Hai Nie

We report an effective method to enhance and modify the magnetic plasmon (MP) resonance in three-dimensional (3D) optical metamaterials consisting of periodic arrays of silver vertical split-ring resonators (VSRRs) for high-sensitivity sensing. By positioning the 3D metamaterials above a thick silver film separated by a silica dielectric spacer layer, the strong coupling between the MP resonance in the VSRRs and the surface plasmons polaritons (SPPs) propagating on the silver film can be realized and gives rise to an ultra-narrowband hybrid MP mode with a huge enhancement of magnetic fields. For the coupling to happen, the magnetic field direction of the SPPs should be parallel to the magnetic moment induced in the VSRRs. More importantly, because the ultra-narrowband hybrid MP mode is extremely sensitive to the surrounding media, the sensitivity and the figure of merit (FOM) of the 3D metamaterials can reach as high as 700 nm/RIU and 170, respectively, suggesting that the proposed 3D metamaterials hold potential applications in label-free biomedical sensing.

We demonstrate a very strong magnetic resonance in metamaterials for high-performance sensing. The metamaterials comprise a periodic array of a pair of closely spaced metal nanodisks that are placed on metal substrate. The strong magnetic resonance is essentially an antisymmetric resonant mode resulting from the near-field plasmon hybridization within the pair of metal nanodisks. Because the magnetic resonance has great electromagnetic field enhancement, ultra-narrow bandwidth and nearly perfect absorption, the metamaterials have very high sensitivity (S = 991 nm/RIU, S* = 47/RIU) and figure of merit (FOM = 124, FOM* = 17 702), which may find potential applications in label-free biosensing.

We study theoretically the interaction effects between optical waveguide modes and magnetic resonances in metamaterials, consisting of periodic arrays of paired metallic nanodisks lying on a dielectric waveguide substrate. The plasmon near-field coupling in individual metallic nanodisk pairs results into magnetic resonances. The periodic arrangement of the paired metallic nanodisks can excite optical waveguide modes propagating in the adjacent dielectric waveguide. When optical waveguide modes are close to magnetic resonances by varying the array period, they interact to form two hybridized modes. A coupling model of two oscillators is also proposed to predict well the positions of the hybridized modes. In the strong interaction regime, the hybridized modes have an obvious anticrossing, and thus exhibit an interesting phenomenon of Rabi splitting. Furthermore, the magnetic fields within metallic nanodisk pairs exhibit a huge enhancement, which could find promising potential applications in magnetic nonlinearity and sensors.

Ammonium nitrogen pollution is a key factor related to water eutrophication. In our works, biochar adsorption for ammonium nitrogen removal from wastewater has been investigated. Transmission Electron Microscope with energy dispersive X-ray spectroscopy, X-ray diffraction, and Fourier Transform Infrared spectroscopy was performed to characterize the prepared biochar. The optimal solution pH, and coexisting ions effect for ammonium nitrogen removal from wastewater was examined. Surface characterization demonstrated the obtained biochar was coarse, unshaped, irregular, and contained a great deal of carbon. With an increase in solution pH, biochar adsorption amount of ammonium nitrogen was decrease. With an increase in coexisting ions concentration, biochar adsorption amount of ammonium nitrogen was decrease.

The paper reports a novel flexible electrode based on Fe3O4-embedded in carbon felt via a facile hydrothermal method. As a binder-free anode for Lithium ion batteries, it exhibits a stable reversible capacity of 590 mA h g−1 after 100 cycles at a current density of 200 mA g−1, together with modified rate capability. The improved lithium storage properties can be attributed to the synergistic effect between nano-sized embedded Fe3O4 and carbon felt substrate. The elastic carbon fibers are beneficial for alleviating the volume expansion of Fe3O4 during continuous discharge/charge cycling. Besides, the designed structure leads to shorter ion transport path and better diffusion of electrolyte, resulting in the enhanced rate capacity and reversible capacity. The structure, morphology and the electrochemical performances of Fe3O4/carbon felt electrode for flexible Lithium ion batteries are analyzed in details.