Jinwoo Lee

Synthesis of new nanoporous carbon materials using nanostructured silica materials as templates

In this review, we summarize recent reports on the synthesis of various nanoporous carbon materials. Many nanoporous carbon materials having variable pore sizes and pore structures have been synthesized using appropriate nanostructured silica materials as templates. Nanoporous carbons with high pore volumes and uniform pore sizes have been produced using silica sol and silica gel as templates. Mesoporous carbons with several different pore structures have been synthesized using mesoporous silica materials such as MCM-48, HMS, SBA-15, MSU, and MCF as templates. Some of these nanoporous carbon materials were successfully used as adsorbents for bulky pollutants and electrodes for supercapacitors and fuel cells.

Development of a new mesoporous carbon using an HMS aluminosilicate template

This work was supported by the Korea Research Foundation (New nMaterials Research 1998) and the KOSEF (Basic Research Program n#98-05-02-03-01-3).

Simple Synthesis of Functionalized Superparamagnetic Magnetite/Silica Core/Shell Nanoparticles and their Application as Magnetically Separable High‐Performance Biocatalysts

Uniformly sized silica-coated magnetic nanoparticles (magnetite@silica) are synthesized in a simple one-pot process using reverse micelles as nanoreactors. The core diameter of the magnetic nanoparticles is easily controlled by adjusting the w value ([polar solvent]/[surfactant]) in the reverse-micelle solution, and the thickness of the silica shell is easily controlled by varying the amount of tetraethyl orthosilicate added after the synthesis of the magnetite cores. Several grams of monodisperse magnetite@silica nanoparticles can be synthesized without going through any size-selection process. When crosslinked enzyme molecules form clusters on the surfaces of the magnetite@silica nanoparticles, the resulting hybrid composites are magnetically separable, highly active, and stable under harsh shaking conditions for more than 15 days. Conversely, covalently attached enzymes on the surface of the magnetite@silica nanoparticles are deactivated under the same conditions.

Synthesis of a new mesoporous carbon and its application to electrochemical double-layer capacitors

A mesoporous carbon with regular three-dimensionally interconnected 2 nm pore arrays using AlMCM-48 as a template has been synthesised; the mesoporous carbon exhibited excellent performance as an electrochemical double layer capacitor.

Highly active heterogeneous Fenton catalyst using iron oxide nanoparticles immobilized in alumina coated mesoporous silica

A highly active heterogeneous Fenton catalyst was fabricated by impregnating iron oxide nanoparticles in alumina coated mesoporous SBA-15 silica.

Single‐Molecule Four‐Color FRET

We developed a single-molecule four-color FRET technique both in confocal and in total-internal-reflection fluorescence microscopies. Real-time determination of six inter-fluorophore FRET efficiencies allowed us to probe the correlated motion of four arms of the Holliday junction. The technique was also applied to assess the correlation of RecA-mediated strand exchange events at both ends of a synaptic complex.

Low-cost and facile synthesis of mesocellular carbon foams.

Mesocellular carbon foam composed of nanometer sized primary particles was synthesized using hydrothermally synthesized MSU-F silica as a template and poly(furfuryl alcohol) as a carbon source.

Single-molecule three-color FRET with both negligible spectral overlap and long observation time.

Full understanding of complex biological interactions frequently requires multi-color detection capability in doing single-molecule fluorescence resonance energy transfer (FRET) experiments. Existing single-molecule three-color FRET techniques, however, suffer from severe photobleaching of Alexa 488, or its alternative dyes, and have been limitedly used for kinetics studies. In this work, we developed a single-molecule three-color FRET technique based on the Cy3-Cy5-Cy7 dye trio, thus providing enhanced observation time and improved data quality. Because the absorption spectra of three fluorophores are well separated, real-time monitoring of three FRET efficiencies was possible by incorporating the alternating laser excitation (ALEX) technique both in confocal microscopy and in total-internal-reflection fluorescence (TIRF) microscopy.

Single-molecule approach to immunoprecipitated protein complexes: insights into miRNA uridylation

Single‐molecule techniques have been used for only a subset of biological problems because of difficulties in studying proteins that require cofactors or post‐translational modifications. Here, we present a new method integrating single‐molecule fluorescence microscopy and immunopurification to study protein complexes. We used this method to investigate Lin28‐mediated microRNA uridylation by TUT4 (terminal uridylyl transferase 4, polyU polymerase), which regulates let‐7 microRNA biogenesis. Our real‐time analysis of the uridylation by the TUT4 immunoprecipitates suggests that Lin28 functions as a processivity factor of TUT4. Our new technique, SIMPlex (single‐molecule approach to immunoprecipitated protein complexes), provides a universal tool to analyse complex proteins at the single‐molecule level.

Experimental studies of strong dipolar interparticle interaction in monodisperse Fe3O4 nanoparticles

Interparticle interaction of monodisperse Fe3O4 nanoparticles has been experimentally investigated by dispersing the nanoparticles in solvents. With increasing the interparticle distances to larger than 100nm in a controlled manner, the authors found that the blocking temperature (TB) of the nanoparticles drops continuously and eventually gets saturated with a total drop in TB of 7–17K observed for 3, 5, and 7nm samples, compared with their respective nanopowder samples. By carefully studying the dependence of TB on the interparticle distance, the authors could demonstrate that the experimental dependence of TB follows the theoretical curve of the dipole-dipole interaction.