posted on 2024-03-08, 03:03authored byPankyu Kim, Hyeongkwon Moon, Heung Chan Lee, Jun Hui Park
We
report a novel detection method for single aqueous
droplets
in organic solvents by the collisional contact of the droplet, inducing
the partial deformation of the ultramicroelectrode (UME) surface.
For various chemical reactions in organic solvents, water impurities
affect the catalytic activity, leading to a loss of productivity and
selectivity. Therefore, it is necessary to monitor the water content
of organic solvents in real time between many chemical production
processes, from the laboratory to the industrial scale. Our method
enables the detection of water contamination by real-time monitoring
of the electrochemical signals or observing morphological changes
in the microelectrode. When an aqueous droplet collides with the UME,
the contact area of the electrode is electrolyzed, forming pits on
the surface where the droplet falls. Current transient analysis shows
a unique current spike corresponding to the reaction inside the adsorbed
single aqueous droplet, which differs from those detected by the faradaic/nonfaradaic
reaction of collision of other particles. Moreover, this analytical
method can record the history of collision events from pits on the
UME surface, implying that inspecting the UME surface could be a quick
screening method for solvent contamination. Based on a comparison
of the electrochemical signals and morphological changes of the electrode
after each event, the sizes of the pits and droplets are related.
A COMSOL simulation is performed to explain the shape of the peak
current and pit formation during collision events. This experimental
concept elucidates the dynamic behavior of aqueous droplets on a positively
biased metal electrode.