Nanostructured ZnO films: A study of molecular influence on transport properties by impedance spectroscopy

• We study electrical transport in nanostructured ZnO films by impedance spectroscopy.
• Bioaggregates on the surface produce strong changes in film transport properties.
• This behavior is explained by modeling data with RC parallel circuits.
• Electrical responses of ZnO films to aggregates are promising for biosensing.

Nanomaterials based on ZnO have been used to build glucose sensors due to its high isoelectric point, which is important when a protein like Glucose Oxidase (GOx) is attached to a surface. It also creates a biologically friendly environment to preserve the activity of the enzyme. In this work we study the electrical transport properties of ZnO thin films (TFs) and single crystals (SC) in contact with different solutions by using impedance spectroscopy. We have found that the composition of the liquid, by means of the charge of the ions, produces strong changes in the transport properties of the TF. The enzyme GOx and phosphate buffer solutions have the major effect in the conduction through the films, which can be explained by the entrapment of carriers at the grain boundaries of the TFs. These results can help to design a new concept in glucose biosensing.

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