2016, Nithiyanantham, Udayashankar, Ramadoss, Ananthakumar, Kundu, Subrata

Self-assembled, aggregated, chain-like SnO₂ nano-assemblies were synthesized at room temperature by a simple wet chemical route within an hour in the presence of DNA as a scaffold. The average size of the SnO₂ particles and the chain diameter were controlled by tuning the DNA to Sn(II) molar ratio and altering the other reaction parameters. A formation and growth mechanism of the SnO₂ NPs on DNA is discussed. The SnO₂ chain-like assemblies were utilized as potential anode materials in an electrochemical supercapacitor. From the supercapacitor study, it was found that the SnO₂ nanomaterials showed different specific capacitance (C_s) values depending on varying chain-like morphologies and the order of C_s values was: chain-like (small size) > chain-like (large size). The highest Cs of 209 F g⁻¹ at a scan rate of 5 mV s⁻¹ was observed for SnO₂ nano-assemblies having chain-like structure with a smaller size. The long term cycling stability study of a chain-like SnO₂ electrode was found to be stable and retained ca. 71% of the initial specific capacitance, even after 5000 cycles. A supercapacitor study revealed that both morphologies can be used as a potential anode material and the best efficiency was observed for small sized chain-like morphology which is due to their higher BET surface area and specific structural orientation. The proposed route, by virtue of its simplicity and being environmentally benign, might become a future promising candidate for further processing, assembly, and practical application of other oxide based nanostructure materials.

2016, Ramadoss, Ananthakumar, Kang, Kyeong-Nam, Ahn, Hyo-Jin, Kim, Sun-I, Ryu, Seung-Tak, Jang, Ji-Hyun

The rapidly developing electronics industry is producing miniaturized electronic devices with flexible, portable and wearable characteristics, requiring high-performance miniature energy storage devices with flexible and light weight properties. Herein, we have successfully fabricated highly porous, binder free three-dimensional flower-like NiCo₂O₄/Ni nanostructures on Ni-wire as a fiber electrode for high-performance flexible fiber supercapacitors. Such a unique structure exhibited remarkable electrochemical performance with high capacitance (29.7 F cm⁻³ at 2.5 mA), excellent rate capability (97.5% retention at 20 mA), and super cycling stability (80% retention, even after 5000 cycles). The remarkable electrochemical performance is attributed to the large active area in the 3D porous architecture and direct contact between the active materials and 3D-Ni current collectors, which facilitate easy ionic/electronic transport. The symmetric fiber supercapacitor showed a gravimetric energy density of 2.18 W h kg⁻¹ (0.21 mW h cm⁻³) and a power density of 21.6 W kg⁻¹ (2.1 mW cm⁻³) with good flexibility and cycling performance, signifying potential applications in high-performance flexible energy storage devices. Further, performance in a self-powered system was demonstrated by charging these wire type NiCo₂O₄/Ni supercapacitors by serially wound DSSCs to drive commercial LEDs. These results suggest that the fabricated device has excellent potential as a power source for flexible, portable and wearable applications as well as self-powered systems.