A Simple Approach to the Solution of the Diffusion Equation at the Microcylinder Electrode-an Inspiration from the Film Projector

Electrochemiluminescence at 3D Printed Titanium Electrodes

The fabrication and electrochemical properties of a 3D printed titanium electrode array are described. The array comprises 25 round cylinders (0.015 cm radius, 0.3 cm high) that are evenly separated on a 0.48 × 0.48 cm square porous base (total geometric area of 1.32 cm²). The electrochemically active surface area consists of fused titanium particles and exhibits a large roughness factor ≈17. In acidic, oxygenated solution, the available potential window is from ~-0.3 to +1.2 V. The voltammetric response of ferrocyanide is quasi-reversible arising from slow heterogeneous electron transfer due to the presence of a native/oxidatively formed oxide. Unlike other metal electrodes, both [Ru(bpy)₃]¹⁺ and [Ru(bpy)₃]³⁺ can be created in aqueous solutions which enables electrochemiluminescence to be generated by an annihilation mechanism. Depositing a thin gold layer significantly increases the standard heterogeneous electron transfer rate constant, k^o, by a factor of ~80 to a value of 8.0 ± 0.4 × 10⁻³ cm s⁻¹ and the voltammetry of ferrocyanide becomes reversible. The titanium and gold coated arrays generate electrochemiluminescence using tri-propyl amine as a co-reactant. However, the intensity of the gold-coated array is between 30 (high scan rate) and 100-fold (slow scan rates) higher at the gold coated arrays. Moreover, while the voltammetry of the luminophore is dominated by semi-infinite linear diffusion, the ECL response is significantly influenced by radial diffusion to the individual microcylinders of the array.

Monitoring colorless electroactive chemicals in complex background based on electrochemical difference absorption spectroscopy with twin flow cells

Conventional UV/Vis absorption spectroscopy is an economical and user-friendly technique for online monitoring, however, by which some electroactive chemicals are hardly determined in the presence of fluctuating background due to the formation of colored chemicals. Here, we propose an electrochemical difference absorption spectroscopy (EDAS) to accurately quantify colorless chemicals based on visible color change via electrolysis with strong variation in the background. EDAS is realized by twin spectroelectrochemical flow cells system, replacing the two cuvette cells of a dual beam spectrophotometer. Each cell consists of a three-electrode system, quartz windows and a thin flow channel. Flowing of analyte from one cell (reference cell) to the other (sample cell) can eliminate the influence of colored interferents even while their concentrations are changing. When different potentials are applied on the sample and reference cells respectively, electrolysis occurs and colored products flowing through quartz windows can absorb the incident light, resulting in difference absorption spectra induced from potential difference. We find that steady-state difference absorbance (ΔA) at characteristic wavelength is linearly changed with sample concentrations. EDAS is firstly verified by Fe(CN)₆^4- at different potentials and flow rates, in good agreements with a simplified theory that describes linear relationship between ΔA and analyte concentration. Then EDAS is used to determine Cu(I) in Cu(I)-Cu(II) mixed solutions and tetramethylbenzidine in its partially oxidized solutions to illustrate the powerful ability to detect colorless chemicals with varied background, implying its promising potential applications in the chemical industry.

On approximations to a class of Jaeger integrals

The object of this paper is to revisit a family of improper integrals first investigated by Jaeger (Jaeger 1942 Proc. R. Soc. Edinb., A 61 , 223–228). Of particular interest is a sub-class related to axisymmetric diffusion as it occurs in contemporary electrochemistry, specifically chronopotentiometry and chronoamperometry; applications that demand precision well beyond what can be achieved by simple interpolation of the tabulated solutions given by Jaeger and coworkers. To that end, the paper first outlines the less known numerical techniques necessary to solve such integrals and then employs them to obtain numerical solutions over a broad range of the temporal parameter τ , which includes the asymptotic approximations for small and large τ . Computed also are time integrals not previously calculated. More useful to practitioners, however, are approximations to the integrals that are easy to evaluate and sufficiently simple to be manipulated analytically, and the remainder of the work is devoted to such approximants. Each is constructed from a base function which captures the precise asymptotic behaviour at small and large τ plus a correction function, which is fitted either by a half-range Fourier sine series or an inverse power series in τ . Inclusion of sufficiently many terms in each series allows the approximants to realize an accuracy concordant with that of the numerical solutions. The approximants may also be integrated with respect to τ to obtain appropriate time integrals for use in convolution algorithms.