Gaseous and dissolved oxygen sensing with stabilized pyrene in ionic liquid modified electrospun slides

Abstract

Pyrene dye has many superior characteristics for oxygen sensing studies such as long fluorescence lifetime, high quantum yield, and good sensitivity. It is preferred in some cases over ruthenium dyes for its more lipophilic character and higher sensitivity. However, easy photodegradation of pyrene is a challenging problem. In this study, pyrene dye was for the first time immobilized in an ethyl cellulose matrix and used for oxygen sensing in the form of thin films and electrospun sensing slides. The hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate was used as additive for the first time for dissolved oxygen sensing studies. The oxygen sensitivity of the dye was evaluated with both steady state- and fluorescence lifetime-based measurements. The sensing slides were stable for 45 min under continuous irradiation and could be stored for 100 days under ambient laboratory conditions. This storage time is the longest reported lifetime for pyrene-based sensors. The enhanced stability can be attributed to the presence of ionic liquid, which behaves like a sink for oxidative, reductive, acidic, and/or basic effects. The sensor response time was between 6 and 20 s, depending on the oxygen concentration. The method can be applied for both dissolved and gaseous oxygen measurements.