Stable LiF-Rich Electrode-Electrolyte Interface toward High-Voltage and High-Energy-Density Lithium Metal Solid Batteries.

Lithium-rich layered oxide (LRLO) materials have attracted significant attention due to their high specific capacity, low cost, and environmental friendliness. However, owing to its unique capacity activation mechanism, the release of lattice oxygen during the first charge process leads to a series of problems, such as severe voltage decay, poor cycle stability, and poor rate performance. Herein, a fluorinated quasi-solid-state electrolyte (QSSE) via a simple thermal polymerization method toward lithium metal batteries with LRLO materials is reported. The well-designed QSSE exhibits an ionic conductivity of 6.4 × 10-4 S cm-1 at 30 °C and a wide electrochemical stable window up to 5.6 V. Most importantly, XPS spectra demonstrate the generation of a LiF-rich electrode-electrolyte interface (EEI), where the in situ generated LiF provides strong protection against the structural degradation of LRLO materials and directs the uniform plating/stripping behaviors of lithium-ions to inhibit the formation of lithium dendrites. As a result, LRLO/QSSE/Li batteries exhibit excellent rate performance and demonstrate a large initial capacity for 209.7 mA h g-1 with a capacity retention of 80.8% after 200 cycles at 0.5C. This work provides a new insight for the LiF-rich EEI design of safe, high-performance quasi-solid-state lithium metal batteries.

Architecting Braided Porous Carbon Fibers Based on High-Density Catalytic Crystal Planes to Achieve Highly Reversible Sodium-Ion Storage.

Carbonaceous materials are considered strong candidates as anode materials for sodium-ion batteries (SIBs), which are expected to play an indispensable role in the carbon-neutral era. Herein, novel braided porous carbon fibres (BPCFs) are prepared using the chemical vapour deposition (CVD) method. The BPCFs possess interwoven porous structures and abundant vacancies. The growth mechanism of the BPCFs can be attributed to the polycrystalline transformation of the nanoporous copper catalyst in the early stage of CVD process. Density functional theory calculations suggest that the Na+ adsorption energies of the mono-vacancy edges of the BPCFs (-1.22 and -1.09 eV) are lower than that of an ideal graphene layer (-0.68 eV), clarifying in detail the adsorption-dominated sodium storage mechanism. Hence, the BPCFs as an anode material present an outstanding discharge capacity of 401 mAh g-1 at 0.1 A g-1 after 500 cycles. Remarkably, this BPCFs anode, under high-mass-loading of 5 mg cm-2, shows excellent long-term cycling ability with a reversible capacity of 201 mAh g-1 at 10 A g-1 over 1000 cycles. This study provided a novel strategy for the development of high-performance carbonaceous materials for SIBs.

A High-Kinetics Sulfur Cathode with a Highly Efficient Mechanism for Superior Room-Temperature Na-S Batteries.

Applications of room-temperature-sodium sulfur (RT-Na/S) batteries are currently impeded by the insulating nature of sulfur, the slow redox kinetics of sulfur with sodium, and the dissolution and migration of sodium polysulfides. Herein, a novel micrometer-sized hierarchical S cathode supported by FeS2 electrocatalyst, which is grown in situ in well-confined carbon nanocage assemblies, is presented. The hierarchical carbon matrix can provide multiple physical entrapment to polysulfides, and the FeS2 nanograins exhibit a low Na-ion diffusion barrier, strong binding energy, and high affinity for sodium polysulfides. Their combination makes it an ideal sulfur host to immobilize the polysulfides and achieve reversible conversion of polysulfides toward Na2 S. Importantly, the hierarchical S cathode is suitable for large-scale production via the inexpensive and green spray-drying method. The porous hierarchical S cathode offers a high sulfur content of 65.5 wt%, and can deliver high reversible capacity (524 mAh g-1 over 300 cycles at 0.1 A g-1 ) and outstanding rate capability (395 mAh g-1 at 1 A g-1 for 850 cycles), holding great promise for both scientific research and real application.

Facile Synthesis of Hierarchical Hollow CoP@C Composites with Superior Performance for Sodium and Potassium Storage.

Hierarchical hollow CoP and carbon composites were obtained through a facile synthetic method, where carbonization and phosphorization of the precursor were completed within one single step. The composites are composed of hollow CoP@C spheres, which are further made up of CoP nanoparticles with a thin outer carbon layer. Electrochemical performances of the prepared CoP@C composites as anodes for sodium and potassium storage were evaluated and compared. In situ TEM, in situ synchrotron XRD, and DFT calculations were conducted to study the structural evolution and the interaction between Na/K and CoP during cycling processes. Benefiting from the synergistic effect of conductive carbon layer and hierarchical hollow structure, the as-prepared CoP@C composites demonstrate superior sodium and potassium storage capability as anode materials for rechargeable batteries.

High Density Static Charges Governed Surface Activation for Long-Range Motion and Subsequent Growth of Au Nanocrystals.

How a heavily charged metal nanocrystal, and further a dual-nanocrystals system behavior with continuous electron charging? This refers to the electric dynamics in charged particles as well as the crystal growth for real metal particles, but it is still opening in experimental observations and interpretations. To this end, we performed an in-situ electron-beam irradiation study using transmission electron microscopy (TEM) on the Au nanocrystals that freely stand on the nitride boron nanotube (BNNT). Au nanocrystalline particles with sizes of 2⁻4 nm were prepared by a well-controlled sputtering method to stand on the BNNT surface without chemical bonding interactions. Au nanoparticles presented the surface atomic disorder, diffusion phenomena with continuous electron-beam irradiation, and further, the long-range motion that contains mainly the three stages: charging, activation, and adjacence, which are followed by final crystal growth. Firstly, the growth process undergoes the lattice diffusion and subsequently the surface-dominated diffusion mechanism. These abnormal phenomena and observations, which are fundamentally distinct from classic cases and previous reports, are mainly due to the overcharging of Au nanoparticle that produces a surface activation state in terms of high-energy plasma. This work therefore brings about new observations for both a single and dual-nanocrystals system, as well as new insights in understanding the resulting dynamics behaviors.

Self-Assembly of CoPt Magnetic Nanoparticle Arrays and its Underlying Forces.

Nanoparticles covered with surfactants are often used to study particle motion patterns and self-assembly processes in solutions. Surfactants have influence on the interparticle interactions and therefore on the particle motion tracks and final patterns. In this study, CoPt nanoparticles are synthesized in aqueous solution without any surfactant. In situ transmission electron microscopy observation is performed to monitor the self-assemble process. Two types of magnetic nanoparticle superlattice arrays are formed: hexagonal equal distance superlattice arrays when particle size is 3 nm, and tight unequal distance superlattice arrays when particle size is 4.5 nm. It is interesting to observe that two small arrays merge into a large one through rotational and translational movements. A Monte Carlo simulation is carried out which successfully restores the whole process. It is identified that the underlying forces are van der Waals and magnetic dipolar interactions. The latter is responsible for orientation of each particle during the whole process. This investigation leads to a better understanding of the formation mechanism of magnetic nanoparticle superlattice arrays.

Analysis of oxidation degree of graphite oxide and chemical structure of corresponding reduced graphite oxide by selecting different-sized original graphite.

The thermal exfoliation and reduction of graphite oxide (GO) is the most commonly used strategy for large-scale preparation of graphene, and the oxidation degree of GO would influence the chemical structure of prepared graphene, thereby affecting its final physical and chemical properties. In addition to serving as the precursor for synthesizing graphene, GO also possesses great potential for various important applications owing to its abundant oxygen-containing groups and hybrid electronic structure. Therefore, systematically studying the influencing factors on the oxidation degree of GO and clarifying the effect of oxidation degree on the corresponding graphene is particularly important. Herein, we have studied the effect of the lateral size of the original graphite on the oxidation degree of GO in order to control the oxidation degree of GO. GOs with different degrees of oxidation were synthesized using a modified Hummers method. The results of X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and Raman spectroscopy revealed that decreased lateral size of the original graphite would lead to increased oxidation degree of GO. Furthermore, the interlayer spacing of the GO samples achieved 0.9-1.0 nm, which indicated that the modified Hummers method could make well oxidized graphite. The corresponding reduced graphite oxide (rGO) was also prepared by low-temperature exfoliation of GO at 140 °C under ambient atmosphere. It was found that a larger lateral size of GO resulted in rGO with fewer oxygen-containing functional groups, but a smaller lateral size of graphite possessed a higher exfoliation degree with a larger specific surface area. More importantly, the relationship between binding energy (E B) of photoelectron of C atom in oxygen-containing groups and the number of oxygen-containing groups in GO and rGO samples was analyzed theoretically.

In situ preparation of Fe3O4 in a carbon hybrid of graphene nanoscrolls and carbon nanotubes as high performance anode material for lithium-ion batteries.

A new conductive carbon hybrid combining both reduced graphene nanoscrolls and carbon nanotubes (rGNSs-CNTs) is prepared, and used to host Fe3O4 nanoparticles through an in situ synthesis method. As an anode material for LIBs, the obtained Fe3O4@rGNSs-CNTs shows good electrochemical performance. At a current density of 0.1 A g-1, the anode material shows a high reversible capacity of 1232.9 mAh g-1 after 100 cycles. Even at a current density of 1 A g-1, it still achieves a high reversible capacity of 812.3 mAh g-1 after 200 cycles. Comparing with bare Fe3O4 and Fe3O4/rGO composite anode materials without nanoscroll structure, Fe3O4@rGNSs-CNTs shows much better rate capability with a reversible capacity of 605.0 and 500.0 mAh g-1 at 3 and 5 A g-1, respectively. The excellent electrochemical performance of the Fe3O4@rGNSs-CNTs anode material can be ascribed to the hybrid structure of rGNSs-CNTs, and their strong interaction with Fe3O4 nanoparticles, which on one hand provides more pathways for lithium ions and electrons, on the other hand effectively relieves the volume change of Fe3O4 during the charge-discharge process.

Determination of Silicon in Gasoline by Directly Measuring under Organic Phase Using Inductively Coupled Plasma Optical Emission Spectroscopy.

A simple and accurate method was developed for determining silicon in gasoline using inductively coupled plasma optical emission spectroscopy (ICP-OES). For sample inroduction a Burgener nubulizer and a Cyclonic spray chamber were used. A gasoline sample was diluted with isooctane and then introduced into the cooled spray chamber of the ICP-OES. Good linearity was achieved in the silicon concentration range 0.1 - 10.0 mg x kg(-1), and the correlation coefficient was 0.999 96. The detection limit for silicon was 0.012 mg x kg(-1) and the silicon recoveries from gasoline samples were 95.8% - 98.4%, with relative standard deviations of less than 3.0% The method was proved to be simple, reliable and highly sensitive, and suitable for determining silicon in samples of motor gasoline, ethanol-gasoline and methanol-gasoline fuel mixtures those containing not more than 15% (V/V) oxygenates.

Dopant-induced shape evolution of colloidal nanocrystals: the case of zinc oxide.

The electrical, optical and other important properties of colloidal nanocrystals are determined mainly by the crystals' chemical composition, size and shape. The introduction of specific dopants is a general approach of modifying the properties of such nanocrystals in well-controlled ways. Here we show that in addition to altering the atomic composition of the nanocrystals the introduction of specific dopants can also lead to dramatic changes in morphology. The creation of Mg-doped ZnO nanocrystals provides an excellent example of this procedure; depending on the molar ratio of dopant precursor in the reagents, doped nanocrystals with well-defined shapes, from tetrapods to ultrathin nanowires, which exhibit tunable optoelectronic properties, are obtained for the first time. We find that the Mg dopants play an important role in the primary growth stage, resulting in initial growth seeds having diverse crystallographic structures, which are critical for the generation of doped nanocrystals with different shapes. We demonstrate that this "greener" synthetic scheme can be extended to other dopant systems and provides an attractive and effective strategy for fabricating doped ZnO nanocrystals with interesting compositional and spatial complexity.

[Sperm-fluorescence in situ hybridization analysis in patients with pericentric inversions of Y chromosome].

OBJECTIVE: To analyze the sex chromosome meiotic segregation in inv(Y) patients by fluorescence in situ hybridization (FISH). METHODS: Conventional cytogenetic procedures (GTG and CBG banding) and FISH were performed on metaphase chromosome. Three-color FISH was performed on sperm samples using a probe mixture containing CEPX, Tel Xp/Yp and Tel Xq/Yq to investigate the sex chromosome segregation of five inv(Y) (p11.1q11.2) carriers. A healthy man with normal semen parameters was used as control. RESULTS: There was no statistical difference in the abnormal sex chromosome number and recombination frequencies in each spermatozoon from the patient in comparison with that in the control. CONCLUSION: There was no apparent sex chromosome abnormality in the sperm of the inv(Y) (p11.1q11.2) carriers. Sperm-FISH allows further understanding of the sex chromosome segregation pattern and an accurate genetic counseling.