Charging and discharging of nanometer-sized and tunable-shaped objects are very important to fundamental research as well as to potential applications. For instance, isolated external charges can be used as an electrostatic gating for material transport in the nano-channels. On the other hand charging and discharging of objects provide a powerful tool to studying the electrostatic properties on the nanometer scale. Here, we report on the charging of individual graphene oxide (GO) sheets (Fig. 1) with varied degrees of reduction by using electrically biased atomic force microscope (AFM) tips. AFM measurements indicate that the apparent height of reduced GO (rGO) sheets increases sharply after charging, while the charging ability is enhanced when the GO sheets are deeply reduced. Charging on isolated areas with tunable shape and size on single-layered GO has been achieved. In addition, charge transfer between rGO sheets separated in hundreds of nanometers on insulating substrates was investigated. It was found that the rGO sheet collects charges from the adjacent charged rGO sheet through the dielectric surfaces. The efficiency of charge transfer between the separated rGO sheets is dependent on their separation distance, gap length, and the substrate type. The findings suggest that the charge interflow should not be neglected in a graphene circuit.

Charging and discharging of nanometer-sized and tunable-shaped objects are very important to fundamental research as well as to potential applications. For instance, isolated external charges can be used as an electrostatic gating for material transport in the nano-channels. On the other hand charging and discharging of objects provide a powerful tool to studying the electrostatic properties on the nanometer scale. Here, we report on the charging of individual graphene oxide (GO) sheets (Fig. 1) with varied degrees of reduction by using electrically biased atomic force microscope (AFM) tips. AFM measurements indicate that the apparent height of reduced GO (rGO) sheets increases sharply after charging, while the charging ability is enhanced when the GO sheets are deeply reduced. Charging on isolated areas with tunable shape and size on single-layered GO has been achieved. In addition, charge transfer between rGO sheets separated in hundreds of nanometers on insulating substrates was investigated. It was found that the rGO sheet collects charges from the adjacent charged rGO sheet through the dielectric surfaces. The efficiency of charge transfer between the separated rGO sheets is dependent on their separation distance, gap length, and the substrate type. The findings suggest that the charge interflow should not be neglected in a graphene circuit.