• Title/Summary/Keyword: Colloids

Search Result 146, Processing Time 0.128 seconds

Experimental Study on Uranium Sorption onto Silica Colloids: Effects of Geochemical Parameters

  • Baik, Min-Hoon;Hahn, Pil-Soo
    • Nuclear Engineering and Technology
    • /
    • v.33 no.3
    • /
    • pp.261-269
    • /
    • 2001
  • In this study, sorption experiments of uranium onto silica colloids were carried out and the effects of important geochemical parameters such as pH, ionic strength, carbonate concentration, colloid concentration, and total concentration of uranium were investigated. The sorption coefficients of uranium for silica colloids named as pseudo-colloid formation constants were about 10$^4$~ 10$^{5}$ mL/g depending on the experimental conditions. The effects of the geochemical parameters were found to be important in the sorption of uranium onto silica colloids. A Langmuir type sorption isotherm of uranium between silica colloids and the solution phase was also presented. The sorption mechanisms were explained by analyzing the effects of the geochemical parameters.

  • PDF

The Effect of pH-adjusted Gold Colloids on the Formation of Gold Clusters over APTMS-coated Silica Cores

  • Park, Sang-Eun;Park, Min-Yim;Han, Po-Keun;Lee, Sang-Wha
    • Bulletin of the Korean Chemical Society
    • /
    • v.27 no.9
    • /
    • pp.1341-1345
    • /
    • 2006
  • An electrostatic interaction is responsible for the attachment of gold seeds of 1-3 nm onto APTMS (3-aminopropyl trimethoxysilane)-coated silica cores in the formation of gold clusters. A surface plasmon resonance and morphology of gold clusters were significantly affected by the pH of gold colloids prepared by THPC reducing agent. Gold colloids of alkaline pH induced the heterogeneous deposition of gold seeds onto the silica nanoparticles, probably due to the continuous reduction of residual gold ions during the attachment process. Gold colloids of acidic pH induced the monodisperse deposition of gold seeds, consequently leading to the formation of smooth gold layer on the silica nanoparticles surface. The gold nanoshells (core radius = 80 nm) prepared by gold colloids of pH 3.1 exhibited the more red-shift and relatively stronger intensity of plasmon absorption bands, compared with gold nanoshells prepared by alkaline gold colloids of pH 9.7.

Production of Functional Colloids and Fibers from Phase Separation During Electrohydrodynamic Process

  • Jeong, Un-Ryong
    • Proceedings of the Materials Research Society of Korea Conference
    • /
    • 2011.10a
    • /
    • pp.1.2-1.2
    • /
    • 2011
  • Electrohydrodynamics is a good approach to produce uniform-sized colloids and fibers in a continuous process. The dimension can be controlled from tens of nanometers to a few micrometers. The structure of the colloids and nanofibers from electrohydrodynamics has been diversified according to the uses. Especially, core-shell structure and hybridization with functional nanomaterials are fascinating due to their possible uses in drug-delivery systems, multifunctional scaffolds, organic/inorganic hybrids with new functions, and highly sensitive gas- or bio-sensors. This talk will present the structural variations in the colloids and fibers by simply employing phase separation during electrohydrodynamic process and demonstrate their possible applications.

  • PDF

Formation of surface mediated iron colloids during U(VI) and nZVI interaction

  • Shin, Youngho;Bae, Sungjun;Lee, Woojin
    • Advances in environmental research
    • /
    • v.2 no.3
    • /
    • pp.167-177
    • /
    • 2013
  • We investigated that removal of aqueous U(VI) by nano-sized Zero Valent Iron (nZVI) and Fe(II) bearing minerals (controls) in this study. Iron particles showed different U(VI) removal efficiencies (Mackinawite: 99%, green rust: 95%, nZVI: 91%, magnetite: 87%, pyrite: 59%) due to their different PZC (Point of Zero Charge) values and surface areas. In addition, noticeable amount of surface Fe(II) (181 ${\mu}M$) was released from nZVI suspension in 6 h and it increased to 384 ${\mu}M$ in the presence of U(VI) due to ion-exchange of U(VI) with Fe(II) on nZVI surface. Analysis of Laser-Induced Breakdown Detection (LIBD) showed that breakdown probabilities in both filtrates by 20 and 200 nm sizes was almost 24% in nZVI suspension with U(VI), while 1% of the probabilities were observed in nZVI suspension without U(VI). It indicated that Fe(II) colloids in the range under 20 nm were generated during the interaction of U(VI) and nZVI. Our results suggest that Fe(II) colloids generated via ion-exchange process should be carefully concerned during long-term remediation site contaminated by U(VI) because U could be transported to remote area through the adsorption on Fe(II) colloids.

Surface-functionalized Hexagonal Mesoporous Silica Supported 5-(4-Carboxyphenyl)-10,15,20-triphenyl Porphyrin Manganese(III) Chloride and Their Catalytic Activity

  • Zhang, Wei-Jie;Jiang, Ping-Ping;Zhang, Ping-Bo;Zheng, Jia-Wei;Li, Haiyang
    • Bulletin of the Korean Chemical Society
    • /
    • v.33 no.12
    • /
    • pp.4015-4022
    • /
    • 2012
  • Manganese(III) 5-(4-carboxyphenyl)-10,15,20-triphenyl porphyrin chloride (Mn(TCPP)Cl) was grafted through amide bond on silica zeolite Y (HY), zeolite beta ($H{\beta}$) and hexagonal mesoporous silica (HMS). XRD, ICP-AES, $N_2$ physisorption, SEM, TEM, FTIR and thermal analysis were employed to analyse these novel heterogeneous materials. These silica supported catalysts were shown to be used for epoxidation and good shape selectivity was observed. The effect of support structure on catalytic performance was also discussed. The catalytic activity remained when the catalysts were recycled five times. The energy changes about epoxidation of alkenes by $NaIO_4$ and $H_2O_2$ were also computationally calculated to explain the different catalytic efficiency.

Peroxopolyoxotungsten-based Ionic Hybrid as a Highly Efficient Recyclable Catalyst for Epoxidation of Vegetable oil with H2O2

  • Wu, Jianghao;Jiang, Pingping;Qin, Xiaojie;Ye, Yuanyuan;Leng, Yan
    • Bulletin of the Korean Chemical Society
    • /
    • v.35 no.6
    • /
    • pp.1675-1680
    • /
    • 2014
  • A peroxopolyoxotungsten-based ionic hybrid was synthesized by anion-change of peroxopolyoxometalate (POM) $PW_4O{_{24}}^{3-}$ with dicationic long-chain alkyl imidazolium ionic liquids. The characterization was conducted by FT-IR, TGA, $^1H$-NMR and CHN Elemental analyses. Its catalytic performance was evaluated by the epoxidation of soybean oil with $H_2O_2$ under solvent-free condition, including testing of organic cations influence, catalytic reusability and reaction conditions. The catalyst was proved to be a highly efficient recyclable catalyst for epoxidation of various vegetable oils with $H_2O_2$, showing high $H_2O_2$ utilization efficiency, high catalytic activity, convenient recovery and good reuse ability.

The Fluorescence Study on the Inducing Orientation of 4-Biphenyl Acetonitrile Adsorbed on Metal Colloids (금속콜로이드 표면에 흡착된 4-Biphenyl Acetonitrile의 흡착배향 유도에 관한 형광 연구)

  • Song, Won-Sik;Lee, Jun-Kyeng;Yu, Soo-Chang
    • Journal of the Korean Chemical Society
    • /
    • v.53 no.4
    • /
    • pp.399-406
    • /
    • 2009
  • The fluorescence study was performed to see whether the adsorption orientation of 4-biphenyl acetonitrile(BPAN) on metal colloids can be changed by forming an inclusion complex with $\alpha$-cyclodextrin($\alpha$-CD). The fluorescence quenching was observed with increasing temperature to confirm the direct adsorption of BPAN to the Au and Ag colloidal surfaces. BPAN adsorbed on the metal colloids formed inclusion complex with $\alpha$-CD regardless of the kinds of metal colloids. The formation constants, 32 $M^{-1}$ and 13 $M^{-1}$ for Au and Ag colloids respectively, were obtained with Benesi-Hildebrand plot. The molecules adsorbed on both the Au and Ag colloidal surfaces behaved similarly to each other, leading to the conclusion that the orientation of BPAN adsorbed on the metal colloids can be modified with $\alpha$-CD.

Preparation of Ag, Pd, and Pt50-Ru50 colloids prepared by γ-irradiation and electron beam and electrochemical immobilization on gold surface

  • Kim, Kyung-Hee;Seo, Kang-Deuk;Oh, Seong-Dae;Choi, Seong-Ho;Oh, Sang-Hyub;Woo, Jin-Chun;Gopalan, A.;Lee, Kwang-Pill
    • Analytical Science and Technology
    • /
    • v.19 no.4
    • /
    • pp.333-341
    • /
    • 2006
  • PVP-protected Ag, Pd and $Pt_{50}-Ru_{50}$ colloids were prepared independently by using ${\gamma}$-irradiation and electron beam (EB) at ambient temperature. UV-visible spectra of these colloids show the characteristic bands of surface resonance and give evidence for the formation of nanoparticles. Transmission electron microscopy (TEM) experiments were used to know the morphology of nanoparticles prepared by ${\gamma}$-irradiation and EB. The size of Ag, Pd, and $Pt_{50}-Ru_{50}$ nanoparticles prepared by ${\gamma}$-irradiation was ca. 13, 2-3, 15 nm, respectively. While, the size of Ag, Pd, and $Pt_{50}-Ru_{50}$ nanoparticles prepared by EB was ca. 10, 6, and 1-3 nm, respectively. Cyclic voltamograms (CV) were recorded for the Au electrodes immobilized with these nanoparticles. CVs indicated the modifications in the surface as a result of immobilization.

Synergistic Effect of Copper and Cobalt in Cu-Co-O Composite Nanocatalyst for Catalytic Ozonation

  • Dong, Yuming;Wu, Lina;Wang, Guangli;Zhao, Hui;Jiang, Pingping;Feng, Cuiyun
    • Bulletin of the Korean Chemical Society
    • /
    • v.34 no.11
    • /
    • pp.3227-3232
    • /
    • 2013
  • A novel Cu-Co-O composite nanocatalyst was designed and prepared for the ozonation of phenol. A synergistic effect of copper and cobalt was observed over the Cu-Co-O composite nanocatalyst, which showed higher activity than either copper or cobalt oxide alone. In addition, the Cu-Co-O composite revealed good activity in a wide initial pH range (4.11-8.05) of water. The fine dispersion of cobalt on the surface of copper oxide boosted the interaction between catalyst and ozone, and the surface Lewis acid sites on the Cu-Co-O composite were determined as the active sites. The Raman spectroscopy also proved that the Cu-Co-O composite was quite sensitive to the ozone. The trivalent cobalt in the Cu-Co-O composite was proposed as the valid state.

A Study on the Seed Step-coverage Enhancement Process (SSEP) of High Aspect Ratio Through Silicon Via (TSV) Using Pd/Cu/PVP Colloids (Pd/Cu/PVP 콜로이드를 이용한 고종횡비 실리콘 관통전극 내 구리씨앗층의 단차피복도 개선에 관한 연구)

  • Lee, Dongryul;Lee, Yugin;Kim, Hyung-Jong;Lee, Min Hyung
    • Journal of the Korean institute of surface engineering
    • /
    • v.47 no.2
    • /
    • pp.68-74
    • /
    • 2014
  • The seed step-coverage enhancement process (SSEP) using Pd/Cu/PVP colloids was investigated for the filling of through silicon via (TSV) without void. TEM analysis showed that the Pd/Cu nano-particles were well dispersed in aqueous solution with the average diameter of 6.18 nm. This Pd/Cu nano-particles were uniformly deposited on the substrate of Si/$SiO_2$/Ti wafer using electrophoresis with the high frequency Alternating Current (AC). After electroless Cu deposition on the substrate treated with Pd/Cu/PVP colloids, the adhesive property between deposited Cu layer and substrate was evaluated. The Cu deposit obtained by SSEP with Pd/Cu/PVP colloids showed superior adhesion property to that on Pd ion catalyst-treated substrate. Finally, by implementing the SSEP using Pd/Cu/PVP colloids, we achieved 700% improvement of step coverage of Cu seed layer compared to PVD process, resulting in void-free filling in high aspect ratio TSV.