Gaohui Du

Visualizing the electrochemical reaction of ZnO nanoparticles with lithium by in situ TEM: two reaction modes are revealed

The lithiation reaction of ZnO as an anode in a lithium-ion battery (LIB) is unclear. The electrochemical behavior of ZnO was investigated inside a transmission electron microscope (TEM) by constructing a nano-LIB using an individual ZnO/graphene sheet as the electrode. The lithiation reaction of ZnO/graphene was monitored by simultaneous determination of the structure with high-resolution TEM, electron diffraction pattern and electron energy-loss spectroscopy. Two kinds of reaction modes were revealed in terms of different reaction rates. One was the violent reaction mode, in which one particle can evolve into an aggregate of many nanoparticles within the Li2O matrix in 1-2xa0min. The other was the peaceful evolution mode, in which each ZnO nanoparticle evolves into a core-shell particle with multi-domains constituted of Zn and LiZn nanograins. Abnormally large Zn nanocrystals grow quickly in the violent reaction mode, which can suppress the formation of LiZn and impair the reversible capacity. Our observations give direct evidence and important insights for the lithiation mechanism of metal oxide anodes in LIBs.

Colorimetric Sensing of Toxic Metal and Antibacterial Studies by Using Bioextract Synthesized Silver Nanoparticles

Here, we report the simple and cost effective colorimetric technique for the determination of toxic metals (Hg2+) in aqueous sample by using bioextract silver nanoparticles (AgNPs). The indigenous AgNPs were synthesised by green and ecologically friendly style using extract of fig (Ficus carica) leaf. The synthesized AgNPs were confirmed by UV–vis spectroscopy, FT-IR spectroscopy, and scanning electron microscopy methods. The synthesis of AgNPs was observed by its colour changing from light yellow to dark brownish. The existence of furanocoumarins bioactive materials in the fig leaf extract, which act as bio-reducing and capping agent, help in the formation of stabilized silver nanoparticles. In addition, the bacterial activity of the synthesized silver nanoparticles was tested against gram-negative (Klebsiella oxytocam, Pseudomonas aeruginosam, Shigella flexneri and Proteus mirabilis), gram-positive (Staphylococcus aureus and Micrococcus luteus) and one Candida (Candida albicans) human pathogen and the results showed moderate activity.