Rute Ferreira - Academia.edu (original) (raw)
Papers by Rute Ferreira
Nature communications, 2014
White light-emitting diodes (WLEDs) are candidates to revolutionize the lighting industry towards... more White light-emitting diodes (WLEDs) are candidates to revolutionize the lighting industry towards energy efficient and environmental friendly lighting and displays. The current challenges in WLEDs encompass high luminous efficiency, chromatic stability, high colour-rending index and price competitiveness. Recently, the development of efficient and low-cost downconverting photoluminescent phosphors for ultraviolet/blue to white light conversion was highly investigated. Here we report a simple route to design high-efficient WLEDs by combining a commercial ultraviolet LED chip (InGaAsN, 390 nm) and boehmite (γ-AlOOH) hybrid nanoplates. Unusually high quantum yields (ηyield=38-58%) result from a synergic energy transfer between the boehmite-related states and the triplet states of the benzoate ligands bound to the surface of the nanoplates. The nanoplates with ηyield=38% are able to emit white light with Commission International de l'Eclairage coordinates, colour-rendering index and correlated colour temperature values of (0.32, 0.33), 85.5 and 6,111 K, respectively; overwhelming state-of-the-art single-phase ultraviolet-pumped WLEDs phosphors.
Advances in Intelligent Systems and Computing, 2014
Revista Portuguesa de Endocrinologia, Diabetes e Metabolismo, 2015
ABSTRACT In the last years there was an increasing interest about diabetes and driving. Nowadays ... more ABSTRACT In the last years there was an increasing interest about diabetes and driving. Nowadays there are strict rules for diabetic drivers in most countries. The aim of this study was to assess whether the patients and the doctors were aware of the rules and recommendations in Portugal.Methods An anonymous questionnaire was applied to diabetic patients who were drivers attending our center for 8 weeks. A web-based questionnaire was e-mailed to the Endocrinology, Diabetes and Metabolism Portuguese Society and Diabetes Portuguese Society associates.ResultsNinety-three patients were surveyed. Only 20 patients had discussed this subject with their doctor and 69.9% thought there was not any risk to driving by being a diabetic. Twenty-nine percent never tests blood glucose prior to driving and for the majority it is safe to drive until blood glucose is 60 mg/dl. One patient reported a crash due to hypoglycemia. Eighty-eight doctors completed the questionnaire. Fourteen did not associate diabetes with an increased risk of car accidents and 59.1% discuss the driving and diabetes issue with less than 50% of their diabetic patients. Only 54% advise their patients to test blood glycaemia prior to driving and for 46.6% it is safe to drive with blood glucose lower than 90 mg/dl. Sixteen did not know recurrent hypoglycemia was a contraindication to driving and eight that impaired awareness of hypoglycemia might also be a contraindication.Discussion/conclusionsThis study shows a lack of patients’ knowledge about safe driving and the rules they must follow. In our opinion, it is fundamental to improve doctor's and patients’ knowledge in this subject.
Endocrine Abstracts, 2014
Endocrine Abstracts, 2014
Revista Portuguesa de Endocrinologia, Diabetes e Metabolismo, 2014
Endocrine Abstracts, 2014
RSC Advances
A new photoluminescent bimetallic-3-hydroxypicolinate/graphene oxide composite was prepared by in... more A new photoluminescent bimetallic-3-hydroxypicolinate/graphene oxide composite was prepared by incorporation of the complex Na 5 [EuW 2 O 6 (picOH) 8 ] (1; HpicOH being 3-hydroxypicolinic acid) on graphene oxide (GO). Photoluminescence studies (emission and excitation spectra and 5 D 0 emission decay curves) were performed on 1 and the composite 1/GO suggesting an effective interaction between the picOH 2 ligands and the graphene oxide.
ChemInform, 2008
A new template-free layered manganese(III) phosphate, Na 3 MnH(P 0.9 O 4 ) 2 , has been hydrother... more A new template-free layered manganese(III) phosphate, Na 3 MnH(P 0.9 O 4 ) 2 , has been hydrothermally synthesized. The crystal structure was solved ab initio from powder X-ray diffraction data, and the model was confirmed using the Rietveld method. The material crystallizes in triclinic space group P1 j (No. 2) with lattice parameters a ) 5.2925
Chemistry (Weinheim an der Bergstrasse, Germany), Jan 17, 2012
Scientific reports, 2014
Nano-graphene oxide (nano-GO) is a new class of carbon based materials being proposed for biomedi... more Nano-graphene oxide (nano-GO) is a new class of carbon based materials being proposed for biomedical applications due to its small size, intrinsic optical properties, large specific surface area, and easy to functionalize. To fully exploit nano-GO properties, a reproducible method for its production is of utmost importance. Herein we report, the study of the sequential fracture of GO sheets onto nano-GO with controllable lateral width, by a simple, and reproducible method based on a mechanism that we describe as a confined hot spot atomic fragmentation/reduction of GO promoted by ultrasonication. The chemical and structural changes on GO structure during the breakage were monitored by XPS, FTIR, Raman and HRTEM. We found that GO sheets starts breaking from the defects region and in a second phase through the disruption of carbon bonds while still maintaining crystalline carbon domains. The breaking of GO is accompanied by its own reduction, essentially by the elimination of carboxylic and carbonyl functional groups. Photoluminescence and photothermal studies using this nano-GO are also presented highlighting the potential of this nanomaterial as a unique imaging/therapy platform. N owadays, one of the most prompt methods to prepare graphene oxide (GO) or reduced graphene oxide (rGO) is through the wet chemical exfoliation of graphite. This approach has the advantage of large scale production, procedure simplicity, high efficiency and low cost 1 . The exfoliation of graphite in solution occurs through extensive intercalation of oxygen moieties on the aromatic structure. This increases the interplanar carbon distance and consequently weakening the interactions between adjacent carbon planes 2 .
2012 17th Opto-Electronics and Communications Conference, 2012
ABSTRACT In this work we investigate the dynamics of the fuse effect propagation in bend loss ins... more ABSTRACT In this work we investigate the dynamics of the fuse effect propagation in bend loss insensitive fibers. The fuse velocity, threshold power and void period values were compared with those obtained for standard single mode fibers. The results show that the power dependent optical discharge velocity coefficient is 32% higher in G.657 fibers than that in G.652 fibers.
Inorganic Chemistry
A novel layered zinc phosphate, [N 2 C 6 H 12 ] 2 [Zn 7 H 3 (HPO 4-x ) 5 (PO 4 ) 3 ] H 2 O, with ... more A novel layered zinc phosphate, [N 2 C 6 H 12 ] 2 [Zn 7 H 3 (HPO 4-x ) 5 (PO 4 ) 3 ] H 2 O, with unique 10-membered-ring ellipsoidal channels running perpendicularly to ladder-shaped tetrahedral layers, has been synthesized ionothermally via in situ generation of 1,4-diazabicyclo[2.2.2] octane.
ChemInform, 2008
Luminescence D 6540 Photoluminescent Layered Y/Er Silicates. -New layered rare-earth silicates K ... more Luminescence D 6540 Photoluminescent Layered Y/Er Silicates. -New layered rare-earth silicates K 3 [Y 1-x Er x Si 3 O 8 (OH) 2 ] (x = 0.005-1) are synthesized from aqueous solutions containing SiO2, Na2O, KOH, YCl3, and ErCl3 (autoclave, 230°C, 7 d). Thermal degradation of the samples leads to K3[Y1-xErxSi3O9]. The samples are characterized by powder XRD, SEM, and Raman spectroscopy. The photoluminescence properties of the materials are discussed and compared. The calcination process increases the intensity of the Er 3+ emission and the importance of the Er 3+ -Er 3+ interactions as a quenching emission channel. -(KOSTOVA, M. H.; ANANIAS, D.; CARLOS*, L. D.; ROCHA, J.; J.
International Conference on Transparent Optical Networks, 2010
In this paper, direct UV-laser writing was used to produce channel waveguides and diffraction gra... more In this paper, direct UV-laser writing was used to produce channel waveguides and diffraction gratings on thin films of siliceous-based organic-inorganic hybrid materials. The optical quality of the films surface was studied by light scattering measurements. The produced Y-power splitters, optical filters and Fabry-Perot cavities were experimentally characterized for propagation in the near infrared spectral region.
Microporous and Mesoporous Materials, 2008
A luminescent material has been prepared by formation of the Eu3+ β-diketonate complex Eu(NTA)3L″... more A luminescent material has been prepared by formation of the Eu3+ β-diketonate complex Eu(NTA)3L″ {NTA = 1-(2-naphthoyl)-3,3,3-trifluoroacetonate; L″ = ethyl[3-(2-pyridyl)-1-pyrazolyl]acetate} within the channels of MCM-41-type ordered mesoporous silica. Using simple wet impregnation methods, the ligand L″ was first encapsulated followed by treatment with the complex Eu(NTA)3(H2O)2. An analogous Gd3+ supported material was also prepared, as well as the model complexes Ln(NTA)3L′ {Ln = Eu, Gd; L′ = 2-[3(5)-pyrazolyl]pyridine}. The materials were characterized by powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), FTIR and FT Raman spectroscopies, 13C and 29Si MAS NMR, and photoluminescence spectroscopy. The spectroscopic studies showed that exchange of the H2O ligands for the bidentate ligand L″ occurred to give the desired 8-coordinate species Ln(NTA)3L″, with a local Ln3+ coordination environment similar to that for the model complexes. The low (−259 °C) and room temperature emission spectra of the Eu-modified mesoporous material displayed the typical Eu3+ intra-4f6 lines ascribed to transitions between the 5D0,1 excited states and the ground multiplet (7F0–4). Negligible emission from the organic part of the encapsulated species was observed, indicating that energy transfer from the ligands to the Eu3+ ion was quite efficient. The 5D0 quantum efficiency was estimated to be 21.1%, compared with 46.1% for the model complex Eu(NTA)3L′. This difference is attributed to the presence of an excited state of the organic ligands in the supported material that lies approximately resonant with the 5D1 intra-4f6 level, opening up an additional non-radiative channel that is not present in the corresponding model complexes.
Polyhedron, 2006
The adduct Eu(NTA)3 · bipy was prepared by the reaction of Eu(NTA)3 · 2H2O with 2,2′-bipyridine i... more The adduct Eu(NTA)3 · bipy was prepared by the reaction of Eu(NTA)3 · 2H2O with 2,2′-bipyridine in a 1:1 ratio in chloroform [NTA = 1-(2-naphthoyl)-3,3,3-trifluoroacetonate]. Recrystallization of the complex from a chloroform/diethyl ether solvent mixture gave crystals suitable for X-ray diffraction. The structure contained chloroform molecules in partially occupied sites and was found to be different from the two forms previously reported for the same adduct (one unsolvated and the other containing isopropanol molecules). A single eight-coordinate geometry was found for Eu(NTA)3 · bipy · 0.44CHCl3, corresponding to a distorted square antiprism, with the bidentate ligands spanning opposite sides of the ‘square’ faces. A 2:1 (host-to-guest) inclusion compound comprising β-cyclodextrin (CD) and Eu(NTA)3 · bipy was obtained by co-precipitation from a mixed water/ethyl acetate solvent mixture. The formation of a true inclusion complex was supported by powder XRD, thermogravimetric analysis and 13C CP MAS NMR spectroscopy. Photoluminescence spectroscopy indicated the presence of only one low-symmetry environment for the Eu3+ cations in non-included Eu(NTA)3 · bipy and the inclusion compound. However, upon encapsulation of the complex in β-CD, some of the Eu3+ intra-4f65D0 → 7F0–4 lines shifted in energy, and the number of Stark components for the 5D0 → 7F1–2 transitions increased, indicating a lowering of the symmetry of the Eu3+ local coordination environment. The room temperature excitation spectrum of the inclusion compound revealed an enhancement of the Eu3+ sensitized process as a result of encapsulation of the Eu(NTA)3 · bipy molecules.The crystal structure of the compound Eu(NTA)3 · bipy · 0.44CHCl3 was determined by X-ray diffraction and compared with previously reported structures containing the adduct Eu(NTA)3 · bipy. Encapsulation of Eu(NTA)3 · bipy in β-cyclodextrin gave an inclusion compound which exhibited photoluminescence and excitation spectra different from those of the non-included complex, revealing, in particular, an enhancement of the Eu3+ sensitized process.
Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2006
A 1:1 inclusion compound between octakis(2,3,6-tri-O-methyl)-γ-cyclodextrin (TRIMEG) and the chel... more A 1:1 inclusion compound between octakis(2,3,6-tri-O-methyl)-γ-cyclodextrin (TRIMEG) and the chelate complex Eu(NTA)3·2H2O (NTA=1-(2-naphthoyl)-3,3,3-trifluoroacetonate) was prepared and characterized by powder X-ray diffraction, thermogravimetric analysis and photoluminescence spectroscopy. The results were compared with those obtained for the corresponding native γ-CD adduct. Excitation and emission spectra were measured, and the lifetimes were determined for the Eu3+ first excited state (5D0). The results indicate the presence of only one low-symmetry environment for the Eu3+ cations in the inclusion compounds. Encapsulation of the Europium complex in the two CDs increases the quantum efficiency of the ligand-to-metal energy transfer pathway, but the efficiency of the Eu3+ sensitization was significantly higher with TRIMEG as the host molecule. This may be related with the observation that the two hosts appear to have different influences on the Eu3+ coordination environments for the guest molecule.
Spectroscopy Letters, 2010
Urea-based bis-silylated bipyridine (bpy) organic-inorganic 25 hybrids incorporating different la... more Urea-based bis-silylated bipyridine (bpy) organic-inorganic 25 hybrids incorporating different lanthanide (Ln 3þ ) ions (Eu 3þ , Gd 3þ , Tb 3þ or Eu 3þ =Tb 3þ ) were obtained by the sol-gel process. The structure and the emission characteristics of the hybrids were ascertained using X-ray diffraction, nuclear magnetic resonance, Fourier transform infrared spectroscopy, photoluminescence, and quantum yield measurements. The 30 hybrids feature both the emission of the host and the Eu 3þ and=or Tb 3þ transitions allowing a fine-tuning of the color from the blue to the red, orange, or green spectral regions. Bpy-to-Ln 3þ and Tb 3þ -to-Eu 3þ energy transfer mechanisms are demonstrated and the hybrids present slightly distinct Ln 3þ coordination spheres due to the different bpy=Ln 3þ ratios. 35
Nature communications, 2014
White light-emitting diodes (WLEDs) are candidates to revolutionize the lighting industry towards... more White light-emitting diodes (WLEDs) are candidates to revolutionize the lighting industry towards energy efficient and environmental friendly lighting and displays. The current challenges in WLEDs encompass high luminous efficiency, chromatic stability, high colour-rending index and price competitiveness. Recently, the development of efficient and low-cost downconverting photoluminescent phosphors for ultraviolet/blue to white light conversion was highly investigated. Here we report a simple route to design high-efficient WLEDs by combining a commercial ultraviolet LED chip (InGaAsN, 390 nm) and boehmite (γ-AlOOH) hybrid nanoplates. Unusually high quantum yields (ηyield=38-58%) result from a synergic energy transfer between the boehmite-related states and the triplet states of the benzoate ligands bound to the surface of the nanoplates. The nanoplates with ηyield=38% are able to emit white light with Commission International de l'Eclairage coordinates, colour-rendering index and correlated colour temperature values of (0.32, 0.33), 85.5 and 6,111 K, respectively; overwhelming state-of-the-art single-phase ultraviolet-pumped WLEDs phosphors.
Advances in Intelligent Systems and Computing, 2014
Revista Portuguesa de Endocrinologia, Diabetes e Metabolismo, 2015
ABSTRACT In the last years there was an increasing interest about diabetes and driving. Nowadays ... more ABSTRACT In the last years there was an increasing interest about diabetes and driving. Nowadays there are strict rules for diabetic drivers in most countries. The aim of this study was to assess whether the patients and the doctors were aware of the rules and recommendations in Portugal.Methods An anonymous questionnaire was applied to diabetic patients who were drivers attending our center for 8 weeks. A web-based questionnaire was e-mailed to the Endocrinology, Diabetes and Metabolism Portuguese Society and Diabetes Portuguese Society associates.ResultsNinety-three patients were surveyed. Only 20 patients had discussed this subject with their doctor and 69.9% thought there was not any risk to driving by being a diabetic. Twenty-nine percent never tests blood glucose prior to driving and for the majority it is safe to drive until blood glucose is 60 mg/dl. One patient reported a crash due to hypoglycemia. Eighty-eight doctors completed the questionnaire. Fourteen did not associate diabetes with an increased risk of car accidents and 59.1% discuss the driving and diabetes issue with less than 50% of their diabetic patients. Only 54% advise their patients to test blood glycaemia prior to driving and for 46.6% it is safe to drive with blood glucose lower than 90 mg/dl. Sixteen did not know recurrent hypoglycemia was a contraindication to driving and eight that impaired awareness of hypoglycemia might also be a contraindication.Discussion/conclusionsThis study shows a lack of patients’ knowledge about safe driving and the rules they must follow. In our opinion, it is fundamental to improve doctor's and patients’ knowledge in this subject.
Endocrine Abstracts, 2014
Endocrine Abstracts, 2014
Revista Portuguesa de Endocrinologia, Diabetes e Metabolismo, 2014
Endocrine Abstracts, 2014
RSC Advances
A new photoluminescent bimetallic-3-hydroxypicolinate/graphene oxide composite was prepared by in... more A new photoluminescent bimetallic-3-hydroxypicolinate/graphene oxide composite was prepared by incorporation of the complex Na 5 [EuW 2 O 6 (picOH) 8 ] (1; HpicOH being 3-hydroxypicolinic acid) on graphene oxide (GO). Photoluminescence studies (emission and excitation spectra and 5 D 0 emission decay curves) were performed on 1 and the composite 1/GO suggesting an effective interaction between the picOH 2 ligands and the graphene oxide.
ChemInform, 2008
A new template-free layered manganese(III) phosphate, Na 3 MnH(P 0.9 O 4 ) 2 , has been hydrother... more A new template-free layered manganese(III) phosphate, Na 3 MnH(P 0.9 O 4 ) 2 , has been hydrothermally synthesized. The crystal structure was solved ab initio from powder X-ray diffraction data, and the model was confirmed using the Rietveld method. The material crystallizes in triclinic space group P1 j (No. 2) with lattice parameters a ) 5.2925
Chemistry (Weinheim an der Bergstrasse, Germany), Jan 17, 2012
Scientific reports, 2014
Nano-graphene oxide (nano-GO) is a new class of carbon based materials being proposed for biomedi... more Nano-graphene oxide (nano-GO) is a new class of carbon based materials being proposed for biomedical applications due to its small size, intrinsic optical properties, large specific surface area, and easy to functionalize. To fully exploit nano-GO properties, a reproducible method for its production is of utmost importance. Herein we report, the study of the sequential fracture of GO sheets onto nano-GO with controllable lateral width, by a simple, and reproducible method based on a mechanism that we describe as a confined hot spot atomic fragmentation/reduction of GO promoted by ultrasonication. The chemical and structural changes on GO structure during the breakage were monitored by XPS, FTIR, Raman and HRTEM. We found that GO sheets starts breaking from the defects region and in a second phase through the disruption of carbon bonds while still maintaining crystalline carbon domains. The breaking of GO is accompanied by its own reduction, essentially by the elimination of carboxylic and carbonyl functional groups. Photoluminescence and photothermal studies using this nano-GO are also presented highlighting the potential of this nanomaterial as a unique imaging/therapy platform. N owadays, one of the most prompt methods to prepare graphene oxide (GO) or reduced graphene oxide (rGO) is through the wet chemical exfoliation of graphite. This approach has the advantage of large scale production, procedure simplicity, high efficiency and low cost 1 . The exfoliation of graphite in solution occurs through extensive intercalation of oxygen moieties on the aromatic structure. This increases the interplanar carbon distance and consequently weakening the interactions between adjacent carbon planes 2 .
2012 17th Opto-Electronics and Communications Conference, 2012
ABSTRACT In this work we investigate the dynamics of the fuse effect propagation in bend loss ins... more ABSTRACT In this work we investigate the dynamics of the fuse effect propagation in bend loss insensitive fibers. The fuse velocity, threshold power and void period values were compared with those obtained for standard single mode fibers. The results show that the power dependent optical discharge velocity coefficient is 32% higher in G.657 fibers than that in G.652 fibers.
Inorganic Chemistry
A novel layered zinc phosphate, [N 2 C 6 H 12 ] 2 [Zn 7 H 3 (HPO 4-x ) 5 (PO 4 ) 3 ] H 2 O, with ... more A novel layered zinc phosphate, [N 2 C 6 H 12 ] 2 [Zn 7 H 3 (HPO 4-x ) 5 (PO 4 ) 3 ] H 2 O, with unique 10-membered-ring ellipsoidal channels running perpendicularly to ladder-shaped tetrahedral layers, has been synthesized ionothermally via in situ generation of 1,4-diazabicyclo[2.2.2] octane.
ChemInform, 2008
Luminescence D 6540 Photoluminescent Layered Y/Er Silicates. -New layered rare-earth silicates K ... more Luminescence D 6540 Photoluminescent Layered Y/Er Silicates. -New layered rare-earth silicates K 3 [Y 1-x Er x Si 3 O 8 (OH) 2 ] (x = 0.005-1) are synthesized from aqueous solutions containing SiO2, Na2O, KOH, YCl3, and ErCl3 (autoclave, 230°C, 7 d). Thermal degradation of the samples leads to K3[Y1-xErxSi3O9]. The samples are characterized by powder XRD, SEM, and Raman spectroscopy. The photoluminescence properties of the materials are discussed and compared. The calcination process increases the intensity of the Er 3+ emission and the importance of the Er 3+ -Er 3+ interactions as a quenching emission channel. -(KOSTOVA, M. H.; ANANIAS, D.; CARLOS*, L. D.; ROCHA, J.; J.
International Conference on Transparent Optical Networks, 2010
In this paper, direct UV-laser writing was used to produce channel waveguides and diffraction gra... more In this paper, direct UV-laser writing was used to produce channel waveguides and diffraction gratings on thin films of siliceous-based organic-inorganic hybrid materials. The optical quality of the films surface was studied by light scattering measurements. The produced Y-power splitters, optical filters and Fabry-Perot cavities were experimentally characterized for propagation in the near infrared spectral region.
Microporous and Mesoporous Materials, 2008
A luminescent material has been prepared by formation of the Eu3+ β-diketonate complex Eu(NTA)3L″... more A luminescent material has been prepared by formation of the Eu3+ β-diketonate complex Eu(NTA)3L″ {NTA = 1-(2-naphthoyl)-3,3,3-trifluoroacetonate; L″ = ethyl[3-(2-pyridyl)-1-pyrazolyl]acetate} within the channels of MCM-41-type ordered mesoporous silica. Using simple wet impregnation methods, the ligand L″ was first encapsulated followed by treatment with the complex Eu(NTA)3(H2O)2. An analogous Gd3+ supported material was also prepared, as well as the model complexes Ln(NTA)3L′ {Ln = Eu, Gd; L′ = 2-[3(5)-pyrazolyl]pyridine}. The materials were characterized by powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), FTIR and FT Raman spectroscopies, 13C and 29Si MAS NMR, and photoluminescence spectroscopy. The spectroscopic studies showed that exchange of the H2O ligands for the bidentate ligand L″ occurred to give the desired 8-coordinate species Ln(NTA)3L″, with a local Ln3+ coordination environment similar to that for the model complexes. The low (−259 °C) and room temperature emission spectra of the Eu-modified mesoporous material displayed the typical Eu3+ intra-4f6 lines ascribed to transitions between the 5D0,1 excited states and the ground multiplet (7F0–4). Negligible emission from the organic part of the encapsulated species was observed, indicating that energy transfer from the ligands to the Eu3+ ion was quite efficient. The 5D0 quantum efficiency was estimated to be 21.1%, compared with 46.1% for the model complex Eu(NTA)3L′. This difference is attributed to the presence of an excited state of the organic ligands in the supported material that lies approximately resonant with the 5D1 intra-4f6 level, opening up an additional non-radiative channel that is not present in the corresponding model complexes.
Polyhedron, 2006
The adduct Eu(NTA)3 · bipy was prepared by the reaction of Eu(NTA)3 · 2H2O with 2,2′-bipyridine i... more The adduct Eu(NTA)3 · bipy was prepared by the reaction of Eu(NTA)3 · 2H2O with 2,2′-bipyridine in a 1:1 ratio in chloroform [NTA = 1-(2-naphthoyl)-3,3,3-trifluoroacetonate]. Recrystallization of the complex from a chloroform/diethyl ether solvent mixture gave crystals suitable for X-ray diffraction. The structure contained chloroform molecules in partially occupied sites and was found to be different from the two forms previously reported for the same adduct (one unsolvated and the other containing isopropanol molecules). A single eight-coordinate geometry was found for Eu(NTA)3 · bipy · 0.44CHCl3, corresponding to a distorted square antiprism, with the bidentate ligands spanning opposite sides of the ‘square’ faces. A 2:1 (host-to-guest) inclusion compound comprising β-cyclodextrin (CD) and Eu(NTA)3 · bipy was obtained by co-precipitation from a mixed water/ethyl acetate solvent mixture. The formation of a true inclusion complex was supported by powder XRD, thermogravimetric analysis and 13C CP MAS NMR spectroscopy. Photoluminescence spectroscopy indicated the presence of only one low-symmetry environment for the Eu3+ cations in non-included Eu(NTA)3 · bipy and the inclusion compound. However, upon encapsulation of the complex in β-CD, some of the Eu3+ intra-4f65D0 → 7F0–4 lines shifted in energy, and the number of Stark components for the 5D0 → 7F1–2 transitions increased, indicating a lowering of the symmetry of the Eu3+ local coordination environment. The room temperature excitation spectrum of the inclusion compound revealed an enhancement of the Eu3+ sensitized process as a result of encapsulation of the Eu(NTA)3 · bipy molecules.The crystal structure of the compound Eu(NTA)3 · bipy · 0.44CHCl3 was determined by X-ray diffraction and compared with previously reported structures containing the adduct Eu(NTA)3 · bipy. Encapsulation of Eu(NTA)3 · bipy in β-cyclodextrin gave an inclusion compound which exhibited photoluminescence and excitation spectra different from those of the non-included complex, revealing, in particular, an enhancement of the Eu3+ sensitized process.
Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2006
A 1:1 inclusion compound between octakis(2,3,6-tri-O-methyl)-γ-cyclodextrin (TRIMEG) and the chel... more A 1:1 inclusion compound between octakis(2,3,6-tri-O-methyl)-γ-cyclodextrin (TRIMEG) and the chelate complex Eu(NTA)3·2H2O (NTA=1-(2-naphthoyl)-3,3,3-trifluoroacetonate) was prepared and characterized by powder X-ray diffraction, thermogravimetric analysis and photoluminescence spectroscopy. The results were compared with those obtained for the corresponding native γ-CD adduct. Excitation and emission spectra were measured, and the lifetimes were determined for the Eu3+ first excited state (5D0). The results indicate the presence of only one low-symmetry environment for the Eu3+ cations in the inclusion compounds. Encapsulation of the Europium complex in the two CDs increases the quantum efficiency of the ligand-to-metal energy transfer pathway, but the efficiency of the Eu3+ sensitization was significantly higher with TRIMEG as the host molecule. This may be related with the observation that the two hosts appear to have different influences on the Eu3+ coordination environments for the guest molecule.
Spectroscopy Letters, 2010
Urea-based bis-silylated bipyridine (bpy) organic-inorganic 25 hybrids incorporating different la... more Urea-based bis-silylated bipyridine (bpy) organic-inorganic 25 hybrids incorporating different lanthanide (Ln 3þ ) ions (Eu 3þ , Gd 3þ , Tb 3þ or Eu 3þ =Tb 3þ ) were obtained by the sol-gel process. The structure and the emission characteristics of the hybrids were ascertained using X-ray diffraction, nuclear magnetic resonance, Fourier transform infrared spectroscopy, photoluminescence, and quantum yield measurements. The 30 hybrids feature both the emission of the host and the Eu 3þ and=or Tb 3þ transitions allowing a fine-tuning of the color from the blue to the red, orange, or green spectral regions. Bpy-to-Ln 3þ and Tb 3þ -to-Eu 3þ energy transfer mechanisms are demonstrated and the hybrids present slightly distinct Ln 3þ coordination spheres due to the different bpy=Ln 3þ ratios. 35