Receptor free fluorescent and colorimetric sensors for solution and vapor phase detection of hazardous pollutant nitrobenzene; a new structural approach to design AIEE active and piezofluorochromic sensors

Two new AIEE active fluorenes 2 and 3 were synthesized via a Suzuki coupling reaction. Sensors, that are free from any receptor showed highly selective detection of active hazardous material, nitrobenzene (NB) in solution and vapor phase based on fluorescence quenching response. The highly selective fluorescence detection of NB was attributed to the adjustable smaller size of NB that eases it to penetrate the cavities of sensors. The fluorescence based detection limits (LOD) of sensors 2 and 3 were determined as 1.21 nM and 1.55 nM, respectively. To the best of our knowledge, these are the first receptor free fluorescent sensors that are used for the convenient detection of NB both in solution and vapor phase. Possible interaction between sensor and NB was evaluated through 1H NMR titration, dynamic light scattering (DLS), and computational methodologies. Moreover, sensors displayed highly selective colorimetric detection of NB that was successfully recorded through the smartphonebased application (Color Assist). Contact mode detection of NB was accomplished through economical and portable test strips. Sensors were also used for the detection of NB in industrial samples. Additionally, sensors possess distinct solvatochromic, piezofluorochromic characters and were used as fluorescent ink that provides them additional advantages.

Automated summary

Two new AIEE active fluorenes were synthesized and used as receptor-free fluorescent sensors for the highly selective detection of nitrobenzene in solution and vapor phase. These sensors exhibited adjustable size cavities that allowed for the penetration of nitrobenzene, resulting in highly selective fluorescence quenching response. The sensors also displayed colorimetric detection and could be used as fluorescent ink, providing additional advantages.