Chemical Synthesis Lab

Abstract A method of fabricating ultrathin (≈22–53 nm thick) graphene nanofiltration membranes (uGNMs) on microporous substrates is presented for efficient water purification using chemically converted graphene (CCG). The prepared uGNMs show well packed layer structure formed by CCG sheets, as characterized by scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The performance of the uGNMs for water treatment was evaluated on a dead end filtration device and the pure water flux of uGNMs was high (21.8 L m −2 h −1 bar −1 ). The uGNMs show high retention (>99%) for organic dyes and moderate retention (≈20–60%) for ion salts. The rejection mechanism of this kind of negatively charged membranes is intensively studied, and the results reveal that physical sieving and electrostatic interaction dominate the rejection process. Because of the ultrathin nature of uGNMs, 34 mg of CCG is sufficient for making a square meter of nanofiltration membrane, indicating that this new generation graphene‐based nanofiltration technology would be resource saving and cost‐effective. The integration of high performance, low cost, and simple solution‐based fabrication process promises uGNMs great potential application in practical water purification.

Phosphorescent organic light-emitting devices (OLEDs) have attracted increased attention from both academic and industrial communities due to their potential practical application in high-resolution full-color displays and energy-saving solid-state lightings. The performance of phosphorescent OLEDs is mainly limited by the phosphorescent transition metal complexes (such as iridium(III), platinum(II), gold(III), ruthenium(II), copper(I) and osmium(II) complexes, etc.) which can play a crucial role in furnishing efficient energy transfer, balanced charge injection/transporting character and high quantum efficiency in the devices. It has been shown that functionalized main-group element (such as boron, silicon, nitrogen, phosphorus, oxygen, sulfur and fluorine, etc.) moieties can be incorporated into phosphorescent emitters and their host materials to tune their triplet energies, frontier molecular orbital energies, charge injection/transporting behavior, photophysical properties and thermal stability and hence bring about highly efficient phosphorescent OLEDs. So, in this review, the recent advances in the phosphorescent emitters and their host materials functionalized with various main-group moieties will be introduced from the point of view of their structure-property relationship. The main emphasis lies on the important role played by the main-group element groups in addressing the key issues of both phosphorescent emitters and their host materials to fulfill high-performance phosphorescent OLEDs.

Garlic belongs to the Allium family of plants that produce organosulfur compounds, such as allicin and diallyl disulfide (DADS), which account for their pungency and spicy aroma. Many health benefits have been ascribed to Allium extracts, including hypotensive and vasorelaxant activities. However, the molecular mechanisms underlying these effects remain unknown. Intriguingly, allicin and DADS share structural similarities with allyl isothiocyanate, the pungent ingredient in wasabi and other mustard plants that induces pain and inflammation by activating TRPA1, an excitatory ion channel on primary sensory neurons of the pain pathway. Here we show that allicin and DADS excite an allyl isothiocyanate-sensitive subpopulation of sensory neurons and induce vasodilation by activating capsaicin-sensitive perivascular sensory nerve endings. Moreover, allicin and DADS activate the cloned TRPA1 channel when expressed in heterologous systems. These and other results suggest that garlic excites sensory neurons primarily through activation of TRPA1. Thus different plant genera, including Allium and Brassica, have developed evolutionary convergent strategies that target TRPA1 channels on sensory nerve endings to achieve chemical deterrence.

This perspective provides information on durability challenges and future actions of anion exchange membrane fuel cells.

Diabetes causes increased oxidative stress, which is thought to play an important role in the pathogenesis of various diabetic complications. However, the source of the hyperglycemia-induced oxidative stress is not clear. It was found that the polyol pathway is the major contributor to oxidative stress in the lenses and nerves of diabetic mice. The first enzyme in the pathway, aldose reductase (AR), reduces glucose to sorbitol, which is then converted to fructose by sorbitol dehydrogenase (SDH). Transgenic mice that overexpress AR specifically in their lenses showed a significant increase in oxidative stress when they became hyperglycemic, as indicated by a decrease in GSH and an increase in malondialdehyde in their lenses. Introducing an SDH-deficient mutation into these transgenic mice significantly normalized the GSH and malondialdehyde levels. These results indicate that both enzymes of the polyol pathway contributed to hyperglycemia-induced oxidative stress in the lens. In the wild-type mice, diabetes caused a significant decrease in GSH in their sciatic nerves, indicative of oxidative stress. In the AR null mutant mice, diabetes did not lead to any decrease in the nerve GSH level. These results indicate that similar to the situation in the lens, AR is also the major contributor to hyperglycemia-induced oxidative stress in the nerve. Although increased flux of glucose through the polyol pathway leads to diabetic lesions in both the lenses and nerve, the mechanisms may be different. AR-induced osmotic stress seems to be the cause of diabetic cataract, whereas AR-induced oxidative stress is probably the cause of neuronal dysfunction.

The ACS Green Chemistry Institute® Pharmaceutical Roundtable has assembled an updated list of key research areas to highlight transformations and reaction media where more sustainable technologies would be most impactful.

Recent advances in deep-blue emitters furnishing high performance OLEDs and associated critical issues are discussed and reviewed.

We present results of ideal epitaxial nucleation and growth of III−V semiconductor nanowires on silicon substrates. This addresses the long-time challenge of integrating high performance III−V semiconductors with mainstream Si technology. Efficient room-temperature generation of light on silicon is demonstrated by the incorporation of double heterostructure segments in such nanowires. We expect that advanced heterostructure devices, such as resonant tunneling diodes, superlattice device structures, and heterostructure photonic devices for on-chip communication, could now become available as complementary device technologies for integration with silicon.

Understanding the durability-limiting factors of anion exchange membrane water electrolyzers operating under pure water-, KOH- and K₂CO₃-fed conditions.

The catalytic activity and hydrocarbon selectivity in electrochemical carbon dioxide (CO2) reduction on cuprous oxide (Cu2O) derived copper nanoparticles is discussed. Cuprous oxide films with [100], [110] and [111] orientation and variable thickness were electrodeposited by reduction of copper(ii) lactate on commercially available copper plates. After initiation of the electrochemical CO2 reduction by these oxide structures, the selectivity of the process was found to largely depend on the parent Cu2O film thickness, rather than on the initial crystal orientation. Starting with thin Cu2O films, besides CO and hydrogen, selective formation of ethylene is observed with very high ethylene-to-methane ratios (∼8 to 12). In addition to these products, thicker Cu2O films yield a remarkably large amount of ethane. Long term Faradaic efficiency analysis of hydrocarbons shows no sign of deactivation of the electrodes after 5 hours of continuous experiment. Online mass spectroscopy studies combined with X-ray diffraction data suggest the reduction of the Cu2O films in the presence of CO2, generating a nanoparticulate Cu morphology, prior to the production of hydrogen, CO, and hydrocarbons. Optimizing coverage, number density and size of the copper nanoparticles, as well as local surface pH, may allow highly selective formation of the industrially important product ethylene.

Over the past 15 years, increased attention has been directed at social skills and their relationship to learning disabilities. Using the methods of meta-analysis, this investigation explores the nature of social skill deficits among students with learning disabilities. Across 152 studies, quantitative synthesis shows that, on average, about 75% of students with learning disabilities manifest social skill deficits that distinguish them from comparison samples. Approximately the same level of group differentiation is found across different raters (teachers, peers, self) and across most dimensions of social competence. Although social skill deficits appear to be an integral part of the learning disability experience, a number of questions about the relationship between learning disability and social skill deficits remain unanswered. Until these questions are answered, social skill deficits are best viewed as one among many elements of the learning disability constellation, and no significant definitional changes related to social skill deficits appear warranted.

A sort of novel high-flux nanofiltration membrane was fabricated by synergistic assembling of graphene and multiwalled carbon nanotubes (MWNTs), in which graphene played the role of molecular sieving and MWNTs expanded the interlayer space between neighbored graphene sheets. The MWNT-intercalated graphene nanofiltration membrane (G-CNTm) showed a water flux up to 11.3 L m(-2) h(-1) bar(-1), more than 2 times that of the neat graphene nanofiltration membrane (GNm), while keeping high dye rejection (>99% for Direct Yellow and >96% Methyl Orange). The G-CNTm also showed good rejection ratio for salt ions (i.e., 83.5% for Na2SO4, 51.4% for NaCl). We also explored the antifouling performance of G-CNTm and GNm with bovine serum albumin (BSA), sodium alginate (SA) and humic acid (HA). Both G-CNTm and GNm possessed excellent antifouling performance for SA and HA but inferior for BSA because of the strong interaction between protein and graphene sheets.

information are at the core of this modality for superb imaging. Herein, we review the recently developed fluorophores including carbon nanotubes, organic small molecules, quantum dots, conjugated polymers and rare-earth-doped materials to present superior and multifunctionality of biomedical imaging in the NIR-II regions (1000-1700 nm).

RATIONALE: Idiopathic pulmonary fibrosis (IPF) is a chronic dysregulated response to alveolar epithelial injury with differentiation of epithelial cells and fibroblasts into matrix-secreting myofibroblasts resulting in lung scaring. The prognosis is poor and there are no effective therapies or reliable biomarkers. Galectin-3 is a β-galactoside binding lectin that is highly expressed in fibrotic tissue of diverse etiologies. OBJECTIVES: To examine the role of galectin-3 in pulmonary fibrosis. METHODS: We used genetic deletion and pharmacologic inhibition in well-characterized murine models of lung fibrosis. Further mechanistic studies were performed in vitro and on samples from patients with IPF. MEASUREMENTS AND MAIN RESULTS: Transforming growth factor (TGF)-β and bleomycin-induced lung fibrosis was dramatically reduced in mice deficient in galectin-3, manifest by reduced TGF-β1-induced EMT and myofibroblast activation and collagen production. Galectin-3 reduced phosphorylation and nuclear translocation of β-catenin but had no effect on Smad2/3 phosphorylation. A novel inhibitor of galectin-3, TD139, blocked TGF-β-induced β-catenin activation in vitro and in vivo and attenuated the late-stage progression of lung fibrosis after bleomycin. There was increased expression of galectin-3 in the bronchoalveolar lavage fluid and serum from patients with stable IPF compared with nonspecific interstitial pneumonitis and controls, which rose sharply during an acute exacerbation suggesting that galectin-3 may be a marker of active fibrosis in IPF and that strategies that block galectin-3 may be effective in treating acute fibrotic exacerbations of IPF. CONCLUSIONS: This study identifies galectin-3 as an important regulator of lung fibrosis and provides a proof of principle for galectin-3 inhibition as a potential novel therapeutic strategy for IPF.

This review summarizes the recent research progress made in nanostructured metal nitrides for electrochemical and photo(electro)chemical water splitting.

It is known that the room-temperature plastic deformation of bulk metallic glasses is compromised by strain softening and shear localization, resulting in near-zero tensile ductility. The incorporation of metallic glasses into engineering materials, therefore, is often accompanied by complete brittleness or an apparent loss of useful tensile ductility. Here we report the observation of an exceptional tensile ductility in crystalline copper/copper-zirconium glass nanolaminates. These nanocrystalline-amorphous nanolaminates exhibit a high flow stress of 1.09 +/- 0.02 GPa, a nearly elastic-perfectly plastic behavior without necking, and a tensile elongation to failure of 13.8 +/- 1.7%, which is six to eight times higher than that typically observed in conventional crystalline-crystalline nanolaminates (<2%) and most other nanocrystalline materials. Transmission electron microscopy and atomistic simulations demonstrate that shear banding instability no longer afflicts the 5- to 10-nm-thick nanolaminate glassy layers during tensile deformation, which also act as high-capacity sinks for dislocations, enabling absorption of free volume and free energy transported by the dislocations; the amorphous-crystal interfaces exhibit unique inelastic shear (slip) transfer characteristics, fundamentally different from those of grain boundaries. Nanoscale metallic glass layers therefore may offer great benefits in engineering the plasticity of crystalline materials and opening new avenues for improving their strength and ductility.

We report the first systematic study of initiator density on surface-initiated polymerizations. We used mixed monolayers comprising of undecanethiol and ω-mercaptoundecyl bromoisobutyrate (1) to initiate the controlled radical polymerization of methyl methacrylate (MMA) and glycidyl methacrylate (GMA) from gold. We found that SAMs composed of 10% and 50% of initiator 1 grow PMMA brushes to approximately 1/10 and 1/2 the thickness of polymer brushes grafted from SAMs comprising 100% 1. We did not find a clear maximum initiator density, beyond which no further increase in polymer brush thickness is observed. We show that the initiator density at the start of the polymerization determines the ultimate “footprint” and hence density of polymer molecules in polymer brushes.

Semiconductor heterostructures and their implementation into electronic and photonic devices have had tremendous impact on science and technology. In the development of quantum nanoelectronics, one-dimensional (1D) heterostructure devices are receiving a lot of interest. We report here functional 1D resonant tunneling diodes obtained via bottom-up assembly of designed segments of different semiconductor materials in III/V nanowires. The emitter, collector, and the central quantum dot are made from InAs and the barrier material from InP. Ideal resonant tunneling behavior, with peak-to-valley ratios of up to 50:1 and current densities of 1 nA/μm2 was observed at low temperatures.

Chiral amino acids are extensively applied in the pharmaceutical, food, cosmetic, agricultural, and feedstuff industries. The development of synthetic methodologies for optically pure amino acids has been driven by their significant applications. Among the various synthesis methods for the production of chiral amino acids, enzymatic asymmetric synthesis is a unique preparation strategy that shows great potential. This review provides an overview of the reported methods for enzymatic asymmetric synthesis of chiral amino acids, including asymmetric reductive amination of keto acids, asymmetric transfer of an amino group to keto acids, enantioselective addition of ammonia to α,β-unsaturated acids, and aldol condensation of an amino acid to aldehydes.

The term functionalized isocyanides refers to all those isocyanides in which a neighbouring functional group can finely tune the reactivity of the isocyano group or can be exploited in post-functionalization processes. In this manuscript, we have reviewed all the isocyanides in which the pendant functional group causes either deviation from or reinforces the normal reactivity of the isocyano group and categorized them to highlight their common features and differences. An analysis of their synthetic potential and the possible unexplored directions for future research studies is also addressed.