Oskar Paris

Infrared Emitting and Photoconducting Colloidal Silver Chalcogenide Nanocrystal Quantum Dots from a Silylamide-Promoted Synthesis

Here, we present a hot injection synthesis of colloidal Ag chalcogenide nanocrystals (Ag(2)Se, Ag(2)Te, and Ag(2)S) that resulted in exceptionally small nanocrystal sizes in the range between 2 and 4 nm. Ag chalcogenide nanocrystals exhibit band gap energies within the near-infrared spectral region, making these materials promising as environmentally benign alternatives to established infrared active nanocrystals containing toxic metals such as Hg, Cd, and Pb. We present Ag(2)Se nanocrystals in detail, giving size-tunable luminescence with quantum yields above 1.7%. The luminescence, with a decay time on the order of 130 ns, was shown to improve due to the growth of a monolayer thick ZnSe shell. Photoconductivity with a quantum efficiency of 27% was achieved by blending the Ag(2)Se nanocrystals with a soluble fullerene derivative. The co-injection of lithium silylamide was found to be crucial to the synthesis of Ag chalcogenide nanocrystals, which drastically increased their nucleation rate even at relatively low growth temperatures. Because the same observation was made for the nucleation of Cd chalcogenide nanocrystals, we conclude that the addition of lithium silylamide might generally promote wet-chemical synthesis of metal chalcogenide nanocrystals, including in as-yet unexplored materials.

CHAPTER 8:The Mineralized Crustacean Cuticle: Hierarchical Structure and Mechanical Properties

Arthropod cuticle is an excellent biological model system of a hierarchical nanocomposite for studying inner structure and architecture in connection with mechanical performance. While the hierarchical structure of non‐mineralized arthropod cuticle has been widely studied, only recently the particular biomineralization patterns found in crustaceans has attracted the interest of scientists from different fields. This chapter reviews some of the current knowledge about the hierarchical structure and mechanical properties of the crustacean exoskeleton, putting special emphasis on the relevance of mineral type and distribution for the mechanical function. In particular also the role of amorphous versus crystalline mineral phases is discussed.