Optical sensing of electrochemical reactions on a bio-hybrid nanoparticle

An electron transfer pathway between Cytochrome c (Cyt c) molecules, a 30nm Au nanoparticle and an ITO working electrode in an electrochemical cell is constituted by molecular junctions. The scattering spectrum of single Au nanoparticle is measured simultaneously with the cyclic voltammogram. The plasmon resonance wavelength and the scattering cross section of the single Au nanoparticle are affected by the redox reactions of less than 200 cyt c molecules on its surface and exhibit cyclic variations. The electron shuttling between Cyt c molecules and ITO electrode through the Au nanoparticle in the redox process as well as the conformation change of the Cyt c molecules between ferric and ferrous states are accounted the reasons for the change of the plasmon resonance wavelength and scattering cross section. The presented study of the interaction of biological electron transporter protein and photonic nanostructure provide a nano-scale system to probe the electron transfer events in the biological system. It also has the implicational importance to the development of future hybrid bio-optoelectronic devices.