Significant enhancement of UV emission in ZnO nanorods subject to Ga＋ ion beam irradiation

Applications of ZnO nanomaterials in optoelectronics are still limited due to their insufficient photoluminescence efficiency. In order to optimize the photoluminescence properties of ZnO nanorods, the UV emission of vertically aligned ZnO nanorods grown on a Si substrate, in correlation with Ga＋ ion irradiation at different ion energies （0.5 keV-16 keV）, was investigated in the present study. We found that the UV intensity increased rapidly with increasing Ga＋ ion energy, up to its maximum around 2 keV, at which point the intensity was approximately 50 times higher than that produced by as-grown ZnO nanorods. The gentle bombardment of low-energy Ga＋ ions removes defects from ZnO nanorod surfaces. The Ga＋ ions, on the other hand, implant into the nanorods, resulting in compressive strain. It is believed that the perfect arrangement of the crystal lattice upon removal of surface defects and the introduction of compressive strain are two factors that contribute to the significant enhancement of UV light generation.

Gd^(3+) ion induced UV upconversion emission and temperature sensing in Tm^(3+)/Yb^(3+):Y_(2)O_(3) phosphor

Cubic phase Tm^(3+)/Yb^(3+):Y_(2)O_(3) and Tm^(3+)/Yb^(3+)/Gd^(3+):Y_(2)O_(3) phosphors were prepared by low temperature combustion technique for upconversion emission in UV-visible range.The 980 nm excitation has generated UV emission at 314 nm in tridoped phosphor due to the energy transfer from Tm^(3+) to Gd^(3+)ion.Characteristic emission bands from Tm^(3+) are also observed in both the phosphors.Thermally coupled Stark sublevels ^(1)G_(4(a))(476 nm) and ^(1)G_(4(b))(488 nm) of Tm^(3+) ion were utilised for optical thermometry using fluorescent intensity ratio(FIR) method.The result shows that maximum absolute sensitivity in tridoped phosphor is observed to be 1.33 × 10^(-3) K^(-1) at 298 K.Moreover,temperature rise of phosphor at various pump power densities was also measured and it is estimated to achieve 407 K at the pump power density of 38.46 W/cm^(2).

Exciplex formation and electroluminescent absorption in ultraviolet organic light-emitting diodes

We investigated the formation of exciplex and electroluminescent absorption in ultraviolet organic light-emitting diodes（UV OLEDs） using different heterojunction structures.It is found that an energy barrier of over 0.3 eV between the emissive layer（EML） and adjacent transport layer facilitates exciplex formation.The electron blocking layer effectively confines electrons in the EML,which contributes to pure UV emission and enhances efficiency.The change in EML thickness generates tunable UV emission from 376 nm to 406 nm.In addition,the UV emission excites low-energy organic function layers and produces photoluminescent emission.In UV OLED,avoiding the exciplex formation and averting light absorption can effectively improve the purity and efficiency.A maximum external quantum efficiency of 1.2%with a UV emission peak of 376 nm is realized.

Influence of Iodine Vapour Pressure on Formation of XeI in Xe/I_2 Mixture

The influence of the iodine vapour pressure on the mechanisms of XeI^＊ formation is investigated in Xe/I2 mixture by dielectric barrier discharge. The iodine vapour pressure is measured as a function of the ultraviolet （UV） intensity of XeI^＊ emission at 253 nm, and found that the UV intensity reaches a maximum at 0.9 Torr of iodine at a xenon pressure of 300 Torr, then decreases slowly with the iodine pressure larger than 0.9 Torr. The discharge mode transforms from a hybrid discharge at a xenon pressure of 760 Torr with 1.0 Torr of iodine to a diffuse mode at 10 Torr of iodine. These results are quite different from those of other rare-gas halogen excimers and indicate a different mechanism of XeI^＊ formation from those of other rare-gas halogen excimers.

Origin and structures of solar eruptions Ⅰ: Magnetic flux rope

Coronal mass ejections(CMEs) and solar flares are the large-scale and most energetic eruptive phenomena in our solar system and able to release a large quantity of plasma and magnetic flux from the solar atmosphere into the solar wind. When these high-speed magnetized plasmas along with the energetic particles arrive at the Earth, they may interact with the magnetosphere and ionosphere, and seriously affect the safety of human high-tech activities in outer space. The travel time of a CME to 1 AU is about 1–3 days, while energetic particles from the eruptions arrive even earlier. An efficient forecast of these phenomena therefore requires a clear detection of CMEs/flares at the stage as early as possible. To estimate the possibility of an eruption leading to a CME/flare, we need to elucidate some fundamental but elusive processes including in particular the origin and structures of CMEs/flares. Understanding these processes can not only improve the prediction of the occurrence of CMEs/flares and their effects on geospace and the heliosphere but also help understand the mass ejections and flares on other solar-type stars. The main purpose of this review is to address the origin and early structures of CMEs/flares, from multi-wavelength observational perspective. First of all, we start with the ongoing debate of whether the pre-eruptive configuration, i.e., a helical magnetic flux rope(MFR), of CMEs/flares exists before the eruption and then emphatically introduce observational manifestations of the MFR. Secondly, we elaborate on the possible formation mechanisms of the MFR through distinct ways. Thirdly, we discuss the initiation of the MFR and associated dynamics during its evolution toward the CME/flare. Finally, we come to some conclusions and put forward some prospects in the future.

Particulate matter characterization in a steelworks using conventional sampling and innovative lidar observations

Particulate matter （PM） emissions from steelworks cause public concern. Although end-of-pipe and pro- cess integrated measures have led to a significant drop in emissions of large particles from stacks, fine aerosols were not specifically considered, nor were emissions from fugitive and open sources. In this study, we deployed aerosol samplers together with a scanning ultra-violet （UV） lidar to characterize total suspended particles （TSP）, PM10, and PM2.5, in emissions from a large integrated steelworks in Spain over a 16-day period. We determined the content of carbonaceous, soluble inorganic, mineral dust, and metal species. A positive matrix factorization was carried out on our dataset. Despite mineral dust being predominant in all size fractions, the steelworks was clearly a source of carbonaceous species, resulting in production of secondary inorganic aerosols. In particular, stack emissions were a major contributor of fine particles, while open sources dominated the emissions of TSP, yielding up to 80% of particles larger than PM10. UV lidar provided 2D maps of aerosols in real time, with an ability to detect PM emissions and to visualize complex plumes. We suggest that air quality management of steelworks needs to focus on controlling large and coarse oarticle emissions, esoeciallv those from onen sources.