77 research outputs found
Adsorption of Silver Ions from Aqueous Solution onto Thiol Modified Polyvinyl Alcohol Nanofibers
No full textAggregation and Stabilization of Carboxylic Acid Functionalized Halloysite Nanotubes (HNT-COOH)
No full textWe modified the functional groups of holloysite nanotubes (HNT) from hydr 000016A0 oxyl groups (HNT-OH) to carboxylic acids (HNT-COOH). Aggregation and dispersion properties of HNT-COOH under dry conditions were probed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Moreover, the degree of aggregation and dispersion of HNT-COOH in acidic, basic, and neutral solutions were measured by multiple angle polarized dynamic light scattering (MA-DLS). HNT-COOH formed aggregates in neutral solution; however, the material was dispersed in basic and acidic solutions. This occurrence is due to hydrogen bonds (HB) between the carboxyl groups of HNT-COOH in neutral solution, which decrease in acidic and basic solution due to charge dispersion.This work has been supported by the research fund from Korea Research Fund (KRF) for the basic research program
Formation and characterization of poly(acrylic acid) on silica particles irradiated by gamma-ray radiation
No full textOrganic/inorganic hybrid gels were directly prepared by polymerization on the peroxide surface of silica particles where the particle surface was irradiated by a (60)Co gamma-ray. These hydrogels have no residues of initiators or cross-linkers, so they can be used in biocompatible gel applications. Wide Raman spectroscopy was used to verify the interaction between the particles and poly(acrylic acid) (PAA). We observed that covalent bonds existing between the peroxide particles and acrylic acid, and the hydrogen bonds between the acrylic acids. For these studies, we prepared hydrogels by varying the particles' concentration and the size of the silica particles to classify the number of reaction sites, which are the dominant factor for the chemical reaction between the silica particles and PAA.This work has been supported by the Basic Research Program of NRF in Korea. DS thanks to Dr. Y. M. Im for the use of the gamma-ray source at KAERI, Jeongup, Korea, and to Hanyang University (HY-2011-HYURS)
Comparison of fabrication methods for the effective loading of Ag onto PVA nanofibers
No full textWe investigated and compared three different methods for synthesizing Ag/PVA nanofibers by effectively dispersing and loading Ag particles onto PVA nanofibers and preventing the detachment of Ag from the nanofibers. The three methods were: (a) the solution reduction method (Method 1) in which the reduction of Ag+ was conducted before electrospinning, resulting in mixing the polymer and the Ag nanoparticles in the electrospinning solution; (b) the immersion method (Method 2) in which electrospun PVA nanofibers were immersed in the Ag+ solution, resulting in loading the Ag particles onto the PVA nanofibers; and (c) the nanofiber reduction method (Method 3) in which the Ag+/PVA solution underwent electrospinning followed by the reduction process with Ag+/PVA nanofibers. All of the electrospun nanofibers had a crosslinked structure that resulted from the chemical reaction of glutaraldehyde with the hydroxyl group of PVA, to prevent dissolution in the aqueous solution. Fourier transform infrared spectra provided evidence of the successful formation of the crosslinked structure of the nanofibers, and x-ray photoelectron spectroscopy and transmission electron microscopy confirmed the loading of Ag nanoparticles onto the nanofibers. The release profiles were investigated by inductively coupled plasma, and the morphology of the nanofibers was observed by scanning electron microscopy. Method 3 had the best performances for loading Ag particles onto the nanofibers and for minimizing the loss of Ag nanoparticles from the nanofibers. These findings identified an effective method for fabricating metal/polymer composite nanofibers, and will allow the expansion of the applications of metal/polymeric composite nanofibers
Recent Advances on Nanofiber Fabrications: Unconventional State-of-the-Art Spinning Techniques
No full textIn this review, we describe recent relevant advances in the fabrication of polymeric nanofibers to address challenges in conventional approaches such as electrospinning, namely low throughput and productivity with low size uniformity, assembly with a regulated structure and even architecture, and location with desired alignments and orientations. The efforts discussed have mainly been devoted to realize novel apparatus designed to resolve individual issues that have arisen, i.e., eliminating ejection tips of spinnerets in a simple electrospinning system by effective control of an applied electric field and by using mechanical force, introducing a uniquely designed spinning apparatus including a solution ejection system and a collection system, and employing particular processes using a ferroelectric material and reactive precursors for atomic layer deposition. The impact of these advances to ultimately attain a fabrication technique to solve all the issues simultaneously is highlighted with regard to manufacturing high-quality nanofibers with high- throughput and eventually, practically implementing the nanofibers in cutting-edge applications on an industrial scale
Lamellar Thickness of Poly(ethylene oxide) Film Crystallized from the Gel State
No full textThe
lamellar thickness of poly(ethylene oxide) (PEO) film established
from a gel state was investigated in an effort to understand the crystalline
structure which forms from the cross-linked network. Crystalline films
were prepared with PEO solutions irradiated by γ-rays. The structural
aspect of the films was revealed in terms of the exposed radiation
energy and the polymer concentration by using differential scanning
calorimetry, X-ray diffraction, and small-angle X-ray scattering.
The long-period distance, lamellar thickness, and amorphous thickness
in the crystalline films were analyzed based on the small-angle X-ray
scattering patterns. The wide distribution and nonuniformity of the lamellar stacks were observed in the
elongated and the swollen films. The lamellar thickness was compared
to the chain lengths between the cross-links, and the possible presence
of cross-links in the lamellar stacks was discussed. The results revealed
the lamellar thickness influenced by the cross-links and demonstrated
the structural changes associated with both the crystalline phase
and cross-linking
The Chemical Deposition Method for the Decoration of Palladium Particles on Carbon Nanofibers with Rapid Conductivity Changes
Get PDFPalladium (Pd) metal is well-known for hydrogen sensing material due to its high sensitivity and selectivity toward hydrogen, and is able to detect hydrogen at near room temperature. In this work, palladium-doped carbon nanofibers (Pd/CNFs) were successfully produced in a facile manner via electrospinning. Well-organized and uniformly distributed Pd was observed in microscopic images of the resultant nanofibers. Hydrogen causes an increment in the volume of Pd due to the ability of hydrogen atoms to occupy the octahedral interstitial positions within its face centered cubic lattice structure, resulting in the resistance transition of Pd/CNFs. The resistance variation was around 400%, and it responded rapidly within 1 min, even in 5% hydrogen atmosphere conditions at room temperature. This fibrous hybrid material platform will open a new and practical route and stimulate further researches on the development of hydrogen sensing materials with rapid response, even to low concentrations of hydrogen in an atmosphere.H.L. gratefully acknowledges the support from the Division of Frontier Fibers, the Institute for Fiber Engineering (IFES), and the Interdisciplinary Cluster for Cutting Edge Research (ICCER) at Shinshu University. D.S. thanks to the Natinal Research Foundation of Korea (NRF: 2015R1D1A1A01059591) grant funded by the Korean government (MEST). S.-G.O. acknowledges the support from the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2016R1A6A1A03013422)
The effects of dopant on morphology formation in polyaniline graphite nanoplatelet composite
No full textColoration and Chromatic Sensing Behavior of Electrospun Cellulose Fibers with Curcumin
No full textThe effective approach for coloration and chromatic sensing of electrospun cellulose fabrics with a natural colorant, curcumin, is demonstrated. To achieve high surface area, the morphology of fiber was controlled to have rough and porous surface through an electrospinning of a cellulose acetate (CA) solution under optimized electrospinning parameters and solvent system. The resulting CA fibers were treated with a curcumin dye/NaOH ethanol solution, in which deacetylation of the CA fiber and high-quality coloration with curcumin were simultaneously achieved. As a control, a cotton fiber with similar diameter and smooth surface morphology was treated by the same method, resulting in poor coloration quality. The difference can be attributed to high surface area as well as trapping of dye molecules inside of cellulose fiber during deacetylation. Both fibers were further utilized for a chromatic sensing application for specific toxic gases. The incorporated curcumin dye responded to hydrogen chloride and ammonia gases reversibly via keto-enol tautomerism, and, as a consequence, the color was reversibly changed between reddish-brown and yellow colors. The cellulose fiber fabricated by the electrospinning showed ten times higher and two times quicker responsiveness compared to curcumin-colored cotton fiber sample prepared with the same immersion method
- …
