Tamm Plasmon Resonance as Optical Fingerprint of Silver/Bacteria Interaction

Abstract

The incorporation of responsive elements into photonic crystals is an effective strategy for fabricating active optical components to be used as sensors, actuators, and modulators. In particular, the combination of simple multilayered dielectric mirrors with optically responsive plasmonic materials has proven to be successful. Recently, Tamm plasmon (TP) modes have emerged as powerful tools for these purposes. These modes arise at the interface between a distributed Bragg reflector (DBR) and a plasmonic layer and can be excited at a normal incidence angle. Although the TP field is located usually at the DBR/metal interface, recent studies have demonstrated that nanoscale corrugation of the metal layer permits access to the TP mode from outside, thus opening exciting perspectives for many real-life applications. In this study, we show that the TP resonance obtained by capping a DBR with a nanostructured layer of silver is responsive to Escherichia coli. Our data indicate that the modification of the TP mode originates from the well-known capability of silver to interact with bacteria, within a process in which the release of Ag+ ions leaves an excess of negative charge in the metal lattice. Finally, we exploited this effect to devise a case study in which we optically differentiated between the presence of proliferative and nonproliferative bacteria using the TP resonance as a read-out. These findings make these devices promising all-optical probes for bacterial metabolic activity, including their response to external stressors.

Hybrid magneto-plasmonic structure consisting of hexagonal periodic nanodisks array with giant transverse magneto-optical Kerr effect for sensing application

“…One category involves the use of optical sensors constructed using the optical Tamm state existing in onedimensional photonic crystals or distributed Bragg gratings. An advantage of this approach is that it allows for adjustment of the response peak by changing the thickness of the photonic crystal dielectric layer [5,6]. Another common type of sensor is a sensing device based on surface plasmon resonance (SPR) technology, which utilizes the electromagnetic field enhancement effect generated by electron oscillations on the metal surface to increase sensitivity to the surrounding environment.…”