Nanoelectroanalysis with Carbon Nanopipettes Based on Prussian Blue-NiHCF for Hydrogen Peroxide Sensing.

Carbon nanopipettes (CNPs) have emerged as powerful tools to track intracellular redox processes with high spatial resolution. Their implementation for robust H2O2 sensing, however, is still limited by stability and mechanistic constraints largely attributed to the surface chemistry of the electrode under nanoconfinement. To address this challenge, we report for the first time a combination of Prussian Blue-Nickel hexacyanoferrate (PB-NiHCF) modified carbon nanopipettes for the electrochemical detection of H2O2 under nanoconfined conditions. Electrodeposition strategies and stabilization protocols for the growth of PB-NiHCF thin films are thoroughly inspected. Cyclic voltammetry and double-potential step chronoamperometry (DPSC) are used to rationalize the thin-layer regime established within the nanometric inner tip of the CNPs. Attention is devoted to the nature and catalytic properties of the electrodeposited materials, which are key factors governing the sensing performance. Notably, both the open-circuit potential of the modified nanopipette and the management of the applied potential at the working electrode prove crucial for the detection mechanism. The analytical performance of the system is evaluated by DPSC, demonstrating stable sensing and a linear response up to 500 μM H2O2 (R2 = 0.996), with a limit of detection of 28.9 μM at physiological pH, supporting further in vivo single-cell analysis. Overall, this work provides an analytical framework for H2O2 detection in thin-layer electrochemical cells, opening new perspectives for nanoscale electroanalysis in confined environments and coulometric sensor development.