• Journal of the Korean Vacuum Society
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• v.5 no.4
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• pp.315-326
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• 1996

The electronic structures of 3d and 4d core-levels of rare-earth atoms in the insulating rare-earth (Sm, Eu, Gd, and Tb) compounds were studied with x-ray photoelectron spectroscopy(XPS). It is shown that the intrinsic satellite structure due to the hybridization disappears for chemically stable-earth trivalent heavy rare-earth insulating compounds as the hybridization between f electrons of rare-earth atoms and p electrons of anion atoms decreases due to the lanthanide contraction. Eu atoms at the surface of the stable insulating trivalent Eu compounds are found to be divalent. The satellite peak of Eu 3d core-level spectra at about 10eV higher binding energy side relative the main peak comes from the multiplet structures of $\underline{3d}4f^6$ configuration. The satellite structure appearing at about 15 eV higher binding energy side relative to the main peak in all insulating rare-earth compounds is due to an energy loss process of creating a plasmon.

• Journal of the Mineralogical Society of Korea
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• v.15 no.1
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• pp.78-84
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• 2002

New pyrochlore-type phases($A_2$$B_2$$O_{7}$) were synthesized in the systems: CaO-C$eO_2$-T$iO_2$, CaO-$UO_2$(T$hO_2$)-Z$rO_2$, CaO-$UO_2$(T$hO_2$)-$Gd_2$$O_3$-T$iO_2$-Z$rO_2$, 및 CaO-T$hO_2$-S$nO_2$. The starting materials were pressed with the pressure of 200~400 MPa and sintered at 1500~ 155$0^{\circ}C$ for 4~8 hours in air and at 1300~ 135$0^{\circ}C$ for 5 ~50 hours under oxygen atmosphere. The products were characterized using XRD, SEM/EDS and TEM. In the bulk compositions of CaCe$Ti_2$$O_{7}$, CaTh$Zr_2$$O_{7}$,($Ca_{0.5}$ Gd$Th_{0.5}$)(ZrTi)$O_{7}$) ($Ca_{0.5}$Gd$Th_{0.5}$)(ZrTi)$O_{7}$, ($Ca_{0.5}$G$dU_{0.5}$)(ZrTi)$O_{7}$ and CaTh$Sn_2$$O_{7}$ , pyrochlore was the major phase, together with other oxide phase $of_2$$O_{7}$ fluorite structure. In the samples with target compositions CaU$Zr_2$$O_2$및 $Ca_{0.5}$ G$dU_{0.5}$)$Zr_2$T$iO_{7}$ pyrochlore was not identified, but a fluorite-structured phase was detected. The formation factor as the stable phase depended on crystal chemical characteristics of the actinide and lanthanide elements of the system concerned.

• The Korean Journal of Physiology and Pharmacology
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• v.18 no.6
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• pp.503-508
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• 2014

Spontaneous myometrial contraction (SMC) in pregnant uterus is greatly related with gestational age and growing in frequency and amplitude toward the end of gestation to initiate labor. But, an accurate mechanism has not been elucidated. In human and rat uterus, all TRPCs except TRPC2 are expressed in pregnant myometrium and among them, TRPC4 are predominant throughout gestation, suggesting a possible role in regulation of SMC. Therefore, we investigated whether the TRP channel may be involved SMC evoked by mechanical stretch in pregnant myometrial strips of rat using isometric tension measurement and patch-clamp technique. In the present results, hypoosmotic cell swelling activated a potent outward rectifying current in G protein-dependent manner in rat pregnant myocyte. The current was significantly potentiated by $1{\mu}M$ lanthanides (a potent TRPC4/5 stimulator) and suppressed by $10{\mu}M$ 2-APB (TRPC4-7 inhibitor). In addition, in isometric tension experiment, SMC which was evoked by passive stretch was greatly potentiated by lanthanide ($1{\mu}M$) and suppressed by 2-APB ($10{\mu}M$), suggesting a possible involvement of TRPC4/5 channel in regulation of SMC in pregnant myometrium. These results provide a possible cellular mechanism for regulation of SMC during pregnancy and provide basic information for developing a new agent for treatment of premature labor.

• Journal of the Korean Chemical Society
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• v.43 no.3
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• pp.257-263
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• 1999

Ln-macrocyclic([20]DOTA) complexes, [Ln([20]DPTA)(NO_{3})(H_{2}O)](NO_{3})_{2} \cdotxH_{2}O{Ln(III)=Pr, Sm, Gd, Dy}, which had been synthesized from 2, 6-diformyl-p-cresol(DFPC), was placed in methanol for 2 days, and $[Ln([20]DPTA)(NO_{3})(CH_{3}OH)]^{2+}$ was formed. The equilibrium constants(L) for the substitution of coordinated $CH_{3}OH$ in the Ln-[20]DOTA complexes by various auxiliary ligands, $L_{a}(=monodentate ligands; pyridine, imidazole, triethylamine, diethylamine, piperidine) were determined spectroscopically at $25^{\circ}C$ and 0.1M. The pKa of auxiliary ligand is in the order of pyridine < imidazole < triethylamine < diethylamine < piperidine, however the K has shown the trend of pyridine < imidzole < diethylamine < piperidine < triethylamine.

• Journal of the Korean Chemical Society
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• v.38 no.8
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• pp.590-597
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• 1994

The chemical behavior of the trivalent lanthanide$(Pr^{3+}, Eu^{3+}, Gd^{3+} 그리고 Yb^{3+})$complexes with organo-ligand (2,2,6,6-tetramethyl-3,5-heptanedione) has been investigated by the use of UV/Vis-spectrophotometric, magnetics, and electrochemical method. The two or three energy absorption bands are observed by the spectra of these complexes. The magnetitude of crystal field splitting energy, the spin pairing energy and bond stength was obtained from the spectra of the complexes. These are found to be localization, low-spin (or high-spin state, and strong bonding strength. The magnetic dipole moment are found to be diamagnetic complexes (or paramagnetic). The electrochemical behavior of complexes was observed by the use of cyclic voltammetry in aprotic media. These reduction peaks were irreversible two and three step reduction processes by electron transfer.

• Journal of the Korean Chemical Society
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• v.37 no.1
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• pp.83-91
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• 1993

The eletrochemical behavior of light lanthanide complexes has been investigated by several electrochemical techniques in alkaline solutions. The composition of the complexes was determined by spectrophotometric method to be 1 : 1 and reduction mechanism was two steps 1 electron transfer reaction. The half wave potential of first peak depended on pH and cathodic current showed remarkably adsorptive properties. The results of DC and CV investigation demonstrated the quise-reversible nature of the electron transfer. The anion radical formed after first one electron reduction process, dimerizes to form dimer. The apparent irreversible behavior of the second wave is a result of the existence of a fast protonation following the second electron transfer. An exhaustive electrolysis was carried out at controlled potential of -1.80 V, deep blue color of the solution became progressively weaker, and then the solution became colorless solution. The final product of an exhaustive electrolysis is electro-inactive. The appearance of four steps may be explained by the fact the reduction of Ln-OCP elucidated ECEC mechanism.

• Bulletin of the Korean Chemical Society
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• v.24 no.1
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• pp.49-54
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• 2003

TiO₂nanoparticles were synthesized using the metallorganic chemical vapor deposition process. Particles with and without metal ion dopants were obtained. X-ray photoelectron and energy dispersive X-ray spectroscopic measurements confirmed the stoichiometry of the TiO₂nanoparticles. X-ray diffraction patterns showed a polycrystalline anatase structure of TiO₂. Transmission electron microscopy revealed that these particles are of nanoscale dimensions. Exact particle size and size distribution analyses were carried out by dynamic light scattering. The average particle size was determined to be 22 nm. The nanosize particles provided large surface area for photocatalysis and a large number of free surface-charge carriers, which are crucial for the enhancement of photocatalytic activity. To improve the photocatalytic activity, metal ions, including transition metal ions $(Pd^{2+},\;Pt^{4+},\;Fe^{3+})$ and lanthanide ion $(Nd^{3+})$ were added to pure TiO₂nanoparticles. The effects of dopants on photocatalytic kinetics were investigated by the degradation of 2-chlorophenol under an ultraviolet light source. The results showed that the TiO₂nanoparticles with the metal ion dopants have higher photocatalytic activity than undoped TiO₂. The $Nd^{3+}$ ion of these dopant metal ions showed the highest catalytic activity. The difference in the photocatalytic activity with different dopants is related to the different ionic radii of the dopants.

• Journal of the Korean Chemical Society
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• v.37 no.4
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• pp.442-447
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• 1993

The thermodynamic parameters (${\Delta}$G, ${\Delta}$H and ${\Delta}$S) of lanthanides(III)-benzoylformate complexes in aqueous solution have been determined in the ionic medium of 0.1M $NaClO_4$ at 25$^{\circ}C$, using pH and enthalpy titration method. The stability constants of the lanthanide(III)-benzoylformate complexes (1 : 1) agree well with the general relationships for the bidentate ligands (e.g., log${\beta}_1$ vs. p$K_a$). Thermodynamic evidences show that the oxygen atom in ketone group is coordinated along with the carboxylate group. It is ascribed to the increasing charge density on the oxygen atom in ketone group due to the conjugation effect in the benzoylformate ligand. Thermodynamic results also indicate that the complexes are stabilized by the enthalpy effect caused by the ionic interaction of metal-oxygen bond as well as the entropy effect.

• Bulletin of the Korean Chemical Society
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• v.33 no.4
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• pp.1303-1309
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• 2012

A novel ligand N,N'-(2,6-pyridinedicarbonyl)bis[N-(carboxymethyl)] (L1) was designed and synthesized. Four co-luminescence groups of Sm-La-pyridyl carboxylic acids systems were researched, which are $K_4Sm_{(1-x)}-La_x(L_1)Cl_3{\cdot}y_1H_2O$, $K_4Sm_{(1-x)}La_x(L_2)Cl_3{\cdot}y_2H_2O$, $K_6Sm_{2(1-x)}La_{2x}(L_3)Cl_6{\cdot}y_3H_2O$, $K_4Sm_{(1-x)}La_x(L_4)Cl_3{\cdot}y_4H_2O$. The results indicated the addition of La(III) could sensitize the luminescence of Sm(III) obviously in a certain range, enhancing emission intensity of Sm-pyridyl carboxylic acids relative to the undoped ones. The optimal mole percentages of La(III) in the mixed ions for $L_1$, $L_2$, $L_3$, $L_4$ were confirmed to be 0.6, 0.5, 0.3, 0.6, respectively. The mechanism of the fluorescence enhancement effect was discussed in detail. Furthermore, the binding interaction of $K_4Sm_{0.4}La_{0.6}(L_4)Cl_3{\cdot}5H_2O$ with bovine serum albumin (BSA) have been investigated due to its potential biological activity. The binding site number n was equal to 1.0 and binding constant $K_a$ was about $2.5{\times}10^5\;L{\cdot}mol^{-1}$.

• Journal of the Korean Ceramic Society
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• v.43 no.11 s.294
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• pp.688-692
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• 2006

Ferroelectric lanthanides-substituted $Bi_4Ti_3O_{12}$ $(Bi_{4-x}Ln_xTi_3O_{12}, BLnT)$ thin films approximately 200 nm in thickness were deposited by metal organic chemical vapor deposition onto Pt(111)/Ti/SiO$_2$/Si(100) substrates. Many researchers reported that the lanthanides substitution for Bi in the pseudo-perovskite layer caused the distortion of TiO$_6$ octahedron in the a-b plane accompanied with a shift of the octahedron along the a-axis. In this study, the effect of lanthanides (Ln=Pr, Eu, Gd, Dy)-substitution and crystallization temperature on their ferroelectric properties of bismuth titanate $(Bi_4Ti_3O_{12}, BIT)$ thin films were investigated. As BLnT thin films were substituted to lanthanide elements (Pr, Eu, Gd, Dy) with a smaller ionic radius, the remnant polarization (2P$_r$) values had a tendency to increase and made an exception of the Eu-substituted case because $Bi_{4-x}Eu_xTi_3O_{12}$ (BET) thin films had the smaller grain sizes than the others. In this study, we confirmed that better ferroelectric properties can be expected for films composed of larger grains in bismuth layered peroskite materials. The crystallinity of the thin films was improved and the average grain size increased as the crystallization temperature,increased from 600 to 720$^{\circ}C$. Moreover, the BLnT thin film capacitor is characterized by well-saturated polarization-electric field (P-E) curves with an increase in annealing temperature. The BLnT thin films exhibited no significant degradation of switching charge for at least up to $1.0\times10^{11}$ switching cycles at a frequency of 1 MHz. From these results, we can suggest that the BLnT thin films are the suitable dielectric materials for ferroelectric random access memory applications.