Myung-Hwan Whangbo

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A new composite photocatalyst Ag/AgBr/WO(3).H(2)O was synthesized by reacting Ag(8)W(4)O(16) with HBr and then reducing some Ag(+) ions in the surface region of AgBr particles to Ag nanoparticles via the light-induced chemical reduction. Ag nanoparticles are formed from AgBr by the light-induced chemical reduction reaction. The Ag/AgBr particles are on the(More)
The efforts to produce photocatalysts operating efficiently under visible light have led to a number of plasmonic photocatalysts, in which noble metal nanoparticles are deposited on the surface of polar semiconductor or insulator particles. In the metal-semiconductor composite photocatalysts, the noble metal nanoparticles act as a major component for(More)
Nanoparticles (NPs) of noble metals can strongly absorb visible light because of their plasmon resonance, which is greatly influenced by their morphology and size. The phenomenon of plasmon resonance gives rise to important applications such as colorimetric sensors, photovoltaic devices, photochromic devices, and photocatalysts. Noble metal NPs exhibit(More)
It is highly desirable to produce narrow-width graphene nanoribbons (GNRs) with smooth edges in large scale. In an attempt to solve this difficult problem, we examined the hydrogenation of GNRs on the basis of first principles density functional calculations. Our study shows that narrow GNRs can be readily obtained from wide GNRs by partial hydrogenation.(More)
X-ray scattering by multiferroic LuFe2O4 is reported. Below 320 K, superstructure reflections indicate an incommensurate charge order with propagation close to (1/3 1/3 3/2). The corresponding charge configuration, also found by electronic structure calculations as most stable, contains polar Fe/O double layers with antiferroelectric stacking. Diffuse(More)
By performing density functional calculations, we investigate the origin of the Skyrmion state and ferroelectricity in Cu2OSeO3. We find that the Dzyaloshinskii-Moriya interactions between the two different kinds of Cu ions are extremely strong and induce the helical ground state and the Skyrmion state in the absence and presence of a magnetic field,(More)
The ferroelectricity of the spiral magnets LiCu2O2 and LiCuVO4 was examined by calculating the electric polarizations of their spin spiral states on the basis of density-functional theory with spin-orbit coupling. Our work unambiguously reveals that spin-orbit coupling is responsible for the ferroelectricity with the primary contribution from the spin-orbit(More)
Ferroelectricity is a potentially crucial issue in halide perovskites, breakthrough materials in photovoltaic research. Using density functional theory simulations and symmetry analysis, we show that the lead-free perovskite iodide (FA)SnI3, containing the planar formamidinium cation FA, (NH2CHNH2)(+), is ferroelectric. In fact, the perpendicular(More)