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A metallic nanoantenna, under resonant illumination, injects nonequilibrium hot electrons into a nearby graphene structure, effectively doping the material. A prominent change in carrier density was observed for a plasmonic antenna-patterned graphene sheet following laser excitation, shifting the Dirac point, as determined from the gate-controlled transport characteristic. The effect is due to hot electron generation resulting from the decay of the nanoantenna plasmon following resonant excitation. The effect is highly tunable, depending on the resonant frequency of the plasmonic antenna, as well as on the incident laser power. Hot electron-doped graphene represents a new type of hybrid material that shows great promise for optoelectronic device applications.

Ag nanowire with the receiving and transmitting Ag bow tie antenna pairs at its incident and emission ends was patterned on the SiO(2) substrate to realize an enhanced surface plasmon emission with a factor of 45 compared to the single Ag nanowire without antenna pairs. The receiving and transmitting bow tie antenna pairs enhanced the plasmon coupling and emission efficiencies of the Ag nanowire. And the maximum plasmon emission sensitively depended on the length of Ag nanowire, the arm length of bow tie antennas, and the incident angle of optical excitation. This enhanced plasmon emission was confirmed by finite-difference time-domain simulations and explored with analytical calculations using the impedance matching theory at optical frequency.

Plasmonic focusing was investigated in symmetry broken nanocorrals under linearly polarized illumination. Near-field optical measurements of the perpendicular electric field show that a single subwavelength spot size of 320 nm can be generated. The interference pattern within the corral can be controlled by changing the polarization of optical excitation and the degree of symmetry breaking. The intensity enhancement factor was investigated using finite-difference time-domain simulations and confirmed by analytical calculations taking into account the plasmon damping and multiple reflections against the corral wall.

We report the color-tuning and switching optical transport characters of CdS hybrid plasmonic waveguide by using near-field optical microscopy. The guided photoluminescence spectra under various waveguide lengths demonstrate a spectroscopic red-shift for the part of CdS nanoribbon placed on the sapphire substrate and an energy compensation at Ag film. Surface plasmon polariton leakage and radiation are explored by near-field characterizations. Finite difference time domain simulations have good agreement with the experimental observations of subwavelength confinement and propagation. With a strong end facet emission, the suggested hybrid plasmonic waveguide can serve as a color-changeable optical nanosource in integrated photonic devices.

Monolayered transition metal dichalcogenides (TMDs) are one kind of hexagonal 2D semiconductors with a direct bandgap structure. Due to the property of natural broken inversion symmetry in the lattice, the strong spin–orbit coupling of electrons in TMDs can induce degenerate levels with antiparallel spins in K and K′ valleys, which selectively respond with external light excitations. Surface plasmon resonance with efficient electromagnetic enhancement and near‐field coupling provides excellent potential opportunities to modulate valley emission of TMDs. Efforts have been devoted to investigating the interaction principles and applications of this research field. This review focuses on plasmonic modulation of valleytronic emission in TMDs with surface plasmon polaritons (SPP) and localized surface plasmons (LSP) based on different modulation principles, respectively, and discusses possible research directions for future device applications. [ABSTRACT FROM AUTHOR]

Charge transfer introduced by a conductive junction bridging a nanoparticle dimer can have a pronounced effect on the optical properties of the system. We have extended the plasmon hybridization model to include conductive junctions and charge transfer effects. From our model, we are able to derive all the plasmon resonances of the bridged dimer, including the charge transfer plasmon (CTP), and predict their trends when system parameters are varied. In particular, we find that CTP is a result of a sufficiently narrow monopole mode interacting with multipolar (including dipolar) modes. The screening arising from charge transfer induces a blueshift of the hybridized bonding dimer modes and decreases the electric field in the junction. Our model may serve as an important guide for optical properties of bridged nanoparticle aggregates. [ABSTRACT FROM AUTHOR]

When an Au nanoparticle in a liquidmedium is illuminated withresonant light of sufficient intensity, a nanometer scale envelopeof vapora “nanobubble”surrounding theparticle, is formed. This is the nanoscale onset of the well-knownprocess of liquid boiling, occurring at a single nanoparticle nucleationsite, resulting from the photothermal response of the nanoparticle.Here we examine bubble formation at an individual metallic nanoparticlein detail. Incipient nanobubble formation is observed by monitoringthe plasmon resonance shift of an individual, illuminated Au nanoparticle,when its local environment changes from liquid to vapor. The temperatureon the nanoparticle surface is monitored during this process, wherea dramatic temperature jump is observed as the nanoscale vapor layerthermally decouples the nanoparticle from the surrounding liquid.By increasing the intensity of the incident light or decreasing theinterparticle separation, we observe the formation of micrometer-sizedbubbles resulting from the coalescence of nanoparticle-“bound”vapor envelopes. These studies provide the first direct and quantitativeanalysis of the evolution of light-induced steam generation by nanoparticlesfrom the nanoscale to the macroscale, a process that is of fundamentalinterest for a growing number of applications. [ABSTRACT FROM AUTHOR]

In this paper, we propose and simulate the surface plasmon polariton nanofocusing process by using Finite-difference Time-domain (FDTD) method. The maximum enhancement factor at the taper end area is optimized with different wavelength of the excitation laser. With the advantage of SNOM, the SPP nanofocusing is experimentally observed by illuminating the tapered CdS nanoribbon deposited on the Ag film. The SPP dispersion is used to predict the optimal taper angles of the structure. As the emission of the focused SPP at the taper end, the proposed plasmonic structure can be severed as a light nanosource emitter in the future optical integrated circuits. [ABSTRACT FROM AUTHOR]

With great advances in wet chemical synthesis of nanoparticles (NPs), plasmonic NPs with various sizes and morphologies are easily available nowadays and demonstrate great potentials in optical, electronic, and biomedical applications. Plasmonic circular dichroism (CD), relating to circular dichroism responses at localized surface plasmon resonance of metal nanostructures, has emerged as a research direction of plasmonics with promising prospects in enantioselective catalysis, chiral separation, and ultrasensitive detections. Herein, plasmonic CD responses of gold nanoparticle based nanostructures are summarized. Two kinds of plasmonic CD phenomena are investigated: structural CD and induced CD. Structural CD is the response from chiral assemblies composed of plasmonic NPs with strong dipole–dipole interactions. Induced CD is the response of nonchiral plasmonic NPs with chiral molecules attached at surface. The weak CD is the result of Coulomb interaction between chiral molecules and plasmonic NPs. Efforts on how to achieve strong CD signals for these two configurations by using chiral molecules and Au nanoparticles are reported. The fabrication of chiral nanostructures, tuning and amplification of CD responses, CD‐based biosensors, chiral catalysis, and future perspectives are presented. The importance of the shape anisotropy of gold nanorods in the generation and amplification of CD signals is especially highlighted. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR) is widely used as light trapping schemes in solar cells, because it can concentrate light fields surrounding metal nanostructures and realize light management at the nanoscale. SPR in photovoltaics generally occurs at the metal/dielectric interfaces. A well-defined interface is therefore required to elucidate interfacial SPR processes. Here, we designed a photovoltaic device (PVD) with an atomically flat TiO2 dielectric/dye/graphene/metal nanoparticle (NP) interface for quantitatively studying the SPR enhancement of the photovoltaic conversion. Theoretical and experimental results indicated that the graphene monolayer was transparent to the electromagnetic field. This transparency led to significant substrate-induced plasmonic hybridization at the heterostructure interface. Combined with interparticle plasmonic coupling, the substrate-induced plasmonics concentrated light at the interface and enhanced the photo-excitation of dyes, thus improving the photoelectric conversion. Such a mechanistic understanding of interfacial plasmonic enhancement will further promote the development of efficient plasmon-enhanced solar cells and composite photocatalysts. [ABSTRACT FROM AUTHOR]