Abstract The detection of dopamine represents an intriguing and relevant field of application for electrochemical sensors. The sensors tailored with inorganic species are of great interest due to their high tuneability in both morphology and chemical features. In this work, we investigate the effect of different amounts of poly(ethylene glycol) used as template agent for ultrasound assisted synthesis of bismuth oxynitrates on composition and morphology. We found that the increase in poly(ethylene glycol) induced a surface defectiveness on bismuth oxynitrate boosting electrochemical sensing performances reaching sensitivity of up to 16 μA/mM and LOD close to 2 μM and achieving a sixfold increase in the electron transfer rate compared with the bare electrode.