Polyaniline/nano-titanium dioxide composites (PANI/n-TiO2) were prepared using alpha-dextrose as surfactant and ammonium per sulfate as oxidant. The PANI/n-TiO2 composite is characterized by Fourier transform infrared spectra and confirmed the presence of benzenoid and qunoide ring structures and also formation of free ions. The transmission electron microscopy study reveals that the size of TiO2 is in the order of 7 nm where as the composite size is of the order of 13 nm; further, it is observed that the TiO2 particles are intercalated to form a core shell of PANI. The X-ray diffraction (XRD) studies show that the monoclinic structure of the composites. ac Conductivity, permittivity, and tangent loss studies on these samples suggest that these composites may be well suited for gas sensor. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 675-680, 2011