• Korean Journal of Optics and Photonics
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• v.7 no.3
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• pp.227-231
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• 1996

The reflection spectrum of a $2H-PbI_2$ single crystal grown by vapour phase method were measured at 10 K near the fundamental absorption edge. The n= 1,2,3 Wannier exciton series and $A_{EP}$ reflection line were obtained from the reflection spectrum. Based on the 2nd phonon energy in the Raman spectrum, which is different from Nagamune's report, we suggest that $A_{EP}$ line is due to the bound state between the n=2 exciton and the 2nd phonon which surmise that this is LO phnon due to the second Raman process. The L-T splitting energy of n=1 exciton line was 6.56 meV and was consistent with the emission spectrum. The temperature dependence of the reflection spectrum showed that n=1 exciton peak was shifted to longer wavelength while, as the temperatre is raised, the sharpness of that with the increase of the L-T splitting energy decrease. From Wannier exiton series, the exciton binding energy and exciton radius was 30 meV and 14$\AA$, respectively.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.457-465
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• 2014

Size-controlled lead sulfide (PbS) quantum dots were synthesized by the typical hot injection method using oleic acid (OA) as the stabilizing agent. Subsequently, the ligand exchange reaction between OA and thioacetic acid (TAA) was employed to obtain TAA-capped PbS quantum dots (PbS-TAA QDs). The condensation reaction of the TAA ligands on the surfaces of the QDs enhanced the conductivity of the PbS-TAA QDs thin films by about 2-4 orders of magnitude, as compared with that of the PbS-OA QDs thin films. The electron transport mechanism of the PbS-TAA QDs thin films was investigated by current-voltage (I-V) measurements at different temperatures in the range of 293 K-473 K. We found that the charge transport was due to sequential tunneling of charge carriers via the QDs, resulting in the thermally activated hopping process of Arrhenius behavior.

• Korean Journal of Materials Research
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• v.12 no.11
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• pp.875-879
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• 2002

$Pb_{1-x}$ $Cd_{x}$ $I_2$ (x=0.0, 0.2, 0.5, 0.7, 0.9, 1.0) single crystals were grown by using Bridgman method and their structural and optical properties were investigated from the measurement of X-ray diffraction, optical absorption and photoluminescence. As-grown single crystals have hexagonal closed packed layered structure. The values of lattice constant c decrease with increasing composition x. Direct and indirect transition optical energy band gaps are calculated from optical absorption spectra measured at room temperature. They increase exponentially from 2.3eV to 3.2 eV with increasing composition x. The energies of photoluminescence peak due to donor bound exciton measured at 6K increase with increasing composition . However, the peak energies of donor-acceptor pair (DAP) are independent of the optical energy band gaps of $Pb_{1-x}$/$Cd_{x}$ $I_2$ single crystals.

• Bulletin of the Korean Chemical Society
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• v.29 no.8
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• pp.1464-1466
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• 2008

Tetrabutylammonium Fluorodichloroplumbate(II), N$(C_4H_9)_4$[$PbCl_2F$], TBAFDiCP and Tetrabutylammonium Fluorodiiodoplumbate(II), [$(C_4H_9)_4$N][$PbI_2F$], TBAFDiIP are the first examples of fluoroplumbate salts that have been prepared from the reaction of $(C_4H_9)_4$NF with $PbCl_2$ and $PbI_2$ respectively using either $CH_3CN$ solvent. These new compound characterized by elemental analysis, IR, UV/Visible, $^1H$ NMR, and $^{19}F$ NMR techniques.

• Analytical Science and Technology
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• v.12 no.2
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• pp.159-165
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• 1999

The adsorption and separation behaviors of transition metal ions using a merrifield resin bound 1,12-diaza-3,4:9,10-dibenzo-5,8-dioxacyclopentadecane (NTOE) and 1,12,15-triaza-3,4:9,10-dibenzo-5,8-dioxacycloheptadecane(NDOE) were investigated in aqueous solution. The orders of adsorption degree(E) and distribution ratio(D) of transition metal ions were Cu(II)$t_R$) of metal ions were affected by adsorption degree(E) and distribution ratio(D). This results showed good separation efficiency of Ag(I) from mixed metal solution.

• Biomolecules & Therapeutics
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• v.12 no.4
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• pp.209-214
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• 2004

Lead has long been considered as a toxic environmental pollutant that severely damages the central nervous system. In various neurogenerative diseases, actrocytes become activated by proinflammatory cytokines. In the present study, we investigated whether lead (Pb$^{2+}$) affects inducible nitric oxide synthase (iNOS) expression in activated glial cells. Rat primary glial cells were stimulated with lipopolysaccharide (LPS, 1 ${\mu}$g/ml) plus IFN$_{\gamma}$(100 U/ml). Pre-treatment of Pb$^{2+}$ increased nitric oxide (NO) production in LPS/IFN$_{\gamma}$-stimulated glial cells. Lead itself, however, suppressed the basal production of NO in control glial cells. Addition of the iNOS inhibitors L-NAME (1 mM) and L-NNA (800 ${\mu}$M) prevented the Pb$^{2+}$-induced increase in NO production. Western blot analysis showed that pre-treatment of Pb$^{2+}$ augmented LPS/IFN$_{\gamma}$-induced increase in iNOS immunoreactivity, which was well correlated with the increased NO production. In addition, pre-treatment of Pb$^{2+}$ synergistically increased the iNOS mRNA expression induced by LPS and IFN${\gamma}$. The present results indicate that lead intoxication adversely affect brain function by potentiating iNOS expression and NO production in activated glial cells observed in various neurodegenerative diseases.

• Journal of the Korean Ceramic Society
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• v.32 no.6
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• pp.748-760
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• 1995

Pyroelectric properties, figure of merits, and the other properties of the Pb(Zn1/3Nb2/3)O3-Pb(Fe1/2Nb1/2)O3 system, as expected to have excellent pyroelectric properties in the operating temperature range of pyroelectric type infrared sensor, were investigated. In the Pb(Zn1/3Nb2/3)O3-Pb(Fe1/2Nb1/2)O3 system, suppression of the pyrochlore phase depended on sintering condition, as like sintering temperature, holding time, sintering atmosphere. The specimen, sintered by the same composition atmosphere powder at 105$0^{\circ}C$ for 1.5h, possessed the best physical property. It was found that the piezoelectric parameters were mainly depended on the amount of spontaneous polarization and then the 0.2PZN-0.8PFN showed the best pyro- and piezoelectric properties. In terms of the experimental method, two pyroelectric-testing methods, i.e. static and dynamic methods, had a same tendency. Also the result of pyroelectric testing by the static method indicated that the diffuse phase transitiion resulted in the temperature difference of phase transition between dielectric constant and pyroelectric coefficient.

• Analytical Science and Technology
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• v.7 no.2
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• pp.225-232
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• 1994

The podands I-VII, acyclic polyethers, expected high extractability for $Ag^+$ against $Pb^{2+}$ were designed and synthesized with high yields. Using podands I-VII as extractants, the %extraction(%Ex) of $Ag^+$ and $Pb^{2+}$ as picrates were determined in water/chloroform systems. The stability constants(log K) for the complexation of $Ag^+$ with podands I-VII were also determined by potentiometry. %Ex($Ag^+$) were proportional to the numbers of substituted sulfur donor atoms. Podand VI(log K : 7.65) having 3 substituted sulfur and podand VII(log K : 9.15) having 4 substituted sulfur, however, exhibited almost 100% of extractability, respectively. In %Ex($Ag^+/Pb^{2+}$, oxygen-sulfur mixed donor podands(IV-VII) showed the higher values. Otherwise, the values of log K and %Ex($Ag^+$) largely depended on the variation of donor-site of sulfur. From the results of NMR experiments, it seems that it is due to the ${\pi}-{\pi}$ stacking interaction between the aromatic end-groups.

• Journal of the Korean Ceramic Society
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• v.19 no.4
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• pp.300-308
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• 1982

A new perovskite type compound, (Pb1a-χKy□χ-y) (Zr0.33Ti0.67)O3-χ+y/2 was proposed and synthesized by "Wet-Dry Combination Technique". This defect ferroelectric material was characterized by partial substitutions of K+ for Pb+2 in Pb(Zr0.33Ti0.67)O3. This material was mono-phasic perovskite compound at 800℃ for 1hr., but ZrO2 was more or less isolated from the (Pb1a-χKy□χ-y) (Zr0.33Ti0.67)O3-χ+y/2. As a result, snitering temperature, sintered density, curie temperature, and dielectric constant of test pieces decreased and a-axis was nearly constant, while c-axis gradually decreased with the value x in the region of tetragonal phase of PZT. It was also recognized that the defect structure caused by adding K+ was found in both A-site cation and O-site anion vacancies in the defect PZT.

• Advances in materials Research
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• v.7 no.1
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• pp.73-81
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• 2018

$TiO_2/CH_3NH_3Pb_{1-x}Sb_xI_{3-3x}Br_{3x}-based$ photovoltaic devices were fabricated by a spin-coating method using mixture solutions with $SbBr_3$. Effects of $SbBr3$, CsI or RbBr addition to $CH_3NH_3PbI_3$ precursor solutions on the photovoltaic properties where investigated. The short-circuit current densities and photoconversion efficiencies were improved by adding a small amount of $SbBr_3$, CsI or RbBr to the perovskite phase, which would be due to the doping effect of Sb, Br and Cs/Rb atom at the Pb, I and $CH_3NH3$ sites, respectively.