engleski

DME as adhesion sensor for micro-particles in aquatic environment

Dissolved organic molecules and nano-particles in aquatic environments are traced through their collective adsorption response. We will show that individual micro-particles can be studied through current spikes caused by adhesion at a localized fraction of the mercury electrode/aqueous electrolyte interface. Adhesion and spreading of a micro-particle at DME causes double-layer charge displacement and a dramatic decrease of interfacial tension at the contact interface, followed by a transient local increase in the interfacial turbulence which results in a current transient at millisecond time-scale. The amplitude of the spike-shaped signal (adhesion signal) reflects the particle size and magnitude of adhesion forces. Particle abundance in the medium can be determined from the signal frequency expressed as the average number of signals per drop-life. The electrochemical technique is based on chronoamperometry of oxygen reduction at the potentials of streaming maximum at DME. This is a modification of a widely used polarographic technique for measurements of dissolved surfactants founded by Gosmann and Heyrovsky in 1931 as the Adsorption Analysis.

chronoamperometry; current transients; microparticles

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