No abstract

The well-known fluorophore, namely 1,3,6,8-tetrakis[(trimethylsilyl)ethynyl]pyrene, has been studied profoundly as a fluorescent sensor toward nitroaromatic compounds in solutions and vapor phase. Three prototypes of fluorescent materials for vapor sensing were prepared via electrospinning and drop-casting onto the melamine formaldehyde foam with the fluorophore as a pure solid or as a dopant in the polystyrene matrix. It has been shown that this fluorophore and solid fluorescent materials based on it have high detection limits toward nitroaromatic compounds within the range of 10−8 to 10−9 M in acetonitrile solution and within the up to ppb range in the vapor phase. The model, expanding on Frisch’s permeation model, was utilized to characterize the fluorescence response of materials relative to vapor concentration and duration of exposure to vapor. All prototypes can be used as sensor materials exhibiting a good sensitivity and selectivity for the original hand-made sniffer for detecting nitro-containing explosives in the vapor phase for real-time application.

Integration of fluorescent substances into polymeric matrices can improve their sensory properties and photostability. In this work, fluorescent materials based on fluorophore-doped polystyrene were obtained and characterized as sensors towards the ecotoxicant nitrobenzene in gas phase. Melamine-formaldehyde foam has been proposed as a permeable substrate for the sensor material deposition applicable for gas-phase measurements. The effect on sensor properties of the porous material surface obtained via Breath Figure pore generation technique was investigated. Limits of detection and calibration relationships of obtained materials towards nitrobenzene were evaluated by materials exposure to low concentrations of nitrobenzene vapors. The sorption properties of polystyrene allow the retention of the quencher near the fluorophore, leading to improved detection limits compared with pure fluorophores. Obtaining a porous surface of the polymer material by the Breath Figure technique increases the scale of its fluorescence quenching by vapors. Detection limits (down to 0.45 ppm) and detectable concentration ranges (0.5 - 371.6 ppm) have been experimentally established. The relative standard deviations of the fluorescent signal of polymer materials do not exceed 13.3 % for a number of concentrations in the detectable range. The applicability of the calibration linear relationship of the logarithm of the fluorescent signal on the logarithm of the nitrobenzene vapor concentration is shown. Fluorescence signal measurements were performed using the original sensor element and the luminescence detector employing an array of fluorescent materials. The developed device is simple in application, portable, automated, and in combination with the used polymeric materials allows detection of nitrobenzene vapors in concentrations 2.5 times lower than the maximum permissible level.