Preparation of conductive gold nanowires in confined environment of gold-filled polymer nanotubes.

Continuous conductive gold nanofibers are prepared via the "tubes by fiber templates" process. First, poly(l-lactide) (PLLA)-stabilized gold nanoparticles (AuNP) with over 60 wt% gold are synthesized and characterized, including gel permeation chromatography coupled with a diode array detector. Subsequent electrospinning of these AuNP with template PLLA results in composite nanofibers featuring a high gold content of 57 wt%. Highly homogeneous gold nanowires are obtained after chemical vapor deposition of 345 nm of poly(p-xylylene) (PPX) onto the composite fibers followed by pyrolysis of the polymers at 1050 °C. The corresponding heat-induced transition from continuous gold-loaded polymer tubes to smooth gold nanofibers is studied by transmission electron microscopy and helium ion microscopy using both secondary electrons and Rutherford backscattered ions.

Tea-bag-like polymer nanoreactors filled with gold nanoparticles.

Gold-containing polymer nanotubes, which showed both catalytic activity and resistance to leaching, were prepared by the "tubes by fiber templates" (TUFT) process. For this purpose, electrospun polymer nonwovens with incorporated poly(L-lactide)-stabilized gold nanoparticles were coated with poly(p-xylylene) by the chemical vapor deposition process, and then the inner fiber templates were removed. The resulting polymer tubes carried encapsulated gold nanoparticles which were shown to be immobilized and featured pronounced catalytic activity towards the hydrolytic oxidation of dimethylphenylsilane and the alcoholysis of dimethylphenylsilane with n-butanol. The macroscopic nonwovens could be used as tea-bag-like catalyst systems and showed excellent reusability.

Ultrasound-mediated synthesis of high-molecular weight polystyrene-grafted silver nanoparticles by facile ligand exchange reactions in suspension.

Ultrasound mediated facile ligand exchange method in suspension for the formation of polystyrene-grafted silver nanoparticles is reported. Amazingly, this method allows even grafting of very high molecular weight polystyrenes (up to 217 200 g mol(-1) ) having a single terminal thiol group at the chain end. Detailed studies are carried out to gain insights in the role of molecular weight of the ligands and the mechanism of the ligand exchange reactions. Key factors are determined to be the droplet formation by ultrasonification and low silver content, which enhances the availability of the terminal thiol end group significantly. The extraordinary compatibility of the ligand exchange method in particular regarding high molecular weights is attributed to hydrophilic orientation of the terminal thiol groups at the liquid-liquid interphase. This is proved conclusively by using an in situ method as a reference approach in which agglomeration occurs at considerably lower molecular weights due to the absence of preferred end group orientation within the polymer coil. In homogeneous phase only the chain length is found to be the crucial factor in stabilization of silver nanoparticles.

Biocompatible drug delivery system for photo-triggered controlled release of 5-Fluorouracil.

The synthesis of a photo-triggered biocompatible drug delivery system on the basis of coumarin-functionalized block copolymers is reported. The coumarin-functionalized block copolymers poly(ethylene oxide)-b-poly(n-butyl methacrylate-co-4-methyl-[7-(methacryloyl)oxyethyloxy]coumarin)) (PEO-b-P(BMA- co-CMA)) were synthesized via atom transfer radical polymerization (ATRP). The micelle-drug conjugates were made by covalent bonding of anticancer drug 5-fluorouracil (5-FU) to the coumarin under UV irradiation at wavelength >310 nm. These micelle-drug conjugates possessed spherical morphology with diameters of 70 nm from TEM images. In vitro drug release experiments showed the controlled release of anticancer drug 5-FU from the micelle-drug conjugates under UV irradiation (254 nm). These micelle-drug conjugates also showed excellent biocompatibility by the in vitro cytotoxicity experiments. The results suggest that these micelle-drug conjugates could be a promising candidate for the delivery of anticancer agents with low side effects on normal cells and excellent therapeutic efficacy to cancer cells.