Colloidal nanocrystals, a study on more efficient synthesis and deposition methods

Colloidal nanoparticles gained great interest due their size dependent optical properties. Several synthesis methods have been developed to improve the environmental impact of the chemical used. However these procedures bases mainly on homogeneous ODE-Se also show limitation regarding the yield and the tuning of optical properties. In the thesis an approach based on the use of a heterogeneous ODE-Se is investigated. The new precursor leads to high yield reactions as well as high tenability of the particle size. The new precursor has been used also to obtain homogeneous Cd(S,Se) alloys increasing in this way the degree of freedom in the tuning of the emission wavelength. Core/shell quantum dots have been studied to improve the luminescence properties of the particles. In particular a new method has been developed to overcome the time limitation imposed by the reactions commonly used in literature to create such structures. This method consists in a seed growth of core/shell quantum dots in a time span of few minutes and shell thickness up to 15 monolayers. Colloidal CdSe quantum dot shave been also investigated to understand the charging dynamics that lead to solution with a fraction of the particles carry a positive or negative charge. Finally iron oxide nanocrystals are synthesized, deposited and used as catalyst for the growth of carbon nanotubes, creating a flexible system that can optimize the different phases of the process in an independent wa