Fate of bis-(4-tert-butyl phenyl)-iodonium under photolithography relevant irradiation and the environmental risk properties of the formed photoproducts

Xi Zhi Niu, Richard D. Pepel, Rodrigo Paniego, Leif Abrell, James A Field, Jon Chorover, Reyes Sierra-Alvarez

Research output: Contribution to journalArticlepeer-review

Abstract

Aryl-iodonium salts are utilized as photoacid generators (PAGs) in semiconductor photolithography and other photo-initiated manufacturing processes. Despite their utilization and suspected toxicity, the fate of these compounds within the perimeter of semiconductor fabrication plants is inadequately understood; the identification of photolithography products is still needed for a comprehensive environmental impact assessment. This study investigated the photolytic transformation of a representative iodonium PAG cation, bis-(4-tert-butyl phenyl)-iodonium, under conditions simulating industrial photolithography. Under 254-nm irradiation, bis-(4-tert-butyl phenyl)-iodonium reacted rapidly with a photolytic half-life of 39.2 s; different counter ions or solvents did not impact the degradation kinetics. At a semiconductor photolithography-relevant UV dosage of 25 mJ cm−2, 33% of bis-(4-tert-butyl phenyl)-iodonium was estimated to be transformed. Six aromatic/hydrophobic photoproducts were identified utilizing a combination of HPLC–DAD and GC–MS. Selected photoproducts such as tert-butyl benzene and tert-butyl iodobenzene had remarkably higher acute microbial toxicity toward bacterium Aliivibrio fischeri compared to bis-(4-tert-butyl phenyl)-iodonium. Octanol–water partition coefficients estimated using the Estimation Programs Interface Suite™ indicated that the photoproducts were substantially more hydrophobic than the parent compound. The results fill a critical data gap hindering the environmental impact assessment of iodonium PAGs and provide clues on potential management strategies for both iodonium compounds and their photoproducts. Graphical abstract: [Figure not available: see fulltext.]

Original languageEnglish (US)
Pages (from-to)25988-25994
Number of pages7
JournalEnvironmental Science and Pollution Research
Volume29
Issue number17
DOIs
StatePublished - Apr 2022

Keywords

  • Bis-(4-tert-butyl phenyl)-iodonium
  • Iodonium photoacid generators
  • Microbial toxicity
  • Octanol–water partition
  • Photolytic transformation

ASJC Scopus subject areas

  • Environmental Chemistry
  • Pollution
  • Health, Toxicology and Mutagenesis

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