The metallic nanostructures with unique properties of tunable plasmon resonance and large field enhancement have been cooperated with semiconductor to construct hetero-nanostructures for various applications. Herein, a general and facile approach to synthesize uniform dumbbell-like gold–sulfide core–shell hetero-nanostructures is reported. The transformation from Au nanorods (NRs) to dumbbell-like Au NRs and coating of metal sulfide shells (including Bi₂S₃, CdS, Cu_xS, and ZnS) are achieved in a one-pot reaction. Due to the reshaping of Au core and the deposition of sulfide shell, the plasmon resonances of Au NRs are highly enhanced, especially the about 2 times enhancement for the visible transverse plasmon resonance compared with the initial Au NRs. Owing to the highly enhanced visible light absorption and strong local electric field, we find the photocatalytic activity of dumbbell-like Au–Bi₂S₃ NRs is largely enhanced compared with pure Bi₂S₃ and normal Au–Bi₂S₃ NRs by testing the photodegradation rate of Rhodamine B (RhB). Moreover, the second-layer sulfide can be coated and the double-shell Au–Bi₂S₃–CdS hetero-nanostructures show further improved photodegradation rate, especially about 2 times than that of Degussa P25 TiO₂ (P25) ascribing to the optimum band arrangement and then the prolonged lifetime of photo-generated carriers.

Metal/semiconductor Au/Ag₂S core/shell hetero-nanorods with controlled morphology are synthesized and their tunable plasmon enhancements (involving linear and nonlinear optical processes) are demonstrated. The synthesis involves site-selective deposition of Ag layer onto Au nanorod seeds, followed by site-selective sulfuration of the Ag layer, resulting in three types of Au/Ag₂S core/shell nanorods with complete, corner-opened, or end-opened shells. The plasmon resonance and local field confinements varing with shell morphology are analyzed using FDTD calculations. Nonlinear measurements reveal that the Ag₂S shell with appropriate morphology leads to the nonlinear refraction and saturable intensity of the Au nanorods increasing 7.6 and 4.1 times, respectively, which indicates strong plasmon enhancements and energy relaxation in the Au/Ag₂S core/shell nanorods. This site-selective shell growth strategy offers a constructive bottom-up approach to maneuver the optical properties of plasmonic nanocrystals for various applications.

The synthesis of large lattice mismatch metal-semiconductor core–shell hetero-nanostructures remains challenging, and thus the corresponding optical properties are seldom discussed. Here, we report the gold-nanorod-seeded growth of Au–CdS core–shell hetero-nanorods by employing Ag₂S as an interim layer that favors CdS shell formation through a cation-exchange process, and the subsequent CdS growth, which can form complete core–shell structures with controllable shell thickness. Exciton–plasmon interactions observed in the Au–CdS nanorods induce shell thickness-tailored and red-shifted longitudinal surface plasmon resonance and quenched CdS luminescence under ultraviolet light excitation. Furthermore, the Au–CdS nanorods demonstrate an enhanced and plasmon-governed two-photon luminescence under near-infrared pulsed laser excitation. The approach has potential for the preparation of other metal-semiconductor hetero-nanomaterials with complete core–shell structures, and these Au–CdS nanorods may open up intriguing new possibilities at the interface of optics and electronics.

The chemical growth of silver nanorings that possess singly twinned crystals and a circular cross section via a reductive reaction solution is reported. The wire and ring diameters of the synthesized nanorings are in the ranges 80–200 nm and 4.5–18.0 μm, respectively. By lighting up the multipolar dark plasmons with slanted illumination, the silver nanoring exhibits unique focused scattering and large local-field enhancement. We also demonstrate strong exciton–plasmon interactions between a monolayer of CdSe/ZnS semiconductor quantum dots and a single silver antenna-like nanoring (nanoantenna) at the “hot spots” located at the cross points of the incident plane and nanoring; the position of these spots are tunable by adjusting the incidence angle of illumination. The tunable plasmonic behavior of the silver nanorings could find applications as optical nanoantennae or plasmonic nanocavities.