A label-free electrochemical sensor constructed with layer-by-layer assembly of GCE-AuNPs-Q[7]·HAuCl 4 for detection of diphenylamine.

Metal-organic frameworks (MOFs) including cucurbit[7]uril block (Q[7]·HAuCl 4 ) were employed to develop a diphenylamine (DPA) sensor in electrochemical method, the presence of HAuCl 4 improved the conductivity of the macrocyclic compound. To further enhance of the sensitivity, Au nanoparticles were inserted between the surface of glassy carbon electrode and Q[7]·HAuCl 4 MOFs (GCE-AuNPs-Q[7]·HAuCl 4 ). Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) were applied for evaluation on the electrochemical behavior. For the electrochemical inertness of DPA, a label-free electrochemical sensor in 5 mM K 3 [Fe(CN) 6 ] solution was achieved, to produce a limit of detection as low as 4.6 µM in a linear range of 5-1000 µM with good reproducibility, high stability and acceptable anti-interference ability. Application of the proposed electrode for the quantitative determination of DPA in tap water and apple juice confirms its real value.