Tunable electromagnetically induced absorption based on coupled-resonators in a compact plasmonic system.

Electromagnetically induced absorption (EIA) exhibits abnormal dispersion and novel fast-light features, making it a crucial aspect of nanophotonics. Here, the EIA phenomenon is numerically predicted in a compact plasmonic waveguide system by introducing a slot resonator above a square cavity. Simulation results reveal that the EIA response can be easily tuned by altering the structure's parameters, and double EIA valleys can be observed with an additional slot resonator. Furthermore, the investigated structures demonstrate a fast-light effect with an optical delay of ∼ -1.0 ps as a result of aberrant dispersion at the EIA valley, which enable promising applications in the on-chip fast-light area. Finally, a plasmonic nanosensor with a sensitivity of ∼1200 nm/RIU and figure of merit of ∼16600 is achieved based on Fano resonance. The special features of our suggested structure are applicable in realization of various integrated components for the development of multifunctional high-performance nano-photonic devices.

Plasmon-Induced Transparency for Tunable Atom Trapping in a Chiral Metamaterial Structure.

Plasmon-induced transparency (PIT), usually observed in plasmonic metamaterial structure, remains an attractive topic for research due to its unique optical properties. However, there is almost no research on using the interaction of plasmonic metamaterial and high refractive index dielectric to realize PIT. Here, we report a novel nanophotonics system that makes it possible to realize PIT based on guided-mode resonance and numerically demonstrate its transmission and reflection characteristics by finite element method simulations. The system is composed of a high refractive-index dielectric material and a two-dimensional metallic photonic crystal with 4-fold asymmetric holes. The interaction mechanism of the proposed structure is analyzed by the coupled-mode theory, and the effects of the parameters on PIT are investigated in detail. In addition, we first consider this PIT phenomenon of such fields on atom trapping (87Rb), and the results show that a stable 3D atom trapping with a tunable range of position of about ~17 nm is achieved. Our work provides a novel, efficient way to realize PIT, and it further broadens the application of plasmonic metamaterial systems.

Single-Walled Carbon Nanotube-Germanium Heterojunction for High-Performance Near-Infrared Photodetector.

In this research, we report on a high-performance near-infrared (near-IR) photodetector based on single-walled carbon nanotube-germanium (SWCNT-Ge) heterojunction by assembling SWCNT films onto n-type Ge substrate with ozone treatment. The ozone doping enhances the conductivity of carbon nanotube films and the formed interfacial oxide layer (GeOx) suppresses the leakage current and carriers' recombination. The responsivity and detectivity in the near-IR region are estimated to be 362 mA W-1 and 7.22 × 1011 cm Hz1/2 W-1, respectively, which are three times the value of the untreated device. Moreover, a rapid response time of ~11 µs is obtained simultaneously. These results suggest that the simple SWCNT-Ge structure and ozone treatment method might be utilized to fabricate high-performance and low-cost near-IR photodetectors.

2D-3D graphene-coated diatomite as a support toward growing ZnO for advanced photocatalytic degradation of methylene blue.

In this work, a diatomite@graphene@ZnO (ZGD) photocatalyst was synthesized by chemical vapor deposition and hydrothermal methods and used for the photocatalytic degradation of methylene blue. The characterization of the prepared nanocomposite was performed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), and N2 adsorption-desorption techniques. Ultraviolet-visible diffuse reflectance spectroscopy (DRS) showed that the prepared ZGD photocatalyst enhanced the absorption of visible light and induced a red-shift. Photoluminescence spectroscopy (PL) revealed that the recombination of electron and hole pairs can be effectively suppressed. Besides, the synergistic effect of diatomite and graphene avoids the agglomeration of ZnO, increases the number of surface adsorption sites, and limits the electron transport, consequently improving the photocatalytic activity of ZnO. When ZGD-3 was UV-irradiated (λ = 663 nm) for 90 minutes, the degradation effectiveness of methylene blue (MB) was 100%. After the fifth repetition, the photocatalytic degradation efficiency was always greater than 95%. Simply put, the ZGD nanocatalyst can be used as an efficient photocatalyst for dye wastewater treatment.

'Nanoreactors' for photocatalytic H2 evolution in oil-water biphase systems.

Optimization of reaction systems plays a key role in preventing the backward reaction of water splitting. 'Nanoreactors' are formed with nanoporous photocatalyst in a facile H(2) production system, hexane-water biphase system. The rate of H(2) evolution could reach 63.37 mmol h(-1) g(-1) in the biphase system (40% higher than that in the single phase system).

Uniform core-shell titanium phosphate nanospheres with orderly open nanopores: a highly active Brønsted acid catalyst.

We have successfully designed and synthesized core-shell multicomponent TiP nanospheres with a stable crystal core and orderly open nanopores, which have uniform distribution and good dispersion and offer great potential as a highly active Brønsted acid catalyst.