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 gl ycol monododecyl ether), and aqueous silver ion solution by the reduction o f the silver ions using the surfactant itself as reductant. The effects of temperature, composition, and ageing are studied by W-vis absorption spectr oscopy and transmission electron microscopy (TEM). It has been shown that t he obtained ribbons either at 50 degrees C or at room temperature mainly co nsist of roughly close-packed silver nanoparticles about 2-3 nm and a few l arger silver nanoparticles distributed in or attached on the ribbons. The n anoparticles constituting the ribbons are revealed to have a crystal order corresponding to metallic silver. These ribbons, which are up to several hu ndred 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 increas ing water layer thickness, the sizes of the smaller particles that form the ribbons remain essentially unchanged whereas the proportion and/or sizes o f the larger particles are increased. The proportion of the larger particle s also increases with ageing. (C) 1999 Elsevier Science B.V. All rights res erved.