Optical response of nanoalloy hydrogen sensors from first-principles
Typ
Examensarbete för masterexamen
Program
Applied physics (MPAPP), MSc
Publicerad
2020
Författare
Rosendal, Victor
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Hydrogen shows promise as a replacement for conventional fossil fuels. However,
its high flammability and gas permeability pose high demands on sensors, which
must respond quickly and accurately. Nanoscaling improves the kinetics and allows
for optical hydrogen sensing. A nanoscaled metallic sensor typically shows a welldefined
extinction peak in the optical regime and one proposed sensing technique is
to detect the shift in said peak due to hydrogenation.
The aim of this thesis is to, from first-principles, study the optical response of PdAu
nanodisks as a function of hydrogenation. PdAu:H was mainly treated as a random
alloy but thermodynamic structures were also investigated. Cluster expansions were
used in combination with Monte Carlo simulations to generate thermodynamically
representative PdAu:H structures. The dielectric functions for the random and the
thermodynamic structures were calculated by applying static and time-dependent
density functional theory. Optical extinction spectra of PdAu:H nanodisks were obtained
via electromagnetic finite-difference time-domain simulations using the previously
calculated dielectric functions.
The extinction peak of nanodisks with a diameter of 100 nm and height 20 nm
showed a redshift due to hydrogenation over the entire range of gold concentrations
of 0 to 42% considered here, and the redshift is approximately linear with respect to
hydrogen. Even though there is non-trivial ordering in the thermodynamic PdAu:H
structures, no clear difference between the random and thermodynamic case was
observed in the optical response.
Beskrivning
Ämne/nyckelord
hydrogen , sensing , palladium , gold , nanodisk , extinction , spectra , plasmonics , TDDFT , DFT