Euh Duck Jeong

Band gap tuning of lead-substituted BaSnO3 for visible light photocatalysis

The Pb substitution effect was investigated experimentally and theoretically on the crystal structure of BaSnO3 and on the photo-oxidation activity of H2O. The chemically doped Pb in BaSnO3 induced a concentration-dependent redshift of the experimental band gap (BG). The BaPb0.8Sn0.2O3 system produced 32μmol∕h of O2 under λ⩾420nm photons, but no O2 for BaSnO3. The DFT calculations of BaPbxSn1−xO3 (x=0,0.5,1) by using generalized approximation, implying the BG alteration and the photocatalytic activity of BaPbxSn1−xO3, are due to the induced Pb 6s orbital in the BG of BaSnO3. Thus Pb modified the insulating nature of BaSnO3 to semiconducting and semimetallic.

Engineered Nanorod Perovskite Film Photocatalysts to Harvest Visible Light

The recent fl ourishing of nanostructured materials has widened its potential applications in the much-desired effi cient energy materials. Specifi cally, materials for solar hydrogen production by water splitting should possess superior optoelectric properties in addition to suitable band energetics and durability in aqueous solutions. The tunability of the physicochemical properties of nanostructred materials by virtue of their size and shape renders a wider applicability. Since the critical limitation of popular TiO 2 photocatalyst that absorbs only UV light, [ 1 , 2 ] the fi eld of visible light water splitting photocatalyst is currently being nurtured by various kinds of conventional and new single component materials (CdS, WO 3 , Fe 2 O 3 , TaON, etc.), as well as composite materials. [ 3–20 ] However, there is still much potential for nanostructured materials in this area. There have been several reports on the binary [ 3–6 ] and ternary metal oxides, [ 7–13 ]

Enhanced ferroelectric properties of LiNbO3 substituted Na0.5K0.5NbO3 lead-free thin films grown by chemical solution deposition

We have fabricated environmental friendly lead-free ferroelectric Na0.5K0.5NbO3 (NKN) and 0.95Na0.5K0.5NbO3–0.05LiNbO3 (0.95NKN-0.05LN) thin films by chemical solution deposition using metal-organic compounds, and studied the effects of LN substitution through the dielectric and ferroelectric properties. The small amount of LN substitution for NKN thin film led to a marked improvement in leakage current properties at the high electric field region. Furthermore, the 0.95NKN-0.05LN thin film (350nm) displayed clear ferroelectricity with well saturated P-E hysteresis loop with 2Pr and 2Ec values of 19.5μC∕cm2 and 91kV∕cm, respectively. The 0.95NKN-0.05LN films will be interesting for applications in lead-free ferroelectric and piezoelectric devices.

Photocatalytic Ohmic layered nanocomposite for efficient utilization of visible light photons

The WO3∕W∕PbBi2Nb1.9Ti0.1O9 photocatalyst was fabricated by depositing the tungsten clusters over the p-type perovskite base material with the chemical vapor deposition method, and later partly oxidizing the surfaces of these clusters to obtain n-type WO3 overlayers and W metal layer as an Ohmic junction. This NCPC showed unprecedented high activity for the photocatalytic oxidation of water, photocurrent generation, and acetaldehyde decomposition under visible light irradiation (λ⩾420nm).

Removal of Heavy Metal Ions by using Calcium Carbonate Extracted from Starfish Treated by Protease and Amylase

CaCO3 extracted from starfish by using the commercial protein lyase having α-amylase, β-amylase, and protease is applied to remove heavy metal ions. The extracted CaCO3 shows excellent characteristics in removing heavy metal ions such as Cu 2+ , Cd 2+ , Pb 2+ , and Cr 6+ compared with conventional materials such as crab shells, sawdust, and activated carbon except for removing Zn 2+ . SEM images reveal that the extracted CaCO3 has a good morphology and porosity. We characterize the removal efficiencies of the extracted CaCO3 for the heavy metal ions according to the concentrations, pH, temperatures, and conditions of empty bed contact times.

Liquid chromatographic resolution of proton pump inhibitors including omeprazole on a ligand exchange chiral stationary phase

A ligand exchange chiral stationary phase (CSP) developed previously in this laboratory by bonding (R)-phenylglycinol derivative, sodium N-[(R)-2-hydroxy-1-phenylethyl]-N-undecylaminoacetate, to silica gel was successfully applied to the resolution of proton pump inhibitors (PPIs) including omeprazole, pantoprazole, lansoprazole and rabeprazole. For example, the separation factors (α) for the resolution of omeprazole, pantoprazole, lansoprazole and rabeprazole were 4.27, 5.28, 2.77 and 4.06, respectively, and the resolutions (R(S)) were 2.53, 2.55, 1.93, and 2.01, respectively, when 65% acetonitrile aqueous solution containing 0.5mM CuSO(4) and 0.05mM triethylamine was used as a mobile phase. Based on the chromatographic behaviors for the resolution of PPI analogues on CSP 1, a chiral recognition mechanism utilizing the sulfoxide oxygen and the benzimidazole ring nitrogen of PPIs as bidentate coordination donors to form an enantioselective ternary complex with the central Cu(II) ion and the chiral stationary bidentate ligand was proposed.

Development of an improved ligand exchange chiral stationary phase based on leucinol for the resolution of proton pump inhibitors

As an effort to develop improved ligand exchange chiral stationary phases (CSPs) for the resolution of chiral drugs, the residual silanol groups on the silica surface of a CSP based on sodium N-[(S)-1-hydroxymethyl-3-methylbutyl]-N-undecylaminoacetate, a (S)-leucinol derivative, were protected with n-octyl groups. The residual silanol group-protected CSP was applied to the resolution of proton pump inhibitors (PPIs) such as omeprazole, pantoprazole, lansoprazole and rabeprazole. The resolution of PPIs on the residual silanol group-protected CSP was excellent with the separation factors (α) in the range of 4.32-6.42 and the resolution factors (RS) in the range of 6.70-7.15. The improved chiral recognition ability of the residual silanol group-protected CSP was rationalized to be originated from the protection of the non-enantioselective interaction sites on the silica surface and the improved lipophilicity of the stationary phase.

Effect of the residual silanol group protection on the liquid chromatographic resolution of α‐amino acids and proton pump inhibitors on a ligand exchange chiral stationary phase

A new ligand exchange chiral stationary phase (new CSP) containing residual silanol group-protecting n-octyl groups on the silica surface was prepared by treating a ligand exchange CSP (original CSP) based on sodium N-[(R)-2-hydroxy-1-phenylethyl]-N-undecylaminoacetate bonded to silica gel with excess n-octyltriethoxysilane. The new and original CSPs containing an identical amount of chiral selector were applied to the resolution of α-amino acids and proton pump inhibitors (PPIs) including omeprazole, pantoprazole, lansoprazole, and rabeprazole. The separation factors (α) and resolutions (RS) were greater on the new CSP than on the original CSP except for the resolution of asparagine. The trends of the retention factors (k1) for the resolution of α-amino acids on the new and original CSPs with the variation of the organic modifier content in aqueous mobile phase were opposite to those for the resolution of PPIs. Removal of the nonenantioselective interactions between the residual silanol groups and the analytes and the improved lipophilicity of the new CSP were proposed to be responsible for the improved chiral recognition ability of the new CSP and the different retention behaviors of the enantiomers between the new and original CSPs.

Organoiodine(III) mediated intramolecular oxidative cyclization of 1-(3-arylisoquinolin-1-yl)-2-(arylmethylene)hydrazines to 5-aryl-3-(aryl)-[1,2,4]triazolo[3,4-a] isoquinolines

A series of 5-aryl-3-(aryl)-[1,2,4]triazolo[3,4-a]isoquinolines, 4 were obtained by oxidative cyclization of 1-(3-arylisoquinolin-1-yl)-2-(arylmethylene)hydrazines, 3, in the presence of a hypervalent iodine oxidant (iodobenzene diacetate, IDB) and dichloromethane at ambient temperature. This methodology involves a proficient metal-free intramolecular C–N bond formation, facilitated by a hypervalent iodine reagent.

Facile synthesis of 3-aryl-1-((4-aryl-1,2,3-selenadiazol-5-yl)sulfanyl)isoquinolines

A new series of 1,2,3-selenadiazoles containing an aryl or a 3-arylisoquinoline sulfanyl moiety at carbons 4 and 5, respectively, was prepared by cyclization of the respective semicarbazones in the presence of selenium(II) oxide and tetrahydrofuran at 70–75°C. Semicarbazones required for the reaction were obtained from 2-((3-arylisoquinolin-1-yl)sulfanyl)-1-phenylethanones, I, by a reaction with semicarbazide hydrochloride in ethanol/water mixture and potassium acetate base.