Development of sulphonated co-polyimide based sensor for metal ions detection in aqueous media

This study reports a facile approach towards sensing properties of hydrophilic sulphonated co-polyimide (OBM-20) for the detection of metal ions in water through UV-vis spectroscopy. Anionic sulphonated co-polyimide (OBM-20) was synthesized by a two-step thermal imidization reaction. Hydrophilic anionic sulphonate group possessing strong affinity towards heavy metal ions resulted in improved interaction of OBM-20 with metal ions in aqueous media. OBM-20 showed different absorptions in UV region upon interacting with Ni (II), Co (II), and Cr (III) ions in deionized water at room temperature and neutral pH. Interestingly, OBM-20 demonstrated that it can serve as an optical chemical sensor and metal ion receptor for nanomolar detection of toxic metal ions, particularly Ni (II), Co (II), and Cr (III) existing in aqueous media. Sulphonated co-polyimide resulted in efficient sensing of Ni (II) as compared to slightly larger metals such as Co (II) and Cr (III) in aqueous solution. Ultimately, the assessment of the sensing properties of OBM-20 revealed that it can function as a selective Ni (II) ions sensor.