Deciphering Three Beneficial Effects of 2,2 '-Bipyridine-N,N '-Dioxide on the Luminescence Sensitization of Lanthanide(III) Hexafluoroacetylacetonate Ternary Complexes

Lanthanide hexafluoroacetylacetonate ternary complexes with 2,2'-bipyridine-N,N'-dioxide, [Ln(hfa)3(bpyO2)], were synthesized for Ln = Eu, Gd, Tb, and Lu and fully characterized by elemental, thermal, and mass-spectrometric analyses. The X-ray crystal structure of [Eu(hfa) 3(bpyO2)].0.5C6H6 reveals an octa-coordinate metal ion lying in a severely distorted trigonal dodecahedron geometry; the Eu-O distances lie in the range 2.36-2.44 Å with no significant difference between hfa- and bpyO2. A detailed comparative photophysical investigation has been carried out to determine the exact influence of the introduction of bpyO2 in the inner coordination sphere of the metal ion in replacement of the two water molecules in [Ln(hfa)3(H2O)2]. While this replacement is detrimental for Tb, it leads to a 15-fold increase in the overall quantum yield for Eu. This large improvement originates from (i) a better sensitization efficiency, the ancillary ligand being responsible for 3/4 of the energy transfer, (ii) elimination of nonradiative deactivation pathways through harmonics of O-H vibrations, and (iii) reduction in the radiative lifetime. The latter influence is rarely documented, but it accounts here for ã25% increase in the intrinsic quantum yield, so that more attention should be given to this parameter when designing highly luminescent lanthanide complexes. © 2011 American Chemical Society

Global Spore Sampling Project: A global, standardized dataset of airborne fungal DNA

Novel methods for sampling and characterizing biodiversity hold great promise for re-evaluating patterns of life across the planet. The sampling of airborne spores with a cyclone sampler, and the sequencing of their DNA, have been suggested as an efficient and well-calibrated tool for surveying fungal diversity across various environments. Here we present data originating from the Global Spore Sampling Project, comprising 2,768 samples collected during two years at 47 outdoor locations across the world. Each sample represents fungal DNA extracted from 24 m3 of air. We applied a conservative bioinformatics pipeline that filtered out sequences that did not show strong evidence of representing a fungal species. The pipeline yielded 27,954 species-level operational taxonomic units (OTUs). Each OTU is accompanied by a probabilistic taxonomic classification, validated through comparison with expert evaluations. To examine the potential of the data for ecological analyses, we partitioned the variation in species distributions into spatial and seasonal components, showing a strong effect of the annual mean temperature on community composition.publishedVersio

A cultura escolar em conflito: ensino técnico e matemática moderna em Portugal

Disponível em: http://www2.pucpr.br/reol/pb/index.php/dialogo?dd1=16276&dd99=view&dd98=pbO artigo estuda as transformações exigidas às escolas do ensino profissional português durante a reforma da matemática moderna que ocorrem a partir de finais dos anos 1960. Em primeiro lugar, traça um quadro das normas associadas às escolas técnicas portuguesas antes da reforma, recorrendo à legislação fundadora, aos manuais e a artigos de opinião de professores. Em segundo, detalha o debate que antecipou a introdução da reforma recorrendo a artigos e aopiniões expressas durante os cursos preparatórios, onde são notórias as pressões para mudanças na cultura escolar, especialmente nas suas representações, suscitadas pela nova matemática. Finalmente, observar-se como se materializou a reforma nos livros de texto da experiência

Airborne DNA reveals predictable spatial and seasonal dynamics of fungi.

Fungi are among the most diverse and ecologically important kingdoms in life. However, the distributional ranges of fungi remain largely unknown as do the ecological mechanisms that shape their distributions1,2. To provide an integrated view of the spatial and seasonal dynamics of fungi, we implemented a globally distributed standardized aerial sampling of fungal spores3. The vast majority of operational taxonomic units were detected within only one climatic zone, and the spatiotemporal patterns of species richness and community composition were mostly explained by annual mean air temperature. Tropical regions hosted the highest fungal diversity except for lichenized, ericoid mycorrhizal and ectomycorrhizal fungi, which reached their peak diversity in temperate regions. The sensitivity in climatic responses was associated with phylogenetic relatedness, suggesting that large-scale distributions of some fungal groups are partially constrained by their ancestral niche. There was a strong phylogenetic signal in seasonal sensitivity, suggesting that some groups of fungi have retained their ancestral trait of sporulating for only a short period. Overall, our results show that the hyperdiverse kingdom of fungi follows globally highly predictable spatial and temporal dynamics, with seasonality in both species richness and community composition increasing with latitude. Our study reports patterns resembling those described for other major groups of organisms, thus making a major contribution to the long-standing debate on whether organisms with a microbial lifestyle follow the global biodiversity paradigms known for macroorganisms4,5

On Strategic Orientation of Student Educational Activity

The article deals with the research in the field of the strategic orientation of educational activities in higher education. The necessity of applying a student-centered approach in such studies is revealed. It is noted that the factors influencing the strategic orientation of the student educational activity relate either to the space of ‘due’ or to the space of ‘being’. The invariant core of the graduate competence model belongs to the target-oriented space of the ‘due’. It includes 12 clusters of competencies and describes the normative context of the strategic orientation of the student educational activity. The personal context of this orientation is formed on the basis of a va riety of students’ goals in the space of ‘being’. It is characterized by student’s ideas about the relative importance of the qualities that one will need in future after graduation. The technique of establishing a hierarchy of combined graduate qualities is described. This hierarchy is determined by the student’s goals, which can be reflected through the subjective significance of the considered qualities for one. The analysis of results showed that the gender of the student and the character of his future labour activity significantly influence one’s strategic orientation

Reactive Chemical Vapor Deposition Method as New Approach for Obtaining Electroluminescent Thin Film Materials

The new reactive chemical vapor deposition (RCVD) method has been proposed for thin film deposition of luminescent nonvolatile lanthanide aromatic carboxylates. This method is based on metathesis reaction between the vapors of volatile lanthanide dipivaloylmethanate (Ln(dpm)3) and carboxylic acid (HCarb orH2Carb′) and was successfully used in case of HCarb. Advantages of the method were demonstrated on example of terbium benzoate (Tb(bz)3) and o-phenoxybenzoate thin films, and Tb(bz)3 thin films were successfully examined in the OLED with the following structure glass/ITO/PEDOT:PSS/TPD/Tb(bz)3/Ca/Al. Electroluminescence spectra of Tb(bz)3 showed only typical luminescent bands, originated from transitions of the terbium ion. Method peculiarities for deposition of compounds of dibasic acids H2Carb′ are established on example of terbium and europium terephtalates and europium 2,6-naphtalenedicarboxylate

Dimeric lanthanide hexafluoroacetylacetonate adducts with 4-cyanopyridine-N-oxide

A series of new dimeric complexes with composition [Ln2(hfa)6(4-cpyNO)3] (2:3 adduct, Ln = SmIII–DyIII, TmIII) were synthesized and fully characterized. X-ray diffraction data of [Tb2(hfa)6(4-cpyNO)3]·CHCl3 confirmed the dimeric structure; Tb ions are nine-coordinated by six O atoms from three hfa− ligands and three O atoms from three bridging 4-cpyNO molecules. The photophysical properties (absolute quantum yields and luminescence lifetimes) of the EuIII and TbIII 2:3 adducts are presented and compared with those of the 2:2 adducts

Dimeric Complexes of Lanthanide(III) Hexafluoroacetylacetonates with 4-Cyanopyridine N-Oxide: Syn thesis, Crystal Structure, Magnetic and Photoluminescent Properties

A series of new mixed-ligand lanthanide complexes [Ln(hfa)3(4-cpyNO)]2 (Ln = SmIII-HoIII and TmIII; hfa- = hexafluoroacetylacetonate; 4-cpyNO = 4-cyanopyridine N-oxide) have been synthesised by treating the corresponding lanthanide hexafluoroacetylacetonates with 4-cpyNO (molar ratio 1:1) in chloroform. Single-crystal X-ray analysis revealed that [Tb(hfa)3(4-cpyNO)]2 and [Ho(hfa)3(4-cpyNO)]2 are isostructural and are comprised of two types of symmetrically independent dimetallic molecules. Within a dimer, the eightfold-coordinated metal atoms are bridged by two 4-cpyNO ligands through the oxygen atoms of the N-oxide groups. The magnetic susceptibility data for the GdIII and TbIII complexes indicate the presence of weak antiferromagnetic interactions within the dimetallic Ln2O2 units. The thermal stability of the [Ln(hfa)3(4-cpyNO)]2 adducts was studied by thermogravimetric analysis and their volatility estimated from sublimation experiments under reduced pressure. The photoluminescent properties were measured for solid samples upon excitation at 330-360 nm. The mixed-ligand complexes of SmIII, EuIII, TbIII, DyIII and TmIII exhibit metal-centred luminescence in the entire visible spectral range with characteristic pink, red, green, yellow and blue emission, respectively. The introduction of ancillary 4-cpyNO molecules into the coordination sphere of the lanthanide(III) ions was found to significantly affect their luminescence quantum yields. [Eu(hfa)3(4-cpyNO)]2 thin films on quartz substrates were obtained by the vacuum evaporation technique and their photoluminescent properties were found to be enhanced when compared with those of the bulk samples. This suggests that these dimers could be good candidates for the fabrication of emitting layers for light-emitting diodes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006

Role of the Ancillary Ligand N,N-Dimethylaminoethanol in the Sensitization of EuIII and TbIII Luminescence in Dimeric β-Diketonates

Two types of dimeric complexes [Ln2(hfa)6(í2-O(CH2)2NHMe2)2] and [Ln(thd)2(í2,è2-O(CH2)2NMe2)]2 (Ln ) YIII, EuIII, GdIII, TbIII, TmIII, LuIII; hfa- ) hexafluoroacetylacetonato, thd- ) dipivaloylmethanato) are obtained by reacting [Ln(hfa)3(H2O)2] and [Ln(thd)3], respectively, with N,N-dimethylaminoethanol in toluene and are fully characterized. X-ray single crystal analysis performed for the TbIII compounds confirms their dimeric structure. The coordination mode of N,N-dimethylaminoethanol depends on the nature of the â-diketonate. In [Tb2(hfa)6(í2-O(CH2)2NHMe2)2], eight-coordinate TbIII ions adopt distorted square antiprismatic coordination environments and are O-bridged by two zwitterionic N,N-dimethylaminoethanol ligands with a Tb1âââTb2 separation of 3.684(1) Å. In [Tb(thd)2(í2,è2-O(CH2)2NMe2)]2, the N,N-dimethylaminoethanol acts as chelating-bridging O,N-donor anion and the TbIII ions are seven-coordinate; the Tb1âââTb1A separation amounts to 3.735(2) Å within centrosymmetric dimers. The dimeric complexes are thermally stable up to 180 °C, as shown by thermogravimetric analysis, and their volatility is sufficient for quantitative sublimation under reduced pressure. The EuIII and TbIII dimers display metal-centered luminescence, particularly [Eu2(hfa)6(O(CH2)2NHMe2)2] (quantum yield QLn L ) 58%) and [Tb(thd)2(O(CH2)2NMe2)]2 (32%). Consideration of energy migration paths within the dimers, based on the study of both pure and EuIII- or TbIII-doped (0.01-0.1 mol %) LuIII analogues, leads to the conclusion that both the â-diketone and N,N-dimethylaminoethanol ligands contribute significantly to the sensitization process of the EuIII luminescence. The ancillary ligand increases considerably the luminescence of [Eu2(hfa)6(O(CH2)2NHMe2)2], compared to [Ln(hfa)3(H2O)2], through the formation of intra-ligand states while it is detrimental to TbIII luminescence in both â-diketonates. Thin films of the most luminescent compound [Eu2(hfa)6(O(CH2)2NHMe2)2] obtained by vacuum sublimation display photophysical properties analogous to those of the solid-state sample, thus opening perspectives for applications in electroluminescent devices