Eun-Bum Cho - Academia.edu (original) (raw)
Papers by Eun-Bum Cho
New journal of chemistry, 2024
Microporous and Mesoporous Materials, Aug 1, 2008
... the BJH method. The Brunauer–Emmet–Teller (BET) specific area and the total pore volume were ... more ... the BJH method. The Brunauer–Emmet–Teller (BET) specific area and the total pore volume were calculated at the relative pressure range from 0.06 to 0.2 and at a fixed relative pressure of 0.99, respectively. The solid-state ...
Chemical Communications, 2010
Experimental 1. Materials. (3-aminopropyl)triethoxysilane (99% APTES, Aldrich) and 4-(trimethoxys... more Experimental 1. Materials. (3-aminopropyl)triethoxysilane (99% APTES, Aldrich) and 4-(trimethoxysilyl)aniline (90% TMA, Gelest) were used as amine sources and triethoxysilyl butyraldehyde (90% TEBA, Gelest) was used as an aldehyde-containing organosilica source. 1,2-bis(triethoxysilyl)ethane (96% BTEE, Aldrich), 1,4-bis(triethoxysilyl)benzene (96% BTEB, Aldrich) and 2,5-bis(triethoxysilyl)thiophene (96% BTET, JSI silicone) were used as bridged organosilanes. Organosilica precursors were used as purchased without further purification. Silver nitrate (AgNO 3 , Fisher Scientific), hydrogen peroxide (35 wt% H 2 O 2 , Acros) and acetonitrile (CH 3 CN, Fisher Scientific) were used for oxidation of aldehydes to carboxylic acids inside the PMO materials. Poly(ethylene oxide)-poly(DL-lactic acid-co-glycolic acid)-poly(ethylene oxide), EO 16 (L 29 G 7)EO 16 , triblock copolymer (LGE538, M n (GPC) = 5310, M n (NMR) = 4220, polydispersity index (PI) = 1.28, and fraction Φ PEO = 0.38) was synthesized through a ring opening polymerization. LGE538 triblock copolymer was used as a soft template for hexagonal mesostructure. 2. Preparation of Multifunctional Periodic Mesoporous Organosilicas. The multifunctional LBMA-PMOs were synthesized by self-assembly of LGE538, BTEB, APTES and TEBA under 0.1 M HCl acidic conditions. The 1:1 molar ratio of APTES and TEBA was used in the synthesis of LBMA-PMOs by varying the composition of reactive organosilanes in relation to BTEB as follows: ([APTES] + [TEBA]):[
Small, Sep 21, 2010
The fi rst successful approach to synthesizing ultrabright fl uorescent mesoporous silica nanopar... more The fi rst successful approach to synthesizing ultrabright fl uorescent mesoporous silica nanoparticles is reported. Fluorescent dye is physically entrapped inside nanochannels of a silica matrix created during templated sol-gel self-assembly. The problem of dye leakage from open channels is solved by incorporation of hydrophobic groups in the silica matrix. This makes the approach compatible with virtually any dye that can withstand the synthesis. The method is demonstrated using the dye Rhodamine 6G. The obtained 40-nm silica particles are about 30 times brighter than 30-nm coated water-soluble quantum dots. The particles are substantially more photostable than the encapsulated organic dye itself.
International Journal of Hydrogen Energy
Molecules, Jun 2, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
International Journal of Energy Research, May 20, 2022
Polymer(Korea), Mar 1, 2017
This study describes the effect of crosslinking types on chemical and physical properties and UV ... more This study describes the effect of crosslinking types on chemical and physical properties and UV resistance of fluoroethylene vinyl ether (FEVE) layer over poly(vinylidene fluoride) (PVDF) in coil-coating. Hexamethoxymethylmelamine (HMMM) of melamine type and hexamethylene diisocyanate (HDI) of isocyanate type were used respectively as crosslinkers of high gloss and transparent FEVE layer on the PVDF coating layer. The evaluation of physical property and UV (UV-B) resistance was processed within ASTM standards. Urethane-reaction group using HDI showed relatively much better stability against UV (UV-B) than melamine reaction group of HMMM, while some physical and chemical resistances were found to be weaker. Also, in spite of the same melamine reaction group, the UV resistance was varied according to the ratio of HMMM cross-linker. From this study, it is expected to enhance weatherability as well as minimize the film deterioration from UV through optimizing crosslinking reaction in FEVE/PVDF double layer coating as a building exterior application.
MRS Proceedings, 2000
Mesoporous organosilicas based on a bridged organosilicate have been synthesized using a triblock... more Mesoporous organosilicas based on a bridged organosilicate have been synthesized using a triblock PEO-PLGA-PEO copolymer containing more hydrophobic poly(DL-lactic acid-coglycolic acid) block and the structural difference between mesoporous organosilicas prepared from PEO-PLGA-PEO and PEO-PPO-PEO block templates is discussed.
Nanomaterials, Sep 27, 2021
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Ceramics International, Feb 1, 2020
This work presents the tailoring of distinct titania (titania oxide) (TiO 2) crystal structures i... more This work presents the tailoring of distinct titania (titania oxide) (TiO 2) crystal structures inside the mesoporous silica and organosilica using several different block copolymer templates in acidic aqueous solution with different acidity. Different crystal structures of TiO 2 have been obtained as rutile and anatase phases, mainly depending on the chemical composition of block copolymer templates used in this study. A PEO-PLGA-PEO (EO 17 (L 28 G 7)EO 17 , LGE54) triblock copolymer, as well as typical Pluronic P123 (EO 20 PO 70 EO 20) and F127 (EO 106 PO 70 EO 106) triblock copolymers was employed as structure-directing templates for the sol-gel reaction of silane precursors. As silica and organosilica precursors, tetraethyl orthosilicate (TEOS), 1,2-bis(triethoxysilyl) ethane (BTEE), and 1,4-bis(triethoxysilyl)benzene (BTEB) were utilized with a titanium butoxide precursor. The crystal structure of TiO 2 and its corresponding band gap were investigated using X-ray diffraction (XRD) and ultraviolet-visible spectroscopy (UV-vis) measurements, respectively. Anatase crystalline phase of TiO 2 was found in the mesoporous sample prepared with Pluronic copolymer (i.e. P123 and F127) templates. On the other hand, the rutile phase was developed only in mesoporous samples prepared with an LGE54 PEO-PLGA-PEO triblock copolymer template. It was found the TiO 2 crystal structure is varied mainly depending on the polymer template under various strong acidic conditions. It seems that a thermodynamically more stable rutile phase can be formed using a more hydrophobic LGE54 template which supplies stronger micelle core as a platform. Further, it is known that the incorporation of TiO 2 in mesoporous silica and organosilica samples induces the conduction activity, especially toward the blue light region. Thus, this work can be applied to produce effective blue region semiconductor material with different crystallite structures by tuning the precursors and copolymer templates.
RSC Advances, 2018
Ca-and Li-doped mesoporous silicas have been prepared successfully using cetyltrimethylammonium b... more Ca-and Li-doped mesoporous silicas have been prepared successfully using cetyltrimethylammonium bromide (CTAB) surfactant in basic media. Sol-gel synthesis and hydrothermal treatment produced highly ordered mesoporous Ca and Li loaded silica particles. The MCM-41 type mesostructures, the porosity, the pore sizes as well as the surface area of Ca-and Li-silicas have been thoroughly investigated using small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and N 2 sorption analysis. Samples prepared with varying amounts of Li and Ca loading have been further analyzed using inductive coupled plasma-atomic emission spectroscopy (ICP-AES) and field-emission scanning electron microscopy (FESEM) with an energy dispersive spectral attachment (EDS), which confirmed quite a large amount of Ca while the amount of Li was not enough. Additionally, H 2 and CO 2 gas uptake studies of these metal-loaded silicas have been carried out using a thermogravimetric analyzer (TGA) at normal temperature (25 C) and pressure (1 atm). H 2 uptake of up to 10 mmol g À1 by Ca-doped silica was recorded. CO 2 and H 2 selectivity were tested with both pure metal-MCM-41 and amine loaded silica using pure N 2 gas and a mixed flow of CO 2 /N 2 and H 2 /N 2. The effect of temperature on CO 2 uptake was also studied using Ca-MCM-41 materials.
Dalton Transactions, 2017
Figure S1: The plot of C/C 0 versus time (t) for degradation of Rhodamine B dye using only H 2 O ... more Figure S1: The plot of C/C 0 versus time (t) for degradation of Rhodamine B dye using only H 2 O 2. Inset represents a plot of ln(C/C 0) versus time (t) to calculate the rate constant.
Journal of Physical Chemistry B, Jul 1, 2009
Sulfonated mesoporous benzene-silicas were introduced into a poly(vinyl alcohol) (PVA) polymer ma... more Sulfonated mesoporous benzene-silicas were introduced into a poly(vinyl alcohol) (PVA) polymer matrix to act as a barrier for methanol crossover, to prepare composite electrolyte membranes for direct methanol fuel cell applications. Highly ordered 2D hexagonal mesoporous benzene-silicas were prepared using 1,4-bis(triethoxysilyl)benzene (BTEB) organosilica precursor and two kinds of organic templates, such as an octadecyltrimethylammonium bromide (ODTMA) and a Pluronic P123 poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer, to investigate the effect of the morphology and the pore size on the methanol permeability and the proton conductivity of the membranes. The sulfonated mesoporous benzene-silica and PVA were mixed with a sulfosuccinic acid (SSA) cross-linker to improve the membrane stability from mechanical and conductive viewpoints. The physical and chemical characterization of the hybrid electrolyte membranes was performed by varying the contents of sulfonated mesoporous benzene-silicas and SSA. All the hybrid membranes studied showed good performance in lowering the methanol crossover (i.e., approximately 68% reduction in comparison with the Nafion117 membrane), and mesoporous benzene-silica with smaller particle morphology and pores (2-3 nm) was observed to be a more effective additive.
New journal of chemistry, 2024
Microporous and Mesoporous Materials, Aug 1, 2008
... the BJH method. The Brunauer–Emmet–Teller (BET) specific area and the total pore volume were ... more ... the BJH method. The Brunauer–Emmet–Teller (BET) specific area and the total pore volume were calculated at the relative pressure range from 0.06 to 0.2 and at a fixed relative pressure of 0.99, respectively. The solid-state ...
Chemical Communications, 2010
Experimental 1. Materials. (3-aminopropyl)triethoxysilane (99% APTES, Aldrich) and 4-(trimethoxys... more Experimental 1. Materials. (3-aminopropyl)triethoxysilane (99% APTES, Aldrich) and 4-(trimethoxysilyl)aniline (90% TMA, Gelest) were used as amine sources and triethoxysilyl butyraldehyde (90% TEBA, Gelest) was used as an aldehyde-containing organosilica source. 1,2-bis(triethoxysilyl)ethane (96% BTEE, Aldrich), 1,4-bis(triethoxysilyl)benzene (96% BTEB, Aldrich) and 2,5-bis(triethoxysilyl)thiophene (96% BTET, JSI silicone) were used as bridged organosilanes. Organosilica precursors were used as purchased without further purification. Silver nitrate (AgNO 3 , Fisher Scientific), hydrogen peroxide (35 wt% H 2 O 2 , Acros) and acetonitrile (CH 3 CN, Fisher Scientific) were used for oxidation of aldehydes to carboxylic acids inside the PMO materials. Poly(ethylene oxide)-poly(DL-lactic acid-co-glycolic acid)-poly(ethylene oxide), EO 16 (L 29 G 7)EO 16 , triblock copolymer (LGE538, M n (GPC) = 5310, M n (NMR) = 4220, polydispersity index (PI) = 1.28, and fraction Φ PEO = 0.38) was synthesized through a ring opening polymerization. LGE538 triblock copolymer was used as a soft template for hexagonal mesostructure. 2. Preparation of Multifunctional Periodic Mesoporous Organosilicas. The multifunctional LBMA-PMOs were synthesized by self-assembly of LGE538, BTEB, APTES and TEBA under 0.1 M HCl acidic conditions. The 1:1 molar ratio of APTES and TEBA was used in the synthesis of LBMA-PMOs by varying the composition of reactive organosilanes in relation to BTEB as follows: ([APTES] + [TEBA]):[
Small, Sep 21, 2010
The fi rst successful approach to synthesizing ultrabright fl uorescent mesoporous silica nanopar... more The fi rst successful approach to synthesizing ultrabright fl uorescent mesoporous silica nanoparticles is reported. Fluorescent dye is physically entrapped inside nanochannels of a silica matrix created during templated sol-gel self-assembly. The problem of dye leakage from open channels is solved by incorporation of hydrophobic groups in the silica matrix. This makes the approach compatible with virtually any dye that can withstand the synthesis. The method is demonstrated using the dye Rhodamine 6G. The obtained 40-nm silica particles are about 30 times brighter than 30-nm coated water-soluble quantum dots. The particles are substantially more photostable than the encapsulated organic dye itself.
International Journal of Hydrogen Energy
Molecules, Jun 2, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
International Journal of Energy Research, May 20, 2022
Polymer(Korea), Mar 1, 2017
This study describes the effect of crosslinking types on chemical and physical properties and UV ... more This study describes the effect of crosslinking types on chemical and physical properties and UV resistance of fluoroethylene vinyl ether (FEVE) layer over poly(vinylidene fluoride) (PVDF) in coil-coating. Hexamethoxymethylmelamine (HMMM) of melamine type and hexamethylene diisocyanate (HDI) of isocyanate type were used respectively as crosslinkers of high gloss and transparent FEVE layer on the PVDF coating layer. The evaluation of physical property and UV (UV-B) resistance was processed within ASTM standards. Urethane-reaction group using HDI showed relatively much better stability against UV (UV-B) than melamine reaction group of HMMM, while some physical and chemical resistances were found to be weaker. Also, in spite of the same melamine reaction group, the UV resistance was varied according to the ratio of HMMM cross-linker. From this study, it is expected to enhance weatherability as well as minimize the film deterioration from UV through optimizing crosslinking reaction in FEVE/PVDF double layer coating as a building exterior application.
MRS Proceedings, 2000
Mesoporous organosilicas based on a bridged organosilicate have been synthesized using a triblock... more Mesoporous organosilicas based on a bridged organosilicate have been synthesized using a triblock PEO-PLGA-PEO copolymer containing more hydrophobic poly(DL-lactic acid-coglycolic acid) block and the structural difference between mesoporous organosilicas prepared from PEO-PLGA-PEO and PEO-PPO-PEO block templates is discussed.
Nanomaterials, Sep 27, 2021
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Ceramics International, Feb 1, 2020
This work presents the tailoring of distinct titania (titania oxide) (TiO 2) crystal structures i... more This work presents the tailoring of distinct titania (titania oxide) (TiO 2) crystal structures inside the mesoporous silica and organosilica using several different block copolymer templates in acidic aqueous solution with different acidity. Different crystal structures of TiO 2 have been obtained as rutile and anatase phases, mainly depending on the chemical composition of block copolymer templates used in this study. A PEO-PLGA-PEO (EO 17 (L 28 G 7)EO 17 , LGE54) triblock copolymer, as well as typical Pluronic P123 (EO 20 PO 70 EO 20) and F127 (EO 106 PO 70 EO 106) triblock copolymers was employed as structure-directing templates for the sol-gel reaction of silane precursors. As silica and organosilica precursors, tetraethyl orthosilicate (TEOS), 1,2-bis(triethoxysilyl) ethane (BTEE), and 1,4-bis(triethoxysilyl)benzene (BTEB) were utilized with a titanium butoxide precursor. The crystal structure of TiO 2 and its corresponding band gap were investigated using X-ray diffraction (XRD) and ultraviolet-visible spectroscopy (UV-vis) measurements, respectively. Anatase crystalline phase of TiO 2 was found in the mesoporous sample prepared with Pluronic copolymer (i.e. P123 and F127) templates. On the other hand, the rutile phase was developed only in mesoporous samples prepared with an LGE54 PEO-PLGA-PEO triblock copolymer template. It was found the TiO 2 crystal structure is varied mainly depending on the polymer template under various strong acidic conditions. It seems that a thermodynamically more stable rutile phase can be formed using a more hydrophobic LGE54 template which supplies stronger micelle core as a platform. Further, it is known that the incorporation of TiO 2 in mesoporous silica and organosilica samples induces the conduction activity, especially toward the blue light region. Thus, this work can be applied to produce effective blue region semiconductor material with different crystallite structures by tuning the precursors and copolymer templates.
RSC Advances, 2018
Ca-and Li-doped mesoporous silicas have been prepared successfully using cetyltrimethylammonium b... more Ca-and Li-doped mesoporous silicas have been prepared successfully using cetyltrimethylammonium bromide (CTAB) surfactant in basic media. Sol-gel synthesis and hydrothermal treatment produced highly ordered mesoporous Ca and Li loaded silica particles. The MCM-41 type mesostructures, the porosity, the pore sizes as well as the surface area of Ca-and Li-silicas have been thoroughly investigated using small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and N 2 sorption analysis. Samples prepared with varying amounts of Li and Ca loading have been further analyzed using inductive coupled plasma-atomic emission spectroscopy (ICP-AES) and field-emission scanning electron microscopy (FESEM) with an energy dispersive spectral attachment (EDS), which confirmed quite a large amount of Ca while the amount of Li was not enough. Additionally, H 2 and CO 2 gas uptake studies of these metal-loaded silicas have been carried out using a thermogravimetric analyzer (TGA) at normal temperature (25 C) and pressure (1 atm). H 2 uptake of up to 10 mmol g À1 by Ca-doped silica was recorded. CO 2 and H 2 selectivity were tested with both pure metal-MCM-41 and amine loaded silica using pure N 2 gas and a mixed flow of CO 2 /N 2 and H 2 /N 2. The effect of temperature on CO 2 uptake was also studied using Ca-MCM-41 materials.
Dalton Transactions, 2017
Figure S1: The plot of C/C 0 versus time (t) for degradation of Rhodamine B dye using only H 2 O ... more Figure S1: The plot of C/C 0 versus time (t) for degradation of Rhodamine B dye using only H 2 O 2. Inset represents a plot of ln(C/C 0) versus time (t) to calculate the rate constant.
Journal of Physical Chemistry B, Jul 1, 2009
Sulfonated mesoporous benzene-silicas were introduced into a poly(vinyl alcohol) (PVA) polymer ma... more Sulfonated mesoporous benzene-silicas were introduced into a poly(vinyl alcohol) (PVA) polymer matrix to act as a barrier for methanol crossover, to prepare composite electrolyte membranes for direct methanol fuel cell applications. Highly ordered 2D hexagonal mesoporous benzene-silicas were prepared using 1,4-bis(triethoxysilyl)benzene (BTEB) organosilica precursor and two kinds of organic templates, such as an octadecyltrimethylammonium bromide (ODTMA) and a Pluronic P123 poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer, to investigate the effect of the morphology and the pore size on the methanol permeability and the proton conductivity of the membranes. The sulfonated mesoporous benzene-silica and PVA were mixed with a sulfosuccinic acid (SSA) cross-linker to improve the membrane stability from mechanical and conductive viewpoints. The physical and chemical characterization of the hybrid electrolyte membranes was performed by varying the contents of sulfonated mesoporous benzene-silicas and SSA. All the hybrid membranes studied showed good performance in lowering the methanol crossover (i.e., approximately 68% reduction in comparison with the Nafion117 membrane), and mesoporous benzene-silica with smaller particle morphology and pores (2-3 nm) was observed to be a more effective additive.