Plasmonic nanostructures have tremendous potential to be applied in photocatalytic CO 2 reduction, since their localized surface plasmon resonance can collect low-energy-photons to derive energetic "hot electrons" for reducing the CO 2 activation-barrier. However, the hot electron-driven CO 2 reduction is usually limited by poor efficiency and low selectivity for producing kinetically unfavorable hydrocarbons. Here, a new idea of plasmonic active "hot spot"confined photocatalysis is proposed to overcome this drawback. W 18 O 49 nanowires on the outer surface of Au nanoparticles-embedded TiO 2 electrospun nanofibers are assembled to obtain lots of Au/TiO 2 /W 18 O 49 sandwichlike substructures in the formed plasmonic heterostructure. The short distance (< 10 nm) between Au and adjacent W 18 O 49 can induce an intense plasmon-coupling to form the active "hot spots" in the substructures. These active "hot spots" are capable of not only gathering the incident light to enhance "hot electrons" generation and migration, but also capturing protons and CO through the dual-hetero-active-sites (Au-O-Ti and W-O-Ti) at the Au/TiO 2 /W 18 O 49 interface, as evidenced by systematic experiments and simulation analyses. Thus, during photocatalytic CO 2 reduction at 43± 2 °C, these active "hot spots" enriched in the well-designed Au/TiO 2 /W 18 O 49 plasmonic heterostructure can synergistically confine the hot-electron, proton, and CO intermediates for resulting in the CH 4 and CO productionrates at ≈35.55 and ≈2.57 µmol g −1 h −1 , respectively, and the CH 4 -product selectivity at ≈93.3%.

With an implicit Particle-in-cell/Monte Carlo model, capacitively coupled plasmas are studied in two-dimensional and axisymmetric geometry. Self-bias dc voltage effects are self-consistently considered. Due to finite length effects,the self-bias dc voltages show sophisticating relations with the electrode areas. Two-dimensional kinetic effects are also illuminated. Compare to the fluid mode, PIC/MC model is numerical-diffusion-free and thus finer properties of the plasmas are simulated.

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bAtmospheric-pressure N 2 , He, air, and O 2 microplasma arrays have been used to inactivate Escherichia coli cells suspended in aqueous solution. Measurements show that the efficiency of inactivation of E. coli cells is strongly dependent on the feed gases used, the plasma treatment time, and the discharge power. Compared to atmospheric-pressure N 2 and He microplasma arrays, air and O 2 microplasma arrays may be utilized to more efficiently kill E. coli cells in aqueous solution. The efficiencies of inactivation of E. coli cells in water can be well described by using the chemical reaction rate model, where reactive oxygen species play a crucial role in the inactivation process. Analysis indicates that plasma-generated reactive species can react with E. coli cells in water by direct or indirect interactions.Plasma, called the fourth fundamental state of matter, in addition to solids, liquids, and gases, consists of equal numbers of positive ions and negative electrons (negative ions in some cases) and other reactive species, generally resulting from the ionization of neutral gases. Due to the reactive species in plasma, gas-based reactive plasmas are thought to be effective in killing various microorganisms (1-3). Therefore, recently, the inactivation of microorganisms in water by atmospheric-pressure cold plasmas (APCP) has attracted great attention for biomedical and environmental applications due to their lethal effects on bacteria and fungi (4-8), since APCP include many reactive species similar to those in the conventional methods of microorganism inactivation, such as ozone generation (9), UV irradiation (10), chemical agents (11), electrical fields (12, 13), and microwave irradiation (14).The chemical reaction rates of these plasma-activated species may be improved greatly when atmospheric-pressure nonequilibrium plasmas are generated in water (4-7, 15). These short-lived species can be formed in the vicinity of microorganisms and efficiently kill microorganisms in water. Usually, it is relatively hard to generate stable atmospheric-pressure plasmas in water. Among various plasma sources (4, 5, 7), atmospheric-pressure arc discharge has frequently been used for killing microorganisms in water. Compared to other sources, the strong arc discharges are less influenced by the aqueous environment while obviously leading to an increase in the water temperature with high energy consumption. This arc discharge can also cause serious damage to heat-sensitive materials, and the volume of treated aqueous solution is limited, since the arc plasma is usually controllable only in a small processing space.Previously (16), we designed an atmospheric-pressure air microplasma array to inactivate Pseudomonas fluorescens cells in aqueous media. The microplasma produced by hollow-fiberbased microplasma jets is stable and extremely efficient in killing P. fluorescens cells in aqueous media. This design demonstrates potential application for large-volume plasma inactivation of bacterial cells in water. In this study, we repor...

He-induced W nanofuzz growth over the W divertor target is one of the main limiting factors affecting the current design and development of fusion reactors. In this paper, based on He reaction rate model in W, we simulate the growth and evolution of He nanobubbles during W nanofuzz formation under fusion-relevant He+ irradiation conditions. Our modeling unveils the existence of He nanobubble-enriched W surface layer (<10 nm), formed due to the He diffusion in W crystal into defect sites. At an elevated temperature, the growth of He bubbles in the W surface layer prevents He atoms diffusing into the deep layer (>10 nm). The formation of W nanofuzz at the surface is attributed to surface bursting of high-density He bubbles with their radius of ~4 nm, and an increase in the surface area of irradiated W. Our findings have been well confirmed by the experimental measurements.

The plasma density radial profiles in capacitive discharges driven over a wide frequency range (60-220 MHz) are measured by a floating double probe, and the results measured at 60 MHz are compared with those obtained from the electrostatic models, i.e. particle in cell/Monte Carlo collision (PIC/MCC) and the fluid models. It was found that at low pressure the plasma density peaks at the center of the reactor, while it peaks at the electrode edge at high pressure, indicating that the power deposition transitions from 'non-local' to 'local' with increasing pressure. The plasma radial profiles obtained from the PIC/MCC simulation and fluid model show a qualitative agreement with the experiment at low pressure and high pressure, respectively. This is primarily due to the fact that at low pressure the fluid model substantially under-predicts sheath heating, which, however, is the main electron heating mechanism at low pressure. So the total power into electrons and therefore the plasma density is also under-predicted. In contrast, the PIC/MCC model takes into account these electron collisionless heating effects at low pressure, and thus the plasma density is enhanced in the central region of electrodes. At high pressure, due to local power deposition, both the experiment and fluid simulation show that as rf power increases, a density peak at the electrode edge appears, indicating an enhancement in edge field. Compared with the electrostatic case, at a higher frequency, the plasma density profile is determined by electromagnetic (EM) effects, especially the standing wave effect. To be specific, we found that the standing wave effect exhibits multi-node structure within the electrode at 130 MHz or above, and the wavelength becomes smaller as the excitation frequency increases. At high excitation frequency and high pressure, the rf power is mainly deposited at the electrode periphery due to the fact that the EM waves are strongly damped when they propagate from the discharge edge to the center. In addition, our experimental results show that the standing wave wavelength increases with rf power.

A large-power inductively coupled plasma source was designed to perform the continuous helium ions (He +) irradiations of polycrystalline tungsten (W) under International Thermonuclear Experimental Reactor (ITER) relevant conditions. He + irradiations were performed at He + fluxes of 2.310 21-1.610 22 /m 2 s and He + energies of 12-220 eV. Surface damages and microstructures of irradiated W were observed by scanning electron microscopy. This study showed the growth of nano-fuzzes with their lengths of 1.3-2.0 m at He + energies of >70 eV or He + fluxes of >1.310 22 /m 2 s. Nanometer-sized defects or columnar microstructures were formed in W surface layer due to low-energy He + irradiations at an elevated temperature (>1300 K). The diffusion and coalescence of He atoms in W surface layers led to the growth and structures of nano-fuzzes. This study indicated that a reduction of He + energy below 12-30 eV may greatly decrease the surface damage of tungsten diverter in the fusion reactor.

A one dimensional hybrid model has been proposed to study the Ar and CF4 mixture gas in a dual-frequency (DF) capacitively coupled plasma. To achieve the more precise spatiotemporal distributions of the electric field and ions flux, the ion momentum equations are adopted instead of the drift-diffusion model with the effective electric field approximation. By adjusting DF sources, the evolutions of ions densities, ion energy distributions, and ion angular distributions are obtained and the modulation effects are discussed. Finally, the comparison between the simulation and experimental result shows that the hybrid model could qualitatively describe the characteristic of the mixtures in less time, which will be more promising in two dimensional and three dimensional simulations.