N-methylene phosphonic acid chitosan/graphene sheets decorated with silver nanoparticles as green antimicrobial agents.

A green and scalable approach for the preparation of few-layered graphene utilizing the biowaste of potato peels has been developed. The potato peels have been dried and carbonized to obtain a new graphite structure that has been exfoliated in N-methylene phosphonic acid chitosan (MPC). The exfoliation process assisted the formation of graphene sheets with a high size diameter and quality of 50% based on the weight of graphite structure. The graphene sheets were green decorated with silver nanoparticles using microwave power to obtain new nanocomposites. The mass ratio between the graphite and silver nitrate was optimized and observed to change the morphology and size diameter of silver nanoparticles. The as-prepared MPC structure, graphene, and silver decorated graphene nanocomposites were characterized using 1HNMR, FTIR, XRD, UV/Vis spectrophotometer, SEM, and TEM besides tested as antimicrobial agents. The bacterial performance was also controlled by changing the number of AgNPs distributed on graphene sheets based on the mass ratios of graphite/AgNO3. The inhibition diameter of silver decorated graphene was considerably increased to 24.8, and 20.1 mm as in the case of MPC-GRP-Ag30 composite compared to the pure graphene (11.2, 13.5 mm) for E. coli and S. aureus, consecutively proposing that the blade edge of graphene sheets can destroy the bacteria membrane and release silver cations promptly that are directed for the interaction with the cytoplasmic parts of the bacteria cell. Such findings offer green and biocompatible antibacterial agents based on the graphene derived from the biowaste products.

Chemical Synthesis of Sea-Urchin Shaped 3D-MnO2 Nano Structures and Their Application in Supercapacitors.

Sea-urchin shaped α-MnO2 hierarchical nano structures have been synthesized by facile thermal method without using any hard or soft template under the mild conditions. The structural and morphology of the 3D-MnO2 was characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). From the XRD analysis indicates that MnO2 present in the α form. Morphology analysis shows that α-MnO2 sea-urchins are made by stacked nanorods, the diameter and length of the stacked nanorods present in the range of 50-120 nm and 200-400 nm respectively. The electrochemical behaviour of α-MnO2 has been investigated by cyclic voltammetry (CV) and charge-discharge (CD). The specific capacitance, energy density and power density are 212.0 F g(-1), 21.2 Wh kg(-1) and 1200 W kg(-1) respectively at the current density of 2 A g(-1). The retention of the specific capacitance after completion of 1000 charge-discharge cycles is around 97%. The results reveal that the prepared Sea-urchin shaped α-MnO2 has high specific capacitance and exhibit excellent cycle life.