Version 2 2021-03-09, 20:15Version 2 2021-03-09, 20:15
Version 1 2021-03-08, 16:36Version 1 2021-03-08, 16:36
journal contribution
posted on 2021-03-09, 20:15authored byQuaid Zaman, Jefferson S. Costa, Tahir, Arthur R. J. Barreto, Jefferson F. D. F. Araujo, Luís D. Carlos, Albano N. Carneiro Neto, Marco Cremona, Zubair Ahmed, André Felipe S. Cruz, Nadson Welkson P. Souza, Karlo Q. da Costa, Victor Dmitriev, Anna Laurenzana, Francesca Margheri, Tommaso Del Rosso
An
alternative approach to classical surface plasmon resonance
spectroscopy is dielectric-loaded waveguide (DLWG) spectroscopy, widely
used in the past decades to investigate bio-interaction kinetics.
Despite their wide application, a successful and clear approach to
use the DLWGs for the one-step simultaneous determination of both
the thickness and refractive index of organic thin films is absent
in the literature. We propose here, for the first time, an experimental
protocol based on the multimodal nature of DLWGs to be followed in
order to evaluate the optical constants and thickness of transparent
thin films with a unique measurement. The proposed method is general
and can be applied to every class of transparent organic materials,
with a resolution and accuracy which depend on the nature of the external
medium (gaseous or liquid), the geometrical characteristics of the
DLWG, and the values of both the thickness and dielectric constant
of the thin film. From the experimental point of view, the method
is demonstrated in a nitrogen environment with an accuracy of about
3%, for the special case of electroluminescent thin films of Eu3+β-diketonate complexes, with an average thickness of
about 20 nm. The high value of the refractive index measured for the
thin film with the Eu(btfa)3(t-bpete) complex was confirmed
by the use of a spectroscopic model based on the Judd–Ofelt
theory, in which the magnetic dipole transition 5D0 → 7F1 (Eu3+) for
similar films containing Eu3+ complexes is taken as a reference.
The DLWGs are finally applied to control the refractive index changes
of the organic thin films under UVA irradiation, with potential applications
in dosimetry and monitoring light-induced transformation in organic
thin films.