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.

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Electrically insulating boron nitride (BN) nanosheets possess thermal conductivity similar to and thermal and chemical stabilities superior to those of electrically conductive graphenes. Currently the production and application of BN nanosheets are rather limited due to the complexity of the BN binary compound growth, as opposed to massive graphene production. Here we have developed the original strategy "biomass-directed on-site synthesis" toward mass production of high-crystal-quality BN nanosheets. The strikingly effective, reliable, and high-throughput (dozens of grams) synthesis is directed by diverse biomass sources through the carbothermal reduction of gaseous boron oxide species. The produced BN nanosheets are single crystalline, laterally large, and atomically thin. Additionally, they assemble themselves into the same macroscopic shapes peculiar to original biomasses. The nanosheets are further utilized for making thermoconductive and electrically insulating epoxy/BN composites with a 14-fold increase in thermal conductivity, which are envisaged to be particularly valuable for future high-performance electronic packaging materials.

Elemental boron arouses great interest from both scientific and technological areas of research because it has unique chemical and physical properties and its theoretical tubular structures may have higher electrical conductivity than carbon nanotubes. [1][2][3][4][5][6][7] High conductivity and chemical stability of boron or boride nanostructures have made it an attractive candidate for future applications in ideal cold-cathode materials, high-temperature semiconductor devices, or fieldeffect transistors. [8][9][10][11][12][13][14] In particular, for the application of field emission (FE), it is especially useful to synthesize large, vertical arrays of boron nanowires (BNWs) with the desired surface work function and FE behavior. So far, to our knowledge, while both amorphous [15][16][17][18][19][20] and crystalline boron nanowires [21,22] have been fabricated by magnetron sputtering, laser ablation, or chemical vapor methods, vertical arrays of single-crystal boron nanowires over a large area have not been synthesized in a one-step process. In addition, little attention [23][24][25] has been paid to the measurements of the physical properties of an individual boron nanowire. In this Communication, we report the successful synthesis of high-density, vertically aligned single-crystal boron nanowire arrays with a nanowire diameter of approximately 20-40 nm by a thermal carbon-reduction method. Moreover, we have measured the FE behavior and surface work function of a single boron nanowire, which is critical to evaluate the possibility of using boron nanowires as field-emission materials. For the purpose of better understanding the field-emission mechanism of a boron nanowire, the field-emission properties of a BNW film are also measured to compare with those of an individual nanowire. Figure 1 shows large-scale boron nanowire arrays on a Si(001) substrate after approximately 2-4 h of growth. As shown in Figure 1A, the high-density arrays are aligned vertically on the silicon substrate. Figure 1B is the highresolution scanning electron microscopy (SEM) image of the aligned BNWs, in which one can see that the length of the BNW is about 5 mm and the morphology of the nanowires is uniform. The aspect ratio of each boron nanowire is about 200, which is high enough for a field-emission application. The side and top views of the boron nanowire are shown in Figure 1C and D, respectively, which reveals the detailed morphology of the BNWs. The boron nanowires have a diameter of about 20-40 nm and no catalyst is found at their tip. The catalysts, however, were found to lie on the substrate arbitrarily when we peeled off some nanowire film from the substrate, as shown in Figure 1C. Thus, we believe that the growth is through a vapor-liquid-solid (VLS) mechanism and the binding force between the Fe 3 O 4 catalyst and the silicon substrate is strong. This strong binding leads to good conductivity between the boron nanowires and the substrate, which may contribute to their good field-emission properties. The alignment of BNWs can...

Single crystalline boron nanocones are obtained by a simple chemical vapor deposition method. Electric conductivity values of boron nanocones are (1.0–7.3) × 10–5 (Ω cm)–1. Results of field emission show the low turn‐on and threshold electric fields of about 3.5 V μm–1 and 5.3 V μm–1, respectively. Boron nanocones with good electrical transport and field emission properties are promising candidates for application in flat panel displays and nanoelectronics building blocks.

By adjusting the type of catalysts, the controlled growth of micropatterned WO 2 and WO 3 nanowire arrays has been first accomplished at low temperature (450-600 °C). The as-prepared WO 2 and WO 3 nanowires are proven to be single crystalline structures with a single phase by Raman and transmission electron microscopy (TEM) techniques. Their formation mechanisms are attributed to the vapor-liquid-solid (VLS) mechanism. It is found that both micropatterned WO 2 and WO 3 nanowire arrays have very excellent field emission (FE) properties with quite low turn-on field (1.36 V/μm) and threshold field (2.38 V/μm), which is very similar to carbon nanotubes (CNTs) with best FE behaviors. In addition, the physical properties of an individual WO 2 and individual WO 3 nanowire are compared to probe the determinant factor for their different FE behaviors and understand their FE mechanism. Their very excellent FE performance suggests that this novel growth method is a useful technique for low-temperature preparation of micropatterned nanoemitter cathode arrays.

A novel screw-like molybdenum nanostructure has been synthesized based on a simple thermal vapor deposition method. Each thread circle of the nanoscrews is formed by several crystalline Mo grains, which have a certain deflection with each other. The growth mechanism is described as a spiral growth mode, which depends heavily on the degree of supersaturation (σ) of deposited Mo vapors. The electrical property measurements and field emission properties on a single Mo nanoscrew show that their electrical conductivity should reach 3.44 × 10(4)-7.74 × 10(4) Ω(-1) cm(-1) and its maximum current should reach 15.8 μA. Mo nanoscrew film is also proved to have excellent field emission properties in different voltage driver modes. The largest emission current densities can reach 106.39 mA cm(-2) in the DC voltage driver mode and 0.66 A cm(-2) in the pulsed mode. A low turn-on field, good site distribution and remarkable emission stability is also recorded. These experimental results show that the highly conductive molybdenum nanoscrews should have potential applications as a cold cathode material for high current vacuum electron devices.

Graphene has great potential for enhancing light−matter interactions in a two-dimensional regime due to surface plasmons with low loss and strong light confinement. Further utilization of graphene in nanophotonics relies on the precise control of light localization properties. Here, we demonstrate the tailoring of electromagnetic field localizations in the mid-infrared region by precisely shaping the graphene into nanostructures with different geometries. We generalize the phenomenological cavity model and employ nanoimaging techniques to quantitatively calculate and experimentally visualize the two-dimensional electromagnetic field distributions within the nanostructures, which indicate that the electromagnetic field can be shaped into specific patterns depending on the shapes and sizes of the nanostructures. Furthermore, we show that the light localization performance can be further improved by reducing the sizes of the nanostructures, where a lateral confinement of λ0/180 of the incidence light can be achieved. The electromagnetic field localizations within a nanostructure with a specific geometry can also be modulated by chemical doping. Our strategies can, in principle, be generalized to other two-dimensional materials, therefore providing new degrees of freedom for designing nanophotonic components capable of tailoring two-dimensional light confinement over a broad wavelength range.