TURN-ON fluorescence detection of cyanide using an ensemble system consisting of a dansyl-based cationic probe and dicyanovinyl derivative

• Published in: Dyes and pigments 2019-03, Vol.162, p.348-357
• Main Authors: Jeong, Eunhye, Yoon, Soyoung, Lee, Hyun Sung, Kumar, Ashwani, Chae, Pil Seok
• Format: Article
• Language: English
• Subjects: CN− sensor; Dansyl fluorophore; Fluorogenic probe; Supramolecular self-assembly
• ISSN: 0143-7208; 1873-3743
• DOI: 10.1016/j.dyepig.2018.10.033

An imidazolium-bearing dansyl-based probe (probe 1; D) and three dicynovinyl group-containing substrates with different alkyl chain length (S1, S2 and S3) were prepared. Three binary ensembles, designated DS1, DS2, and DS3, were generated for CN− detection in a buffer solution of HEPES: DMSO (2:8) (pH = 7.4) by combining these probe and substrates. Upon addition of CN−, each ensemble gave a large fluorescence emission enhancement, but showed little response to the addition of other anions, indicating the high selectivity toward CN− detection. DS1 including an octyl pendant-bearing substrate (S1) gave a high association constant (Ka,app = 2.38 × 108 M−1) and a low LOD (200 nM) for CN− sensing in HEPES: DMSO (2:8) (pH = 7.4). Dynamic light scattering (DLS), transmission electron microscopy (TEM) and 1H NMR studies indicate that the substrate (S1) was associated with cationic probe 1 to form supramolecular self-assemblies following its addition reaction with a nucleophilic CN−. This assembly formation that causes the dansyl fluorophore of probe 1 to reposition from a hydrophilic water to the hydrophobic assembly interiors is likely responsible for a significant increase in the fluorescence intensity of the ensemble system. The other ensemble systems (DS2 and DS3) containing relatively short alkyl chains (pentyl and methyl, respectively) were inferior to the long alkyl chain system (DS1), indicating the importance of the alkyl chain length for highly sensitive CN− detection. A binary ensemble system (DS1) gave a selective and sensitive detection toward CN−, with an LOD of 200 nM. [Display omitted] •We prepared three binary ensembles comprising a dansyl-based probe and three dicyanovinyl substrates.•Three binary ensemble systems (DS1-DS3) showed a selective CN− detection in a solution of HEPES: DMSO (2:8).•Upon addition of CN−, the ensembles produced a large supramolecular assemblies.•The alkyl chain lengths of the dicyanovinyl substrates were important in determining detection sensitivity.•An LOD of DS1 for CN− sensing was as low as 200 nM.