On the other hand, graphene has extremely high electron mobility, excellent rate capability, reversibility, and high chemical stability; it has improved electrochemical performance compared with other carbon family materials such as activated carbon, carbon nanotubes, etc. [3]. Moreover, graphene oxide (GO) is considered to be a better choice for the electrodes of supercapacitors than graphene [4]. However, both ZnO NWs and GO suffered from limitations in the real applications. For ZnO NWs, it exhibits low abundance and exhibit poor rate capability and reversibility during the charge/discharge process. For the GO, it is still

limited by the low capacitance. Therefore, it is highly desirable for integrating these two materials together because both the double-layer capacitance of GO and pseudocapacitance AZD1152 chemical structure of ZnO NWs can contribute to the total capacitive performances. Though a few reports have been found on the electrochemical properties of ZnO nanostructures/GO nanocomposites [5–8], however, research on the performance of vertically aligned ZnO NWs/GO heterostructures are very limited although much progress in the controllable synthesis of vertically aligned ZnO nanorods on GO or graphene has been

made [9–12]. In this letter, vertically aligned ZnO NWs were grown on GO films using low-temperature hydrothermal method. The optical properties and electrochemical properties of the ZnO NWs/GO heterostructures were studied. Our results showed that the oxygen-containing groups on the surface of GO films can check details act as the nucleation sites and facilitate the next vertical growth of ZnO NWs. Photoluminescence (PL) spectra demonstrated that the deep-level light emission of ZnO NWs grown on GO films were greatly suppressed. Electrochemical property measurement proved that the capacitance of the ZnO NWs/GO heterostructures were much larger than that of the single GO films or ZnO NWs, indicating that such a structure can indeed improve the performance of supercapacitors. Since ZnO NWs are widely studied as sensors, Selonsertib clinical trial nanogenerators,

etc. [13–15] and reduced GO is a good transparent electrode material, we believe that such ZnO NWs/GO heterostructures presented here will also have many other potential applications in all kinds of nanodevices. Methods Overall, the procedures to synthesize ZnO NWs/GO heterostructures are as follows (Figure 1): (a) pretreating a copper mesh using an ultrasonic cleaner, (b) coating GO film onto the copper mesh substrate, (c) hydrothermal growth of ZnO NWs, and (d) separating the copper mesh from the ZnO NWs/GO heterostructure. Figure 1 Schematic diagram of the fabrication process of ZnO NWs/GO heterostructures. GO film was synthesized via a modified Hummers method. The product was dispersed in deionized water by a Branson Digital Sonifier (S450D, 200W, 40%; Branson Ultrasonics Corporation, Danbury, CT, USA).