Sequential Deposition of Polyaminothiophenols and Gold Nanoparticle on Wool Fabrics: Fabric Composites as Efficient Catalysts in the Reduction of Nitroarenes

Merino wool, a highly abundant natural fabric, was successfully transformed into a valuable substrate for preparing easily recoverable catalyst materials by depositing gold nanoparticles (AuNPs) through a series of modification steps. The functionality of wool was enhanced by cleaving-SH groups using NaHS chemical reduction. Subsequently, the reduced wool keratin (WSH) was covalently attached to 3-amino thiophenol (3-ATP) or 4-amino thiophenol (4-ATP) monomers via S-S linkages. The surface was further modified by grafting P3ATP or P4ATP through oxidative polymerization of 3-ATP or 4-ATP using ammonium persulfate as an oxidant. Finally, AuNPs were deposited onto the P3ATP or P4ATP-grafted wool (P3ATP-g-WSH or P4ATP-g-WSH) by immersing the samples in an aqueous HAuCl4 solution. Additionally, P3ATP or P4ATP-coated composites (P3ATP/WSH or P4ATP/WSH) were prepared to assess the AuNP formation ability of the grafting. The structural and morphological changes occurred in the wool, and the presence of AuNPs was revealed by ATR-FTIR, XPS, SEM, and contact angle. The catalytic performance of the AuNP-containing composites in reducing various nitroarenes to aminoarenes using an excess of electron-donor (NaBH4) was monitored by UV-vis spectroscopy. The developed composites demonstrated high efficiency, reusability, and rapid catalytic activity, achieving the highest apparent rate constant of 3.79 min-1, even within 1 min. Schematic illustration of the modification of wool fabrics through disulfide cleaving, immobilization of 3-ATP or 4-ATP, grafting of P3ATP or P4ATP polymers, and subsequently AuNPs deposition. In the image, the grafting phenomenon is structurally visualized by the grafting of 3-ATP onto the WSH fabrics. Finally, the developed materials were employed as simple catalyst in reduction of different nitroarene compounds.image