Photoelectrochemical determination for acid phosphatase activity based on an electron inhibition strategy

In the present work, inspired by the excellent photoelectrochemical (PEC) properties of TiO2 and g-C3N4, a simple and sensitive TNA/g-C3N4/DAT sensor for determination of acid phosphatase (ACP) was constructed based on the electron inhibition performance of 3,5-diamino-1,2,4-triazole (DAT) and coordination of Fe(II) with DAT. DAT was oxidized by sodium nitrite to its diazonium salt and then was electrochemically grafted onto the surface of TNA/g-C3N4 to form the TNA/g-C3N4/DAT, which significantly hindered the electron transfer of TNA/g-C3N4, and reduced the photocurrent response of TNA/g-C3N4 under visible light irradiation. After immersion the TNA/g-C3N4/DAT in the mixing solution containing Fe(III), AAP and ACP enzyme, the photocurrent of the TNA/g-C3N4/DAT sensor increased due to the dephosphorylation of AAP to AA catalyzed by ACP enzyme, the reduction of Fe(III) to Fe(II) by AA, and the coordination reaction of Fe(II) with DAT, the increase value of photocurrent was linear with the concentration of ACP under the optimal experimental conditions. Therefore, the constructed TNA/g-C3N4/DAT PEC sensor exhibited a satisfying linear range (0.05-100 U L-1), low limit of detection (0.016 U L-1) and good selectivity towards ACP determination, which has been successfully applied for the analysis of real human serum samples with good precision of RSD less than 4.2 % and good accuracy of the recoveries ranged from 97 % to 104 %.