Light responsive, electrochemically dimerizable, capture and release device based on photochromic oxazine for nanomolar level detection of Hg2+ions

Photochromic oxazine was synthesized and screened for the colorimetric detection of heavy metal ions in an aqueous solution. The OX (closed) form of the oxazine converted rapidly to the IN (open) form in presence of mercuric ions. The mercuric ion-induced structural alteration led to the appearance of an intense band in the visible region of the absorption spectrum in an aqueous acetonitrile medium. Naked eye, UV-Visible, cyclic voltammetry (CV), and smartphone-based techniques were successfully employed to study the detection process. The probe provided a 40 nM limit of detection value for Hg2+ ions using CV. The 1H NMR spectroscopy confirmed the interaction of the mercury ion with the oxazine unit and the ring-opening process. The cyclic voltammetric studies indicated the formation of C-C bonds producing dimeric oxazine. The process of formation of a C-C bond was investigated in the presence of Hg2+ ions, which was used as a detection method. The development of color in the complex was exploited to develop the solution and paper-based detection techniques aided by digital images of easily available smartphones and software. The probe-Hg2+ complex released mercuric ion upon exposure to visible light (450 nm) in water.

Automated summary

The research successfully synthesized a photochromic oxazine compound and utilized mercuric ion-induced structural alteration for colorimetric detection of heavy metal ions. The detection process was studied using various techniques including naked eye observation, UV-Visible spectroscopy, cyclic voltammetry, and smartphone-based methods.