Graphene nanostructures with plasma polymerized allylamine biosensor for selective detection of mercury ions

Despite the high toxicity of mercury (Hg), it has broad-ranging applications such as in thermometers and batteries. Consequently, serious environmental pollution is inevitable. In this study, we prepared graphene nanostructures used as highly sensitive and selective DNA sensors for the determination of Hg2+ ions. The sensors consisted of multiple layers of nanostructured plasma-polymerized allylamine (PPAA) and nanosheets of conductive graphene. After immobilizing the probe DNA onto the sensitive layer and upon introducing the target analyte, Hg2+ ions became intercalated into the DNA poly-ion complex membrane based on T-Hg2+-T coordination chemistry. Experimental results revealed that the frequency variation of the quartz chip of our system increased with increased Hg2+ level in the sample and had limits of detection of 0.031 and 0.017 nM determined by QCM and electrochemical measurements, respectively. The strategy afforded high selectivity of Hg2+ against other interfering metal ions. In addition, the developed DNA sensor for the determination of Hg2+ ions could be reproduced up to 10 cycles at approximately 88% recovery.