Catalytically Active Gold Nanoparticles on Star Block Co-polymer Matrix: Synthesis of Nanocomposite Film Exploring the Langmuir–Blodgett Technique

Abstract

Nanocomposites with metal nanoparticles and block copolymers distributed in a stable and robust thin film are preferred for various applications. Here, synthesis of such a nanocomposite is reported, which is composed of gold nanoparticles (AuNPs) embedded in a tetronic 701 (T701) and 90R4 (T90R4) thin film matrix generated using the Langmuir−Blodgett (LB) thin film technique. Tetronics contain a monoprotonated central ethylenediamine group at pH 5 due to the presence of chloroauric acid (HAuCl 4 ) in the subphase, along with poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) blocks, both of which have the capacity to serve as the reducing agent toward chloroaurate anion (AuCl 4 − ). Calorimetric experiments have shown that T90R4 has a better interaction with AuCl 4 − , probably due to its better electrostatic interaction with AuCl 4 − ions due to the higher % of the hydrophilic PEO group. On the other hand, the T701−AuNP interaction turned out to be more spontaneous due to the higher hydrophobicity of T701 (higher PPO/PEO ratio). The optical properties and structure/morphology of these nanocomposites are characterized by UV−vis spectroscopy, FTIR spectroscopy, XRD, and TEM. The composite thin film has the ability to catalyze the organic electron transfer process between p-nitrophenol and paminophenol in the presence of sodium borohydride. A clear correlation has been found between the reaction rates and the kind of tetronic present in the nanocomposite, which acted as a matrix and stabilizer toward AuNPs.