Multifunctional Colloids with Reversible Phase Transfer between Organic and Aqueous Media via Layer-by-Layer Assembly

Yoon, Miseon,Choi, Jungkyu,Cho, Jinhan American Chemical Society 2013 Chemistry of materials Vol.25 No.9

<P>We report the successful multifunctional colloids that enable reversible phase transfer between organic and aqueous phases via layer-by-layer (LbL) assembly. These colloids exhibited a high level of dispersion stability in a variety of solvents ranging from nonpolar to aqueous media, based on the type of outermost layer adsorbed onto the colloids. Hydrophobic nanoparticles (NPs) synthesized using carboxylic acid or ammonium moiety-based ligands (i.e., oleic acid or tetraoctylammonium) in a nonpolar solvent (toluene, hexane, or chloroform) were directly deposited onto dendrimer-coated SiO<SUB>2</SUB> colloids via ligand exchange between the hydrophobic ligands and the amine-functionalized dendrimers in the same organic solvent. Additionally, these hydrophobic NPs were adsorbed onto the colloids forming the densely packed layer structure that could not be easily achieved by conventional electrostatic LbL assembly. The subsequent adsorption of amine-functionalized dendrimers onto hydrophobic NP-coated colloids led to well-dispersed colloids in aqueous media as well as alcohol solvent and possibly induced the deposition of electrostatic LbL-assembled films, such as (cationic Au<SUB>NP</SUB>/anionic polyelectrolyte (PE))<SUB><I>n</I></SUB> or (cationic PE/anionic enzyme)<SUB><I>n</I></SUB> multilayers. Furthermore, the additional deposition of ligand exchange-induced multilayers (i.e., (dendrimer/hydrophobic NP)<SUB><I>n</I></SUB>) onto electrostatic multilayer-coated colloids produced colloids with highly dispersible properties in organic media. Given that previous approaches to the reversible phase transfer of colloids have depended on the physicochemical properties of selective ligands under limited and specific conditions, our approach may provide a basis for the design and exploitation of high-performance colloids with tailored functionality in a variety of solvents.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2013/cmatex.2013.25.issue-9/cm400207d/production/images/medium/cm-2013-00207d_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm400207d'>ACS Electronic Supporting Info</A></P>

Colloidal Optics and Photonics: Photonic Crystals, Plasmonics, and Metamaterials

이재원,이승우 한국광학회 2023 Current Optics and Photonics Vol.7 No.6

The initial motivation in colloid science and engineering was driven by the fact that colloids can serve as excellent models to study atomic and molecular behavior at the mesoscale or microscale. The thermal behaviors of actual atoms and molecules are similar to those of colloids at the mesoscale or microscale, with the primary distinction being the slower dynamics of the latter. While atoms and molecules are challenging to observe directly in situ, colloidal motions can be easily monitored in situ using simple and versatile optical microscopic imaging. This foundational approach in colloid research persisted until the 1980s, and began to be extensively implemented in optics and photonics research in the 1990s. This shift in research direction was brought by an interplay of several factors. In 1987, Yablonovitch and John modernized the concept of photonic crystals (initially conceptualized by Lord Rayleigh in 1887). Around this time, mesoscale dielectric colloids, which were predominantly in a suspended state, began to be self-assembled into three-dimensional (3D) crystals. For photonic crystals operating at optical frequencies (visible to near-infrared), mesoscale crystal units are needed. At that time no manufacturing process could achieve this, except through colloidal self-assembly. This convergence of the thirst for advances in optics and photonics and the interest in the expanding field of colloids led to a significant shift in the research paradigm of colloids. Initially limited to polymers and ceramics, colloidal elements subsequently expanded to include semiconductors, metals, and DNA after the year 2000. As a result, the application of colloids extended beyond dielectric-based photonic crystals to encompass plasmonics, metamaterials, and metasurfaces, shaping the present field of colloidal optics and photonics. In this review we aim to introduce the research trajectory of colloidal optics and photonics over the past three decades; To elucidate the utility of colloids in photonic crystals, plasmonics, and metamaterials; And to present the challenges that must be overcome and potential research prospects for the future.

혈량증량제: 교질용액의 종류와 특성

이재진,김재환 대한의사협회 2013 대한의사협회지 Vol.56 No.10

Fluid therapy remains an important therapeutic maneuver in managing surgical, medical, and the critically ill intensive care patient. However, the ideal volume replacement strategy remains under debate. The debate on whether patients should be managed with crystalloids, colloids, or both has for many years been mainly a debate about effectiveness. The dispute over crystalloids versus colloids has been enlarged to a colloid versus colloid debate because of the varying properties of different colloids. The natural colloid albumin and artificial colloids such as gelatin, dextran, and hydroxyethyl starch continue to enjoy widespread usage for clinical fluid management. Colloid is an effective plasma volume expander and is able to restore the hemodynamic profile with less total volume than crystalloid. However, colloid is associated with coagulation abnormalities, renal impairment, and allergic reactions. Albumin is considered to be one of the safe colloids. However, due to its cost, albumin cannot be recommended for hypovolemia. Gelatin and dextran can also cause coagulation abnormalities and renal impairment. Dextran is not used anymore due to its high anaphylactic potency. Each hydroxyethyl starch has different properties by concentration, mean molecular weight, molar substitution, and its C2/C6 ratio. New hydroxyethyl starches with a lower mean molecular weight and molar substitution than the old hydroxyethyl starch may be promising by improving volume management therapy with lower risks of coagulation abnormalities and renal impairment. The selection of colloid for plasma volume expansion should be based on the patients’ clinical conditions and the characteristics of each colloid.

Superparamagnetic Colloids: Controlled Synthesis and Niche Applications

Jeong, U.,Teng, X.,Wang, Y.,Yang, H.,Xia, Y. WILEY-VCH Verlag 2007 Advanced Materials Vol.19 No.1

<P>The aim of this article is to provide a comprehensive review of current research activities that center on superparamagnetic colloids. We begin with an overview of synthetic strategies that have been developed for generating both nanoscale and mesoscale superparamagnetic colloids, with a focus on those systems that can be prepared as monodisperse samples and in relatively large quantities. We then discuss a variety of techniques that have been exploited for modifying surface properties, as well as for controlling the assembly and patterning of these magnetically active colloids. Towards the end, we highlight a range of innovative applications enabled by the unique combination of superparamagnetism and colloidal suspension. We conclude this review article with personal remarks and perspectives on the directions toward which future research in this area might be directed.</P> <B>Graphic Abstract</B> <P>Current research activities on superparamagnetic colloids (see figure) are comprehensively reviewed. In this review, three broad aspects are discussed: synthetic strategies for generating superparamagnetic colloids; techniques for modifying their surface property, as well as for controlling the assembly and patterning; and associated innovative applications. <img src='wiley_img/09359648-2007-19-1-ADMA200600674-content.gif' alt='wiley_img/09359648-2007-19-1-ADMA200600674-content'> </P>

Solvent-Free Nanocomposite Colloidal Fluids with Highly Integrated and Tailored Functionalities: Rheological, Ionic Conduction, and Magneto-Optical Properties

Kim, Donghee,Kim, Younghoon,Cho, Jinhan American Chemical Society 2013 Chemistry of materials Vol.25 No.19

<P>We introduce a unique and facile strategy for the preparation of solvent-free nanocomposite colloidal fluids that allows accurate control over the integration of functionalities as well as the composition and dimensions of the nanocomposite structure. For the preparation of colloidal fluids with highly integrated functionalities, oleic acid (OA)-stabilized magnetic nanoparticles (i.e., OA-Fe<SUB>3</SUB>O<SUB>4</SUB> NPs) and CdSe@ZnS quantum dots (QDs) were first synthesized in nonpolar solvent. In this case, OA-QDs dispersed in toluene were successively phase transferred to thiol-functionalized imidazolium-type ionic liquid (IL-SH) media with rheological and ionic conduction properties. After the functional NPs were synthesized, amine-functionalized dendrimers and OA-Fe<SUB>3</SUB>O<SUB>4</SUB> NPs were alternately deposited onto silica colloids (i.e., SiO<SUB>2</SUB>/(dendrimer/OA-Fe<SUB>3</SUB>O<SUB>4</SUB>)<I><SUB>n</SUB></I>) using a ligand-exchange-induced LbL-assembly in organic media. Electrostatic LbL-assembled (anionic polyelectrolyte (PE)/cationic IL-SH-QD)<I><SUB>n</SUB></I> multilayers were then sequentially adsorbed onto the outermost dendrimer layer of the magnetic colloids. The resulting functional colloidal fluids were devoid of colloidal aggregation and exhibited strong superparamagnetic, fluorescent, rheological, and ionic conduction properties at room temperature. Furthermore, mixtures of photoluminescent colloidal fluids with and without OA-Fe<SUB>3</SUB>O<SUB>4</SUB> NPs behaved effectively as magneto-optically separable colloidal fluids. Because a variety of inorganic NPs ranging from metal to transition-metal oxides can be easily incorporated into colloidal substrates via LbL-assembly, our approach provides a basis for exploiting and designing functional colloidal fluids with liquidlike behavior at room temperature.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2013/cmatex.2013.25.issue-19/cm401560r/production/images/medium/cm-2013-01560r_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm401560r'>ACS Electronic Supporting Info</A></P>

Multifaceted and Nanobored Particle Arrays Sculpted Using Colloidal Lithography

Choi, D.-G.,Jang, S. G.,Kim, S.,Lee, E.,Han, C.-S.,Yang, S.-M. WILEY-VCH Verlag 2006 Advanced Functional Materials Vol.16 No.1

<P>A novel method of fabricating multifaceted and nanobored particle arrays via colloidal lithography using colloidal-crystal layers as masks for anisotropic reactive-ion etching (RIE) is reported. The shape of the sculpted particles is dependent on the crystal orientation relative to the etchant flow, the number of colloidal layers, the RIE conditions, and the matrix (or mask) structure in colloidal lithography. Arrays of non-spherical particles with sculpted shapes, which to date could not otherwise be produced, are fabricated using a tilted anisotropic RIE process and the layer-by-layer growth of a colloidal mask. These non-spherical particles and their ordered arrays can be used for antireflection surfaces, biosensors, and nanopatterning masks, as well as non-spherical building blocks for novel colloidal crystals. In addition, polymeric particles with patterned holes of controlled depths obtained by the present method can be applied to the fabrication of functional composite particles.</P> <B>Graphic Abstract</B> <P>A novel method of colloidal lithography using anisotropic reactive-ion etching (RIE) is reported. Arrays of non-spherical particles with sculpted shapes (see Figure), which to date could not otherwise be produced, are fabricated using a tilted RIE process and the layer-by-layer growth of a colloidal mask. <img src='wiley_img/1616301X-2006-16-1-ADFM200500365-content.gif' alt='wiley_img/1616301X-2006-16-1-ADFM200500365-content'> </P>

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

Baik, Min-Hoon,Hahn, Pil-Soo Korean Nuclear Society 2001 Nuclear Engineering and Technology Vol.33 No.3

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.

Preparation of ZnO Thin Film by Electrophoretic Deposition(EPD)

Jun, Byung-Sei The Korean Ceramic Society 2012 한국세라믹학회지 Vol.49 No.1

The electrophoretic deposition(EPD) of ZnO nano-sized colloids is investigated by changing the colloid number concentration, applied force, and deposition time. The change of the colloid size in a suspension was examined by the different colloid number concentrations (N = $3.98{\times}10^{15}$, N = $3.98{\times}10^{14}$, and N = $3.98{\times}10^{13}$) with an increase of the deposition time and applied forces. Deposition behavior was investigated by changing the applied fields (from DC 5 V to 50 V) and the deposition time (5 min to 25 min). The surface microstructures of the as-deposited films were investigated by SEM. The dried films were sintered from $850^{\circ}C$ to $1,050^{\circ}C$ for 2 h and then the microstructures were also explored by SEM. The agglomeration rate was enhanced by increasing the colloid number concentration of colloids. Colloid number concentration in a suspension must be rapidly decreased at higher values of the electric field. ZnO nano-sized colloids had the highest zeta potential value of over -28 mV in methanol. A homogeneous microstructure was obtained at colloid number concentration of N = $3.98{\times}10^{13}$, applied DC field of 5 V/cm and 15 min of deposition time at an electrode distance of 1.5 cm. Under these conditions, the deposited films were sintered at $850^{\circ}C$ and $1,050^{\circ}C$ for 2 h. The results show a typical pore-free surface morphology of a uniform thickness of 400 nm under these experimental conditions.

Preparation of ZnO Thin Film by Electrophoretic Deposition(EPD)

전병세 한국세라믹학회 2012 한국세라믹학회지 Vol.49 No.1

The electrophoretic deposition(EPD) of ZnO nano-sized colloids is investigated by changing the colloid number concentration, applied force, and deposition time. The change of the colloid size in a suspension was examined by the different colloid number concentrations (N = 3.98 × 1015, N = 3.98 × 1014, and N = 3.98 × 1013) with an increase of the deposition time and applied forces. Deposition behavior was investigated by changing the applied fields (from DC 5 V to 50 V) and the deposition time (5 min to 25 min). The surface microstructures of the as-deposited films were investigated by SEM. The dried films were sintered from 850oC to 1,050oC for 2 h and then the microstructures were also explored by SEM. The agglomeration rate was enhanced by increasing the colloid number concentration of colloids. Colloid number concentration in a suspension must be rapidly decreased at higher values of the electric field. ZnO nano-sized colloids had the highest zeta potential value of over -28 mV in methanol. A homogeneous microstructure was obtained at colloid number concentration of N = 3.98 × 1013, applied DC field of 5 V/cm and 15 min of deposition time at an electrode distance of 1.5 cm. Under these conditions, the deposited films were sintered at 850oC and 1,050oC for 2 h. The results show a typical pore-free surface morphology of a uniform thickness of 400 nm under these experimental conditions.

Sorptionof Eu(III) Th(IV) on Bentonite Colloids Considering Their Precipitation an Colloid Formation

Min-Hoon Baik,Jae-Kwang Lee,Seung-Yeop Lee,Seung-Soo Kim 한국방사성폐기물학회 2008 방사성폐기물학회지 Vol.6 No.2

본 연구에서는 국내산 경주벤토나이트를 이용하여 제조한 벤토나이트 콜로이드에 대한 산화환원 반응에 대체적으로 안정한 다가 핵종인 Eu(III)와 Th(IV)의 실험적 수착 연구를 수행하였다. 수착실험에 대한 공시험을 수행하여 반응용기 벽면에 의해, 침전에 의해, 콜로이드 형성에 의해 손실된 핵종들의 양을 평가하였다. 그리고 이러한 손실들을 반영한 Eu(III)와 Th(IV)의 벤토나이트 콜로이드에 대한 수착분배계수 값을 구하고 조사하였다. 세 종류의 손실양을 반영한 벤토나이트 콜로이드의 순수한 수착분배계수 값은 pH 변화에 따라 Eu(III)의 경우 정도의 값을 가지고, Th(IV)의 경우 정도의 값을 가지는 것으로 관측되었다. 특히 Eu(III)의 경우엔 pH 5 이상에서 침전의 영향이 크게 나타났고, Th(IV)의 경우엔 pH 3 이후에 콜로이드 형성과 침전의 영향이 크게 나타났다. 따라서 주어진 농도에서 콜로이드 형성 및 침전 영향이 커지는 pH 이후에는 Eu(III) 및 Th(IV)과 같은 다가 핵종들의 정확한 수착분배계수를 구하기 위해서는 이러한 침전 및 콜로이드 형성과 같은 영향이 반영되어야 할 것이다. In this study, a sorption experiment of multivalent nuclides such as Eu(III) and Th(IV) relatively stable for redox reactions was carried out for bentonite colloids which had been prepared from the domestic Gyeongju bentonite. The amounts of the nuclides lost by an attachment to bottle walls, by a precipitation, and by a colloid formation were estimated by performing blank tests for the sorption experiments. Sorption coefficients, , reflecting the mass losses were obtained and investigated for the sorption of Eu(III) and Th(IV) onto the bentonite colloids. The net sorption coefficients considering all the three mass losses were measured as about and for Eu(III) and Th(IV), respectively, depending on pH. In particular, a precipitation occurred mainly at a pH greater than 5 for Eu(III) and a precipitation and colloid formation significantly occurred at a pH greater than 3 for Th(IV). The precipitation and colloid formation of the multivalent nuclides of Eu(III) and Th(IV) therefore should be considered when are rightly obtained over the pH range where their precipitation and colloid formation become significant at a given concentration.