Activation of Glassy Carbon Surfaces by Alkaline Anodization Enhances Dopamine Adsorption and Electron-Transfer Kinetics

Surface activation can increase the sensitivity of carbon electrodes for electrochemical detection of neurotransmitters, such as dopamine (DA). However, fully understanding the changes in DA behavior after electrode activation remains elusive. Herein, we use scanning electrochemical cell microscopy (SECCM) to investigate DA adsorption and electrochemistry on glassy carbon (GC) after anodization in alkaline media. Through localized microscale anodization to different extents (two distinct times and same potential), followed by spatially-resolved SECCM, we achieve direct visualization of DA electrochemistry across unmodified and anodized GC regions, with complementary microscopy and spectroscopy unraveling the effects of co-located carbon surface chemistry and structure. Our findings reveal that short anodization times (60 s) enhance DA adsorption, rapidly reaching nearly complete monolayer coverage. Longer anodization (300 s) induces further changes in electrochemical surface area so that although the DA surface concentration increased based on geometric area, it was smaller based on specific surface area. This work highlights that even small differences in surface properties after activation can significantly impact electrode performance for neurotransmitter sensing, and separating the individual contribution of chemical and topographical factors remains challenging. SECCM provides an excellent platform to assess activation methods in a high throughput format to help accelerate the discovery of optimal modified electrodes.