Optical detection of quaternary ammonium compounds in complex fluids

Quaternary ammonium compounds (QACs) are commonly used in disinfectants, household cleaners, cosmetics, preservatives, etc. The COVID-19 pandemic has resulted in increased use in QAC-based disinfectants to mitigate virus burden. These QAC compounds have also been detected in soil, surface water, vegetables, indoor dust particles, human blood and breast milk. Recent findings showed that exposure to some QACs can cause skin irritation, immunotoxicity, adverse respiratory effect, and metabolic disorders with an increase in inflammatory cytokines, decreased mitochondrial functions, and disruption of cholesterol homeostasis. Therefore, there is a growing concern regarding long-term biological impact from QACs. Thus, detection and monitoring QACs in various environments is crucial.

Semiconducting single-walled carbon nanotubes (SWCNTs) are emerging materials for the development of optical probes and sensors due to their outstanding photophysical characteristics in the near-infrared spectral range. SWCNT-based optical sensors could facilitate the optical detection of various classes of molecules in solution, in vitro, and in vivo. Herein, we show that carbon nanotube-based optical sensors allow detection of QACs in complex fluids. The findings from this research could provide a basis for engineering molecular probes in environmental and biological samples.