When plasmons supported by metal nanoparticles interact strongly with molecular excitons or excitons of semiconducting quantum dots, plexcitons are formed in the strong coupling regime. The hybrid plexcitonic nanoparticles with a wide range of sizes and shapes have been synthesized by using wet chemistry methods or have been fabricated on solid substrates by using lithographic techniques. In order to deeply understand plasmon−exciton interaction at the nanoscale dimension and boost the performance of nanophotonic devices made of plexcitonic nanoparticles, new types of plexcitonic nanoparticles with tunable optical properties and outstanding stability at room temperature are urgently needed. Herein, we for the first time report pure colloidal nanodisk shaped plexcitonic nanoparticles with very large Rabi splitting energies, i.e., more than 350 meV. We synthesize silver nanoprisms by using seed mediated synthesis and then convert nanoprisms to nanodisks at a high temperature. Localized plasmon resonance of the silver nanodisk in the visible spectrum can be effectively tuned by heating. Subsequently, self-assembly of J-aggregate dyes on plasmonic nanodisks produces plexcitonic nanoparticles. We envision that colloidal nanodisk shaped plexcitonic nanoparticles with very large Rabi splitting energies and outstanding stability at room temperature will enlarge the application of plexcitonic nanoparticles in a variety of fields such as polariton laser, biosensor, plasmon molecular nanodevices, and energy flow at nanoscale dimensions.

Nobel-metal nanostructures strongly localize and manipulate light at nanoscale dimension by supporting surface plasmon polaritons. In fact, the optical properties of the nobel-metal nanostructures strongly depend on their morphology and composition. Until now, various metal nanostructures such as nanocubes, nanoprisms, nanorods, and recently hollow nanostructures have been demonstrated. In addition, the plasmonic field can be further enhanced at nanoparticle dimers and aggregates because of highly localized and intense optical fields, which is known as "plasmonic hot spots". However, colloidally synthesized and circular-shaped nanoring nanostructures with plasmonic hot spots are still lacking. We, herein, show for the first time that colloidal bimetallic nanorings with plasmonic nanocavities and tunable plasmon resonance wavelengths can be synthesized via colloidal synthesis and galvanic replacement reactions. In addition, in the strong coupling regime, plasmons in nanorings and excitons in J-aggregates interact strongly and nanoring-shaped colloidal plexcitonic nanoparticles are demonstrated. The results reveal that the optical properties of the nanoring and the onset of strong coupling can be tamed by the galvanic replacement reaction. Further, the plasmonic nanocavity in the nanorings has immense potential for applications in sensing and spectroscopy because of the space, enclosed by the plasmonic nanocavity, is empty and accessible to a variety of molecules, ions, and quantum dots.

All inorganic colloidal halide perovskite nanoplatelets and nanowires are highly anisotropic shaped semiconductor nanocrystals with highly tunable optical properties in the visible spectrum. These nanocrystals have large exciton binding energies...

J-aggregates are fantastic self-assembled chromophores with a very narrow and extremely sharp absorbance band in the visible and near-infrared spectrum, and hence they have found many exciting applications in nonlinear optics, sensing, optical devices, photography, and lasing. In silver halide photography, for example, they have enormously improved the spectral sensitivity of photographic process due to their fast and coherent energy migration ability. On the other hand, graphene, consisting of single layer of carbon atoms forming a hexagonal lattice, has a very low absorption coefficient. Inspired by the fact that J-aggregates have carried the role to sense the incident light in silver halide photography, we would like to use Jaggregates to increase spectral sensitivity of graphene in the visible spectrum. Nevertheless, it has been an outstanding challenge to place isolated J-aggregate films on graphene to extensively study interaction between them. We herein noncovalently fabricate isolated J-aggregate thin films on graphene by using a thin film fabrication technique we termed here membrane casting (MC). MC significantly simplifies thin film formation of water-soluble substances on any surface via porous polymer membrane. Therefore, we reversibly modulate the Dirac point of graphene in the J-aggregate/graphene van der Waals (vdW) heterostructure and demonstrate an all-carbon phototransistor gated by visible light. Owing to the hole transfer from excited excitonic thin film to graphene layer, graphene is hole-doped. In addition, spectral and power responses of the all-carbon phototransistor have been measured by using a tunable laser in the visible spectrum. The first integration of J-aggregates with graphene in a transistor structure enables one to reversibly write and erase charge doping in graphene with visible light that paves the way for using J-aggregate/graphene vdW heterostructures in optoelectronic applications.

The advances in colloid chemistry and nanofabrication allowed us to synthesize Noble monometallic and bimetallic nanocrystals with tunable optical properties in the visible and near infrared region of the electromagnetic...