Electrochemical sensor based on metal-free materials composed of graphene and graphene oxide for sensitive detection of cadmium ions in water

In this work, a high-speed dispersive homogenizer as an exfoliating device, and graphite oxide was used to prepare graphene and graphene oxide metal-free composite materials (GR/GO composites) for electrochemical detection of cadmium ions (Cd2+) present in water. Glassy carbon electrode was modified with GR/GO composite by placing a suspension of the composite on the electrode and evaporating the solvent. The fabricated GR/GO composite had a sheet-like structure in which the presence of GO enhanced the hydrophilicity, whereas the presence of GR improved the conductivity. The higher hydrophilicity in a wide pH range of the composite electrode made it favorable to have better contacts with Cd2+ and the good conductivity; these enhanced the response of electrochemical signals. As a result, the assembled electrochemical Cd2+ sensor with GR/GO composite electrode exhibited superior analysis performances than those with GR and GO respectively, which exhibited wide linear range (0–10 μM), low value of detection limit (0.087 μM), reliable stability and selectivity. Moreover, the sensor based on GR/GO composites showed satisfactory detection accuracy for tap water samples, suggesting that the GR/GO composites are promising materials for electrochemical heavy metal ion sensors. [Display omitted] •This preparation technology realized the integration of exfoliation and in-situ compounding.•The fabricated GR/GO composites show sheet-like structure with around 2 layers.•The GR/GO composites have both good electron transport properties and excellent hydrophilicity.•The GR/GO electrode displayed good reproducibility and high stability during Cd2+ detection.•The GR/GO electrode successfully used for the detection of Cd2+ in tap water.