• Analytical Science and Technology
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• v.8 no.4
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• pp.643-648
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• 1995

Cyclic voltammetric method is used to survey microscopic environments which take place at the surfactant-modified carbon electrode when the hydrophobic and hydrophilic environments of $Ru(ph){_3}^{2+}$(tris 1,10-phenanthroline ruthenium(II) chloride) is created by the addition of anionic surfactant, sodium dodecyl sulfate(SDS). Critical micelle concentration(CMC) of SDS in $Ru(ph){_3}^{2+}$ measured by cyclic voltammetry(CV) is in aggrement with that by surface tensiometry. Influence of the concentration of supporting electrolyte at surfactant-modified carbon electrode is investigated.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.97-97
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• 2013

The exterior structures of natural organisms have continuously evolved by controlling wettability, such as the Namib Desert beetle, whose back has hydrophilic/hydrophobic contrast for water harvesting by mist condensation in dry desert environments, and some plant leaves that have hierarchical micro/nanostructures to collect or repel liquid water. In this work, we have provided a method for wettability contrast on metals by both nano-flake or needle patterns and tuning of the surface energy. Metals including steel alloys and aluminum were provided with hierarchical micro/nanostructures of metaloxides induced by fluorination and a subsequent catalytic reaction of fluorine ions on metal surfaces in water with various ranges from room to boiling temperature of water. Then, a hydrophobic material was deposited on the structured surfaces, rendering superhydrophobicity. Plasma oxidization induces the formation of superhydrophilic surfaces on selective regions surrounded by superhydrophobic surfaces. We show that wettability contrast surfaces align liquid water within patterned hydrophilic regions during the condensation process. Furthermore, this method could have a greater potential to align other liquids or living cells.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.122-122
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• 2012

The exterior structures of natural organisms have continuously evolved by controlling wettability, such as the Namib Desert beetle, whose back has hydrophilic/hydrophobic contrast for water harvesting by mist condensation in dry desert environments, and some plant leaves that have hierarchical micro/nanostructures to collect or repel liquid water. In this work, we have provided a method for wettability contrast on metals by both nano-flake or needle patterns and tuning of the surface energy. Metals including steel alloys and aluminum were provided with hierarchical micro/nanostructures of metaloxides induced by fluorination and a subsequent catalytic reaction of fluorine ions on metal surfaces in water with various ranges from room to boiling temperature of water. Then, a hydrophobic material was deposited on the structured surfaces, rendering superhydrophobicity. Plasma oxidization induces the formation of superhydrophilic surfaces on selective regions surrounded by superhydrophobic surfaces. We show that wettability contrast surfaces align liquid water within patterned hydrophilic regions during the condensation process. Furthermore, this method could have a greater potential to align other liquids or living cells.

• Journal of the Korean institute of surface engineering
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• v.54 no.5
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• pp.222-229
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• 2021

Icing causes various serious problems, where water vapor or water droplets adhere at cold conditions. Therefore, understanding of ice adhesion on solid surface and technology to reduce de-icing force are essential for surface finishing of metallic materials used in extreme environments and aircrafts. In this study, we controlled wettability of aluminum alloy using anodic oxidation, hydrophobic coating and lubricant-impregnation. In addition, surface porosity of anodized oxide layer was controlled to realize superhydrophilicity and superhydrophobicity. Then, de-icing force on these surfaces with a wide range of wettability and mobility of water was measured. The results show that the enhanced wettability of hydrophilic surface causes strong adhesion of ice. The hydrophobic coating on the nanoporous anodic oxide layer reduces the adhesion of ice, but the volume expansion of water during the freezing diminishes the effect. The lubricant-impregnated surface shows an extremely low adhesion of ice, since the lubricant inhibits the direct contact between ice and solid surface.

• Journal of Integrative Natural Science
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• v.7 no.2
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• pp.120-123
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• 2014

When a hydrophobic and hydrophilic environments of bis(2,2'-bipyridyl) copper(II) ($Cu(bpy)_2{^{2+}}$) are produced in the presence of anionic surfactant sodium dodecyl sulfate (SDS), cyclic voltammetry is used to investigate the microscopic environments which occurs at the glassy carbon electrode. In order to see the relation between ${\Delta}E_p$ and a critical micelle concentration (CMC), ${\Delta}E_p$ vs. -Log[SDS] for the redox couples are plotted. The concentration at the intersection of two lines is 2.57 mM SDS, and this concentration can be determined as the CMC (relative error: below 0.03%; 2.63 mM SDS by surface tensiometry).

• Advances in materials Research
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• v.1 no.4
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• pp.269-284
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• 2012

Thermoresponsive hydrogels based on N-Isopropylacrylamide (NIPAM) and 2-Hydroxyethylacrylate (HEA) were prepared by free radical polymerization. The hydrogels were characterized by elemental (CHN) analysis, differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA). DSC thermogram showed two endothermic transitions which are due to hydration of water present in different environments. One near $0^{\circ}C$ called melting transition of ice and was used to calculate the quantitative determination of the amounts of freezing and non freezing water. The other transition above the ambient temperature was due to the combination of hydrophobic hydration and hydrophilic hydration which changes with the copolymer compositions. Swelling and deswelling studies of the hydrogels were carried out using the aqueous media, salt and urea solutions. The experimental results from swelling studies revealed that copolymers have lower rates of swelling and deswelling than the homopolymer.

• Bulletin of the Korean Chemical Society
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• v.30 no.11
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• pp.2589-2594
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• 2009

Aging phenomena of plasma polymer films were studied by using the surface analysis techniques of contact angle measurement, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOFSIMS), and atomic force microscopy (AFM). The polymer films were grown on an aluminum substrate by using a plasma polymerization method from a gas mixture of acetylene and helium, and the films were subsequently modified to have a hydrophilic surface by oxygen plasma treatment. Aging of the polymer films was examined by exposing the samples to water and air environments. The aging process increased the hydrophobicity of the surface, as revealed by an increase in the advancing contact angle of water. XPS analysis showed that the population of oxygen-containing polar groups increased due to the uptake of oxygen during the aging, whereas TOF-SIMS analysis revealed a decrease in the polar group population in the uppermost surface layer. The results suggest that the change in surface property from hydrophilic to hydrophobic nature results from the restructuring of polymer chains near the surface, rather than compositional change of the surface. Oxidative degradation may enhance the mobility and the restructuring process of polymer chains.

• Nuclear Engineering and Technology
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• v.38 no.3
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• pp.201-210
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• 2006

This article presents a brief overview of an important area of neutron scattering: the general principles and techniques of elastic, quasielastic and inelastic scattering from a system composed predominately of incoherent scatterers. The methodology is then applied to the study of water, specifically when it is confined in nanometer-scale environments. The confined water exhibits uniquely anomalous properties in the supercooled state. It also nourishes biological functions, and supports essential chemical reactions in living systems. We focus on recent investigations of water encapsulated in nanoporous silica and carbon nanotubes, hydrated water in proteins and water or hydroxyl species incorporated in nanostructured minerals. Through these scientific examples, we demonstrate the advantages derived from the high sensitivity of incoherent neutron spectroscopy to hydrogen atom motions and hydrogen-bond dynamics, aided by rigorous data interpretation method using molecular dynamics simulations or theoretical modelling. This enables us to probe the inter-/intramolecular vibrations and relaxation/diffusion processes of water molecules in a complex environment.

• Applied Chemistry for Engineering
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• v.28 no.1
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• pp.1-7
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• 2017

Polydimethylsiloxane (PDMS) can be deposited on various substrates using chemical vapor deposition process, which results in the formation of PDMS thin films with thickness below 5 nm. PDMS layers can be evenly deposited on surfaces of nanoparticles composed of various chemical compositions such as $SiO_2$, $TiO_2$, ZnO, C, Ni, and NiO, and the PDMS-coated surface becomes completely hydrophobic. These hydrophobic layers are highly resistant towards degradation under acidic and basic environments and UV-exposures. Nanoparticles coated with PDMS can be used in various environmental applications: hydrophobic silica nanoparticles can selectively interact with oil from oil/water mixture, suppressing fast diffusion of spill-oil on water and allowing more facile physical separation of spill-oil from the water. Upon heat-treatments of PDMS-coated $TiO_2$ under vacuum conditions, $TiO_2$ surface becomes completely hydrophilic, accompanying formation oxygen vacancies responsible for visible-light absorption. The post-annealed $PDMS-TiO_2$ shows enhanced photocatalytic activity with respect to the bare $TiO_2$ for decomposition of organic dyes in water under visible light illumination. We show that the simple PDMS-coating process presented here can be useful in a variety of field of environmental science and technology.