A composite thin film of simultaneously formed carbon and SnO 2 QDs for supercapacitor application

A uniform size and structure of a composite material are critical assets that determine the properties, such as charge transfer, thermal, photoluminescence, mechanical, etc. , and consequently the applications of the material; herein, we report the concept of flame/combustion at a liquid–liquid interface for the first time to synthesize in situ a thin film of a composite consisting of two or more quantum dots. The synthesis of the thin films of a composite containing C and SnO 2 QDs having particle sizes below 2 nm was successfully carried out. As compared to single quantum dot systems, the formed composite showed significantly improved specific capacitance due to the synergistic effect arising from the strong interaction between C and SnO 2 QDs. This was confirmed by XPS, and UV visible spectroscopy. Moreover, it was confirmed that even after 1000 charge/discharge cycles, the interaction between C and Sn remained unaltered; this indicated significant stability of the capacitance. Some of the advantages of this method include a one-step eco-friendly process and use of ambient conditions. The generality of the method was established by synthesizing C–ZnO and C–TiO 2 composite thin films. This new approach can be extended to form many other valuable composite thin films for various applications.