A smart hydrogel carrier for silver nanoparticles: an improved recyclable catalyst with temperature-tuneable catalytic activity for alcohol and olefin oxidation

Abstract

Radical polymerization reactions were employed to synthesize thermo-responsive poly(N-isopropylacrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid) hydrogels at room temperature. The results of Fourier Transform Infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) confirmed the chemical composition of the synthesized thermo-sensitive hydrogels. The following steps were used to construct P(NIPAM-co-AMPS)-Ag-L/H (1) loading Ag into thermo-sensitive hydrogels at 25 °C and 60 °C, (2) removing loosely-bound Ag ions, and (3) reducing Ag ions with sodium borohydride (NaBH₄). Transmission electron microscopy (TEM) and high resolution X-ray photoelectron spectroscopy (HRXPS) were used to depict metal nanoparticle embedded p(NIPAM-co-AMPS)-Ag. To identify the hydrodynamic radius of the combinations and the thermo-sensitivity of the synthesized hydrogels, dynamic light scattering (DLS) was utilized. Atomic absorption spectroscopy (AAS) was also employed to measure the concentrations of metals in all compounds. In the process of alcohol and olefin oxidation, p(NIPAM-co-AMPS)-Ag composites with different parameters functioned as catalysts. The results confirmed the easy separation of the prepared catalysts from the reaction media. Moreover, the catalysts could efficiently be recycled eight times without losing their quality. FT-IR spectroscopy and atomic absorption spectroscopy also proved that the catalysts were recyclable, durable, and leaching-resistant.