Photoelectrochemical determination of ractopamine based on inner filter effect between gold nanoparticles and graphitic carbon nitride-copper(II) polyphthalocyanine coupled with 3D DNA stabilizer

Copper(II) polyphthalocyanine (CuPPc) was combined with graphitic carbon nitride (g-C 3 N 4 ) to form a heterojunction with enhanced photoelectrochemical (PEC) signal. A sensitive PEC method was developed for determination of ractopamine based on a PEC inner filter effect between gold nanoparticles (AuNPs) and the g-C 3 N 4 /CuPPc. A gold electrode was modified with g-C 3 N 4 /CuPPc and the DNA was linked to the AuNPs. Initially, the PEC signal is weak due to the inner filter effect between the AuNPs and g-C 3 N 4 /CuPPc. In the presence of ractopamine, it interacts with the aptamer and the complementary chain (C chain) is released. This triggers the entropy-driven cyclic amplification and results in the release of the substrate B chain (SB chain) from three-dimensional DNA stabilizer. The probe is released from the electrode due to the interaction of probe DNA and the SB chain. As a result, the PEC signal increases linearly in the 0.1 pmol·L −1 to 1000 pmol·L −1 ractopamine concentration range. The detection limit is 0.03 pM, and the relative standard deviation is 3.4% (at a 10 pmol·L −1  level; for n  = 11). The method has been successfully applied to the determination of ractopamine in pork samples. Schematic presentation of detection method based on PEC inner filter effect between AuNPs and the g-C 3 N 4 /CuPPc being fabricated for ractopamine. 3D DNA was used as stabilizer to decrease the PEC blank signal.