Abstract: A device comprising: two mutually immiscible conductive liquids arranged to form an interface therebetween; a plurality of nanoparticles localised at the said interface, the said nanoparticles each having a first region formed of a semiconductor having a first bandgap, the first region being surrounded by a second region having a second bandgap, the second bandgap being larger than the first bandgap; and means for applying an electric field to the said nanoparticles and thus, through the Stark effect, altering the optical absorption or emission characteristics of the nanoparticles.

Abstract: Systems and methods provide control of nanoparticle coverage of an interface between a first medium and a second medium through variation of an electric potential across such interface; the first medium and the second medium are immiscible media, and transparent or substantially transparent to visible light. The first medium can be a first electrolytic solution and the second medium can be a second electrolytic solution; thus, the interface can become an interface of two immiscible electrolytic solutions (ITIES). The nanoparticle coverage of the interface, e.g., the ITIES, can be regulated to vary between approximately zero and a full or nearly a full monolayer. The nanoparticle coverage of the interface can dictate at least one optical property of the interface, rendering the interface transparent or substantially transparent, or a mirror, or providing Faraday rotation of the optical polarization of light incident normal to the interface and propagating through the interface.

Abstract: A device comprising: two mutually immiscible conductive liquids arranged to form an interface therebetween; a plurality of nanoparticles localised at the said interface, the said nanoparticles each having a first region formed of a semiconductor having a first bandgap, the first region being surrounded by a second region having a second bandgap, the second bandgap being larger than the first bandgap; and means for applying an electric field to the said nanoparticles and thus, through the Stark effect, altering the optical absorption or emission characteristics of the nanoparticles.

Abstract: A device comprising: a chamber containing two immiscible conductive liquids, the liquids having an interface therebetween; and electrodes arranged to apply a voltage across the interface between the said liquids such as to control the shape of the interface.