Title: Importance of poly(ethylene glycol) conformation for the synthesis of silver nanoparticles in aqueous solution Authors
Submitted to: Journal of Nanoparticle Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 14, 2011
Publication Date: March 1, 2011
Citation: Nam, S., Parikh, D.V., Condon, B.D., Zhao, Q., Yoshioka-Tarver, M. 2011. Importance of poly(ethylene glycol) conformation for the synthesis of silver nanoparticles in aqueous solution. Journal of Nanoparticle Research. 13(9):3755-3764. Interpretive Summary: The therapeutic value of silver has been known since the 5th century. Ciro the Great ordered his troops to transport water in silver pots to protect drinking water to preserve its potability. Silver (i) is active against Gram positive and Gram negative bacteria, fungi and several viruses. At the Southern Regional Research Center (SRRC), we have undertaken green method of synthesis of silver nanoparticles (NPs) using entangled Polyethylene glycol (PEG 100) in aqueous solution with mild silver nitrate solution. Silver NPs can be directly loaded on cotton and other fiber textile substrate for their antimicrobial applications. The manuscript discusses effectiveness of entangled structure in producing fine silver NPS in range of 1-3 nm, or ten time bigger 10-30 nm depending on the reaction conditions employed. Nanotechnology is concerned with materials that are very small. One nanometer (nm) is one billionth of a meter (10-9 ). There are many opportunities for using nanoscale materials within nanotechnogy and we will be examining them in our subsequent manuscript.
Technical Abstract: In the formation of silver nanoparticles (NPs) using silver nitrate in a poly(ethylene glycol) (PEG) aqueous solution, which acts as both a reducing and stabilizing agent, the PEG chain structure was found to play a significant role. Even though PEG 100 (100 kg/mol) has limited reducing sites of hydroxyl terminal groups, UV/Vis spectroscopy and transmission electron microscopy (TEM) showed the remarkably greater capability of PEG 100 to produce silver NPs (1-3 nm) compared with that of PEG 2 (2 kg/mol). This efficient formation by PEG 100 was attributed to its chain entanglements. On the entangled PEG network, the diffusion of PEG chains and silver ions is controlled to facilitate their reduction reaction, and the local aggregation of reduced silver atoms is favored to form NPs. PEG 100 exhibited a coordinative complex with silver ions and steady silver NP formation at increased reaction temperatures and prolonged reaction times. Such interaction and stable reactions, however, were not achieved by PEG 2, whose short chains are widely separated and behave as single coils. The particle agglomeration observed at increased PEG 100 concentration also indicates that the density of an entangled structure influences the stabilization of silver NPs.