Single Fe atoms dispersed on hierarchically structured porous carbon (SA‐Fe‐HPC) frameworks are prepared by pyrolysis of unsubstituted phthalocyanine/iron phthalocyanine complexes confined within ...micropores of the porous carbon support. The single‐atom Fe catalysts have a well‐defined atomic dispersion of Fe atoms coordinated by N ligands on the 3D hierarchically porous carbon support. These SA‐Fe‐HPC catalysts are comparable to the commercial Pt/C electrode even in acidic electrolytes for oxygen reduction reaction (ORR) in terms of the ORR activity (E1/2=0.81 V), but have better long‐term electrochemical stability (7 mV negative shift after 3000 potential cycles) and fuel selectivity. In alkaline media, the SA‐Fe‐HPC catalysts outperform the commercial Pt/C electrode in ORR activity (E1/2=0.89 V), fuel selectivity, and long‐term stability (1 mV negative shift after 3000 potential cycles). Thus, these nSA‐Fe‐HPCs are promising non‐platinum‐group metal ORR catalysts for fuel‐cell technologies.
Stay single: Single‐atom catalysts with Fe atoms dispersed on hierarchical porous carbons were prepared by pyrolysis of iron phthalocyanine and unsubstituted phthalocyanine complexes confined within micropores of the porous carbon supports. The resulting catalysts outperformed the commercial Pt/C electrode in alkaline electrolytes and showed an electrocatalytic activity comparable to the commercial Pt/C electrode in acidic media with a better long‐term stability.
Bimetal nitrogen‐doped carbon with both Fe and Co, derived from the pyrolysis carbon of iron and cobalt phthalocyanine‐based conjugated polymer networks, possesses a few‐layer graphene‐like texture ...with hierarchical porosity in meso/micro multimodal pore size distribution. The novel electrocatalyst exhibits Pt‐like catalytic activity and much higher catalytic durability for oxygen reduction.
Replacing precious metal electrocatalysts with high-performance and low-cost nonprecious metal electrocatalysts (NPMCs) is crucial for the commercialization of fuel cell technologies. Herein, we ...present a novel and facile route for synthesis of iron-, cobalt-, and nitrogen-codoped carbon nanopolyhedra electrocatalysts (Fe,Co,N-CNP) by one-step pyrolysis of a new type of Fe/Co bimetal zeolitic imidazolate framework (Fe,Co-ZIF) crystals that were self-assembled by oxygen-free solvothermal reaction of Fe2+ and Co2+ with 2-methylimidazole. During the pyrolysis process, the Fe2+ ions in Fe,Co-ZIF not only effectively inhibit the aggregation of Co nanoparticles but also increase the specific surface area (SSA) and N content of the resultant electrocatalysts. The optimized Fe,Co,N-CNP(0.3) (Fe/Co molar ratio of 0.3 in Fe,Co-ZIF) electrocatalyst exhibited a highly promising activity for oxygen reduction reaction (ORR) with a positive half-wave potential (E 1/2) of 0.875 V (29 mV higher than that of the commercial Pt/C), excellent methanol tolerance, and electrochemical stability in the alkaline electrolyte. Also, Fe,Co,N-CNP(0.3) presents comparable ORR catalytic activity as Pt/C in the acidic electrolyte with E 1/2 of 0.764 V and superior methanol tolerance and electrochemical stability. The outstanding ORR performance of Fe,Co,N-CNP(0.3) is ascribed to the synergistic contribution of homogeneous Fe, Co, and N codoping structure, high SSA, and hierarchically porous structure for rapid mass transport. This novel and rational methodology for controlled synthesis of ZIFs-derived nitrogen-doped porous carbon nanopolyhedras offers new prospects in developing highly efficient NPMCs for ORR.
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•PB nanocubes decorated on N-doped hierarchically porous carbon was synthesized.•PB nanocubes are well distributed on the carbon networks with a high surface area.•The obtained ...PB/NHPC exhibits a remarkable adsorption performance for Cs+.•Cs+ are inserted into PB nanocrystals to generate a new phase after adsorption.
Eliminating the radioactive 137Cs from nuclear waste is critical to the human health and environment. Prussian blue (PB)-based materials are considered as promising adsorbents for the removal of cesium. Herein, we demonstrate a facile strategy to achieve controllable synthesis of PB nanocrystals decorated on nitrogen-doped hierarchically porous carbon (NHPC) derived from cattle bone as adsorbent to remove cesium. The PB nanocrystals with a nanocube morphology are well distributed on NHPC, which is beneficial to increase the reachable surface area during adsorption. The resulting adsorbent exhibits a remarkable adsorption performance with a capacity of 125.31 mg g−1, a superior recyclability with 87 % of initial capacity retained after 5 cycles, and an outstanding adsorption selectivity for cesium. X-ray diffraction, X-ray photoelectron spectroscopy combined with 57Fe Mössbauer spectroscopy results reveal that cesium ions are inserted into the crystal channels of PB to generate a new phase (CsFe2(CN)6·3H2O) after adsorption. Moreover, the adsorption process is spontaneous and endothermic which can be described by the Langmuir isotherm and pseudo-second-order kinetic models. This strategy for synthesis of PB/carbon adsorbents offers efficient candidate for removal of 137Cs from wastewater.
A rational and effective strategy for the synthesis of a high‐performance non‐precious metal electrocatalyst for oxygen reduction reaction (ORR) was developed by inducing reconstruction of Fe‐Nx site ...on pig‐bone‐derived nitrogen‐doped hierarchically porous carbon. The resultant Fe/N‐doped carbon electrocatalyst possessed abundant atomically dispersed non‐planar Fe‐N4 ORR active sites, with absolute presence of active D1 (FeII‐N4) and D3 (N‐FeII‐N2+2) sites, as well as large specific surface area and three‐dimensional porous structure with hierarchical micro‐/meso‐/macro‐pore distribution, which increased the utilization of active sites and promoted mass transport of ORR reactants. This resulted in a remarkably superior ORR activity with half‐wave potential of 0.87 V (20 mV higher than Pt/C) and kinetic current density of 10.9 mA cm−2 at 0.85 V (2.3‐fold of Pt/C) in alkaline electrolyte. This methodology provides a route for atomic‐level design of high‐performance ORR electrocatalyst.
Iron man: High‐performance atomically dispersed Fe/N‐doped porous carbon electrocatalyst for oxygen reduction reaction was synthesized by inducing atomic‐level reconstruction of Fe‐N4 site.
Tumor-associated macrophages (TAMs) have been proven to be a driving force in the initiation, proliferation, metastasis and angiogenesis of various tumors. Specifically, alterations in the functions ...of TAMs exhibited inhibitory effects on tumor growth. However, there is currently no research being conducted on the targeting delivery of drugs into TAMs for cell-specific tumor immunotherapy. In the present study, we developed a TAMs targeted delivery system that is triggered by the acidic microenvironment in the tumor to release a TAMs-recognizing nano-complex loaded with oligonucleotides. By using this system, we demonstrated a significant anti-tumor effect of an oligonucleotide combination of CpG oligonucleotide, anti-IL-10 and anti-IL-10 receptor oligonucleotides. These nucleic acid drugs delivered by the delivery system accumulated in the TAMs of an allograft hepatoma murine model by intravenous injection, suppressed the pro-tumor functions and stimulated the anti-tumor activities of TAMs. More importantly, the nucleic acid drug-based immune-regulation was restricted to the tumor microenvironment and did not cause an upregulation of serum inflammatory cytokines. Our present study provides an effective therapeutic strategy for regulating cell-specific functions using nucleic acid drugs.
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Electromagnetic waves carrying orbital angular momentum (OAM) can be applied in various regions. Much research endeavor has been devoted to developing broadband and polarization-insensitive OAM beams ...that are preferred in many intriguing applications. This work reports a broadband polarization-insensitive millimeter-wave OAM generator based on high-refractive-index brick-shaped dielectric resonators and studies the relationship between the permittivity of the bricks and OAM beam bandwidth. Based on proper design of the resonators, the broadband, polarization-insensitive, and full phase control can be realized in a broad millimeter-wave band. It is also found that the resonator with higher permittivity leads to a wider OAM beam bandwidth. This structure and conclusion can find a variety of applications in imaging, lithography, and information processing.
Sustained activation of hepatic stellate cells (HSCs) leads to hepatic fibrosis, which is characterized by excessive collagen production, and for which there is no available drug clinically. Despite ...tremendous progress, the cellular activities underlying HSC activation, especially the driving force in the perpetuation stage, are only partially understood. Recently, microRNA-21 (miR-21) has been found to be prevalently up-regulated during fibrogenesis in different tissues, although its detailed role needs to be further elucidated. In the present study, miR-21 expression was examined in human cirrhotic liver samples and in murine fibrotic livers induced by thioacetamide or carbon tetrachloride. A dramatic miR-21 increase was noted in activated HSCs. We further found that miR-21 maintained itself at constant high levels by using a microRNA-21/programmed cell death protein 4/activation protein-1 (miR-21/PDCD4/AP-1) feedback loop. Disrupting this loop with miR-21 antagomir or AP-1 inhibitors significantly suppressed fibrogenic activities in HSCs and ameliorated liver fibrosis. In contrast, reinforcing this loop with small interfering RNA (siRNA) against PDCD4 promoted fibrogenesis in HSCs. Further analysis indicated that the up-regulated miR-21 promoted the central transforming growth factor-β (TGF-β) signaling pathway underlying HSC activation. In summary, we suggest that the miR-21/PDCD4/AP-1 autoregulatory loop is one of the main driving forces for hepatic fibrosis progression. Targeting this aberrantly activated feedback loop may provide a new therapeutic strategy and facilitate drug discovery against hepatic fibrosis.
Background: MicroRNA-21 is important in hepatic fibrosis development, but the mechanism is unclear.
Results: MicroRNA-21 is predominantly up-regulated in activated hepatic stellate cells and could form a double negative feedback loop that links fibrogenic machinery.
Conclusion: The microRNA-21-mediated loop is a main driving force for hepatic fibrosis progression.
Significance: It suggests a mechanism for how microRNA-21 contributes to hepatic fibrosis.
L-Theanine, a green tea amino acid derivative, has cardiovascular qualities. The focus of the current evaluation was to examine the suppression of L-theanine on cultured vascular smooth muscle cell ...(VSMC) proliferation and migration that is prompted by angiotensin II (Ang II). The VSMCs were treated with non-cytotoxic concentrations of L-theanine and then stimulated with Ang II. The CCK-8 and Transwell chamber assays were monitored on the proliferation and migration rate, respectively. We discovered that L-theanine (50 and 100 µM) significantly halted Ang II-induced VSMC proliferation and migration. This was joined by a decline in the amount of cyclin D1. An additional discovery was that L-theanine lowered the proportion of S-phase cells, whereas the number of G1/G0-phase cells in Ang II-stimulated VSMCs was elevated, based on flow cytometry. Western blotting analyses indicated that L-theanine had no impact on extracellular-signal-regulated kinase 1/2 (ERK1/2) activation prompted by Ang II. Nevertheless, L-theanine significantly lowered Ang II-prompted phosphorylation of Janus kinase 2 (JAK2), c-Src tyrosine kinase, and signal transducer and activators of transcription 3 (STAT3). The outcomes revealed that L-theanine subdued the Ang II-prompted proliferation and migration of VSMC, partly via the obstruction of the JAK/STAT3 pathway instead of via just the ERK pathway.
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