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 CoOH@ZIF-67. The Michaelis-Menten constant of CoOH@ZIF-67 to HO and glucose is 121 μM and 3.95 mM, respectively. Using the photoelectrode of CoOH@ZIF-67/TiO nanotubes (NTs), glucose was oxidized firstly by dissolved oxygen to generate HO under the catalysis of CoOH film as the mimics of GOx. The product of HO enhanced the photocurrent of TiO 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 CoOH@ZIF-67/TiO NTs and Pt electrode, ZIF-67/TiO 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.