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The effect of isovalent chemical substitution of [Eu.sup.3+] into the [Tb.sup.3+] sites on the magnetic and electrical properties of ([Tb.sub.1-x][Eu.sub.x])Mn[O.sub.3] (0 less than equal to x less than equal to 1.0) system is examined. The results have shown that the increase in the Eu content has increased both the tolerance factor and Mn-O bond distance, leading to the reduction in the octahedral distortion and Jahn-Teller (JT) effect.

A series of heteroleptic bis(phthalocyaninato) europium(lll) complexes with one, two, three and four 15-crowns-5 voids attached at different positions of one of the two phthalocyninato ligands in the double-decker molecules are devised and prepared by Eu(Pc)(acac)-induced (Hacac = acetylacetone) mixed cyclization of the two corresponding phthalonitriles. Their electrochemistry and supramolecular structure-formation properties are studied.

Memory effects in single-layer organic light-emitting devices based on Sm(super 3+), Gd(super 3+) and Eu(super 3+) rare earth complexes were realized. Results indicate that the rare earth organic complexes are promising materials for high-density, low-cost memory application besides the potential application as organic light-emitting materials in display devices.

The electron-transfer (ET) fluorescence quenching of aromatic hydrocarbons by trivalent lanthanide ions M(super 3+) [europium ion Eu(super 3+) and ytterbium ion Yb(super 3+)] and the ET reactions of the geminate and free radical recombination are studied, to understand the effects of molecular size on photo induced ET reactions. It is observed that the shift of the switchover of the fluorescence mechanism, yielding the geminate radical ion pairs, is due to the difference in their molecular size of the quenchers.

Two models based on detailed rate equations are presented to describe the dynamics of Q-switched clad-pumped Er(super 3+) -Yb(super 3+) codoped fiber lasers. The full wavelength-dependent model is considered as a standard, and the simplified model is derived from it by assuming single wavelengths in both 1080- and 1550-nm bandwidths.

The reactions and reductions of various metal ions are examined. A detailed explanation of the chemistry of MeReO3, which acts as a catalyst for hydrogen evolution, is also presented.

Quenching of cathodoluminescent (CL) efficiency of La2O2S:Eu(super 3+) prepared by combustion reaction is investigated by measuring the temporal dependence of the CL intensities. The findings show that based on the thermal quenching data for the (super 5)D(sub 0) yields (super 7)F(sub 2) transition, the quenching observed at high current densities is only partially explained by electron-beam heating.

The experimental results on the modification of the SpE rate of an emissive layer embedded within a metal-clad microcavity are presented. The role of the reflectivity of the mirrors in the control of SpE by using metallic reflection of differing thicknesses is studied.

Continuously illuminated single europium ions incorporated in d [Eu (super 3+): Y2O3] nanocrystals (5-15 nm diameter) undergo on-off blinking on a variable time scale ranging from hundreds of milliseconds to several seconds. The study indicates the first report of fluorescence imaging of single rare-earth ions in metal oxide nanoparticles, and the first observation of multiple bright states in the luminescence of a single chromophore.

Multiferroic single crystals R[Mn.sub.2][O.sub.5] (R = Bi, Eu and Dy) are analyzed by using the temperature dependent Raman scattering study. The anomalous phonon behaviors in bending and stretching modes are consistent with the spin-phonon coupling in a scenario of strong magnetic correlations.

The demonstration of visible laser action on silicon is reported. Eu-doped GaN is utilized for the active medium within a structure consisting of multiple AlGaN layers grown by molecular-beam epitaxy on a Si substrate.

Electrical, magnetic and Mossbauer measurements are performed on [La.sub.0.67-x][Eu.sub.x][Ca.sub.0.33]Mn[O.sub.3] in order to study different grain size materials. The combined effect of chemical pressure induced due to the additional rare earth doping and smaller grain size has led to a more stable AFM phase where no such hysteresis is observed in field cooled cooling and warming cycles of magnetization measurements.

Solution based methods are used for preparing LaP[O.sub.4]:[Eu.sup.3+] doped and LaP[O.sub.4]/[Eu.sub.2][O.sub.3] core-shell nanocrystals. Judd-Ofelt parameters are calculated for understanding the asymmetric nature of the dopant [Eu.sup.3+] ion in LaP[O.sub.4] nanocrystals host of various morphologies and crystal phases.

Several studies are conducted to explain the different quenching mechanisms exhibited by the optical centers present in the [Eu.sup.3+]-doped nanophosphors under charge transfer excitation. The various mechanisms that can be adopted for enhancing the luminescence efficiency of these nanophosphors are also discussed.

Self-assembled GaN quantum dots (QDs) stacked in superlattices (SL) with AlN spacer layers are implanted with Europium ions. The studies have shown that in the sample implanted with the lowest fluence, the [Eu.sup.3+] emission has occurred from Eu incorporated inside the QDs while for the higher fluences only the emission from Eu inside the AlN-buffer, capping and spacer layers is observed.

A europium(III) DO3A-tris(amide) complex is described for imaging pH by MRI by using ratiometric chemical exchange saturation transfer (CEST) principles. The collection of two CEST images at two slightly different activation frequencies has provided a direct readout of solution pH without the need of a concentration marker.

Gadolinium doped europium sulfides ([Eu.sub.1-x][Gd.sub.x]S) are prepared by the thermal decomposition of the precursors Eu[([S.sub.2]CN[Et.sub.2]).sub.3]Phen/Gd[([S.sub.2]CN[Et.sub.2]).sub.3]Phen. The magnetic properties have helped in determining that the paramagnetic Curie temperature has varied with doping level, in a similar way to [Eu.sub.1-x][Gd.sub.x]O displaying an increase at low doping levels.

Yttrium silicate powders doped with [Eu.sup.3+] and codoped with [E.sup.3+] and [Yb.sup.3+] are prepared by combustion synthesis and the Judd-Ofelt intensity parameters are calculated along with the radiative and nonradiative relaxation rates. The luminescence is achieved because of the cooperative upconversion (CUC) process involving energy transfer (ET) from pairs of yttrerbium ions to europium ions.

Several experimental studies are conducted to analyze the origin of the two-photon-excited luminescence exhibited by a [Eu.sup.3+]-doped lithium niobate crystal. The different kinds of [Eu.sup.3+] centers exhibited by the system are also analyzed.

A combination of Raman spectra and other techniques is employed to explain the synthesis, characterization and the emission properties of the [Y.sub.2-x][Ln.sub.x][Ti.sub.2][O.sub.7] (Ln = Eu and Gd, x = 0.0,0.05) compounds. Particle size and short range order are found to be the main factors leading to the changes observed in the emission intensity of [Eu.sup.3+].

Several studies are conducted to explain the various effects of the distorted lattice and nonequal-valence substitution observed on the long lasting phosphorescence of [Eu.sup.2+] and [Gd.sup.3+] doped R[Mg.sub.2][([PO.sub.4]).sub.2] (R = Sr,Ba) phosphors. The electron storage ability of the compounds is shown to get highly enhanced because of the codoping of [Gd.sup.3+].

The energy transfer between Eu-Mn in [Ba.sub.0.75][Al.sub.11][O.sub.17.25]-BaMg[Al.sub.10][O.sub.17] solid solution is evaluated by preparing [Ba.sub.0.75][Al.sub.11][O.sub.17.25]-BaMg[Al.sub.10][O.sub.17]:[Eu.sup.2+],[Mn.sup.2+] phosphors by using by flux method. A redshift of green emission peak and a decrease in decay time with the increase in [Mn.sup.2+] concentration are observed, which are attributed to the formation of [Mn.sup.2+] paired centers after analysis by a method of Pade approximations.

Several studies are conducted to analyze the fabrication and the properties of the europium doped zinc oxide nanoparticles, nanorods and urchins. The structures are shown to exhibit highly dominant defect related emissions, as compared to the near band edge emission.

The excitation-dependent photoluminescence approach is employed to explain the properties and the trapping states present in the CdS:Eu nanobelts. The near-band edge emissions of the system is shown to be highly dependent on the power.

The SnTe, [Sn.sub.1-x][Eu.sub.x]Te and [Sn.sub.1-x][Sr.sub.x]Te films are prepared by hot wall epitaxy and optical transmission spectra are measured. Optical transmission spectra of the SnTe are simulated by assuming bumped band edge structures and a band inversion model is proposed for the [Sn.sub.1-x][Eu.sub.x]Te and [Sn.sub.1-x][Sr.sub.x]Te systems.

The structural and optical properties of Eu-doped ZnO thin films made by sol-gel technique and magnetron reactive sputtering on Si (100) substrate are examined. The photoluminescence excitonic spectra has displayed efficient energy transfer from the ZnO matrix to the [Eu.sup.3+] ion, which is similar for both films although the sputtered films have a better structural quality when compared to the sol-gel process grown films.

The effect of rare-earth clustering in dielectric media on the electroluminescence (EL) intensity, the charge trapping and the EL quenching is examined by using Tb and Eu-implanted Si[O.sub.2] layers. It is shown that in the case of Eu-implanted Si[O.sub.2], the quenching of the main EL line of [Eu.sup.3+] is correlated with positive charge trapping in the bulk of the dielectric.

Several studies are conducted to determine the various luminescence properties of the [Eu.sup.3+] doped germanate glasses with silver or gold nanoparticles. The various effects of these metallic nanoparticles on the electric- and magnetic-dipole transitions taking place in the glasses are also explained.

Nanoparticles of [Dy.sup.3+] and [Eu.sup.3+] doped YV[O.sub.4] are prepared by urea-hydrolysis in ethylene glycol medium and are heated to grow particles as well ass remove unwanted hydrocarbon/[H.sub.2]O, which has acted as quencher in luminescence. Luminescence intensity is improved because of the extent of reduction in surface [Eu.sup.+]/[Dy.sup.3+] of particles and cross-relaxation reduction among [Eu.ssup.3+]/[Dy.sup.3+] ions, after covering core-nanoparticles with undoped YV[O.sub.4] shell.

The optical and physical effects of high europium concentration on the europium gallium oxide [([Eu.sub.x][Ga.sub.1-x]).sub.2][O.sub.3] thin films are analyzed by using photoluminescence (PL) spectroscopy, x-ray diffraction and Rutherford backscattering spectrometry. The studies have shown that the optimal doping for optoelectronic devices based on [([Eu.sub.x][Ga.sub.1-x]).sub.2][O.sub.3] thin films is between 5 and 10 mol%.

Efficient phosphors based on YNb[O.sub.4] and doped by [Eu.sup.3+], [Ga.sup.3+], and [Al.sup.3+] are prepared with different fluxes under different thermal conditions and are examined under x-ray excitation and Raman spectroscopy. The samples codoped by [Al.sup.3+] and [Ga.sup.3+] have displayed higher intensity under x-ray excitation when compared with YNb[O.sub.4]:[Eu.sup.4+] phosphors.

Several studies are conducted to analyze the magnetic properties, magnetocaloric effect and the refrigerant capacity that is observed in the various Sr-doped [Eu.sub.8][Ga.sub.16][Ge.sub.30] type-I clathrates. These compounds are shown to be extremely beneficial for numerous cryogenic magnetic refrigeration applications.

The article explains the formation, electronic structure and the various magnetic and transport properties of the different Eu[Mn.sub.2] films. The resistivity of these films is shown to be completely dependent on the temperature.

The photoluminescence and x-ray luminescence of lanthanum-stabilized cubic barium chloride with europium ([Eu.sup.2+]) doping. The measurement of the x-ray luminescence intensity when compared to a standard commercial [Gd.sub.2][O.sub.2]S:Tb phosphor sheet has shown equal brightness.

Electronic flexibility and colossal magnetoresistance effects are discovered in the perovskite oxynitrides EuW[O.sub.1+x][N.sub.2-x] and ammonolysis of [Eu.sub.2][W.sub.2][O.sub.9] has produced scheelite-type intermediates EuW[O.sub.4-y][N.sub.y] with a small degree of nitride substitution. Both the Eu and W oxidation states and the hole/electron doping are tuned by varying the O/N ratio, EuW[O.sub.1+x][N.sub.2-x] phases order ferromagnetically at 12 K and colossal magnetoresistances (CMR) are seen in the least doped sample.

A near UV excitable phosphor [Sr.sub.2.85][Eu.sub.0.1][Al.sub.0.9][In.sub.0.1][O.sub.4-[alpha]][F.sub.1-[delta]] is made by reducing as-made [Sr.sub.2.85][Eu.sub.0.1][Al.sub.0.9][In.sub.0.1][O.sub.4]F, which has disclosed defect-induced broad-band photoluminescence emissions. The combined line and broad-band emitters have the potential when combined with another broad-band emitting phosphor to create white light by converting near-UV light from a [Ga.sub.1-x][In.sub.x]N light-emitting device.

X-ray diffraction (XRD) and transmission electron microscopy (TEM) are applied to study the structural properties of single phase cubic [Gd.sub.2][O.sub.3] nanophosphor codoped with [Eu.sup.3+] and [Yb.sup.3+] ions synthesized via solution combustion route. The sample annealed at 1200 degree [Celsius] on 355 nm excitation showed nearly twenty two times enhancement in the intensity of the hypersensitive transition along with an increase in the decay time.

The role of [Ce.sup.3+] concentration on the luminescence intensity of [Eu.sup.3+] in [Ce.sup.3+]- and [Eu.sup.3+]-doped YP[O.sub.4] is examined. A luminescent study is performed for the first time with a change of solvent from [H.sub.2]O to [D.sub.2]O and remarkable improvement is found in luminescence.

Emission from europium ions inside a planar waveguide is described, where the waveguide is constituted by a Mg[F.sub.2]:[Eu.sup.2+] film between walls. A guided mode is produced by incident light through a thin metallic film at an angle of incidence such that its wave vector component parallel to the waveguide has coupled resonantly to the mode.