Haritz Etxeberria

Effect of different aqueous synthesis parameters on the size of CdSe nanocrystals

The variation of CdSe nanoparticle size as a function of synthesis conditions is presented. Cadmium sulphate (CdSO4), cadmium chloride (CdCl2) and sodium selenosulphate (Na2SeSO3) solutions were used as precursors. Nanoparticles were synthesized by aqueous chemical methods. The synthesis parameters studied were pH, Cd:Se ratio and the type of stabilizing agent. Three different stabilizing agents were used, thioglycolic acid, mercaptoethanol and poly(vinyl pyrrolidone). Fourier transform infrared spectroscopy results confirmed the presence of the stabilizing agent on the surface of the nanoparticles. Ultraviolet visible and X-ray powder diffraction measurements were used to estimate the trend of size variations of the particles with different synthesis parameters, which agreed fairly by both techniques and the crystal structure. Additionally, the size of the nanoparticles was obtained by transmission electron microscopy measurements. Whilst the effect of pH was different for each of the different stabilizing agents due to the different chemical groups in the thiol compounds and the size of the nanoparticles varied with the used stabilizing agents, the effect of Cd:Se ratio in the size of nanoparticles showed the same tendency for the several stabilizing agents.

Effect of CdSe nanoparticle addition on nanostructuring of PS-b-P4VP copolymer via solvent vapor exposure

The surface morphology of poly(styrene-b-4 vinyl pyridine) (PS-b-P4VP) diblock copolymer thin films after solvent vapor annealing has been studied. Morphological features can be switched upon exposure to vapors of a solvent selective for one of the blocks. Self-assembled nanostructures such as hexagonal or striped morphologies were obtained varying vapor exposure time. In addition, the effect of the presence of CdSe nanoparticles located in the P4VP block on obtained nanostructures was analyzed. Atomic force microscopy (AFM) was used for morphological characterization of the block copolymer and the nanocomposites. AFM images showed that nanostructuring was different depending on the amount of CdSe nanoparticles, due to the decrease in P4VP chain mobility.