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- 검색키워드
- 저자 : Faheem A. Sheikh (검색결과 24 건)
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Faheem A. Sheikh,Naseer A. M. Barakat,Muzafar A. Kanjwal,박수진,박대광,김학용 한국고분자학회 2010 Macromolecular Research Vol.18 No.1
This study examined the mechanical properties of a disc consisting of electrospun poly(vinyl alcohol)(PVA) nanofibers incorporated with high purity hydroxyapatite (HAp) nanoparticles (NPs) for potential hard tissue engineering applications. As HAp NPs are insoluble in a PVA aqueous solution, electrospinning of a colloidal solution was used instead of the conventional process, which is based on completely miscible solutions. The PVA/HAp colloidal solutions were characterized by dynamic light scattering (DLS) and electrophoratic light scattering (ELS),which indicated a unimodal size distribution and negative zeta potential. The physiochemical characterizations confirmed the production of PVA electrospun nanofibers incorporating HAp NPs. To investigate the bioactivity of the produced nanofiber mats, compacted mats with a disc shape were incubated in stimulated body fluid (SBF)at 37 ºC for 6 days. SEM indicated that the incorporation of HAp strongly activates the precipitation of the apatitelike materials because the HAp NPs act as seeds that accelerate the crystallization of biological HAp from the utilized SBF.
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Sheikh, Faheem A.,Barakat, Nasser A. M.,Kanjwal, Muzafar A.,Jeon, Seol-Hee,Kang, Hyung-Sub,Kim, Hak-Yong Wiley Subscription Services, Inc., A Wiley Company 2010 Journal of applied polymer science Vol.115 No.6
<P>In this study, we are introducing a new class of Polyurethane (PU) nanofibers containing silver nanoparticles (NPs) by electrospinning. A simple method not depending on the addition of foreign chemicals has been used to self-synthesize of silver NPs in/on PU nanofibers. Typically, a sol−gel consisting of AgNO<SUB>3</SUB>/PU/N,N-dimethylformamide (DMF) has been electrospun and aged for a week, so silver NPs have been created in/on PU nanofibers. Syntheses of silver NPs were carried out by exploiting the reduction ability of the DMF solvent which is the main constituent to obtain PU electrospun nanofibers in decomposition of silver nitrate precursor into silver NPs. Physiochemical characterizations confirmed well oriented nanofibers and good dispersing of pure silver NPs. Various parameters affecting utilizing of the prepared nanofibers on various nano-biotechnological fields have been studied. For instance, the obtained nanofiber mats were checked for mechanical properties which showed the improvement of the tensile strength upon increase in silver NPs content. Moreover, the nanofibers were subjected to 10 times successive washing experiments with using solid to liquid ratio of 3 : 5000 for 25 h, UV spectroscopy analysis reveals no losses of silver NPs from the PU nanofibers. 3T3-L1 fibroblasts were cultured in presence of the designed nanofibers. The morphological features of the cells attached on nanofibers were examined by BIO-SEM, which showed well attachment of cells to fibrous mats. The cytotoxicity results indicated absence of toxic effect on the 3T3-L1 cells after cell culturing. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010</P>
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Gallium Arsenide (GaAs) Nanofibers by Electrospinning Technique as Future Energy Server Materials
Sheikh, Faheem A.,Barakat, Nasser A.M.,Kanjwal, Muzafar A.,Park, S.J.,Kim, Hern,Kim, Hak-Yong 한국섬유공학회 2010 FIBERS AND POLYMERS Vol.11 No.3
Gallium arsenide (GaAs) does have superior electronic properties compared with silicon. For instant, it has a higher saturated electron velocity and higher electron mobility. Weak mechanical properties and high production cost are the main drawbacks of this interesting semiconductor. In this study, we are introducing production of GaAs nanofibers by electrospinning methodology as a very low cost and yielding distinct product technique. In general, nano-fibrous shape is strongly improving the physical properties due to the high surface area to volume ratio of this nanostructure. The mechanical and environmental properties of the GaAs compound have been modified since GaAs nanofibers have been produced as a core inside a poly(vinyl alcohol) (PVA) shell. GaAs/PVA nanofibers were prepared by electrospinning of gallium nitrate/PVA solution in presence of arsenic vapor. The whole process was carried out in a closed hood equipped with nitrogen environment. FT-IR, XPS, TGA and UV-Vis spectroscopy analyses were utilized to confirm formation of GaAs compound. Transmission electron microscope (TEM) analysis has revealed that the synthesized GaAs compound is crystalline and does have nano-fibrous shape as a core inside PVA nanofibers. To precisely recommend the prepared GaAs nanofiber mats to be utilized in different applications, we have measured the electric conductivity and the band gap energies of the prepared nanofiber mats. Overall, the obtained results affirmed that the proposed strategy successfully remedied the drawbacks of the reported GaAs structures and did not affect the main physical properties of this important semiconductor.
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Sheikh, Faheem A.,Barakat, Nasser A.M.,Kanjwal, Muzafar A.,Chaudhari, Atul A.,Jung, In-Hee,Lee, John-Hwa,Kim, Hak-Yong The Polymer Society of Korea 2009 Macromolecular Research Vol.17 No.9
In this study, a new class of polyurethane (PU) nanofibers containing silver (Ag) nanoparticles (NPs) was synthesized by electrospinning. A simple method that did not depending on additional foreign chemicals was used to self synthesize the silver NPs in/on PU nanofibers. The synthesis of silver NPs was carried out by exploiting the reduction ability of N,N-dimethylformamide (DMF), which is used mainly to decompose silver nitrate to silver NPs. Typically, a sol-gel consisting of $AgNO_3$/PU was electrospun and aged for one week. Silver NPs were created in/on PU nanofibers. SEM confirmed the well oriented nanofibers and good dispersion of pure silver NPs. TEM indicated that the Ag NPs were 5 to 20 nm in diameter. XRD demonstrated the good crystalline features of silver metal. The mechanical properties of the nanofiber mats showed improvement with increasing silver NPs content. The fixedness of the silver NPs obtained on PU nanofibers was examined by harsh successive washing of the as-prepared mats using a large amount of water. The results confirmed the good stability of the synthesized nanofiber mats. Two model organisms, E. coli and S. typhimurium, were used to check the antimicrobial influence of these nanofiber mats. Subsequently, antimicrobial tests indicated that the prepared nanofibers have a high bactericidal effect. Accordingly, these results highlight the potential use of these nanofiber mats as antimicrobial agents.
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Barakat, Nasser A. M.,Farrag, Taha E.,Kanjwal, Muzafar A.,Park, Soo-Jin,Sheikh, Faheem A.,Yong Kim, Hak WILEY-VCH Verlag 2010 European journal of inorganic chemistry Vol.2010 No.10
<P>In this study, we have introduced electrospinning of a colloidal solution rather than the conventional sol–gel process as a novel strategy to produce silver nanofibres. Typically, a silver acetate/polyvinyl alcohol colloidal solution was successfully electrospun. Electrophoretic light scattering (ELS) and dynamic light scattering (DLS) analyses have affirmed that the electrospun solution is a colloid with a ζ-potential of –2 mV and average particle diameter of 373 ± 1 nm. Moreover, FTIR analysis affirmed that neither the polymer nor silver acetate nanoparticles were affected during the electrospinning process. Calcination of the electrospun mats at 700 °C in an argon atmosphere produced smooth and unbroken pure silver nanofibres. Surface plasmon resonance of the resultant silver nanofibres was detected at 962 nm which is biologically beneficial. Furthermore, the synthesised silver nanofibres revealed thermal hysteresis in the electrical conductivity properties. These advantageous physical features strongly suggest utilising the prepared nanofibres in various fields.</P> <B>Graphic Abstract</B> <P>Electrospinning of a colloidal silver acetate solution rather than the conventional sol–gel process was introduced as a novel strategy to produce silver nanofibres. Electrophoretic light scattering and dynamic light scattering analyses have affirmed that theelectrospun solution is a colloid. Calcination of the electrospun mats produced smooth and unbroken pure silver nanofibres. The advantageous physical features of the fibres suggest utilising the prepared nanofibres in various fields. <img src='wiley_img_2010/14341948-2010-2010-10-EJIC200900453-fig000.gif' alt='wiley_img_2010/14341948-2010-2010-10-EJIC200900453-fig000'> </P>
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Sheikh, Faheem A,Ju, Hyung Woo,Moon, Bo Mi,Park, Hyun Jung,Kim, Jung Ho,Lee, Ok Joo,Park, Chan Hum Springer 2013 Nanoscale research letters Vol.8 No.1
<P>Electrospinning technique is commonly used to produce micro- and/or nanofibers, which utilizes electrical forces to produce polymeric fibers with diameters ranging from several micrometers down to few nanometers. Desirably, electrospun materials provide highly porous structure and appropriate pore size for initial cell attachment and proliferation and thereby enable the exchange of nutrients. Composite nanofibers consisting of silk and hydroxyapatite nanoparticles (HAp) (NPs) had been considered as an excellent choice due to their efficient biocompatibility and bone-mimicking properties. To prepare these nanofiber composites, it requires the use of acidic solutions which have serious consequences on the nature of both silk and HAp NPs. It is ideal to create these nanofibers using aqueous solutions in which the physicochemical nature of both materials can be retained. However, to create those nanofibers is often difficult to obtain because of the fact that aqueous solutions of silk and HAp NPs can precipitate before they can be ejected into fibers during the electrospinning process. In this work, we had successfully used a three-way stopcock connector to mix the two different solutions, and very shortly, this solution is ejected out to form nanofibers due to electric fields. Different blend ratios consisting HAp NPs had been electrospun into nanofibers. The physicochemical aspects of fabricated nanofiber had been characterized by different state of techniques like that of FE-SEM, EDS, TEM, TEM-EDS, TGA, FT-IR, and XRD. These characterization techniques revealed that HAp NPs can be easily introduced in silk nanofibers using a stopcock connector, and this method favorably preserves the intact nature of silk fibroin and HAp NPs. Moreover, nanofibers obtained by this strategy were tested for cell toxicity and cell attachment studies using NIH 3 T3 fibroblasts which indicated non-toxic behavior and good attachment of cells upon incubation in the presence of nanofibers.</P>
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Sheikh, Faheem A.,Zargar, Mohammad Afzal,Tamboli, Ashif H.,Kim, Hern Elsevier 2016 APPLIED SURFACE SCIENCE - Vol.385 No.-
<P><B>Abstract</B></P> <P>Nanofibers fabricated from Poly(vinylidene fluoride) (PVDF) possesses potential applications in the field of filtrations, because of their excellent resistance towards harsh chemicals. However, the hydrophobicity restricts its further application. In this work, we focus on optimal parameters for post-electrospun tethering of Poly(vinyl alcohol) (PVA) as superhydrophilic domain onto each individual PVDF nanofibers by exploiting the in situ hydrothermal approach. The results indicated an increase in nanofiber diameters due to coating of PVA and improved surface wettability of PVDF nanofibers. The tensile tests of nanofibers indicated that mechanical properties of PVDF nanofibers could be sharply tuned from rigid to ductile. Furthermore, the studies strongly suggest that in situ hydrothermal treatment of post-electrospun nanofibers can improve the water contact angle and these nanofibers can be used in varied applications (e.g., in water purification systems).</P> <P><B>Highlights</B></P> <P> <UL> <LI> PVA coated PVDF nanofibers can be easily prepared by hydrothermal treatment. </LI> <LI> The inherent hydrophobicity of PVDF nanofibers can be changed to hydrophilic. </LI> <LI> The hydrogen bonding interaction can induce the crystalline conformation of PVDF. </LI> <LI> Resultant nanofibers have significant improvement in the tensile strength. </LI> <LI> Prepared membranes promise to aid in filtration due to involvement of PVA coating. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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