An in situ, reversible fluorescent paper sensor for selective detection of ambient CO2

Abstract

Analyzing the components and contents of environmental gases is of great importance for industrial production, human health, and environmental safety. Carbon dioxide (CO₂) has drawn great concern for its adverse effects on climate change and physical health. Simple, in situ, and selective methods for CO₂ detection are thus highly demanded. This work presents a versatile and easily fabricated paper sensor for the selective detection of ambient CO₂. The sensor consists of two components with a fluorescent molecule ANT-PPh₃ as the sensing element and an ionic liquid [DBUH]⁺[Im]⁻ for the absorption of CO₂. Based on the photo-induced electron transfer (PET) between ANT-PPh₃ and [DBUH]⁺[Im]⁻, the sensor exhibited fluorescence enhancement in the presence of CO₂, and the response process is reversible. The sensor exhibits improved selectivity for CO₂ over SO₂ and NO₂ compared with most reported works, with good stability and fast response to human breath. Without complex instrumentation and gas pre-collection processes, the early notification of high indoor CO₂ concentrations was realized using this sensor. Taking advantage of its intuitive fluorescence changes, specific responsiveness, and convenience, we believe our designed CO₂ sensor could be applied practically in monitoring and indicating high indoor CO₂ concentrations in living scenarios.