ABSTRACT
ZnO nanoparticles ( ZnO NPs ) were obtained by a direct precipitation method. With the as-prepared ZnO NPs as seeds, Au/ZnO heterostructure was synthesized by seed-mediated growth method without any surfactant, and the diameters of ZnO NPs and Au NPs were about 50 nm and 10 nm, respectively. Then ionic liquids (ILs), trihexyltetradecylphosphonium bis (trifluoromethylsulfonyl) imide ([P(C6)3C14] [ Tf2 N] ) , and functionalized graphene ( GN ) were prepared under room temperature. The ILs as bridges could connect Au/ZnO heterostructure to form a new kind of graphene nanocomposite, Au/ZnO/GN. Then the penicillinase and hematein were immobilized on Au/ZnO/GN. And the biosensors based on penicillinase-hematein-Au/ZnO/GN (PH-AZG) were used for detecting penicillin G. In PBS buffer solution (pH 7. 0), PH-AZG exhibited a detection range from 2 . 5 × 10-14 to 3 . 3 × 10-6 mol/L with a detection limit of 1 . 5 × 10-14 mol/L (S/N≥3). Five PH-AZG electrodes were prepared with the same conditions, and the RSDs for their current response were less than 3. 2%. Furthermore, the standard curves were linear in the range of 5× 10-14-5×10-7 mol/L for milk. The average recoveries were 99. 7%-101. 4% with RSDs of 2. 3%-3. 5%(n=5). The method is sensitive and repeatable, and can be applied to the field of residue analysis about penicillins G with low concentration levels.