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UID:69d8d1c2c8aed
DTSTART:20221107T110000Z
SEQUENCE:0
TRANSP:OPAQUE
LOCATION:Online (Teams)
SUMMARY:ICFO | NESTOR BAREZA
CLASS:PUBLIC
DESCRIPTION:Mid-infrared (mid-IR) spectroscopy in the wavelength region bet
 ween 2 and 20 &mu\;m is a powerful technique to identify vibrational absor
 ption signatures of molecules\, finding in this way extensive applications
  in healthcare\, environmental monitoring\, and chemical analysis. Enhance
 d IR light-molecules interactions can be achieved by exploiting nanostruct
 ured surfaces supporting polaritons &ndash\; hybrid excitations of light a
 nd dipolar elements of matter. Recently\, polaritons of two-dimensional va
 n der Waals (2D-vdW) materials unveiled a vibrant playground for mid-IR sp
 ectroscopy as they possess remarkable properties such as light trapping at
  deep nanoscale. This dissertation aims to investigate 2D-vdW materials fo
 r technological sensing applications. Hence\, we explore the mid-IR sensin
 g performance of nanostructures of widely studied 2D-vdW crystals: graphen
 e (the pioneering vdW material with tunable plasmon polaritons) and hexago
 nal boron nitride (hBN\, sustaining ultralow-loss phonon polaritons). Rele
 vant functionalization layers\, such as polymer adsorber and antibodies\, 
 are combined with the 2D-vdW nanostructures to create gas and for bio-mole
 cular sensors\, respectively.\nHere\, we present three main experimental w
 orks of 2D-vdW-based mid-IR molecular sensing. First\, we investigate the 
 CO2 detection using graphene nanoribbons functionalized with ultrathin CO2
 -chemisorbing polyethylenimine (PEI). The localized surface plasmon resona
 nce (LSPR) of graphene is modulated by varying CO2 gas concentration\, who
 se substantial shifts are influenced by the reversible PEI-induced doping 
 of graphene. Second\, we examine the phonon-enhanced CO2 detection of hBN 
 nanoresonators functionalized with thin PEI layer. The phonon-polariton re
 sonance is modulated by varying CO2 levels with high signal-to-noise ratio
  signals. Third\, we present a quantitative bioassay by transducing differ
 ent vitamin B12 target concentrations into LSPR shifts of bio-functionaliz
 ed graphene nanostructures (subsequent addition of pyrene linkers and reco
 mbinant anti-vB12 antibody fragments). Additionally\, we observed the same
  result-trends for the same bioassay using graphene nanostructures fabrica
 ted both by small-scale (i.e.\, electron beam lithography) and large-scale
  (i.e.\, nanoimprint lithography) methods.\nOur proof-of-concept mid-IR se
 nsing experiments show quantitative results for the detection of gas and b
 iomarker with functionalized 2D-vdW nanostructures. The opportunity of com
 bining the mid-IR spectroscopy with industrially large-scale 2D-vdW nanost
 ructures (e.g.\, nanoimprinted GNH in this dissertation) would enable cost
 -effective technologies in future developments. This dissertation contribu
 tes to the field of 2D-vdW-based mid-IR spectroscopic sensors towards expl
 oring novel designs and improved sensitivity\, which eventually could lowe
 r the limit of detection for molecular analytes in various applications.\n
 &nbsp\;\nThesis Directors: Prof Dr. Valerio Pruneri and Dr. Bruno Paulillo
DTSTAMP:20260410T103234Z
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