Strong light-matter coupling manifested by Rabi splitting has attracted tremendous attention due to its fundamental importance in cavity quantum-electrodynamics research and great potentials in quantum information applications. A prerequisite for practical applications of the strong coupling in future optoelectronic devices is an all-solid-state system exhibiting room-temperature Rabi splitting with active control. Here we realized such a system in heterostructure consisted of monolayer WS and an individual plasmonic gold nanorod. By taking advantages of the small mode volume of the nanorod and large transition dipole moment of the WS exciton, giant Rabi splitting energies of 91-133 meV can be achieved at ambient conditions, which only involve a small number of excitons. The strong light-matter coupling can be dynamically tuned either by electrostatic gating or temperature scanning. These findings can pave the way toward active nanophotonic devices operating at room temperature.

the reaction system have a significant influence on the formation of hollow Ni spheres. The shape of the original template was imprinted after the reaction. It is expected that this emulsion system can be extended to the synthesis of other hollow metal spheres. Such hollow metal spheres have a variety of promising applications, for example: as catalysts; as magnetic and gas storage materials; and as low-density materials. Currently, the preparation and properties of Ni and other hollow metal spheres are underway in our laboratories. ExperimentalMaterials: Nickel sulfate, boric acid, ammonium fluoride, sodium hypophosphite monohydrate, cyclohexane, and polyglycol (M w 20 000) were of commercial grade and were used without further purification.Preparation of the Hollow Ni Submicrometer-Size Spheres: In a typical experiment, 2.5 g of polyglycol was first dissolved in 20 mL of deionized water, and then 47 mg (67.5 mM) NH 4 F, 246 mg (200 mM) H 3 BO 3 , 112 mg (20.0 mM) NiSO 4 , and 212 mg (100 mM) NaH 2 PO 2´H2 O were added to the solution. After that, 0.5 mL of cyclohexane was injected into 5 mL of the above solution. This mixture first was treated under ultrasonic radiation for 30 min at 20 C to make an emulsion system, and then at 75 C to induce the reducing reaction. After a period of time, the mixture foamed and the color of the mixture turned from green to light black, meaning that nickel was formed. The color of the mixture gradually turned blacker. 5 or 10 min after the mixture turned from green to light black, the mixture was cooled to room temperature. Finally, the mixture was separated by centrifugation. The deposit was collected, washed with deionized water several times, and dried in air: black, hollow nickel spheres were obtained.Structural characterization was performed by means of X-ray diffraction using a D/Max-RA diffractometer with Cu Ka radiation, TEM (JEM-200CX TEM) working at an accelerating voltage of 100 kV, and SEM operating at an accelerating voltage of 20 kV. EDS was performed on the microscope with a PV9100 scanning electron microanalyzer. Room-temperature magnetic characterization of the hollow Ni spheres was performed by using a Lake Shore 7303-9309 vibrating sample magnetometer (VSM). There is growing interest in nanowires of metals and related oxides because of their potential applications in nanoscale electronic and optoelectronic devices. [1,2] The template-based method is one of the techniques used for synthesizing nanowires.[3±7] However, for large-area electronic applications, such as field-emission displays, new synthetic methods may COMMUNICATIONS

We investigated the stability of reduced graphene oxide for oxygen density ranging from 6.25% to 50% with the density functional theory and found the most, the second most, and the third most stable oxygen configurations. The effect of relaxation of lattice on the electronic properties is found to be negligible for low O coverage and crucial for higher O coverage, respectively. The densities of states and the band gaps were calculated. The bandgap is found to be a non-monotonic function of oxygen density, with minima at O/C = 11.1% and 25%.

Due to its difficulty, experimental measurement of field emission from a single-layer graphene has not been reported, although field emission from a two-dimensional (2D) regime has been an attractive topic. The open surface and sharp edge of graphene are beneficial for field electron emission. A 2D geometrical effect, such as massless Dirac fermion, can lead to new mechanisms in field emission. Here, we report our findings from in situ field electron emission characterization on an individual singe-layer graphene and the understanding of the related mechanism. The measurement of field emission from the edges was done using a microanode probe equipped in a scanning electron microscope. We show that repeatable stable field emission current can be obtained after a careful conditioning process. This enables us to examine experimentally the typical features of the field emission from a 2D regime. We plot current versus applied field data, respectively, in ln(I/E(3/2)) ∼ 1/E and ln(I/E(3)) ∼ 1/E(2) coordinates, which have recently been proposed for field emission from graphene in high- and low-field regimes. It is observed that the plots all exhibit an upward bending feature, revealing that the field emission processes undergo from a low- to high-field transition. We discuss with theoretical analysis the physical mechanism responsible for the new phenomena.

We report on how to tune the density of zinc oxide (ZnO) nanowire arrays in a wide range (more than 5 orders of magnitude) in a low temperature (80 °C) solution-phase growth process. A model based on the coexistence of nanowire growth and etching of the ultrathin (<3.5 nm) ZnO seed-layer was proposed to explain the effect. It was demonstrated that when the seed-layer thickness changes from 1.5 to 3.5 nm, the nanowire density increases from 6.8 × 104 to 2.6 × 1010 cm−2. This significant variation of density with the seed-layer thickness was found to happen only when the layer thickness is within a few nanometers. If it is too thick (>3.5 nm), the variation is very narrow, and if it is too thin (<1.5 nm), no nanowires can grow. In addition, the density variation was accompanied by the change of both diameter and height of the nanowires, which leads to a change in aspect ratio. Both changes in density and aspect ratio were found to obviously affect the field emission characteristics. It was demonstrated that optimal conditions can be found to grow ZnO nanowire films with better field emission characteristics.