Lasing in robust cesium lead halide perovskite nanowires.

The rapidly growing field of nanoscale lasers can be advanced through the discovery of new, tunable light sources. The emission wavelength tunability demonstrated in perovskite materials is an attractive property for nanoscale lasers. Whereas organic-inorganic lead halide perovskite materials are known for their instability, cesium lead halides offer a robust alternative without sacrificing emission tunability or ease of synthesis. Here, we report the low-temperature, solution-phase growth of cesium lead halide nanowires exhibiting low-threshold lasing and high stability. The as-grown nanowires are single crystalline with well-formed facets, and act as high-quality laser cavities. The nanowires display excellent stability while stored and handled under ambient conditions over the course of weeks. Upon optical excitation, Fabry-Pérot lasing occurs in CsPbBr3 nanowires with an onset of 5 µJ cm(-2) with the nanowire cavity displaying a maximum quality factor of 1,009 ± 5. Lasing under constant, pulsed excitation can be maintained for over 1 h, the equivalent of 10(9) excitation cycles, and lasing persists upon exposure to ambient atmosphere. Wavelength tunability in the green and blue regions of the spectrum in conjunction with excellent stability makes these nanowire lasers attractive for device fabrication.

Strongly Quantum Confined Colloidal Cesium Tin Iodide Perovskite Nanoplates: Lessons for Reducing Defect Density and Improving Stability.

Within the last several years, metal halide perovskites such as methylammonium lead iodide, CH3NH3PbI3, have come to the forefront of scientific investigation as defect-tolerant, solution-processable semiconductors that exhibit excellent optoelectronic properties. The vast majority of study has focused on Pb-based perovskites, which have limited applications because of their inherent toxicity. To enable the broad application of these materials, the properties of lead-free halide perovskites must be explored. Here, two-dimensional, lead-free cesium tin iodide, (CsSnI3), perovskite nanoplates have been synthesized and characterized for the first time. These CsSnI3 nanoplates exhibit thicknesses of less than 4 nm and exhibit significant quantum confinement with photoluminescence at 1.59 eV compared to 1.3 eV in the bulk. Ab initio calculations employing the generalized gradient approximation of Perdew-Burke-Ernzerhof elucidate that although the dominant intrinsic defects in CsSnI3 do not introduce deep levels inside the band gap, their concentration can be quite high. These simulations also highlight that synthesizing and processing CsSnI3 in Sn-rich conditions can reduce defect density and increase stability, which matches insights gained experimentally. This improvement in the understanding of CsSnI3 represents a step toward the broader challenge of building a deeper understanding of Sn-based halide perovskites and developing design principles that will lead to their successful application in optoelectronic devices.

Synthesis of Composition Tunable and Highly Luminescent Cesium Lead Halide Nanowires through Anion-Exchange Reactions.

Here, we demonstrate the successful synthesis of brightly emitting colloidal cesium lead halide (CsPbX3, X = Cl, Br, I) nanowires (NWs) with uniform diameters and tunable compositions. By using highly monodisperse CsPbBr3 NWs as templates, the NW composition can be independently controlled through anion-exchange reactions. CsPbX3 alloy NWs with a wide range of alloy compositions can be achieved with well-preserved morphology and crystal structure. The NWs are highly luminescent with photoluminescence quantum yields (PLQY) ranging from 20% to 80%. The bright photoluminescence can be tuned over nearly the entire visible spectrum. The high PLQYs together with charge transport measurements exemplify the efficient alloying of the anionic sublattice in a one-dimensional CsPbX3 system. The wires increased functionality in the form of fast photoresponse rates and the low defect density suggest CsPbX3 NWs as prospective materials for optoelectronic applications.

Absence of transmission of NDM and OXA-48 carbapenemase genes in a chronic care unit of a long-term care facility.

Infection prevention and control measures are used to contain outbreaks of carbapenemase-producing Enterobacteriaceae. We report the absence of transmission of Klebsiella pneumoniae carrying New Delhi metallo-ß-lactamase and oxacillinase-48 genes among 19 screened contacts of an index case after 14 months of routine practices in a long-term care facility.

Improving Mental Performance in an Athletic Population with the Use of Arepa®, a Blackcurrant Based Nootropic Drink: A Randomized Control Trial.

A range of dietary bioactive ingredients have claimed to improve mental clarity and reduce fatigue, including blackcurrant, pine bark, and l-theanine. These active ingredients provide a good source of dietary polyphenols which could be useful in reducing mental fatigue in a sports setting. The aim of the investigation was to test the effect of Arepa® a blackcurrant-based nootropic-drink also containing pine-bark and l-theanine (BC+), on mental clarity in a sport setting. Twenty-three rugby league players completed a cross-over design, randomized, double-blind, controlled trial. Intervention and control phases lasted 7 days, with a washout in between. Cognition was assessed pre and post intervention following a standardized training session. Our study found the total score, accuracy, and average time per response scores improved significantly more after drinking the BC+ drink (p = 0.001, 0.003, and 0.043 respectively). The BC+ improved the perception that participants were reliable (p = 0.02) and less distracted (p = 0.03), while placebo supplementation increased participant perception they could control their nervousness (p = 0.03). Thematic analysis of post-trial questionnaire indicated participants found the BC+ sour, most reported no side effects, and opinion on which drink was more effective was not unanimous. The results indicate that the BC+ drink may be useful for athletes.

Growth and Photoelectrochemical Energy Conversion of Wurtzite Indium Phosphide Nanowire Arrays.

Photoelectrochemical (PEC) water splitting into hydrogen and oxygen is a promising strategy to absorb solar energy and directly convert it into a dense storage medium in the form of chemical bonds. The continual development and improvement of individual components of PEC systems is critical toward increasing the solar to fuel efficiency of prototype devices. Within this context, we describe a study on the growth of wurtzite indium phosphide (InP) nanowire (NW) arrays on silicon substrates and their subsequent implementation as light-absorbing photocathodes in PEC cells. The high onset potential (0.6 V vs the reversible hydrogen electrode) and photocurrent (18 mA/cm(2)) of the InP photocathodes render them as promising building blocks for high performance PEC cells. As a proof of concept for overall system integration, InP photocathodes were combined with a nanoporous bismuth vanadate (BiVO4) photoanode to generate an unassisted solar water splitting efficiency of 0.5%.

Physical and genetic interactions of cytosolic malate dehydrogenase with other gluconeogenic enzymes.

A truncated form (deltanMDH2) of yeast cytosolic malate dehydrogenase (MDH2) lacking 12 residues on the amino terminus was found to be inadequate for gluconeogenic function in vivo because the mutant enzyme fails to restore growth of a Deltamdh2 strain on minimal medium with ethanol or acetate as the carbon source. The DeltanMDH2 enzyme was also previously found to be refractory to the rapid glucose-induced inactivation and degradation observed for authentic MDH2. In contrast, kinetic properties measured for purified forms of MDH2 and deltanMDH2 enzymes are very similar. Yeast two-hybrid assays indicate weak interactions between MDH2 and yeast phosphoenolpyruvate carboxykinase (PCK1) and between MDH2 and fructose-1,6-bisphosphatase (FBP1). These interactions are not observed for deltanMDH2, suggesting that differences in cellular function between authentic and truncated forms of MDH2 may be related to their ability to interact with other gluconeogenic enzymes. Additional evidence was obtained for interaction of MDH2 with PCK1 using Hummel-Dreyer gel filtration chromatography, and for interactions of MDH2 with PCK1 and with FBP1 using surface plasmon resonance. Experiments with the latter technique demonstrated a much lower affinity for interaction of deltanMDH2 with PCK1 and no interaction between deltanMDH2 and FBP1. These results suggest that the interactions of MDH2 with other gluconeogenic enzymes are dependent on the amino terminus of the enzyme, and that these interactions are important for gluconeogenic function in vivo.