Do Heo - Academia.edu (original) (raw)

Papers by Do Heo

Ceramist, 2020

Metal-organic frameworks (MOFs) and MOF-derived materials have been used for several applications... more Metal-organic frameworks (MOFs) and MOF-derived materials have been used for several applications, such as hydrogen storage and separation, catalysis, and drug delivery, owing to have a significantly large surface area and open pore structure. In recent years, MOFs have also been applied to thin-film solar cells, and attractive results have been obtained. In perovskite solar cells (PSCs), the MOF materials are used in the form of an additive for electron and hole transport layers, interlayer, and hybrid perovskite/MOF. MOFs have the potential to be used as a material for obtaining PSCs with high efficiency and stability. In this study, we briefly explain the synthesis of MOFs and the performance of organic and dye-sensitized solar cells with MOFs. Furthermore, we provide a detailed overview on the performance of the most recently reported PSCs using MOFs.

Materials, 2020

Planar perovskite solar cells were fabricated on F-doped SnO2 (FTO) coated glass substrates, with... more Planar perovskite solar cells were fabricated on F-doped SnO2 (FTO) coated glass substrates, with 4,4’-((1E,1’E)-((1,2,4-thiadiazole-3,5-diyl)bis(azaneylylidene))bis(methaneylylidene))bis(N,N-di-p-tolylaniline) (bTAThDaz) as hole transport material. This imine was synthesized in one step reaction, starting from commercially available and relatively inexpensive reagents. Electrochemical, optical, electrical, thermal and structural studies including thermal images and current-voltage measurements of the full solar cell devices characterize the imine in details. HOMO-LUMO of bTAThDaz were investigated by cyclic voltammetry (CV) and energy-resolved electrochemical impedance spectroscopy (ER-EIS) and were found at −5.19 eV and −2.52 eV (CV) and at −5.5 eV and −2.3 eV (ER-EIS). The imine exhibited 5% weight loss at 156 °C. The electrical behavior and photovoltaic performance of the perovskite solar cell was examined for FTO/TiO2/perovskite/bTAThDaz/Ag device architecture. Constructed devi...

Journal of speech-language & hearing disorders, 2020

The Journal of Physical Chemistry C, 2019

Materials, 2018

CH3NH3PbI3-xClx species were fabricated as light-absorbing layers for perovskite solar cells (PSC... more CH3NH3PbI3-xClx species were fabricated as light-absorbing layers for perovskite solar cells (PSCs), by employing NH4I, NH4Br, and NH4Cl as additives via annealing at 100 °C for different times. Solutions containing CH3NH3I, PbI2, and PbCl2 (4:1:1 molar ratio) in N,N-dimethylformamide were used to prepare perovskites with NH4I, NH4Br, and NH4Cl as additives, at concentrations of 0.1 M and 0.3 M. The additives helped increase the grain size and reduce pinholes in the perovskite films, as confirmed by field-emission scanning electron microscopy. The X-ray diffraction profiles of CH3NH3PbI3-xClx clearly showed peaks at 14° and 28° for the samples with additives, indicative of crystallinity. The best PSC performance with a power conversion efficiency of 9.13%, was achieved using 0.1 M NH4I by annealing for 5 min, whereas the power conversion efficiency of the perovskite solar cells without additives was 5.40%.

The Journal of Physical Chemistry C, 2018

The role of additives on the performance of CsPbI 3 perovskite solar cells (PSCs) was investigate... more The role of additives on the performance of CsPbI 3 perovskite solar cells (PSCs) was investigated. Different kinds of cations and anions were used as additives in a N,N-dimethylformamide (DMF) solution containing CsI and PbI 2 (1:1 molar ratio). These include HI, HBr, HCl, NH I, NH Br, and NH Cl. Additive cations (H + and NH 4 +) as well as halide ions (I-, Brand nd Cl-) are important for the properties of PSCs. Especially, the addition of iodine ion showed good characteristics compared to Brand Cl-. Among the CsPbI 3 layers prepared with different kinds of additives and annealed at different temperatures, the X-ray diffraction peaks of CsPbI 3 were clearly found at 14° and 28° for the sample annealed at 150 °C with 50 µL HI, suggesting the formation of a cubic structure at the low temperature of 150 °C. The field emission scanning electron microscopy images indicate that the surface of the perovskite layer with hydrogen halide additive (H + based additive) is more uniform than that with ammonium additive. The roughness profiles determined by atomic force microscopy indicate that the CsPbI 3 film with HI additive shows the least roughness among the samples with "H + " based additives. Therefore, the best power conversion efficiency (PCE) of 4.72% is obtained for CsPbI 3 PSCs annealed at 150 °C with HI (50 µL). The "H + "-based additives seem to react with PbI 2 in DMF solution, increasing the solubility of PbI 2 and thus lowering the processing temperature. Furthermore, the PCE of CH 3 NH 3 PbI 3-x Cl x PSCs decreased from 7.45 to 0.23%, whereas that of CsPbI 3 PSCs with 50 µL HI only decreased from 3.55 to 2.78% after exposing the samples to air for 3 h. These results indicate that "H + " based additives, especially HI, have more impact on the CsPbI 3 PSCs in terms of lowering the processing temperature and improving the performance.

PLOS ONE, 2016

Penicillium spp. are known to harbor a wide array of secondary metabolites with cryptic bioactivi... more Penicillium spp. are known to harbor a wide array of secondary metabolites with cryptic bioactivities. However, the metabolomics of these species is not well-understood in terms of different fermentation models and conditions. The present study involved metabolomics profiling and transcriptomic analysis of Penicillium expansum 40815 under solid-state fermentation (SSF) and submerged fermentation (SmF). Metabolite profiling was carried out using ultra-performance liquid chromatography quadruple time-of-flight mass spectrometry with multivariate analysis, followed by transcriptomic analyses of differentially expressed genes. In principal component analysis, the metabolite profiling data was studied under different experimental sets, including SSF and SmF. The significantly different metabolites such as polyketide metabolites (agonodepside B, rotiorin, verrucosidin, and ochrephilone) and corresponding gene transcripts (polyketide synthase, aromatic prenyltransferase, and terpenoid synthase) were primarily detected under SmF conditions. In contrast, the meroterpenoid compounds (andrastin A and C) and their genes transcripts were exclusively detected under SSF conditions. We demonstrated that the metabolite production and its corresponding gene expression levels in P. expansum 40815 were significantly influenced by the varying growth parameters and the immediate environment. This study further provides a foundation to produce specific metabolites by regulating fermentation conditions.

Chemistry & Biology, 2014

Fibroblast growth factor receptors (FGFRs) regulate diverse cellular behaviors that should be exq... more Fibroblast growth factor receptors (FGFRs) regulate diverse cellular behaviors that should be exquisitely controlled in space and time. We engineered an optically controlled FGFR (optoFGFR1) by exploiting cryptochrome 2, which homointeracts upon blue light irradiation. OptoFGFR1 can rapidly and reversibly control intracellular FGFR1 signaling within seconds by illumination with blue light. At the subcellular level, localized activation of optoFGFR1 induced cytoskeletal reorganization. Utilizing the high spatiotemporal precision of optoFGFR1, we efficiently controlled cell polarity and induced directed cell migration. OptoFGFR1 provides an effective means to precisely control FGFR signaling and is an important optogenetic tool that can be used to study diverse biological processes both in vitro and in vivo.

Journal of agricultural and food chemistry, Jan 27, 2014

Metabolite profiling of red and white pitayas (Hylocereus polyrhizus and Hylocereus undatus) was ... more Metabolite profiling of red and white pitayas (Hylocereus polyrhizus and Hylocereus undatus) was performed using gas chromatography-time-of-flight-mass spectrometry and ultraperformance liquid chromatography-quadrupole-time-of-flight-mass spectrometry with multivariate analysis. Different species and parts of pitayas (red peel, RP; white peel, WP; red flesh, RF; and white flesh, WF) were clearly separated by partial least-squares discriminate analysis. Furthermore, betalain-related metabolites, such as betacyanins and betaxanthins, or their precursors were described on the basis of their metabolites. The results of antioxidant activity tests [1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), and ferric reducing ability of plasma (FRAP)], total phenolic contents (TPC), total flavonoid contents (TFC), and total betacyanin contents (TBC) showed the following: RP ≥ WP > RF > WF. TPC, TFC, TBC, and betalain-relat...

Bioscience, biotechnology, and biochemistry, 2014

A new bioactive compound, namely desmodianone H(1), and another known compound uncinanone B(2) we... more A new bioactive compound, namely desmodianone H(1), and another known compound uncinanone B(2) were first isolated using bioactivity-guided isolation from the leaves of Lespedeza maximowiczii and structures were elucidated by comprehensive analysis of their nuclear magnetic resonance and mass spectrometry data. Compounds 1 and 2 exhibited strong inhibitory effects on mushroom tyrosinase activity.

The Plant Cell, 2000

Ca 2 ؉-ATPases are key regulators of Ca 2 ؉ ion efflux in all eukaryotes. Animal cells have two d... more Ca 2 ؉-ATPases are key regulators of Ca 2 ؉ ion efflux in all eukaryotes. Animal cells have two distinct families of Ca 2 ؉ pumps, with calmodulin-stimulated pumps (type IIB pumps) found exclusively at the plasma membrane. In plants, no equivalent type IIB pump located at the plasma membrane has been identified at the molecular level, although related isoforms have been identified in non-plasma membrane locations. Here, we identify a plant cDNA, designated SCA1 (for soybean Ca 2 ؉-ATPase 1), that encodes Ca 2 ؉-ATPase and is located at the plasma membrane. The plasma membrane localization was determined by sucrose gradient and aqueous two-phase membrane fractionations and was confirmed by the localization of SCA1p tagged with a green fluorescent protein. The Ca 2 ؉-ATPase activity of the SCA1p was increased approximately sixfold by calmodulin (K 1/2 ‫ف‬ 10 nM). Two calmodulin binding sequences were identified in the N-terminal domain. An N-terminal truncation mutant that deletes sequence through the two calmodulin binding sites was able to complement a yeast mutant (K616) that was deficient in two endogenous Ca 2 ؉ pumps. Our results indicate that SCA1p is structurally distinct from the plasma membrane-localized Ca 2 ؉ pump in animal cells, belonging instead to a novel family of plant type IIB pumps found in multiple subcellular locations. In plant cells from soybean, expression of this plasma membrane pump was highly and rapidly induced by salt (NaCl) stress and a fungal elicitor but not by osmotic stress.

International Journal of Precision Engineering and Manufacturing, 2010

Cohesive models are increasingly applied to simulate fracture and fragmentation processes in vari... more Cohesive models are increasingly applied to simulate fracture and fragmentation processes in various materials. The multiple-domain boundary element method (MDBEM) may be more suitable than the often-applied finiteelement method (FEM) because debonding is also a boundary surface problem. In this study, a modified damage initiation criterion possessing a linear relationship to the MDBEM is proposed for the cohesive model. Numerical examples are presented to demonstrate the validity of this procedure.

Biophysical Journal, 2012

Recordings of force, fluorescence, or ionic membrane current from single molecules show directly ... more Recordings of force, fluorescence, or ionic membrane current from single molecules show directly their individual trajectories, but many events need to be aggregated to obtain reaction paths and mean kinetic parameters. A procedure termed 'post-synchronization' has been developed to combine individual interactions that are either noisy or complicated by successive states that have similar signals. To create a post-synchronized ensemble, many trajectories are temporally lined up at an identifiable 'trigger' transition and averaged revealing the dynamics of the process leading up to and following the synchronized transition. Averaged recordings following a trigger have the same properties as an ensemble perturbation experiment, i.e., rate constants can be determined similarly to temperature jump or rapid mixing experiments. However, determining rate constants from averaged recordings leading up to aligned trigger transitions is not as straightforward if the reaction has reversible steps or branches. The averaged traces have properties of a timereversed kinetic scheme. A general method to determine rate constants for the ''reversed time'' scheme leading up to the trigger is the following: (0) Add a reaction to complete the enzymatic cycle, if necessary. (1) Solve the relative steady state concentrations. (2) Calculate the transition rates for the time-reversed scheme from P(A i | B iþ1) = P(A) P(B iþ1 | A i) / P(B), where P(A) and P(B) are steady-state occupancies, P(B iþ1 | A i) is a normal forward transition probability of entering state B from state A, and P(A i | B iþ1) is the time-reversed transition probability that it was in A given it's in B at a later time. (3) Estimate the kinetics of the ''time-reversed'' perturbation experiment using the rate constants determined in step (2). Supported by NIH grants P01-GM087253 and R01-GM080376.

Korean Journal of Environmental Agriculture, 2019

BACKGROUND: Weathering of bottom ash (BA) might induce change of its surface texture and pH and a... more BACKGROUND: Weathering of bottom ash (BA) might induce change of its surface texture and pH and affect physical and chemical properties of soil associated with greenhouse gas emission, when it is applied to the arable soil. This study was conducted to determine effect of weathering of BA in mitigating emission of greenhouse gases from upland soil. METHODS AND RESULTS: In a field experiment, methane (CH 4), carbon dioxide (CO 2), and nitrous oxide (N 2 O) emitted from the soil was periodically monitored using closed chamber. Three month-weathered BA and non-weathered BA were applied to an upland soil at the rates of 0, 200 Mg ha-1. Maize (Zea mays L.) was grown from July 1 st to Oct 8 th in 2018. Both BAs did not affect cumulative CH 4 emission. Cumulative CO 2 emission were 23.1, 19.8, and 18.8 Mg/ha/100days and cumulative N 2 O emission were 35.8, 20.9, and 17.7 kg/ha/100days for the control, non-weathered BA, and weathered BA, respectively. Weathering of BA did not decrease emission of greenhouse gases significantly, compared to the weathered BA in this study. In addition, both BAs did not decrease biomass yields of maize. CONCLUSION: BA might be a good soil amendment to mitigate emissions of CO 2 and N 2 O from arable soil without adverse effect on crop productivity.