Hanyang University · Engineering
Professor Jaegeun Noh's research lab specializes in the fundamental understanding of self-assembled monolayers (SAMs) at solid-liquid and solid-vacuum interfaces, with a focus on molecular-scale structure, dynamics, and stability. The lab employs advanced surface characterization techniques such as scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and high-resolution electron energy loss spectroscopy (HREELS) to investigate molecular packing, phase transitions, and interfacial interactions in thiophene, alkanethiol, and disulfide-based SAMs on gold and graphite substrates. Key research directions include the role of molecular interactions—such as cofacial π–π stacking and hydrogen bonding—in determining monolayer organization, as well as the kinetics and thermodynamics of surface reconstruction and desorption processes under various environmental conditions. The lab’s work provides critical insights into the design of functional nanostructures for applications in molecular electronics, sensors, and surface engineering.
Figures are computed from collected data and may differ slightly.
Structure and binding condition of thiophene self-assembled monolayers (SAMs) formed on Au(111) were investigated by using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). The STM study revealed the first molecularly resolved image for closely packed thiophene SAMs having two domain structures: disordered phases near domain boundaries and ordered domains consisting of pairs of molecules separated from each other by 4.35 Å, from the next row by 3.9 Å, and from the n
Scanning tunneling microscopy (STM) and high-resolution electron energy loss spectroscopy (HREELS) were used to examine the structural transitions and interface dynamics of octanethiol (OT) self-assembled monolayers (SAMs) caused by long-term storage or annealing at an elevated temperature. We found that the structural transitions of OT SAMs from the c(4 x 2) superlattice to the (6 x square root 3) superlattice resulting from long-term storage were caused by both the dynamic movement of the adso
Time-dependent phase transitions of closely packed alkanethiol self-assembled monolayers (SAMs) on Au(111) were investigated by scanning tunneling microscopy (STM). We report a new phase, the 6 × √3 superlattice, that exhibits deviations from the hexagonal packing arrangement formed through long-term rearrangement of the usual c(4 × 2) superlattice of alkanethiol SAMs. Our STM images show clearly systematic phase transitions with molecular-scale images from the c(4 × 2) phase to the 6 × √3 phase
The formation of striped phases of dialkyl disulfides and dialkyl sulfides on Au(111) and graphite has been monitored by scanning tunneling microscopy (STM) to investigate differences in adsorption of the sulfide to the gold surface. Striped phases formed by C18H37S- moieties after S−S bond cleavage of dioctadecyl disulfide on the gold surface were observed. On the other hand, self-assembled monolayers (SAMs) of dioctadecyl disulfide and dioctadecyl sulfide adsorbed on a graphite surface display
We have monitored the adsorption process of 11-hydroxyundecyl octadecyl disulfide (CH3(CH2)17SS(CH2)11OH, HUOD) self-assembled monolayers (SAMs) on the Au(111) surface during the initial SAM growth stage using scanning tunneling microscopy (STM). STM imaging clearly exhibits two types of phase-separated domains having different corrugation periodicities which are consistent with the lengths of CH3(CH2)17S and HO(CH2)11S molecules, respectively. This is the first direct observation of the dissoci
The structural changes as a function of the immersion time of predeposited hexanethiol self-assembled monolayers (SAMs) chemisorbed on an Au(111) surface in diethyl ether at room temperature have been investigated by scanning tunneling microscopy (STM). High-resolution STM images show molecular-scale morphological changes of the monolayers resulting from the desorption of molecules from the surface and provide a significant implication for the stability of the monolayers in pure organic solvent.
Surface and adsorption structures of dioctadecyl sulfide (DOS) self-assembled monolayers (SAMs) on Au(111) were examined by scanning tunneling microscopy (STM) and high-resolution electron energy loss spectroscopy (HREELS). In comparison with alkanethiol or dialkyl disulfide SAMs, the molecularly resolved STM images clearly showed that DOS SAMs have significant structural differences in the formation of depressions and ordered domains, and in the lattice structure, including the presence of conf
The formation and structure of tetrahydrothiophene (THT) self-assembled monolayers (SAMs) on Au(111) were examined using X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). XPS measurements revealed that THT molecules, containing endo-sulfur aliphatic rings, can form chemisorbed SAMs, in contrast with the formation of physisorbed SAMs by dialkyl monosulfide, suggesting that the adsorption ability of monosulfide compounds on gold strongly depends on the structure of ta
Although the adsorption of benzenethiols (BT) on Au(111) usually leads to the formation of disordered phases, we demonstrate here that the displacement of preadsorbed cyclohexanethiol self-assembled monolayers (SAMs) on Au(111) by BT molecules can be a successful approach to obtain two-dimensional BT SAMs with long-range ordered domains.
The surface structure and electrochemical behavior of self-assembled monolayers (SAMs) formed by aromatic thiols on Au(111) were investigated by scanning tunneling microscopy (STM) and cyclic voltammetry. Benzenethiol (BT) forms disordered phases on Au(111) which are composed of many bright domains, while benzyl mercaptan (BM), with a methylene unit between the aromatic group and sulfur atom, forms twodimensional ordered SAMs on Au(111). In addition, two phase-separated domains consisting of dis
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