Mechanistic Insights into the Intercalation and Interfacial Chemistry of Mesocarbon Microbeads Anode for Potassium Ion Batteries.

Mesocarbon microbeads (MCMB) are highly desirable as anode materials for rechargeable potassium ion batteries (PIBs) due to their commercially availability, high stability and low-cost. However, their charge storage and interfacial mechanisms are still unclear. In this work, the intercalation mechanisms and the solid-electrolyte-interphase (SEI) formation of the MCMB in four different electrolytes is comprehensively studied. The MCMB anodes exhibit superior rate and cycle performances via a naked K-ions sequentially staging intercalation mechanism, realizing the complete transformation from graphite to KC8 . Whereas a solvated K-ions co-intercalation mechanism of the MCMB occurs in ether-based electrolytes, which might induce graphite exfoliation and result in unsatisfied specific capacity and capacity decay. Nevertheless, this co-intercalation behavior could be effectively suppressed by a highly concentrated electrolytes. Interfacial analyses unveil the distinct SEI components, which vary with the electrolyte chemistries. These SEI components also varies from surface to bulk and especially attention should be paid to the accurate control of the concentration of the fluoroethylene carbonate additives. This work provides a panoramic understanding of the intercalation and interfacial mechanisms on the MCMB anodes for PIBs.

A Robust Strategy for Engineering Fe7S8/C Hybrid Nanocages Reinforced by Defect-Rich MoS2 Nanosheets for Superior Potassium-Ion Storage.

Metal sulfides have attracted tremendous research interest for developing high-performance electrodes for potassium-ion batteries (PIBs) for their high theoretical capacities. Nevertheless, the practical application of metal sulfides in PIBs is still unaddressed due to their intrinsic shortcomings of low conductivity and severe volume changes during the potassiation/depotassiation process. Herein, robust Fe7S8/C hybrid nanocages reinforced by defect-rich MoS2 nanosheets (Fe7S8/C@d-MoS2) were designed, which possess abundant multichannel and active sites for potassium-ion transportation and storage. Kinetic analysis and theoretical calculation verify that the introduction of defect-rich MoS2 nanosheets dramatically promotes the potassium-ion diffusion coefficient. The ex-situ measurements revealed the potassium-ion storage mechanism in the Fe7S8/C@d-MoS2 composite. Benefitting from the tailored structural design, the Fe7S8/C@d-MoS2 hybrid nanocages show high reversible capacity, exceptional rate property, and superior cyclability.

Novel Mesoporous Flowerlike Iron Sulfide Hierarchitectures: Facile Synthesis and Fast Lithium Storage Capability.

The 3D flowerlike iron sulfide (F-FeS) is successfully synthesized via a facile one-step sulfurization process, and the electrochemical properties as anode materials for lithium ion batteries (LIBs) are investigated. Compared with bulk iron sulfide, we find that the unique structural features, overall flowerlike structure, composed of several dozen nanopetals and numerous small size iron sulfide particles embedded within the fine nanopetals, and hierarchical pore structure features provide signification improvements in lithium storage performance, with a high-rate discharge capacity of 779.0 mAh g-1 at a rate of 5 A g-1, due to effectively alleviating the volume expansion during the lithiation/delithiation process, and shorting the diffusion length of both lithium ion and electron. Especially, an excellent cycling stability are achieved, a high discharge capacity of 890 mAh g-1 retained at a rate of 1.0 A g-1, suggesting its promising applications in lithium ion batteries (LIBs).

Graphene oxide/ferroferric oxide/polyethylenimine nanocomposites for Congo red adsorption from water.

Graphene oxide/ferroferric oxide/polyethylenimine (GO/Fe3O4/PEI) nanocomposites were synthesized by an in situ growth of Fe3O4 nanoparticles on GO sheets, and then modified by PEI. The GO/Fe3O4/PEI nanocomposites showed extremely high removal efficiency for anionic dye Congo Red (CR) due to the positively charged PEI molecules (methylene blue was also tested but with low adsorption capacity due to its cationic property). The CR removal capacity was 574.7 mg g-1, higher than most of reported results. The adsorption kinetics could be well described by a pseudo-second-order model. Furthermore, GO/Fe3O4/PEI nanocomposites could be easily recycled by magnetic separation. The removal efficiency remained above 70% after five cycles.

Oil sorbents with high sorption capacity, oil/water selectivity and reusability for oil spill cleanup.

A sorbent for oil spill cleanup was prepared through a novel strategy by treating polyurethane sponges with silica sol and gasoline successively. The oil sorption capacity, oil/water selectivity, reusability and sorption mechanism of prepared sorbent were studied. The results showed that the prepared sorbent exhibited high sorption capacity and excellent oil/water selectivity. 1g of the prepared sorbent could adsorb more than 100 g of motor oil, while it only picks up less than 0.1 g of water from an oil-water interface under both static and dynamic conditions. More than 70% of the sorption capacity remained after 15 successive sorption-squeezing cycles, which suggests an extraordinary high reusability. The prepared sorbent is a better alternative of the commercial polypropylene sorbent which are being used nowadays.

Ultrasensitive DNA detection by cycle isothermal amplification based on nicking endonuclease and its application to logic gates.

In recent years, an intense interest has grown in the DNA logic gates having high potential for computation at literally the "nano-size" level. A limitation of traditional DNA logic gates is that each target strand hybridizes with only a single copy of the probe. This 1:1 hybridization radio limits the gain of the approach and thus its sensitivity. The exponential amplification of nucleic acids has become a core technology in medical diagnostics and has been widely used for the construction of DNA sensor, DNA nanomachine and DNA sequencing. It would be of great interest to develop DNA-based logic systems with exponential amplification for the output signal. In the present study, a series of three-input DNA logic gates with the cycle isothermal amplification based on nicking endonuclease (NEase) are designed. Very low concentrations of the analytes were sufficient to initiate an autocatalytic cascade, achieving a significant improvement of the detection limit, 100-fold improvement compared to the non-autocatalytic system. This was achieved by engineering a simple and flexible biological circuit designed to initiate a cascade of events to detect and amplify a specific DNA sequence. This procedure has the potential to greatly simplify the logic operation because amplification can be performed in "one-pot".

A label-free immunosensor based on modified mesoporous silica for simultaneous determination of tumor markers.

A label-free multiplexed immunoassay strategy was proposed for the simultaneous detection of two tumor markers, carcinoembryonic antigen (CEA) and α-fetoprotein (AFP). Monoclonal antibody of CEA was co-immobilized with ferrocenecarboxylic acid (FCA) inside the channels of mesoporous silica (MPS) to prepare the label-free probe for CEA. Also, monoclonal antibody of AFP was co-immobilized with horseradish peroxidase (HRP) inside the channels of MPS to prepare the label-free probe for AFP by using o-phenylenediamine (OPD) and H(2)O(2) as the electrochemical substrates. Thus, the multianalyte immunosensor was constructed by coating the probes of CEA and AFP respectively onto the different areas of indium-tin oxide (ITO) electrode. When the immunosensor was incubated with sample antigens, CEA and AFP antigens were introduced into the mesopores of MPS after the immunoassay reaction. Because all of the Si-OH groups on the external surface of MPS were blocked with Si(CH(3))(3), the proteins and substrates were limited to be embedded on the internal pore walls. Therefore, the electric response transfer was confined inside the pore channels. The nonconductive immunoconjugates blocked the electron transfer and the peak responses changed on the corresponding surface respectively. Then, the simultaneous detection of CEA and AFP achieved. The linear ranges of CEA and AFP were 0.5-45ngmL(-1) and 1-90ngmL(-1) with the detection limits of 0.2ngmL(-1) and 0.5ngmL(-1) (S/N=3), respectively. The fabricated immunosensor shows appropriate sensitivity and offers an alternative to the multianalyte detection of antigens or other bioactive molecules.

[Content of soil heavy metals and characteristics of environmental quality in tea plantations of Changsha Baili Tea Zone].

The distributing and changing characteristics and content of soil heavy metals was studied using methods of field survey and sampling, indoor analysis, and pollution index were used to investigate the soil environmental quality in the tea plantations of Changsha Baili Tea Zone. The results showed that the content of soil total Pb, Hg, Cd, Cr, As, Ni basically was in the soil background value, their averages were 42.7, 0.068, 0.074, 92.2, 12.4 and 19.5 mg/kg respectively. The content of heavy metals was lower than the standard of Environmental Qualification of Nuisance Free Tea Producing Area (NY 5020-2001). Simultaneity, soil environmental quality in tea plantations of Baili Tea Zone, it answered for the second grade of State Environmental Quality Standard for Soils (GB 15618-1995), achieved safe class, and the content of soil Hg, Cd, Ni accorded to the first grade of GB 15618-1995, these results showed the Changsha Baili Tea Zone were propitious to develop nuisance free tea production. Besides the single pollution index of Cr was 0.837 and in warning class at the tea plantation of Xiangfeng, the others were all less than 0.7, and in the safe class. The integrated index of 6 tea bases was all less than 0.7, in the safe class, the soil environmental quality was cleanness on the whole at Changsha Baili Tea Zone, and the soils were suitable for non-polluted agricultural production.