No abstract

As a highly toxic heavy metal ion, divalent mercuric ion (Hg 2+ ) is one of the most widely diffused and hazardous environmental pollutants. In this work, a simple, portable, and inexpensive fiber-optic sensor based on surface plasmon resonance (SPR) effect was developed for Hg 2+ detection, which takes advantage of 4-mercaptopyridine (4-MPY)-functionalized Au nanoparticles (Au NPs/4-MPY) as a signal amplification tag. Based on the coordination between Hg 2+ and nitrogen in the pyridine moiety, we developed the sensor by self-assembling 4-MPY on Au film surfaces to capture Hg 2+ and then introducing Au NPs/ 4-MPY to generate a plasmonic coupling structure with the configuration of nanoparticle-on-mirror. The coupling between localized SPR increased changes in SPR wavelength, which allowed highly sensitive Hg 2+ sensing in aqueous solution. The sensor exhibited superior selectivity for Hg 2+ detection compared with other common metal ions in water. The sensor's Hg 2+ detection limit is 8 nM under optimal conditions. Furthermore, we validated the sensor's practicality for Hg 2+ detection in tap water samples and demonstrated its potential application for environmental water on-site monitoring.

First principles calculations of electronic and optical properties of multiferroic oxide BiFeO3 are used in combination with a plasmonic device model of optical switch to show that a BiFeO3 based device can have much better performance than devices based on existing materials. This arises from the combination of octahedral tilts, ferroelectricity and G‐type antiferromagnetism in BiFeO3 leading to a strong dependence of the optical refractive indices on the orientation with respect to the polarization. A prototype of a plasmonic resonator with an R‐BFO thin film layer is used as an example and shows excellent switch and modulation responses. The proposed approach provides potential opportunities to develop high performance nanophotonic devices for optical communication.