Circularly Polarized Luminescence from Pure and Eu-Doped Trigonal TbPO·HO Nanocrystals.

In this contribution, we describe the preparation, by means of a precipitation reaction from aqueous solution at 40 °C, and the structural characterization of nanocrystalline powders of trigonal TbEuPO·HO (with = 0, 0.005, 0.01, 0.

PbVO under compression: near zero-linear compressibility and pressure-induced change in vanadium coordination.

This study presents evidence that lead metavanadate, PbVO, is a material with zero-linear compressibility, which maintains its crystal size in one crystallographic direction even under external pressures of up to 20 GPa. The orthorhombic polymorph of PbVO (space group ) was studied up to 20 GPa using synchrotron powder X-ray diffraction, Raman spectroscopy, and density-functional theory simulations to investigate its structural and vibrational evolution under compression. Up to this pressure we find no evidence of any structural phase transitions by any diagnostic technique, however, a progressive transformation of the coordination polyhedron of vanadium atoms is revealed which results in the zero-linear compressibility.

Dynamics of the Energy Transfer Process in Eu(III) Complexes Containing Polydentate Ligands Based on Pyridine, Quinoline, and Isoquinoline as Chromophoric Antennae.

In this work, we investigated from a theoretical point of view the dynamics of the energy transfer process from the ligand to Eu(III) ion for 12 isomeric species originating from six different complexes differing by nature of the ligand and the total charge. The cationic complexes present the general formula [Eu(L)(HO)] (where L = bpcd = ,'-bis(2-pyridylmethyl)--1,2-diaminocyclohexane ,'-diacetate; bQcd = ,'-bis(2-quinolinmethyl)--1,2-diaminocyclohexane ,'-diacetate; and bQcd = ,'-bis(2-isoquinolinmethyl)-1,2-diaminocyclohexane ,'-diacetate), while the neutral complexes present the Eu(L)(HO) formula (where L = PyC3A = -picolyl-,','--1,2-cyclohexylenediaminetriacetate; QC3A = -quinolyl-,','-1,2-cyclohexylenediaminetriacetate; and QC3A = -isoquinolyl-,','-1,2-cyclohexylenediaminetriacetate). Time-dependent density functional theory (TD-DFT) calculations provided the energy of the ligand excited donor states, distances between donor and acceptor orbitals involved in the energy transfer mechanism (), spin-orbit coupling matrix elements, and excited-state reorganization energies.

Systematic Analysis of the Crystal Chemistry and Eu Spectroscopy along the Series of Double Perovskites CaLnSbO (Ln = La, Eu, Gd, Lu, and Y).

Eu (1 mol %)-doped CaLnSbO (replacing Ln; Ln = Lu, Y, Gd, and La) and CaEuSbO were synthesized and structurally characterized by means of X-ray powder diffraction. The Eu luminescence spectroscopy of the doped samples and of CaEuSbO has been carefully investigated upon collection of the excitation/emission spectra and luminescence decay curves of the main excited states. Surprisingly, apart from the dominant red emission from D, all the doped samples show an uncommon blue and green emission contribution from D ( = 1, 2, and 3).

PrVO under High Pressure: Effects on Structural, Optical, and Electrical Properties.

In the pursuit of a systematic characterization of rare-earth vanadates under compression, in this work we present a multifaceted study of the phase behavior of zircon-type orthovanadate PrVO under high-pressure conditions, up to 24 GPa. We have found that PrVO undergoes a zircon to monazite transition at around 6 GPa, confirming previous results found by Raman experiments. A second transition takes place above 14 GPa, to a BaWO-II type structure.

Templated-Construction of Hollow MoS Architectures with Improved Photoresponses.

Despite the outstanding optoelectronic properties of MoS and its analogues, synthesis of such materials with desired features including fewer layers, arbitrary hollow structures, and particularly specifically customized morphologies, via inorganic reactions has always been challenging. Herein, using predesigned lanthanide-doped upconversion luminescent materials (e.g.

Precise Characterization of the Rich Structural Landscape Induced by Pressure in Multifunctional FeVO.

We have studied the high-pressure behavior of FeVO by means of single-crystal X-ray diffraction (XRD) and density functional theory (DFT) calculations. We have found that the structural sequence of FeVO is different from that previously assumed. In particular, we have discovered a new high-pressure phase at 2.

Phase Behavior of TmVO under Hydrostatic Compression: An Experimental and Theoretical Study.

We present a structural and optical characterization of magnetoelastic zircon-type TmVO at ambient pressure and under high pressure. The properties under high pressure have been determined experimentally under hydrostatic conditions and theoretically using density functional theory. By powder X-ray diffraction we show that TmVO undergoes a first-order irreversible phase transition to a scheelite structure above 6 GPa.

Eu(iii) and Tb(iii) complexes of 6-fold coordinating ligands showing high affinity for the hydrogen carbonate ion: a spectroscopic and thermodynamic study.

In the present contribution, four classes of Ln(iii) complexes (Ln = Eu and Tb) have been synthesized and characterized in aqueous solution. They differ by charge, Ln(bpcd)+ [bpcd2- = N,N'-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane N,N'-diacetate] and Ln(bQcd)+ (bQcd2- = N,N'-bis(2-quinolinmethyl)-trans-1,2-diaminocyclohexane N,N'-diacetate) being positively charged and Ln(PyC3A) (PyC3A3- = N-picolyl-N,N',N'-trans-l,2-cyclohexylenediaminetriacetate) and Ln(QC3A) (QC3A3- = N-quinolyl-N,N',N'-trans-l,2-cyclohexylenediaminetriacetate) being neutral. Combined DFT, spectrophotometric and potentiometric studies reveal the presence, under physiological conditions (pH 7.

High-Pressure High-Temperature Stability and Thermal Equation of State of Zircon-Type Erbium Vanadate.

The zircon to scheelite phase boundary of ErVO has been studied by high-pressure and high-temperature powder and single-crystal X-ray diffraction. This study has allowed us to delimit the best synthesis conditions of its scheelite-type phase, determine the ambient-temperature equation of state of the zircon and scheelite-type structures, and obtain the thermal equation of state of the zircon-type polymorph. The results obtained with powder samples indicate that zircon-type ErVO transforms to scheelite at 8.

All-inorganic perovskite nanocrystal scintillators.

The rising demand for radiation detection materials in many applications has led to extensive research on scintillators. The ability of a scintillator to absorb high-energy (kiloelectronvolt-scale) X-ray photons and convert the absorbed energy into low-energy visible photons is critical for applications in radiation exposure monitoring, security inspection, X-ray astronomy and medical radiography. However, conventional scintillators are generally synthesized by crystallization at a high temperature and their radioluminescence is difficult to tune across the visible spectrum.

Circularly Polarized Luminescence from an Eu(III) Complex Based on 2-Thenoyltrifluoroacetyl-acetonate and a Tetradentate Chiral Ligand.

A new chiral complex {[EuL(tta)(HO)]CFSO; L = N, N'-bis(2-pyridylmethylidene)-1,2-( R, R + S, S)-cyclohexanediamine; tta = 2-thenoyltrifluoroacetyl-acetonate} has been synthesized and characterized from a structural and spectroscopic point of view. The molecular structure in the solid state shows the presence of one chiral L, two tta, and one water molecules bound to the metal center. L and tta molecules can efficiently harvest and transfer to Eu(III) the UV light absorbed in the 250-400 nm range.

Disorder-Induced Breaking of the Local Inversion Symmetry in Rhombohedral Pyrochlores MLaSbO (M = Mg or Ca): A Structural and Spectroscopic Investigation.

A detailed investigation of the overall crystal structure, and in particular of the local structure around the cations in MLaSbO (M = Mg, Ca) was accomplished using X-ray diffraction, steady state luminescence spectroscopy and decay kinetics, and state of the art density functional calculations. The computational tool was also used to investigate the structure of MnLaSbO. The Eu dopant ion was employed as an optical probe of the local symmetry at the cationic sites.

High Pressure Raman, Optical Absorption, and Resistivity Study of SrCrO.

We studied the electronic and vibrational properties of monazite-type SrCrO under compression. The study extended the pressure range of previous studies from 26 to 58 GPa. The existence of two previously reported phase transitions was confirmed at 9 and 14 GPa, and two new phase transitions were found at 35 and 48 GPa.

Nanophotonic rare-earth quantum memory with optically controlled retrieval.

Optical quantum memories are essential elements in quantum networks for long-distance distribution of quantum entanglement. Scalable development of quantum network nodes requires on-chip qubit storage functionality with control of the readout time. We demonstrate a high-fidelity nanophotonic quantum memory based on a mesoscopic neodymium ensemble coupled to a photonic crystal cavity.

Color Control of Pr Luminescence by Electron-Hole Recombination Energy Transfer in CaTiO and CaZrO.

Controlling luminescence in phosphors able to produce several emissions from different stable excited states determines their use in optical devices. We investigate the color control mechanism that quenches the greenish-blue emission in favor of the red one in the archetype phosphor CaTiO:Pr. State-of-the-art ab initio calculations indicate that direct host-to-dopant energy transfer (released by electron-hole recombination following the interband excitation and structural reorganization) selectively populates the D red luminescent state of Pr and bypasses the P greenish-blue emitter.

Lanthanide-Activated Phosphors Based on 4f-5d Optical Transitions: Theoretical and Experimental Aspects.

The synthesis of lanthanide-activated phosphors is pertinent to many emerging applications, ranging from high-resolution luminescence imaging to next-generation volumetric full-color display. In particular, the optical processes governed by the 4f-5d transitions of divalent and trivalent lanthanides have been the key to enabling precisely tuned color emission. The fundamental importance of lanthanide-activated phosphors for the physical and biomedical sciences has led to rapid development of novel synthetic methodologies and relevant tools that allow for probing the dynamics of energy transfer processes.

Inorganic Phosphor Materials for Lighting.

This chapter addresses the development of inorganic phosphor materials capable of converting the near UV or blue radiation emitted by a light emitting diode to visible radiation that can be suitably combined to yield white light. These materials are at the core of the new generation of solid-state lighting devices that are emerging as a crucial clean and energy saving technology. The chapter introduces the problem of white light generation using inorganic phosphors and the structure-property relationships in the broad class of phosphor materials, normally containing lanthanide or transition metal ions as dopants.

Tuning of the sensing properties of luminescent Eu(3+) complexes towards the nitrate anion.

A new family of imine-based ligands containing pyridine or furan as an aromatic donating ring [N,N'-bis(2-pyridylmethylidene)-1,2-(R,R + S,S)-cyclohexanediamine, L1; N,N'-bis(2-furanylmethylidene)-1,2-(R,R + S,S)-cyclohexanediamine, L2 and N,N'-bis(2-thienylmethylidene)-1,2-(R,S)-cyclohexanediamine, L3] has been prepared in high yield by means of an easy synthetic protocol. Their trifluoromethansulphonate (CF3SO3(-), OTf(-)) Eu(iii) complexes have been employed for luminescence sensing of the NO3(-) anion in an anhydrous acetonitrile solution. Spectrophotometric titrations have been carried out to define the speciation in the solution and study the formation of ternary species occurring with the addition of NO3(-) anions.

Boosting the sensitivity of Nd(3+)-based luminescent nanothermometers.

Luminescence thermal sensing and deep-tissue imaging using nanomaterials operating within the first biological window (ca. 700-980 nm) are of great interest, prompted by the ever-growing demands in the fields of nanotechnology and nanomedicine. Here, we show that (Gd1-xNdx)2O3 (x = 0.

Theoretical and Experimental Study of the Crystal Structures, Lattice Vibrations, and Band Structures of Monazite-Type PbCrO4, PbSeO4, SrCrO4, and SrSeO4.

The crystal structures, lattice vibrations, and electronic band structures of PbCrO4, PbSeO4, SrCrO4, and SrSeO4 were studied by ab initio calculations, Raman spectroscopy, X-ray diffraction, and optical-absorption measurements. Calculations properly describe the crystal structures of the four compounds, which are isomorphic to the monazite structure and were confirmed by X-ray diffraction. Information is also obtained on the Raman- and IR-active phonons, with all of the vibrational modes assigned.

Enhancing optical forces on fluorescent up-converting nanoparticles by surface charge tailoring.

3D remote control of multifunctional fluorescent up-converting nanoparticles (UCNPs) using optical forces is being required for a great variety of applications including single-particle spectroscopy, single-particle intracellular sensing, controlled and selective light-activated drug delivery and light control at the nanoscale. Most of these potential applications find a serious limitation in the reduced value of optical forces (tens of fN) acting on these nanoparticles, due to their reduced dimensions (typically around 10 nm). In this work, this limitation is faced and it is demonstrated that the magnitude of optical forces acting on UCNPs can be enhanced by more than one order of magnitude by a controlled modification of the particle/medium interface.

Structural, optical and sensing properties of novel Eu(III) complexes with furan- and pyridine-based ligands.

A new family of imine and amine-based racemic ligands containing furan or pyridine as an aromatic donating ring [N,N′-bis(2-pyridylmethylidene)-1,2-(R,R + S,S)-cyclohexanediamine, L1; N,N′-bis(2-furanylmethylidene)-1,2-(R,R + S,S)-cyclohexanediamine, L2; N,N′-bis(2-pyridylmethyl)-1,2-(R,R + S,S)-cyclohexanediamine, L3; and N,N′-bis(2-furanylmethyl)-1,2-(R,R + S,S)-cyclohexanediamine, L4] and their trifluoromethanesulphonate (CF3SO3(−), OTf(−)) and nitrate Eu(III) complexes is studied in acetonitrile (AN) solution. The stoichiometry and stabilities of the formed complexes are obtained by means of spectrophotometric titrations: when Eu(III) triflate is used as a starting salt, two mononuclear species (1:1 and 1:2) are detected, while only the 1:1 complex is observed when the nitrate salt is employed. The stability of these complexes, as well as the geometry of their Eu(III) environment, is significantly dependent on the nature of the ligand employed (imine or amine, furan or pyridine-based).

Tunable luminescence of Bi(3+)-doped YP(x)V(1-x)O4 (0 ≤ x ≤1).

A systematic investigation of the luminescence spectroscopy of Y(P,V)O4:Bi(3+) is presented. The emission spectra and the decay curves are measured as a function of the host morphology, composition, temperature, excitation wavelength, and doping concentration. On this basis, the nature of the excited states and the radiative and non-radiative relaxation processes are discussed.