Scanning Electrochemical Microscopy of Single Spherical
Nanoparticles: Theory and
Particle Size Evaluation
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Abstract
Experiments at individual metal nanoparticles
(NPs) can provide
important information about their electrochemical and catalytic properties.
The scanning electrochemical microscope (SECM) equipped with a nanometer-sized
tip was recently used to image single 10 or 20 nm gold particles and
quantitatively investigate electrochemical reactions occurring at
their surfaces. In this Article, the theory is developed for SECM
current vs distance curves obtained with a disk-shaped tip approaching
a comparably sized, surface-bound conductive or insulating spherical
NP. The possibility of evaluating the size of a surface-bound particle
by fitting the experimental current–distance curve to the theory
is shown for NPs and tips of different radii. The effects of the NP
being partially buried into an insulating layer and the imperfect
positioning of the tip with respect to the NP center are considered.
The collection efficiency is calculated for redox species generated
at the nanoparticle surface and collected at the tip