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We report on the in-situ chemical growth of unique core-shell quantum dots (QDs) with single layer graphene on the surface of CuO QDs and their structural, optical and electrical properties. The CuO/graphene QDs were synthesized through a simple and hydrothermal technique. In order to enhance performance electrochemical energy storages, we have developed core (active material)/shell (conductive material) type CuO/graphene QDs as electrode materials using the combined electrolytes (KOH + LiCl). As a result, the performance of electrochemical energy storages exhibits specific capacitance of 154 F g−1 at current density of 1 A g−1 and cycling stability with 84% capacitance retention after 3,000 cycles.

Optoelectronic devices with dual-function consisting of LEDs and OBDs, both containing ZnO QDs dispersed in a hybrid poly N-vinylcarbazole (PVK) and polymethylmethacrylate (PMMA) polymer layer, were fabricated on indium-tin-oxide (ITO)-coated glass substrates using a simple spin-coating technique. Transmission electron microscopy images showed that the ZnO QDs were distributed around the PVK and the PMMA. The laminated devices showed the electroluminescence of LEDs and the electrical bistabilities of OBDs. To make the OBDs into the LEDs, a PEDOT:PSS hole injection layer and a PVK hole transport layer were inserted between the active layers and the electrodes, respectively. Luminescence mechanisms of the LEDs and operating mechanisms of the OBDs are described on the basis of the experimental results.

The tungsten oxide nonvolatile memory devices were fabricated using the photothermal in-situ oxidation method. The photothermal in-situ oxidation method can monitor the oxidation process in real time. Raman spectra revealed that tungsten oxides were formed by thermal oxidation. The ON/OFF ratio of the current bistability for the device was as large as ~ 102 at a 2 V reading voltage, and the cycling endurance of the ON/OFF switching for the devices was stable without noticeable degradation. Memory mechanisms for device are described using fitted the I–V curves.