A general route via formamide condensation to prepare atomically dispersed metal-nitrogen-carbon electrocatalysts for energy technologies

Single-atom electrocatalysts (SAECs) have gained tremendous attention due to their unique active sites and strong metal–substrate interactions. However, the current synthesis of SAECs mostly relies on costly precursors and rigid synthetic conditions and often results in very low content of single-site metal atoms. Herein, we report an efficient synthesis method to prepare metal–nitrogen–carbon SAECs based on formamide condensation and carbonization, featuring a cost-effective general methodology for the mass production of SAECs with high loading of atomically dispersed metal sites. The products with metal inclusion were termed as formamide-converted metal–nitrogen–carbon (shortened as f-MNC) materials. Seven types of single-metallic f-MNC (Fe, Co, Ni, Mn, Zn, Mo and Ir), two bi-metallic (ZnFe and ZnCo) and one tri-metallic (ZnFeCo) SAECs were synthesized to demonstrate the generality of the methodology developed. Remarkably, these f-MNC SAECs can be coated onto various supports with an ultrathin layer as pyrolysis-free electrocatalysts, among which the carbon nanotube-supported f-FeNC and f-NiNC SAECs showed high performance for the O2 reduction reaction (ORR) and the CO2 reduction reaction (CO2RR), respectively. Furthermore, the pyrolysis products of supported f-MNC can still render isolated metallic sites with excellent activity, as exemplified by the bi-metallic f-FeCoNC SAEC, which exhibited outstanding ORR performance in both alkaline and acid electrolytes by delivering ∼70 and ∼20 mV higher half-wave potentials than that of commercial 20 wt% Pt/C, respectively. This work offers a feasible approach to design and manufacture SAECs with tuneable atomic metal components and high density of single-site metal loading, and thus may accelerate the deployment of SAECs for various energy technology applications

Multi-Assay-Based Compound Prioritization via Assistance Utilization: A Machine Learning Framework

Effective prioritization of chemical compounds that show promising bioactivities from compound screenings represents a first critical step toward identifying successful drug candidates. Current development on computational approaches for compound prioritization is largely focused on devising advanced ranking algorithms that better learn the ordering among compounds. However, such methodologies are fundamentally limited by the scarcity of available data, particularly when the screenings are conducted at a relatively small scale over known promising compounds. Instead, in this work, we explore the structures of bioassay space and leverage such structures to improve ranking performance of an existing strong ranking algorithm. This is done by identifying <i>assistance</i> bioassays and <i>assistance</i> compounds intelligently and leveraging such assistance within the existing ranking algorithm. By leveraging the assistance bioassays and assistance compounds, the data scarcity can be properly compromised. Along this line, we develop a suite of assistance bioassay selection methods and assistance compound selection methods. Our experiments demonstrate an overall 8.34% improvement on the ranking performance over the state of the art

Natural Organic Matter Concentration and Hydrochemistry Influence Aggregation Kinetics of Functionalized Engineered Nanoparticles

Understanding the colloidal stability of functionalized engineered nanoparticles (FENPs) in aquatic environments is of paramount importance in order to assess the risk related to FENPs. In this study, gold nanoparticles (GNPs) of 68 and 43 nm diameter, coated with citrate and 11-mercaptoundecanoic acid (MUA) respectively, were used as models of FENPs. Time-resolved dynamic light scattering was employed to investigate the aggregation kinetics of two types of GNPs. The results show that without Suwannee river natural organic matter (SRNOM), MUA coating resulted in greater stability than citrate coating for GNPs. Cations have a destabilizing effect on both GNPs following the order Ca²⁺ ≈ Mg²⁺ ≫ Na⁺; different anions (Cl^– and SO₄^2–) showed no difference in effects. In the fast aggregation regime, adding SRNOM enhanced the stability of MUA-coated GNPs in both Ca²⁺ and Mg²⁺ solutions. However citrate-coated GNPs were only stabilized in Mg²⁺ solution but enhanced aggregation occurred in high Ca²⁺ concentration due to interparticle bridging. For the investigated GNPs and in the presence of SRNOM, Ca²⁺ does not always act as a strong coagulant. This indicates that for the new materials emerging from the application of nanotechnology the well-described aggregation mechanisms of colloids in the environment require a detailed re-examination

Added-Metal-Free Catalytic Nucleophilic Addition of Grignard Reagents to Ketones

On the basis of the investigation of the combinational effect of quaternary ammonium salts and organic bases, an added-metal-free catalytic system for nucleophilic addition reactions of a variety of Grignard reagents to diverse ketones in THF solvent has been developed to produce tertiary alcohols in good to excellent yields. By using tetrabutylammonium chloride (NBu₄Cl) as a catalyst and diglyme (DGDE) as an additive, this system strongly enhances the efficiency of addition at the expense of enolization and reduction. NBu₄Cl should help to shift the Schlenk equilibrium of Grignard reagents to the side of dimeric Grignard reagents to favor the additions of Grignard reagents to ketones via a favored six-membered transition state to form the desired tertiary alcohols, and DGDE should increase the nucleophilic reactivities of Grignard reagents by coordination. This catalytic system has been applied in the efficient synthesis of Citalopram, an effective U.S. FDA-approved antidepressant, and a recyclable version of this catalytic synthesis has also been devised

Association of Elevated High Sensitivity Cardiac Troponin T(hs-cTnT) Levels with Hemorrhagic Transformation and 3-Month Mortality in Acute Ischemic Stroke Patients with Rheumatic Heart Disease in China

<div><p>Background and Objective</p><p>Elevated levels of high sensitivity cardiac troponin T (hs-cTnT) occur in a substantial proportion of patients with acute ischemic stroke (AIS) and can predict poor outcome and mortality after stroke. Whether elevated hs-cTnT levels can also predict hemorrhagic transformation (HT) or prognosis in AIS patients with rheumatic heart disease (RHD) remains unclear.</p><p>Methods</p><p>Data from the Chengdu Stroke Registry on consecutive AIS patients with RHD admitted to West China Hospital within1 month of stroke onset from October 2011 to February 2014 were examined. Clinico-demographic characteristics, HT, functional outcomes and stroke recurrence were compared between patients with elevated hs-cTnT levels(≥14ng/L) and patients with normal hs-cTnT levels (<14ng/L).</p><p>Results</p><p>The final analysis involved 84 patients (31 males; mean age, 61.6±12.2years), of whom serum hs-cTnT levels were elevated in 58.3%. Renal impairment was independently associated with elevated hs-cTnT levels (OR 4.184, 95%CI 1.17 to 15.01, <i>P</i> = 0.028), and patients with elevated hs-cTnT levels were at significantly higher risk of HT, 3-month mortality and 3-month disability/mortality (all <i>P</i>≤0.029). After controlling for age, sex, hypertension, renal impairment and National Institutes of Health Stroke Scale score on admission, the risk of HT and 3-month mortality was, respectively, 4.0- and 5.5-fold higher in patients with elevated hs-cTnT levels than in patients with normal hs-cTnT levels.</p><p>Conclusion</p><p>Elevated hs-cTnT levels are independently associated with HT and 3-month mortality in AIS patients with RHD. These results with a small cohort should be verified and extended in large studies.</p></div

Polymerized-Small-Molecule Acceptors Featuring Siloxane-Terminated Side Chains for Mechanically Robust All-Polymer Solar Cells

Flexible and stretchable organic solar cells (OSCs) show great promise in wearable and stretchable electronic applications. However, current high-performance OSCs consisting of polymer donors (PDs) and small-molecule acceptors (SMAs) face significant challenges in achieving both high power conversion efficiency (PCE) and excellent stretch-ability. In this study, we synthesized a new polymerized-small-molecule acceptor (P-SMA) PY-SiO featuring siloxane-terminated side chains and compared its photovoltaic and mechanical performance to that of the reference PY-EH with ethylhexyl-terminated side chains. We found that the incorporation of siloxane-terminated side chains in PY-SiO enhanced the molecular aggregation and charge transport, leading to an optimized film morphology. The resultant of all-polymer solar cells (all-PSCs) based on PBDB-T/PY-SiO showed a higher PCE of 12.04% than the PY-EH-based one (10.85%). Furthermore, the siloxane-terminated side chains also increased the interchain distance and provided a larger free volume for chain rotation and reconfiguration, resulting in a higher film crack-onset strain (COS: 18.32% for PBDB-T/PY-SiO vs 11.15% for PBDB-T/PY-EH). Additionally, the PY-SiO-based stretchable all-PSCs exhibited an impressive PCE of 9.8% and retained >70% of its original PCE even under a substantial 20% strain, exceeding the performance of the PY-EH-based stretchable all-PSCs. Our result suggests the great potential of the siloxane-terminated side chain for achieving high-performance and stretchable OSCs

Univariate analysis of hemorrhagic transformation(HT) or prognosis in patients with elevated or normal hs-cTnT levels.

<p>Univariate analysis of hemorrhagic transformation(HT) or prognosis in patients with elevated or normal hs-cTnT levels.</p

Bottom-Up Assembly of Hydrophobic Nanocrystals and Graphene Nanosheets into Mesoporous Nanocomposites

A general strategy for constructing graphene-based nanocomposites is achieved by emulsion-based bottom-up self-assembly of hydrophobic nanocrystals (NCs) to positively charged colloidal spheres, followed by the electrostatic assembly of NC colloidal spheres with negatively charged graphene oxide in an acidulous aqueous solution. With a simple heat treatment, 3D mesoporous NC spheres/graphene composites are obtained. TiO₂/graphene composites typically exhibit a better rate capability and cycle performance than do the corresponding isolated TiO₂ spheres

Multivariate analysis of hemorrhagic transformation (HT) and prognosis in patients with elevated or normal hs-cTnT levels.^*

<p>Multivariate analysis of hemorrhagic transformation (HT) and prognosis in patients with elevated or normal hs-cTnT levels.^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0148444#t004fn001" target="_blank">*</a>}</p

Triphenyl Phosphite as the Phosphorus Source for the Scalable and Cost-Effective Production of Transition Metal Phosphides

Transition metal phosphides have great potential to optimize a number of functionalities in several energy conversion and storage applications, particularly when nanostructured or in nanoparticle form. However, the synthesis of transition metal phosphide nanoparticles and its scalability is often limited by the toxicity, air sensitivity, and high cost of the reagents used. We present here a simple, scalable, and cost-effective “heating up” procedure to produce metal phosphides using inexpensive, low-toxicity, and air-stable triphenyl phosphite as source of phosphorus and chlorides as metal precursors. This procedure allows the synthesis of a variety of phosphide nanoparticles, including phosphides of Ni, Co, and Cu. The use of carbonyl metal precursors further allowed the synthesis of Fe₂P and MoP nanoparticles. The fact that minor modifications in the experimental parameters allowed producing nanoparticles with different compositions and even to tune their size and shape shows the high potential and versatility of the triphenyl phosphite precursor and the presented method. We also detail here a methodology to displace organic ligands from the surface of phosphide nanoparticles, which is a key step toward their application in energy conversion and storage systems