Optical manipulation of quantum dots and single magnetic nanostructures
Author
Rodríguez Rodríguez, HectorEntity
UAM. Departamento de Física de MaterialesDate
2019-05-31Subjects
Nanotecnología - Tesis doctorales; FísicaNote
Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física de Materiales. Fecha de lectura: 31-05-2019Esta tesis tiene embargado el acceso al texto completo hasta el 30-11-2020
Esta obra está bajo una licencia de Creative Commons Reconocimiento-NoComercial-SinObraDerivada 4.0 Internacional.
Abstract
Optical capture is a technique that makes contactless manipulation of colloidal
nanoparticles accessible by means of a focused laser beam. In the
present thesis, experiments were performed in a weakly focused optical trap,
which allow the direct measurement of the optical forces exerted on the trapped
object. Due to this peculiarity, optical forces exerted on generic individual
nanoparticles have been studied and the conditions under which a stable
trap is formed have been determined. These conditions have been verified
for individual iron oxide nanoparticles encapsulated in silica, and the photoinduced
heating resulting from the absorption of light from the laser has
been investigated. The theoretical results have been experimentally verified
by means of the study of the viscosity in the environment of the trapped
nanoparticle, whose decrease when increasing the power of the laser is related
to heating. Likewise, it has been shown that the same experimental conditions
do not allow the manipulation of individual colloidal quantum dots
encapsulated in silica. On the contrary, aggregates of these nanoparticles are
easily trapped and show photoluminescence as a result of a two-photon absorption
process. The photodynamic processes affecting their emission and
limiting their use as remotely controlled sensors have been studied. It has
been observed that the isolation of the quantum dots by means of a sulfur intermediate
passivating layer and a silica cover delays their degradation in the
optical trap. Finally, the manipulation of silver sulfide nanoparticles, which
show great interest in fluorescence microscopy in the near-infrared range, is
demonstrated.
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