Fluorene based fluorescent and colorimetric sensors for ultrasensitive detection of nitroaromatics in aqueous medium

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Chemistry., 2022-03, Vol.425, p.113660, Article 113660
• Main Authors: Tahir Waseem, Muhammad, Muhammad Junaid, Hafiz, Gul, Hira, Ali Khan, Zulfiqar, Yu, Cong, Anjum Shahzad, Sohail
• Format: Article
• Language: English
• Subjects: Fluorescence sensor; FRET; Knoevenagel condensation; PET; Picric acid; Suzuki coupling
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/j.jphotochem.2021.113660

[Display omitted] •New fluorene based sensors 4 and 5 were synthesized and characterized.•Ultrasensitive sensing of picric acid (PA) was detected selectively with low limit of detection (LOD) of 22 ppt for sensor 4.•Sensor 5 exhibited PA detection with very low LOD of 0.23 ppt through FRET, IFE and PET based fluorescence quenching mechanisms.•Both sensors were used for rapid detection of picric acid in real samples.•Sensors displayed ultra-selective colorimetric detection of picric acid.•Plausible interaction of sensors with PA was supported by 1HNMR, UV Vis., DLS, and computational studies. New butterfly-shaped π-extended sensors 4 and 5 were synthesized through the Knoevenagel condensation and the Suzuki-Miyaura coupling reaction. Sensors were employed for sensitive detection of nitroaromatics. Among nitroaromatic compounds (NACs), sensors 4 and 5 exhibited ultrasensitive fluorescence quenching response to picric acid (PA) with quenching efficiency >45 and >260 folds and limit of detection (LOD) 22.0 and 0.23 ppt (parts per trillion), respectively. This ultra-sensitivity was contributed by FRET and IFE processes. Selective interaction of sensors with PA was evaluated by fluorescence, UV–Vis., 1H NMR titration, dynamic light scattering (DLS), and density functional theory (DFT) calculations. These sensors were successfully employed for detection of picric acid in real water samples. Interestingly, sensors 4 and 5 showed selective colorimetric recognition of picric acid. Moreover, sensors’ coated test strips were fabricated for an immediate naked eye detection of PA that demonstrated rapidity, simplicity, and convenience for on-site detection of PA. Robust sensitivity for PA illustrated that these sensors can be employed in the development of new detection tools for PA analysis in real samples.