GREEN SYNTHESIS OF Ag@Au CORE-SHELL NANOPARTICLES FOR COLORIMETRIC DETECTION OF CYANIDE

Abstract

Cassava is considered one of the most important economic crops in Thailand.  Cassava roots are the most commonly consumed or processed because of high carbohydrate or starch contents.  However, cassavas contain cyanogenic glucosides, which are enzymatically degraded to extremely toxic hydrogen cyanide or cyanide.  This work proposed an alternative method for the cyanide detection, which was rapid, simple and highly sensitive, to meet agricultural and industrial demands.  Based on a colorimetric sensing for cyanide, the green-synthesized colloidal Ag@Au core-shell nanoparticles (NPs) were transparent purple solution and metallic core-shell NPs had spherical shape with a diameter of approximately 22 nm.  When cyanide was added to the Ag@Au core-shell NPs solution, cyanide ion would etch the gold shell followed by the silver core, leading to gradual change of the solution color from purple to orange, yellow, and finally to colorless.  The changes of the solution color could be potentially utilized for the colorimetric sensing of cyanide in a range of 0 – 0.8 mM with a detection time within 5 minutes. This study therefore reported a successfully developed cyanide measurement technique that was suitable for utilization in import/export businesses and classification of cassava varieties between sweet and bitter types.