Matryoshka-caged gold nanorods： Synthesis, plasmonic properties, and catalytic activity

将 Matryoshka 关入笼中的金 nanorods (mCGNRs ) 被在一个调停种子的银涂层方法和流电的代替反应(GRR ) 之间轮流出现成功地综合。当 mCGNRs 的 matryoshka 层的数字增加了，拓宽并且是转移红的电浆子回声山峰，和向 4-nitrophenol (4-NTP ) 的减小的催化活动增加了。当有 6 层的 mCGNRs 在 4-nitrophenol 的减小被用作 nanocatalysts 时，反应率系数分别地比 gold-nanorod- 和 4-nitrophenol 的 caged-gold-nanorod-catalyzed 减小的高是 5.2-times 和 3.7-times。另外，光的 surface-plasmon-resonance-based 吸收提高了 mCGNRs 的催化表演。与聚氨酯泡沫的支持， mCGNRs 在这研究综合了能作为 recyclable 被使用为 4-nitrophenol 的减小的异构的催化剂。

Experimental demonstration of an electrically tunable broadband coherent perfect absorber based on a graphene–electrolyte–graphene sandwich structure

We propose and experimentally demonstrate the operation of an electrically tunable, broadband coherent perfect absorption(CPA) at microwave frequencies by harnessing the CPA features of a graphene–electrolyte–graphene sandwich structure(GSS). Using both a simplified lumped circuit model and full-wave numerical simulation, it is found that the microwave coherent absorptivity of the GSS can be tuned dynamically from nearly 50% to 100% by changing the Fermi level of the graphene. Strikingly, our simplified lumped circuit model agrees very well with the full-wave numerical model, offering valuable insight into the CPA operation of the device. The angle dependency of coherent absorption in the GSS is further investigated, making suggestions for achieving CPA at wide angles up to 80°. To show the validity and accuracy of our theory and numerical simulations, a GSS prototype is fabricated and measured in a C-band waveguide system. The reasonably good agreement between the experimental and the simulated results confirms that the tunable coherent absorption in GSS can be electrically controlled by changing the Fermi level of the graphene.

Selective excitation of a three-dimensionally oriented single plasmonic dipole

We experimentally demonstrate a scheme to deterministically excite a three-dimensionally oriented electric dipole in a single Au nanosphere by using a tightly focused radially polarized beam whose focal field possesses polarization states along three-dimensional(3D) orientations owing to the spatial overlap between longitudinal and radial electric field components. Experiment observations indicate that the orientation of an excited dipole moment gradually changes from out-of-plane to in-plane when the nanosphere is moved away from the beam center, which is reconfirmed by full-wave simulations. Moreover, rigorous calculation based on Mie theory reveals that a reduced effective ambient permittivity accompanies the rotation of the dipole moment, leading to a blue-shifted and narrowed resonance peak. We envision that our results could find applications in detecting the 3D orientation of isolated molecules and benefit the fine manipulation of light–matter interactions at the single-molecule level.

Cylindrical vector beam-excited frequency-tunable second harmonic generation in a plasmonic octamer

We report a method to tune the second harmonic generation(SHG) frequency of a metallic octamer by employing cylindrical vector beams as the excitation. Our method exploits the ability to spatially match the polarization state of excitations with the fundamental target plasmonic modes, enabling flexible control of the SHG resonant frequency.It is found that SHG of the octamer is enhanced over a broad band(400 nm) by changing the excitation from the linearly polarized Gaussian beam to radially and azimuthally polarized beams. More strikingly, when subjected to an azimuthally polarized beam, the SHG intensity of the octamer becomes 30 times stronger than that for the linearly polarized beam even in the presence of Fano resonance.

Optimal Configuration of Dispersion Compensation Modules with Installation Limits

Selecting a cost optimum subset of discrete-value dispersion compensation modules (DV-DCMs) subject to maximum module count from an available set of DV-DCMs is a NP-hard problem. We derive a novel dynamic programming algorithm with pseudo-polynomial time bound and show that DV-DCM cost re-scaling can improve the running time.

Self-Assembled Plasmonic Pyramids from Anisotropic Nanoparticles for High-Efficient SERS

Surface-enhanced Raman scattering(SERS)substrates play important roles for the enhancement of inelastic scattering signals.Traditional substrates such as roughened electrodes and colloidal aggregates suffer from well-known signal reproducibility issues,whereas for current dominant two-dimensional planar systems,the hot spot distributions are limited by the zero-,one-or two-dimensional plane.The introduction of a three-dimensional(3D)system such as a pyramid geometry breaks the limitation of a single Cartesian SERS-active area and extends it into the z-direction,with the tip potentially offering additional benefits of strong field enhancement and high sensitivity.However,current 3D pyramidal designs are restricted to film deposition on prepared pyramid templates or self-assembly in pyramidal molds with spherical building blocks,hence limiting their SERS effectiveness.Here,we report on the fabrication of a new class of low cost and well-defined plasmonic nanoparticle pyramid arrays from different anisotropic shaped nanoparticles using combined top-down lithography and bottom-up self-assembly approach.These pyramids exhibit novel optical scattering properties that can be exploited for the design of reproducible and sensitive SERS substrate.The SERS intensity was found to decrease drastically in accordance with a power law function as the focal planes move from the apex of the pyramid structure towards the base.In comparison to sphere-based building blocks,pyramids assembled from anisotropic rhombic dodecahedral gold nanocrystals with numerous sharp tips exhibited the strongest SERS performance.Graphical Abstract Macroscale pyramidal array films with plasmonic tunability as a new class of SERS substrate for sensitive detection of chemicals.

Augmenting photoluminescence of monolayer MoS_(2) using high order modes in a metal dimer-on-film nanocavity

Plasmonic particle-on-film nanocavities,supporting gap modes with ultra-small volume,provide a great solution to boost light–matter interactions at the nanoscale.In this work,we report on the photoluminescence(PL)enhancement of monolayer MoS_(2) using high order modes of an Au nanosphere dimer-on-film nanocavity(DoFN).The high order plasmon modes,consisting of two bonding quadrupoles in the dimer and their images in the Au film,are revealed by combining the polarization-resolved scattering spectra with the numerical simulations.Further integrating the monolayer MoS_(2) into the DoFN,these high order modes are used to enhance PL intensity through simultaneously boosting the absorption and emission processes,producing a 1350-fold enhancement factor.It opens an avenue to enhance the light–matter interaction with high order plasmon modes and may find applications in future optoelectronics and nanophotonics devices.