SÃntese e caracterizaÃÃo de nanopartÃculas de nÃquel para Ãptica nÃo linear / SÃntese e caracterizaÃÃo de nanopartÃculas de nÃquel para Ãptica nÃo linear

AUTOR(ES)

Gemima Barros Correia

DATA DE PUBLICAÇÃO

2008

RESUMO

In this work, we describe the synthesis of nickel nanoparticles (NPs) stabilized using poly (vinyl pyrrolidone), their structural and optical (linear and nonlinear) characterization. In Chapter 1 we present a general introduction describing the work performed. In Chapter 2 it is presented a review of nickel NPsâ properties and some synthesis processes. In Chapter 3 we present methods for preparation of nickel NPs, where we manipulate variables of synthesis (addition of reduction agent, temperature, and ratio between metallic precursor and polymer) and we evaluate their influence on the NPsâ size. The obtained results indicated that temperature is of fundamental importance in the preparation of NPs. The samples were structurally characterized by X-ray diffractometry and transmission electron microscopy. Nickel NPs with diameters of 2.5 nm and 8.6 nm were synthesized. In Chapter 4 it is described the optical characterization experiments of colloids containing Ni NPs. The linear and nonlinear optical experiments were made using UV-Vis spectroscopy and the z-scan technique, respectively. The nonlinear refraction index ( 2 n ) and the nonlinear absorption coefficient ( 2 α ) of the nickel NPs were determined and the results are discussed. The results show that the NPsâ nonlinear refractive index is negative. The nonlinear absorption coefficient measurements show that there is an inversion of the signal when the average NPs diameter changes from 8.6 nm to 2.5 nm

ASSUNTO(S)

nickel nonlinear optical polyol method nÃquel magnetic nanoparticles ciencias exatas e da terra mÃtodo poliol nanopartÃculas magnÃticas Ãptica nÃo linear

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