Nitrogen-Doped and Phosphorus-Doped Epoxy-Sealed Carbon Fiber Ultramicroelectrodes as Electrochemical Sensors for Detection of Hydrogen Peroxide

Ultramicroelectrodes (UMEs) are useful as probes for evaluating electroactive species in confined spaces (e.g., inside living cells) and for measuring fast electrochemical reactions. However, UME applications often require modification of the electrode surface to improve selectivity and sensitivity towards target analytes. Previous research in our group demonstrated that a simple soft nitriding method introduces surface nitrogen (N)-containing groups on carbon fiber (CF), leading to improved electroreduction of hydrogen peroxide (H2O2) on CF-UMEs. However, sensitivity for H2O2 detection using N-CF-UMEs was low compared to that for other modified UMEs. As an alternative to N-CF-UMEs, a simple strategy for preparing phosphorus (P)-doped CF-UMEs was first investigated. Since P-CF-UMEs performed similarly to N-CF-UMEs, an alternative epoxy sealing strategy for preparing CF-UMEs and doped-CF-UMEs was also developed. Compared to P-CF-UMEs and N-CF-UMEs prepared by traditional laser-assisted pipette pulling, the epoxy-sealed electrodes exhibited 20-50 times higher sensitivities and 2-3 times lower detection limits for H2O2