Carbon nanotube growth from Langmuir-Blodgett deposited Fe3O4 nanocrystals.

We investigate colloidal Fe(3)O(4) nanocrystals as a catalyst system for carbon nanotube (CNT) growth that allows for decoupling the CNT growth step from the catalyst shaping and activation step. The system consists of 6.4 nm Fe(3)O(4) nanocrystals synthesized using a solution-based thermal decomposition reaction and, subsequently, transferred as hexagonally ordered Langmuir-Blodgett (LB) monolayers on TiN substrates.

The different nature of band edge absorption and emission in colloidal PbSe/CdSe core/shell quantum dots.

We present a quantitative analysis of the absorption and luminescence of colloidal PbSe/CdSe core/shell quantum dots (QDs). In absorption, both the energy and the oscillator strength of the first exciton transition coincide with that of plain PbSe QDs. In contrast, luminescence lifetime measurements indicate that the oscillator strength of the emitting transition is reduced by at least a factor of 4 compared to PbSe core QDs.

Utilizing self-exchange to address the binding of carboxylic acid ligands to CdSe quantum dots.

We use solution NMR techniques to analyze the organic/inorganic interface of CdSe quantum dots (Q-CdSe) synthesized using oleic acid as a surfactant. It is shown that the resulting Q-CdSe are stabilized by tightly bound oleic acid species that only exchange upon addition of free oleic acid. The NMR analysis points toward a two-step exchange mechanism where free ligands are initially physisorbed within the ligand shell to end up as bound, chemisorbed ligands in a second step.

Langmuir-Blodgett monolayers of colloidal lead chalcogenide quantum dots: morphology and photoluminescence.

Monolayers of PbSe and PbS quantum dots and PbSe/CdSe core/shell quantum dots made by Langmuir-Blodgett deposition are compared, with a focus on the formation, the morphology and the photoluminescence properties of the films. It is shown that PbSe quantum dots suffer from oriented attachment and a complete quenching of their photoluminescence after Langmuir-Blodgett processing. While the oriented attachment can be resolved by growing a CdSe shell around the PbSe core QDs, the photoluminescence of PbSe/CdSe Langmuir-Blodgett monolayers remains largely quenched.

Langmuir-Schaefer deposition of quantum dot multilayers.

The application of colloidal nanocrystals in various devices requires their assembly into well-defined mono- or multilayers. We explore the possibilities of the Langmuir-Schaefer technique to make such layers, using CdSe quantum dots as a model system. The layer quality is assessed using atomic force microscopy, transmission electron microscopy, and UV-vis absorption spectroscopy.

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.

Novel biotransformation and physiological properties of norursodeoxycholic acid in humans.

Experiments were performed in 2 volunteers to define the biotransformation and physiological properties of norursodeoxycholic acid (norUDCA), the C(23) (C(24)-nor) homolog of UDCA. To complement the in vivo studies, the biotransformation of norUDCA ex vivo using precision-cut human liver slices was also characterized. In the human studies, both a tracer dose given intravenously and a physiological dose (7.

In situ analysis of mediaeval wall paintings: a challenge for mobile Raman spectroscopy.

Raman spectroscopy is an analytical technique, which is gaining attention as a molecular technique for the investigation of objects of art. Especially the non-destructive properties of the method make this application suitable for the in situ analysis of artefacts. However, although using mobile, fibre optics Raman instrumentation for this type of research seems to be straightforward, some practical obstacles may hamper the investigation.