Sulphuric acid catalized oxidaitive stabilizaition of polyacrylonitrile nanofibers and their electrochemical sensory usage

Various concentration of sulfuric acid (1, 2, 5, 10, 15, 20 % (v/v) respect to water) treated as-spun PAN nanofibers are heat treated at 100, 130, 160 and 180 oC. The results revealed that addition of sulfuric acid could decrease the stabilization temperature at lower values. Beside the morphological investigations, chemical and thermal characterizations were conducted. Nanofibers were also coated on the cylindrical graphite electrode then treated with aqueous sulfuric acid solutions and heat for electrochemical analysis. Single strand DNA (ssDNA) molecules were immobilized on the heat treated electrodes and electrochemical meausrements were applied by investigating guanine oxidation signal on immobilized ssDNA molecules. It was observed that guanine oxidation sensation was decreased and finally diminished with sulfuric acid treatment and a following heat treated samples. Because sulfuric acid did not evaporate significantly at the examined temperatures and the residual sulfuric acid on the electrode surfaces did not allow the attachment of the DNA molecules properly on the surface and hence guanine oxidation signal was not perceived appropriately by the electrodes. Additionally, sulfuric acid was added into PAN/DMF electrospining solutions with a appriate rates. As-spun nanofibers were obtained both directly and collecting on the cylindrical graphite surfaces then heat treated at 180 oC for 1 hour. Guaninine oxidaiton signal was also obserced by using these samples. Signal intensity first increased and decreased again by increasing sulfuric acit content. Heat treatment and electrochemical DNA biosesnors results revealed that the nanofibers produced by the addition of sulfuric acid to the electrospinning PAN/DMF solution is more effective compared to the PAN nanofibers obtained from PAN/DMF solution a following with sulfuric acid treatment.