WC Nanocrystals Grown on Vertically Aligned Carbon Nanotubes: An Efficient and Stable Electrocatalyst for Hydrogen Evolution Reaction

Single nanocrystalline tungsten carbide (WC) was first synthesized on the tips of vertically aligned carbon nanotubes (VA-CNTs) with a hot filament chemical vapor deposition (HF-CVD) method through the directly reaction of tungsten metal with carbon source. The VA-CNTs with preservation of vertical structure integrity and alignment play an important role to support the nanocrystalline WC growth. With the high crystallinity, small size, and uniform distribution of WC particles on the carbon support, the formed WC–CNTs material exhibited an excellent catalytic activity for hydrogen evolution reaction (HER), giving a η₁₀ (the overpotential for driving a current of 10 mA cm^–2) of 145 mV, onset potential of 15 mV, exchange current density@ 300 mV of 117.6 mV and Tafel slope values of 72 mV dec^–1 in acid solution, and η₁₀ of 137 mV, onset potential of 16 mV, exchange current density@ 300 mV of 33.1 mV and Tafel slope values of 106 mV dec^–1 in alkaline media, respectively. Electrochemical stability test further confirms the long-term operation of the catalyst in both acidic and alkaline media

Photovoltaic Performance Improvement of D–A Copolymers Containing Bithiazole Acceptor Unit by Using Bithiophene Bridges

Two bithiophene-bridged D–A copolymers, PDTSBTBTz and PBDTBTBTz, based on bithiazole acceptor unit and dithienosiole (DTS) or benzodithiophene (BDT) donor unit, were synthesized by the Pd-catalyzed Stille-coupling reaction. The two copolymers exhibit good thermal stability, strong absorption in the visible region, and relatively lower HOMO energy level at ca. −5.10 eV. The hole mobilities of PDTSBTBTz and PBDTBTBTz measured by SCLC method are 1.85 × 10^–3 and 1.77 × 10^–3 cm²/(V s), respectively. Power conversion efficiency (PCE) of the polymer solar cell (PSC) based on PDTSBTBTz: PC₇₀BM (1:1, w/w) was 3.82% with <i>J</i>_sc = 8.68 mA/cm², <i>V</i>_oc = 0.72 V, and FF = 0.611, under the illumination of AM1.5, 100 mW/cm². In contrast, the PCE of the PSC based on PBDTBTBTz:PC₇₀BM (1:1, w/w) reached 4.46% with <i>J</i>_sc = 9.01 mA/cm², <i>V</i>_oc = 0.82 V, and FF = 0.603. These results indicate that bithiophene-bridged D–A copolymers are promising photovoltaic donor materials for the application in PSCs

Micellization of Lactosylammonium Surfactants with Different Counter Ions and Their Interaction with DNA

So far, the studies about the physical chemical properties of sugar-based surfactants have been still unsystematic; most of the studies have been focused on nonionic sugar-based surfactants. In the present work, we studied the micellization of four lactose-based surfactants, with the same headgroup (lactosylammonium) and the same hydrophobic alkyl chain (dodecyl) but different counterions (malonate, adipate, propionate, and hexanoate), at 25.0 and/or 50.0 °C. We found that these four surfactants could decrease the surface tension of water to ca. 30 mN/m. When the number of carboxylate groups in the counterion was the same, the counterion having a shorter alkyl chain could lead to a smaller minimum area per surfactant molecule. Moreover, the surfactants with monocarboxylates as counterions had much lower critical micelle concentrations than those with dicarboxylates as counterions, and the micelles from the former surfactants had a lower counterion binding degree. The lactosylammonium surfactants could bind with DNA, and low content of the surfactant could decrease the CD signal of DNA, while high content of the surfactant could make DNA unfold somewhat

Silver Ions Induce Lateral Etching of Gold Nanorods by K₂PtCl₄

Selective etching is significant for fabrication of novel nanostructures. Here silver ions are introduced to control the lateral etching of gold nanorods by K₂PtCl₄ in a hot solution, producing a number of dumbbell-like PtAu-Au thin gold nanorods. Silver ions control the selective deposition of the reduced Pt⁰ atoms, causing the selective etching of the unprotected Au. The middle diameter of the obtained dumbbell-like nanorods can be adjusted from 12 nm to <10 nm. It is believed that this is an effective method to reduce the diameter of gold nanorods

Selectivity of PEG/Salt Aqueous Two-Phase System Enhanced by Surfactant@MWCNT Composites

Aqueous two-phase systems (ATPS) are considered a new type of green separation system, but their low selectivity to target molecules limits their practical application. In this study, we used surfactant@MWCNT as an adjuvant to improve the selectivity of PEG/(NH4)2SO4 ATPS. The surfactants used include Triton X-100 (TX-100), Tween 80, sodium dodecyl sulfate (SDS), sodium dodecyl benzenesulfonate (SDBS), and bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT). Nine aromatic compounds, including syringic acid, vanillin, tryptophan, phenylalanine, tyrosine, mandelic acid, theophylline, theobromine, and cephalexin, were selected as model extracts. The results showed that the use of the surfactant@MWCNT composite as an adjuvant significantly improved the selectivity of the ATPS toward syringic acid among the nine extracts. Moreover, the selectivity of the ATPS for syringic acid with the TX-100/MWCNT composite as the adjuvant is better than that with the Tween 80/MWCNT composite as the adjuvant, followed by that with the anionic surfactant/MWCNT composite as the adjuvant. The enhanced selectivity of ATPS by the surfactant/MWCNT composite is ascribed to the spatial effect and the electrostatic and hydrophobic interactions between the extract and the surfactant adsorbed on the MWCNT

Lateral Etching of Core–Shell Au@Metal Nanorods to Metal-Tipped Au Nanorods with Improved Catalytic Activity

Selective growth/etching of hybrid materials is very important for the rational synthesis of hierarchical structures and precise modulation of their physical properties. Here, the lateral etching of the core–shell Au@Ag nanorods is achieved by FeCl₃ at room temperature, producing a number of dumbbell-like Ag-tipped Au nanorods. This selective etching at the side of the core–shell nanorods is attributed to the increased reactivity of the side facets, due to less surface passivation of cetyltrimethylammonium bromide. The similar synthetic strategy has also been demonstrated to be successful for the Pd-tipped Au nanorods that have not been reported before, indicating the great potential of this selective etching. The Ag-tipped Au nanorods are examined as a catalyst for the reduction of <i>p</i>-nitrophenol at room temperature. The Ag-tipped Au nanorods exhibit a higher catalytic activity than Au nanorods and core–shell Au@Ag nanorods, which could be attributed to the electronic effect and the unique structure in the Ag-tipped Au nanorods

HDAC inhibitors block the proliferative rate of radial glia cells.

<p>(A). Representative co-staining images showing the BrdU- and BLBP-positive cells in control (A1–A3), TSA-treated (50 nM, A4–A6) and VPA-treated (1 mM, A7–A9) tecta. The BLBP-positive cell bodies reside along the midline of the ventricular layer of the tectum (arrows) with endfeet on the edge of neuropil (arrow heads). The control tectum was outlined with a white dotted line (A3), which was put on TSA- (A6) or VPA-treated (A9) tectum. The TSA- (A6) or VPA-treated (A9) tectum was outlined with a solid line, which is smaller than control tectum (A3). Scale: 50 μm. (B-C) Quantification data showing that the number of BrdU- and BLBP-positive cells were significantly decreased in TSA- or VPA-treated tecta compared to the control. (BrdU: Ctrl, 163.2 ± 7.9, N = 5, TSA, 119.4 ± 9.3, N = 5, VPA, 136.0 ± 5.7, N = 3; BLBP: Ctrl, 179.2 ± 7.2, N = 5, TSA, 137.0 ± 12.2, N = 5, VPA, 109.7 ± 3.5, N = 3; *p<0.05, **p<0.01). (D). Most of BrdU-labeling cells are colocalized to BLBP-positive cells (Control: 82.3% ± 1.2%, N = 5, TSA: 81.4% ± 1.1%, N = 3, VPA: 77.3% ± 3.4%, N = 3).</p

Developmental changes in HDAC1 and colocalization with BLBP in the <i>Xenopus</i> tectum.

<p>(A). Representative immunofluorescent images showing HDAC1 staining in cells of the developing tectum at stages 35 (A1–A4), 42 (A5–A8) and 48 (A9–A12), respectively. Scale: 50 μm. Zoomed in images are demarked by red lines and are shown to the right of each original figure (A4, A8, A12). Scale: 5 μm. Arrow heads indicate cell nuclei stained for DAPI alone, whereas arrows indicate nuclei that also contain HDAC1. (B). Representative immunofluorescent images showing colocalization of HDAC1 and BLBP staining at stages 42 (B1–B4, zoom in: B5–B8), and 48 (B9–B12, zoom in: B13–B16), respectively. Arrow heads indicate the processes of BLBP-stained RGs. Arrows indicate BLBP-staining RGs contain HDAC1. Scale: 50 μm (zoom in: 10 μm).</p

HDAC1 Regulates the Proliferation of Radial Glial Cells in the Developing <i>Xenopus</i> Tectum

<div><p>In the developing central nervous system (CNS), progenitor cells differentiate into progeny to form functional neural circuits. Radial glial cells (RGs) are a transient progenitor cell type that is present during neurogenesis. It is thought that a combination of neural trophic factors, neurotransmitters and electrical activity regulates the proliferation and differentiation of RGs. However, it is less clear how epigenetic modulation changes RG proliferation. We sought to explore the effect of histone deacetylase (HDAC) activity on the proliferation of RGs in the visual optic tectum of <i>Xenopus laevis</i>. We found that the number of BrdU-labeled precursor cells along the ventricular layer of the tectum decrease developmentally from stage 46 to stage 49. The co-labeling of BrdU-positive cells with brain lipid-binding protein (BLBP), a radial glia marker, showed that the majority of BrdU-labeled cells along the tectal midline are RGs. BLBP-positive cells are also developmentally decreased with the maturation of the brain. Furthermore, HDAC1 expression is developmentally down-regulated in tectal cells, especially in the ventricular layer of the tectum. Pharmacological blockade of HDACs using Trichostatin A (TSA) or Valproic acid (VPA) decreased the number of BrdU-positive, BLBP-positive and co-labeling cells. Specific knockdown of HDAC1 by a morpholino (HDAC1-MO) decreased the number of BrdU- and BLBP-labeled cells and increased the acetylation level of histone H4 at lysine 12 (H4K12). The visual deprivation-induced increase in BrdU- and BLBP-positive cells was blocked by HDAC1 knockdown at stage 49 tadpoles. These data demonstrate that HDAC1 regulates radial glia cell proliferation in the developing optical tectum of <i>Xenopus laevis</i>.</p></div

M₃C (M: Fe, Co, Ni) Nanocrystals Encased in Graphene Nanoribbons: An Active and Stable Bifunctional Electrocatalyst for Oxygen Reduction and Hydrogen Evolution Reactions

Transition metal carbide nanocrystalline M₃C (M: Fe, Co, Ni) encapsulated in graphitic shells supported with vertically aligned graphene nanoribbons (VA-GNRs) are synthesized through a hot filament chemical vapor deposition (HF-CVD) method. The process is based on the direct reaction between iron group metals (Fe, Co, Ni) and carbon source, which are facilely get high purity carbide nanocrystals (NCs) and avoid any other impurity at relatively low temperature. The M₃C-GNRs exhibit superior enhanced electrocatalystic activity for oxygen reduction reaction (ORR), including low Tafel slope (39, 41, and 45 mV dec^–1 for Fe₃C-GNRs, Co₃C-GNRs, and Ni₃C-GNRs, respectively), positive onset potential (∼0.8 V), high electron transfer number (∼4), and long-term stability (no obvious drop after 20 000 s test). The M₃C-GNRs catalyst also exhibits remarkable hydrogen evolution reaction (HER) activity with a large cathodic current density of 166.6, 79.6, and 116.4 mA cm^–2 at an overpotential of 200 mV, low onset overpotential of 32, 41, and 35 mV, small Tafel slope of 46, 57, and 54 mV dec^–1 for Fe₃C-GNRs, Co₃C-GNRs, and Ni₃C-GNRs, respectively, as well as an excellent stability in acidic media