Synthèse de Nano-agrégats Et de Matériaux Nanohybrides À Base D'oxyde de Zinc Par Ablation Laser Femtoseconde en Phase Liquide
Author | : Csaba Lảszlỏ Sajti |
Publisher | : |
Total Pages | : 310 |
Release | : 2007 |
ISBN-10 | : OCLC:494058433 |
ISBN-13 | : |
Rating | : 4/5 (33 Downloads) |
Book excerpt: Throughout this thesis, we have developed a method to synthesize ZnO nanoclusters and dye-grafted ZnO nanohybrids using femtosecond laser ablation in liquid environment. The average particle size, the size distribution and the optical properties of ejected species are controlled by the properties of the surrounding liquid, the laser parameters and concentration of the additives. Photoluminescence measurements revealed synthesized ZnO nanoparticles with very high optical quality. For nanoclusters ablated with mild laser fluence, we observed clear modifications in optical properties due to quantum confinement effects, resulting from size-reduced nanoparticles. ZnO nanohybrids were synthesized via two different techniques. ZnO nanoparticles are crystallized as spheres, whereas nanohybrids showed well-developed faceted surfaces indicating the change in growth condition owing to the presence of grafted chromophores on the nanoparticle surface. When exciting the ZnO core of the nanohybrids we observed efficient excitation exchange from the nanoparticles toward the attached dye molecules. The same effect was observed by two-photon excitation in the near IR region proving that the nanoparticles contribute to the grafted dye emission. Rapid exctitation exchange process was confirmed from the ZnO core material toward the grafted chromophores by time-correlated single photon fluorescence spectroscopy.