Novel electrochemical sensor based on graphene quantum dots/riboflavin nanocomposite for the detection of persulfate

A novel and sensitive electrochemical sensor based on graphene quantum dots/riboflavin modified glassy carbon (GC/GQDs/RF) electrode was constructed and utilized to determine persulfate (S2O82-). GQDs were expected to have the significant properties of graphene materials as well as new functions resulting from their quantum confinement and edge effects. The UV-vis, photoluminescence spectroscopy and transmission electron microscopy (TEM) techniques were used for characterizing the GQDs. The modified electrode showed stable and well-defined redox couples at a wide pH range (1-10), with surface confined characteristics. The electron transfer coefficient (a) and the heterogeneous electron transfer rate constant (k(s)) for redox reaction of RF were found to be 0.52 and 6.59 s(-1), respectively. The GC/GQDs/RF electrode exhibits an excellent electrocatalytic activity for a S2O82- reduction, with a measured k(cat) of similar to 4.8 x 10(3) M-1 s(-1). This catalytic reduction allows an amperometric detection of S2O82- at a potential of -0.1 V with detection limit of 0.2 mu M, concentration calibration range of 1.0 mu M to 1 mM and sensitivity of 4.7 nA mu M-1, respectively. (C) 2014 Elsevier B.V. All rights reserved.