Sam Gon Ryu

Redox and catalytic behaviors of chromium oxide supported on zirconia

Chromium oxide supported on zirconia was prepared by dry impregnation of powdered Zr(OH)4with an aqueous solution of (NH4)2CrO4 followed by calcining in air. Upon the addition of only a small amount of chromium oxide (1 wt% Cr) to ZrO2, both the acidity and acid strength of the catalyst increased remarkably. The redox and catalytic behaviors of the samples were investigated through XPS and the reaction of cumene using a pulse technique. It was found that Cr6+ species existing on the surface of catalyst were responsible for the formation of strong acid sites and the catalytic activity for cracking of cumene. However, the Cr6+ species were easily reduced to Cr3+ species during the catalytic reaction of cumene and the reduced Cr3+ species were active for α-methylstyrene formation due to the dehydrogenation of cumene. The reduced Cr3+ species could be reoxidized by treatment with O2 and subsequently the reoxidized catalyst exhibited catalytic activity for the cracking reaction of cumene.

Size and morphological control of a metal–organic framework Cu-BTC by variation of solvent and modulator

Abstract A metal–organic framework of copper 1,3,5-benzenetricarboxylate (Cu-BTC) has been synthesized using the microwave-assisted method, with different solvents. Synthesized compounds were washed repeatedly with a mixture of deionized water and ethanol to ensure the removal of impurities. Finally, purified samples were characterized using XRD and SEM to understand their morphological and structural features. The effect of solvent and modulator (dodecanoic acid) on the crystallinity and morphology of synthesized particles was investigated. The crystallinity depends on the dielectric constant and dielectric loss factor of the solvent used. The Cu-BTC crystals synthesized using ethylene glycol at low concentration [mole ratio of copper salt (1) to ethylene glycol (180)] were octahedral, but increasing the concentration [mole ratio of copper salt (1) to ethylene glycol (36)] changed the crystal morphology from octahedral to hexagonal. Interestingly, a dramatic change in the particle size and morphology was observed for Cu-BTC synthesized using ethylene glycol with coordination modulator.

Zirconium Hydroxide‐coated Nanofiber Mats for Nerve Agent Decontamination

Diverse innovative fabrics with specific functionalities have been developed for requirements such as self-decontamination of chemical/biological pollutants and toxic nerve agents. In this work, Zr(OH)4 -coated nylon-6,6 nanofiber mats were fabricated for the decontamination of nerve agents. Nylon-6,6 fabric was prepared via the electrospinning process, followed by coating with Zr(OH)4 , which was obtained by the hydrolysis of Zr(OBu)4 by a sol-gel reaction on nanofiber surfaces. The reaction conditions were optimized by varying the amounts of Zr(OBu)4 ,the reaction time, and the temperature of the sol-gel reaction. The composite nanofibers show high decontamination efficiency against diisopropylfluorophosphate, which is a nerve agent analogue, due to its high nucleophilicity that aids in the catalysis of the hydrolysis of the phosphonate ester bonds. Composite nanofiber mats have a large potential and can be applied in specific fields such as military and medical markets.

Toward a detoxification fabric against nerve gas agents: guanidine-functionalized poly[2-(3-butenyl)-2-oxazoline]/Nylon-6,6 nanofibers

A novel guanidine-functionalized polymer, poly[2-(3-butenyl)-2-oxazoline] (PBuOxz), has been co-electrospun with Nylon-6,6 to form fibers that could be used for the decontamination of chemical warfare agents (CWAs). PBuOxz was obtained from the living cationic polymerization of 2-(3-butenyl)-2-oxazoline, which was synthesized starting from 4-pentenoic acid. This clickable PBuOxz polymer could be easily functionalized through the introduction of amine groups via thiol–ene click chemistry, followed by guanidinylation to form guanidine-functionalized PBuOxz (G-PBuOxz). The synthesized G-PBuOxz/Nylon-6,6 fibers are an active hydrolysis species for diisopropyl fluorophosphate (DFP), an organophosphate mimic of nerve agents. The decontamination efficiency for DFP could be as high as 100% under trace aqueous solution conditions using this G-PBuOxz/Nylon-6,6 fiber as the decontamination agent at the ratio of [guanidine]/[DFP] = 100/1 in 2 hours. The hydrolysis occurs via a general SN2 mechanism for this G-PBuOxz-based catalysis. Furthermore, the kinetics of decontamination were also investigated based on time and guanidine concentration. Hence, this G-PBuOxz/Nylon-6,6 fiber is effective as a hydrolyzing agent against toxic organophosphates, and thus exhibits potential as a material for protecting against chemical warfare agents.

Genetic diversity of Korean Bacillus anthracis isolates from soil evaluated with a single nucleotide repeat analysis.

Bacillus (B.) anthracis, the etiological agent of anthrax, is one of the most genetically monomorphic bacteria species in the world. Due to the very limited genetic diversity of this species, classification of isolates of this bacterium requires methods with high discriminatory power. Single nucleotide repeat (SNR) analysis is a type of variable-number tandem repeat assay that evaluates regions with very high mutation rates. To subtype a collection of 21 isolates that were obtained during a B. anthracis outbreak in Korea, we analyzed four SNR marker loci using nucleotide sequencing analysis. These isolates were obtained from soil samples and the Korean Center for Disease Control and Prevention. The SNR analysis was able to detect 13 subgenotypes, which allowed a detailed evaluation of the Korean isolates. Our study demonstrated that the SNR analysis was able to discriminate between strains with the same multiple-locus variable-number tandem repeat analysis genotypes. In summary, we obtained SNR results for four SNR marker loci of newly acquired strains from Korea. Our findings will be helpful for creating marker systems and help identify markers that could be used for future forensic studies.

Whole Transcriptomic Analysis of Bacillus anthracis during Hydrogen Peroxide Decontamination

Decontamination of biological agents utilizes hydrogen peroxide() for its effectiveness and safeness. Bacillus anthracis is a major target for decontamination. To assess the effect of on B. anthracis and identify biomarkers for decontamination, whole transcriptomic profiling of -treated B. anthracis was performed. Here we identified deregulation in stress response genes, transcription factors and cellular homeostasis genes. We also found that expression of antisense RNAs increased in B. anthracis during decontamination. We postulate that B. anthracis prioritizes survival and adaptation in response to treatment by changing its gene expression pattern.

Decontamination Condition of Geobacillus Stearothermophilus Spore on the Surface of Various Coupons using Hydrogen Peroxide Vapor

Biological decontamination means the removal of microorganisms from the inanimate object such as building or equipment. In this study, hydrogen peroxide vapor efficacy test using VHP 1000ED system(Steris LifeSciences) were conducted for G. stearothermophilus spore with agent materials(aluminum, stainless steel, poly-carbonate, viton, silicone, kapton and glass). Total recovered spores exposed to hydrogen peroxide vapor(1.0 g/min) during 7, 15, 30, 60 min were calculated. As a result, all agent materials were totally decontaminated within 60 min at 1.0 g/min concentration with 35% hydrogen peroxide vapor. Finally, we could confirmed that hydrogen peroxide vapor possess sporicidal capacity of G. stearothermophilus and found the optimum decontamination conditions with VHP1000ED system.