National Nanotechnology Laboratory of INFM, Department of Innovative Engineering, University of Lecce, via Arnesano, I-73100 Lecce, Italy
Thanks to their natural functional characteristics which involve inter- and intra-molecular electron transfer properties, metalloproteins are good candidates for biomolecular nanoelectronics. In particular, blue copper proteins like azurin, can bind gold via a disulfide site present on the protein surface, and have a natural electron transfer activity that can be exploited for the realization of molecular switches whose conduction state can be controlled by tuning their redox state through an external voltage source.
Recent experiments carried out by electrochemical scanning tunneling microscopy (EC-STM) on Az molecules immobilized on Au(111) surfaces have demonstrated the possibility of eliciting current flow through the redox level of a single molecule, providing the physical ground for using these metalloproteins as molecular switches. In this talk we give an overview on the problem of realizing a prototype of biomolecular device in the solid state and operating in air, based on such class of proteins. We prove the effectiveness of the charge transfer process in protein devices by using proteins with different redox centers (metal atoms) and by controlling their orientation in the solid state through different immobilization methods. A biomolecular electron rectifier is demonstrated by interconnecting two gold nanoelectrodes with an azurin monolayer immobilized on SiO2. The device exhibits a clear rectifying behavior with discrete current steps in the positive wing of the current-voltage curve, which are ascribed to resonant tunnelling through the redox active center. On the base of these results we were able to implement Azurin-based three terminal devices. Preliminar tests performed on these novel devices will be presented and discussed.