Efficient, robust surface functionalization and stabilization of gold nanorods with quaternary ammonium-containing ionomers as multidentate macromolecular ligands

Surface functionalization of gold nanorods (GNRs) is critical to their applications in various fields. While there are several existing strategies, we report in this article a new general strategy for the surface functionalization of GNRs with quaternary ammonium-containing ionomers as a novel class of multidentate macromolecular surface ligands. A range of tetralkylammoniumcontaining hyperbranched polyethylene- and linear poly(n-butyl acrylate)-based ionomers has been specifically designed and employed in the strategy. Acting as multidentate macromolecular analogues of cetyltrimethylammonium bromide (CTAB), the ionomers have been demonstrated to bind onto the GNR surface by displacing the surface-bound CTAB species via ligand exchange to render CTAB-free ionomer-modified GNRs. By properly designing the enabling ionomers, we have shown that the modified GNRs can be endowed with some desired properties, such as excellent dispersibility in various organic solvents, robust stability under multiple rounds (up to 12 investigated) of high-speed centrifugation in organic solvents, amphiphilicity with dispersibility in both aqueous and organic media, fluorescence, and capability in carrying hydrophobic guest species. This strategy thus provides potential new ways for the construction of novel multifunctional GNR nanocomposites

Two birds with one stone: Goal conflict handling and its effect on well-being

A tourist’s journey is often shaped by the pursuit of diverse and sometimes conflicting goals. In this study, we investigate how tourists handle conflicting goals during their travels. Drawing upon life history theory, we have developed and tested a conceptual model that examines how life history strategies (LHS, fast vs. slow) influence goal management approaches (highlighting vs. balancing) and their subsequent impact on tourist well-being. Through a combination of surveys, field and lab experiments, and a meta-analysis, our research reveals that when confronted with goal conflicts, tourists with a fast LHS tend to prefer a highlighting approach, while those with a slow LHS gravitate towards a balancing approach, with perceived deservingness serving as a mediator in this relationship. Moreover, matching (vs. mismatching) LHS with goal management enhances overall well-being. These findings offer valuable insights for both theoretical advancement and practical management in tourism

Quaternary ammonium cationic polymer as a superior bifunctional binder for lithium – sulfur batteries and effects of counter anion

Bifunctional polymer binders featured with both strong binding and superior polysulfide trapping properties are highly desired for the fabrication of sulfur cathodes with suppressed polysulfide shuttling in Li–S batteries. In this paper, we have explored the potential of a quaternary ammonium cationic polymer, polydiallyldimethylammonium (PDADMA-X; X = T, B, P, and Cl) with different counter anions (TFSI–, BF4−, PF6−, and Cl−, respectively) as the bifunctional binder. We have also revealed the dramatic effects of the counter anion on the performance of the cationic polymer binder. PDADMA-X's containing the former three weakly associating anions have been demonstrated to show polysulfide adsorption capability. In particular, PDADMA-T having the largest, least interacting TFSI– anion shows the optimum performance, with strong binding strength and the best polysulfide adsorption capability. Relative to commercial PVDF and PDADMA-X's of other counter anions, it offers sulfur cathodes with lowered polarization, higher discharge capacity, significantly better capacity retention, and improved cycling stability. With its convenient synthesis from commercially available PDADMA-Cl, cationic PDADMA-T having the TFSI– anion is a promising bifunctioal binder for sulfur cathodes in practical Li-sulfur batteries

Ni-Doped Sr\u3csub\u3e2\u3c/sub\u3eFe\u3csub\u3e1.5\u3c/sub\u3eMo\u3csub\u3e0.5\u3c/sub\u3eO\u3csub\u3e6-δ\u3c/sub\u3e as Anode Materials for Solid Oxide Fuel Cells

10% Ni-doped Sr2Fe1.5Mo0.5O6-δ with A-site deficiency is prepared to induce in situ precipitation of B-site metals under anode conditions in solid oxide fuel cells. XRD, SEM and TEM results show that a significant amount of nano-sized Ni-Fe alloy metal phase has precipitated out from Sr1.9Fe1.4Ni0.1Mo0.5O6-δ upon reduction at 800◦C in H2. The conductivity of the reduced composite reaches 29 S cm−1 at 800◦C in H2. Furthermore, fuel cell performance of the composite anode Sr1.9Fe1.4Ni0.1Mo0.5O6-δ-SDC is investigated using H2 as fuel and ambient air as oxidant with La0.8Sr0.2Ga0.87Mg0.13O3 electrolyte and La0.6Sr0.4Co0.2Fe0.8O3 cathode. The cell peak power density reaches 968 mW cm−2 at 800◦C and the voltage is relatively stable under a constant current load of 0.54 A cm−2. After 5 redox cycles of the anode at 800◦C, the fuel cell performance doesn’t suffer any degradation, indicating good redox stability of Sr1.9Fe1.4Ni0.1Mo0.5O6-δ. Peak power density of 227 mW cm−2 was also obtained when propane is used as fuel. These results indicate that a self-generated metal-ceramic composite can been successfully derived from Sr2Fe1.5Mo0.5O6-δ by compositional modifications and Sr1.9Fe1.4Ni0.1Mo0.5O6-δ is a very promising solid oxide fuel cell anode material with enhanced catalytic activity and inherited good redox stability from the parent ceramic material

Modification of cellulose nanocrystals with quaternary ammonium-containing hyperbranched polyethylene ionomers by ionic assembly

In this article, we demonstrate the first surface modification of cellulose nanocrystals (CNCs) with quaternary ammonium-containing ionomers by ionic binding of their positively charged ammonium ions onto the negatively charged surface of CNCs. A range of hyperbranched polyethylene ionomers (I1–I6) having different ionic content (0.2–2.3 mol %) has been designed and employed for this purpose. The simple dropwise addition and mixing of the aqueous dispersion of CNCs with the ionomer solution in tetrahydrofuran (THF) conveniently renders the ionomer-modified CNCs (mCNC1–mCNC6). The presence of adsorbed ionomers on the modified CNCs is confirmed with spectroscopic and X-ray diffraction evidence and quantified through thermogravimetric analysis. The effects of the ionomer to CNC feed mass ratio and the ionomers of different ionic content on the modification have been examined. A study on the morphology of the modified CNCs by atomic force microscopy discloses the occurrence of side-to-side and/or end-to-end assembly of the CNC rods due to the “cross-linking” or bridging effects of the multidentate ionomers. Because of the hydrophobic hyperbranched polyethylene segments in the adsorbed ionomers, the modified CNCs can be dispersed in nonpolar or low-polarity organic solvents (such as THF, toluene, and chloroform). In particular, the THF dispersions of modified CNCs prepared with ionomers having ionic content ≥0.7 mol % (I3–I6) behave as thixotropic organo-gels at concentrations ≥40 mg mL–1. Further, the modified CNCs better disperse than unmodified CNCs in a hydrophobic ethylene–olefin copolymer (EOC) elastomer matrix and show better thermal stability than a surfactant-modified CNC sample. Tensile testing confirms that the EOC composites, filled with the ionomer-modified CNCs, are significantly reinforced with a tensile modulus nearly doubled that of neat EOC, and they demonstrate better elongation at break relative to those filled with unmodified CNCs or surfactant-modified CNCs.Natural Science and Engineering Research Council (NSERC) of Canad

High-performance iron oxide-graphene oxide nanocomposite adsorbents for arsenic removal

We report the synthesis of a new range of iron oxide-graphene oxide (GO) nanocomposites having different iron oxide content (36–80 wt%) as high-performance adsorbents for arsenic removal. Synthesized by co-precipitation of iron oxide on GO sheets that are prepared by an improved Hummers method, the iron oxide in the nanocomposites is featured primarily in the desirable form of amorphous nanoparticles with an average size of ca. 5 nm. This unique amorphous nanoparticle morphology of the iron oxide beneficially endows the nanocomposites with high surface area (up to 341 m2 g-1 for FeOx-GO-80 having the iron oxide content of 80 wt%) and predominant mesopore structures, and consequently increased adsorption sites and enhanced arsenic adsorption capacity. FeOx-GO-80 shows high maximum arsenic adsorption capacity (qmax) of 147 and 113 mg g−1 for As(III) and As(V), respectively. These values are the highest among all the iron oxide-GO/reduced GO composite adsorbents reported to date and are also comparable to the best values achieved with various sophisticatedly synthesized iron oxide nanostructures. More strikingly, FeOx-GO-80 is also demonstrated to nearly completely (>99.98%) removes arsenic by reducing the concentration from 118 (for As(III)) or 108 (for As(V)) to < 0.02 μg L−1, which is far below the limit of 10 μg L−1 recommended by the World Health Organization (WHO) for drinking water. The excellent adsorption performance, along with their low cost and convenient synthesis, makes this range of adsorbents highly promising for commercial applications in drinking water purification and wastewater treatment

Foreign Aid and Economic Growth: Does It Plays Any Significant Role in Sub-Saharan Africa?

The effectiveness of foreign aid on economic growth is a much debated topic on the field of Development Economics. As such, a huge body of literature is available with the vast majority concluding that aid contributes in increasing growth (Hansen and Tarp, 2000); although some scholars, amongst them Boone (1996), Ovaka (2003), and Moyo (2009) hold a different and an opposite view. Aware of the fact that Sub-Saharan Africa is the poorest region in the world (Chen and Ravallion, 2012), (World Bank, 2012), and that Sub-Saharan Africa is the region which is the biggest beneficiary of aid (Lancaster, 1999), (OECD, 2010); but nevertheless aid in this region seems not to produce the expected results. There is a high volume of literature on the impact of foreign aid on development in Africa, yet not many of them recognize all the factors that contribute to aid (in) effectiveness. The focus is often on macro-economic indicators which do not fairly represent the realities of poverty and suffering in many African countries. We offer an analysis of the theories that have been propounded to explain the relationship between aid and (under) development in Africa. In this paper, we critically examine such findings Keywords: Corruption; Foreign aid, Economic growth, Sub-Saharan Africa

Curcumin alleviates experimental colitis in mice by suppressing necroptosis of intestinal epithelial cells

Curcumin, the primary bioactive substance in turmeric, exhibits potential therapeutic effects on ulcerative colitis. However, its mechanism for regulating necroptosis in colitis has not been fully elucidated. In this study, the effect of curcumin on experimental colitis-induced necroptosis of intestinal epithelial cells was investigated, and its molecular mechanism was further explored. We found that curcumin blocked necroptosis in a dose-dependent manner by inhibiting the phosphorylation of RIP3 and MLKL instead of RIP1 in HT-29 cells. Co-Immunoprecipitation assay showed that curcumin weakened the interaction between RIP1 and RIP3, possibly due to the direct binding of curcumin to RIP3 as suggested by drug affinity responsive target stability analysis. In a classical in vivo model of TNF-α and pan-caspase inhibitor-induced necroptosis in C57BL/6 mice, curcumin potently inhibited systemic inflammatory responses initiated by the necroptosis signaling pathway. Then, using a dextran sodium sulfate-induced colitis model in C57BL/6 mice, we found that curcumin inhibited the expression of p-RIP3 in the intestinal epithelium, reduced intestinal epithelial cells loss, improved the function of the intestinal tight junction barrier, and reduced local intestinal inflammation. Collectively, our findings suggest that curcumin is a potent targeted RIP3 inhibitor with anti-necroptotic and anti-inflammatory effects, maintains intestinal barrier function, and effectively alleviates colitis injury

Modeling the Commuting Travel Activities within Historic Districts in Chinese Cities

The primary objective of this study is to analyze the characteristics of commuting activities within the historical districts in cities of China. The impacts of various explanatory variables on commuters&apos; travels are evaluated using the structural equation modeling (SEM) approach. The household survey was conducted in the historical districts in Yangzhou, China. Based on the data, various individual and household attributes were considered exogenous variables, while the subsistence activity characteristics, travel times, numbers of three typical home-based trip chains, trip chains, and travel mode were considered as the endogenous variables. Commuters in our study were classified into two main groups according to their working location, which were the commuters in the historic district and those out of the district. The modeling results show that several individual and household attributes of commuters in historic district have significant impacts on the characteristics of travel activities. Additionally, the characteristics of travel activities within the two groups are quite different, and the contributing factors related to commuting travels are different as well