• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.268-274
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• 1999

The chitosan solution was prepared by dissolving chitosan into 2 wt % aqueous acetic acid solution and then chitosan beads were made by sol-gel method. The average molecular weight and the degree of deacetylation of the chitosan used here were determined to be $8.2{\times}10^5$ and 85%, respectively. chitosan beads were highly porous which was confirmed by SEM photography and BET. Adsorption equilibrium of $Cu^{2+}$ on porous chitosan beads could be represented by Sips equation. The diffusion of cupric ions in the chitosan beads could be explained by pore and surface diffusion mechanisms. Adsorption dynamics of $Cu^{2+}$ in fixed-bed could be simulated by linear driving force approximation (LDFA). It was proven that porous chitosan beads manufactured in this work are good adsorbents for the removal of $Cu^{2+}$.

• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.569-573
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• 1998

A water soluble polymer, polycondensate of 1-butylamine and epichlorohydrin (PBE), was synthesized by condensation of 1-butylamine and epichlorohydrin. The characteristics of PBE were determined by IR spectroscopy, low angle light scattering measurement, and $\zeta$ potential measurement. Its interactions with colloidal bentonite particles in aqueous medium were also studied. The results of the studies are as follows : PBE is a cationic polyelectrolyte carrying tertiary ammonium ions on its backbone. The average molecular weight of PBE is found to be about 1,600. The adsorption of PBE on the colloidal bentonite particles are well described with Langmuir adsorption isotherm. As the amounts of PBE adsorbed on the bentonite particles increase, the $\zeta$ potential of the particles changes its sign from negative to positive. This inversion of charge confirms that PBE is cationic in nature. The adsorption of PBE onto the bentonite particles was found to occur through cation exchange reaction. It has been shown that PBE has flocculation effects on the colloidal suspension of bentonite. It has also enhanced effects of filtrability on the digested sludge.

• Journal of Environmental Science International
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• v.30 no.1
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• pp.97-108
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• 2021

In the current study, MIL-101(Cr)-SO3H[HCl] as metal-organic frameworks (MOFs) was fabricated via a hydrothermal method. The physicochemical properties of the synthesized material were characterized using XRD, FT-IR, FE-SEM, TEM, and BET surface area analysis. The XRD diffraction pattern of the prepared MIL-101(Cr)-SO3H[HCl] was similar to previously reported patterns of MIL-101(Cr) type materials, indicating successful synthesis of MIL-101(Cr)-SO3H[HCl]. The FT-IR spectrum revealed the molecular structure and functional groups of the synthesized MIL-101(Cr)-SO3H[HCl]. FE-SEM and TEM images indicated the formation of rectangular parallelopiped structures in the prepared MIL-101(Cr)-SO3H[HCl]. Furthermore, the EDS spectrum showed that the synthesized material consisted of the elements of Cr, O, S, and C. The fabricated MIL-101(Cr)-SO3H[HCl] was then employed as an adsorbent for the removal of Sr2+ and Cs+ from aqueous solutions. The adsorption kinetics and adsorption isotherm models were studied in detail. The maximum adsorption capacities of MIL-101(Cr)-SO3H[HCl] for Sr2+ and Cs+ according to pH (3, 5.3~5.8, 10) were 35.05, 43.35, and 79.72 mg/g and 78.58, 74.58, and 169.74 mg/g, respectively. These results demonstrate the potential of the synthesized MOFs, which can be effectively applied as an adsorbent for the removal of Sr2+ and Cs+ ions from aqueous solutions and other diverse applications.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.2
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• pp.203-210
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• 2000

The preparative methods of a chitosan-deposited activated carbon and its characteristics were studied by using three kinds of chitosan with different degree of deacetylation and average molecular weight. The procedure was consisted of the dissolution of chitosan into acid solution, impregnation of activated carbon, agitation, evaporation, and drying. When the chitosan-dissolved acid and its concentration, amounts of chitosan deposited, and agitation conditions were changed, the specific surface area, deposition state on surface, and stability were investigated, and amounts of Cr(VI) adsorbed was measured. In the preparation process, it was proper to agitate the chitosan-dissolved acetic acid solution at room temperature for 1hr. In the deposition of chitosan with low molecular weight, the specific surface area of activated carbon was greatly decreased even at low chitosan loading, but in the case of high molecular weight it was not nearly changed to 10wt% loading. It was known that chitosan was uniformly and physically deposited on activated carbon. The chitosan-deposited activated carbon was stable into the solution over about pH 6. The removal of Cr(VI) was remarkably enhanced by adding the adsorption function of chitosan to the surface of activated carbon with about 5wt% chitosan. It may be therefore used as an adsorbent for removing the pollutants in air and wastewater.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.63.2-63.2
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• 2015

Controlling and sensing spin states of magnetic molecules such as metallo-porphyrins at the single molecule level is essential for spintronic molecular device applications. Axial coordinations of diatomic molecules to metallo-porphyrins also play key roles in dynamic processes of biological functions such as blood pressure control and immune response. However, probing such reactions at the single molecule level to understand their physical mechanisms has been rarely performed. Here we present on our single molecule association and dissociation experiments between diatomic and metallo-porphyrin molecules on Au(111) describing its adsorption structures, spin states, and dissociation mechanisms. We observed bright ring shapes in NO adsorbed metallo-porphyrin compelxes and explained them by considering tilted binding and precession motion of NO. Before NO exposure, Co-porphryin showed a clear zero-bias peak in scanning tunneling spectroscopy, a signature of Kondo effect in STS, whereas after NO exposures it formed a molecular complex, NO-Co-porphyrin, that did not show any zero-bias feature implying that the Kondo effect was switched off by binding of NO. Under tunneling junctions of scanning tunneling microscope, both positive and negative energy pulses. From the observed power law relations between dissociation rate and tunneling current, we argue that the dissociations were inelastically induced with molecular orbital resonances. Our study shows that single molecule association and dissociation can be used to probe spin states and reaction mechanisms in a variety of axial coordination between small molecules and metallo-porphyrins.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.149-152
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• 2000

In recent years, various artificial molecular photodiode have been fabricated by mimicking the electron transport function of biological photosynthesis. And now, we have been investigated the protein-organic hetero thin film photodiode using GFP as an sensitizer based on the redox potential difference of functional molecules. In this paper, shows molecular photodiode consisting of green fluorescence protein(GFP). viologen and TCNQ. The TCNQ and viologen were deposited onto ITO coated glass by LB technique. And GFP molecule was adsorption onto the viologen LB film surface by self-assembly method. Finally, The Al deposition onto GFP/viologen/TCNQ film surface was performed to make a top electrode. As a result, The MIM(metal/Insulator/Metal) structured device was constructed. The input light of 460nm wavelength was generated by the xenon lamp system, and then the photocurrent produced from the molecular device was detected through a current-voltage(I-V) measuring unit (SMU Model 236, Keithley, USA). An artificial molecular photodiode using protein(GFP)-adsorbed hetero-LB film is presented as a model system for the bioelectronic device based on the biomimesis.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.26-26
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• 2011

Self-assembled monolayers (SAMs) prepared by sulfur-containing organic molecules on metal surfaces have drawn much attention for more than two decades because of their technological applications in wetting, chemical and biosensors, molecular recognition, nanolithography, and molecular electronics. In this talk, we will present self-assembly mechanism and two-dimensional (2D) structures of various organic thiol SAMs on Au(111), which are mainly demonstrated by molecular-scale scanning tunneling microscopy (STM) observation. In addition, we will provide some idea how to control 2D molecular arrangements of organic SAMs. For instance, the formation and surface structure of pentafluorobenzenethiols (PFBT) self-assembled monolayers (SAMs) on Au(111) formed from various experimental conditions were examined by means of STM. Although it is well known that PFBT molecules on metal surfaces do not form ordered SAMs, we clearly revealed for the first time that adsorption of PFBT on Au(111) at $75^{\circ}C$ for 2 h yields long-range, well-ordered self-assembled monolayers having a $(2{\times}5\sqrt{13})R30^{\circ}$ superlattice. Benzenethiols (BT) SAMs on gold usually have disordered phases, however, we have clearly demonstrated that the displacement of preadsorbed cyclohexanethiol self-assembled monolayers (SAMs) on Au(111) by BT molecules can be a successful approach to obtain BT SAMs with long-range ordered domains. Our results will provide new insight into controlling the structural order of BT or PFBT SAMs, which will be very useful in precisely tailoring the interface properties of metal surfaces in electronic devices.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.6
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• pp.423-430
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• 2013

In this research, a paramteric study to account for the effect of interfacial strength and nanotube agglomeration on the elastoplastic behavior of carbon nanotube reinforced polypropylene composites is performed. At first, the elastoplastic behavior of nanocomposites is predicted from molecular dynamics(MD) simulations. By combining the MD simulation results with the nonlinear micromechanics model based on the Mori-Tanaka model, a two-step domain decomposition method is applied to inversely identify the elastoplastic behavior of adsorption interphase zone inside nanocomposites. In nonlinear micromechanics model, the secant moduli method combined with field fluctuation method is used to predict the elastoplastic behavior of nanocomposites. To account for the imperfect material interface between nanotube and matrix polymer, displacement discontinuity condition is applied to the micromechanics model. Using the elastoplastic behavior of the adsorption interphase zone obtained from the present study, stress-strain relation of nanocomposites at various interfacial bonding condition and local nanotube agglomeration is predicted from nonlinear micromechanics model with and without the adsorption interphase zone. As a result, it has been found that local nanotube agglomeration is the most important design factor to maximize reinforcing effect of nanotube in elastic and plastic behavior.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.265-265
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• 2012

The adsorption of molecular $NH_3$ on rutile $TiO_2(110)-1{\times}1$ surfaces was investigated using a temperature-programmed desorption (TPD) technique combined with a molecular beam apparatus. A quantitative investigation into the TPD spectra of $NH_3$ was made for $NH_3$ adsorbed on two kinds of rutile $TiO_2(110)-1{\times}1$ surfaces with the oxygen vacancy ($V_O$) concentration of ~0% (p-$TiO_2(110)$) and ~5% (r-$TiO_2(110)$), respectively. On both surfaces, non-dissociative adsorption of $NH_3$ was inferred from a quantitative analysis on the amount of adsorbed $NH_3$ and those desorbed. With increasing coverage, the monolayer desorption feature shifted from 400 K toward lower temperatures until it saturates at 160 K, suggesting a repulsive nature in the interaction between $NH_3$ molecules. At the very low coverage regime, the desorption features were found to extend up to 430 K and 400 K on p-$TiO_2(110)$ and p-TiO(110), respectively. As a result, the saturation coverage of monolayer of $NH_3$ was higher on the p-$TiO_2(110)$ surface than on the p-TiO(110) by about 10%. The desorption energy ($E_d$) of $NH_3$ obtained by inversion of the Polanyi-Wigner equation indicated that the difference between the $E_d$'s of $NH_3$ (that is, $E_d(on\;p-TiO_2(110)$) - $E_d$(on p-TiO(110)) was 14 kJ/mol at ${\theta}(NH_3)=0$ and decreased to 0 as the coverage approached to a monolayer. The observed adsorption behavior of $NH_3$ was interpreted using an interaction model between $NH_3$ and surface defects on $TiO_2$ such as VO's and $Ti^{3+}$ interstitials.

• Journal of the Korean Chemical Society
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• v.48 no.1
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• pp.7-11
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• 2004