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

A thick nano-crystalline graphite film (NCG, similar to 350 nm) was grown on dielectric substrate (SiO2, similar to 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 (similar to 340 U/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 X 10(-5) and 1.0 X 10(-3) M, and very good capabilities against real samples analysis. The reproducibility of the developed sensor was assessed in the presence of 0.1mM caffeic acid and the relative standard deviation was 5.84% (n = 11). (c) 2019 Elsevier Ltd. All rights reserved.