Facile and rapid thermo-regulated biomineralization of gold by pullulan and study of its thermodynamic parameters

A novel method for the production of gold nanoparticles (AuNPs) using pullulan as reducing and stabilizing agent has been developed. Quasi-spherical shaped AuNPs in the range of 50-100 nm were produced at three different temperature regimes 80°C, 90°C and 100°C as characterized using UV-vis spectrophotometer, TEM and DLS. Study of reaction kinetics and thermodynamic parameters indicated that the reaction between pullulan and chloroauric acid for AuNPs formation followed first order reaction kinetics and higher temperature was favorable for the synthesis of smaller sized AuNPs. FT-IR data analyses, provided an insight towards the mechanism of gold nanoparticle formation which suggested that, the free CH2OH groups of pullulan molecule were oxidized to carboxylate ions resulted in formation of AuNPs whereas the basic skeletal structure of pullulan remained unaltered. This study may open up new avenues for synthesis of tailor made biogenic AuNPs with possible application in biomedical field.