With sodium dodecylbenzene sulfonate (SDBS) solutions in N.N-Dimethylformamide (DMF) as sheath fluids to surround the core polymer solutions, a series of polyacrylonitrile (PAN) nanofibers with fine diameters, narrow diameter distributions, smooth surfaces and uniform structures have been successfully generated. The fiber diameters (D, nm) could be manipulated through adjusting the SDBS concentration in the sheath fluid (C, mg ml(-1)) with a scaling law of D = 790 C-0.41 (R-2 = 0.9903) within a range of 5-50 mg ml(-1). The mechanism of sheath SDBS solutions on the evaporation of DMF and the solidification of core polymer jets is discussed. The replacement of SDBS solutions for traditional atmosphere in single fluid electrospinning can lend itself to smoothen the electrospinning process through adjusting the core solvent evaporation rate. It is concluded that coaxial electrospinning with an ion surfactant solution comprises a facile process for producing high quality polymer nanofibers. (C) 2011 Elsevier B.V. All rights reserved.