• 한국재료학회지
• /
• 제25권9호
• /
• pp.480-486
• /
• 2015

$Pb_{1-x}MoO_4:Er^{3+}/Yb^{3+}$ phosphors with various doping concentrations of $Er^{3+}$ and $Yb^{3+}$ ($x=Er^{3+}+Yb^{3+}$, $Er^{3+}=0.05$, 0.1, 0.2, and $Yb^{3+}=0.2$, 0.45) are successfully synthesized using a microwave sol-gel method, and the up-conversion photoluminescence properties are investigated. Well-crystallized particles, which are formed after heat treatment at $900^{\circ}C$ for 16 h, exhibit a fine and homogeneous morphology with particle sizes of $2-5{\mu}m$. Under excitation at 980 nm, the $Pb_{0.7}MoO_4:Er_{0.1}Yb_{0.2}$ and $Pb_{0.5}MoO_4:Er_{0.05}Yb_{0.45}$ particles exhibit a strong 525 nm emission band, a weak 550 nm emission band in the green region, and a very weak 655 nm emission band in the red region. The Raman spectra of the doped particles indicate the presence of strong peaks at higher and lower frequencies induced by the disordered structures of $Pb_{1-x}MoO_4$ through the incorporation of the $Er^{3+}$ and $Yb^{3+}$ ions into the crystal lattice, which results in the unit cell shrinkage accompanying the new phase formation of the $MoO_{4-x}$ group.

• Journal of Electrochemical Science and Technology
• /
• 제10권4호
• /
• pp.424-432
• /
• 2019

Planar BiVO₄ and 3 wt% Mo-doped BiVO₄ (abbreviated as Mo:BiVO₄) film were prepared by the facile spin-coating method on fluorine doped SnO₂(FTO) substrate in the same precursor solution including the Mo precursor in Mo:BiVO₄ film. After annealing at a high temperature of 450℃ for 30 min to improve crystallinity, the films exhibited the monoclinic crystalline phase and nanoporous architecture. Both films showed no remarkably discrepancy in crystalline or morphological properties. To investigate the effect of surface passivation exploring the Al₂O₃ layer, the ultra-thin Al₂O₃ layer with a thickness of approximately 2 nm was deposited on BiVO₄ film using the atomic layer deposition (ALD) method. No distinct morphological modification was observed for all prepared BiVO₄ and Mo:BiVO₄ films. Only slightly reduced nanopores were observed. Although both samples showed some reduction of light absorption in the visible wavelength after coating of Al₂O₃ layer, the Al₂O₃ coated BiVO₄ (Al₂O₃/BiVO₄) film exhibited enhanced photoelectrochemical performance in 0.5 M Na₂SO₄ solution (pH 6.5), having higher photocurrent density (0.91 mA/㎠ at 1.23 V vs. reversible hydrogen electrode (RHE), briefly abbreviated as V_RHE) than BiVO₄ film (0.12 mA/㎠ at 1.23 V_RHE). Moreover, Al₂O₃ coating on the Mo:BiVO₄ film exhibited more enhanced photocurrent density (1.5 mA/㎠ at 1.23 V_RHE) than the Mo:BiVO₄ film (0.86 mA/㎠ at 1.23 V_RHE). To examine the reasons, capacitance measurement and Mott-Schottky analysis were conducted, revealing that the significant degradation of capacitance value was observed in both BiVO₄ film and Al₂O₃/Mo:BiVO₄ film, probably due to degraded capacitance by surface passivation. Furthermore, the flat-band potential (V_FB) was negatively shifted to about 200 mV while the electronic conductivities were enhanced by Al₂O₃ coating in both samples, contributing to the advancement of PEC performance by ultra-thin Al₂O₃ layer.

• 센서학회지
• /
• 제17권4호
• /
• pp.281-288
• /
• 2008

Polyacrylonitrile(PAN)/metal oxide(MO) nanocomposite mats with a thickness of 0.12 mm were electrospun by adding 0 to 10 wt% of MO nanoparticles ($Fe_2O_3$, ZnO, $SnO_2$, $Sb_2O_3-SnO_2$) into PAN. Pt electrode was patterned on $Al_2O_3$ substrate by DC sputtering and then the PAN(/MO) mats on the Pt patterned $Al_2O_3$ were electrically wired to investigate the $CO_2$ gas sensing properties. As the MO content rose, the fiber diameter decreased due to the presence of lumps caused by the presence of MOs in the fiber. The PAN/2% ZnO mat revealed a faster response time of 93 s and a relatively short recovery of 54 s with a ${\Delta}R$ of 0.031 M${\Omega}$ at a $CO_2$ concentration of 200 ppm. The difference in sensitivity was not observed significantly for the PAN/MO fiber mats in the $CO_2$ concentration range of 100 to 500 ppm. It can be concluded that an appropriate amount of MO nanoparticles in the PAN backbone leads to improvement of the $CO_2$ gas sensing properties.

• 공업화학
• /
• 제27권3호
• /
• pp.307-312
• /
• 2016

$PbMoO_4$를 계면활성제를 이용하여 수열합성법으로 합성하였고, XRD, Raman, TEM, PL, BET 및 DRS 등에 의해 특성 분석을 하였다. 이들을 사용하여 자외선 조사 하에서 Rhodamine B의 광분해 반응에서의 활성을 조사하였다. XRD 및 Raman의 분석 결과로부터 계면활성제를 이용한 손쉬운 수열합성에 의해 잘 결정화된 $PbMoO_4$ 구조를 가진 촉매들이 합성되었으며 52에서 69 nm의 크기를 나타내었다. cetyltrimethylammonium bromide (CTAB)를 계면활성제로 사용하여 합성된 $PbMoO_4$는 P-25와 순수한 $PbMoO_4$ 보다 높은 광촉매 활성을 나타내었다. pH 9에서 합성된 $PbMoO_4$ 촉매가 가장 높은 활성을 나타내었다. 모든 촉매들은 540 nm 부근에서 강하고 넓은 PL 흡수밴드가 나타났으며, 이 피크의 세기가 커질수록 Rhodamine B의 광분해 활성이 증가하는 것으로 나타났다.

• 공업화학
• /
• 제21권4호
• /
• pp.435-439
• /
• 2010

Pt-$MoO_3$ 혼합전극을 20 mM의 $H_2PtCl_6$ 수용액과 10 mM Mo-Peroxo 전해질을 이용하여 전기화학적 증착법에 의해 합성하였다. Pt와 증착 순서를 바꿔가며 혼합 전극을 합성하여 같은 양의 Pt가 증착된 순수한 Pt전극과 메탄올 산화반응 특성을 비교하였다. SEM (Scanning Electron Microscopy) 분석을 통하여 합성된 박막의 표면입자의 형태를 확인하였으며, X-선 회절(X-ray Diffraction)분석과 광전자 분광기(X-ray Photoelectron Spectroscopy; Thermo-scientific, ESCA 2000)분석을 통해 합성된 전극의 결정성과 산화가를 각각 조사하였다. 메탄올 산화에 대한 전기화학적 촉매활성과 안정성을 평가한 결과 Pt를 증착한 후 $MoO_3$를 증착한 전극의 경우, 순수한 Pt전극에 비해 높은 촉매활성과 안정성을 나타내었는데, Pt와 $MoO_3$의 접촉이 좋을 경우 $MoO_3$가 조촉매로 작용해 메탄올 산화반응의 활성이 증가함을 확인하였다.

• Bulletin of the Korean Chemical Society
• /
• 제15권9호
• /
• pp.766-771
• /
• 1994

A number of molybdenum(VI), -(V), and -(IV) oxo complexes with S-methyl 3-(2-hydroxyphenyl)methylenedithiocarbazate and its derivatives as the ONS-donor metal-binding substrate are synthesized. The Mo(VI)-dioxo complexes are cis-dioxo Mo$O_2$L(D), where D is solvent molecules such as MeOH, DMF, Py(pyridine), DMSO, and ${\gamma}$-Pic(${\gamma}$-picoline). The Mo(V)-oxo complexes are of the type (PyH)[MoO(NCS$)_2$L] with an octahedral geometry. The Mo(IV)-oxo complexes, MoOL are derived from corresponding Mo(VI)-dioxo complexes by oxo abstraction with PP$h_3$. The complexes are characterized by IR, $^1$H-NMR, UV-Vis spectroscopy and cyclic voltammetry. On the basis of ligand displacement reaction, the qualitative order of D binding for Mo$O_2$L(D) complexes is also discussed.

• Advances in materials Research
• /
• 제1권3호
• /
• pp.191-204
• /
• 2012

In this paper, we report on the obtention of nanocrystalline $SrMoO_4$ synthesized through modified combustion process. These powders were characterized by X-ray diffraction, Fourier Transform Raman and Infrared Spectroscopy. These studies reveal that the scheelite-type $SrMoO_4$ crystallizes in tetragonal structure with I41/${\alpha}$ (N#88) space group. Transmission electron microscopy image shows that the nanocrystalline $SrMoO_4$ powders have average size of 18 nm. The optical band gap determined from the UV-V is absorption spectra for the as prepared sample is 3.7 eV. These powders showed a strong green photoluminescence emission. The samples are sintered at a relatively low temperature of $850^{\circ}C$. The morphology of the sintered pellet is studied with scanning electron microscopy. The dielectric constant and loss factor values obtained at 5 MHz for a well sintered $SrMoO_4$ pellet has been found to be 9.50 and $7.5{\times}10^{-3}$ respectively. Thus nano $SrMoO_4$ is a potential candidate for low temperature co-fired ceramics and luminescent applications.

• 센서학회지
• /
• 제8권1호
• /
• pp.24-31
• /
• 1999

감도가 우수하고 동작온도가 낮으며 반응속도가 빠른 암모니아 가스 센서를 제작하기 위해 ZnO에 촉매불순물 $MoO_3$의 첨가비와 박막 성장분위기 가스를 변화시키면서 RF 마그네트론 스펏터링 방법으로 박막을 성장하였다. 전기적 안정성을 향상시키기 위해 성장된 박막들을 aging 하여 센서를 제작한 후 암모니아 가스의 검지 특성을 조사하였다. 촉매불순물을 첨가하거나 산소분위기에서 성장된 박막의 경우 감도가 향상되었으며, 이는 표면 캐리어 농도와 전자이동도의 증가를 나타냈다. ZnO에 $MoO_3$를 무게비로 0.875 wt.% 첨가한 박막으로 제작한 센서가 160 ppm의 암모니아 가스 농도와 $300^{\circ}C$의 동작온도에서 70정도의 최대감도를 보였다. 산소분위기에서 $330^{\circ}C$로 72시간 동안 aging한 박막으로 만든 센서는 감도가 57정도로 감소하였으나, 센서의 동작온도가 $250^{\circ}C$로 낮아졌고, 선형성이 좋았으며 더 안정된 특성을 나타냈다.

• 대한화학회지
• /
• 제28권1호
• /
• pp.54-61
• /
• 1984

질산 산성에서 얻은 $MoO_4^{2-}$와 $WO_4^{2-}$의 용리곡선과 Z값에 따른 텅스텐의 UV스펙트럼 변화로부터 질산 농도 변화에 따른 이들 이온들의 화학종과 평형관계를 연구하였다. 물리브덴은 0.05M 이상의 질산 용액에서$Mo_8O_{26}^{4-} + 20H^+$ ${\rightleftharpoons}$ $8MoO_2^{2+}$ + $10H_2O$반응에 의해 $MoO_2^{2+}$이온을 생성하여 이 이온이$MoO_2(NO_3)_2$와 같은 질산착물을 생성하는 것으로 보인다. 질산 산성에서 텅스텐산의 용리현상은 과염소산에서와 유사하다. 그래서 과염소산에서 존재하는 텅스텐의 평형관계가 질산 산성에서도 존재한다고 생각된다. 이들 텅스텐의 용리현상 결과를 Z값에 따른 텅스텐의 UV스펙트럼 변화와 비교하였다.

• Bulletin of the Korean Chemical Society
• /
• 제2권2호
• /
• pp.37-41
• /
• 1981

The elution behaviors of molybdate and tungstate through anion exchange column have been investigated in the various concentration of hydrochloric and perchloric acid. A discussion is made to evaluate the existing these equilibrium and constant according to acidity. In both acids of 0.01-2.0 M concentration range, the existing equilibrium for molybdate and its constant calculated at $20^{\circ}C$ is $10^{18.9}$ for $Mo_8O_2^{4-} + 20H^+ {\rightleftharpoons} 8MoO_2^{2+} + 10H_2O$. In the 3-3.5 M hydrochloric acid it is 0.16 for $MoO_2Cl_2 + Cl^- {\rightleftharpoons} MoO_2Cl^{3-}$ and for the case of tungstate, in the both acids of 0.01-1.0 M concentration range $10^{6.6}$ for $W_{12}O_{39}^{6-} + 6H^+ {\rightleftharpoons} 12WO_3{\cdot}3H_2O$. In higher concentration than 1.0 M both acids the following equilibrium seems to be existed. $12WO_3{\cdot}3H_2O {\rightleftharpoons} 12WO_3 + 3H_2O$