posted on 2021-07-26, 14:34authored byLennart
J. K. Weiß, Emir Music, Philipp Rinklin, Lea Straumann, Leroy Grob, Dirk Mayer, Bernhard Wolfrum
Stochastic impact
electrochemistry is a promising concept to detect
ultralow concentrations of nanoparticles in solution. However, statistically
reliable sensor outputs require an appropriate number of observed
nanoparticle collision events. Here, arrays of individually addressable
electrodes allow increasing the effective detection area, and thereby
the number of collision events, without sacrificing the signal-to-noise
ratio. At the same time, however, these measurements typically increase
the surface-to-volume ratio of the system, leading to a stronger influence
of adsorption on the number of available particles. We address this
issue of nanoparticle adsorption by controlling the electrode–electrolyte
interface close to the detection electrodes. We use a direct nanoimpact
experiment to demonstrate that a negatively charged surface leads
to electrostatic repulsion, which results in a 2.5-fold increase in
the number of detected collision events. Adding to this improved sensor
performance, a tunable shield electrode offers a versatile tool to
study nanoparticle adsorption at the solid–liquid interface.