Origin of Violet‐Blue Emission in Ti‐Doped Gahnite

ZnAl₂O₄ doped with Ti⁴⁺ (2%) was synthesized by the hydrothermal method at 220°C at pressure of 25 bars. An average grain size of the as‐prepared sample was 3 nm, the samples with biggest grain size were obtained after annealing at 300°C, 500°C, 600°C, 700°C, and 900°C, diameter of the latter was about 33 nm. IR spectroscopy indicated that ZnAl₂O₄ was partially inverted. The degree of the inversion decreases with increase in the annealing temperature but increases with increasing Ti⁴⁺ content. Absorption and emission spectra as well as emission decay profiles were recorded at 300 and 77 K. The observed spectra are due to charge‐transfer O^2??Ti⁴⁺ transitions. Color of the emission depends on the nanocrystal size and with increase in its diameter changes from violet to blue, accordingly the absorption bands exhibit redshift. The calculations based on Density Functional Theory confirmed the experimental results. 3d electrons of titanium ions form the bottom of the ZnAl₂O₄:Ti⁴⁺ conduction band, oxygen, aluminum or zinc vacancies create additional levels in the gahnite energy band gap. It was also found that in ZnAl₂O₄ aluminum or zinc vacancy induces magnetism with relatively high magnetic moment close to 1 μ_B per vacancy.     

Photocatalytic Degradation of 4,4′-Isopropylidenebis(2,6-dibromophenol) on Magnetite Catalysts vs. Ozonolysis Method: Process Efficiency and Toxicity Assessment of Disinfection By-Products

Flame retardants have attracted growing environmental concern. Recently, an increasing number of studies have been conducted worldwide to investigate flame-retardant sources, environmental distribution, living organisms’ exposure, and toxicity. The presented studies include the degradation of 4,4′-isopropylidenebis(2,6-dibromophenol) (TBBPA) by ozonolysis and photocatalysis. In the photocatalytic process, nano- and micro-magnetite (n-Fe₃O₄ and μ-Fe₃O₄) are used as a catalyst. Monitoring of TBBPA decay in the photocatalysis and ozonolysis showed photocatalysis to be more effective. Significant removal of TBBPA was achieved within 10 min in photocatalysis (ca. 90%), while for ozonation, a comparable effect was observed within 70 min. To determine the best method of TBBPA degradation concentration on COD and TOC, the removals were examined. The highest oxidation state was obtained for photocatalysis on μ-Fe₃O₄, whereas for n-Fe₃O₄ and ozonolysis, the COD/TOC ratio was lower. Acute toxicity results show noticeable differences in the toxicity of TBBPA and its degradation products to Artemia franciscana and Thamnocephalus platyurus. The EC₅₀ values indicate that TBBPA degradation products were toxic to harmful, whereas the TBPPA and post-reaction mixtures were toxic to the invertebrate species tested. The best efficiency in the removal and degradation of TBBPA was in the photocatalysis process on μ-Fe₃O₄ (reaction system 1). The examined crustaceans can be used as a sensitive test for acute toxicity evaluation.     

Hydrostatic pressure influence on electric relaxation response of bismuth manganite ceramics

Electrical impedance of bismuth manganite ceramics was studied under ambient and high hydrostatic pressure. Local disorder of crystal lattice was confirmed using XRD and DSC. Two relaxation processes were discerned. One was attributed to small polarons, which showed a changeover from variable range hopping features related to Fermi glass and structural disorder to the nearest neighbor hopping behavior in higher temperature range related to uniform distribution of energy levels. Hydrostatic pressure shortened relaxation times that would be interesting for applications. The second process, which was assigned to the nearest neighbor hopping of polarons, also exhibited a changeover to glassy features in a high-temperature range.     

90年代及未来的汽车用珠光颜料

装扮车辆,使之异彩纷呈,珠光颜料是一个有力的工具。珠光颜料的珠光效果成为了车辆的一个赢得客户欢心的卖点。统计数据表明,以珠光涂料涂饰的轿车其销售比率总是要高出平均销售率的。因此,全球对珠光颜料的需求都在增长,当新技术使汽车制造商能够大大地增益其饰面的...     

Synthesis of Novel Phosphonic‐Type Activity‐Based Probes for Neutrophil Serine Proteases and Their Application in Spleen Lysates of Different Organisms

Neutrophils are a type of granulocyte important in the “first line of defense” of the innate immune system. Upon activation, they facilitate the destruction of invading microorganisms by the production of superoxide radicals, as well as the release of the enzymatic contents of their lysozymes. These enzymes include specific serine proteases: cathepsin G, neutrophil elastase, proteinase 3, as well as the recently discovered neutrophil serine protease 4 (NSP4). Under normal conditions, the proteolytic activity of neutrophil proteases is tightly regulated by endogenous serpins; however, this mechanism can be subverted during tissue stress, thereby resulting in the uncontrolled activity of serine proteases, which induce chronic inflammation and subsequent pathology. Herein, we describe the development of low‐molecular‐weight activity‐based probes that specifically target the active sites of neutrophil proteases.     

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Multi-heterojunction large area HgCdTe long wavelength infrared photovoltaic detector for operation at near room temperatures

This paper describes a new multi-heterojunction n ⁺pp photovoltaic infrared photodetector. The device has been developed specifically for operation at temperatures of 200–300K in the long wavelength (8–14 μm) range of the infrared spectrum. The new structure solves the perennial problems of poor quantum efficiency and low dynamic resistance found in conventional long wavelength infrared photovoltaic detectors when operated near room temperature. Computer simulations show that devices with properly optimized multiple heterojunctions are capable of achieving the performance limits imposed by the statistical nature of thermal generation-recombination processes. In order to demonstrate the technology, multiple heterojunction devices have been fabricated on epilayers grown by isothermal vapor phase epitaxy of HgCdTe and in situ As p-type doping. The detector structures were formed using a combination of conventional dry etching, angled ion milling, and angled thermal evaporation for contact metal deposition. These multi-junction n ⁺pp HgCdTe heterostructure devices exhibit performances which make them useful for many applications. D* of optically immersed multiple heterostructure photovoltaic detectors exceeding 10⁸cmHz^1/2/W were measured at λ=10.6 μm and T=300K.