Ratiometric electrochemical glucose biosensor based on GOD/AuNPs/Cu-BTC MOFs/macroporous carbon integrated electrode

Cu-trimesic acid metal-organic frameworks (Cu-BTC MOFs) were firstly grown on three-dimensional macroporous carbon integrated electrode (3D-KSCs), then Au nanoparticles (AuNPs) were electrodeposited on Cu-BTC MOFs/3D-KSCs electrode and finally glucose oxidase (GOD) was immobilized to construct a ratiometric electrochemical glucose biosensor. Scanning electron microscopy was employed to monitor the modified process of GOD/AuNPs/Cu-BTC MOFs/3D-KSCs electrode. Electrochemical techniques were applied to explore the electrochemical behaviors of GOD/AuNPs/Cu-BTC MOFs/3D-KSCs electrode, which showed the reduction peaks of O2 and Cu-BTC MOFs. The reduction peak current density of O2 decreased and the reduction peak current density of Cu-BTC MOFs increased with the increase of glucose concentration less than 4 mM. However, the reduction peak current of O2 was still declined while the reduction peak current of Cu-BTC MOFs maintained constant with the addition of glucose beyond 4 mM. The jO2/jCu-BTC was considered as the response signal which exhibited a good linear range with the glucose concentration from 44.9 μM to 4.0 mM and from 4.0 to 19 mM, and the detection limit was 14.77 μM. The as-prepared biosensor also showed high accuracy, high selectivity and good reproducibility. The work gave a first example to use electroactive MOFs as reference signal for ratiometric electrochemical sensor.