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Hollow red cell-like Na2Ti3O7/nitrogen-doped carbon are synthesized by a template-self strategy.

Uranium extraction from radioactive nuclear waste is vital for sustainable energy supply and ecological security. Herein, a polyethyleneimine-chitosan composite microspheres n-PEI/ECH-CTS (n = 0.1, 0.2, 0.3, 0.4, 0.5) were synthetized for efficient and selective uranium adsorption. The prepared chitosan microspheres with uniform size, uniform dispersion and good mechanical strength combine cost-effectiveness and environmental benefits. The 0.4-PEI/ECH-CTS exhibits the highest adsorption capacity of 380.65 mg g

The thermal annealing method is regarded as a general and promising method for preparation of carbon-based electrocatalysts. However, this method always suffers from complex and harsh preparative c...

In order to enhance the catalytic performance of the Gd-modified Co

Developing advanced hydrogen evolution reaction (HER) electrocatalysts is of great significance. Herein, we report porous rodlike cobalt–nickel bimetal nitrides (CoxNiyN) as high-efficiency HER electrocatalysts in a wide pH range through nitridation from a bimetal–organic framework (MOF-74) precursor. Thanks to collaborative superiorities of high surface areas, abundant mesoporous structure, perfect metal element dispersion, and electron modulation effect, the as-prepared CoxNiyN possess a superior catalytic ability toward HER at all pH values. In particular, the optimal Co2Ni1N requires overpotentials of 102.6 and 92.0 mV to afford a current density of 10 mA cm–2 in alkaline and acidic solution, respectively. In addition, it also presents favorable activity in neutral media and excellent stability under different pH conditions. The present study not only offers a strategy for the design and synthesis of porous bimetal nitrides derived from binuclear MOF but also brings up new avenues for the development ...

Designing high-efficiency electrocatalysts for luteolin detection is essential and vital in biological and medical field. Herein, CuCo coated nitrogen-enriched porous carbon polyhedron (CuCo@NPCP) materials are fabricated as a highly sensitive electrochemical luteolin sensor by simple and mild approach. As characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, N2 adsorption-desorption isotherms and electrochemical methods, CuCo@NPCP materials possess high specific surface area, 3D porous framework, amounts of available active sites, which all contribute to the adsorption and catalysis for luteolin. Meanwhile, vast mesoporous structure of CuCo@NPCP further affords more mass transport channels and enhances the mass transfer capacity. Thanks to above-mentioned characteristics, optimal Cu1Co3@NPCP presents superior analytical performance: a wide linear range from 0.2 nM to 2.5 μM, a ultrahigh sensitivity of 134.57 μA μM−1 surpassing to other reported catalysts previously, a low detection limit of 0.08 nM, as well as satisfactory selectivity, reproducibility, and long-term stability. This work offers an attractive catalyst derived from MOFs for constructing effective luteolin sensors.

Imidazolium-based ionic liquids (ILs) are a promising candidate for efficient separation of radioactive pertechnetate (TcO

Rational design and synthesis of multifunctional electrocatalysts with high-efficient activity and robust stability toward the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are highly desirable, but remain a challenging step. Herein, a novel hollow bimetallic carbide/nitrogen-doped carbon nanotube (Co6Mo6C2@NCNT) is successfully synthesized through the simple pyrolysis of polypyrrole (PPy)-supported metal-organic framework (MOF) composite. Remarkable characteristics of the large surface area, hollow and porous structure, rich active sites and synergistic effect between Co6Mo6C2 and NCNT arouse high catalytic efficiency. Notably, the Co6Mo6C2@NCNT presents excellent ORR catalytic activity (a high half-wave potential of 0.875 V vs. reversible hydrogen electrode (RHE) and diffusion-limited current density of 6.22 mA cm−2) via a four-electron pathway, together with outstanding stability and methanol tolerance over commercial Pt/C in 0.1 M KOH solution. The composite also exhibits superior HER performance, delivering a low overpotential of 122.14 mV at current density of 10 mA cm−2, as well as good catalytic performance for OER in 1.0 M KOH solution. This work may provide some insight in design multifunctional electrocatalysts derived from MOF with advanced performance for sustainable energy technologies.

Imidazolium-based ionic liquids (ILs) are a promising candidate for efficient separation of radioactive pertechnetate (TcO4-) from nuclear waste. However, their effective fixation, availability of active sites and slow adsorption kinetics remain challenges. Here, we incorporated the bisimidazolium-based ILs into porous metal-organic frameworks (MOFs) via a combination of immersion grinding and in-situ polymerization. 3,3′-divinyl-1,1′(1,4-butanediyl) diimidazolium dichloride is tightly bound inside and outside the porous MOFs matrix by uniform immersion grinding, which facilitates the exposure of more adsorption sites and provides channels for the anions to travel through quickly. Solvent-free polymerization reduces environmental pollution and energy consumption. Notably, the composite P[C4(VIM)2]Cl2@MIL-101 possesses an admirable removal efficiency (673 mg g−1) compared with the pristine poly(ionic liquid)s (215 mg g−1). Meanwhile, it exhibits fast sorption kinetics (92% in 2 min), good β and γ radiation-resistance, excellent regeneration and eminent removal efficiency in high alkaline conditions (83%). These superior traits endow that P[C4(VIM)2]Cl2@MIL-101 effectively separated TcO4- from simulated Hanford Low-activity Waste (LAW) Melter off-gas scrubber solution tested in this work. DFT density functional theory confirms that the strong electrostatic attraction and minimum Gibbs free energy (−6.2 kcal mol−1) achieve high selective adsorption for TcO4-. P[C4(VIM)2]Cl2@MIL-101 demonstrates the considerable potential to remove TcO4- from radioactive contaminants.

Rational synthesis and development of earth-abundant materials with efficient electrocatalytic activity and stability for water splitting is a critical but challenging step for sustainable energy application. Herein, a family of bimetal (CoFe, CoCu, CoNi) embedded nitrogen-doped carbon frameworks is developed through a facile and simple thermal conversion strategy of metal-doped zeolitic imidazolate frameworks. Thanks to collaborative superiorities of abundant M-N-C species, modulation action of secondary metal, cobalt-based electroactive phases, template effect of MOFs and unique porous structure, bimetal embedded nitrogen-doped carbon frameworks materials manifest good oxygen and hydrogen evolution catalytic activity. Especially, after modulating the species and molar ratio of metal sources, optimal Co0.75Fe0.25 nitrogen-doped carbon framework catalyst just requires a low overpotential of 303 mV to achieve 10 mA cm−2 with a low Tafel slope (39.49 mV dec−1) for oxygen evolution reaction, which even surpasses that of commercial RuO2. In addition, the optimal catalyst can function as an efficient bifunctional electrocatalyst for overall water splitting with satisfying activity and stability. This development offers an attractive direction for the rational design and fabrication of porous carbon materials for electrochemical energy applications.

Electrochemical oxygen reduction reaction (ORR) represents a crucial cathodic process of different fuel cells. The development of highly active and stable noble metal-free ORR electrocatalysts remains as one of major challenges. Herein, we report cobalt/nitrogen co-doped porous carbon materials (Co-N-C) from well-designed bimetal-organic frameworks (Zn100-xCox-ZIF) as efficient ORR electrocatalysts in both pH-neutral and alkaline solutions. The compositional and structural features, and the corresponding ORR activity can be tailored by tuning the Zn/Co ratio in the precursor. Remarkable features of large surface-area and suitable graphitization degree and well-dispersed Co-N-C moieties, enable a high catalytic efficiency. The optimized electrocatalyst registers considerable ORR performance with a high half-wave potential of 0.65 V vs RHE and a saturated current density of 5.30 mA cm−2 close to the value of the commercial Pt/C in 0.1 M pH 7.0 PBS, and considerable operational stability and tolerance to glucose. A preliminary one-compartment hybrid glucose/O2 enzymatic biofuel cell, consisting of Co-N-C-10 abiotic cathode and glucose oxidising bioanode, is constructed and tested. Furthermore, Co-N-C also presents reasonable ORR electrocatalytic activity and operational stability in alkaline condition.

In this study, novel ZIF-67@carbon fiber composites were fabricated by a simple and facile approach. In order to explore the influence of carbon fiber structure on enhancing the electrocatalytic efficiency of the ZIF-67, different structural carbon fibers (hollow porous carbon fiber (PCF) and solid carbon fiber (SCF)) were used for preparing ZIF-67/carbon fiber catalysts. ZIF-67/carbon fiber composites were characterized via X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and electrochemical methods. Thanks to excellent hollow structural characteristic of PCF, ZIF-67/PCF possesses more exposed active sites, smaller particle size of ZIF-67, better conductivity, electrochemical stability, more mass transport channels as well as superior electrocatalytic abilities than ZIF-67/SCF. Furthermore, ZIF-67/PCF(1:1) sample-modified glassy carbon electrode presents a linear range to nitrobenzene that is composed by two line segments, i.e. from 0.3 to 50 μM with a sensitivity of 454.7 μA mM-1 and from 50 to 390 μM with a sensitivity of 132.0 μA mM-1, and a low detection limit of 0.16 μM. It also exhibits a wide linear response to l-cysteine in the range of 5-160 μM and 160-1580 μM with a rapidly response within 1.0 s as well as high catalytic rate constant, good stability and anti-interference ability. Our work provides useful information for searching and choosing carbon materials with excellent structure benefit to electrochemical applications.

Transcription factor σ 28 in Chlamydia trachomatis (σ 28 Ct ) plays a role in the regulation of genes that are important for late-stage morphological differentiation. In vitro mutational and genetic screening in Salmonella enterica serovar Typhimurium was performed in order to identify mutants with mutations in region 4 of σ 28 Ct that were defective in σ 28 -specific transcription. Specially, the previously undefined but important interactions between σ 28 Ct region 4 and the flap domain of the RNA polymerase β subunit (β-flap) or the −35 element of the chlamydial hctB promoter were examined. Our results indicate that amino acid residues E206, Y214, and E222 of σ 28 Ct contribute to an interaction with the β-flap when σ 28 Ct associates with the core RNA polymerase. These residues function in contacts with the β-flap similarly to their counterpart residues in Escherichia coli σ 70 . Conversely, residue Q236 of σ 28 Ct directly binds the chlamydial hctB −35 element. The conserved counterpart residue in E. coli σ 70 has not been reported to interact with the −35 element of the σ 70 promoter. Observed functional disparity between σ 28 Ct and σ 70 region 4 is consistent with their divergent properties in promoter recognition. This work provides new insight into understanding the molecular basis of gene regulation controlled by σ 28 Ct in C. trachomatis.

The identification of surface-exposed components of the major outer membrane protein (MOMP) of Chlamydia is critical for modeling its three-dimensional structure, as well as for understanding the role of MOMP in the pathogenesis of Chlamydia-related diseases. MOMP contains four variable domains (VDs). In this study, VDII and VDIV of Chlamydia trachomatis serovar F were proven to be surface-located by immuno-dot blot assay using monoclonal antibodies (MAbs). Two proteases, trypsin and endoproteinase Glu-C, were applied to digest the intact elementary body of serovar F under native conditions to reveal the surface-located amino acids. The resulting peptides were separated by SDS-PAGE and probed with MAbs against these VDs. N-terminal amino acid sequencing revealed: (1) The Glu-C cleavage sites were located within VDI (at Glu61) and VDIII (at Glu225); (2) the trypsin cleavage sites were found at Lys79 in VDI and at Lys224 in VDIII. The tryptic peptides were then isolated by HPLC and analyzed with a matrix-assisted laser desorption/ionization time-of-flight mass spectrometer and a quadrupole-orthogonal-TOF mass spectrometer coupled with a capillary liquid chromatograph. Masses and fragmentation patterns that correlated to the peptides cleaved from VDI and VDIII regions, and C-terminal peptides Ser333–Arg358 and Ser333–Lys350 were observed. This result demonstrated that these regions are surface-exposed. Data derived from comparison of nonreduced outer membrane complex proteolytic fragments with their reduced fractions revealed that Cys26, 29, 33, 116, 208, and 337 were involved in disulfide bonds, and Cys26 and 337, and 116 and 208 were paired. Based on these data, a new two-dimensional model is proposed.

Chlamydia trachomatis is the most common sexually transmitted bacterial disease worldwide. Untreated C. trachomatis infections may cause inflammation and ultimately damage tissues. Here, we evaluated the ability of Andrographolide (Andro), a natural diterpenoid lactone component of Andrographis paniculata, to inhibit C. trachomatis infection in cultured human cervical epithelial cells. We found that Andro exposure inhibited C. trachomatis growth in a dose- and time-dependent manner. The greatest inhibitory effect was observed when exponentially growing C. trachomatis was exposed to Andro. Electron micrographs demonstrated the accumulation of unusual, structurally deficient chlamydial organisms, correlated with a decrease in levels of OmcB expressed at the late stage of infection. Additionally, Andro significantly reduced the secretion of interleukin6, CXCL8 and interferon-γ-induced protein10 produced by host cells infected with C. trachomatis. These results indicate the efficacy of Andro to perturb C. trachomatis transition from the metabolically active reticulate body to the infectious elementary body and concurrently reduce the production of a proinflammatory mediator by epithelial cells in vitro. Further dissection of Andro's anti-Chlamydia action may provide identification of novel therapeutic targets.

Chlamydia trachomatis is the most common bacterial infection of the human reproductive tract globally; however, the mechanisms underlying the adaptation of the organism to its natural target cells, human endocervical epithelial cells, are not clearly understood. To secure its intracellular niche, C. trachomatis must modulate the host cellular machinery by secreting virulence factors into the host cytosol to facilitate bacterial growth and survival. Here we used primary human endocervical epithelial cells and HeLa cells infected with C. trachomatis to examine the secretion of bacterial proteins during productive growth and persistent growth induced by ampicillin. Specifically, we observed a decrease in secretable chlamydial protease-like activity factor (CPAF) in the cytosol of host epithelial cells exposed to ampicillin with no evident reduction of CPAF product by C. trachomatis. In contrast, the expression of CopN and Tarp was downregulated, suggesting that C. trachomatis responds to ampicillin exposure by selectively altering the expression of secretable proteins. In addition, we observed a greater accumulation of outer-membrane vesicles from C. trachomatis in persistently infected cells. Taken together, these results suggest that the regulation of both gene expression and the secretion of chlamydial virulence proteins is involved in the adaptation of the bacteria to a persistent infection state in human genital epithelial cells.

The σ transcription factor confers the promoter recognition specificity of RNA polymerase (RNAP) in eubacteria. Chlamydia trachomatis has three known sigma factors, σ 66 , σ 54 , and σ 28 . We developed two methods to facilitate the characterization of promoter sequences recognized by C. trachomatis σ 28 (σ 28 Ct ). One involved the arabinose-induced expression of plasmid-encoded σ 28 Ct in a strain of Escherichia coli defective in the σ 28 structural gene, fliA . The second was an analysis of transcription in vitro with a hybrid holoenzyme reconstituted with E. coli RNAP core and recombinant σ 28 Ct . These approaches were used to investigate the interactions of σ 28 Ct with the σ 28 Ct -dependent hctB promoter and selected E. coli σ 28 (σ 28 Ec )-dependent promoters, in parallel, compared with the promoter recognition properties of σ 28 EC . Our results indicate that RNAP containing σ 28 Ct has at least three characteristics: (i) it is capable of recognizing some but not all σ 28 EC -dependent promoters; (ii) it can distinguish different promoter structures, preferentially activating promoters with upstream AT-rich sequences; and (iii) it possesses a greater flexibility than σ 28 EC in recognizing variants with different spacing lengths separating the −35 and −10 elements of the core promoter.