New approaches to stretched film sample alignment and data collection for vibrational linear dichroism

Paul Wormell*, Pavel Michal, Adam Scott, Koushik Venkatesan, Kausala Mylvaganam, Tobias von Arx, Junya Kitamura, Jun Koshoubu, Alison Rodger*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
98 Downloads (Pure)

Abstract

Rapid measurements of vibrational linear dichroism (VLD) infrared spectra are shown to be possible by using stretched polymer films and an extension of existing instrumentation designed for vibrational circular dichroism spectroscopy. Earlier techniques can be extended using additional inexpensive polymer substrates to record good-quality VLD spectra of a significantly wider range of compounds with comparatively short sample-preparation times. The polymer substrates used, polyethylene and polytetrafluoroethylene, are commonly available and inexpensive, and samples are more easily prepared than that for many earlier stretched-film and crystal studies. Data are presented for neutral hydrophobic organic molecules on hydrophobic films including acridine, anthracene, fluorene, and recently synthesized S-(4-((4-cyanophenyl)ethynyl)phenyl)ethanethioate. We extend the approach to polar or ionic species, including 2,2 ' -bipyridine, 1,10-phenanthroline, and sodium dodecyl sulfate, by oxidizing polyethylene films to change their wetting properties. The combination of new instrumentation and modified sample preparation methods is useful in basic spectroscopy for untangling and assigning complicated infrared spectra. Nevertheless, it is not a panacea as surface-adsorbed molecules are often not monodispersed, and higher analyte concentrations can lead to aggregation and resonance phenomena that have previously been observed for infrared spectra on surfaces. These effects can be assessed by varying the sample concentration. The focus of this paper is experimental, and detailed analysis of most of the spectra lies outside its scope, including some well-studied compounds such as acridine and anthracene that allow comparisons with earlier research.
Original languageEnglish
Pages (from-to)37490-37500
Number of pages11
JournalACS Omega
Volume8
Issue number40
Early online date28 Sept 2023
DOIs
Publication statusPublished - 10 Oct 2023

Bibliographical note

Copyright the Author(s) 2023. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

  • Polarized infrared-spectra
  • Midinfrared spectroscopy
  • Fundamental vibrations
  • Circular-dichroism
  • Ir spectroscopy
  • Ft-ir
  • Polyethylene
  • Raman
  • Molecules
  • Symmetry

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