Quan Shi

Carbon-Coated Si Nanoparticles Dispersed in Carbon Nanotube Networks As Anode Material for Lithium-Ion Batteries

Si has the highest theoretical capacity among all known anode materials, but it suffers from the dramatic volume change upon repeated lithiation and delithiation processes. To overcome the severe volume changes, Si nanoparticles were first coated with a polymer-driven carbon layer, and then dispersed in a CNT network. In this unique structure, the carbon layer can improve electric conductivity and buffer the severe volume change, whereas the tangled CNT network is expected to provide additional mechanical strength to maintain the integrity of electrodes, stabilize the electric conductive network for active Si, and eventually lead to better cycling performance. Electrochemical test result indicates the carbon-coated Si nanoparticles dispersed in CNT networks show capacity retention of 70% after 40 cycles, which is much better than the carbon-coated Si nanoparticles without CNTs.

One-step synthesis of silver nanoparticle-filled nylon 6 nanofibers and their antibacterial properties

A novel and facile one-step approach to in situ synthesize silver nanoparticle-filled nylon 6 nanofibers by electrospinning is reported. The method does not need post-treatments and can be carried out at ambient conditions without using additional chemicals. It employs the electrospinning solvent as a reducing agent for in situ conversion of AgNO3 into silver nanoparticles during the solution preparation. The resultant silver nanoparticle-filled nylon 6 hybrid nanofibers show an excellent fibrous structure (fiber diameter at 50–150 nm), with narrow size 2–4 nm silver nanoparticles uniformly dispersed throughout the nylon 6 matrix. DSC analysis shows that the in situ incorporation of silver nanoparticles increased the Tg and crystallinity of the resultant nanofibers. These silver nanoparticle-filled nylon 6 nanofibers exhibit a steady and long-lasting silver ion release behavior, and robust antibacterial activity against both Gram-positive B. cereus and Gram-negative E. coli microorganisms.

Multifunctional ZnO/Nylon 6 nanofiber mats by an electrospinning-electrospraying hybrid process for use in protective applications.

Abstract ZnO/Nylon 6 nanofiber mats were prepared by an electrospinning–electrospraying hybrid process in which ZnO nanoparticles were dispersed on the surface of Nylon 6 nanofibers without becoming completely embedded. The prepared ZnO/Nylon 6 nanofiber mats were evaluated for their abilities to kill bacteria or inhibit their growth and to catalytically detoxify chemicals. Results showed that these ZnO/Nylon 6 nanofiber mats had excellent antibacterial efficiency (99.99%) against both the Gram-negative Escherichia coli and Gram-positive Bacillus cereus bacteria. In addition, they exhibited good detoxifying efficiency (95%) against paraoxon, a simulant of highly toxic chemicals. ZnO/Nylon 6 nanofiber mats were also deposited onto nylon/cotton woven fabrics and the nanofiber mats did not significantly affect the moisture vapor transmission rates and air permeability values of the fabrics. Therefore, ZnO/Nylon 6 nanofiber mats prepared by the electrospinning–electrospraying hybrid process are promising material candidates for protective applications.

Plasma-Electrospinning Hybrid Process and Plasma Pretreatment to Improve Adhesive Properties of Nanofibers on Fabric Surface

Electrospun nanofiber mats are inherently weak, and hence they are often deposited on mechanically-strong substrates such as porous woven fabrics that can provide good structural support without altering the nanofiber characteristics. One major challenge of this approach is to ensure good adhesion of nanofiber mats onto the substrates and to achieve satisfactory durability of nanofiber mats against flexion and abrasion during practical use. In this work, Nylon 6 nanofibers were deposited on plasma-pretreated woven fabric substrates through a new plasma-electrospinning hybrid process with the objective of improving adhesion between nanofibers and fabric substrates. The as-prepared Nylon 6 nanofiber-deposited woven fabrics were evaluated for adhesion strength and durability of nanofiber mats by carrying out peel strength and flex resistance tests. The test results showed significant improvement in the adhesion of nanofiber mats on woven fabric substrates. The nanofiber-deposited woven fabrics also exhibited good resistance to damage under repetitive flexion. X-Ray photoelectron spectroscopy and water contact angle analyses were conducted to study the plasma effect on the nanofibers and substrate fabric, and the results suggested that both the plasma pretreatment and plasma-electrospinning hybrid process introduced radicals, increased oxygen contents, and led to the formation of active chemical sites on the nanofiber and substrate surfaces. These active sites helped in creating crosslinking bonds between substrate fabric and electrospun nanofibers, which in turn increased the adhesion properties. The work demonstrates that the plasma-electrospinning hybrid process of nanofiber mats is a promising method to prepare durable functional materials.

Atmospheric plasma application to improve adhesion of electrospun nanofibers onto protective fabric

Nylon 6 electrospun nanofibers were deposited on plasma-pretreated woven fabric substrates with the objective of improving adhesion between them. The prepared samples were evaluated for adhesion strength and durability of nanofiber mats by carrying out peel strength, flex resistance, and abrasion resistance tests. The test results showed significant improvement in the adhesion of nanofiber mats on woven fabric substrates due to atmospheric plasma pretreatment. The samples also exhibited good flex and abrasion resistance characteristics. X-ray photoelectron spectroscopy and water contact angle analyses indicate that plasma pretreatment introduces radicals, increases the oxygen content on the substrate surface, and leads to formation of active chemical sites that may be responsible for enhanced cross-linking between the substrate fabric and the electrospun nanofibers, which in turn increases the adhesion properties. The work demonstrates that the plasma treatment of the substrate fabric prior to deposition of electrospun nanofiber mats is a promising method to prepare durable functional materials.

Plasma-Assisted Preparation of High-Performance Chitosan Nanofibers/Gauze Composite Bandages

In this work, novel composite bandages were prepared by electrospinning chitosan nanofibers on 100% cotton substrate fabric. In the composite bandages, chitosan nanofiber web serves as a primary wound dressing whereas cotton substrate as a backing material. Cotton substrate was given plasma pretreatment and composite bandages were given plasma posttreatment to improve the durability of composite bandages and adhesion between nanofiber and cotton substrate layers. The adhesion of the nanofibers to the substrates was assessed by qualitative and quantitative techniques. Plasma pretreatment of the substrate with 100% helium and 99% helium/1% oxygen plasmas showed up to four times increase in force required to peel off the nanofiber layer. Even more increase in adhesion was obtained when composite bandages were given plasma pretreatment to substrate as well as posttreatment to composite bandages. Storage modulus, glass transition temperature, and crystallinity of untreated He and He/O2-plasma treated chitosan nanofiber web were studied to observe the effect of plasma treatment on the chitosan nanofibers using dynamic mechanical analysis, differential scanning calorimetry, and wide angle X-ray diffraction, respectively. To understand the mechanism of improved adhesion, surface elemental analysis of plasma treated chitosan nanofibers and cotton substrate was carried out using X-ray photoelectron spectroscopy. GRAPHICAL ABSTRACT

Surface-engineered Blood Adsorption Device for Hyperphosphatemia Treatment

Correspondence: Melanie S. Joy, PharmD, PhD, University of Colorado Skaggs School of Pharmacy and Pharmaceutical Sciences, Department of Pharmaceutical Sciences, Mail Stop C238, Room V20-4108, 12850 East Montview Blvd, Aurora, CO 80045. Email: Melanie.Joy@ucdenver.edu The research employed surface engineering methods to develop, optimize, and characterize a novel textile-based hemoadsorption device for hyperphosphatemia in hemodialysis-dependent end-stage kidney disease. Phosphate adsorbent fabrics (PAFs) were prepared by thermopressing alumina powders to polyester filtration fabrics and treatment with trimesic acid (TMA). For static experiments, phosphate adsorption capacity in buffer solution, plasma, and blood were evaluated by submersing the PAFs in 100 ml. For dynamic experiments, PAFs were equipped in a device prototype and incorporated in a pump-driven circuit. Phosphates were determined by a colorimetric assay and an Ortho Clinical Diagnostics Vitros 5600 Integrated analyzer. The maximum loading amount of TMA-alumina on PAFs was approximately 35 g/m2 under 260°C processing temperature. Phosphate adsorption capacity increased with initial concentration. Adsorption isotherms from buffer demonstrated a maximum phosphate adsorption capacity of approximately 893 mg/m2 at 37.5°C, pH 7.4, with similar results from plasma and whole blood. Measured phosphate concentrations during simulations demonstrated a 42% reduction, confirming the high capacity of the PAFs for removing phosphate from whole blood. Results from the current study indicated that an alumina-TMA treated PAF can dramatically reduce phosphate concentrations from biological samples. The technology could potentially be used as a tunable adsorbent for managing hyperphosphatemia in kidney disease.