In this work, a novel type electrode based on RuO2 nanoparticles-modified vertically aligned carbon nanotubes (RuO2/MWCNTs) was prepared by magnetron sputtering deposition. This RuO2/MWCNTs electrode not only shows a high capacity nature, but also possesses a good response to the pH value. The pH sensor based on the RuO2/MWCNTs nanocomposite electrode exhibits some advantages over the conventional pH sensors. It shows good reproducibility, long-term storage stability (over 1 month) and linear response in the whole pH range (2-12) of Britton-Robinson (B-R) buffer solutions with near-Nernstian response (about -55 mV/pH). The hysteretic widths of the nanocomposite electrode are 6.4 mV, 5.1 mV and 10.2 mV in pH 7-4-7-10-7, pH 7-10-7-4-7 and pH 2-8-12-8-2 loop cycles, respectively. Moreover, the RuO2/MWCNTs electrode displays an excellent anti-interference property and fast response time (less than 40 s). According to the electrochemical impedance measurements, the pH sensing properties of the RuO2/MWCNT5 electrode were also discussed. (C) 2010 Elsevier Ltd. All rights reserved.