Role of sp² carbon in non-enzymatic electrochemical sensing of glucose using boron-doped diamond electrodes

Boron-doped diamond (BDD) is of increasing interest for applications in electrochemical sensing. It is well known that the sp² carbon content in BDD influences its electrochemical properties as electrode material. In this work, evidence is provided that the surface sp² carbon content plays a crucial role in the electrochemical sensitivity of BDD towards glucose. Single-crystal BDD, freestanding polycrystalline BDD and glassy carbon (sp² carbon reference material) were examined by voltammetry. Neither single-crystal BDD, which is free of sp² carbon, nor pure sp² glassy carbon could detect glucose in the range of 0.2–1.0 V. On the other hand, glucose oxidation was observed on polycrystalline BDD, and with increasing intensity with increase of sp² carbon content. Thus, an optimum amount of (B-doped) sp² carbon in the BDD electrode is needed for best sensing performance. Understanding this, and being able to control the composition of BDD, are not only important to glucose detection but to any electrochemical sensing application involving BDD.