In this article, we report a method for effective immobilization of Au nanoparticles (AuNPs) on thiolated single-stranded DNA (thiol-ssDNA) modified Au electrode (AuE) surface via coordination interactions between the nitrogen atoms of DNA bases and AuNPs. It suggests that the resultant AuNP-immobilized AuE exhibits notable catalytic performance for hydrazine oxidation and the loading of AuNPs on the AuE surface and hence the effective catalytic area can be tuned by the immobilization time of thiol-ssDNA and adsorption time of AuNPs. This hydrazine sensor has a fast amperometric response time of less than 4 s. The linear range and detection limit are estimated to be from 0.1 mM to 100 mM (r = 0.998) and 0.56 mu M at a signal-to-noise ratio of 3, respectively. (C) 2011 Elsevier BM. All rights reserved.