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Estudos espectroscópicos de novos complexos B-dicetonatos de íons lantanídeos com emissão no visível e infravermelho próximoMoura, Jandeilson de Lima 13 February 2017 (has links)
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Previous issue date: 2017-02-13 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / This work reports the synthesis, characterization and investigation of the
luminescent properties of new lanthanide -diketonate complexes, Ln(-
dic)2(NO3)L2, Ln(TTA)3L2 and Ln(DBM)3L (TPPO), where thenoyltrifluoroacetone
(TTA) and dibenzoylmethane (DBM), L = triphenylphosphine oxide (TPPO),
tributylphosphine oxide (TBPO), and trioctylphosphine oxide (TOPO). Eu3+ ion
complexes were also synthesized with triphenylarsine oxide (TPAsO) and
tricyclohexylphosphine (TCHPO) as auxiliary ligands. The complexes were
characterized by complexometric titration with EDTA, CHN elemental analysis,
Fourier transform infrared (FTIR) absorption spectroscopy and thermogravimetric
analysis (TGA). The photoluminescent properties in the visible and near infrared
(NIR) regions of the synthesized complexes were investigated from excitation,
emission and luminescence decay curves. The excitation spectra are
characterized by the presence of large bands associated with transitions centered
on the ligands, evidencing the efficiency of the luminescence sensitization by the
antenna ligands. The emission spectra in the visible region of the compounds of
the Sm3+ and Eu3+ ions show narrow bands attributed to intraconfigurationtransitions
and are dominated by
the hypersensitive transitions (~645 nm) and (~612
nm). The values of the intensity parameters and for the complexes of
Sm3+ and Eu3+ presented a good correlation, evidencing that the chemical
environment influence in a similar way the spectroscopic properties of these ions.
The photoluminescent properties of the Eu3+ ion complexes were investigated by
the intensity parameters and , radiative and nonradiative ( and ),
lifetime of the emitting state () and quantum emission efficience . The
highest values of are found for Eu(-dic)2(NO3)L2 complexes, in the range of
51-86%. It was observed that the Eu(-dic)3L2 compounds exhibited shorter
lifetimes, which may be related to the presence of a suppressor channel, resulting
in higher values of . The intensity parameters and vary only slightly
when changes occur in the number and nature of the ligands of the first
coordination sphere, with parameter being more sensitive to changes in
coordination geometry. The emission spectra in the NIR region of the bis- and trisdiketonate
complexes of Pr3+, Nd3+, Sm3+, Er3+ and Yb3+ ions present characteristic
luminescence. Changes in the nature and number of ligands coordinated to the
Ln3+ ion slightly influence the spectral profiles. The results obtained for the studied
systems suggest that these are potential candidates to act as Molecular Light
Converting Devices. / Este trabalho reporta a síntese, caracterização e investigação das
propriedades luminescentes de -dicetonatos de íons lantanídos, Ln(-
dic)2(NO3)L2, Ln(TTA)3L2 e Ln(DBM)3L, em que Ln3+ = Pr3+, Nd3+, Sm3+, Eu3+, Er3+ e
Yb3+, -dic = 2-tenoilltrifluoroacetona (TTA) e dibenzoilmetano (DBM), L = óxido de
trifenilfosfina (TPPO), tributilfosfina (TBPO) e trioctilfosfina (TOPO). Para os
compostos do íon Eu3+, foram também sintetizados os complexos com o óxido de
trifenilarsina (TPAsO) e triciclohexilfosfina (TCHPO) como ligantes auxiliares. Os
complexos sintetizados foram caracterizados por titulação complexométrica com
EDTA, análise elementar CHN, espectroscopia de absorção na região do
infravermelho com transformada de Fourier (FTIR) e análise termogravimétrica
(TGA). As propriedades fotoluminescentes nas regiões do visível e infravermelho
próximo (NIR) dos complexos sintetizados foram investigadas a partir dos
espectros de excitação, emissão e curvas de decaimento de luminescência. Os
espectros de excitação são caracterizados pela presença de bandas largas
associadas às transições centradas nos ligantes , evidenciando a
eficiência na sensibilização da luminescência pelos ligantes antenas. Os
espectros de emissão, na região do visível, dos compostos dos íons Sm3+ e Eu3+,
exibem bandas finas oriundas das transições intraconfiguracionaise
são dominados pelas transições
hipersensíveis (~645 nm) e (~612 nm). Os valores dos
parâmetros de intensidade e dos complexos de Sm3+ e Eu3+
apresentaram uma boa correlação, evidenciando que o ambiente químico
influência de maneira semelhante as propriedades espectroscópica destes íons.
As propriedades fotoluminescentes dos complexos do íon Eu3+ foram investigados
por meio dos parâmetros de intensidade e , taxas de radiativa e nãoradiativa
( e ), tempo de vida do estado () e, eficiência quântica de
emissão ( ). Os maiores valores de são encontrados para os complexos Eu(-
dic)2(NO3)L2, na faixa de 51-86%. Observou-se que os compostos Eu(-dic)3L2
exibiram tempo de vida mais curto, o que pode estar relacionado com a presença
de uma canal supressor, resultando assim em maiores valores de . Os
parâmetros de intensidade e , variam apenas ligeiramente quando ocorre
alterações no número e na natureza dos ligantes da primeira esfera de
coordenação, sendo o 2 mais sensível as alterações na geometria de
coordenação. Os espectros de emissão na região do NIR dos complexos bis- e
tris-dicetonatos dos íons Pr3+, Nd3+, Sm3+, Er3+ e Yb3+ apresentam luminescência
característica. As alterações na natureza e número de ligantes coordenados ao
íon Ln3+ influenciam ligeiramente os perfis espectrais. Os resultados obtidos para
os sistemas estudados sugerem que estes são potenciais candidatos a atuarem
como Dispositivos Moleculares Conversores de Luz.
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Synthesis and Energetics of Gold Nanoclusters Tailored by Interfacial Bonding StructureZhenghua, Tang 07 August 2012 (has links)
In addition to the well known quantum confinement effects resulted from size and shape, interfacial bond structure is another factor, affecting the properties of the nanomaterial that is rarely studied. Inspired by the “Au-S-Au” staple motif discovered from the crystal structure of monothiol protected Au102 nanocluster (Science, 2007, 318, 430), dithiol molecules (e. g. 1, 2-dithiol, 1, 4-dithiol, etc.) with molecular structural constraint have been employed to create dithiolate protected clusters or mixed monothiolate and dithiolate protected clusters. The structure and properties of the Au clusters are expected to change due to two effects: The entropy gain of dithiol over monothiol protection and the constraint to the formation of the thiol bridging motif. DMPS (1, 2-dithiol molecule) stabilized clusters with characteristic absorption bands have been obtained, and characterized by multiple techniques. Monolayer reaction on gold core surface between the monothiol tiopronin and dithiol DMPS has been performed, and the mechanism has been probed. Mixed phenylethanethiolate and durene-dithiolate (1, 4-dithiol molecule) protected Au130 clusters with rich electrochemical features have been created, and the optical and electrochemical energetics have been successfully correlated based on core and core-ligand energy states. Furthermore, the impact of 1, 4-dithiolate-Au bonding on the near infrared luminescence has been studied.
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Capteurs optiques en fibres de verre de chalcogénure dopées terres rares appliqués à la surveillance du stockage géologique de CO2 / Rare earth doped chalcogenide glasses optical fiber sensors applied for monitoring and storage of CO2Chahal, Radwan 01 October 2015 (has links)
L'augmentation des émissions de CO2 entraîne un réchauffement de la planète préjudiciable aux équilibres écologiques terrestres. Dans ce contexte, le stockage de CO2 dans des formations géologiques terrestres et sous-marines se pose comme un moyen intéressant de limiter les conséquences de ces émissions. Cependant cette solution nécessite une surveillance continue afin de détecter d'éventuelles fuites au niveau d'une zone de stockage. Les travaux de thèse présentés concernent le développement d'un capteur optique en fibre de chalcogénures pour la détection de CO2 gazeux fonctionnant dans le moyen infrarouge. Cette détection est basée sur un phénomène de luminescence, jouant le rôle de source déportée et partiellement absorbée en présence de CO2. Le développement de ces fibres optiques a demandé un important travail en sciences des matériaux et en caractérisation spectroscopique. Un prototype a été fabriqué et utilisé avec succès sur le terrain lors de campagnes de mesure menées in-situ. / The increase of CO2 emissions causes global warming harmful to ecological balances in earth. In this context, CO2 storage in geological formations is an interesting way to limit the consequences of these emissions. However, this solution requires continuous monitoring to detect possible leaks at storage area. The presented work involves the development of an optical fiber sensor based on chalcogenide glasses for the CO2 gas detection operating in the infrared. This detection is based on a luminescent phenomenon, acts as a remote source and partly absorbed in the presence of CO2. The development of these fiber optic asked important work in materials science and spectroscopic characterization. A prototype was manufactured and successfully used in the field during measurement campaigns in situ.
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