The　density　of　electronic　states　(DOS)　is　an　intrinsic　electronic　property　that　works　conclusively　in　the　electrochemistry　of　carbon　materials.　However,　seldom　has　it　been　reported　how　the　DOS　at　the　Fermi　level　influences　the　electrochemical　activity.　In　this　work,　we　synthesized　partially　and　fully　unzipped　carbon　nanotubes　by　longitudinally　unzipping　pristine　carbon　nanotubes　(CNTs).　We　then　studied　the　electrochemical　activity　and　biosensitivity　of　carbon　materials　by　means　of　the　CNTs　and　their　derivatives　to　elucidate　the　effect　of　the　DOS　on　their　electrochemical　performances.　Tailoring　of　the　DOS　for　the　CNT　derivatives　could　be　conveniently　realized　by　varying　the　sp2/sp3　ratio　(i.e.,　graphite　concentration)　through　manipulating　the　oxidative　unzipping　degree.　Despite　the　diverse　electron　transfer　mechanisms　and　influence　factors　of　the　four　investigated　redox　probes　(IrCl62-,　[Fe(CN)6]3-,　Fe3+,　and　ascorbic　acid),　the　CNT　derivatives　exhibited　consistent　kinetic　behaviors,　wherein　CNTs　with　a　high　DOS　showed　superior　electrochemical　response　compared　with　partially　and　fully　unzipped　carbon　nanotubes.　For　biological　detection,　the　CNTs　could　simultaneously　distinguish　ascorbic　acid,　dopamine,　and　uric　acid,　while　the　three　CNT　derivatives　could　all　differentiate　phenethylamine　and　epinephrine　existed　in　the　newborn　calf　serum.　Moreover,　the　three　CNT　derivatives　all　presented　wide　linear　detection　ranges　with　high　sensitivities　for　dopamine,　phenethylamine,　and　epinephrine.　©　2015　American　Chemical　Society.