New nano-composite potentiometric sensor composed of graphene nanosheets/thionine/molecular wire for nanomolar detection of silver ion in various real samples.

A novel nanographene carbon composite potentiometric sensor for the determination of trace amounts of silver(I) ion was fabricated. Its sensing layer was prepared with the addition of graphene nanosheets into the matrix consisting of graphite powder, diphenylacetylene "a typically molecular wire (MW) as the conductive binder" and thionine as an efficient ionophore. For investigation of the ion-to-electron transducing ability of graphene nanosheets and molecular wire on the electrode surface, the electrochemical impedance spectroscopy measurements were done and the morphology and properties of the electrode surfaces were characterized by scanning electron microscopy. Under the optimized experimental conditions, the suggested potentiometric silver(I) sensor exhibited an excellent Nernstian slope of 59.70 mV decade(-1) with a rapid response to silver(I) ion within ~ 6s. The response was linear in the range 8.00 × 10(-9) to 1.00 × 10(-2) mol L(-1) and calculated detection limit was 4.17 × 10(-9) mol L(-1). The suggested sensor was successfully applied to the determination of silver in radiological film, environmental and drug samples with satisfactory results.