During a Post Doc at the Fritz Haber Institute in the inorganic chemistry department, I worked on the synthesis, characterization and the study of the catalitic properties of vanadium oxide nanoparticles.

Divanadium pentoxide (V₂O₅) nanorods and nanowires have been synthesized by the reverse micelle technique [1,2] . The length can be tuned easily by keeping the particles in micellar solution after the synthesis from 40 nm to 2 µm. The particles awere characterized by transmission electron microscopy, x-ray photoemission spectroscopy, electron energy loss spectrometry, infrared spectroscopy and x-ray diffraction. These techniques show that the nanorods and nanowires consist of divanadium pentoxide and crystallize in the gamma phase. Such an uniform and well defined nanomaterial offers the opportunity to study selective oxidation on a model system with well defined surface morphology and high crystalline order containing the oxidation state V⁵⁺ that is difficult to obtain with more conventional PVD methods.

Figure 1: Divanadium pentoxide nanorods and nanowires synthesized in reverse micelles. Just after synthesis (a), after 24h (b), 4 days (c) and 100 days (d) in micellar solution respectively

My PhD work was mainly focused on the synthesis and the characterization of CdS nanotriangles

The optical properties of semiconductor nanocrystals can be tuned by two parameters: the size and the shape[3,4]. With the reverse micelle technique we were able to tune the size of the nanocrystals from 3 to 10 nm and to change the shape from spherical to triangular. The TEM image of triangular CdS nanocrystals is shown in Figure 2 a. The HRTEM image and the power spectrum (Fig. 2 b and c) shows that the nanotriangles are well crystallized. The structure and the shape of these nanotriangles have been studied by advanced electron microscopy techniques. These techniques show that the nanotriangles are crystallized in the wurtzite structure without the presence of any default and that the particles are flat.
The optical properties of triangular CdS nanocrystals are strictly related to the shape of the nanocrystals[3]. In fact, we observe a quantum size effect even if the side length of the nanotriangles is 10 nm. This is due to the fact that the smallest distance (i.e. the thickness which is < 6 nm) is responsible of the quantum size effect.

Figure 2: TEM image of CdS triangular shaped nanocrystals (A). HRTEM of a single nanocrystal (B) and its power spectrum (C)