Ultrafast exciton dynamics in InAs/ZnSe nanocrystal quantum dots.

Colloidal nanocrystal quantum dots with a band gap in the near infra-red have potential application as the emitters for telecommunications or in vivo imaging, or as the photo-absorbing species in next generation solar cells or photodetectors. However, electro- and photoluminescence yields and the efficiency with which photo-generated charges can be extracted from quantum dots depend on the total rate of recombination, which can be dominated by surface-mediated processes. In this study, we use ultrafast transient absorption spectroscopy to characterise the recombination dynamics of photo-generated charges in InAs/ZnSe nanocrystal quantum dots. We find that recombination is dominated by rapid, sub-nanosecond transfer of conduction band electrons to surface states. For the size of dots studied, we also find no evidence of significant multiple exciton generation for photon energies up to 3.2 times the band gap, in agreement with our theoretical modelling.

Quantum dot-labelled polymer beads by suspension polymerisation.

CdSe quantum dots with polymerisable ligands have been incorporated into polystyrene beads, via a suspension polymerisation reaction, as a first step towards the optical encoding of solid supports for application in solid phase organic chemistry.

Analysis of metal-containing granules in the barnacle Tetraclita squamosa.

Metal-containing granules were isolated from specimens of the barnacle Tetraclita squamosa collected from a metal contaminated site in Hong Kong. The chemical composition, crystallographic and morphological properties of the deposits were analysed by X-ray powder diffraction, electron microscopy, energy dispersive analysis by X-rays and infrared spectroscopy. The most abundant metals were iron, calcium and zinc and the major anion was phosphate. Oxalates, carbonates and sulfur derivates were also found in small amounts. The deposits were amorphous to X-ray and electron diffraction and were approximately spherical in shape with diameters between 100 and 500 nm.

Spinel ferrite/MnO core/shell nanoparticles: chemical synthesis of all-oxide exchange biased architectures.

In this communication, we report the synthesis and characterization of organic-capped core/shell CoFe2O4/MnO nanoparticles. Magnetic properties of the core/shell nanoparticles were compared to those of individual CoFe2O4 and MnO nanoparticles prepared with similar methods. Magnetic measurements revealed that the core/shell nanoparticles displayed a shift in the hysteresis loops corresponding to exchange biasing exchange fields of about 0.6 kOe, due to the ferrimagnetic/antiferromagnetic interface.