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Zinc-air batteries (ZABs) have been considered as one of the most promising energy storage devices to solve the problem of energy crisis and environmental pollution. In this work, we reported the synthesis of nitrogen doped MnO2 (N-MnO2) to replace the noble metal electrocatalysts for air cathode in ZABs. The doped N atoms here introduced more Mn3+ and oxygen vacancies for MnO2, enhancing charge transfer property and accelerating surface intermediate product during the oxygen reduction reaction (ORR). Hence, the best N-MnO2 achieved remarkable electrocatalytic activities towards ORR (half-wave potential of 0.797 V vs. RHE), and reversible oxygen overpotential of around 0.842 V, which is better than or comparable to the Pt/C and Mn-based catalysts reported recently. Moreover, the homemade ZABs based on N-MnO2 showed the maximum power density of 132.8 mW cm-2 and excellent cyclic stability.

Zinc ion hybrid capacitors (ZIHCs) with carbon-based material cathodes have shown considerable potential in many energy-related applications since they have the advantages of supercapacitors and batteries. However, these carbon-based materials still suffer from the limitations of low energy density and poor cycle stability as cathodes in ZIHCs because of their low surface areas and unsatisfied chemical structures. Herein, nitrogen and oxygen dual-doped porous carbon materials were prepared in situ by using the precursors of nature macromolecular chitosan with abundant amino and hydroxyl groups. Due to the developed mesopores, solid structures, and fast redox response from the dual-doped N and O heteroatoms, the prepared ZIHCs based on these novel carbon materials show high specific capacity of 100 mAh g−1, outstanding energy density of 172.24 Wh kg−1 and good stability over 20,000 cycles at large charging/discharging current density of 5 A g−1. These findings will contribute greatly to the development of environmentally friendly Zn-based energy devices.

Novel branch-trunk Ag hierarchical nanostructures were fabricated by hydrothermal process combined with microwave-assisted synthesis. Te nanowires prepared by hydrothermal process were used as template. And then the branch-truck Ag hierarchical nanostructures were constructed on Te nanowires via galvanic replacement reaction with the Te nanowires as the sacrifice temple with microwave-assisted synthesis method. We further investigated the potential application of the obtained hierarchical nanostructures as sensors for the electrochemical analysis of ascorbic acid. Results showed that the as-prepared sensors had a wide linear range of 0.17 μM to 1.80 mM (R = 0.999) and a detection limit of approximately 0.06 μM (S/N = 3). These indicated that the branch-trunk Ag hierarchical nanostructures were excellent candidate materials for sensing applications.

Advanced anode materials for lithium ion batteries are central to the area of electrical energy storage devices. Herein, we have developed a two-step strategy for synthesizing MoS2@polypyrrole (MoS2@PPY) core-shell microspheres. In such a novel architecture, the MoS2 microspheres are homogeneously wrapped by conductive polypyrrole coating forming core-shell microspheres. As a preliminary test, the obtained MoS2@PPY microspheres exhibit greatly enhanced electrochemical performances for lithium storage compared with un-modified MoS2 microspheres. The MoS2@PPY microsphere electrode displays a high specific capacity of 1012 mAh g−1 after 200 cycles at 200 mA g−1 and high rate performance (600 mAh g−1 at 4000 mA g−1). The superior electrochemical performances are attributed to the advantageous combination of hierarchical microsphere structure and conductive PPY coating.

To clarify the biologically significant sequence effect existing in the formation of the pyrimidine-type radicals induced DNA intrastrand cross-links, addition mechanisms between the uridine-5-methyl (˙UCH2), 6-hydroxy-5,6-dihydrothymidine-5-yl (˙T6OH), and 6-hydroxy-5,6-dihydrocytidine-5-yl (˙C6OH) radicals and their 3′/5′ neighboring deoxyguanosines (dG) are explored in the present study employing the model 5′-G(˙UCH2)-3′, 5′-(˙UCH2)G-3′, 5′-G(˙T6OH)-3′, 5′-(˙T6OH)G-3′, 5′-G(˙C6OH)-3′, and 5′-(˙C6OH)G-3′ sequences. It is found that the 5′ G/C8 additions of the three radicals are all simple direct one-step reactions inducing only relatively small structural changes, while a conformational adjustment involving orientation transitions of both nucleobase moieties and twisting of the DNA backbone is indispensable for each 3′ G/C8 addition. Furthermore, markedly positive reaction free energy requirements are estimated for these conformational transformations making the 3′ G/C8 additions of the three radicals thermodynamically much more unfavorable than the corresponding 5′ G/C8 additions. Such essential conformational adjustments along the 3′ G/C8 addition paths that structurally greatly influence the local DNA structures and thermodynamically substantially reduce the addition efficiencies may be the reasons responsible for the differences in the formation yields and biological consequences of the pyrimidine-type radicals induced DNA intrastrand cross-link lesions.

Considering the fact that the efficiency of the uridine-5-methyl radical in producing cytotoxic DNA intrastrand cross-link lesions is greatly higher than that of the uridine-5-yl radical, the radiosensitizing action of 5-(halomethyl)uridines (5-XCH2U, X = F, Cl, or Br) is studied in the present work. It is found that 5-XCH2U has sufficient electron affinity to capture a pre-hydrated or a hydrated electron, and electron attachment leads to significantly facile X− elimination forming the uridine-5-methyl radical. All these three halogenated uridine derivatives are shown to be potential radiosensitizers, with their radiosensitizing abilities increased in an order 5-FCH2U

The development of electrocatalysts with high activity and low cost has attracted growing attentions in recent years. Herein, we reported the Mn-doped CoP nanosheet arrays on flexible activated carbon cloth (Mn–CoP/CC) for the effective oxygen evolution reaction (OER) at low overpotential and high current density. Due to the novel 3D nanostructures of the carbon cloth and doping effect of the Mn element, the Mn doped CoP/CC electrode delivered the best overpotential of 317 mV for water splitting with the current density of 10 mA/cm2, a Tafel slope of ∼65.1 mV/dec, and excellent stability over 16 h in 1.0 mol/L KOH, which is superior or comparable to the most of the reported cobalt-based catalysts. Thus outstanding electrocatalytic performance originates from the Mn doping effect, which resulted in increased surface area and fast charge-transfer. It is believed that these findings would help us to develop high effective and stable electrocatalysts for water splitting.

The state-of-the-art energy storage devices are highly attractive for the ever-worsening energy depletion and environmental deterioration. Among various candidates, supercapacitors (SCs) have been considered as one of the most promising energy storage devices. As the key factors for the development of SCs, the electrode materials have been widely exploited, and great achievements have been made. Among these materials, carbon-fiber materials, such as carbon nanofibers (CNFs), carbon cloths (CCs), and carbon fiber papers (CFPs), are considered as promising candidates as electrodes and support /current-collector for other electrode materials, due to their special physical/chemical properties and structures. This review aims to provide an overview of recent advances and technologies to improve the electrochemical performance of these carbon fiber materials and their composite electrodes, and we will also give out brief current challenges and perspectives for development of these carbon-fiber materials and carbon-fiber-based composite electrode materials.

Porous carbon nanomaterials with significant capacitive performance were successfully prepared through a simple two-step process of thermal-polymerization and carbonization without an additional template. As a result, the as-prepared porous carbon nanomaterials of sample-A and sample-B exhibited an amorphous phase with low graphitization. And sample-A showed a moderate specific surface area of 476.39 m2/g, larger than that of sample-B (280.94 m2/g). The relatively high mass specific capacitance of 205.1 F/g at a scan rate of 5 mV/s and 211 F/g at a current density of 4 A/g was obtained by sample-A, which are higher than those of sample-B (82.6 F/g at 5 mV/s and 78.6 F/g at 4 A/g). Sample-A also showed excellent conductivity and superior cyclic stability with 94.19% capacitance retention after 5000 cycles, which are also higher than those of sample-B. This work proposed a cost-effective, green, and promising strategy for the large-scale preparation of porous carbon nanomaterial electrodes.

The development of Fe 2 O 3 with high conductivity and energy density is crucial for practical utilizations of supercapacitors. Here, we demonstrated the preparation of novel Fe 2 O 3 /graphene oxide paper (Fe 2 O 3 /GP) hybrid electrode for high density supercapacitors. Due to the characteristic features of large surface areas and fast electron transportation, the specific areal capacitance of the Fe 2 O 3 /GP was around 3.08 F cm −2 at the charge-discharge current density of 5 mA cm −2 , which is nearly 14 times of the Fe 2 O 3 /carbon paper (Fe 2 O 3 /CP, 0.22 F cm −2 ). More importantly, the Fe 2 O 3 /GP hybrid electrode also retained about 95% of the initial capacitance after long-term cyclic process. These findings would help us to develop high effective and stable materials for energy storage devices.

A non-enzymatic glucose sensor was fabricated facilely by immobilization of bimetallic Cu 2 O@Pd nanocomposites onto the surface of a pretreated bare glassy electrode via the galvanic replacement reaction. The morphology and composition of the hollow-cubic Cu 2 O@Pd nanocomposites were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD) and inductively coupled plasma optical emission spectrometry (ICP-OES). The electrocatalytic properties of the modified electrode towards glucose oxidation were evaluated by cyclic voltammetry (CV) and chronoamperometry. The hollow-cubic Cu 2 O@Pd nanocomposites modified glassy carbon electrode showed high electrocatalytic activity towards the oxidation of glucose in alkaline media due to the facile mass transport of the hollow-cubic structure and the synergistic and bifunctional effects between Pd and Cu 2 O. Under experimentally optimal conditions, the designed sensor showed a linear range from 0.49 μM to 8.0 mM with a current sensitivity of 19.44 μA mM −1 and a low detection limit of 0.16 μM. Furthermore, high selectivity, favorable reproducibility, and long-term performance stability were observed. In addition, test results demonstrated that optimized electrodes can be applied to determining the glucose in real blood serum samples. All these observations manifest that the hollow-cubic Cu 2 O@Pd nanocomposites modified electrodes are potential candidates for routine glucose analysis.

With the fast-growing populations and development, energy crisis have raised critical requirements for utilization of clean solar energy. Some effective methods to capture and convert the solar energy now include photocatalytic degradation, hydrogen production, dye-sensitized solar cells, and photocatalytic selective reaction of organic compounds and so on. As the key factors for the utilization of solar energy, many photocatalysts have been exploited and great achievements have been made. Ceria (CeO2), which possesses unique 4f electrons, has attracted much interest due to their special electronic and optical structures, outstanding physical and chemical properties. This review aims to provide an overview of present progress on the study of photocatalytic performance of the CeO2 and CeO2-based materials for photo-degradation, solar hydrogen production and photo-selective reactions. We also discuss the factors which affect photocatalytic performance of these photocatalysts, including the morphologies, structure and constitution of the CeO2 and CeO2-based nanomaterials. Moreover, the current challenges and future opportunities of the CeO2 and CeO2-based materials for the capture and conversion of solar energy are also discussed.

Additional file 1: Figure S1. (a) SEM of cross-sectional PAN@TiO2 nanofiber membrane (b) SEM at 10 μm and (c) TEM imagine at 500 nm of PAN@TiO2 nanofiber membrane. (TiO2 content of 3%). Figure S2. EDS image of PAN@TiO2 nanofiber membrane. Figure S3. EDS image of C Kα1 (a) and Ti Kα1 (b). Figure S4. XRD of PAN-TiO2 nanofiber membrane. Figure S5. FTIR of PAN:TiO2 and PAN-co-PMA:TiO2 NFM(Nanofiber Membrane). Figure S6. Simulated polluted air test device. Figure S7. SEM of PAN nanofibers with(a) and without (b) the TiO2, PM2.5 filtration efficiency of PAN nanofibers &PAN:TiO2 nanofibers in Simulated polluted air test device (120min).

Background Brassinosteroids (BRs) have a positive effect on many processes during plant growth and development, and in response to various abiotic stressors. Low-temperature (LT) stress constricts the geographic distribution, growth, and development of wucai (Brassica campestris L. ssp. chinensis var. rosularis Tsen). However, there is little information on the global gene expression of BRs under LT stress in wucai. In this study, the molecular roles of 24-epibrassinolide (EBR) after exogenously application, were explored by RNA sequencing under LT conditions. Results According to the Gene Ontology (GO) term and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, photosynthesis was significantly enriched after spraying EBR under LT. The transcripts encoding the photosystem II (PSII) oxygen-evolving enhancer protein, photosystem I (PSI) subunit, light-harvesting chlorophyll protein complexes I and II, and ferredoxin were up-regulated after the application of EBR. Transcripts encoding several key enzymes involved in chlorophyll biosynthesis were also up-regulated, accompanied by significant differences in the contents of 5-aminolevulinic acid (ALA), porphobilinogen (PBG), protoporphyrin IX (Proto IX), Mg-protoporphyrin IX (Mg-proto IX), protochlorophyllide (Pchl), and photosynthetic pigments. Notably, transcriptional and physiological analyses revealed that under LT stress, plant responses to EBR involved a major reorientation of photosynthesis, as well as porphyrin and chlorophyll metabolism. Conclusion This study explored the role of EBR as an LT stress tolerance mechanism in wucai. At the transcription level, LT tolerance manifests as an enhancement of photosynthesis, and the amelioration of porphyrin and chlorophyll metabolism.

The fast and accurate detection of Carcinoembryonic Antigen (CEA) plays an important role in clinical cancer treatment and therapy. An ultrasensitive photoelectrochemical (PEC) immunosensor for the detection of CEA was constructed using CdSe@BiVO

The genotype WS-1, previously identified from novel wucai germplasm, is tolerant to both low-temperature (LT) and high-temperature (HT) stress. However, it is unclear which signal transduction pathway or acclimation mechanisms are involved in the temperature-stress response. In this study, we used the proteomic method of tandem mass tag (TMT) coupled with liquid chromatography-mass spectrometry (LC-MS/MS) to identify 1022 differentially expressed proteins (DEPs) common to WS-1, treated with either LT or HT. Among these 1022 DEPs, 172 were upregulated in response to both LT and HT, 324 were downregulated in response to both LT and HT, and 526 were upregulated in response to one temperature stress and downregulated in response to the other. To illustrate the common regulatory pathway in WS-1, 172 upregulated DEPs were further analyzed. The redox homeostasis, photosynthesis, carbohydrate metabolism, heat-shockprotein, and chaperones and signal transduction pathways were identified to be associated with temperature stress tolerance in wucai. In addition, 35S:BcccrGLU1 overexpressed in Arabidopsis, exhibited higher reduced glutathione (GSH) content and reduced glutathione/oxidized glutathione (GSH/GSSG) ratio and less oxidative damage under temperature stress. This result is consistent with the dynamic regulation of the relevant proteins involved in redox homeostasis. These data demonstrate that maintaining redox homeostasis is an important common regulatory pathway for tolerance to temperature stress in novel wucai germplasm.

The genotype WS-1, previously identified from novel wucai germplasm, is tolerant to both low-temperature (LT) and high-temperature (HT) stress. However, it is unclear which signal transduction pathway or acclimation mechanisms are involved in the temperature-stress response. In this study, we used the proteomic method of tandem mass tag (TMT) coupled with liquid chromatography-mass spectrometry (LC-MS/MS) to identify 1022 differentially expressed proteins (DEPs) common to WS-1, treated with either LT or HT. Among these 1022 DEPs, 172 were upregulated in response to both LT and HT, 324 were downregulated in response to both LT and HT, and 526 were upregulated in response to one temperature stress and downregulated in response to the other. To illustrate the common regulatory pathway in WS-1, 172 upregulated DEPs were further analyzed. The redox homeostasis, photosynthesis, carbohydrate metabolism, heat-shockprotein, and chaperones and signal transduction pathways were identified to be associated with temperature stress tolerance in wucai. In addition, 35S:BcccrGLU1 overexpressed in Arabidopsis, exhibited higher reduced glutathione (GSH) content and reduced glutathione/oxidized glutathione (GSH/GSSG) ratio and less oxidative damage under temperature stress. This result is consistent with the dynamic regulation of the relevant proteins involved in redox homeostasis. These data demonstrate that maintaining redox homeostasis is an important common regulatory pathway for tolerance to temperature stress in novel wucai germplasm.

Boosting electrochemical sodium storage properties is achieved by utilizing functionalized N-doped carbon nanotube arrays (NCNAs) as anode materials. The NCNA anodes are first fabricated by self-polymerization of dopamine on cobalt hydroxide nanorod arrays as the template. The NCNAs with diameters of 100-120 nm are grown vertically to Ni foam, forming self-supported nanotube arrays. Such a structure has attractive advantages including large porosity and surface area, good electrical conductivity and mechanical strength. Consequently, the NCNAs are demonstrated to achieve excellent sodium storage performances with high capacity (335 mA h g

Chlorophyll is a vital photosynthetic pigment that plays a key role in plant development, participating in light energy capture and energy conversion. In this study, a novel wucai ( Brassica campestris L.) germplasm with green outer leaves and yellow inner leaves at the adult stage (W7-2) was used to examine chlorophyll metabolism response to cold acclimation. A green leaf wucai genotype without leaf color changes named W7-1 was selected as the control to evaluate the chlorophyll metabolism changes of W7-2. Compared to W7-1, the contents of chlorophyll a (Chl a) and chlorophyll b (Chl b) in W7-2 were significantly reduced at five developmental stages (13, 21, 29, 37, and 45 days after planting (DAP)). An iTRAQ-based quantitative proteomic analysis was carried out at 21 and 29 DAP according to the leaf color changes in both of genotypes. 1409 proteins were identified, while 218 of them displayed differential accumulations between W7-2 and W7-1 during the two developmental stages. The differentially expressed proteins (DEPs) mainly assigned to chlorophyll biosynthesis, photosynthesis, carbohydrate metabolism, ribosome metabolism and posttranslational modification. Among these DEPs, NADPH-protochlorophyllide oxidoreductase (PORB) and Mg-protoporphyrin IX chelatase 1 (CHLI1) were the key enzymes participating in chlorophyll (Chl) biosynthesis, which was down-regulated at 21 DAP and up-regulated at 29 DAP in W7-2 compared with W7-1, respectively. The expression analysis of genes of three subunits of Mg-chelatase ( CHLI1, CHLD, and CHLH), Genomes Uncoupled 4 ( GUN4), and Thioredoxin ( TRX3) associated with chlorophyll metabolism also displayed significant down-regulation in W7-2. In particular, PORB showed significant up-regulation in W7-2, significantly affecting chlorophyll biosynthesis. Additionally, differences in chlorophyll metabolism between W7-2 and W7-1 were in terms of altered photosynthesis, carbohydrate, and energy metabolism. We found that the transcription levels of most photosynthesis proteins showed significantly lower levels, and the genes expression level, associated with carbohydrate and energy metabolism, were lower in W7-2 than in W7-1. Therefore, the present study results help understand the physiological and molecular mechanisms underlying leaf coloring responding to cold acclimation.

Particulate matter is one of the main pollutants, causing hazy days, and it has been serious concern for public health worldwide, particularly in China recently. Quality of outdoor atmosphere with a pollutant emission of PM2.5 is hard to be controlled; but the quality of indoor air could be achieved by using fibrous membrane-based air-filtering devices. Herein, we introduce nanofiber membranes for both indoor and outdoor air protection by electrospun synthesized polyacrylonitrile:TiO2 and developed polyacrylonitrile-co-polyacrylate:TiO2 composite nanofiber membranes. In this study, we design both polyacrylonitrile:TiO2 and polyacrylonitrile-co-polyacrylate:TiO2 nanofiber membranes with controlling the nanofiber diameter and membrane thickness and enable strong particulate matter adhesion to increase the absorptive performance and by synthesizing the specific microstructure of different layers of nanofiber membranes. Our study shows that the developed polyacrylonitrile-co-polyacrylate:TiO2 nanofiber membrane achieves highly effective (99.95% removal of PM2.5) under extreme hazy air-quality conditions (PM2.5 mass concentration 1 mg/m3). Moreover, the experimental simulation of the test in 1 cm3 air storehouse shows that the polyacrylonitrile-co-polyacrylate:TiO2 nanofiber membrane (1 g/m2) has the excellent PM 2.5 removal efficiency of 99.99% in 30 min.

People are increasingly concerned about the nutritional value of the foods they consume, and consequently the best cultivation practices are needed to produce crops that contain high functional nutrients [1].

The development of highly efficient and inexpensive electrocatalysts has attracted great attention due to the large demand for renewable energy conversion devices. Magnetite-based electrocatalyst, which is stable in natural environment, has been widely considered as one of the most promising candidates. However, its electrocatalytic performance is still unsatisfactory because it has the characteristics of large resistance and large energy barriers to form intermediate species during water oxidation. In this report, we demonstrate a convenient method to synthesize Fe3O4/FeS2 NP catalyst from MIL-101(Fe) for oxygen evolution reaction and zinc-air batteries. The Fe3O4/FeS2 NP catalyst shows outstanding activity with lower overpotential of 265 mV to reach the current density of 10 mA cm−2, which is better than or comparable to the recently reported Fe-based or Co-based catalysts. Systematic research reveals that thus enhancement can be ascribed to the increase of electrochemically active surface areas and the decrease of bonding energy of intermediates. Based on thus novel Fe3O4/FeS2 NP electrodes, the as-prepared zinc-air batteries can achieve specific capacity of around 560 mAh gZn −1 and impressive cyclic stability. It is believed that these findings would help us to develop high-performance and sustainable electrocatalysts.

Tungsten disulfide (WS2) has been emerging as an attractive electrode material for supercapacitors because of its intrinsically layered structure and high capacitance. Unfortunately, most of the currently developed WS2-based electrodes suffer from poor conductivity and fast capacitance fading. In this work, we demonstrated that the durability of WS2 nanosheets can be remarkably boosted via improving their crystallinity and the first example of using these WS2 nanosheets as a high-energy and stable negative electrode for flexible asymmetric supercapacitors (ASCs). Electrochemical results reveal the WS2 nanosheets with enhanced crystallinity were able to deliver an excellent durability with more than 82% capacitance retention after 10 000 cycles and an areal capacitance of 0.93 F cm−2 at 4 mA cm−2. Importantly, when using the as-prepared WS2 nanosheets as a negative electrode, a flexible and stable ASC device with an extraordinary volumetric energy density of 0.97 mW h cm−3 is obtained. This work affords new opportunities to use WS2 nanostructures and other 2D TMDs in constructing high-performance energy-storage devices.

Currently, all known DNA intrastrand cross-links are found to be induced by pyrimidine-type radicals; however, whether or not purine-type radicals are able to cause DNA intrastrand cross-links remains unclear. In the present study, probable additions of the highly reactive deoxyguanosine-8-yl radical to its 3'/5' neighboring pyrimidine nucleotides in four model compounds, 5'-G˙T-3', 5'-TG˙-3', 5'-G˙C-3', and 5'-CG˙-3', were studied using density functional theory (DFT) methods. In single-stranded DNA, the deoxyguanosine-8-yl radical is preferred to efficiently attack the C5 site of its 3' neighboring deoxythymidine or deoxycytidine, forming the G[8-5]T or G[8-5]C intrastrand cross-link rather than the C6 site forming the G[8-6]T or G[8-6]C intrastrand cross-link. The four corresponding sequence isomers, namely T[5-8]G, T[6-8]G, C[5-8]G, and C[6-8]G, formed by additions of deoxyguanosine-8-yl radical to its 5' neighboring pyrimidine nucleotides are predicted to be formed inefficiently. In double-stranded DNA, considering the detrimental effects of stabilizing weak interactions on related structural adjustments required in each addition reaction path, relatively lower reaction yields are suggested for the G[8-5]T and G[8-5]C intrastrand cross-links, while the formation of the other six intrastrand cross-links becomes quite difficult. All calculations definitely demonstrate that, in addition to pyrimidine-type radicals, the purine-type deoxyguanosine-8-yl radical is able to attack its 3'/5' neighboring pyrimidine nucleotides forming several DNA intrastrand cross-links.

Pyrimidine-type radicals have been demonstrated to be able to attack their 3′ or 5′ neighboring purine nucleotides forming diverse DNA intrastrand cross-links, but whether or not these radicals can attack their surrounding pyrimidine nucleotides forming pyrimidine–pyrimidine type DNA intrastrand cross-links remains unclear. To resolve this question, probable additions of the uracil-5-methyl (˙UCH2) radical to the C5C6 double bond of its 3′/5′ neighboring pyrimidine nucleotides in the four models, 5′-T(˙UCH2)-3′, 5′-C(˙UCH2)-3′, 5′-(˙UCH2)T-3′, and 5′-(˙UCH2)C-3′, are explored in the present work employing density functional theory (DFT) methods. The C6 site of its 5′ neighboring thymidine is the preferred target for ˙UCH2 radical addition, while additions of the ˙UCH2 radical to the C6 and C5 sites of its 5′ neighboring deoxycytidine are found to be competitive reactions. The ˙UCH2 radical can react with both the C6 and C5 sites of its 3′ neighboring pyrimidine nucleotides, but the efficiencies of these reactions are predicted to be much lower than those of the corresponding addition reactions to its 5′ neighboring pyrimidine nucleotides, indicating the existence of an obvious sequence effect. All the addition products could be finally transformed into closed-shell intrastrand cross-links, the molecular masses of which are found to be exactly the same as certain MS values determined in a recent study of an X-irradiated deoxygenated aqueous solution of calf thymus DNA. The present study thus not only definitely corroborates the fact that the reactive ˙UCH2 radical can attack its 3′/5′ neighboring pyrimidine nucleotides forming several pyrimidine–pyrimidine type DNA intrastrand cross-links, but also provides a plausible explanation for the identities of these structurally unknown intrastrand cross-links.

High levels of iron–nitrogen doped porous carbon materials are obtained from MOF-253 using a step-by-step post-synthetic modification strategy. MOF-253 possessing open 2,2′-bipyridine nitrogen sites not only serves as a precursor but also provides chelate bonding sites for Fe2+. Followed by further impregnation of 1,10-phenanthroline, high surface area porous carbon materials are obtained. For comparison, when iron-1,10-phenanthroline species as a whole are incorporated into MOF-253, carbon materials with less active sites and low surface area are obtained. The porous carbon materials derived from MOF-253 by using a step-by-step post-synthetic modification strategy demonstrate excellent ORR activity, high selectivity (direct 4e− reduction of oxygen to water) and stability under both alkaline and acidic conditions. The onset potential of the porous carbon material under alkaline conditions (980 mV) is the same as that of Pt/C (20 wt%) (980 mV) and the half-wave potential (E1/2) is 840 mV, which is 20 mV more than that of Pt/C (20 wt%). Under acidic conditions, the onset potential and the half-wave potential are only 20 mV and 30 mV less than those of Pt/C (20 wt%). The developed step-by-step post-synthetic modification route of MOFs has expanded the ways to prepare functionalized porous carbon for energy related applications.

Rechargeable zinc-air batteries are promising next-generation energy storage systems due to their large energy density and high safety. However, air-cathodes based on Pt/C and RuO2 suffer from poor catalytic activity and stability in rechargeable zinc-air batteries. Here, we report novel bifunctional Fe7S8/Fe2N nanoparticle (Fe7S8/Fe2N NPs) electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) by carbonizing the metal-organic framework precursors. Due to the synergistic function between the Fe7S8 and Fe2N with high conductivity and high electrochemical stability, the Fe7S8/Fe2N NPs show outstanding OER and ORR electrocatalytic activities versus precious metal catalysts and pristine Fe2N nanoparticles. Prototype liquid and solid-state zinc-air batteries were also fabricated, and they both show significant rechargeable activities and cyclic stability.

At the density functional theory (DFT) level, addition reactions between the guanine-8-yl radical and its 3'/5' neighboring purine deoxynucleosides forming the purine-purine type intrastrand cross-links were studied. It is found that addition of the guanine-8-yl radical to the C8 site of its 5' neighboring deoxyguanosine or deoxyadenosine is a two-step reaction consisting of a structurally relatively unfavourable conformational transformation step, while the corresponding 3' C8 addition is straightforward and kinetically more efficient. The 3' C8 preference of the guanine-8-yl radical additions indicates the existence of an obvious sequence effect, which is completely opposite to that observed in the formation of pyrimidine radicals induced DNA intrastrand cross-links. The detrimental effects from steric hindrance and stabilizing weak interactions make these addition reactions markedly suppressed in double stranded DNA. This work broadens our knowledge about the possible types of DNA intrastrand cross-links.

Additional file 10: Table S6. Primers of photosynthesis genes.

The authors describe a simplified chemical precipitation method and silver mirror reaction to synthesize a nanocomposite consiting of silver nanoparticles on a thin and porous nickel oxide film. Placed on a glassy carbon electrode (GCE), it allows for the determination of levofloxacin (LEV) via square wave voltammetry (SWV). Under optimal detection conditions, the voltammetric signal (typically measured at around 0.96 V vs. SCE) increases linearly in the 0.25-100 μM LEV concentration range. And the detection limit was calculated as 27 nM (at S/N = 3). The sensor is highly selective, stable and repeatable. It was applied to the determination of LEV in spiked human serum samples, and the satisfactory results confirm the applicability of this sensor to practical analyses. Graphical abstract Schematic of a two-step method to synthesize a nanocomposite consisting of nickel oxide porous thin-film supported silver nanoparticles. The composite was used for improved voltammetric determination of levofloxacin.

The development of high-capacity, Earth-abundant, and stable cathode materials for robust aqueous Zn-ion batteries is an ongoing challenge. Herein, ultrathin nickel cobaltite (NiCo2 O4 ) nanosheets with enriched oxygen vacancies and surface phosphate ions (P-NiCo2 O4-x ) are reported as a new high-energy-density cathode material for rechargeable Zn-ion batteries. The oxygen-vacancy and surface phosphate-ion modulation are achieved by annealing the pristine NiCo2 O4 nanosheets using a simple phosphating process. Benefiting from the merits of substantially improved electrical conductivity and increased concentration of active sites, the optimized P-NiCo2 O4-x nanosheet electrode delivers remarkable capacity (309.2 mAh g-1 at 6.0 A g-1 ) and extraordinary rate performance (64% capacity retention at 60.4 A g-1 ). Moreover, based on the P-NiCo2 O4-x cathode, our fabricated P-NiCo2 O4-x //Zn battery presents an impressive specific capacity of 361.3 mAh g-1 at the high current density of 3.0 A g-1 in an alkaline electrolyte. Furthermore, extremely high energy density (616.5 Wh kg-1 ) and power density (30.2 kW kg-1 ) are also achieved, which outperforms most of the previously reported aqueous Zn-ion batteries. This ultrafast and high-energy aqueous Zn-ion battery is promising for widespread application to electric vehicles and intelligent devices.

To achieve high-performance fuel cells and metal–air batteries, inexpensive and earth-abundant catalysts with enhanced activity and durability for the oxygen reduction reaction (ORR) are currently sought after. Herein, three-dimensional (3D) α-MnO2 and e-MnO2 hierarchical star-like architectures with tunable crystal phases and desirable ORR activity were readily prepared by a facile hydrothermal method with no surfactants or templates. The effects of reaction temperature, anion type, and dwell time on the morphologies of the MnO2 products were studied in detail, and the possible formation mechanism of the 3D MnO2 hierarchical stars was proposed. Due to the improved electrical conductivity and O2 adsorption ability, the resulting α-MnO2 catalyst showed substantially enhanced ORR activity, compared to the e-MnO2 and bulk MnO2 catalysts, with a more positive onset potential, a larger limiting current density, and better durability. Our results provide a facile chemical route towards the phase-controlled synthesis of 3D MnO2 architectures, which can serve as efficient catalysts for ORR-based applications.