A trinuclear copper(I) complex, [Cu-3(I)(L)(L')(2)][L' = the 1-[(2-carboxymethyl)benzene]-3-[benzothiazole] triazene ion][L = 1-[(2-carboxyethyl)benzene]-3-[benzothiazole] triazene] (1), was synthesized and characterized by single crystal X-ray diffraction (XRD) studies. The complex 1 was then immobilized on the surface of Au electrode through Au-S covalent bonds. The chemical properties of the modified electrode was investigated using X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). The immobilized complex 1 on the Au electrode can quickly transfer electrons. Upon addition of hydrogen peroxide, it inhibits the direct electron transfer of the modified electrode due to the generation of the [Cu-3(I)(L)(L')(2)]-H2O2-complex. Based on this quenching mechanism, the modified electrode as hydrogen peroxide sensor is developed. Under the optimum conditions, the ultralow detection limit of 0.042 mu M (S/N = 3) is achieved and the linear concentration is 0.05-60 mu M with the correlation coefficients of 0.9988. The modified electrode allowed sensitive, stable and fast electrochemical sensing of H2O2. The analysis of medical disinfection solution real samples was performed using the proposed method and the obtained results were satisfactory. (C) 2015 Elsevier B.V. All rights reserved.