New crystalline layered zinc phosphate with 10-membered-ring channels perpendicular to layers.

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.

Functionalization of atomic force microscope tips by dielectrophoretic assembly of Gd(2)O(3):Eu(3+) nanorods.

An atomic force microscopy (AFM) tip has been coated with photoluminescent Eu(3+)-doped Gd(2)O(3) nanorods using a dielectrophoresis technique, which preserves the red emission of the nanorods (quantum yield 0.47). The performance of the modified tips has been tested by using them for regular topography imaging in tapping and contact modes. Both a regular AFM standard grid and a patterned surface (of an organic-inorganic methacrylate Zr-based oxo-cluster and poly(oxyethylene)/siloxane hybrid) have been used. Similar depth values have been measured using a conventional silicon tip and the nanorod-modified tip. The tips before and after use exhibit similar SEM images and photoluminescence spectra and, thus, seem to be stable under working conditions. These tips should find applications in scanning near-field optical microscopy and other scanning techniques.

Photoluminescent layered Y(III) and Tb(III) silicates doped with Ce(III).

The synthesis and structural characterization of new layered rare-earth silicates K(3)[M(1-a)Ce(a)Si(3)O(8)(OH)(2)], M = Y(3+), Tb(3+), a << 1 (AV-22 materials), have been reported. These materials combine the properties of layered silicates, such as intercalation chemistry, and photoluminescence and may find applications in new types of sensor devices. For mixed Tb/Ce-AV-22, evidence has been found for the energy transfer from the large Ce(3+) 4f( 1) --> 5d(1) broad band to the sharp Tb(3+) 4f (8) lines. This energy transfer allows the fine-tuning of the color emission in the blue-green region of the chromaticity diagram. Upon Ce(3+) excitation (342 nm), the radiance of Tb/Ce-AV-22 is approximately 2 times higher than that measured under direct Tb(3+) excitation, which reinforces the existence of effective room-temperature Ce(3+)-to-Tb(3+) energy transfer.

Optical properties of lanthanide-doped lamellar nanohybrids.

In this article a detailed study of the optical properties of lanthanide doped lamellar nanohybrids synthesized by the "benzyl alcohol route" is presented. The synthetic approach results in the formation of a highly ordered lamellar nanocomposite consisting of yttrium or gadolinium oxide crystalline layers with a confined thickness of about 0.6 nm, separated from each other by organic layers of intercalated benzoate molecules. When the inorganic layers are doped with optically-active lanthanide ions they show outstanding emission properties in the green (Tb(3+)), red (Eu(3+)) and near infrared (Nd(3+)). The local environment of the emitting ions and the energy transfer processes involving the phenyl ring of the benzoate complexes and the lanthanide ions are presented, as well as radiance and lifetime measurements. The radiance values are comparable and in some cases even larger than those of standard phosphors, proving that these nanohybrids can compete, from an emission efficiency point of view, with commercial phosphors. Furthermore, in these nanohybrids it is possible by simply changing the excitation wavelength, to tune the emission colour chromaticity without loosing the radiance.

Spectroscopic study of a UV-photostable organic-inorganic hybrids incorporating an Eu3+ beta-diketonate complex.

New europium and gadolinium tris-beta-diketonate complexes have been prepared and incorporated in sol-gel-derived organic-inorganic hybrids, named di-ureasils. The general formula [Ln(btfa)3(4,4'-bpy)(EtOH)] (Ln=Eu, Gd; 4,4'-bpy=4,4'-bipyridine; btfa=4,4,4-trifluoro-1-phenyl-1,3-butanedione) for the complexes was confirmed by X-ray crystallography and elemental analysis. The ground-state geometry of the Eu3+ complex was calculated from the Sparkle/AM1 model. The calculated quantum yield obtained from the Sparkle model and from the crystal structure (both 46%) are in satisfactory agreement with the experimental value (38+/-4%). In the isolated complex the most efficient luminescence channel is S0-->S1-->T-->(5D1, 5D0)-->7F0-6, where the exchange mechanism dominates in the energy-transfer channel T-->(5D1, 5D0). For the Eu3+-based di-ureasils a 50% quantum yield enhancement compared to the Eu3+ complex is observed, which suggests an effective hybrid host-metal ion interaction and an active energy-transfer channel between the hybrid host and the Eu3+ complex. The Eu3+-based di-ureasils are photostable under UVA (360 nm) excitation, whereas under UVB (320 nm) and UVC (290 nm) photodegradation occurs.

Calix[4]azacrowns as novel molecular scaffolds for the generation of visible and near-infrared lanthanide luminescence.

Two calix[4]azacrowns, capped with two aminopolyamide bridges, were used as ligands for the complexation of lanthanide ions [Eu(III), Tb(III), Nd(III), Er(III), La(III)]. The formation of 1:2 and 1:1 complexes was observed, and stability constants, determined by UV absorption and fluorescence spectroscopy, were found to be generally on the order of log beta(11) approximately 5-6 and log beta(12) approximately 10. The structural changes of the ligands upon La(III) complexation were probed by 1H NMR spectroscopy. The two ligands were observed to have opposite fluorescence behaviors, namely, fluorescence enhancement (via blocking of photoinduced electron transfer from amine groups) or quenching (via lanthanide-chromophore interactions) upon metal ion complexation. Long-lived lanthanide luminescence was sensitized by excitation in the pi,pi band of the aromatic moieties of the ligands. The direct involvement of the antenna triplet state was demonstrated via quenching of the ligand phosphorescence by Tb(III). Generally, Eu(III) luminescence was weak (Phi(lum)