Azo dye functionalized graphene nanoplatelets for selective detection of bisphenol A and hydrogen peroxide

Abstract

Graphene nanoplatelets (GNP) have emerged as promising electrode material for electrochemical sensing applications because of their high conductivity, large surface-to-volume ratio, biocompatibility, and low cost. However, GNP are not soluble in water. We dispersed GNP in water with the assistance of a tri-azo dye, Direct Blue 71 (DB). Thin films prepared with GNP/DB dispersions were characterized by scanning electron microscopy (SEM), Raman spectroscopy, and UV-vis spectroscopy, which indicated the binding of DB with GNP films. A GNP/DB film coated glassy carbon electrode (GCE) exhibited high electrocatalytic activity to oxidation of bisphenol A (BPA) and reduction of hydrogen peroxide (H₂O₂). The GNP/DB film greatly enhanced the BPA oxidation peak current at +524 mV, and the H₂O₂ reduction peak current at −400 mV vs. Ag/AgCl in pH 7.0 phosphate-buffered saline (PBS) solution. The oxidation peak current was proportional to the BPA concentration from 10 nM to 100 nM and 100 nM to 25 μM, with a limit of detection of 1.23 nM. The GNP/DB-modified GCE also showed a remarkable decrease of over-potential for the reduction of H₂O₂ with a fast amperometric response of less than 2 s, a good linear range of 10 μM to 1.9 mM, and a high sensitivity of 57.6 μA mM⁻¹. The fabricated sensor shows good reproducibility and stability with limited interference. Furthermore, the sensor was successfully applied to determine BPA in spiked commercial milk and juice samples.