Plasma-Induced Interfacial Processes in Metal Halides FTIR Gas Cell Windows

TY - JOUR

T1 - Plasma-Induced Interfacial Processes in Metal Halides FTIR Gas Cell Windows

AU - Olenik, Jaka

AU - Shvalya, Vasyl

AU - Modic, Martina

AU - Ekar, Jernej

AU - Kovač, Janez

AU - Cvelbar, Uroš

AU - Walsh, James L.

N1 - Funding Information: The authors gratefully acknowledge financial support from the Public Agency for Research Activity of the Republic of Slovenia (awards J2-4490, J2-4451 and L2-4481), the UK Engineering and Physical Sciences Research Council (EPSRC) (awards EP/S025790/1 and EP/N021347/1) and NATO (award G5814). Publisher Copyright: © 2023, The Author(s).

PY - 2023/12/12

Y1 - 2023/12/12

N2 - Fourier transform infrared spectroscopy (FTIR) is one of the most widely used vibrational diagnostic techniques to investigate gas-phase reactive oxygen and nitrogen species (RONS). However, the technique carries intrinsic challenges, particularly in relation to interfering peaks in the spectral data. This study explores the interfacial processes that occur when reactive oxygen and nitrogen species generated by a non-equilibrium air plasma interact with the metal halide windows of an FTIR gas cell, leading to the appearance and evolution of spurious absorption peaks which complicate spectral interpretation. Raman spectroscopy, X-ray photoelectron spectroscopy, time of flight secondary ion mass spectrometry and attenuated total reflectance-FTIR spectroscopy were used to elucidate the origin of spurious absorption peaks spanning the 1400–1300 cm−1 spectral range as a result of KBr exposure to plasma generated species. It was found that plasma exposed KBr contained a lower atomic fraction of Br which was replaced by the NO3 nitrate group, the main absorbance peak of which progressively evolved with plasma exposure and affected the window transparency over the corresponding FTIR region. A correlation was revealed between KNO3 formation, plasma power and exposure time to a growth and change in molecular vibrational energies corresponding to asymmetric NO3 stretching vibrations in the KNO3 structure.

AB - Fourier transform infrared spectroscopy (FTIR) is one of the most widely used vibrational diagnostic techniques to investigate gas-phase reactive oxygen and nitrogen species (RONS). However, the technique carries intrinsic challenges, particularly in relation to interfering peaks in the spectral data. This study explores the interfacial processes that occur when reactive oxygen and nitrogen species generated by a non-equilibrium air plasma interact with the metal halide windows of an FTIR gas cell, leading to the appearance and evolution of spurious absorption peaks which complicate spectral interpretation. Raman spectroscopy, X-ray photoelectron spectroscopy, time of flight secondary ion mass spectrometry and attenuated total reflectance-FTIR spectroscopy were used to elucidate the origin of spurious absorption peaks spanning the 1400–1300 cm−1 spectral range as a result of KBr exposure to plasma generated species. It was found that plasma exposed KBr contained a lower atomic fraction of Br which was replaced by the NO3 nitrate group, the main absorbance peak of which progressively evolved with plasma exposure and affected the window transparency over the corresponding FTIR region. A correlation was revealed between KNO3 formation, plasma power and exposure time to a growth and change in molecular vibrational energies corresponding to asymmetric NO3 stretching vibrations in the KNO3 structure.

KW - Cold atmospheric-pressure plasma

KW - Gas-phase FTIR

KW - IR windows

KW - KBr

KW - RONS

KW - Surface functionalisation

UR - http://www.scopus.com/inward/record.url?scp=85179332517&partnerID=8YFLogxK

U2 - 10.1007/s41664-023-00274-y

DO - 10.1007/s41664-023-00274-y

M3 - Article

AN - SCOPUS:85179332517

SN - 2096-241X

VL - 7

SP - 392

EP - 404

JO - Journal of Analysis and Testing

JF - Journal of Analysis and Testing

IS - 4

ER -