Functionalized nanofibers

FIGURE 8.7 Transmission emission microscope (TEM) image of a single polyethylene oxide nanofiber embedded with nano MgO at regular intervals. (Hussain, M.M. and Ramkumar, S.S., 2006, Functionalized nanofibers for advanced applications, Indian J. Fiber Text. Res.. 31, 41-51.)... 

The electrospun PAN nanoflber membranes were plasma-treated prior to the LbL deposition of an aqueous solution of PHA and PVG (Chen et al. 2010). Multilayer polyelectrolyte coatings on the PAN fibers were produced by alternately dipping the nanofiber membrane in 10 mM PVG and PHA aqueous solutions. The dipping time in each polyelectrolyte solution was 60 min, followed by rinsing in deionized water for 3 min. The PVG/PHA-functionalized nanofiber membrane demonstrated potent bactericidal capability over representative strains of E. coli and S. epidermidis, when used as biological protective fabrics. 

Sundarrajan, S. and Ramakrishna, S. 2010. Fabrication of functionalized nanofiber membranes containing nanoparticles. 

At the present time, synthesis and fabrication of functional nanofibers represent one of the most interesting fields of nanoiesearch. Combining the advanced structural features of metal-organic fiamewoiks with the fabrication technique may generate new functionalized nanofibers for more multiple purposes. 

Chen et al. (2009) functionahzed polyacrylonitrile (PAN) nanofibers so as to enable their use in the development of self-detoxifying chemical protection fabrics. The authors reacted PAN nanofibers with excess of hydroxylamine in methanol at 70 °C. The oximation of the nanofiber mats resnlted in the formation of polyaciylamidoxime on the snrface of the fibers. The authors proved that the functionalized nanofibers snccessfully hydrolyzed diisopropyl fluorophosphate (DFP) in the presence of water. The rate constant of the pseudo-first order reactions was found to increase with the presence of water in the nanofiber mats. According to the authors, the water in the mats facihtates the nucleophilic attack of amidoximes to accelerate the decomposition of DFP." ... 

The literature reports some examples of functional nanofiber mats prepared by simultaneously electrospinning a polymer solution and electrospraying a particle suspension on the same metallic collector. In electrospraying, when the electric force is higher than the surface tension of the liquid, the jets are atomized into fine droplets that are collected as solid particles. In electrospinning, the electric repulsion force cannot overcome the intermolecular forces in the liquid and, hence, the jet extends, bends and eventually reaches the collector, forming a solid fiber. The resulting nonwoven mat is composed of nanoparticles located on the fiber surface and within the pores of the nonwoven structure (Fig. 20). 

Inasmuch as we focus on the composite applications of nanofibers, only the most important fields are introduced here, and even those only briefly. The first one is filtration, which is currently the primary utilization of electrospun nanofibers. Nanofibrous mats axe available in the market and can be applied in industrial filters, and in air and water cleaning systems. It is also an example for functionalized nanofibers because these nanomaterials contain activated carbon particles and therefore can fQter out different chemicals in addition to submicron particles [44]. 

The incorporation of nanofibers with smaller nanoparticles can be classified into two different categories, which also means two different approaches. The first one is to embed nanoparticles into nanofibers. In this case, the aim is to reinforce or functionalize nanofibers. The other one is the group of exocomposites or decorated nanofibers where nanopart-... 

Chase George G, Raghavan B. Key principles of nanofibers for filtration. In Fei Q, editor. Functional nanofibers and their applications. Woodhead publishing 2012. p. 121—49. 

Yoon K, Hsiao BS, Chu B. Functional nanofibers for enviromnental applications. J Mater Chem 2008 18 5326-34. 

CeO nanoparticles were attached to the surface of the nanofiber substrate due to the strong interfacial and electrostatic interactions between the carboxylic or hydroxyl groups of the cellulose nanofiber and the CeO nanoparticles, which is effectively prevented nanoparticle fall-off. Compared to the natural cotton cellulose nanofibers, the modified natural cotton cellulose nanofibers by hydrothermal incorporation of CeOj nanoparticles showed excellent protection against UV radiation because of the function of the CeO particles. This functional nanofiber will have potential applications in various areas, such as the medical, military, biological, and optoelectronic industrial fields including UV protection for data storage or memory devices, in the future. 

---