Synthesis of ribbons of silver nanoparticles in lamellar liquid crystals

Ribbons of silver nanoparticles have been synthesized in lamellar lyotropic liquid crystals formed from a nonionic surfactant, C12E4 (tetraethylene glycol monododecyl ether), and aqueous silver ion solution by the reduction of the silver ions using the surfactant itself as reductant. The effects of temperature, composition, and ageing are studied by W-vis absorption spectroscopy and transmission electron microscopy (TEM). It has been shown that the obtained ribbons either at 50 degrees C or at room temperature mainly consist of roughly close-packed silver nanoparticles about 2-3 nm and a few larger silver nanoparticles distributed in or attached on the ribbons. The nanoparticles constituting the ribbons are revealed to have a crystal order corresponding to metallic silver. These ribbons, which are up to several hundred nanometers wide and several micrometers long, can withstand repeated sonication in ethanol and can readily twist and fold into three-dimensional spatial configurations. On decreasing C12E4 concentration, i.e. on increasing water layer thickness, the sizes of the smaller particles that form the ribbons remain essentially unchanged whereas the proportion and/or sizes of the larger particles are increased. The proportion of the larger particles also increases with ageing. (C) 1999 Elsevier Science B.V. All rights reserved.