Intercalation of Diverse Organic Guests into Layered Europium Hydroxides – Structural Tuning and Photoluminescence Behavior
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Abstract Organic anions of two benzenepolycarboxylic acids [1,3,5‐benzenetricarboxylic acid (BTA) and 2,2′‐biphenyldicarboxylic acid (BDA)], two pyridinecarboxylic acids [quinolinic acid (QA) and 2,5‐pyridinedicarboxylic acid (PDA)], and two amino acids [phenylalanine (Phe) and tyrosine (Tyr)] were intercalated into the galleries of NO 3 – ‐type layered europium hydroxide (NO 3 –LEuH). All the prepared products displayed XRD patterns with series of diffractions due to layered materials. The composite structures and the arrangement of the guests in the galleries were investigated in detail. The structure of the organic guests (such as the number and position of carboxyl groups) affects the arrangement in the interlayer. SEM observations showed that the NO 3 –LEuH precursor and its intercalates crystallize in a columnar or layered stacking structure composed of hexagonal thin platelets. The luminescence study indicated that all samples display the typical red emission of Eu 3+ . Efficient energy transfer between intercalated BTA/BDA anions and Eu 3+ centers takes place, markedly enhancing the Eu 3+ luminescence, whereas QA–LEuH and PDA–LEuH with pyridinedicarboxylic acid anions show no obvious change in luminescence intensity. When amino acid anions such as Phe and Tyr were introduced into the interlayer, the Eu 3+ emission was strongly quenched. The simple soft chemical method can open great opportunities for developing organic–inorganic multifunctional luminescent materials or biological probes for detecting certain amino acids.Keywords:
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The stacking of layers forming three-dimensional periodic structures is explored in the general case, where neither the layers nor the stacking need to be close-packed, and the connectivity number for the system may be either two or four. Procedures are described whereby all possible stacking variants can be systematically derived for a given number of layers, and for a given number of possible stacking positions. The latter depends on the structure of the layer and on the stacking vector.
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In this work, we present a detailed investigation of the low temperature emission properties of ZnSeO alloys by means of photoluminescence, micro-photoluminescence, and time-resolved photoluminescence. We show that the low temperature broad photoluminescence spectrum of ZnSeO attributed to the recombination of localized excitons is composed of sharp lines related to individual trapping states. Based on studies of photoluminescence thermal quenching from individual trapping states and photoluminescence dynamics, the mechanism of nonradiative recombination in ZnSeO alloys is discussed. Moreover, an unexpected decrease of the low temperature Stokes shift with increasing oxygen content is observed in contrast to what has been reported for GaAs based highly mismatched alloys. The possible origin of this effect is proposed.
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Two new europium (III) complexes luminescent materials, Eu-PDA and Eu-PDA-Phen, were prepared by the reaction of Eu(NO3)3·6H2O with 2, 3-pyrazinedicarboxylic acid (PDA) and 1,10-phenanthroline, respectively. The luminescent properties of two europium (III) complexes in solid and in organic solvents have been studied. The effect of organic solvents and metal ions (Ca2+ and Mg2+) on the luminescent intensity of the Eu (III) complexes have also been investigated. The results show that the metal ions (Ca2+ and Mg2+) could enhance the luminescent intensity of Eu-PDA-Phen complex and reduce luminescent intensity of Eu-PDA complex. The polarity of organic solvents is an important factor on the luminescent intensity of two complexes.
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We examined the change in photoluminescence spectra of porous Si when it is oxidized then deoxidized chemically. After both steps, photoluminescence shifted to higher frequencies and increased in intensity. These shifts to higher frequencies indicate the photoluminescence is a result of the quantum size effect. Moreover, the increase in photoluminescence intensity after oxidation suggests that termination by hydrogen on the porous Si surface does not always play a key role in the photoluminescence mechanism.
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The europium-151 Mossbauer spectra of the Eu(14)MnP(11), Eu(14)MnAs(11), and Eu(14)MnSb(11) Zintl compounds, measured between 4.2 and 100 K, reveal europium(II) for all four crystallographically inequivalent europium sites in Eu(14)MnAs(11) and Eu(14)MnSb(11) and europium(II) and europium(III) for the three 32g and the 16f europium sites in Eu(14)MnP(11), respectively. Below the ordering temperatures of 52, 74, and 92 K, only very small hyperfine fields of 2-4 T are observed at the europium sites as a result of the polarization by the manganese magnetic moments. At 4.2 K, the europium(II) magnetic moments are ordered, and hyperfine fields of 24.4, 24.8, and 19.3 T are observed in Eu(14)MnP(11), Eu(14)MnAs(11), and Eu(14)MnSb(11), respectively, fields that are typical for magnetically ordered europium(II) ions. At 4.2 K the 16f europium(III) sites in Eu(14)MnP(11) experience a transferred hyperfine field of 33 T from the neighboring ordered europium(II) moments. Between its Curie temperature and 4.2 K, the europium-151 Mossbauer spectra of Eu(14)MnSb(11) reveal that the europium(II) moments order below ca. 13 K, i.e., below the second magnetic transition observed in magnetic measurements. Between their Curie temperatures and 4.2 K, the europium-151 Mossbauer spectra of Eu(14)MnP(11) and Eu(14)MnAs(11) are complex and have been analyzed with two models, models that give equivalently good fits. However, the second model in which the spectra are fit with a three-dimensional relaxation of the europium(II) and europium(III) hyperfine fields is preferred for its physical meaning and its reduced number of fitted parameters.
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Abstract Employing a standard protocol for the preparation of a trisbenzoylacetonato europium(III) complex with 4‐bromo benzoylacetone 2 as ligand, a new europium species was synthesized and characterized. The X‐ray crystal structure analysis revealed a new europium cluster consisting of six europiumcentres.
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