Combustion of magnesium in dry ice and a simple subsequent acid treatment step resulted in a MgO-decorated few-layered graphene (FLG) composite that has a specific surface area of 393 m(2)/g and an average pore volume of 0.9 cm(3)/g. As an anode material in Li-ion batteries, the composite exhibited high reversible capacity and excellent cyclic performance in spite of high first-cycle irreversible capacity loss. A reversible capacity as high as 1052 mAh/g was measured during the first cycle. Even at the end of the 60th cycle, more than 83% of the capacity could be retained. Cyclic voltammetry results indicated pseudocapacitance behavior due to electrochemical absorption and desorption of lithium ions onto graphene. An increase in the capacity has been observed during long-term cycling owing to electrochemical exfoliation of graphene sheets. Owing to its good thermal stability and superior cyclic performance with high reversible capacities, MgO-decked FLG can be an excellent alternative to graphite as an anode material in Li-ion batteries, after suitable modifications.

Exfoliated graphene oxide (EG)/MoO2 composites are synthesized by a simple solid-state graphenothermal reduction method. Graphene oxide (GO) is used as a reducing agent to reduce MoO3 and as a source for EG. The formation of different submicron sized morphologies such as spheres, rods, flowers, etc., of monoclinic MoO2 on EG surfaces is confirmed by complementary characterization techniques. As-synthesized EG/MoO2 composite with a higher weight percentage of EG performed excellently as an anode material in lithium-ion batteries. The galvanostatic cycling studies aided with postcycling cyclic voltammetry and galvanostatic intermittent titrations followed by ex situ structural studies clearly indicate that Li intercalation into MoO2 is transformed into conversion upon aging at low current densities while intercalation mechanism is preferably taking place at higher current rates. The intercalation mechanism is found to be promising for steady-state capacity throughout the cycling because of excess graphene and higher current density even in the operating voltage window of 0.005-3.0 V in which MoO2 undergoes conversion below 0.8 V.

This paper describes an approach to the fabrication of flexible electronics i.e., a wearable temperature sensor and infrared (IR) photodetector on flexible polyimide (PI) substrate. Solar exfoliated reduced graphene oxide (SrGO) and graphene flakes are used as the sensing materials for developing the sensors on a PI substrate. PI, apart from being flexible and compatible with microfabrication processes, also helps in reducing the mobility and recombination of the photo-generated electrons of graphene due of its dielectric nature, thus enabling IR detection. Current responsivity and external quantum efficiency of IR photodetector for graphene flakeand SrGO-based devices were found to be 0.4 A W −1 , 16.53% and 0.8 A W −1 , 33.06% respectively which are higher than those of commercially available photodetectors. In addition, we demonstrate an ultrasensitive wearable human body temperature sensor in the temperature range of 35 °C to 45 °C, wherein both graphene flakeand SrGO-based devices exhibited a negative temperature coefficient of −41.30 × 10 −4 °C−1 and −74.29 × 10 −4 °C−1 respectively, which are higher than commercially available counterparts. Plausible underlying mechanisms to both IR sensing and temperature sensing have been studied. Furthermore, as a proof of concept, we investigated the effect of IR radiation emitted by a human hand on the device. Interestingly it was found that the device was very sensitive to it, indicating that the sensor can be used for motion detection which has potential applications in security, surveillance etc. The strategy presented here provides a new, simple, cost effective approach for the fabrication of nextgeneration wearable and bio-implantable devices based on a polyimide substrate that can be easily integrated onto the surface of a leaf, skin, paper, clothes etc owing to its versatile nature.

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Exfoliated graphene oxide (EG)/manganese­(II) oxide (MnO) composite powder is synthesized by simple solid state graphenothermal reduction process. Structural, chemical, and morphological studies confirm the formation of EG/MnO composite in which cubic MnO crystallites are found to anchor onto EG surfaces. The as-synthesized EG/MnO composite is constituted with 65 and 35 wt % of MnO and EG, respectively. The EG/MnO composite exhibits a specific surface area of ∼82 m2 g–1 and an average pore size of ∼12 nm. As an anode in lithium-ion batteries, the EG/MnO composite shows a high reversible capacity of 936 mAh g–1 at a current rate of 75 mA g–1. Capacity retention of ∼84% (784 mAh g–1) is observed even at the 100th cycle which corresponds to a Coulombic efficiency of ∼99%. Cyclic voltammetry studies on the composite show that Li storage is owing to reversible conversion reactions of MnO and electrochemical absorption/desorption by EG. Electrochemical impedance spectroscopy studies clearly show easy lithiation kinetics. Owing to the electrochemical performance of EG/MnO composite and its easy, reproducible, and scalable synthesis procedure, it is an excellent addition to this class of similar materials.