The Co3O4 nanofibers were prepared by electrospinning and their gas sensing characteristics were investigated. The Co3O4 sensors prepared by heat treatment of as-spun precursor fibers at 500 and 600 degrees C showed well-developed one-dimensional morphologies and exhibited high responses to 100 ppm C2H5OH (R-g/R-a = 51.2 and 45.3; R-g, resistance in gas; R-a, resistance in air) at 301 degrees C with negligible cross-responses to 100 ppm CO, C3H8, and H-2 (R-g/R-a = 1.02-2.7). In contrast, the most of one-dimensional morphology of the Co3O4 specimen was lost and the response to 100 ppm C2H5OH became significantly lower when the heat treatment temperature was increased to 700 degrees C or when the nanofibers were ultrasonically disintegrated into primary particles. The significant decrease of the gas response was explained and discussed in relation to the gas sensing mechanism of a p-type semiconductor, the morphology of specimens, and the connecting configuration between nanoparticles and nanofibers. (C) 2011 Elsevier B.V. All rights reserved.