In the work presented, a dipyrromethene with a thiol group has been applied to gold electrode modification. The blocking behaviour of mixed dipyrromethene-thiol (DPT)/dodecanethiol (DDT) self-assembled monolayers (SAMs) has been studied as a function of pH using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It has been shown that hydrogen-bonding between adjacent ligands affects the pH properties of SAMs studied. in the modification solution, an optimum ratio dipyrromethane-thiol/dodecanethiol was found to get the strongest pH response of SAM. The dipyrrromethene-thiol/dodecanethiolSAMs have been characterized also by FTIR and wettability contact angle measurements. The possible application of the mixed dipyrromethane-thiol/dodecanethil SAMs presented will be discussed. (c) 2008 Elsevier Ltd. All rights reserved.