Aqueous ZnO nanoparticle dispersions interaction with a dioleoyl phosphatidylcholine (DOPC) monolayer is reported in this paper. ZnO-DOPC interactions were investigated using rapid cyclic voltammetry (RCV) by focusing on the effect of the interactions on the characteristics of the capacitance current peaks representing two potential induced phase transitions. Results showed: - (1) The order of interaction of common commercially sourced nanoparticles with DOPC coated Hg electrodes was NanoTek > NanoShield > metals basis. This extent of interaction was inversely related to the ZnO particle size where the metals basis nanoparticles were strongly aggregated. The contribution of the non-ionic dispersant added by manufacturer to the NanoTek and NanoShield interaction was uncertain. (2) Freshly prepared aqueous Nanosun ZnO nanoparticle (similar to 25 nm) dispersions interacted with and penetrated DOPC coated Hg electrodes. Aggregation of the nanoparticles, coating of the ZnO with phosphate and coating of the ZnO with fulvic acid minimised ZnO-DOPC interaction. (3) In-house synthesised ZnO nanoparticles of lower primary particle size (similar to 6 nm) than Nanosun ZnO nanoparticles interacted strongly with DOPC coated Hg electrodes with no evidence of penetration of the nanoparticle in the DOPC monolayer. Even after considerable aggregation of the particle to between 1 and 10 mu m, a strong interaction of the in-house synthesised ZnO with DOPC was observed. (C) 2013 Elsevier Inc. All rights reserved.