Jouhahn Lee

Jouhahn Lee
Korea Basic Science Institute KBSI · Advanced Nano Surface Research Group

Doctor of Philosophy, King's College London

About

71
Publications
12,542
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
2,722
Citations
Citations since 2016
28 Research Items
2005 Citations
20162017201820192020202120220100200300
20162017201820192020202120220100200300
20162017201820192020202120220100200300
20162017201820192020202120220100200300

Publications

Publications (71)
Article
Point defects can stabilize various metastable polymorph phases of complex oxides showing unique physical properties, even though their role in the stabilization of the metastable phase is unclear. In this study, we examined the role of oxygen point defects in stabilizing a polymorph M3-VO2 phase and its transition characteristics. Raman spectrosco...
Article
Full-text available
We report the discovery of a new three-dimensional (3D) topological Dirac semimetal (TDS) material KZnBi, coexisting with a naturally formed superconducting state on the surface under ambient pressure. Using photoemission spectroscopy together with first-principles calculations, a 3D Dirac state with linear band dispersion is identified. The charac...
Article
A clear experimental explanation of the contribution of Mott and Peierls transition on the insulator-metal-transition (IMT) characteristics in vanadium dioxide (VO2) is still lacking. Examining the crystal and electronic structure of epitaxial VO2 films grown at various deposition temperatures, Mott or Peierls transition was observed. For the film...
Article
We examined the magnetic, structural, and chemical properties of CoFe2O4 films deposited on Al2O3 substrates using RF-magnetron sputtering under Ar and Ar + O2 environments. Perpendicular magnetic anisotropy with large magnetization was observed in the case of the film deposited under the Ar + O2 environment. However, no significant anisotropy appe...
Article
Full-text available
The discovery of new families, beyond graphene, of two-dimensional (2D) layered materials has always attracted great attention. However, it has been challenging to artificially develop layered materials with honeycomb atomic lattice structure composed of multicomponents such as hexagonal boron nitride. Here, through the dimensional manipulation of...
Article
In this paper, a nickel (Ni) catalyst with large surface area supported by a graphitic layer is proposed. The graphitic layer is formed on a Ni foil by chemical vapor deposition (CVD) using CH4 as a source. The Ni foil is partially etched by a chemical etchant to increase the surface to volume ratio. The H2 generation rates of the catalysts for dif...
Article
While controlling the cation contents in perovskite rare-earth nickelate thin films, a metal-to-insulator phase transition is reported. Systematic control of cation stoichiometry has been achieved by manipulating the irradiation of excimer laser in pulsed laser deposition. Two rare-earth nickelate bilayer thin-film heterostructures with the control...
Article
Silicon nanowires (SiNWs) opened up exciting possibilities in a variety of research fields due to their unique anisotropic morphologies, facile tuning capabilities, and accessible fabrication methods. The SiNW-based photoelectrochemical (PEC) conversion has recently been known to provide an efficiency superior to various photo-responsive semiconduc...
Article
Full-text available
Herein, we fabricated a super-hydrophobic SERS substrate using Sn-doped indium oxide (Indium-tin-oxide: ITO) nano-branches as a template. ITO nano-branches with tens of nanometer diameter are first fabricated through the vapor–liquid–solid (VLS) growth to provide roughness of the substrate. 10 nm thickness of Ag thin film was deposited and then tre...
Article
The asymmetric response of the cation distribution on [0 0 1] oriented CoFe2O4 films were examined. Depending on the deposition temperature and substrates (MgO(0 0 1) or SrTiO3(0 0 1)), the films exhibited a range of compressive or tensile strain states along the out-of-plane. With increases in deposition temperature, the initial compressive (tensi...
Article
Semiconductor quantum dots have intriguing electronic and optical properties distinguished from bulk owing to quantum confinement effects. Among the two-dimensional materials, black phosphorus (BP) has generated enormous excitement due to its tunable direct band gap and high p-type semiconducting properties. We prepared BP quantum dots (BPQDs) by s...
Article
Full-text available
The catalytic activity of transition metals with regard to carbo-hydroxyl molecules (CxHy) has triggered new technological developments in graphene growth. Both the opening of the Dirac-point by controlling the number of graphene layers as well as the patterning of the graphene are critical for applications such as transistor-based electronics. In...
Article
Full-text available
We synthesized poly-trimethoxyphenylsilane (PTMS) and applied it as the carrier film to CVD graphene transfer process for the first time. Since the PTMS particles are not fully crosslinked due to the presence of bulky groups, they do not have crystallinity in the long-range order on the graphene surface and are easily removed by solvent such as tol...
Article
The thermal transport growth of various metal oxide (MOx) nanostructures using graphene as a catalytic layer was studied. Graphene was synthesized by Cu-catalyzed chemical vapor deposition and transferred onto a SiO2-covered Si substrate using bubble transfer methods. Due to the catalytic activity of the atomic-thick carbon layer, control of the po...
Article
Electric field-induced charge trapping and exciton dissociation were demonstrated at a penatcene/grapheme quantum dot (GQD) interface using a bottom contact bi-layer field effect transistor (FET) as an electrical nano-probe. Large threshold voltage shift in a pentacene/GQD FET in the dark arises from field-induced carrier trapping in the GQD layer...
Article
Multifunctional carbon-based nanodots (C-dots) are synthesized using atmospheric plasma treatments involving reactive gases (oxygen and nitrogen). Surface design was achieved through one-step plasma treatment of C-dots (AC-paints) from polyethylene glycol used as a precursor. These AC-paints show high fluorescence, low cytotoxicity and excellent ce...
Article
We have fabricated high quality bismuth vanadate (BiVO4) polycrystalline thin films as photoanodes by pulsed laser deposition (PLD) without post-annealing process. The structure of the grown films is the photocatalytically active phase of scheelite-monoclinic BiVO4 which was obtained by X-ray diffraction (XRD) analysis. The change of surface morpho...
Article
Amorphous CoFe2O4 films with different thicknesses were deposited on MgO(001) substrates to examine the correlation between the oxygen vacancy and magnetic properties of the films. As the film thickness increased, the films became packed and smooth with well-defined interfaces. The magnetic hysteresis loop on the out-of-plane and in-plane showed an...
Article
This study examined the microscopic aspects of macroscopic physical property variations of hydrogen annealed VO2 films, deposited on Al2O3(0001) substrates by RF magnetron sputtering. The temperature-dependent electrical resistivity showed that the as-grown film exhibited a metal-insulator-transition (MIT) at 55.20 °C and 49.26 °C during heating an...
Article
The surface morphology of copper (Cu) often changes after the synthesis of graphene by chemical vapor deposition (CVD) on a Cu foil, which affects the electrical properties of graphene, as the Cu step bunches induce the periodic ripples on graphene that significantly disturb electrical conduction. However, the origin of the Cu surface reconstructio...
Article
Full-text available
We report an effect involving hydrogen (H2)-plasma-treated nanoporous TiO2(H-TiO2) photocatalysts that improve photocatalytic performance under solar-light illumination. H-TiO2 photocatalysts were prepared by application of hydrogen plasma of assynthesized TiO2(a-TiO2) without annealing process. Compared with the a-TiO2, the H-TiO2 exhibited high a...
Article
Full-text available
Lithium-sulfur (Li-S) batteries are expected to overcome the limit of current energy storage devices by delivering high specific energy with low material cost. However, the potential of Li-S batteries has not yet been realized because of several technical barriers. Poor electrochemical performance is mainly attributed to the low electrical conducti...
Article
Full-text available
Few-layer black phosphorus (BP) is the most promising material among the two-dimensional materials due to its layered structure and the excellent semiconductor properties. Currently, thin BP atomic layers are obtained mostly by mechanical exfoliation of bulk BP, which limits applications in thin-film based electronics due to a scaling process. Here...
Article
Full-text available
We have investigated the cytotoxic assay of Fe-aminoclay (FeAC) nanoparticles (NPs) and simultaneous imaging in HeLa cells by photoluminescent carbon nanodots (CD) conjugation. Non-cytotoxic, photostable, and CD NPs are conjugated with cationic FeAC NPs where CD NPs play a role in bio-imaging and FeAC NPs act as a substrate for CD conjugation and...
Article
Recently, the appeal of 2D black phosphorus (BP) has been rising due to its unique optical and electronic properties with a tunable band gap (≈0.3-1.5 eV). While numerous research efforts have recently been devoted to nano- and optoelectronic applications of BP, no attention has been paid to promising medical applications. In this article, the prep...
Article
Full-text available
Fluorescent carbon nanomaterials, especially zero-dimensional (0D) carbon nanodots (CDs), are widely used in broad biological and optoelectronic applications. CDs have unique characteristics such as strong fluorescence, biocompatibility, sunlight response, and capability of mass-production. Beyond the previous green CD obtained from harmful natural...
Article
Owing to the possibilities of achieving high theoretical energy density and gravimetric capacity, sulfur has been considered as a promising cathode material for rechargeable lithium batteries. However, sulfur shows rapid capacity fading due to the irreversible loss of soluble polysulfides and the decrease in active sites needed for conducting agent...
Article
The current–voltage (I–V) characteristics of Al/p-type Si Schottky diodes with pristine and 5 wt.% sorbitol-doped organic PEDOT:PSS interlayers have been investigated. It was found that the barrier heights of the diodes with pristine and sorbitol-doped PEDOT:PSS are higher than those of a conventional Al/p-type Si Schottky diode because of the modi...
Article
We have fabricated the Ni-germanosilicide using Ni deposition on relaxed Si1-x Ge x layers (x = 0.15, 0.25), followed by the pulsed KrF laser annealing with the energy densities of 600 and 800 mJ/cm2, and investigated their electrical and structural properties. Regardless of Ge contents in Si1-x Ge x layer, the Ni(Si1-x Ge x )2 film was epitaxially...
Article
Full-text available
Over the past few decades, two-dimensional (2D) and layered materials have emerged as new fields. Due to the zero-band-gap nature of graphene and the low photocatalytic performance of MoS2, more advanced semiconducting 2D materials have been prompted. As a result, semiconductor black phosphorus (BP) is a derived cutting-edge post-graphene contender...
Article
The electronic structure and nature of the defect states below the conduction band edge of an HfO2 gate dielectric grown on InP substrate prepared by atomic layer deposition was examined using x-ray photoelectron spectroscopy (XPS), x-ray absorption spectroscopy (XAS), and density functional theory (DFT). When the HfO2 dielectric was deposited on a...
Article
The current–voltage characteristics and the carrier-transport mechanism of the Er–silicide (ErSi1.7) Schottky contacts to strained-silicon-on-insulator (sSOI) and silicon-on-insulator (SOI) were investigated. Barrier heights of 0.74 eV and 0.82 eV were obtained for the sSOI and SOI structures, respectively. The barrier height of the sSOI structure...
Article
Full-text available
The design of DNA nanostructures is of fundamental importance, the intrinsic value of DNA as a building-block material lies in its ability to organize other bio-molecules with nanometer-scale spacing. Here, we report the fabrication of DNA scaffolds with nano-pores (<10 nm size) that formed easily without the use of additives (i.e., avidin, biotin,...
Article
Full-text available
It is known that water purified by conventional TiO2 photocatalysts may not be safe enough for drinking, due to the toxicity by tiny existence of TiO2 nanoparticles after water treatment. We herein demonstrate a facile design of a three-dimensional (3D) TiO2 photocatalyst structure with which both the efficiency of purification and the safety level...
Article
The plasma treatment method was employed to characterize nitrogen (N)-doped nanoporous TiO2 photocatalysts (N-nTiO(2)) of similar to 18 nm diameter. With respect to the organic dye degradation efficiencies and antibacterial properties after exposure to visible-light irradiation, N-nTiO(2) showed better performance than the alternative commercial 5...
Article
For purposes of selective CO2 uptake under ambient conditions, a few number of primary amine groups are selected, including aminoclay (H2N-CL), 3-aminopropyltriethoxysilane (APTES), and dopamine hydrochloride (DA). Coatings of both H2N-CL into activated carbon (AC) show enhanced CO2 adsorption capacity at 273 and 298 K and 1 atm, resulting in 3.069...
Article
Full-text available
High-quality N-doped graphene quantum sheets are successfully fabricated from as-grown monolayer graphene on Cu using nitrogen plasma, which can be transferred as a film-like layer or easily dispersed in an organic solvent for further optoelectronic or photoelectrochemical applications.
Article
Angle-resolved X-ray photoelectron spectroscopy (AR-XPS) and atomic force microscopy (AFM) were employed to investigate the detailed surface bonding structure and morphology of polyethyleneimine (PEI) layers coated on a SiO2 substrate in concentrations of 0.5-10.0 mass%. With an increase in the PEI concentration, the C-N bonds corresponding to the...
Article
Full-text available
Using a simple method of mass production of green carbon nanotags (G-tags) from harmful cyanobacteria, we developed an advanced and efficient imaging platform for the purpose of anticancer therapy. Approximately 100 grams of G-tags per 100 kilograms of harmful cyanobacteria were prepared using our eco-friendly approach. The G-tags possess high solu...
Article
We developed a photocatalyst (T–FC) that incorporated anatase TiO2 (T) nanoparticles on magnetically enhanced carbon [iron oxide (F; α,γ-Fe2O3–Fe3O4) supported on activated carbon (C)] for use as a highly visible-light-active, low-cost, recyclable, and photostable catalyst for the degradation of organic dyes and bacterial sterilization. The T–FC ph...
Data
Full-text available
We have developed a simple approach for the large-scale synthesis of water-soluble green carbon nanodots (G-dots) from many kinds of large food waste-derived sources. About 120 g of G-dots per 100 kg of food waste can be synthesized using our simple and environmentally friendly synthesis approach. The G-dots exhibit a high degree of solubility in w...
Article
We have developed a simple approach for the large-scale synthesis of water-soluble green carbon nanodots (G-dots) from many kinds of large food waste-derived sources. About 120 g of G-dots per 100 kg of food waste can be synthesized using our simple and environmentally friendly synthesis approach. The G-dots exhibit a high degree of solubility in w...
Article
We report three-dimensional polycrystalline anatase TiO2 photocatalysts (3D a-TiO2) for environmental and bio-medical applications. The 3D a-TiO2 was synthesized without thermal treatment by the growth of rod-like polycrystals on Degussa P25 (P25) via low temperature hydrothermal processing and ultrasound irradiation. X-ray diffraction and high-res...
Article
Full-text available
Carbon-based catalysts have been attracting attention in renewable energy technologies due to the low cost and high stability, but their insufficient activity is still a challenging issue. Here, we suggest that monolayer graphene can be used as a catalyst for solar-driven hydrogen evolution reaction on Si-photocathodes, and its catalytic activity i...
Article
To use visible-light more efficiently in photocatalytic reactions, nanoporous nitrogen-doped titanium dioxide (N-TiO2) was synthesized at room temperature, without thermal treatment, using modified sol–gel processing and ultrasound irradiation. In addition, the N-TiO2 was irradiated with visible-light to improve the hydrophilicity of its surface. T...
Article
Zinc oxide (ZnO) is one of the most powerful materials for purifying organic pollutants using photocatalytic activity. In this study, we have introduced a novel method to design highly photoreactive flexible 3 dimensional (3D) ZnO nanocomposite [F-ZnO-m (m: reaction time, min)] by electrospinning and simple-step ZnO growth processing (one-step ZnO...
Article
In this study nanoporous TiO2 photocatalysts with high crystallinity and large surface areas (213.6–586.4 m2/g) [CnTiO2-m] were synthesized at room temperature by sol–gel processing and ultrasound irradiation. A cationic surfactant [CH3(CH2)nN(CH3)3Br; CnTAB] and tetra-n-butyl titanate (TBOT) were used as the surfactant and titanium precursor, resp...
Article
We report highly active visible-light driven nitrogen-doped three-dimensional polycrystalline anatase TiO2 photocatalysts (N-3D TiO2) for environmental and biomedical applications. N-3D TiO2 is synthesized at a low temperature (<90°C) without thermal treatment via a modified hydrothermal process (HP) and ultrasound irradiation (UI). The N-3D TiO2 i...
Article
We report highly visible-light active nanoporous carbon-doped TiO2 (C-TiO2) and sulfur-doped TiO2 (S-TiO2) for environmental and biomedical applications. C-TiO2 and S-TiO2 were synthesized at room temperature without thermal treatment using modified sol–gel processing and ultrasound irradiation. Under visible-light irradiation, the highest photocat...
Article
Anatase–brookite bicrystalline TiO2 photocatalysts were successfully synthesized by a surfactant-assisted sol–gel route. Cetyltrimethylammonium chloride and tetra-n-butyl titanate were used as a surfactant and a titanium precursor, respectively. The bicrystalline TiO2 photocatalyst samples were aged at different temperatures (RT ~ 100 °C) and were...
Article
Surface tensions of micellar block copolymers of poly(styrene-b-dimethylsiloxane) (PS-b-PDMS) films are obtained by X-ray diffuse scattering. PS-b-PDMS films on Si substrates with the thicknesses from 36 to 588 nm were investigated at temperatures of 30 - 215 degrees C. The surface tension reflects the concentration of PDMS micelles which are prefe...
Article
We have studied the interface electronic structures of Ca/tris-(8-hydorxyquinoline)aluminum (Alq(3)), Ca/NaF/Alq(3), and Ca/MgF2/Alq(3) by using X-ray and UV photoelectron spectroscopy (XPS and UPS). The UPS revealed that the Ca deposition on MgF2/Alq(3) created weak gap states similar to Ca/Alq(3) case, while the deposition or Ca on NaF/Alq(3) sho...
Article
Full-text available
Copper nitride nanoparticles supported on a mesoporous superparamagnetic silica microsphere exhibit superior activity toward the Huisgen cycloaddition of azides and alkynes. The nitride catalyst offers significant advantages over homogeneous Cu catalysts.
Chapter
There is nowadays a rapid growth of the Research and Development of organic thin film and molecular-scale electronics. Most of the presently feasible applications use thin films where multilayer of organic material is sandwiched between metal or oxide electrodes. Since device functions come from charge transport, the electronic structure of such ma...
Article
Full-text available
Regioregular poly(3-hexylthiophene) (RR-P3HT) nanorod arrays were prepared on the indium tin oxide (ITO) substrate by capillary force in a vacuum oven (0.855 torr, 250 °C) using a drop-coating of RR-P3HT and anodic aluminium oxide (AAO) templates. The AAO templates were prepared by a two step anodizing process in an oxalic acid electrolyte. The tem...