β-Cyclodextrin (β-CD)-modified CdSe (β-CD/CdSe) and CdSe-CdS core-shell structured (β-CD/ CdSe-CdS) quantum dots (QDs) were synthesized by a single-phase approach in aqueous solutions. These receptor-modified QDs are very soluble and stable in water over a wide range of pH values and ionic strengths. Coating a CdS shell on the CdSe core greatly increased the quantum yield (QY) of original CdSe QDs. Photoactivation of these particles by the room light results in 46% QY for β-CD/ CdSe-CdS in water. The surface-anchored β-CD still retains its host capability for the complexation of different organic species in aqueous solutions. More interestingly, the fluorescence sensitivity of these QDs to the same substrate is ten times higher than that of their counterparts reported in our previous work. Furthermore, the fluorescence of these receptor-modified QDs could be reversibly tuned in two directions, enhancement or quenching, by selectively introducing different redox-active substrates in aqueous media.

The mechanical compressive properties of individual thin-wall and thick-wall TiO(2) nanotubes were directly measured for the first time. Nanotubes with outside diameters of 75 and 110 nm and wall thicknesses of 5 and 15 nm, respectively, were axially compressed inside a 400 keV high-resolution transmission electron microscope (TEM) using a new fully integrated TEM-atomic force microscope (AFM) piezo-driven fixture for continuous recording of the force-displacement curves. Individual nanotubes were directly subjected to compressive loading. We found that the Young's modulus of titanium dioxide nanotubes depended on the diameter and wall thickness of the nanotube and is in the range of 23-44 GPa. The thin-wall nanotubes collapsed at approximately 1.0 to 1.2 microN during axial compression.

Understanding the effect of conductivity in electrospinning solutions is crucial in order to improve or control the electrospinning process. In this paper the effect of adding small amounts (0.039–0.259 mol · kg−1) of three different conductive additives to aqueous solutions of polyvinyl alcohol has been investigated. The salts were HMICl (a room temperature ionic liquid), TEBAC (a quaternary ammonium salt) and KCl. Addition of these salts caused a steady increase in the solution conductivity but the fiber diameter was typically greater than that of PVA alone, and exhibited an oscillatory trend. The oscillatory trend on the fiber diameter is attributed to fiber backbuilding and fusion that occurs prior to deposition on the collector.magnified image

The Sonogashira reaction was efficiently catalyzed by b-cyclodextrin-capped Pd nanoparticles (b-CD/Pd) in aqueous solution at room temperature. In addition, PPh 3 was not necessary to be present in the reaction media, and CuI, one major requirement for the typical homogeneous Sonogashira reaction, could be completely omitted without affecting the catalytic activity of b-CD/Pd nanoparticles. This study offers a new example of using b-CD-capped metal nanoparticles as a novel nanocatalyst for catalytic organic reaction in aqueous solution.

Improving the conductivity of electrospinning solutions is often achieved by adding small amounts of conductive additives. HMIMCl, a room temperature ionic liquid, and TEBAC, a quaternary ammonium salt, were added to polylactic acid in chloroform and their effects on solution properties, electrospinning, and fiber properties were investigated. Both additives increased the conductivity which decreased the fiber diameter, but differences were observed on the fiber dispersity and fiber morphology. The conductive solutions caused fiber backbuilding with aggregation and fiber fusion. Reasons for the differences in fiber diameter and fiber morphology are discussed.magnified image