Cobalt nanoparticles with a typical size of 5 nmwere decorated on multi-walled carbon nanotubes by the use of a simple, rapid, solvent less thermal decomposition method. The cathodic electrogenerated chemiluminescence (ECL) behavior of luminol was investigated on a glassy carbon electrode modified with cobalt nanoparticles decorated multi-walled carbon nanotubes. The prepared sensor exhibited excellent electrocatalytic activity towards production of reactive oxygen species (ROSs) and consequently oxygen reduction reaction. Sweep of potential in cathodic direction produced an ECL signal at the potential about -0.5 V versus Ag vertical bar AgCl vertical bar KClsat due to the reaction between deprotonated form of luminol and ROSs. The produced cathodic ECL signal intensity was linear towards luminol in the concentration range between 5 and 770 mu M (r = 0.9984) with a detection limit of 110 nM. Also, under optimal conditions, the ECL signal intensity of luminolwas linear towards dissolved O-2 in the concentration range between 0.08 and 0.94 mM (r = 0.9914) with a detection limit of 0.04 mM. The relative standard deviations (RSD) for repetitive measurements of 20 mu M luminol (n = 10) and 0.50 mM oxygen (n = 10) at pH = 9.0 were of 3.0 and 3.9%, respectively. A possible mechanism for cathodic ECL reaction of luminol has been discussed. (C) 2014 Elsevier Ltd. All rights reserved.