Microarrays of Ring-Recessed Disk Electrodes in Transient Generator-Collector Mode: Theory and Experiment

Abstract

The fabrication, characterisation and use of arrays of ring-recessed disk microelectrodes is reported. This devices are operated in generator-collector mode with a disc acting as generator and the ring as the collector. We report experiments and simulations relating to time of flight experiments in which material electrogenerated at a disc is diffusionally transported to the ring. Analysis of the current transient measured at the latter when it is potentiostatted at a value to ensure diffusionally controlled "collection" is shown to sensitively reflect the diffusion coefficients of the species forming the redox couple being driven at the generator electrode. The method is applied to the ferrocene/ferrocenium couple in the room temperature ionic liquid [N 6,2,2,2 ][NTf 2 ] and the results found to agree with independent measurements.

Dual-microdisk electrodes in transient generator–collector mode: Experiment and theory

“…Baur et al assumed a semi-infinite boundary at a distance of 12 radii divided by the diffusional distance moved each step -for example, where a semi-infinite boundary is set at 60 diffusional distances from the electrode surface, and thus after 60 steps, an element could have hit the electrode, then a side boundary, and re-enter the other side, much like an array, despite the simulation being run over 10,000 steps. This is in contrast to common simulation practice, where a diffusion domain size proportional to the experimental time has been extensively used successfully [43,[54][55][56][57][58][59] and is known to sufficiently exceed the diffusion layer in all cases [60]. Also of note, is the method by which Brownian diffusion was modelled -a pseudo pyramidal diffusion from the electrode is observed due to tri-axial random movement being considered, rather than an easily implementable spherical diffusion model.…”

“…Such measurements can also be operated in transient mode, where 'time of flight' experiments reflect, in a highly sensitive manner, both the diffusion coefficient and the homogeneous chemical reaction rates of electro-generated species; such experiments are normally conducted with a potential step at the generator electrode with the collector current measured at a potential corresponding to a transport limited detection of the product or intermediate of interest. These systems have been studied extensively in terms of two dimensional diffusion, where the collector and generator are both parallel microbands [25][26][27][28][29][30], channel electrodes [27,31,32], walljet electrodes [33,34], or at a ring-disk electrode [35][36][37][38][39][40][41][42][43]. To a lesser extent, due to the stimulatory three-dimensional nature of the system, the dual-microdisk generator collector system has also been probed [23,24,36,44], as well as dual micro-hemispheroidal electrode systems [24,45,46].…”

Profiling of oxygen in biofilms using individually addressable disk microelectrodes on a microfabricated needle

“…Thus, it is possible to create nano-and microelectrodes and their arrays [18][19][20][21], including disks [20,22], bands [23,24] and 3D structures [25][26][27], and wire them either in parallel or individually [18,20]. On top of that, microfabrication techniques allow the cost-effective mass-production of microsensors that can be deployed in a vast number of applications.…”

Dual band electrodes in generator–collector mode: Simultaneous measurement of two species

“…[45][46][47] The uses of collector-generator systems have proved at least as varied as their geometries!…”