Applying response surface methodology to optimize partial nitrification in sequence batch reactor treating salinity wastewater.

In this study, the operation parameters of a partial nitrification process (PN) treating saline wastewater were optimized using the Box-Behnken design via the response surface methodology (BBD-RSM). A novel strategy based on the control of the carbon/nitrogen ratio (C/N), alkalinity/ammonia ratio (K/A), and salinity in three stages was used to achieve PN in a sequence batch reactor. The results demonstrated that a high and stable PN was completed after 50 d with an ammonia removal efficiency (ARE) of 98.37 % and nitrite accumulation rate (NAR) of 85.93 %. Next, BBD-RSM was applied, where ARE and NAR were the responses. The highest responses from the confirmation experiment were 99.9 % ± 0.04 and 95.25 % ± 0.32 when the optimum C/N, K/A, and salinity were identified as 0.84, 2, and 5.5 (g/L), respectively. The results were higher than those for the nonoptimized reactor. The developed regression model adequately forecasts the PN performance under optimal conditions. Therefore, this study provides a promising strategy for controlling the PN process and shows how the BBD-RSM model can improve the PN performance.

Controlling Horizontal Dipole Orientation and Emission Spectrum of Ir Complexes by Chemical Design of Ancillary Ligands for Efficient Deep-Blue Organic Light-Emitting Diodes.

Deep-blue emitting Iridium (Ir) complexes with horizontally oriented emitting dipoles are newly designed and synthesized through engineering of the ancillary ligand, where 2',6'-difluoro-4-(trimethylsilyl)-2,3'-bipyridine (dfpysipy) is used as the main ligand. Introduction of a trimethylsilyl group at the pyridine and a nitrogen at the difluoropyrido group increases the bandgap of the emitter, resulting in deep-blue emission. Addition of a methyl group (mpic) to a picolinate (pic) ancillary ligand or replacement of an acetate structure of pic with a perfluoromethyl-triazole structure (fptz) increases the horizontal component of the emitting dipoles in sequence of mpic (86%) > fptz (77%) > pic (74%). The organic light-emitting diode (OLED) using the Ir complex with the mpic ancillary ligand shows the highest external quantum efficiency (31.9%) among the reported blue OLEDs with a y-coordinate value lower than 0.2 in the 1931 Commission Internationale de L'Eclairage (CIE) chromaticity diagram.

Triplet Harvesting by a Fluorescent Emitter Using a Phosphorescent Sensitizer for Blue Organic-Light-Emitting Diodes.

The development of highly efficient blue organic light-emitting diodes (OLEDs) with good stability is currently the most important issue in OLED displays and lighting. This paper reports an efficient blue fluorescent OLED based on a deep-blue-emitting phosphorescent sensitizer [(dfpysipy)2Ir(mpic)] and a conventional fluorescent emitter (TBPe). Efficient triplet harvesting by the fluorescent emitter occurs in the OLED because of sensitization even though the difference in the emission energy between the phosphorescent and fluorescent emissions was only 0.05 eV. These results clearly demonstrate the potential for realizing highly efficient blue fluorescent OLEDs using phosphorescent sensitizers without requiring ultraviolet-emitting phosphorescent dye.

Super-contrast-enhanced darkfield imaging of nano objects through null ellipsometry.

We rediscover the null ellipsometry principle for an outstanding image-contrast enhancement method for darkfield imaging. Simply by adding polarizers, compensators, and a photodiode sensor to a conventional darkfield imaging system and applying the null principle, Si nano-cylinder structures as small as D20 nm (H20 nm) on non-patterned wafer, and gap defects as small as 14.6 nm and bridge defects as small as 21.9 nm on 40 nm line and 40 nm space patterns (H40 nm), which are invisible in conventional darkfield imaging, can be distinguished from scattered noise. To the best of our knowledge, no method has been successful for identifying such small non-metal (silicon) nanoscale objects with such low magnification (×20) optics.

Highly Efficient, Conventional, Fluorescent Organic Light-Emitting Diodes with Extended Lifetime.

Highly efficient, yellow-fluorescent organic light-emitting diodes with a maximum external quantum efficiency exceeding 25.0% and extended lifetime are reported using iridium-complex sensitizers doped in an exciplex host. Energy transfer processes reduce the lifetime of the exciplex and excitons on the Ir complexes and enable an excited state to exist in a conventional fluorescent emitter, thereby increasing device lifetime. The device stability depends on the location of the excited state.