Preparation of sulfonic-functionalized graphene oxide as ion-exchange material and its application into electrochemiluminescence analysis

Graphene oxide (GO) obtained from chemical oxidation of flake graphite was derivatized with sulfonic groups to form sulfonic-functionalized GO (GO–SO3−) through four sulfonation routes: through amide formation between the carboxylic group of GO and amine of sulfanilic acid (AA–GO–SO3−), aryl diazonium reaction of sulfanilic acid (AD–GO–SO3−), amide formation between the carboxylic group of GO and amine of cysteamine and oxidation by H2O2 (CA–GO–SO3−), and alkyl diazonium reaction of cysteamine and oxidation by H2O2 (CD–GO–SO3−). Results of Fourier transform infrared spectroscopy and X-ray photoelectrospectrocopy showed that –SO3− groups were attached onto GO. Thermo gravimetric analysis showed that derivatization with sulfonic groups improved thermo stability of GO. X-ray diffraction results indicated that GO–SO3− had more ordered π–π stacking structure than the original GO. GO–SO3− and cationic polyelectrote, poly (diallyldimethylammoniumchloride) (PDDA) were adsorbed at indium tin oxide (ITO) glass surface through layer-by-layer assembling to form (GO–SO3−/PDDA)n/ITO multilayers. After tris-(2,2′-bipyridyl) ruthenium (II) dichloride (Ru(bpy)32+) was incorporated into the multilayers, the obtained Ru(bpy)32+/(GO–SO3−/PDDA)n/ITO electrodes can be used as electrochemiluminescence sensors for detection of organic amine with high sensitivity (limit of detection of 1 nM) and stability.