A novel dendritic polymer based turn- off fluorescence sensor for the selective detection of cyanide ion in aqueous medium

Porphyrin cored polyepichlorohydrin (POR-PECH) dendritic polymer was identified as an efficient turn-off fluorescence probe for selective determination of cyanide ion in aqueous medium. The dendritic polymer showed strong red fluorescence at 656 and 718 nm which was quenched in the presence of cyanide ion. POR-PECH showed high selectivity towards cyanide ion over other relevant anions including Cl-, Br-, F-, I-, NO2-, NO3-, CH3COO,- SO32-, CO32-, SCN-, HCO3-, HPO42-, H2PO4- etc. The proposed sensor is highly selective, sensitive which showed quick response towards cyanide ion. The limit of detection of proposed method was found to be 1.2 mu M which was admirably lower than the maximum allowed cyanide content in drinking water (1.9 mu M) as recommended by WHO. Back folding of self assembled porphyrin cored PECH dendritic chains by the addition of cyanide ion caused the quenching of fluorescence. The time resolved fluorescence life time, FE-SEM image and DFT studies supported the quenching mechanism.