Nano-crystalline graphite film on SiO2: Electrochemistry and electro-analytical application

A thick nano-crystalline graphite film (NCG, ∼350 nm) was grown on dielectric substrate (SiO2, ∼110 nm) using plasma-enhanced chemical vapour deposition (PECVD) aiming the development of an electrochemical sensor for caffeic acid. The obtained sensor was characterised using several investigation techniques such as atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The data evidenced the coexistence in the investigated sample of the nano-crystalline graphite/graphene domains, while the NCG sheet resistance (∼340 Ω/sq.) is matching well the value reported for few-layers graphene film, revealing for the nano-crystalline graphite film a better ordered graphene structure and an improved electrical conduction in the interconnected graphene domains. The sensor for caffeic acid, operating at an applied potential of +0.4 V vs. Hg/Hg2Cl2 reference electrode showed a linear working range comprised between 5.0 × 10−5 and 1.0 × 10−3 M, and very good capabilities against real samples analysis. The reproducibility of the developed sensor was assessed in the presence of 0.1 mM caffeic acid and the relative standard deviation was 5.84% (n = 11).