Edge-carboxylated graphene anchoring magnetite-hydroxyapatite nanocomposite for an efficient 4-nitrophenol sensor

The surface chemistry and physical properties of edge-carboxylated graphene (ECG) have to date been over looked in terms of understanding the real world practical applications. The accurate identification of each possible oxygenated group on the surface of the basal plane as well as the edges of ECG is necessary to understand the properties for their potential multifunctional applications. Herein, we report the use of a simple high energy ball mill to prepare a large scale production of ECG from natural graphite flakes through interaction with aspartic acid under solid conditions. These 2 dimensional ECG sheets were anchored with magnetite-hydroxyapatite (m-HAp) using a simple hydrothermal process. The prepared materials were systematically investigated by various analytical techniques to realize the structural, morphological, compositional and functional properties. These m-HAp dispersed ECG sheets can be further used to modify the glassy carbon electrode (GCE) for the sensitive and selective detection of 4-nitrophenol (4-NP) by cyclic voltammogram (CV) and differential pulsed voltammetry (DPV). The high specific surface area of 130 m² g^-1 for the m-HAp on ECG displays an excellent catalytic activity with reversible redox behavior of 4-NP. The modified electrode possesses a good detection limit and high sensitivity of 0.27 μM and 0.587 μA μM^-1 cm^-2, respectively, towards 4-NP, rendering practical industrial applications.