Current Projects
I research the properties and behaviors of matter at the molecular level
STM-BJ Technique
The scanning tunneling microscope-based break-junction (STM-BJ) technique is a powerful tool for investigating the behavior of single molecules. This technique involves pulling one electrode away from another until a molecule links the gap between them, forming a single-molecule circuit. The conductance (resistance) of the molecule can then be measured, typically by combining thousands of traces to determine the average conductance. Throughout the measurements, experimental conditions such as temperature, electrochemical environments, and light irradiation can be varied to further study the behavior of the molecule.
Thermal Control
Using a custom-built variable-temperature STM-BJ setup, I research how temperature affects electron transport through single-molecule junctions. This research aims to identify and understand factors such as structure rearrangement, electron transport mechanisms, and molecular conformation that contribute to temperature-dependent conductance. Recently, I found that oligo[n]phenylenes exhibit clear temperature-dependent conductance, and proposed a theoretically verified hypothesis.
Electrochemical Control
Controlling the redox state of molecules in single-molecule junctions is one of my research interests. Through the use of electrochemical environments such as gating electrodes and chemical oxidizing/reducing reagents, I can precisely manipulate the redox state of the molecule and investigate the resulting changes in current flow. Additionally, the redox state can affect the binding between the molecule and the electrodes, resulting in the formation of junctions only in specific redox states. These redox-active single-molecule junctions hold promise for the development of switchable single-molecule devices.
Optical Control
By combining a microscopy setup with the STM-BJ technique, I study how light-molecule interaction affects electron transport through single-molecule junctions. The aim of the project is to improve the performance of single-molecule devices with optical-induced effects. On the other hand, I investigate the effect of an electric field (E-field) strongly generated between two electrodes on single-molecule devices. The expected effects of E-field include modification of molecular optical properties, such as fluorescence, as well as in-situ monitoring of chemical reactions catalyzed by E-field such as Ullmann coupling.
Previous Projects (at SKKU)
I studied the dynamics of polymer films
Ellipsometry
Designed a chamber for an Ellipsometry experiment (constant cooling rate in the vacuum condition)
Devised methods to vary deposition parameters of polymer thin films (Spin-coating and Langmuir-Blodgett)
Identified the glass transition temperature variation depending on deposition parameters by using an ellipsometer
Fluorescence Microscope
Built a microscope for measuring the ensemble rotational dynamics of fluorescent probe molecules, and identifying the dynamics of single probe molecules
Built a microscope for conducting FRAP & FRET experiments, and conducted an FRAP study on polystyrene (PS) dynamics
Developed analysis program (using MATLAB) for the FRAP experiment
Glass Transition Temperature (Tg) Determination Using AIE (Aggregation-Induced Emission)
Designed a vacuum fluorometer, and conducted a study on determining the Tg of glass materials by using AIE molecules
Contributed to preparing grant applications and proposals for government-funded research projects
Polymer thin films (PMMA and PEMA) doped with AIE molecules show different intensity values of fluorescence depending on temperature.
Since AIE molecules have a kinetic origin, these molecules can be used as probe molecules in polymer films in determining Tg of the polymer.
