Time-resolved inductively coupled plasma mass spectrometry measurements with individual, monodisperse drop sample introduction

Individual ion clouds, each produced in the ICP from a single drop of sample, were monitored using time-resolved mass spectrometry and optical emission spectrometry simultaneously. The widths of the ion clouds in the plasma as a function of distance from the point of initial desolvated particle vaporization in the ICP were estimated. The Li(+) cloud width (full width at halfmaximum) varied from 85 to 272 μs at 3 and 10 mm from the apparent vaporization point, respectively. The Sr(+) cloud width varied from 97 to 142 μs at 5 and 10 mm from the apparent vaporization point, respectively. The delays between optical and mass spectrometry signals were used to measure gas velocities in the ICP. The velocity data could then be used to convert ion cloud peak widths in time to cloud sizes in the ICP. Li(+) clouds varied from 2.1 to 6.6 mm (full width at half-maximum) and Sr(+) clouds varied from 2.4 to 3.5 mm at the locations specified above. Diffusion coefficients were estimated from experimental data to be 88, 44, and 24 cm(2)/s for Li(+), Mg(+), and Sr(+), respectively. The flight time of ions from the sampling orifice of the mass spectrometer to the detector were mass dependent and varied from 13 to 21 μs for Mg(+) to 93 to 115 μs for Pb(+).     

Reversible nanopore formation in Ge nanowires during lithiation-delithiation cycling: an in situ transmission electron microscopy study

Retaining the high energy density of rechargeable lithium ion batteries depends critically on the cycle stability of microstructures in electrode materials. We report the reversible formation of nanoporosity in individual germanium nanowires during lithiation-delithiation cycling by in situ transmission electron microscopy. Upon lithium insertion, the initial crystalline Ge underwent a two-step phase transformation process: forming the intermediate amorphous Li(x)Ge and final crystalline Li(15)Ge(4) phases. Nanopores developed only during delithiation, involving the aggregation of vacancies produced by lithium extraction, similar to the formation of porous metals in dealloying. A delithiation front was observed to separate a dense nanowire segment of crystalline Li(15)Ge(4) with a porous spongelike segment composed of interconnected ligaments of amorphous Ge. This front sweeps along the wire with a logarithmic time law. Intriguingly, the porous nanowires exhibited fast lithiation/delithiation rates and excellent mechanical robustness, attributed to the high rate of lithium diffusion and the porous network structure for facile stress relaxation, respectively. These results suggest that Ge, which can develop a reversible nanoporous network structure, is a promising anode material for lithium ion batteries with superior energy capacity, rate performance, and cycle stability.     

Fast, completely reversible li insertion in vanadium pentoxide nanoribbons

Layered-structure nanoribbons with efficient electron transport and short lithium ion insertion lengths are promising candidates for Li battery applications. Here we studied at the single nanostructure level the chemical, structural, and electrical transformations of V2O5 nanoribbons. We found that transformation of V2O5 into the omega-Li3V2O5 phase depends not only on the width but also the thickness of the nanoribbons. Transformation can take place within 10 s in thin nanoribbons, suggesting a Li diffusion constant 3 orders of magnitude faster than in bulk materials, resulting in a significant increase in battery power density (360 C power rate). For the first time, complete delithiation of omega-Li3V2O5 back to the single-crystalline, pristine V2O5 nanoribbon was observed, indicating a 30% higher energy density. These new observations are attributed to the ability of facile strain relaxation and phase transformation at the nanoscale. In addition, efficient electronic transport can be maintained to charge a Li3V2O5 nanoribbon within less than 5 s. These exciting nanosize effects can be exploited to fabricate high-performance Li batteries for applications in electric and hybrid electric vehicles.     

An accelerator-based neutron microbeam system for studies of radiation effects

A novel neutron microbeam is being developed at the Radiological Research Accelerator Facility (RARAF) of Columbia University. The RARAF microbeam facility has been used for studies of radiation bystander effects in mammalian cells for many years. Now a prototype neutron microbeam is being developed that can be used for bystander effect studies. The neutron microbeam design here is based on the existing charged particle microbeam technology at the RARAF. The principle of the neutron microbeam is to use the proton beam with a micrometre-sized diameter impinging on a very thin lithium fluoride target system. From the kinematics of the ?Li(p,n)?Be reaction near the threshold of 1.881 MeV, the neutron beam is confined within a narrow, forward solid angle. Calculations show that the neutron spot using a target with a 17-μm thick gold backing foil will be <20 μm in diameter for cells attached to a 3.8-μm thick propylene-bottomed cell dish in contact with the target backing. The neutron flux will roughly be 2000 per second based on the current beam setup at the RARAF singleton accelerator. The dose rate will be about 200 mGy min?1. The principle of this neutron microbeam system has been preliminarily tested at the RARAF using a collimated proton beam. The imaging of the neutron beam was performed using novel fluorescent nuclear track detector technology based on Mg-doped luminescent aluminum oxide single crystals and confocal laser scanning fluorescent microscopy.     

A Molecularly Engineered Cathode Lithium Compensation Agent for High Energy Density Batteries

Prelithiating cathode is considered as one of the most promising lithium compensation strategies for practical high energy density batteries. Whereas most of reported cathode lithium compensation agents are deficient owing to their poor air-stability, residual insulating solid, or formidable Li-extracting barrier. Here, this work proposes molecularly engineered 4-Fluoro-1,2-dihydroxybenzene Li salt (LiDF) with high specific capacity (382.7 mAh g⁻¹) and appropriate delithiation potential (3.6–4.2 V) as an air-stable cathode Li compensation agent. More importantly, the charged residue 4-Fluoro-1,2-benzoquinone (BQF) can synergistically work as an electrode/electrolyte interface forming additive to build uniform and robust LiF-riched cathode/anode electrolyte interfaces (CEI/SEI). Consequently, less Li loss and retrained electrolyte decomposition are achieved. With 2 wt% 4-Fluoro-1,2-dihydroxybenzene Li salt initially blended within the cathode, 1.3 Ah pouch cells with NCM (Ni92) cathode and SiO/C (550 mAh g⁻¹) anode can keep 91% capacity retention after 350 cycles at 1 C rate. Moreover, the anode free of NCM622+LiDF||Cu cell achieves 78% capacity retention after 100 cycles with the addition of 15 wt% LiDF. This work provides a feasible sight for the rational designing Li compensation agent at molecular level to realize high energy density batteries.     

超级电容电池用碳类复合负极材料的研究

研制了新型储能器件超级电容电池用石墨和活性炭复合负极材料,应用恒流充放电法,考察了这种复合负极材料的电化学性能.结果表明这种碳复合负极材料兼具良好的电容特性和电池特性,在基本保持电池特性的同时,能将电容器电位窗口从2.5V提高至3.5V vs Li/Li+,能量密度从21.7Wh/kg提高至40.3wh/kg,增大近两倍;有很好的倍率性能,电流密度从0.1A/g增加到1A/g时,比容量仅下降了1.3F/g;同时能保持良好的循环性能,10次容量保持率即使在3.5V高压下仍有96.7%.     

In situ transmission electron microscopy observation of pulverization of aluminum nanowires and evolution of the thin surface Al2O3 layers during lithiation-delithiation cycles

Lithiation-delithiation cycles of individual aluminum nanowires (NWs) with naturally oxidized Al(2)O(3) surface layers (thickness 4-5 nm) were conducted in situ in a transmission electron microscope. Surprisingly, the lithiation was always initiated from the surface Al(2)O(3) layer, forming a stable Li-Al-O glass tube with a thickness of about 6-10 nm wrapping around the NW core. After lithiation of the surface Al(2)O(3) layer, lithiation of the inner Al core took place, which converted the single crystal Al to a polycrystalline LiAl alloy, with a volume expansion of about 100%. The Li-Al-O glass tube survived the 100% volume expansion, by enlarging through elastic and plastic deformation, acting as a solid electrolyte with exceptional mechanical robustness and ion conduction. Voids were formed in the Al NWs during the initial delithiation step and grew continuously with each subsequent delithiation, leading to pulverization of the Al NWs to isolated nanoparticles confined inside the Li-Al-O tube. There was a corresponding loss of capacity with each delithiation step when arrays of NWs were galvonostatically cycled. The results provide important insight into the degradation mechanism of lithium-alloy electrodes and into recent reports about the performance improvement of lithium ion batteries by atomic layer deposition of Al(2)O(3) onto the active materials or electrodes.     

Aptamer-based immunosensor on the ZnO nanorods networks

This paper presents the fabrication and characteristics of a new aptamer-based electrochemical immunosensor on the patterned zinc oxide nanorod networks (ZNNs) for detecting thrombin. Aptamers are single-stranded RNA or DNA sequence that binds to target materials with high specificity and affinity. An antibody-antigen-aptamer sandwich structure was employed to this immunosensor for detecting thrombin. First, hydrothermally grown ZNNs were patterned on the patterned 0.02 cm2 Au/Ti electrodes on a glass substrate by lift-off process. The high isoelectric point (IEP, approximately 9.5) of nanostructured ZnO makes it suitable for immobilizing proteins with low IEP. Then 5 microL of the 500 nM antibody was immobilized on the ZNNs electrode. 5 micro/L of the mixture of 1 microM aptamer labeled by ferrocene (Fc) and thrombin was dropped on the electrode for antibody-antigen binding. The peak oxidation currents of the immunosensors at various thrombin concentrations were measured by using cyclic voltammetry. The peak oxidation current was observed at 340 mV versus Ag/AgCl electrode, and the peak oxidation current increased linearly from 62.26 nA to 354.13 nA with the logarithmic concentration of thrombin in the range from 100 pM to 250 nM. Fabrication of an aptamer-based immunosensor for thrombin detection is a new attempt and the characteristics of the fabricated immunosensors showed that the fabricated aptamer-baded immunosensor worked electrochemically well and had a low detection limit (approximately 91.04 pM) and good selectivity.     

The possibility of intercalating alkali metals in a glass of the system V2O5 - P2O5

A semi-conducting phosphovanadate glass was tested as a possible material for positive electrode in solid state batteries.O.c. voltage with alkali metal (3.6 V/Li and 3.4 V/Na) is higher than for crystallized vanadium oxides and chemical intercalation of sodium or lithium is obtained using halogenated salts dissolved in organic solvents.     

Displacement of particles in microfluidics by laser-generated tandem bubbles

The dynamic interaction between laser-generated tandem bubble and individual polystyrene particles of 2 and 10 μm in diameter is studied in a microfluidic channel (25 μm height) by high-speed imaging and particle image velocimetry. The asymmetric collapse of the tandem bubble produces a pair of microjets and associated long-lasting vortices that can propel a single particle to a maximum velocity of 1.4 m∕s in 30 μs after the bubble collapse with a resultant directional displacement up to 60 μm in 150 μs. This method may be useful for high-throughput cell sorting in microfluidic devices.     

Spindle-like Mesoporous α-Fe(2)O(3) Anode Material Prepared from MOF Template for High-Rate Lithium Batteries

Spindle-like porous α-Fe(2)O(3) was prepared from an iron-based metal organic framework (MOF) template. When tested as anode material for lithium batteries (LBs), this spindle-like porous α-Fe(2)O(3) shows greatly enhanced performance of Li storage. The particle with a length and width of ～0.8 and ～0.4 μm, respectively, was composed of clustered Fe(2)O(3) nanoparticles with sizes of <20 nm. The capacity of the porous α-Fe(2)O(3) retained 911 mAh g(-1) after 50 cycles at a rate of 0.2 C. Even when cycled at 10 C, comparable capacity of 424 mAh g(-1) could be achieved.     

Characterization of the electrochemical reactions in the Li(1+x)V3O8/Li cell by soft X-ray absorption spectroscopy and two-dimensional correlation analysis

We applied soft X-ray absorption spectroscopy (XAS) and two-dimensional (2D) correlation analysis to the first lithium insertion-extraction cycle in a Li(1+x)V3O8/Li cell in order to investigate the electrochemical reactions of lithium with the Li(1+x)V3O8 electrode. The V L(II,III)-edge and O K-edge spectra of the Li(1+x)V3O8 electrode were obtained for varying electrode lithium content. The insertion of lithium leads to the reduction of the V5+ species present in the pristine Li(1+x)V3O8 electrode, and to the red shift and the broadening of the spectral features of the V L(II,III) edge compared to those of the pristine electrode. In the extraction process, the main spectral features at the highest value of the extraction of lithium show some differences compared to the features of the pristine electrode spectrum due to the residual lithium ions in the Li(1+x)V3O8 structure. The O K-edge spectra revealed that the insertion of lithium mainly affects the V 4sp-O 2p bonds and consequently induces a change in bonding geometry. The 2D correlation analysis of these spectra clearly shows that V-O bonds are significantly perturbed by the insertion-extraction of lithium into the Li(1+x)V3O8 electrode.     

Calibration of the cloud and aerosol spectrometer for coal dust composition and morphology

The cloud and aerosol spectrometer (CAS) was calibrated to enable CAS sizing of coal dust for studies on flammable dust control. Coal dust sizes were determined by light-scattering theories for irregular particles that account for particle composition and morphology in computing coal dust diameters. Coal dust size computations were compared with test dust that was generated by cyclone separation and air-jet sieving and characterized by aerodynamic particle sizer (APS) and computer-controlled scanning electron microscopy (CCSEM) measurements. For test dust in the range of 0.5–32 μm, coal dust size distributions were consistent with cyclone-separated and sieve-segregated sizes. For the 3–20 μm size range, the coal dust size distribution had a mass median diameter that was 14% larger than that of the APS. This difference was reasonable considering that the basic calibration for glass spheres had 13% uncertainty. For the 20–32 μm and 32–45 μm test dusts, mass median diameters differed from CCSEM measurements by only 4% and 5%, respectively. Overall, the results suggest agreement between test dust sizes and computations for coal dust. Alternatively, using conventional Mie theory computations for spheres, coal dust mass median diameters were 35% and 40% larger than APS and CCSEM measurements, respectively.     

Dual‐Graphene Rechargeable Sodium Battery

Sodium (Na) ion batteries are attracting increasing attention for use in various electrical applications. However, the electrochemical behaviors, particularly the working voltages, of Na ion batteries are substantially lower than those of lithium (Li) ion batteries. Worse, the state‐of‐the‐art Na ion battery cannot meet the demand of miniaturized in modern electronics. Here, we demonstrate that electrochemically exfoliated graphene (EG) nanosheets can reversibly store (PF₆⁻) anions, yielding high charging and discharging voltages of 4.7 and 4.3 V vs. Na⁺/Na, respectively. The dual‐graphene rechargeable Na battery fabricated using EG as both the positive and negative electrodes provided the highest operating voltage among all Na ion full cells reported to date, together with a maximum energy density of 250 Wh kg⁻¹. Notably, the dual‐graphene rechargeable Na microbattery exhibited an areal capacity of 35 μAh cm⁻² with stable cycling behavior. This study offers an efficient option for the development of novel rechargeable microbatteries with ultra‐high operating voltage and high energy density.     

Azo Compounds Derived from Electrochemical Reduction of Nitro Compounds for High Performance Li‐Ion Batteries

Organic compounds are desirable alternatives for sustainable lithium‐ion battery electrodes. However, the electrochemical properties of state‐of‐the‐art organic electrodes are still worse than commercial inorganic counterparts. Here, a new chemistry is reported based on the electrochemical conversion of nitro compounds to azo compounds for high performance lithium‐ion batteries. 4‐Nitrobenzoic acid lithium salt (NBALS) is selected as a model nitro compound to systemically investigate the structure, lithiation/delithiation mechanism, and electrochemical performance of nitro compounds. NBALS delivers an initial capacity of 153 mAh g^?1 at 0.5 C and retains a capacity of 131 mAh g^?1 after 100 cycles. Detailed characterizations demonstrate that during initial electrochemical lithiation, the nitro group in crystalline NBALS is irreversibly reduced into an amorphous azo compound. Subsequently, the azo compound is reversibly lithiated/delithiated in the following charge/discharge cycles with high electrochemical performance. The lithiation/delithiation mechanism of azo compounds is also validated by directly using azo compounds as electrode materials, which exhibit similar electrochemical performance to nitro compounds, while having a much higher initial Coulombic efficiency. Therefore, this work proves that nitro compounds can be electrochemically converted to azo compounds for high performance lithium‐ion batteries.     

The Regulating Role of Carbon Nanotubes and Graphene in Lithium‐Ion and Lithium–Sulfur Batteries

The ever‐increasing demands for batteries with high energy densities to power the portable electronics with increased power consumption and to advance vehicle electrification and grid energy storage have propelled lithium battery technology to a position of tremendous importance. Carbon nanotubes (CNTs) and graphene, known with many appealing properties, are investigated intensely for improving the performance of lithium‐ion (Li‐ion) and lithium–sulfur (Li–S) batteries. However, a general and objective understanding of their actual role in Li‐ion and Li–S batteries is lacking. It is recognized that CNTs and graphene are not appropriate active lithium storage materials, but are more like a regulator: they do not electrochemically react with lithium ions and electrons, but serve to regulate the lithium storage behavior of a specific electroactive material and increase the range of applications of a lithium battery. First, metrics for the evaluation of lithium batteries are discussed, based on which the regulating role of CNTs and graphene in Li‐ion and Li–S batteries is comprehensively considered from fundamental electrochemical reactions to electrode structure and integral cell design. Finally, perspectives on how CNTs and graphene can further contribute to the development of lithium batteries are presented.     

气溶胶在岩体裂隙中迁移特性的实验研究

为得到实际岩体裂隙中气溶胶的穿透行为特性,为山体中存储间的选址及洞室工程防护措施的制定提供精确的数据支持,利用电子低压碰撞器对气溶胶在岩体裂隙中的穿透率进行实验测量,得到气流速度、粒径大小、裂隙长度、裂隙高度等参数对穿透率的影响。结果表明,在较低的流速下,小粒径粒子的穿透率随流速的增大稍微增大,大粒径粒子趋势不明显;随着气溶胶粒径的增大,穿透率先增大后减小,峰值在0.3～1.0μm之间;随着裂隙长度的增加,穿透率呈指数减小,且不同长度裂隙、不同粒径气溶胶粒径的穿透率减小趋势基本一致;裂隙高度的增加使气溶胶的穿透率显著增大,高为1.0 mm的裂隙中,气溶胶的穿透率更大,更接近理论结果;在常温常压下,高为0.1 mm的裂隙中,流速为5.6 m/s时,粒径为0.3μm的气溶胶在0.1 mm宽岩体裂隙中的迁移距离非常有限。粒子除了受重力沉积和扩散沉积作用,还受到碰撞效应等作用。     

An Enzyme Switch Employing Direct Electrochemical Communication between Horseradish Peroxidase and a Poly(aniline) Film

An enzyme switch, or microelectrochemical enzyme transistor, responsive to hydrogen peroxide was made by connecting two carbon band electrodes (～10 μm wide, 4.5 mm long separated by a 20-μm gap) with an anodically grown film of poly(aniline). Horseradish peroxidase (EC 1.11.1.7) was either adsorbed onto the poly(aniline) film or immobilized in an insulating poly(1,2-diaminobenzene) polymer grown electrochemically on top of the poly(aniline) film to complete the device. In the completed device, the conductivity of the poly(aniline) film changes from conducting (between - 0.05 and + 0.3 V vs SCE at pH 5) to insulating (>+0.3 V vs SCE at pH 5) on addition of hydrogen peroxide. The change in conductivity is brought about by oxidation of the poly(aniline) film by direct electrochemical communication between the enzyme and the conducting polymer. This was confirmed by measuring the potential of the poly(aniline) film during switching of the conductivity in the presence of hydrogen peroxide. The devices can be reused by rereducing the poly(aniline) electrochemically to a potential below +0.3 V vs SCE. A blind test showed that the device can be used to determine unknown concentrations of H(2)O(2) in solution and that, when used with hydrogen peroxide concentrations below 0.5 mmol dm(-)(3), the same device maybe reused several times. The possible development of devices of this type for use in applications requiring the measurement of low levels of hydrogen peroxide or horseradish peroxidase is discussed.     

Modelling peptide nanotubes for artificial ion channels

We investigate the van der Waals interaction of D,L-Ala cyclopeptide nanotubes and various ions, ion-water clusters and C(60) fullerenes, using the Lennard-Jones potential and a continuum approach which assumes that the atoms are smeared over the peptide nanotube providing an average atomic density. Our results predict that Li(+), Na(+), Rb(+) and Cl(-) ions and ion-water clusters are accepted into peptide nanotubes of 8.5 ? internal diameter whereas the C(60) molecule is rejected. The model indicates that the C(60) molecule is accepted into peptide nanotubes of 13 ? internal diameter, suggesting that the interaction energy depends on the size of the molecule and the internal diameter of the peptide nanotube. This result may be useful for the design of peptide nanotubes for drug delivery applications. Further, we also find that the ions prefer a position inside the peptide ring where the energy is minimum. In contrast, Li(+)-water clusters prefer to be in the space between each peptide ring.     

Pulse voltammetric and ac impedance spectroscopic studies on lithium ion transfer at an electrolyte/Li4/3Ti5/3O4 electrode interface

Pulse voltammetry and ac impedance spectroscopy were used to study the lithium ion kinetics at a lithium ion insertion electrode consisting of Li4/3Ti5/3O4 thin films in an organic electrolyte. In the cyclic voltammogram, two redox peaks appeared at around 1.56 V vs Li/Li+ due to the insertion and extraction of lithium ion at the electrode. Differential pulse voltammetry gave a large reduction current at approximately 1.56 V during a cathodic scan due to lithium ion insertion into the electrode. From the peak current and potential, the charge-transfer resistance was evaluated by quantitative analysis using approximate equations for irreversible reactions. In the Nyquist plot, one semicircle was observed at 1.56 V, which was assigned to the charge-transfer resistance due to lithium ion transfer at the electrode/electrolyte interface. The value of the charge-transfer resistance at 1.56 V was almost identical to that evaluated by differential pulse voltammetry with an identical characteristic relaxation time. This result shows that both dc differential pulse voltammetry and ac impedance spectroscopy are useful for elucidating the phase transfer kinetics of lithium ion at insertion electrodes.