Abstract
The present study investigated the naked eye colorimetric and turn on fluorescent detection of cyanide ions in aqueous medium using marine macroalgae (seaweed) mediated biosynthesized silver nanoparticles (AgNPs). The bioactive metabolites in the seaweed extract act as reducing agents to produce nanoparticles. They also act as capping agent and stabilizer for them. Since no extra reducing and stabilizing agents were used in the synthetic route, it is completely a green chemistry approach. In addition, this method is facile, fast and cost effective. The biosynthesized AgNPs were characterized using UV–vis spectroscopy, HR-TEM and XRD techniques. The biogenic AgNPs are dark brown in colour due to the intense surface plasmon resonance absorption band. In the presence of CN- ions, the brown AgNPs solution turned to colourless accompanying the disappearance of absorption maximum at 414 nm along with a sizable enhancement in fluorescence intensity. The selectivity and sensitivity of biogenic AgNPs towards CN- ions were also studied and the limit of detection was found to be 1 μM. The cyanide sensing mechanism is also proposed based on TEM analysis. Moreover a test strip approach is developed for real time detection of CN- ions. The proposed method has been successfully used for the determination of cyanide in water samples.
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