Young-Ho Khang

The platelet-rich fibrin (PRF) is known as a rich source of autologous cytokines and growth factors and universally used for tissue regeneration in current clinical medicine. However, the microstructure of PRF has not been fully investigated nor have been studied the key molecules that differ PRF from platelet-rich plasma. We fabricated PRF under Choukroun's protocol and produced its extract (PRFe) by freezing at -80°C. The conventional histological, immunohistological staining, and scanning ele

We perform first-principles calculations to investigate the electronic and vibrational spectra and the electron mobility of β-Ga₂O₃. We calculate the electron-phonon scattering rate of the polar optical phonon modes using the Vogl model in conjunction with Fermi's golden rule; this enables us to fully take the anisotropic phonon spectra of the monoclinic lattice of β-Ga₂O₃ into account. We also examine the scattering rate due to ionized impurities or d

The catalytic activity for the hydrogen evolution reaction (HER) at the anion vacancy of 40 2D transition-metal dichalcogenides (TMDs) is investigated using the hydrogen adsorption free energy (Δ G_H) as the activity descriptor. While vacancy-free basal planes are mostly inactive, anion vacancy makes the hydrogen bonding stronger than clean basal planes, promoting the HER performance of many TMDs. We find that ZrSe₂ and ZrTe₂ have similar Δ G_H as Pt, th

Zinc‐based metal oxide semiconductors have attracted attention as an alternative to current silicon‐based semiconductors for applications in transparent and flexible electronics. Despite this, metal oxide transistors require significant improvements in performance and electrical reliability before they can be applied widely in optoelectronics. Amorphous indium–zinc–tin oxide (a‐IZTO) has been considered an alternative channel layer to a prototypical indium–gallium–zinc oxide (IGZO) with the aim

Obesity-induced insulin resistance and diabetes are significantly associated with infiltrates of inflammatory cells in adipose tissue. Previous studies recognized the involvement of autophagy in the regulation of metabolism in multiple tissues, including β-cells, hepatocytes, myocytes, and adipocytes. However, despite the importance of macrophages in obesity-induced insulin resistance, the role of macrophage autophagy in regulating insulin sensitivity is seldom addressed. In the present study, w

Cesium lead halides in the perovskite crystal structure are promising absorbers to enable cheap, high-performance photovoltaics or light-emitting devices. Using first-principles calculations plus Boltzmann transport theory, the authors report an intrinsic limit on the room-temperature carrier mobility of CsPb${X}_{3}$ that is due to scattering via electron-phonon coupling. Using different halides $X$ in the compound can change the mobility by a factor of 3---5, because of the change in electroni

Photovoltaic (PV) absorbers are key components of PV cells used to harvest solar energy, which is an attractive renewable energy resource. In this study, a high-throughput computational screening is conducted to discover potential PV absorbers. While direct-gap semiconductors are usually favored as PV absorbers, herein, we focus on indirect-gap semiconductors that could exhibit a long lifetime of photocarriers because of the low probability of band-to-band recombination, enabling high-performanc

Using the multiscale simulation combining ab initio calculations and kinetic Monte Carlo (KMC) simulations, we theoretically investigate the hydrogen evolution reaction (HER) on the sulfur vacancy of a MoS2 monolayer. Unlike metal catalysts, the protonation step and the charging step proceed independently in semiconducting MoS2. Interestingly, the barrier for hydrogen evolution decreases when the vacancy site is hyper-reduced with extra electrons. The turnover frequency and polarization curve ob

In order to establish the reliable $GW$ scheme that can be consistently applied to post-transition-metal oxides (post-TMOs), we carry out comprehensive $GW$ calculations on electronic structures of ZnO, ${\text{Ga}}_{2}$${\text{O}}_{3}$, ${\text{In}}_{2}$${\text{O}}_{3}$, and ${\text{SnO}}_{2}$, the four representative post-TMOs. Various levels of self-consistency (${G}_{0}{W}_{0}$, $G{W}_{0}$, and $QPG{W}_{0}$) and different starting functionals (GGA, GGA + $U$, and hybrid functional) are teste

Using first‐principles calculation, we investigate the nature of oxygen vacancy ( V O ), namely shallow versus deep, in the amorphous oxide semiconductor InGaZnO 4 ( a ‐IGZO), which has not been fully clarified despite its technological importance. Oxygen‐deficient amorphous models are generated through the hybrid functional molecular dynamics (MD) simulations that allow for finding stable V O configurations while minimizing computational approximations. From eight independent models, we consist

We determine the influence of substitutional defects on perovskite quantum dots through experimental and theoretical investigations. Substitutional defects were introduced by trivalent dopants (In, Sb, and Bi) in CsPbBr3 by ligand-assisted reprecipitation. We show that the photoluminescence (PL) emission peak shifts toward shorter wavelengths when doping concentrations are increased. Trivalent metal-doped CsPbBr3 enhanced the PL quantum yield (~10%) and air stability (over 10 days). Our findings

Abstract The persistent photoconductivity (PPC) in ZnO has been a critical problem in opto-electrical devices employing ZnO such as ultraviolet sensors and thin film transistors for the transparent display. While the metastable state of oxygen vacancy ( V O ) is widely accepted as the microscopic origin of PPC, recent experiments on the influence of temperature and oxygen environments are at variance with the V O model. In this study, using the density-functional theory calculations, we propose

We investigate the vertical ionization potential (IP) and electron affinity (EA) of organic semiconductors in the solid state that govern the optoelectrical property of organic devices using a fully ab initio way. The present method combines the density functional theory and many-body perturbation theory based on $GW$ approximations. To demonstrate the accuracy of this approach, we carry out calculations on several prototypical organic molecules. Since IP and EA depend on the molecular orientati

We theoretically investigate the electron transport mechanism in crystalline In-Ga-Zn oxides using the semi-classical transport theory. The site disorder of Ga and Zn atoms is treated based on the virtual crystal approximation. The valence difference between Ga3+ and Zn2+, modeled by screened Coulomb potential, plays a critical role in determining the total electron mobility. The temperature and carrier-density dependences of the calculated electron mobility are in excellent agreement with exper

Abstract Although C 1 species such as CO and CH 4 constitute the majority of CO 2 reduction (CO 2 R) products on known catalysts, recent experiments showed that 1‐propanol with two C−C bonds is produced as the main CO 2 R product on MoS 2 single crystals in aqueous electrolytes. Herein, the CO 2 R mechanism on MoS 2 is investigated by using first‐principle calculations. Focusing on S‐vacancies ( V S ) as the catalytic site, potential free‐energy pathways to various CO 2 R products are obtained b