Synthesis and high activity of vertical graphene nanoflake films for detecting biomolecules

In this work, we report an efficient method of chemical vapour deposition, without use of any metal catalysts, for the successful synthesis of vertical graphene nanoflake films (GNFs) on Si substrate. Effects of the growth condition on the surface morphology, microstructure, and chemical composition of GNFs are characterized by using scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The constituent nanoflakes have a highly graphitized knife-edge structure with a 2 - 3 nm thick sharp edge and show a preferentially vertical orientation with respect to the Si substrate. This leads to the surface of the GNFs being terminated with a large amount of active edge planes. Their electrocatalytic property is studied by using cyclic voltammetry and differential pulse voltammetry. They demonstrated excellent activity for electrooxidating various biomolecules such as dopamine and ascorbic acid and well distinguish them when they co-exist, much better than other solid electrodes. This work will pave the way to the development of highly sensitive, highly selective graphene based biosensors for our community.