Tuning the nucleation and decomposition of Li2O_(2) by fluorine-doped carbon vesicles towards high performance Li-O_(2) batteries

Li-O_(2) batteries provide an attractive and potential strategy for energy conversion and storage with high specific energy densities.However,large over-potential in oxygen evolution reactions (OER) caused by the decomposition obstacles of Li_(2)O_(2) seriously impedes its electrochemical performances.Herein,a novel N,O,S and F co-doping vesicular carbon was prepared by self-template pyrolysis method and used in LiO_(2) battery to tune the nucleation and decomposition of Li_(2)O_(2).The introduction of F in the carbon matrix with suitable content can regulate the adsorption of intermediates,through which the morphology of Li_(2)O_(2) can be controlled to film,favorable to its decomposition in charge process.The cathode based on the optimized F doped carbon vesicle exhibits improved electrochemical performances including a low over-potential,large capacity and a long-term stability.Density functional theory (DFT) results show that F and C in C–F bond hasve a strong interaction to Li and O in Li_(2)O_(2),respectively,which can enhance the transfer of electrons from Li_(2)O_(2) to the carbon matrix to generate hole polaron and thus accelerate the delithiation and decomposition of Li_(2)O_(2).This work provides a new sight into understanding the mechanism of nucleation and decomposition of Li_(2)O_(2) for the development of high-performance Li-O_(2) batteries.

Regulating the nucleation of Li_(2)CO_(3) and C by anchoring Li-containing carbonaceous species towards high performance Li-CO_(2) batteries

Li-CO_(2) batteries provide an attractive and potential strategy for CO_(2) utilization as well as energy conversion and storage with high specific energy densities.However,the poor reversibility caused by the decomposition obstacles of Li_(2)CO_(3) and C products is still a challenge for Li-CO_(2) batteries,which seriously influences its electrochemical performances.Herein,a free-standing MnOOH arrays cathode has been prepared and employed in Li-CO_(2) battery,which realizes a great improvement of electrochemical performances by adjusting the discharge products distribution.Experiments coupled with theoretical calculations verifies that the formation of Li-containing carbonaceous species(LiCO_(2),LiCO and Li_(2) CO_(3))bonded with MnOOH through Li ion regulates the nucleation behavior of Li_(2)CO_(3) and C,making them grown on MnOOH uniformly.The fine Li_(2) CO_(3) grains(with a size about 5 nm)embedded into carbon matrix greatly enlarges the contact interface between them,facilitating the transmission of electrons through the discharge products and finally improves CO_(2) evolution activity.This ingenious design strategy of regulating discharge products distribution to improve electrochemical performances provides a promising way to develop advanced Li-CO_(2) batteries.

In-situ X-ray computed tomography tensile tests and analysis of damage mechanism and mechanical properties in laser powder b e d fused Invar 36 alloy

Laser powder bed fusion(LPBF)is a potential additive manufacturing process to manufacture Invar 36 alloy components with complicated geometry.Whereas it inevitably introduces specific microstructures and pore defects,which will further influence the mechanical properties.Hence,aiming at exploring the LPBF process-related microstructures and pore defects,and especially their influences on the damage mechanism and mechanical properties,Invar 36 alloy was manufactured by LPBF under designed different laser scanning speeds.The microstructure observations reveal that higher scanning speeds lead to equiaxed and short columnar grains with higher dislocation density,while lower scanning speeds result in elongated columnar grains with lower dislocation density.The pore defects analyzed by X-ray computed tomography(XCT)suggest that the high laser scanning speed gives rise to numerous lamellar and large lack-of-fusion(LOF)pores,and the excessively low laser scanning speed produces relatively small keyhole pores with high sphericity.Moreover,the insitu XCT tensile tests were originally performed to evaluate the damage evolution and failure mechanism.Specifically,high laser scanning speed causes brittle fracture due to the rapid growth and coalescence of initial lamellar LOF pores along the scan-ning direction.Low laser scanning speed induces ductile fracture originating from unstable depressions in the surfaces,while metallurgical and keyhole pores have little impact on damage evolution.Eventually,the process-structure-property correlation is established.The presence of high volume fraction of lamel-lar LOF pores,resulting from high scanning speed,leads to inferior yield strength and ductility.Besides,specimens without LOF pores exhibit larger grain sizes and lower dislocation density at decreased scanning speeds,slightly reducing yield strength while slightly enhancing ductility.This understanding lays the foundation for widespread applications of LPBF-processed Invar 36 alloy.

RNA nanostructure transformation into DNA ones

RNAs and their assemblies can form diverse nano-structures and nano-shapes,offering various biological functions.However,by simply mimicking RNA sequences,DNAs cannot normally form the corresponding nanostructures,which makes the natureinspired transformations and designs challenging.To understand the possible designs and connections between related RNA and DNA nano-shapes,herein we have reported several DNA squares transformed and derived from an RNA assembled square,by gradually replacing RNA with DNA nucleotides.We have found that there were key RNA nucleotides:Their presences maintained the square,while their absences disrupted it.Interestingly,we have revealed that as long as the conditions of higher ionic strengths or longer duplexes were included,the square RNA assembly could be completely replaced with DNA nucleotides,still offering the stable DNA nano-shapes.Our experimental results have demonstrated that similar RNA nanostructure can be easily transformed into DNA ones via designing and increasing ionic strengths or duplex lengths.

Continuous culture of urine-derived bladder cancer cells for precision medicine

Dear Editor,Bladder cancer is the most common type of genitourinary cancer in China,with an estimated 80,500 new cases and 32,900 related deaths in 2015 alone(Chen et al.,2016).Unlike many other cancers,there has been no significant improvement in survival rates for bladder cancer over the last three decades.Specific treatment regimens for bladder cancer and their efficacy vary depending not only on clinical stages,but also on associated risk factors and other per­sonal clinical characteristics.Patients with non-muscle invasive bladder cancer(NMIBC)have a high 5-year recur­rence rate of 60%-70%(Berdik,2017)and those with muscle invasive bladder cancer(MIBC)has a relatively poor prognosis with approximately 65%risk of death within 5-year follow-up(Kamat et al.,2016).Therefore,there is an urgent need to develop models for bladder cancer to screen for rational treatment strategies by personalized medicine to improve the clinical assessment and treatment of bladder cancer.

Enhancing the process of CO_(2) reduction reaction by using CTAB to construct contact ion pair in Li-CO_(2) battery

Aprotic Li-CO_(2)batteries have attracted growing interest due to their high theoretical energy density and its ability to use green house gas CO_(2)for energy storage.However,the poor ability of activating CO_(2)in organic electrolyte often leads to the premature termination of CO_(2)reduction reaction(CO_(2)RR)directly.Here in this work,cetyl trimethyl ammonium bromide(CTAB)was introduced into a dimethyl sulfoxide(DMSO)based Li-CO_(2)battery for the first time to enhance the CO_(2)RR.Significantly improved electrochemical performances,including reduced discharge over-potential and increased discharge capacity,can be achieved with the addition of CTAB.Ab initio molecular dynamics(AIMD)simulations show that quaternary ammonium group CTA^(+) can accelerate CO_(2)reduction process by forming more stable contact ion pair(CIP)with CO_(2)^(–),reducing the energy barrier for CO_(2)RR,thus improving the CO_(2)reduction process.In addition,adding CTA^(+) is also favorable for the solution-phase growth of discharge products because of the improved migration ability of stable CTA^(+)-CO_(2)^(–) CIP in the electrolyte,which is beneficial for improving the utilization ratio of cathode.This work could facilitate the development of CO_(2)RR by providing a novel understanding of CO_(2)RR mechanism in organic system.