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Fabrication of Carbon Nanotubes on Tungsten Tips
Phan Ngoc Hong,Phan Ngoc Minh,Vo Viet Cuong,Bui Hung Thang,Phan Hong Khoi 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
In this paper, we present the results of fabrication of carbon nanotubes on sharp W tips for advanced electron emiters and scanning probe microscopy. A calculation to optimize the elec- trochemical etching conditions for geting ultra-sharp W tips was caried out. W tips of 50 nm in diameter were formed by electrochemical etching of a 0.3-mm W wire in a 5 % KOH solution. Fe catalytic nanoparticles were deposited at the apex of the W tip by electroplating in a FeCl3 solution. By using hot-lament chemical vapor deposition in C2H2/H2 gases, we have sucesfuly grown individual CNTs of 4 m in length and 20 nm in diameter on a W tip.
New Technique for the Synthesis of Carbon Nanotubes
Phan Ngoc Minh,Phan Hong Khoi,Nguyen Van Chuc,Phan Ngoc Hong,Ngo Thi Thanh Tam 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
Carbon nanotubes (CNTs) are considered as a promising material for various applications. However, due to their limited availability and high purchasing costs, at the present time, only a few of these applications have been realized. The realization of CNT-based devices and CNT-based materials depends on success in material synthesis and on the possibility of controlling the nanotube's chirality, diameter and purity. This paper describes new simple techniques for (i) synthesis of vertically-aligned carbon nanotubes (VA-CNTs), (ii) mass and low-cost production of multiwall carbon nanotubes (MWCNTs) and (iii) growth of individual CNTs on tungsten tips.
Synthesis of Carbon Nanotubes on Steel Foils
Nguyen Van Chuc,Nguyen Duc Dung,Phan Ngoc Hong,Le Dinh Quang,Phan Hong Khoi,Phan Ngoc Minh 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
Carbon nanotubes (CNTs) were synthesized by using a thermal chemical vapor deposition (CVD) at 800 ℃ in a mixture of C₂H₂, H₂ and N₂ gases with steel foils as both catalysts and substrates. More than 2 grams of CNTs were grown on approximately 7 grams of steel foil with a 0.5 cm² surface area after 30 minutes of growth. The effects of CVD parameters, such as the growth temperature and the deposition time, on the size and the morphology of the CNTs were studied using scanning electron microscopy (SEM). We found that the optimized temperature and growth time for having high quality CNTs were 800 ℃ and 30 minutes, respectively. The purity of the CNTs was evaluated by using thermogravimetric analysis (TGA) and the result showed that the carbon content was approximately 93 wt.%. The graphite crystallinity of the CNTs was analyzed by using Raman spectroscopy. The steel foil was found to maintain its catalytic behavior after several growths. The technique holds great promise for use in mass production (approximately 120 grams CNTs per day) with signicantly reduced cost. Carbon nanotubes (CNTs) were synthesized by using a thermal chemical vapor deposition (CVD) at 800 ℃ in a mixture of C₂H₂, H₂ and N₂ gases with steel foils as both catalysts and substrates. More than 2 grams of CNTs were grown on approximately 7 grams of steel foil with a 0.5 cm² surface area after 30 minutes of growth. The effects of CVD parameters, such as the growth temperature and the deposition time, on the size and the morphology of the CNTs were studied using scanning electron microscopy (SEM). We found that the optimized temperature and growth time for having high quality CNTs were 800 ℃ and 30 minutes, respectively. The purity of the CNTs was evaluated by using thermogravimetric analysis (TGA) and the result showed that the carbon content was approximately 93 wt.%. The graphite crystallinity of the CNTs was analyzed by using Raman spectroscopy. The steel foil was found to maintain its catalytic behavior after several growths. The technique holds great promise for use in mass production (approximately 120 grams CNTs per day) with signicantly reduced cost.
Thach Phan Van,Quang Khai Phan,Hoa Pham Quang,Gia Bao Pham,Ngoc Han Ngo Thi,Hong Tham Truong Thi,Anh Duy Do 한국식품영양과학회 2023 Preventive Nutrition and Food Science Vol.28 No.4
Kombucha is a widely consumed fermented tea beverage with diverse health benefits. In a previous study, we demonstrated that the use of cascara as a substrate results in a special kombucha beverage with high bioactivity. Traditional kombucha fermentation using a symbiotic culture of bacteria and yeast (SCOBY) can lead to inconsistent product quality because of the lack of control over microbial composition. We successfully isolated and identified yeast and bacteria, including Saccharomyces cerevisiae, Komagataeibacter rhaeticus, and Lactobacillus brevis that are appropriate starter cultures for cascara kombucha fermentation. We also demonstrated that a supplementation with lactic acid bacteria (LAB) and a mixture of S. cerevisiae and K. rhaeticus resulted in higher total polyphenol and flavonoid content of cascara kombucha compared with the traditionally fermented product using SCOBY as the inoculum. The free radical scavenging activity, inhibitory effects on α-amylase, tyrosinase activity, and antibacterial properties of cascara kombucha were also enhanced as a result of LAB supplement. These findings provide valuable insights into the controlled microbiological composition required for the fermentation of cascara kombucha, thereby ensuring consistent quality and enhanced bioactivity of the product. Further, the use of cascara as a substrate for kombucha production not only offers various health benefits and biological effects, but also repurposes by-products from the coffee industry, which contributes to sustainable development and is eco-friendly.
New Dibenzocyclooctadiene Lignan from Kadsura induta and Their Cytotoxic Activities
Pham, Thi Hong Minh,Do, Tien Lam,Nguyen, Quyet Tien,Nguyen, Ngoc Tuan,Vu, Phuong Nhung,Nong, Van Hai,Phan, Van Kiem,Nguyen, Xuan Nhiem,Chau, Van Minh,Park, SeonJu,Kim, Seung Hyun Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.6
Carrier Phase-Shift PWM to Reduce Common-Mode Voltage for Three-Level T-Type NPC Inverters
Nguyen, Tuyen D.,Phan, Dzung Quoc,Dao, Dat Ngoc,Lee, Hong-Hee The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.6
Common-mode voltage (CMV) causes overvoltage stress to winding insulation and damages AC motors. CMV with high dv/dt causes leakage currents, which create noise problems for equipment installed near the converter. This study proposes a new pulse-width modulation (PWM) strategy for three-level T-type NPC inverters. This strategy substantially eliminates CMV. The principle for selecting suitable triangle carrier signals for the three-level T-type NPC is described. The proposed method can mitigate the peak value of CMV by 50% compared with the phase disposition pulse-width modulation method. Furthermore, the proposed method exhibits better harmonic spectrum and lower root mean square value for the CMV than those of the reduced-CMV method on the basis of the phase opposition disposition PWM scheme with modulation index higher than 0.5. The proposed modulation can easily be implemented using software without any additional hardware modifications. Both simulation and experimental results demonstrate that the proposed carrier phase-shift PWM method has good output waveform performance and reduces CMV.
Nhiem, Nguyen Xuan,Kiem, Phan Van,Minh, Chau Van,Ban, Ninh Khac,Cuong, Nguyen Xuan,Tung, Nguyen Huu,Ha, Le Minh,Ha, Do Thi,Tai, Bui Huu,Quang, Tran Hong,Ngoc, Tran Minh,Kwon, Young-In,Jang, Hae-Dong,K The Pharmaceutical Society of Japan 2010 Chemical & pharmaceutical bulletin Vol.58 No.5
<P>Fourteen cucurbitane-type triterpene glycosides (1—14) were isolated from a methanol extract of <I>Momordica charantia</I> fruits, including three new compounds, charantosides A—C (1, 5, 6). Their structures were elucidated by chemical and spectroscopic methods. All isolated compounds were evaluated for α-glucosidase inhibitory effect. Of which, 12 and 13 showed moderate inhibitory activity against α-glucosidase. Whereas, 2, 3, 6—11, and 14 showed weak inhibitory activity, and 1, 4, and 5 were inactive.</P>
An overview bioactive compounds on the skin of frogs (Anura)
Tran Thi Huyen,Phan Thi Hoang Anh,Nguyen Thi Anh Hong,Nguyen Ngoc Duyen,Le Pham Tan Quoc,Tran Dinh Thang 한국수산과학회 2023 Fisheries and Aquatic Sciences Vol.26 No.4
The robust development of frog farming offered high economic benefits but created a large waste residue of frog bones and skin that received little attention. Over the years, inedible by-products have often been processed into biomolecules of potential value and environmental benefits, such as collagen, gelatin, and bioactive peptides. An overview of bioactive compounds on frog skins from various countries indicated that brevinin was the most abundant biological peptide found in frog skin. Other remaining compounds also possessed their highlighted activities, including antibacterial, stimulating insulin release and gastric hormone release, anti-cancer, and neuroregulatory. Notably, various components have been analyzed in the structure and sequence to give meaningful insight into clustering components related to their biological activity. This review may create a source of raw materials for the developmental research of by-products from frog skin and concomitantly reduce environmental pollution.