Shell Modulation of Hollow Metal Sulfide Nanocomposite for Stable Potassium Storage at Room and High Temperature.

The large size of K-ion makes the pursuit of stable high-capacity anodes for K-ion batteries (KIBs) a formidable challenge, particularly for high temperature KIBs as the electrode instability becomes more aggravated with temperature climbing. Herein, we demonstrate that a hollow ZnS@C nanocomposite (h-ZnS@C) with a precise shell modulation can resist electrode disintegration to enable stable high-capacity potassium storage at room and high temperature. Based on a model electrode, we identify an interesting structure-function correlation of the h-ZnS@C: with an increase in the shell thickness, the cyclability increases while the rate and capacity decreases, shedding light on the design of high-performance h-ZnS@C anodes via engineering the shell thickness. Typically, the h-ZnS@C anode with a shell thickness of 60 nm can deliver an impressive comprehensive performance at room temperature; the h-ZnS@C with shell thickness increasing to 75 nm can achieve an extraordinary stability (88.6% capacity retention over 450 cycles) with a high capacity (450 mAh g-1) and a superb rate even at an extreme temperature of 60 ℃, which is much superior than those reported anodes. This contribution envisions new perspectives on rational design of functional metal sulfides composite toward high-performance KIBs with insights into the significant structure-function correlation.

Use of green fluorescent protein to visualize rice root colonization by Azospirillum irakense and A. brasilense.

To visualize rice root colonization by two Azospirillum species, A. irakense KBC1 was equipped with a plasmid expressing the enhanced green fluorescent protein (EGFP) and A. brasilense Sp7 was equipped with a plasmid expressing the enhanced yellow fluorescent protein (EYFP). In both cases, intensive fluorescence was observed under the epifluorescent microscope. Striking differences for association with roots of rice seedlings were observed between the two species: (i) A. irakense cells attached faster than A. brasilense to rice roots following inoculation; (ii) A. irakense attached to rice roots as vibroid cells, while A. brasilense occurred as rounded cyst-like cells; (iii) A. irakense cells were mainly found on root hairs, whereas A. brasilense cells were mainly concentrated on root surfaces. The two Azospirillum species obviously do not compete with each other for colonization of rice roots. These results demonstrate that the two Azospirillum species differ in their mode of rice root colonization. Asthe two Azospirillum species are extensively studied for unravelling mechanisms of plant root colonization and plant growth promotion, labelling with fluorescent protein is a useful additional tool for these studies.