Tuning sulfur doping in graphene for highly sensitive dopamine biosensors

S-doped graphene has attracted extensive interest in recent years due to its high catalytic activity. However, most of the previously reported S-doped graphene materials present diverse types of S-bonding configurations, it is hard to distinguish which configuration is mainly responsible for the catalytic activity. Here, homogeneous thiophene S-doped graphene can be synthesized through solid-state reaction between graphene oxide and sulfate, and the doping amount can be easily tuned by the sulfate dosage. More importantly, abundant micropores and some mesopores are formed in the surface of graphene sheets during S-doping. Due to its high S-loading mass, thiophenic sulfur species and unique porous structure, S-doped graphene shows high electrocatalytic activity toward the redox reaction of dopamine, such as high selectivity, high sensitivity and low detection limit (3.94 μM μA−1, 1.5 × 10−8 M at S/N = 3).