A simple procedure was developed to prepare a glassy carbon (GC) electrode modified with nickel oxide (NiOx) nanoparticles and water-soluble dyes. By immersing the GC/NiOx modified electrode into thionine (TH) or celestine blue (CB) solutions for a short period of time (5-120 s), a thin film of the proposed molecules was immobilized onto the electrode surface. The modified electrodes showed stable and a well-defined redox couples at a wide pH range (2-12), with surface confined characteristics. In comparison to usual methods for the immobilization of dye molecules, such as electropolymerization or adsorption on the surface of preanodized electrodes, the electrochemical reversibility and stability of these modified electrodes have been improved. The surface coverage and heterogeneous electron transfer rate constants (k(s)) of thionin and celestin blue immobilized on a NiOx-GC electrode were approximately 3.5 x 10(-10) mol cm(-2), 6.12 s(-1), 5.9 x 10(-10) mol cm(-2) and 6.58 s(-1), respectively. The results clearly show the high loading ability of the NiOx nanoparticles and great facilitation of the electron transfer between the immobilized TH, CB and NiOx nanoparticles. The modified electrodes show excellent electrocatalytic activity toward hydrogen peroxide reduction at a reduced overpotential. The catalytic rate constants for hydrogen peroxide reduction at GC/NiOx/CB and GC/NiOx/TH were 7.96(+/- 0.2) x 10(3) M-1 s(-1) and 5.5 (+/- 0.2) x 10(3) M-1 s(-1), respectively. The detection limit, sensitivity and linear concentration range for hydrogen peroxide detection were 1.67 mu M, 4.14 nA mu M-1 nA mu M-1 and 5 mu M to 20 mM, and 0.36 mu M, 7.62 nA mu M-1, and 1 mu M to 10 mM for the GC/NiOx/TH and GC/NiOx/CB modified electrodes, respectively. Compared to other modified electrodes, these modified electrodes have many advantages, such as remarkable catalytic activity, good reproducibility, simple preparation procedures and long-term stabilities of signal responses during hydrogen peroxide reduction. (c) 2009 Elsevier Ltd. All rights reserved.