S. Liu

Comparison study of gold nanohexapods, nanorods, and nanocages for photothermal cancer treatment.

Gold nanohexapods represent a novel class of optically tunable nanostructures consisting of an octahedral core and six arms grown on its vertices. By controlling the length of the arms, their localized surface plasmon resonance peaks could be tuned from the visible to the near-infrared region for deep penetration of light into soft tissues. Herein we compare the in vitro and in vivo capabilities of Au nanohexapods as photothermal transducers for theranostic applications by benchmarking against those of Au nanorods and nanocages. While all these Au nanostructures could absorb and convert near-infrared light into heat, Au nanohexapods exhibited the highest cellular uptake and the lowest cytotoxicity in vitro for both the as-prepared and PEGylated nanostructures. In vivo pharmacokinetic studies showed that the PEGylated Au nanohexapods had significant blood circulation and tumor accumulation in a mouse breast cancer model. Following photothermal treatment, substantial heat was produced in situ and the tumor metabolism was greatly reduced for all these Au nanostructures, as determined with (18)F-flourodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT). Combined together, we can conclude that Au nanohexapods are promising candidates for cancer theranostics in terms of both photothermal destruction and contrast-enhanced diagnosis.

Universal field-emission model for carbon nanotubes on a metal tip

Electron-field-emission properties have been investigated systematically for carbon nanotubes (CNTs) fabricated on a metal tip. With a vacuum gap of 0.7u2009mm, the threshold field is as low as 0.7u2009V/μm and the current density approaches 10u2009mA/cm2 at an electronic field of 1.0u2009V/μm. The emission current is quite stable with very low fluctuation. The emission behavior is in excellent agreement with Fowler–Nordheim theory and no current saturation is found even with an emission current reaching 1u2009A/cm2. A universal relationship 1/β=d2/d+1/β0 between the field amplification factor β and the vacuum gap d is developed within a two-region field-emission model. This relationship provides the basis for a microscopic understanding of CNT emitters and is applicable to other systems as well.

Lithium storage in polymerized carbon nitride nanobells

Polymerized carbon nitride nanobells (CNNBs) have been intercalated by a large amount of Li ions using an electrochemical method. Li nanocrystals are observed on the inside surface of CNNB walls, which is direct evidence that a Li nanocrystal can exist at the micropore structure at a heavy intercalating level. Graphene layers are expanded and become partly disordered by Li intercalation, while after deintercalation, they are reordered to a certain degree, and Li nanocrystals disappear. The samples show a reversible Li storage capacity of 480 mAhg−1, much higher than 330 mAhg−1 of commercial carbon materials used for Li ion batteries.

Efficient surface plasmon amplification from gain-assisted gold nanorods

We report on the efficient surface plasmon amplification by stimulated emission of radiation (spaser) from a gold nanorod coated with proper gain media. Numerical simulations show that the threshold of the nanorod-based spaser is nearly 1 order of magnitude lower than that of the core-shell nanosphere, which is verified by analysis with electrostatic theory. Furthermore, it is found that the nanorod-based nanosystem possesses unique optical properties such as wavelength tunability and polarization sensitivity.

High Surface‐Enhanced Raman Scattering Performance of Individual Gold Nanoflowers and Their Application in Live Cell Imaging

Molecular imaging techniques based on surface-enhanced Raman scattering (SERS) face a lack of reproducibility and reliability, thus hampering its practical application. Flower-like gold nanoparticles have strong SERS enhancement performance due to having plenty of hot-spots on their surfaces, and this enhancement is not dependent on the aggregation of the particles. These features make this kind of particle an ideal SERS substrate to improve the reproducibility in SERS imaging. Here, the SERS properties of individual flower-like gold nanoparticles are systematically investigated. The measurements reveal that the enhancement of a single gold nanoparticle is independent of the polarization of the excitation laser with an enhancement factor as high as 10(8) . After capping with Raman signal molecules and folic acid, the gold nanoflowers show strong Raman signal in the living cells, excellent targeting properties, and a high signal-to-noise ratio for SERS imaging.

Anisotropic and enhanced absorptive nonlinearities in a macroscopic film induced by aligned gold nanorods

Anisotropic and enhanced nonlinear absorption (NLA) has been observed from aligned gold nanorods (GNRs) embedded in a poly(vinyl alcohol) film, which was realized by a stretched-film method. Open-aperture Z-scan experiments revealed that the stretch process enhanced the NLA coefficient by approximately nine times and increased the anisotropic factor of NLA to ∼20. The enhancement in the NLA coefficient reached as high as ∼91 times after increasing the concentration of GNRs by four times and this is attributed to the plasmonic interaction between densely packed GNRs.

Patterned growth of coiled carbon nanotubes by a template-assisted technique

A method for controlled synthesis of coiled carbon nanotubes (CNTs) is demonstrated, in which three-dimensional columns of aligned CNTs are used as a template. The coiled CNTs with pitches and coil diameters from 100 to 300 nm are regrown on the straight CNT arrays and the mesoporous structure between the CNT arrays produces an asymmetric growth condition for the coil formation. As observed using transmission electron microscopy, the graphitic layers on the tube wall are stacking-disordered due to the coil geometry. The growth mechanism of the coiled CNTs is also proposed.

Recent advances in long-pulse high-confinement plasma operations in Experimental Advanced Superconducting Tokamaka)

A long-pulse high confinement plasma regime known as H-mode is achieved in the Experimental Advanced Superconducting Tokamak (EAST) with a record duration over 30u2009s, sustained by Lower Hybrid wave Current Drive (LHCD) with advanced lithium wall conditioning and divertor pumping. This long-pulse H-mode plasma regime is characterized by the co-existence of a small Magneto-Hydrodynamic (MHD) instability, i.e., Edge Localized Modes (ELMs) and a continuous quasi-coherent MHD mode at the edge. We find that LHCD provides an intrinsic boundary control for ELMs, leading to a dramatic reduction in the transient power load on the vessel wall, compared to the standard Type I ELMs. LHCD also induces edge plasma ergodization, broadening heat deposition footprints, and the heat transport caused by ergodization can be actively controlled by regulating edge plasma conditions, thus providing a new means for stationary heat flux control. In addition, advanced tokamak scenarios have been newly developed for high-performance ...

Dynamics of L-H transition and I-phase in EAST

The turbulence and flows at the plasma edge during the L–I–H, L–I–L and single-step L–H transitions have been measured directly using two reciprocating Langmuir probe systems at the outer midplane with several newly designed probe arrays in the EAST superconducting tokamak. The Exa0×xa0B velocity, turbulence level and turbulent Reynolds stress at ∼1xa0cm inside the separatrix ramp-up in the last ∼20xa0ms preceding the single-step L–H transition, but remain nearly constant near the separatrix, indicating an increase in the radial gradients at the plasma edge. The kinetic energy transfer rate from the edge turbulence to the Exa0×xa0B flows is significantly enhanced only in the last ∼10xa0ms and peaks just prior to the L–H transition. The Exa0×xa0B velocity measured inside the separatrix, which is typically in the electron diamagnetic drift direction in the L-mode, decays towards the ion diamagnetic drift direction in response to fluctuation suppression at the onset of the single-step L–H, L–I–L as well as L–I–H transitions. One important distinction between the L–I–H and the L–I–L transitions has been observed, with respect to the evolution of the edge pressure gradient and mean Exa0×xa0B flow during the I-phase. Both of them ramp up gradually during the L–I–H transition, but change little during the L–I–L transition, which may indicate that a gradual buildup of the edge pedestal and mean Exa0×xa0B flow during the I-phase leads to the final transition into the H-mode. In addition, the transition data in EAST strongly suggest that the divertor pumping capability is an important ingredient in determining the transition behaviour and power threshold.

Direct observation of amplified spontaneous emission of surface plasmon polaritons at metal/dielectric interfaces

We report on direct observation of amplified spontaneous emission (ASE) of surface plasmon polaritons (SPPs) at the interface of a silver film and a gain medium. Based on a typical Kretschmann configuration incorporated with Rhodamine 6G molecules, the growing ASE spectra of SPPs have been clearly identified by carefully conducting a pump-dependent angle-resolved spectral measurement. Spectral narrowing effects induced by the SPP amplification are also demonstrated. The observed phenomena are helpful in understanding the fundamental interactions between SPPs and gain medium, which could enable wide applications on plasmonic sources and sensors.