A facile method for coal to graphene oxide and its application to a biosensor

Abstract

The classic methods of synthesis of graphene oxide derived from graphite require harsh oxidation with excessive chemicals (H2SO4, H3PO4, KMnO4, etc.) and multiple processes. In this paper, we present a facile one-pot process using HNO3 to obtain graphene oxide from coal (Coal-GO). Coal has a unique molecular structure comprising of small regions or clusters of graphene-like and aliphatic side chains, for which our process is successfully able to exclude aliphatic compounds while preserving graphene domains during oxidization and subsequent exfoliation. The Coal-GO was converted to reduced graphene oxide (Coal-rGO) by conventional method to produce a few-layered graphene nanosheets in lateral size of 300–700 nm. The surface characteristics of the Coal-GO indicate the persistence of N from the raw coal as well as that introduced in the process. Notably, the Coal-GO shows a considerable amount of COOH compared to the other oxygen groups. Our data indicates that the process is effective in oxidative scissoring of the edges of coal, with minimal effect on swelling of coal towards the c-direction. Lastly, we demonstrate that compared to Graphite-GO, the Coal-GO has superior interaction with single stranded DNA aptamer, which could result in higher sensitivity chemiluminescence resonance energy transfer-based biosensors.