We have prepared nanopores with conical geometries and we have shown the translocation properties of poly(ethylene terephthalate) (PET) membranes. In order to obtain conically shaped nanopores, asymmetric etching procedure was followed. The characterization of PET membranes were performed by electrochemical methods and SEM measurements. The sensing was performed based on resistive-pulse sensing and current-potential (I-V) measurements. Finally, we have reported the resistive-pulse sensing of Ba2+ using single nanoporous membranes and examined the potential dependence of resistive-pulse sensing. Effect of metal ion concentration on the ion - current rectification was also shown and it was concluded that a higher Ba2+ concentration can be correlated with rectification ratios.