A colorimetric method for determination of Selenium based on surface Plasmon resonance properties of silver nanoprisms

Silver nanoprisms are one of the most important anisotropic metal nanoparticles which have attracted tremendous attention due to their unique optical properties [1]. One of the unique features of Ag NPs which is extensively applied to establish analytical sensor is surface Plasmon resonance (SPR). This feature of metal NPs is affected by various structural and environmental parameters such as size, shape, architecture, composition of nanoparticles spacing between nanoparticles and their surroundings. Recently, due to exceptional optical, surface and structural properties of anisotropic noble metal NPs, the colorimetric methods based on these NPs have attracted considerable attention [2]. Herein we report on a novel plasmonic probe for detection of ultra-trace amounts of Se(IV) based on morphological transformation of silver nanoprisms (AgNPRs). This nano particles were synthesized in a mild condition and characterized by UV-Vis absorption spectroscopy and transmission electron microscopy (TEM). It was found that in the presence of Se(IV), SPR peak of AgNPRs at 720 nm shifts to lower wavelengths and the color of solution changes from light blue to violet. This is due to the shape transformation of AgNPRs to nanodisks which is proved by TEM images, and results from the etching of corners of NPRs by selenite ions. Based on this phenomenon, a sensitive colorimetric probe was developed for determination of Se(IV) in the concentration range of 2.5-100 μg L-1 with a detection limit of 1.2 μg L-1. The developed method was applied for the analysis of water and food samples.