Towards the fabrication of a label-free amperometric immunosensor using SWNTs for direct detection of paraoxon

► A label-free immunosensor based on SWNTs for detection of paraoxon is presented. ► SWNTs are vertically aligned on diazonium salt modified interface by CC bonding. ► The immunosensor shows high specificity, selectivity, and sensitivity to paraoxon. ► Paraoxon can be detected by a displacement assay with a detection limit of 2 ppb. ► The sensing system has potential for on-site detection of a spectrum of pesticides.