Fitting Kinetics of Arbitrarily-Shaped Finite Reactive Features Using Their Scanning Electrochemical Microscopy Images

Abstract

Computer modelling of scanning electrochemical microscopy (SECM) images allows for the kinetics of chemical reactions at surfaces to be fit. Until recently, methods for fitting kinetics from SECM images of reactive features required models with custom geometries that approximated the feature shape.[1,2] The kinetics of arbitrarily-shaped features can be fit by discretizing the surface into pixels and modelling the surface rate constant of a reaction as a discrete function. The shapes of the underlying reactive feature responsible for hot spots in an SECM image were determined by deconvolution,[3] edge detection,[4] or microscopy and were used to control the surface reaction boundary condition in finite element method simulations. The use of deconvolution or edge detection to obtain an estimate for the shape of the underlying features seen in SECM images was of particular interest since they did not require any characterization of the surface beyond SECM.Simulated SECM images of reactive features on flat surfaces were controlled using three parameters: the tip to substrate distance of the scanning electrode, the rate constant for the reaction at the surface feature and the erosion and dilation of the initial estimate of the shape of the reactive feature. The parameters of these SECM images were optimized such that the simulated images fit experimental SECM images to obtain shape and kinetic information of reactive sites.The ability to accurately fit arbitrarily shaped features dramatically broadens the scope of reactive features that can be treated to include features of interest such as grain boundaries, scratches and irregularly shaped inclusions.[1] Filice, F. P.; Li, M. S. M.; Ding, Z. Simulation Assisted Nanoscale Imaging of Single Live Cells with Scanning Electrochemical Microscopy. Adv. Theory Simul. 2018, 2, 1800124[2] Leslie, N.; Mena-Morcillo, E.; Morel, A.; Mauzeroll, J. Fitting Kinetics from Scanning Electrochemical Microscopy Images of Finite Circular Features. Anal. Chem. 2022, 94, 44, 15315–15323[3] Stephens, L. I.; Payne, N. A.; Mauzeroll, J. Super-resolution Scanning Electrochemical Microscopy. Anal. Chem. 2020, 92, 3958– 3963[4] Stephens, L. I.; Payne, N. A.; Skaanvik, S. A.; Polcari, D.; Geissler, M.; Mauzeroll, J. Evaluating the Use of Edge Detection in Extracting Feature Size from Scanning Electrochemical Microscopy Images. Anal. Chem. 2019, 91, 3944– 3950