A differential photoelectrochemical method for glucose determination based on alkali-soaked zeolite imidazole framework-67 as both glucose oxidase and peroxidase mimics

A differential photoelectrochemical (PEC) method for glucose determination is reported using a nanocomposite with double mimic enzymes of glucose oxidase (GOx) and peroxidase. The nanocomposite was prepared by soaking zeolite imidazole framework-67 (ZIF-67) in 0.1 M NaOH solution at room temperature for 30 min, abbreviated as Co_xO_yH_z@ZIF-67. The Michaelis-Menten constant of Co_xO_yH_z@ZIF-67 to H₂O₂ and glucose is 121 μM and 3.95 mM, respectively. Using the photoelectrode of Co_xO_yH_z@ZIF-67/TiO₂ nanotubes (NTs), glucose was oxidized firstly by dissolved oxygen to generate H₂O₂ under the catalysis of Co_xO_yH_z film as the mimics of GOx. The product of H₂O₂ enhanced the photocurrent of TiO₂ NTs under the catalysis of ZIF-67 as the mimics of peroxidase. The molecular sieve effect of ZIF-67 frameworks reduces the interferences from molecules with size larger than the apertures in ZIF-67. Under the excitation of a 150 W xenon lamp with full spectrum, the photocurrent was measured in a two-electrode system without external additional potential. By using the photocurrent difference between two photocells, i.e Co_xO_yH_z@ZIF-67/TiO₂ NTs and Pt electrode, ZIF-67/TiO₂ NTs and Pt electrode, as the signal, the selectivity for glucose determination is improved further. The differential PEC method was applied to the determination of glucose with a linear range 0.1 μM~1 mM and a detection limit of 0.03 μM. Graphical abstract.