The aggregates and gels commonly observed during protein crystallization have generally been considered disordered phases without further characterization. Here their physical nature is addressed by investigating protein salting-out in ammonium sulfate and sodium chloride for six proteins (ovalbumin, ribonuclease A, soybean trypsin inhibitor, lysozyme, and beta-lactoglobulin A and B) at 4 degrees C, 23 degrees C, and 37 degrees C. When interpreted within the framework of a theoretical phase diagram obtained for colloidal particles displaying short-range attractive interactions, the results show that the formation of aggregates can be interpreted theoretically in terms of a gas-liquid phase separation for aggregates that are amorphous or gel-like. A notable additional feature is the existence of a second aggregation line observed for both ovalbumin and ribonuclease A in ammonium sulfate, interpreted theoretically as the spinodal. Further investigation of ovalbumin and lysozyme reveals that the formation of aggregates can be interpreted, in light of theoretical results from mode-coupling theory, as a kinetically trapped state or a gel phase that occurs through the intermediate of a gas-liquid phase separation. Despite the limitations of simple theoretical models of short-range attractive interactions, such as their inability to reproduce the effect of temperature, they provide a framework useful to describe the main features of protein phase behavior.

A nonwoven fabric with paperlike qualities composed of silicon nanowires is reported. The nanowires, made by the supercritical-fluid-liquid-solid process, are crystalline, range in diameter from 10 to 50 nm with an average length of >100 μm, and are coated with a thin chemisorbed polyphenylsilane shell. About 90% of the nanowire fabric volume is void space. Thermal annealing of the nanowire fabric in a reducing environment converts the polyphenylsilane coating to a carbonaceous layer that significantly increases the electrical conductivity of the material. This makes the nanowire fabric useful as a self-supporting, mechanically flexible, high-energy-storage anode material in a lithium ion battery. Anode capacities of more than 800 mA h g(-1) were achieved without the addition of conductive carbon or binder.

Solution-grown germanium (Ge) nanowires were tested as high capacity anodes in lithium ion (Li-ion) batteries. Nanowire films were formulated and cast as slurries with conductive carbon (7:1 Ge:C w/w), PVdF binder and 1.0 M LiPF(6) dissolved in various solvents as electrolyte. The addition of fluorethylene carbonate (FEC) to the electrolyte was critical to achieving stable battery cycling and reversible capacities as high as 1248 mA h g(-1) after 100 cycles, which is close to the theoretical capacity of 1,384 mA h g(-1). Ge nanowire anodes also exhibited high rate capability, with reversible cycling above 600 mA h g(-1) for 1200 cycles at a rate of 1C. The batteries could also be discharged at 10C with a capacity of 900 mA h g(-1) when charged at 1C.

Both silicon and germanium are leading candidates to replace the carbon anode of lithium ions batteries. Silicon is attractive because of its high lithium storage capacity while germanium, a superior electronic and ionic conductor, can support much higher charge/discharge rates. Here we investigate the electronic, electrochemical and optical properties of Si(1-x)Gex thin films with x = 0, 0.25, 0.5, 0.75, and 1. Glancing angle deposition provided amorphous films of reproducible nanostructure and porosity. The film's composition and physical properties were investigated by X-ray photoelectron spectroscopy, four-point probe conductivity, Raman, and UV-vis absorption spectroscopy. The films were assembled into coin cells to test their electrochemical properties as a lithium-ion battery anode material. The cells were cycled at various C-rates to determine the upper limits for high rate performance. Adjusting the composition in the Si(1-x)Gex system demonstrates a trade-off between rate capability and specific capacity. We show that high-capacity silicon anodes and high-rate germanium anodes are merely the two extremes; the composition of Si(1-x)Gex alloys provides a new parameter to use in electrode optimization.

A tin (Sn)-seeded supercritical fluid−liquid−solid (SFLS) synthesis of silicon (Si) nanowires with trisilane reactant was developed. When used as anodes in lithium ion (Li-ion) batteries, films of the nanowires with poly(vinylidene) fluoride (PVdF) or sodium alginate (NaAlg) binder, carbon conductor, and fluoroethylene carbonate (FEC)-containing electrolyte gave reversible, high charge storage capacities of 1,800 mA h g −1 . The nanowires also exhibited relatively good rate capability, with capacities of 400 mA h g −1 at the relatively fast cycling rates of 2C.