Evolution of photoluminescence across dimensionality in lanthanide silicates

The dehydratation process of layered lanthanide silicates K3[LnSi3O8(OH)2], Ln = Y, Eu, Tb, and Er, and the structural characterization of the obtained small-pore framework K3LnSi3O9, Ln = Y, Eu, Tb, and Er solids, named AV-23, have been reported. The structure of AV-23 has been solved by single-crystal X-ray diffraction (XRD) methods and further characterized by chemical analysis, thermogravimetry, scanning electron microscopy, and 29Si MAS NMR. The photoluminescence (PL), radiance, and lifetime values of AV-23 have been studied and compared with those of AV-22. Both materials have a similar chemical makeup and structures sharing analogous building blocks, hence providing a unique opportunity for rationalizing the evolution of the PL properties of lanthanide silicates across dimensionality. Although Tb-AV-23 contains a single crystallographic Tb(3+) site, PL spectroscopy indicates the presence of Ln(3+) centers in regular framework positions and in defect regions. PL evidence suggests that Eu-AV-23 contains a third type of Ln(3+) environment, namely, Eu(3+) ions replacing K(+) ions in the micropores. The radiance values of the Tb-AV-22 and Tb-AV-23 samples are of the same order of magnitude as those of standard Tb(3+) green phosphors. For the samples K3(Y1-aEraSi3O9), a = 0.005-1, efficient emission and larger 4I13/2 lifetimes (ca. 7 ms) are detected for low Er(3+) content, indicating that the Er(3+)-Er(3+) interactions become significant as the Er(3)+ content increases.     

Effect of high-energy milling and thermal treatment on the solid-phase reactions in apatite–ammonium sulphate system

The phosphorous fertilizers are a product of natural sedimentary phosphorite ores. Using this raw material to produce phosphoric acid and classic phosphorous fertilizers has generated well-known ecological problems. A new and perspective way to use the same materials is creating a new type of time-delayed fertilizers applying high-energy milling (HEM) activation method. The impact of the mechanical forces over the solids is mostly revealed through the changes of the quantities being related to the energetic stability and reactivity of the solid phase. The aim of this work is to report the results from the investigation on the chemical and thermal reactions in composites of natural apatite , which are HEM activated for different times and thermally treated, (from Tunisia) and ammonium sulphate. The Tunisian phosphorite belongs to the ‘basic’ apatites having a Ca/P ratio of 1.70–1.77 and is characterized by a complex mineral composition with major component carbonate-fluorapatite. The used ammonium sulphate—(NH₄)₂SO₄ is obtained as a by-product from cleaning industrial waste gases, using e-beam technology. The composites of Tunisian phosphorite ores and ammonium sulphate, mixed in a mass ratio 1:1, were HEM activated during 10 min to 50 h with 20 mm Fe-milling bodies and temperature treated up to 1,100 °C. As a result, the chemical properties of the treated composites changed. Proofs were found for (i) formation of new phases during HEM activation such as NH₄Ca(PO₃)₃ (NH₄)₂CaH₄(P₂O₇)₂, (NH₄)₂Ca₃(P₂O₇)₂.6H₂O, CaH₂P₂O₇ and α-Ca₂P₂O₇; and (ii) decreasing of temperature intervals of phase changes in comparison to untreated composite.     

Tautomerism in 5-Bromouracil: Relationships with Other 5-Haloderivatives and Effect of the Microhydration

A comparative analysis on the effect of the water on the molecular structure and spectroscopy of 5-halogenated uracils was carried out. Solvent effects were considered by using a variable number (1–10) of explicit water molecules surrounding the 5-halouracil derivatives in order to simulate the first hydration shell. More than 300 cluster structures with water were analyzed. B3LYP and MP2 quantum chemical methods were used. For cases where literature data are available, the computed values were in good agreement with previous experimental and theoretical studies. Several general conclusions were underlined.     

Vibrational characterization and prooxidant activity of newly synthesized dysprosium(III) complex

The dysprosium(III) complex of 5-aminoorotic acid (HAOA) was synthesized by reaction of the respective inorganic salt in amounts equal to ligand, molar ratio of 1:3. The structure of the complex was determined by means of elemental analysis, FTIR and FT-Raman spectroscopies. Significant differences in the IR and Raman spectra of the complex were observed as compared to the spectra of the free ligand. Detailed vibrational analysis of HAOA and Dy(III)-AOA systems revealed that the binding mode in the complex was bidentate through the carboxylic oxygen atoms. Dy(III) complex of 5-aminoorotic acid (DyAOA) exhibited prooxidant properties in the presence of the model system X/XO. In the DyAOA complex, the ion diminished the antioxidant properties of the AOA ligands.     

ICP-AES分析光谱条件对中药蒲公英无机元素吸收的影响

在全密闭植物工厂中水培种植中药蒲公英,以发射不同波段光谱的荧光灯及LED灯作为药材生长光源,并结合ICP–AES技术分析了不同光谱条件对蒲公英无机元素吸收和积累的影响。结果表明:(1)相近的光合有效辐射(PAR)条件下,单一红光R及混合光FLRB有利于水培蒲公英可食生物量的积累,单一蓝光B处理下可食生物量最低;(2)荧光灯FL条件下蒲公英地上部分常量无机元素含量比值为K∶Ca∶P∶Mg∶Na=79.74∶32.39∶24.32∶10.55∶1.00,微量无机元素含量比值为Fe∶Mn∶B∶Zn∶Cu=9.28∶9.71∶3.82∶2.08∶1.00;(3)峰值为660nm的红光有利于蒲公英对Ca,Fe,Mn,Zn元素的吸收,Cu元素含量受光谱条件的影响不明显;(4)蒲公英地上部分对Ca,Na,Mn,Zn四种元素的积累量均在纯红光R下最高,而对其余六种元素的积累量以混合光FLRB条件下最高。     

4,4-Bis(methylthio)azetidin-2-ones as synthons of 1,2- and 1,3-dicarbonyl systems

The importance of β-lactams as synthetic building blocks has been widely recognized in organic synthesis due to possible ring cleavage at any of the four single bonds of the β-lactam ring. We now report reactions involving breaking of the N1-C4 bond in differently substituted at C3 4,4-bis(methylthio)azetidin-2-ones, leading to formation of 1,2- and 1,3-dicarbonyl systems.     

Determination of manganese by a new spectrophotometry method using toluidine blue

The formation of the ion associate of manganese(VII) with Toluidine Blue is studied spectropho-tometrically in water-organic media. The composition of the complex is established as TB: MnO₄ ^- =1:1. The molar absorptivity ε290 = (2.46 ± 0.09) × 10⁴ L/mol cm is determined. The selectivity of the reaction is studied and the method for determination of manganese(VII) 0.1—2.9 fug/mL is developed. Investigations of extraction in the system discussed were carried out. The characteristic values for the extraction equilibrium and the equilibrium in the aqueous phase were determined: extraction constant K_ex = 1 × 10⁴, distribution constant KD = 26.08, and association constant β = 3.83 × 10². A rapid and selective extractive-photometric method for the determination of manganese(VII) in plants was proposed.     

New radon and gamma device using TLD and SSNTD to carry out monitoring in the environment

The research program, that we are leading, concerns and takes into consideration the potential risk of the natural and artificial radio-elements in the environment and particularly to consider their migration from environment to the people and with special respect to radon effects. To begin these investigations, we developed a new passive detectors using two solid nuclear track detector techniques: thermo-luminescent detectors (TLDs) (gamma measuring) and solid state nuclear track detectors (SSNTDs) (alpha measuring). The characteristics of the cell provide for alpha (SSNTD - LR115) and gamma-radioactivity (TLD-CaSO₄:Dy) measuring in different soil depths. The used technologies are with a low priced. The instrumentation has been first validated in laboratory to quality precisely its response and then, we have performed the survey for one site in Bulgaria.