Hyun-Jung Kim

Particle-larly good! Thermal annealing and etching of physical composite butyl-capped Si gels and SiO2 nanoparticles at 900 °C under an Ar atmosphere is a versatile method for the formation of 3D porous bulk Si particles (see picture). Complete etching of the SiO2 from the SiO2/carbon-coated Si (c-Si) composite results in the retention of the remaining c-Si as a highly porous but interconnected structure, which preserves the starting morphology.

Thermische Behandlung und Ätzen eines physikalischen Gemischs aus einem Si-Gel mit Butyl-Endgruppen und SiO2-Nanopartikeln bei 900 °C in Argonatmosphäre führen zu dreidimensionalen porösen Si-Partikeln (siehe Bild). Nach dem vollständigen Entfernen des SiO2 verbleibt kohlenstoffbeschichtetes Si (c-Si) als hoch poröse, aber zusammenhängende Struktur mit der ursprünglichen Morphologie.

Layered transition metal dichalcogenides ${\mathrm{MoTe}}_{2}$ and ${\mathrm{WTe}}_{2}$ share almost similar lattice constants as well as topological electronic properties except their structural phase transitions. While the former shows a first-order phase transition between monoclinic and orthorhombic structures, the latter does not. Using a recently proposed van der Waals density functional method, we investigate structural stability of the two materials and uncover that the disparate phase t

The exploration of topological states is of significant fundamental and practical importance in contemporary condensed matter physics, for which the extension to two-dimensional (2D) organometallic systems is particularly attractive. Using first-principles calculations, we show that a 2D hexagonal triphenyl-lead lattice composed of only main group elements is susceptible to a magnetic instability, characterized by a considerably more stable antiferromagnetic (AFM) insulating state rather than th

BACKGROUND: Dexamethasone is a potent glucocorticoid with anti-inflammatory effects. Dexamethasone can protect ischemic cardiomyocytes from apoptosis. To apply the anti-apoptotic effect of dexamethasone to ischemic disease gene therapy, dexamethasone-conjugated polyethylenimine (PEI-Dexa) was synthesized and evaluated as an anti-apoptotic gene carrier. METHODS: PEI-Dexa was synthesized with low molecular weight polyethylenimine (PEI2K, 2 kDa). The transfection efficiency and cytotoxicity of PEI-

Recent experimental evidence that fluorinated graphene creates local magnetic moments around F adatoms has not been supported by semilocal density-functional theory (DFT) calculations where the adsorption of an F adatom induces no magnetic moment in graphene. Here, we show that such an incorrect prediction of the nonmagnetic ground state is due to the self-interaction error inherent in semilocal exchange-correlation functionals. The present hybrid DFT calculation for an F adatom on graphene pred

The Lyman spectrum of substitutional boron acceptors in diamonds with natural composition and that in a ${}^{13}\mathrm{C}$ diamond exhibit remarkably similar features, but shifted to higher energies in the latter by 0.4--1.5 meV. Additional lines appear when the spectra are recorded as a function of temperature, indicating the thermal population of a level ${\ensuremath{\Delta}}^{\ensuremath{'}}\ensuremath{\sim}2\mathrm{meV}$ above the ground state; this can be interpreted as the spin-orbit spl

The precise driving force of the phase transition in indium nanowires on Si(111) has been controversial whether it is driven by a Peierls instability or by a simple energy lowering due to a periodic lattice distortion. The present van der Waals (vdW) corrected hybrid density functional calculation predicts that the low-temperature 8×2 structure whose building blocks are indium hexagons is energetically favored over the room-temperature 4×1 structure. We show that the correction of self-interacti

van der Waals energy-corrected density functional theory (DFT $+$ vdW) as well as the exact exchange with electron correlation in the random-phase approximation are used to study the adsorption of benzene on the Si(001) surface with respect to two controversial adsorption structures (termed ``butterfly'' and ``tight bridge''). Our finding that the tight-bridge structure is energetically favored over the butterfly structure agrees with standard DFT but conflicts with previous vdW-inclusive calcul

Grain boundaries (GBs) are ubiquitous in solids and have been of central importance in understanding the nature of polycrystals. In addition to their classical roles, topological insulators (TIs) offer a chance to realize GBs hosting distinct topological states that can be controlled by their crystal symmetries. However, such roles of crystalline symmetry in two-dimensional (2D) TIs have not been definitively measured yet. Here, we present the first direct evidence of a symmetry-enforced metalli

We report the first observation of the electronic Raman effect in semiconducting p-type, isotopically controlled diamonds. The Raman transition between the spin-orbit split 1s ground states of boron acceptors occurs at ${\ensuremath{\Delta}}^{\ensuremath{'}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2.07\left(1\right)$ and 2.01(1) meV in natural and ${}^{13}\mathrm{C}$ diamonds, respectively. Polarization features show the transition to be predominantly ${\ensuremath{\gamma}}_{5}$ in cha

Using a hybrid density-functional theory (DFT) calculation including spin-orbit coupling (SOC), we predict that the zigzag antiferromagnetic (AFM) ground state of the honeycomb layered compound Na₂IrO₃ opens the observed insulating gap through a long-range magnetic order. We show that the effect of SOC and the correction of self-interaction error inherent in previous local or semilocal DFT calculations play crucial roles in predicting the band gap formation in Na₂IrO₃. It is revealed that the it

This study examines the social network of scholars in the field of Communication by using author co-citation data. A matrix containing the number of co-cited documents between pairs of authors is created for social network analysis of scholars who are on the editorial board of Journal of Communication, and the networked map of the scholars is used to visualize the knowledge structure of the field by identifying groups of authors who are more central than others. Social Science Citation Index (SS

The Zeeman effect of the ${\ensuremath{\Delta}}^{\ensuremath{'}}$ $[1s({p}_{3/2}):{\ensuremath{\Gamma}}_{8}\ensuremath{\rightarrow}1s({p}_{1/2}):{\ensuremath{\Gamma}}_{7}]$ Raman line of boron acceptors in diamond exhibits the predicted eight components and four transitions within the ${\ensuremath{\Gamma}}_{8}$ multiplet, discovered under diverse polarization configurations with high resolution Fabry-P\'erot interferometry. A theory in terms of the pronounced hole mass anisotropy explains the o

Using first-principle density-functional calculations, we investigate the competition between Peierls instability and spin ordering in a zigzag C chain generated in an H-passivated graphene. We find that such a quasi-one-dimensional (1D) C chain of infinite length stabilizes a Peierls instability showing bond alternation with a band-gap opening. As the chain length becomes finite, the Peierls distortion is enhanced at even-numbered chains, while a ferrimagnetic spin ordering with the atomic stru