Synthesis of Silver Nanoparticles-Agarose Composite and Its Application to the Optical Detection of Cyanide Ion.

A highly sensitive and selective colorimetric method was developed for the detection of CN ion based on the surface plasmon resonance of silver nanoparticles (AgNPs) embedded in a transparent agarose matrix. The AgNPs were prepared by chemical reduction of Ag in the presence of sodium borohydride as the reducing agent and agarose as the stabilizing agent. Characterization of the nanoparticles was performed with UV/Vis spectrometry and scanning electron microscopy. A calibration curve was derived for the absorbance of the sensor at 410 nm, that was linear over a range from 1.5 to 120 μmol L with an R value of 0.998 (n = 8). A detection limit of 0.69 μmol L and a relative standard deviation of 3.8% were obtained for CN for 8 replicates. A reproducibility of about 6.1% was also obtained for four batches of the sensor. The sensor showed excellent selectivity for CN ion at the presence of a number of interfering ions with concentrations exceeding 50 times of that of the analyte. The results showed successful application of the AgNPs-agarose as a colorimetric sensor for easy and selective monitoring of CN ion in aqueous solutions.