Electrochemical Behavior of Paraquat on a Highly Ordered Biosensor Based on an Unmodified DNA-3D Gold Nanoparticle Composite and Its Application

•Construction of unmodified DNA-3D gold nanoparticle composite was investigated.•Fabrication of hairpin DNA on GNPs was studied.•Redox mechanism of paraquat on the modified electrode was elucidated.•Determination method of paraquat on the modified electrode was established.