RESUMO
Chitosan-capped gold nanoparticles (CS-AuNPs) were synthesized via a rapid method by exposing 0.75 mL of 10 mM HAuCl4 and 5 mL of 0.1% w/v chitosan solution to microwave irradiation at 125 °C for 40 s. The resulting red colloidal solution contained monodispersed, spherical, and stable CS-AuNPs with a mean diameter of 17.8 nm and showed the maximum absorption peak at 520 nm. Owing to the positively charged surface, CS-AuNPs were applied to the assay of the polyanionic compound disodium edetate based on the aggregation-induced red-to-blue color change of the particles and the measurement of increased absorbance at 670 nm. The assay was accurate and precise; its results were comparable to those obtained from the titrimetric reference method. Moreover, gold was shown to be easily recovered from CS-AuNPs through alkaline-induced precipitation followed by acid treatment and heating, which provides a facile and efficient means for treatment of laboratory waste.
