Sung-Nam Park

A novel strategy for designing highly efficient and activatable photosensitizers that can effectively generate reactive oxygen species (ROS) under both normoxia and hypoxia is proposed. Replacing both oxygen atoms in conventional naphthalimides (RNI-O) with sulfur atoms led to dramatic changes in the photophysical properties. The remarkable fluorescence quenching (ΦPL ≈ 0) of the resulting thionaphthalimides (RNI-S) suggested that the intersystem crossing from the singlet excited state to the re

Abstract Novel BODIPY photosensitizers were developed for imaging‐guided photodynamic therapy. The introduction of a strong electron donor to the BODIPY core through a phenyl linker combined with the twisted arrangement between the donor and the BODIPY acceptor is essential for reducing the energy gap between the lowest singlet excited state and the lowest triplet state (Δ E ST ), leading to a significant enhancement in the intersystem crossing (ISC) of the BODIPYs. Remarkably, the BDP‐5 with th

Hydrogen bond dynamics of water in NaBr solutions are studied by using ultrafast 2D IR vibrational echo spectroscopy and polarization-selective IR pump-probe experiments. The hydrogen bond structural dynamics are observed by measuring spectral diffusion of the OD stretching mode of dilute HOD in H(2)O in a series of high concentration aqueous NaBr solutions with 2D IR vibrational echo spectroscopy. The time evolution of the 2D IR spectra yields frequency-frequency correlation functions, which pe

Hydrogen bond dynamics of water in highly concentrated NaBr salt solutions and reverse micelles are studied using ultrafast 2D-IR vibrational echo spectroscopy and polarization-selective IR pump-probe experiments performed on the OD hydroxyl stretch of dilute HOD in H(2)O. The vibrational echo experiments measure spectral diffusion, and the pump-probe experiments measure orientational relaxation. Both experimental observables are directly related to the structural dynamics of water's hydrogen bo

for absorption and emission bandwidths, and 0.209, 0.371, and 0.262 for the logarithm of the extinction coefficient, PLQY, and emission lifetime, respectively. Finally, we demonstrated how a blue emitter with desired optical and photophysical properties could be efficiently virtually screened and developed by DL optical spectroscopy. DL optical spectroscopy can be efficiently used for developing chromophores and fluorophores in various research areas.

The structural and dynamical properties of aqueous ionic solutions influence a wide range of natural and biological processes. In these solutions, water has the opportunity to form hydrogen bonds with other water molecules and anions. Knowing the time scale with which these configurations interconvert represents a key factor to understanding the influence of molecular scale heterogeneity on chemical events in aqueous ionic solutions. We have used ultrafast IR spectroscopy and Car-Parrinello mole

Experimental databases on the optical properties of organic chromophores are important for the implementation of data-driven chemistry using machine learning. Herein, we present a series of experimental data including various optical properties such as the first absorption and emission maximum wavelengths and their bandwidths (full width at half maximum), extinction coefficient, photoluminescence quantum yield, and fluorescence lifetime. A database of 20,236 data points was developed by collecti

Organic thermally activated delayed fluorescence (TADF) materials are emerging as potential candidates for time-resolved fluorescence imaging in biological systems. However, the development of purely organic TADF materials with bright aggregated-state emissions in the red/near-infrared (NIR) region remains challenging. Here, we report three donor-acceptor-type TADF molecules as promising candidates for time-resolved fluorescence imaging, which are engineered by direct connection of electron-dona

Electron dynamics in Au nanorods are studied with femtosecond nonlinear spectroscopic techniques, by directly exciting and probing the longitudinal surface plasmon resonance. The dispersive and absorptive parts of the third-order signal are measured using optical heterodyne detected four-wave-mixing spectroscopy. These signals are used to describe dynamics in Au nanorods in terms of frequency shift and broadening of the plasmon resonance. Pump−probe experiments are performed with a series of pum

Tubular materials formed by self-assembly of small organic molecules find great utility in chemical and material science. Conventional tubular structures often lack stability because noncovalent molecular interactions are responsible for their conformational integrities. Herein we report the development of covalently linked chromogenic organic nanotubes which are prepared by using topochemical polymerization of self-assembled macrocyclic diacetylenes (MCDAs). Crystal structures of five MCDAs hav

Vibrational chromophores that are sensitive to local electrostatic environment are useful probes of structural variations of proteins on subnanosecond time scales, but their short vibrational lifetimes often limit their applicability. Here we explore a possibility to increase the lifetime of nitrile probes by introducing heavy atoms between the probe and protein side chains. Stereoisomers of thiocyanato- and selenocyanato-derivatized prolines, Pro-SCN and Pro-SeCN, are synthesized, and their CN

A single component polymer solar cell with a CDABP film annealed at 180 °C showed a maximum power conversion efficiency of 5.28%, which is much higher than that (2.62%) of the device with the as-cast film.

We have used time-resolved multidimensional vibrational spectroscopy, generally termed 2DIR spectroscopy, to study the equilibrium dynamics of ligand exchange in an aqueous solution containing 3.4 M Mg(ClO(4))(2) and 1.2 M NaSCN. The sensitivity of the CN stretching frequency of thiocyanate (SCN(-)) to contact ion pair formation with Mg(2+) ions generates distinct spectroscopic signatures for the MgNCS(+) contact ion pair and the free SCN(-). We have utilized 2DIR spectroscopy to successfully re