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 (α) and the heterogeneous electron transfer rate constant (ks) 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 kcat of ∼4.8 × 103 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 μM, concentration calibration range of 1.0 μM to 1 mM and sensitivity of 4.7 nA μM−1, respectively.