Sung Soo Kim

Systematic phase control of periodic mesoporous organosilicas using Gemini surfactants

Highly ordered periodic mesoporous organosilica (PMO) materials with various mesostructures, including lamellar, bicontinuous cubic Ia3d, 2D hexagonal (P6mm), 3D hexagonal (P63/mmc) and cubic Pm3n, have been synthesized using Gemini surfactants with general formulas of [CnH2n+1N(CH3)2(CH2)sN (CH3)2CnH2n+1]Br2 (n = 6–18 and s = 3–12, Cn-s-n). The nature of the Gemini surfactant such as alkyl chain length (n) and spacer length (s), and the synthetic conditions such as reaction temperatures and molar compositions are controlling parameters for desired mesostructures. The PMO materials, synthesized at room temperature from Cn-6-n, exhibit phase transition from lamellar to bicontinuous cubic Ia3d, 2D hexagonal, 3D hexagonal and cubic Pm3n as the chain length decreases, whereas only the lamellar and 2D hexagonal PMO materials with different lattice parameters depending on the chain length are obtained at high reaction temperature (373 K). The Cn-8-n and Cn-10-n surfactants also yield 2D hexagonal PMO material in a very wide range of synthetic condition at 373 K. The PMO materials with various mesostructures thus obtained exhibit high BET surface areas in the range of 900–1500 m2 g−1 and total pore volumes of about 0.5–1.4 cm3 g−1.

MALDI-TOF-MS analysis of small molecules using modified mesoporous material SBA-15 as assisted matrix

Mesoporous silica, SBA-15 was successfully functionalized with quinoline moiety, and was applied as a matrix in the MALDI-TOF-MS analysis of small molecules. The modified SBA-15 material [SBA-15-8-(3-(triethoxysilyl)propoxy) quinoline, SBA-15-8QSi] was obtained by using calcined SBA-15 and 8-hydroxy quinoline. The structure of the functionalized mesoporous material was systemically characterized by TEM, the N2 adsorption-desorption isotherm technique and FT-IR spectra. Compared with DHB and SBA-15, SBA-15-8QSi demonstrated several advantages in the analysis of small molecules with MALDI-TOF-MS, such as less background interference ions, high homogeneity, and better reproducibility. Based on these results, the various analytical parameters were optimized. The ideal operating conditions were (1) methanol used as the dissolving solvent; (2) sample first dropping method; (3) a ratio between the analyte and the matrix of 3.5:10. Under these optimization conditions, a low detection limit (8 pmol for L-Arginine-HCl) and high reproducibility (≤29%) were obtained. This technique was successfully applied to the analysis of various types of small molecules, such as saccharides, amino acids, metabolites, and natural honey.

Anthraquinone sulfonate modified, layered double hydroxide nanosheets for dye-sensitized solar cells.

Dye-sensitized solar cells (DSCs) have been extensively investigated for solar energy conversion by using various combinations of inorganic semiconductors and organic sensitizers because of their low cost, easy production, and high efficiency. For efficient visible-light absorption, various organic dyes have been intensively exploited because of their advantages, such as their high molar extinction coefficients and tunable optical bands, in which they are anchored on mesoscopic TiO2 semiconductors. Recently, inorganic semiconducting materials, such as quantum dots (CdSe, CdS,) and organometal perovskites, have been proposed as inorganic sensitizers in photovoltaic cells to overcome some drawbacks of the organic dyes such as their relatively low heat stability and narrow absorption bands. One possible approach to improving the inherent light-harvesting ability of the organic dyes is to hybridize them with nanosized multifunctional inorganic materials such as layered double hydroxides (LDHs), which can provide a stable chemical environment, higher heat or photostability, and are environmentally friendly. The LDHs, also known as anionic or hydrotalcite-like clays, are useful in new multifunctional systems such as biological carriers, catalysts, and hybrid optical layers. Recently, Duan et al. reported an ultrathin hybrid film consisting of LDH nanosheets and luminescent polyanions, in which the LDH nanosheets induced a welldefined photoluminescence of polymer monolayers that are individually separated by the exfoliated LDH nanosheets. Moreover, the LDHs provide a stable chemical environment to increase the photochemical function and thermal stability of the intercalated organic photochromic dyes. In this study, LDH nanosheets are suggested as the inorganic matrix in an attempt to induce an intense photochromic function of the organic photochromic dyes, anthraquinone sulfonate anion (AQS), that are chemically immobilized on the surface of the LDH nanosheets. Herein, we report a new hybrid light sensitizer for DSCs, in which the AQS anion is selected as the organic sensitizer and the LDH nanosheets as the inorganic host. This is believed to be the first example of hybrid LDH/organic nanosheets used as a light sensitizer in photovoltaic devices. The chemical structure and photochromic behavior of the LDH AQS nanosheets in formamide are shown in Figure 1a. The powder X-ray diffraction (XRD) pattern of LDH AQS microcrystals indicated a well-crystallized rhombohedral hydrotalcite-like, 3R1 phase with lattice parameters of a=3.05 and c=60.0 . An antiparallel arrangement of the AQS would be the best model by assuming that the length of the AQS anion was 12.9 . Notably, a transparent solution was obtained by ultrasound treatment for 10 min, indicating the successful exfoliation of the platelike LDH AQS microcrystals. Typical Tyndall light scattering of the resulting solution demonstrated the presence of exfoliated LDH nanosheets as shown in Figure 1a. Interestingly, the suspension showed a strong photoinduced coloration that was not seen in the AQS–formamide solution. In (4) of Figure 1b, the UV/Vis absorption spectra for the irradiated suspension of the LDH AQS nanosheets show extremely enhanced absorption bands in the range of 400–600 nm, where the absorption bands at 435 and 525 nm are characteristic signals for the reduction state of anthraquinone sulfonate (AQS ) that have a long-term stability in a high pH condition, whereas formamide (the solvent) might be oxidized during the photoreaction. Under continuous irradiation of the exfoliated LDH AQS solution shown in (2) of Figure 1b, the band intensities gradually increased as a function of the irradiation time and then decreased after the light was cut off. The rate constants for photocoloration and decay were 0.072 and 0.059 min , respectively. This may be [a] Dr. J. H. Lee, J. Chang, J.-H. Cha, Prof. D.-Y. Jung, S. S. Kim, Prof. J. M. Kim Department of Chemistry-BK21 and Sungkyunkwan Advanced Institute of Nanotechnology Institute of Basic Sciences, Sungkyunkwan University Suwon, 440-746 (Korea) Fax: (+82)31-290-7075 E-mail : dyjung@skku.edu Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201000703.

SYNTHESIS OF MESOPOROUS IRON OXIDE NANOPARTICLES FROM MESOPOROUS SILICA TEMPLATE VIA NANO-REPLICATION

Highly ordered mesoporous iron oxide (α-Fe2O3) material has been successfully obtained from mesoporous silica template, KIT-6 (3-D Cubic Ia3d symmetry), through nano-replication method. The mesoporous α-Fe2O3 material thus obtained exhibits well-defined mesopores (2.7 nm in diameter), high surface area (148 m2/g), high pore volume (0.47 cm3/g) and crystalline frameworks. The morphology of the mesoporous α-Fe2O3 material is very uniform in spherical shape of which the average particle size is about 100 nm in diameter.

Redox-buffer effect of Fe2+ ions on the selective olefin/paraffin separation and hydrogen tolerance of a Cu+-based mesoporous adsorbent

In the present work, a new mesoporous adsorbent containing ferrous/cuprous ionic species (Fe–Cu/MCM-41) has been developed for selective separation of 1-butene/n-butane. Co-impregnation of Fe2+ ions with Cu+ ions within mesopores gives superior 1-butene/n-butane separation ability. Fe–Cu/MCM-41 exhibits much higher heat of adsorption for 1-butene (−23.4 kJ mol−1) compared to that of Cu/MCM-41 (−11.2 kJ mol−1), resulting in a larger adsorption amount of 1-butene over Fe–Cu/MCM-41 (4.4 mmol g−1 at 1 atm) than that over Cu/MCM-41 (2.8 mmol g−1 at 1 atm). The results indicate that Fe–Cu/MCM-41 exhibits superior π-complexation ability for 1-butene than Cu/MCM-41. Moreover, the adsorption ability of Fe–Cu/MCM-41 does not change very much upon H2-treatment at different temperatures in the range of 273 K to 473 K, revealing the excellent hydrogen tolerance of the adsorbent. Physicochemical analyses indicated that the existence of Fe2+ species prevented the oxidation and reduction of Cu+ species during the adsorbent preparation and during the separation process in the presence of a reducing gas such as hydrogen, i.e., the Fe2+ species may act as a kind of redox buffer in the Fe–Cu/MCM-41 adsorbent for improving the chemical stability of Cu+ species that are highly effective for π-complexation with olefin.

Organic Plasma-Polymer Thin Film Coatings on Super-Hydrophilic Coated Surface for Increasing the Surface Durability against Scratch without Changing of Surface Wettability

In this study, the SiO polymer coating film was prepared the containing tetraethyl orthosilane (TEOS) solution by the sol-gel method on soda lime glass. After then, the plasma polymer coating was deposited on SiO polymer coated glass by plasma enhanced chemical vapor deposition (PECVD) method at room temperature during 15 seconds. The thiophene monomer was used as organic precursor. It was heat up to 60 oC and bubbled with hydrogen gas which flow rate was 50 sccm. Plasma was ignited by radio frequency (RF, 13.56 MHz) and its power was 10 W. SiO polymer and plasma polymer coated SiO polymer films were investigated by Fourier Transform Infrared (FT-IR), scanning electron microscopy (SEM), ultraviolet-visible (UV-Vis.), water contact angle, the adhesion test, and the pencil hardness test. The IR spectra shows evidence of very thin organic plasma polymer, which could not be measured by SEM cross image. The SEM images show that the morphology of each film was not changed by plasma polymer coating. Low water contact angles showed with both coating. Moreover surface hardness was increased by plasma polymer coating.

Fixation of Carbon Nanotube Within Mesoporous Titania Particles

Carbon nanotube (CNT) and mesoporous TiO2 composite (CNT/meso-TiO2) was synthesized by a nanocasting method using CNT-implanted mesoporous silica material as the template. The CNT was successfully incorporated within a mesoporous TiO2 particle, and the CNT/meso-TiO2 composite obtained exhibits a high surface area and well-established mesoporosity. Moreover, the composite material exhibits much lower electric resistance than those of mesoporous TiO2 only and physical mixture of CNT and mesoporous TiO2, which probably due to the large interface area and strong junction between the implanted CNT and TiO2 framework in the composite.