Electrochemical plasmonic sensors.

The enormous progress of nanotechnology during the last decade has made it possible to fabricate a great variety of nanostructures. On the nanoscale, metals exhibit special electrical and optical properties, which can be utilized for novel applications. In particular, plasmonic sensors including both the established technique of surface plasmon resonance and more recent nanoplasmonic sensors, have recently attracted much attention. However, some of the simplest and most successful sensors, such as the glucose biosensor, are based on electrical readout. In this review we describe the implementation of electrochemistry with plasmonic nanostructures for combined electrical and optical signal transduction. We highlight results from different types of metallic nanostructures such as nanoparticles, nanowires, nanoholes or simply films of nanoscale thickness. We briefly give an overview of their optical properties and discuss implementation of electrochemical methods. In particular, we review studies on how electrochemical potentials influence the plasmon resonances in different nanostructures, as this type of fundamental understanding is necessary for successful combination of the methods. Although several combined platforms exist, many are not yet in use as sensors partly because of the complicated effects from electrochemical potentials on plasmon resonances. Yet, there are clearly promising aspects of these sensor combinations and we conclude this review by discussing the advantages of synchronized electrical and optical readout, illustrating the versatility of these technologies.