorosulfonated Ionomer-Entrapped Sol−Gel-Derived Silica Nanocomposite for Spectroelectrochemical Sensing of Re(DMPE)₃⁺

Abstract

The influence of the initial molar ratio of water relative to tetraethyl orthosilicate (TEOS) precursor and the content of Nafion ionomer in sol−gel-derived silica composites on the voltammetric response of electrodes modified with these composites for [ReI(DMPE)3]+ was investigated. The slow diffusion of [ReI(DMPE)3]+ in Nafion can be significantly improved by dispersing Nafion in sol−gel-derived silica, and the diffusion of [ReI(DMPE)3]+ in such a composite increases with the increase in water/TEOS molar ratio and the decrease in Nafion content. With the mass ratio of Nafion relative to sol−gel-derived silica being 40:100 and the initial molar ratio of water relative to TEOS being 20:1, the electrodes modified with the derived Nafion−silica nanocomposite exhibited an apparent peak current increase rate, during preconcentration of [ReI(DMPE)3]+, that was approximately three times faster than the corresponding Nafion-modified electrode. Compared with bare indium−tin oxide (ITO) glass, the composite-coated ITO glass showed a 25-fold enhancement in voltammetric response to [ReI(DMPE)3]+. The suitability of the developed optically transparent Nafion−silica composite for spectroelectrochemical sensing of [ReI(DMPE)3]+ was demonstrated. The [ReI(DMPE)3]+ extracted into the coating (∼0.4 μm in thickness) was electrolyzed to [ReII(DMPE)3]2+. Under attenuated total reflection mode, the in-situ electrogenerated chromophore [ReII(DMPE)3]2+ was monitored by probing its interaction with the evanescent field of light of a selected wavelength. Thus, the elements required for a spectroelectrochemical sensor with three modes of selectivity were demonstrated: partitioning into the film on an electrode surface and an electrochemically modulated optical signal.

Waveguide surface plasmon resonance studies of surface reactions on gold electrodes

“…When used in this way the waveguide structure responds to changes in the imaginary part of the complex refractive index of the superstrate, in contrast to the planar waveguide surface plasmon resonance device which responds to changes in both the real and imaginary parts of the refractive index. For example, Piraud et al 21,22 have described an electrochemically regenerated chlorine sensor based on a lutetium phthalocyanine coated integrated waveguide structure, Dunphy et al 18,19 have used grating coupled step index slab waveguides to study adsorption of strongly coloured species at electrode surfaces, and Heineman et al 23,[25][26][27][28] have recently combined electrochemical modulation, selective adsorption into thin coatings, and planar waveguide optical measurements to develop highly sensitive and selective solution phase chemical sensors. In contrast a bare handful of papers describe SPR studies employing waveguide structures, despite the evident potential advantages of this approach.…”

Fluorescent phosphinimine as possible precursor to an anionic and fluorescent sensor for Tc-99

“…The absorption spectrum remains virtually unchanged, eliminating the thought of ground-state interactions. The fine (< 450 nm) and broadband (∼ 450 nm) structural features are also present to a much lesser extent in the emission spectra of the protonated form of compound (1), and compounds (2) − ] to the anthracene sample does not change the original spectrum in terms of overall spectral features or intensity.…”

“…Samples analyzed for technetium contamination must undergo manual chemical separation to pre-concentrate the technetium. There are a wide variety of analytical methods available to detect technetium once it has been pre-concentrated [1][2][3][4][5], with times for chemical separation plus analysis often ranging from weeks to months depending on the total number of samples. Development of a sensor for rapid detection and quantitation of 99 Tc would be useful.…”

Design and Development of a New Hybrid Spectroelectrochemical Sensor

“…In order to demonstrate the general applicability of the sensor to positively and negatively charged inorganic coordination compounds and organic compounds, we have shown the sensor concept to work for the following compounds in addition to ferrocyanide described in the previous section: Ru ( (18), and methyl viologen. In general, the performance of the sensor for these other analytes is similar to that described above for ferrocyanide.…”

“…The capability of simultaneously monitoring the electrochemical and optical events of the rhenium complex, and by extension the analogous technetium complex, was demonstrated (18).…”