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Three-dimensional architecture of carbon nanotube-anchored polymer nanofiber composite
Xuyen, Nguyen Thi,Kim, Tae Hyung,Geng, Hong-Zhang,Lee, Il Ha,Kim, Ki Kang,Lee, Young Hee Royal Society of Chemistry 2009 Journal of materials chemistry Vol.19 No.42
<P>Carbon nanotube (CNT)-anchored polymer nanofiber mats were designed by <I>in situ</I> spraying of carbon nanotubes while simultaneously electrospinning polymer nanofibers. The improved conductivity of the composite mat, high catalytic current (3400 mA/cm<SUP>2</SUP>/mg Pt) and long term stability of the composite mat was attributed to the efficient formation of CNT bridges between nanofibers.</P> <P>Graphic Abstract</P><P>An <I>in situ</I> spray–electrospinning process for a t-MWCNTs/PAA nanofiber. The 3D-architecture of an anchored t-MWCNTs/PAA nanofiber composite mat. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b913762a'> </P>
Xuyen, Nguyen Thi,Jeong, Hae Kyung,Kim, Gunn,So, Kang Pyo,An, Kay Hyeok,Lee, Young Hee Royal Society of Chemistry 2009 Journal of materials chemistry Vol.19 No.9
<P>Electrospun polyimide (PI)-based carbon nanofibers have recently garnered much interest due to their high conductivity and high mechanical strength. Promising applications include electrodes for supercapacitors, filters, sensors, and fuel cells. Here, we demonstrate that Pt nanoparticles can be loaded on the surface of PI nanofibers <I>via</I> an immobilization process induced by hydrolysis. The uniform distribution and sizes of Pt nanoparticles were controlled further by carbonization. Pt(acac)<SUB>2</SUB> dissolved in acetone was impregnated on the hydrolyzed PI nanofibers. Pt ions were localized exclusively on the surface of PI nanofibers by precise control of the hydrolysis process. Our X-ray photoelectron spectroscopy results show that Pt ions in Pt(acac)<SUB>2</SUB> molecules (40%) are immobilized on the hydrolyzed PI surface while some of them (60%) bind to O in the carboxylic group to form a PtO structure, and then are fully decomposed into Pt nanoparticles during carbonization. Using density functional calculations, we show that the binding of Pt(acac)<SUB>2</SUB> on hydrolyzed PI is strong with a binding energy of −4.3 eV, which originates mostly from Pt–O binding and π-stacking between (acac) and PAA, confirming experimental observations of robust formation of Pt nanoparticles on hydrolyzed PI. The cyclic voltammetric test demonstrates that our robust carbon nanofiber mat can be utilized for fuel cell electrodes.</P> <P>Graphic Abstract</P><P>Pt(acac)<SUB>2</SUB> is loaded on the surface of a hydrolyzed-polyimide nanofiber mat with two forms of PtO and Pt(acac)<SUB>2</SUB> adsorption. With further carbonization, uniform and highly dense Pt nanoparticles/carbon nanofiber electrodes are achieved for fuel cell applications. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b813486c'> </P>
Xuyen, Nguyen Thi,Sanchez, David P. V.,Kim, Tae Hyung,Park, Ho Il,Yun, Minhee,Lee, Young Hee Royal Society of Chemistry 2010 Journal of materials chemistry Vol.20 No.26
<P>We propose a simple and efficient method of synthesizing highly electrocatalytic Pt nanoparticles on a carbon nanofiber mat. Pt(acac)<SUB>2</SUB> molecules are absorbed on the functionalized carbon nanofibers and further reduced to Pt nanoparticles by diffusion-limited sublimation in a confined space. Pt nanoparticles are formed with sizes of 2.9 ± 0.4 nm and 100% loading yield. By further electrochemical activation <I>via</I> a cyclic voltammetry, high active surface area of Pt nanoparticles is obtained due to the formation of specific crystalline facets. The methanol oxidation current density per mg Pt of Pt-loaded carbon nanofiber sample is about 60 times as high as the commercially available (E-tek) sample and superior to other existing samples. The Pt-loaded carbon nanofiber mat is used as an anode in a microbial fuel cell application. The activated Pt nanoparticles chaperon the electron transport from the bacterial matrix to the carbon nanofiber mat. The electrochemically activated electrode shows a significantly higher current density (0.6 A m<SUP>−2</SUP>) than the untreated sample and higher than an e-beam deposited Pt/carbon microfiber paper. The long-term stability at this current is four times (150 hours) longer than the reported values. We believe that this method can be practically applied to load the organometallic compound-based catalyst on various carbon-based supports.</P> <P>Graphic Abstract</P><P>Pt/electrospun carbon nanofiber exhibited the high activity for methanol oxidation and microbial fuel cell application. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c000654h'> </P>
Coffee Husk By-Product as Novel Ingredients for Cascara Kombucha Production
( Bao Xuyen Nguyen Le ),( Thach Phan Van ),( Quang Khai Phan ),( Gia Bao Pham ),( Hoa Pham Quang ),( Anh Duy Do ) 한국미생물생명공학회 2024 Journal of microbiology and biotechnology Vol.34 No.3
Kombucha, a fermented beverage, is gaining popularity due to its numerous beneficial health effects. Various substrates such as herbs, fruits, flowers, and vegetables, have been used for kombucha fermentation in order to enhance the flavor, aroma, and nutritional composition. This study aims to investigate the potential suitability of cascara as a novel ingredient for kombucha production. Our findings suggested that cascara is a suitable substrate for kombucha production. Fermentation elevated the total phenolic and flavonoid content in cascara, which enhanced the antioxidant, antibacterial, and prebiotic characteristics of the product. Furthermore, the accumulation of acetic acid-induced the pH lowering reached 2.7 after 14 days of fermentation, which achieved the microbiological safety of the product. Moreover, 14 days of fermentation resulted in a balanced amalgamation of acidity, sweetness, and fragrance according to sensory evaluation. Our findings not only highlight the potential of cascara kombucha as a novel substrate for kombucha production but also contribute to repurposing coffee by-products, promoting environmentally friendly and sustainable agricultural development.
Outage Performance of Opportunistic Routing in Multi-Hop Wireless Networks
Tran Thi Xuyen(찬 디 수엔),Hyung-Yun Kong(공형윤) 대한전기학회 2010 정보 및 제어 심포지엄 논문집 Vol.2010 No.4
In this paper, we propose a novel routing strategy in multi-hop cooperative networks in which at each hop, a link is established between of two members of two adjacent clusters. if the established link is not good, a new link must be found and the procedure of selecting a good link between two clusters is performed. If the receiving node cannot decode the signal received from a transmitter of the previous cluster successfully, it sends a NACK message to inform a retransmission. The performance evaluation of the proposal is implemented through theoretical analysis and simulations.
Preparation of Polydivinylbenzene/Au Core-Shell Beads
Phan, K.Xuyen,Cho, Mi Suk,Nam, Jae Do,Choi, Hyouk Ryeol,Koo, Ja Choon,Lee, Young Kwan Trans Tech Publications, Ltd. 2006 Key Engineering Materials Vol.326 No.-
<P>A novel core-shell material composed of closely packed gold shells on poly (divinylbenzene) (PDVB) cores was fabricated via the reduction of a gold complex. PDVB beads (2-5 +m) were synthesized by precipitation polymerization. The surface of the PDVB beads was modified by three different methods, viz. sulfonation, chloromethylation, and thiolation. The modification of the surface of the PDVB beads was designed to allow the facile attachment of the gold layer onto the PDVB cores. The gold seeding layer was initially formed on the modified PDVB cores by the chemical reduction of a gold-phenanthroline complex. The subsequent growing reactions of NH2OH and HAuCl4 increased the gold coverage to more than 90%. The structure of the PDVB/Au core-shell material was characterized by SEM, XPS, and FT-IR.</P>
( Tran Thi Xuyen ),( Hyung Yun Kong ) 한국인터넷정보학회 2010 KSII Transactions on Internet and Information Syst Vol.4 No.5
In this paper, two selection relaying schemes are proposed and compared with each other in terms of packet error rate (PER) and diversity order. Moreover, the comparison is performed over two different fading environments including fast and slow fading environments in which the diversity order is considered as the important factor to reach the decision which scheme is suitable for each fading environment. Numerical results validate the analytical results and indicate significant differences on the PER performance of two schemes over two fading environments.