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Gold nanoparticles standing on PEG/PAMAM/thiol-functionalized nanographene oxide as aqueous catalysts

Taking advantage of biocompatible poly(ethylene glycol) and hyperbranched polyamidamine (PAMAM) dendrimer, two polymer/thiol-functionalized nanographene oxide platforms (SH-NGO-PEG and SH-PAMAM-NGO-PEG) with well dispersity and adequate thiol active groups were constructed by conjugating the oxygen-containing functionalities on surface of NGO with PEG and PAMAM via facile covalent approaches including PEGylation via amidation reaction and consequent ring-opening reaction with PAMAM, followed by the introduction of thiol active groups. Gold nanoparticles (AuNPs) were aptly in situ grown on PEG/PAMAM-functionalized NGO via Au-to-thiol bonds, i.e., AuNP@SH-NGO-PEG and AuNP@SH-PAMAM-NGO-PEG nanocomposites, which acquire the intrinsic activity of AuNPs and function as homogeneous catalysts in aqueous media. The PEG/PAMAM-functionalized NGO and the corresponding AuNP complex were characterized using different techniques to confirm the sequential covalent modification of NGO with different functional polymers and the uniformity of the AuNPs scattered over the NGO sheets. AuNP@SH-NGO-PEG and AuNP@SH-PAMAM-NGO-PEG nanocomposites displayed high potential as efficient, stable, and recyclable aqueous catalysts for the reduction of 4-nitrophenol, 4-nitroaniline, and Congo red.