Evolution of Photoluminescence across Dimensionality in Lanthanide Silicates

Kostova, Mariya H.; Ananias, Duarte; Paz, Filipe A. Almeida; Ferreira, Artur; Rocha, João; Carlos, Luı́s D.

doi:10.1021/jp068559u

“…The field of multifunctional materials has seen very rapid progress since the discovery of structures with a variety of technologically useful properties such as nanoporosity,1–3 luminescence, and magnetism for sensors,4–6 lasers,7, 8 nonlinear optics,9 displays,10 and electroluminescent devices 11. After these discoveries, one of the most appealing aims is to explore multifunctionality, especially in designed materials, which combine in the same crystal a set of well‐defined properties for specific applications.…”

Section: Experimental 5d0 Lifetime Radiative (Kr) and Nonradiative (mentioning

confidence: 99%

Metal–Organic Nanoporous Structures with Anisotropic Photoluminescence and Magnetic Properties and Their Use as Sensors

Harbuzaru

¹

,

Corma

²

,

Rey

³

et al. 2008

Self Cite

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The field of multifunctional materials has seen very rapid progress since the discovery of structures with a variety of technologically useful properties such as nanoporosity, [1][2][3] luminescence, and magnetism for sensors, [4][5][6] lasers, [7,8] nonlinear optics, [9] displays, [10] and electroluminescent devices.[11]After these discoveries, one of the most appealing aims is to explore multifunctionality, especially in designed materials, which combine in the same crystal a set of well-defined properties for specific applications. Lanthanide-based porous metal-organic frameworks (Ln-MOFs) [12][13][14][15][16][17] are excellent candidates to create multifunctional materials for sensors, provided that their photoluminescence and emission lifetimes are not influenced at ambient conditions by the presence of water. [5,[18][19][20] Existing Ln-MOF materials are thermally stable in air only up to approximately 673 K, [5,18,21] while pore diameters are too small to allow the diffusion of molecules of interest. [21,22] These properties preclude their use in luminescence sensors working in the presence of moisture at ambient temperature.MOFs that combine magnetic and anisotropic properties with high emission quantum yields under ambient conditions will open new possibilities for low-cost sensors.[23] Herein, we have synthesized, by rational design, novel crystalline MOFs containing rare-earth ions that combine hydrophobicity, high adsorption capacity, high thermal resistance, anisotropic photoluminescence, and magnetic properties. These materials preserve their photoluminescence properties in the presence of water and show excellent sensor capabilities.For achieving the above properties, we have chosen an organic spacer that fulfils the following requirements: high hydrophobicity, antenna effect, strong interaction with the metal center, and at least two coordination centers in order to obtain microporous 3D structures. High hydrophobicity was attained with ultrahydrophobic ligands, such as multiaromatic and C(sp 3 ) fluorinated spacers. The antenna effect can be present in a spacer with aromatic or multiaromatic groups. Moreover, rare-earth ions have high affinity for oxygencontaining molecules, for example those with carboxy groups, which produce robust framework architectures.[24] One spacer that fulfills the above requirements and that can be adequate to synthesize MOFs [25][26][27] is 4,4'-(hexafluoroisopropylidene)-bis(benzoic acid) (HFIPBB).Herein, under appropriate synthesis conditions and in the presence of HFIPBB, new Ln 3+ -based materials ITQMOF-1 and ITQMOF-2 (ITQMOF = Instituto de Tecnologia Quimica Metal Organic Framework), with similar properties but different crystallographic structures, have been obtained. To obtain the desired properties (luminescence and magnetism), different samples have been prepared with all the Ln elements except for the radioactive promethium. For mixed Ln 3+ samples, their molar composition (%) is given in parenthesis.The ITQMOF-1 material was obtained by reacting the HFIPBB...

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“…

The field of multifunctional materials has seen very rapid progress since the discovery of structures with a variety of technologically useful properties such as nanoporosity, [1][2][3] luminescence, and magnetism for sensors, [4][5][6] lasers, [7,8] nonlinear optics, [9] displays, [10] and electroluminescent devices. [11] After these discoveries, one of the most appealing aims is to explore multifunctionality, especially in designed materials, which combine in the same crystal a set of well-defined properties for specific applications.

…”

mentioning

confidence: 99%

Metal–Organic Nanoporous Structures with Anisotropic Photoluminescence and Magnetic Properties and Their Use as Sensors

Harbuzaru

¹

,

Corma

²

,

Rey

³

et al. 2008

Self Cite

View full text Add to dashboard Cite

The field of multifunctional materials has seen very rapid progress since the discovery of structures with a variety of technologically useful properties such as nanoporosity, [1][2][3] luminescence, and magnetism for sensors, [4][5][6] lasers, [7,8] nonlinear optics, [9] displays, [10] and electroluminescent devices.[11]After these discoveries, one of the most appealing aims is to explore multifunctionality, especially in designed materials, which combine in the same crystal a set of well-defined properties for specific applications. Lanthanide-based porous metal-organic frameworks (Ln-MOFs) [12][13][14][15][16][17] are excellent candidates to create multifunctional materials for sensors, provided that their photoluminescence and emission lifetimes are not influenced at ambient conditions by the presence of water. [5,[18][19][20] Existing Ln-MOF materials are thermally stable in air only up to approximately 673 K, [5,18,21] while pore diameters are too small to allow the diffusion of molecules of interest. [21,22] These properties preclude their use in luminescence sensors working in the presence of moisture at ambient temperature.MOFs that combine magnetic and anisotropic properties with high emission quantum yields under ambient conditions will open new possibilities for low-cost sensors.[23] Herein, we have synthesized, by rational design, novel crystalline MOFs containing rare-earth ions that combine hydrophobicity, high adsorption capacity, high thermal resistance, anisotropic photoluminescence, and magnetic properties. These materials preserve their photoluminescence properties in the presence of water and show excellent sensor capabilities.For achieving the above properties, we have chosen an organic spacer that fulfils the following requirements: high hydrophobicity, antenna effect, strong interaction with the metal center, and at least two coordination centers in order to obtain microporous 3D structures. High hydrophobicity was attained with ultrahydrophobic ligands, such as multiaromatic and C(sp 3 ) fluorinated spacers. The antenna effect can be present in a spacer with aromatic or multiaromatic groups. Moreover, rare-earth ions have high affinity for oxygencontaining molecules, for example those with carboxy groups, which produce robust framework architectures.[24] One spacer that fulfills the above requirements and that can be adequate to synthesize MOFs [25][26][27] is 4,4'-(hexafluoroisopropylidene)-bis(benzoic acid) (HFIPBB).Herein, under appropriate synthesis conditions and in the presence of HFIPBB, new Ln 3+ -based materials ITQMOF-1 and ITQMOF-2 (ITQMOF = Instituto de Tecnologia Quimica Metal Organic Framework), with similar properties but different crystallographic structures, have been obtained. To obtain the desired properties (luminescence and magnetism), different samples have been prepared with all the Ln elements except for the radioactive promethium. For mixed Ln 3+ samples, their molar composition (%) is given in parenthesis.The ITQMOF-1 material was obtained by reacting the HFIPBB...

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“…They are built from tetrahedral SiO 4 and polyhedral LnO n (n P 6) building blocks and exhibit a rich structural chemistry and interesting physical and chemical properties. Most of these compounds are prepared under mild hydrothermal conditions (150-240°C) in Teflon-lined autoclaves [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], by flux-growth techniques [20][21][22], and high temperature (above 500°C) and high autogenous pressures [23,24]. The aim of many of these reports is the engineering of photoluminescent trivalent lanthanide (Ln 3+ ) centers into such materials.…”

Section: Introductionmentioning

confidence: 99%