Monitoring Chemical Reactions with Terahertz Rotational Spectroscopy

Dayne F. Swearer, Samuel Gottheim, Jay G. Simmons, Dane J. Phillips, Matthew J. Kale, Michael J. McClain, Phillip Christopher, Naomi J. Halas*, Henry O. Everitt

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


Rotational spectroscopy is introduced as a new in situ method for monitoring gas-phase reactants and products during chemical reactions. Exploiting its unambiguous molecular recognition specificity and extraordinary detection sensitivity, rotational spectroscopy at terahertz frequencies was used to monitor the decomposition of carbonyl sulfide (OCS) over an aluminum nanocrystal (AlNC) plasmonic photocatalyst. The intrinsic surface oxide on AlNCs is discovered to have a large number of strongly basic sites that are effective for mediating OCS decomposition. Spectroscopic monitoring revealed two different photothermal decomposition pathways for OCS, depending on the absence or presence of H2O. The strength of rotational spectroscopy is witnessed through its ability to detect and distinguish isotopologues of the same mass from an unlabeled OCS precursor at concentrations of <1 nanomolar or partial pressures of <10 μTorr. These attributes recommend rotational spectroscopy as a compelling alternative for monitoring gas-phase chemical reactants and products in real time.

Original languageEnglish (US)
Pages (from-to)3097-3106
Number of pages10
JournalACS Photonics
Issue number8
StatePublished - Aug 15 2018
Externally publishedYes


  • aluminum nanocrystals
  • carbonyl sulfide
  • photocatalysis
  • plasmonics
  • rotational spectroscopy

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biotechnology
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering


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