ELFT HÍRADÓ

[Szeminárium koordinátor <sem-admin AT szfki.hu>]

SZFI SeminarDatz DánielWigner RCP SZFIPolaritonic enhancement in boron 
nitride nanotubes measured by near-field infrared spectroscopyTuesday, 2 
February 2021, 10:00, video conference, 
https://letsmeet.wigner.hu/szeminariumChemical reactions in confined space, 
especially inside nanotubes have been an exciting topic for many reasons: new 
reaction pathways can be established resulting in unique products of specific 
structure (regioselectivity) or electronic properties (electronic 
selectivity), leading to various applications such as gas storage, catalysis 
and battery electrodes. However, finding the characterization methods to 
follow these reactions on the nanoscale remains a serious challenge. We 
demonstrate the possibility to investigate the products of chemical reactions 
between encapsulated molecules in nano-sized cavities in boron nitride 
nanotubes (BNNTs) in-situ with 20 nm spatial resolution. This small-scale 
investigation allows us to study the correlation of chemical reactivity with 
topology or other variables in the local environment. Scattering type 
near-field spectroscopy has been extensively applied to analyze collective 
optical properties of materials at the nanoscale. However, the near-field 
optical properties of the vibrational modes of small molecules were only 
recognizable in close proximity to a metallic resonator. We show that phonon 
polaritons of boron nitride nanotubes enhance the near-field vibrational 
spectra of molecules in close proximity of the surface. By encapsulating C60 
fullerene in BNNTs, we can reach a sensitivity level of a few hundred 
molecules. Furthermore, we show by the photopolymerization of C60 that 
products of chemical reactions inside the tubes can be identified, so long as 
their vibrational signatures lie in the polariton gap of the BNNT. The 
theoretical description of the scattering process is also being formulated 
based on the extension of the Mie scattering formalism. In this formalism, 
the electric field is expanded in the linear combination of spherical 
harmonics centered around the scattering particles. Reflection from surfaces 
and multiple scattering centers can also be handled, thus enabling the 
calculation of the backscattered electric field in the SNOM 
setup. Minden érdeklődőt szívesen látunk! - Everyone is welcome to 
attend.Róbert Juhászsem-admin AT szfki.hu