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SUMMARY:Eveline Mayner's Public Defense
DTSTART:20260529T040000
DTEND:20260529T220000
DTSTAMP:20260524T044515Z
UID:9af8a97840261455794b0ed200bfb1f7723fca10ff6bd0766ff1bba7
CATEGORIES:Miscellaneous
DESCRIPTION:Eveline Mayner\n\nAleksandra Radenovic\nTwo-dimensional (2D) m
 aterials have emerged as a versatile platform at the intersection of funda
 mental physics and applied science. Their atomically thin nature gives ris
 e to distinctive electronic and optical properties\, while simultaneously 
 enabling them to function as highly sensitive\, readily integrable probes 
 of their local environment. Advanced optical techniques\, such as super-re
 solution microscopy\, have opened new opportunities to interrogate these m
 aterials at the nanoscale\, providing optical access to individual defect 
 behaviors\, exciton diffusion and recombination dynamics\, and charge tran
 sport pathways. Such approaches not only deepen our understanding of intri
 nsic material behavior but also position 2D systems as powerful sensors ca
 pable of resolving local dielectric variations\, electric and magnetic fie
 lds\, and other environmental perturbations.\nCentral to this work is hexa
 gonal boron nitride (hBN)\, a transparent\, wide bandgap semiconductor tha
 t serves as a host for optically active defects. These defects function as
  reaction centers\, single-photon emitters\, and spatially resolved nanosc
 ale sensors that can be readily integrated into electronic and photonic ar
 chitectures. Owing to its optical transparency\, chemical stability\, and 
 compatibility with diverse material platforms\, hBN provides an exceptiona
 l foundation for optical sensing. Building upon this foundation\, we explo
 re material properties and present new methods for spatially resolved in s
 itu optical imaging with hBN to advance dynamic\, wide-field optical sensi
 ng.\nWe investigate a previously reported class of emitters that arise fro
 m interactions between native hBN and organic solvents. These emitters are
  believed to originate from defect sites that bind transiently to solvent 
 molecules. To study their behavior\, we develop a platform for imaging the
  dynamics of these transient emitters while varying the electrochemical po
 tential and applying electric fields with controlled orientations. By trac
 king the spectra of individual emitters\, we enable multiplexed measuremen
 ts that allow spatially resolved electrochemical imaging. Through systemat
 ic analysis\, we rule out modulation mechanisms based on direct electric f
 ield effects or charge transfer. Instead\, we identify a mechanism driven 
 by changes in H⁺ concentration\, which is modulated during the oxidation
  of trace water present in the solvent. This finding opens the possibility
  of using this platform for sensitive detection of H⁺ and trace water in
  methanol fuel cells\, where such species critically influence operational
  efficiency.\nIn the final part of the thesis\, we focus on a well-charact
 erized spin defect in hBN\, the negatively charged boron vacancy\, and exp
 lore strategies to enhance its photoluminescence (PL) through heterostruct
 ure engineering that facilitates energy and exciton transfer. We demonstra
 te the coupled structure’s improved utility in optical magnetometry comp
 ared to the defect by itself and discuss how improvements in PL could adva
 nce the development of wide-field optically detected magnetic resonance (O
 DMR) imaging using this spin defect. Using a defect in hBN would leverage 
 2D materials’ exceptional sensing capabilities and planar integrability.
 \nOverall\, this thesis aims to highlight the strengths of integrating 2D 
 materials with optical sensing and to develop transferable techniques for 
 introducing controlled stimuli\, such as electrochemical potentials\, elec
 tric fields\, or electromagnetic waves\, with high fidelity and minimal ar
 tifacts. These advances not only demonstrate the potential of hBN as a ver
 satile sensing platform but also establish methodologies applicable to a w
 ide range of low-dimensional material systems.\n\nFor zoom:\n Meeting ID:
  611 3428 2068 Passcode: 952027
LOCATION:ELA 1 https://plan.epfl.ch/?room==ELA%201 https://epfl.zoom.us/j/
 61134282068?pwd=zurg0qXVsUx4ln0hxCcrvjDCiHhwSx.1
STATUS:CONFIRMED
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