A5068442965- Photochemistry and Electron Transfer Studies
- Spectroscopy and Quantum Chemical Studies
- Photoreceptor and optogenetics research
- Porphyrin and Phthalocyanine Chemistry
- ZnO doping and properties
- Ga2O3 and related materials
- Quantum Dots Synthesis And Properties
- Photosynthetic Processes and Mechanisms
- Laser-Matter Interactions and Applications
- Advanced Fluorescence Microscopy Techniques
- Luminescence and Fluorescent Materials
- Molecular spectroscopy and chirality
- Carbon Nanotubes in Composites
- Chalcogenide Semiconductor Thin Films
- Electron Spin Resonance Studies
- Photochromic and Fluorescence Chemistry
- Organic Electronics and Photovoltaics
- GaN-based semiconductor devices and materials
- Mechanical and Optical Resonators
- Lipid Membrane Structure and Behavior
- DNA and Nucleic Acid Chemistry
- Free Radicals and Antioxidants
- Molecular Junctions and Nanostructures
- Copper-based nanomaterials and applications
- Advanced Fiber Laser Technologies
Pohang University of Science and Technology
2016-2025
Nanyang Technological University
2020
Government of the Republic of Korea
2015
Korea Post
2012
Seoul National University
2005-2012
University of California, Los Angeles
2012
Center for Integrated Nanotechnologies
2012
Los Alamos National Laboratory
2012
Ajou University
2010-2011
Korea University
2008-2011
A novel coumarin-based fluorogenic probe bearing the 2-picolyl unit (1) was developed as a fluorescent chemosensor with high selectivity and suitable affinity in biological systems toward Cu2+ over other cations tested. The fluorescence on−off mechanism studied by femtosecond time-resolved (TRF) upconversion technique ab initio calculations. receptor can be applied to monitoring of ion aqueous solution pH span 4−10. To confirm suitability 1 for applications, we also employed it detection...
Several closely related third-order nonlinear time-resolved spectroscopic techniques, pump/probe transient absorption, grating, and three pulse stimulated photon echo peak shift measurements, are investigated theoretically experimentally. It is shown in detail, through the consideration of response functions numerical simulations including both finite durations detuning from exact resonance, how solvation dynamics manifested these spectroscopies. that measurement grating can give accurate...
Size‐controlled soft‐template synthesis of carbon nanodots (CNDs) as novel photoactive materials is reported. The size the CNDs can be controlled by regulating amount an emulsifier. As increases, exhibit blue‐shifted photoluminescence (PL) or so‐called inverse PL shift. Using time‐correlated single photon counting, ultraviolet photoelectron spectroscopy, and low‐temperature measurements, it revealed that are composed sp 2 clusters with certain energy gaps their oleylamine ligands act...
The time-integrated three-pulse photon echo is discussed in terms of the line-shape functions which are shown to be directly related solvation dynamics. By using short-time approximation function, an algebraic form signal SPE (τ, T) obtained as a function two delay times, τ and T, between pulses. On basis approximate signal, peak shift with respect second time (population evolution period) derived found linearly proportional time-dependent fluorescence Stokes for times greater than bath...
The lipid-rafts hypothesis proposes that naturally occurring lipid aggregates exist in the plane of membrane are involved signal transduction, protein sorting, and transport. To understand their roles cell biology, a direct visualization such domains living cells is essential. For this purpose, 6-dodecanoyl-2-(dimethylamino)naphthalene (laurdan), probe sensitive to polarity membrane, has often been used. We have synthesized characterized...
The energy transfer from the accessory bacteriochlorophylls (B) to special pair (P) in photosynthetic reaction center has been time resolved with pump−probe polarization anisotropy measurements using 20−25 fs duration pulses near 800 nm. experiments were carried out at low pulse energies (500 pJ a 34 μm spot), repetition rates (5 kHz), and high sample flow velocities (100 cm/s) avoid artifacts saturation photoexcitation of incompletely relaxed centers. pump excitation corresponds 1.4 × 106...
Synthesis of a size series colloidal ZnTe/ZnSe (core/shell) quantum dots (QDs) is reported. Because the unique Type-II characters, their emission can range over an extended wavelength regime, showing photoluminescence (PL) from blue to amber. The PL lifetime measures as long 77 ns, which clearly indicates characteristics. (Core/Shell) QDs be further passivated by ZnS layers, rendered in water, while preserving optical and chemical stabilities thus proved potentials toward “nontoxic”...
Structural factors governing the poor emission of dipolar dyes in aqueous media are identified, leading to new acedan derivatives with brighter fluorescence and enhanced two-photon properties.
Initiated by excited-state intramolecular proton transfer (ESIPT) reaction, an overall reaction cycle of 4-(2-hydroxybenzylidene)-1,2-dimethyl-1H-imidazol-5(4H)-one (o-HBDI), analogue the core chromophore green fluorescent protein (GFP), has been investigated. In contrast to native GFP core, 4-(4-hydroxybenzylidene)-1,2-dimethyl-1H-imidazol-5(4H)-one (p-HBDI), which requires hydrogen-bonding relay accomplish in vivo, o-HBDI possesses a seven-membered-ring hydrogen bond and thus provides...
Proton transfer is one of the most important elementary reactions in chemistry and biology. The role proton course transfer, whether it active or passive, has been subject intense investigations. Here we demonstrate excited state intramolecular (ESIPT) 10-hydroxybenzo[h]quinoline (HBQ). ESIPT HBQ proceeds 12 ± 6 fs, rate slowed down to 25 5 fs for DBQ where reactive hydrogen replaced by deuterium. results are consistent with ballistic wave packet within experimental uncertainty. This...
We report on photoluminescence (PL) spectra of ZnO films grown by low pressure metalorganic vapor phase epitaxy. For PL measurements, high quality thin were epitaxially Al2O3(0001) substrates. Time-integrated the at 10 K clearly exhibited free A and B excitons 3.376 3.382 eV bound exciton peaks 3.360, 3.364, 3.367 eV. With increasing temperature, intensities drastically decreased a peak was dominant above 40 K. Furthermore, time-resolved measurements carried out room temperature. The decay...
The underlying dynamics of the B800 absorption band in isolated LH2 Rb. sphaeroides at room temperature is studied by transient absorption, grating, and photon echoes using 30 fs pulses. energy transfer time from to B850 determined be 800 fs, similar value reported previously. three pulse stimulated echo identifies several important contributions line shape thereby system involved: low frequency intramolecular vibrations, ultrafast bath (solvent protein) responses, static inhomogeneity...
The three-pulse photon echo peak shift technique is used to study room temperature solvation dynamics in acetonitrile, benzonitrile, methanol, ethanol, ethylene glycol, and chloroform utilizing the tricarbocyanine dye, IR144 as probe molecule. In all cases, an ultrafast component, ascribed inertial solvent motion, was evident after very rapid dephasing of intramolecular vibrational modes. All solvents except acetonitrile show biexponential behavior on picosecond (diffusive) time scale. case...
Femtosecond fluorescence anisotropy measurements for a variety of cyclic porphyrin arrays such as Zn(II)porphyrin m-trimer and hexamer are reported along with o-dimer monomer reference molecules. In the arrays, pair moieties joined together via triphenyl linkage to ensure rigid structures. Anisotropy decay times can be well described by Förster incoherent excitation hopping process between units. Exciton coupling strengths 74 264 cm(-1) estimated from observed energy rates close those B800...
Size dependence of the time-resolved photoluminescence (TRPL) has been investigated for ZnO nanorods fabricated by catalyst-free metalorganic chemical vapor deposition. The have a diameter 35 nm and lengths in range 150 to 1.1 μm. TRPL decay rate decreases monotonically as length increases 600 nm. Decrease radiative exciton-polariton invoked account results.
We report a new two-photon fluorescence turn-on probe 6-[(E)-3-oxo-1-dodecenyl]-2-[N-methyl-N-(carboxymethyl)amino]naphthalene (CL2) that is designed specifically for visualizing lipid rafts in living cells and tissues. This emits much brighter excited than non-raft domains allows direct visualization of the live pyramidal neuron layer CA1 region at depth 100−250 μm tissues using microscopy.
Excited state intramolecular proton transfer (ESIPT) and subsequent charge (ICT) dynamics of a 2-(2'-hydroxyphenyl)benzoxazole derivative conjugated with an electron withdrawing group (HBOCE) in solutions polymer film has been investigated by femtosecond time-resolved fluorescence (TRF) TRF spectra measurements without the conventional spectral reconstruction method. high enough resolution (<100 fs) reveals that ESIPT HBOCE liquids proceeds at least two time constants approximately 250 fs...
An ultra-fast chemical reaction can act as an impulsive excitation of the vibrations. Excited state intramolecular proton transfer in 10-hydroxybenzo[h]quinoline proceeds 13 fs. As a result, product vibrational modes with their periods longer than (13 × 2) fs are coherently excited potential surface, which be observed most unambiguously by oscillations time-resolved fluorescence signal keto isomer.
Abstract Poly(3‐hexylthiophene) (P3HT) hybrids with single‐walled carbon nanotubes (SWNTs) were prepared using a series of SWNTs various defect contents on their surfaces. The synthesized by exploiting the π – interaction between P3HT and SWNTs, resulting in efficient dispersion solution. UV‐visible photoluminescence (PL) spectra showed that quench PL hybrids, indicating electron transfer occurs from photo‐excited to SWNTs. This was disrupted presence defects SWNT However, lifetime found be...
Reaction-based fluorescent probes for monoamine oxidases A and B are developed based on a new two-photon absorbing compound its precursor. The show turn-on fluorescence response to the enzymes owing produced by enzymatic activity, as monitored one- well microscopy first time.
Good solvent, poor solvent: A simple precipitation method enabled the spontaneous formation of homogeneous C70 cube crystals by self-crystallization in cavities a good solvent (mesitylene) surrounded (isopropyl alcohol, IPA; see picture). The enormously increased photoluminescence (PL) intensity relative to that powder was mainly attributed high crystallinity cubes. Detailed facts importance specialist readers are published as ”Supporting Information”. Such documents peer-reviewed, but not...
The electronic dephasing of two oxazine dyes dissolved in ethylene glycol at room temperature is investigated by femtosecond degenerate four wave mixing (DFWM) experiments. Both two-pulse and three-pulse DFWM with simultaneous detection the signals distinct phase-matching directions permits detailed investigation dynamics a liquid. At least stochastic processes are responsible for observed dephasing: one treated empirically as an exponential decay; second regarded full analytic form Kubo...
The temperature dependence of the optical dephasing mechanism in an organic polymer glass, polymethylmethacrylate (PMMA), was studied from 300 K to 30 using dye IR144 as a probe. Transient grating and three pulse photon echo measurements were made, peak shift (3PEPS) recorded function temperature. data reveal time constants ∼6 fs ∼60 fs, along with vibrational beats long-time constant value for shift. 6 component is attributed intramolecular vibrations 60 librational degrees freedom PMMA...
While it is accepted that protein flexibility plays a role in folding, catalysis, and molecular recognition, few techniques are capable of the rigorous measurement motions required to quantify flexibility. Three-pulse photon echo shift spectroscopy can be used measure time scale motions, we have this technique, along with steady-state binding structural data, examine immunological evolution an anti-fluorescein antibody. Two light chain somatic mutations increase affinity for fluorescein by...