Highly Enhanced Gas Sorption Capacities of N‑Doped Porous Carbon Spheres by Hot NH₃ and CO₂ Treatments

Highly enhanced CO₂ and H₂ adsorption properties were achieved with a series of phenolic resin-based carbon spheres (resorcinol–formaldehyde carbon (RFC) and phenol–formaldehyde carbon (PFC)) by carbonization of RF and PF polymer (RFP and PFP) spheres synthesized via a sol–gel reaction and subsequent activation with hot CO₂ or NH₃ treatment. Monodisperse and size-tunable (100–600 nm) RFC and PFC spheres had intrinsic nitrogen contents (ca. 1.5 wt %), which are attributed to the synthesis conditions that utilized NH₃ as a basic catalyst as well as nitrogen precursor. A series of CO₂-activated and N-doped RFC and PFC spheres showed almost perfect correlation (<i>R</i>² = 0.99) between CO₂ adsorption capacities and accumulated pore volumes of fine micropores (ultramicropore <1 nm) obtained using the nonlocal density functional theory (NLDFT) model. Interestingly, NH₃ activation served not only as an effective method for heteroatom doping (i.e., nitrogen) into the carbon framework but also as an excellent activation process to fine-tune the surface area and pore size distribution (PSD). Increased nitrogen doping levels up to ca. 2.8 wt % for NH₃-activated RFC spheres showed superior CO₂ adsorption capacities of 4.54 (1 bar) and 7.14 mmol g^–1 (1 bar) at 298 and 273 K, respectively. Compared to CO₂-activated RFC spheres with similar ultramicropore volume presenting CO₂ uptakes of 4.41 (1 bar) and 6.86 mmol g^–1 (1 bar) at 298 and 273 K, respectively, NH₃-activated nitrogen-enriched RFC was found to have elevated chemisorption ability. Moreover, prolonged activation of RFC and PFC spheres provided ultrahigh surface areas, one of which reached 4079 m²g^–1 with an unprecedented superb H₂ uptake capacity of 3.26 wt % at 77 K (1 bar), representing one of the best H₂ storage media among carbonaceous materials and metal–organic frameworks (MOFs)

Variation in Crystalline Phases: Controlling the Selectivity between Silicon and Silicon Carbide via Magnesiothermic Reduction using Silica/Carbon Composites

Magnesiothermic reduction of various types of silica/carbon (SiO₂/C) composites has been frequently used to synthesize silicon/carbon (Si/C) composites and silicon carbide (SiC) materials, which are of great interest in the research areas of lithium-ion batteries (LIBs) and nonmetal oxide ceramics, respectively. Up to now, however, it has not been comprehensively understood how totally different crystal phases of Si or SiC can result from the compositionally identical parent materials (SiO₂/C) via magnesiothermic reduction. In this article, we propose a formation mechanism of Si and SiC by magnesiothermic reduction of SiO₂/C; SiC is formed at the interface between SiO₂ and carbon when silicon intermediates, mainly <i>in situ</i>-formed Mg₂Si, encounter carbon through diffusion. Otherwise, Si is formed, which is supported by an <i>ex situ</i> reaction between Mg₂Si and carbon nanosphere that results in SiC. In addition, the resultant crystalline phase ratio between Si and SiC can be controlled by manipulating the synthesis parameters such as the contact areas between silica and carbon of parent materials, reaction temperatures, heating rates, and amount of the reactant mixtures used. The reasons for the dependence on these synthesis parameters could be attributed to the modulated chance of an encounter between silicon intermediates and carbon, which determines the destination of silicon intermediates, namely, either thermodynamically preferred SiC or kinetic product of Si as a final product. Such a finding was applied to design and synthesize the hollow mesoporous shell (ca. 3–4 nm pore) SiC, which is particularly of interest as a catalyst support under harsh environments

Bioinspired Synthesis of Melaninlike Nanoparticles for Highly N‑Doped Carbons Utilized as Enhanced CO₂ Adsorbents and Efficient Oxygen Reduction Catalysts

Highly N-doped nanoporous carbons have been of great interest as a high uptake CO₂ adsorbent and as an efficient metal-free oxygen reduction reaction (ORR) catalyst. Therefore, it is essential to produce porosity-tunable and highly N-doped carbons through cost-effective means. Herein, we introduce the bioinspired synthesis of a monodisperse and N-enriched melaninlike polymer (MP) resembling the sepia biopolymer (SP) from oceanic cuttlefish. These polymers were subsequently utilized for highly N-doped synthetic carbon (MC) and biomass carbon (SC) spheres. An adequate CO₂ activation process fine-tunes the ultramicroporosity (<1 nm) of N-doped MC and SC spheres, those with maximum ultramicroporosities of which show remarkable CO₂ adsorption capacities. In addition, N-doped MC and SC with ultrahigh surface areas of 2677 and 2506 m²/g, respectively, showed excellent ORR activities with a favored four electron reduction pathway, long-term durability, and better methanol tolerance, comparable to a commercial Pt-based catalyst

Phloroglucinol down-regulates lipid peroxidation, protein carbonylation and DNA base modification induced by 6-OHDA treatment in SH-SY5Y cells.

<p>(<b>A</b>) Lipid peroxidation was assayed by determination of 8-isoprostane levels. 8-Isoprostane levels were determined in the culture medium by use of a commercial enzyme immunoassay and were performed according to the manufacturer's instructions. (<b>B</b>) The amount of carbonyl formation in protein was determined using an ELISA kit and expressed as nM. (<b>C</b>) The 8-hydroxyguanine content in DNA was determined using a Bioxytech 8-OHdG-ELISA kit purchased from OXIS Health Products and was performed according to the manufacturer's instructions. Cellular DNA was isolated using the DNAzol reagent and quantified using a spectrophotometer. (ANOVA, <i>post-hoc</i> by Duncan, * <i>p</i><0.05, **<i>p</i><0.01).</p

Phloroglucinol exerts protective effects against 6-OHDA in SH-SY5Y cells.

<p>(<b>A</b>) Cell viability was measured by an MTT assay. SH-SY5Y cells were treated with a range of different concentrations of 6-OHDA (0, 25, 50, 100, and 200 µM of 6-OHDA). The IC₅₀ was determined to be 90 µM 6-OHDA. (<b>B</b>) The cells were pre-treated with phloroglucinol (5, 10, 20, and 40 µg/ml) 1 h before treatment with 6-OHDA. The percentage of cell viability was measured compared to control. (ANOVA, <i>post-hoc</i> by Duncan, * <i>p</i><0.05, **<i>p</i><0.01). (<b>C</b>) Apoptotic bodies (arrows) were observed in cells stained with Hoechst 33342 dye and quantified by fluorescence microscopy. (ANOVA, <i>post-hoc</i> by Duncan, * <i>p</i><0.05, **<i>p</i><0.01).</p

Phloroglucinol attenuates the 6-OHDA-mediated loss of Nrf2 and p-Nrf2 in the nuclear fraction and p-Akt in SH-SY5Y cells and rat brains.

<p>(<b>A</b>) The protein levels of Nrf2 and p-Nrf2 in the ipsilateral midbrain region were assessed with Western blotting. The blot is the representative of the two independent experiments. TATA box binding protein (TBP) was used as a loading control for nuclear fraction. (<b>B</b>) Cells were transfected with an ARE-luciferase construct (1 µg per well). After overnight, cells were treated with phloroglucinol or 6-OHDA, cell lysates were mixed with a luciferase substrate, and the luciferase activity was measured by a luminometer. (ANOVA, <i>post-hoc</i> by Duncan, * <i>p</i><0.05, **<i>p</i><0.01). (<b>C</b>) The protein levels of p-Akt and Akt in the ipsilateral midbrain region were assessed with Western blotting. The blot is the representative of the two independent experiments. The intensity of the bands was measured relative to the amount of Akt in each sample. The relative densitometric value of p-Akt <i>vs.</i> that of Akt is shown in graph.</p

Phloroglucinol reduces the intracellular ROS caused by treatment with 6-OHDA in SH-SY5Y cells.

<p>(<b>A</b>) Cells were seeded in a 96-well plate at 1.5×10⁴ cells/well. After16 h plating, the cells were treated with phloroglucinol at 10 µg/ml. After 1 h, 90 µM of 6-OHDA was added to the plates. The cells were incubated for an additional 24 h at 37°C. After the addition of 25 µM of DCF-DA solution for 10 min, the fluorescence of the DCF was detected using a PerkinElmer LS-5B spectrofluorometer. (<b>B</b>) The intracellular ROS level was evaluated using a flow cytometry as previously described. (<b>C</b>) Microscopic images were collected using laser scanning confocal microscope 5 PASCAL. (ANOVA, <i>post-hoc</i> by Duncan, * <i>p</i><0.05, **<i>p</i><0.01).</p

Phloroglucinol attenuates 6-OHDA-induced loss of dopaminergic neurons and synapses in the midbrain.

<p>(<b>A</b>) (<b>C</b>) Immunoreactivity of TH (red), synaptophysin (green) and DAPI (blue) was evaluated in ipsilateral (A) and contralateral sides (C) of the midbrain of each animal group by IHC, resspectively. All of the slides were examined on a LSM510 confocal microscope. (<b>B</b>) Quantitative analysis of TH immunoreactivity was performed and marked as a percentage of the control group. (<b>D</b>) The protein levels of TH and synaptophysin in the midbrain region were assessed with Western blotting. The relative densitometric value of TH or synaptophysin <i>vs.</i> that of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is shown in graph. (ANOVA, <i>post-hoc by Duncan,*p</i><0.05, <i>**p</i><0.01, *** <i>p</i><0.001).</p

Phloroglucinol ameliorates 6-OHDA induced motor deficits in rats.

<p>(<b>A</b>) All of the animals of the four groups performed seven trials of the accelerated rota-rod test at 2 weeks after administration of vehicle, phloroglucinol, 6-OHDA or 6-OHDA plus phloroglucinol. Animals were placed on the rota-rod treadmill at an accelerating speed from 6 round/min to 30 round/min in 3 min. The latency to fall was measured and three training sessions were performed before each test. Animals were tested with seven trials on a given day. (ANOVA, <i>post-hoc</i> by Duncan, * <i>p</i><0.05). (<b>B</b>) All of the animals of the four groups performed the apomorphine-induced rotation test at 3 weeks after the administration of vehicle, phloroglucinol, 6-OHDA or 6-OHDA plus phloroglucinol. Apomorphine was subcutaneously injected at 0.5 mg/kg, and the rotation was monitored for 60 min using the apparatus described by Ungerstedt and Arbuthnott <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071178#pone.0071178-Ungerstedt1" target="_blank">[9]</a>. The results were expressed as contralateral or ipsilateral net turns/60 min. (ANOVA, <i>post-hoc</i> by Duncan, ** <i>p</i><0.01, ***<i>p</i><0.001).</p

Phloroglucinol attenuates the 6-OHDA-mediated loss of antioxidant enzymes in SH-SY5Y cells and rat brains.

<p>(<b>A</b>) 50 µg of protein was added to 50 mM phosphate buffer (pH 7) containing 100 mM H₂O₂. The reaction mixture was incubated for 2 min at 37°C and the absorbance was monitored at 240 nm for 5 min. The change in absorbance over time was proportional to the breakdown of H₂O₂. The catalase activity was expressed as units/mg protein and one unit of enzyme activity was defined as the amount of enzyme required to breakdown 1 µM of H₂O₂. (<b>B</b>) Protein levels of catalase were evaluated with Western blotting in SH-SY5Y cells. (<b>C</b>) The harvested cells were suspended in 10 mM phosphate buffer (pH 7.5). The cells were centrifuged at 12,000× g for 30 min at 4°C to remove the tissue debris. Glutathione peroxidase activity was determined using the FR 17 assay kit according to the manufacturer's protocol. The enzyme reaction was assessed by adding the substrate, tert-butyl hydroperoxide and was recorded at 340 nm. The rate at which the absorbance (340 nm) decreased is directly proportional to the activity of glutathione peroxidase (expressed in mU/ml). (<b>D</b>) The protein levels of glutathione peroxidase in SH-SY5Y cells were evaluated with Western blotting in SH-SY5Y cells. (<b>E</b>) The protein levels of catalase in the ipsilateral midbrain region were assessed with Western blotting. (<b>F</b>) The protein levels of glutathione peroxidase in the ipsilateral midbrain region were assessed with Western blotting. (ANOVA, <i>post-hoc</i> by Duncan, * <i>p</i><0.05, **<i>p</i><0.01).</p