A paper-based vapoluminescent chemosensor based on a Zinc(II) salen-type complex for the selective and sensitive detection of n-butylamine vapours

Aliphatic amines are widely involved in chemical industries and their presence in food products is often related to food spoilage processes. Furthermore, aliphatic amines with short chain length (C2 – C6) possess high volatility and toxicity at low concentrations (ppm). Among them, n-butylamine (BA) is used in chemical industries as reactant, or intermediate in many synthetic routes. Because of its high volatility (93 mmHg at 25 °C) the main risk for human health is the inhalation. Prolonged exposure to this amine vapours can cause nausea, vomiting, and, in some cases, damage to the nervous system. For this reason, its quantitative detection is very important for human safety. To this end, a Lewis acidic Zn(salen)-type complex1,2 was chosen for the development of a new molecular material with vapoluminescent properties, as potential chemosensor for vapour-phase detection of BA. A paper-based sensor, fabricated by the dip-coating technique using THF solutions of the complex, was used for the quantitative detection of BA vapours. Static exposure experiments, show a linear response between 0 and 50 ppm, with a limit of detection of 2.0 ppm, below the permissible exposure limit (5 ppm) established by OSHA for BA. The effect of exposure time, exposure temperature and relative humidity on the sensor performance was also evaluated. Competitive experiments demonstrate the high selectivity of this sensor towards BA. In summary the developed paper-based sensor of the Zn(II) complex represents a simple, disposable, and cost-effective chemosensor for the selective and sensitive direct in-situ detection of BA vapours. This research is funded by European Union (NextGeneration EU), through the MUR-PNRR project SAMOTHRACE (ECS00000022).