Seunghun Hong

Bio: Seunghun Hong is an academic researcher from Seoul National University. The author has contributed to research in topics: Carbon nanotube & Nanolithography. The author has an hindex of 55, co-authored 273 publications receiving 14681 citations. Previous affiliations of Seunghun Hong include Florida State University & Purdue University.

"Dip-Pen" Nanolithography

Abstract: A direct-write “dip-pen” nanolithography (DPN) has been developed to deliver collections of molecules in a positive printing mode. An atomic force microscope (AFM) tip is used to write alkanethiols with 30-nanometer linewidth resolution on a gold thin film in a manner analogous to that of a dip pen. Molecules are delivered from the AFM tip to a solid substrate of interest via capillary transport, making DPN a potentially useful tool for creating and functionalizing nanoscale devices.

Current-Voltage Characteristics of Self-Assembled Monolayers by Scanning Tunneling Microscopy

Abstract: This paper presents a comparison of the theoretical and experimental current-voltage (I-V) characteristics of a self-assembled monolayer of $\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}}\ensuremath{-}\mathrm{x}\mathrm{y}\mathrm{l}\mathrm{y}\mathrm{l}$ dithiol molecules on a gold substrate measured with a scanning tunneling microscope probe. Good quantitative agreement is obtained with the tip-molecule distance as the only ``fitting parameter.'' Several other thiol-coupled molecules that we have studied also show similar agreement. The conceptual picture presented in this paper could be useful for the interpretation of I-V measurements on molecular monolayers in general.

Enhanced Differentiation of Human Neural Stem Cells into Neurons on Graphene

Abstract: However, most previous studies report that hNSCs, without biochemical motifs or co-culturing, differentiated more towards glial cells than neurons. [ 6–8 ] On the other hand, although graphene has attracted much interest for biological applications due to its exotic properties such as biocompatibility, electric conductivity, and transparency, [ 9–12 ] it has not been explored for neural stem cell behavior, yet. Herein, we report a graphene substrate that enhanced the differentiation of hNSCs into neurons. Microarray studies were performed to explore a plausible explanation for this effect. Furthermore, we demonstrated an electrical stimulation on the cells differentiated from hNSCs using graphene as a transparent electrode. Our fi ndings suggest that graphene has a unique surface property that can promote the differentiation of hNSCs toward neurons rather than glia, which should open up tremendous opportunities in stem cell research, neuroscience, and regenerative medicine. Our experimental procedure is summarized in Figure 1 . Graphene was synthesized on a large scale and transferred onto a glass substrate, following a previously reported method (see also Figure S1 and S2 in the Supporting Information). [ 10,11 ] The graphene fi lm on glass was then placed into a laminin solution (20 μ g mL − 1 in culture media for 4 h) so that laminin molecules adhered to both the graphene and the glass and helped hNSC attachment. The hNSCs were seeded on the substrate

Conductance spectra of molecular wires

Abstract: A relatively simple and straightforward procedure for characterizing molecular wires is to measure the conductance spectrum by forming a self-assembled ordered monolayer (SAM) on a metallic surface and using a high scanning-tunneling microscope resolution (STM) tip as the other contact. We find that the conductance spectrum (dI/dV vs. V) can be understood fairly well in terms of a relatively simple model, provided the spatial profile of the electrostatic potential under bias is properly accounted for. The effect of the potential profile is particularly striking and can convert a symmetric conductor into a rectifier and vice versa. The purpose of this paper is to (1) describe the theoretical model in detail, (2) identify the important parameters that influence the spectra and show how these parameters can be deduced directly from the conductance spectrum, and (3) compare the theoretical prediction with experimentally measured conductance spectra for xylyl dithiol and phenyl dithiol.

Multiple ink nanolithography: toward a multiple-Pen nano-plotter

Abstract: The formation of intricate nanostructures will require the ability to maintain surface registry during several patterning steps. A scanning probe method, dip-pen nanolithography (DPN), can be used to pattern monolayers of different organic molecules down to a 5-nanometer separation. An "overwriting" capability of DPN allows one nanostructure to be generated and the areas surrounding that nanostructure to be filled in with a second type of "ink."

Functionalization of Graphene: Covalent and Non-Covalent Approaches, Derivatives and Applications

Abstract: Approaches, Derivatives and Applications Vasilios Georgakilas,† Michal Otyepka,‡ Athanasios B. Bourlinos,‡ Vimlesh Chandra, Namdong Kim, K. Christian Kemp, Pavel Hobza,‡,§,⊥ Radek Zboril,*,‡ and Kwang S. Kim* †Institute of Materials Science, NCSR “Demokritos”, Ag. Paraskevi Attikis, 15310 Athens, Greece ‡Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University Olomouc, 17. listopadu 12, 771 46 Olomouc, Czech Republic Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang 790-784, Korea Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo naḿ. 2, 166 10 Prague 6, Czech Republic

Fabrication of novel biomaterials through molecular self-assembly.

Abstract: Two complementary strategies can be used in the fabrication of molecular biomaterials. In the 'top-down' approach, biomaterials are generated by stripping down a complex entity into its component parts (for example, paring a virus particle down to its capsid to form a viral cage). This contrasts with the 'bottom-up' approach, in which materials are assembled molecule by molecule (and in some cases even atom by atom) to produce novel supramolecular architectures. The latter approach is likely to become an integral part of nanomaterials manufacture and requires a deep understanding of individual molecular building blocks and their structures, assembly properties and dynamic behaviors. Two key elements in molecular fabrication are chemical complementarity and structural compatibility, both of which confer the weak and noncovalent interactions that bind building blocks together during self-assembly. Using natural processes as a guide, substantial advances have been achieved at the interface of nanomaterials and biology, including the fabrication of nanofiber materials for three-dimensional cell culture and tissue engineering, the assembly of peptide or protein nanotubes and helical ribbons, the creation of living microlenses, the synthesis of metal nanowires on DNA templates, the fabrication of peptide, protein and lipid scaffolds, the assembly of electronic materials by bacterial phage selection, and the use of radiofrequency to regulate molecular behaviors.

"Dip-Pen" Nanolithography

Abstract: A direct-write “dip-pen” nanolithography (DPN) has been developed to deliver collections of molecules in a positive printing mode. An atomic force microscope (AFM) tip is used to write alkanethiols with 30-nanometer linewidth resolution on a gold thin film in a manner analogous to that of a dip pen. Molecules are delivered from the AFM tip to a solid substrate of interest via capillary transport, making DPN a potentially useful tool for creating and functionalizing nanoscale devices.