Electrochemical amination of graphene using nanosized PAMAM dendrimers for sensing applications

Abstract

In this work, a graphene film was electrochemically functionalized by anodic oxidation of amine terminated PAMAM (4^th generation PAMAM-(NH₂)₆₄) dendrimer molecules via a covalent linkage (C–N) between graphene and PAMAM. This simple functionalization provides ≈37.51 × 10¹⁵ PAMAM molecules per cm² on the versatile graphene, which is eleven times higher than the PAMAM molecules attached on the glassy carbon electrode (3.33 × 10¹⁵ molecules per cm²). Thus, the facile electrochemical functionalization route on graphene yields a high density of amine functional groups on graphene which offers an opportunity to load a larger number of enzymes, proteins, DNA, antibodies, antigens, etc. to develop highly sensitive graphene based bio and chemical sensors. To demonstrate this with a model, the horseradish peroxidase enzyme was immobilized onto the functionalized graphene film to detect H₂O₂. The as constructed platform shows enhanced electrocatalytic activity, high storage stability up to one month, lower applied potential and exhibits a high sensitivity of 29.86 μA mM⁻¹ cm⁻² which was 5 times greater than the functionalized GCE for the detection of H₂O₂. The sensor was also used to detect H₂O₂ in human serum to testify the feasibility of the sensor in practical application. These results demonstrate that the electrografting of PAMAM on graphene is a promising approach for the fabrication of the sensors which exhibit enhanced electrocatalytic activity, sensitivity and stability.