Gadolinium Chloride (GdCl3) has been employed as dopant to synthesize conductive polyaniline (PANT) using chemical method. The resulting products were characterized using infrared spectroscopy, UV-vis spectra, scanning electron microscope, differential thermal analyzer, and X-ray diffraction. It was found that Gd3+ can interact with PANT chains and induce changes on the properties of PANI. The addition of GdCl3 could greatly increase electrical conductivity and crystalline degree of PANT. Changes in UV-vis and FTIR spectra show that there exists interaction between gadolinium ions and PANT chain. The effect of different proportions of ammonium persulfate on the properties of PANT was also discussed. When the molar ratios of GdCl3 to aniline is 2: 1 and ammonium persulfate to aniline is 1 : 1, the more uniform and regular PANT nanofiber can be prepared. (c) 2006 Wiley Periodicals, Inc.