Zirconium-Based Metal–Organic Framework Thin Films with Large Mesopores for Amplifying Electrochemical Sensing Response toward Dopamine

High Resolution Image Download MS PowerPoint Slide Electrochemical sensing provides a simple and facile route to detect neurotransmitters such as dopamine (DA). Herein, a water-stable zirconium-based metal–organic framework (MOF), UiO-66-NH 2, is utilized as the porous coating on top of the sensing electrode to preconcentrate DA molecules near the electrode surface, in order to amplify the electrochemical sensing response. In addition, soft-template-assisted synthesis is employed to synthesize UiO-66-NH 2 materials with large mesopores (∼20 nm), small mesopores (∼6 nm), and no mesopores in their crystals, respectively, with almost the same micropore volume originating from their crystallographic structures. Crystallinity, porosity and the degree of defects in each MOF are characterized, and each MOF thin film is deposited on the graphene oxide-modified electrode to investigate the effect of such MOF overlayers with diverse pore sizes on the electrochemical sensing performance of DA. Results indicate that larger mesopores in the MOF coating can amplify the electrochemical response of DA more, owing to the facilitated mass transfer of DA in the MOF thin film. By using the MOF coating with large mesopores, a sensitivity of 10630 μA/mM-cm 2 and a limit of detection of 0.45 μM for DA sensing can be achieved, outperforming those achieved by the electrode without MOF coating (795 μA/mM-cm 2; 4.15 μM) and that with the regular microporous UiO-66-NH 2 (5212 μA/mM-cm 2; 2.26 μM). Findings here highlight the importance of large pore sizes in MOF thin films when they are employed in various electrochemical sensing applications.