Co₃O₄@(Fe-Doped)Co(OH)₂ Microfibers: Facile Synthesis, Oriented-Assembly, Formation Mechanism, and High Electrocatalytic Activity

Cobalt oxide or hydroxide nanoarchitectures, often synthesized via solvothermal or electrodeposition or templated approaches, have wide technological applications owing to their inherent electrochemical activity and unique magnetic responsive properties. Herein, by revisiting the well-studied aqueous system of Co/NaBH₄ at room temperature, the chainlike assembly of Co₃O₄ nanoparticles is attained with the assistance of an external magnetic field; more importantly, a one-dimensional hierarchical array consisting of perpendicularly oriented and interconnected Co­(OH)₂ thin nanosheets could be constructed upon such well-aligned Co₃O₄ assembly, generating biphasic core–shell-structured Co₃O₄@Co­(OH)₂ microfibers with permanent structural integrity even upon the removal of the external magnetic field; isomorphous doping was also introduced to produce Co₃O₄@Fe–Co­(OH)₂ microfibers with similar structural merits. The cobalt-chemistry in such a Co/NaBH₄ aqueous system was illustrated to reveal the compositional and morphological evolutions of the cobalt species and the formation mechanism of the microfibers. Owing to the presence of Co₃O₄ as the core, such anisotropic Co₃O₄@(Fe-doped)­Co­(OH)₂ microfibers demonstrated interesting magnetic-responsive behaviors, which could undergo macro-scale oriented-assembly in response to a magnetic stimulus; and with the presence of a hierarchical array of weakly crystallized thin (Fe-doped) Co­(OH)₂ nanosheets with polycrystallinity as the shell, such microfibers demonstrated remarkable electrocatalytic activity toward oxygen evolution reactions in alkaline conditions

Wortmannin, a specific inhibitor of PI3K, enhanced the sensitization of C2C12 myoblast cells to thimerosal-induced apoptosis.

<p><b>A.</b> C2C12 myoblast cells were treated with thimerosal (125 nM, 250 nM and 500 nM) for 24 or 48 h. Cells were lysed, and the expression of Akt and pAkt^Ser473 were assayed by western blot analysis. GAPDH was used as a loading control, and the blots were quantified by densitometry. <b>B.</b> C2C12 myoblast cells were treated with wortmannin at concentrations of 2.5, 5.0 or 10 µM for 24 h. Expression of total Akt and pAkt^Ser473 was assayed by western blot analysis and densitometry. <b>C.</b> Cells were co-treated with thimerosal (250 nM) and wortmannin (5 µM) for 24 h and stained with annexin V-FITC/propidium iodide. The columns illustrate the flow cytometric results. <b>D.</b> After co-treatment, proteins from total cell lysates were separated by SDS-PAGE gel electrophoresis and immunoblotted with antibodies against Akt, pAkt^Ser473, cytochrome c, cleaved caspase-9, cleaved caspase-3 and GAPDH followed by densitometric quantification. Data are means±S.E.M. of values from three independent experiments. **P<0.01 vs. single treatment with 250 nM thimerosal; ## P<0.01 vs. untreated cells.</p

Thimerosal induced apoptosis in C2C12 myoblast cells.

<p>C2C12 myoblast cells were treated with thimerosal (125, 250 and 500 nM) for 24 or 48 h. <b>A.</b> After treatment, cells were stained with Annexin V-FITC/propidium iodide and measured by flow cytometry. The columns illustrate the flow cytometric results. <b>B.</b> After exposure to thimerosal for 48 h, cells were stained with Hoechst 33258 and observed under a fluorescence microscope. The magnification was ×200. <b>C.</b> After treatment, proteins from total cell lysates were separated by SDS-PAGE gel electrophoresis and immunoblotted with antibodies against cytochrome c, cleaved caspase-9, cleaved caspase-3 and GAPDH followed by densitometric quantification. Data are means±S.E.M. of values from three independent experiments. **P<0.01 vs. control.</p

Overexpression of survivin inhibited thimerosal-induced apoptosis in C2C12 myoblast cells.

<p><b>A.</b> C2C12-survivin with overexpression of survivin, C2C12-puro with control vector and normal C2C12 cells (Mock) were subjected to western blot analysis with antibody against survivin followed by densitometric quantification. **P<0.01 vs. C2C12-puro <b>B.</b> C2C12-survivin and C2C12-puro were treated with or without thimerosal (250 nM) for 48 h and stained with Annexin V-FITC/propidium iodide followed by flow cytometry. <b>C.</b> After treatment with or without thimerosal, proteins from C2C12-survivin and C2C12-puro were analyzed by immunoblotting with antibodies against survivin, cytochrome c, cleaved caspase-9, cleaved caspase-3 and GAPDH followed by densitometric quantification. Data are means±S.E.M of the values from three independent experiments. **P<0.01 vs. single treatment with 250 nM thimerosal.</p

The effect of Z-LEHD-FMK and Z-DEVD-FMK on thimerosal-induced apoptosis in C2C12 myoblast cells.

<p>C2C12 cells were treated with Z-LEHD-FMK, an inhibitor of caspase-9, or with the caspase-3 inhibitor Z-DEVD-FMK at a concentration of 50 µM for 24 h and then incubated with or without thimerosal (250 nM) for 48 h. <b>A.</b> After treatment, cells were stained with Annexin V-FITC/propidium iodide followed by flow cytometry. <b>B.</b> After treatment, proteins from total cell lysates were separated by SDS-PAGE gel electrophoresis and immunoblotted with antibodies against cleaved caspase-9, cleaved caspase-3 and GAPDH followed by densitometric quantification. Data are means±S.E.M of the values from three independent experiments. **P<0.01 vs. single treatment with 250 nM thimerosal.</p

Effects of thimerosal on proliferation of C2C12 myoblast cells.

<p>C2C12 myoblast cells were treated with thimerosal (125, 250 and 500 nM) for 24, 48 or 72 h. <b>A.</b> C2C12 myoblast cell viability determined by WST-1. <b>B.</b> Cell cycle distribution of C2C12 myoblast cells analyzed by flow cytometry. <b>C.</b> The percentage of cells in the various phases of the cell cycle. All data are reported as the mean±S.E.M. of three independent experiments. **P<0.01 compared with control.</p

Activation of PI3K/Akt signaling inhibited thimerosal-induced apoptosis in C2C12 myoblast cells.

<p><b>A.</b> C2C12 cells were treated with mIGF-I at concentrations of 25, 50, or 100 ng/mL for 24 h. Expression of total Akt and pAkt^Ser473 was assayed by western blot analysis followed by densitometry. <b>B.</b> Cells were co-treated with thimerosal (250 nM) and mIGF-I (50 ng/mL) for 48 h and stained with Annexin V-FITC/propidium iodide followed by flow cytometry. <b>C.</b> After co-treatment, proteins from total cell lysates were separated by SDS-PAGE gel electrophoresis and immunoblotted with antibodies against Akt, pAkt^Ser473, cytochrome c, cleaved caspase-9, cleaved caspase-3 and GAPDH followed by densitometric quantification. Data are means±S.E.M of values from three independent experiments. **P<0.01 vs. single treatment with 250 nM thimerosal.</p

SiRNA against survivin enhanced the sensitization of C2C12 myoblast cells to thimerosal-induced apoptosis.

<p><b>A.</b> After 48 h transfection with non-targeted (NC) or survivin (S1, S2 and S3) siRNA or mock transfection without siRNA (MOCK), the expression of survivin was assayed by western blot analysis and densitometry. **P<0.01 vs. non-targeted (NC) <b>B.</b> After transfection with non-targeted (NC) or survivin S1 siRNA for 48 h, cells were treated with or without thimerosal (250 nM) for 24 h and stained with Annexin V-FITC/propidium iodide followed by flow cytometry. <b>C.</b> After treatment of siRNA and thimerosal, proteins from total cell lysates were separated by SDS-PAGE gel electrophoresis and immunoblotted with antibodies against survivin, cytochrome c, cleaved caspase-9, cleaved caspase-3 and GAPDH followed by densitometric quantification. Data are means±S.E.M of the values from three independent experiments. **P<0.01 vs. single treatment with 250 nM thimerosal; ## P<0.01 vs. untreated cells.</p

Thimerosal decreases the expression of survivin via the PI3K/Akt pathway.

<p><b>A.</b> C2C12 myoblast cells were treated with thimerosal (125 nM, 250 nM or 500 nM) for 24 or 48 h. Cells were lysed, and the expression of survivin was assayed by western blot analysis and densitometry. GAPDH was used as a loading control. <b>B.</b> C2C12 cells were treated with wortmannin at concentrations of 2.5, 5.0 and 10 µM for 24 h. The expression of survivin was assayed by western blot analysis followed by densitometry. <b>C.</b> Cells were co-treated with thimerosal (250 nM) and mIGF-I (50 ng/mL) for 48 h, and survivin expression was quantitated by western blotting and densitometry. Data are means±S.E.M of the values from three independent experiments.</p

Porous Graphitic Carbon Loading Ultra High Sulfur as High-Performance Cathode of Rechargeable Lithium–Sulfur Batteries

Porous graphitic carbon of high specific surface area of 1416 m² g^–1 and high pore volume of 1.11 cm³ g^–1 is prepared by using commercial CaCO₃ nanoparticles as template and sucrose as carbon source followed by 1200 °C high-temperature calcination. Sulfur/porous graphitic carbon composites with ultra high sulfur loading of 88.9 wt % (88.9%S/PC) and lower sulfur loading of 60.8 wt % (60.8%S/PC) are both synthesized by a simple melt-diffusion strategy, and served as cathode of rechargeable lithium–sulfur batteries. In comparison with the 60.8%S/PC, the 88.9%S/PC exhibits higher overall discharge capacity of 649.4 mAh g^–1_(S–C), higher capacity retention of 84.6% and better coulombic efficiency of 97.4% after 50 cycles at a rate of 0.1<i>C</i>, which benefits from its remarkable specific capacity with such a high sulfur loading. Moreover, by using BP2000 to replace the conventional acetylene black conductive agent, the 88.9% S/PC can further improve its overall discharge capacity and high rate property. At a high rate of 4<i>C</i>, it can still deliver an overall discharge capacity of 387.2 mAh g^–1_(S–C). The porous structure, high specific surface area, high pore volume and high electronic conductivity that is originated from increased graphitization of the porous graphitic carbon can provide stable electronic and ionic transfer channel for sulfur/porous graphitic carbon composite with ultra high sulfur loading, and are ascribed to the excellent electrochemical performance of the 88.9%S/PC