SiOx encapsulated FeSi2–Si eutectic nanoparticles as durable anode of lithium-ion batteries

Low-cost and high-efficiency production of silicon-based material is the key to improve the energy density of lithium-ion batteries. Herein, we propose a novel structure of FeSi₂–Si eutectic nanoparticles protected by the SiO_x shell. FeSi₂, as a buffer phase can improve the electrochemical stability of the electrode. A SiO_x shell is formed on the surface of the nanoparticles through the passivation process. SiO_x encapsulated FeSi₂–Si eutectic nanoparticles exhibit excellent capacity of 674.9 mAh/g after 500 charge/discharge cycles. The capacity retention rate is above 90% after the stabilization process. This work provides a new nanomaterial design for high performance silicon-based anode materials of lithium-ion batteries.     

Highly elastic cobweb-like SiO/CNF composites with reconstructed heterostructure for high-efficient lithium storage

The silicon-based materials are promising candidates for lithium-ion batteries owing to their high energy density. However, achieving long lifespan under realistic conditions remains a challenge because of the volume expansion and low conductivity. In this work, the highly elastic cobweb-like composite materials consisted by SiO and nanofibers are designed and fabricated for high-efficient lithium storage by ball-milling & electrostatic spinning method. The reconstructed heterostructure and highly elastic nanofibers can simultaneously increase the conductivity and inhibit the “expansion effect” of silicon-based materials. The constructed electrode of n-SiO/CNF delivers an initial capacity of 1700 mAh/g, and maintains the capacities over 1000 mAh/g after 100 cycles at the current density of 500 mA/g. Meanwhile, this electrode can give an initial coulombic efficiency over 85% and maintains at 98% in the following charge/discharge processes. Furthermore, it exhibits efficient long-term electrochemical performance, maintaining the capacity at about 1000 mAh/g at a high current density of 1000 mA/g after 1000 cycles. This work could provide a promising strategy for enhancing the performance of silicon-based composite materials for practical application in lithium-ion batteries.     

4-Silapiperidine and 4-silapiperidinium derivatives: syntheses and structural characterization

A series of novel 4-silapiperidine and 4-silapiperidinium derivatives, with two silicon-bound aryl groups and various N-organyl groups, have been synthesized and structurally characterized (solution ¹H, ¹³C, ¹⁹F, and ²⁹Si NMR spectroscopy; eight crystal structure analyses). These synthetic and structural investigations provide the basis for the development of novel silicon-based drugs containing a 4-silapiperidine or 4-silapiperidinium skeleton.     

The geometric pattern of a pillared substrate influences the cell-process distribution and shapes of fibroblasts

Fibroblasts alter their shape, direction of movement, cytoskeleton arrangement, and focal contact when placed upon square array pillars. We prepared pillars of 1 μm diameter, separated by 3 μm, and having 1, 5, and 10 μm heights using substrates displaying identical surface chemistry. When cells seeded initially onto the tops of the pillars, fibroblasts subsequently were immobilized in situ by several pillars that visibly protruded through, but did not pierce, the cell bodies. The cytoplasma then migrated outward with long straight lamella along the interval of the pillars and formed several discrete attachment zones at their side walls – the value of their form index (FI) was as high as 35 – which altered the cellular shape entirely. Most of the cells interacted with the pillar substrate by spreading preferentially in a particular direction, but some of them had the ability to undergo coincident two-direction (x and y) migration; right-angle turn orientations led to the growth of dramatic cellular morphologies. Interestingly, this fibroblast's behavior variation was gradually in proportion to the pillar height of substrate. Our results confirm that cellular migration and cellular shape are both strongly affected by the geometry of the growth microenvironment.     

β-Carbonylsilanes with a silacyclohexane skeleton and additional C-functionalized organyl groups at the silicon atom: synthesis, reactivity, and NMR-spectroscopic characterization

A series of novel β-carbonylsilanes, with a silacyclohexane skeleton and additional C-functionalized organyl groups at the silicon atom, were synthesized, their reactivity was explored, and they were structurally characterized by multinuclear NMR spectroscopy. The aim of these investigations was to provide the basis for the development of novel silicon-based drugs containing a silacyclohexane skeleton, with a CH₂C(O)R substituent and an additional C-functionalized organyl group at the silicon atom.     

Drying methods for XPS analysis of PureVision™, Focus Night&Day™ and conventional hydrogel contact lenses

The surface composition of hydrogel contact lenses that contain silicon-based monomers, PureVision™ (balafilcon A) and Focus^® Night&Day™ (lotrafilcon A), were investigated by X-ray photoelectron spectroscopy (XPS). Conventional and daily disposable hydrogel lenses based on hydroxyethyl methacrylate (HEMA) were also studied, with the commonly prescribed 1-day Acuvue^® lens (etafilcon A) used as a control. All the lenses were pre-washed and dehydrated by three different methods, including drying in air, drying in nitrogen or freezing with subsequent freeze-drying, before the XPS analysis. The lenses dried in air had more impurities on the surface, and the lenses that were freeze-dried lost transparency, suggesting that drying lenses in nitrogen is the preferred preparation method for XPS analysis. Surface compositions for all lens materials were obtained and this data can be used as a control/base-value for future analysis of the interactions of soft contact lens materials with chemicals such as drugs or tear components.     

First-principles studies of the hydrogenation effects in silicene sheets

Using density functional theory (DFT) with both the generalized gradient approximation (GGA) and hybrid functionals, we have investigated the structural, electronic and magnetic properties of a two-dimensional hydrogenated silicon-based material. The compounds, i.e. silicene, full- and half-hydrogenated silicene, are studied and their properties are compared. Our results suggest that silicene is a gapless semimetal. The coverage and arrangement of the absorbed hydrogen atoms on silicene influence significantly the characteristics of the resulting band structures, such as the direct/indirect band gaps or metallic/semiconducting features. Moreover, it is interesting to see that half-hydrogenated silicene with chair-like structure is shown to be a ferromagnetic semiconductor.     

Total synthesis of (+)-papulacandin D

A total synthesis of (+)-papulacandin D has been achieved in 31 steps, in a 9.2% overall yield from commercially available materials. The synthetic strategy divided the molecule into two nearly equal sized subunits, the spirocyclic C-arylglycopyranoside and the polyunsaturated fatty acid side-chain. The C-arylglycopyranoside was prepared in 11 steps in a 30% overall yield from triacetoxyglucal. The fatty acid side-chain was also prepared in 11 steps in a 30% overall yield from geraniol. The key strategic transformations in the synthesis are: (1) a palladium-catalyzed, organosilanolate-based cross-coupling reaction of a dimethylglucal-silanol with an electron-rich and sterically hindered aromatic iodide and (2) a Lewis-base catalyzed, enantioselective allylation reaction of a dienal and allyltrichlorosilane. A critical element in the successful execution of the synthesis was the development of a suitable protecting group strategy that satisfied a number of stringent criteria.     

载流子色散型硅基CMOS光子器件

为了实现硅基单片光电子集成器件的实用化,介绍了采用P-I-N、双极型场效应晶体管、金属氧化物半导体和PN结结构的载流子色散型硅基CMOS光子器件的发展状况和特点,并汇报了硅基CMOS光子器件的设计和制作方面的工作.利用商业的CMOS工艺线制作的器件获得了较好的结果,光调制器消光比约18 dB,1×2光开关消光比约21 dB,谐振环的消光比8～12 dB.采用CMOS技术研制硅基光子器件,将能使集成光子学的发展上一个新的台阶.     

应用于塑料光纤通信接收芯片的集成光电探测器(英文)

基于0.5μm标准Biplor、互补金属氧化物半导体和双扩散金属氧化物工艺设计了两种不同结构不同尺寸的光电探测器,包括传统的P+/N-EPI/BN+结构光电探测器和多叉指P+/N-EPI/BN+结构的光电探测器.通过仿真优化设计了光电探测器的结构参量和性能,测试结果表明:多叉指状P+/NEPI/BN+光电探测器能够改善650nm的响应度以及降低结电容.选择该结构大面积P+/N-EPI/BN+光电探测器用于和跨阻放大器以及后端放大器的单片集成,采用0.5μm标准Biplor、互补金属氧化物半导体和双扩散金属氧化物工艺实现了一个用于650nm塑料光纤通信的单片集成光接收芯片.该光接收芯片的测试结果表明:对650nm的入射光,在160 Mb/s速率的伪随机二进制序列以及小于10-9的误码率条件下,光接收芯片的灵敏度为-15dBm,并能得到清晰的眼图.因此,本文设计的光电探测器可以很好地应用于宽带接入网中的高速塑料光纤通信系统的光接收芯片中.