Meso-tetra(4-sulfonatophenyl)porphyrin silver/Ag nanoparticles/graphene-phase CN with a sandwich-like structure and double-faced active centers two-step room-temperature photocatalytic synthesis for ractopamine detection.

Photochemical synthesis under visible light irradiation is a novel approach in the field of green chemistry, and composites with abundant active centers for electrochemical detection are highly attractive. Herein, a meso-tetra(4-sulfonatophenyl)porphyrin silver/Ag nanoparticles/graphene phase CN nanosheets (AgTPPS/AgNPs/ng-CN) material with a sandwich-like structure was synthesized using a two-step photocatalytic reaction at room temperature (25 °C). In the first visible light irradiation step and in the presence of a hole capture agent, Ag ions were photocatalytically reduced onto the surface of ng-CN that was used as a photocatalyst. Then, the protons (H) in the core of HTPPS were substituted by photo-oxidized Ag during the second visible light irradiation step and in the presence of an electron capture agent. The electrochemical response of AgTPPS and ng-CN to ractopamine (RAC) results in the unique double-faced active centers of AgTPPS/AgNPs/ng-CN, and the cores (AgNPs) are beneficial as bridges for the connection between AgTPPS and ng-CN and for high-efficiency electron transfer. Hence, as-synthesized AgTPPS/AgNPs/ng-CN exhibits high sensitivity (a low detection limit of 5.1 × 10 M, S/N = 3.0), a wide linear range (1 × 10 to 1.2 × 10 M), and long-term stability. Based on the experimental verification of the electrochemical dynamics and electrostatic attraction at the interface between the dual-active-center surface and RAC, the electrochemical mechanism has been clarified. Specifically, in the multi-cycle oxidation of RAC, the blue shift of specific UV-vis peaks also confirms the electrocatalytic oxidation of the two terminal hydroxyl groups of RAC. In brief, AgTPPS/AgNPs/ng-CN with a sandwich-like structure and double-faced active centers enhances the detection sensitivity and electrocatalytic efficiency towards RAC.