Kinetic Approach to Elucidate Size Controllable Features in Nanocomposites of Gold Nanoparticles and Poly(3,4-ethylenedioxythiophene) in Aqueous Dispersion Stabilized by Gum Acacia

Research and development of conductive nanomaterials based on biocompatible matrices has been greatly rising in the past decade since synergistic properties can be achieved by combining metallic nanoparticles and natural/conductive polymers. Poly­(3,4-ethylenedioxythiophene) (PEDOT) is known to be an intrinsically conductive polymer, difficult to handle in aqueous medium. Therefore, in this work, we present a physical-chemical perspective in the development of novel aqueous dispersible nanocomposites of gold nanoparticles (AuNPs) and PEDOT, obtained through a one-pot synthesis, using the biopolymer gum acacia (GA) as stabilizer. A thorough kinetic study was carried out and correlated with microscopy analyses, evidencing that the concentration of GA influences the AuNP size by affecting their nucleation and growth stages. A quantitative detailing using kinetic models is shown, which to the best of our knowledge is the first report relating mechanism and rate constants with size controllable features of the stabilizer. Two distinct kinetic profiles were obtained and related to a critical concentration of GA (1%_w/v): (i) above, a characteristic nucleation–growth sigmoidal profile and (ii) below, an unexpected bilogistic profile, accounted to a two-step growth process. Indeed, the bilogistic kinetic model, usual in population growth studies, is presented herein for the first time regarding NP formation. These results incite the targeted design of novel nanomaterials, using kinetic studies as a promising tool to understand the mechanism of the size-controllable features of GA. Overall, we evidence that the nanocomposite characteristics can be optimized rationally. Also, considering the natural occurrence of GA, we contribute to the sustainable development of highly water-dispersible PEDOT-derived nanocomposites