A Facile Method for Synthesis of Porous NiCo2O4 Nanorods as a High‐Performance Anode Material for Li‐Ion Batteries

Porous electrode materials with large specific surface area, relatively short diffusion path, and higher electrical conductivity, which display both better rate capabilities and good cycle lives, have huge benefits for practical applications in lithium‐ion batteries. Here, uniform porous NiCo₂O₄ nanorods (PNNs) with pore‐size distribution in the range of 10–30 nm and lengths of up to several micrometers are synthesized through a convenient oxalate co‐precipitation method followed by a calcining process. The PNN electrode exhibits high reversible capacity and outstanding cycling stability (after 150 cycles still maintain about 650 mA h g^?1 at a current density of 100 mA g^?1), as well as high Coulombic efficiency (>98%). Moreover, the PNNs also exhibit an excellent rate performance, and deliver a stable reversible specific capacity of 450 mA h g^?1 even at 2000 mA g^?1. These results demonstrate that the PNNs are promising anode materials for high‐performance Li‐ion batteries.     

A Paper‐Based Platform for Long‐Term Deposition of Nanoparticles with Exceptional Redispersibility,Stability, and Functionality

Although nanoparticles (NPs) can be carefully engineered to have maximal stability and functionality desirable for use in diverse applications, they are generally not suitable for long‐term storage in solution. It is also difficult to store NPs in a dry state because dried NPs generally become aggregated and cannot easily be redispersed. Thus, a new strategy allowing long‐term storage of NPs with high stability, redispersibility, and functionality is highly demanded. By passivating the 13 nm gold nanoparticle (AuNP) surface with stabilizing agents and treating a paper substrate with both bovine serum albumin and sucrose after coating with a hydrophobic polyvinyl butyral layer, it is possible to fully redisperse (≈100%) dried AuNPs with colloidal stability comparable to that of as‐prepared AuNPs. Furthermore, AuNPs physically stabilized with polyvinylpyrrolidone can react with thiol‐containing compounds, such as 1,4‐dithiothreitol (DTT). Taking advantage of the oxidation reaction of hypochlorous acid with DTT, it is possible to demonstrate a paper‐based colorimetric sensor for detection of residual chlorine in water. Since this strategy is applicable to large‐sized AuNPs (30–90 nm), silver NPs, oleic acid‐capped magnetic NPs, and cetrimonium bromide‐passivated gold nanorods, it can be used for diverse NPs requiring long‐term storage for many applications.