Kyoung-Soo Kim

Organics and Polymers with High Two-Photon Activities and their Applications

This review describes some of the recent developments in materials which exhibit enhanced two-photon absorption that can initiate photopolymerization or up-converted emission. Various optical methods including femtosecond time-resolved pump-probe experiments to characterize the two-photon properties are discussed. Finally, the applications of two-photon processes to optical power limiting, up-converted lasing, 3-D data storage, 3-D micro-fabrication, two-photon fluorescence microscopy and bio-imaging, and two-photon photodynamic therapy are presented.

DC Magnetic Field Induced Magnetocytolysis of Cancer Cells Targeted by LH-RH Magnetic Nanoparticles in vitro

Major advances in nanotechnology and cancer biology have occurred throughout the last 30 years. The concept of “magnetic nanoclinic” demonstrated here, combines these advances in cancer and nanotechnology forming the basis for a new generation of non-invasive anti-cancer tools. This nanoclinic is a multifunctional nanoparticle (< 50 nm) that has been fabricated to selectively enter, provide optical imaging capability and administer externally controled therapy from within the cell. The magnetic nanoclinics were designed with an Fe2O3 core for magnetocytolysis using a DC magnetic field and a two-photon fluorescent probe to aid in optical tracking. Surface labeling with the peptide analog of luteinizing hormone releasing hormone (LH-RH) provides targetting to specific cancer cell types. These nanoclinics demonstrate the ability to selectively lyse cells expressing LH-RH receptors upon exposure to a DC magnetic field similar to that used for magnetic resonance imager in diagnostic settings. This study demonstrates the fabrication of and in vitro feasibility of nanoclinics as a non-invasive approach to the treatment of selected cancers using a DC magnetic field.

Lanthanum-catalysed synthesis of microporous 3D graphene-like carbons in a zeolite template

Three-dimensional graphene architectures with periodic nanopores—reminiscent of zeolite frameworks—are of topical interest because of the possibility of combining the characteristics of graphene with a three-dimensional porous structure. Lately, the synthesis of such carbons has been approached by using zeolites as templates and small hydrocarbon molecules that can enter the narrow pore apertures. However, pyrolytic carbonization of the hydrocarbons (a necessary step in generating pure carbon) requires high temperatures and results in non-selective carbon deposition outside the pores. Here, we demonstrate that lanthanum ions embedded in zeolite pores can lower the temperature required for the carbonization of ethylene or acetylene. In this way, a graphene-like carbon structure can be selectively formed inside the zeolite template, without carbon being deposited at the external surfaces. X-ray diffraction data from zeolite single crystals after carbonization indicate that electron densities corresponding to carbon atoms are generated along the walls of the zeolite pores. After the zeolite template is removed, the carbon framework exhibits an electrical conductivity that is two orders of magnitude higher than that of amorphous mesoporous carbon. Lanthanum catalysis allows a carbon framework to form in zeolite pores with diameters of less than 1 nanometre; as such, microporous carbon nanostructures can be reproduced with various topologies corresponding to different zeolite pore sizes and shapes. We demonstrate carbon synthesis for large-pore zeolites (FAU, EMT and beta), a one-dimensional medium-pore zeolite (LTL), and even small-pore zeolites (MFI and LTA). The catalytic effect is a common feature of lanthanum, yttrium and calcium, which are all carbide-forming metal elements. We also show that the synthesis can be readily scaled up, which will be important for practical applications such as the production of lithium-ion batteries and zeolite-like catalyst supports.

Occurrence of perfluorooctanoate and perfluorooctanesulfonate in the Korean water system: Implication to water intake exposure

Perfluorinated compounds (PFCs) measured in surface running waters indicated the existence of different emission sources in eight main city basins. The tap water reflected the contamination pattern and levels in their corresponding source water basins. The daily intakes through tap water consumption ranged from <0.01 to 0.73 ng kg(-1) d(-1) for perfluorooctanoate (PFOA) and <0.01 to 0.08 ng kg(-1) d(-1) for perfluorooctanesulfonate (PFOS). Tap water intake-derived exposure accounted for 8.6%-101% (for PFOA) and while <10% (for PFOS) of total daily exposure, which was estimated from Korean serum concentrations using a pharmacokinetic model. Our findings indicate that tap water intake could be an important contributor to PFOA exposure in Korean populations; accordingly, additional efforts are necessary to improve the removal efficiency of perfluorinated compounds (PFCs) in the water purification process. However, more fundamentally the aim would be to reduce the discharge of PFCs from potential sources within the basin.

Evaluation of mono- to deca-brominated diphenyl ethers in riverine sediment of Korea with special reference to the debromination of DeBDE209.

The measured concentrations of polybrominated diphenyl ethers (PBDEs) in inland sediments, from mono- to deca-BDE congeners, ranged from 0.46 to 1760 ng/g dry weight (dw) with mean and median values of 55±230 ng/g dw and 12 ng/g dw, respectively. These concentrations were comparable to or lower than those reported in other countries. The large contributions of the nona- and octa-BDE congeners (14.6±5.0% of total PBDEs) in the present study highlight the necessity of examining these congeners. A high population density and wastewater discharge around the sampling sites are related to the high PBDE concentration. The most predominant congener was DeBDE209 (average proportion, 70.9±12.4%), which is in good agreement with the large amounts of commercial deca-BDE products used in Korea. Statistical analyses also confirmed the ubiquity of DeBDE209 in river sediment from the use of commercial deca-BDE products, such as Saytex-102E and DE-83R. On the other hand, the relatively large contributions of tri- to hepta-BDE congeners compared to the small quantities of commercial penta- and octa-BDE products used in Korea indicate the debromination potential for highly brominated congeners.

100 ps time-resolved solution scattering utilizing a wide-bandwidth X-ray beam from multilayer optics

A new method of time-resolved solution scattering utilizing X-ray multilayer optics is presented.

Recent progress in developing highly efficient nonlinear optical chromophores and side-chain dendronized polymers for electro-optics

Recent progress in developing high-performance nonlinear optical chromophores and polymers for electro-optics is reviewed. Using the single-mode focused microwave irradiation, a diversified family of 2,5-dihydrofuran derivatives has been synthesized as a new class of tunable electron acceptors. Very large r33 values (128 and 116 pm/V at 1.3 μm) have been demonstrated by doping one of the 2-dicyanomethylen-3-cyano-4,5,-dimethyl-5-trifluoromethyl-2,5-dihydrofuran (CF3-TCF)-based chromophores in poly(methyl methacrylate) (PMMA) and a high Tg polyquinoline (PQ-100), respectively. An excellent long-term temporal stability at 85°C has also been maintained in the PQ system. Two side-chain dendronized NLO polymers have been synthesized. Using a mild, simple, and generally applicable post-functionalization method, highly polarizable chromophores with dendritic modification has been covalently attached to side chains of poly(4-hydroxystryene). This approach provides the combined advantages of achieving better poling efficiency through the dendritic effect and shortening the development time required for E-O dendrimer synthesis. Systematic property comparison between these polymers and other conventional NLO polymers, such as guest-host and simple side-chain polymers, has been performed. Exceptionally high poling efficiency (a very large E-O coefficient of 97 pm/V at 1.3 μm) and good temporal stability at room temperature were dmeonstrated in this dendronized side-chain polymer system.

N-doped zeolite-templated carbon as a metal-free electrocatalyst for oxygen reduction

Nitrogen-doped, zeolite-templated carbon was synthesized using aqueous acetonitrile as a nitrogen-containing carbon source, and beta zeolite as a template. The carbon had a three-dimensionally ordered microporous structure with a large surface area, which consisted of sp2-carbon. The nitrogen content was approximately 4 wt%. In the electrocatalytic oxygen reduction reaction, the nitrogen-doped zeolite-templated carbon showed a notably high current density and a positive onset potential as compared to nitrogen-doped reduced graphene oxide. The surface of this carbon also had a lower work function than that of planar graphene. The high catalytic performance with the low work function of this carbon seems to come from a curved graphene-like framework structure containing nitrogen.

P‐182: New Deep‐Blue EML Materials Based on Fully Substituted Ethylene and Anthracene Derivatives

New blue fluorescent compounds containing tetra-substituted ethylene moieties have been designed and synthesized. By fabricating multilayered non-doped OLED devices using these new blue materials, we achieved luminance efficiencies of 4.00 lm/W (10.33 cd/A at 8.1 V) for BPBAPE[CB-104] and 1.82 lm/W (3.93 cd/A at 6.8 V) for BTPPA [CB-105B] at 10 mA/cm2. The BPBAPE [CB-104] and BTPPA [CB-105B] devices exhibited sky blue emission (0.195, 0.303) and deep blue emission (0.159, 0.135) at 10mA/cm2 respectively. We also synthesized new kinds of blue materials such as CB-201, 202, and 203. CB-203 device showed 3.11cd/A of current efficiency and (0.148, 0.088) CIE value.

New Blue and Bluish Green Electroluminescent Properties of Fully Substituted Ethylene Moieties

We synthesized 1,1,2,2-tetrakis(4′-tert-butylbiphenyl)ethene[TBBPE] and 1,2-di(4′-tert-butyl-phenyl)-1,2-bis(4′-tert-butyl-biphenyl) ethene [BPBBPE]. TBBPE and BPBBPE film showed PL maximum value of 489 nm and 511 nm due to longer conjugation length of TBBPE. In EL device, TBBPE device showed slightly better I-V curve than BPBBPEs because there is lower energy barrier between Alq3 and TBBPEs LUMO levels. We observed luminance efficiency of 1.87 cd/A with blue color as (0.177, 0.249) CIE value in BPBBPE emitting system and 4.44 cd/A with (0.240, 0.435) CIE value in TBBPE device.