• Journal of Electrochemical Science and Technology
• /
• v.15 no.1
• /
• pp.198-206
• /
• 2024

Given the high theoretical capacity (1,675 mAh g^-1) and the inherent affordability and ubiquity of elemental sulfur, it stands out as a prominent cathode material for advanced lithium metal batteries. Traditionally, sulfur was sequestered within conductive porous carbons, rooted in the understanding that their inherent conductivity could offset sulfur's non-conductive nature. This study, however, pivots toward a transformative approach by utilizing diatom shell (DS, diatomite)-a naturally abundant and economically viable siliceous mineral-as a sulfur host. This approach enabled the development of a sulfurlayered diatomite/S composite (DS/S) for cathodic applications. Even in the face of the insulating nature of both diatomite and sulfur, the DS/S composite displayed vigorous participation in the electrochemical conversion process. Furthermore, this composite substantially curbed the loss of soluble polysulfides and minimized structural wear during cycling. As a testament to its efficacy, our Li-S battery, integrating this composite, exhibited an excellent cycling performance: a specific capacity of 732 mAh g^-1 after 100 cycles and a robust 77% capacity retention. These findings challenge the erstwhile conviction of requiring a conductive host for sulfur. Owing to diatomite's hierarchical porous architecture, eco-friendliness, and accessibility, the DS/S electrode boasts optimal sulfur utilization, elevated specific capacity, enhanced rate capabilities at intensified C rates, and steadfast cycling stability that underscore its vast commercial promise.

• Korean Journal of Food Science and Technology
• /
• v.30 no.2
• /
• pp.272-277
• /
• 1998

In order to study storage stability of fresh jujube fruits (Zizyphus jujuba Miller) controlled atmosphere storage, polyethylene film packaging and non-packaging were compared. Jujube fruits were stored on the following gas compositions: 1.5% carbon dioxide and 5, 8, 10, 12% oxygen at $7^{\circ}C$, respectively. And 0.05 mm PE packaging and non-packaging were stored at $1^{\circ}C,\;4^{\circ}C\;and\;7^{\circ}C$. Safe storage period of Bokjo jujube fruits was four weeks when stored in CA condition of $O_2\;10%\;and\;CO_2\;1.5%$ in terms of their overall quality. The rate of weight loss was not much changed either by storage method of CA or by PE film packaging. In surface color the a value of jujube fruits increased but L and b values decreased during the storage period. Hardness showed the trend of increase in all the treatment for 2 weeks of storage while in CA it decreased more than the others after 4 weeks of storage. Soluble solids and titratable acidity were changed slightly. Vitamin C contents were gradually decreased in all treatments, but non-packed jujubes at $1^{\circ}C$ were slightly increased.

• Journal of Microbiology and Biotechnology
• /
• v.13 no.6
• /
• pp.960-968
• /
• 2003

A bacterial isolate showing a strong endochitosanase activity was isolated from soil and then characterized. The isolate was identified and designated as Bacillus cereus P16, based on morphological and biochemical properties, assimilation tests, cellular fatty acids pattern, along with 16S rRNA gene sequence. The optimized medium for producing extracellular chitosanase in a batch culture contained 1% tryptone, 0.5% chitosan, and 1% NaCl (pH 7.0). Powder chitosan and tryptone served the best as carbon and nitrogen sources, respectively, for the chitosanase production. Chitosanase activity was the highest when culture was completed at $37^{\circ}C$ among various temperatures ($20-42^{\circ}C$) tested in a shaking incubator (200 rpm). The levels of chitosanase activity in the culture fluid were 2.0 U/ml and 3.8 U/ml, respectively, when incubated in a flask for 60 h and in a jar fermenter for 24 h. The culture supernatant showed a strong liquefying activity on the soluble chitosan. The viscosity of 1% chitosan solution, that was incubated with the culture supernatant, was rapidly decreased, suggesting the secretion of endochitosanolytic enzymes by P16. The culture fluid revealed six endo-type chitosanase isozymes, two major (38 and 45 kD), and four minor (54, 65, 82, and 96 kD) forms by staining profile. The crude enzymes were very stable, and full activity was maintained for 4 weeks at $4^{\circ}C\;or\;-20^{\circ}C$ in the culture supernatant, suggesting a highly desirable stability rate for making an industrial application of the crude enzymes. The supernatant also cleaved the insoluble chitosan powder, but the hydrolysis rate was much lower. The enzymic degradation products of chitosan contained $(GlcN)_n$ (n=2-8). The concentration of chitosan in the reaction mixture of the crude enzyme affected the chitooligosaccharides composition of the hydrolysis products. When the higher concentration of chitosan was used, the higher degree of polymerized chitooligosaccharides were produced. By comparison with other commercial chitosanase preparations, P16 was indeed found to be a valuable enzyme source for industrial production of chitooligosaccharides from chitosan.

• Microbiology and Biotechnology Letters
• /
• v.9 no.4
• /
• pp.197-205
• /
• 1981

Penicillin amidase of Bacillus megaterium was recovered from the fermentation broth by adsorption on celite and immobilized by entrapping the adsorbed enzyme in acrylamide gel. The operational stability in column reactor was greatly increased by entrappment as compared with that of without entrappment. The optimum pH of the immobilized enzyme was 8.7 with broader activity profile than that of the free enzyme, while the most stable pH range appeared to be between pH 7.5 and 8.0. The optimum temperature was shifted to 5$0^{\circ}C$ from 45$^{\circ}C$ for the soluble enzyme. The values of Km and the inhibition constants for 6-APA( $K_{ia}$ ) and phenylacetic acid ( $K_{ip}$ ), were 4.55 mM, 36.5mM, and 10.5mM, respectively. No significant internal pore diffusion limitation was found since the value of effectiveness factor was 0.95. The operational half life in a column reactor at pH 8.0 was 6.8 days at 4$0^{\circ}C$ and 47 days at 3$0^{\circ}C$, whereas that of without entrappment was only 1 day and 4 days, respectively. The performance of a batch and a column reactor was also discussed with respect to the productivity. The results demonstrated that the entrappment of an adsorbed enzyme for the enhancement of the operational stability of the immobilized enzyme was useful especially when an extracellular enzyme was used.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.40 no.7
• /
• pp.981-985
• /
• 2011

The effects of germinated brown rice flour on the quality characteristics of white wheat flour noodles were investigated. The insoluble dietary fiber and soluble dietary fiber content of germinated brown rice flour were 5.1% and 4.2%, respectively. Water absorption, development time, and stability of farinogram decreased when germinated brown rice flour was added to white wheat flour. Brightness ($L^*$) decreased, but redness ($a^*$) increased in noodles made from germinated brown rice. Volume of cooked noodles did not change upon addition of germinated brown rice flour, but weight of cooked noodles decreased and the turbidity of cooked water increased. The cutting force of cooked noodles did not change upon addition of germinated rice flour. Addition of 10% germinated brown rice flour to white wheat flour did not have any effects on flavor, color, taste, appearance, and overall acceptability in sensory evaluation.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.46 no.2
• /
• pp.133-145
• /
• 2020

This study utilized nano-liposomes for the purpose of stabilizing and increasing the solubility of biotin, a water-soluble active material with low solubility. The particle size, zeta potential, and polydispersity index were confirmed with a nano zetasizer. It was possible to manufacture nano liposomes at 100 to 250 nm of particle size and -80 to -30 mV of zeta potential. Dialysis membrane method (DMM) was used to measure the capsulation efficiency of biotin in biotin nano-liposomes, and results showed that pH increased biotin nano-liposomes had higher capsulation efficiency than normal biotin nano-liposome. Through this experiment, it was confirmed that the pH has a great influence on the stability of biotin nano-liposomes. In vitro franz diffusion cell method was used to measure in vitro skin absorption rate of biotin nano-liposomes. The shape of the formulation and biotin solubility in nano-liposome was observed by cryogenic transmission electron microscopy (cryo-TEM). Through this study, we confirmed that biotin, which is introduced as closely related to hair health, can be incorporated into a nano-liposome drug delivery system, to make biotin nano-liposome with improved solubility and precipitation problems.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.46 no.4
• /
• pp.529-536
• /
• 2017

Nutritional constituents and physicochemical properties of lipids of forest resources were studied in order to examine their practical utilization in the lipid industry. In this study, Garae, Dongback, Mougwi, and Muwhanja were chosen as sources of fat-soluble components. Fatty acid profiles of forest resources showed more than 80% polyunsaturated fatty acids in total fatty acids. For total tocopherol contents, Garae showed higher content than others; moreover, Dongback was a good source of ${\alpha}$-tocopherol. Phytosterols of forest resources ranged from $55.96{\pm}2.23$ to $194.94{\pm}21.42mg$/100 g, and Muwhanja showed the highest phytosterol contents. Chemical properties such as acid value, peroxide value, and p-anisidine value showed good oxidative stability of lipids of forest resources. For physical properties, browning intensity and color parameters were studied. Induction times, as an indicator of oxidative stability, were measured and ranged from $0.70{\pm}0.01$ to $18.40{\pm}1.02h$ in four forest resources. Taken together, contents of lipid constituents and physicochemical properties can be used as an important preliminary database for utilization of lipids of forest resources.

• Clean Technology
• /
• v.18 no.4
• /
• pp.366-372
• /
• 2012

Three acrylic copolymers containing tris(8-hydroxyquinoline) aluminum (AlQ3) pendant group (25 wt%), acrylateco-HEMA-$AlQ_3$ (25 wt%), were successfully synthesized by free radical polymerization from acrylates [methyl methacrylate (MMA), acrylonitrile (AN) or 2-hydroxyethyl methacrylate (HEMA)] with HEMA functionalized with AlQ3 pendant groups (HEMA-p-$AlQ_3$). The glass transition temperatures ($T_g$) of MMA-co-HEMA-p-$AlQ_3$ (copolymer 1), AN-co-HEMA-p-$AlQ_3$ (copolymer 2) and HEMA-co-HEMA-p-$AlQ_3$ (copolymer 3) were found to be 158, 150 and $126^{\circ}C$, respectively. They have good thermal stability: a very desirable feature for the stability of OLEDs. Their solubility, thermal properties, UV-visible absorption and photoluminescence behaviors were investigated. They were found to be soluble in various organic solvents such as tetrahydrofuran (THF), dimethylformamide (DMF), toluene and chloroform. It was also found that the UV-visible absorption and photoluminescence behaviors of these copolymers were similar to those of pristine $AlQ_3$. Green organic light-emitting diodes (OLEDs) have also been fabricated using these copolymers as light emission/electron transport components obtained easily by spin coating, and their current density voltage (J-V) curves were compared. The OLED device of the copolymer 3 had the lowest turn-on voltage of about 2 V compared to other copolymer types devices.

• Bulletin of the Korean Chemical Society
• /
• v.14 no.6
• /
• pp.687-691
• /
• 1993

Complexation of $Cd^{2+},\;Pb^{2+}\;and\;Hg^{2+}$ ions with four cryptands were studied by potentiometry and solution calorimetry in various weight percent methanol-aqueous solvent at 25${\circ}$C under $CO_2$free nitrogen atmosphere. The stabilities of the complexes were dependent on the cavity size of macrocycles. The $Hg^{2+}$ ion stability constants are higher than those of $Cd^{2+}\;and\;Pb^{2+}$ ion. All the cryptands formed complexes having 1 : 1 (metal to ligand) mole-ratio except for $Hg^{2+}-L_1$ (cryptand 1,2b: 3,5-benzo-9,14,17-trioxa-1,7-diazabicyclo-(8,5,5) heptadecane) and $Cd^{2+}-L_2$ (cryptand 2,2b: 3,5-benzo-10,13,18,21-tetraoxa-1,7-diazabicyclo (8,5,5) eicosane) complexes. $Hg^{2+}-L_1$ complex was a sandwitch type, and the $Cd^{2+}-L_2$ complex showed two stepwise reactions. Thermodynamic parameters of the $Cd^{2+}-L_2$ complex were $6.08(log\;K_1)$, -7.28 Kcal/mol $({\Delta}H_1)$, and $4.78\;(log\;K_2)$, -4.62 Kcal/mol $({\Delta}H_2)$, respectively, for 1 : 1 and 2: 1 mole-ratio. The sequences of the selectivity were increased in the order of $Hg^{2+}\;>Pb^{2+}\;>Cd^{2+}$ ion for $L_3\;and\;L_4$ macrocycles, and the $L_2$-macrocycle has a selectivity for $Cd^{2+}$ ion relative to $Zn^{2+},\;Ni^{2+},\;Pb^{2+}\;and\;Hg^{2+}$ ions. Thus, it is expected that the $L_2$ can be used as carrier for seperation of the post transition metals by macrocycles-mediated liquid membrane because $L_2$ is not soluble in water, and the difference of stability constants of the metal complexes with $L_2$ are large as compared with the other transition metal complexes. The $^1H\;and\;^{13}C-NMR studies indicated that the nitrogen atoms of cryptands have greater affinity to the post transition metal ions than the oxygen atoms, and that the planarities of the macrocycles were lost by complexation with the metal ions because of the perturbation of ring current of benzene molecule attached to macrocycles and counter-anions.

• Journal of the Korean Wood Science and Technology
• /
• v.52 no.3
• /
• pp.221-233
• /
• 2024

Lignin, a prominent constituent of woody biomass, is abundant in nature, cost-effective, and contains various functional groups, including hydroxyl groups. Owing to these characteristics, they have the potential to replace petroleum-based polyols in the polyurethane industry, offering a solution to environmental problems linked to resource depletion and CO₂ emissions. However, the structural complexity and low reactivity of lignin present challenges for its direct application in polyurethane materials. In this study, Kraft lignin (KL), a representative technical lignin, was fractionated with ethanol, an eco-friendly solvent, and mixed with conventional polyols in varying proportions to produce polyurethane films. The results of ethanol fractionation showed that the polydispersity of ethanol-soluble lignin (ESL) decreased from 3.71 to 2.72 and the hydroxyl content of ESL increased from 4.20 mmol/g to 5.49 mmol/g. Consequently, the polyurethane prepared by adding ESL was superior to the KL-based film, exhibiting improved miscibility with petrochemical-based polyols and reactivity with isocyanate groups. Consequently, the films using ESL as the polyol exhibited reduced shrinkage and a more uniform structure. Optical microscope and scanning electron microscope observations confirmed that lignin aggregation was lower in polyurethane with ESL than in that with KL. When the hydrophobicity of the samples was measured using the water contact angle, the addition of ESL resulted in higher hydrophobicity. In addition, as the amount of ESL added increased, an increase of 7.4% in the residual char was observed, and a 4.04% increase in Tmax the thermal stability of the produced polyurethane was effectively improved.