Size-dependent optical properties of colloidal PbS quantum dots.

We quantitatively investigate the size-dependent optical properties of colloidal PbS nanocrystals or quantum dots (Qdots), by combining the Qdot absorbance spectra with detailed elemental analysis of the Qdot suspensions. At high energies, the molar extinction coefficient epsilon increases with the Qdot volume d(3) and agrees with theoretical calculations using the Maxwell-Garnett effective medium theory and bulk values for the Qdot dielectric function. This demonstrates that quantum confinement has no influence on epsilon in this spectral range, and it provides an accurate method to calculate the Qdot concentration.

The growth of Co:ZnO/ZnO core/shell colloidal quantum dots: changes in nanocrystal size, concentration and dopant coordination.

We report a synthesis route for the growth of Co:ZnO/ZnO core/shell quantum dots. This procedure consists of successive steps, comprising the addition of diluted precursor salt solutions, and heat treatment at 50 degrees C. By deriving a relation between the extinction coefficient at 250 nm and the nanocrystal diameter, we are able to monitor changes in quantum dot concentration during shell growth.

Lead isotopic analysis of infant bone tissue dating from the Roman era via multicollector ICP-mass spectrometry.

Archaeological samples originating from a cemetery of a Roman settlement, Pretorium Agrippinae (1st-3rd century A.D.), excavated near Valkenburg (The Netherlands) have been subjected to Pb isotopic analysis.