CW laser-induced photothermal conversion and shape transformation of gold nanodogbones in hydrated chitosan films |
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| Authors: | Fulvio Ratto Paolo Matteini Alberto Cini Sonia Centi Francesca Rossi Franco Fusi Roberto Pini |
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| Institution: | (1) Institute of Applied Physics, National Research Council of Italy, Via Madonna del Piano 10, 50019 Sesto Fiorentino, FI, Italy;(2) Department of Physics and Astronomy, University of Florence, Viale delle Idee 16, 50019 Sesto Fiorentino, FI, Italy;(3) Department of Clinical Physiopathology, University of Florence, Viale G. Pieraccini 6, 50139 Florence, Italy |
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| Abstract: | We investigate the photothermal conversion and transformation of gold nanoparticles with an initial dogbone shape after dispersion
in hydrated chitosan films, which is a representative model of biological tissue, and excitation by a CW diode laser for 1 min.
Gold nanodogbones are observed to undergo a distinct modification above a sharp threshold of ~11 W cm−2 and 110 °C. Surprisingly, the very same modification is achieved up to at least 36 W cm−2 and 250 °C. We use an analytical model derived from Gans theory to associate the change in color of the films with the change
in shape statistics of these gold nanoparticles. This model proves both convenient and dependable. We interpret the photothermal
transformation as a rearrangement of particles with a dogbone shape and an aspect ratio of 4.1 into rods with an aspect ratio
of 2.5, where material from the end lobes of the dogbones may relocate to the waists of the rods. In turn, additional transitions
to stable gold nanospheres may exhibit fairly slower kinetics. |
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