Efficient Metal-Free Electrocatalysts for Oxygen Reduction: Polyaniline-Derived N- and O‑Doped Mesoporous Carbons

The oxygen reduction reaction (ORR)one of the two half-reactions in fuel cellsis one of the bottlenecks that has prevented fuel cells from finding a wide range of applications today. This is because ORR is inherently a sluggish reaction; it is also because inexpensive and sustainable ORR electrocatalysts that are not only efficient but also are based on earth-abundant elements are hard to come by. Herein we report the synthesis of novel carbon-based materials that can contribute to solving these challenges associated with ORR. Mesoporous oxygen- and nitrogen-doped carbons were synthesized from <i>in situ</i> polymerized mesoporous silica-supported polyaniline (PANI) by carbonization of the latter, followed by etching away the mesoporous silica template from it. The synthetic method also allowed the immobilization of different metals such as Fe and Co easily into the system. While all the resulting materials showed outstanding electrocatalytic activity toward ORR, the metal-free, PANI-derived mesoporous carbon (dubbed PDMC), in particular, exhibited the highest activity, challenging conventional paradigms. This unprecedented activity by the metal-free PDMC toward ORR was attributed to the synergetic activities of nitrogen and oxygen (or hydroxyl) species that were implanted in it by PANI/mesoporous silica during pyrolysis

Additional File 5: Figure S5.

Pre-exposing astrocyte cultures to rTNF enhances parasite load in Trypanosoma cruzi-infected astrocytes. C57BL/6 primary astrocyte cultures were seeded, exposed to rTNF and infected as described in Fig. 5a. At 24 and 48 h of infection, the frequencies of infected astrocytes were stratified by classes according to the number of amastigote-like forms harbored in the cytoplasm. Data are presented as means ± SEM of triplicates. *, p < 0.05, **, p < 0.01 untreated (NT) vs. rTNF-treated astrocytes. (TIFF 1045 kb

Additional File 6: Figure S6.

rTNF amplifies the pro-inflammatory profile of human astrocytes exposed to Trypanosoma cruzi infection. Human astrocytes were submitted to treatment with rTNF and left non-infected (NI) or infected by T. cruzi (MOI 1:1). At 4 h of infection, supernatants were collected and submitted to detection of cytokines by CBA. Data are presented as means ± SEM of triplicates. *, p < 0.05, untreated (NT) vs. rTNF-treated astrocytes. (TIFF 1375 kb

Additional File 2: Figure S2.

Astrocytes from neonatal C57BL/6 mice are susceptible to in vitro infection by Trypanosoma cruzi. (a) Monotypic astrocyte cell cultures were allowed to interact during 4 or 24 h with Vero cells-born trypomastigote forms of the Colombian T. cruzi strain, at a MOI of 1:1 or 10:1. (b-e) Astrocyte infected with T. cruzi at a MOI of 1:1 and analyzed after 4 h (b, c, d) or 24 h (e) of interaction. (f) Parasites per 100 cells and frequency of T. cruzi-infected astrocytes after 4 and 24 h of T. cruzi/astrocyte interaction at a MOI of 1:1 or 10:1 Data are presented as means ± SEM of triplicates. *, p < 0.05 and **, p < 0.01 MOI 1:1 vs. MOI 10:1 in each analyzed interval; #, p < 0.05 and ##, p < 0.01 4 h vs. 24 h of infection in each analyzed MOI. (TIFF 1349 kb

Additional File 1: Figure S1.

Primary cell cultures of C57BL/6 cerebral cortex are enriched in astrocytes. CNS cells of seven to ten days of primary culture were seeded at a density of 105 cells per 13-mm-diameter coverslip and analyzed 24 h later. (a, b, c) Giemsa staining reveals cells resembling astrocytes with thin extensions, delicate branches, recognizable nucleoli and cytoplasm lightly stained. (d, e, f) Simultaneous immunohistochemical staining for GFAP and CD11b was used to determine the cell composition of primary astrocyte cultures. (e) Insert showing RAW 264.7 mouse macrophage lineage used as positive control for CD11b staining. (TIFF 1266 kb

Additional File 4: Figure S4.

Pre-treatment of fibroblast with rTNF does not affect infection by Trypanosoma cruzi. (a) Experimental scheme showing that L-929 fibroblasts were pre-treated with TNF (1 ng/mL) and subsequently infected with trypomastigote forms of the Colombian T. cruzi strain. (b-c) The percentage of infected cells and the number of parasites per cells were analyzed at 4 h (b) and 24 h (c) of infection, at a MOI of 1:1 or 10:1. Data are presented as mean ± SEM of duplicates. (TIFF 1430 kb

Additional File 7: Figure S7.

rTNF effects on Trypanosoma cruzi/astrocyte interaction are conserved in primary astrocyte cultures of C3H/He mice. (a) Monotypic primary astrocyte cell cultures of C3H/He mice were seeded, left untreated or treated with rTNF and infected with trypomastigote forms of the Colombian T. cruzi strain at a MOI of 1:1 or 10:1. (b) After 4 h of interaction, the frequencies of infected cells and the number in untreated (NT), rTNF-treated astrocytes are shown. (c) Data show the frequencies of infected astrocytes stratified by classes according to the number of amastigote-like forms harbored in the cytoplasm. Data are presented as means ± SEM of triplicates. *, p < 0.05, ***, p < 0.001 untreated (NT) vs. rTNF-treated astrocytes. #, p < 0.05, ##, p < 0.01, ###, p < 0.001 MOI 1:1 vs. MOI 10:1. (TIFF 1337 kb

Conducting MoS₂ Nanosheets as Catalysts for Hydrogen Evolution Reaction

We report chemically exfoliated MoS₂ nanosheets with a very high concentration of metallic 1T phase using a solvent free intercalation method. After removing the excess of negative charges from the surface of the nanosheets, highly conducting 1T phase MoS₂ nanosheets exhibit excellent catalytic activity toward the evolution of hydrogen with a notably low Tafel slope of 40 mV/dec. By partially oxidizing MoS₂, we found that the activity of 2H MoS₂ is significantly reduced after oxidation, consistent with edge oxidation. On the other hand, 1T MoS₂ remains unaffected after oxidation, suggesting that edges of the nanosheets are not the main active sites. The importance of electrical conductivity of the two phases on the hydrogen evolution reaction activity has been further confirmed by using carbon nanotubes to increase the conductivity of 2H MoS₂

Additional file 1: of Genome-wide association between single nucleotide polymorphisms with beef fatty acid profile in Nellore cattle using the single step procedure

Manhattan plot of the genome-wide association study for fatty acids in Nellore. The X-axis represents the chromosomes, and the Y-axis shows the proportion of genetic variance explained by windows of 10 adjacent SNPs in the following 18 fatty acids: arachidonic, CLA-cis, CLA-trans, docosahexaenoic, eicosatrienoic,myristoleic, MUFA, PUFA, myristic, n6:n3, oleic, omega-3, palmitic, stearic, palmitoleic and PUFA:SFA ratio in Nellore. (ZIP 1395 kb

Additional file 3: Table S1. of Gene expression profile of intramuscular muscle in Nellore cattle with extreme values of fatty acid

Differentially expressed genes for C14:0. Table S2. Differentially expressed genes for C16:0. Table S3. Differentially expressed genes for C18:0. Table S4. Differentially expressed genes for C18:1 cis-9. Table S5.Differentially expressed genes for C18:2 cis-9trans-11. Table S6. Differentially expressed genes for C18:2 cis-6 cis -12 n6. Table S7. Differentially expressed genes for C18:3 n3. Table S8. Differentially expressed genes for SFA. Table S9. Differentially expressed genes for MUFA. Table S10. Differentially expressed genes for PUFA. Table S11. Differentially expressed genes for relationship between PUFA and SFA. Table S12. Differentially expressed genes. Table S13. Differentially expressed genes for n6. Table S14. Differentially expressed genes for the ratio of ω6/ω3. (XLS 486 kb