Myung Hwa Kim

RuO2 nanorods on electrospun carbon nanofibers were simply grown by precipitation and recrystallization methods for studying their capacitive behaviors for supercapacitor applications. Recrystallization by heat treatment is carefully performed at various temperatures: 180, 220, and 300 °C. Under optimal growth conditions, application of RuO2-carbon nanofibers annealed at 220 °C with a very low loading concentration of Ru as the electrode material in a KOH aqueous electrolyte leads to a good capa

Ion imaging reveals distinct photodissociation dynamics for propanal cations initially prepared in either the cis or gauche conformation, even though these isomers differ only slightly in energy and face a small interconversion barrier. The product kinetic energy distributions for the hydrogen atom elimination channels are bimodal, and the two peaks are readily assigned to propanoyl cation or hydroxyallyl cation coproducts. Ab initio multiple spawning dynamical calculations suggest that distinct

Polydiacetylenes (PDAs), a family of conjugated polymers, are very intriguing materials in several aspects. Especially, the stimulus-induced apparent blue-to-red transition of the PDAs has led to the development of a variety of PDA-based chemosensors. In the current work, we synthesized PDA monomers bearing trimethyl amine (PCDA-DMEDA) and incorporated them with Poly(ethylene oxide) (PEO) into electrospun fibers. For the first time, we successfully demonstrated that PDA-based electrospun fibers

An ESIPT based fluorescent probe, containing a hydroxyphenyl-benzothiazole fluorophore and an oxime reaction site, serves as a selective probe for a nerve gas mimic, diethyl cyanophosphonate (DECP), in solutions and the gas phase. The probe exhibits more than a 60-fold fluorescence enhancement in the presence of the target, has a limit of detection of 1.3 nM and displays high selectivity toward DECP over closely related substances, including sulfur mustard stimulants and other nerve agent mimics

Because of the current shortage of first-generation phosgene sensors, increased attention has been given to the development of fluorescent and colorimetric based methods for detecting this toxic substance. In an effort focusing on this issue, we designed the new, second-generation phosgene chemosensor 1 and demonstrated that it undergoes a ring-opening reaction with phosgene in association with color and fluorescent changes with a detection limit of 3.2 ppb. Notably, in comparison with the first

Nanometer-sized liquid droplets formed at temperatures below the bulk melting point become supercooled as they grow through Ostwald ripening or coalescence and can be exploited to grow nanowires without any catalyst. We used this simple approach to synthesize a number of highly crystalline metal oxide nanowires in a chemical or physical vapor deposition apparatus. Examples of nanowires made in this way include VO(2), V(2)O(5), RuO(2), MoO(2), MoO(3), and Fe(3)O(4), some of which have not been pr

The temperature dependence of the dissociation constants for formic acid and 2,6-dinitrophenol (2,6-DNP) has been determined in aqueous solutions from 25 to 175 °C using spectrophotometric measurements. The optical indicator 2,6-DNP was employed to measure the pH of a buffer solution by deconvolution of absorption spectra of 2,6-DNP at various temperatures. First, using the temperature dependence of pKa for acetic acid, pKi of 2,6-DNP were determined in acetate buffer solutions as a function of

Photoswitchable materials have attracted considerable attention in various fields. Developing excellent solid-state dual-mode photoswitches is an important but challenging task. Herein, we propose a new strategy to construct an excited-state intramolecular proton transfer (ESIPT) inspired photoswitch (DiAH-pht) that possesses aggregation-induced emission (AIE) features and displays a fast molecular isomerization process characterized by dual-mode behavior in the solid state. Mechanistic studies

A new imaging technique, reflectron multimass velocity map ion imaging, is used to study the vibrationally mediated photodissociation dynamics in the ethylene cation. The cation ground electronic state is prepared in specific vibrational levels by two-photon resonant, three-photon ionization via vibronic bands of (pi, nf) Rydberg states in the vicinity of the ionization potential of ethylene, then photodissociated through the (B 2A(g)) excited state. We simultaneously record spatially resolved i

Ni_xRh_1–x bimetallic alloy nanofibers synthesized by H₂-reduction of NiRh₂O₄ exhibited outstanding pH-universal HER electrocatalytic activity with high stability.