Luminescent polyoxotungstoeuropate anion-pillared layered double hydroxides

Novel luminescent polyoxometalate anion-pillared layered double hydroxides (LDHs) were prepared by aqueous ion exchange of a Zn–Al LDH precursor in nitrate form with the europium-containing polyoxotungstate anions [EuW10O36]9–, [Eu(BW11O39)(H2O)3]6– and [Eu(PW11O39)2]11–. The host– guest interaction has a strong influence on the nature of the final intercalated species, as evidenced by elemental analy- Introduction Layered double hydroxides are an important class of ionic lamellar solids with the general formula [M2+ 1–xM3+ x(OH)2](Am–)x/m·nH2O (M2+ = Mg2+, Zn2+, Ni2+ etc., M3+ = Al3+, Cr3+, Ga3+ etc).[1] The positively charged layers, containing divalent and trivalent cations in octahedral positions, are separated by charge balancing anions and water molecules. The water molecules are connected to both the metal hydroxide layers and the interlayer anions through extensive hydrogen bonding. A range of organic or inorganic guests may be incorporated into LDHs by either ion exchange, direct synthesis or hydrothermal reconstruction of calcined precursors.[2,3] In particular, intercalation chemistry has been explored with the aim of introducing catalytically active sites and photo- and electroactive species. Many different types of metal coordination compounds and oxometalates have been immobilized in LDHs, including phthalocyanines, cyanocomplexes, oxalate complexes and polyoxometalates (POMs).[4] The first report of LDHs containing polyoxometalates concerned their use as exhaust gas and hydrocarbon conversion catalysts.[5] Since then, a variety of iso- and heteropolyanions with different nuclearities and structures (Keggin, Dawson, Preyssler, Finke) have been incorporated into the interlayer space of these materials.[6–18] Two factors assume considerable importance for the successful intercalation of polyoxometalates into an LDH compound. First, the heteropoly species should carry sufficient charge in order to be [a] Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal E-mail: [email protected] [b] Department of Physics, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal © 2006 Wiley-VCH Verlag 726 GmbH & Co. KGaA, Weinheim Eur. J. Inorg. Chem. 2006, 726–734 sis, powder X-ray diffraction (XRD), infra-red (IR) and Raman spectroscopy, solid state magic-angle spinning (MAS) 11B and 31P NMR spectroscopy, and photoluminescence spectroscopy.FCT - POCT

Relationship between transpulmonary ^99mTc-MAA passage and the alveolar-arterial oxygen difference (A-aDO₂) in normoxic and hypoxic exercise.

<p>Line represents the result of a general linear model analysis in which the transpulmonary ^99mTc-MAA passage was linearly correlated with the A-aDO₂ (R² = 0.63), but this relationship was not dependent on the FIO₂ (p>0.05).</p

Anthropometric characteristics of the seven participants completing the study.

<p>FVC, forced vital capacity; FEV₁, forced expired volume in 1 second; DL_CO, diffusion capacity for carbon monoxide; VO₂max; relative maximal oxygen uptake.</p><p>^*indicates p<0.05. Values in parentheses are percent predicted (23–25).</p

Relationship between transpulmonary ^99mTc-MAA passage with exercise in normoxia vs. hypoxia (A) and between rest and exercise in hypoxia (B).

<p>The transpulmonary passage of ^99mTc-MAA with exercise in hypoxia was well-correlated with that measured at rest with hypoxic gas breathing. Dashed line indicates the line of identity.</p

Arterial blood gases, respiratory quotient (R), and the alveolar-arterial PO₂ difference (A-aDO₂), measured at rest and at 85% of the maximal attainable wattage during the resting and exercise visits.

<p>^*indicates p<0.05 compared to values measured at rest on the same day.</p>†<p>indicates p<0.05 compared to normoxic exercise.</p

Change in the transpulmonary passage (%) of ^99mTc-MAA compared to resting, normoxic gas breathing.

<p>Dashed line indicates the repeatability coefficient (0.92%) Transpulmonary ^99mTc-MAA passage was noted in 6/7 participants performing exercise in normoxia and 4/7 participants performing exercise in hypoxia. Breathing hypoxic gas at rest increased ^99mTc-MAA passage in all participants relative to hypoxic exercise. ** indicates a difference compared to hypoxic rest (p = 0.001).</p