Generation–Collection Electrochemistry Inside a Rotating Droplet

Abstract

In this work, we explore generation-collection electrochemistry in a rotating droplet hydrodynamic system, where a 70 μL droplet containing a redox active species (ferrocyanide) is sandwiched between an upper rotating rod and bottom nonmoving generator and collector planar electrodes. In such a system, we studied the effect of the counter electrode reaction on the recorded generator current, and the effect of the generator-collector distance (ranging from 3 to ca. 500 μm) on the collection efficiencies obtained at rotation rates ranging from 50 to 1100 rpm. We found that the counter electrode reaction competes with the collector reaction for the regeneration of the electroactive species; thus, collection efficiencies of 100% are probably impossible to obtain with this system geometry. We found that the collection efficiency increases with the droplet rotation rate and decreases with the generator-collector distance. The highest collection efficiency we obtained is 62% for the generator-collector distance of 3 μm, which is more than two times higher than that for typical bulk experiments with a commercial rotating ring disk electrode. We show that the increased collection efficiency can be successfully used in epinephrine detection for filtering out signals from ascorbic acid and uric acid interferents.

3D Printed Rotating Acentric Binary-Disk Electrode

“…where i l-back is the limiting current of the back electrode; D′ is the diffusion coefficient of the product collected at the back electrode and generated at the front one; γ 0 is a parameter correlated with a given method and dual electrode system geometry, 19 while all other symbols have been defined above; k l-back is the slope of the i l-back versus ω 1/2 Levich plot (Figure S2). The collection efficiency coefficient N RABDE can then be evaluated from the values of each current at each rotation rate through Eqn (S1).…”

“…Since most of the data used in the following were obtained in a range of scan rates where i conv has a negligible effect, for the sake of simplicity we use the classical Levich formulation in eq . Note that i l‑back is not significantly affected because the mass transfer that potential curve for the reoxidation of Fe­(CN) 6 4– at the back couples the generator and collector electrodes depends exclusively on the value of the tangential flow, that is, only on the value of ω 1/2 : where i l‑back is the limiting current of the back electrode; D ′ is the diffusion coefficient of the product collected at the back electrode and generated at the front one; γ 0 is a parameter correlated with a given method and dual electrode system geometry, while all other symbols have been defined above; k l‑back is the slope of the i l‑back versus ω 1/2 Levich plot (Figure S2). The collection efficiency coefficient N RABDE can then be evaluated from the values of each current at each rotation rate through Eqn (S1).…”

Electrochemical Detection of Dopamine and Serotonin in the Presence of Interferences in a Rotating Droplet System

“…18 Electrodes with CNPs modified with phenylsulfonate groups are known to have desirable properties such as porosity, which ensures a large surface area. 29 Moreover, the CNPs used in this research have been previously shown to be good for the detection of neurotransmitters in the presence of common interfering agents. 18 One explanation can be that the CNPs are negatively charged, as are the common interfering agents AA and UA at physiological pH.…”

“…In the present study, we suggest the use of carbon nanoparticles (CNPs) encapsulated in a silica matrix . Electrodes with CNPs modified with phenylsulfonate groups are known to have desirable properties such as porosity, which ensures a large surface area . Moreover, the CNPs used in this research have been previously shown to be good for the detection of neurotransmitters in the presence of common interfering agents .…”

Fabrication of ITO microelectrodes and electrode arrays using low-cost CO2 laser plotter

“…Another interesting example is the pattern formation on ITO films coated on borosilicate glass by scanning a linearly polarized nanosecond pulsed laser beam, making use of a self-organization phenomenon named laser-induced periodic surface structures (LIPSS) [18]. Apart from these examples, there are other reports on laser patterning of ITO using other lasers, such as an UV-excimer laser and femtosecond-pulsed laser [19], but none of these gives the advantage of being widely available and preferably affordable means of fabrication of microelectrodes. Currently, CO2 lasers, emitting infrared radiation at a wavelength of 10.6 µm, are the highest power continuous wave lasers available.…”