We develop graphene-based devices fabricated by alternating current dielectrophoresis (ac-DEP) for highly sensitive nitric oxide (NO) gas detection. The novel device comprises the sensitive channels of palladium-decorated reduced graphene oxide (Pd-RGO) and the electrodes covered with chemical vapor deposition (CVD)-grown graphene. The highly sensitive, recoverable, and reliable detection of NO gas ranging from 2 to 420 ppb with response time of several hundred seconds has been achieved at room temperature. The facile and scalable route for high performance suggests a promising application of graphene devices toward the human exhaled NO and environmental pollutant detections.

The chemical vapor deposition (CVD) fabrication of high-density three-dimension graphene macroscopic objects (3D-GMOs) with a relatively low porosity has not yet been realized, although they are desirable for applications in which high mechanical and electrical properties are required. Here, we explore a method to rapidly prepare the high-density 3D-GMOs using nickel chloride hexahydrate (NiCl2·6H2O) as a catalyst precursor by CVD process at atmospheric pressure. Further, the free-standing 3D-GMOs are employed as electrolytic electrodes to remove various heavy metal ions. The robust 3D structure, high conductivity (~12 S/cm) and large specific surface area (~560 m2/g) enable ultra-high electrical adsorption capacities (Cd2+ ~ 434 mg/g, Pb2+ ~ 882 mg/g, Ni2+ ~ 1,683 mg/g, Cu2+ ~ 3,820 mg/g) from aqueous solutions and fast desorption. The current work has significance in the studies of both the fabrication of high-density 3D-GMOs and the removal of heavy metal ions.