Turn-on Fluorescence Sensor for Detection of Cyanide based a novel dicyanovinyl phenylacetylene
A novel phenylacetylene derivative containing dicyanovinyl group (3) was successfully synthesized via Sonogashira coupling and Knoevenagel reaction. Compound 3 can be used as a highly selective and sensitive turn on fluorescent sensor for detection of cyanide ion aqueous solution.. Upon the addition of cyanide ion, compound 3 changed the color from yellow to colorless redily observable by naked eye, along with the increase of blue fluorescent emission under black light (365 nm) illumination. With the measurement of fluorescence intensity, a linear dynamic range for contitative analysis of cyanide concentration is 0-80 µM with the detection limit of 0.68 µM which is below the 1.9 µM limit recommended by World Health Organization (WHO) for drinking water. 1H-NMR titration confirms that the flurescence turn on signal is the result of a nucleophilic addition of cyanide ion to the β-position of the dicyanovinyl carbon. The addition of cyanide ion disrupts the π-conjugation between the fluorescent phenylacethnylene unit and the strong electron withdrawing dicyanovinyl group, and thus inhibiting the non-radiative intramolecular charge transfer (ICT) process. The application of compound 3 for determination of cyanide in spiked samples of water and tapioca starch showed satisfactory results.