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result(s) for
"Kim, Se-Jun"
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High-performance p-channel transistors with transparent Zn doped-CuI
2020
‘Ideal’ transparent
p
-type semiconductors are required for the integration of high-performance thin-film transistors (TFTs) and circuits. Although CuI has recently attracted attention owing to its excellent opto-electrical properties, solution processability, and low-temperature synthesis, the uncontrolled copper vacancy generation and subsequent excessive hole doping hinder its use as a semiconductor material in TFT devices. In this study, we propose a doping approach through soft chemical solution process and transparent
p
-type Zn-doped CuI semiconductor for high-performance TFTs and circuits. The optimised TFTs annealed at 80 °C exhibit a high hole mobility of over 5 cm
2
V
−1
s
−1
and high on/off current ratio of ~10
7
with good operational stability and reproducibility. The CuI:Zn semiconductors show intrinsic advantages for next-generation TFT applications and wider applications in optoelectronics and energy conversion/storage devices. This study paves the way for the realisation of transparent, flexible, and large-area integrated circuits combined with
n
-type metal-oxide semiconductor.
Designing efficient thin-film transistors and circuits based on transparent p-type semiconductors remains a challenge. Here, the authors propose a solution-based doping approach to realize high performance transparent inorganic p-type semiconductors (Zn-doped CuI) by spin coating at 80 C with good operational stability.
Journal Article
Redirecting dynamic surface restructuring of a layered transition metal oxide catalyst for superior water oxidation
2021
Rationally manipulating the in situ formed catalytically active surface of catalysts remains a tremendous challenge for a highly efficient water electrolysis. Here we present a cationic redox-tuning method to modulate in situ catalyst leaching and to redirect the dynamic surface restructuring of layered LiCoO
2–
x
Cl
x
(
x
= 0, 0.1 or 0.2), for the electrochemical oxygen evolution reaction (OER). Chlorine doping lowered the potential to trigger in situ cobalt oxidation and lithium leaching, which induced the surface of LiCoO
1.8
Cl
0.2
to transform into a self-terminated amorphous (oxy)hydroxide phase during the OER. In contrast, Cl-free LiCoO
2
required higher electrochemical potentials to initiate the in situ surface reconstruction to spinel-type Li
1±
x
Co
2
O
4
and longer cycles to stabilize it. Surface-restructured LiCoO
1.8
Cl
0.2
outperformed many state-of-the-art OER catalysts and demonstrated remarkable stability. This work makes a stride in modulating surface restructuring and in designing superior OER electrocatalysts via manipulating the in situ catalyst leaching.
Rationally manipulating the in-situ-formed catalytically active surface of catalysts is a challenging but promising endeavour. Now, the surface of LiCoO
2
during water oxidation is engineered by Cl doping via a cationic redox-tuning method that modulates in situ leaching and redirects the dynamic surface restructuring.
Journal Article
Multilayer Conductive Hybrid Nanosheets as Versatile Hybridization Matrices for Optimizing the Defect Structure, Structural Ordering, and Energy‐Functionality of Nanostructured Materials
by
Kwon, Nam Hee
,
Kim, Hyungjun
,
Kim, Se‐Jun
in
defect structure control
,
Electrodes
,
enhanced charge/mass transport
2022
The hybridization of conductive nanospecies has garnered significant research interest because of its high efficacy in improving the diverse functionalities of nanostructured materials. In this study, a novel synthetic strategy is developed to optimize the defect structure, structural ordering, and energy‐related functionality of nanostructured‐materials by employing a multilayer multicomponent two‐dimenstional (2D) graphene/metal oxide/graphene nanosheet (NS) as a versatile hybridization matrix. The hybridization of the robust trilayer, polydiallyldiammonium (PDDA)‐anchored reduced‐graphene oxide (prGO)/metal oxide/prGO NS effectively enhance the structural ordering and porosity of the hybridized MoS2/MnO2 NS through suppression of defect formation and tight stacking. In comparison with monolayer rGO/RuO2 NS‐based homologs, the 2D superlattice trilayer prGO/RuO2/prGO NS hybrids deliver better functionalities as a hydrogen evolution electrocatalyst and as a supercapacitor electrode, demonstrating the merits of hybridization with multilayer NSs. The advantages of using multilayer multicomponent conductive NSs as hybridization matrices arise from the enhancement of charge and mass transport through the layer flattening or defect suppression of the hybridized NSs and the increase in porosity, as evidenced by density functional theory calculations. Finally, the universal utility of multilayer NSs is confirmed by investigating the strong effect of the stacking order on the electrocatalytic functionality of MoS2/rGO/RuO2 films fabricated through layer‐by‐layer deposition. A new concept of synthetic strategy to improve various energy functionalities and mass/charge transports of nanostructured materials is developed by employing multilayer conductive graphene/inorganic/graphene nanosheet (NS) as an emerging versatile hybridization matrix. The universal usefulness of hybridization with multilayer multicomponent NSs in exploring high‐performance functional materials originates from optimization of the defect structure, structural ordering, and porosity of hybridized species.
Journal Article
Surface Optimization of Noble‐Metal‐Free Conductive Mn1/4Co1/2Ni1/4O2 Nanosheets for Boosting Their Efficacy as Hybridization Matrices
2024
Conductive 2D nanosheets have evoked tremendous scientific efforts because of their high efficiency as hybridization matrices for improving diverse functionalities of nanostructured materials. To address the problems posed by previously reported conductive nanosheets like poorly‐interacting graphene and cost‐ineffective RuO2 nanosheets, economically feasible noble‐metal‐free conductive [MnxCo1−2xNix]O2 oxide nanosheets are synthesized with outstanding interfacial interaction capability. The surface‐optimized [Mn1/4Co1/2Ni1/4]O2 nanosheets outperformed RuO2/graphene nanosheets as hybridization matrices in exploring high‐performance visible‐light‐active (λ >420 nm) photocatalysts. The most efficient g‐C3N4–[Mn1/4Co1/2Ni1/4]O2 nanohybrid exhibited unusually high photocatalytic activity (NH4+ formation rate: 1.2 mmol g−1 h−1), i.e., one of the highest N2 reduction efficiencies. The outstanding hybridization effect of the defective [Mn1/4Co1/2Ni1/4]O2 nanosheets is attributed to the optimization of surface bonding character and electronic structure, allowing for improved interfacial coordination bonding with g‐C3N4 at the defect sites. Results from spectroscopic measurements and theoretical calculations reveal that hybridization helps optimize the bandgap energy, and improves charge separation, N2 adsorptivity, and surface reactivity. The universality of the [Mn1/4Co1/2Ni1/4]O2 nanosheet as versatile hybridization matrices is corroborated by the improvement in the electrocatalytic activity of hybridized Co−Fe‐LDH as well as the photocatalytic hydrogen production ability of hybridized CdS. A rational design method for the synthesis of noble‐metal‐free conductive metal oxide nanosheets is developed for versatile hybridization matrices to develop economical and efficient photo‐/electro‐catalyst materials. The hybridization effect of the optimized [MnxCo1−2xNix]O2 nanosheets is maximized due to fine control of surface bonding character and defect structure, enabling to form interfacial coordination bonding with catalyst materials.
Journal Article
Surface Optimization of Noble‐Metal‐Free Conductive Mn 1/4 Co 1/2 Ni 1/4 O 2 Nanosheets for Boosting Their Efficacy as Hybridization Matrices
2024
Conductive 2D nanosheets have evoked tremendous scientific efforts because of their high efficiency as hybridization matrices for improving diverse functionalities of nanostructured materials. To address the problems posed by previously reported conductive nanosheets like poorly‐interacting graphene and cost‐ineffective RuO 2 nanosheets, economically feasible noble‐metal‐free conductive [Mn x Co 1−2x Ni x ]O 2 oxide nanosheets are synthesized with outstanding interfacial interaction capability. The surface‐optimized [Mn 1/4 Co 1/2 Ni 1/4 ]O 2 nanosheets outperformed RuO 2 /graphene nanosheets as hybridization matrices in exploring high‐performance visible‐light‐active (λ >420 nm) photocatalysts. The most efficient g‐C 3 N 4 –[Mn 1/4 Co 1/2 Ni 1/4 ]O 2 nanohybrid exhibited unusually high photocatalytic activity (NH 4 + formation rate: 1.2 mmol g −1 h −1 ), i.e., one of the highest N 2 reduction efficiencies. The outstanding hybridization effect of the defective [Mn 1/4 Co 1/2 Ni 1/4 ]O 2 nanosheets is attributed to the optimization of surface bonding character and electronic structure, allowing for improved interfacial coordination bonding with g‐C 3 N 4 at the defect sites. Results from spectroscopic measurements and theoretical calculations reveal that hybridization helps optimize the bandgap energy, and improves charge separation, N 2 adsorptivity, and surface reactivity. The universality of the [Mn 1/4 Co 1/2 Ni 1/4 ]O 2 nanosheet as versatile hybridization matrices is corroborated by the improvement in the electrocatalytic activity of hybridized Co−Fe‐LDH as well as the photocatalytic hydrogen production ability of hybridized CdS.
Journal Article
Characterization of the chimeric seven-transmembrane protein containing conserved region of helix C–F of microbial rhodopsin from Ganges River
by
Jung, Kwang-Hwan
,
Jung, Byung Hoon
,
Kim, Se Jun
in
absorption
,
Artificial chromosomes
,
Bacteria
2013
Proteorhodopsin (PR) is a light-driven proton pump that has been found in a variety of marine bacteria. Recently, many PR-like genes were found in non-marine environments. The goal of this study is to explore the function of rhodopsins that exist only as partial proteo-opsin genes using chimeras with marine green PR (GPR). We isolated nine partial genes of PR homologues using polymerase chain reaction (PCR) and chose three homologues of GPR from the surface of the Ganges River, which has earned them the name “CFR, Chimeric Freshwater Rhodopsin.” In order to characterize the proteins, we constructed the cassette based on GPR sequence without helices C to F and inserted the isolated conserved partial sequences. When expressed in
E
.
coli
, we could observe light-driven proton pumping activity similar to proteorhodopsin, however, photocycle kinetics of CFRs are much slower than proteorhodopsin. Half-time decay of O intermediates of CFRs ranged between 143 and 333 ms at pH 10; their absorption maxima were between 515 and 522 nm at pH 7. We can guess that the function of native rhodopsin, a retinal protein of fresh water bacteria, may be a light-driven proton transport based on the results from chimeric freshwater rhodopsins. This approach will enable many labs that keep reporting partial PCR-based opsin sequences to finally characterize their proteins.
Journal Article
Photoluminescence characteristics of Y3Al5O12:Tb3+ phosphors synthesized using the combustion method
by
Yoon, Hyon-Hee
,
Choi, Hyung-wook
,
Park, Sang-Joon
in
Aluminum
,
Ceramics
,
Characterization and Evaluation of Materials
2009
For this study, terbium-doped yttrium aluminum garnet (YAG:Tb) phosphor powders were prepared via the combustion process using the 1:1 ratio of metal ions to reagents. The characteristics of the synthesized nano powder were investigated by means of X-ray diffraction (XRD), scanning electron microscope (SEM), and photoluminescence. Single-phase cubic YAG:Tb crystalline powder was obtained at 800 °C by directly crystallizing it from amorphous materials, as determined by XRD techniques. There were no intermediate phases such as yttrium aluminum perovskite (YAlO
3
) and yttrium aluminum monoclinic (Y
4
Al
2
O
9
) observed in the sintering process. The SEM image showed that the resulting YAG:Tb powders had uniform sizes and good homogeneity. With the increase in the sintering temperature, the grain size increased. The photoluminescence spectra of the YAG:Tb nanoparticles were investigated to determine the energy level of electron transition related to luminescence processes. There were three peaks in the excited spectrum, and the major one was a broad band of around 274 nm. Also, the YAG:Tb nanoparticles showed two emission peaks in the range of 450 × 500 and 525 × 560 nm, respectively, and had maximum intensity at 545 nm.
Journal Article
Metabolic networks in the tumor microenvironment: roles of amino acid and lipid metabolism pathways in cancer progression and therapy
2026
Metabolic rewiring, a defining hallmark of cancer, sustains cell proliferation and biosynthesis while coordinating adaptive interactions within the tumor microenvironment (TME). Recent advances reveal that metabolism in the TME-comprising stromal, immune and endothelial components forms a complex metabolic network in which intercellular competition, cooperation and plasticity profoundly influence tumor progression and therapeutic responses. Here we integrate emerging evidence on the organizational principles of amino acid and lipid metabolism within the TME, emphasizing how nutrient fluxes shape immune evasion, therapeutic resistance and metabolic symbiosis. We highlight key mechanisms through which cancer and nonmalignant cells engage in reciprocal nutrient manipulation, focusing on glutamine, arginine, tryptophan, branched-chain amino acids and lipids. The dual roles of these metabolites in immune regulation and tumor growth reveal the limitations of traditional single-pathway targeting and advocate for a network-centric therapeutic approach. We further discuss how metabolite-derived signaling and epigenetic regulation reinforce cell state transitions and immune suppression. Current and emerging therapeutic strategies, including multitarget combinations and immune–metabolic synergies, are evaluated alongside translational challenges. Finally, we underscore the need for spatial metabolomics, liquid biopsy platforms and artificial intelligence-driven modeling to map nutrient competition and cooperative exchange within the TME, offering new opportunities for precision metabolic interventions.
Journal Article
Role of Peroxisome Proliferator-Activated Receptor α-Dependent Mitochondrial Metabolism in Ovarian Cancer Stem Cells
2024
Peroxisome proliferator-activated receptors (PPARs), including PPAR-α, PPAR-β/δ, and PPAR-γ, are involved in various cellular responses, including metabolism and cell proliferation. Increasing evidence suggests that PPARs are closely associated with tumorigenesis and metastasis. However, the exact role of PPARs in energy metabolism and cancer stem cell (CSC) proliferation remains unclear. This study investigated the role of PPARs in energy metabolism and tumorigenesis in ovarian CSCs. The expression of PPARs and fatty acid consumption as an energy source increased in spheroids derived from A2780 ovarian cancer cells (A2780-SP) compared with their parental cells. GW6471, a PPARα inhibitor, induced apoptosis in A2780-SP. PPARα silencing mediated by small hairpin RNA reduced A2780-SP cell proliferation. Treatment with GW6471 significantly inhibited the respiratory oxygen consumption of A2780-SP cells, with reduced dependency on fatty acids, glucose, and glutamine. In a xenograft tumor transplantation mouse model, intraperitoneal injection of GW6471 inhibited in vivo tumor growth of A2780-SP cells. These results suggest that PPARα plays a vital role in regulating the proliferation and energy metabolism of CSCs by altering mitochondrial activity and that it offers a promising therapeutic target to eradicate CSCs.
Journal Article
CD109 Promotes Drug Resistance in A2780 Ovarian Cancer Cells by Regulating the STAT3-NOTCH1 Signaling Axis
by
Kim, Jae Ho
,
Kim, Dae Kyoung
,
Lee, Seo Yul
in
ABC transporters
,
Adenosine triphosphate
,
Animals
2023
Epithelial ovarian cancer (EOC) is the most lethal gynecological malignancy owing to relapse caused by resistance to chemotherapy. We previously reported that cluster of differentiation 109 (CD109) expression is positively correlated with poor prognosis and chemoresistance in patients with EOC. To further explore the role of CD109 in EOC, we explored the signaling mechanism of CD109-induced drug resistance. We found that CD109 expression was upregulated in doxorubicin-resistant EOC cells (A2780-R) compared with that in their parental cells. In EOC cells (A2780 and A2780-R), the expression level of CD109 was positively correlated with the expression level of ATP-binding cassette (ABC) transporters, such as ABCB1 and ABCG2, and paclitaxel (PTX) resistance. Using a xenograft mouse model, it was confirmed that PTX administration in xenografts of CD109-silenced A2780-R cells significantly attenuated in vivo tumor growth. The treatment of CD109-overexpressed A2780 cells with cryptotanshinone (CPT), a signal transducer and activator of transcription 3 (STAT3) inhibitor, inhibited the CD109 overexpression-induced activation of STAT3 and neurogenic locus notch homolog protein 1 (NOTCH1), suggesting a STAT3-NOTCH1 signaling axis. The combined treatment of CD109-overexpressed A2780 cells with CPT and N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester (DAPT), a NOTCH inhibitor, markedly abrogated PTX resistance. These results suggest that CD109 plays a key role in the acquisition of drug resistance by activating the STAT3-NOTCH1 signaling axis in patients with EOC.
Journal Article