A novel fluorescent nano-scale sensor for detection of trace amounts of Ca (II) ions

A photo-induced electron transfer (PET) based sensing approach for the direct determination of trace amounts of calcium ions is presented. The Ca ²⁺ selective fluoroionophore Bis, 2,2'-{1,2 phenylenebis [nitrilomethylylidene]} diphenol (DMK) was encapsulated in polymeric ethyl cellulose. The sensing membranes were fabricated in form of nanofibers, exploiting the prepared polymer. When embedded in nanomaterials, the DMK dye yielded strong absorbance, large Stoke's shift, high fluorescence quantum yield, and excellent short and long-term photostability. The sensing ability of the nanofibers was tested by steady state and time resolved fluorescence spectroscopy. To our knowledge, this is the first attempt using the DMK-doped electrospun nanofibrous materials for calcium sensing. The offered nanosensor displays a sensitive response with a detection limit of 0.016 nM for Ca ²⁺ ions over a wide concentration range, 1.0×10 ^-10-1.0×10^-4 M, and exhibits high selectivity over Mg ²⁺ and other cations. Accuracy of the sensing system was proven by recovery tests.