Photothermal lens spectrometry of metallic nanoparticles colloids

ABSTRACT We report on pump-probe mode-mismatched photothermal le ns experiments of metallic nanoparticles water solutions. We show that metallic nanoparticles colloids exhibit nonlinear absorption effects related to attraction or repulsion forces that result from the interaction with the electromagnetic radiation. Gold and iron oxide nanoparticles show a double peak Z-scan shape that is associated to the presence of attraction forces. We calibrate the experiment using the linear absorption values of the samples obtaining their corresponding nonlinear absorption coefficients. Keywords: Photothermal lens spectrometry, metallic colloid properties, absorption spectroscopy 1. INTRODUCTION Metallic colloids, metallic particles of micrometer or nanome ter dimensions dissolved in water or other solvents, have been the field of study of a number of researchers thanks to their potential applications in Biophotonics and Biomedicine. 1-5 Of particular interest is the understanding of m echanism of interaction with electromagnetic radiation. Several authors have proposed the used of photothermal lens (PTL) method for characterization of optical absorption of metallic colloids.