Graphene-carbon black-SrO sensor enables sensitive theobromine detection at neutral pH

Researchers at Oregon State University (OSU), National Taipei University of Technology and Ming Chi University of Technology have developed a nanoscale electrochemical sensor that can measure theobromine in beverages with high sensitivity and accuracy. The central concept is engineered interfacial chemistry: the material creates localized alkaline microdomains directly at the electrode surface, enabling efficient electrochemical oxidation of theobromine while the bulk solution remains at neutral pH.

The sensing layer is a ternary nanocomposite combining strontium oxide (SrO), functionalized carbon black (f‑CB) and reduced graphene oxide (r‑GO). SrO forms nanoscale alkaline domains that facilitate interfacial proton abstraction from theobromine, effectively activating this weakly electroactive molecule at neutral pH. Reduced graphene oxide provides a highly conductive, high-surface-area network and engages in π–π interactions with the heterocyclic xanthine core of theobromine, enhancing adsorption at the electrode. Functionalized carbon black strengthens cross‑nanointerface electron transfer and remains a dominant pathway for charge transport, improving overall electrochemical performance.

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