Graphene oxide (GO) and carbon nanotubes (CNT) were dispersed in chitosan (CS) or sulfonated chitosan (sCS) aqueous solution followed by casting films on glassy carbon electrodes (GCE) for investigations on the electrocatalytic activities of the films by cyclic voltammetry (CV) for developments of electrochemical sensors for dopamine (DA), uric acid (UA), and ascorbic acid (AA). The impacts of the water soluble GO and sCS on the electrocatalytic activity of the modified electrodes and the detection capacities for the three analytes were especially investigated. CV curves revealed that GO/CNT/CS/GCE exhibited much higher electrocatalytic activity and selective detection capacity for DA, UA, and AA than CNT/CS/GCE, GO/CS/GCE, CS/GCE, and bare GCE. The GO-assisted dispersion of the conductive CNT in the GO/CNT/CS film was attributed for the observed high electrocatalytic activity. By replacing CS with sCS, the GO/CNT/sCS/GCE exhibited much more enhanced electrocatalytic activities than the GO/CNT/CS/GCE toward the oxidations of the three analytes. The expandable sCS in aqueous solutions of analytes leading to enhanced porosity in the GO/CNT/sCS film was attributed for its much more enhanced electrocatalytic activities. For selective detections of DA, UA, and AA, the GO/CNT/sCS/GCE had wider linear concentration ranges, higher sensitivities, and shorter response times for detections of DA and UA than the GO/CNT/CS/ GCE. For detection of AA, the two modified GCEs were insignificantly different. (C) 2014 Elsevier B.V. All rights reserved.