• Journal of the Korean Chemical Society
• /
• v.54 no.4
• /
• pp.419-428
• /
• 2010

Here we describe a fast and rapid technique for preparation of amino acid hydrazide as well as peptide hydrazide derivatives using diisopropylcarbodiimide (DIC)/1-hydroxybenzotriazoles (HOXt) (X = A or B) under microwave irradiation employing a multimode reactor (Synthos 3000 Aton Paar, GmbH, 1400 W maximum magnetron). A comparison between conventional and microwave irradiation was described. The microwave methodology is rapid, convenient, proceeds under mild conditions. Diisopropylcarbodiimide (DIC)/7-aza-1-hydroxybenzotriazole (HOAt) always gave much better yield (95 - 98%) and purity than diisopropylcarbodiimide (DIC)/1-hydroxybenzotriazole (HOBt).

• Korean Chemical Engineering Research
• /
• v.59 no.2
• /
• pp.260-268
• /
• 2021

Adsorption is the most promising technology used to adsorb CO2 to reduce its concentration in the atmosphere due to its functional effectiveness. Various porous materials have been extensively synthesized to boost CO2 adsorption efficiency, for example, zeolite. Here, we report the synthesis process of zeolite adsorbent impregnated with amine, combining the benefit of these two substances. We compared conventional heating with microwave-assisted heating by varying concentrations of monoethanolamine in methanol (10% v/v and 40% v/v) as a liquid solution. The results showed that monoethanolamine impregnation helps significantly increase adsorption capacity, where adsorption occurs as a physisorption and not as chemisorption due to the adsorbent's steric hindrance effect. The highest adsorption capacity of 0.3649 mmol CO2 / gram adsorbent was reached by microwave exposure for 10 minutes. This work also reveals that a decrease in CO2 adsorption capacity was observed at a longer exposure period, and it reached a constant 40-minute adsorption rate. Impregnating activated zeolite with 40% monoethanolamine for 10 minutes in addition to microwave exposure (0.8973 mmol CO2 / gram adsorbent) is the maximum adsorption ability achieved.

• Korean Journal of Materials Research
• /
• v.17 no.12
• /
• pp.669-675
• /
• 2007

Hydroxyapatite (HAp) and biphasic calcium phosphate (BCP) nano powders were synthesized using the microwave-assisted synthesis process dependent on pH and microwave irradiation time. The average size of a powder was less than 100 nm in diameter. Through in-vitro cytotoxicity tests by an extract dilution method, the HAp and BCP nano powders have shown to be cytocompatible for L-929 fibroblast cells, osteoblastlike MG-63 cells and osteoclast-like Raw 264.7 cells. The activation of osteoblast was estimated by alkaline phosphatase (ALP) activity. When the HAp and BCP were treated to MG-63 cells, alkaline phosphatase activities increased on day 3, compared with those of the untreated cells. Also, the collagen fibers increased when the HAp and BCP powders suspension were treated to MG-63 cells, compared to those of the untreated cells. Quantitative alizarin red S mineralization assays showed a trend toward increasing mineralization in osteoblast cultured with powder suspension. In conclusion, hydroxyapatite and biphasic calcium phosphate appeared to be a bone graft substitute material with optimal biocompatibility and could be further applied to clinical use as an artificial bone graft substitute.

• Journal of the Korean Applied Science and Technology
• /
• v.31 no.3
• /
• pp.525-533
• /
• 2014

ZnO has attracted much attention such as photocatalysts, sensors, piezoelectricity and etc. At present, an economical and rapid synthesis route based on the efficient microwave polyol process is used to synthesized metal-doped ZnO nanoclusters. Diethylene glycol has a property of high polarizability, and is an excellent microwave absorbing agent, thus leading to a high heating rate and a significantly shorter reaction time. In this study, metal-doped ZnO nanoclusters are obtained with different seed volumes, when zinc acetate dihydrate is used as a precursor, and metal acetate hydrate is used as a doped-metal and diethylene glycol is used as a solvent. The obtained metal-doped ZnO nanoclusters were characterized by FE-SEM, XRD, Raman and PSA.

• Elastomers and Composites
• /
• v.39 no.4
• /
• pp.309-317
• /
• 2004

Synthesis of fullerene oxides [$C_{70}O_n$] ($n=1{\sim}3$ or n=1) in solid state by fullerene [$C_{70}$] and several oxidants such as 3-chloroperoxy benzoic acid, chromium(VI) oxide, benzoyl peroxide, and trichloroisocyanuric acid was taken place under microwave irradiation. The reactivity in solid state oi fullerene [$C_{70}$] with various oxidants under same microwave condition increased in the order of 3-chloroperoxy benzoic acid > chromium(VI) oxide > trichloroisocyanuric acid ${\simeq}benzoyl$ peroxide. The MALDI-TOF-MS, UV-visible spectra and HPLC analysis confirmed that the products of fullerene oxidation were [$C_{70}O_n$] ($n=1{\sim}3$ or n=1).

• Applied Chemistry for Engineering
• /
• v.22 no.2
• /
• pp.214-218
• /
• 2011

Zeolite A was synthesized from coal fly ash by the microwave heating as well as the conventional heating method. The effects of reaction time, the amount of sodium aluminate, and the reaction temperature on the crystallization of zeolite A were investigated. The optimum crystallization time was about 3 to 6 h in the temperature range of $80{\sim}100^{\circ}C$. The amount of sodium aluminate was found to be optimum when the molar ratio $SiO_2/Al_2O_3$ of starting solution was in the range of 0.44 to 1.05 at above $90^{\circ}C$, However, The more amount of sodium aluminate was required to get zeolite A at $80^{\circ}C$. Although the rate of crystallization was slightly faster in the microwave heating than that in the conventional heating, the reaction time need to obtain fully crystallized zeolite A was similar in both methods. Therefore, the influence of the microwave heating was not so large compared with the conventional heating in the synthesis of zeolite A from coal fly ash.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.5
• /
• pp.1219-1222
• /
• 2010

A simple and efficient method has been developed for conversion of arenecarbaldehyde-3-methylquinoxalin-2-ylhydrazones to 3-(2-methylquinoxalin-3-yl)-2-(substitutedphenyl)thiazolidin-4-ones in good yields using microwave irradiation technique on silica as solid support under solvent free conditions. The synthesized compounds were characterized by elemental microanalysis, infrared spectroscopy, $^1H$ NMR, and mass spectroscopy. All the synthesized thiazolidinones were investigated for their antimicrobial and antifungal activities. The results of the biological activities revealed that the compounds 3b, 3d, 3f and 3h exhibited excellent antibacterial activities while 3d and 3h exhibited good antifungal activity.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.12
• /
• pp.2382-2388
• /
• 2007

A series of dimethine cyanine dyes were synthesized in a fast, efficient and high yield by the condensation of quaternary salts with 1H-indole-3-carbaldehyde in the presence of piperidine under solvent-free microwave irradiation. The products were identified by 1H NMR, IR, UV-Vis spectra and elemental analysis. The absorption and fluorescence properties of these dyes were investigated both experimentally and theoretically. Calculations performed at a combination of time-dependent density functional theory (TD-DFT) and the polarizable continuum model (PCM) reproduced the π-π* type absorption bands of the dyes. Regression analysis was used for studying theoretical results of the absorption maxima in different solvents. Compared with experimental counterparts, estimated overall uncertainties in the absorption maxima were about ±2%.

• Transactions on Electrical and Electronic Materials
• /
• v.16 no.4
• /
• pp.198-200
• /
• 2015

The microwave plasma enhanced chemical vapor deposition (PECVD) system was used to grow a carbon nanowall (CNW) on a silicon (Si) substrate with hydrogen (H₂) and methane (CH₄) gases. To find the growth mechanism of CNW, we increased the growth time of CNW from 5 to 30 min. The vertical and surficial conditions of the grown CNWs according to growth time were characterized by field emission scanning electron microscopy (FE-SEM). Energy dispersive spectroscopy (EDS) measurements showed that the CNWs consisted solely of carbon.

• Journal of the Korean Ceramic Society
• /
• v.32 no.9
• /
• pp.1009-1018
• /
• 1995

(Ti.Si)C composite powders were synthesized by SHS method using microwave energy. Compositional and structural characterization of the powder were carried out by using scanning electron microscopy and X-ray diffraction. The average particle size of the synthesized (Ti.Si)C composite powders was smaller than that of the starting materials. From the results of the temperature profile, combustion temperature and velocity were decreased with increasing Si molar ratio. With increasing C molar ratio combustion temperature and velocity did not change. (Ti.Si)C composite was sintered at 185$0^{\circ}C$ for 60 min by using hot-pressing with 30 MPa. The best properties were obtained from the sintered specimen whose composition was 1 : 1 : 1.9 molar ratio of Ti : Si : C. The sintering density, flexural strength and vickers hardness of the sintered body were 4.71 g/㎤, 423 MPa and 21 GPa, respectively.