Synthesis, characterization and mechanical properties of nylon–silver composite nanofibers prepared by electrospinning L. Francis a , F. Giunco a , A. Balakrishnan b , E. Marsano a, * a University of Genova, Department of Chemistry and Industrial Chemistry, via Dodecaneso 31, 16146 Genova, Italy b Laboratoire SIMaP – GPM2, Grenoble-INP/UJF/CNRS BP46, 38042 Saint Martin d’Hères cedex, France article info Article history: Received 6 October 2009 Accepted 8 December 2009 Available online 6 January 2010 Keywords: Fibers Polymer–matrix composites Strength Nano-structures abstract Silver (Ag) nanoparticles (3 nm) were synthesized using silver nitrate as the starting precursor, ethylene glycol as solvent and poly (N-vinylpyrrolidone) (PVP) introduced as a capping agent. These nano-Ag par- ticles were reinforced in nylon matrix by electrospinning of nylon-6/Ag solution in 2,2,2-trifluoroethanol and composite nanofibrous membranes were synthesized. The effects of solution concentration and rel- ative humidity (RH) on the resultant fibrous membranes were studied. Scanning electron microscopy and Transmission electron microscopy was used to study the size and morphology of the fibers. It was observed that concentration and RH could be used to modulate the fiber diameter. Tensile test was used to evaluate the mechanical property of these electrospun composite membranes. The composite mem- branes showed higher strength (approx. 2–3 times increase in strength) compare to as synthesized nylon fibers. Ó 2009 Elsevier B.V. All rights reserved. 1. Introduction Electrospinning is a simple, versatile and economical approach for fabricating long, continuous fibers from a variety of materials, such as polymers [1–3], inorganic [4–6], and hybrid (organic–inor- ganic) compounds [7,8]. In recent years the utilization of electro- spun polymer nanofibers with embedded silver nanoparticles has attracted much attention mainly due to its antimicrobial activities [9]. Most of these silver-releasing polymers studied for example, poly(L-lactide) [10], activated carbon [11], polypropylene [12], ny- lon 6,6 [13], cellulose acetate [14] and poly(ethylene terephthal- ate)/chitosan [15] have been electrospun successfully, and their antibacterial activity has been observed. However not much has been reported on the mechanical strength of these fibers embed- ded with silver particles. Strength of these fibers is an important characteristic to study since there has been increasing interest in the subject of textile materials with good mechanical strength and antibacterial properties [16] especially for filtration purposes. Studies have shown filtering particles of size between 0.1 and 0.5 lm can be achieved by using the nanofibrous filtering media [17]. Electrospinning makes it possible to produce such nanofi- brous membranes having submicronic interconnected pore like structure [18,19]. If the strength of these mats can be increased, the performance of such filters can be significantly enhanced. Hence in the present work, synthesized silver nanoparticles were incorporated into nylon-6 nanofibers by electrospinning to make composite fiber membranes. The mechanical strength of these composite membranes were studied and compared with pure ny- lon-6 fiber membranes also produced by electrospinning. It was seen that nano-Ag incorporation into nylon matrix resulted in 2–3 times increase in the strength. Besides the strength, we also investigate the effect of humidity and solution concentration on the size and morphology of nylon fibers with and without the incorporation of nano-Ag particles. 2. Methods and materials Silver nitrate (AgNO 3 ) (Sigma Aldrich) was used as the starting precursor for the colloidal silver preparation. Ethylene glycol (Sig- ma Aldrich) was used as a solvent and reducing agent for AgNO 3 . Poly (N-vinylpyrrolidone) (PVP, Sigma Aldrich, M w = 10,000) was used as a capping agent. Firstly, the PVP polymer was completely dissolved in ethylene–glycol at room temperature. To this solution, 250 mg of AgNO 3 was added and stirred at 60 °C for 6 h in an oil bath. This uniformly dispersed solution was aged for 24 h at room temperature. To this resultant yellow colored solution, acetone (1:5 by volume) was added and centrifuged. This highly viscous centrifugate solution was dissolved in ethanol. The presence of Ag ions in the solution was characterized by UV-spectroscopy (Avatar 380, Thermo Nicolet, Waltham, USA). This solution was dried at 60 °C in air for 24 h in dry oven to get PVP capped Ag nano- particles (PVP/Ag). Phase analysis of synthesized PVP/Ag was done 1567-1739/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.cap.2009.12.025 * Corresponding author. Tel.: +39 010 3538727. E-mail address: marsano@chimica.unige.it (E. Marsano). Current Applied Physics 10 (2010) 1005–1008 Contents lists available at ScienceDirect Current Applied Physics journal homepage: www.elsevier.com/locate/cap