Development a simple and sensitive method for determination low trace of nickel by local surface plasmon resonance of citrate capped silver nanoparticles

Nickel is a toxic transition metal which can create serious problems in health of humans and wildlife. Thus determination of nickel in environmental samples like waters is important and inevitable. In this research a simple and sensitive method for determination of nickel in water was described based on aggregation of citrate capped silver nanoparticles. Silver nanoparticles were prepared by reduction of silver nitrate with sodium borohydride. Cefixime was as chelating agent in the assay and when nickel was added to the mixture of citrate capped silver nanoparticles and cefixime, color of citrate capped silver nanoparticles changed from light yellow to red that depend on Ni^2+ concentration. As a result of aggregation, localized surface plasmon resonance (LSPR) band of silver nanoparticles around 395 nm decreased and a new peak appeared in 550 nm. Control experiments with 10 other ions carried out and did not a distinct change in color or spectrum. Under optimized conditions, linear relationship between Ni^2+ concentrations and the absorbance ratio of A550/A395 and limit of detection were found in the range of 2.70 μmol L^-1 to 17.10 μmol L^-1 and 0.80 μmol L^-1, respectively. The method was applied in tap and well waters that indicate the colorimetric method has acceptable accuracy and good stability.