Prussian blue nanofilm-sensitized plasmonic electrochemical microscopy for spatially resolved detection of the localized delivery of hydrogen peroxide

Hydrogen peroxide (H₂O₂) sensing has been widely investigated using various electrochemical methods, yet the challenge of finding an imaging technique capable of real-time, spatially resolved detection remains. Addressing this, we introduce a Prussian blue (PB) nanofilm-sensitized plasmonic electrochemical microscopy (PEM) technique that successfully visualizes the localized delivery of H₂O₂. The PB nanofilm was carefully characterized, and its sensing capability towards H₂O₂ was demonstrated in amperometric mode. Employing a precise micromanipulator system, we controlled a micropipette to create a localized concentration gradient on the sensor surface and monitored the gradient through the PB nanofilm-sensitized PEM. The accuracy of the obtained concentration values was further validated by numerical simulations based on finite-element methods. Our technique ensures dependable localized detection, and we anticipate that advancements in film uniformity will further improve the resolution. The potential applications of this technique are broad and significant, including the opportunity to investigate single-cell exocytosis with neurotransmitters like dopamine, thus offering a promising avenue for future biomedical research.